A bonding wafer and its fabrication method, and a filter

Abstract

This invention provides a bonding wafer and its fabrication method, as well as a filter. The fabrication method includes: providing a wafer substrate, the wafer substrate including a first substrate surface and a second substrate surface; providing a piezoelectric layer and adjusting the piezoelectric layer to be located on one side of the first substrate surface, the piezoelectric layer including a first piezoelectric surface and a second piezoelectric surface; bonding the piezoelectric layer and the wafer substrate and fabricating bonding units; thinning the second piezoelectric surface of the bonding units and fabricating a second piezoelectric thinning surface, the second piezoelectric thinning surface including a first thinning unit and a second thinning unit; polishing the second piezoelectric thinning surface and fabricating a second piezoelectric polished surface; wherein the maximum distance from the surface of the polishing unit away from the second substrate surface to the second substrate surface is h3, the minimum distance from the surface of the polishing unit away from the second substrate surface to the second substrate surface is h4, and (h3-h4)≤300 nm. The bonding wafer fabricated using the fabrication method provided in this invention can improve the overall film thickness uniformity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor materials, and particularly to a bonded wafer, a preparation method thereof and a filter. BACKGROUND

[0002] With the development of 5G and future mobile communication technologies, the performance requirements of surface acoustic wave filters are continuously rising, and traditional SAW and BAW filters gradually show deficiencies in high rectangularity, low loss and large bandwidth, etc. Among them, the filter of the bonded wafer can achieve a steeper cutoff characteristic and significantly improve the rectangularity.

[0003] However, in the current bonded wafer processing, thinning and polishing need to be performed by mechanical equipment. In the processing process, the consistency difference between batches of raw materials, internal stress generated during processing, and uneven distribution of polishing liquid can easily cause the thickness of the bonded wafer to be uneven. More troublesome is that once the film thickness is uneven, it is extremely difficult to correct subsequently. SUMMARY

[0004] The embodiments of the present application provide a bonded wafer, a preparation method thereof and a filter, which can improve the film thickness uniformity of the bonded wafer by adjusting the thinning and polishing of the bonding unit.

[0005] In a first aspect, the present application provides a preparation method of a bonded wafer,

[0006] A wafer substrate is provided, which includes a first substrate surface and a second substrate surface arranged oppositely;

[0007] A piezoelectric layer is provided and adjusted to be located on one side of the first substrate surface; the piezoelectric layer includes a first piezoelectric surface and a second piezoelectric surface arranged oppositely, and the first piezoelectric surface is located on the side of the second piezoelectric surface close to the wafer substrate;

[0008] The piezoelectric layer and the wafer substrate are bonded to prepare a bonding unit; the distance between the second piezoelectric surface and the second substrate surface is h0;

[0009] The second piezoelectric surface of the bonding unit is thinned to prepare a second piezoelectric thinned surface, the second piezoelectric thinned surface includes a plurality of thinned units, and the thinned units at least include a first thinned unit and a second thinned unit; along the thickness direction of the wafer substrate, the distance between the surface of the first thinned unit away from the second substrate surface and the second substrate surface is h1, and the distance between the surface of the second thinned unit away from the second substrate surface and the second substrate surface is h2, wherein h0>h1, h0>h2, and |h1-h2|>0;

[0010] The second piezoelectric thinning surface is polished to prepare a second piezoelectric polished surface, which includes multiple polishing units. The first thinning unit is polished to prepare a first polishing unit, and the second thinning unit is polished to prepare a second polishing unit. Along the thickness direction of the wafer substrate, the maximum distance from the surface of the polishing unit away from the surface of the second substrate to the surface of the second substrate is h3, and the minimum distance from the surface of the polishing unit away from the surface of the second substrate to the surface of the second substrate is h4, wherein (h3-h4)≤300 nanometers.

[0011] Optionally, the second piezoelectric surface of the bonding unit is thinned to form a second piezoelectric thinned surface, the second piezoelectric thinned surface comprising a plurality of thinning units, the thinning units comprising at least a first thinning unit and a second thinning unit comprising:

[0012] The second piezoelectric surface is thinned to prepare the first thinning unit and the second thinning unit; wherein, h1-h2=ha;

[0013] Polishing the second piezoelectric thinning surface to prepare a second piezoelectric polished surface, the second piezoelectric polished surface comprising multiple polishing units, polishing the first thinning unit to prepare a first polishing unit, and polishing the second unit to prepare a second polishing unit comprising:

[0014] The first thinning unit is polished and the first polishing unit is prepared by controlling the first polishing thickness, and the second thinning unit is polished and the second polishing unit is prepared by controlling the second polishing thickness; the first polishing thickness is h5, the second polishing thickness is h6, where h6-h5=hb, (ha×hb)>0, and ||ha|-|hb|| / |hb|≤20%.

[0015] Optionally, the second piezoelectric surface of the bonding unit is thinned to form a second piezoelectric thinned surface, the second piezoelectric thinned surface comprising a plurality of thinning units, the thinning units comprising at least a first thinning unit and a second thinning unit comprising:

[0016] A mechanical thinning device is controlled to thin the second piezoelectric surface and prepare the second piezoelectric thinned surface, wherein the second thinning unit surrounds the first thinning unit; wherein the mechanical thinning device includes an adjustment structure and a limiting structure, the limiting structure surrounds the adjustment structure; the bonding unit is located on one side of the adjustment structure, and the adjustment structure adjusts the height and / or angle of the bonding unit, and the limiting structure limits the bonding unit;

[0017] Polishing the second piezoelectric thinning surface to prepare a second piezoelectric polished surface, the second piezoelectric polished surface comprising multiple polishing units, polishing the first thinning unit to prepare a first polishing unit, and polishing the second unit to prepare a second polishing unit comprising:

[0018] The first thinning unit and the second thinning unit are partitioned and pressure-polished to prepare the first polishing unit and the second polishing unit. The first thinning unit is polished with a first pressure value to prepare the first polishing unit, and the second thinning unit is polished with a second pressure value to prepare the second polishing unit. The first pressure value is P1, the second pressure value is P2, and |P1-P2|>0.

[0019] Optionally, controlling the mechanical thinning equipment to thin the second piezoelectric surface and prepare the second piezoelectric thinned surface includes:

[0020] The mechanical thinning equipment is controlled to thin the second piezoelectric surface and prepare the second piezoelectric thinned surface. The second piezoelectric thinned surface further includes a third thinning unit and a fourth thinning unit. The third thinning unit surrounds the second thinning unit, and the fourth thinning unit surrounds the third thinning unit. The distance from the surface of the third thinning unit away from the second substrate surface to the second substrate surface is h7, and the distance from the surface of the fourth thinning unit away from the second substrate surface to the second substrate surface is h8, where h0 > h7, h0 > h8, and |h7-h8| > 0.

