Classifications

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  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/77—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate
  • H01L21/78—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices
  • H01L21/7806—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices involving the separation of the active layers from a substrate
  • H01L21/7813—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices involving the separation of the active layers from a substrate leaving a reusable substrate, e.g. epitaxial lift off
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• • C—CHEMISTRY; METALLURGY
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  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
  • C23C16/32—Carbides
  • C23C16/325—Silicon carbide
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  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
  • C30B25/02—Epitaxial-layer growth
  • C30B25/18—Epitaxial-layer growth characterised by the substrate
  • C30B25/20—Epitaxial-layer growth characterised by the substrate the substrate being of the same materials as the epitaxial layer
• • C—CHEMISTRY; METALLURGY
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  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/10—Inorganic compounds or compositions
  • C30B29/36—Carbides
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B31/00—Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor
  • C30B31/20—Doping by irradiation with electromagnetic waves or by particle radiation
  • C30B31/22—Doping by irradiation with electromagnetic waves or by particle radiation by ion-implantation
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  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
  • C30B33/08—Etching
  • C30B33/10—Etching in solutions or melts
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  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02041—Cleaning
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  • H01L21/02104—Forming layers
  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
  • H01L21/02436—Intermediate layers between substrates and deposited layers
  • H01L21/02439—Materials
  • H01L21/02441—Group 14 semiconducting materials
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  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
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  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/76—Making of isolation regions between components
  • H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
  • H01L21/7624—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology
  • H01L21/76251—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology using bonding techniques
  • H01L21/76254—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology using bonding techniques with separation/delamination along an ion implanted layer, e.g. Smart-cut, Unibond

Definitions

• TITLE PROCESS FOR MANUFACTURING A COMPOSITE STRUCTURE INCLUDING A THIN SIC MONOCRISTALLINE SIC LAYER ON A CRYSTALLINE SIC SUPPORT SUBSTRATE
• the present invention relates to the field of semiconductor materials for microelectronic components. It relates in particular to a method of manufacturing a composite structure comprising a thin layer of monocrystalline silicon carbide on a support substrate of crystalline silicon carbide, and in particular poly-crystalline.
• SiC silicon carbide
• Power devices and integrated power supply systems based on single crystal silicon carbide can handle a much higher power density compared to their traditional silicon counterparts, and with smaller active area dimensions.
• Monocrystalline SiC substrates intended for the microelectronics industry nevertheless remain expensive and difficult to supply in large size. It is therefore advantageous to have recourse to thin film transfer solutions, to produce composite structures typically comprising a thin monocrystalline SiC film on a lower cost support substrate.
• a well-known thin film transfer solution is the Smart Cut TM process, based on implantation of light ions and direct bonding assembly. Such a process makes it possible, for example, to manufacture a composite structure comprising a thin layer of monocrystalline SiC (c-SiC), taken from a c-SiC donor substrate, in direct contact with a support substrate of poly-crystalline SiC (p- SiC), and allowing vertical electrical conduction.
• c-SiC monocrystalline SiC
• p- SiC poly-crystalline SiC
• F. Mu et al (ECS Transactions, 86 (5) 3-21, 2018) implement direct bonding, after activation of the surfaces to be assembled by argon bombardment (SAB for “Surface Activation bonding”): such a treatment prior to bonding generates a very high density of pendant bonds, which promote the formation of covalent bonds at the assembly interface, and therefore a high bonding energy.
• SAB surface Activation bonding
• This method nevertheless has the drawback of generating an amorphous layer, on the surface of the monocrystalline SiC donor substrate, which impacts unfavorably the vertical electrical conduction between the thin c-SiC film and the p-SiC support substrate.
• a brittle plane buried in a c-SiC donor substrate delimiting a thin layer between said buried brittle plane and a front surface of the donor substrate, the deposition of a metal layer, for example made of tungsten or molybdenum , on the front surface of the donor substrate to form the support substrate of sufficient thickness to fulfill the role of stiffener,
• the composite structure comprising the metal support substrate and the thin c-SiC layer, and on the other hand, the rest of the c-SiC donor substrate.
