WO2006082467A1

WO2006082467A1 - Substrate for crystal growing a nitride semiconductor

Info

Publication number: WO2006082467A1
Application number: PCT/IB2005/000436
Authority: WO
Inventors: Bruce Faure; Fabrice Letertre; Hacène Lahreche
Original assignee: Soitec SA; Picogiga International
Current assignee: Soitec SA; Picogiga International
Priority date: 2005-02-01
Filing date: 2005-02-01
Publication date: 2006-08-10
Anticipated expiration: 2007-08-01

Abstract

The invention relates to a substrate (10) for crystalline growing an alloy, comprising at least one atomic element of column III and nitrogen, on the front side (1) of the substrate (10), characterized in that the substrate (10) comprises in its rear side (2) a rear layer (12) of a non-metallic infraredabsorptive/emittive material. The invention also relates to a wafer comprising such a substrate and a layer grown on this substrate. The invention also relates to the method of manufacturing the said substrate.

Description

Substrate for crystal growing a nitride semiconductor

TECHNICAL FIELD

This invention relates to a substrate used as a support for a crystalline growth, especially heteroepitaxy of nitrides such as gallium nitride (GaN), aluminium nitride (AIN), indium nitride (InN), and alloys of this compounds (AIGaN, InGaN, ...), as well as the manufacturing of such a substrate.

Nitride materials (or nitrides semiconductors) are mainly used for optics or optoelectronics applications, such alloys can be for instance found in LEDs and LDs.

A first main application is found in light transmitters of electromagnetic radiation with wavelength below 500 nm, particularly colours from green (500-578 nm) to ultraviolet (280-400 nm), through the blue. Indeed, these wavelengths are accessible due the fact that the gap bandwith of such nitrides semiconductors can be varied function of their composition in the requested wavelength range.

A second main application of these nitrides semiconductors is those of high-frequency power components. Indeed, the nitrides semiconductors have properties of charge transport (high saturation velocity of the carriers under high voltage, high breakdown voltage,...) better than materials like SiC or AsGa for high-frequency power applications. Especially, the HEMT type components obtained based on GaN and AIGaN type materials have already shown greater performances for high-frequency power applications.

TECHNICAL BACKGROUND

Such nitrides semiconductors are usually manufactured by crystalline growth on substrates mainly chosen among sapphire (AI₂O₃) and silicon carbide (SiC). Other substrates can be used, such as (111 ) silicon (Si), gallium arsenide (AsGa), or composite substrates (made of different layers of such materials) obtained by various technique such as Smart-Cut® (for more details on Smart-Cut® technique, see for instance "Silicon-On- Insulator Technology: Materials to VLSE, 2^nd Edition" of J. P. Collinge, Kluwer Academic Publishers, p. 50-51 ).

The crystalline growth of nitrides semiconductor materials can, be performed by different techniques, mainly epitaxy techniques like MBE (Molecular Beam Epitaxy), MOCVD (Metallo-Organic Chemical Vapour Deposition) and HVPE (Hydride Vapour Phase Epitaxy). In order to use one of these techniques it is necessary to heat the substrate, at a given temperature under a controlled atmosphere including the precursors of the different atomic elements of the nitrides semiconductor alloys to form, For heating the substrate, indirect heating of the gaseous atmosphere around the substrate (HVPE or MOCVD) or a direct heating of the substrate by infrared absorption if working in a very high vacuum (MBE) can be used. Depending on the nature of the substrate and the material to be grown, it is necessary to define the range of temperatures very precisely in order to dissociate the precursors and to insure an organised growth of the required material.

To reach this purpose, the substrate temperature has to be known very precisely for improving the readability and the performance of the crystalline growth process. In the case of an atmospheric pressure atmosphere, the substrate temperature can be controlled by the measurements of the gas temperature.

But a more accurate method for evaluating this temperature at the surface of the substrate consists of measuring the infrared radiation emitted by the substrate.

However, lots of materials typically used as support for the crystalline growth of nitrides semiconductors are transparent to infrared wavelengths range, such as SiC and sapphire.

Consequently, temperature of wafers made of such materials cannot be measured easily by infrared measurements, due to the fact that they are not transmitters of infrared wavelength. Additionally, wafers made of such materials cannot be substrates for MBE epitaxy of nitrides semiconductors which requires an infrared heating of the substrate (as previously discussed).

