Valérie Malavergne
email: valerie.malavergne@u-pem.fr

Hélène Bureau

Caroline Raepsaet

Fabrice Gaillard

Mélissa Poncet

Suzy Surble

David Sifré

Svyatoslav Shcheka

Chloé Fourdrin

Damien Deldicque

Val Érie Malavergne

H Él Ène Bureau

Élissa Poncet

Suzy Surbl

David Sifr

Chlo

Damien Fourdrin

Hicham Deldicque

Khodja

Suzy Surblé

Hicham Khodja

Experimental constraints on the fate of H and C during planetary core-mantle differentiation. Implications for the Earth

A C C E P T E D M

A N U S C R I P T slightly siderophile and slightly decreases the highly siderophile nature of C. This implies that the capacity of a growing core to retain significant amounts of H or C is mainly controlled by the size of the planet: small planetary bodies may retain C in their cores while H may have rather been lost in space; larger bodies may store both H and C in their cores.

During the Earth's differentiation, both C and H might be sequestrated in the core. However, the H content of the core would remain one or two orders of magnitude lower than that of C since the (H/C) core ratio might range between 0.04 and 0.27.

Keywords: Planetary differentiation, hydrogen, carbon, core segregation, primitive Earth.

A C C E P T E D M

A N U S C R I P T 1. Introduction.

Telluric planets formed by accretion of chondritic-like materials. These chondritic materials might contain significant amounts of Hydrogen (H) and Carbon (C) as observed, for example, in carboneous chondrites (e.g. [START_REF] Morbidelli | Building Terrestrial Planets[END_REF][START_REF] Marty | The origins and concentrations of water, carbon,nitrogen and noble gases on Earth[END_REF][START_REF] Yang | Molecular hydrogen in mantle minerals[END_REF][START_REF] Iizuka-Oku | Hydrogenation of iron in the early stage of Earth's evolution[END_REF]. Unfortunately, the exact nature of the terrestrial precursor materials and the redox conditions at early stages of the Earth formation (e.g. [START_REF] Okuchi | Hydrogen partitioning into molten iron at high pressure: implications for Earth's core[END_REF][START_REF] Frost | The Redox State of Earth's Mantle[END_REF][START_REF] Hirschmann | Solubility of molecular hydrogen in silicate melts and consequences for volatile evolution of terrestrial planets[END_REF][START_REF] Jacobson | Accretion and differentiation of the terrestrial planets with implications for the compositions of early-formed Solar System bodies and accretion of water[END_REF] remain uncertain. In case of incomplete devolatilization of the Earth during its accretion (e.g. [START_REF] Albarede | Asteroidal impacts and the origin of terrestrial and lunar volatiles[END_REF][START_REF] Yang | Molecular hydrogen in mantle minerals[END_REF][START_REF] Iizuka-Oku | Hydrogenation of iron in the early stage of Earth's evolution[END_REF][START_REF] Tikoo | The fate of waterwithin Earth and super-Earths and implications for plate tectonics[END_REF], the mantle (e.g. [START_REF] Frost | The Redox State of Earth's Mantle[END_REF][START_REF] Yang | Molecular hydrogen in mantle minerals[END_REF] and possibly the core (e.g. [START_REF] Okuchi | Hydrogen partitioning into molten iron at high pressure: implications for Earth's core[END_REF][START_REF] Ohtani | Iron-water reaction at high pressure and temperature, and hydrogen transport into the core[END_REF][START_REF] Ohtani | Hydrous minerals and the Storage of water in the deep mantle[END_REF][START_REF] Iizuka-Oku | Hydrogenation of iron in the early stage of Earth's evolution[END_REF] likely trapped H and C. [START_REF] Defouiloy | Ion Microprobe Determination of Concentration and Isotopic ratio in Extraterrestrial Metallic Alloys[END_REF] have found around 100 -200 wt ppb of H in Fe-Ni alloys of iron meteorites, implying that H was present during the formation of their parental body and could potentially enter the core. Results of [START_REF] Hallis | Evidence for primordial water in Earth's deep mantle[END_REF], based on H isotope systematics of Baffin Island and Iceland lavas, showed that the water from the Earth's mantle might have a protosolar nebula origin. In parallel, [START_REF] Marty | Origins of volatile elements (H, C, N, noble gases) on Earth and Mars in light of recent results from the ROSETTA cometary mission[END_REF] showed that volatiles of the Earth might originate from both the nebular gas and accreting materials. Taken together, all these results suggest that H was not entirely lost during the accretion of the Earth and suggest that a significant amount of H remained stored deep in Earth's interior. The Earth's core is mainly composed of Fe-Ni alloy, with iron being the major constituent.

The addition of ~10% of light elements (S, Si, O, C and H) is required to account for the density deficit observed between pure Fe and core models (e.g [START_REF] Poirier | Light elements in the Earth's outer core : a critical review[END_REF][START_REF] Chabot | The effect of oxygen as a light element in metallic liquids on partitioning behavior[END_REF]. It has been shown that H or C can easily be combined with iron at high pressures (HP) and high temperatures (HT) and could explain such a density deficit (e.g. Fukai, 1984 ;[START_REF] Badding | High-pressure chemistry of hydrogen in metals: in situ study of iron hydride[END_REF][START_REF] Yagi | Iron hydride formed by the reaction of iron, silicate, and water: implications for the light element of the Earth's core[END_REF]Wood et al, 1996 ;[START_REF] Okuchi | Hydrogen partitioning into molten iron at high pressure: implications for Earth's core[END_REF] et al, 2004 ;[START_REF] Sakamaki | Melting phase relation of FeHx up to 20 GPa: implication for the temperature of the Earth's core[END_REF][START_REF] Shibazaki | Hydrogen partitioning between iron and ringwoodite: implications for water transport into the Martian core[END_REF][START_REF] Shibazaki | Effect of hydrogen on the melting temperature of FeS at high pressure: implications for the core of Ganymede[END_REF][START_REF] Dasgupta | High pressure melting relations in Fe-C-S systems: Implications for formation, evolution, and structure of metallic cores in planetary bodies[END_REF][START_REF] Dasgupta | The deep carbon cycle and melting in Earth's interior[END_REF][START_REF] Narygina | X-ray diffraction and Mössbauer spectroscopy study of fcc iron hydride FeH at High pressures and implications for the composition of the Earth's core[END_REF][START_REF] Shibazaki | Sound velocity measurements in dhcp-FeH up to 70 GPa with inelastic X-ray scattering: Implications for the composition of the Earth's core[END_REF][START_REF] Shibazaki | High-pressure and high-temperature phase diagram for Fe 0.9 Ni 0.1 -H alloy[END_REF][START_REF] Sakamaki | Constraints on Earth's inner core composition inferred from measurements of the sound velocity of hcp-iron in extrême conditions[END_REF][START_REF] Iizuka-Oku | Hydrogenation of iron in the early stage of Earth's evolution[END_REF][START_REF] Dasgupta | Carbon solution and partitioning between metallic and silicate melts in a shallow magma ocean: implications for the origin and distribution of terrestrial carbon[END_REF][START_REF] Lord | Melting in the Fe-C system to 70 GPa[END_REF][START_REF] Tsuno | Core-mantle fractionation of carbon in Earth and Mars : the effects of sulfur[END_REF] . However, a recent study of [START_REF] A C C E P T E D M A N U S C R I P T Clesi | Low hydrogen contents in the cores of terrestrial planets[END_REF] showed that H is lithophile during core -mantle equilibration and it might be a very minor element in the Earth's core. [START_REF] A C C E P T E D M A N U S C R I P T Clesi | Low hydrogen contents in the cores of terrestrial planets[END_REF] noticed a decrease of the lithophile character of H at HP-HT but these conclusions seemed at odds with [START_REF] Okuchi | Hydrogen partitioning into molten iron at high pressure: implications for Earth's core[END_REF], who observed a clear siderophile behavior for H in a pioneer study. These conflicting observations imply that we do not have a clear picture on whether H would be siderophile or lithophile at the P-T-redox conditions of core formation in a magma ocean.

At the Hadean, the magma ocean might have been extremely reduced (e.g. [START_REF] Javoy | The chemical composition of the Earth: enstatite chondrite models[END_REF][START_REF] Jacobson | Accretion and differentiation of the terrestrial planets with implications for the compositions of early-formed Solar System bodies and accretion of water[END_REF]. Assuming that planetary precursors could be differentiated to some extent and that an equilibrium between the proto-core and primitive ocean magma might occur during the differentiation (e.g. [START_REF] Righter | Terrestrial planet formation[END_REF][START_REF] Tikoo | The fate of waterwithin Earth and super-Earths and implications for plate tectonics[END_REF], a wide range of pressures, temperatures and redox conditions should be considered while studying core formation.

Accordingly, the main goals of this study are: (i) to provide new data on the distribution of H and C between the core and the mantle during planetary differentiation at variable pressures, temperatures and redox conditions relevant to magma oceans prevailing on planetary bodies and the primitive Earth, (ii) to evaluate the C and H contents of the Earth's forming core, (iii) to propose C and H contents for other planetary bodies.

2. Experimental and analytical procedures.

Starting materials

Two different synthetic glasses (Tables 1 and2), a natural brucite Mg(OH) 2 and different synthetic metallic alloys (Fe-Ni and Fe-Ni-Si) (Table 1 and2) were used as starting materials.

A C C E P T E D M A N U S C R I P T

The metallic alloys were synthesized and characterized at the Institute of Chemistry and Materials (ICMPE, Créteil, France). The relative proportions of each material (brucite, synthetic glass, metallic alloy) before HP-HT experiments, as well as the P-T-fO 2 conditions are given in Table 2. In order to avoid the massive formation of H-rich bubbles in the metallic phases of our samples, that was observed in [START_REF] Okuchi | Hydrogen partitioning into molten iron at high pressure: implications for Earth's core[END_REF], we worked at low H contents, and far from the hydride (FeH x ) stability field. FeH x are known to decompose during the quenching of the experimental charges triggering H 2 -bubbles. This process makes the determination of the H content in metal very difficult or impossible. The H-bearing starting compositions (silicate glass + brucite + metal) were loaded in the graphite capsule by adding small metallic chips to the "silicate+brucite" mix and were weighed in order to obtain the appropriate relative proportion.

High-pressure and high-temperature experiments.

The lowest pressure experiments (1 GPa) were performed with a piston-cylinder apparatus (non-end loaded) (ISTO, Orleans, France and NASA/LPI, Houston, USA). Each H-bearing sample was held in a double capsule: the starting materials were contained in a graphite capsule, which was itself loaded in a Pt capsule. This capsule setup was used in previous studies in order to retain as much H as possible within the samples (e.g. [START_REF] Stanley | Solubility of C-O-H volatiles in graphite-saturated martian basalts[END_REF].

For the H-free sample, a single graphite capsule was used. The samples were loaded in conventional high-pressure assemblies consisting of a lead sheet, talc-pyrex pressure cell and graphite furnace. The assembly components, except the graphite and Pt parts, were first dried in an oven at 1000°C for 12 hours to remove impurities and later kept in an oven at 150°C. The samples were first pressurized at room temperature and then heated in the range 1400-1700°C for durations ranging from 2 to 30 min (Table 2). The temperature during the experiment was monitored with a B-type thermocouple contained in an alumina ceramic tube.

