Abstract:
A method for manufacturing an electronic, optic, optoelectronic or photovoltaic structure of a substrate having a thin layer on one face thereof, by forming an embrittled substrate having first and second faces and an embrittlement zone therebetween, the embrittlement zone defining the substrate and a remainder; depositing a thin layer of material on both the first and second faces of the embrittled substrate; and cleaving the embrittled substrate at the embrittlement zone to obtain the structure having the thin layer of deposited material on one face and one face that is exposed.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method of manufacture of a structure for electronics, optics, optoelectronics or photovoltaics, the structure comprising a substrate and a layer formed by depositing a material on one of the sides of the substrate. 
       RELATED BACKGROUND ART 
       [0002]    The state of the art shows that it is possible to select the side of a substrate on which a thin layer will be deposited according to a technology adapted such as PECVD (acronym for “Plasma-Enhanced Chemical Vapour Deposition). Nevertheless, the process is complex, it can lead to metallic contaminations and the deposited layer can delaminate. 
         [0003]    The use of a non-selective technique results in a deposit on both faces of the substrate. It is then possible to eliminate the layer deposited on the face on which it is not desired. For this purpose, one can bond, for example, the layer which one wishes to conserve on another material, so as to protect it, then to perform an etching in order to eliminate the layer on the non-protected side. However, according to the nature of this layer (notably, if it is in SiN, AlN or diamond), its withdrawal is sometimes very difficult and non-selective compared with the material of the substrate. 
         [0004]    It is also possible to use an RIE etching (acronym for “Reactive Ion Etching”) the description of which is found in the work; “Silicon Processing for the VLSI Era, Vol. 1: Process Technology” by Stanley Wolf and Richard N. Tauber, Lattice Press; 2 nd  edition (Nov. 1, 1999), ISBN-10: 0961672161 in Chapter “14, Dry Etching for VLSI”. This dry etching assisted by plasma permits the selection of the face to clean without having to protect the other face, but its efficiency depends on the material to remove. Moreover, this relatively difficult technology requires the use of very toxic gases and pollutants such as NF 3  or SF 6 . It involves, therefore, specialized operating conditions, in particular a special confinement 
         [0005]    A particular example of this problem is encountered during the formation of a layer of polycrystalline silicon on the rear face of a SopSiC (acronym of “Silicon on Polycrystalline SiC”) or a SiCopSiC (acronym of “Silicon Carbide On Polycrystalline SiC”) substrate. 
         [0006]    The SopSiC substrate being principally transparent to infrared radiation, it is not possible to heat it sufficiently through the rear face of this substrate in order to attain a temperature suited for the realization, on the front face, of a molecular beam epitaxy (MBE). 
         [0007]    A layer of polycrystalline silicon deposited on the rear face, which absorbs the infrared radiation, can be heated to a high temperature and allows thereby the heating of the SopSiC substrate by conduction so as to reach the temperatures necessary to achieve epitaxy. In this respect, one might consult the publications, U.S. Pat. No. 5,296,385, US 2004/0152312, EP 0 449 524, WO 2006/082467 and FR 07 54172. 
         [0008]    Currently, the method of realization consists in depositing polycrystalline silicon without selection of the face on the SopSiC substrate i.e., on both faces of the latter, then to perform an etching to eliminate the layer formed on the face where it is not desired. 
         [0009]    Referring to  FIG. 1A , an embrittlement zone  510  delimiting a layer  500  is formed by implantation in a substrate  520  in monocrystalline silicon. 
         [0010]    Referring to  FIG. 1B , a structure  100  designated as SopSiC is formed by bonding, thanks to a bonding layer  300  in SiO 2 , the substrate  520  in monocrystalline silicon on a support  400  in polycrystalline SiC (also noted as p-SiC) and by transferring the layer  500  on the support  400 . 
         [0011]    Referring to  FIG. 1C , the bonding of the structure  100  is stabilized by an annealing under an atmosphere of water vapour at a temperature of about 800 to 1200° C., which contributes to the formation of layers  110  and  120  of SiO 2  on both sides of the structure  100  by thermal oxidation of silicon and SiC, i.e., by consumption of silicon on the surface of the layers  400  and  500 . 
         [0012]    Referring to  FIG. 1D , next a deposit of layers  200  of polycrystalline silicon (also noted p-Si) is performed without distinction of face on the structure obtained previously. For this purpose, a LPCVD technique (Low Pressure Chemical Vapor Deposition) can be used at a temperature of 620° C. 