SUMMARY OF THE INVENTION

In order to solve these problems, the invention proposes, according to a first aspect, a substrate for crystalline growing an alloy, comprising at least one atomic element of column III and nitrogen, on the front side of the substrate, characterized in that the substrate comprises in its rear side a rear layer of a non-metallic infrared-absorptive/emittive material. Other possible characteristics of this substrate are:

- the rear layer is of an amorphous material or a polycrystalline material, such as amorphous silicon or polysilicon;

- the substrate further comprises a bulk structure; - the bulk structure is transparent to infrared;

- the bulk structure is of SiC, sapphire (AI₂O₃), GaN, AIN, or ZnO;

- the front face is a free face of the bulk structure;

- the substrate further comprises a composite structure, the composite structure comprising a mechanical support and a front layer, the front face of the substrate being the free surface of the front layer;

- the front layer is of Si with (111) crystalline orientation, SiC, sapphire (AI₂O₃), AsGa, GaN, AIN, or ZnO;

- the mechanical support is of an infrared - transparent material;

- the mechanical support is of SiC, AIN, sapphire (AI₂O₃), GaN, ZnO, or diamond;

- the composite structure is globally transparent to infrared. According to a second aspect, the invention proposes a wafer comprising the said substrate and a layer of an alloy comprising at least one atomic element of column III and nitrogen. According to a third aspect, the invention proposes a method of manufacturing a substrate used as a support for the crystalline growth of an alloy comprising at least one atomic element of column III and nitrogen on the front side of this substrate, characterized in that it comprises the forming of a rear layer, on the rear side of a wafer, with a non-metallic infrared- absorptive/emittive material. Other possible aspects of this method of manufacturing a substrate are:

- the technique for forming the rear layer is chosen among technique for forming a layer of an amorphous material or a layer of a polycrystalline material; - the technique for forming the rear layer is chosen among technique for forming an amorphous silicon layer or of a polysilicon layer;

- the method further comprises, before the forming of the rear layer, the forming of a protection layer, for example of SiO₂, on the front side of the substrate so as to protect the front side of the substrate from the atomic elements used during the forming of the rear layer;

- the rear layer is formed on the rear side of a bulk structure, the substrate being then constituted of the bulk structure and the rear layer;

- the bulk structure is of SiC, sapphire (AI₂O₃), GaN, AIN, or ZnO;

- the substrate further comprises the forming of a composite structure, the composite structure comprising a support structure and a front layer, the substrate then comprising the composite structure and the rear layer, the front face of the substrate being the free surface of the front layer;

- the front layer is formed on the support structure by implementing the following steps: S providing a donor substrate with a crystalline material on top of it, this crystalline material being the same as those of the front layer to be formed;

S bonding the donor substrate to the support substrate at the said top face; S thinning the donor substrate so as to only keep a layer of material comprising the said front layer, this front layer being thus transferred onto the support substrate;

- the front layer is formed on the support structure by implementing the following steps:

S providing a donor substrate with a crystalline material on top of it, this crystalline material being the same as those of the front layer to be formed;

V implanting atomic species through the top face of the donor substrate, for forming an embrittlement zone at a determinate depth; s bonding the donor substrate to the support substrate at the said top face;

S providing energy so as to detach a layer of material from the donor substrate at the embrittlement zone, this layer of material comprising the said front layer, this front layer being thus transferred onto the support substrate;

- the forming of the front layer on the support substrate further comprises, before the bonding step, the forming of at least one bonding layer, for example of SiO₂ or Si₃N₄, on the top face of the donor substrate, on the bonding face of the support substrate or on both of them;

- the method further comprises a step of finishing the surface of the detached layer of material in order to finally have the front layer with a smoothed and cleaned surface; - the rear layer is formed after the forming of the front layer or before the bonding step;

- the front layer is of Si with (111 ) crystalline orientation, SiC, sapphire (AI₂O₃), AsGa, GaN, AIN, or ZnO;

- the support structure is of SiC, sapphire (AI₂O₃), AIN, GaN, ZnO, or diamond. BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, aims and advantages of the present invention will be described in the following detailed specification, giving of non-limiting examples, and done with reference to the following drawings, in which: Figure 1 shows a first substrate for crystalline growth of nitride semiconductor according to the invention.

Figure 2 shows a second substrate for crystalline growth of nitride semiconductor according to the invention.

Figure 3 shows a third substrate for crystalline growth of nitride semiconductor according to the invention.