The samples were quenched by switching off the electrical power and the quench rate was (2015) and in [START_REF] A C C E P T E D M A N U S C R I P T Malavergne | The formation of nanonuggets of highly siderophile elements in quenched silicate melts at high temperature: before or during the silicate quench?[END_REF]. The highest pressure experiments (5-15 GPa) were performed in Kawaii-type multianvil presses with tungsten carbide cubes as secondary anvils at the Bayerisches Geoinstitut, Bayreuth, Germany. Pressure calibration curves reported in [START_REF] Tronnes | Peridotite melting and mineralmelt partitioning of major and minor elements at 22-24.5 GPa[END_REF] were used. Experiments at 5, 6-10 and 15 GPa were carried out with 25/17, 18/11 and 14/8 assemblies (octahedral edge length/truncation edge length in mm), respectively. The pressure assembly consisted of octahedral Cr-doped MgO pressure medium, ZrO 2 sleeve, LaCrO 3 heater and MgO sleeve containing the sample capsule. Components of the high-pressure assemblies were fired at 1000°C for 1 hour before experiment to remove moisture. The assembled octahedra were dried in a vacuum oven at 130°C overnight before each experiment. In all experiments the temperature was monitored with an axial W 3 Re/W 25 Re thermocouple. The samples were first compressed to the target pressure within 4 hours and then heated at the rate 100°C/min to the target temperature (1600-2200°C) for durations ranging from 2 to 10 min (Table 2). The temperature uncertainty was estimated to be ±100°C (e.g. [START_REF] Agee | Pressure-temperature phase diagram for the Allende meteorite[END_REF] for the highest temperature experiments. The samples were quenched by switching off the electrical power and the quench rate was approximately 500°C/s. The samples were then decompressed over 12 hours. Because of the use of graphite capsules, our samples are saturated by carbon. This high carbon abundance in our systems does not represent the most relevant chemistry for primitive planetary conditions. However, the choice of these graphite containers for our samples remains one of the best technological solutions to protect them from the rest of the assembly without contaminating reactions. All experimental charges (multianvil and piston-cylinder experiments) were mounted in epoxy resin, sectioned, and polished to reveal the samples. The samples were analyzed by all the methods presented below but the ion microprobes. After that, the epoxy resin was removed in

A C C E P T E D M A N U S C R I P T
order to avoid any possible H contamination during the nuclear microprobe analysis. The samples were finally mounted in indium.

Analytical Methods

Scanning Electron Microscope (SEM). A JEOL JSM-5910LV SEM was used for initial evaluation of experiments (at Ecole Normale Supérieure de Paris, France) to determine the homogeneity of phases. SEM investigations were performed at 15 kV accelerating voltage and a working distance of about 8 mm. Qualitative and quantitative chemical analyses were acquired using a Silicon Drift Detector (SDD).

Electron probe microanalyzers (EPMA).

A CAMECA SX-100 equipped with wavelength dispersive X-ray spectrometers (WDS) was used to analyze the samples (at CAMPARIS, Jussieu, Paris, France). The oxygen concentrations in the silicate were calculated based on standard valences for the measured major elements: 4+ for Si and Ti; 3+ for Al and Cr; 2+ for Fe, Mn, Mg, Ca; 1+ for Na and K. EPMA were performed with an accelerating voltage of 15 kV and a beam current of 10 or 40 nA with a spot size ranging from around 1 to 10 m, depending on the analyzed phases. The standards used to analyze the silicates were Fe 2 O 3 , Fe or olivine for Fe, clinopyroxene for Si, Ca and Mg, MnTiO 3 for Mn and Ti, orthoclase for Al and K, NiO for Ni, Cr 2 O 3 for Cr, albite for Na. The standards used to analyze the metals were pure Fe, Ni, Cr, Mn and Pt for Fe, Ni, Cr, Mn, Pt and FeSi alloy for Si. The compositions of all phases in our samples are reported in Tables 3. The uncertainty is defined by the (/√N) where  is the standard deviation of the measurements and N is the number of analyses. The uncertainty is generally less than 3 wt% for major elements and less than 15 wt% for minor elements.

Nuclear microprobe. Ion beam analyses were performed at the nuclear microprobe of Saclay [START_REF] Khodja | The Pierre Süe Laboratory nuclear microprobe as a multi-disciplinary analysis tool[END_REF] in order to obtain the C and H concentrations in metal and silicate. The spectra of the reaction products (X-rays, charged particles) resulting from the interaction of an A C C E P T E D M A N U S C R I P T energetic ion beam with the target allowed the determination of the local elemental composition. The approach used to quantify C and H present in our samples requires two different ion beam conditions and analysis techniques. Hydrogen determination was made by Elastic Recoil Detection Analysis (ERDA) [START_REF] Bureau | Determination of hydrogen content in geological samples using Elastic Recoil Detection Analysis (ERDA)[END_REF][START_REF] Withers | Calibration of infrared spectroscopy by elastic recoil analysis of H in synthetic olivine[END_REF][START_REF] A C C E P T E D M A N U S C R I P T Clesi | Low hydrogen contents in the cores of terrestrial planets[END_REF]. An incident beam of alpha particles was accelerated in order to arrive on the sample (with a size of 12*3 µm 2 ) with a high energy (3 MeV). The beam ejected the hydrogen atoms of the sample. The spectrum of the H atoms ejected was collected in a 17 mSr Si detector shielded with a 15 µm Al foil. Backscattered alpha particles and X-ray spectra were also used to select the regions of analysis and the relevant phases, silicates or metal as shown in Fig. 1.

The H contents are given with an accuracy of about 16wt% for both phases and confirmed by the analysis of well-known silicate glasses from the STR series (Stromboli glasses, [START_REF] Bureau | Determination of hydrogen content in geological samples using Elastic Recoil Detection Analysis (ERDA)[END_REF]. A 1500 keV deuteron microbeam was used to measure the C contents of the metallic and silicate phases thanks to the nuclear reaction 12 C(d,p) 13 C. A 50 μm Mylar filter stopped backscattered deuterons. Protons generated after incident 2 H + impact with sample were detected at 170° using an annular detector with a solid angle of 110 mSr. All measurements were performed by scanning different areas (between 50 × 200 μm 2 to 100 × 400 μm 2 depending on samples) by a 3 × 3 μm 2 beam. The carbon region (between 2.0 and 2.3 MeV), corresponding to the deep carbon (i.e. the carbon without surface contamination), allowed us to determine the real concentration of carbon in metal and silicate phases. As for the ERDA measurements, the elemental X-ray maps allowed the extraction of the ERDA elemental maps, in order to distinguish the metallic and silicate phases. The uncertainty is determined based on the standard deviations of the standard sample measurements. The carbon content in metal is given with an accuracy of 4 to 8wt% and the carbon content in silicate is given with an accuracy of 15 to 17wt%. Concentrations are confirmed by the analysis of Certificate Carbon standards from the British Chemical

A C C E P T E D M

A N U S C R I P T standards for metal analysis (white cast iron 247/5 with 2.93 wt.% C and carbon steel 215/1 with 0.925 wt% C) and from the silicate glass STR9 (154 ppm C, [START_REF] Bureau | Determination of hydrogen content in geological samples using Elastic Recoil Detection Analysis (ERDA)[END_REF].

Elemental maps of the regions of interest, with sizes ranging from 25*25 to 400*400 µm 2 , depending of the method of analysis and the homogeneity of the area have been made. Data analysis was performed using RISMIN [START_REF] Daudin | Development of "position-charge-time" tagged spectrometry for ion beam microanalysis[END_REF] and SIMNRA [START_REF] Mayer | SIMNRA, a simulation program for the analysis of NRA, RBS and ERDA[END_REF] programs.

Secondary Ion Mass Spectrometry (SIMS). In five samples, the H and C contents of the silicate phases were also measured by Secondary Ion Mass Spectrometry (SIMS) at the ion microprobe INSU CNRS national facility, CRPG Nancy (France). The analyses were performed with the Cameca IMS 1270 E7 ion microprobe, with a 2 nA Cs+ primary ion beam focused on a 15 µm diameter area and the electron gun for the charge compensation. The negative secondary ions 12 C -, 17 O -, 16 OH -, 27 Al -, and 30 Si -were measured with a mass resolution of 7000 (M/∆M). The hydrogen contents determined by this method were exclusively those present as OH -in the silicates. Before each measurement, the sample was pre-sputtered for 180 seconds with a beam rastering on 15 µm 2 in order to remove sample surface contamination. The measurements were made by ion counting in mono-collection mode (or on Faraday cup for counting rate higher than 3x10 5 cps) by peak switching with counting time and waiting time of 4s and 2s, respectively, for each peak. 12 successive acquisition cycles were accumulated for each measurement. The H and C concentrations were calculated using the OH -/Si -and C -/Si -ratios, with Relative Sensitivity Factors (RSF) determined on 4 experimental standard glasses (M35, M40, M43, M48: [START_REF] Shishkina | Solubility of H 2 O-and CO 2 -bearing fluids in tholeiitic basalts at pressures up to 500 MPa[END_REF]. Between three to five points were measured on each sample, and the H and C content are given with an accuracy of about 20%. These contents are reported in the Table 3.

Raman micro-spectrometry. Raman measurements were carried out on a Renishaw INVIA spectrometer equipped with a microscope and a CCD detector (LGE, France). A 532 nm

A C C E P T E D M A N U S C R I P T

solid-state green (Nd:YAG) laser was used with a maximal power of 25 mW. The acquisitions were performed through a Leica (x100) magnification objective after a calibration achieved on a silicon standard. The Rayleigh scattering component was removed by an Edge filter. The Raman-scattered light was dispersed by a holographic grating with 1800 lines/mm. The integration time was set at 60 s. The spectra of the pristine glass and the quenched silicate melt of #O2-16 were accumulated 10 and 30 times respectively (Fig. 2a-b).

The sample #O2-16 was the only one for which the liquid silicate had quenched as a glass.

fO 2 calculations.