         [0013]    Referring to  FIG. 1E , the layer  200  of p-Si situated at the side of the layer in monocrystalline silicon  500  is removed from the SopSiC structure by an RIE etching. 
         [0014]    Referring to  FIG. 1F , the layer  110  of SiO 2  situated at the side of the monocrystalline silicon layer  500  is removed from the SopSiC structure by the action of a solution of HF which dissolves selectively the SiO 2  and leaves the silicon intact. Finally, the surface of the layer  500  in monocrystalline silicon is cleaned to prepare it for the epitaxy by MBE. 
         [0015]    It is understood that this method comprises a large number of steps and utilizes a complex and costly technology to implement in order to carry out the selective etching. 
         [0016]    Moreover, a layer  120  in SiO 2  which is a strong thermal insulator is formed between the rear layer  200  in silicon polycrystalline and the layer  400  in SiC polycrystalline, which decreases the efficiency of the heating by this rear layer. The suppression of this layer  120  of SiO 2  would necessitate a supplemental etching step which is very costly to implement. 
         [0017]    One of the objects of the invention is therefore to propose a method of manufacturing a structure in which a layer of material is deposited on only one face of a substrate using a non-selective deposition technique which is simple and low in cost to implement which does not cost much to implement, and avoids resorting to an etching of the RIE type. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0018]    According to the invention, it is proposed to provide a method of manufacturing a structure for use in electronics, optics, optoelectronics or photovoltaics, the structure comprising a substrate and a layer formed by the depositing of a material on one of the faces of the substrate, the method being characterized in that it comprises the steps of:
       forming an embrittled substrate comprising an embritlement zone defining, on the one hand, the said substrate and, on the other hand, a remainder,   depositing of a layer of said material on each of the two faces of the embrittled substrate,   cleavage of the embrittled substrate,
 
so as to form said structure in which a face of the substrate is covered by the layer of material deposited while its other side is exposed. By exposed is meant in this text the fact that said face of the substrate is not covered by a layer.
       
 
         [0022]    According to an embodiment, the thermal budget of cleavage is greater than the thermal budget provided by the deposition. The depositing step is therefore performed before the cleavage step. 
         [0023]    According to a second embodiment, the thermal budget of cleavage is less than the thermal budget provided by the deposition. 
         [0024]    The cleavage step can therefore be performed during the deposition step. The embrittled substrate is preferably held such that the cleaved parts do not move apart from one another; in a manner particularly advantageous, it is held horizontal during the deposition step. 
         [0025]    According to a preferred embodiment, the cleavage step is performed in the depositing chamber of the material of the layer. 
         [0026]    According to a variant of the implementation of the invention, the method comprises the successive steps of:
       deposition on both faces of the embrittled substrate of the material in amorphous form,   cleavage of the embrittled substrate,   annealing to a temperature suitable to cristallise the material.       
 
         [0030]    According to other possible characteristics of the invention:
       the embrittlement zone is formed by implantation of ionic species in the substrate;   the substrate is a composite substrate comprising a support substrate and a seed layer;   the substrate comprises one of the following materials: Al 2 O 3 , ZnO, the materials of group III/V and their ternary and quaternary alloys, Si, SiC, polycrystalline SIC, diamond, Ge and their alloys;   the material deposited is chosen among the following materials: amorphous Si, monocrystalline Si, polycrystalline Si, Ge, SiC, polycrystalline SiC, amorphous SiC, the materials of group III/V and their ternary and quaternary alloys, Al 2 O 3 , SiO 2 , Sl 3 N 4  and diamond;   the substrate is a composite structure of the type SopSiC or SiCopSIC and the layer of material deposited is in polycrystalline silicon;   the method comprises additionally the carrying out of a molecular beam epitaxy on the exposed face of the substrate of the structure thus formed.       
