1 From bugger to homosexual: the English sodomite as criminally deviant (1533-1967) 1Dr Jérôme Grosclaude Senior Lecturer, Blaise-Pascal (Clermont-Ferrand II) University Agrégé de l'Université (EA 1087: Espaces Humains et Interactions Culturelles) [James Bond] had put forward the proposition that, if MI5 and the Secret Service were to concern themselves seriously with the atom age 'intellectual spy', they must employ a certain number of intellectuals to counter them. (…) 'Retired officers of the Indian Army', Bond had pronounced, 'can't possibly understand the thought processes of a Burgess or a Maclean. (…) Once Burgess and Maclean went to Russia, the only way to make contact with them again (…) would have been to send their closest friends to Moscow and Prague and Budapest with orders to wait until one of these chaps crept out of the masonry and made contact. (…)' 'Oh really', [Captain] Troop had said with icy calm. 'So you suggest we should staff the organization with long-haired perverts. That's quite an original notion. I thought we were all agreed that homosexuals were about the worst security risk there is. I can't see the Americans handing over many atom secrets to a lot of pansies soaked in scent.' (Fleming, 2006: 130-131) Captain Troop's reaction, as well as the fact that 'the other committee members had ranged themselves more or less with Troop' (Fleming, 2006: 131), is obviously a way for the author to give us an unflattering image of the bureaucrats of the MI6, contrasting sharply with James Bond's clear-sighted and down-to-earth approach. However, it is also a fitting example of the deviant character homosexuality has long assumed in British minds, and of the unreasonable fear that homosexuality and sodomy could (and maybe can still) arouse in British minds. I mentioned homosexuality, but this paper is really about sodomy (or 'buggery' if one wants to use the proper legal term enshrined in the Buggery Act 1533) and not about homosexuality, although the two will necessarily overlap.

To begin with, homosexuality, that is to say 'a sexual propensity for one's own sex' (Oxford English Dictionary, 2002: vol. 7-345), has never been a criminal offence in the United Kingdom nor in any of its component nations, contrary to sodomy (that is, anal penetration by a man's penis) which was illegal in the United Kingdom from 1533 to the late XXth century. The reader will have understood that the most likely persons to commit such acts would be men sexually drawn to other men, but one can note a few prosecutions for consensual heterosexual sodomy.

To understand further why this article will not be about homosexuality in itself, it should be understood that the notion of homosexuality as we know it was not formulated before the 1860s, and took time to be accepted by the general public. It was not until 1869 that the word 'homosexual' (as opposed to 'heterosexual') was first used by the Austro-Hungarian Károly Mária Kertbeny (the alias of Karl Maria Benkert) (Leroy-Forgeot, 1997: 5).

Havelock Ellis was probably the first to use the word widely in English in the 1890s (Weeks, 1990: 3). Until maybe the XVIIIth century, and certainly no later than the late XIXth century, most people saw sodomy as the ultimate perversion but it was not conceived as precluding the sodomite from having (or wishing to have) sexual relations with women. Indeed, the modern idea that most people are exclusively sexually attracted either to men OR to women took time to become widespread. For all these reasons, to speak of 'homosexuality' before the end of the XIXth century would represent an anachronism.

The opening paragraph of this article mentioned a link between sodomy and treason. As a matter of fact, the image of the sodomite as a traitor (alleged or proven) was only one of the many stages through which 'buggers' have gone. From sinner (and thus offender against God) to mentally ill, these are the (sometimes concurrent) different stages through which sodomites have gone through in terms of public perception during the period studied in this article.

These different categories, the reader will have gathered, all have a common point: a deviant character, linked to the danger allegedly posed by sodomy to society and the social fabric, for political and/or religious reasonsin the XVIth century, for example, 'the love of boys was seen as the most extreme act of sexual libertinism and, not untypically, was often associated with religious scepticism, and even republican politics as well' (Franceschina, 1997: 111) and/or for medical reasons. If homosexuality (and homosexual acts) now generally enjoy a more positive social status in the British public eye, the notion of sodomy as a deviance is never far from the surface as witnessed by the recent debates around same-sex marriage.

Professor Randolph Trumbach was never more justified than when he asserted in 1987 that '[t]he history of sodomy in the eighteenth century is not simply the history of repression. It encapsulates the history of all of society' (Trumbach, 1987: 109). Indeed, the same could be said for every century in the period covered in this chapter.

We can therefore ask the following question: To what extent have the different labels cast upon male homosexuals reflected the changing perceptions of the deviance they were alleged to represent? The question will be answered by first outlining the Religious and legal foundations of the condemnation of sodomy before focusing on three different (broadly successive but sometimes overlapping) representations of male homosexuality in England and Wales: the traitor; the perverted libertine; and the mentally ill.

I. Religious and legal foundations of the condemnation of sodomy

The sodomite as sinner: Biblical foundations Before engaging in the discussion of the stigmatization of sodomy in England, it is necessary to describe the religious bases of the condemnation of sodomy and of homosexuality.

A common and age-old basis for a Biblical, and thus Jewish and Christian, condemnation of sodomy is to be found at Leviticus 18, 22.29: 'You shall not lie with a male as with a woman; it is an abomination. (…) For whoever commits any of these abominations shall be cut off from their people'. 2 The prohibition is repeated in a different form two chapters later, in Leviticus 20, 13, along with another, more precise, penalty to be imposed: 'If a man lies with a male as with a woman, both of them have committed an abomination; they shall be put to death; their blood is upon them'.

To these prohibitions, Jewish, and later Christian, scholars also added the episode of Sodom and Gomorrah. One night, two angels come to stay at Lot's (Abraham's nephew) house, and 'the men of the city, the men of Sodom, both young and old, all the people to the last man, surrounded the house; and they called to Lot, "Where are the men who came to you tonight? Bring them out to us, so that we may know them"' (Genesis 19,(4)(5). When Lot tries to protect his guests, he is 'pressed hard' by the men and is only saved by the supernatural intervention of the angels who then tell him to flee with his relatives, adding: 'we are about to destroy this place, because the outcry against its people has become great before the LORD' (Genesis 19,12).

The wish of the men of Sodom to 'know' the strangers has usually been construed as meaning carnal knowledge. The logical conclusion to reach was then that Sodom was destroyed because its male inhabitants practised anal intercourse with each other, and that it was a particularly heinous crime in the eyes of God who had earlier remarked to Abraham: 'How great is the outcry against Sodom and Gomorrah and how very grave their sin' (Genesis 18,20). This interpretation, combined with the Levitical condemnation I mentioned earlier, is the bulk of Biblical condemnation. To this could be added St Paul's raging against 'those who by their wickedness suppress the truth' (Romans 1, 18), about whom he observes: God gave them up to degrading passions. Their women exchanged natural intercourse for unnatural, and in the same way also the men, giving up natural intercourse with women, were consumed with passion for one another. (Romans 1,(26)(27) Elsewhere, the Apostle to the Gentiles includes sodomites among the 'wrongdoers [who] will not inherit the kingdom of God' (1 Corinthians 6, 9) and those whose acts are 'contrary to the sound teaching that conforms to the glorious gospel of the blessed God'

(1 Timothy 1, 8-10).

On these biblical references, Christian tradition later built a philosophical condemnation of sodomy which would be expanded by several theologians, among which St Augustine of Hippo in his Confessions:

[O]ffenses against nature are everywhere and at all times to be held in detestation and should be punished. Such offenses, for example, were those of the Sodomites; and, even if all nations should commit them, they would all be judged guilty of the same crime by the divine law, which has not made men so that they should ever abuse one another in that way. For the fellowship that should be between God and us is violated whenever that nature of which he is the author is polluted by perverted lust. (Augustine of Hippo, 1955: 45) Likewise, St Thomas Aquinas in his Summa Theologica, condemns 'copulation with an undue sex, male with male, or female with female' as 'a special kind of deformity whereby the venereal act is rendered unbecoming' (Aquinas, 1920: Part II of Part II, Q154, §11).

From these various references, it will be clear to the reader that the sodomite had no place in the City of God. The practising sodomite being a dangerous sinner, it is necessary to cast him out of the society of Christians. It was widely thought that the divine prohibition against sodomy was grounded on 'practical' reasons: sodomy is unnatural and unprocreative (Borrillo, 2001: 57). To this should be added that sodomy implies a reversal or a confusion of the roles, the passive male partner playing the part usually devoted to the woman as the passive 'object' of the penetration (Tamagne, 2001: 9).

The religious basis for the repression of homosexuality having been laid out, I will now proceed to study its legal repression in England, which began in 1533 the year after Henry VIII broke with Rome. The legal basis for the prosecution of sodomy in Britain, the Buggery Act 1533, remained in force until 1861 (except during the short period of the reign of Mary I Stuart). To fully understand the consequences of this law, it is necessary to examine the context in which the Buggery Act was passed. It is then necessary to go back in time to study its consequences.

Legal basis for the repression of sodomy

Henry VIII's break with Rome, which effectively occurred in 1534 with the passing of the Act of Supremacy, was preceded by various episodes, notably the 1532 submission of the clergy and the Act in Conditional Restraint of Annates, and, the following year, the Act in Restraint of Appeals (with effect from January 1534) which forbade appeals from English church courts to Rome and which at the time seemed to precede the total abolition of canon law and the church courts empowered to administer it (Baker, 2002: 130-131). Eventually, the old ecclesiastical legal apparatus was allowed to continue in existence alongside the civil (that is, lay) jurisdictions, 'except where it was contrary to the common or statute law or the king's prerogative' (Baker, 2002: 131).