[0021] Polishing the second piezoelectric thinning surface and preparing the second piezoelectric polished surface includes:

[0022] Polishing the first thinning unit prepares the first polishing unit; polishing the second thinning unit prepares the second polishing unit; polishing the third thinning unit prepares the third polishing unit; polishing the fourth thinning unit prepares the fourth polishing unit.

[0023] Optionally, after providing the wafer substrate, the following may also be included:

[0024] The surface of the second substrate is thinned to prepare a second substrate thinning surface;

[0025] Polish the thinned surface of the second substrate and prepare a polished surface for the second substrate;

[0026] The first substrate thinning surface is prepared by thinning the surface of the first substrate;

[0027] Polish the thinned surface of the first substrate to prepare a polished surface of the first substrate.

[0028] Optionally, thinning the surface of the first substrate to prepare the first substrate thinning surface includes:

[0029] The amount of thinning of the first substrate surface is adjusted in conjunction with the morphology of the first piezoelectric surface, and the thinned surface of the first substrate is prepared.

[0030] Polishing the thinned surface of the first substrate and preparing the polished surface of the first substrate includes:

[0031] The polishing amount of the first substrate thinning surface is adjusted in combination with the morphology of the first piezoelectric surface, and the polished surface of the first substrate is prepared.

[0032] Optionally, thinning the surface of the second substrate and preparing a second substrate thinning surface includes:

[0033] The surface of the second substrate is thinned by a first thinning amount to prepare a second substrate sub-thinning surface;

[0034] The second substrate thinning surface is thinned by a second thinning amount and the second substrate thinning surface is prepared; wherein, the first thinning amount is greater than the second thinning amount, and the TTV of the second substrate thinning surface is a1, where a1 < 40 nm;

[0035] Polishing the thinned surface of the second substrate and preparing the polished surface of the second substrate includes:

[0036] The thinned surface of the second substrate is planar polished to prepare a polished surface of the second substrate, the roughness of which is Ra, where Ra < 0.2 nanometers.

[0037] Optionally, bonding the piezoelectric layer and the wafer substrate and fabricating the bonding unit includes:

[0038] Bonding units are prepared by bonding the piezoelectric layer and the wafer substrate using surface activation.

[0039] In a second aspect, embodiments of the present invention provide a bonding wafer, applied to the bonding wafer fabrication method described in any one of the first aspects, wherein the bonding wafer comprises:

[0040] A wafer substrate and a piezoelectric layer, wherein the wafer substrate includes a first substrate surface and a second substrate surface disposed opposite to each other, and the piezoelectric layer includes a first piezoelectric surface and a second piezoelectric surface disposed opposite to each other, wherein the first piezoelectric surface is located on the side of the second piezoelectric surface closer to the wafer substrate;

[0041] The second piezoelectric surface includes a second piezoelectric polished surface, which includes a plurality of polishing units. Along the thickness direction of the wafer substrate, the maximum distance from the surface of the polishing unit away from the surface of the second substrate to the surface of the second substrate is h3, and the minimum distance from the surface of the polishing unit away from the surface of the second substrate to the surface of the second substrate is h4, wherein (h3-h4)≤300 nanometers.

[0042] Thirdly, embodiments of the present invention provide a filter comprising the bonding wafer described in any one of the first aspects.

[0043] This invention provides a bonding wafer and its fabrication method. The fabrication method includes: providing a wafer substrate, the wafer substrate including a first substrate surface and a second substrate surface; providing a piezoelectric layer and adjusting the piezoelectric layer to be located on one side of the first substrate surface, the piezoelectric layer including a first piezoelectric surface and a second piezoelectric surface; bonding the piezoelectric layer and the wafer substrate and fabricating a bonding unit; thinning the second piezoelectric surface of the bonding unit and fabricating a second piezoelectric thinning surface, the second piezoelectric thinning surface including a first thinning unit and a second thinning unit; polishing the second piezoelectric thinning surface and fabricating a second piezoelectric polished surface, the second piezoelectric polished surface including multiple polishing units, polishing the first thinning unit to fabricate a first polishing unit, and polishing the second thinning unit to fabricate a second polishing unit; wherein the maximum distance from the surface of the polishing unit away from the second substrate surface to the second substrate surface is h3, the minimum distance from the surface of the polishing unit away from the second substrate surface to the second substrate surface is h4, and (h3-h4)≤300 nm. By adjusting the thinning and polishing processes during the fabrication of bonding units, the film thickness of the fabricated bonding wafers can be made uniform, thereby improving the structural stability and reliability of the bonding units. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0045] Figure 1 This is a schematic flowchart of a method for preparing a bonded wafer provided in Embodiment 1 of the present invention;

[0046] Figure 2 This is a schematic diagram of the fabrication process of a bonding wafer provided in Embodiment 1 of the present invention;

[0047] Figure 3 This is a top view schematic diagram of a second piezoelectric thinning surface provided in Embodiment 1 of the present invention;

[0048] Figure 4 This is a schematic diagram of the film thickness of a second piezoelectric thinning surface provided in Embodiment 1 of the present invention;

[0049] Figure 5 This is a top view schematic diagram of a second piezoelectric polished surface provided in Embodiment 1 of the present invention;

[0050] Figure 6This is a schematic diagram of the film thickness of a second piezoelectric polished surface provided in Embodiment 1 of the present invention;

[0051] Figure 7 This is a schematic flowchart of a method for preparing a bonded wafer provided in Embodiment 2 of the present invention;

[0052] Figure 8 This is a schematic flowchart of a method for preparing a bonded wafer provided in Embodiment 3 of the present invention;

[0053] Figure 9 This is a schematic diagram of the mechanical thinning device provided in Embodiment 3 of the present invention;

[0054] Figure 10 This is a top view schematic diagram of a second piezoelectric thinning surface provided in Embodiment 3 of the present invention;

[0055] Figure 11 This is a schematic diagram of the film thickness of the first type of piezoelectric layer provided in the prior art;

[0056] Figure 12 This is a top view schematic diagram of a second piezoelectric polished surface provided in Embodiment 3 of the present invention;

[0057] Figure 13 This is a schematic diagram of the film thickness of the second type of piezoelectric layer provided in the prior art;

[0058] Figure 14 This is a schematic flowchart of a method for preparing a bonded wafer provided in Embodiment 4 of the present invention;

[0059] Figure 15 This is a schematic diagram of the film thickness of a wafer substrate provided by existing technology;

[0060] Figure 16 This is a schematic diagram of a bonding wafer structure provided in Embodiment 5 of the present invention;

[0061] Figure 17 This is a schematic diagram of the structure of a filter provided in an embodiment of the present invention;

[0062] Wherein, 1-filter, 10-bonding wafer, 100-wafer substrate, 101-first substrate surface, 102-second substrate surface, 200-piezoelectric layer, 201-first piezoelectric surface, 202-second piezoelectric surface, 202a-second piezoelectric thinning surface, 202a1-first thinning unit, 202a2-second thinning unit, 202a3-third thinning unit, 202a4-fourth thinning unit, 202b-second piezoelectric polishing surface, 202b1-first polishing unit, 202b2-second polishing unit, 202b3-third polishing unit, 202b4-fourth polishing unit, 300-bonding unit, 20-mechanical thinning equipment, 21-adjustment structure, 22-limiting structure. Detailed Implementation

[0063] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0064] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0065] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0066] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0067] Example 1

[0068] Figure 1 This is a schematic flowchart of a method for preparing a bonded wafer provided in Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the fabrication process of a bonding wafer provided in Embodiment 1 of the present invention, for reference. Figure 1 and Figure 2 As shown, this embodiment of the invention provides a method for preparing a bonding wafer, the method comprising:

[0069] S110 provides wafer substrates.