 
     
    
     
       RIEF DESCRIPTION OF THE DRAWINGS 
         [0037]    Other characteristics, objectives and advantages of the invention will appear more clearly from the reading of the description which follows, from the drawings attached on which: 
           [0038]      FIGS. 1A to 1F  illustrate the steps of a non-selective deposition method of the prior art, 
           [0039]      FIGS. 2A to 2C  illustrate the formation of the embrittlement zone in the source substrate; 
           [0040]      FIGS. 3A and 3B  illustrate the steps of a first embodiment of the invention 
           [0041]      FIGS. 4A and 4B  illustrate the steps of a second embodiment of the invention 
           [0042]      FIGS. 5A to 5C  illustrate the steps of a third embodiment of the invention, 
           [0043]      FIG. 6  represents a structure obtained by the method according to the invention and the structure and the residual structure, 
           [0044]      FIGS. 7A to 7H  illustrate a first example of application of the invention of the deposition of a rear layer in p-Si on a SopSiC substrate, according to a first variant, 
           [0045]      FIGS. 8A to 8D  illustrate a second variant of application of the invention of the deposition of a rear layer in p-Si on a SopSiC substrate, 
           [0046]      FIGS. 9A to 9D  illustrate an example of application of the invention of the deposition of a rear layer in p-Si on a SiCopSIC substrate. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0047]    In a general manner, the invention comprises the manufacture of a substrate  12 , which may be bulk or composite (i.e., comprising a plurality of layers of different materials), substrate  12  comprising an embrittlement zone  11  according to which the substrate  12  can be cleaved. 
         [0048]    By “cleavage” or “fracture”, is meant the action of splitting a substrate in two layers according to a plane parallel to the surface of the initial substrate, allowing thereby their later removal or detachment: the two layers thereby formed are independent, but a phenomenon of capillarity or a suction effect can create a certain adherence between them. It is specified, therefore, that the step of removal is a step posterior to cleavage and is distinct from the latter. In the description which follows, when a cleaved substrate is mentioned, it must be understood that the two layers are still in contact with each other. 
         [0049]    After the formation of the embrittlement zone, comes the deposition of material on the two faces of the embrittled substrate and the cleavage of the embrittled substrate. 
         [0050]    According to the cases which will be detailed below, the step of cleavage can take place during or after the deposition step. 
         [0051]    Finally, the steps of deposition and cleavage described above are followed by the removal of the two cleaved parts from substrate  12 , so as to obtain a structure  1  formed from the part  10  of substrate  12 , the face of which have undergone the implantation is exposed and the other face is covered by the deposited material. The exposed face can be prepared for a later use, for example, an epitaxy. 
         [0052]    The different steps of the method according to the invention will now be described in detail. 
         [0053]    The invention is applicable as well to a bulk substrate  10  as well as to a composite substrate, i.e., formed from at least two different layers of material, or from materials having different crystalline characteristics. 
         [0054]    In the case of a bulk substrate, the face of this substrate is chosen which will not be subsequently covered by the deposited layer. The question of selection can be posed when the material of the substrate is polar or according to the later intended usage such as an epitaxy, for example. According to the roughness, for example, or the density or defects, the person skilled in the art would choose the one or the other of the faces of the substrate. In the following text below, the “front face” is called the face of the substrate which will have to stay exposed and “rear face” the face covered with deposited material. 
         [0055]    In the case of an epitaxy on a composite substrate comprising a support substrate and a seed layer, the front face will be the free surface of the seed layer, in a material in general selected by its lattice parameter adapted to that of the material epitaxied. 
         [0056]    The substrate  10  can be chosen among the following materials: Al 2 O 3 , ZnO, the materials of the group III/V (for example: GaAs, InP, InSb, GaSb, InN, GaN, AlN, p-AlN; P-BN, BN and their ternary and quaternary alloys such as InGaN, AlGaN, InAlGaN), or even from the materials of group IV such as Si, SiC, p-SiC, Ge and their alloys. Among the composite substrates, one could cite, for example, the substrates of the type SopSiC or SiCopSiC as being particularly well adapted for epitaxies of materials III/N binaries, ternaries, quaternaries such as GaN, AlN, AlGaN, and InGaN. 
         [0057]    When substrate  10  is bulk, it is preferable to bond a substrate having the function of a stiffener on the face through which the implantation is performed, intended to be removed in order to facilitate its detachment. 
         [0058]    The material deposited can be chosen among the following materials: Si amorphous, monocristalline or polycrystalline Si, amorphous SiC, mono or polycrystalline SiC, Ge, the materials of group III/V (InP, GaAs, AlN, p-AlN . . . ), Al 2 O 3 , SiO 2 , Si 3 N 4 , diamond. 
         [0059]    When the invention concerns substrates transparent to infrareds that are intented for use in MBE, the material deposited is chosen for absorbing the infrareds. Generally it is sought to obtain a deposited crystalline layer rather than an amorphous layer in order to guarantee a better adherence to the substrate during the later thermal treatments. 