The oxygen fugacity of the samples was determined relative to the iron-wüstite (IW) equilibrium, as in many previous studies (e.g. [START_REF] Berthet | Evolution of Indarch (EH4 chondrite) at 1 GPa and high temperature: implications for early planetary differentiation processes[END_REF][START_REF] Dasgupta | Carbon solution and partitioning between metallic and silicate melts in a shallow magma ocean: implications for the origin and distribution of terrestrial carbon[END_REF][START_REF] Chi | Partitioning of carbon between Fe-rich alloy melt and silicate melt in a magma ocean -implications for the abundances and origins of volatiles in Earth, Mars and Moon[END_REF][START_REF] Li | Carbon and Sulfur budget of the silicate Earth explained by accrétion of differentiated planetary embryos[END_REF][START_REF] Tsuno | Core-mantle fractionation of carbon in Earth and Mars : the effects of sulfur[END_REF], according to the following equation:

IW = logfO 2 experiment -logfO 2 IW = 2log(a FeO /a Fe ) (1)
with a FeO = FeO xFeO (activity of FeO in the silicate melt), and aFe = Fe xFe (activity of Fe in the Fe-rich metallic alloy). For Fe in metallic quenched melts, we used activities values, which incorporated non-ideal interactions amongst the different constituents [START_REF] Ma | Thermodynamic description for concentrated metallic solutions using interaction parameters[END_REF]. We calculated the activity of Fe in the metallic melt (and the interactions between all the elements present in the metal) using a metal activity calculator (http://norris.org.au/metalact, Norris software) provided by the University of Oxford as in [START_REF] Tsuno | Core-mantle fractionation of carbon in Earth and Mars : the effects of sulfur[END_REF]. For FeO in the silicate melt, previous studies (O 'Neill and Eggins, 2002;[START_REF] Holzheid | The activities of NiO, CoO and FeO in silicate melts[END_REF] showed that the activity coefficient  FeO is around 1.50. We found fO 2

for our samples ranging from around IW-1.5 (i.e. 1.5 log units below the IW buffer) down to IW-5.2 (i.e. 5.2 log units below the IW buffer) (Table 2). A maximum uncertainty of 0.4 log unit was estimated for these fO 2 calculations. We also did the fO 2 calculations in the ideal solution case (Table 2) and we observed a maximum difference of 0.5 log units with the nonideal case as in many previous studies (e.g. [START_REF] Dasgupta | Carbon solution and partitioning between metallic and silicate melts in a shallow magma ocean: implications for the origin and distribution of terrestrial carbon[END_REF][START_REF] Chi | Partitioning of carbon between Fe-rich alloy melt and silicate melt in a magma ocean -implications for the abundances and origins of volatiles in Earth, Mars and Moon[END_REF].

A C C E P T E D M A N U S C R I P T 3. Results.
3.1. Textures and phase assemblages in the samples.

The main phases present in all experimental samples consisted of two quenched immiscible melts: a silicate and a metallic one (Fig. 3). Their compositions are given in Tables 3A-3B.

The presence of only two immiscible melts (silicate and metal) in all samples showed that the starting brucite (when present) completely reacted with the silicates after its decomposition into MgO and H 2 O-rich fluid during the runs. Periclase and the H 2 O-rich fluid reacted with the silicate melt during the experiment. The silicates quenched once to a glass (sample #O2-16) or to an aggregate of tiny dendrites (e.g. sample #V527, Fig3b). These dendritic textures are well known and are interpreted as typical quenched structures (e.g. [START_REF] Berthet | Evolution of Indarch (EH4 chondrite) at 1 GPa and high temperature: implications for early planetary differentiation processes[END_REF].

The metallic phases contained very tiny quenched structures as illustrated in Fig. 3. When some brucite was initially present in the runs, then the metallic phases had always few small spherical voids (Fig. 3a). In the runs without brucite, the metallic part of the samples did not exhibit spherical microstructures (Fig. 3b) showing that the presence of hydrogen in the sample was responsible of these textures in the metals. These spherical voids had already been observed in previous studies and were interpreted as possible "bubbles" of H 2 that appeared during the quench of the samples (e.g. [START_REF] Okuchi | Hydrogen partitioning into molten iron at high pressure: implications for Earth's core[END_REF]. Based on SEM highresolution images, it was possible to measure the ratio A Surfaces of the area occupied by the H 2 bubbles to that of the bubble-free metal. The A Surfaces values ranged between ~0.004 (in the samples M6E2, O1-16, O1-14 and O2-16) and ~0.015 (in the samples B1-10, B2-10 and H4178). As in [START_REF] Okuchi | Hydrogen partitioning into molten iron at high pressure: implications for Earth's core[END_REF], we took a value of  H2 = 0.13 g/cm 3 and we made the assumption that the ratio of the surfaces (bubbles / metal) was similar to the ratio of the volumes (bubbles / metal). For each sample we found a negligible contribution of the H outgassed (between ~0.2 ppm, in the poorest H metal contents of our study, and ~2 ppm in the

A C C E P T E D M A N U S C R I P T
highest H one), compared to the H dissolved in metal (between ~20 to ~240 wt ppm, Table 3B). We therefore decided to neglect the bubble contributions to the H content in metals.

The Raman spectra of the quenched silicate melt of sample #O2-16 is presented in Fig. 2, with a spectrum of the starting anhydrous glass (Fig. 2a) and quenched silicate melt after HP-HT reaction (Fig. 2b). to the vibration of certain atomic groups to the Raman bands: OH stretching (large band at ~3600 cm -1 ), CH 4 or methyl group (band at ~2900 cm -1 ), possibly the one caused by C-H stretching in alkyne group (band at ~3290 cm -1 ), C-O (band at ~2130 cm -1 ), CO 3 2-carbonate (doublets at ~1430 and 1520 cm -1 ), the characteristic Si-O stretching of silicate glasses (band at ~700 and 900 cm -1 ) in the silicate melts.

Major element compositions of the samples.

The compositions of the quenched silicate melts reflected an increase in Mg due to the presence of brucite in some samples after HP-HT reactions, but also a strong depletion of Fe in the most reduced samples. The quenched silicate melts had Si and Mg contents varying from about 22 to 31 wt% and from about 13 to 21 wt% respectively (Table 3A). The concentrations of Mg in the silicates are in good agreement with the brucite amounts in the starting mixtures (from 0 up to 2.2 wt%, Table 2). The Fe-content of the quenched silicate melts of each sample ranged between 13.60 wt% in the most oxidized run to 0.20 wt% in most reduced one. No compositional gradient was observed either in the quenched silicate melts or in the metallic melts, suggesting that equilibrium was reached before the quench of our experiments. The quenched metallic melts in all runs were Fe-Ni-rich, with Fe

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concentrations ranging from about 88 to 94 wt% and Ni from about 1 wt% to 6.5 wt% (Table 3B).

3.4. Carbon and Hydrogen concentrations of the samples.

Carbon was a major element in the metallic melts (with a concentration ranging from 3.4 to 7 wt%) in contrast to silicates where it was a minor element (with a concentration ranging between 0.03 to 0.41 wt% C). At lower Ni content in metal (around 1wt%) the C concentration in metal increased, as already observed by [START_REF] Chi | Partitioning of carbon between Fe-rich alloy melt and silicate melt in a magma ocean -implications for the abundances and origins of volatiles in Earth, Mars and Moon[END_REF]. The presence of Si in metal seemed to have a negative effect on C as can be seen in the run #M6E2 which contained 2wt% Si and the lowest C content (3.4wt%). The C contents in metal increased slightly with pressure and temperature, while only a small positive pressure effect was observed in silicate. Raman spectroscopy showed that OH -and CH 4 groups were present in our quenched silicate melts (Fig. 2b). Furthermore, H contents, obtained by SIMS (sensitive only to OH -), were slightly lower than those measured by ERDA, and supported the presence of CH 4 groups together with hydroxyls in the silicate melts (Table 3A and Fig. 2b). Hydrogen remained a trace element in both metallic and silicate phases (with a concentration ranging between 20 to 236 ppm in metal and between 72 to 1243 ppm in silicate). The H contents in metal increased with pressure. No noticeable pressure or temperature effect on H contents of silicates was observed.

Attainment of equilibrium in the samples

We argue that all experiments reached equilibrium because:

(1) There were no compositional gradients of the major, minor and trace elements as revealed by multiple analyses (EPMA and SIMS) or mapping (ERDA and NRA) across the silicate and/or metallic melts. The chemical homogeneity of the phases strongly suggested that all the experiments reached equilibrium. Moreover, analysis of the shortest duration runs were consistent with the longest runs (Table 2 and4).

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(2) We performed mass balance calculations in order to check if the samples lost significant H during the HT-HP runs or during the quench as suggested by [START_REF] Okuchi | Hydrogen partitioning into molten iron at high pressure: implications for Earth's core[END_REF].

The initial H concentrations before HT-HP runs were known (Table 2). The H contents of the recovered samples (after HP-HT experiment) were calculated from H analysis in each phase (Tables 3) assuming that the proportions of metal and silicate did not change before and after the HP-HT runs. This is confirmed by mass balance of Fe before and after HP-HT experiments (Table 2). The results of these mass balance calculations (reported in Table 2)

showed that H in our samples did not massively escape.

(3) The five data points obtained for samples at anhydrous conditions (without brucite) (#4269, #4270, #V527, #SB17 and #SB21, see Table 2) showed a small increase of D Fe metal-silicate compared to the H-bearing samples synthesized at similar conditions (Table 4).

For similar redox and pressure conditions, we observed an increase of ~30% at 1 and 10 GPa elements vary from ~10 -7 cm 2 s -1 to ~10 -4 cm 2 s -1 at the P-T of our experiments (e.g. [START_REF] Walker | Partitioning ''equilibrium'', temperature gradients, and constraints on Earth differentiation[END_REF][START_REF] Mookherjee | Hydrous silicate melt at high pressure[END_REF][START_REF] Posner | Experimental determination of oxygen diffusion in liquid iron at high pressure[END_REF][START_REF] A C C E P T E D M A N U S C R I P T Clesi | Low hydrogen contents in the cores of terrestrial planets[END_REF]. They correspond to characteristic diffusion distances within the range ~ 300 -800 m, indicating that equilibrium attainment should not be impeded by diffusive processes even considering the very short experimental durations.

Equilibrium in our samples was not only based on the diffusion processes of H and C, but also on the kinetics of oxidation and reduction reactions. In addition, the textural and chemical homogeneity of H and C in both silicates and metallic phases were another argument to demonstrate that chemical equilibrium was reached in the samples of this study.

3.6. Experimental distributions of H between metal and silicate at HP-HT. fO 2 and T. The nbo/t parameter is the ratio of tetrahedrally coordinated cations (t) to nonbridging oxygen ions (nbo) [START_REF] Mysen | Relationships between properties and structure of aluminosilicate melts[END_REF]; the larger this ratio is, the less polymerized is the melt. It also helps to understand a potential effect of the structure of the silicate on the partition coefficients.

Fig. 4 shows that D H metal-silicate depends on pressure and to a lesser extent on fO 2 relative to IW (IW), T and nbo/t. First, the values of D H metal-silicate increase with pressure at almost constant fO 2 ( IW-2), from 0.04 at 1 GPa to 0.5 at 10 GPa (Table 4 and Fig. 4); second, D H metal-silicate can reach 0.22 at 1 GPa at IW-5.2. Therefore, a 10 fold increase in pressure (1 to 10 GPa) makes H more siderophile than a 1000 fold decrease in fO 2 (IW-1.8 to IW-5.2). Fig 4c

shows that H becomes less lithophile with pressure, and demonstrates siderophile behaviour (meaning D H metal-silicate >1) at around 15 to 22 GPa. The partition coefficients calculated from the data of [START_REF] Okuchi | Hydrogen partitioning into molten iron at high pressure: implications for Earth's core[END_REF] are slightly above 1 at 7.5 GPa and 1500°C while in the present work they are always below 1, increasing with pressure. In [START_REF] Okuchi | Hydrogen partitioning into molten iron at high pressure: implications for Earth's core[END_REF], experiments were performed without graphite capsule (no C) while our experiments were performed at C saturation. The presence of C may affect the behavior of H at HP-HT by decreasing its contents in the metal compared to a C-free system (e.g. [START_REF] Terasaki | Repulsive nature for hydrogen incorporation to Fe 3 C up to 14 GPa[END_REF].

