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  • H10P90/00—Preparation of wafers not covered by a single main group of this subclass, e.g. wafer reinforcement
• • H—ELECTRICITY
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  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/20—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials
  • H10P14/34—Deposited materials, e.g. layers
  • H10P14/3402—Deposited materials, e.g. layers characterised by the chemical composition
  • H10P14/3404—Deposited materials, e.g. layers characterised by the chemical composition being Group IVA materials
  • H10P14/3408—Silicon carbide
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  • H10P90/00—Preparation of wafers not covered by a single main group of this subclass, e.g. wafer reinforcement
  • H10P90/19—Preparing inhomogeneous wafers
  • H10P90/1904—Preparing vertically inhomogeneous wafers
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  • H10P10/00—Bonding of wafers, substrates or parts of devices
  • H10P10/12—Bonding of semiconductor wafers or semiconductor substrates to semiconductor wafers or semiconductor substrates
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  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/20—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials
  • H10P14/24—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials using chemical vapour deposition [CVD]
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  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/20—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials
  • H10P14/29—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials characterised by the substrates
  • H10P14/2901—Materials
  • H10P14/2902—Materials being Group IVA materials
  • H10P14/2903—Carbon, e.g. diamond-like carbon
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  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/20—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials
  • H10P14/29—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials characterised by the substrates
  • H10P14/2901—Materials
  • H10P14/2902—Materials being Group IVA materials
  • H10P14/2904—Silicon carbide
• • H—ELECTRICITY
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  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/20—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials
  • H10P14/32—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials characterised by intermediate layers between substrates and deposited layers
  • H10P14/3202—Materials thereof
  • H10P14/3204—Materials thereof being Group IVA semiconducting materials
  • H10P14/3208—Silicon carbide
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  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/20—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials
  • H10P14/34—Deposited materials, e.g. layers
  • H10P14/3402—Deposited materials, e.g. layers characterised by the chemical composition
  • H10P14/3404—Deposited materials, e.g. layers characterised by the chemical composition being Group IVA materials
  • H10P14/3406—Carbon, e.g. diamond-like carbon
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  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P90/00—Preparation of wafers not covered by a single main group of this subclass, e.g. wafer reinforcement
  • H10P90/19—Preparing inhomogeneous wafers
  • H10P90/1904—Preparing vertically inhomogeneous wafers
  • H10P90/1906—Preparing SOI wafers
  • H10P90/1914—Preparing SOI wafers using bonding
  • H10P90/1916—Preparing SOI wafers using bonding with separation or delamination along an ion implanted layer, e.g. Smart-cut
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  • H10W10/00—Isolation regions in semiconductor bodies between components of integrated devices
  • H10W10/10—Isolation regions comprising dielectric materials
  • H10W10/181—Semiconductor-on-insulator [SOI] isolation regions, e.g. buried oxide regions of SOI wafers

Definitions

• TITLE METHOD FOR MANUFACTURING A SUPPORT SUBSTRATE FROM
• the present invention relates to the field of semiconductor materials for microelectronic components. It relates in particular to a process for manufacturing a polycrystalline silicon carbide support substrate, particularly suitable for producing a composite structure comprising a thin layer of monocrystalline silicon carbide placed on said support substrate.
• SiC is increasingly widely used for the manufacture of innovative power devices, to meet the needs of rising areas of electronics, such as electric vehicles.
• power devices and integrated power systems based on monocrystalline silicon carbide can handle much higher power density compared to their traditional silicon counterparts, and this with smaller active area dimensions.
• c-SiC monocrystalline SiC
• p-SiC Polycrystalline SiC
• the document US2019153616 proposes a process for manufacturing a p-SiC support substrate on which a thin c-SiC layer can be transferred.
• the support substrate comprises grains of average size of the order of 10 ⁇ m and has a grain size variation rate between its front and rear faces, reduced to its thickness, of less than or equal to 0.43%; this last characteristic makes it possible to limit the residual stress in the support substrate and therefore its curvature.
• the manufacturing process involves a first base carbon substrate on which a thick layer (typically 2mm) of p-SiC is produced by chemical vapor deposition.
• a second p-SiC base substrate about 350 ⁇ m thick, is extracted from the thick layer of p-SiC, by removing the first carbon base substrate and by mechanically thinning the two faces of the thick layer.