         [0060]    Preferably, the invention concerns substrates principally transparent to infrareds in order to realize epitaxies by MBE. 
         [0061]    The materials of these substrates can be chosen, for example, among SiC, sapphire (Al 2 O 3 ), GaN, AlN (monocristalline as well as polycrystalline), BN, ZnO, InSb or diamond. These materials form the support substrate in the case of a composite substrate  10 . 
         [0062]    In fact, even if the seed layer is formed in absorbing material, the assembly of the composite substrate  10  remains, in principle, transparent to infrareds. The material deposited on the face of the substrate  10  opposite to the face which will serve for the epitaxy will be then chosen among the materials absorbing infrared rays such as silicon (amorphous, monocristalline, polycrystalline), Ge, InP and GaAs. 
         [0063]    Formation of the Embrittlement Zone 
         [0064]    In reference to  FIG. 2A , for a bulk substrate  12 , after the preparation of the substrate on which one wishes to deposit a layer of material on one of the faces, a first step of the method consists in creating, in this substrate  12 , an embrittlement zone  11  according to which the substrate could be cleaved. 
         [0065]    Typically, the creation of this embrittlement zone is implemented by the implantation of ionic species in the substrate. The person skilled in the art can determine, according to the substrate to implant, the species implanted and the depth desired of the embrittlement zone, the conditions (dosage and energy) of the implantation. 
         [0066]    The depth of the embrittlement zone defines the thickness of the substrate which will be removed with the layer of the material deposited on the face of the substrate intended to be kept exposed. Consequently, the implantation is preferably performed through the face of the substrate which will not have to be covered in the end by the deposited layer. The person of skill in the art will generally be interested in realizing an embrittlement zone of little depth so as to limit the loss of material of the initial substrate. 
         [0067]    The embrittlement zone permits defining two layers in the substrate  12  (namely, substrate  10  which will belong to the final structure and a remainder), but these two layers are not independent at this stage. 
         [0068]    In the scope of the invention, it is the application of an appropriate thermal budget which will allow their cleaving. By thermal budget, one understands the application of a determined temperature range during a defined time period. 
         [0069]    The thermal budget of cleavage depends on the conditions of the implantation previously performed and on the materials considered. Typically, if one decreases the dose of implanted species, it will be necessary to apply a larger thermal budget to perform the cleavage. The determination of the thermal budget is within the skilled person&#39;s reach. 
         [0070]    In the preceding case described and illustrated in  FIG. 2A , the substrate  10  is bulk and the substrate  12  is equally so. 
         [0071]    According to a variant of realisation, in order to obtain a bulk substrate  10 , it can be advantageous, in reference to  FIG. 2B , to form first a composite substrate  12  by bonding a stiffener  10 B to a bulk substrate  10 A on the face of the substrate which, in the end, will not have to be covered with the deposited layer. 
         [0072]    In this case, the embrittlement zone  11  is created in the substrate  10 A by exposed implantation, i.e., before the bonding of the stiffener which is too thick to be traversed by the implantation such as to define the bulk substrate. The presence of the stiffener facilitates the detachment of the cleaved parts from the substrate  12  by rigidifying the fine layer of the substrate  10 A which will be removed with the deposited layer. 
         [0073]    In the case where the substrate  10  is composite, a substrate  12  is formed which is also composite and comprises, in reference to  FIG. 2C , a support substrate  10 C and a source substrate  10 E embrittled beforehand so as to define a seed layer  10 D. The implantation is performed, before the bonding, by means of the oxide layer  10 F which serves for the bonding of the source substrate  10 E on the support substrate  10 C (In this respect, refer to the detailed description of examples 1 and 2). 
         [0074]    First case: The Thermal Budget Provided by the Deposition is Less than the Thermal Budget Necessary for Cleavage. 
         [0075]    By deposition, it is understood in this text molecular beam epitaxy (MBE) or the techniques known under the name CVD: LPCVD (“Low Pressure Chemical Vapor Deposition”, PECVD (“Plasma Enhanced Chemical Vapor Deposition”) or even MOCVD (“Metal Organic Chemical Vapor Deposition”). 