It is in this context that the passage of the Buggery Act 1533 must be understood since the King was anxious to take as much power away from the Church as he could, and such a law ensured that cases of sodomy would from then on be exclusively judged by civil courts.

Until then, it should be noted, only canon law punished sodomy, as it was never a common law offence in England (Baker, 2002: 531). Prosecutions for buggery were rare in Early Modern England, and the penalties imposed by ecclesiastical courts on convicted sodomites were usually very lenient (Greenberg, 1988: 303).

The Buggery Act was a particularly harsh law, as was most of the Tudor criminal legislation. After having denounced the 'detestable and abominable Vice of Buggery committed with mankind or beast', the statute laid down the sentence: 'such pains of death and losses and penalties of their good chattels debts lands tenements and hereditaments as felons do according to the Common Laws of this Realme'.

The religious and legal bases for the prosecution of sodomy having been now laid out, we will see the different stages through which the apprehension of sodomy by the State was to go through.

II. 'Their blood shall be upon them': The Repression of Sodomy

The Buggery Act as a purely political tool For most of the period between 1533 and the Glorious Revolution, convictions for buggery remained exceptional. By 1641, only three people had been convicted of buggery: Lord Walter Hungerford in 1540, Mervyn Tuchet, 2nd Earl of Castlehaven, in 1631 and, nine years later, the Church of Ireland Bishop of Waterford & Lismore John Atherton. The latter is a good example of the political use of the Buggery Act: he was hanged for adultery, fornication and buggery, but it is now judged highly probable that he 'was the victim of revenge for his successful recovery of church lands' from the 1st Earl of Cork (Oxford Dictionary of National Biography, 2004: 2-811). In all three cases, the Buggery Act had been invoked in the course of politically motivated cases, where discrediting the defendant could be useful to the powers that be. The exceptional character of the prosecution of buggers is confirmed by a study of assizes and quarter-sessions indictments in Essex between 1620 and 1680: out of the 8,557 cases, only one was for buggery, dropped for lack of evidence. The situation was very similar in Kent, Sussex and Hertfordshire during an earlier period (1559-1625) (Greenberg, 1988: 326).

The 150 years after the passage of the Buggery Act could then seem to validate the theory that there was no political desire to root out or to fight sodomy, since in the only three condemnations for buggery during this time the accusation was very probably or certainly used as a means to further discredit men it was deemed urgent to suppress by any means possible for religious or political reasons. We find here one of the four reasons behind the almost universal repression of buggery in Europe at the time listed by Dr Flora Leroy-Forgeot in 1997: 'political opportunism (…) which can be summed up in the syllogism: "The sodomite is the worst kind of criminal, the enemy of my group is the worst kind of criminal, so the enemy of my group is a sodomite"' (Leroy-Forgeot, 1997: 22).

The decades following the Glorious Revolution were however marked by a shift in the repression of sodomy, which I will now study.

New representations and heightened repression

The last years of the XVIIth century witnessed a turning point in the history of sodomy as an anti-social behaviour since it began to be fought per se, and quite harshly so. There are two main reasons for such a change: first, the appeasement of the religious quarrels and fears which had characterised the XVIth and XVIIth centuries allowed the public and the political leaders to turn their attention to threats less serious than popery, political sedition or witchcraft (Greenberg, 1988: 328-329); second, the creation, from the 1690s, of Societies for the Reformation of Manners, religious societies which prosecuted blasphemers, prostitutes, pornographers and buggers (Trumbach, 1977: 11).

It should be noted that, in the absence of a professional police force, it was extremely difficult to find evidences of an offence usually committed in private by two consenting persons. All the more so since the case law imposed very stringent conditions for establishing the offence of buggery: evidence had to be brought of actual penetration and emission of semen, something which was rarely feasible (Gilbert, 1976: 73). The Societies for the Reformation of Manners conducted raids on 'molly houses', these places of gatherings for men interested in homosexual intercourses and/or in transvestism. The London Society alone was responsible for 90,000 arrests between 1692 and 1725 (which means an average of more than seven arrests per day) (Greenberg, 1988: 329). The judicial repression was however quite lenient, when one bears in mind that sodomy was a capital offence, and judges usually sentenced to a small fine and a few hours in the pillory for attempted sodomy (since the actual offence was very difficult to prove). Although the pillory was the lightest penalty a judge could impose, such a sentence could have grave consequences for the defendant: in addition to the public humiliation of being thus exposed, mobs were not infrequently known to pelt pilloried offenders with eggs or even stones (Greenberg, 1988: 339), especially when the condemned person had been convicted of a sodomy-related offence, with one such death recorded in London (Trumbach, 1977: 21).

An element could explain the sudden new intensity of the repression of buggery: the perception of sodomy as a sexual deviance (as opposed to a political or religious one) had undergone a change by the end of the XVIIth century. The idea became prevalent in Britain that sodomy was gaining ground, and that buggers were more and more numerous. What we would now call 'homosexuality' was all the more threatening that sodomy was more and more associated with a particular class of men, usually effeminate, who liked to meet in the molly houses mentioned above to have sexual relations and shunned the society of women (Tamagne, 2001: 59), thus confirming the abnormality of sodomites who naturally were seen as a danger to family, the basis of society. 3This new perception of sodomy has a direct relation with the object of this chapter: the political, moral and religious arguments against sodomy, without disappearing, were superseded by rationalist and 'hygienist' arguments presenting buggery as a cancer and a hidden threat, as well as a social disorder which needed to be regulated for the benefit of society (Tamagne, 2001: 71-72). Of particular importance seems to have been the realization that sodomy was not limited to the aristocracy or the upper class: 'Vice and scandal worried the British authorities then because they were perceived for the first time to be endemic rather than merely courtly, aristocratic, orstill worse -foreign' (Rousseau, 1987: 133).

However, this new perception was accompanied by a contrary intellectual trend which called for the decriminalization of sodomy, not because of its innocuousness or its acceptability, but because of a new conception of what Law could and could not regulate. Thus, in France, Diderot privately wrote in 1769 that 'everything that is cannot be against nature, nor outside nature' ('tout ce qui est ne peut être ni contre nature ni hors de nature') (Diderot, 1951: 940), thus refuting a traditional argument against sodomy. The idea also began to appear that the moral transgression of sodomy belonged to the fields of sin and thus to canon law, but not to civil law (Leroy-Forgeot, 1997: 50-51). Likewise, in his Essay on Paederasty (written in 1785 but not published until 1931), Jeremy Bentham, although also reproving sodomy, notes that he cannot find any reason justifying the criminalization of 'offences against one's self' (Bentham, 2002: 10).

These contradictory trendssodomy still seen as dangerously deviant and needing to be eliminated for the welfare of the Commonwealth, while at the same time conceived as something pertaining to the realm of morals and not necessarily of Lawfinally led to a paradoxical state of mind where sodomy was allowed to be publicly ignored and taboo but could occasionally be harshly punished if too visible.

III. 'May I not speak, my Lord?': the sodomites' right to be silenced

Sodomy as a symptom of mental illness

In October 1884, the famous psychiatrist Dr George Savage MD described in the Journal of Mental Science a female patient with a 'powerful lust towards those of her own sex' and wondered if 'this perversion is as rare as it appears' (Weeks, 1990: 28). Dr Savage was not an exception, and cases of homosexuality recorded in medical journals of the time were often treated 'as if a new type of human being had been discovered' (Weeks, 1990: 28). In a trend consistent with the 'hygienist' view of the sodomite I mentioned when discussing the XVIIIth century, homosexuality was then often seen as a mental illness and, as such, cases were usually mentioned in the context of prisons or lunatic asylums. Havelock Ellis claimed that he had been the first to record homosexual cases unconnected with such backgrounds (Weeks, 1990: 28) and he was most probably right. However, he too, in his seminal Sexual Inversion (1897), co-written with John Addington Symonds, asserted a link between 'sexual inversion' and mental problems:

The sexual invert is specially liable to suffer from a high degree of neurasthenia, often involving much nervous weakness and irritability, loss of self-control and genital hyperaesthesia [i.e. an abnormally high sensitivity to stimuli of the senses]. This is a condition which may be ameliorated, and it may be treated in much the same way as if no inversion existed (…). The inversion is not thus removed (Ellis & Symonds, 1970: 144). This change of perspective has been aptly described by Randolph Trumbach: 'Beginning in the late 19th century it was no longer the act that was stigmatised, but the state of mind. Men were no longer sodomites but homosexuals, though they were still seen as effeminate and dangerous -no longer heretics but sexual perverts' (Trumbach, 1977: 9). Not that this change of perspective was unwelcome by Victorian and Edwardian society: 'Madness was the only explanation which did not undermine the middle-class norm' (Weeks, 1990: 28). And in this middle-class norm, sodomy could not exist; it had to be pushed into the shadow where it could be safely ignored, and starkly punished if it ever came out.

Shadow men

The thinkers I mentioned in the previous part provided the rationale for a continuing reprobation of sodomy while at the same time keeping its repression low on the official agenda. Buggery was still seen as a threat but it appeared more urgent to conceal it from view and to ignore it than to punish it, since punishment put the transgression in plain sight.

A marking feature in the history of sodomy in the XIXth century is the fact that the legal penalties appeared to be more and more lenient: in 1816, the Pillory Abolition Act restricted the use of this punishment to the offence of perjury, and, in 1837, the pillory was abolished altogether. As for the offence of buggery itself, it stopped being a capital offence in 1861 when the Offences against the Person Act abolished the Buggery Act and made the 'abominable Crime of Sodomy and Buggery' liable of a prison sentence comprised between ten years and life ( § 61). As for the attempt, which could only be committed on a male person, was punishable by either from three to ten years of penal servitude or by at most two years in prison (with or without hard labour) ( § 62).

