Composite piezoelectric substrate and preparation method and application thereof

Abstract

The invention provides a composite piezoelectric substrate and a preparation method and application thereof. The composite piezoelectric substrate comprises a supporting substrate, a polycrystalline silicon layer, a SiO2 layer, a SiOx layer and a piezoelectric material layer which are sequentially stacked; the atomic ratio of O to Si in the SiOx layer is (0.2-0.5): 1, and the SiOx layer is prepared in an oxygen diffusion mode. According to the invention, the polycrystalline silicon layer, the SiO2 layer and the SiOx layer are laminated between the supporting substrate and the piezoelectric material layer, so that the modification of a bonding interface is realized, and the admittance ratio and the response capability of the device are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a composite piezoelectric substrate and a preparation method and application thereof. Background Art

[0002] Nowadays, devices such as surface acoustic wave devices and resonators prepared with piezoelectric materials such as LT (lithium tantalate) and LN (lithium niobate) have superior performance. The preparation of composite piezoelectric materials by room temperature bonding technology can avoid the problems caused by the difference in thermal expansion coefficient between the supporting substrate and the material layer, thermal mismatch of materials, etc. However, since LT, LN and silicon oxide materials cannot be directly bonded at room temperature, an intermediate dielectric layer is required to achieve effective bonding, such as an amorphous silicon layer. Amorphous silicon layers of different compositions / thicknesses have different effects on device performance. In addition, the existing technology cannot achieve effective control of the admittance ratio of the piezoelectric substrate using a single amorphous silicon layer.

[0003] Therefore, it is urgent to modify the bonding interface of the composite piezoelectric substrate so that the admittance ratio of the device can be improved and the response capability of the device can be enhanced. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a composite piezoelectric substrate and its preparation method and application. The present invention stacks a polysilicon layer, a SiO2 layer and a SiO2 layer between a support substrate and a piezoelectric material layer. x The layer realizes the modification of the bonding interface and effectively improves the admittance ratio and response capability of the device.

[0005] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a composite piezoelectric substrate, the composite piezoelectric substrate comprising a supporting substrate, a polycrystalline silicon layer, a SiO2 layer, a SiO x layer and a piezoelectric material layer;

[0007] The SiO x The atomic ratio of O and Si in the layer is (0.2-0.5):1, and the SiO x The layer was prepared by oxygen diffusion.

[0008] The present invention stacks a polysilicon layer, a SiO2 layer and a SiO2 layer between a support substrate and a piezoelectric material layer. x The layer realizes the modification of the bonding interface and effectively improves the admittance ratio and response capability of the device.

[0009] In the present invention, SiO xThe atomic ratio of O and Si in the layer is (0.2-0.5):1, for example, it can be 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1 or 0.5:1, etc.

[0010] In the present invention, if SiO x If the atomic ratio of O and Si in the layer is too large, the admittance ratio of the device will decrease. x The atomic ratio of O and Si in the layer is too small, and the improvement of the admittance ratio of the resonator is not obvious.

[0011] Preferably, the SiO x The thickness of the layer is 1-25 nm, for example, 1 nm, 5 nm, 10 nm, 15 nm, 20 nm or 25 nm, etc., preferably 3-15 nm.

[0012] In the present invention, within the above-mentioned suitable thickness range, the admittance ratio of the device increases with the increase of thickness. x If the thickness of the layer is too large, the admittance ratio will no longer increase. x The layer is not conducive to improving process efficiency.

[0013] Preferably, the support substrate is made of silicon material, preferably high-resistance silicon material.

[0014] Preferably, the resistivity of the high-resistance silicon material is greater than 1000Ω·m, for example, it may be 1500Ω·m, 2000Ω·m, 2500Ω·m, 3000Ω·m, 3500Ω·m or 4000Ω·m, etc., preferably ≥3000Ω·m, and further preferably 5000-15000Ω·m.

[0015] In the present invention, the high-resistance silicon material is used as a supporting substrate to reflect sound waves and reduce harmonic interference.

[0016] Preferably, the material of the support substrate is spinel.

[0017] It should be noted that when the spinel of the present invention is used as the material of the supporting substrate, the material of the piezoelectric material layer can be lithium tantalate.

[0018] Preferably, the density of the spinel is ≥3.58 g / cm 3 , for example, it can be 3.6 g / cm 3 、3.7g / cm 3 、3.8g / cm 3 、3.9g / cm 3 or 4g / cm 3 wait

[0019] Preferably, the thickness of the polysilicon layer is 500-3000 nm, for example, 500 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm or 3000 nm.