Consequently, D H metal-silicate would be lower in C-saturated system than in a C-free environment (as in [START_REF] Okuchi | Hydrogen partitioning into molten iron at high pressure: implications for Earth's core[END_REF].

A multiple linear regression produced the following relation for all the data except the most reduced:

log D H metal-silicate (±0.16) = -4.26 ±1.75 *1000/T(K) +0.18 ±0.03 *1000*P(GPa) / T(K) -0.5 IW (1)

No significant dependence on nbo/t was found in this multi-parameter analysis, which is corroborated by independent analysis of the H 2 O solubility database in mafic melts [START_REF] Iacono-Marziano | New experimental data and semi-empirical parameterization of H 2 O-CO 2 solubility in mafic melts[END_REF]. This relationship, where the fO 2 dependence of 0.5 was imposed,

A C C E P T E D M A N U S C R I P T

reflects the fact that, close to IW-2 (between IW-1 and IW-3 from Fig. 4a), H might depend mainly on the following reaction:

OH in silicate melt H in metal melt + 0.5 O 2 (2)

Under more reducing conditions, ie. IW-5.2, the following reaction might mainly characterize the H behavior, which should, in principle, be fO 2 independent:

H 2 in silicate melt  2 H in metal melt (3)
Finally, due to the presence of carbon, an inversion of the fO 2 dependence is expected at low fO 2 according to the reactions: These possible trends are qualitatively outlined in fig. 4a, where D H metal-silicate that might be controlled by equations ( 2), ( 3) and (4) (or ( 5), ( 6)) is drawn. More data would be needed to confirm (or not) these hypothesis.

CH 4 in

Experimental distributions of C between metal and silicate at HP-HT.

The partition coefficient D C metal-silicate was calculated as the ratio of the C concentration in metal (in wt%) versus the C concentration in silicate (in wt%). The values are given in Table 4. In this work, we measured the Carbon Content at Carbon Saturation (CCCS) in the silicate and metal melts. The partition coefficient of an element between two phases is generally determined when the element is diluted in the system in order to be relevant to geophysical with a decrease of fO 2 (Fig. 5a) and (ii) a decrease of D C metal-silicate with an increase of pressure (Fig. 5b). The negative value of the slope for Fig. 5a is ~ -0.5. This value corresponds to the average valence state of 2 for C in silicate (e.g. Chi and Dasgputa, 2014), which may be summarized by the following reaction:

A C C E P T E D M A N U S C
CO in silicate melt  0.5 O 2 + C in metal melt (7)

A multiple linear regression gave the following relation for our data: log D C metal-silicate (±0.4) = 1.70 ±0.65 *1000/T(K) -0.14 ±0.07 *1000*P(GPa) / T(K) -0.5 IW (8)

No significant dependence on nbo/t was found in this multi-parameter analysis with our data.

However, below IW-3, the relation ( 7) should not be used anymore as the behavior of C at lower fO 2 might change due to the formation of CH 4 (e.g. reactions (4) or ( 5) or ( 6)) as suggested by our Raman results. Equation ( 1) and ( 5) must be seen as empirical fit that can be used for interpolation of our experimental data remaining within a restricted range of nbo/t

A C C E P T E D M A N U S C R I P T

and total H content. Calculations of H and C partitioning can conservatively be conducted up to 15 GPa, the maximum experimental pressure of our study, while a thorough error propagation formalism must be considered for P calculation up to 20 GPa. All statistical uncertainties are provided in equation ( 1) and ( 5). For some runs without brucite in the starting material, a small increase of the D C metal-silicate was observed compared to the H-bearing samples obtained at similar conditions. This increase, even small, remained significant because it was greater than the error on =63 in the H-free sample #V527 at 5-6GPa). The increase of D C metal-silicate under anhydrous conditions is much more pronounced in the present study than in previous works [START_REF] Dasgupta | Carbon solution and partitioning between metallic and silicate melts in a shallow magma ocean: implications for the origin and distribution of terrestrial carbon[END_REF].

Discussion.

From the partition coefficients of H and C between metal and silicate melts at HP-HT and at different fO 2 , we show:

(i) a decrease of the lithophile behavior of H at HP-HT (Fig. 4).

(ii) H might become siderophile at 15GPa (Fig. 4).

(iii) a decrease of the siderophile character of C with an increase of pressure (Fig. 5).

(iv) The presence of H might slightly decrease D C metal-silicate at HP-HT.

Below, we discuss two additional points:

(i) due to the decrease of the siderophile nature of C at HP-HT and a decrease of the lithophile affinity of H, a strong decrease of the (C/H) ratio must be observed during the segregation of a planetary core (see Fig. 6).

(ii) H might be a minor element in the Earth's core.

A C C E P T E D M

A N U S C R I P T These estimations of H contents might increase if the metal-silicate melts equilibrium process took place at higher pressures (~40-60 GPa) as proposed in recent models (e.g. [START_REF] Siebert | Metal-silicate partitioning of Ni and Co in a deep magma ocean[END_REF]. According to [START_REF] Terasaki | Stability of Fe-Ni hydride after the reaction between Fe-Ni alloy and hydrous phase (-AlOOH) up to 1.2 Mbar: Possibility of H contribution to the core density deficit[END_REF] and [START_REF] Narygina | X-ray diffraction and Mössbauer spectroscopy study of fcc iron hydride FeH at High pressures and implications for the composition of the Earth's core[END_REF], about 1 to 1.3 wt% H in the core would be enough to account for all the density deficit of the terrestrial outer core. Our results suggest that H would not be the major light element of the core. Indeed, it would be necessary to have at least ~2.5 -3.5 wt% of water (or ~ 0.3-0.4 wt% H) in the primitive bulk

Earth to build a core containing 1% H. Such high H contents could be delivered by some undifferentiated water-rich planetary embryos as, for example, the parent bodies of the CM and/or CI chondrites for example (between 13 to 18 wt% of CI or between 20 to 27 wt% of CM), or by other differentiated water-rich embryos, like Ceres, the largest object in the asteroid belt, which might contain up to 50 vol% of water [START_REF] Park | A partially differentiated interior for Ceres deduced from its gravity field and shape[END_REF]. Finally, the largest hydrous planetary bodies present in the solar nebula (e.g. Hallis et al, 2012;[START_REF] Jacobson | Accretion and differentiation of the terrestrial planets with implications for the compositions of early-formed Solar System bodies and accretion of water[END_REF][START_REF] Park | A partially differentiated interior for Ceres deduced from its gravity field and shape[END_REF] could then segregate a core with H contents approaching up to ~0.5 wt% depending on their exact size and their H primitive mantle contents. In contrast, for the smallest hydrous planetary bodies (with a central pressure less than 15 GPa), H would

A C C E P T E D M A N U S C R I P T
partition in the magma ocean and/or be lost in space by H 2 O degassing (i.e. [START_REF] Gaillard | A theoretical framework for volcanic degassing chemistry in a comparative planetology perspective and implications for planetary atmospheres[END_REF].

Carbon in planetary cores.

We estimated the C amounts that might enter into the Earth's forming core through metalsilicate melts equilibrium processes (with P equilibrium ~20 GPa, between 1600-2500K and at fO 2 within the range IW-2 -IW-5) with a C content for the primitive mantle deduced from different models of the literature ranging between ~20 or ~300 ppm (e.g. [START_REF] Hirschmann | The H/C ratios of Earth's near-surface and deep reservoirs, and consequences for deep Earth volatile cycles[END_REF]. We found the following range of values:

~0.06 wt% ≤ C in Earth's core ≤ ~8 wt% (solubility limit, e.g. [START_REF] Chi | Partitioning of carbon between Fe-rich alloy melt and silicate melt in a magma ocean -implications for the abundances and origins of volatiles in Earth, Mars and Moon[END_REF].

These values might decrease at higher pressures. Whether the Earth's core could incorporate C to its solubility limit (ie. the CCCS) is discussed below and the consequence of accretion at C-undersaturated conditions is discussed in section 3.7. The decrease of the siderophile nature of C at HP-HT has important implications for early planetary differentiation. If hydrous or anhydrous small planetary bodies were present in the solar nebula (e.g. Hallis et al, 2012;[START_REF] Jacobson | Accretion and differentiation of the terrestrial planets with implications for the compositions of early-formed Solar System bodies and accretion of water[END_REF], then they might segregate a core with high C contents (up to 3-5 wt%). The cores of the biggest bodies would contain less C than the small ones. The most reduced small planetary bodies (Mercury-like bodies) might also sequester high amounts of C in their cores (theoretically close to C solubility limit, depending on the size and the exact redox conditions of the body) except if silicon (Si), due to very low fO 2 , entered the core (e.g. [START_REF] Malavergne | Highly reducing conditions during core formation on Mercury: Implications for internal structure, the distribution of heatproducing elements and the origin of a magnetic field[END_REF][START_REF] Malavergne | How Mercury can be the most reduced terrestrial planet and still store iron in its manthe[END_REF]. Indeed, it has been shown that the presence of Si in Fe-Ni-C alloys greatly decreases the concentration of C in metal, and can lower the C solubility by a factor 3 (e.g. [START_REF] Li | Carbon and Sulfur budget of the silicate Earth explained by accrétion of differentiated planetary embryos[END_REF]. Such effect can also be expected if a realistic amount of S enters the Earth's core composition. [START_REF] Li | Carbon and Sulfur budget of the silicate Earth explained by accrétion of differentiated planetary embryos[END_REF] have shown that a few wt% of S reduces by a factor 5 the carbon content at graphite saturation.

Finally, the presence of H might slightly decrease the C contents of these planetary cores. The

A C C E P T E D M A N U S C R I P T

decrease would be enhanced with the size of the body as the siderophile nature of C decrease at HP-HT. All in all, planetary accretion and core-mantle segregations at conditions close to carbon saturation may be a hypothesis, justifying that we do not consider here the effects of C dilution in metal on the D C metal-silicate .

4.3. The cross fate of H and C during planetary differentiation.

We assume the Primitive Mantle (PM) contents of C (between 20 and 300 ppm, e.g.

Hirschmann and Dasgupta, 2009) and H (between 110 and 600 ppm, e.g. Marty, 2012;

Albarede et al, 2013; Rubie et al, 2015) by using models found in the literature. The variations of ratio as a function of pressure, temperature and fO 2 (between IW-1

and IW-3) can be deduced by our experimental data. This ratio showed an obvious trend only with pressure (Fig. 6). More data are clearly needed to deduce the variations of this ratio with temperature or fO 2 . These ratios ranged from values ~0.0003 at 1 GPa to ~0.04 at 10 GPa. Assuming the following equation:

(9), we estimated possible ranges of and we deduced the possible (H/C) ratios during the core segregation for 1-10 GPa and variable fO 2 :

0.03  H core C core        0.27 (10)
The Earth's core must contain other light elements: around 3-7 wt% Si, 2-4 wt% O and 1-3 wt% S (e.g. [START_REF] Jacobson | Accretion and differentiation of the terrestrial planets with implications for the compositions of early-formed Solar System bodies and accretion of water[END_REF]Fischer et al, 2015). The contents of H and C would depend on the oxidized or reduced environment of the primitive Earth during the segregation of the core.

