Method for manufacturing piezoelectric layer on substrate

Abstract

The invention relates to a method for producing a piezoelectric layer (10) on a substrate (11), characterized in that it comprises the following steps:-forming a pseudo-seed layer (102) of a first piezoelectric material on a donor substrate (100) by a first epitaxy; -transferring the seed layer (102) and a portion (103) of the donor substrate (100) onto the acceptor 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) in order to expose the surface of the seed layer (102); -forming a single crystal layer (104) of a second piezoelectric material on the seed layer (102).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a piezoelectric layer on a substrate. Background Art

[0002] Various acoustic components are used for filtering in the radio frequency domain, including surface acoustic wave (SAW for short) filters, which typically include a thick piezoelectric layer (i.e., usually several tens of nm to several tens of μm thick) and two electrodes in the form of two interdigital metal combs deposited on the surface of the piezoelectric layer. An electrical signal (usually a voltage change) applied to the electrodes is converted into an elastic wave propagating on the surface of the piezoelectric layer. If the frequency of the elastic wave corresponds to the frequency band of the filter, the propagation of the wave is advantageous. When the wave reaches the other electrode, it is converted back into an electrical signal again. The piezoelectric layer must have excellent crystalline quality to avoid attenuation of the surface wave. Therefore, a single crystal layer is preferably used here. Currently, materials suitable for industrial applications are quartz, LiNbO 3 or LiTaO 3 .

[0003] Currently, the piezoelectric layer is obtained by cutting an ingot of one of the materials, which results in low thickness accuracy of the layer and non-uniformity of the thickness of the entire layer.

[0004] In addition, the diameter of the ingot of the piezoelectric material is smaller than the diameter of the ingot of the material (such as silicon) used for the substrate. However, for direct transfer (specifically, Smart Cut TM type layer transfer), the donor substrate and the acceptor substrate need to have the same diameter.

[0005] There is still a need for methods that can form uniform, high-quality thick piezoelectric layers on large-diameter substrates. Summary of the Invention

[0006] An object of the present invention is to design a method for manufacturing a substrate for microelectronic devices, photonic devices or optical devices (including but not limited to surface acoustic wave devices), specifically, by enabling the obtaining of a thick (i.e., thickness greater than 5 μm, or even greater than 15 μm), uniform, high-quality layer with a large diameter (i.e., diameter greater than 15 cm or 20 cm).

[0007] According to the present invention, there is provided a method for manufacturing a piezoelectric layer on a substrate, characterized in that the method comprises the following steps:

[0008] - forming a seed layer of a first piezoelectric material on a donor substrate by first epitaxy,

[0009] - transferring the seed layer and a part of the donor substrate to an acceptor substrate via at least one electrically insulating layer and / or at least one conductive layer suitable for allowing relaxation of the seed layer,

[0010] - Remove the transferred portion of the donor substrate to expose the surface of the seed layer.

[0011] - Form a single crystal layer of a second piezoelectric material on the seed layer.

[0012] According to the first embodiment, the step of transferring the seed layer and a portion of the donor substrate includes the following steps:

[0013] - Form a brittle region in the donor substrate to define the portion to be transferred.

[0014] - Bond the donor substrate to a receptor substrate, where the seed layer is located at the bonding interface.

[0015] - Separate the receptor substrate along the brittle region, and form the seed layer on the donor substrate before forming the brittle region.

[0016] According to the second embodiment, the step of transferring the seed layer and a portion of the donor substrate includes the following steps:

[0017] - Form a brittle region in the donor substrate to define the portion to be transferred.

[0018] - Bond the donor substrate to a receptor substrate, where the seed layer is located at the bonding interface.

[0019] - Separate the receptor substrate along the brittle region, and form the seed layer on the donor substrate after forming the brittle region.

[0020] The brittle region can be formed by ion implantation of, in particular, hydrogen and / or helium into the donor substrate.

[0021] Preferably, the seed layer is formed on the donor substrate by atomic layer deposition. Alternatively, the seed layer is formed on the donor substrate by molecular beam epitaxy.

[0022] Preferably, the single crystal layer of the second piezoelectric material is formed by a second epitaxy.