         [0076]    In the case where the thermal budget provided by the deposition of material is less than the thermal budget of cleavage, the method comprises successively:
       the deposition of material on the embrittled substrate: in reference to the  FIG. 3A , a layer  21  is deposited on the front face of substrate  12  and a layer  20  on the rear face;   the cleavage of the embrittled substrate (schematically shown, in  FIG. 3B , by the thickly dotted lines at the place of the embrittlement zone  11 );   detachment of the two parts of the cleaved substrate.       
 
         [0080]    The cleavage is principally performed by the application of a thermal budget but it can be finalized by insertion of a blade or the application of a mechanical pressure. 
         [0081]    Second case: The Thermal Budget Provided by the Deposition is Greater than the Thermal Budget Necessary for Cleavage 
         [0082]    In the case where the thermal budget necessary for cleavage is less than the thermal budget provided by the deposition of the material, two different manners of operation are possible:
       A first option is to perform successively the following steps:   realize the cleavage of the embrittled substrate  12  by providing the necessary thermal budget (as schematically illustrated in  FIG. 4A );   depositing the material without selection of the face at the temperature adapted to the manner of depositing a layer  21  in the front face and a layer  20  in the rear face ( FIG. 4B )   detaching the two parts of the cleaved substrate       
 
         [0087]    One considers in this case that the cleavage takes place during the deposition step; in fact, the ramp of temperature applied in view of the deposition per se, and which provides the thermal budget necessary for cleavage, is considered as being a part of the deposition step. 
         [0088]    The cleavage taking place before the deposition of the material, it is in this case desirable to hold the embrittled substrate such that after the fracture, the two cleaved parts do not detach in order to avoid that the material settles in the interstices. In this regard, the substrate  12  is preferably placed horizontally so that, under the weight of the upper part, the two parts stay in contact with each other during the depositing step. 
         [0089]    A second option consists of performing the steps in the following order: 
         [0090]    depositing the material under amorphous form on the embrittled substrate. 
         [0091]    For this purpose, a thermal budget is applied less than the one necessary for cleavage. Referring to  FIG. 5A , an amorphous layer  21 A is formed in the front face and an amorphous layer  20 A in the rear face.
       realising the cleavage of the embrittled substrate covered with amorphous material by providing the thermal budget for cleavage ( FIG. 5B )   making the deposited material crystalline by augmenting the temperature: in reference to  FIG. 5C , the crystalline layers  21  and  20 , respectively, in the front face and the rear face of the substrate,   detaching the two parts of the cleaved substrate.       
 
         [0095]    Whatever the order of the steps of deposition and cleavage, the thermal budget provided at the time of the deposition of material contributed to the budget of fracture of the embrittled substrate. Moreover, the operations of deposition and cleavage can be carried out in the same enclosure, by simple adaptation of the ramps of temperature and the thermal budgets applied. This makes it possible to limit the number of steps required to obtain substrate  10  covered with only one layer. However, in the case where the fractured material produces particles which can contaminate the deposition chamber, it is preferable to realize the cleavage outside of the chamber. If the cleavage is realized before depositing, the embrittled substrate  12  will be manipulated so as to keep the cleaved parts in contact until deposition. 
         [0096]    Detachment 
         [0097]    Finally, in all of the cases, the two parts of the cleaved substrate are detached. For this purpose, two tweezers can be used which, with an aspiration system, make it possible to handle the substrate. Referring to  FIG. 6 , a final structure  1  is obtained, on the one hand, comprising a substrate  10  covered, on the desired face (rear face  1 B), of a deposited layer  20  and, on the other hand, a residual structure  2  comprising a remainder of substrate  12  covered by layer  21  deposited on the other face. This residual structure  2  can be eliminated but can also be recycled by eliminating the deposited layer  21  and the polishing of the remainder of the source substrate  12  before reusing it. 
         [0098]    Later steps 
         [0099]    The front face  1 A of the final structure  1 , deprived of the deposited layer  21 , can subsequently be prepared in view of the later use (for example, a molecular beam epitaxy). 
         [0100]    In the case of the manufacture of a composite structure  1 , it is preferable to perform a stabilization annealing of this structure intended to strengthen the bonding energy between the different layers. 
         [0101]    In the case (cf.  FIG. 2C ) where the transferred layer  10 D not covered is in a material (such as silicon, for example) forming a native oxide in the contact of air, it is necessary to define the depth of the implantation in the source substrate  10 E so as to obtain a final thickness of the desired layer  10 D by taking into account its partial consumption during the formation of the SiO 2  during the stabilization annealing: the final thickness of the layer  10 D transferred after withdrawal of the oxide is slighter from this fact to this than the initial thickness transferred. Likewise, if the material of the deposited layer  20  is in a material forming a native oxide, it is necessary to provide for the thickness which will be consumed by the formation of the oxide and to deposit a greater thickness of the material as a result. 