[0020] Preferably, the thickness of the SiO2 layer is 500-3000 nm, for example, it may be 500 nm, 1000 nm, 1500 nm, 2000 nm, 2500 nm or 3000 nm.

[0021] Preferably, the piezoelectric material layer includes a lithium niobate layer and / or a lithium tantalate layer.

[0022] Preferably, the thickness of the piezoelectric material layer is 0.4-1.2 μm, for example, 0.4 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm or 1.2 μm.

[0023] In a second aspect, the present invention provides a method for preparing the composite piezoelectric substrate as described in the first aspect, the preparation method comprising the following steps:

[0024] (a) depositing a polysilicon layer and a SiO2 layer in sequence on one side surface of a supporting substrate, and performing ion implantation on the surface to be bonded of a piezoelectric material donor to form a damaged layer;

[0025] (b) preparing the bonded body by any one of the following methods, including:

[0026] Method 1: depositing an amorphous silicon layer on the surface of the SiO2 layer away from the support substrate, and then bonding the surface to be bonded of the piezoelectric material donor and the surface of the amorphous silicon layer on the support substrate;

[0027] Method 2: depositing an amorphous silicon layer on the surface to be bonded of the piezoelectric material donor, and then bonding the side surface of the amorphous silicon layer on the piezoelectric material donor to the side surface of the SiO2 layer on the supporting substrate;

[0028] Method three: depositing a first amorphous silicon layer on the surface of the SiO2 layer away from the supporting substrate, depositing a second amorphous silicon layer on the surface to be bonded of the piezoelectric material donor, and then bonding the surface of the second amorphous silicon layer on the piezoelectric material donor to the surface of the first amorphous silicon layer on the supporting substrate;

[0029] (c) performing a splitting process on the bonded body so that the bonded body is split along the damaged layer to obtain a composite piezoelectric substrate precursor and a residual layer, and then performing oxygen diffusion along the crack surface of the composite piezoelectric substrate precursor and diffusing it to the amorphous silicon layer so that the amorphous silicon layer is transformed into SiO x layer to obtain the composite piezoelectric substrate.

[0030] The present invention transforms the amorphous silicon layer into SiO by means of oxygen diffusion. x This process helps to modify the bonding interface and improve the device's admittance ratio and response capability.

[0031] Preferably, the deposition method of the polysilicon layer and the SiO2 layer comprises:

[0032] A polysilicon source layer is deposited on one side surface of a supporting substrate, and then a surface layer of the polysilicon source layer is subjected to thermal oxidation treatment to form a SiO2 layer.

[0033] It should be noted that the present invention does not limit the deposition method of the polysilicon source layer. Exemplary method thereof may be LPCVD (low pressure chemical vapor deposition).

[0034] Preferably, the temperature of the thermal oxidation treatment is 900-1100°C, for example, 900°C, 1000°C or 1100°C.

[0035] Preferably, the ion implantation in step (a) is performed using hydrogen ions and / or helium ions.

[0036] Preferably, the depth of the ion implantation in step (a) is 0.5-1.5 μm, for example, 0.5 μm, 0.7 μm, 1 μm, 1.2 μm, 1.4 μm or 1.5 μm.

[0037] Preferably, the dose of the ion implantation in step (a) is 5×10 16 -1×10 17 Ions / cm 2 , for example, it can be 5×10 16 Ions / cm 2 , 6×10 16 Ions / cm 2 ,7×10 16 Ions / cm 2 , 8×10 16 Ions / cm 2 ,9×10 16 Ions / cm 2 or 1×10 17 Ions / cm 2 wait.

[0038] Preferably, the bonding pressure in method 1, the bonding pressure in method 2 and the bonding pressure in method 3 in step (b) are independently 1-100KN, for example, 1KN, 5KN, 10KN, 30KN, 50KN, 70KN or 100KN.

[0039] Preferably, the deposition method of the amorphous silicon layer, the first sub-amorphous silicon layer and the second sub-amorphous silicon layer in step (b) comprises a PVD (physical vapor deposition) method.

[0040] Preferably, the temperature of the splitting treatment in step (c) is 180-290°C, for example, it can be 180°C, 200°C, 220°C, 240°C, 260°C or 280°C, and the time is 0.5-10h, for example, it can be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, etc.

[0041] It should be noted that the present invention preferably adopts a vertical placement method when performing the splitting process. The advantage of vertical placement is that the residual material layer after splitting will be tilted and separated due to its own weight, thereby forming a gap between the residual material layer and the composite piezoelectric substrate precursor, leaving space for oxygen diffusion. If the slice is placed horizontally, the residual material layer after splitting will still cover the composite piezoelectric substrate precursor, and the residual material layer needs to be taken out before oxygen diffusion, which requires re-creating the temperature environment, increasing the manufacturing cost.