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

[0024] Alternatively, a single crystal layer is formed on the seed layer by depositing the second piezoelectric material in an amorphous form and then recrystallizing the 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 to the receptor substrate has a thickness of less than 2 μm and 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 μm.

[0028] In a specific embodiment, the method includes the following steps: after forming a single crystal layer of the second piezoelectric material, transferring at least a portion of the layer of the second piezoelectric material to a final substrate.

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

[0030] The receptor substrate or the final substrate may include at least one electronic device or interconnect.

[0031] The receptor substrate or the final substrate may include a trap-rich 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] In one embodiment, before forming the seed layer, an intermediate layer suitable for epitaxial growth of the seed layer on the donor substrate may be formed on the donor substrate.

[0034] Another object relates to a method of manufacturing a surface acoustic wave device, the method including the following steps: forming two interdigital electrodes on the surface of a piezoelectric layer, characterized in that the method includes: manufacturing the piezoelectric layer by the method described above.

[0035] Another object relates to a method of manufacturing a photonic device, the method including the following steps: forming at least one photonic component, such as a laser or a light-emitting diode, at least partially in a piezoelectric layer, characterized in that the method includes: manufacturing the piezoelectric layer by the method described above.

[0036] Another object relates to a surface acoustic wave device, characterized in that the surface acoustic wave device includes a piezoelectric layer obtainable by the method described above and two interdigital electrodes located on one surface of the piezoelectric layer.

[0037] Another object relates to a photonic device, characterized in that the photonic device includes a piezoelectric layer obtainable by the method described above and at least one photonic component, such as a laser, a modulator, a waveguide or a multiplexer, formed at least partially in the piezoelectric layer.

[0038] The present invention also relates to a structure that includes at least one such surface acoustic wave device and one such photonic device, the structure including a single piezoelectric layer on which the surface acoustic wave device and the photonic device are arranged. Description of the Drawings

[0039] Other features and advantages of the present invention will become apparent from the following detailed description with reference to the accompanying drawings, in which:

[0040] - Figure 1 is a cross-sectional schematic view of a surface acoustic wave filter,

[0041] - Figure 2A and Figure 2B illustrates two consecutive first steps in a method of manufacturing a single crystal piezoelectric layer according to a first embodiment of the present invention,

[0042] - Figure 3A and Figure 3B illustrates two consecutive first steps in the method according to a second embodiment of the present invention,

[0043] - Figures 4 to 8 illustrates consecutive steps in the method according to a first or second embodiment of the present invention,

[0044] - Figures 9 to 11 illustrates optional additional steps of the method.

[0045] For the sake of readability of the drawings, some elements are not necessarily drawn to scale. Moreover, elements denoted by the same reference numerals in different drawings are identical. Detailed Description

[0046] Figure 1 is a schematic view of a surface acoustic wave filter,

[0047] The filter includes a piezoelectric layer 10 and two electrodes 12, 13 in the form of two interdigital metal combs deposited on the surface of the piezoelectric layer. On the side opposite to the electrodes 12, 13, the piezoelectric layer is located on a substrate 11. The piezoelectric layer 10 is single crystal because excellent crystal quality is preferred to avoid attenuation of surface waves.

[0048] Generally, the present invention proposes to form a single crystal piezoelectric layer by transferring a seed layer of epitaxial growth of a first piezoelectric material to a donor substrate, the transfer being from the donor substrate to a receptor substrate. Then, a layer of a second piezoelectric material is formed on the seed layer to achieve a desired thickness of the single crystal layer of the second piezoelectric material.

[0049] The donor substrate can be a single crystal block substrate of the first piezoelectric material or another material. Alternatively, the donor substrate can be a composite substrate, i.e., formed by a stack of at least two different materials, one surface layer of which consists of the first single crystal piezoelectric material or another single crystal material. The single crystal material is suitable for epitaxial growth of the seed layer; specifically, the single crystal material has lattice parameters sufficiently close to those of the seed layer so that no crystal defects are generated during the growth of the seed layer.