         [0102]    Different examples of the implementation of the method conforming to the invention will now be explained. 
       EXAMPLE 1 
     Formation of a Rear Layer in p-Si on a Composite Substrate SopSiC 
       [0103]    Variant 1: Cleavage is Performed During the Deposition Stage 
         [0104]    Referring to  FIG. 7A , a source substrate  1200  in monocrystalline silicon is oxidized to form a layer  3000  of SiO 2  of about 2000 Å of thickness. Referring to  FIG. 7B , a embrittlement zone  1100  is created by implantation in this source substrate  1200  through the layer  3000  so as to define a seed layer  1000 . The implantation energy is adapted by the person skilled in the art according to the depth which is desired to be obtained; the dose of implantation is in the region of 5.10 e 16 atoms/cm 2 . Referring to  FIG. 7C , a hydrophilic bonding is performed by putting in contact through layer  3000  of SiO 2  the embrittled source substrate  1200  with a support  4000  in polycrystalline SiC so as to form a embrittled structure  12 , the surfaces having been prepared in an adequate manner. 
         [0105]    This embrittled structure  12  is placed in a deposition chamber so that the two parts do not move apart from one another after cleavage, then the structure is heated to 350° C. to effect a first stabilization of the bonding between the monocrystalline Si and the p-SiC. 
         [0106]    Referring to  FIG. 7D , a ramp of temperature intended to lead the temperature from 350° to 620° C. is applied so that the cleavage can take place under 500° C. in the course of the ramp. 
         [0107]    Referring to  FIG. 7E , one proceeds to the depositing of polycrystalline silicon during 6h30 without selection of the face at 620° C. Thus, two layers  20  and  21  are thereby formed of 5 micrometers thickness on each of the faces of the structure  12 . 
         [0108]    The temperature is decreased by an appropriate ramp before the opening of the chamber. 
         [0109]    Referring to  FIG. 7F , the cleaved parts are detached from the structure  12 , for example, with the aid of tweezers. The face in monocrystalline silicon of the substrate SopSiC  10  is thus exposed. 
         [0110]    Referring to  FIG. 7G , a second stabilization annealing is then performed under the atmosphere of water vapour at 900° C. which leads to the formation of a layer  50  of SiO 2  on each of the two faces. The formation of oxide is made by consumption of silicon present on the two faces of the SopSiC substrate and, in particular of monocrystalline silicon deteriorated to the level of the embrittlement zone by the implantation, which contributes to eliminate this zone rich in defects. 
         [0111]    Referring to  FIG. 7H , the layers  50  of SiO 2  are removed with the aid of a solution of HF, the HF being selective to SiO 2  and not attacking the silicon. 
         [0112]    Finally, the surface of monocrystalline silicon of the SopSiC is cleaned to prepare it for a later epitaxy. 
         [0113]    The remaining substrate of monocrystalline silicon can be recycled, for example, by a polishing of its two surfaces. 
         [0114]    Variant 2: Cleavage is Performed After the Deposition The method commences with the same steps which were described in reference to  FIGS. 7A to 7C  of the first variant. 
         [0115]    Referring to  FIG. 8A , the embrittled substrate is placed in the deposition chamber. 
         [0116]    The cleavage being performed after the deposition, the problem of spacing of the cleaved parts is not posed and the substrate can be placed, for example, vertically. The substrate is heated to 350° C. to perform a first stabilization of the adhesive bonding between the monocrystalline silicon and the p-SiC, then depositing silicon in amorphous form at 350° C., so as to form two layers  20 A and  21 A on each side of the substrate. 
         [0117]    Referring to  FIG. 8B , a ramp of heating up to 620° C. is applied, which allows the fracture of the substrate  12  according to the embrittlement zone. 
         [0118]    Referring to the  FIG. 8C , a ramp of temperature up to 620° C. is subsequently performed for crystallising the silicon of the layers  20 A and  21 A in layers  20  and  21 . 
         [0119]    Referring to the  FIG. 8D , the cleaved parts of the structure are separated outside of the chamber, the front face in monocrystalline silicon of SopSiC  10  being free from deposit. 
