Process for manufacturing a piezoelectric layer on a substrate

Abstract

The invention relates to a process for manufacturing a piezoelectric layer (10) on a substrate (11), characterized in that the process involves: - forming, by a first epitaxy, a pseudomorphic seed layer (102) of a first piezoelectric material on a donor substrate (100), - transferring the seed layer (102) and a portion (103) of the donor substrate (100) onto a receiver substrate (110) via at least one electrically insulating layer and / or at least one electrically conductive layer (105) adapted to allow relaxation of the seed layer, - removing the transferred portion (103) of the donor substrate (100) so as to expose a surface of the seed layer (102), - forming a monocrystalline layer (104) of a second piezoelectric material on the seed layer (102).

Description

[0001] METHOD FOR PRODUCING A PIEZOELECTRIC LAYER ON A SUBSTRATE

[0002] TECHNICAL FIELD

[0003] The invention relates to a method of manufacturing a piezoelectric layer on a substrate.

[0004] STATE OF THE ART

[0005] Various acoustic components are used for filtering in the radio frequency domain, including surface acoustic wave filters, known by the acronym SAW (from the English term "Surface Acoustic Wave"), which typically comprise a thick piezoelectric layer (i.e. generally with a thickness of several tens of nm to several tens of pm) and two electrodes in the form of two interdigitated metal combs deposited on the surface of said piezoelectric layer. An electrical signal, typically a variation in electrical voltage, applied to an electrode is converted into an elastic wave which propagates on the surface of the piezoelectric layer. The propagation of this elastic wave is favored if the frequency of the wave corresponds to the frequency band of the filter. This wave is again converted into an electrical signal upon reaching the other electrode.The piezoelectric layer must have excellent crystalline quality to avoid attenuation of the surface wave. Therefore, it is preferable to use a monocrystalline layer here. Currently, suitable materials for industrial use are quartz, LiNbOs or LiTaCX.

[0006] Currently, the piezoelectric layer is obtained by cutting an ingot of one of said materials, which results in low precision for the thickness of said layer as well as non-uniform thickness across the entire layer.

[0007] In addition, the diameters of piezoelectric material ingots are smaller than the diameters of the ingots of materials used for the substrate, such as silicon for example. However, to achieve a direct transfer, in particular a Smart Cut™ type layer transfer, it is necessary that the donor and recipient substrates have the same diameter.

[0008] There remains a need to date for methods to form a high-quality, uniform, thick piezoelectric layer on a large-diameter substrate.

[0009] BRIEF DESCRIPTION OF THE INVENTION

[0010] An aim of the invention is to design a method for manufacturing a substrate for a microelectronic, photonic or optical device, in particular but not limited to a surface acoustic wave device, in particular by making it possible to obtain thick layers (i.e. with a thickness greater than 5 μm, or even greater than 15 μm), uniform, of high quality and of large diameter (i.e. with a diameter greater than 15 or 20 cm).

[0011] According to the invention, there is provided a method of manufacturing a piezoelectric layer on a substrate, characterized in that it comprises;

[0012] - the formation by a first epitaxy of a seed layer of a first piezoelectric material on a donor substrate,

[0013] - the transfer of the seed layer and a portion of the donor substrate onto a receiving substrate via at least one electrically insulating layer and / or at least one electrically conductive layer adapted to allow relaxation of the seed layer,

[0014] - removing the portion of the transferred donor substrate so as to expose a surface of the seed layer,

[0015] - the formation of a monocrystalline layer of a second piezoelectric material on the seed layer.

[0016] According to a first embodiment, the transfer of the seed layer and the portion of the donor substrate comprises the following steps: the formation of a weakening zone in the donor substrate so as to delimit the portion to be transferred, the assembly of the donor substrate on the receiving substrate, the seed layer being at the assembly interface, the detachment of the donor substrate along the weakening zone, and the formation of the seed layer on the donor substrate is carried out before the formation of the weakening zone.