[0050] Advantageously, the seed layer is pseudomorphic, i.e., for example, by atomic force, the actual lattice parameters of the seed layer material are made to substantially match the lattice parameters of the donor substrate on which the seed layer material is formed. For this purpose, the thickness of the seed layer must not exceed a critical thickness, beyond which stress relaxation and defect generation will occur in the seed layer. This critical thickness depends on the material of the seed layer. For example, for a germanium seed layer formed on a silicon substrate, the critical thickness is typically less than 5 nm. Generally, the critical thickness is between 2 nm and 20 nm, depending on the materials selected for the seed layer and the substrate.

[0051] In some embodiments, an intermediate layer (referred to as an "epitaxial intermediate layer") adapted to grow the seed layer material on the donor substrate may be formed on the donor substrate before forming the seed layer. The usefulness of such an intermediate layer specifically depends 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 the interaction or chemical reaction between the seed layer material and the donor substrate material, then no intermediate layer is required. On the other hand, if the chemical interaction or reaction between the seed layer material and the donor substrate material may prevent the growth of the seed layer, then it is desirable to use an intermediate layer made of a material that is stable with respect to both 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 facilitate 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 (SrTiO 3 ), single crystal aluminum oxide (Al 2 O 3 ), single crystal lanthanum aluminate (LaAIO 3 ), or a single crystal metal such as aluminum.

[0052] The receptor substrate serves as a mechanical support for the seed layer. It can be of any type suitable for epitaxy (especially in terms of heat resistance), and advantageously but not necessarily, suitable for the intended application. It can be a solid or a composite material. Advantageously, the receptor substrate may include at least one electronic device or interconnect.

[0053] At least one intermediate layer (referred to as a "relaxation intermediate layer") is sandwiched between the receptor substrate and the seed layer. For example, such an intermediate layer can be conductive or electrically insulating. Those skilled in the art will be able to select the material and thickness of this layer according to the properties they wish to impart to the radio frequency device intended to include the piezoelectric layer. This intermediate layer allows the seed layer to relax freely. The transferred pseudomorphic seed layer can thus freely regain its lattice parameters during transfer, or between transfer and the formation of the second layer of the second piezoelectric material, or during the formation of the second layer of the second piezoelectric material.

[0054] The material of the intermediate layer can advantageously be selected from silicon oxide (SiO 2) nitride or metal.

[0055] The intermediate layer can be formed on a donor substrate (on a seed layer) or on a receptor substrate.

[0056] An intermediate layer made of silicon oxide can be deposited or obtained by thermal oxidation. The technique used to form the layer is specifically selected according to the substrate on which the layer is to be formed and any restrictions to be observed (e.g., thermal restrictions). For example, if the intermediate layer is formed on a receptor substrate and the receptor substrate contains electronic components, a technique with a thermal budget that poses no risk of damaging the components will be selected.

[0057] Advantageously, the receptor substrate can be made of a semiconducting material. For example, this can be a silicon substrate.

[0058] In some embodiments, specifically, when the receptor substrate is the final support for the piezoelectric layer, the receptor substrate includes a trap-rich layer, which can be formed on the receptor substrate or in a surface region of the receptor substrate. The trap-rich layer is thus located between the seed layer and the receptor substrate and improves the electrical insulation properties of the receptor substrate. The trap-rich layer can be formed of at least one polycrystalline, amorphous, or porous semiconductor material, specifically but not limited to polysilicon, amorphous silicon, or porous silicon. In addition, depending on the temperature resistance of the trap-rich layer for epitaxy, an additional layer can be advantageously introduced between the receptor substrate and the trap-rich layer to avoid recrystallization of the trap-rich layer during heat treatment.

[0059] Compared to the thickness of the final single-crystal piezoelectric layer, the seed layer has a negligible thickness. Therefore, it is considered that there is no significant impact on the operation of the radio frequency device incorporating the single-crystal piezoelectric layer.

[0060] The seed layer generally has a thickness between 1 nm and 20 nm.

[0061] 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 in terms of minimum or maximum values. The thickness of the final piezoelectric layer generally ranges between 20 nm and 15 μm.