Figures 4a to 4d show different steps of a first method of manufacturing of a substrate according to the invention.

Figures 5a to 5g show different steps of a method of manufacturing a composite substrate according to the invention. Figures 6a to 6g show different steps of another method of manufacturing a composite substrate according to the invention.

Figures 7a to 7e show different steps of another method of manufacturing a composite structure according to the invention.

DETAILLED DESCRIPTION OF THE INVENTION

Referring to figure 1 , a substrate 10 for crystal growth of nitrides semiconductors, such as alloys comprising at least one atomic element of column III and a nitrogen like InN, GaN, AIN, or compounds of one of these elements, is shown. This crystal growth will occur on the front side 1 of the substrate 10. This front side is "epi-ready", meaning it has a surface prepared for the next nucleation.

The substrate 10 is here composed of two parts: - a support structure 11 for the further crystal growth, which has a free surface 1 which defines the front side 1 of the substrate 10 for receiving the deposited elements during the crystal growth, the front side 1 being used as a nucleation surface during crystal growth; - a rear layer 12 included in the rear side 2 of the substrate 10 made of a non metallic infrared absorptive material.

In a first embodiment, referring to figure 1 , the support structure 11 is a bulk structure made of a monocrystalline or polycristalline material, such as SiC, sapphire, AIN, GaN, or ZnO which are adapted materials for crystal growth of nitrides semiconductors.

In a second embodiment, referring to figure 2, the support structure 11 is composed of a mechanical structure 14, for example of a bulk SiC or a bulk sapphire, and a front layer 13 made of a semiconductor material chosen for receiving on its free surface 1 the deposited nitrides elements during the crystal growth.

The mechanical structure 14 can be made of a material chosen among polycrystalline SiC, polycrystalline AIN, Sapphire, ZnO, GaN, diamond.

The front layer 13 can be made of a material chosen among monocrystalline Si(111 ), monocrystalline SiC (6H, 4H or 3C), GaN, AIN, ZnO, AsGa, sapphire.

In a third embodiment, referring to figure 3, the support structure 11 is composed of a mechanical structure 14, for example made of SiC or sapphire, a front layer 13 for receiving the deposited nitrides elements during crystal growth, and a buried dielectric material 16 between said front layer 13 and said mechanical structure 14.

The buried layer 16 can be made of silicon oxide (SiO₂) or silicon nitride (Si₃N₄), or silicon oxinitride (Si_xO_yN_z), or other dielectric material.

The materials chosen for the mechanical structure 14 and for the front layer 13 can be identical to those chosen in the second embodiment.

The rear layer 12 is made of a non-metallic infrared-absorptive/emittive material.

This rear layer 12 can be made of silicon, in a polycrystalline state or in an amorphous state. This material is well adapted for the present application as the polycrystalline state or amorphous state can be easily obtained on all types of substrates, with known epitaxy techniques like LPCVD (Low Pressure Chemical Vapour Deposition) or PECVD (Plasma Enhanced Chemical Vapour Deposition). Furthermore, the silicon is one of the least expensive materials used in electronics. Additionally, a rear layer 12 sufficiently thick (i.e. more than around 1 μm of thickness), can be easily obtained, so that the infrared absorption by and emission from the rear layer 12 allow the readability of the temperature (for example by means of an optical pyrometer), and can eventually allow the heating of the substrate by infrared radiation in the case of MBE growth.

Then, the presence of the rear layer 12 in the substrate 10 allows a temperature measurement by infrared detection, and eventually a heating of the substrate 10 by infrared (especially in the case of a MBE epitaxy operating on this substrate 10 for forming the nitride semiconductor). This rear layer 12 is especially useful when the support structure 11 is of an infrared-transparent bulk material such as bulk SiC or bulk sapphire, or when the support structure is a composite structure globally transparent to infrared (referring to figures 2 and 3) composed of a mechanical support 14 transparent to infrared and a front layer 13 (used for the nucleation of the crystal growth) not thick enough to absorb and transmit sufficiently the infrared radiation. In this last case, such a composite support structure 11 is typically manufactured by epitaxy or by the Smart-Cut® technique. The Smart-Cut® technique (described more in details below) implies firstly the formation of an embrittlement zone in a wafer by atomic implantation, then a bonding of this wafer to the mechanical support 14, and finally the formation of the front layer 13 by detaching it from the donor substrate at the embrittlement zone.