[0042] Preferably, before the bonding body is split in step (c), the bonding body is thinned first. The specific steps include: thinning the non-bonding surface of the piezoelectric material donor in the bonding body so that the thickness of the piezoelectric material layer is 10-30μm, for example, it can be 10μm, 15μm, 20μm, 25μm or 30μm, etc.

[0043] In the present invention, thinning is performed to reduce thermal mismatch stress caused by differences in thermal expansion coefficients in subsequent steps, and to prevent composite substrate fragmentation.

[0044] Preferably, the oxygen diffusion temperature is 450-550°C, for example, 450°C, 475°C, 500°C, 525°C or 550°C.

[0045] In the present invention, the temperature of oxygen diffusion affects the SiO x The oxygen content of the layer. If the temperature of oxygen diffusion is too low, the oxygen atoms do not have enough kinetic energy and cannot diffuse effectively. At the same time, the lattice defects of the piezoelectric wafer caused by ion implantation cannot be repaired. If the temperature of oxygen diffusion is too high, the piezoelectric wafer will easily lose its piezoelectric properties and the device performance will be lost.

[0046] Preferably, the constant temperature time for oxygen diffusion is 4-20 h, for example, it can be 4 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h or 20 h.

[0047] Preferably, during the oxygen diffusion process, the flow rate of the gas source is 5-20 slm, for example, 5 slm, 10 slm, 15 slm or 20 slm.

[0048] Preferably, the preparation method comprises the following steps:

[0049] (1) depositing a polycrystalline silicon source layer on one side surface of a silicon substrate, and then thermally oxidizing the surface layer of the polycrystalline silicon source layer at a temperature of 900-1100° C. to form a SiO2 layer;

[0050] Performing hydrogen ion and / or helium ion implantation on the surface to be bonded of the piezoelectric material donor, with the depth of the ion implantation being 0.5-1.5 μm, to form a damaged layer;

[0051] (2) In a vacuum environment, a bonded body having a structure of a silicon substrate / polycrystalline silicon layer / SiO2 layer / amorphous silicon layer / piezoelectric material donor is prepared by any one of the following methods, including:

[0052] Method 1: depositing an amorphous silicon layer with a thickness of 1-25 nm on the surface of the SiO2 layer away from the silicon substrate, and then bonding the surface to be bonded of the piezoelectric material donor and the surface of the amorphous silicon layer on the silicon substrate, with a bonding pressure of 1-100 KN;

[0053] Method 2: depositing an amorphous silicon layer with a thickness of 1-25 nm on the bonding surface of the piezoelectric material donor, and then bonding the side surface of the amorphous silicon layer on the piezoelectric material donor to the side surface of the SiO2 layer on the silicon substrate, with a bonding pressure of 1-100 KN;

[0054] Method three: depositing a first amorphous silicon layer on the surface of the SiO2 layer away from the silicon substrate, depositing a second amorphous silicon layer on the surface to be bonded of the piezoelectric material donor, wherein the total thickness of the first amorphous silicon layer and the second amorphous silicon layer is 1-25 nm, and then bonding the surface of the second amorphous silicon layer on the piezoelectric material donor to the surface of the first amorphous silicon layer on the silicon substrate, with a bonding pressure of 1-100 KN;

[0055] (3) thinning the non-bonding surface of the piezoelectric material donor in the bonded body so that the thickness of the piezoelectric material donor is 10-30 μm, and then performing a splitting treatment at 180-290° C. for 0.5-10 h, so that the bonded body is split along the damaged layer to obtain a composite piezoelectric substrate precursor and a residual layer;

[0056] Then, the temperature is raised to 450-550°C, and an oxygen source with a flow rate of 5-10 slm is introduced to diffuse oxygen along the crack surface of the composite piezoelectric substrate precursor. The constant temperature time of oxygen diffusion is 4-20 hours, and the oxygen diffuses into the amorphous silicon layer so that the amorphous silicon layer is transformed into SiO x layer to obtain the composite piezoelectric substrate.

[0057] In a third aspect, the present invention provides an application of the composite piezoelectric substrate as described in the first aspect, wherein the composite piezoelectric substrate is used to manufacture a surface acoustic wave device or a resonator.

[0058] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] The present invention stacks a polysilicon layer, a SiO2 layer and a SiO2 layer between a support substrate and a piezoelectric material layer. x The layer realizes the modification of the bonding interface and effectively improves the admittance ratio and response capability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is a schematic structural diagram of the composite piezoelectric substrate provided in Example 1 of the present invention.