However, as a corollary, repression was allowed to become more systematic: the penalty for actual sodomy was less harsh, but the necessity to prove the emission of seed to constitute the offence was removed by § 63 of the 1861 Act. At the same time, the penalty was actually harsher for attempted sodomy, that is to say the offence which sodomites were usually found guilty of. The final touch was put in 1885 when the 'Labouchère Amendment' (after the Liberal MP Henry Labouchère who moved it), Section 11 of the Criminal Law Amendment Act created the offence of 'gross indecency' committed by a male person upon another male person. The misdemeanour was not further defined, which allowed for the prosecution of virtually any homosexual act when actual sodomy could not be proved.

It was punishable of at most two years, with or without hard labour. The fact that the offence was not even defined is representative of the hidden status of deviant sexuality (indeed of all sexuality) under the Victorian era, as was the 1896 Publication of Indecent Evidence Bill defended by the then Lord Chancellor, the 1 st Earl of Halsbury, and supported by the Conservative Prime Minister, the 3 rd Marquess of Salisbury, which, if adopted, would have forbidden the press from reporting on trials dealing with homosexuality (Tamagne, 2000: 29).

Such laws or bills were also representative of an urge to fight all types of perversions, be they feminine or masculine: the Criminal Law Amendment Act 1885 as a whole was designed to repress female prostitution and sexual abuses directed at young girls (Weeks, 1990: 16-20). The target of this 'purity campaign' was male lust, which was felt by many to be the ultimate root of many disorders in society (Weeks, 1990: 16). Thus, in 1895, W. T.

Stead called for the law to protect the young girls sexually exploited by unscrupulous men as strictly as it had 'protected' young men from Oscar Wilde's unnatural lifestyle (Foldy, 1997: 129-130).

The paradoxes of the second type of public attitude towards sodomybuggery becomes invisible and legal penalties are even toned down but repression quietly continueswere to become obvious to all in 1895 when Oscar Wilde decided to prosecute the 9th Marquess of Queensberry.

The Wilde trials: backlash and watershed

It may well be true that Oscar Wilde is the homosexual who is most famous for being homosexual. It is at least true that his fall from grace in the 1890s has made him an eminently tragic figure and an enduring symbol of the repression of homosexuality. Not that he achieved that status at the time, nor even in the following decades. The prevalent opinion in the 1890s was rather that the Establishment had allowed the corruption of one of its most brilliant members to go unchecked and that his punishment had long been overdue. The desire to obliterate Wilde from the national conscience can find a symbol in Wilde's last, unanswered apostrophe to his judge after the sentence had been pronounced: 'And I, may I not speak, my Lord?' (Foldy, 1997: 47) In February 1895, desirous to put an end to the 40-year-old Oscar Wilde's affair with his 25-year-old son, Lord Alfred Douglas, the Marquess of Queensberry left his calling card at Wilde's club with the inscription 'For Oscar Wilde, posing as a somdomite [sic]'. Being thus accused of a criminal offence, Wilde decided to prosecute the aristocrat for libel. The Marquess's defending team then set out to prove that the statement was true and that it had been made for the public benefit (Foldy, 1997: 1).

What the public benefit was can be summed up in this way: 'Wilde had been proved to have been associating with disreputable young men who were not his coequals in either age or station' (Foldy, 1997: 19) and had exercised a 'corrupting influence' on a young man. Much to Oscar Wilde's surprise, the defense team claimed they were able to call to the bar a number of young men, often of very low degree, to prove that the writer had indeed had sexual relations with other men. The deviant, anti-social character of Oscar Wilde's lifestyle was there, in his breaking twice the norms of Victorian England: first, by having 'unnatural' sexual intercourses, and, second, by breaking the class barrier.

Confronted to a backlash which he had strangely not foreseen, Wilde dropped his prosecution in April but was in turn immediately prosecuted for 'acts of gross indecency' under the Labouchère Amendment. After the jury of the first trial was unable to reach a verdict, he was again tried for the same offence. The fact that the prosecution in the latter trial was led by the Solicitor General, Sir Frank Lockwood MP, leaves no doubt about the importance of the trial in the eyes of the then Liberal Government (Holland, 2003: xxxiiixxxiv).

Wilde's sentence of two years of hard labour, and his subsequent lifewhich saw him survive three years as a social outcast, a broken and a bankrupt manmay well have been seen by some contemporaries as a cautionary tale. There is indeed no doubt that Wilde and his 'vice' were very widely seen as anti-social, as a threat to the Victorian society. The trial and its outcome were often described using hygienist words: thus, addressing the jury, the first prosecutor, Charles Gill, told them they 'owe[d] a duty to society (…) to protect society from such scandals by removing from its heart a sore which cannot fail in time to corrupt and taint it all' (Foldy, 1997: 37). During the second trial, anticipating the widely-expected verdict of guilt on Wilde's part, The Daily Telegraph described the moral condemnation British society would bestow on Wilde as 'the indirect sentence which eliminates him from the society he has disgraced' (Foldy, 1997: 54).

However, and paradoxically, the trials of Oscar Wilde were in retrospect the prelude to a more positive public view of sodomy and homosexuality: one which was to lead political leaders to push for the acceptance of homosexuals.

IV. 'They have to have a gay world': Tolerance and acceptance (?)

According to Havelock Ellis, The Oscar Wilde trial with its wide publicity and the fundamental nature of the questions it suggested appears to have generally contributed to give definiteness and self-consciousness to the manifestations of homosexuality, and have aroused inverts to take up a definite stand (Weeks, 1990: 22).

However, the decades following Oscar Wilde's trials did not immediately show a change in the vision British society had of sodomites. Even if homosexuals started to organize (Weeks, 1990: 133), British society was not ready to approve of sodomy until at least the 1960s (Weeks, 1990: 158). Some individuals, such as Edward Carpenter (1844Carpenter ( -1929)), and organizations such as the British Society for the Study of Sex Psychology or the Sex Education Society attempted to change the public view of homosexuality (Weeks, 1990: 133) through learned articles or books. A constant of these endeavours was to try to better understand the mechanisms of human sexuality and sexual attractions, taking a '"scientific' (that is, humane and rational) approach to the problems of sex' (Weeks, 1990: 133). A cliché in the literature of the time, from the middle of the XIXth century, being to assimilate homosexuality and narcissism, some tried to compile list of homosexuals of the past having been useful socially (Tamagne, 2001: 97). Thus, in The Intermediate Sex (1908), Edward Carpenter shows that 'Uranians' constituted a positive force for the Nation, and he underlined their role as artists, teachers or inventors (Carpenter, 1908: 60-64). However, such works and lists remained essentially confidential and had no impact on the repression of homosexual offences, which intensified and became more systematic in the interwar period (Tamagne, 2000: 457), with the trend continuing after the Second World War (Weeks, 1990: 159). There can be no doubt there was a conscious desire to fight sodomy in the latter period, when the Conservative Home Secretary Sir David Maxwell-Fyfe declared in the Commons in 1953 that 'homosexuals in general are exhibitionists and proselytisers and are a danger to others, especially the young' (Weeks, 1990: 159).

The change in perspective concerning sodomy was essentially due to a change in society as a whole. What Geoffrey Weeks has called the 'new hedonism' of the 1960s (Weeks, 1990: 158), with its emphasis on sexual pleasure, made the situation of homosexuals appear strange since they were officially denied the right to experience it. Already, in 1957, the special committee on homosexual offences and prostitution chaired by Sir John Wolfenden had recommended the decriminalization of consented homosexual acts carried out in private between two adults. This recommendation, which, the committee stressed, was not to be seen as countenancing sodomy (Wolfenden, 1963: 45 & 48), was based essentially on an argument we have already encountered: 'Unless a deliberate attempt is made by society, acting through the agency of the law, to equate the sphere of crime with that of sin, there must remain a realm of private morality and immorality which is, in brief and crude terms, not the law's business' (Wolfenden, 1963: 48).

Generally, the committee took it as a line that homosexual acts were to be treated just like heterosexual acts (Wolfenden, 1963: 49). They claimed they were able, after careful scrutiny, to dismiss most of the arguments usually given for defending the criminalization of sodomy: it was no more dangerous for family life than other sexual behaviours such as 'adultery, fornication or lesbian behavior' that were not criminalized (Wolfenden, 1963: 44-45) and homosexuality was not a disease (Wolfenden, 1963: 44-45). Far from being a danger to society, homosexuality could even be, for some, 'the motivation for activities of the greatest value to society' (Wolfenden, 1963: 30).

The report's recommendations on homosexuality were nonetheless not translated into law. The decriminalization of buggery (and other homosexual offences) had to wait until 1967, essentially thanks to the stubbornness of a Labour backbencher, Leo Abse, who introduced a Private Member's Bill eventually adopted by Parliament in July 1967. The Labour government of Harold Wilson discreetly supported the Bill, but made no effort to help its sponsor pass it, except by giving Leo Abse as much Parliamentary time for the debate as he judged adequate (Abse, 1973: 152). It should be noted that no Church or organization officially opposed the Bill (Weeks, 1990: 175), so true was it that '[b]y 1967, the heat had largely been dissipated from the question' (Weeks, 1990: 156). This new tolerance was nonetheless fraught with ambiguities, and the 1967 law proved an ambiguous landmark. No homosexual group was consulted by Leo Abse (Weeks, 1990: 176), who, as a result, accepted a number of compromises for tactical reasons (Abse, 1973: 156-157), notably excepting the Armed Forces and the Merchant Navy from the provisions of the Act, thus giving credence to the idea that sodomites were a danger to the Armed Forces and to the Country they were to protect. Abse also confessed in his memoirs (published in 1973) that, in order for his Bill to be adopted, homosexuals had to be placed at a distance, suffering a distinctive and terrible fate so different from that enjoyed by Honourable Members blessed with normality children and the joys of a secure family life. To hint that the homosexual component in a man's nature plays a large part in helping him understand and thus form a deep relationship with a woman, would have aroused discomfort (Abse, 1973: 153).