[0017] According to a second embodiment, the transfer of the seed layer and the portion of the donor substrate comprises the following steps:

[0018] - the formation of a weakening zone in the donor substrate so as to delimit the portion to be transferred,

[0019] - the assembly of the donor substrate on the recipient substrate, the seed layer being at the assembly interface,

[0020] - detachment of the donor substrate along the weakening zone, and the formation of the seed layer on the donor substrate is carried out after the formation of the weakening zone.

[0021] The embrittlement zone can be formed by ion implantation, particularly of hydrogen and / or helium, into the donor substrate.

[0022] Preferably, the formation of the seed layer on the donor substrate is carried out by atomic layer deposition. Alternatively, the formation of the seed layer on the donor substrate is carried out by molecular beam epitaxy. Preferably, the formation of the monocrystalline layer of the second piezoelectric material is carried out by a second epitaxy.

[0023] Preferably, the second epitaxy of the second piezoelectric material on the seed layer is organometallic chemical vapor deposition.

[0024] Alternatively, the formation of the monocrystalline layer on the seed layer is carried out by deposition of the second piezoelectric material in amorphous form followed by recrystallization of said second material.

[0025] Advantageously, the thickness of the seed layer is between 2 nm and 20 nm.

[0026] Advantageously, the portion of the donor substrate transferred onto the recipient substrate has a thickness of less than 2 μm, preferably less than 1 μm.

[0027] Advantageously, the thickness of the layer of the second piezoelectric material at the end of the second epitaxy is between 20 nm and 15 pm.

[0028] According to a particular embodiment, the method comprises, after the formation of the monocrystalline layer of the second piezoelectric material, the transfer of at least a portion of the layer of the second piezoelectric material onto a final substrate.

[0029] Advantageously, the part of the layer of the second piezoelectric material transferred onto the final substrate has a thickness of less than 2 μm, preferably less than 1 μm.

[0030] The receiving substrate or the final substrate may comprise at least one electronic device or an interconnection.

[0031] The receiving substrate or the final substrate may comprise a charge trapping layer.

[0032] The first piezoelectric material and the second piezoelectric material may be the same. Alternatively, the first piezoelectric material and the second piezoelectric material may be different.

[0033] According to one embodiment, an intermediate layer suitable for epitaxial growth of the seed layer on the donor substrate may be formed on the donor substrate prior to formation of the seed layer.

[0034] Another subject matter relates to a method of manufacturing a surface acoustic wave device, comprising forming two interdigitated electrodes on the surface of a piezoelectric layer, characterized in that it comprises manufacturing the piezoelectric layer by a method as described above.

[0035] Another subject matter relates to a method of manufacturing a photonic device, comprising forming at least one photonic component, such as a laser or a light-emitting diode, at least partly in a piezoelectric layer, characterized in that it comprises manufacturing the piezoelectric layer by a method as described above. Another subject matter relates to a surface acoustic wave device, characterized in that it comprises a piezoelectric layer obtainable by a method as described above, and two interdigitated electrodes on one face of the piezoelectric layer.

[0036] Another subject relates to a photonic device, characterized in that it comprises a piezoelectric layer capable of being obtained by a method as described above, and at least one photonic component, such as a laser, a modulator, a waveguide or a multiplexer, formed at least in part in said piezoelectric layer.

[0037] The invention also relates to a structure comprising at least one such surface acoustic wave device and one such photonic device, comprising the same piezoelectric layer in which said surface acoustic wave device and said photonic device are arranged.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Other characteristics and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings in which: Figure 1 is a sectional view of a surface acoustic wave filter, Figures 2A and 2B illustrate two first successive steps of the method for manufacturing a monocrystalline piezoelectric layer according to a first embodiment of the invention, Figures 3A and 3B illustrate two first successive steps of said method according to a second embodiment of the invention, Figures 4 to 8 illustrate successive steps of said method according to the first or second embodiment of the invention, Figures 9 to 11 illustrate optional subsequent steps of said method.

[0040] For reasons of readability of the figures, the elements illustrated are not necessarily represented to scale. Furthermore, elements designated by the same reference signs in different figures are identical.

[0041] DETAILED DESCRIPTION OF EMBODIMENTS

[0042] Figure 1 is a schematic view of a surface acoustic wave filter.