• the second base substrate has a grain size variation rate between its front and rear faces, reduced to its thickness, of less than or equal to 0.43%.
• a new layer of p-SiC (typically of the order of 400 ⁇ m) is then formed by chemical vapor deposition on the second base substrate: separated from the second base substrate, for example by laser irradiation, this new layer of p -SiC constitutes the support substrate in p-SiC intended to be used in a composite structure.
• the second base substrate can then be reused.
• the step consisting in forming the second base substrate can prove to be complex because the removal of the first carbon base substrate generally induces a very significant curvature of the thick p-SiC layer, which can cause the breakage of said thick layer, or at least which complicates or even prevents the performance of the thinning step required to reach the thickness of the second base substrate.
• this thinning is very substantial (of the order of 1.5 mm) and expensive in p-SiC material and in deposition and thinning steps.
• the present invention proposes a manufacturing process addressing the aforementioned problem. It relates to a process for manufacturing a support substrate in polycrystalline SiC, which is economical and simplified. Said support substrate is also particularly suitable for the manufacture of a composite structure comprising a thin c-SiC layer placed on said p-SiC support substrate.
• the invention relates to a process for manufacturing a support substrate in polycrystalline silicon carbide comprising the following steps: a) the growth of an initial substrate in polycrystalline silicon carbide on a seed in graphite or in silicon; at the end of step a), the initial substrate having a free front face and a rear face in contact with the seed, b) the formation of a carbon stiffening film, on the front face of the initial substrate, the initial substrate having, in the plane of its front face and just before the formation of the stiffening film, a first average size of silicon carbide grains, c) the removal of the seed, so as to free the rear face of the initial substrate, this last presenting, in the plane of its face behind and just after the removal of the seed, a second average size of silicon carbide grains, smaller than the first average size, d) the thinning of the rear face of the initial substrate, down to a thickness for which the initial substrate has, in the plane of its thinned rear face, a third average grain size equal to the first average grain size to within
• the stiffening film has a thickness between lOOnm and several millimeters, for example 10mm;
• the stiffening film has a thickness of between 100 nm and 10 ⁇ m;
• the carbon stiffening film has a crystallographic structure of the diamond type or of the vitreous carbon type
• step b) is carried out by spreading a polymer resin comprising carbon-carbon bonds preformed in three dimensions, in the form of a viscous layer, on the front face of the initial substrate, and by annealing at a temperature between 500 °C and 2000°C, to form the stiffening carbon film;
• the polymer resin is based on coal tar, phenol formaldehyde, polyfurfuryl alcohol, polyvinyl alcohol, polyacrylonitrile, polyvinylidene chloride, and/or polystyrene;
• step b) is carried out by plasma deposition, deposition by ion bombardment or evaporation deposition; • the manufacturing process comprises a step a'), between step a) and step b), of grinding the front face and/or a perimeter of the initial substrate, to reduce a surface roughness of said face and/or a variation in thickness of said substrate, and/or to regularize its periphery;
• step a′ comprises mechanical or mechano-chemical thinning
• the manufacturing process comprises: a step e), after step d), of removing the stiffening film, and/or
• step d or after step e), of heat treatment at a temperature greater than or equal to 1500°C.
• the invention also relates to a method for manufacturing a composite structure, implementing the above method and further comprising a step f) of transferring a thin layer of monocrystalline silicon carbide onto a first or onto a second face of the support substrate, directly or via an intermediate layer, to form the composite structure.
• the intermediate layer is formed by the carbon stiffening film retained on the first face of the support substrate
• the transfer of the thin layer is carried out on one of the faces of the support substrate and an additional carbon film is placed on the other free face of the support substrate prior to the transfer; • the additional film is removed, preferably after the composite structure has undergone all heat treatments at temperatures above 1400° C. required for its manufacture or that of components on and/or in said structure.
• FIG. 2d Figures 2a to 2d show other steps of the manufacturing method according to the invention.
• FIG. 3e Figures 3a to 3e show variants of steps of the 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 purpose 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 observed in the figures.
• the present invention relates to a method of manufacturing a support substrate 10 made of polycrystalline silicon carbide (p-SiC).