Based on this study and on current models (e.g.

H PM C PM       A C C E P T E D M A N U S C R I P T
undergone reduced fO 2 conditions that became increasingly oxidized. If terrestrial accretion began under very reducing conditions (between IW-3 and IW-5), the distribution of C would be strongly in favor of the metal of the core at the detriment of the mantle. For the lowest fO 2 , however, silicon (Si) could be easily combined with the core (e.g. [START_REF] Malavergne | How Mercury can be the most reduced terrestrial planet and still store iron in its manthe[END_REF]. The presence of Si in metal might decrease the C contents of the core (e.g. Li et al, 2015). Thus, low fO 2 might strengthen the decrease of the highly siderophile nature of C. H would become increasingly siderophile with increasing depths (corresponding to pressure values of 15-22 GPa) in the magma ocean of the proto-planet. Moreover, the results of Iizuka-Oku et al (2017), suggest that H might no longer be a trace element in the cores of small differentiated bodies, which might be part of the Earth's accretion. The siderophile character of C would gradually decrease as pressure increased. For the Earth, we found that the H contents in the core might range between ~0.0005 wt% and ~0.3 wt%. We could then determine possible ranges for C in the Earth's forming core using the relation ( 9). We proposed that the C content may have minimum values of ~0.6 -1 wt% and maximum values around ~2.4 wt%. Finally, our work showed that the metallic core might store H and C throughout its formation.

The differentiation of smaller planetary bodies in the primitive solar nebula would impact the (H/C) fractionation differently from Earth's size body. As the ratio is increasing with pressure, H and C would be more and more fractionated during the growth of the body. The degree of (H/C) fractionation of planetary materials (as chondrites and achondrites for example) could thus be an indirect indicator of the size of the planetary body.

The smallest bodies (like Vesta for example) would have the highest (H/C) ratio while the bigger bodies (e.g. like the Moon for example) the lowest. The cores of the smallest planetary bodies would then contain only traces of H unlike C, which could exceed several wt% (but always less than 7-8 wt%). The cores of the Earth's size planetary bodies might

D H metal -silicate D C metal -silicate A C C E P T E D M A N U S C R I P T
well reach up to ~0.5 wt% H, levels which might be more comparable with possible contents of C.

Conclusion.

We have experimentally determined the partition coefficients of H and C between metal and silicate melts between 1-15 GPa, 1600-2200°C and IW-2 -IW-5.5. Our results showed that increasing pressure makes H less lithophile and C slightly less siderophile. We proposed that the capacity of a planet or a planetary body to keep H and C in the core would be controlled by HP-HT equilibration processes at the depth of the core -magma ocean boundary. The smallest cores would retain most of the C whereas H would partition in the magma ocean and/or be lost in space. The cores in the largest planets, like the Earth, would store both H and C, but HP-HT equilibration should enable the mantle to retain a significant part of H and C. In the Earth's core, the H content might reach a maximum value of ~0.3 wt% and at least a few tens of ppm, while the C content could reach ~2.4 wt% in the most favorable scenario.

Acknowledgments: This study was partly funded by the German Science Foundation via Core Facility Programme of the Bayerisches Geoinstitut (Germany). We are grateful to the BGI staff for their constant availability and more especially to H. Schulze for his help during sample preparation and Dan Frost for fruitful discussions. The authors wish to thank the nuclear microprobe committee for accepting the project. We are also grateful to Didier

Guillier and Yvan Kilisky for the accelerator operation. The authors wish to thank the CRPG ion microprobe committee for accepting the project. We are also grateful to Nordine Bouden H metal-silicate ) between metal and silicate melts as a function of (a) oxygen fugacity relative to IW buffer (IW), a linear regression line fitted the most oxidized data with a slope of 0.5. The other linear fits (with a slope of 1 and parallel to X-axis) were deduced from our Raman results and reactions (3), ( 4), (5) and ( 6 --: values below detection limit ;* Total without the contribution of ERDA and RNA analysis.

N is the number of EPMA measurements averaged to obtain the composition reported.

A C C E P T E D M

A N U S C R I P T D X metal-silicate is the partition coefficient of X (= C, Fe or H) between metallic and silicate melts and derived by dividing the concentration of element X (by weight) in metallic melt by its concentration (by weight) in silicate melt.

  s. More details about the experimental setups are given in Sifre et al.

(

  at 10 GPa: D Fe metal-silicate =10 for the H-bearing sample #B1-10, while D Fe metal-silicate =13.6 for #4270 (H-free); at 1 GPa: D Fe metal-silicate =8 for the H-bearing sample #O1-16, while D Fe metalsilicate = 10 for the H-free sample #SB17). These results are in very good agreement with those of Clesi et al (2016) who observed similar increase for D Fe metal-silicate due to H at similar P, T and fO 2 . This increase was significantly higher than the error of D Fe metal-silicate determination and supported achievement of equilibrium during experiments. (4) Previous studies at the same experimental conditions (P -T -run durations) produced equilibrated H-bearing samples (e.g. Okuchi, 1997; Dasgupta et al, 2013; Stanlay et al, 2014; Chi et al, 2014; Li et al, 2015; Amstrong et al, 2015; Clesi et al, 2016; Li et al, 2016; Clesi et al, 2018). Our D H metal-silicate are in good agreement with those of Clesi et al (2018) (Fig. 4), an internal consistency suggesting equilibrium attainment for both studies. Accordingly, silicate-liquid diffusion coefficients of major (mainly Si, Mg and O in silicates or Fe and C in metals), minor or trace (H in silicates and metals and C in silicates)

  Fig. 4 represents the variation of the partition coefficients of H and C (respectively) between metal and silicate melts D H metal-silicate at HP-HT as a function of pressure (P), nbo/t,

and

  Etienne Deloule for the SIMS analysis. Valerie Paul Boncour and Jean-Marc Joubert from the Institute of Chemistry and Materials (ICMPE, Créteil, France) are thanked for their help and assistance during the alloys synthesis and their characterizations.

Figure 1 :Figure 2 :Figure 3 :Figure 4 :

 1234 Figure 1: ERDA measurements. MEB image of sample H4178 and the associated ERDA spectra for two areas of interest in metal (black) and silicate (gray) phases. The central metallic phase is surrounded by the silicate. H measurements have been made in regions of 200*200 µm 2 squares.ERDA spectra of the protons are presented for both phases, in normalized arbitrary units, as a function of the proton energy. The contaminated surface contribution in H can be clearly separated from the bulk signal, corresponding to the real H concentration of the phase.

Figure 5 :

 5 Figure 4: Partition coefficient of H (D Hmetal-silicate ) between metal and silicate melts as a function of (a) oxygen fugacity relative to IW buffer (IW), a linear regression line fitted the most oxidized data with a slope of 0.5. The other linear fits (with a slope of 1 and parallel to X-axis) were deduced from our Raman results and reactions (3), (4), (5) and (6) (see text for details); (b) nbo/t; (c) pressure, the two linear fits showed the lowest and highest pressure ranges for which D H metal-silicate became siderophile; (d) temperature. These data confirm a linear decrease of log(D H metal-silicate melt ) with fO 2 and pressure. Our results are compared with literature data. a.b.

Figure 6 :

 6 Figure 6: (D Hmetal-silicate / DCmetal -silicate ) ratio obtained from our results as a function of pressure. The slope of the regression line was 0.22 and the correlation coefficient 0.97. This ratio showed no obvious trend with T, nbo/t and IW.

  These Raman results clearly showed the presence of H and C in the quenched silicate melt and the absence of detectable amount of C and H in the majority of anhydrous glasses used as starting materials for all experiments. Based on previous similar studies (e.g.[START_REF] Mysen | Solution behavior of reduced C-O-H volatiles in silicate melts at high pressure and temperature[END_REF][START_REF] Mysen | Silicate-COH melt and fluid structure, their physicochemical properties, and partitioning of nominally refractory oxides between melts and fkuids[END_REF][START_REF] Hirschmann | Solubility of molecular hydrogen in silicate melts and consequences for volatile evolution of terrestrial planets[END_REF][START_REF] Dasgupta | Carbon solution and partitioning between metallic and silicate melts in a shallow magma ocean: implications for the origin and distribution of terrestrial carbon[END_REF]

[START_REF] Stanley | Solubility of C-O-H volatiles in graphite-saturated martian basalts[END_REF][START_REF] Kadik | Solution behavior of C-O-H volatiles in FeO-Na2O-Al2O3-SiO 2 melts in equilibrium with liquid iron. And graphite at 4 GPa and 1550[END_REF]

, we were able to attribute the frequencies characteristic

  We used D H metal-silicate to make mass balance calculations for primitive Earth and to allow easier comparison with previous partitioning studies of different elements between metal and silicate (e.g.[START_REF] A C C E P T E D M A N U S C R I P T Clesi | Low hydrogen contents in the cores of terrestrial planets[END_REF][START_REF] Dasgupta | Carbon solution and partitioning between metallic and silicate melts in a shallow magma ocean: implications for the origin and distribution of terrestrial carbon[END_REF][START_REF] Stanley | Solubility of C-O-H volatiles in graphite-saturated martian basalts[END_REF][START_REF] Kadik | Solution behavior of C-O-H volatiles in FeO-Na2O-Al2O3-SiO 2 melts in equilibrium with liquid iron. And graphite at 4 GPa and 1550[END_REF].

	K H metal-silicate and D H metal-silicate can be used in order to understand the distribution of metal and
	silicate during planetary differentiation. The major difference between D H	metal-silicate and
	K H metal-silicate is that D H metal-silicate can be <1 while K H metal-silicate >1 because H is a very light
	element with respect to the atomic mass of the metal. For example, at 10 GPa, we found
	D H metal-silicate values of 0.5( 0.1) and 0.33( 0.07) while their K H metal-silicate values were 1.3(
	0.3) and 0.83( 0.17) respectively. Therefore, at 10 GPa H could be considered as slightly
	siderophile.

The partition coefficient D H metal-silicate was calculated as the ratio of the H concentration in metal (in wt%) versus the H concentration in silicate (in wt%). The values of D H metal-silicate are given in Table 4. The molar partition coefficient K H metal-silicate is defined as the ratio of the molar concentration of H in metal versus the molar concentration of H in silicate. Both,

  silicate melt + O 2 = CO 2 in silicate melt + 4H in metal melt (4) CH 4 in silicate melt + 0.5 O 2  CO in silicate melt + 4H in metal melt (5)

CH 4 is detected in our samples (Fig.

2

) and

[START_REF] Armstrong | Speciation and solubility of reduced C-O-H-N volatiles in mafic melt: implications for volcanism, atmospheric evolution, and deep volatile cycles in the terrestrial planets[END_REF]

actually described CH 4 as the main H-species at fO 2 < IW-3. Eq. (

3

) implies that the fO 2 dependence at fO 2 <IW-3 should become inverse and H becomes increasingly lithophile as fO 2 decreases.

