Method and apparatus for thinning lithium tantalate bonded wafers

Abstract

The thinning method and device for lithium tantalate bonded wafers provided by the present invention relate to the technical field of wafer thinning. First, the initial surface shape data is detected, and then the inclination angle of the coarse grinding wheel is adjusted according to the positive and negative values ​​of the initial BOW value of the initial surface shape data, and then the wafer is rough thinned. Then, the rough grinding surface shape data of the thinned wafer is detected again, and then the inclination angle of the fine grinding wheel is adjusted according to the positive and negative values ​​of the coarse grinding BOW value of the coarse grinding surface shape data, and then the wafer is fine thinned. Compared with the prior art, the present invention uses coarse thinning and fine thinning to thin the wafer. Before the thinning action, the inclination angle of the grinding wheel is adjusted according to the BOW value, so that the grinding wheel can better fit the wafer during the thinning process. On the one hand, it can reduce the risk of brittle fractures such as chipping and slow down the sub-surface damage layer. On the other hand, it can adaptively correct the wafer to solve the serious warping problem caused by thinning. It can effectively improve the quality of ultra-thin lithium tantalate bonded wafers after thinning.

Description

Technical Field

[0001] The present invention relates to the technical field of wafer thinning, and in particular to a method and device for thinning a lithium tantalate bonded wafer. Background Art

[0002] Lithium tantalate wafers, as an important semiconductor material, are widely used in fields such as sensors. With technological advancements, the demand for ultra-thin lithium tantalate wafers is increasing. Lithium tantalate is primarily used in key components such as high-performance filters, where its excellent material properties make it increasingly irreplaceable.

[0003] In summary, due to the low hardness, high brittleness, and strong anisotropy of lithium tantalate crystals, they are prone to brittle failure, warping, and deep subsurface damage during the thinning process. Therefore, existing thinning methods are unable to meet the mass production needs of high-quality ultra-thin bonded wafers. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and equipment for thinning lithium tantalate bonded wafers, which can effectively improve the quality of ultra-thin lithium tantalate bonded wafers after thinning, reduce the risk of brittle fracture during thinning, and solve the serious warping problem caused by thinning.

[0005] In a first aspect, the present invention provides a method for thinning a lithium tantalate bonded wafer, comprising:

[0006] Detecting initial surface data of the cleaned wafer, wherein the initial surface data includes an initial BOW value;

[0007] Adjusting the inclination angle of the coarse grinding wheel relative to the thinning machine platform according to the positive or negative value of the initial BOW value so that the coarse grinding wheel fits the initial surface shape of the wafer;

[0008] performing rough thinning on the wafer;

[0009] detecting rough-grinding surface data of the wafer after rough thinning, wherein the rough-grinding surface data includes a rough-grinding BOW value;

[0010] Adjusting the inclination angle of the fine grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the rough grinding BOW value, so that the fine grinding wheel fits the surface shape of the wafer after rough thinning;

[0011] performing fine thinning on the wafer;

[0012] Detect the fine grinding surface data of the wafer after fine thinning.

[0013] In an optional embodiment, the step of adjusting the inclination angle of the coarse grinding wheel relative to the thinning machine platform according to the initial BOW value includes:

[0014] If the initial BOW value is positive, the coarse grinding wheel is tilted toward the inside of the wafer to adjust a first preset angle;

[0015] If the initial BOW value is negative, the coarse grinding wheel is tilted toward the outside of the wafer to adjust a second preset angle.

[0016] In an optional embodiment, the first preset angle is 0.5°-2°, and the second preset angle is 0.5°-2°.

[0017] In an optional embodiment, the step of adjusting the inclination angle of the fine grinding wheel relative to the thinning machine platform according to the positive or negative value of the rough grinding BOW value includes:

[0018] If the rough grinding BOW value is positive, the fine grinding wheel is tilted toward the inner side of the wafer to adjust a third preset angle;

[0019] If the rough grinding BOW value is negative, the fine grinding wheel is tilted toward the outside of the wafer to adjust a fourth preset angle.

[0020] In an optional embodiment, the third preset angle is less than 1°, and the fourth preset angle is 1°-3°.

[0021] In an optional embodiment, before the step of adjusting the inclination angle of the grinding wheel relative to the thinning machine platform according to the positive or negative value of the initial BOW value, the method further includes:

[0022] The thinning machine platform is leveled so that the horizontal deviation of the thinning machine platform is less than or equal to 1 μm.

[0023] In an optional embodiment, after the step of fine thinning the wafer, the method further comprises:

[0024] Pressing and grinding the wafer for a first preset time;

[0025] The wafer is idling and polished for a second preset time.

[0026] In an optional implementation, the first preset time is 2-3 seconds, and the second preset time is 5-10 seconds.

[0027] In an optional embodiment, the mesh number of the coarse grinding wheel is 3000-4000; the mesh number of the fine grinding wheel is 6000-8000.

[0028] In an optional embodiment, the initial surface shape data also includes the TTV value and film thickness value of the wafer before thinning; the rough-ground surface shape data also includes the TTV value and film thickness value of the wafer after rough thinning; and the fine-ground surface shape data includes the TTV value, film thickness value and LTV value of the wafer after fine thinning.

