Process for manufacturing a donor substrate for the transfer of a piezoelectric layer and process for the transfer of a piezoelectric layer to a support substrate - Patents.com

Abstract

The invention relates to a process for the manufacture of a donor substrate for the transfer of a piezoelectric layer to a support substrate, the process comprising the steps of preparing a handling substrate, in particular a silicon-based substrate, preparing a piezoelectric substrate, depositing a polymer layer on the handling substrate or on the piezoelectric substrate, forming an intermediate layer on a free surface of the piezoelectric substrate, and assembling the piezoelectric substrate to the handling substrate such that the intermediate layer formed on the piezoelectric substrate is sandwiched between the polymer layer and the piezoelectric substrate to form a donor substrate. The invention also relates to a donor substrate manufactured by such a process and to a process for the transfer of a piezoelectric layer using such a donor substrate.

Description

[Technical field]

[0001] The present invention relates to a process for the manufacture of a donor substrate for the transfer of a piezoelectric layer, to a donor substrate and to a process for the transfer of such a piezoelectric layer to a support substrate. [Background technology]

[0002] Piezoelectric-on-insulator (POI) substrates comprise a thin layer of piezoelectric material on a substrate. To manufacture such POI substrates, the process used involves starting with a thicker substrate of piezoelectric material and transferring a thin piezoelectric layer to a supporting substrate.

[0003] For this, a donor substrate is first used, in which a bulk substrate of piezoelectric material is assembled with a handling substrate by bonding with a polymer layer. The donor substrate then undergoes a stage of thinning of the bulk piezoelectric substrate so as to form a thinner piezoelectric layer before being assembled with a support substrate. Finally, the transfer of the piezoelectric layer to the support substrate is carried out mechanically or thermally at the level of the fracture zone previously created in the thinned piezoelectric layer. The donor substrate is introduced into the process in order to limit the adverse effects of differences in the thermal expansion coefficients between the piezoelectric material of the POI and the support substrate. This is because a heat treatment is carried out to strengthen the bonding interface between the different substrates and the transfer of the thin layer. An example of this type of process is described in WO 2019 / 186032 A1.

[0004] In practice, the donor substrate must undergo several steps of thermal and / or mechanical treatment so that delamination of the bonding interface between the piezoelectric substrate and the polymer layer can occur. Summary of the Invention

[0005] One object of the present invention is to overcome the aforementioned disadvantages and in particular to design a donor substrate for the transfer of a piezoelectric layer of a piezoelectric material substrate to a support substrate that exhibits better mechanical strength.

[0006] The object of the present invention is achieved by a process for the manufacture of a donor substrate for the transfer of a piezoelectric layer to a support substrate, the process comprising the steps of preparing a handling substrate, in particular a silicon-based substrate, preparing a piezoelectric substrate, forming an intermediate layer on a free surface of the piezoelectric substrate, depositing a polymer layer on the intermediate layer of the piezoelectric substrate, and assembling the piezoelectric substrate to the handling substrate to form a donor substrate.

[0007] The formation of an intermediate layer between the piezoelectric substrate and the polymer layer makes it possible to obtain a more stable bond between the piezoelectric material and the polymer layer by choosing an intermediate layer that exhibits good adhesion to the piezoelectric substrate and also to the polymer layer. The process according to the invention therefore makes it possible to obtain a donor substrate with improved mechanical stability between the piezoelectric substrate and the polymer layer of the handling substrate compared to the prior art.

[0008] The object of the present invention is also achieved by a process for the manufacture of a donor substrate for the transfer of a piezoelectric layer to a support substrate, the process comprising the steps of preparing a handling substrate, in particular a silicon-based substrate, depositing a polymer layer on a free surface of the handling substrate, preparing a piezoelectric substrate, forming an intermediate layer on the free surface of the piezoelectric substrate, and assembling the piezoelectric substrate to the handling substrate such that the intermediate layer formed on the piezoelectric substrate is sandwiched between the polymer layer and the piezoelectric substrate of the handling substrate to form a donor substrate.

[0009] The formation of an intermediate layer between the piezoelectric substrate and the polymer layer of the handling substrate makes it possible to obtain a more stable bond between the piezoelectric material and the polymer layer by choosing an intermediate layer that exhibits good adhesion to the piezoelectric substrate and also to the polymer layer. The process according to the invention therefore makes it possible to obtain a donor substrate with improved mechanical stability between the piezoelectric substrate and the polymer layer of the handling substrate compared to the prior art.

