Preparation method of heterogeneous film substrate

Abstract

The invention discloses a preparation method of a heterogeneous film substrate, and belongs to the field of semiconductor material preparation. The preparation method of the heterogeneous film substrate comprises the steps that a first piezoelectric substrate and a second piezoelectric substrate which are in bonding connection are provided, the first piezoelectric substrate is arranged on the second piezoelectric substrate, and the first piezoelectric substrate and the second piezoelectric substrate are the same in cutting type and opposite in polarity; performing ion implantation on one surface, far away from the second piezoelectric substrate, of the first piezoelectric substrate, and forming a defect layer in the first piezoelectric substrate to obtain a reverse piezoelectric substrate; bonding and connecting the reverse piezoelectric substrate with the supporting substrate to obtain a heterostructure substrate; and annealing stripping and post-processing are carried out on the heterostructure substrate, so that the piezoelectric film layer is transferred from the reverse piezoelectric substrate to the supporting substrate, and the heterogeneous film substrate is obtained. According to the method, warping can be reduced, thermal stress in annealing can be reduced, the steps of wafer thinning, double-sided injection and the like do not need to be added, and the qualified rate of the heterogeneous film substrate is improved while the preparation efficiency is improved.

Description

Technical Field

[0001] The present application relates to a method for preparing a heterogeneous thin film substrate, and belongs to the field of semiconductor material preparation. Background Art

[0002] Composite thin film substrates are usually composed of functional layers, intermediate layers and substrate layers. The substrate layer provides support for the intermediate layers and functional layers. The functional layer mainly realizes the conversion of electrical-acoustic signals, while the intermediate layer is often used for temperature compensation or improving bonding force. Composite thin film substrates are widely used in nonlinear optics, ferroelectric materials, piezoelectric devices, electro-optical technology and other fields because of their piezoelectric, ferroelectric, photoelectric, photoelastic, pyroelectric, photorefractive and nonlinear properties.

[0003] At present, in the preparation process of composite thin film substrates, there are the following problems: on the one hand, during the ion implantation of the piezoelectric substrate, due to the increase in temperature, a large warp is easily generated, which affects the subsequent bonding process; on the other hand, during the annealing process, due to the different thermal expansion coefficients of the piezoelectric substrate and the supporting substrate, a large thermal stress is introduced, which easily leads to the fragmentation of the bonding structure. Among them, the deformation caused by ion implantation is related to the thickness of the piezoelectric substrate. The warp can be reduced by increasing the thickness of the piezoelectric substrate. However, increasing the thickness of the piezoelectric wafer will introduce a large stress in the subsequent annealing process, resulting in the fragmentation of the bonding structure. In addition, double-sided implantation of the piezoelectric wafer can also offset the warp. However, this method doubles the ion implantation time and reduces the preparation efficiency. At the same time, both methods require a wafer grinding process to thin the piezoelectric wafer, thereby reducing the annealing thermal stress of the heterogeneous bonding structure. This not only causes a large amount of material waste, but also introduces new stress and damage layers, thus affecting the subsequent process. Summary of the invention

[0004] In order to solve the above problems, a method for preparing a heterogeneous thin film substrate is provided, which can reduce warping and thermal stress during annealing, and does not require additional steps such as wafer thinning and double-sided injection. This improves the qualification rate of the heterogeneous thin film substrate while improving the preparation efficiency.

[0005] The present application provides a method for preparing a heterogeneous thin film substrate, comprising the following steps:

[0006] S1, providing a first piezoelectric substrate and a second piezoelectric substrate that are bonded to each other, wherein the first piezoelectric substrate is disposed on the second piezoelectric substrate, and the first piezoelectric substrate and the second piezoelectric substrate have the same cut shape and opposite polarities;

[0007] S2, performing ion implantation on a surface of the first piezoelectric substrate away from the second piezoelectric substrate to form a defect layer in the first piezoelectric substrate to obtain an inverse piezoelectric substrate;

[0008] S3, bonding the reverse piezoelectric substrate to a support substrate, wherein a surface of the first piezoelectric substrate away from the second piezoelectric substrate is in contact with the support substrate, to obtain a heterostructure substrate;

[0009] S4, performing annealing, peeling and post-processing on the heterostructure substrate to transfer the piezoelectric film layer from the reverse piezoelectric substrate to the supporting substrate to obtain a heterogeneous film substrate.