In many applications, polycrystalline silicon can be preferred for the rear layer 12, thanks to its perfect compatibility with the known techniques (chemical cleaning, ...) for preparing the substrate 10 to the further crystal growth on the front side 1. Moreover, the polysilicon is stable even at high temperature (around 1 ,200⁰C). Additionally, it becomes more absorbent for infrareds at high temperature and it is perfectly clean for the under ultra high vacuum that exists in frames for MBE.

Referring to figures 4a to 4d, a first embodiment of manufacturing a substrate 10 according to the invention, is shown. Referring to figure 4a, a wafer 11 , nextly called a support structure 11 , is provided.

This support structure 11 can be made of a crystalline bulk structure, such as a monocrystalline SiC, a polycrystalline SiC, a monocrystalline AIN₁ a polycrystalline AIN, a monocrystalline sapphire, a monocrystalline ZnO, a polycrystalline ZnO, a monocrystalline GaN, a polycrystalline GaN.

But this support structure 11 can also be a composite structure (not shown) composed of a substrate and at least one layer epitaxied on the substrate.

Materials of the support substrate 11 are chosen for processing a crystal growth of nitrides on the front surface 1.

Referring to figure 4b, a protection layer 15 is eventually formed on the front side 1 of the support substrate 11. This protection layer 15 is formed so as to protect the front side 1 of the support substrate 11 the treatment implemented during next steps. Indeed, the front side 1 of the support substrate 11 can be already prepared for receiving the deposited elements of the next crystal growth of nitrides, and protection of it is then preferred.

The protection layer 15 can be for instance of Siθ₂ with a sufficient thickness to protect the front side 1 from the next implemented treatments. If a thermal oxidation is used, Siθ₂ material is formed on both face of the substrate (not shown in fig 4b).

Referring to figure 4c, a rear layer 12 is formed on the rear side of the support substrate 11 with a non-metallic infrared-absorptive/emittive material. This rear layer 12 can be formed by deposition of polycrystal silicon or amorphous silicon, done for example by LPCVD (Low Pressure Chemical Vapor Deposition) or PECVD (Plasma Ehanced Chemical Vapor Deposition) at low temperature (typically less than 500°C). This deposition of the rear layer 12 is processed for forming a rear layer 12 sufficiently thick for both absorbing and emitting sufficient infrared radiation, in the nitrides crystal growth conditions, for being detected by infrared measurements means (like an optical pyrometer). For example, a thickness of about or more than 1 μm can be sufficient for performing this result.

The thickness of the rear layer 12 can also be sufficient for heating the support structure during nitrides MBE.

In the case of the deposited elements for forming the rear layer 12 are also deposited on the front side of the support substrate 11 , the method further comprises a step of removing these elements on the front side, using for example an etching onto the protection layer 15. A first method for performing such a chemical etching can include a first step of thermal oxidation if the protection layer 12 comprises silicon, or a Siθ₂ deposition compatible with the said elements.

Oxide is formed by any technique on the substrate 11 to protect it during front side layer 12 removal. Removing parasitic layer 12 on layer 15 on the front side is then made by etching using a selective etching between layer 12 material and layer 15 material. By this way, surface 1 is completely protected.

In a first embodiment, the removal of the said deposited elements on the front face of the support substrate 11 is performed by spin-etching. For that, the substrate is rotated and a spray of an etch agent is directed to the front side for etching the silicon, the etch agent chosen can be for example TMAH in solution.

In a second embodiment, for performing the removal of the deposited elements on the front face of the support substrate 11 , a dry etch assisted by plasma (also called RIE for Reactive Ion Etching) is chosen by employing SFe or NF₃ agents for removing the silicon elements. This kind of etching is selective due to its great efficiency for silicon removing and its no efficiency for SiO₂ removing, the Siθ₂ layer being then an etch stop. We can then succeed of suppressing any silicon element on the substrate without damaging the front side 1 for the next nucleation.

Finally, the structure shown in figure 4c is obtained.

Referring to figure 4d, a step of removing the protection layer 15 is processed in order to reveal the front surface 1 of the substrate which will be used as a nucleation surface for the next crystal growth of nitride layer(s).

For that, in the case of the protection layer 15 is of Siθ₂, a HF solution can be used. The front side 1 of the substrate 10 may then be prepared for being

"epi-ready" for a following crystal growth of nitrides semiconductor layer. For that, chemico-mechanical planarization (CMP), and/or chemical cleaning (for example with SC1 and SC2 solutions) can be used.