• Such a manufacturing process is however not compatible when the material forming the support substrate is p-SiC requiring deposition at temperatures above 1200 ° C. (usual temperatures for the manufacture of p-SiC). Indeed, at these high temperatures, the growth kinetics of the cavities present in the buried fragile plane is faster than the growth kinetics of the p-SiC layer and the thickness required for a stiffening effect is not reached before the appearance of the blistering phenomenon, linked to the deformation of the layer directly above the cavities.
• the present invention relates to an alternative solution to those of the state of the art, and aims to remedy all or part of the aforementioned drawbacks. It relates in particular to a process for manufacturing a composite structure comprising a high quality c-SiC thin layer arranged on a crystalline SiC support substrate.
• the invention relates to a method of manufacturing a composite structure comprising a thin film of monocrystalline silicon carbide disposed on a support substrate of silicon carbide.
• the method comprises: a) a step of providing an initial substrate made of monocrystalline silicon carbide, b) a step of growing by epitaxy of a donor layer of monocrystalline silicon carbide on the initial substrate, to form a donor substrate, the donor layer having a density of crystalline defects lower than that of the initial substrate, c) a step of ion implantation of light species in the donor layer, to form a buried fragile plane delimiting the thin layer between said buried fragile plane and a free surface of said donor layer, d) a step of forming a silicon carbide support substrate on the free surface of the donor layer, comprising a deposition at a temperature between 400 ° C and 1100 ° C, and defining a non- interface insulating between the donor layer and the support substrate, e) a separation step along the buried fragile plane, to form on the one hand the
• step d) is carried out at a temperature between 600 ° C and 900 ° C, or even preferably between 700 ° C and 800 ° C, and is based on a chemical vapor deposition technique or a technique sintering or a liquid phase deposition technique of a ceramic powder solution;
• step d) is a chemical vapor deposition assisted by direct liquid injection
• step d) is a chemical vapor deposition at low pressure or plasma assisted
• step d) • the deposition of step d) is carried out at a speed greater than 10 microns / hour, or even preferably greater than 50 microns / hour; • at the end of the deposition of step d), the support substrate has a thickness greater than or equal to 50 microns, or even a thickness greater than or equal to 100 microns;
• step a) comprises the formation, on the initial substrate, of a monocrystalline conversion layer, to convert defects of the dislocation type of the basal plane of the initial substrate into defects of the through wedge dislocation type;
• step b) of growth by epitaxy is carried out at a temperature above 1200 ° C, preferably between 1500 ° C and 1650 ° C;
• the light species implanted during step c) are chosen from hydrogen and / or helium;
• separation step e) is carried out at a temperature greater than or equal to the temperature of the deposit of step d);
• separation step e) is carried out by applying a mechanical stress to a stack comprising the support substrate integral with the donor substrate;
• step f) comprises simultaneous mechanical-chemical polishing of a front face and a rear face of the composite structure
• the process comprises a heat treatment step at a temperature between 1000 ° C and 1800 ° C, before or after step f);
• the method comprises a second step g) of growth by epitaxy of an additional layer of monocrystalline silicon carbide on the thin layer of the composite structure;
• the method comprises a step of reconditioning the remainder of the donor substrate with a view to reuse as an initial substrate or as a donor substrate;
• FIG. 1 shows a composite structure produced according to a manufacturing process according to the invention
• FIG. 2g Figures 2a to 2g show steps of a manufacturing process according to the invention
• FIG. 3b Figures 3a and 3b show steps of a manufacturing process according to the invention.
• the same references in the figures may be used for elements of the same type.
• the figures are schematic representations which, for the sake of readability, are not to scale.
• the thicknesses of the layers along the z axis are not to scale with respect to the lateral dimensions along the x and y axes; and the relative thicknesses of the layers between them are not necessarily respected in the figures.
• the present invention relates to a method of manufacturing a composite structure 1 comprising a thin layer 10 of monocrystalline silicon carbide disposed on a support substrate 20 of silicon carbide (FIG. 1).
• the support substrate 20 is crystalline, and advantageously poly-crystalline (“p-SiC” will be used subsequently by speaking of poly-crystalline SiC).
• the method firstly comprises a step a) of providing an initial substrate 11 made of monocrystalline silicon carbide (FIG. 2a).
• c-SiC will be used to refer to monocrystalline silicon carbide.
• the initial substrate 11 is preferably in the form of a wafer with a diameter of 100mm or 150mm or even 200mm and a thickness typically between 300 and 800 microns. It has a front face 11a and a rear face 11b.