[0070] A wafer substrate is provided, wherein the wafer substrate is a silicon substrate. For details, please refer to [reference needed]. Figure 2 As shown in step a, the wafer substrate 100 includes a first substrate surface 101 and a second substrate surface 102 disposed opposite to each other along the thickness direction of the wafer substrate 100.

[0071] S120, Provide a piezoelectric layer and adjust the piezoelectric layer to be located on one side of the surface of the first substrate.

[0072] Furthermore, a piezoelectric layer is provided, wherein the material of the piezoelectric layer may include lithium tantalate. The embodiments of the present invention do not specifically limit the material of the piezoelectric layer, and the material of the piezoelectric layer can be adaptively adjusted according to actual conditions.

[0073] For details, please refer to Figure 2 As shown in step b, the provided piezoelectric layer 200 includes a first piezoelectric surface 201 and a second piezoelectric surface 202 disposed opposite to each other along the thickness direction of the piezoelectric layer 200. Further, refer to... Figure 2 As shown in step c, the piezoelectric layer 200 is aligned with the wafer substrate 100, and the piezoelectric layer 200 is located on one side of the first substrate surface 101. Specifically, the first piezoelectric surface 201 is located on the side of the second piezoelectric surface 202 close to the wafer substrate 100.

[0074] S130, bonding piezoelectric layer and wafer substrate and fabricating bonding units.

[0075] Furthermore, after the piezoelectric layer and the wafer substrate are aligned and placed, they are bonded together using a bonding process to fabricate the bonding unit. For details, refer to... Figure 2As shown in steps c to d, after the piezoelectric layer 200 and the wafer substrate 100 are aligned and placed, the first substrate surface 101 and the first piezoelectric surface 201 are bonded together to form a bonding unit 300. It should be noted that the bonding unit 300 can be understood as a composite structure formed after the piezoelectric layer 200 and the wafer substrate 100 are initially bonded. Further processing of the bonding unit 300 is required in subsequent processes to form the final bonded wafer.

[0076] Further reference Figure 2 As shown in step d, the distance between the second piezoelectric surface 202 and the second substrate surface 102 is h0. This can also be understood as the overall thickness of the bonded unit 300 after bonding being h0. It should be noted that since the surface of the second piezoelectric surface 202 has not undergone thinning and polishing, it currently has a non-planar surface structure. Therefore, h0 can be understood as the average thickness of the second piezoelectric surface 202 and the second substrate surface 102. The specific value of h0 is not specifically limited in this embodiment of the invention and can be adaptively adjusted according to the thickness of the selected wafer substrate 100 and the thickness of the piezoelectric layer 200.

[0077] S140. Thinning the second piezoelectric surface of the bonding unit and preparing a second piezoelectric thinning surface, the second piezoelectric thinning surface including a plurality of thinning units, the thinning units including at least a first thinning unit and a second thinning unit.

[0078] Furthermore, the bonding units are thinned. Specifically, the second piezoelectric surface is thinned to form a second piezoelectric thinned surface. The second piezoelectric thinned surface formed by thinning includes multiple thinning units, and each thinning unit includes at least a first thinning unit and a second thinning unit. This can be understood as forming multiple different thinning units on the second piezoelectric surface by thinning the second piezoelectric surface to different degrees, with each thinning unit forming a surface structure by reducing the thickness by different values.

[0079] For details, please refer to Figure 2 As shown in step e, the second piezoelectric surface 202 of the bonding unit 300 is thinned to prepare a second piezoelectric thinned surface 202a. The second piezoelectric thinned surface 202a includes multiple thinning units, each including at least a first thinning unit 202a1 and a second thinning unit 202a2. The first thinning unit 202a1 and the second thinning unit 202a2 can have various positional relationships. The number of thinning units can be adaptively adjusted according to the actual dimensions; this embodiment of the invention does not impose a specific limitation on this. Figure 3 This is a top view schematic diagram of a second piezoelectric thinning surface provided in Embodiment 1 of the present invention, for reference. Figure 2 Step e and referenceFigure 3 As shown, the second thinning unit 202a2 surrounds the first thinning unit 202a1 for example.

[0080] Further reference Figure 2 As shown in step e, along the thickness direction of the wafer substrate 100, the distance from the surface of the first thinning unit 202a1 away from the second substrate surface 102 to the second substrate surface 102 is h1, and the distance from the surface of the second thinning unit 202a2 away from the second substrate surface 102 to the second substrate surface 102 is h2, where h0 > h1 and h0 > h2. This can be understood as forming the corresponding first thinning unit 202a1 and second thinning unit 202a2 by thinning the bonding unit 300. Furthermore, |h1-h2| > 0, meaning that the values ​​of h1 and h2 are different, indicating that the first thinning unit 202a1 and the second thinning unit 202a2 are thinning units prepared by different degrees of thinning. For example, Figure 2 In step e, if h1 is greater than h2, then the second piezoelectric thinning surface 202a prepared in this case can be understood as a "concave" surface structure. Alternatively, h1 can be less than h2, in which case the second piezoelectric thinning surface 202a prepared in this case can be understood as a "concave" surface structure.

[0081] By thinning the bonding unit 300 to different degrees in different areas, combined with the subsequent polishing process, it is beneficial to ensure that the film thickness in different areas is uniform. Figure 4 This is a schematic diagram of the film thickness of a second piezoelectric thinning surface provided in Embodiment 1 of the present invention, for reference. Figure 4 As shown in the figure, x and y represent different extension directions, and the values ​​on the x and y coordinate systems represent the numerical dimensions of the second piezoelectric thinning surface 202a. Figure 4 The colors on the right side of the diagram correspond one-to-one with the marked values, representing the detected film thickness. The same principle applies to subsequent diagrams illustrating film thickness. (Combined with...) Figure 4 As shown, by preparing multiple different thinning units for the bonding unit 300 during thinning, the film thickness uniformity at different thinning units is ensured.

[0082] S150. Polish the second piezoelectric thinning surface and prepare a second piezoelectric polished surface. The second piezoelectric polished surface includes multiple polishing units. Polish the first thinning unit to prepare a first polishing unit, and polish the second thinning unit to prepare a second polishing unit.