[0062] The first piezoelectric material is advantageously selected from compounds of the formula ABO 3 where A is selected from barium and lithium, and B is selected from titanium and niobium. However, the interest in these materials is not limited to their piezoelectric properties. Specifically, for other applications (such as integrated optical devices), for example, their dielectric constant, refractive index, or thermoelectric, ferroelectric, or ferromagnetic properties may also be of interest.

[0063] The first epitaxy can be carried out using any technique suitable for achieving high crystal quality, such as atomic layer deposition (ALD) or molecular beam epitaxy (MBE). These techniques are characterized by a very low growth rate. However, since the seed layer has a low thickness, using one of these techniques to grow the seed layer has a low economic impact on the method, but a crystallization quality is indeed achieved in the seed layer that will promote the crystallization quality of the single-crystal layer of the second piezoelectric material.

[0064] According to a first alternative, a layer of the second piezoelectric material can be formed on the seed layer by a second epitaxy.

[0065] The second epitaxy can be carried out using any technique that provides a higher growth rate than the first epitaxy, specifically, metalorganic chemical vapor deposition (MOCVD). Although it provides a lower crystal quality than the ALD technique or the MBE technique, this second epitaxy is more economical for growing relatively thick single-crystal layers.

[0066] According to a second alternative, a layer of the second piezoelectric material can be formed by depositing the piezoelectric material in an amorphous form and then recrystallizing the material to give it a single-crystal structure. Alternatively, the method can be carried out in a plurality of consecutive cycles, each cycle including depositing an amorphous piezoelectric material to a certain thickness and then recrystallizing the material at that thickness until the desired total thickness of the layer of the second piezoelectric material is obtained.

[0067] The amorphous material can be deposited by any technique known to those skilled in the art and advantageously by MOCVD, low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), or sputtering.

[0068] Those skilled in the art will be able to determine the reactants and operating conditions based on the piezoelectric material to be grown and the technique selected.

[0069] Transferring the seed layer generally includes the steps of bonding a donor substrate to a receptor substrate (wherein the seed layer and the intermediate relaxation layer are at the bonding interface), followed by thinning the receptor substrate to expose the seed layer for subsequent epitaxy.

[0070] The bonding step can be carried out, for example, by direct molecular bonding (referred to as wafer bonding) with or without an additional intermediate layer.

[0071] Particularly advantageously, the transfer is carried out using the Smart Cut TM method, which is well known for transferring semiconductor thin films (especially silicon).

[0072] For this purpose, reference is made to Figure 2A, according to the first embodiment, a donor substrate 100 is provided, and a layer of a first single-crystalline piezoelectric material (referred to as the seed layer 102) is grown epitaxially for the first time. The first piezoelectric material has a lattice parameter close to that of the donor substrate. In this way, the donor substrate 100 imposes its lattice parameter and enables the growth of a single-crystalline material of good quality. The growth is stopped when the desired thickness of the seed layer is reached. In this figure, the donor substrate 100 is shown as a solid, but as described above, it can also be a composite material.

[0073] Advantageously but optionally, an intermediate epitaxial layer 106 can be formed on the donor substrate 100 before the epitaxy of the seed layer 102. For simplicity, the layer 106 is not shown in the following figures.

[0074] Reference Figure 2B , a embrittlement region 101 is formed by ion implantation (as indicated by the arrow) through the seed layer into the donor substrate, thereby defining a single-crystalline layer 103 to be transferred (including a part of the seed layer and the donor substrate). Advantageously and depending on the piezoelectric material under discussion, the implanted substance is hydrogen or helium (alone or in combination). Those skilled in the art will be able to determine the dose and implantation energy of these substances to form an embrittlement region at a given depth, which is preferably between 0.2 μm and 0.6 μm; generally, and again depending on the piezoelectric material and the implanted substance under consideration, the dose is in the range of 2E+16 ion substances / cm 2 to 2E+17 ion substances / cm 2 , and the implantation energy is from 30 keV to 500 keV. The buried embrittlement layer can also be obtained by any other means known to those skilled in the art, such as by porosification of the material or by laser irradiation. However, as will be described below, there are transfer methods that do not require ion implantation, and these methods can be used to implement the present invention.