However, imperfect as the law was, the Private Member's Bill effectively freed homosexuals from the fear of prosecution in England. The 1967 turning point introduced an era where, as the Wolfenden committee had expressed the hope, the State decided that it was none of its business to inquire what two people had consensually decided to do, however disturbing it could have appeared to outsiders. Buggery was decriminalized (with the same exceptions as in England) in Scotland by the Criminal Justice (Scotland) Act 1980, and in Northern Ireland by The Homosexual Offences (Northern Ireland) Order 1982.

In 1994, during the discussion of the Criminal Justice and Public Order Act, when the Government proposed to extend to members of the Armed forces and of the Merchant Navy the benefit of the laws decriminalizing buggery, it did not meet any opposition from MPs (Parliamentary Debates, 1994: 169-172).

Conclusion

With the disappearance of the offence of buggery, this article necessarily concludes, although the last word is not said when it comes to the broader subject of homophobia or anti-gay discrimination. However, my object was not to write a history of LGBT rights in England and Wales, but to trace the history of buggery/sodomy as a deviance.

The adoption of the 1967 law, or of the 1994 law, did not of course mean that homosexuality was deemed acceptable by the British people, or even by a majority of them.

In 2007, the 90-year-old Leo Abse4 deeply disturbed gay novelist Geraldine Bedell when he observed while she interviewed him: Those of us putting the bill through thought that, by ending criminality, we'd get the gays to integrate. But I was disconcerted and frightened at first because they were coming out and turning themselves into a self-created ghetto. (...) The ghetto suggests they are not at ease. They've got to have a gay world. [START_REF] Bedell | Coming out of the dark ages[END_REF]. G. Bedell, however angry at the former MP's comments, nonetheless noted that, 'terribly flawed (...) mealy-mouthed, half-hearted, embarrassed by itself as it was, the [1967] act made possible the equality that has since been so painstakingly fought for' [START_REF] Bedell | Coming out of the dark ages[END_REF].

One cannot deny that it was a necessary step towards making homosexuals more visible and 'acceptable'. The debates around 'gay marriage' which took place in 2013 are for that matter a reminder of how much the cause of homosexuality has gone, but also the proof of how much remains to be done for 'buggers' to be considered full-fledged members of British society. No more and no less.

I wish to dedicate this article to my mother-in-law, Dr Dominique Badard MD, who has always supported me in my various endeavours.

Except when otherwise stated, all the Biblical quotations included in this paper will be from the New Revised Standard Version, first published in 1989.

It is from this period that we can date the stereotype 'that if a man were married, he could not be a sodomite. Some men at their trials attempted (…) to disprove the charge of sodomy by producing a wife, a father-in-law or a child'(Trumbach, 1977: 15).

The reader will not be surprised to know that, in his memoirs, Leo Abse takes great pains to point out that he was not homosexual.


J-G Simiz

T Hasan

F Staals

B Le-Gratiet

P Gilgenkrantz

A Villaret

F Pasqualini

W T Tel

C Prentice

A Tishchenko

Predictability and impact of product layout induced topology on across-field focus control

Keywords: depth of focus, intrafield, scanner levelling, topography, scanner, product design layout effect, PLS regression analysis

 show that even though the intrafield component stays the same this becomes a larger relative percentage of the overall DOF. Process induced topography along with reduced Process Window can lead to yield limitations and defectivity issues on the wafer. To improve focus margin, a study has been started to determine if some correlations between scanner levelling performance, product layout and topography can be observed. Both topography and levelling intrafield fingerprints show a large systematic component that seems to be product related. In particular, scanner levelling measurement maps present a lot of similarities with the layout of the product. The present paper investigates the possibility to model the level sensor's measured height as a function of layer design densities or perimeter data of the product. As one component of the systematics from the level sensor measurements is process induced topography due to previous deposition, etching and CMP, several layer density parameters were extracted from the GDS's. These were combined through a multiple variable analysis (PLS: Partial Least Square regression) to determine the weighting of each layer and each parameter. Current work shows very promising results using this methodology, with description quality up to 0.8 R² and expected prediction quality up to 0.78 Q². Since product layout drives some intrafield focus component it is also important to be able to assess intrafield focus uniformity from post processing. This has been done through a hyper dense focus map experiment which is presented in this paper.

INTRODUCTION

For low k1 lithography, the scanner control capabilities are very similar to the process window of critical features so that process margin is drastically reduced. In early phase of technology development TWINSCAN NXT:1950i focus budget breakdown shows values that are sometimes larger than the depth of focus of some critical patterns within the chip. In this scope, bringing process to maturity requires actions to retrieve appropriate process margin to secure the yield. Some of these actions will address random dynamic behaviour of the scanner while others will focus on systematic fingerprint and their mitigation.

The depth of focus can be enhanced or controlled using a number of different methods.

 Process window enhancement (Mask3D/Resist3D aware OPC, SMO, etc.)  Feature to feature Best Focus shift mitigation through mask enhancement (mask blank)  Precision and accuracy gains for Best Focus determination using new methods  In-line monitoring  Topography compensation (Design for Manufacturing, other processes)  Levelling control (TWISCN NXT:1970Ci, UV-LS, AGILE2)  Interfield focus control (BaseLiner Focus, Field Width Optimized Levelling, Chuck Deformation Map updating, Imaging Optimizer)  Layout (or hotspot) aware scanner control( Process Window Optimizer) Figure 1: Scanner focus budget breakdown vs. process DOF of the studied reference pattern for the 14FDSOI technology Figure 1 shows the current focus budget breakdown for 14FDSOI versus the depth of focus of the process at Contact layer [ Ref 1]. Intrafield and interfield focus components count together for more than 2/3 of the total budget for both 28 and 14FDSOI technologies. This paper will look into the topological and levelling component of the focus budget.

I -SCANNER LEVELLING FLOW

During the lithographic exposure processes, it is important to ensure that the mask image is correctly focused on the dies in the wafer. For this correct positioning of the wafer, levelling is used in the lithographic tools. Levelling can be referred to as the process of measuring the 'vertical' position of the wafer by a Level Sensor (LS) and using this information to keep the wafer in (best) focus during exposure. Level Sensor is an optical interferometric sensor that measures the surface height using optical triangulation method. From the level sensor measurement, a 'wafer map' containing the surface height of the wafer placed on a wafer stage is created. Figure 2 shows a wafer map. A wafer map can be divided into multiple areas corresponding to dies or fields. After subtracting the global shape from the wafer map, an average height map of the fields are then calculated and shown in figure 2 (right). The latter is representative of the intra field topography measured by the level sensor (LS).

iW iF

Tool

Human

Level sensors used for the wafer map measurements can be subject to process dependency [ Ref 6]. Process dependency is a form of measurement error in which level sensor provide differing results depending on how the measured wafer has previously been processed. For example, a level sensor may provide a particular height measurement for a wafer including a silicon substrate coated with a single layer of resist, and may provide a different height measurement for a wafer including a silicon substrate coated with several layers of resist, even if both wafers' surface are at the same actual height. One error caused by process dependency is referred to as process dependent apparent surface depression, and is understood to be caused by an optical effect known as the Goos-Haenchen shift [ Ref 7]. The Goos-Haenchen shift is a lateral translation of light along a reflecting surface (in this case the resist) during reflection. The shift is dependent upon the material and layer structure of the substrate and is due to the visible light used by the Level Sensor. The newest scanner generation has a level sensor using UV light suffering less from this effect.

𝐿𝑆 = 𝐴𝑐𝑡𝑢𝑎𝑙 𝑡𝑜𝑝𝑜𝑔𝑟𝑎𝑝ℎ𝑦 + 𝑃𝑟𝑜𝑐𝑒𝑠𝑠 𝑑𝑒𝑝𝑒𝑛𝑑𝑒𝑛𝑐𝑦 (1)
As a result of process dependency, a die may not be correctly located in the focal plane of the projection lens. To overcome this, process dependency corrections are applied to the level sensor measured wafer map. ASML's commercial products 'Air Gauge (AG)' and 'AGILE' (Air Gauge Improved Levelling)" is used to do this correction. So, the process dependency corrected intra field height map is more accurate measurement of the intra field topography. The wafer map is used to derive setpoints to actuate the wafer stage to position the dies in focus at the location where the projection takes place. Due to the finite size and rectangular nature of the exposure slit, some of the surface topography cannot be leveled completely. This non-level-able residual is called non-correctable errors (NCE). During a scanned exposure, the non-correctable errors change continuously as the slit is scanned over a particular position on the wafer. In the latter case, the average value of the non-correctable errors over exposure time, defines the average defocus that this position experiences. This average value is termed as the moving average of the non-correctable errors (MA-NCE). Topography changes that are smoother than the slit dimensions can be leveled by adjusting the stage height and tilt angle accordingly. If the topography varies within the slit dimensions, the height changes cannot be leveled effectively. Hence, a large part of the highly variant topography is non correctable and is often present in the MA NCE map. The study that is initiated in this paper consists of a multi-source data analysis. Inputs include scanner log files, GDS's, on-product and bare-wafer focus and topography measurements. They are processed together in a multivariate analysis tooling (Partial Least square regression software) in order to generate a prediction model. Figure 4 above summarizes the different sources of data and their availability in the manufacturing flow.