[0043] Said filter comprises a piezoelectric layer 10 and two electrodes 12, 13 in the form of two interdigitated metal combs deposited on the surface of said piezoelectric layer. On the side opposite the electrodes 12, 13, the piezoelectric layer rests on a substrate 11. The piezoelectric layer 10 is monocrystalline, an excellent crystalline quality being in fact preferable so as not to cause attenuation of the surface wave. In general, the invention proposes the formation of a monocrystalline piezoelectric layer by means of a transfer of a seed layer produced by epitaxy of a first piezoelectric material on a donor substrate, said transfer being carried out from the donor substrate to a receiving substrate. Then, a layer of a second piezoelectric material is formed on the seed layer so as to obtain the desired thickness for the monocrystalline layer of the second piezoelectric material.

[0044] The donor substrate may be a monocrystalline bulk substrate of the first piezoelectric material or of another material. Alternatively, the donor substrate may be a composite substrate, i.e. formed from a stack of at least two layers of different materials, a surface layer of which is made of the first monocrystalline piezoelectric material or of another monocrystalline material. Said monocrystalline material is suitable for epitaxial growth of the seed layer; in particular, it has a lattice parameter sufficiently close to the lattice parameter of the seed layer so as not to generate crystal defects during the growth of the seed layer.

[0045] Particularly advantageously, the seed layer is pseudomorphic, i.e., the actual lattice parameter of the seed layer material is forced, for example by atomic forces, to substantially match the lattice parameter of the donor substrate on which it is formed. For this purpose, the thickness of the seed layer must not exceed a critical thickness beyond which there would be stress relaxation and generation of defects in the seed layer. This critical thickness depends on the seed layer material. For example, the critical thickness is typically less than 5 nm for a germanium seed layer formed on a silicon substrate. Generally, the critical thickness is between 2 nm and 20 nm depending on the materials chosen for the seed layer and for the substrate.

[0046] In some embodiments, an intermediate layer (referred to as an "epitaxy intermediate layer") of a material suitable for growing the seed layer on the donor substrate may be formed on the donor substrate prior to the formation of the seed layer. The usefulness of such an intermediate layer depends in particular on the chemical stability between the seed layer and the donor substrate. Thus, if the growth of the seed layer directly on the donor substrate is not hindered by chemical interactions or reactions between the material of the seed layer and that of the donor substrate, it is not necessary to use an intermediate layer.On the other hand, if interactions or chemical reactions between the seed layer material and the donor substrate material are likely to prevent the growth of the seed layer, it is desirable to use an intermediate layer made of a material stable with respect to the donor substrate material and the seed layer material. For example, a single-crystal germanium layer may be formed on a silicon donor substrate to promote the growth of the seed layer of the first piezoelectric material. In other embodiments, the intermediate layer may be made of single-crystal strontium titanate (SrTiOs), single-crystal aluminum oxide (AI2O3), single-crystal lanthanum aluminate (LaAIO3), or a single-crystal metal such as aluminum.

[0047] The receiving substrate has a mechanical support function for the seed layer. It can be of any type suitable for implementing epitaxy (particularly in terms of temperature resistance) and, advantageously but not necessarily, suitable for the intended application. It can be solid or composite. Advantageously, the receiving substrate can comprise at least one electronic device or an interconnection.

[0048] At least one intermediate layer (called a "relaxation intermediate layer") is interposed between the receiving substrate and the seed layer. For example, such an intermediate layer may be electrically conductive or electrically insulating. A person skilled in the art is able to choose the material and thickness of this layer according to the properties that he wishes to confer on the radiofrequency device intended to comprise the piezoelectric layer. This intermediate layer allows the free relaxation of the seed layer. The pseudomorphic transferred seed layer can thus freely resume its lattice parameter during the transfer, or between the transfer and the formation of the second layer of the second piezoelectric material, or even during the formation of the second layer of the second piezoelectric material.

[0049] The material of the intermediate layer can advantageously be chosen from silicon oxide (SiC>2), a nitride or a metal.