[0075] Figure 3A and Figure 3B illustrates a second embodiment of a method for manufacturing a single-crystalline piezoelectric layer. The second embodiment is Figure 2A and Figure 2B an alternative to the first embodiment shown, in which the implantation in the donor substrate is carried out before the formation of the seed layer by the first epitaxy.

[0076] Reference Figure 3A , a donor substrate 100 is provided, and an embrittlement region 101 is formed by ion implantation (as indicated by the arrow) into the donor substrate 100, thereby defining a single-crystalline layer 103 to be transferred.

[0077] Reference Figure 3B, a layer of a first single-crystalline piezoelectric material (referred to as the seed layer 102) is grown on the layer 103 to be transferred by means of a first epitaxy. As previously mentioned, the donor substrate 100 imposes its lattice parameters and enables the growth of a single-crystalline material of good quality. The first piezoelectric material has lattice parameters close to those of the donor substrate. The growth is stopped when the desired thickness of the seed layer is reached. In this figure, the donor substrate 100 is shown as a solid, but as described above, it can also be a composite material.

[0078] Advantageously, the thermal budget of the first epitaxy is lower than the thermal budget that may cause the donor substrate to break along the embrittlement region. In this way, the donor substrate maintains its mechanical cohesion until the growth of the seed layer is completed.

[0079] After Figure 2A and Figure 2B or Figure 3A and Figure 3B the steps shown, a seed layer 102 is obtained on the donor substrate 100, where an embrittlement region has been formed by implantation, and the embrittlement region defines the layer 103 to be transferred including the seed layer 102.

[0080] Referring Figure 4 , at least one electrically insulating or conductive intermediate relaxation layer 105 is formed on the surface of the receptor substrate 110. The receptor substrate 110 may also include a trap-rich layer 107. For simplicity, the layer 107 is not shown in the following figures.

[0081] Referring Figure 5 , the embrittled donor substrate 100 is bonded to the receptor substrate 110, where the seed layer 102 and the intermediate relaxation layer 105 are located at the bonding interface.

[0082] Referring Figure 6 , the donor substrate 100 is separated along the embrittlement region 101. This separation can be achieved by any means known to those skilled in the art (e.g., thermal, mechanical, chemical, etc.). The layer 103 is then transferred to the receptor substrate 110. Advantageously, the remaining part of the donor substrate can then be recycled.

[0083] Referring Figure 7 , for example, the surface part of the transferred layer is removed by mechanical polishing and / or chemical etching. The purpose of this material removal is to expose the seed layer 102. The result of the removal is a thinned layer 102 on the receptor substrate 110, which will serve as the seed layer for the next step.

[0084] Referring Figure 8, a layer 104 of a second piezoelectric material is formed on the seed layer 102. The material of the layer 104 has lattice parameters that are close to or the same as those of the seed layer 102. In this way, the seed layer 102 imposes its lattice parameters and enables the growth of a single-crystal material with good quality. The layer 104 can be slightly different in nature from the seed layer 102, specifically, by the controlled introduction of a small amount of impurities for various purposes (doping, adjustment of piezoelectric properties, optimization of crystal defect / dislocation density, surfactants, etc.). The growth is stopped when the desired thickness of the single-crystal piezoelectric layer is reached. The final piezoelectric layer 10 is formed by stacking the seed layer 102 and the layer 104.

[0085] The first piezoelectric material and the second piezoelectric material can be the same.

[0086] Alternatively, the first piezoelectric material and the second piezoelectric material can be different.

[0087] As described above, it is considered that the seed layer has no effect or has a second-order effect on the operation of a radio frequency device incorporating a piezoelectric layer formed on the seed layer. Thus, even if the implantation carried out to implement the Smart Cut TM method damages the seed layer and interferes with its piezoelectric properties, these defects cause little or no damage.

[0088] In an unillustrated embodiment, a embrittlement region is not formed in the donor substrate. In this case, the transfer of the seed layer to the receptor substrate is achieved by bonding the donor substrate to the receptor substrate and then etching the donor substrate until the seed layer is exposed. However, compared to the method that includes forming an embrittlement region in the donor substrate, this method is not preferred because it results in greater material loss.