         [0120]    The method is completed with the same steps as those described in reference to  FIGS. 7G and 7H  of the preceding variant. In the particular example of the formation of a layer in p-Si in the rear face of a substrate SopSiC, the realisation of two variants of which have just been described, the method permits the increasing of efficiency of infrared absorption of SopSiC by means of the rear layer in p-Si since, contrary to the known method described in reference to  FIGS. 1A to 1F , there is not any insulating layer of SiO 2  between the substrate SopSiC and the p-Si (cf. layer  120  of  FIG. 1F ). This advantage can be confirmed in a general manner for the manufacture of all composite substrates in which the support substrate forms a native oxide with air. 
         [0121]    In addition, the material to cleave for manufacturing the SopSiC being in silicon, the particles formed during cleavage are in silicon. They do not contaminate the deposition chamber of silicon so that cleavage is advantageously realized in the chamber. 
       EXAMPLE 2 
     Formation of a Rear Layer in Polycrystalline Si on a Composite substrate SiCopSiC. 
       [0122]    Referring to  FIG. 9A , a substrate  1200  in monocrystalline SiC is oxidized, on the one hand, during 2 hours at 1150° C. under oxygen to form a layer  3000  of SiO 2  of 5000 angstroms of thickness. 
         [0123]    Then a embrittlement zone  1100  is created in this substrate by implantation through this layer with a dose in the region of 5.10 e 16 atoms/cm 2 , the energy being parametered by the person of skill in the art according to the depth of the desired implantation. 
         [0124]    On the other hand, a layer  6000  of oxide SiO 2  of 5000 Å of thickness is deposited on the front face of a support  4000  in SiC polycrystalline. 
         [0125]    Next, the surfaces of the layers of oxide  3000  and  6000  are activated in view of a bonding. For this purpose, a polishing of the oxide  3000  is performed so as to remove 500 Å and to diminish the roughness. Likewise, a polishing of the oxide  6000  is performed to eliminate 2500 Å and smooth its surface. Techniques of polishing are well known to the person of skill in the art; one can implement, in particular, a chemical-mechanical polishing (CMP). 
         [0126]    The substrate  1200  in SiC and the support  4000  in p-SiC are bonded thanks to the oxide layers  3000  and  6000 , putting in contact the two prepared faces. The structure obtained is illustrated in  FIG. 9A . 
         [0127]    Referring to  FIG. 9B , this embrittled structure  12  is placed in the deposition chamber. The structure  12  can be disposed either vertically or horizontally. A temperature ramp up to 620° C. is applied, then polycrystalline silicon is deposited during 6h30 so as to form two layers  20  and  21  of 5 micrometers of thickness on each face of the structure  12 . 
         [0128]    Referring to  FIG. 9C , one proceeds to a heating to 1000° C. which leads to a cleavage of the substrate  1200  in monocrystalline SiC. 
         [0129]    Referring to  FIG. 9D , the two cleaved parts are detached outside of the chamber. A substrate  10  (designated SiCopSiC) is thereby obtained, the front face of which, in monocrystalline SiC, is exposed. 
         [0130]    The following steps are the same as those described in reference to the  FIGS. 7G and 7H  of the variant  1  of the first example. 
         [0131]    The remainder of the source substrate  1200  of monocrystalline SiC may be recycled by stripping off the deposited silicon (layer  21 ) and polishing the surface. 
       EXAMPLE 3 
     Formation of a Rear Layer in Polycrystalline Si on a Bulk Substrate in Monocrystalline SiC 
       [0132]    Referring to  FIG. 2 , an embrittlement zone situated in the vicinity of the surface of a substrate  12  of SiC is created by implantation with a dose in the region of 5.10 e 16 atoms/cm 2 , and the embrittled substrate is placed in the deposition chamber. 
         [0133]    Referring to  FIG. 3A , one proceeds to the deposition of polycrystalline Si at a temperature of 620° C., without distinction of face. Two layers  20  and  21  are thereby formed on the embrittled substrate  12 . 
         [0134]    Referring to  FIG. 3B , a ramp of temperature is applied up to 900° C. in order to cleave the substrate  12  along the embrittlement zone  11 . 
         [0135]    Referring to  FIG. 6 , the two cleaved parts are separated outside of the deposition chamber, and a substrate  10  is recovered, the face  1 B of which, is covered with deposited polycrystalline Si (layer  20 ), and the other face  1 A is exposed and can be prepared in view of a later epitaxy.