[0029] In a second aspect, an embodiment of the present invention provides a thinning device for a lithium tantalate bonded wafer, which is applicable to the aforementioned thinning method, and the thinning device includes:

[0030] A surface shape detection device, the surface shape detection device is used to detect the initial surface shape data of the wafer after cleaning, the rough-ground surface shape data of the wafer after rough thinning, and the fine-ground surface shape data of the wafer after fine thinning;

[0031] A thinning machine platform, the thinning machine platform is used to carry the wafer;

[0032] a coarse grinding wheel, the coarse grinding wheel being used for roughly thinning the wafer;

[0033] A fine grinding wheel, used for fine thinning the wafer;

[0034] Among them, the initial surface shape data includes an initial BOW value, the rough grinding surface shape data includes a rough grinding BOW value, and the thinning machine platform is also used to adjust the inclination angle of the rough grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the initial BOW value, and to adjust the inclination angle of the fine grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the rough grinding BOW value.

[0035] The beneficial effects of the embodiments of the present invention include:

[0036] The thinning method and device for lithium tantalate bonded wafers provided by the embodiments of the present invention can achieve thinning of lithium tantalate bonded wafers. The method includes: first detecting the initial surface shape data of the wafer after cleaning, the initial surface shape data at least including the initial BOW value, then adjusting the inclination angle of the coarse grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the initial BOW value, so that the coarse grinding wheel can match the initial surface shape of the wafer, and then performing rough thinning on the wafer. Since the inclination angle of the coarse grinding wheel is changed according to the positive and negative BOW value, the wafer warping can be preliminarily corrected during the rough thinning process. Then, the rough grinding surface shape data of the wafer after thinning is detected again, the rough grinding surface shape data at least including the rough grinding BOW value, and then adjusting the inclination angle of the fine grinding wheel relative to the thinning machine according to the positive and negative values ​​of the rough grinding BOW value, so that the fine grinding wheel can match the surface shape of the wafer after rough thinning, and then performing fine thinning on the wafer. Finally, the fine grinding surface shape data of the wafer after fine thinning is detected again. Compared to existing technologies, the present invention uses a graded process of coarse and fine thinning to achieve thinning of lithium tantalate bonded wafers. Before thinning, the inclination angle of the coarse or fine grinding wheel is adjusted based on the BOW value, allowing the grinding wheel to better fit the wafer during thinning. This reduces the risk of brittle fractures such as edge chipping and mitigates the development of subsurface damage. Furthermore, the BOW value of the wafer can be adaptively corrected, addressing the severe warping problem caused by thinning. Consequently, the quality of ultra-thin lithium tantalate bonded wafers after thinning can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 A flowchart of the steps of a method for thinning a lithium tantalate bonded wafer provided in an embodiment of the present invention;

[0039] Figure 2 A schematic diagram of the wafer surface before thinning according to the thinning method of the lithium tantalate bonded wafer provided in Example 1 of the present invention;

[0040] Figure 3 A schematic diagram of the wafer surface after thinning according to the thinning method of the lithium tantalate bonded wafer provided in Example 1 of the present invention;

[0041] Figure 4 A schematic diagram of the wafer surface before thinning according to the thinning method of the lithium tantalate bonded wafer provided in Comparative Example 1 of the present invention;

[0042] Figure 5 A schematic diagram of the wafer surface after thinning according to the thinning method of the lithium tantalate bonded wafer provided in Comparative Example 1 of the present invention;

[0043] Figure 6 Schematic diagram of the wafer after thinning according to the thinning method of the lithium tantalate bonded wafer provided in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0045] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0046] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0047] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the product of the invention is usually placed when in use. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0048] In addition, the terms "first", "second", etc., if used, are merely used to distinguish and describe, and should not be understood as indicating or implying relative importance.

[0049] An embodiment of the present invention provides a method for thinning a lithium tantalate bonded wafer, which can effectively improve the quality of the ultra-thin lithium tantalate bonded wafer after thinning, reduce the depth of the subsurface damage layer, reduce the risk of brittle fracture during thinning, and solve the problem of severe warping caused by thinning.

[0050] See also Figure 1 The thinning method of the lithium tantalate bonded wafer provided in the embodiment of the present invention is used to thin the lithium tantalate bonded wafer, and the thinning method comprises the following steps:

[0051] S1: Detect the initial surface data of the wafer after cleaning.

[0052] First, the wafer to be thinned needs to be cleaned and then subjected to surface inspection. A single-sided scrubber can be used to scrub the wafer during cleaning. It should be noted that the initial surface data here includes the wafer's initial BOW value, TTV (Total Thickness Variation), and film thickness before thinning, so surface inspection can be performed on the wafer before thinning.

[0053] It should be noted that the wafer here needs to be bonded to the substrate for thinning. The bonding process can refer to the existing wafer bonding process, which will not be introduced in detail here. The wafers mentioned in this embodiment all refer to lithium tantalate wafers bonded to the substrate.

[0054] S2: Level the thinning machine platform.