[0062] Figure 2 This is a schematic structural diagram of the composite piezoelectric substrate precursor provided in Example 1 of the present invention.

[0063] Figure 3 This is a schematic structural diagram of a composite piezoelectric substrate for a resonator provided by the present invention.

[0064] Figure 4 The SiO provided by the present invention x Curve showing the effect of layer thickness on the electromechanical coupling coefficient of the resonator.

[0065] Figure 5 The SiO provided by the present invention x Curve showing the effect of layer thickness on the center frequency of the resonator.

[0066] Figure 6 The SiO provided by the present invention x Curve showing the effect of layer thickness on the resonator admittance ratio.

[0067] Among them, 1-high-resistance silicon substrate; 2-polysilicon layer; 3-SiO2 layer; 4-SiO x layer; 5-piezoelectric material layer; 6-amorphous silicon layer; 7-Al film. DETAILED DESCRIPTION

[0068] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0069] Example 1

[0070] This embodiment provides a composite piezoelectric substrate, such as Figure 1 As shown, the composite piezoelectric substrate comprises a high-resistance silicon substrate 1, a polycrystalline silicon layer 2, a SiO2 layer 3, and a SiO x layer 4 and a piezoelectric material layer 5;

[0071] The SiO x The atomic ratio of O to Si in layer 4 is 0.35:1. x The layer is prepared by oxygen diffusion, and the SiO x The thickness of the layer is 15 nm;

[0072] The resistivity of the high-resistance silicon substrate 1 is 3000Ω·m;

[0073] The thickness of the polysilicon layer 2 is 1 μm, the thickness of the SiO2 layer 3 is 500 nm, and the piezoelectric material layer 4 is a lithium tantalate layer with a thickness of 0.6 μm.

[0074] This embodiment also provides a method for preparing the composite piezoelectric substrate, the method comprising the following steps:

[0075] (1) depositing a polysilicon source layer on one side surface of a 6-inch high-resistance silicon substrate 1, and then thermally oxidizing the surface of the polysilicon source layer at a temperature of 900° C. to form a SiO2 layer 3;

[0076] Hydrogen ion implantation was performed on the bonding surface of the 6-inch piezoelectric material donor. The depth of hydrogen ion implantation was 1 μm and the ion implantation dose was 7.5×10 16 Ions / cm 2 , forming a damaged layer;

[0077] (2) In a vacuum environment, a bonding body having a structure of a high-resistance silicon substrate 1 / polycrystalline silicon layer / SiO2 layer / amorphous silicon layer / piezoelectric material donor is prepared by the following method, including:

[0078] An amorphous silicon layer with a thickness of 15 nm is deposited on the surface of the SiO2 layer away from the high-resistance silicon substrate 1, and then the bonding surface of the piezoelectric material donor and the surface of the amorphous silicon layer on the high-resistance silicon substrate 1 are bonded, and the bonding pressure is 50 KN;

[0079] (3) The non-bonding surface of the piezoelectric material donor in the bonding body is thinned to make the thickness of the piezoelectric material donor 15 μm, and then the bonding body is cracked along the damaged layer at 230° C. for 5 hours to obtain the following: Figure 2The composite piezoelectric substrate precursor and residual layer shown, the composite piezoelectric substrate precursor comprises a high-resistance silicon substrate 1, a polysilicon layer 2, a SiO2 layer 3, an amorphous silicon layer 6 and a piezoelectric material layer 5 which are stacked in sequence;

[0080] Then the temperature was raised to 450°C, and an oxygen source with a flow rate of 8 slm was introduced to diffuse oxygen along the crack surface of the composite piezoelectric substrate precursor. The constant temperature time of oxygen diffusion was 6 hours, and the oxygen diffused into the amorphous silicon layer so that the amorphous silicon layer was transformed into SiO x layer to obtain the composite piezoelectric substrate.

[0081] Example 2

[0082] This embodiment provides a composite piezoelectric substrate, which includes a high-resistance silicon substrate, a polysilicon layer, a SiO2 layer, and a SiO x layer and a piezoelectric material layer;

[0083] The SiO x The atomic ratio of O and Si in the layer is 0.2:1. x The layer is prepared by oxygen diffusion, and the SiO x The thickness of the layer is 25 nm;

[0084] The resistivity of the high-resistance silicon substrate is 3000Ω·m;

[0085] The thickness of the polysilicon layer is 1.5 μm, the thickness of the SiO2 layer is 0.5 μm, and the piezoelectric material layer is a lithium tantalate layer with a thickness of 1.2 μm.