• the method firstly comprises a step a) of growing an initial substrate 1 of polycrystalline silicon carbide on a seed 2 of low quality graphite or monocrystalline or polycrystalline silicon carbide (FIG. la).
• the seed 2 is preferably in the form of a wafer whose diameter is substantially that which is targeted for the support substrate 10, for example 100mm, 150mm, 200mm or even 300mm.
• the growth of the initial p-SiC substrate 1 is carried out by a known technique of chemical vapor deposition (CVD), at a temperature typically between 1100° C. and 1500° C.
• the precursors can be chosen from methylsilane, dimethyldichlorosilane or even dichlorosilane and i-butane, preferably with a C/Si ratio close to or greater than 1.
• doping species such as nitrogen or phosphorus, for example
• the doping levels usually targeted are greater than 1E18/cm 3 , or even greater than 1E20/cm 3 .
• the initial substrate 1 has a free front face and a rear face 1b in contact with the seed 2.
• the thickness of the initial substrate 1 is less than 1 mm, preferably less than 550 ⁇ m. It should be noted that the range of thicknesses usually desired, for a support substrate 10 intended for the development of a composite structure, is 100 ⁇ m-500 ⁇ m.
• the initial substrate 1 may comprise silicon carbide grains of the 4H, 6H and/or 3C type, depending on the CVD deposition conditions.
• the average size of the grains at the level of the rear face 1b of the initial substrate 1 is relatively small, typically less than or equal to 1 ⁇ m, or even less than or equal to 100 nm; said grains correspond to the p-SiC material produced at the start of CVD deposition (nucleation phase) on the graphite seed 2.
• the size of a grain, delimited by the grain boundaries corresponds to the largest dimension of said grain, in the plane of the considered face of the substrate.
• the mean size of the grains is defined by the mean of the sizes of the different grains in said plane.
• SEM scanning electron microscopy
• EBSD electron diffraction
• X-ray crystallography When the face considered mainly comprises grains of micrometric size (typically from a few microns to a few tens of microns), very small grains, typically less than 50 nm, are preferentially excluded from the measurement, to limit measurement uncertainties.
• the p-SiC grains increase in size, until they reach a relatively stable average size, for a deposition thickness which can vary between a few micrometers and a few tens of micrometers, depending on the conditions of deposit.
• the average size of the grains at the level of the front face of said substrate 1 may typically vary between 1 and 10 ⁇ m.
• the average size of the p-SiC grains at the level of the front face 1a of the initial substrate 1 will be called the first average size
• the average size of the p-SiC grains at the level of the rear face 1b of the initial substrate 1 will be called second medium size.
• the first average size of the p-SiC grains (front face side 1a) is greater than the second average grain size (rear face side 1b), the latter corresponding to the nucleation phase.
• the manufacturing method then comprises a step b) of forming a carbon stiffening film 3, on the front face 1a of the initial substrate 1 (FIG. 1b).
• the stiffening film 3 can have a thickness ranging from 100 nm to several millimeters, for example 10 mm. Preferably, its thickness is between 100 nm and 10 ⁇ m.
• the carbon stiffening film 3 has a crystallographic structure of the diamond type, that is to say comprising sp3 carbon-carbon atomic bonds, or glassy carbon type, comprising carbon-carbon sp2 atomic bonds.
• the stiffening film 3 can be formed by various conventional deposition techniques, such as in particular plasma deposition, deposition by ion bombardment or even deposition by evaporation.
• step b) can be carried out by spreading a polymer resin comprising carbon-carbon bonds preformed in three dimensions, in the form of a viscous layer, on the front face 1a of the initial substrate 1. This spreading can be carried out by centrifugation. Then, annealing is applied at a temperature between 500° C. and 2000° C., typically between 600° C. and 1100° C., under nitrogen, to form the carbon stiffening film 3, by chemical decomposition of the resin (pyrolysis) . The temperature ramps are typically chosen on the order of 10° C./min and the duration of the annealing is on the order of an hour. The temperature rise is controlled so that the effective temperature remains below the resin/carbon glass transition temperature.
• the polymeric resin can be formed from coal tar, phenol formaldehyde, polyfurfuryl alcohol, polyvinyl alcohol, polyacrylonitrile, polyvinylidene chloride, and/or polystyrene, etc.