[0083] Furthermore, after preparing the second piezoelectric thinning surface on the bonding unit, the second piezoelectric thinning surface is then polished to form the second piezoelectric polished surface. The second piezoelectric polished surface includes multiple polishing units; the first polishing unit is formed by polishing the first thinning unit, and the second polishing unit is formed by polishing the second thinning unit. This can be understood as follows: after forming multiple thinning units, further polishing is performed to form different polishing units. During the polishing process of the second piezoelectric thinning surface, on the one hand, the overall roughness can be reduced, ensuring the structural smoothness of the bonded wafer. On the other hand, during the polishing process, the film thickness is continuously adjusted. Therefore, the film thickness can be adaptively adjusted based on the distance between different thinning units and the second substrate surface, ensuring the uniformity of the overall thickness of the finally prepared bonded wafer.

[0084] For details, please refer to Figure 2 As shown in steps e to f, the second piezoelectric thinning surface 202a is polished to prepare the second piezoelectric polished surface 202b. The second piezoelectric polished surface 202b includes multiple polishing units. The first thinning unit 202a1 is polished to prepare the first polishing unit 202b1, and the second thinning unit 202a2 is polished to prepare the second polishing unit 202b2. Figure 5 This is a top view schematic diagram of a second piezoelectric polished surface provided in Embodiment 1 of the present invention, with corresponding reference. Figure 3 and Figure 5 As shown, the first thinning unit 202a1 is polished to form the first polishing unit 202b1, and the second thinning unit 202a2 is polished to form the second polishing unit 202b2.

[0085] Further reference Figure 2As shown in step f, along the thickness direction of the wafer substrate 100, the maximum distance from the surface of the polishing unit away from the second substrate surface 102 to the second substrate surface 102 is h3, and the minimum distance from the surface of the polishing unit away from the second substrate surface 102 to the second substrate surface 102 is h4, where (h3-h4)≤300 nm. In other words, the thickness difference between the maximum and minimum distance points on the second piezoelectric polishing surface 202b and the second substrate surface 102 is less than or equal to 300 nm. The maximum distance point on the second piezoelectric polishing surface 202b and the second substrate surface 102 can be located at the first polishing unit 202b1 or the second polishing unit 202b2. Similarly, the minimum distance point on the second piezoelectric polishing surface 202b and the second substrate surface 102 can be located at the first polishing unit 202b1 or the second polishing unit 202b2. This embodiment of the invention does not impose specific limitations on this. By polishing the second piezoelectric thinning surface and preparing the second piezoelectric polished surface, it is equivalent to thinning and polishing the bonding unit to form a bonding wafer. This results in a smaller difference in film thickness within the bonding wafer, indicating better structural uniformity and a more regular and reliable structure.

[0086] For example, Figure 6 This is a schematic diagram of the film thickness of a second piezoelectric polished surface provided in Embodiment 1 of the present invention, combined with... Figure 6 As shown, after polishing the bonding units, the film thickness of the bonding wafer exhibits uniformity. This demonstrates that the bonding wafer prepared by the method provided in this embodiment of the invention has good film thickness uniformity.

[0087] In summary, the embodiments of the present invention provide a bonding wafer and a method for fabricating the same. The fabrication method includes: providing a wafer substrate, the wafer substrate including a first substrate surface and a second substrate surface; providing a piezoelectric layer and adjusting the piezoelectric layer to be located on one side of the first substrate surface, the piezoelectric layer including a first piezoelectric surface and a second piezoelectric surface; bonding the piezoelectric layer and the wafer substrate and fabricating a bonding unit; thinning the second piezoelectric surface of the bonding unit and fabricating a second piezoelectric thinning surface, the second piezoelectric thinning surface including a first thinning unit and a second thinning unit; polishing the second piezoelectric thinning surface and fabricating a second piezoelectric polished surface, the second piezoelectric polished surface including multiple polishing units, polishing the first thinning unit to fabricate a first polishing unit, and polishing the second thinning unit to fabricate a second polishing unit; wherein the maximum distance from the surface of the polishing unit away from the second substrate surface to the second substrate surface is h3, the minimum distance from the surface of the polishing unit away from the second substrate surface to the second substrate surface is h4, and (h3-h4)≤300 nm. By adjusting the thinning and polishing processes during the fabrication of bonding units, the film thickness of the fabricated bonding wafers can be made uniform, thereby improving the structural stability and reliability of the bonding units.

[0088] Example 2

[0089] Figure 7 This is a schematic flowchart of a bonding wafer fabrication method provided in Embodiment 2 of the present invention, for reference. Figure 7 As shown, the method for preparing a bonding wafer provided in this embodiment of the invention further includes:

[0090] S210 provides wafer substrates.

[0091] S220, Provide a piezoelectric layer and adjust the piezoelectric layer to be located on one side of the surface of the first substrate.

[0092] S230, bonding piezoelectric layer and wafer substrate and fabricating bonding units.

[0093] S240, Thinning the second piezoelectric surface and preparing the first thinning unit and the second thinning unit.

[0094] Wherein, along the thickness direction of the wafer substrate, the distance from the surface of the first thinning unit away from the surface of the second substrate to the surface of the second substrate is h1, and the distance from the surface of the second thinning unit away from the surface of the second substrate to the surface of the second substrate is h2, where h1-h2=ha.

[0095] This can be understood as forming the corresponding first thinning unit 202a1 and second thinning unit 202a2 by thinning the bonding unit 300. Furthermore, |h1-h2|>0, meaning that h1 and h2 have different values, indicating that the first and second thinning units are prepared by different degrees of thinning. Further, h1-h2=ha, where ha can be understood as the thickness difference between the prepared first and second thinning units.

[0096] S250, control the polishing of the first thinning unit to a first polishing thickness and prepare the first polishing unit, and control the polishing of the second thinning unit to a second polishing thickness and prepare the second polishing unit.

[0097] Specifically, a second piezoelectric polished surface is prepared by polishing the second piezoelectric thinning surface. A first polishing unit is prepared by polishing the first thinning unit, and a second polishing unit is prepared by polishing the second thinning unit. Further, given the thickness difference between the first and second thinning units, the first thinning unit is polished to a controlled first polishing thickness to prepare the first polished unit, and the second thinning unit is polished to a controlled second polishing thickness to prepare the second polished unit. The first polishing thickness is h5, and the second polishing thickness is h6, where h6 - h5 = hb. hb can be understood as the difference between the first and second polishing thicknesses, that is, the difference in film layer change during the preparation of the first and second polishing units.

[0098] Furthermore, ha and hb satisfy the following conditions: (ha×hb)>0, ||ha|-|hb|| / |hb|≤20%. That is, ha and hb have similar or identical values. Specifically, if h1 is greater than h2, ha is positive, then h6 is also greater than h5, and hb is also positive; if h1 is less than h2, ha is negative, then h6 is also less than h5, and hb is also negative. For example, taking h1 being greater than h2, this can be understood as the overall film thickness from the first thinning unit to the second substrate surface being greater than the overall thickness from the second thinning unit to the second substrate surface when thinning the second piezoelectric surface. The resulting second piezoelectric thinned surface can be understood as a "centrally convex" surface structure. To ensure a small overall thickness difference in the final bonded wafer and maintain overall film flatness, the first and second polishing thicknesses are adjusted based on the morphology of the second piezoelectric thinning surface. Specifically, the first polishing thickness is made smaller than the second polishing thickness. This adjustment adaptively compensates for the thickness difference caused by thinning, thus ensuring overall film flatness in the bonded wafer. Optionally, combining thinning and polishing in the fabrication of the bonded wafer can guarantee structural flatness, reduce film thickness differences, and ensure the reliability and practicality of the bonded wafer.