𝐿𝑆 𝐴𝐺𝑐𝑜𝑟𝑟𝑒𝑐𝑡𝑒𝑑 = 𝐿𝑆 -𝑃𝑟𝑜𝑐𝑒𝑠𝑠 𝐷𝑒𝑝𝑒𝑛𝑑𝑒𝑛𝑐𝑦 𝐶𝑜𝑟𝑟𝑒𝑐𝑡𝑖𝑜𝑛 ≈ 𝐴𝑐𝑡𝑢𝑎𝑙 𝑇𝑜𝑝𝑜𝑔𝑟𝑎𝑝ℎ𝑦 (2)

II -METHODOLOGY / CONCEPT

GDS extracted data

It is possible to generate layer density and perimeter files directly from the product GDS. Density and perimeter data are extracted at both a millimetre and micrometre scale to match the scanner reports, the focus uniformity maps and the topography measurements layouts. Density maps correspond to spatial density of patterns, i.e. to the density of top surface of patterns for a given area. The extracted perimeter data is the density of sidewall of patterns for a given area. Both density and perimeter influence the material distribution, which has some impact on the optical modulation that the level sensor is suffering from (Level Sensor Process Dependency), and process induced topography interfield and

FeedForward FeedBack

Post process intrafield (previous CMP and deposition steps). This data can be used to generate a high density map of wafer topography, which may be used as one of the inputs for Process Window Optimizer.

Scanner reports

These logs are automatically generated for every lot that is processed on the scanner. The levelling part of the report contains information on the wafer topology at a millimetre resolution for every wafer in the lot. Data that can be extracted from these files are the following:

 Optical Level Sensor raw maps  Process Dependency corrected LS maps  Process Dependency maps of the LS  Non-correctable errors (NCE) maps

Focus uniformity mappings

Interfield and intrafield focus maps are measured by CDSEM at 52 locations across field on product exposures. This was done by measuring CD on 7 product wafers with 15nm focus steps between each wafer. A Bossung was then reconstructed at each measurement location and the Bossung top was taken as the best focus position. These exposures were done on a TWINSCAN NXT:1950i with AGILE enabled and Baseliner Focus disabled. An inline alternative to this technique is on-product intrafield and interfield focus measurements using ASML's uDBF targets.

Topography measurements

Intrafield and interfield topography measurements can be performed at micrometre resolution using multiple different offline optical measurement tools [Ref 4]. This gives high frequency topography maps that the scanner cannot measure due to the resolution of the level sensor and AirGauge sensor. With this extra information it will be possible to perform a 1 time verification of the results from the GDS density design analysis and use the data for optimizing scanner focus control. Note that for this paper, these data are not yet fully available and analysed.

Short loop focus monitoring

The Single Shot Focal test was exposed with 13x19 FOCAL marks per field on a bare silicon wafer with the same field layout as the product wafers. This was measured using the scanners alignment sensor to give the interfield scanner focus fingerprint. The test was executed on a TWINSCAN NXT:1950i with AGILE enabled and without Baseliner Focus correction (which is used to correct for the scanner fingerprint in production). This means that the SSF fingerprint contains correctable errors as well as scanner non-correctable errors.

Multivariate analysis

The Partial Least Square (PLS) regression analysis was chosen to investigate the correlations that exist between each of the previous datasets. PLS is a linear multivariate method. GDS is the most predictive file that is available since it exists before any silicon is processed in the waferfab. It will be utilized as the x-input of each of the following analysis. Scanner levelling data, focus maps and topography measurement were used as y-values in the regression tooling. Figure 5 gives a schematic view of the analysis process. Two correlation parameters are calculated by the PLS analysis tooling.

 R² or goodness of fit of the model. It gives the description quality of the model.  Q² or goodness of prediction. It is related to the capability of prediction that can be expected from the model. The best model is the one with the best couple (R², Q²).

Here the PLS is used to answer to the following question:

 Can scanner levelling data and topography be anticipated from design data? How does it relate to focus?

III -GDS DESIGN DENSITY ANALYSIS INTRAFIELD LEVELLING PREDICTABILITY

The scanner levelling measurements are related to the product layout as described in chapter I. If the levelling capabilities of the scanner could be predicted, it would be possible to anticipate the existence and the extent of the uncorrected parts of the chip. Figure 6: Scanner levelling reports vs. Product layout (the yellow box is the part of the chip that is being measured by the levelling system of the scanner). Visually, the shape of the levelling fingerprints seems to be related to the product layout.

The methodology consists of reconstructing what is on the wafer before the exposure step using all the previous layer design data from GDS's. Extractions were performed for every previous patterning layer. These may be single patterning, double patterning or the convolution of two layers that are expected to contribute to topography together. It can also be a perimeter density or a spatial density maps. All underlying layers were investigated but only the ones that showed correlation were kept. As Figure 6 suggests, it seems that a correlation exists between the product layout and the levelling data of the scanner. The optimal underlying GDS density selection for achieving best possible correlation is shown in figure 7 for three 14FDSOI layers.

Due to the fact that it was expected to have more topography, the Contact layer has been specifically studied into more details. GDS extracted densities were used as X parameters for the model building and the 14FDSOI Contact layer scanner reports were set as the output of the modelling. Running the simulation several times, it was possible to select the best combination of GDS data and the layers with the most influence on topography, level sensor performances, levelling non-correctable errors. The same GDS inputs were used in all cases. These results are presented in Figure 8. It shows the reconstructed intrafield levelling fingerprint using the modelled data versus the measurements as well as correlation plots and coefficients (R² and Q²).

Single layers input Density and Perimeter

Layer N-7 X X X Layer N-6 X X X

Convolutions of layers (double patterning, stack effects…) Density and Perimeter

Convolution 1 X X X Convolution 2 X X X Convolution 3 X X X Convolution 4 X X Convolution 5 X

Level Sensor without AGILE

For the level sensor alone, the model has a R² of 0.80 and a Q² of 0.78. This shows that the level sensor measurements have a high correlation to the stack densities. The next step is to check if this reading can be calculated beforehand using another maskset. The level sensor measurement is giving both topography measurements and a certain amount of optical modulation induced reading error. The two parts are explained in sections III.2 and III.3.

Process Dependency

The delta map between the LS and the LS with AGILE measurement contains process dependency of the LS. It is an indirect measurement of the optical modulation of the stack. With the model, about 72% of this reading error can be explained and around 71% could be predicted. As shown in Figure 9, SOI (Silicon on Insulator) parts of the chip measure a lower topography compared to the rest of the field which Once again, the absence of trilayer planarization effects causes some error. Other processes such as CMP or doping could be added to the model in order to increase the correlation coefficients since these layers create different stacks that have different effects on the optical LS and may have an influence topography build-up.

Level Sensor Process Dependency corrected

Using the AGILE sensor, it is possible to extract the wafer topography without the process dependency error that may be present in the optical LS measurements.

The model shows a 0.52R² correlation to product layout and a prediction of around 50% can be expected applying the model to GDS extracted data. The correlation is lower than for the LS alone but this was expected since the material distribution induced optical modulation is not taken into account. The model also only considers the patterned material that is present on the wafer and the planarizing effects of the litho stack (trilayer) were not added to the modelling parameters. As expected, it is the previous layer (named Trench) that has the largest influence on the wafer topography at the Contact layer.

Levelling Non-Correctable Errors

Non-correctable errors do not show a strong correlation to the GDS density model (R² = 0.23, Q² = 0.20). This is expected since the non-correctable errors include the scanner levelling model (in which the exposure slit is fitted through the data) and the GDS design does not.

As a conclusion to part III, this model has been built on a specific maskset and has yet to be checked with another dataset. The model will be applied on the GDS densities of the new product and compared with real-life measurements (FEM, Levelling reports, topography) on silicon wafers.

IV -7 WAFER FEM ANALYSIS

In order to qualify on-product total focus uniformity performance, 7 product wafers were exposed with focus offsets in a range of +/-45 nm around best focus. Per full field 52 identical product features were measured by CD-SEM. For each of the almost 5000 points on the wafer the local defocus is fitted, as shown in Figure 10. A plot of the measured CD values as a function of focus setpoint plus local defocus shows the fit quality as the 'bandwidth' of points around the fitted Bossung shape; see Figure 11. The remaining bandwidth is the result of inevitable scanner wafer-to-wafer variation and SEM noise. Figure 12 shows the average field defocus map. All fields not too far to the edge are used for averaging. Levelling MAz residual correction is applied.

In-die on-product focus measurement and control could be used to correct for the linear wedge (tilt over Y) component. For correction of the average X curvature, lens tuning is needed. Locally (between neighbouring points) no large focus offsets are seen, which could be because all measured points are in sub-scribes, where similar topography is expected.

Figure 12: Measured intra field defocus map with and without levelling MA correction; the latter is also split into a low order shape and a spatially high frequent part (to be compared to topography measurements); the estimated accuracy per point is around 2 nm 3σ

In Figure 13 we see that the on-product inter field defocus map contains global and more local components. The difference map contains a clear global shape. Spatially intermediate frequencies like field offsets are caught by both FEM and SSF. These frequencies do catch our eye, and that's why the resemblance between FEM and SSF seems so good. Actually around 50% of the on-product defocus variance measured by FEM is caught by the SSF measurement.