[0050] Said intermediate layer can be formed on the donor substrate (on the seed layer) or on the recipient substrate.

[0051] As it is an intermediate layer of silicon oxide, it can be deposited or obtained by thermal oxidation. The technique for forming said layer is chosen in particular according to the substrate on which it is to be formed and any limits (for example, thermal) to be respected. For example, if the intermediate layer is formed on the receiving substrate and this contains electronic components, a technique with a thermal budget that does not risk damaging said components will be chosen.

[0052] Advantageously, the receiving substrate may be made of a semiconductor material. It may be, for example, a silicon substrate.

[0053] In certain embodiments, in particular when the receiving substrate constitutes the final support of the piezoelectric layer, the receiving substrate comprises a “trap-rich” type layer (which can be translated into French as a charge trapping layer), which can be either formed on the receiving substrate or formed in a surface region of the receiving substrate. Said “trap-rich” type layer is thus located between the seed layer and the receiving substrate and makes it possible to improve the electrical insulation performance of the receiving substrate. Said “trap-rich” type layer can be formed by at least one semiconductor material of polycrystalline, amorphous or porous type, in particular polycrystalline silicon, amorphous silicon or porous silicon, without being limited to these materials.Furthermore, depending on the temperature resistance of the “trap-rich” type layer for carrying out epitaxy, it may prove advantageous to introduce an additional layer between the receiving substrate and said “trap-rich” type layer, in order to avoid recrystallization of the latter during heat treatment.

[0054] The seed layer has a negligible thickness compared to the thickness of the final monocrystalline piezoelectric layer. Therefore, it is considered that it does not significantly influence the operation of the radiofrequency device incorporating the monocrystalline piezoelectric layer.

[0055] The seed layer typically has a thickness between 1 nm and 20 nm.

[0056] The thickness of the layer of the second piezoelectric material formed on the seed layer depends on the specifications of the device intended to incorporate the single-crystal piezoelectric layer. In this regard, the thickness of the layer formed on the seed layer is not limited either in terms of minimum or maximum value. The thickness of the final piezoelectric layer is typically between 20 nm and 15 pm.

[0057] The first piezoelectric material is advantageously chosen from a compound of formula ABO3, where A is chosen from barium and lithium and B is chosen from titanium and niobium. However, the interest that can be shown in these materials is not limited to their piezoelectric character. In particular for other applications, for example related to integrated optics, one can also be interested in them where appropriate for their dielectric permittivity, for their refractive indices, or even for their pyroelectric, ferroelectric or even ferromagnetic properties for example and depending on the cases.

[0058] The first epitaxy can be carried out by any technique suitable for obtaining high crystalline quality, in particular by atomic layer deposition (ALD) or by molecular beam epitaxy (MBE), etc. These techniques are characterized by a very low growth rate. However, since the seed layer is thin, using one of these techniques to grow the seed layer has a low economic impact on the process but makes it possible to obtain a crystalline quality of the seed layer, which will promote the crystalline quality of the monocrystalline layer of the second piezoelectric material.

[0059] According to a first alternative, the formation of the layer of the second piezoelectric material on the seed layer can be carried out by a second epitaxy.

[0060] The second epitaxy can be carried out by any technique providing a faster growth rate than the first epitaxy, in particular by metal organic chemical vapor deposition (MOCVD). Although providing a lower crystalline quality than ALD or MBE techniques, this second epitaxy is more economical for growing a relatively thick monocrystalline layer.

[0061] According to a second alternative, the formation of the layer of the second piezoelectric material can be carried out by depositing said piezoelectric material in amorphous form followed by recrystallization of said material in order to give it a monocrystalline structure. Optionally, it is possible to proceed in several successive cycles each comprising a deposition of the amorphous piezoelectric material over a certain thickness, followed by recrystallization of the material over said thickness, until the desired total thickness for the layer of the second piezoelectric material is obtained.