[0099] Example 3

[0100] Figure 8 This is a schematic flowchart of a bonding wafer fabrication method provided in Embodiment 3 of the present invention, for reference. Figure 8 As shown, the method for preparing a bonding wafer provided in this embodiment of the invention further includes:

[0101] S310 provides wafer substrates.

[0102] S320, Provide a piezoelectric layer and adjust the piezoelectric layer to be located on one side of the surface of the first substrate.

[0103] S330, bonding piezoelectric layer and wafer substrate and fabricating bonding units.

[0104] S340, control the mechanical thinning equipment to thin the second piezoelectric surface and prepare the second piezoelectric thinning surface, the second thinning unit surrounds the first thinning unit.

[0105] Furthermore, mechanical thinning equipment can be used to thin the second piezoelectric surface in sections, forming a second piezoelectric thinned surface comprising multiple thinning units. Specifically, an example is given where the second piezoelectric thinned surface includes a first thinning unit and a second thinning unit. The second thinning unit surrounds the first thinning unit; therefore, the second piezoelectric thinned surface can be understood as a structure in which multiple thinning units are arranged in a ring.

[0106] Figure 9This is a schematic diagram of the mechanical thinning device provided in Embodiment 3 of the present invention, for reference. Figure 9 As shown, the mechanical thinning apparatus 20 used in fabricating bonded wafers includes an adjustment structure 21 and a limiting structure 22, with the limiting structure 22 surrounding the adjustment structure 21; the bonding unit 300 is located on one side of the adjustment structure 21, and the adjustment structure 21 adjusts the height and / or angle of the bonding unit 300, while the limiting structure 22 limits the bonding unit 300. (Referring to...) Figure 9 As shown, taking the limiting structure 22 as an example, which is a cylindrical structure, the interior of the limiting structure 22 is a hollow groove. The adjusting structure 21 can be located within the hollow groove of the limiting structure 22, that is, the limiting structure 22 surrounds the adjusting structure 21. Further, refer to... Figure 9 As shown, the bonding unit 300 is located on one side of the adjustment structure 21, and the adjustment structure 21 can adjust the height and / or angle of the bonding unit 300. The limiting structure 22 can fix the position of the bonding unit 300 supported by the adjustment structure 21, preventing excessive movement of the bonding unit 300. By adjusting the height and / or angle of the bonding unit 300 through the adjustment structure 21, the area requiring thinning can be exposed on the surface of the limiting structure 22 and thinned accordingly.

[0107] For example, multiple thinning units can be effectively formed on the second piezoelectric surface using a mechanical thinning device. Specifically, the mechanical thinning device used for bonding unit thinning includes an adjustable structure that can adjust the height. By raising or lowering the adjustable structure, a concave or convex morphology can be created on the second piezoelectric surface. This aims to produce a concentric film thickness profile (e.g., the second thinning unit surrounds the first thinning unit), which is beneficial for subsequent polishing processes. Furthermore, the thinning process can be divided into coarse thinning and fine thinning to achieve a more refined thinning process. The specific parameters for coarse and fine thinning can be adaptively adjusted according to actual needs, and this embodiment of the invention does not impose specific limitations on them.

[0108] Figure 10 This is a top view schematic diagram of a second piezoelectric thinning surface provided in Embodiment 3 of the present invention, for reference. Figure 10 As shown, the mechanical thinning equipment is controlled to thin the second piezoelectric surface and prepare the second piezoelectric thinned surface 202a. The second piezoelectric thinned surface 202a also includes a third thinning unit 202a3 and a fourth thinning unit 202a4. The third thinning unit 202a3 surrounds the second thinning unit 202a2, and the fourth thinning unit 202a4 surrounds the third thinning unit 202a3.

[0109] Further reference Figure 10As shown, multiple thinning units can be formed at the second piezoelectric thinning surface 202a. The thinning units may include a first thinning unit 202a1, a second thinning unit 202a2, a third thinning unit 202a3, and a fourth thinning unit 202a4. The second thinning unit 202a2 surrounds the first thinning unit 202a1, the third thinning unit 202a3 surrounds the second thinning unit 202a2, and the fourth thinning unit 202a4 surrounds the third thinning unit 202a3, thus demonstrating that the multiple thinning units form a ring-shaped structure. In this design, the distance from the surface of the third thinning unit 202a3 away from the second substrate surface 102 to the second substrate surface 102 is h7, and the distance from the surface of the fourth thinning unit 202a4 away from the second substrate surface 102 to the second substrate surface 102 is h8. Here, h0 > h7, h0 > h8, and |h7-h8| > 0, meaning that h7 and h8 have different values, indicating that the third thinning unit 202a3 and the fourth thinning unit 202a4 are thinning units prepared to different degrees. Furthermore, h1, h2, h7, and h8 can all have different values. By performing different degrees of partitioned thinning on the bonding unit 300, combined with the subsequent polishing process, it is beneficial to ensure the uniformity of the film thickness in different regions.

[0110] Figure 11 This is a schematic diagram of the film thickness of the first type of piezoelectric layer provided in the prior art, for comparison and reference. Figure 11 and Figure 4 As shown, Figure 4 The paper demonstrates that this thinning process can achieve multiple different thinning units and ensure good uniformity of film thickness at each thinning unit. Figure 11 The surface of the piezoelectric layer is thinned using existing thinning techniques, compared to... Figure 11 and Figure 4 It can be concluded that by partitioning and thinning the bonding unit 300 to different degrees, it is beneficial to ensure that the film thickness in different regions is uniform.

[0111] S350, Partition pressure polishing is applied to the first thinning unit and the second thinning unit to prepare the first polishing unit and the second polishing unit, and the first thinning unit is polished with a first pressure value to prepare the first polishing unit, and the second thinning unit is polished with a second pressure value to prepare the second polishing unit.

[0112] Furthermore, after forming a ring-shaped thinning unit around the second piezoelectric thinning surface, each thinning unit is polished to different degrees. Specifically, a zoned pressure polishing method is used to polish each thinning unit. Zoned pressure polishing allows control of the polishing pressure and the rotation speed of the polishing disk in the corresponding area to achieve different degrees of polishing. Specifically, the first thinning unit is polished to prepare the first polishing unit using a first pressure value, and the second thinning unit is polished to prepare the second polishing unit using a second pressure value. The first pressure value is P1, and the second pressure value is P2, where |P1-P2|>0. If the thickness of the first thinning unit to the second substrate surface at the second piezoelectric thinning surface is greater than that of the second thinning unit to the second substrate surface, the first pressure value can be adjusted to be greater than the second pressure value to balance the overall film thickness. This ensures that the film thickness of each area of ​​the bonded wafer prepared after polishing is uniform, minimizes the overall film thickness difference of the bonded wafer, and improves the overall flatness of the bonded wafer. Polishing has a much higher precision in processing the film layer than thinning. Therefore, thinning and polishing can be combined to improve the overall flatness of the film layer on the bonded wafer.