[0089] In a further unillustrated embodiment, an embrittlement region is not formed in the donor substrate, but a separable interface is formed by a chemical or thermal reaction. In this case, the transfer of the seed layer to the receptor substrate is achieved by bonding the donor substrate to the receptor substrate and then separating the interface after the chemical or thermal reaction to expose the seed layer.

[0090] As Figure 8 shown, this method produces a substrate for a surface acoustic wave device that includes a receptor substrate 110 and a single-crystal piezoelectric layer 10 located on the substrate 110. Such a substrate may also prove useful for other applications (such as optoelectronic devices and integrated optical devices).

[0091] The layer 10 is characterized by the presence of two parts with different properties:

[0092] - A first part 102, which is located at the interface with the receptor substrate 110 and corresponds to the seed layer,

[0093] - The second part 104, which extends from the first part 102 and corresponds to a layer formed on the part 102. The second part may have a crystallization quality different from that of the first part (e.g., the quality can be adjusted and optimized during the second epitaxial step) and / or a different composition (especially if impurities such as dopants have been introduced during epitaxy), thereby possibly imparting special properties to the layer formed on the part 102.

[0094] The substrate is advantageously used for manufacturing surface acoustic wave devices as shown in Figure 1 and / or any other microelectronic, photonic or optical device including a piezoelectric layer.

[0095] In some cases, the recipient substrate to which the seed crystal coating is transferred may not be optimal for the intended application. In some embodiments, due to the fact that the recipient substrate must undergo epitaxial operating conditions, the choice of suitable materials is limited. Specifically, the recipient substrate cannot contain layers or elements that may be damaged by the epitaxial temperature. Thus, it may be advantageous to transfer the piezoelectric layer 10 onto a final substrate 120 (the properties of which are selected according to the intended application) via the surface of the layer 104 formed on the seed crystal layer 102 (see Figure 9 ), and to remove the recipient substrate (see Figure 10 ). Any of the transfer techniques described above can be used for this transfer. Another advantage of this transfer to the final substrate is that the seed crystal layer 102 buried in the structure created by the formation of the layer of the second piezoelectric material is now exposed and can be removed if necessary (especially if it has defects) (see Figure 11 ). Thus, only the layer 104 of the second piezoelectric material remains on the final substrate 120.

[0096] The final substrate can be a solid or composite material.

[0097] Advantageously, the final substrate can include at least one electronic device or interconnect.

[0098] In some embodiments, the final substrate includes a trap-rich layer (designated as 121 in Figure 9 ), which can be formed on or in a surface region of the final substrate. The trap-rich layer is thus located between the piezoelectric layer and the final substrate, thereby improving the electrical insulation properties of the final substrate. The trap-rich layer can be formed from at least one polycrystalline, amorphous or porous semiconductor material, specifically but not limited to polycrystalline silicon, amorphous silicon or porous silicon.

[0099] In the case of surface acoustic wave devices, metal electrodes 12, 13 in the form of two interdigital combs are deposited on the surface of the piezoelectric layer 10 opposite the acceptor substrate or the final substrate (as the case may be) (whether the acceptor substrate 110 or the final substrate 120, the substrate forming Figure 1 the support substrate labeled 11 in

[0100] In other applications, at least one photonic component (such as a laser, a modulator, a waveguide or a multiplexer) can be formed in the piezoelectric layer, or in a stack of layers including the piezoelectric layer.

[0101] Particularly advantageously, surface acoustic wave devices and photonic devices can be integrated in the same substrate. To this end, 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. These devices as described can also be combined with other devices present in the acceptor substrate or the final substrate, with a view to known 2D, 2.5D and 3D device co-integration methods.

Claims

1. A method for producing a piezoelectric layer (10) on a substrate (11), characterized in that, the method comprises the following steps: - forming a seed layer (102) of a first piezoelectric material on a donor substrate (100) by a first epitaxy, - transferring the seed layer (102) and a part (103) of the donor substrate (100) to a receptor substrate (110) via at least one electrically insulating layer and / or at least one conductive layer (105) suitable for allowing relaxation of the seed layer, - removing the transferred part (103) of the donor substrate (100) so as to expose the surface of the seed layer (102), - forming a single crystal layer (104) of a second piezoelectric material on the seed layer (102).