[0062] The deposition of amorphous material can be carried out by any technique known to those skilled in the art, and advantageously by MOCVD, by chemical vapor deposition carried out at subatmospheric pressure (LPCVD, acronym for the English term “Low-Pressure Chemical Vapor Deposition”), by plasma-enhanced chemical vapor deposition (PECVD, acronym for the English term “Plasma-Enhanced Chemical Vapor Deposition”) or by sputtering.

[0063] A person skilled in the art is able to determine the reagents and operating conditions depending on the piezoelectric material to be grown and the technique chosen.

[0064] Seed layer transfer typically involves a step of bonding the donor substrate and the recipient substrate, with the seed layer and the relaxation interlayer at the bonding interface, and then a step of thinning the recipient substrate so as to expose the seed layer for subsequent epitaxy.

[0065] The bonding step can be carried out, for example, by direct molecular bonding of the “wafer bonding” type, with or without an additional intermediate layer.

[0066] Particularly advantageously, the transfer is carried out using the Smart Cut™ process, which is well known for the transfer of thin semiconductor layers, particularly silicon.

[0067] For this purpose, with reference to Figure 2A, according to a first embodiment, a donor substrate 100 is provided and a layer of a first monocrystalline piezoelectric material, called seed layer 102, is grown by a first epitaxy. The first piezoelectric material has a lattice parameter close to that of the donor substrate. Thus, the donor substrate 100 imposes its lattice parameter and allows the growth of a good quality monocrystalline material. The growth is stopped when the desired thickness for the seed layer is reached. In this figure, the donor substrate 100 is shown solid but, as indicated above, it could possibly be composite. Advantageously but optionally, an intermediate epitaxy layer 106 can be formed on the donor substrate 100 before the epitaxy of the seed layer 102. For the sake of simplification of the figures, said layer 106 has not been shown in the following figures.

[0068] With reference to Figure 2B, a weakening zone 101 is formed by ion implantation (shown schematically by the arrows) through the seed layer in the donor substrate, which delimits a monocrystalline layer 103 to be transferred, comprising the seed layer and a portion of the donor substrate. Advantageously, and depending on the piezoelectric material considered, the implanted species are hydrogen or helium, alone or in combination. A person skilled in the art is able to determine the dose and the implantation energy of these species to form the weakening zone at a determined depth, which is preferably between 0.2 pm and 0.6 pm: typically and still depending on the piezoelectric material and the implanted species considered, the dose is in the range of 2 E+16 to 2 E+17 ionic species / cm 2, and the implantation energy is from 30keV to 500keV. The buried weakened layer can also be obtained by any other means known to those skilled in the art, for example by porosification of the material, or by laser irradiation. However, as explained below, there are transfer methods which do not require the implementation of ion implantation, and the present invention can be implemented with these methods.

[0069] Figures 3A and 3B illustrate a second embodiment of the method for manufacturing a single-crystal piezoelectric layer. The second embodiment is an alternative to the first embodiment, illustrated in Figures 2A and 2B, in which the implantation in the donor substrate is carried out before the formation of the seed layer by a first epitaxy.

[0070] With reference to FIG. 3A, a donor substrate 100 is provided and, by ion implantation (shown schematically by the arrows) in the donor substrate 100, a weakening zone 101 is formed which delimits a monocrystalline layer 103 to be transferred.

[0071] With reference to Figure 3B, a layer of a first monocrystalline piezoelectric material, called seed layer 102, is grown by a first epitaxy on the layer to be transferred 103. As explained previously, the donor substrate 100 imposes its lattice parameter and allows the growth of a good quality monocrystalline material. The first piezoelectric material has a lattice parameter close to that of the donor substrate. The growth is stopped when the desired thickness for the seed layer is reached. In this figure, the donor substrate 100 is shown solid but, as indicated above, it could possibly be composite.

[0072] Advantageously, the thermal budget of the first epitaxy is lower than the thermal budget likely to cause fracture of the donor substrate along the embrittlement zone. Thus, the donor substrate retains its mechanical cohesion until the end of seed layer growth.

[0073] Following the steps illustrated in Figures 2A and 2B or 3A and 3B, a seed layer 102 is obtained on the donor substrate 100 in which a weakening zone has been formed by implantation and which defines a layer to be transferred 103 which comprises the seed layer 102.