[0010] Optionally, the first piezoelectric substrate and the second piezoelectric substrate as well as the reverse piezoelectric substrate and the supporting substrate are permanently bonded, and the bonding strength is 0.5-3 joules / square meter.

[0011] Optionally, the thickness of the first piezoelectric substrate and the thickness of the second piezoelectric substrate are both 250-1000 microns.

[0012] Optionally, the thickness of the first piezoelectric substrate is the same as the thickness of the second piezoelectric substrate.

[0013] Optionally, the piezoelectric film layer has a thickness of 100-1000 nanometers.

[0014] Optionally, the support substrate has a thickness of 250-1000 microns.

[0015] Optionally, the material of the first piezoelectric substrate and the material of the second piezoelectric substrate include lithium niobate or lithium tantalate;

[0016] The material of the support substrate includes one or a combination of silicon, sapphire, silicon carbide, quartz single crystal, silicon nitride, fused quartz or lanthanum gallium silicate.

[0017] Optionally, the ion type of the ion implantation includes one of hydrogen ions, helium ions, nitrogen ions, oxygen ions or argon ions;

[0018] The energy of the ion implantation is 100-200 kiloelectronvolts;

[0019] The ion implantation dose is 1×10 16 -1×10 17 Pieces / square centimeter.

[0020] Optionally, the annealing and stripping includes a first annealing treatment and a second annealing treatment;

[0021] The temperature of the first annealing treatment is 100-300°C, the time is 20-40 hours, and the heating rate is 0.1-1°C / min;

[0022] The temperature of the second annealing treatment is 300-800° C., the time is 30-50 hours, and the heating rate is 1-5° C. / minute.

[0023] Optionally, the post-processing includes a polishing and thinning step:

[0024] The surface is treated by chemical mechanical polishing until the surface roughness Ra of the piezoelectric film layer is less than 0.5 nm.

[0025] The beneficial effects of this application include but are not limited to:

[0026] The preparation method of the heterogeneous thin film substrate of the present application, by bonding the two positive polarity surfaces of the first piezoelectric substrate and the second piezoelectric substrate, utilizes the mutual offset of deformation of the two when heated, effectively reduces the warping problem of the piezoelectric substrate during ion implantation, and is conducive to the subsequent bonding of the reverse piezoelectric substrate and the supporting substrate. At the same time, the thermal expansion coefficients of the first piezoelectric substrate and the second piezoelectric substrate offset each other, so that the reverse piezoelectric substrate has a near-zero temperature coefficient, which is closer to the supporting substrate, and can greatly reduce the thermal stress of the annealing heat treatment, avoiding the problem of fragmentation of the heterogeneous thin film substrate. In addition, the double-layer piezoelectric substrate that has been permanently bonded can be recycled as a whole after simple treatment, saving a lot of production time and reducing costs. The heterogeneous thin film substrate obtained by the preparation method of the heterogeneous thin film substrate of the present application has the advantages of reducing the deformation of the piezoelectric substrate and the annealing thermal stress, while eliminating the steps of wafer thinning, double-sided injection, temporary bonding and debonding, while improving the preparation efficiency and improving the qualified rate of the heterogeneous thin film substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0028] Figure 1 It is a schematic flow chart of a method for preparing a heterogeneous thin film substrate according to an embodiment of the present application.

[0029] Figure 2 This is a schematic structural diagram of the bonding connection between the first piezoelectric substrate and the second piezoelectric substrate involved in an embodiment of the present application.

[0030] Figure 3 It is a structural schematic diagram of a method for preparing a heterogeneous thin film substrate involved in an embodiment of the present application.

[0031] Figure 4 This is a schematic structural diagram of a method for preparing a heterogeneous thin film substrate according to Comparative Example 1 of the present application.

[0032] Figure 5 This is a measured diagram of the warping of the reverse piezoelectric substrate involved in Example 1 of the present application.

[0033] Figure 6 This is a measured diagram of the warping of the reverse piezoelectric substrate involved in Example 2 of the present application.