• the surface roughness of the front face 11a is advantageously chosen to be less than 1 nm Ra, average roughness ("average roughness" according to English terminology) measured by atomic force microscopy (AFM) on a scan of 20 microns x 20 microns .
• the method then comprises a step b) of growth by epitaxy of a donor layer 110 of monocrystalline silicon carbide on the initial substrate 11, to form a donor substrate 111 (FIG. 2b).
• the epitaxy growth step is carried out so that the donor layer 110 has a density of crystal defects lower than that of the initial substrate 11.
• the initial substrate 11 in c-SiC is of polytype 4H or 6H, exhibiting a disorientation ("offcut") less than 4.0 ° with respect to the crystallographic axis ⁇ 11-20> ⁇ 0.5 ° , and a density of through dislocations (“Micropipes”) less than or equal to 5 / cm 2 , or even less than 1 / cm 2 .
• N-type doped (nitrogen) it has a resistivity preferably between 0.015 ohm.cm and 0.030 ohm.cm.
• an initial substrate 11 having a low density of defects of the basal plane dislocation or BPD type typically less than or equal to 3000 / cm 2 .
• C-SiC substrates having BPD densities of the order of 1500 / cm 2 are reasonably available, which facilitates their supply.
• the donor layer 110 from which the thin c-SiC layer 10 of the composite structure 1 will be formed at the end of the process of the present invention, has a higher crystalline quality than that of the initial substrate 11. , to meet the required specifications of the vertical components intended to be produced on said thin film 10.
• different types of extended defects are present in a c-SiC layer or substrate. These widespread faults can affect the performance and reliability of components.
• BPD type defects are killers for bipolar components: indeed, a Shockley or SSF type stacking defect (for “Shockley stacking fault”) is extended from the dislocation when the recombination energy d 'an electron-hole pair is available. The expansion of an SSF stacking defect within the active region of the component results in an increase in the on resistance of the component.
• the c-SiC donor layer 110 is therefore produced so as to have a BPD type defect density of less than or equal to 1 / cm 2 .
• step b) of growth by epitaxy is carried out at a temperature above 1200 ° C, preferably between 1500 ° C and 1650 ° C.
• the precursors used are monosilane (SiH4), propane (C3H8) or ethylene (C2H4); the carrier gas may be hydrogen with or without argon.
• the low rate of BPD defects in the donor layer 110 is obtained by favoring the conversion of the BPD defects present in the initial substrate 11 into through-wedge dislocations or TED (for “Threading Edge Dislocations”).
• step a) comprises the formation of a monocrystalline conversion layer 13, preferably in c-SiC, to maximize the conversion of BPD type defects of the initial substrate 11 into TED type defects (FIG. 3a).
• a monocrystalline conversion layer 13 preferably in c-SiC
• Step b) then consists in carrying out the epitaxial growth of the donor layer 110 on said conversion layer 13 (FIG. 3b).
• a c-SiC donor layer 110 having a BPD-type defect density less than or equal to 1 / cm 2 or even less than 0.1 / cm 2 .
• the probability of bipolar degradation (probability of a hole arriving below the BPD / TED conversion point) at the end of the process according to the present invention is negligible ( ⁇ 0.1%), the monocrystalline conversion layer 13 n ' being not intended to be transferred into the composite structure 1.
• a recombination layer (doped with nitrogen beyond 1 E 18 at / cm 3 ).
• This layer can, at the cost of a thickness of 10ym and a concentration greater than 5 E 18 / cm 3 , reduce the probability of the presence of holes to 0.1% compared to the basic structure not comprising this layer. recombination.
• the monocrystalline conversion layer 13 not being transferred, the probability that a hole reaches the nucleation point of bipolar degradation (BPD - TED conversion point or any BPD point) is at least less than 0.1% or even close to 0%.
• step b) of growth by epitaxy could be carried out prior to the removal.
• the manufacturing method according to the invention further comprises a step c) of ionic implantation of light species in the donor layer 110, to a determined depth representative of the thickness of thin layer 10 desired and in all the cases not reaching the initial substrate 11 (and / or the conversion layer 13, when the latter is present).
• This implantation generates a brittle plane buried 12 in the donor layer 110 which delimits the thin layer 10 between said buried brittle plane 12 and a free surface 11a of said donor layer 110 (FIG. 2c).