[0086] This embodiment also provides a method for preparing the composite piezoelectric substrate, the method comprising the following steps:

[0087] (1) depositing a polysilicon source layer on one side surface of a 6-inch high-resistance silicon substrate, and then thermally oxidizing the surface of the polysilicon source layer at a temperature of 920° C. to form a SiO2 layer;

[0088] Hydrogen ion implantation was performed on the bonding surface of the 6-inch piezoelectric material donor. The depth of hydrogen ion implantation was 0.5 μm and the ion implantation dose was 7×10 16 Ions / cm 2 , forming a damaged layer;

[0089] (2) In a vacuum environment, a bonding body having a structure of a high-resistance silicon substrate / polycrystalline silicon layer / SiO2 layer / amorphous silicon layer / piezoelectric material donor is prepared by the following method, including:

[0090] Depositing an amorphous silicon layer with a thickness of 25 nm on the bonding surface of the piezoelectric material donor, and then bonding the side surface of the amorphous silicon layer on the piezoelectric material donor to the side surface of the SiO2 layer on the high-resistance silicon substrate, with a bonding pressure of 50 KN;

[0091] (3) thinning the non-bonding surface of the piezoelectric material donor in the bonded body so that the thickness of the piezoelectric material donor is 30 μm, and then performing a splitting treatment at 180° C. for 10 hours so that the bonded body is split along the damaged layer to obtain a composite piezoelectric substrate precursor and a residual layer;

[0092] Then, the temperature was raised to 500°C, and an oxygen source with a flow rate of 8 slm was introduced to diffuse oxygen along the crack surface of the composite piezoelectric substrate precursor. The constant temperature time of oxygen diffusion was 5 hours, and the oxygen diffused into the amorphous silicon layer so that the amorphous silicon layer was transformed into SiO x layer to obtain the composite piezoelectric substrate.

[0093] Example 3

[0094] This embodiment provides a composite piezoelectric substrate, which includes a high-resistance silicon substrate, a polysilicon layer, a SiO2 layer, and a SiO x layer and a piezoelectric material layer;

[0095] The SiO x The atomic ratio of O and Si in the layer is 0.5:1. x The layer is prepared by oxygen diffusion, and the SiO x The thickness of the layer is 3 nm;

[0096] The resistivity of the high-resistance silicon substrate is 1000Ω·m;

[0097] The thickness of the polysilicon layer is 1 μm, the thickness of the SiO2 layer is 0.5 μm, and the piezoelectric material layer is a lithium tantalate layer with a thickness of 1 μm.

[0098] This embodiment also provides a method for preparing the composite piezoelectric substrate, the method comprising the following steps:

[0099] (1) depositing a polysilicon source layer on one side surface of a 6-inch high-resistance silicon substrate, and then thermally oxidizing the surface of the polysilicon source layer at a temperature of 920° C. to form a SiO2 layer;

[0100] Hydrogen ion implantation was performed on the bonding surface of the 6-inch piezoelectric material donor. The depth of hydrogen ion implantation was 1.5 μm and the ion implantation dose was 9×10 16 Ions / cm 2 , forming a damaged layer;

[0101] (2) In a vacuum environment, a bonding body having a structure of a high-resistance silicon substrate / polycrystalline silicon layer / SiO2 layer / amorphous silicon layer / piezoelectric material donor is prepared by the following method, including:

[0102] Depositing a first amorphous silicon layer on the surface of the side of the SiO2 layer away from the high-resistance silicon substrate, depositing a second amorphous silicon layer on the surface to be bonded of the piezoelectric material donor, wherein the total thickness of the first amorphous silicon layer and the second amorphous silicon layer is 1 nm, and then bonding the surface of the second amorphous silicon layer on the piezoelectric material donor to the surface of the first amorphous silicon layer on the high-resistance silicon substrate, with a bonding pressure of 50 KN;

[0103] (3) thinning the non-bonding surface of the piezoelectric material donor in the bonded body so that the thickness of the piezoelectric material donor is 10 μm, and then performing a splitting treatment at 220° C. for 0.5 h so that the bonded body is split along the damaged layer to obtain a composite piezoelectric substrate precursor and a residual layer;

[0104] Then the temperature was raised to 550°C, and an oxygen source with a flow rate of 10 slm was introduced to diffuse oxygen along the crack surface of the composite piezoelectric substrate precursor. The constant temperature time of oxygen diffusion was 4 hours, and the oxygen diffused into the amorphous silicon layer so that the amorphous silicon layer was transformed into SiO x layer to obtain the composite piezoelectric substrate.