[0034] Figure 7 This is a measured diagram of the warping of the reverse piezoelectric substrate involved in Example 3 of the present application.

[0035] Figure 8 This is a measured diagram of the warping of the heterostructure substrate involved in Comparative Example 1 of the present application.

[0036] List of parts and reference numerals:

[0037] 1. First piezoelectric substrate, 101. Residual material layer, 102. Defective layer, 103. Piezoelectric film layer, 2. Second piezoelectric substrate, 3. Reverse piezoelectric substrate, 4. Support substrate, 5. Heterostructure substrate. DETAILED DESCRIPTION

[0038] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0039] If no specific conditions are specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The raw materials or instruments used, if no manufacturer is specified, are all conventional products that can be purchased commercially.

[0040] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0041] See also Figure 1 The present invention discloses a method for preparing a heterogeneous thin film substrate, comprising the following steps:

[0042] S1, providing a first piezoelectric substrate 1 and a second piezoelectric substrate 2 that are bonded to each other, wherein the first piezoelectric substrate 1 is disposed on the second piezoelectric substrate 2, and the first piezoelectric substrate 1 and the second piezoelectric substrate 2 have the same cut shape and opposite polarities;

[0043] S2, performing ion implantation on a surface of the first piezoelectric substrate 1 away from the second piezoelectric substrate 2 to form a defect layer 102 in the first piezoelectric substrate 1, thereby obtaining a reverse piezoelectric substrate 3;

[0044] S3, bonding the reverse piezoelectric substrate 3 to the support substrate 4, so that the first piezoelectric substrate 1, one side away from the second piezoelectric substrate 2, contacts the support substrate 4, to obtain a heterostructure substrate 5; the heterostructure substrate 5 includes the support substrate 4 and the reverse piezoelectric substrate 3;

[0045] S4, annealing, peeling and post-processing the heterostructure substrate 5 to transfer the piezoelectric film layer 103 from the reverse piezoelectric substrate 3 to the supporting substrate 4 to obtain a heterogeneous film substrate; the heterogeneous film substrate includes the supporting substrate 4 and the piezoelectric film layer 103 located on the supporting substrate 4.

[0046] After the above steps S1 and S2, the reverse piezoelectric substrate 3 after ion implantation no longer has obvious warping. This is because the first piezoelectric substrate 1 and the second piezoelectric substrate 2 are prone to warping in the high temperature generated by ion implantation. Since the first piezoelectric substrate 1 and the second piezoelectric substrate 2 have opposite polarities and the edge chuck positions are fixed when heated, the warping directions are opposite, which cancel each other out in the reverse piezoelectric substrate 3, thereby eliminating the warping and facilitating the subsequent bonding.

[0047] In the embodiment of the present application, the first piezoelectric substrate 1 and the second piezoelectric substrate 2 with opposite polarities are made of the same material, and polarity reversal is achieved by flipping them during bonding. Figure 2 As shown, after flipping and bonding, the first piezoelectric substrate 1 and the two positive polarity surfaces of the second piezoelectric substrate 2 are bonded, thereby providing a permanent bonding connection between the first piezoelectric substrate 1 and the second piezoelectric substrate 2 with opposite polarities.

[0048] In an optional implementation, before the reverse piezoelectric substrate 3 is bonded to the support substrate 4, the preparation method further comprises: growing an intermediate layer on the surface of the support substrate 4 to obtain the support substrate 4 with the intermediate layer.

[0049] Preferably, the intermediate layer is grown on the surface of the supporting substrate 4 by chemical vapor deposition.

[0050] Furthermore, the reverse piezoelectric substrate 3 is bonded to a support substrate 4 with an intermediate layer to obtain a heterostructure substrate 5; wherein the injection surface of the first piezoelectric substrate 1 is in contact with the intermediate layer of the support substrate 4.

[0051] Optionally, the material of the intermediate layer includes at least one of silicon dioxide, silicon nitride, aluminum oxide and aluminum nitride.

[0052] In an embodiment of the present application, ion implantation is performed on the unbonded surface of the first piezoelectric substrate 1 to form a defect layer 102; wherein the defect layer 102 is located on a side of the first piezoelectric substrate 1 away from the second piezoelectric substrate 2, and the injected particles are distributed in the defect layer 102 to obtain a reverse piezoelectric substrate 3.