Lastly, at graphite saturation, one can consider the following reaction, involving CH 4 , where the partitioning of H would not depend on fO 2 : CH 4 in silicate melt  C in metal melt + 4H in metal melt

(6)

  R I P T systems. Previous metallurgical studies have shown a non-ideal behavior of C in Fe-rich alloy liquids (e.g. Wang et al, 1991) at HT showing that above 2.5wt% C, the activity a C of C was Stanley et al, 2014; Chi et al, 2014; Li et al, 2015; Amstrong et al, 2015; Clesi et al, 2016; Li et al, 2016; Tsuno et al, 2018) represented minimum values. Fig. 5 represents the variation of

	around 3-5 times superior to its C molar fraction X C . Assuming that such a C -X C relationships
	still hold at high pressure, this implied that the C partition coefficient measured at saturation
	conditions might be inferior to the D C	metal-silicate under dilute conditions. Thus, the D C	metal-silicate
	determined in our study, as well as in many previous studies (e.g. Dasgupta et al, 2013;

D C

metal-silicate at HP-HT as a function of pressure (P), nbo/t, fO 2 and T. The C concentrations measured in our samples implied D C metal-silicate well above unity (Fig.

5

and Table

4

) and in agreement with previous work

[START_REF] Dasgupta | Carbon solution and partitioning between metallic and silicate melts in a shallow magma ocean: implications for the origin and distribution of terrestrial carbon[END_REF] Stanlay et al, 2014, Chi and Dasgputa, 2014)

performed under C saturation conditions. This reflects the strong siderophile affinity of C at these P-T-redox conditions. Two trends can be highlighted: (i) an increase of D C metal-silicate

  It has been proposed that the main part of H remained in the Earth's interior during its differentiation (e.g.[START_REF] Hirschmann | Solubility of molecular hydrogen in silicate melts and consequences for volatile evolution of terrestrial planets[END_REF][START_REF] Sarafian | Early accretion of water in the inner solar system from a carbonaceous chondrite-like source[END_REF][START_REF] Hallis | Evidence for primordial water in Earth's deep mantle[END_REF][START_REF] Tikoo | The fate of waterwithin Earth and super-Earths and implications for plate tectonics[END_REF]. In order to test this hypothesis, we can use our experimental results to calculate how much H might enter the growing core through HP-HT metal-silicate melts equilibrium processes (e.g. Righter et al, 2010, with P equilibrium ~20 GPa, between 1600-2500K and around IW-2 -IW-5). From the possible H contents of the primitive mantle (ranging between ~110, ~300 ppm or ~600 ppm; e.g.[START_REF] Marty | The origins and concentrations of water, carbon,nitrogen and noble gases on Earth[END_REF][START_REF] Albarede | Asteroidal impacts and the origin of terrestrial and lunar volatiles[END_REF][START_REF] Jacobson | Accretion and differentiation of the terrestrial planets with implications for the compositions of early-formed Solar System bodies and accretion of water[END_REF], we can estimate ranges of H that could enter the forming core: ~0.0005 wt% ≤ H in Earth's core ≤ ~0.3 wt%.

	4.1. Hydrogen in planetary cores.

  [START_REF] Jacobson | Accretion and differentiation of the terrestrial planets with implications for the compositions of early-formed Solar System bodies and accretion of water[END_REF][START_REF] Righter | Terrestrial planet formation[END_REF], we can describe the cross fate of H and C during terrestrial differentiation which might have first

	D H	metal -silicate
	D C	metal -silicate
							D H	metal -silicate
							D C	metal -silicate
		H core C core   	  =	D H D C   	metal -silicate metal -silicate	   ´HPM  C PM  	  

Table 1 :

 1 Compositions of (A) the synthetic anhydrous glasses (in wt%, EPMA analysis) and (B) the metallic alloys used in the starting compositions of the present study (EPMA analysis).

	A
		Glass 1	Glass 2	Wt%	Glass 1	Glass 2
	Na	1.81 (0.04)	-	Na 2 O	2.44	-
	Si	26.30 (0.5)	23.70 (0.5)	SiO 2	56.33	50.80
	Al	2.91 (0.06)	1.90 (0.04)	Al 2 O 3	5.49	3.60
	K	0.32 (0.01)	-	K 2 O	0.39	-
	Fe	8.21 (0.23)	5.05 (0.15)	FeO	10.56	6.50
	Mg	12.58 (0.26)	21.28 (0.43)	MgO	20.78	35.30
	Ca	1.98 (0.06)	2.14 (0.06)	CaO	2.77	3.00
	Ti	0.29 (0.035)	-	TiO 2	0.49	-
	Cr	0.24 (0.04)	0.10 (0.02)	Cr 2 O 3	0.36	0.14
	Mn	0.21 (0.04)	0.20 (0.03)	MnO	0.27	0.15
	O	45.15 (0.50)	45.63	Total	99.97	99.49

Table 2 :

 2 Experimental conditions and starting compositions.

		P	T	Run	Brucit	Silicate	Metal in	H in	H in	Fe in	Fe in	Type of	I	I
	Samp	(GP	(°C	durati	e in	in	starting	startin	the	startin	the	experim	W	W
	le	a)	)	on	startin	starting	material	g	recover	g	recover	ent	(1)	(2) 
					g	material	s and its	materi	ed	materi	ed
					materi	and its	proporti	al	sample	al	sample
					al	proporti	on	(wt%)	(wt%)*	(wt%)	(wt%)*
					(wt%)	on	(wt%)	*	*	*	*
						(wt%)
	B1-	10 160	3 min 1.20	Glass 1	Fe 90 Ni 5 S	0.041	0.040	29.6	30.0	MA	-1.7 -2.1
	10		0			(72.60)	i 5 (26.20)	(0.00	(0.01)	(0.9)	(0.9)
								6)
	B2-	10 160	3 min 1.00	Glass 1	Fe 95 Ni 5	0.034	0.035	26.4	26.7	MA	-1.6 -2.0
	10		0			(78.00)	(21.00)	(0.00	(0.008)	(0.9)	(0.9)
								5)
	H417	6 180	2 min 0.76	Glass 1	Fe 95 Ni 5	0.026	0.026	50.4	50.1	MA	-1.5 -1.8
	8		0			(50.54)	(48 .70)	(0.00	(0.006)	(0.8)	(0.8)
								4)
	M6E	1 160	2 min 0.13	Glass 1	Fe 85 Ni 5 S	0.0045	0.0044	46.6	45.8	PC	-5.2 -5.5
	2		0			(49.77)	i 10	(0.00	(0.001)	(0.7)	(0.7)
							(50.10)	1)
	O1-	1 160	2 min 0.45	Glass 1	Fe 90 Ni 5 S	0.015	0.015	47.6	46.6	PC	-1.5 -2.1
	16		0			(54.15)	i 5 (45.40)	(0.00	(0.003)	(0.8)	(0.8)
								3)
	O1-	1 140	10	2.20	Glass 1	Fe 95 Ni 5	0.076	0.072	46.4	47.2	PC	-1.4 -1.7
	14		0	min		(53.60)	(42.20)	(0.01	(0.01)	(0.8)	(0.8)
								)
	O2-	1 160	2 min 1.00	Glass 1	Fe 95 Ni 5	0.035	0.033	41.0	40.2	PC	-1.7 -2.2
	16		0			(62.00)	(38.00)	(0.00	(0.005)	(0.8)	(0.8)
								5)
	S426	15 230	3.5	0	Glass 2	Fe 99 Ni 1	-	-	30.9	30.8	MA	-1.8 -2.3
	9		0	min		(72.50)	(27.50)			(0.9)	(0.8)
	S427	10 220	4 min	0	Glass 2	Fe 99 Ni 1	-	-	30.8	30.1	MA	-1.8 -2.2
	0		0			(72.50)	(27.50)			(0.9)	(0.9)
	V527	5 220	4 min	0	Glass 2	Fe 99 Ni 1	-	-	30.9	30.8	MA	-1.8 -2.3
			0			(72.50)	(27.50)			(0.9)	(0.9)
	SB17	1 160	30	0	Glass 2	Fe 95 Ni 5	-	-	29.8	30.3	PC	-1.7 -2.1
			0	min		(72.50)	(27.50)			(0.9)	(0.9)
	SB21	1 170	30	0	Glass 2	Fe 85 Ni 5 S	-	-	27.0	26.1	PC	-4.1 -4.4
			0	min		(72.50)	i 10			(0.9)	(0.9)
							(27.50)
	MA= multi anvil press ; PC= piston cylinder press ; IW = fO 2 relative to IW buffer : (1) was calculated with activity
	coefficients or (2) with ideal behavior, see text for details: * H in the starting materials (before HT-HP run) was

calculated from the proportion of brucite Mg(OH)2 in starting mixtures; ** H and Fe in the recovered sample were

Table 3 :

 3 Sample compositions. A. Silicate phase compositions (in wt%) obtained by EPMA, ERDA (for H, in ppm), SIMS (for C and H exclusively present as OH -), NRA (for C). H from ERDA and C from RNA were used for the partition coefficient calculations. Total without the contribution of SIMS, ERDA and RNA analysis ; N is the number of EPMA measurements averaged to obtain the composition . Metal compositions (in wt%) obtained by EPMA, ERDA (for H, in ppm), NRA (for C) and SEM-EDS.