[0010] According to one embodiment, the formation of the intermediate layer may include the formation of a single layer or several sub-layers.

[0011] According to one embodiment, the formation of the intermediate layer is carried out by a dielectric layer, in particular based on silicon oxide, based on silicon nitride or a combination of silicon nitride and oxide, SiO x N y The use of a dielectric layer formed on the piezoelectric material allows the piezoelectric substrate to be assembled with another substrate to form a donor substrate through this dielectric layer. Thanks to the presence of the dielectric layer creating a connection between the piezoelectric substrate and the handling substrate, the resulting donor substrate has an improved mechanical stability with respect to the different process steps that the donor substrate will subsequently undergo.

[0012] According to one embodiment, a stage of surface treatment of the intermediate layer may be carried out, in particular a plasma treatment, more particularly an oxygen O2 plasma treatment. The plasma treatment is a treatment by dry method that allows the functionalization and / or activation of the surface. The plasma surface treatment consists of a very strong oxidation of the surface of the material. The oxidation of the surface molecules makes it possible to increase the surface tension of the support. The plasma treatment makes it possible to create free radicals at the surface, which promote the successive adhesion of thin layers in contact with these free radicals. The plasma surface treatment therefore makes it possible to improve the chemical properties of the material for a better adhesion to the coating layer. The plasma treatment stage of the process according to the invention therefore makes it possible to improve the adhesion between the dielectric layer formed on the piezoelectric substrate and the polymer layer of the donor substrate, resulting in an improved mechanical stability of the donor substrate compared to the prior art.

[0013] According to an embodiment, a step of thinning of the piezoelectric substrate of the donor substrate can be carried out so as to obtain either a thinned piezoelectric substrate having a thickness t less than the thickness t1 of the piezoelectric substrate, or a piezoelectric layer having a thickness t2 less than the thickness t1 of the piezoelectric substrate. The thinning step can be carried out by a grinding process of the piezoelectric substrate or by a process of chemical etching. Thus, starting from a thick piezoelectric substrate, a thinner piezoelectric substrate or a thinner piezoelectric layer of the desired thickness is obtained, and the donor substrate thus manufactured by the process according to the invention can be used as a donor substrate in a subsequent layer transfer process for transferring a fine layer of piezoelectric material to a support substrate, thus forming a Piezo-on-Insulator (POI) substrate. The use of a finer piezoelectric substrate makes it possible to reduce subsequent problems due to asymmetries in the thermal expansion coefficients, thus minimizing deformations of the assembly during the application of subsequent process steps.

[0014] According to one embodiment, the assembly stage of the process for the manufacture of the donor substrate may include a stage of polymer layer treatment to obtain a cross-linked polymer layer for bonding the handling substrate to the piezoelectric substrate. The formation of a cross-linked polymer layer by a stage of polymer layer treatment is simple to implement and allows for adhesion that satisfies the requirements of the process.

[0015] The object of the invention is also achieved by a donor substrate for the transfer of a piezoelectric layer, characterized in that it comprises a handling substrate, in particular a silicon-based substrate, a piezoelectric substrate and a polymer layer sandwiched between the handling substrate and the piezoelectric substrate, the donor substrate further comprising an intermediate layer sandwiched between the piezoelectric substrate and the polymer layer. Thanks to the presence of the intermediate layer sandwiched between the piezoelectric substrate and the polymer layer, a better bond can be created between the piezoelectric substrate and the polymer layer. This bond results in a donor substrate with improved mechanical stability, making it possible to use this donor substrate later in the process without encountering problems of delamination at the polymer-piezoelectric interface.

[0016] According to one embodiment, the intermediate layer may comprise a single layer or several sub-layers.

[0017] According to one embodiment, the intermediate layer is at least one dielectric layer, in particular silicon oxide and / or silicon nitride or a combination of silicon nitride and oxide, SiO x N y The use of a dielectric layer formed on a piezoelectric material allows the piezoelectric substrate to be subsequently used for assembly with another substrate to form a donor substrate through this dielectric layer in a manner that is robust and stable for the different process steps that the donor substrate will subsequently be subjected to.

[0018] According to one embodiment, the dielectric layer of the intermediate layer can be in direct contact with the polymer layer of the donor substrate, so that the bond between the piezoelectric substrate and the polymer layer of the donor substrate is made through the dielectric layer, which makes it possible to obtain a stable bond for subsequent thermal and / or mechanical process steps of the donor substrate without suffering degradation in the piezoelectric-polymer bond.