• the light species implanted are preferably hydrogen, helium or a co-implantation of these two species. As is well known with reference to the Smart Cut TM process, these light species will form, around the depth determined, microcavities distributed in a thin layer parallel to the free surface 11a of the donor layer 110, that is to say parallel to the plane (x, y) in the figures. This thin layer is called the buried fragile plane 12, for the sake of simplicity.
• the implantation energy of the light species is chosen so as to reach the determined depth in the donor layer 110.
• hydrogen ions will be implanted at an energy of between 10 keV and 250 keV, and at a dose of between 5 E 16 / cm2 and 1 E 17 / cm2, to delimit a thin layer 10 having a thickness of the order of 100 to 1500 nm.
• a protective layer may be deposited on the free face of the donor layer 110, prior to the ion implantation step.
• This protective layer can be composed of a material such as silicon oxide or silicon nitride for example.
• the method according to the invention then comprises a step d) of forming a support substrate 20 of crystalline silicon carbide on the free surface of the donor layer 110 (FIG. 2d).
• This step d) comprises a deposition at a temperature between 400 ° C and 1100 ° C.
• the deposition of step d) is carried out at a temperature between 600 ° C and 900 ° C, or even preferably between 700 ° C and 800 ° C.
• step d) defines a non-insulating interface between donor layer 110 and support substrate 20.
• step d) is carried out so that the interface between donor layer 110 and the support substrate 20 is electrically conductive: the aim will be a specific resistance of the interface typically less than 1 mohm.cm 2 , or even less than 0.1 mohm.cm 2 .
• a removal of the native oxide present on the free face of the donor layer 110 is carried out by HF deoxidation (hydrofluoric acid), wet or dry.
• an overdoping of the first nanometers deposited from the support substrate 20 could promote the electrical conductivity of the interface between the donor layer 110 and the support substrate 20.
• cleaning sequences are applied to the donor substrate 111 to remove all or part of particulate, metallic or organic contaminants potentially present on its free faces.
• step d) The deposition of step d) can be carried out by different techniques.
• the shaping of the support substrate 20 can be carried out by a sintering technique.
• a Sic powder is compacted at high temperature under high pressure. It is thus possible to obtain solid ceramic layers.
• the sintering is carried out directly on the implanted donor substrate 111, in order to obtain, at the end of the sintering, a support substrate 20 which is thick and adheres to the donor layer 110. It is essential that the sintered material (support substrate 20) achieves sufficient cohesion to allow the following separation step e), described below. It is therefore necessary to lower the sintering temperature of the Sic powder below this separation temperature. For this, either conventional additives such as boron, carbon or AIN are used, or Sic nanopowders are used.
• the shaping of the support substrate 20 can be carried out by a technique of deposition in the liquid phase of a solution of ceramic powder.
• a preceramic polymer material PDC, for "polymer derived ceramics ”
• SiC ceramic powder
• a viscous solution is obtained which can be deposited in the form of a layer by spreading, coating by centrifugation (“spin-coating”) or molding.
• Low temperature annealing ⁇ 200 ° C
• the shaping of the support substrate 20 is therefore effective at low temperature.
• anneals at higher temperatures allow pyrolysis of the polymer.
• the material obtained is then a pure ceramic.
• the ceramic fillers are powdered SiC and the PDC from molecules of the family of polycarbosilanes or polyorganosilicones (to obtain SiC) and polyorganosilazanes (to obtain SiCN).
• the deposition of step d) can be carried out by a chemical vapor deposition technique (CVD, for “Chemical vapor deposition”).
• CVD chemical vapor deposition
• the deposition can be carried out by a thermal CVD technique such as deposition at atmospheric pressure (APCVD for “atmospheric pressure CVD) or at low pressure (LPCVD for“ low pressure CVD ”).
• APCVD atmospheric pressure
• LPCVD low pressure CVD
• the precursors can be chosen from methylsilane, dimethyldichlorosilane or alternatively dichlorosilane + i-butane.
• the deposition can either be a plasma-assisted CVD technique (PECVD for “plasma enhanced CVD”), for example with silicon tetrachloride and methane as precursors.
• PECVD plasma-assisted CVD
• the frequency of the source used to generate the electric discharge creating the plasma is of the order of 3.3 MHz, and more generally between 10 kHz and 100 GHz.