	Sam	N Na 2	Mg	Al 2	SiO 2 K 2 O CaO TiO 2 FeO MnO Cr 2 O	Tot	H	H	C	C
	ple		O	O	O 3							3	al*	(pp	(pp	RNA	SIMS
														m)	m)
														ER	SI
														DA	MS
	B1-	1	1.36	21.8	2.39	57.4	-	3.87	0.16	11.5	0.150	0.260	99.0	463	430	0.410	0.520
	10	5	(0.0	0	(0.0	9		(0.0	(0.00	2	(0.0	(0.0	1	(40	(4	(0.03	(0.05
			3)	(0.2	3)	(0.5		6)	4)	(0.1	04)	08)		)	0)	3)	)
				2)		7)				1)
	B2-	1	1.18	21.7	3.89	55.5	0.24	3.49	0.53	12.6	0.190	0.16	99.5	413	440	n.a. 0.170
	10	5	(0.0	0	(0.0	3	(0.0	(0.0	(0.00	0	(0.0	(0.0	1	(35	(4		(0.02
			3)	(0.2	6)	(0.5	07)	5)	14)	(0.1	06)	05)		)	4)		)
				2)		5)				2)
	H41	1	1.67	21.3	3.96	53.5	-	3.63	-	15.1	-	-	99.3	428	350	0.164	0.149
	78	5	(0.	9	(0.	5		(0.		8			8	(3	(4	(0.0	(0.0
			04)	(0.	06)	(0.		05)		(0.				5)	5)	13)	2)
				21)		53)				15)
	M6E	2	1.85	27.6	4.63	59.9	0.48	3.91	0.31	0.25	0.120	0.040	99.2	72	70	0.002	0.002
	2	5	(0.0	9	(0.0	3	(0.0	(0.0	(0.00	(0.0	(0.0	(0.0	1	(7)	(7)	8	0
			4)	(0.2	6)	(0.6	12)	6)	8)	2)	04)	02)				(0.00	(0.00
				7)		0)										03)	02)
	O1-	2	1.98	22.8	5.41	49,8	0.47	4.11	0.41	14.2	0.180	0.230	99.7	277	n.a. n.a.	n.a.
	16	5	(0.0	3	(0.0	7	(0.0	(0.0	(0.01	8	(0.0	(0.0	7	(22
			5)	(0.2	8)	(0.5	12)	6)	)	(0.1	05)	07)		)
				2)		0)				4)
	O1-	2	1.65	22.8	4.91	48.1	0.48	4.19	0.41	17.4	0.170	0.130	99.8	124	115	0.030	0.030
	14	5	(0.0	8	(0.0	3	(0.0	(0.0	(0.01	9	(0.0	(0.0	4	3	4	(0.00	(0.00
			4)	(0.2	7)	(0.4	12)	6)	)	(0.1	05)	04)		(95	(1	3)	3)
				2)		8)				7)				)	15)
	O2-	2	2.15	21.7	4.91	54.8	-	3.91	0.38	11.3	0.200	0.290	99.7	529	n.a. 0.05	n.a.
	16	5	(0.	2	(0.	3		(0.	(0.0	2	(0.0	(0.0	1	(4		(0.0
			05)	(0.	07)	(0.		06)	1)	(0.	06)	09)		4)		07)
				21)		55)				11)
	4269 1	-	32.8	3.73	49.8	-	2.91	-	9.35	0.400	0.290	99.4	-	-	0.25	n.a.
		5		4	(0.0	9		(0.0		(0.0	(0.0	(0.0	1			(0.02
				(0.3	6)	(0.5		5)		9)	1)	09)				)
				2)		0)
	4270 1	-	32.2	3.93	51.1	-	3.35	-	8.64	-	-	99.3	-	-	0.23	n.a.
		5		4	(0.0	8		(0.0		(0.0			4			(0.02
				(0.3	6)	(0.5		5)		8)						)
				2)		1)
	V52	1	-	34.7	3.74	48.9	-	2.93	-	9.07	0.320	-	99.8	-	-	0.07	n.a.
	7	5		9	(0.0	7		(0.0		(0.0	(0.0		2			(0.00
				(0.3	5)	(0.5		4)		9)	1)					7)
				4)		0)
	SB1	2	0.35	28.2	1.98	54.8	-	1.85	-	11.4	0.400	0.59	99.7	-	-	0.04	n.a.
	7	0	(0.0	9	(0.0	8		(0.0		4	(0.0	(0.0	8			(0.00
			08)	(0.2	3)	(0.5		3)		(0.1	1)	2)				4)
				8)		5)				1)
	SB2	2	0.67	26.4	2.32	67.6	-	1.59	-	0.79	0.320	0.100	99.9	-	-	0.02	n.a.
	1	0	(0.0	6	(0.0	9		(0.0		(0.0	(0.0	(0.0	4			(0.00
			2)	(0.2	3)	(0.6		3)		8)	1)	03)				18)
				4)		7)

-: values below detection limit ; n.a. : not analyzed ;* B

Table 4 :

 4 Partition coefficients of H and Fe between metal and quenched silicate melts obtained in this study.

	Sample P (GPa) T (°C) IW (fO 2 relative	NBO/T D Fe metal/silicate	D C	metal/silicate	D H	metal/silicate
				to IW buffer)
	B1-10	10	1600	-1.7	1.8	10.0 (0.5)	10.6 (1.5)	0.50 (0.10)
	B2-10	10	1600	-1.6	1.9	9.4 (0.5)		-	0.33 (0.07)
	H4178	6	1800	-1.5	2.0	7.7 (0.4)	27 (2.5)	0.24 (0.06)
	M6E2	1	1600	-5.2	1.6	455 (18)	1137 (100)	0.22 (0.06)
	O1-16	1	1600	-1.5	1.6	8.0 (0.4)		-	0.047 (0.012)
	O2-16	1	1600	-1.7	1.4	10.4 (0.5)	68 (9)	0.038 (0.01)
	O1-14	1	1400	-1.4	1.8	6.65 (0.4)	137 (12.5)	0.045 (0.012)
	S4269	15	2300	-1.8	2.4	12.8 (0.7)	21.0 (2)	-
	S4270	10	2200	-1.8	2.7	13.6 (0.5)	30.7 (3)	-
	V527	5	2200	-1.8	3.1	13.2 (0.7)	63 (6)	-
	SB17	1	1600	-1.7	2.1	10.1 (0.5)	90 (6)	-
	SB21	1	1700	-4.1	1.2	140 (0.7)	280 (26)	-

calculated from a mass balance by using the proportion of each phase (metal and silicate melts) present in the sample and their H or Fe concentrations (given in the tables 3A and 3B).

A C C E P T E D M

A N U S C R I P T reported.


IBS Frank Torregrosa
email: frank.torregrosa@ion-beam-services.fr

Guillaume Sempere
email: guillaume.sempere@ion-beam-services.fr

Werner Schustereder
email: werner.schustereder@infineon.com

Philippe Godignon
email: philippe.godignon@cnm.es

Yohann Spiegel
email: yohann.spiegel@ion-beam-services.fr

Gael Borvon
email: gael.borvon@ion-beam-services.fr

Moriz Jelinek
email: moriz.jelinek@infineon.com

Marcin Zielinski
email: mzielinski@novasic.com

Laurent Roux
email: laurent.roux@ion-beam-services.fr

Thomas Wuebben
email: thomas.wuebben@infineon.com

Frédéric Morancho
email: morancho@laas.fr

Advantages and challenges of Plasma Immersion Ion Implantation for Power devices manufacturing on Si, SiC and GaN using PULSION ® tool

Keywords: Ion Implantation, Plasma Immersion Ion Implantation, Plasma Doping, Power devices

come   L'archive ouverte pluridisciplinaire

I. INTRODUCTION

Thanks to its ability to implant high doses at low energy with a high throughput and no risk of high energy contamination, Plasma Immersion Ion Implantation (PIII) or Plasma Doping (PLAD) has been widely used, since 2005, in memory application for DRAM poly counter doping or contact doping [1][2][START_REF] Qin | IIT 2014 (Ion Implantation Technology International Conference) school book, chapter 15: Plasma Immersion Ion Implantation (PIII)[END_REF]. The ability to also make 3D implant and to reach high surface concentration also opened new applications for logic devices fabrication (FinFET doping, Material modification application for Vth Tuning or etch stop application) [START_REF] Torregrosa | Recent developments on PULSIONs PIII tool : FinFET 3D doping, High temp implantation, III-V doping, contact and silicide improvement[END_REF][START_REF] Milesi | patent application FR2998090[END_REF]. Despite all the advantages of PIII, nearly no work was reported in the literature for power devices applications. In this paper, thanks to the collaboration of several industrial and academic partners, we tested the efficiency of the PIII tool from IBS (named PULSION ® ) to address several challenging applications for Si power devices manufacturing where beam line tools were not technically or economically efficient:

II. DOPING APPLICATION EXAMPLES FOR SILICON POWER DEVICES

A. Poly doping for CoolMOS (INFINEON / IBS collaboration)

MOS and IGBT power devices are still using doped polysilicon for their gate stack. Initially doped using diffusion processes (PoCl3 for N-Channel and BBr3 for P-Channel MOSFETs), this process is progressively being replaced by Ion Implantation for a better homogeneity and reproducibility as well as for environment friendly considerations. But, the required doses are high (some E16/cm²) and even if the needed implantation energies are higher than for DRAM applications due to the thicker poly-Si thickness (generally around 400nm to 800 nm), throughput of the implantation process is still something to be improved.

As for DRAM or CMOS applications [1,[START_REF] Qin | Performance Evaluation of CMOS Devices Fabricated by PIII/PLAD Doping of Poly-Si Gates[END_REF], PIII, could be an efficient solution to benefit from the advantages of the ion implantation processes while keeping a high throughput and a low cost of ownership. But, due to its limitation in implantation energy (most of the available tools are limited to 10kV), the subsequent diffusion/activation process must be optimized to allow the dopants to diffuse through all the poly-Si and to reach a high enough concentration near the SiO2 gate interface to minimize depletion phenomena while avoiding dopant out-diffusion, implementing cap layers or oxidation steps in the thermal process.

Table 1 presents best results obtained on a 600 nm LPCVD PolySi deposited on SiO2, and submitted to PIII Implantation at 8 kV with doses ranging from 1E16 to 1E17/cm², followed by a 30 min annealing step under argon, with and without oxidation steps. For Phosphorus doping PH3 plasma was used, annealing temperature was ranging from 830°C to 1100°C. For Boron doping, BF3 plasma was used and annealing temperature was ranging from 1050°C to 1140°C.

As can be seen, targeted values (about 10 /sq for Phosphorus doping and 20 /sq for boron doping) were nearly reached with respectively 11.1 /sq and 23.4 /sq. We calculated that the use of PULSION Tool for this process could allow a reduction of the Cost of Ownership by a factor higher than 2 compared to the beam line process of record used at INFINEON.

B. Contact doping doping for SFET (INFINEON / IBS collaboration)

As for memory and logic devices, high surface concentration obtained using PIII is likely to reduce contact resistance and to be cost efficient compared to low energy BL implantation. [START_REF] Qin | IEEE Workshp on Microelectonics and Devices[END_REF] New generations of SFET devices developed at INFINEON require an efficient p-type contact doping at the bottom of always narrower groove contact structures. In this study we compared PULSION doping using BF3 plasma with Beam Line (BL) implantation using BF2 + . For BL implantation, energy was ranging from 10 to 25 keV and doses from 1E15 to 3E15 /cm². For PIII, we used acceleration voltages from 5 to 10 kV and machine doses (including F+ ions) from 2E15 to 6E15/cm². The test was performed on different pitch size real devices without changing any other process steps. Electrical characteristics of the devices (Vth, DiBL, conductance, body lateral resistance) were then measured and compared. Main conclusions were :

-Whatever the pitch size, PIII implantation gives electrical performance in the same range than the process of reference (using beam line) but with a clearly lower DiBL at the same Vth (see fig

C. Trench doping for IGBT (INFINEON / IBS collaboration)

Thanks to its capability to do 3D doping, PIII process is likely to implant the wall of deep trenches needed for power device fabrication [START_REF] Qin | IEEE Workshp on Microelectonics and Devices[END_REF] In order to reduce the Rds(on) of the MOSFET portion of the IGBT, a trench gate structure has been adopted 10 year ago by most of the suppliers: the gate oxide and conductive polysilicon gate electrode are formed in a deep (about 5µm) narrow trench below the chip surface and allow a higher cell current density while eliminating the "parasitic JFET effect" [START_REF] Nizou | Deep Trench doping by plasma immersion ion implantation in silicon[END_REF] , Development of new IGBT generations might require shallow trenches associated with uniform p-type doping within the trench. As this is likely impossible to be obtained using BL ion implantation, we checked the ability of PULSION tool to dope the walls of such trenches using BF3 or B2H6 plasma. Wall doping uniformity was checked using SSRM after annealing (see example on figure 3). Results validated the ability of PIII to be used to dope such trenches, work is still going on to optimize process parameters and process integration on real devices.