Alternatively, the protection layer 15 can be kept at the front side of the substrate 10 for being removed later, when the substrate 10 will be used as a receiver of the deposit elements of the next nitride crystal growth.

Referring to figures 5a to 5g and figures 6a to 6g, are respectively shown different steps of manufacturing a composite substrate 10 according to the invention, by using a Smart-Cut® technique. Referring to figure 5a, a donor wafer 20 is provided.

This donor wafer 20 is either a bulk structure, or a composite structure like a structure having a template layer.

For example, the donor wafer 20 is of monocrystalline Si with (111 ) crystal orientation, a monocrystalline SiC 6H, 4H or 3C, or is a substrate with a template layer of GaN on one side obtained by standard GaN epitaxy technique, or a GaN bulk substrate.

This donor wafer 20 is then implanted by atomic species with determinate atomic species to be implanted, and determinate proportion and energy conditions. This implantation is implemented so as to form an embrittlement zone 25 at a determinate depth in the donor wafer 20 with a determinate mechanical weakness.

For example, these atomic species are H⁺ between 2E16 and 5E17 atoms/cm², especially between 5E16 and 8E16 atoms/cm², implanted with energy between 10 and 210 keV, especially between 20 and 120 keV.

Optionally, before this implantation, a dielectric layer is formed on the surface to be implanted. This dielectric layer can be an oxide (Siθ₂) with a thickness between for example 10 and 10,000 nm, especially between 50 and 5,000 nm.

After implantation, the implanted surface of the donor wafer 20 is then optionally cleaned for eliminating contaminants (metallic elements, particulars, hydrocarbures) and for improving the surface hydrophily.

Optionally, in the case of a dielectric layer was formed on the implanted surface, this dielectric layer can be completely removed.

Referring to figure 5c, a mechanical support 14 is put into contact with the donor wafer 20 at the implanted surface.

Optionally, a dielectric layer was previously formed on the surface of the mechanical support 14 to be bonded. Previously to this contact, the surface of the mechanical support 14 to be bonded, can be prepared to the bonding by processing techniques such as a cleaning for improving its hydrophily and/or for removing contaminants.

Optionally, other kinds of preparations of both surfaces to be bonded can be implemented, such as CMP or plasma activation by oxygen, argon, or nitrogen ions for improving the bonding energy.

Both donor substrate 20 and mechanical support 14 thus prepared are put into contact, for example at room temperature.

The bonding can then be reinforced by heating, for example at around 200⁰C for 2 hours. Referring to figure 5d, a front layer 13 is taken from the donor wafer 20 by detaching it at the embrittlement zone 25. For that, an energy is provided, such as a thermal energy and/or a mechanical energy.

A finishing of the surface of the front layer 13 is processed in order to remove roughness and contaminants that may exist on the front surface 1.

Eventually, this front surface 1 can be prepared for becoming a "epi- ready" surface (i.e. ready for receiving deposited elements of the nitrides crystal growth) by processing for example a CMP and a chemical etching.

Figures 5e, 5f and 5g show steps of the method according to the invention respectively identical to the steps shown in figures 4b, 4c and 4d.

Finally, referring to figure 5g, the substrate 10 is composed of a rear layer 12 and a composite support structure 11 composed of a mechanical support 14 and a front layer 13. The front side 1 of the substrate 10 aiming to receive the deposited elements for the next crystal growth of nitride layer(s) is the free side of the front layer 13.

Referring to figures 6a to 6g, another method for manufacturing a composite substrate 10 for crystal growing nitrides on it, is shown.

This method is quite identical to those illustrated by figures 5a to 5f, except that the rear layer 12 is formed on the rear side of the mechanical support 14 before (and not after) the bonding between the mechanical support 14 and the implanted donor wafer 20 (see figures 6c to 6f).

The final substrate 10, referring to figure 6g, is then the same as the substrate 10 illustrated by figure 5g.

Referring to figures 7a to 7e, are respectively shown different steps of manufacturing a composite substrate 10 according to the invention, by using a "back thinning" technique.