• photosensitive resins can be used, such as the commercial products AZ-4330, AZ-P4620 (registered trademarks) (based on l-methoxy-2-propanol acetate, diazonaphthoquinonesulf onic esters, 2-methoxy -l- propanol acetate, Cresol novolak resin), OCG-825 (based on ethyl-3-ethoxypropionate), SU-8 2000 (based on cyclopentanone, triarylsulfonium/hexafluoroantimonate salts, propylene carbonate, epoxy resin), usually implemented for photolithography steps in the field of microelectronics.
• commercial products AZ-4330, AZ-P4620 registered trademarks
• OCG-825 based on ethyl-3-ethoxypropionate
• SU-8 2000 based on cyclopentanone, triarylsulfonium/hexafluoroantimonate salts, propylene carbon
• Epoxy resins such as for example the Epoxy Novolac EPON product (registered trademark), offered to cover and protect different surfaces in various fields (aeronautics, marine, automotive, construction, etc.), can also be used at the step b) of the process according to the invention.
• the thickness contraction can typically be between 70% and 95%.
• the carbon ratio i.e. the ratio between the mass of the polymer resin layer after pyrolysis (corresponding to the stiffening film 3) and the initial mass of the spread polymer resin layer, must be at least 5 %, preferably greater than 50%.
• the manufacturing process may comprise a step a′), between step a) and step b), of grinding the front face 1a and/or a perimeter 1c of the initial substrate 1, to reduce a surface roughness of said face 1a and/or to reduce a variation in thickness of said substrate 1, and/or to regularize the periphery 1c.
• Step a′) can comprise mechanical or mechanical-chemical thinning (polishing), with material removal of the order of a few microns to a few tens of microns.
• the manufacturing method according to the invention then comprises a step c) of removing the seed 2, so as to free the rear face 1b of the initial substrate 1 (FIG. 1c).
• the withdrawal can be carried out by burning the graphite, by applying a heat treatment, under an oxygen-rich atmosphere (air, for example), at a temperature above 400° C., preferably above 550°C.
• any residues remain on the rear face 1b of the initial substrate 1 after removal of the seed 2, they can be burned (when they are made of graphite) or removed mechanically or chemically by polishing or etching (when they are made of graphite or in SiC).
• This shrinkage typically generates a strong curvature of the initial substrate 1, which can go up to 500 ⁇ .m for a diameter of 150 mm.
• This curvature is mainly due to the constraints associated with the difference in grain sizes between the second face 1b (nucleation grains, of low average size) and the first face 1a.
• the carbon stiffening film 3 makes it possible to greatly limit the increase in curvature during the removal of the seed 2, by mechanically maintaining the initial substrate 1 by its front face 1a.
• the curvature of the initial substrate 1, fitted with the carbon stiffening film 3, does not exceed 200 ⁇ m for a substrate diameter of 150 mm; or even, the curvature is maintained below 100 p.m.
• the initial substrate 1 can be processed without problem in standard lines and equipment, without risk of breakage or failure of the equipment; these issues are essentially encountered for curvatures greater than 300 ⁇ m (diameter 150 mm).
• the manufacturing method finally comprises a step d) of thinning the rear face 1b of the initial substrate 1.
• the initial thinned substrate 1 forms the support substrate 10 (FIG. Id).
• step d) is carried out by mechanical grinding, mechanical polishing and/or mechanical-chemical polishing of the rear face 1b.
• the removal of material is typically between a few tens of microns and 200 ⁇ m, depending on the thickness of the initial substrate 1 at the start of step d), and of course depending on the target thickness for the substrate support 10.
• the thinning is carried out to a thickness for which the initial substrate 1 has, in the plane of its thinned rear face 1b', a third average grain size equal to the first average grain size to within +/- 30% .
• the first average size is for example 5 ⁇ m
• the third average size is expected between 4 ⁇ m and 6 ⁇ m.
• the grain sizes in the plane of the front face 1a or in the plane of the rear face 1b are distributed according to a double population, each peak following a substantially Gaussian distribution.
• the average grain size is calculated by taking the overall average including the two populations, and the first and third average sizes must not differ by more than 30%.