[0113] Figure 12 This is a top view schematic diagram of a second piezoelectric polished surface provided in Embodiment 3 of the present invention, for reference. Figure 10 and Figure 12 The first thinning unit 202a1, the second thinning unit 202a2, the third thinning unit 202a3, and the fourth thinning unit 202a4 at the thinning point of the second piezoelectric surface are subjected to partitioned pressure polishing. Specifically, polishing the first thinning unit 202a1 prepares the first polishing unit 202b1, polishing the second thinning unit 202a2 prepares the second polishing unit 202b2, polishing the third thinning unit 202a3 prepares the third polishing unit 202b3, and polishing the fourth thinning unit 202a4 prepares the fourth polishing unit 202b4. Since the first thinning unit 202a1, the second thinning unit 202a2, the third thinning unit 202a3, and the fourth thinning unit 202a4 are prepared according to different thinning thicknesses, the distances of the first thinning unit 202a1, the second thinning unit 202a2, the third thinning unit 202a3, and the fourth thinning unit 202a4 to the second substrate surface 102 are different. Therefore, a zoned pressure polishing method is adopted, and different polishing pressure values ​​are adjusted for polishing.

[0114] Figure 13 This is a schematic diagram of the film thickness of the second type of piezoelectric layer provided in the prior art, for comparison and reference. Figure 13 and Figure 6 As shown, Figure 6 The process demonstrates that this polishing technique can achieve multiple different polishing units and ensure good uniformity of film thickness at each polishing unit. Figure 13The surface of the piezoelectric layer is polished using existing polishing techniques, compared to... Figure 13 and Figure 6 It can be concluded that by performing partitioned thinning of the bonding unit 300 to different degrees and then performing partitioned pressure polishing, it is beneficial to ensure that the film thickness in different regions is uniform.

[0115] Example 4

[0116] Figure 14 This is a schematic flowchart of a bonding wafer fabrication method provided in Embodiment 4 of the present invention, for reference. Figure 14 As shown, the method for preparing a bonding wafer provided in this embodiment of the invention further includes:

[0117] S410 provides wafer substrates.

[0118] S420, Thin the surface of the second substrate and prepare the thinned surface of the second substrate.

[0119] Thinning the surface of the second substrate of the wafer substrate can help ensure the consistency of the wafer substrate structure, avoid large stress and warping in subsequent processes, and ensure the structural stability of the wafer substrate.

[0120] Optionally, the fabrication process for the thinned surface of the second substrate can be as follows:

[0121] First, the surface of the second substrate is thinned by a first thinning amount to prepare a second substrate sub-thinning surface; then, the second substrate sub-thinning surface is thinned by a second thinning amount to prepare a second substrate thinning surface; wherein, the first thinning amount is greater than the second thinning amount, and the TTV of the second substrate thinning surface is a1, where a1 < 40 nanometers.

[0122] In this process, the first thinning amount is less than the second thinning amount. This can be understood as the process using the first thinning amount being a coarse thinning process, and the process using the second thinning amount being a fine thinning process. The combination of coarse and fine thinning results in a smaller difference in film thickness on the thinned surface of the second substrate, ensuring the flatness of the thinned surface. Specifically, the total thickness transformation (TTV) of the thinned surface of the second substrate prepared through these two thinning processes is a1, where a1 < 40 nm. TTV can be understood as the maximum difference in film thickness on the thinned surface of the second substrate.

[0123] S430, Polish the thinned surface of the second substrate and prepare the polished surface of the second substrate.

[0124] Furthermore, polishing the thinned surface of the second substrate can further ensure the consistency and flatness of the wafer substrate structure. The surface of the second substrate is the surface of the subsequently fabricated bonding wafer; thinning and polishing it can further improve the flatness of the bonding wafer surface and reduce film thickness differences.

[0125] Optionally, the thinned surface of the second substrate is planar polished to prepare a polished surface of the second substrate, the roughness of which is Ra, where Ra < 0.2 nanometers. By planar polishing the already thinned surface of the second substrate, the structural flatness of the wafer substrate 100 is further ensured.

[0126] Figure 15 This is a schematic diagram of the film thickness of a wafer substrate provided by existing technology. If the second substrate surface of the wafer substrate is not thinned and polished, the thickness of the wafer substrate is as follows. Figure 15 As shown. Figure 15 The image shows that the surface of the second substrate is uneven, with significant differences in film thickness. Therefore, the bonded wafer formed after bonding the wafer substrate and the piezoelectric layer has poor structural flatness, affecting its structural stability. To address this, steps S410 and S420 in this fabrication method are used to thin and polish the surface of the second substrate, which helps improve the structural stability of the bonded wafer.

[0127] S440, Thinning the surface of the first substrate to prepare a thinned surface.

[0128] In this process, the first substrate surface of the wafer substrate is subsequently used for bonding with the first piezoelectric surface. Therefore, to ensure the bonding effect between the wafer substrate and the piezoelectric layer, the first substrate surface can be thinned and polished. Specifically, the first substrate surface is first thinned to prepare a first substrate thinned surface.

[0129] Specifically, the amount of thinning on the surface of the first substrate can be adjusted by combining the morphology of the first piezoelectric surface, and a thinned surface of the first substrate can be prepared.

[0130] Since the first substrate surface and the first piezoelectric surface need to be bonded, the surface film layer of the first piezoelectric surface can be considered when thinning the first substrate surface, and the thinning amount can be adjusted accordingly. For example, if the first piezoelectric surface simultaneously has a thicker region (e.g., referred to as the first region) and a thinner region (e.g., referred to as the second region), then when thinning the first substrate surface, the portion corresponding to the first region can be thinned to a thinner degree, and the portion corresponding to the second region can be thinned to a thicker degree. This ensures the alignment and bonding effect between the first substrate surface and the first piezoelectric surface, thereby ensuring the bonding effect.

[0131] S450, Polish the thinned surface of the first substrate and prepare the polished surface of the first substrate.

[0132] Furthermore, the thinned surface of the first substrate is polished to prepare a polished surface, further improving the structural flatness of the wafer substrate. The polished surface of the first substrate is then bonded to the first piezoelectric surface to better ensure the alignment and bonding effect between the first substrate surface and the first piezoelectric surface, thereby ensuring the effectiveness of subsequent bonding.

[0133] Specifically, the polishing amount of the thinned surface of the first substrate can be adjusted by combining the morphology of the first piezoelectric surface, and a polished surface of the first substrate can be prepared.