[0019] According to one embodiment, the polymer layer can be a polymerized adhesive layer for bonding the piezoelectric substrate to the handling substrate through the intermediate layer of the piezoelectric substrate, the presence of the cross-linked polymer layer making it possible to obtain a stable bond with the intermediate layer of the piezoelectric substrate.

[0020] According to an embodiment, the piezoelectric substrate can be a Lithium Tantalate Oxide (LTO), Lithium Niobate (LNO), Aluminum Nitride (AlN), Lead Zirconate Titanate (PZT), Langasite or Langatate substrate. The donor substrate according to the invention can comprise these materials, which play a key role in devices utilizing the piezoelectric effect.

[0021] The object of the present invention can also be achieved by a process for the transfer of a piezoelectric layer to a support substrate, comprising the steps of providing a piezoelectric substrate, thinned or obtained by implementation of a manufacturing process as described above, on a donor substrate as described above, forming a weakened zone inside the piezoelectric substrate, preparing a support substrate, in particular a silicon-based substrate, attaching the donor substrate to the support substrate to obtain a donor substrate-support substrate assembly, and performing a break along the weakened zone to separate the piezoelectric layer from the remaining part of the donor substrate.

[0022] In such a process, thanks to the use of a donor substrate obtained by the manufacturing process described above, which presents a better mechanical stability at the level of bonding of the piezoelectric material with the polymer layer thanks to the presence of an intermediate layer, the risk of delamination of the piezoelectric material in the support substrate-donor substrate assembly during the implementation of different process steps subsequently applied to the donor substrate-support substrate assembly and due to differences in thermal expansion coefficients is reduced. The use of a donor substrate manufactured according to the invention therefore allows the production of POI substrates with a better yield.

[0023] The invention and its advantages will be explained in more detail hereinafter using preferred embodiments and in particular with the support of the following attached drawings in which reference numbers identify the features of the invention. [Brief description of the drawings]

[0024] [Figure 1a] 1A-1D diagrammatically represent a process for manufacturing a donor substrate according to a first embodiment of the invention and a donor substrate; [Figure 1b] 1A-1D diagrammatically represent a process for the manufacture of a donor substrate according to a first alternative of a first embodiment of the invention, and a donor substrate. [Diagram 2] 3A-3D diagrammatically represent a process for the manufacture of a donor substrate according to a second alternative of the first embodiment of the invention, and a donor substrate. [Diagram 3]5A-5D diagrammatically represent a process for the manufacture of a donor substrate according to a second embodiment of the invention, and a donor substrate. [Figure 4] 5A-5D diagrammatically represent a process for the transfer of a piezoelectric layer according to a third embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The present invention will now be described in more detail using advantageous embodiments in an exemplary manner and with reference to the drawings. It should be noted that the described embodiments are merely possible configurations, and that the individual features as described above can be provided independently of one another or can be omitted altogether during the implementation of the present invention.

[0026] FIG. 1a shows diagrammatically a process for the manufacture of a donor substrate, which is used for the transfer of a piezoelectric layer of the donor substrate to a support substrate according to a first embodiment of the invention.

[0027] The process for the manufacture of a donor substrate starts with a step I) of preparing a handling substrate 100, in particular a bulk substrate. A bulk substrate is a substrate based on only one material, usually having a thickness between 300 μm and 800 μm, in particular between 350 μm and 800 μm. The handling substrate 100 is made of a material whose thermal expansion coefficient is close to that of the material of the support substrate onto which the piezoelectric layer is intended to be transferred. The term "close" is understood to mean that the difference in thermal expansion coefficient between the material of the handling substrate 100 and the material of the support substrate is less than or equal to 5%, and preferably equal to or close to 0%.

[0028] The handling substrate 100 may be a substrate based on silicon, sapphire, aluminum nitride (AlN), silicon carbide (SiC) or also gallium arsenide (GaAs). The handling substrate 100 may be a crystalline or polycrystalline substrate.

[0029] During step II), a piezoelectric substrate 106 is provided. This is preferably a bulk substrate made of only one piezoelectric material, the thickness of which is usually of the order of at least 300 μm, preferably at least 350 μm. According to an alternative, the substrate 106 of piezoelectric material can also be a thick layer of piezoelectric material, between 25 μm and 50 μm, formed on another substrate.

[0030] The piezoelectric material may be, for example, lithium tantalate (LTO), lithium niobate (LNO), aluminum nitride (AlN), lead zirconate titanate (PZT), langasite or langatate.