[0105] Example 4

[0106] The difference between this embodiment and embodiment 1 is that SiO x The thickness of the layer is 5 nm.

[0107] The rest of the preparation methods and parameters were the same as those in Example 1.

[0108] Example 5

[0109] The difference between this embodiment and embodiment 1 is that SiO x The thickness of the layer is 6 nm.

[0110] The rest of the preparation methods and parameters were the same as those in Example 1.

[0111] Example 6

[0112] The difference between this embodiment and embodiment 1 is that SiO x The thickness of the layer is 7 nm.

[0113] The rest of the preparation methods and parameters were the same as those in Example 1.

[0114] Example 7

[0115] The difference between this embodiment and embodiment 1 is that SiO x The thickness of the layer is 8 nm.

[0116] The rest of the preparation methods and parameters were the same as those in Example 1.

[0117] Example 8

[0118] The difference between this embodiment and embodiment 1 is that SiO x The thickness of the layer was 9 nm.

[0119] The rest of the preparation methods and parameters were the same as those in Example 1.

[0120] Example 9

[0121] The difference between this embodiment and embodiment 1 is that SiO x The thickness of the layer is 10 nm.

[0122] The rest of the preparation methods and parameters were the same as those in Example 1.

[0123] Example 10

[0124] The difference between this embodiment and embodiment 1 is that SiO x The thickness of the layer is 20 nm.

[0125] The rest of the preparation methods and parameters were the same as those in Example 1.

[0126] Embodiment 11

[0127] The difference between this embodiment and embodiment 1 is that SiO x The thickness of the layer was 5 nm and the temperature of the annealing was 550°C.

[0128] The rest of the preparation methods and parameters were the same as those in Example 1.

[0129] Example 12

[0130] The difference between this embodiment and embodiment 1 is that SiO x The thickness of the layer was 10 nm and the temperature of the annealing was 550°C.

[0131] The rest of the preparation methods and parameters were the same as those in Example 1.

[0132] Example 13

[0133] The difference between this embodiment and embodiment 1 is that SiO x The thickness of the layer is 30 nm.

[0134] The rest of the preparation methods and parameters were the same as those in Example 1.

[0135] Embodiment 14

[0136] The difference between this embodiment and embodiment 1 is that the temperature of oxygen diffusion in step (3) is 400°C.

[0137] The rest of the preparation methods and parameters were the same as those in Example 1.

[0138] Embodiment 15

[0139] The difference between this embodiment and embodiment 1 is that the temperature of oxygen diffusion in step (3) is 600°C.

[0140] The rest of the preparation methods and parameters were the same as those in Example 1.

[0141] Comparative Example 1

[0142] The difference between this comparative example and Example 1 is that no SiO x layer, that is, no amorphous silicon layer is deposited in step (2).

[0143] The rest of the preparation methods and parameters were the same as those in Example 1.

[0144] Comparative Example 2

[0145] The difference between this comparative example and Example 1 is that no oxygen diffusion treatment is performed in step (3), that is, the amorphous silicon layer is not converted.

[0146] The rest of the preparation methods and parameters were the same as those in Example 1.

[0147] Comparative Example 3

[0148] The difference between this comparative example and Example 1 is that by adjusting the oxygen diffusion parameters, SiO x The atomic ratio of O and Si in the layer is 0.1:1.

[0149] The rest of the preparation methods and parameters were the same as those in Example 1.

[0150] Comparative Example 4

[0151] The difference between this comparative example and Example 1 is that by adjusting the oxygen diffusion parameters, SiO x The atomic ratio of O and Si in the layer is 1:1.

[0152] The rest of the preparation methods and parameters were the same as those in Example 1.

[0153] Comparative Example 5

[0154] The difference between this comparative example and Example 1 is that the oxygen diffusion process in step (3) is replaced by an oxygen ion implantation process.

[0155] The rest of the preparation methods and parameters were the same as those in Example 1.

[0156] Performance Testing

[0157] 1. The composite piezoelectric substrates prepared in the above embodiments and comparative examples are made into resonators, and then formed into filters, such as Figure 3 As shown, the resonator comprises a high-resistance silicon substrate 1, a polysilicon layer 2, a SiO2 layer 3, and a SiO x Layer 4 and piezoelectric material layer 5, the surface of the piezoelectric material layer 5 is provided with an Al film 7 with a thickness of 160nm.

[0158] The electromechanical coupling coefficient (K 2 ), center frequency (fc) and admittance ratio (AR) tests.