[0074] With reference to Figure 4, at least one electrically insulating or electrically conductive intermediate relaxation layer 105 is formed on the surface of the receiving substrate 110. The receiving substrate 110 may further comprise a charge trapping layer 107. For the sake of simplification, the layer 107 has not been shown in the following figures.

[0075] With reference to FIG. 5, the donor substrate 100 thus weakened is bonded to the recipient substrate 110, the seed layer 102 and the intermediate relaxation layer 105 being at the bonding interface.

[0076] With reference to FIG. 6, the donor substrate 100 is detached along the weakening zone 101. Such detachment can be caused by any means known to those skilled in the art, for example thermal, mechanical, chemical, etc. The layer 103 is thus transferred to the receiving substrate 110. Advantageously, the remainder of the donor substrate can then be recovered, which can possibly be recycled.

[0077] Referring to Figure 7, a surface portion of the transferred layer is removed, for example by mechanical polishing and / or chemical etching. This removal of material is intended to expose the seed layer 102. At the end of this removal, a thinned layer 102 is obtained on the receiving substrate 110, which will serve as a seed layer in the next step.

[0078] With reference to Figure 8, a layer of a second piezoelectric material 104 is formed on the seed layer 102. The material of the layer 104 has a lattice parameter close to or identical to that of the seed layer 102. Thus, the seed layer 102 imposes its lattice parameter and allows the growth of a good quality monocrystalline material. The layer 104 may be of a slightly different nature compared to the seed layer 102, in particular by the controlled introduction of slight levels of impurities for various purposes (doping, adjustment of the piezoelectric properties, optimization of the densities of crystal defects / dislocations, surfactant, etc.). The growth is stopped when the desired thickness for the monocrystalline piezoelectric layer is reached. The final piezoelectric layer 10 is formed from the stack of the seed layer 102 and the layer 104.

[0079] The first piezoelectric material and the second piezoelectric material may be the same.

[0080] Alternatively, the first piezoelectric material and the second piezoelectric material may be different. As indicated above, the seed layer is considered to have no effect or a second-order effect on the operation of a radiofrequency device incorporating the piezoelectric layer formed on the seed layer. Consequently, even if the implantation carried out for the implementation of the Smart Cut™ process damages the seed layer and disrupts its piezoelectric properties, these defects are not or only slightly penalizing.

[0081] In a non-illustrated embodiment, no weakening zone is formed in the donor substrate. In this case, the transfer of the seed layer to the receiving substrate is carried out by assembling the donor substrate on the receiving substrate and then etching the donor substrate until the seed layer is exposed. This embodiment is, however, less preferred than that involving the formation of a weakening zone in the donor substrate, because it results in a greater loss of material.

[0082] In another embodiment not shown, no weakening zone is formed in the donor substrate but a detachable interface is formed by chemical or thermal reaction. In this case, the transfer of the seed layer onto the recipient substrate is achieved by assembling the donor substrate onto the recipient substrate and then by detaching the interface following a chemical or thermal reaction in order to expose the seed layer.

[0083] As seen in Figure 8, at the end of the process, a substrate for a surface acoustic wave device is obtained which comprises a receiving substrate 110 and a monocrystalline piezoelectric layer 10 on said substrate 110. Such a substrate may also prove useful for other applications, for example for photonics and integrated optics.

[0084] Layer 10 is characterized by the presence of two portions with different characteristics:

[0085] - a first portion 102 located at the interface with the receiving substrate 110, corresponding to the seed layer,

[0086] - a second portion 104 extending from the first portion 102, corresponding to the layer formed on the portion 102, which may have a crystalline quality different from that of the first portion (said quality being able to be adjusted and optimized during the second epitaxy step for example) and / or a different composition (in particular if impurities, such as dopants, have been introduced during the epitaxy), possibly conferring particular properties to the layer formed on the portion 102.