[0053] In an optional implementation, the first piezoelectric substrate 1 and the second piezoelectric substrate 2 as well as the reverse piezoelectric substrate 3 and the supporting substrate 4 are permanently bonded, and the bonding strength is 0.5-3 joules / square meter.

[0054] Optionally, the bonding method adopts one or more of surface activated bonding, hydrophilic bonding, and polymer bonding.

[0055] For example, the reverse piezoelectric substrate 3 is obtained by using hydrophilic bonding, and then the bonding surface between the reverse piezoelectric substrate 3 and the supporting substrate 4 is activated, and the heterostructure substrate 5 is obtained by surface activation bonding.

[0056] In an optional implementation, the first piezoelectric substrate 1 and the second piezoelectric substrate 2 are both at wafer level, and the thickness of the first piezoelectric substrate 1 and the thickness of the second piezoelectric substrate 2 are both 250-1000 microns.

[0057] In an optional implementation, the thickness of the first piezoelectric substrate 1 is the same as the thickness of the second piezoelectric substrate 2 .

[0058] In an optional implementation, the thickness of the piezoelectric film layer 103 is 100-1000 nanometers, which can be adjusted by the ion implantation depth.

[0059] In an optional embodiment, the thickness of the support substrate 4 is 250-1000 microns.

[0060] In an optional embodiment, the material of the first piezoelectric substrate 1 and the material of the second piezoelectric substrate 2 include lithium niobate or lithium tantalate;

[0061] The material of the support substrate 4 includes one or a combination of silicon, sapphire, silicon carbide, quartz single crystal, silicon nitride, fused quartz or lanthanum gallium silicate.

[0062] Preferably, the material of the support substrate 4 is silicon and / or silicon carbide; more preferably, the material of the support substrate 4 is silicon, which has the advantages of low cost and good performance.

[0063] In an optional embodiment, the ion species of the ion implantation includes one of hydrogen ions, helium ions, nitrogen ions, oxygen ions or argon ions;

[0064] The energy of ion implantation is 100-200 keV;

[0065] The ion implantation dose is 1×10 16 -1×10 17 Pieces / square centimeter.

[0066] Preferably, the ion species of the ion implantation are hydrogen ions or helium ions;

[0067] When the ion type of the ion implantation is hydrogen ion, the energy of the ion implantation is 100 keV and the dose is 1×10 17 pcs / cm2;

[0068] When the ion type of the ion implantation is helium ion, the ion implantation energy is 150 keV and the dose is 8×10 16 Pieces / square centimeter.

[0069] In an optional embodiment, the annealing stripping includes a first annealing treatment and a second annealing treatment;

[0070] The first annealing treatment is performed at a temperature of 100-300°C, a time of 20-40 hours, and a heating rate of 0.1-1°C / min;

[0071] The temperature of the second annealing treatment is 300-800° C., the time is 30-50 hours, and the heating rate is 1-5° C. / minute.

[0072] In the embodiment of the present application, the first piezoelectric substrate 1 after ion implantation includes a piezoelectric film layer 103 , a defect layer 102 and a residual layer 101 , and the defect layer 102 is located between the piezoelectric film layer 103 and the residual layer 101 .

[0073] During the first annealing process, bubbles are formed in the defect layer 102 and connected together, causing the injection layer to crack, and the piezoelectric film is separated from the reverse piezoelectric substrate 3 and transferred to the supporting substrate 4 to obtain a heterogeneous film substrate;

[0074] During the second annealing process, the damage to the piezoelectric film layer 103 caused by the ion implantation is restored.

[0075] In an optional embodiment, the post-processing includes the steps of polishing and thinning:

[0076] The surface is treated by chemical mechanical polishing until the surface roughness Ra of the piezoelectric film layer is less than 0.5 nm, in order to remove the damage caused by ion implantation and reduce the roughness.

[0077] In the embodiments of the present application, Figure 3 As shown, after the heterogeneous thin film substrate is obtained by the preparation method of the present application, the reverse piezoelectric substrate 3 can be polished and then ion implanted to form the reverse piezoelectric substrate 3 including the defect layer 102, thereby achieving repeated use and reducing costs.