Referring to figure 7a, a donor wafer 20 is provided. This donor wafer 20 is either a bulk structure, or a composite structure like a structure having a template layer. For example, the donor wafer 20 is of monocrystalline Si with (111 ) crystal orientation, or a monocrystalline SiC 6H, 4H or 3C, or a substrate with a template layer of GaN on one side obtained by standard GaN epitaxy technique, or GaN bulk substrate.

Referring to figure 7b, a mechanical support 14 is provided.

This mechanical support 14 is either a bulk structure, or a composite structure like a structure having a template layer.

For example, the mechanical support 14 is of SiC 6H, 4H or 3C, AIN, Si (111 ), or sapphire (AI₂O₃), in a monocrystalline or polycrystalline orientation.

Referring to figure 7c, the mechanical support 14 is put into contact with the donor wafer 20. A molecular adhesion may then occur.

Optionally, a dielectric layer was previously formed on the surface of the mechanical support 14 to be bonded and/or on the surface of the donor wafer 20 to be bonded.

Previously to this contact, the surface of the mechanical support 14 to be bonded, can be prepared to the bonding by processing techniques such as a chemical cleaning for improving its hydrophily and/or for removing contaminants.

The bonding can then be reinforced by heating, for example at around 200°C for 2 hours. Figure 7d shows the forming of the rear layer 12 on the free side of the mechanical support 14 with a non-metallic infrared-absorptive/emittive material. This rear layer 12 can be formed by deposition of polycrystal silicon or amorphous silicon, done for example by LPCVD (Low Pressure Chemical Vapor Deposition) or PECVD (Plasma Ehanced Chemical Vapor Deposition) at low temperature (typically less than 500⁰C). This deposition of the rear layer 12 is processed for forming a rear layer 12 sufficiently thick for both absorbing and emitting sufficient infrared radiation, in the nitrides crystal growth conditions, for being detected by infrared measurements means (like an optical pyrometer). For example, a thickness of about or more than 1 μm can be sufficient for performing this result.

Referring to figure 7e, a step of thinning the donor substrate 20 is processed, so as to only keep a front layer 13 on the mechanical support 14.

Methods of thinning, such as polishing, etching, grinding, can then be used for reducing the donor substrate 20 until a thickness of about a few ten micrometers. Then, various techniques of CMP are used to finally obtain a remained front layer 13 having a thickness less than 1 micrometer, with a surface "epi- ready".

Of course, the person having ordinary skill in the art will deduce that the rear layer 12 can also be formed at any steps of formation of the substrate 10. Then, rear layer 12 can also be formed before bonding, or after thinning.

The front side 1 of the substrate 10 is then a nucleation surface of the crystal growth of a semiconductor nitride, such as gallium nitride (GaN), aluminium nitride (AIN), indium nitride (InN), and alloys of this compounds (AIGaN, InGaN, ...). If the crystal growth is a HVPE epitaxy or a MOCVD epitaxy, the substrate 10 is heated by an indirect heating of the gaseous atmosphere around the substrate.

If the crystal growth is a MBE epitaxy under high vacuum, the substrate 10 is heated by a direct heating of the substrate by infrared absorption. This epitaxy is possible with the substrate 10 according to the invention even if a main part of the wafer is of an infrared transparent material, the rear layer 12 having a sufficient thickness for sufficiently heating the whole substrate 10. According to the invention, a better control of the temperature is reached, by way of having added to the substrate 10 an infrared- absorptive/emittive layer 12 able to increase the infrared radiation of the substrate 10 at the crystal growth temperatures. Then the detection of the temperature by measuring means (by for example an optical pyrometer) is better, and the temperature measurement is improved.

Claims

1. Substrate (10) for crystalline growing an alloy, comprising at least one atomic element of column III and nitrogen, on the front side (1 ) of the substrate (10), characterized in that the substrate (10) comprises in its rear side (2) a rear layer (12) of a non-metallic infrared-absorptive/emittive material.

2. Substrate according to Claim 1 , characterized in that the rear layer (12) is of an amorphous material or a polycrystalline material.

3. Substrate according to Claim 1 , characterized in that the rear layer

(12) is of amorphous silicon or polysilicon.

4. Substrate according to one of the previous claims, characterized in that it further comprises a bulk structure.

5. Substrate according to the previous claims, characterized in that the bulk structure is transparent to infrared.

6. Substrate according to the previous claims, characterized in that the bulk structure is of SiC, sapphire (AI₂O₃), AIN, GaN, or ZnO.

7. Substrate according to one of the three previous claims, characterized in that the front face (1 ) is a free face of the bulk structure.