• the deposition of step d) can also be based on a chemical vapor deposition technique assisted by direct liquid injection (DLI-CVD, for "Direct Liquid Injection - CVD ”).
• DLI-CVD direct liquid injection
• a technique provides good yields between the materials (precursors) supplied and the thicknesses of deposit achieved, without the need to use chlorinated precursors, which limits costs and environmental constraints.
• the DLI-CVD deposition uses a disilanebutane precursor or a polysilylethylene precursor, said precursor being pure or diluted.
• Such a technique is described in the thesis of Guilhaume Boisselier (2013, “Chemical vapor deposition of chromium, silicon and hafnium carbides assisted by pulsed liquid injection”), for applications of depositing ceramic coatings on parts. , to protect them during treatment at very high temperatures, for example metal parts made of steel or alloys.
• the Applicant has developed a deposition step d) based on the DLI-CVD technique for an entirely different application, namely the formation of an SiC support substrate 20 on a c-SiC donor layer 110, in order to manufacture a composite substrate intended for the microelectronics field.
• the parameters of the deposition (for example, pressure of 6.7 kPa, temperature between 700 ° C and 850 ° C) are determined so that the support substrate 20 exhibits good electrical conductivity, that is to say between 0.015 and 0.03 ohm.cm, a high thermal conductivity, i.e. greater than or equal to 200 Wm _1 .K _1 and a coefficient of thermal expansion similar to that of thin film 10, i.e. typically between 3.8 E -6 / K and 4.2 E -6 / K at room temperature.
• the support substrate 20 can, for example, have the following structural characteristics: poly-crystalline structure, grains of 3C SiC type, oriented 111, of average size 1 to 10ym, N-type doping for a final resistivity less than or equal. at 0.03 ohm.cm.
• the deposition by CVD is carried out at a speed greater than 10 microns / hour, or even greater than 50 microns / hour, or even greater than 100 microns / hour.
• the support layer 20 has a thickness greater than or equal to 50 microns, or even a thickness greater than or equal to 100 microns.
• the stack 211 resulting from step d) comprises the support substrate 20 placed on the donor layer 110, itself placed on the initial substrate 11.
• the method according to the present invention then comprises a step e) of separation along the buried fragile plane 12, to form on the one hand the composite structure 1 and on the other hand the remainder of the donor substrate 111 ′ (FIG. 2e).
• the separation step e) is carried out by applying a heat treatment to the stack 211, at a separation temperature greater than or equal to the temperature of the deposit of step d).
• the microcavities present in the buried fragile plane 12 follow a growth kinetics until the initiation of a fracture wave which will propagate over the entire extent of the buried fragile plane 12 and cause the separation between the structure. composite 1, and the rest of the initial substrate 111 '.
• the temperature may be between 950 ° C and 1200 ° C, depending on the implantation conditions of step c).
• the separation step e) is carried out by applying a mechanical stress to the stack 211.
• the stress could for example be exerted by the insertion of a tool (eg: blade shaver) near the buried fragile plane 12.
• the separation stress may be of the order of a few GPa, preferably greater than 2GPa.
• a step e) of separation along the buried fragile plane 12 takes place during or directly at the end of step d) of forming the support substrate 20, in particular when the temperatures deposits at this stage are in the range 800 ° C - 1100 ° C.
• the free face 10a of the thin layer 10 of the composite structure 1 has a surface roughness of between 5 and 100 nm RMS (by measurement at atomic force microscope (AFM), on scans of 20 microns x 20 microns).
• the method according to the invention therefore comprises a step f) of mechanical and / or chemical treatment (s) of the composite structure 1, to smooth the free surface 10a of the thin layer 10 and to correct the uniformity of thickness of the composite structure 1 (figure 2f).
• Step f) can therefore comprise a chemical-mechanical polishing (CMP) of the free face 10a of the thin layer 10, typically with a material shrinkage of the order of 50 nm to 1000 nm, so as to obtain a roughness final less than 0.5 nm Rms (on an AFM field of 20x20ym), or even less than 0.3 nm.
• Step f) can also comprise a chemical or plasma treatment (cleaning or etching), for example a cleaning of the SC1 / SC2 (Standard Clean 1, Standard Clean 2) and / or HF (hydrofluoric acid) type, or an N2 plasma. , Ar, CF4, etc., to further improve the quality of the free face 10a of the thin layer 10.