[0078] In the embodiments of the present application, in order to solve the warping problem in ion implantation, the conventional process usually uses a thicker wafer for ion implantation, then bonds with the supporting substrate 4, and then thins it to reduce the annealing thermal stress. However, the wafer material removed by thinning is wasted, resulting in excessively high production costs; and the process is complicated, and mechanical grinding introduces a large number of scratches and stresses, which can easily lead to fragmentation and reduce the yield. However, the present application uses a reverse piezoelectric substrate 3 that compensates for thermal deformation, which not only reduces the warping in the ion implantation step, but also reduces the thermal expansion coefficient in the annealing process, greatly reducing thermal stress, thereby eliminating the thinning process, and directly performing annealing and peeling after bonding, thereby improving production efficiency and increasing product yield. In addition, the reverse piezoelectric substrate 3 of the present application can be repeatedly peeled off to achieve reuse and reduce production costs.

[0079] It should be noted that the thermal stress in the heterostructure substrate 5 is closely related to the thermal expansion coefficient of the material. The greater the difference in thermal expansion coefficients between the supporting substrate 4 material and the piezoelectric substrate material, the greater the thermal stress of the heterostructure substrate 5, and cracking is prone to occur at high temperatures. Table 1 shows the thermal expansion coefficients of common substrate materials. It can be seen that the difference in thermal expansion coefficients between the piezoelectric substrate and the supporting substrate 4 is large, and cracking is prone to occur during thermal annealing. Using the preparation method proposed in the present application, the thermal expansion of the first piezoelectric substrate 1 and the second piezoelectric substrate 2 with opposite polarities in the reverse piezoelectric substrate 3 compensates for each other, so that the thermal expansion coefficient of the reverse piezoelectric substrate 3 is small and close to the supporting substrate 4, thereby effectively reducing the annealing thermal stress and avoiding the appearance of fragments due to the large difference in thermal expansion coefficients between the piezoelectric substrate and the supporting substrate 4.

[0080] Table 1

[0081]

[0082] Example 1

[0083] A method for preparing a heterogeneous thin film substrate comprises the following steps:

[0084] S1, providing a first piezoelectric substrate 1 and a second piezoelectric substrate 2 (both are YX lithium niobate double-sided polished wafers, each with a thickness of 500 microns) that are permanently bonded, cleaning the first piezoelectric substrate 1 and the second piezoelectric substrate 2 respectively, flipping the first piezoelectric substrate 1 by 180 degrees, and activating the bonding with the surface of the second piezoelectric substrate 2, with a bonding strength of 3 joules / square meter, thereby obtaining a reverse piezoelectric substrate 3 with opposite polarity and permanent bonding, with a thickness of 1000 microns;

[0085] S2, helium ion implantation is performed on the side of the first piezoelectric substrate 1 in the reverse piezoelectric substrate 3 away from the second piezoelectric substrate 2, with an energy of 150 keV and a dose of 8×10 16 / square centimeter; forming a defect layer 102 in the first piezoelectric substrate 1;

[0086] Among them, ion implantation will cause stress and defects in the piezoelectric substrate, causing warping, but because the present application uses a reverse piezoelectric substrate 3 with opposite polarity and permanent bonding, the deformations cancel each other out, reducing the warping caused by ion implantation. Then, the surface shape of the reverse piezoelectric substrate 3 after ion implantation is characterized. Figure 5 This is the surface shape of the reverse piezoelectric substrate 3 after ion implantation in this embodiment, and its warp value is only 3.191 microns, which meets the bonding requirements;

[0087] S3, providing a double-polished support substrate 4 made of silicon and having a thickness of 500 microns, connecting the reverse piezoelectric substrate 3 to the support substrate 4 by surface activation bonding, with a bonding strength of 2 joules / square meter, and contacting the support substrate 4 with the side of the first piezoelectric substrate 1 away from the second piezoelectric substrate 2, to obtain a heterostructure substrate 5;

[0088] S4, annealing, peeling and post-processing the heterostructure substrate 5, so that the piezoelectric film layer 103 with a thickness of 500 nanometers is transferred from the reverse piezoelectric substrate 3 to the supporting substrate 4, to obtain a heterostructure film substrate;