[0031] According to the invention, a stage III) of the formation of the intermediate layer 108 on the free surface 110 of the piezoelectric substrate 106 is carried out. The formation of the intermediate layer 108 on the free surface 110 of the piezoelectric substrate 106 can be carried out by deposition by spin coating, by thermal growth techniques or by plasma-enhanced deposition such as PECVD or PVD.

[0032] Before carrying out the formation of the intermediate layer 108, one or more steps of cleaning, brushing or polishing the surface of the piezoelectric substrate 106 can be carried out to remove the presence of particles and dust and thus obtain a cleaner free surface 110, which makes it possible to obtain an intermediate layer 108 of better quality.

[0033] According to the invention, the intermediate layer 108 formed on the piezoelectric substrate 106 is a dielectric layer, for example a layer based on silicon oxide or on silicon nitride Si3N4, or a combination of silicon nitride and oxide SiO x N y It is a layer provided with:

[0034] According to an alternative embodiment of the invention, a stage 118 of activation of the surface of the intermediate layer 108 formed on the piezoelectric substrate 106 may be carried out in order to activate the free surface 120 of the intermediate layer 108. In particular, this activation treatment 118 may be a plasma treatment, more particularly an oxygen-based plasma treatment.

[0035] Plasma treatment is a dry treatment that allows the functionalization, activation or cleaning of surfaces by oxidation, or a combination of these effects. The oxidation of surface molecules makes it possible to increase the surface tension of the support, creating pendant bonds on the surface. Plasma treatment makes it possible to create free radicals at the surface, which promote the subsequent adhesion of thin layers in contact with these free radicals. Thus, plasma surface treatment makes it possible to improve the chemical properties of the surface 120 of the dielectric layer 108 of the piezoelectric substrate 106, by creating pendant bond sites, for better adhesion with layers formed by or in contact with the surface 120 of the layer 108 of the piezoelectric substrate 106 during the continuation of the process.

[0036] According to the invention, a stage IV) of deposition of the polymer layer 104 on the intermediate layer 108 of the piezoelectric substrate 106 is carried out. The polymer layer 104 is thus in direct contact with the intermediate layer 108 of the piezoelectric substrate 106 at the interface 126. The presence of the intermediate layer 108 between the piezoelectric substrate 106 and the polymer layer 104 results in a better adhesion with the polymer layer 104 and thus with the piezoelectric substrate 106, compared to the direct bonding between the polymer layer 104 and the piezoelectric substrate 106 of the prior art. This is because it is possible to select the intermediate layer 108 which exhibits good adhesion to the piezoelectric substrate 106 and also to the polymer layer 104.

[0037] The deposition of the polymer layer 104 is advantageously carried out by spin-coating. This technique consists in rotating at a given speed the substrate on which the deposition of the polymer layer 104 is intended to take place, so as to spread said polymer layer 104 evenly over the entire surface of the piezoelectric substrate 106 by centrifugal forces. To this end, the piezoelectric substrate 106 is usually positioned and held by applying a vacuum to a rotating plate. The thickness of the polymer layer 104 obtained depends on the parameters used during the deposition of the layer, i.e. for example on the speed and duration of the rotation of the substrate and on the volume of the polymer solution deposited on the surface of the substrate 106. The thickness of the polymer layer 104 is usually between 1 μm and 6 μm, preferably 3.5 μm.

[0038] The polymer layer 104 may in particular be a photopolymerizable layer based on a thiol-ene resin. For example, the layer sold by Norland Products under the name "NOA61" may be used as the polymer layer 104 in the present invention.

[0039] After deposition by spin coating of the polymer layer 104 onto the piezoelectric substrate 106 , a heat treatment may be performed to improve adhesion of the polymer layer 104 to the active surface 120 of the intermediate layer 108 of the piezoelectric substrate 106 .

[0040] In an alternative embodiment in which a step 118 of activation of the surface 120 of the intermediate layer 108 is performed, the step of deposition of the polymer layer 104 is performed after the step 118 of activation of the surface 120 of the intermediate layer 108. Thus, the deposition of the polymer layer 104 is performed on the active surface 120 of the intermediate layer 108, in direct contact with the active surface 120.

[0041] According to the invention, the piezoelectric substrate 106 obtained after step IV) is then assembled with the handling substrate 100 obtained in step I) during an assembly step V) to form a donor substrate 124 .

[0042] Assembly of the piezoelectric substrate 106 on the handling substrate 100 is performed such that the polymer layer 104 is placed in contact with the layer 108 of the piezoelectric substrate 106 and with the handling substrate 100 .