• CMP chemical-mechanical polishing
• step f) can comprise a chemical-mechanical polishing (CMP) and / or a chemical treatment (etching or cleaning) and / or a mechanical treatment (rectification) of the rear face 20b of the support substrate 20; this in order to improve the uniformity of thickness of said support substrate 20 as well as its roughness on the rear face 20b.
• CMP chemical-mechanical polishing
• etching or cleaning etching or cleaning
• rectification mechanical treatment
• step f) can comprise a chemical-mechanical polishing (CMP) and / or a chemical treatment (etching or cleaning) and / or a mechanical treatment (rectification) of the rear face 20b of the support substrate 20; this in order to improve the uniformity of thickness of said support substrate 20 as well as its roughness on the rear face 20b.
• Roughness less than 0.5 nm RMS by atomic force microscope (AFM) measurement, on fields of 20 microns x 20 microns
• AFM atomic force microscope
• Polishing or rectifying the edges of the composite structure 1 may also be carried out during this step f) in order to make the shape of its circular contour and of the edge drop compatible with the requirements of microelectronic manufacturing processes.
• step f) of mechanical-chemical treatment comprises simultaneous polishing (CMP) of a front face 10a and a rear face 20b of the composite structure 1, in order to smooth and improve the uniformity. thickness of said structure 1.
• the polishing parameters may be different between the front face and the rear face, the smoothing of a c-SiC surface and a p-SiC surface usually requiring different consumables.
• the mechanical component of the polishing is favored for the rear face 20b when the support substrate 20 is made of p-SiC, in order to limit the preferential attack of the grain boundaries by the chemical component of the polishing.
• the polishing parameters such as the speed of rotation (polishing head and plate), the pressure, the concentration and the physical properties of the abrasives (ie diameter of diamond nanoparticles between around ten nm and lym) , can be modified to accentuate the mechanical component.
• a step f ′) of heat treatment at a temperature of between 1000 ° C and 1800 ° C, for approximately one hour and up to a few hours, is operated before or after step f).
• the objective of this step is to stabilize the composite structure 1, by changing, if necessary, the crystalline configuration of the support substrate 20, so that the structure 1 is compatible with subsequent heat treatments at high temperatures, required for the fabrication of components on the thin film 10.
• the method according to the invention can comprise a second step g) of growth by epitaxy of an additional layer 10 ′ of monocrystalline silicon carbide on the thin layer 10 of the composite structure 1 (FIG. 2g).
• a second step g) of growth by epitaxy of an additional layer 10 ′ of monocrystalline silicon carbide on the thin layer 10 of the composite structure 1 (FIG. 2g).
• Such a step is applied when a relatively large thickness of useful layer 100 is necessary for the manufacture of components, typically of the order of 5 to 50 microns.
• the epitaxy conditions can optionally be chosen similar to those of step b), preferably at a lower temperature so as to limit the stresses induced in the useful layer 100 (corresponding to the assembly of thin layer 10 and additional layer 10 ′ ) due to the composite structure 1.
• the manufacturing process can comprise a step of reconditioning the remainder 111 ′ of the donor substrate with a view to reuse as initial substrate 1 or as donor substrate 111.
• a reconditioning step is based on one or more. treatments of the face 110'a (FIG. 2e), by chemical mechanical polishing of the surface or of the edges, and / or by mechanical grinding, and / or by dry or wet chemical etching.
• the thickness of the donor layer 110 formed in step b) is defined so that the remainder 111 ′ of the donor substrate 111 can be reused at least twice as donor substrate 111.
• care will be taken to keep said layer intact, that is to say to always keep a portion of donor layer 10 on it. the rest 111 'of the donor substrate.
• the portion of donor layer 10 is insufficient for the production of a composite structure 1, only the step of growth by epitaxy of donor layer 10 is necessary and not the prior step of growth of the conversion layer 13. .
• the initial substrate 11 supplied in step a) of the manufacturing process is a wafer of c-SiC, of polytype 4H, of orientation 4.0 ° with respect to the axis ⁇ ll -20> ⁇ 0.5 ° , diameter 150mm and thickness 350ym.