• the first two average sizes will be taken into consideration (corresponding to the double population on the side of the front face la) and the two third average sizes (corresponding to the double population on the side of the rear face 1b), which must not differ from each other by more than 30%.
• the thinned rear face 1b' of the initial substrate 1 has an average grain size in p-SiC differing by less than 30% from the average grain size of the front face 1a.
• the residual stress in the initial thinned substrate 1 (which forms the support substrate 10) is then compatible with a low curvature, and at the very least manageable in the manufacturing lines.
• the manufacturing process can then comprise a step e) of removing the stiffening film 3, for example by dry or wet chemical etching (FIG. 1e). After this shrinkage, the support substrate 10 has a curvature of less than 200 ⁇ m, or even less than 100 ⁇ m (for a diameter of 150 mm), due to the reduced residual stress in its volume.
• the support substrate 10 has a first face 10a, a second face 10b and an edge 10c, corresponding respectively to the front face 1a, to the thinned rear face 1b' and to the edge 1e of the initial substrate 1 after step d).
• an initial substrate 1 of 500 ⁇ m can be produced on the seed 2, the initial substrate 1 having a first average size of p-SiC grains at its front face the of the order of 4 ⁇ m.
• a step of correcting the uniformity of the thickness of the initial substrate 1 can be carried out, for example via a removal of 50 ⁇ m.
• a 4 ⁇ m carbon stiffening film 3 is formed on this front face 1a.
• the second average grain size at the level of the rear face 1b of the initial substrate 1 is less than 100 nm; but the curvature of initial substrate 1, due to the presence of the stiffening film 3, is kept below 150 ⁇ m.
• a removal of 100 ⁇ m at its rear face 1b is operated, and the third average size of p-SiC grains at the level of the thinned rear face 1b′, of the order of 3 ⁇ m, respects the condition of equality at 30 % close to the first average grain size.
• the curvature of the support substrate 10 is less than 200 ⁇ m and compatible with subsequent stages of manufacture of a composite structure 100.
• a surface treatment can be applied to the first face 10a of the support substrate 10, in particular if this face 10a is intended to receive the thin layer 20 of the composite structure 100, at a step f ) later in the process.
• This surface treatment may include mechanical rectification, mechanical-chemical polishing or other chemical cleanings, depending on the surface roughness of the first face 10a.
• step d) If the second face 10b of the support substrate 10 is intended to receive the thin layer 20, and step d) has not made it possible to achieve a sufficiently low level of roughness (typically ⁇ Inm RMS, measured by force microscopy atomic on 20 ⁇ .mx20 ⁇ m scans), an additional surface treatment may also be applied.
• a sufficiently low level of roughness typically ⁇ Inm RMS, measured by force microscopy atomic on 20 ⁇ .mx20 ⁇ m scans
• the face of the support substrate 10 intended to form the rear face of the composite structure 100 may have a greater surface roughness, for example of the order of lOnm RMS.
• the manufacturing process may also comprise a heat treatment, after step d) or after step e), at a temperature greater than or equal to 1500°C, typically between 1500°C and 1900°C, so as to stabilize poly structure crystal of the support substrate 10. Indeed, these temperature ranges are likely to be applied later in the process, in particular for the manufacture of a composite structure.
• a support substrate 10 having mechanical characteristics compatible with the specifications of a composite structure for microelectronic applications, can be obtained in a simple manner, without requiring the deposition of an initial substrate p- Very thick SiC, which is more than 80% eliminated, to select a tiny useful portion of p-SiC, as is practiced in the methods of the state of the art.
• the thickness of the initial substrate 1 formed is less than or equal to 1 mm and the removal of material at its front face 1a and/or from its rear face 1b is less than 70%. , or even less than 50% of the initial thickness, which saves material and technological steps.
• the manufacturing method according to the invention can continue with a step f) of transferring a useful layer 20 of monocrystalline silicon carbide onto the support substrate 10, based on a bonding by molecular adhesion (figure If).
• step f) of the process involves implantation of light species according to the principle of the Smart Cut® process.
• a donor substrate 21 in monocrystalline silicon carbide, from which the useful layer 20 will come is provided (FIG. 2a).
• the donor substrate 1 is preferably in the form of a wafer with a diameter of 100mm, 150mm, 200mm or even 300mm (identical to or very close to that of the support substrate 10) and with a thickness typically comprised between 300 ⁇ m and 800 ⁇ m. It has a front face 21a and a rear face 21b.