[0087] This substrate is advantageously used to manufacture a surface acoustic wave device as illustrated in Figure 1 and / or any other microelectronic, photonic or optical device comprising a piezoelectric layer. In certain cases, the receiving substrate onto which the seed layer is transferred may not be optimal for the intended application. Indeed, in certain embodiments, since the receiving substrate must undergo the operating conditions of epitaxy, the choice of suitable materials is limited. In particular, the receiving substrate cannot contain layers or elements likely to be damaged by the epitaxy temperature. It may then be advantageous to transfer the piezoelectric layer 10 onto a final substrate 120 whose properties are chosen according to the intended application, by bonding it to said substrate 120 via the surface of the layer 104 formed on the seed layer 102 (cf.figure 9), and by removing the receiving substrate (see figure 10). This transfer can be carried out by any transfer technique mentioned above. Another advantage of this transfer onto a final substrate is that the seed layer 102, which was buried in the structure resulting from the formation of the layer of the second piezoelectric material, is then exposed and can possibly be removed (see figure 11), in particular in the case where it presents defects. Only the layer of the second piezoelectric material 104 then remains on the final substrate 120.

[0088] The final substrate can be solid or composite.

[0089] Advantageously, the final substrate may comprise at least one electronic device or interconnection.

[0090] In some embodiments, the final substrate comprises a charge trapping layer (designated by reference 121 in FIG. 9), which can either be formed on said final substrate or formed in a surface region of said final substrate. Said charge trapping layer is thus located between the piezoelectric layer and the final substrate and makes it possible to improve the electrical insulation performance of the final substrate. Said charge trapping layer can be formed by at least one semiconductor material of polycrystalline, amorphous or porous type, in particular polycrystalline silicon, amorphous silicon or porous silicon, without being limited to these materials.

[0091] In the case where it is desired to manufacture a surface acoustic wave device, metal electrodes 12, 13 are deposited on the surface of the piezoelectric layer 10 opposite the receiving substrate or, where appropriate, the final substrate (whether it is the receiving substrate 110 or the final substrate 120, said substrate forms the support substrate denoted 11 in FIG. 1), in the form of two interdigitated combs.

[0092] In other applications, at least one photonic component, such as a laser, a modulator, a waveguide or a multiplexer, may be formed in the piezoelectric layer, or in a stack of layers comprising said piezoelectric layer.

[0093] Particularly advantageously, it is possible to integrate a surface acoustic wave device and a photonic device in the same substrate. For this purpose, at least one surface acoustic wave device and one photonic device, such as a laser, a modulator, a waveguide or a multiplexer, are formed in the same piezoelectric layer. It is also possible to combine these devices as described with other devices present in the receiving substrate or the final substrate, thus aiming at known 2D, 2.5D and 3D device co-integration approaches.

Claims

CLAIMS 1. Method for manufacturing a piezoelectric layer (10) on a substrate (11), characterized in that it comprises: the formation by a first epitaxy of a pseudomorphic seed layer (102) of a first piezoelectric material on a donor substrate (100), the transfer of the seed layer (102) and of a portion (103) of the donor substrate (100) on a receiving substrate (110) via at least one electrically insulating layer and / or at least one electrically conductive layer (105) adapted to allow relaxation of the seed layer, removing the portion (103) of the donor substrate (100) transferred so as to expose a surface of the seed layer (102), forming a monocrystalline layer (104) of a second piezoelectric material on the seed layer (102).

2. Method according to claim 1, in which the transfer of the seed layer (102) and the portion (102) of the donor substrate (100) comprises the following steps: the formation of a weakening zone (101) in the donor substrate (100) so as to delimit the portion (103) to be transferred, the assembly of the donor substrate (100) on the recipient substrate (110), the seed layer (102) being at the assembly interface, the detachment of the donor substrate (100) along the weakening zone (101), and wherein the formation of the seed layer (102) on the donor substrate (100) is carried out after the formation of the weakening zone (101).

3. The method of claim 1, wherein the transfer of the seed layer (102) and the portion (103) of the donor substrate (100) comprises the following steps: forming a weakening zone (101) in the donor substrate (100) so as to delimit the portion to be transferred (103), assembling the donor substrate (100) on the recipient substrate (110), the seed layer (102) being at the assembly interface, detaching the donor substrate (100) along the weakening zone (101), and wherein the formation of the seed layer (102) on the donor substrate (100) is carried out before the formation of the weakening zone (101).