[0134] Since the first substrate surface and the first piezoelectric surface need to be bonded, the surface film condition of the first piezoelectric surface can be considered when polishing the thinned surface of the first substrate, and the polishing amount can be adjusted accordingly. Because the film thickness can also be adjusted during the polishing process, if there are both thicker regions (e.g., referred to as the first region) and thinner regions (e.g., referred to as the second region) on the first piezoelectric surface, then when polishing the first substrate surface, the portion corresponding to the first region can be polished with a thinner degree, and the portion corresponding to the second region can be polished with a thicker degree. This ensures the alignment and bonding effect between the first substrate surface and the first piezoelectric surface, thereby ensuring the subsequent bonding effect.

[0135] Furthermore, by adjusting the film thickness on both the first and second substrate surfaces of the wafer substrate, a wide range of wafer substrates can be selected when fabricating bonded wafers. For example, the selected wafer substrate has a TTV of a2, where a2 can satisfy: 0 < a2 < 10 micrometers. In other words, considering process costs, the wafer substrate with a large difference in film thickness can be selected using the bonding wafer fabrication method provided by this invention.

[0136] S460, Provide a piezoelectric layer and adjust the piezoelectric layer to be located on one side of the surface of the first substrate.

[0137] S470: Surface activation is used to bond the piezoelectric layer and the wafer substrate to prepare bonding units.

[0138] Specifically, surface activation bonding is used during the bonding process. For example, at an absolute vacuum of 4 × 10⁻⁶... 4 Under conditions of Pa and a temperature of 23℃, argon ions were used to bombard the surfaces of the piezoelectric layer and the wafer substrate to be bonded, thereby activating them. Bonding was then achieved by applying a certain pressure. After bonding, the bond strength between the piezoelectric layer and the wafer substrate was greater than 1.5 J / cm. 2 The bonding unit is obtained.

[0139] S480, Thinning the second piezoelectric surface of the bonding unit and preparing a second piezoelectric thinning surface, the second piezoelectric thinning surface including a plurality of thinning units, the thinning units including at least a first thinning unit and a second thinning unit.

[0140] S490. Polish the second piezoelectric thinning surface and prepare a second piezoelectric polished surface. The second piezoelectric polished surface includes multiple polishing units. Polish the first thinning unit to prepare a first polishing unit, and polish the second thinning unit to prepare a second polishing unit.

[0141] Example 5

[0142] Figure 16 This is a schematic diagram of a bonding wafer structure provided in Embodiment 5 of the present invention, for reference. Figure 16 As shown, an embodiment of the present invention provides a bonding wafer 10, which includes a wafer substrate 100 and a piezoelectric layer 200. The wafer substrate 100 includes a first substrate surface 101 and a second substrate surface 102 disposed opposite to each other. The piezoelectric layer 200 includes a first piezoelectric surface 201 and a second piezoelectric surface 202 disposed opposite to each other. The first piezoelectric surface 201 is located on the side of the second piezoelectric surface 202 closer to the wafer substrate 100. The second piezoelectric surface 202 includes a second piezoelectric polished surface 202b, which includes a plurality of polishing units. Along the thickness direction of the wafer substrate 100, the maximum distance from the surface of the polishing unit away from the second substrate surface 102 to the second substrate surface 102 is h3, and the minimum distance from the surface of the polishing unit away from the second substrate surface 102 to the second substrate surface 102 is h4, wherein (h3-h4)≤300 nanometers.

[0143] For details, please refer to Figure 16 As shown, the bonding wafer 10 includes a wafer substrate 100 and a piezoelectric layer 200. The wafer substrate 100 includes a first substrate surface 101 and a second substrate surface 102 disposed opposite to each other along the thickness direction of the bonding wafer 10. The piezoelectric layer 200 includes a first piezoelectric surface 201 and a second piezoelectric surface 202 disposed opposite to each other along the thickness direction of the bonding wafer 10. The piezoelectric layer 200 is located on one side of the wafer substrate 100, specifically the first piezoelectric surface 201 is located on the side of the second piezoelectric surface 202 closer to the wafer substrate 100. The bonding wafer 10 structure is fabricated by bonding the first substrate surface 101 and the first piezoelectric surface 201.

[0144] Furthermore, to ensure the flatness and regularity of the bonded wafer 10, the second piezoelectric surface 202 is thinned and polished. Specifically, after bonding the wafer substrate 100 and the piezoelectric layer 200, the second piezoelectric surface 202 is gradually thinned and polished. During the thinning of the second piezoelectric surface 202, multiple thinning units are formed on the second piezoelectric surface 202 (the thinning units are structures formed during the fabrication process).Figure 16 (Not shown in the image). Different thinning units are formed by reducing the thickness of the film. Furthermore, different polishing units are formed by polishing these thinning units to different degrees. The polishing process reduces the overall roughness, ensuring the smoothness of the bonded wafer 10. On the other hand, the thickness of the film layer is continuously adjusted during polishing. Therefore, the amount of polishing can be adaptively adjusted based on the distance between different thinning units and the second substrate surface 102, ensuring the uniformity of the overall thickness of the final bonded wafer 10.

[0145] For details, please refer to Figure 16 As shown, along the thickness direction of the wafer substrate 100, the maximum distance from the surface of the polishing unit away from the second substrate surface 102 to the second substrate surface 102 is h3, and the minimum distance from the surface of the polishing unit away from the second substrate surface 102 to the second substrate surface 102 is h4, where (h3-h4)≤300 nm. In other words, after thinning and polishing the second piezoelectric surface 202, the maximum distance point between its surface and the second substrate surface 102 (h3-h4) is... Figure 16 (shown as m1) and the point of minimum distance between its surface and the surface 102 of the second substrate ( Figure 16 The thickness difference between the layers (shown as m2) is less than or equal to 300 nanometers. The small thickness difference of the film layers reflecting the structure of the wafer substrate 100 results in good flatness.

[0146] In summary, this invention provides a bonding wafer in which the surface of the piezoelectric layer away from the wafer substrate is thinned and polished to form a second piezoelectric polished surface. The second piezoelectric polished surface includes multiple polishing units, wherein the maximum distance from the surface of each polishing unit away from the second substrate surface to the second substrate surface is h3, and the minimum distance is h4, where (h3-h4) ≤ 300 nm. By adjusting the thinning and polishing processes during the fabrication of the bonding units, the uniformity of the film thickness of the prepared bonding wafer can be ensured, improving the structural stability and reliability of the bonding units.

[0147] Example 6

[0148] Based on the same inventive concept, this application also provides a filter. Figure 17 This is a schematic diagram of the structure of a filter provided in an embodiment of the present invention, as shown below. Figure 17 As shown, the filter 1 includes the bonding wafer 10 described in any of the above embodiments. Therefore, the filter 1 provided in this application has the corresponding beneficial effects in the above embodiments, which will not be repeated here.