[0043] After the two substrates are assembled, a bonding step VI) is performed to bond the piezoelectric substrate 106 to the handling substrate 100 so as to form a stable donor substrate 128 .

[0044] The polymer layer 104 undergoes a cross-linking process 130 to modify the mechanical properties of the polymer layer 104. Cross-linking is a general term that describes the process of forming covalent bonds, or an array of relatively short chemical bonds to connect two polymer chains. When the polymer chains are cross-linked, the polymer layer 104 becomes stiffer. Covalent chemical cross-links are mechanically and thermally stable and therefore less likely to break once formed.

[0045] The cross-linking process 130 can be performed by using heat, pressure, by changing the pH or by irradiation. According to the invention, the cross-linking process 130 can be performed by irradiation of the polymer layer 104 with a light beam 130. The irradiation 130 is performed through the piezoelectric substrate 106 or the substrate 100 in order to cross-link the polymer layer 104 and obtain a cross-linked polymer layer 132, also called a polymerized layer 132.

[0046] Irradiation 130 may be performed using a light source, preferably a laser. The optical radiation 130 or light beam is preferably ultraviolet (UV) radiation, preferably having a wavelength between 320 nm and 365 nm.

[0047] The thickness of the crosslinked polymer layer 132 is preferably between 1 μm and 6 μm, in particular about 3.5 μm, depending in particular on the material of the polymer layer 104 deposited before bonding, on the thickness of said polymer layer 140 and on the irradiation conditions.

[0048] Cross-linking of the polymer layer 104 by UV irradiation 130 allows groups to be released, which will cause polymerization of the polymer layer 104. Polymerization of the polymer layer 104 results in chemical bonds that are mechanically and thermally stable and therefore less likely to break once formed. The bond between the polymerized layer 132 and the intermediate dielectric layer 108 thus ensures mechanical intimacy of the donor substrate 128 by keeping the handling substrate 100 and the piezoelectric substrate 106, which form the donor substrate 128, bonded together.

[0049] In the alternative, where the surface activation treatment 118 is performed on the surface 120 of the intermediate layer 108, the adhesion between the cross-linked polymer layer 132 and the dielectric layer 108 of the piezoelectric substrate 106 at the interface 126 is improved by the active surface of the intermediate layer 108, since the pendant bonds present on the active surface of the intermediate dielectric layer 108 of the piezoelectric substrate 106 become to form covalent bonds with the pendant bonds present on the surface of the polymer layer 104. Thus, the contact interface 126 between the intermediate layer 108 of the piezoelectric substrate 106 and the polymer layer 104 is strengthened / reinforced thanks to the surface activation treatment of the intermediate layer 108, resulting in an improved mechanical stability of the donor substrate 124 compared to the prior art.

[0050] In a first alternative of the first embodiment, shown in Fig. 1b, step III) of the process of the formation of the intermediate layer 108 is replaced by the formation of a plurality 112 of sublayers 114, each of which may be the same or different by reason of their material, or by their properties, or by their thickness. All other steps I), II) and IV)-VI) are the same as those described for Fig. 1a. For a detailed description of these steps, reference is therefore made to the description of Fig. 1a.

[0051] At least one layer 116 of the sublayers 114 of the plurality 112 of sublayers is a dielectric layer 116, in particular silicon oxide, silicon nitride Si3N4, or a combination of silicon nitride and oxide SiO x N yIn particular, starting from the piezoelectric substrate 106, the top layer 116, which corresponds to the last layer of the sublayers 114 of the plurality 112, is made of silicon oxide, silicon nitride Si3N4, or a combination of silicon nitride and oxide SiO x N y The plurality 112 of sublayers 114 may be a superposition of a silicon oxide layer and a silicon nitride Si3N4 layer.

[0052] In this alternative, deposition of the polymer layer 104 occurs on an upper layer 116 of the plurality 112 of sublayers 114. The upper layer 116 is thus sandwiched between the polymer layer 104 and the remaining portions of the sublayers 114 of the plurality 112 of sublayers 114 of the piezoelectric substrate 106.

[0053] In this alternative, assembly of the piezoelectric substrate 106 of the handling substrate 100 is performed at the interface 136 between the free surface 102 of the handling substrate 100 and the polymer layer 104 formed on the top layer 116 of the piezoelectric substrate 106. The top layer 116 is thus sandwiched between the polymer layer 104 of the handling substrate and the remaining part of the sublayer 114 of the plurality 112 of the piezoelectric substrate 106, so as to form a heterostructure 134 which becomes a donor substrate 138 after step VI).