• the surface roughness of the front face 1a is advantageously chosen to be less than Inm RMS, or even less than 0.5 nm RMS, measured by atomic force microscopy (AFM) on a scan of 20 ⁇ m ⁇ 20 ⁇ m.
• the donor substrate 21 can be of 4H or 6H polytype, and have an n or p type doping, depending on the requirements of the components which will be produced on and/or in the useful layer 20 of the composite structure 100.
• a second phase f2) corresponds to the introduction of light species into the donor substrate 21 to form a buried fragile plane 22 delimiting, with a front face 21a of the donor substrate 21, the useful layer 20 to be transferred (FIG. 2b).
• the light species are preferably hydrogen, helium or a co-implantation of these two species, and are implanted at a determined depth in the donor substrate 21, consistent with the thickness of the targeted useful layer 20 . These light species will form, around the determined depth, microcavities distributed in a fine layer parallel to the free surface 21a of the donor substrate 21, ie parallel to the plane (x,y) in the figures. This thin layer is called the buried fragile plane 22, for simplicity.
• the implantation energy of the light species is chosen so as to reach the determined depth.
• hydrogen ions will be implanted at an energy of between 10 keV and 250 keV, and at a dose of between 5 E 16/cm 2 and 1 E 17/cm 2 , to delimit a useful layer 20 having a thickness of l order of 100nm to 1500nm.
• a protective layer may be deposited on the front face 21a of the donor substrate 21, prior to the ion implantation step. This protective layer can be composed of a material such as silicon oxide or silicon nitride for example. It is removed prior to the next phase.
• an intermediate layer 4 can be formed on the front face 21a of the donor substrate 21, before or after the second phase f2) of introduction of the light species (FIGS. 3b, 3c, 3d, 3e).
• This intermediate layer 4 can be made of a semiconductor material, for example silicon or silicon carbide, or of a metallic material such as tungsten, titanium, etc.
• the thickness of the intermediate layer 4 is advantageously limited, typically between a few nanometers and a few tens of nanometers.
• the implantation energy (and potentially the dose) of the light species will be adjusted when crossing this additional layer.
• care will be taken to form this layer by applying a thermal budget lower than the bubbling thermal budget, said bubbling thermal budget corresponding to the appearance of blisters on the surface of the donor substrate 21 due to growth and excessive pressurization of the microcavities in the buried fragile plane 22.
• Transfer step f) then comprises a third phase f3) of assembling the donor substrate 21, on the side of its front face 21a, on the support substrate 10, on the side of its first face 10a or its second face 10b, by bonding by molecular adhesion, along a bonding interface 30 (FIG. 2c).
• an intermediate layer 4' can also be deposited on the face to be assembled of the substrate support 10, prior to assembly phase f3) (FIGS. 3d, 3e); it can be chosen of the same nature or of a different nature from the intermediate layer 4 mentioned for the donor substrate 21.
• An intermediate layer 4,4' can optionally be deposited only on one or the other of the two substrates 21, 10 to assemble.
• the objective of the intermediate layer(s) is essentially to promote the bonding energy (especially in the range of temperatures below 1100°C), due to the formation of covalent bonds at more lower temperatures than in the case of two SiC surfaces assembled directly; another advantage of this (these) intermediate layer(s) may be to improve the vertical electrical conduction of the bonding interface 30.
• the intermediate layer can be formed by the carbon stiffening film 3, kept on the first face 10a of the support substrate 10 (FIGS. 3a, 3c).
• step e) of the manufacturing method according to the invention is not carried out and the face to be assembled of the support substrate 10 is its first face 10a provided with the film 3.
• preference will be given to a carbon film with a crystallographic structure of the diamond type.
• an additional carbon film 5 is placed on the face opposite the face to be assembled of the support substrate 10, always prior to the assembly phase f3) (FIG. 3e). Its characteristics can for example be chosen from those proposed for the stiffening film 3 previously in this description.
• this additional film 5 can be implemented in any of the possible configurations mentioned, in particular those illustrated in FIGS. 3a to 3c.
• the additional film 5 can be removed later, preferably after the composite structure 100 has undergone all heat treatments at temperatures above 1400° C. required for its manufacture or that of components on and/or in said structure 100.