[0089] Among them, the first annealing atmosphere is nitrogen, the annealing temperature is 270°C, the time is 30 hours, and the heating rate is 0.5°C / minute; the second annealing atmosphere is nitrogen, the annealing temperature is 400°C, the time is 40 hours, and the heating rate is 5°C / minute. The annealing of the heterostructure substrate 5 usually often causes fragments due to the mismatch of thermal expansion coefficients, and requires thinning. The thermal deformation of the reverse piezoelectric substrate 3 proposed in this application offsets each other, so it has a thermal expansion coefficient similar to that of the supporting substrate 4, and the thinning step can be omitted. The annealing peeling transfer can be directly realized to obtain a heterogeneous thin film substrate. At the same time, the transferred reverse piezoelectric substrate 3 can be reused, which reduces the cost.

[0090] Example 2

[0091] A method for preparing a heterogeneous thin film substrate comprises the following steps:

[0092] S1, providing a first piezoelectric substrate 1 and a second piezoelectric substrate 2 (both are YX lithium tantalate double-sided polished wafers, each with a thickness of 250 microns) that are permanently bonded, cleaning the first piezoelectric substrate 1 and the second piezoelectric substrate 2 respectively, flipping the first piezoelectric substrate 1 by 180 degrees, and activating the bonding with the surface of the second piezoelectric substrate 2, with a bonding strength of 3 joules / square meter, thereby obtaining a reverse piezoelectric substrate 3 with opposite polarity and permanent bonding, with a thickness of 500 microns;

[0093] S2, hydrogen ion implantation is performed on the side of the first piezoelectric substrate 1 in the reverse piezoelectric substrate 3 away from the second piezoelectric substrate 2, with an energy of 100 keV and a dose of 1×10 17 / square centimeter; forming a defect layer 102 in the first piezoelectric substrate 1;

[0094] Among them, ion implantation will cause stress and defects in the piezoelectric substrate, causing warping, but because the present application uses a reverse piezoelectric substrate 3 with opposite polarity and permanent bonding, the deformations cancel each other out, reducing the warping caused by ion implantation. Then, the surface shape of the reverse piezoelectric substrate 3 after ion implantation is characterized. Figure 6 This is the surface shape of the reverse piezoelectric substrate 3 after ion implantation in this embodiment, and its warp value is only 6.299 microns, which meets the bonding requirements;

[0095] S3, providing a double-polished support substrate 4 made of silicon carbide and having a thickness of 250 μm, connecting the reverse piezoelectric substrate 3 to the support substrate 4 by surface activation bonding, with a bonding strength of 2 joules / square meter, and contacting the support substrate 4 with the side of the first piezoelectric substrate 1 away from the second piezoelectric substrate 2, to obtain a heterostructure substrate 5;

[0096] S4, annealing, peeling and post-processing the heterostructure substrate 5, so that the piezoelectric film layer 103 with a thickness of 100 nanometers is transferred from the reverse piezoelectric substrate 3 to the supporting substrate 4, to obtain a heterostructure film substrate;

[0097] Among them, the first annealing atmosphere is nitrogen, the annealing temperature is 100°C, the time is 30h, and the heating rate is 0.1°C / min; the second annealing atmosphere is nitrogen, the annealing temperature is 300°C, the time is 40h, and the heating rate is 5°C / min. The annealing of the heterostructure substrate 5 usually often causes fragments due to the mismatch of thermal expansion coefficients, and requires thinning. The thermal deformation of the reverse piezoelectric substrate 3 proposed in this application offsets each other, so it has a thermal expansion coefficient similar to that of the supporting substrate 4, and the thinning step can be omitted. The annealing peeling transfer can be directly realized to obtain a heterogeneous thin film substrate. At the same time, the transferred reverse piezoelectric substrate 3 can be reused, which reduces the cost.