[0054] According to an alternative, the surface activation treatment 118 may be performed as in the process described with respect to Fig. 1 a The plasma treatment 118 is performed on a free surface 122 of the upper layer 116 of the plurality 112 of sublayers 114.

[0055] The use of the dielectric layer 108, 116 formed on the piezoelectric material 106 allows the piezoelectric substrate 106 to be subsequently assembled with another handling substrate 100 through the polymer layer 104 deposited on this dielectric layer 108, 116 in a robust and stable manner to form a donor substrate. The mechanical stability of the donor substrate 128, 138 thus obtained, thanks to the dielectric layer-polymer layer bond, allows this donor substrate 128, 138 to be subsequently used in other processes and to be subjected to different thermal and mechanical process steps without undergoing deformations at the interface of the piezoelectric material 106.

[0056] FIG. 2 diagrammatically represents a process for the manufacture of a donor substrate for the transfer of a piezoelectric layer to a support substrate according to an alternative of the first embodiment of the invention.

[0057] Features in common with the first embodiment, which use the same reference numbers as above, will not be mentioned again, but reference is made to the above detailed description.

[0058] The process shown in Fig. 2 comprises, after step VI) shown in Fig. 1a, a step VII) of thinning of the piezoelectric substrate 106 of the donor substrate 128, obtained by the process of the first embodiment and its first alternative. In the same way, a donor substrate 138 can be used.

[0059] The thinning stage VII) may be carried out by a process of grinding or by a process of chemical etching of the piezoelectric substrate 106 so as to reduce the thickness t1 of the substrate 106 of the piezoelectric material of the donor substrate 128 in order to obtain a thinned piezoelectric substrate 140 having a thickness t less than t1, or a piezoelectric layer 140 having a thickness t2 of the order of 20 μm, or between 5 μm and 25 μm. In order to improve the quality of the free surface 142 of the piezoelectric layer 140, a treatment of the free surface 142 of the obtained piezoelectric layer 140 may be carried out after the thinning stage VII) is completed.

[0060] 3 shows a second embodiment of the invention, in which the deposition step of the polymer layer 154 is performed on the handling substrate 100 instead of on the piezoelectric substrate 106. All other steps I), II), III) and V) to VII) are the same as in the first embodiment and its alternatives. Features that are common to the first embodiment and its alternatives and that use the same reference numbers as above will not be mentioned again, but reference is made to the detailed description above.

[0061] During stage IV) of the deposition of the polymer layer 154, the polymer layer 154 is deposited in direct contact with the free surface 102 of the handling substrate 100. Before carrying out the deposition of the polymer layer 154, the handling substrate 100 may first undergo one or more stages of cleaning, brushing or polishing its free surface 102 in order to reduce the presence of particles or dust.

[0062] During the assembly stage V), the polymer layer 154 of the handling substrate 100 is directly contacted to the intermediate layer 108 of the piezoelectric substrate 106. Thus, the contact interface 126 between the polymer layer 154 and the intermediate layer 108 of the piezoelectric substrate 106 also exhibits better adhesion, since it is possible to select the intermediate layer 108, which exhibits good adhesion to the piezoelectric substrate 106 and also to the polymer layer 154, in a similar manner as described above. Thus, through the intermediate layer 108, the contact interface 126 between the piezoelectric substrate 106 and the polymer layer 154 is strengthened / reinforced, resulting in an improved mechanical stability of the donor substrate 124 compared to the prior art.

[0063] 4 diagrammatically represents a process for the transfer of a piezoelectric layer according to a second embodiment of the invention using a donor substrate 144. According to alternatives, the process can be carried out using a donor substrate 128, 138 obtained according to other alternatives described with respect to FIGS.

[0064] During step A), the donor substrate 144 and the support substrate 156 are provided. The support substrate 156 may be a bulk substrate based on silicon, sapphire, aluminum nitride (AlN), silicon carbide (SiC) or gallium arsenide (GaAs). The support substrate 156 may be a crystalline or polycrystalline substrate. The donor substrate 144 exhibits mechanical stability, which allows it to be used in a process for the transfer of the piezoelectric layer 152 to the support substrate 156.