Figure 13: About 50% of the inter field focus variance seen by FEM is also seen by Single Shot Focal (SSF) Figure 14: A correlation plot between FEM and SSF shows there is a shape difference ('cloud width'), but not scaling error ('cloud on red 1:1 line')

CONCLUSION

Reticle design GDS maps show high (~0.7 R 2 ) correlation to, predominantly, level sensor raw data and level sensor process dependency. The next step would be to verify this correlation on another mask set. If correlation is seen this could be used to feedforward focus and levelling optimization, improve FEM strategies and die layout optimization. To lesser extent a correlation (~0.5 R 2 ) is seen to wafer topography measured by the scanner level sensor. Further work is ongoing to improve the correlation by measuring micrometre scale topography maps using offline optical tooling. This correlation, also, needs to be verified on another mask set. A strong visual correlation is seen between SSF and onproduct focus fingerprints and about 50% of the variance seen by 7-wafer FEM are also seen by Single Shot Focal (SSF). This indicates that SSF can be used to give a good representation of interfield focus uniformity seen at wafer level. The intrafield on-product focus is dominated by a lower order fingerprint. This can be further corrected by the scanner using wafer tilts. The higher order topography effects are not dominant in this measurement because of the choice of measurement features. Further work can be done by measuring features within the product and the sub-scribes together. This paper has shown correlations between level sensor and reticle design GDS. The next step will be to investigate correlation between on-product focus and topography measurements, and close the circle by confirming the correlation with reticle design GDS maps. The layout dependent local topography investigation in this paper is also linked to focus induced defectivity. The defect detection and control of this is covered in the paper and talk: A new paradigm for inline detection and control of patterning defects [START_REF] Hunsche | A new paradigm for inline detection and control of patterning defects[END_REF].

Figure 2 :

 2 Figure 2: (Left) Level sensor measured wafer surface height map and (Right) average height map of a field (die) of the wafer.

Figure 3 :

 3 Figure 3: (Left) Process dependency correction, (Middle) process dependency corrected intra field topography map and (Right) intra field levelling MA NCE

Figure 4 :

 4 Figure 4: Different data sources and their use in the focus correlation study (GDS: Design layout, Short loop focus monitoring: Single Shot Focal test, On-product focus: Focus Uniformity Map "Bossung top best focus")

Figure 5 :

 5 Figure 5: Schematic view of the process through PLS regression analysis

Figure 7 :

 7 Figure 7: Underlying layers GDS densities used for correlating Trench, Contact and Metal 1 layers

Figure 8 :

 8 Figure 8: Measured and predicted levelling fingerprints; Correlation plots; description correlation coefficient R² and expected prediction capabilities Q² of the model for intrafield levelling data at Contact layer

  SOI, i.e. Bulk, zones. This can be explained simply by the presence of a reflective Silica layer in the SOI part. This layer explains about 50% of the reading errors.

Figure 9 :

 9 Figure 9: SOI/Bulk intrafield layer density (purple is SOI and blue and green are Bulk substrates, at the left) vs. scanner measured process dependency (middle) and correlation plot between the two (right).

Figure 10 :

 10 Figure 10: Defocus map obtained from multi wafer FEM; the estimated accuracy per point is around 3 nm 3s

Prediction Process Post process Design Exposure Monitoring Integration Process Flow On-product focus GDS Levelling Topography All effects Product layout Tool on process Integration & Product layout Correlations ? Focus marginalities: detection & anticipation Levelling Focus monitor -ing On- product focus maps Topo- graphy GDS Scanner Short Loop Focus Monitoring


J-G Simiz

T Hasan

F Staals

B Le-Gratiet

W T Tel

C Prentice

A Tishchenko

Product layout induced topography effects on intrafield levelling

Keywords: depth of focus, intrafield, scanner levelling, topography, GDS, product design layout effect, PLS regression analysis, optical lithography

. This model, built using a multiple variable analysis (PLS: Partial Least Square regression) and GDS densities at different layers showed prediction capabilities of the scanner topography readings up to 0.78 Q² (the equivalent of R² for expected prediction). Using this model, care areas can be defined as parts of the field that cannot be seen nor corrected by the scanner, which can lead to local DOF shrinkage and printing issues. This paper will investigate the link between the care areas and the intrafield focus that can be seen at the wafer level, using offline topography measurements as a reference. Some improvements made on the model are also presented.

INTRODUCTION

For 193 nm immersion lithography focus control is limited by the topography measurement accuracy combined with the scanner correction capability. For the critical features on the layer investigated, the depth of focus is of the same order as the scanner correction capability. This is, in part, driven by high frequency topography effects that cannot be handled fully by the scanner's wafer levelling & focussing systems. Product layout induced topography is an important factor that combined with tight focus control and low DOF values can lead to local yield loss.

In this paper, topography correlation to on-product focus was investigated with the ultimate goal of linking GDS to topography and focus. A new way of using topography data and product layout knowledge is, also, presented by using this information to determine optimized weighting factors during scanner levelling. This work was done on the Contact layer on the 14FDSOI development shuttle.

I -METHODOLOGY / CONCEPT

In a previous paper [START_REF] Simiz | Predictability and impact of product layout induced topology on across-field focus control[END_REF], the possibility of modelling scanner levelling using design densities was investigated. This could be used to test and optimize the intrafield levelling friendliness before any silicon is exposed on the tool. This multi-source data analysis uses scanner log files, GDS's, on-product and bare-wafer focus. They are processed together in a multivariate analysis tooling (Partial Least square regression software) in order to generate the model.

II -BEST FOCUS vs. TOPOGRAPHY ANALYSIS

Local topography effect will affect on-product focus on the wafer. In order to correct for these height variations, the scanner performs a levelling optimization. This involves successively measuring the topography on the wafer and then mechanically correcting for it, by moving the stage during the exposure, to keep the wafer within focus. However, this system cannot correct for high frequency topography variations. And the areas where the topography changes are extreme can lead to defocus. In the case of the 14FDSOI development shuttle, several care areas were defined using data extracted from offline topography measurements. Most of these areas are not expected to be present on a product but are necessary for the development of a technology. The topography measurements were done a Veeco WYKO NT9300 tool in LETI without litho stack [START_REF] Dettoni | High resolution nanotopography characterization at die scale of 28nm FDSOI CMOS front-end CMP processes[END_REF]. The measurements allow a mapping of one field with pixels of a few µm². Figure 3 shows the mapping obtained for one field as well as some areas were due to high spatial frequency topography locally some high defocus is expected. The slope of the correlation curve is not 1 but this can be explained by the fact the reference topography measurements were done without any litho stack and that the tri-layer smooths the topography. Mask CD effects were not taken into account here and that may explain the shift of some point from the curve.

In order to test if this can also be seen on the product, some extra measurements were done within the logic, where the topography variations are much smaller. The same structure was measured in two parts of a logic block showing about 9nm height difference. The best focus shift between the different locations was about 11nm. In both cases, a higher topography leads to a negative best focus shift which corresponds to how the focus is referenced in the scanner where a positive focus offset moves the imaging plane (wafer stage) away from the lens.

III -PRODUCT LAYOUT AWARE LEVELLING OPTIMIZATION

Dense topography information can be used to identify imaging critical locations that are most at risk of causing topography driven focus induced yield loss. Figure 6 shows an example of this process, where weights are specified for different locations in the field. Extra weight is given for the areas that contain most focus critical features. This is done by optimizing the slit z-offset and Ry rotation at each scan position. Figure 7 shows how the slit of the weighted fit is closer to the measured height of the features within the critical locations, with respect to standard levelling. This method of optimizing levelling is a trade-off between improving performance in the critical areas and compromising on the performance outside the critical areas. This is visualized in figure 9. Within the critical area the amount of points with a levelling MA error <15nm increases from 90% of points to 95% of points. However, in the non-critical area the amount of points with a levelling MA error <15nm reduces from 95% to 93%. Using the topography information it is possible to visualize the impact applying weight factors before applying them on the scanner.

Figure 9: Levelling MA error points in spec comparison of standard levelling with respect to weighted levelling for critical and non-critical locations

CONCLUSION

Topography measurements have been correlated to on-product focus showing that a difference in height can cause focus excursions. Using full field topography measurements, it was possible to determine weight factors for different areas of the field. These weight factors were used to calculate an optimized levelling fit and ultimately correct what matters. This resulted in improved focus performance in critical areas. This method of optimization would be especially useful for development shuttles due to the fact that the process is still being optimized and that some non-critical test chips are present on the reticle.

Figure 1 :

 1 Figure 1: Different data sources and their use in the focus correlation study (GDS: Design layout, Short loop focus monitoring:Single Shot Focal test, On-product focus: Focus Uniformity Map "Bossung top best focus")[START_REF] Simiz | Predictability and impact of product layout induced topology on across-field focus control[END_REF]

Figure 2 :

 2 Figure 2: Inputs summary and availability

Figure 3 :

 3 Figure 3: Wyko measurements of one field of 14FDSOI chip at Contact layer without Litho stack. Zooming is done on some defocus care areas defined for the 14FDSOI Contact layer

Figure 4 :

 4 Figure 4: (a) Pattern measured -(b) Position of the measurement points on the area -(c) Best focus vs. topography correlation for care area 1.

Figure 5 :

 5 Figure 5: (a) Logic chip topography mapping -(b) Position of the measurement points on the area -(c) Best focus vs. topography correlation for logic area.