D. Low dose Trench doping for superjunctions (LAAS / IBS collaboration)

Superjunctions have been introduced by ST-MICROELECTRONICS and INFINEON few years ago to improve the ON state resistance of MOSFET devices. It consists in alternation of N and P vertical layers in the drift zone of the devices (see fig. 4). Nevertheless the fabrication of this structure is complex and requires multiple EPI steps. A proposed cost effective solution is to replace these multiple EPI layer by a single N type layer with deep trenches doped all around by P type implantation [START_REF] Noblecourt | Design and realization of deep trench superjunction diode for 600V applications[END_REF]. Breakdown Voltage depends on the size of the trenches as well as on the fine equilibrium between the N EPI and P implanted dopants. For 600V to 1200V devices, the depth of the trenches must be respectively around 30µm and 70µm with a form factor above 10:1. Doping these structures by BL implantation is thus a challenge and PIII appears to be a good candidate. Nevertheless, the optimal boron dose to allow a good breakdown voltage is around 1E12/cm² and the breakdown voltage is really sensitive to any variation of this dose. To be compatible with this application a dose reproducibility of few E10/cm² is required, which still is a challenge for PIII tools.

III. DOPING APPLICATION EXAMPLES FOR WIDE BAND GAP (SIC & GAN) POWER DEVICES

A. Channel mobility improvement on SiC MOSFET (IBS / CSIC)

SiC MOSFET devices are excellent power devices due to high breakdown electric field, high saturation velocity and high thermal conductivity However, the excellent device characteristics expected from these physical properties have yet not been fully realized, due to the issues related to SiO2/SiC interface, leading in a poor channel effective mobility compared to the conventional crystal face (4H-SiC(0001)). [START_REF] Hiyoshi | SiC High Channel Mobility MOSFET[END_REF]. To reduce the interface state density of SiC/SiO2 interface, some specific treatment as N2O thermal oxidation or phosphorus oxide doping have been developed but some progress still need to be done.

In this study, we used PIII implantation of phosphorus to create a very thin and superficial layer of negative charges just below the gate to repulse the channel carriers from the SiC/SiO2 interface and improve the carrier's mobility.

B. Contact doping doping for SiC (IBS)

P-type doping in SiC is done using Aluminum ion implantation. As diffusion coefficient of Al is SiC is really small, multiple implantations at different energies are needed to obtain the desired doping profile. As the implanters used in SiC manufacturing are 150 mm medium current or high energy tools with limited capability in low energies, implanted profiles generally suffer from a reduced surface concentration BCB leading to a non-optimal contact resistance when surface concentration is lower than some E19/cm 3 [12]. This situation can be efficiently improved by the use of an additional PIII implantation.

This is illustrated on fig 7 where we used PULSION tool to implant Al from TMA plasma on top of beam line multi energy implantations (from 30keV to 180 keV) a 3C-SiC. This allowed us to increase the surface concentration of Al from 2E19/cm 3 to 1E20/cm 3 . Fig. 7. SSRM of a trench-IGBT with PIII implanted trenches.

C. PIII doping for normally-off GaN HEMT (LAAS/IBS)

Compared to silicon power devices, gallium nitride (GaN) High Electron Mobility Transistors (HEMTs) exhibit very interesting properties for power switching (reduced onstate resistance, operation at higher frequencies and temperatures), thus addressing the four difficulties of energy systems that are cooling, weight, bulk and efficiency. The major drawback of conventional HEMTs is that they are normally-on devices, exhibiting negative threshold voltages. However, many power applications require the use of normally-off switches, i.e. switches exhibiting positive threshold voltages.

A solution proposed by Hamady et al. [START_REF] Hamady | P-doped region below the AlGaN/GaN interface for normally-off HEMT[END_REF] consists in introducing a P-doped GaN layer into the UnIntentionally Doped (UID) GaN layer, below the gate electrode, under the AlGaN / GaN interface (see fig. 8). One can note that the Pdoping concentration of GaN has to be compensated on both sides of the gate region by incorporating N-types regions with a sufficiently high doping concentration to restore the electron current flow; without these N-GaN regions, the HEMT would be continuously blocked under the effect of the P-GaN region, whatever the voltage applied to the gate. The fabrication technological process of this new device begins with the realization on a silicon substrate (111) of successive epitaxies of the transition layers, the UID GaN layer and the P-GaN layer. Then comes the key step of the process which is the implantation of donors (silicon atoms) in order to realize the N-type regions. PIII appeared to be more suitable than conventional ion implantation since it allows high doses to be implanted at much lower energies, which reduces the depth of ion penetration and generates fewer defects. Thus, several PIII conditions combining different acceleration voltages (5 and 10 kV) and doses (10 15 and 10 16 cm -2 ) were tested. The measurements confirmed the quality of PIII: the surface roughness remained stable and relatively low at around 1.8 nm RMS and the leakage currents of the devices appeared to be much lower than those of devices realized with conventional BL ion implantation whatever the implantation conditions. The measured threshold voltages of the two devices are respectively -5.5 V for the reference and + 0.8 V for the new HEMT, which allows the experimental validation of the new concept proposed. Not only is the HEMT normally-off -even if the value of + 0.8 V would in practice be insufficient for power applications -but the offset of the threshold voltage, brought about by the introduction of the P-GaN region under the gate, is greater than 6 V, which is remarkable.

IV. MATERIAL MODIFICATION APPLICATION EXAMPLE FOR SIC EPI GROWH IMPROVEMENT

The idea of using high dose carbon implantation into silicon crystal to form a compound semiconductor Silicon Carbide is present in the literature since early 70's [START_REF] Borders | [END_REF]. Several potential advantages of ion implantation over other growth techniques were raised: high purity of crystal and implant; perfect control of implant dose and depth, finally relatively low process temperature. However, added to the fact that required doses were very high for BL implanters, even the most recent literature studies [15] report only about the formation of low structural quality, polycrystalline Silicon Carbide layers.

We investigated the possibility of using PULSION tool with a C2H2 plasma to implant and/or deposit high dose of carbon (from 5E16/cm² to 5e17/cm²) on Si (100) substrate to form Si:C layer and convert it in a well oriented seed for epitaxial growth of 3C-SiC. The carbon treated samples were submitted to high temperature annealing in CVD reactor. Various annealing conditions were tested: atmosphere (flow of pure H2, H2/Ar or pure Ar), temperature (1250°C to 1400°C) and duration of annealing plateau (1min -90min). Each annealing experiment was performed simultaneously on pieces of differently carbon treated substrates and on reference, bare Si (100) wafer. For epitaxy experiments a twostep growth process was applied. It was composed of annealing step followed directly by standard CVD step. The process didn't contain any carbonization (exposition to carbon precursor only) step. Epitaxy experiments were performed simultaneously on carbon treated samples, reference Si wafer and pieces of standard 3C-SiC/Si(100) template. Sample characterization by FTIR, SEM and XRD.

As illustrated on fig 10 and detailed in [START_REF] Zielinski | Novel Carbon Treatment to Create an Oriented 3C-SiC Seed on Silicon[END_REF] we demonstrated that by combining PIII with high temperature annealing and by adjusting the annealing conditions we could tune the amount of created 3C-SiC. The formation of oriented seed under specific PIII / annealing conditions was confirmed by the fabrication of good quality 3C-SiC film on the seed. V. CONCLUSION Thanks to its unique capability to implant high doses at low energy on planar or 3D structures and with high throughput PIII can offer unique and cost effective solutions to solve technical challenges encountered in advanced power devices fabrication. Using implantation of several specifies (B, P, Si, Al and C) on Si, SiC and GaN substrates, we demonstrated the efficiency PULSION ® tool to improve characteristics of these power devices and to allow fabrication of new type of devices.

Fig. 1 .

 1 Fig. 1. Vth and DiBLelectrical results on SFET devices showing best performance (same Vth, lower DIBL) on PIII implanted samples)

Fig. 2 .

 2 Fig. 2. Schematic of trench IGBTs

Fig. 4 .

 4 Fig. 4. Schematic of standard and implanted trenches superjunction structures..Thanks to a collaboration with LAAS/CNRS laboratory, we demonstrated that PULSION implantation of BF3 followed by thermal annealing was efficient to obtain a conformal junction of about 0.8 µm deep around the deep trenches (see fig.5).

Fig. 5 .

 5 Fig. 5. Chemical staining of PULSION implanted P -junction around a deep trench for superjonction application.

  Fig 6 show electrical results obtained on N-SiC MOSFET with N2O thermal gate oxide, with and without this PIII implantation. Phosphorus PIII implant allowed to significantly improve the effective channel mobility and increase the output current.

Fig. 6 .

 6 Fig. 6. Compared forward characteristics and extracted max. effective mobility of SIC MOSFET transistors with 2um channel length : PIII implanted devices show a Drain current about 7x higher than reference devices for the same Drain and Gate voltages explained by a higher channel mobility.

Fig. 8 .

 8 Fig. 8. Schematic cross-section of the new normally-off GaN HEMT proposed by Hamady et al. [13].

Fig. 9 .

 9 Fig. 9. SIMS profiles of silicon implanted GaN using PULSION allowing shallow and high concentration n-type layer above the p-type (Mg doped).

Fig. 10

 10 Fig. 10 shows the transfer characteristics Id(Vgs) on the reference GaN HEMT (conventional normally-on HEMT) and on the new GaN HEMT realized with PIII.

Fig. 10 .

 10 Fig. 10. Experimental transfer characteristics Id(Vgs) @ Vds = 1 V for the conventional normally-on HEMT and the new HEMT: 1st demonstration of a normally-off GaN HEMT thanks to PIII doping.

Fig. 11 .

 11 Fig. 11. SEM images and 3C-SiC(002) rocking curves of 1.3µm and 7µm thick EC-SiC epilayes grown on : a annealed Si(100) substrate, b-PIII treated sample, C 2µm 3C-SiC/Si template.

TABLE I .

 I Sheet resistance values obtained on a 600 nm Poly-Si on SiO2 using PIII Phosphorus and Boron doping followed by optimized annealing process.

Poly Si Doping by PIII for CoolMOS devices PIII Implantation Targeted sheet resistance (Ohm/sq) Lowest obtained sheet resistance (Ohm/sq)

	N type doping with Phosphorus
	PH3 PULSION implantation +	≈ 10 /sq	11.1 .sq
	Annealing
	P type doping with Boron
	BF3 PULSION implantation +	≈ 20 /sq	23.4 /sq
	Annealing

ACKNOWLEDGMENT (Heading 5)

The collaboration work between INFINEON and IBS on Si power devices has been done within the framework of European ENIAC and ECSELprojects EPPL and SEMI40. The collaboration work between LAAS and IBS on superjunction doping has been performed with the support of the French ANR project SUPERSWITCH. The collaboration work between NOVASIC and IBS on EPI growth improvement for 3C-SiC is supported by the European H2020 project CHALLENGE.