[0065] 4, the support substrate 156 may comprise a dielectric layer 158 previously formed on a free surface 160 of the support substrate 156, for example by deposition by spin coating, or by a deposition technique such as plasma deposition or evaporation deposition, or by thermal growth. The dielectric layer 158 may be, for example, a layer of silicon oxide, a layer of silicon nitride Si3N4, or a layer of silicon oxynitride SiO x N y The dielectric layer 158 may comprise a combination of silicon nitride and oxide, also known as a silicon nitride layer, or a superposition of a layer of oxide and a layer of nitride. According to an alternative, the formation of the dielectric layer 158 may be followed by a heat treatment to improve the adhesion of the dielectric layer 158 to the support substrate 156. A surface treatment may also be performed to improve the quality of the surface of the formed dielectric layer 158.

[0066] The dielectric layer 158 may also be a layer of native oxide formed on the free surface 160 of the support substrate 156 .

[0067] In alternative embodiments, other layers, for example layers for creating a Bragg mirror or a trapping layer, may be present in the support substrate 156 and / or the dielectric layer 158. In yet another alternative, the support substrate 156 is provided without the dielectric layer 158 and / or without the native oxide layer.

[0068] In the alternative, instead of or in addition to the dielectric layer 158 formed on the support substrate 156, a dielectric layer may be provided on the piezoelectric layer 140 of the donor substrate 144.

[0069] Alternatively, the support substrate 156 may also comprise other layers. For example, layers for producing a Bragg mirror or a trapping layer may be present in the support substrate 156. In particular, a trapping layer of polycrystalline, amorphous or porous silicon type may be present, with a thickness varying between 500 nm and 5 μm.

[0070] Step B) of forming a weakened zone 146 in the piezoelectric layer 140 of the donor substrate 144 is performed to define the area of ​​the piezoelectric layer 152 that is to be transferred from the remaining portion 162 of the piezoelectric layer 140 .

[0071] This step of forming the weakened zone 146 is carried out by implantation 150 of atomic or ionic elements in the piezoelectric layer 140 in the donor substrate 144. The atomic or ionic implantation 150 is carried out in such a way that the weakened zone 146 is located inside the piezoelectric layer 140 and separates the piezoelectric layer 152 from the remaining part 162 of the piezoelectric layer 140. The atomic or ionic elements are implanted at a predetermined depth in the piezoelectric layer 140, which determines the thickness t3 of the piezoelectric layer 152 to be transferred and the thickness t4 of the remaining part 148 of the piezoelectric layer 140. The thickness t3 is typically between 50 nm and 1 μm, in particular around 600 nm. Without being limited thereto, a dielectric layer can be formed on the piezoelectric layer 140 obtained from the donor substrate 144. This dielectric layer can be, for example, a layer of silicon oxide, a layer of silicon nitride Si3N4 or a layer of silicon oxynitride, SiO x N y 150)と、350〜350℃。 Also known as "silica" or "silica", it is a layer comprising a combination of silicon nitride and oxide, also known as "silica" or a superposition of a layer of oxide and a layer of nitride. According to an alternative, the formation of this dielectric layer may be followed by a heat treatment in order to improve the adhesion of the dielectric layer to the piezoelectric layer 140. A surface treatment in order to improve the quality of the surface of this formed dielectric layer may also be carried out, in particular after the step of implantation 150 and before step C) described below.

[0072] During stage C) of the transfer process according to the invention, the donor substrate 144 is assembled with the support substrate 156 in order to obtain a support substrate-donor substrate assembly 170. The assembly 170 of the donor substrate 144 and the support substrate 156 is performed at the level of the dielectric layer 158, so that the piezoelectric layer 140 of the donor substrate 144 is in direct contact with the dielectric layer 158, and the piezoelectric layer 152 to be transferred is sandwiched between the support substrate 156 and the remaining part 162 of the donor substrate 144. In an alternative, as previously described, the assembly 170 of the donor substrate 144 with the support substrate 156 is performed between the dielectric layer 158 and a dielectric layer formed on the donor substrate 144.

[0073] Assembly is effected in a known manner by molecular attachment between the two substrates at the piezoelectric-support substrate interface.

[0074] Thereafter, a breaking step D) is performed along the weakened zone 146 of the donor substrate 144 by applying thermal and / or mechanical energy to separate the piezoelectric layer 152 from the remaining portion 162 of the donor substrate 144.

[0075] In this way, a POI substrate 174 is obtained, comprising the support substrate 156, the dielectric layer 158 and the transferred piezoelectric layer 152.