[0159] The test results are as follows Figure 4 , Figure 5 , Figure 6 And as shown in Table 1.

[0160] Depend on Figure 4-6 It can be seen that the composite piezoelectric substrate provided by the present invention has no effect on the electromechanical coupling coefficient and the center frequency of the resonator, and the admittance ratio of the resonator increases with the increase of thickness.

[0161] Table 1

[0162]

[0163]

[0164] analyze:

[0165] As can be seen from the above table, the composite piezoelectric substrate provided by the present invention realizes the modification of the bonding interface and effectively improves the admittance ratio and response capability of the device. x When the thickness of the layer is ≤20 nm, it has no effect on the electromechanical coupling coefficient of the resonator, has no effect on the center frequency of the resonator, and the resonator admittance ratio increases with increasing thickness.

[0166] It can be seen from Examples 1 and 13 that if SiO x If the thickness of the layer is too large, the admittance ratio cannot be further improved and the cost increases.

[0167] It can be seen from Example 1 and Examples 14-15 that if the temperature of the oxygen diffusion in step (3) is too low, the piezoelectric wafer cannot be effectively repaired; if the temperature of the oxygen diffusion in step (3) is too high, the piezoelectric performance of the piezoelectric wafer will be reduced.

[0168] It can be seen from Example 1 and Comparative Example 1 that if SiO x If the piezoelectric material layer and the SiO2 layer are directly bonded instead of the original layer, the resonator admittance ratio will be reduced.

[0169] It can be seen from Example 1 and Comparative Example 2 that if the amorphous silicon layer is not converted, the resonator K 2 reduce.

[0170] It can be seen from Example 1 and Comparative Examples 3-4 that if SiO x If the atomic ratio of O and Si in the layer is too small, K 2 Reduce; if SiO x If the atomic ratio of O and Si in the layer is too large, the admittance ratio will decrease.

[0171] It can be seen from Example 1 and Comparative Example 5 that if the oxygen diffusion process is replaced by an oxygen ion implantation process, the crystal structure in the piezoelectric material layer will be destroyed, resulting in a decrease in device performance.

[0172] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A composite piezoelectric substrate, characterized in that: The composite piezoelectric substrate comprises a supporting substrate, a polysilicon layer, a SiO2 layer, a SiO x layer and a piezoelectric material layer; The SiO x The atomic ratio of O and Si in the layer is (0.2-0.5):1, and the SiO x The layer was prepared by oxygen diffusion.

2. The composite piezoelectric substrate according to claim 1, characterized in that The SiO x The thickness of the layer is 1-25 nm, preferably 3-15 nm.

3. The composite piezoelectric substrate according to claim 1 or 2, characterized in that: The material of the support substrate is silicon material, preferably high-resistance silicon material; Preferably, the resistivity of the high-resistance silicon material is greater than 1000Ω·m, preferably ≥3000Ω·m, and more preferably 5000-15000Ω·m.

4. The composite piezoelectric substrate according to claim 1 or 2, characterized in that: The material of the supporting substrate is spinel; Preferably, the density of the spinel is ≥3.58 g / cm 3 .

5. The composite piezoelectric substrate according to any one of claims 1 to 4, characterized in that: The thickness of the polysilicon layer is 500-3000nm; Preferably, the thickness of the SiO2 layer is 500-3000nm; Preferably, the piezoelectric material layer includes a lithium niobate layer and / or a lithium tantalate layer; Preferably, the piezoelectric material layer has a thickness of 0.4-1.2 μm.

6. A method for preparing a composite piezoelectric substrate according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (a) depositing a polysilicon layer and a SiO2 layer in sequence on one side surface of a supporting substrate, and performing ion implantation on the surface to be bonded of a piezoelectric material donor to form a damaged layer; (b) preparing the bonded body by any one of the following methods, including: Method 1: depositing an amorphous silicon layer on the surface of the SiO2 layer away from the support substrate, and then bonding the surface to be bonded of the piezoelectric material donor and the surface of the amorphous silicon layer on the support substrate; Method 2: depositing an amorphous silicon layer on the surface to be bonded of the piezoelectric material donor, and then bonding the side surface of the amorphous silicon layer on the piezoelectric material donor to the side surface of the SiO2 layer on the supporting substrate; Method three: depositing a first amorphous silicon layer on the surface of the SiO2 layer away from the supporting substrate, depositing a second amorphous silicon layer on the surface to be bonded of the piezoelectric material donor, and then bonding the surface of the second amorphous silicon layer on the piezoelectric material donor to the surface of the first amorphous silicon layer on the supporting substrate; (c) performing a splitting process on the bonded body so that the bonded body is split along the damaged layer to obtain a composite piezoelectric substrate precursor and a residual layer, and then performing oxygen diffusion along the crack surface of the composite piezoelectric substrate precursor and diffusing it to the amorphous silicon layer so that the amorphous silicon layer is transformed into SiO x layer to obtain the composite piezoelectric substrate.