[0098] Example 3

[0099] A method for preparing a heterogeneous thin film substrate comprises the following steps:

[0100] S1, providing a first piezoelectric substrate 1 and a second piezoelectric substrate 2 (both are YX lithium niobate double-sided polished wafers, each with a thickness of 1000 microns) that are permanently bonded, cleaning the first piezoelectric substrate 1 and the second piezoelectric substrate 2 respectively, flipping the first piezoelectric substrate 1 by 180 degrees, and activating the bonding with the surface of the second piezoelectric substrate 2, with a bonding strength of 3 joules / square meter, thereby obtaining a reverse piezoelectric substrate 3 with opposite polarity and permanent bonding, with a thickness of 2000 microns;

[0101] S2, helium ion implantation is performed on the side of the first piezoelectric substrate 1 in the reverse piezoelectric substrate 3 away from the second piezoelectric substrate 2, with an energy of 150 keV and a dose of 8×10 16 / square centimeter; forming a defect layer 102 in the first piezoelectric substrate 1;

[0102] Among them, ion implantation will cause stress and defects in the piezoelectric substrate, causing warping, but because the present application uses a reverse piezoelectric substrate 3 with opposite polarity and permanent bonding, the deformations cancel each other out, reducing the warping caused by ion implantation. Then, the surface shape of the reverse piezoelectric substrate 3 after ion implantation is characterized. Figure 7 This is the surface shape of the reverse piezoelectric substrate 3 after ion implantation in this embodiment, and its warp value is only 5.043 microns, which meets the bonding requirements;

[0103] S3, providing a double-polished support substrate 4 made of silicon and having a thickness of 1000 microns, connecting the reverse piezoelectric substrate 3 to the support substrate 4 by surface activation bonding, with a bonding strength of 2 joules / square meter, and contacting the support substrate 4 with the side of the first piezoelectric substrate 1 away from the second piezoelectric substrate 2, to obtain a heterostructure substrate 5;

[0104] S4, annealing, peeling and post-processing the heterostructure substrate 5, so that the piezoelectric film layer 103 with a thickness of 1000 nanometers is transferred from the reverse piezoelectric substrate 3 to the supporting substrate 4, to obtain a heterogeneous film substrate;

[0105] Among them, the first annealing atmosphere is nitrogen, the annealing temperature is 300°C, the time is 30h, and the heating rate is 0.1°C / minute; the second annealing atmosphere is nitrogen, the annealing temperature is 800°C, the time is 40h, and the heating rate is 5°C / minute. The annealing of the heterostructure substrate 5 usually often causes fragments due to the mismatch of thermal expansion coefficients, and requires thinning. The thermal deformation of the reverse piezoelectric substrate 3 proposed in this application offsets each other, so it has a thermal expansion coefficient similar to that of the supporting substrate 4, and the thinning step can be omitted. The annealing peeling transfer can be directly realized to obtain a heterogeneous thin film substrate. At the same time, the transferred reverse piezoelectric substrate 3 can be reused, which reduces the cost.

[0106] Comparative Example 1

[0107] A method for preparing a heterogeneous thin film substrate comprises the following steps:

[0108] S1, such as Figure 4 As shown, a first piezoelectric substrate 1 is provided, the thickness of the first piezoelectric substrate 1 is 500 microns, and the first piezoelectric substrate 1 is a YX lithium niobate double-sided polished wafer;

[0109] S2, after cleaning the first piezoelectric substrate 1, helium ion implantation is performed on the polished surface, with an implantation energy of 150 keV and an implantation dose of 8×10 16 pcs / cm2;

[0110] S3, providing a double-polished support substrate 4 made of silicon and having a thickness of 500 microns, and connecting the first piezoelectric substrate 1 to the support substrate 4 by surface activation bonding, with a bonding strength of 2 joules / square meter, to obtain a heterostructure substrate 5;

[0111] S4, ion implantation will cause stress and defects in the first piezoelectric substrate 1, causing warping, so the subsequent bonding result is poor, and there is no need to perform thinning, annealing, peeling and post-processing. The surface shape of the first piezoelectric substrate 1 after ion implantation is characterized, such as Figure 8 As shown, due to the large difference in thermal expansion coefficients between lithium niobate and silicon, the warp value reaches an extremely high 109.79 microns, which is much larger than that of Examples 1-3. Therefore, large bubbles and debonding phenomena will occur after bonding.