• the assembly phase f3) may comprise, prior to bringing the faces 21a, 10a to be assembled into contact, conventional sequences of chemical cleaning (for example, RCA cleaning), surface activation (for example, by oxygen or nitrogen plasma) or other surface preparations (such as cleaning by brushing (“scrubbing”), likely to promote the quality of the bonding interface 30 (low defectivity, high adhesion energy).
• a fourth phase f4) comprises the separation along the buried fragile plane 22, which leads to the transfer of the useful layer 20 onto the support substrate 10 (FIG. 2d).
• the separation along the buried fragile plane 22 usually takes place by the application of a heat treatment at a temperature between 800°C and 1200°C. Such a heat treatment induces the development of cavities and microcracks in the buried fragile plane 22, and their pressurization by the light species present in gaseous form, until the propagation of a fracture along said fragile plane 22.
• a mechanical stress can be applied to the bonded assembly and in particular at the level of the buried fragile plane 22, so as to propagate or help to mechanically propagate the fracture leading to separation.
• the semiconductor structure 100 comprising the support substrate 10 and the useful layer 20 transferred in monocrystalline SiC, and on the other hand, the remainder 21' of the donor substrate.
• the level and the type of doping of the useful layer 20 are defined by the choice of the properties of the donor substrate 21 or can be adjusted subsequently via known techniques for doping semiconductor layers.
• the free surface 20a of the useful layer 20 is usually rough after separation: for example, it has a roughness of between 5 nm and 100 nm RMS (AFM, scan 20 ⁇ m ⁇ 20 ⁇ m).
• Cleaning and/or smoothing phases can be applied to restore a good surface state (typically, a roughness lower than a few Angstroms RMS on a 20 ⁇ m x 20 ⁇ m scan by AFM).
• these phases can comprise a mechanical-chemical smoothing treatment of the free surface of the useful layer 20.
• a removal of between 50 nm and 300 nm makes it possible to effectively restore the surface state of said layer 20.
• They can also comprise at minus one treatment thermal at a temperature between 1300°C and 1800°C.
• Such a heat treatment is applied to evacuate the residual light species from the useful layer 20 and to promote the rearrangement of the crystal lattice of the useful layer 20. It also makes it possible to reinforce the bonding interface 30.
• the heat treatment can also include or correspond to an epitaxy of silicon carbide on the thin layer 20.
• transfer step f) can include a step of reconditioning the rest 21' of the donor substrate with a view to reuse as donor substrate 21 for a new composite structure 100.
• Mechanical and/or chemical treatments similar to those applied to the composite structure 100, can be implemented at the level of the front face 21'a of the remaining substrate 21'.
• the composite structure 100 obtained is extremely robust to heat treatments at very high temperatures that may be applied to improve the quality of the useful layer 20 or to manufacture components on and/or in said layer 20.
• the composite structure 100 according to the invention is particularly suitable for producing one (or more) high-voltage microelectronic component(s), such as for example Schottky diodes, MOSFET transistors, etc. It responds more generally to power microelectronic applications, by allowing excellent vertical electrical conduction, good thermal conductivity and by providing a useful layer in high quality c-SiC.
• high-voltage microelectronic component(s) such as for example Schottky diodes, MOSFET transistors, etc. It responds more generally to power microelectronic applications, by allowing excellent vertical electrical conduction, good thermal conductivity and by providing a useful layer in high quality c-SiC.

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• 2021
  • 2021-09-22 FR FR2109961A patent/FR3127330B1/fr active Active
• 2022
  • 2022-09-06 US US18/692,239 patent/US20240379351A1/en active Pending
  • 2022-09-06 KR KR1020247012435A patent/KR20240056832A/ko active Pending
  • 2022-09-06 JP JP2024516866A patent/JP2024535267A/ja active Pending
  • 2022-09-06 CN CN202280063331.2A patent/CN117999633A/zh active Pending
  • 2022-09-06 WO PCT/FR2022/051682 patent/WO2023047035A1/fr not_active Ceased
  • 2022-09-06 EP EP22789252.8A patent/EP4406004B1/fr active Active
  • 2022-09-07 TW TW111133825A patent/TW202323603A/zh unknown

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