• the growth is carried out in an epitaxy chamber, at a temperature of 1650 ° C, with precursors such as monosilane (Si.H4) and propane (C3H8) or ethylene (C2H4), generating the donor layer 110 in c-SiC 30 microns thick (growth rate: 10 microns / h).
• the donor layer has a BPD defect density of the order of 1 / cm 2 .
• the implantation of hydrogen ions is carried out at an energy of 150 keV and a dose of 6 E 16 H + / cm 2 , through the free surface of the donor layer 110.
• a buried fragile plane 12 is thus created at a depth of d 'approximately 800 nm in the initial substrate 11.
• a cleaning sequence of the RCA + Caro type is carried out on the donor substrate 111, so as to eliminate the potential contaminations on the free face of the donor layer 110.
• a DLI-CVD deposit is carried out on the donor layer 110, at a temperature of 850 ° C., with the precursor disilanebutane (DSB), under a pressure of 6.7 kPa, for 7 minutes, so as to reach a thickness of at minus 10 microns for the support substrate 20. Under these conditions, the support substrate 20 is polycrystalline.
• DSB disilanebutane
• Annealing at 1000 ° C. is then applied to the stack 211 for 50 minutes, and the separation takes place at the level of the fragile buried plane 12 during said annealing.
• the composite structure 1 formed by the thin layer 10 and the support substrate 20 is separated from the remainder 111 ′ of the donor substrate.
• a double-sided polishing is carried out to restore the surface roughness of the thin layer 10 and of the rear face of the support substrate 20.
• the initial substrate 11 supplied in step a) of the manufacturing process is a wafer of c-SiC, of polytype 4H, of orientation 4.0 ° with respect to the axis ⁇ ll -20> ⁇ 0.5 ° , diameter 150mm and thickness 350ym.
• the formation of the conversion layer 13 is carried out in an epitaxy chamber. Before the start of growth epitaxial of this layer 13 on the initial substrate 11, annealing under hydrogen is carried out in the chamber at a temperature of 1700 ° C., for a period of 10 min to 20 min. The epitaxial growth of the conversion layer 13 into c-SiC is then carried out at a temperature of 1650 ° C, with precursors such as monosilane (SiH4) and propane (C3H8) or ethylene (C2H4), and a growth rate of about 6 microns / h, reaching 1 micron thick. The C / Si ratio resulting from the gaseous precursors is maintained around a value close to 1, typically between 0.95 and 1.05.
• precursors such as monosilane (SiH4) and propane (C3H8) or ethylene (C2H4)
• the growth of the donor layer 110 in c-SiC is carried out at a temperature of 1650 ° C, with the same precursors but by adjusting the C / Si ratio around a value of 1.2 or significantly higher.
• the overall throughput of the precursors is increased relative to the throughputs implemented for the growth of the conversion layer 13, for example, the throughputs are doubled.
• a donor layer 10 30 microns thick is obtained after about 180 min (growth rate: 10 microns / h).
• the donor layer 10 has a BPD defect density of the order of or even less than 1 / cm 2 .
• the implantation of hydrogen ions is carried out at an energy of 150 keV and a dose of 6 E 16 H + / cm 2 , through the free surface of the donor layer 110.
• a buried fragile plane 12 is thus created at a depth of d 'approximately 800 nm in the initial substrate 11.
• a cleaning sequence of the RCA + Caro type is applied to the donor substrate 111, so as to eliminate the potential contaminations on the free face of the donor layer 110.
• a PECVD deposition is carried out on the donor layer 110, at a temperature of 800 ° C., in an SiC14 / CH4 / Ar atmosphere, with a frequency for generating the plasma of 3.3 MHz; the pressure in the deposition chamber is adjusted so as to achieve a deposition rate of the order of 300 microns / h for the support substrate 20.
• the deposition rate should not be too high to limit the roughness after deposition of the free surface of the support substrate 20. Under these conditions, the support substrate 20 is polycrystalline.
• Annealing at 1100 ° C. is then applied to the stack 211 for 50 min, and the separation takes place at the level of the brittle plane buried 12 during said annealing.
• the composite structure 1 formed by the thin layer 10 and the support substrate 20 is separated from the remainder 111 ′ of the donor substrate.
• a double-sided polishing is carried out to restore the surface roughness of the thin layer 10 and of the rear face 20b of the support substrate 20.

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