4. Method according to one of claims 2 or 3, in which the weakening zone (101) is formed by ion implantation of hydrogen and / or helium in the donor substrate (100).

5. Method according to one of claims 1 to 4, in which the formation of the seed layer (102) on the donor substrate (100) is carried out by atomic layer deposition.

6. Method according to one of claims 1 to 4, in which the formation of the seed layer (102) on the donor substrate (100) is carried out by molecular beam epitaxy.

7. Method according to one of claims 1 to 6, in which the formation of the monocrystalline layer (104) on the seed layer (102) is carried out by a second epitaxy.

8. The method of claim 7, wherein the second epitaxy of the second piezoelectric material on the seed layer (102) is organometallic chemical vapor deposition.

9. Method according to one of claims 1 to 6, in which the formation of the monocrystalline layer (104) on the seed layer (102) is carried out by deposition of the second piezoelectric material in amorphous form followed by recrystallization of said second material.

10. Method according to one of the preceding claims, in which the thickness of the seed layer (102) is between 2 nm and 20 nm.

11. Method according to one of the preceding claims, in which the portion (103) of the donor substrate (100) transferred onto the receiving substrate (110) has a thickness of less than 2 μm, preferably less than 1 μm.

12. Method according to one of the preceding claims, in which the thickness of the layer (104) of the second piezoelectric material at the end of the second epitaxy is between 20 nm and 15 pm.

13. Method according to one of claims 1 to 12, in which the receiving substrate (110) comprises at least one electronic device or an interconnection.

14. Method according to one of the preceding claims, in which the receiving substrate (110) comprises a charge trapping layer (107).

15. Method according to one of claims 1 to 12, comprising, after the formation of the monocrystalline layer of the second piezoelectric material, the transfer of at least a portion of the layer (104) of the second piezoelectric material onto a final substrate (120).

16. Method according to claim 15, in which the part of the layer (104) of the second piezoelectric material transferred onto the final substrate (120) has a thickness of less than 2 pm, preferably less than 1 pm.

17. Method according to one of claims 15 or 16, in which the final substrate (120) comprises at least one electronic device or an interconnection.

18. Method according to one of claims 15 to 17, in which the final substrate (120) comprises a charge trapping layer (121).

19. Method according to one of claims 1 to 18, in which the first piezoelectric material and the second piezoelectric material are identical.

20. Method according to one of claims 1 to 18, in which the first piezoelectric material and the second piezoelectric material are different.

21. Method according to one of the preceding claims, comprising, before the formation of the seed layer (102), the formation of an intermediate layer (106) on the donor substrate (100), said intermediate layer being suitable for the epitaxial growth of the seed layer (102) on the donor substrate (100).

22. A method of manufacturing a surface acoustic wave device, comprising forming two interdigitated electrodes (12, 13) on the surface of a piezoelectric layer (10), characterized in that it comprises manufacturing the piezoelectric layer (10) by a method according to one of claims 1 to 21.

23. A method of manufacturing a photonic device, comprising forming at least one photonic component, such as a laser, a modulator, a waveguide or a multiplexer, at least partly in a piezoelectric layer, characterized in that it comprises manufacturing the piezoelectric layer (10) by a method according to one of claims 1 to 21.

24. Surface acoustic wave device, characterized in that it comprises a piezoelectric layer (10) capable of being obtained by a method according to one of claims 1 to 21, and two electrodes (12, 13) interdigitated on one face of the piezoelectric layer (10).

25. Photonic device, characterized in that it comprises a piezoelectric layer capable of being obtained by a method according to one of claims 1 to 21, and at least one photonic component, such as a laser, a modulator, a waveguide or a multiplexer, formed at least in part in said piezoelectric layer.

26. A structure comprising a surface acoustic wave device according to claim 24 and a photonic device according to claim 25, wherein said surface acoustic wave device and said photonic device are arranged at least partly in the same piezoelectric layer.

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