7. The preparation method according to claim 6, characterized in that: The deposition method of the polysilicon layer and the SiO2 layer comprises: Depositing a polysilicon source layer on one side surface of the support substrate, and then performing thermal oxidation treatment on the surface of the polysilicon source layer to form a SiO2 layer; Preferably, the temperature of the thermal oxidation treatment is 900-1100°C; Preferably, the ion implantation in step (a) is performed using hydrogen ions and / or helium ions; Preferably, the depth of the ion implantation in step (a) is 0.5-1.5 μm.

8. The preparation method according to claim 6 or 7, characterized in that: In step (b), the bonding pressure in the first mode, the bonding pressure in the second mode, and the bonding pressure in the third mode are independently 1-100 KN; Preferably, the deposition method of the amorphous silicon layer, the first sub-amorphous silicon layer and the second sub-amorphous silicon layer in step (b) comprises a PVD method; Preferably, the temperature of the splitting treatment in step (c) is 180-290° C. and the time is 0.5-10 h; Preferably, before the bonding body is split in step (c), the bonding body is thinned, and the specific steps include: thinning the non-bonding surface of the piezoelectric material donor in the bonding body so that the thickness of the piezoelectric material layer is 10-30 μm.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The temperature of oxygen diffusion is 450-550°C; Preferably, the constant temperature time for oxygen diffusion is 4-20h; Preferably, during the oxygen diffusion process, the flow rate of the gas source is 5-10 slm.

10. The preparation method according to any one of claims 6 to 9, characterized in that: The preparation method comprises the following steps: (1) depositing a polycrystalline silicon source layer on one side surface of a silicon substrate, and then thermally oxidizing the surface layer of the polycrystalline silicon source layer at a temperature of 900-1100° C. to form a SiO2 layer; Performing hydrogen ion and / or helium ion implantation on the surface to be bonded of the piezoelectric material donor, with the depth of the ion implantation being 0.5-1.5 μm, to form a damaged layer; (2) In a vacuum environment, a bonded body having a structure of a silicon substrate / polycrystalline silicon layer / SiO2 layer / amorphous silicon layer / piezoelectric material donor is prepared by any one of the following methods, including: Method 1: depositing an amorphous silicon layer with a thickness of 1-25 nm on the surface of the SiO2 layer away from the silicon substrate, and then bonding the surface to be bonded of the piezoelectric material donor and the surface of the amorphous silicon layer on the silicon substrate, with a bonding pressure of 1-100 KN; Method 2: depositing an amorphous silicon layer with a thickness of 1-25 nm on the bonding surface of the piezoelectric material donor, and then bonding the side surface of the amorphous silicon layer on the piezoelectric material donor to the side surface of the SiO2 layer on the silicon substrate, with a bonding pressure of 1-100 KN; Method three: depositing a first amorphous silicon layer on the surface of the SiO2 layer away from the silicon substrate, depositing a second amorphous silicon layer on the surface to be bonded of the piezoelectric material donor, wherein the total thickness of the first amorphous silicon layer and the second amorphous silicon layer is 1-25 nm, and then bonding the surface of the second amorphous silicon layer on the piezoelectric material donor to the surface of the first amorphous silicon layer on the silicon substrate, with a bonding pressure of 1-100 KN; (3) thinning the non-bonding surface of the piezoelectric material donor in the bonded body so that the thickness of the piezoelectric material donor is 10-30 μm, and then performing a splitting treatment at 180-290° C. for 0.5-10 h, so that the bonded body is split along the damaged layer to obtain a composite piezoelectric substrate precursor and a residual layer; Then, the temperature is raised to 450-550°C, and an oxygen source with a flow rate of 5-10 slm is introduced to diffuse oxygen along the crack surface of the composite piezoelectric substrate precursor. The constant temperature time of oxygen diffusion is 4-20 hours, and the oxygen diffuses into the amorphous silicon layer so that the amorphous silicon layer is transformed into SiO x layer to obtain the composite piezoelectric substrate.

11. An application of the composite piezoelectric substrate according to any one of claims 1 to 5, characterized in that: The composite piezoelectric substrate is used for manufacturing a surface acoustic wave device or a resonator.

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