Figure 6 :

 6 Figure 6: Intra-field topography measurements (left) and location of selected weight factors for optimization example (right)

Figure 7 :

 7 Figure 7: An example of the weighted fit versus standard levelling slit position at 1 scan location

Figure 8 :

 8 Figure 8: Levelling MA non-correctable error with regular levelling (left) and weighted levelling (right)

FeedForward FeedBack Post process Prediction Process Post process Design Exposure Monitoring Integration Process Flow On-product focus GDS Levelling Topography All effects Product layout Tool on process Integration & Product layout Correlations ? Focus marginalities: detection & anticipation

	Short Loop
	Focus Monitoring
	Scanner
	Focus	GDS	Topo-graphy
	monitor			On-
	-ing	Levelling	product focus maps


J-W Gemmink

A Tishchenko

Y Jourlin

J-G Simiz

T Hasan

F Staals

B Le-Gratiet

W T Tel

C Prentice

Verification and application of multi-source focus quantification

Keywords: High resolution topography (Left: Measured; Right: Simulated) -Colour scale is in nm Depth of focus, intrafield, scanner leveling, topography, scanner, product design layout effect, PLS regression analysis

INTRODUCTION

The concept of the multi-source focus correlation method was presented in 2015 [START_REF] Simiz | Predictability and impact of product layout induced topology on across-field focus control[END_REF][START_REF] Simiz | Product layout induced topography effects on intrafieldleveling[END_REF]. A more accurate understanding of real on-product focus can be obtained by gathering information from different sectors: design, scanner short loop monitoring, scanner leveling, on-product focus and topography. In reference [START_REF] Simiz | Predictability and impact of product layout induced topology on across-field focus control[END_REF], the link between scanner monitoring and on-product focus was established as well as the correlation between design and the scanner level sensor measured intra fieldnon-correctable errors after leveling. In [START_REF] Simiz | Product layout induced topography effects on intrafieldleveling[END_REF], the on-product focus to topography correlation has been studied and the concept of smart leveling was proposed. This work will investigate the design to topography and design to focus correlation. It has been shown that chip topography can be predicted from reticle density and perimeter density data, including experimental proof. To visualize the potential applications different pixel sizes will be used to perform the correlation in-line with (i) minimum resolution, (ii) correlation length of Chemical Mechanical Polishing (CMP) effects and (iii) scanner level sensor spot size. Potential applications of the topography determination will be evaluated, including optimizing scanner leveling by ignoring non-critical parts of the field.

I -INTRAFIELD FOCUS CONTROL

Best focus variation, coupled with reduced depth of focus, is a major contribution to tight process margins for the 28nm and 14nm logic nodes.For both intra wafer and intra field, process and tool fingerprints are creating local shifts from the best focus, causing printing issues leading to defectivity and yield losses.

Major contributors to interfield focus arescanner fingerprints [START_REF] Simiz | Predictability and impact of product layout induced topology on across-field focus control[END_REF], edge effects [START_REF] Le-Gratiet | An evaluation of edge roll off on 28nm FDSOI (fully depleted silicon on insulator) product[END_REF] and leveling non-correctable of the wafer topography [2, 3, 4,and 5].

Considering theintrafield, it is possible to distinguish two families of effects: the imaging effects and the spatial effects, summarized in Fig. 2. From imaging, the best focus shift is caused by wave front deformations induced in a large part by the light passing through the mask so that the image focal plane of each pattern shift apart from each other making it more difficult to print [START_REF] El Abidine | Mask Blank Optimization through rigorous EMF approach from IDM perspective, for 28 nm node and beyond[END_REF]. Best focus is pattern shape dependant. Spatial effects are characterized by a best focus change across field for the same pattern. The mask is not perfect and the same pattern may not have been printed exactly the same way for each of its occurrences. Imaging effects (i.e. image plane deviation measured by FOCAL) can also effect the BF of a single pattern differently across the field [START_REF] Brunner | Impact of lens aberrations on optical lithography[END_REF]. The wafer topography also has an intrafield component showing non-correctable systematics that are tightly linked to the on-product focus [START_REF] Simiz | Product layout induced topography effects on intrafieldleveling[END_REF]. For a given pattern, best focus depends on the intrafield position of each of its occurrences across field. This part of the intrafield focus budget is the one studied in this paper.

II -THE TOPOGRAPHY INDUCED FOCUS NON-UNIFORMITY

As written above, focus is a function of the pattern and its position. It has been shown in reference [START_REF] Simiz | Product layout induced topography effects on intrafieldleveling[END_REF] that focus distribution is mainly topography driven. Fig. 3 shows two things that can be derived from offline reference topography measurement done on a Veeco WYKO NT9300 tool in LETI without the photolithography process stack [START_REF] Dettoni | High resolution nanotopography characterization at die scale of 28nm FDSOI CMOS front-end CMP processes[END_REF]. The height distribution in field (in green) which is mainly spread between 45 and 75nm but presents some excursions of a few tens of nanometres in atypical areas of the chip and the best focus to topography correlation (in blue) which shows a slope close to 1with an excellent correlation factor. A correlation was seen with the level sensor measured intrafield height map (with and without process dependency error corrected) andintra fieldleveling non-correctable errors. Process dependency is a measurement error due to optical stack effects on the older generationlevelsensor, and it is corrected by the AGILE Sensor. The PLS gives the Q² parameter thatindicates how well a variable can be predicted. Level sensor measured intrafield height map and process dependency corrected map showed respectively 0.78Q² and 0.50Q² expected prediction capabilities.

As one aspect ofleveling is a measurement of the topography of the wafer, it is expected that the PLS coefficients 𝑤 𝑗 can be calculated for reference topography as well:

𝑇𝑜𝑝𝑜𝑔𝑟𝑎𝑝ℎ𝑦 𝑊𝑦𝑘𝑜 𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑑 = (𝑤 𝑗 𝐿𝐴𝑌𝐸𝑅_𝐷𝐸𝑁𝑆𝐼𝑇𝑌 𝑗 ) 𝑗 (2)
Intrafield wafer topography is layout driven. Each part of the chip has a specific design linked to its electrical behaviour (logic cells, memory cells, electrical protection, analogic devices, antennas, etc.) which all have their specific design, dimensions and densities. This variety of different devices can create some local topography induced by patterning and polishing steps.Some tiling is done within the chip to homogenize the density and mitigate those effects but it is not always sufficient. As a consequence, the assembly of a chip within a mask field will lead to a specific topological map.

III -MODELLING TOPOGRAPHY WITH GDS DENSITIES

In this paper, the same methodology as the one described above (in part II) and in the SPIE 2015 paper [START_REF] Simiz | Predictability and impact of product layout induced topology on across-field focus control[END_REF] was applied in order to link the GDS to offline topography measurements. These were done on a VeecoWYKO NT9300 tool in LETI without the photolithography process stack [START_REF] Dettoni | High resolution nanotopography characterization at die scale of 28nm FDSOI CMOS front-end CMP processes[END_REF]. A topography model was constructed using apartial least square linear prediction method by combining GDS densities of the underlying layers.Differentmodels were investigated with different pixel sizes to be sensitive to several effects at multiple ranges.

• Short range effects These effects are the ones thatbetter match the capabilities of the Wyko in terms of spatial resolution. They are related to the direct impact of the design on a localized area.

• Long range effects These effects are mainly process induced (deposition uniformities, CMP dishing, loading effects on etch). Some layout effects such as assembly can be responsible for these by creating areas with different designs and densities.

The PLS coefficientsfor each effect were calculated on a small part of the chip for 14FDSOI Contact layer and then testedon a larger area of the field containing about 800 times more data points for validation. This first graph (see Fig. 5) shows the comparison between the expected performance of the model regarding prediction capabilities Q² and the actual performances by the model R² test , for each of the pixel sizes chosen in this study. The optimum model comes with pixel sizes of 40 to 50µm.Theseshowed the best description and expected prediction capabilities of the topographyand the best results after testing on a larger area. In order to elect the optimal pixel size, it is necessary to look at other data given by the PLS model such as the predicted range of the values. A model can have a high correlation coefficient and still gives values that are not representative of measured topography. The closer the slope between measurement data and predicted data is to 1, the better the model is representative of the wafer actual topography.

The following figure, Fig. 6, gives the detailed results for the some of the best test cases. It compares model build-up, expected performances vs. actual performance (correlation coefficient, slope) and mappings of the data.

The slope of the correlation plot between measurement and model data is never exactly equal to 1. This can be explained by the fact that the models used in this work are empirical and based on theextraction of the density data at a given pixel size and also because the measurement data is also averaged to the same resolution to perform the validation of the results. This averaging, especially with large pixels, will induce a reduction of the total range of heights since highest peaks and lowest valleys are smoothened by the data averaging.

This second dataset shows best performing models to be the 40 and 45µm-pixel ones. The model parameters were calculated without full use of the PLS analysis capabilities. This statistical method gives not only model coefficients and prediction capabilities forecast but also a ranking of the importance of each input by evaluating the VIP (Variable Importance in the Projection) of every component [START_REF] Eriksson | Multi and Mega-Variate Data Analysis[END_REF][START_REF] Wold | 3D-QSAR in Drug design, Theory, Methods, and Applications[END_REF]. This VIP gives the components that are actually discriminating in the regressionin this case, the layers that will have a substantial influence in the topography built-up.

This prediction enables the definition of care areas i.e. areas in which critical patterns in terms of imaging, determined by full chip LMC [START_REF] Hunsche | A new paradigm for inline detection and control of patterning defects[END_REF][START_REF] Fanton | Process Window Optimizer for pattern based defect prediction on 28nm Metal Layer[END_REF], and high local topography variation might be found, causing high probability of patterning failure.The capability of defining smart care areas is key for process improvement efficiency.Using the VIP information as an input to the design may allow an improvement of the dummification process and chip layout.Simulated topography can also serve as an input for Process Window Optimizer (PWO) but for control plan optimisation by giving care areas to be monitored. It can also be used as an input for a smart scanner leveling capable of correcting preferentially the topography where it matters.This last solution was investigated in this work and is discussed in the next section of the paper.