8. Substrate according to one of the claims 1 to 3, characterized in that the substrate (10) further comprises a composite structure, the composite structure comprising a mechanical support (14) and a front layer (13), the front face (1 ) of the substrate (10) being the free surface of the front layer (13).

9. Substrate according to the previous claim, characterized in that the front layer (13) is of Si with (111 ) crystal orientation, SiC, sapphire (AI₂O₃), AsGa₁ AIN₁ GaN₁ Or ZnO.

10. Substrate according to one of the two previous claims, characterized in that the mechanical support (14) is of an infrared - transparent material.

11. Substrate according to the previous claim, characterized in that the mechanical support (14) is of SiC, AIN, sapphire (AI₂O₃), GaN, or ZnO.

12. Substrate according to one of the claims 8 to 11 , characterized in that the composite structure is globally transparent to infrared.

13.Wafer comprising a substrate according to one of the previous claims and a layer of an alloy comprising at least one atomic element of column III and nitrogen.

14. Method of manufacturing a substrate used as a support for the crystalline growth of an alloy comprising at least one atomic element of column III and nitrogen on the front side of this substrate, characterized in that it comprises the forming of a rear layer, on the rear side of a wafer, with a non-metallic infrared-absorptive/emittive material.

15. Method according to Claim 14, characterized in that the technique for forming the rear layer is chosen among technique for forming a layer of an amorphous material or a layer of a polycrystalline material.

16. Method according to Claim 14, characterized in that the technique for forming the rear layer is chosen among technique for forming an amorphous silicon layer or of a polysilicon layer.

17. Method according to Claim 14, characterized in that it further comprises, before the forming of the rear layer, the forming of a protection layer on the front side of the substrate so as to protect the front side of the substrate from the atomic elements used for forming of the rear layer.

18. Method according to the previous Claim, characterized in that the protection layer is of SiO₂.

19. Method according to one of the claims 14 to 18, characterized in that the rear layer is formed on the rear side of a bulk structure, the substrate then comprising the bulk structure and the rear layer.

20. Method according to the previous claim, characterized in that the bulk structure is of SiC, sapphire (AI₂O₃), GaN, AIN, or ZnO.

21. Method according to one of the claims 14 and 18, characterized in that it further comprises the forming of a composite structure, the composite structure comprising a support structure and a front layer, the substrate then comprising the composite structure and the rear layer, the front face of the substrate being the free surface of the front layer.

22. Method according to claim 21 , characterized in that the front layer is formed on the support structure by implementing the following steps: — providing a donor substrate with a crystalline material on top of it, this crystalline material being the same as those of the front layer to be formed;

- bonding the donor substrate to the support substrate at the said top face; - thinning the donor substrate so as to only keep a layer of material comprising the said front layer, this front layer being thus transferred onto the support substrate.

23. Method according to claim 21 , characterized in that the front layer is formed on the support structure by implementing the following steps: — providing a donor substrate with a crystalline material on top of it, this crystalline material being the same as those of the front layer to be formed;

- implanting atomic species through the top face of the donor substrate, for forming an embrittlement zone at a determinate depth; — bonding the donor substrate to the support substrate at the said top face;

- providing energy so as to detach a layer of material from the donor substrate at the embrittlement zone, this layer of material comprising the said front layer, this front layer being thus transferred onto the support substrate.

24. Method according to one of the two previous claims, characterized in that the forming of the front layer on the support substrate further comprises, before the bonding step, the forming of at least one bonding layer on the top face of the donor substrate, on the bonding face of the support substrate or on both of them.

25. Method according to the previous claim, characterized in that the bonding layer is of SiO₂ or Si₃N₄.

26. Method according to the claim 22 or 23, characterized in that it further comprises a step of finishing the surface of the layer of material in order to finally have the front layer with a smoothed and cleaned surface.

27. Method according to one the claims 22 to 26, characterized in that the rear layer is formed after the forming of the front layer.

28. Method according to one the claims 23 to 26, characterized in that the rear layer is formed before the bonding step.

29. Method according to claim 21 , characterized in that the front layer is of Si with (111 ) crystalline orientation, SiC, sapphire (AI₂O₃), AsGa, GaN, AIN, or ZnO.

30. Method according to the previous claim, characterized in that the support structure is of SiC, sapphire (AI₂O₃), AIN, GaN, or ZnO, or diamond.