[0149] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a bonded wafer, comprising: providing a wafer substrate, the wafer substrate comprising a first substrate surface and a second substrate surface arranged oppositely; providing a piezoelectric layer and adjusting the piezoelectric layer to be located on a side of the first substrate surface; the piezoelectric layer comprising a first piezoelectric surface and a second piezoelectric surface arranged oppositely, the first piezoelectric surface being located on a side of the second piezoelectric surface close to the wafer substrate; bonding the piezoelectric layer and the wafer substrate to prepare a bonded unit; the second piezoelectric surface being at a distance h0 from the second substrate surface; thinning the second piezoelectric surface of the bonded unit to prepare a second piezoelectric thinned surface, the second piezoelectric thinned surface comprising a plurality of thinned units, the thinned units comprising at least a first thinned unit and a second thinned unit; along a thickness direction of the wafer substrate, the first thinned unit being at a distance h1 from the second substrate surface, and the second thinned unit being at a distance h2 from the second substrate surface, wherein h0>h1, h0>h2, and |h1-h2|>0; polishing the second piezoelectric thinned surface to prepare a second piezoelectric polished surface, the second piezoelectric polished surface comprising a plurality of polished units, the first thinned unit being polished to prepare a first polished unit, and the second thinned unit being polished to prepare a second polished unit; along the thickness direction of the wafer substrate, the polished units being at a maximum distance h3 from the second substrate surface, and the polished units being at a minimum distance h4 from the second substrate surface, wherein (h3-h4)≤300nm. 2.The method of claim 1, wherein: thinning the second piezoelectric surface of the bonded unit to prepare a second piezoelectric thinned surface, the second piezoelectric thinned surface comprising a plurality of thinned units, the thinned units comprising at least a first thinned unit and a second thinned unit comprises: thinning the second piezoelectric surface to prepare the first thinned unit and the second thinned unit; wherein h1-h2=ha; polishing the second piezoelectric thinned surface to prepare a second piezoelectric polished surface, the second piezoelectric polished surface comprising a plurality of polished units, the first thinned unit being polished to prepare a first polished unit, and the second thinned unit being polished to prepare a second polished unit comprises: polishing the first thinned unit to prepare the first polished unit at a first polishing thickness, and polishing the second thinned unit to prepare the second polished unit at a second polishing thickness; the first polishing thickness being h5, and the second polishing thickness being h6, wherein h6-h5=hb, (ha×hb)>0, and ||ha|-|hb|| / |hb|≤20%. 3.The method of claim 1, wherein: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ thinning the second piezoelectric surface of the bonding unit and preparing a second piezoelectric thinned surface, the second piezoelectric thinned surface comprising a plurality of thinned units, the thinned units comprising at least a first thinned unit and a second thinned unit comprising: controlling a mechanical thinning device to thin the second piezoelectric surface and prepare the second piezoelectric thinned surface, the second thinned unit surrounding the first thinned unit; wherein the mechanical thinning device comprises an adjusting structure and a limiting structure, the limiting structure surrounding the adjusting structure; the bonding unit is located on one side of the adjusting structure, and the adjusting structure adjusts the height and / or angle of the bonding unit, and the limiting structure limits the bonding unit; polishing the second piezoelectric thinned surface and preparing a second piezoelectric polished surface, the second piezoelectric polished surface comprising a plurality of polished units, polishing the first thinned unit to prepare a first polished unit, and polishing the second thinned unit to prepare a second polished unit comprising: polishing and preparing the first polished unit and the second polished unit by partitioning pressure, controlling the first thinned unit to prepare the first polished unit by polishing at a first pressure value, and controlling the second thinned unit to prepare the second polished unit by polishing at a second pressure value; wherein the first pressure value is P1, and the second pressure value is P2, and |P1-P2|>0.

4. The preparation method of claim 3, wherein controlling a mechanical thinning device to thin the second piezoelectric surface and prepare the second piezoelectric thinned surface comprising: controlling a mechanical thinning device to thin the second piezoelectric surface and prepare the second piezoelectric thinned surface, the second piezoelectric thinned surface further comprising a third thinned unit and a fourth thinned unit, the third thinned unit surrounding the second thinned unit, and the fourth thinned unit surrounding the third thinned unit; wherein the distance from the surface of the third thinned unit away from the second substrate surface to the second substrate surface is h7, and the distance from the surface of the fourth thinned unit away from the second substrate surface to the second substrate surface is h8, wherein h0>h7, h0>h8, and |h7-h8|>0; polishing the second piezoelectric thinned surface and preparing a second piezoelectric polished surface comprising: polishing the first thinned unit to prepare the first polished unit, polishing the second thinned unit to prepare the second polished unit, polishing the third thinned unit to prepare a third polished unit, and polishing the fourth thinned unit to prepare a fourth polished unit.

5. The preparation method according to claim 1, characterized in that, providing a wafer substrate further comprising: thinning the second substrate surface and preparing a second substrate thinned surface; polishing the second substrate thinned surface and preparing a second substrate polished surface; thinning the first substrate surface to prepare a first substrate thinned surface; polishing the first substrate thinned surface and preparing a first substrate polished surface.

6. The preparation method of claim 5, wherein thinning the first substrate surface to prepare a first substrate thinned surface comprising: adjusting the amount of thinning of the first substrate surface in combination with the topography of the first piezoelectric surface and preparing the first substrate thinned surface; Thinning the first substrate surface and preparing a first substrate thinning surface includes: Adjusting the polishing amount of the first substrate thinning surface in combination with the topography of the first piezoelectric surface and preparing the first substrate polishing surface.

7. The preparation method of claim 4, wherein, Thinning the second substrate surface and preparing a second substrate thinning surface includes: Thinning the second substrate surface and preparing a second substrate thinning surface includes: Thinning the second substrate surface and preparing a second substrate thinning surface includes: Polishing the second substrate thinning surface and preparing a second substrate polishing surface includes: Polishing the second substrate thinning surface and preparing a second substrate polishing surface includes:

8. The preparation method of claim 1, wherein, Bonding the piezoelectric layer and the wafer substrate and preparing a bonded unit includes: Bonding the piezoelectric layer and the wafer substrate and preparing a bonded unit includes:

9. A bonded wafer, comprising: Prepared by the preparation method of the bonded wafer of any one of claims 1-8, the bonded wafer includes: A wafer substrate including oppositely arranged first and second substrate surfaces and a piezoelectric layer including oppositely arranged first and second piezoelectric surfaces, the first piezoelectric surface being located on the side of the second piezoelectric surface close to the wafer substrate; The second piezoelectric surface includes a second piezoelectric polishing surface, the second piezoelectric polishing surface includes a plurality of polishing units, along the thickness direction of the wafer substrate, the maximum distance from the surface of the polishing unit away from the second substrate surface to the second substrate surface is h3, the minimum distance from the surface of the polishing unit away from the second substrate surface to the second substrate surface is h4, wherein (h3-h4)≤300nm.

10. A filter, characterized by, The bonded wafer of claim 9.

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