IV -FOCUS CONTROL THROUGH SCANNER LEVELING OPTIMIZATION

High-resolutionintrafield topography modelled from the design layout density can be a useful source to tailor scanner leveling for optimizing the focus control within the care area. Scanner leveling can be referred to as the process of correctly positioning the fields of the wafer in (best) focus during exposure.Levelingis limited by, among others, the physical shape of the exposure slit of the scanner. In the following paragraphs, we proposed a scheme for care and ignored area driven leveling. Levelinguses scanner level sensor measured surface height information of the chucked wafer, known by 'wafer map', as input. Figure 7 shows a wafer mapwhichcontains multiple areas corresponding to dies or fieldsA full wafer map can be decomposed into two parts; a long range height profile (inter field) that represents the global shape of the wafer and a local (intrafield) height map that is sufficiently repetitive among fields. These two parts can be processed separately by the leveling algorithm, and then algebracally summed to generate the wafer stage positioning setpoints. Additionally, in our previous communication [START_REF] Simiz | Predictability and impact of product layout induced topology on across-field focus control[END_REF], and sections above, we showed that layout design density modelled topography map reasonably correlate with the level sensor measured local intrafield topography or even high-resolution topography measurement with external tools(e.g. Wyko). Consequently, we can substitute this local intra-field height map with the intra-field modeled topography map. Thanks to its high resolution, it will allow us to define accurately the care and ignore area and thus,to enable their preferential treatment in leveling for better focus control.

In figure 8 (left), some areas within the field are highlighted as care (green), ignore (red), and non-specific (orange) area. These areas areidentified based on the process and design knowledge. However, they can also be identified using other computational lithography products. These defined areas are then mapped into the dense intra-field topography in figure 8 (right). Although we can, in principle, use the modelled intrafield topography, we used the external tool measured topography in this example since modelled topography was not available for the full field. A modified (weighted) scanner leveling algorithm was applied offline to this care-and-ignore area mapped intrafield topography. The non-correctable errors at care area after such leveling are reduced leading to improved focus control. Figure 9 compares (delta) the non-correctable error after the dense topography-assisted, care-and-ignore area driven leveling and the standard (all area are equally weighted) leveling. Positive (red) values show improvement. Figure 9 shows care area improved (upto 9nm in some area) with a tradeoff deterioration at the non-specific or ignore area. Figure 9 (right) shows the cumulative distribution of the non-correctable error samples (points) within the field. Within the care area, 3% more samples are now in the spec (15nm) without pushing any locations within the non-specific or ignore area beyond their spec (25nm). Spec for the non-specific/ignorearea is larger than that of the care area. Note, although the choice of the spec values in this example isarbitrary, they are representative for this process. Further optimization can lead to larger improvement in the care area. Note, this proposed technique is not currently available in the scanner. Therefore, we also discussed a possibility to achieve similar performance in the scanner by a feed-forward correction mechanismexploitingthe sub-recipe interface of the scanner. The delta between the care-and-ignore area optimized leveling and the standard one can be applied to the scanner through the feed-forward interface after converting them into a correction format suitable for that interface. This dense topography assisted care-and-ignore driven leveling can be used to find optimal configurations of scanner leveling improving edge die focus [START_REF] Hasan | Holistic, model-based optimization of edge leveling as an enabler for lithographic focus control -Application to a memory use case[END_REF].

CONCLUSION

Topography measurements have been modelled and predicted with the Partial Least Square methodology with a high predictability capability up to 0.8Q². The topography being a cause of focus intrafield excursions, this method allows the definition of care areas where focus margin will be reduced and defectivity may occur at a higher rate. The use of this data as an input for PWO [START_REF] Hunsche | A new paradigm for inline detection and control of patterning defects[END_REF][START_REF] Fanton | Process Window Optimizer for pattern based defect prediction on 28nm Metal Layer[END_REF] will allow an improved defect prediction. The care areas were also used as an input for a smart leveling methodology where the scanner will correct preferentially the critical areas of the chip. Some other applications of the topography data, modelled or measured, would be tiling optimization and securing the reticle assembly.

Figure 2 :

 2 Figure 2: Brief overview of some of the sources of intrafied focus variability

Figure 3 :

 3 Figure 3: Correlation plot showing Bossung tops determined on-product focus vs. Local topography measured by a Veeco WYKO NT9300 tool and height distribution through chip.

Fig. 4

 4 illustrates this fact by showing an example of 14FDSOI (Fully depleted silicon on insulator 14nm technology node) test chip shuttle and the topography measured at the Contact layer.

Figure 4 :

 4 Figure 4: Product layout of the 14FDSOI test chip shuttle and topography measured on a complete field before Contact exposure

Figure 5 :

 5 Figure 5: Graph comparing Q² and R² test values for several pixel sizes

Figure 6 :

 6 Figure 6: Performances of a few models for topography prediction  Model build-up (~3mm²): R² shows the data description capability and Q² the data expected prediction capability of the model  Model application on a larger area (20mm²) is compared to high frequency measurement data

Figure 7 :

 7 Figure 7: Wafer height map decomposed into long range height profile and local intrafield topography.

Figure 8 :

 8 Figure 8: Care (green), ignore(red), non-specific (orange) area are highlighted on the design layout (left). Care and ignore area are then mapped into the intrafield topography (right). In right figure, height values of the ignore areas are removed (white) and care area are given higher emphasis and marked with rectangles.

Figure 9 :

 9 Figure 9: (left) Delta map of the non-correctable errors from care-and-ignore area driven leveling and the standard leveling. A positive value means improvement. The right figure shows cumulative distribution of the leveling non-correctable error.

Figure 10 :

 10 Figure 10: A schematic representation showing the possibility to enable care-and-ignore area based optimization through scanner's subrecipe interface feed forward subrecipe correction interface.


P Fanton

R La Greca

V Jain

C Prentice

J-G Simiz

S Hunsche

B Le-Gratiet

L Depre

Process Window Optimizer

Introduction

Traditional computational lithography applications are not directed towards predicting on-wafer performance. Process of record solutions (e-beam and SEM) to find patterning defect locations are not sensitive enough or have low throughput and need improvements in order to be used as systematic defect detection tools. Process Window Optimizer extends the holistic lithography framework towards prediction, detection and verification of on-product patterning defects. The location of these process window limiting "hotspots" are determined using lithography simulations combined with on-product focus measurements and in-line scanner metrology.

Summary

This evaluation has demonstrated the capability of using Process Window Optimizer (PWO) from full chip layout to on-product defect prediction. A computational full chip simulation was combined with on product focus measurements and inline scanner metrology data to predict defect locations. Additionally, user selected hotspots were combined with the hybrid dense focus map and the prediction efficiency of PWO was investigated.

Lithography simulations associated with inline data like dose and focus map is a powerful way to predict patterning issues. PWO demonstrates this and opens a new area for patterning control. PWO will help us to improve our inline defect detection. It will accurately predict defect locations. These locations will be used in our defect detection tool to improve the signal to noise ratio. It will also enable a new way to adjust process within wafer and within field for a given layout. PWO can predict the defect count for several process adjustments and thus help us to find the best within wafer/within field process condition dose/focus to minimize patterning defects.

User provided hotspot flow

The user provided hotspot flow starts with the user selecting some known hotspots. These can be sourced from simulation and/or from measurement or empirical methods. For each of the studied hotspots, we measured FEM data using CD-SEM image collection, combined with Hitachi contour extraction and applied ASML CD verification tool to collect data through FEM. The focus offsets from the hybrid dense focus map at each position in the wafer are converted to predicted CD values, per hotspot, using the FEM curve. A hotspot is considered a defect if it falls below the CD defect threshold.

In order to generate a significant sample of defects for evaluation purposes this study used an off-focus wafers. A check was done to verify if at the predicted defect locations the SEM revealed a defect or whether no defect was present. On average the -75nm set focus wafer had a higher prediction accuracy since this wafer is exposed more out of focus. This is also dependent of the best focus of each hotspot

Computational full chip defect prediction flow

The first step in the computational defect prediction flow is to find the patterns across the full chip that will limit the process window the most. Next, CD through focus for each hotspot is simulated. From which we generate a ranked hotspot list together with two maps that characterize the product reticle in terms of best focus and depth of focus. The depth of focus of this product is most critical at the top right and center right of the field. These locations also have a higher best focus offset than the rest of the field. Optimizing scanner focus and levelling control to have a positive defocus at these locations would be a way to reduce defectivity.

The next step in the flow is to combine the simulated CD through focus information with the effective focus values at hotspots locations in the hybrid dense focus map (HDFM). Wherever the defect CD for the corresponding wafer location focus fall below a given threshold, the hotspot will be flagged as a predicted defect.

Depth of

1

  STMicroelectronics, 850 rue Jean Monnet, F 38926 Crolles Cedex, France *Contact: pierre.fanton@st.com 2 LaHC CNRS-UMR 5516, 18 Rue Professeur Benoît Lauras, F-42000 Saint-Étienne, France 3 ASML US, 399 W Trimble Rd, Jan Jose, CA 95131, United States 4 ASML SARL, 459 chemin des Fontaines, F-38190 Bernin, France

Focus

  induced defects Holistic lithography concept for patterning defect prediction and layout aware scanner control Simplified defect prediction flow Full chip simulated depth of focus and best focus per location (white indicates a non-