[0076] Thanks to the presence of the intermediate dielectric layer 108 between the piezoelectric layer 140 and the polymer layers 120, 132, it is possible to reduce the risk of delamination between the piezoelectric layer 140 and the polymer layers 120, 132 of the donor substrate 144 during fracture of the donor substrate 144. Thus, the use of the donor substrate 144 manufactured according to the present invention allows the manufacture of a POI substrate 174 with a better yield.

[0077] It should be noted that the described embodiments are merely possible configurations, and that individual features of the different embodiments can be combined with each other or can be brought about independently of each other.

Claims

1. 1. A process for the manufacture of a donor substrate (128, 138, 144) for the transfer of a piezoelectric layer to a support substrate, comprising: providing a handling substrate (100), in particular a silicon-based substrate; providing a piezoelectric substrate (106); forming an intermediate layer (108) on a free surface of the piezoelectric substrate (106); depositing a polymer layer (104) onto the intermediate layer (108) of the piezoelectric substrate (106); assembling the piezoelectric substrate (106) to the handling substrate (100) to form the donor substrate (128, 138, 144); The process includes:

2. 1. A process for the manufacture of a donor substrate (128, 138, 144) for the transfer of a piezoelectric layer to a support substrate, comprising: providing a handling substrate (100), in particular a silicon-based substrate; depositing a polymer layer (154) on the free surface of said handling substrate (100); providing a piezoelectric substrate (106); forming an intermediate layer (108, 112) on a free surface of the piezoelectric substrate (106); assembling the piezoelectric substrate (106) to the handling substrate (100) such that the intermediate layer (108, 112) formed on the piezoelectric substrate (106) is sandwiched between the polymer layer (132, 154) of the handling substrate (100) and the piezoelectric substrate (106) to form the donor substrate (128, 138, 144); The process includes:

3. The application of the intermediate layer (108, 112) to the piezoelectric substrate (106) is in particular based on silicon oxide, on silicon nitride or on a combination of silicon oxide and nitride, SiO ｘ N ｙ 3. A process for the manufacture of a donor substrate (128, 138, 144) according to claim 1 or 2, comprising at least forming a dielectric layer based on

4. Surface treatment of the intermediate layer (108, 112), particularly plasma treatment, more particularly O ２ 3. A process for manufacturing a donor substrate (128, 138, 144) according to claim 1 or 2, further comprising a plasma treatment step (118).

5. 3. A process for manufacturing a donor substrate (128, 138, 144) according to claim 1 or 2, further comprising a step of thinning the piezoelectric substrate (106) of the donor substrate (124, 138, 144) to obtain a thinned piezoelectric substrate (140) or a piezoelectric layer (140), in particular by grinding.

6. A donor substrate (124, 138, 144) for transfer of a piezoelectric layer, comprising: a handling substrate (100), in particular a silicon-based substrate; a piezoelectric substrate (106, 140); a polymer layer (104, 154, 132) sandwiched between the handling substrate (100) and the piezoelectric substrate (106, 140); Equipped with the donor substrate (124, 138, 144) further comprises an intermediate layer (108, 112) sandwiched between the piezoelectric substrate (106, 140) and the polymer layer (104, 154, 132); A donor substrate (124, 138, 144).

7. The donor substrate (124, 138, 144) of claim 6, wherein the intermediate layer (108, 112) comprises a single layer (108) or several sublayers (114).

8. The intermediate layer (108, 112) is formed of at least one dielectric layer (108, 116), in particular based on silicon oxide, based on silicon nitride or a combination of silicon nitride and oxide SiO ｘ N ｙ The donor substrate (124, 138, 144) of claim 6, comprising a layer based on

9. The donor substrate (124, 138, 144) of claim 6, wherein the intermediate layer (108, 112) is in direct contact with the polymer layer (104, 154, 132).

10. 7. The donor substrate of claim 6, wherein the piezoelectric substrate is a lithium tantalate (LTO), lithium niobate (LNO), aluminum nitride (AlN), lead zirconate titanate (PZT), langasite, or langatate substrate.

11. 1. A process for the transfer of a piezoelectric layer to a support substrate, comprising: Providing a thinned piezoelectric substrate (140) on a donor substrate (144) according to any one of claims 6 to 10; forming a weakened zone (146) within the piezoelectric substrate (140) of the donor substrate (144); providing a support substrate (156), in particular a silicon-based substrate; attaching the donor substrate (144) to the support substrate (156) to obtain a donor substrate-support substrate assembly (170); performing a fracture along the weakened zone (146) to separate the piezoelectric layer (152) from the remaining portion (162) of the donor substrate (144); The process includes:

Images