[0112] Comparative Example 2

[0113] The heterogeneous thin film substrate obtained by the preparation method in application number 202011334127.9 is prepared by temporarily bonding two layers of piezoelectric substrates to increase the wafer thickness and reduce the warping after injection, and then preparing the piezoelectric heterogeneous film by debonding, annealing and peeling. However, this method adds an additional debonding step, increases the complexity of the process, and also introduces a new damage layer during the debonding process, which affects the subsequent wafer reuse. At the same time, the two piezoelectric substrates are bonded in this method in order to increase the thickness of the overall piezoelectric substrate, thereby making the first piezoelectric substrate have the advantage of small deformation during ion implantation. It does not consider how to narrow the gap in thermal expansion coefficients between adjacent substrates, thereby reducing warping and thermal stress. Therefore, after debonding, due to the different thermal expansion coefficients of the piezoelectric substrate and the supporting substrate, there is still a large thermal mismatch during the annealing process, and the thickness of the piezoelectric substrate layer is required to be high, and it must be a very thin piezoelectric substrate wafer.

[0114] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a heterogeneous thin film substrate, characterized in that: The following steps are involved: S1, providing a first piezoelectric substrate and a second piezoelectric substrate that are bonded to each other, wherein the first piezoelectric substrate is disposed on the second piezoelectric substrate, and the first piezoelectric substrate and the second piezoelectric substrate have the same cut shape and opposite polarities; S2, performing ion implantation on a surface of the first piezoelectric substrate away from the second piezoelectric substrate to form a defect layer in the first piezoelectric substrate to obtain an inverse piezoelectric substrate; S3, bonding the reverse piezoelectric substrate to a support substrate, wherein a surface of the first piezoelectric substrate away from the second piezoelectric substrate is in contact with the support substrate, to obtain a heterostructure substrate; S4, performing annealing, peeling and post-processing on the heterostructure substrate to transfer the piezoelectric film layer from the reverse piezoelectric substrate to the supporting substrate to obtain a heterogeneous film substrate.

2. The method for preparing a heterogeneous thin film substrate according to claim 1, characterized in that: The first piezoelectric substrate and the second piezoelectric substrate as well as the reverse piezoelectric substrate and the supporting substrate are permanently bonded, and the bonding strength is 0.5-3 joules / square meter.

3. The method for preparing a heterogeneous thin film substrate according to claim 1, characterized in that: The thickness of the first piezoelectric substrate and the thickness of the second piezoelectric substrate are both 250-1000 microns.

4. The method for preparing a heterogeneous thin film substrate according to claim 3, characterized in that: The thickness of the first piezoelectric substrate is the same as the thickness of the second piezoelectric substrate.

5. The method for preparing a heterogeneous thin film substrate according to claim 1, characterized in that: The thickness of the piezoelectric film layer is 100-1000 nanometers.

6. The method for preparing a heterogeneous thin film substrate according to claim 1, characterized in that: The thickness of the support substrate is 250-1000 microns.

7. The method for preparing a heterogeneous thin film substrate according to claim 1, characterized in that: The material of the first piezoelectric substrate and the material of the second piezoelectric substrate include lithium niobate or lithium tantalate; The material of the support substrate includes one or a combination of silicon, sapphire, silicon carbide, quartz single crystal, silicon nitride, fused quartz or lanthanum gallium silicate.

8. The method for preparing a heterogeneous thin film substrate according to claim 1, characterized in that: The ion type of the ion implantation includes one of hydrogen ions, helium ions, nitrogen ions, oxygen ions or argon ions; The energy of the ion implantation is 100-200 kiloelectronvolts; The ion implantation dose is 1×10 16 -1×10 17 Pieces / square centimeter.

9. The method for preparing a heterogeneous thin film substrate according to claim 1, characterized in that: The annealing and stripping includes a first annealing treatment and a second annealing treatment; The temperature of the first annealing treatment is 100-300°C, the time is 20-40 hours, and the heating rate is 0.1-1°C / min; The temperature of the second annealing treatment is 300-800° C., the time is 30-50 hours, and the heating rate is 1-5° C. / minute.

10. The method for preparing a heterogeneous thin film substrate according to claim 1, characterized in that: The post-processing includes the steps of polishing and thinning: The surface is treated by chemical mechanical polishing until the surface roughness Ra of the piezoelectric film layer is less than 0.5 nm.

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