2. The method according to claim 1, wherein, the step of transferring the seed layer (102) and the part (103) of the donor substrate (100) comprises the following steps: - forming a brittle region (101) in the donor substrate (100) to define the part (103) to be transferred, - bonding the donor substrate (100) to the receptor substrate (110), wherein the seed layer (102) is located at the bonding interface, - separating the donor substrate (100) along the brittle region (101), and wherein, after forming the brittle region (101), the seed layer (102) is formed on the donor substrate (100).

3. The method according to claim 1, wherein, the step of transferring the seed layer (102) and the part (103) of the donor substrate (100) comprises the following steps: - forming a brittle region (101) in the donor substrate (100) to define the part (103) to be transferred, - bonding the donor substrate (100) to the receptor substrate (110), wherein the seed layer (102) is located at the bonding interface, - separating the donor substrate (100) along the brittle region (101), and wherein, before forming the brittle region (101), the seed layer (102) is formed on the donor substrate (100).

4. The method according to claim 2 or 3, wherein, the brittle region (101) is formed by injecting hydrogen and / or helium ions into the donor substrate (100).

5. The method according to any one of claims 1 to 4, wherein, the seed layer (102) is formed on the donor substrate (100) by atomic layer deposition.

6. The method according to any one of claims 1 to 4, wherein, the seed layer (102) is formed on the donor substrate (100) by molecular beam epitaxy.

7. The method according to any one of claims 1 to 6, wherein, the single crystal layer (104) is formed on the seed layer (102) by a second epitaxy.

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

9. The method according to any one of claims 1 to 6, wherein, forming the single crystal layer (104) on the seed layer (102) is achieved by depositing the second piezoelectric material in an amorphous form and then recrystallizing the second material.

10. The method according to any one of claims 1 to 9, wherein, the seed layer (102) is between 2 nm and 20 nm.

11. The method according to any one of claims 1 to 10, wherein, the portion (103) of the donor substrate (100) transferred to the recipient substrate (110) has a thickness of less than 2 μm and preferably less than 1 μm.

12. The method according to any one of claims 1 to 11, wherein, the layer (104) of the second piezoelectric material has a thickness between 20 nm and 15 μm at the end of the second epitaxy.

13. The method according to any one of claims 1 to 12, wherein, the recipient substrate (110) includes at least one electronic device or interconnect.

14. The method according to any one of claims 1 to 13, wherein, the recipient substrate (110) includes a trap-rich layer (107).

15. The method according to any one of claims 1 to 12, the method comprises the steps of: after forming the single crystal layer of the second piezoelectric material, transferring at least a portion of the layer (104) of the second piezoelectric material onto a final substrate (120).

16. The method according to claim 15, wherein, the portion of the layer (104) of the second piezoelectric material transferred onto the final substrate (120) has a thickness of less than 2 μm and preferably less than 1 μm.

17. The method according to claim 15 or 16, wherein, the final substrate (120) includes at least one electronic device or interconnect.

18. The method according to any one of claims 15 to 17, wherein, the final substrate (120) includes a trap-rich layer (121).

19. The method according to any one of claims 1 to 18, wherein, the first piezoelectric material and the second piezoelectric material are the same.

20. The method according to any one of claims 1 to 18, wherein, the first piezoelectric material and the second piezoelectric material are different.

21. The method according to any one of claims 1 to 20, the method comprises the steps of: before forming the seed layer (102), forming an intermediate layer (106) on the donor substrate (100), the intermediate layer being suitable for epitaxial growth of the seed layer (102) on the donor substrate (100).

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

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

24. A surface acoustic wave device characterized in that the surface acoustic wave device comprises a piezoelectric layer (10) obtainable by the method according to one of claims 1 to 21 and two interdigital electrodes (12, 13) located on one side of the piezoelectric layer (10).

25. A photonic device characterized in that the photonic device comprises a piezoelectric layer obtainable by the 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 partially in the piezoelectric layer.

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

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