[0055] Specifically, the thinning machine platform is used to support the wafer and can achieve leveling in the X-axis and Y-axis directions. After leveling, the horizontal deviation of the thinning machine platform is less than or equal to 1μm, that is, the tilt degree in the X-axis and Y-axis directions after leveling must be ≤1μm, so that the thinning machine platform can be kept as horizontal as possible, which serves as a reference for subsequent adjustments.

[0056] S3: Adjust the inclination angle of the coarse grinding wheel relative to the thinning machine platform according to the positive or negative value of the initial BOW value.

[0057] Specifically, after leveling the thinning machine, the coarse grinding wheel can be adjusted to above the thinning machine platform first, with the roller side of the coarse grinding wheel kept horizontal, and then the inclination angle of the thinning machine platform is adjusted according to the positive and negative values ​​of the initial BOW value, and then the inclination angle of the coarse grinding wheel relative to the thinning machine platform and the wafer is adjusted to make the coarse grinding wheel fit the initial surface shape of the wafer.

[0058] It should be noted that the coarse grinding wheel proposed here fits the initial surface shape of the wafer, which means that the coarse grinding wheel corresponds to the BOW value of the wafer. If the BOW value is positive, the coarse grinding wheel can be adjusted by tilting inward. Conversely, if the BOW value is negative, the coarse grinding wheel can be adjusted by tilting outward.

[0059] Furthermore, in the mass production process, the wafers can be divided into two categories and processed separately according to the positive and negative values ​​of the initial BOW values. The adjustment method of the coarse grinding wheel is: if the initial BOW value is positive, the coarse grinding wheel is tilted toward the inside of the wafer to adjust the first preset angle; if the initial BOW value is negative, the coarse grinding wheel is tilted toward the outside of the wafer to adjust the second preset angle. Among them, the first preset angle is 0.5°-2°, and the second preset angle is 0.5°-2°. During actual adjustment, when the initial Bow value of the wafer to be thinned is positive, it indicates that the wafer is a center-convex warp. At this time, the coarse grinding wheel is tilted toward the inside of the wafer, and the adjustment angle is 0.5°-2°. For example, any point value among 0.5°, 1°, 2° or the value between any two points can be adjusted. When the initial Bow value of the wafer to be thinned is negative, it indicates that the wafer has a central concave warp. At this time, the coarse grinding wheel is tilted toward the outside of the wafer and the adjustment angle is 0.5°-2°. For example, the value can be adjusted to any point among 0.5°, 1°, 2° or a value between any two points.

[0060] S4: Roughly thinning the wafer.

[0061] Specifically, the lithium tantalate bonded wafer can be placed on the thinning machine platform and fixed, and the thinning program can be set. Rough thinning is divided into two stages: the coarse grinding wheel speed is 1750-1850rpm, the platform speed is 301-401rpm, the F1 feed rate is 1-2μm / s, the removal amount is 20-50μm, and the F2 feed rate is 0.5-0.8μm / s, and the removal amount is 3μm. The mesh number of the coarse grinding wheel here can be 3000-4000.

[0062] S5: Detecting the rough-ground surface data of the wafer after rough thinning.

[0063] After rough thinning, the thinning machine platform can be leveled again, and then the wafer surface shape detection can be performed. The rough grinding surface shape data includes the rough grinding BOW value, TTV value and film thickness value of the wafer after rough thinning, so the surface shape detection of the wafer after rough thinning can be performed.

[0064] S6: Adjust the inclination angle of the fine grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the rough grinding BOW value.

[0065] Specifically, after detecting the surface shape data, the fine grinding wheel can be adjusted to above the thinning machine platform first, with the roller side of the fine brush wheel kept horizontal, and then the inclination angle of the thinning machine platform can be adjusted according to the positive and negative values ​​of the rough grinding BOW value, thereby adjusting the inclination angle of the fine grinding wheel relative to the thinning machine platform and the wafer, so that the fine grinding wheel fits the surface shape of the wafer after rough thinning.

[0066] It should be noted that the fine grinding wheel proposed here fits the surface shape of the wafer after thinning, which means that the fine grinding wheel corresponds to the BOW value of the wafer. If the BOW value is positive, the coarse grinding wheel can be adjusted by tilting inward. Conversely, if the BOW value is negative, the coarse grinding wheel can be adjusted by tilting outward.

[0067] Furthermore, the fine grinding wheel is adjusted as follows: if the rough grinding BOW value is positive, the fine grinding wheel is tilted toward the inside of the wafer to adjust the third preset angle; if the rough grinding BOW value is negative, the fine grinding wheel is tilted toward the outside of the wafer to adjust the fourth preset angle. The third preset angle is less than 1°, for example, it can be adjusted to any point value among 0°, 0.5°, 1° or a value between any two points; the fourth preset angle is 1°-3°, for example, it can be adjusted to any point value among 1°, 2°, 3° or a value between any two points. It should be noted that due to the high wear of the fine grinding wheel during fine thinning, regardless of the concave or convex center of the wafer surface, the angle of the fine grinding wheel needs to be adjusted 0.5°-1° toward the outside of the wafer as a whole based on the angle adjustment during rough thinning, that is, the third preset angle should be 0.5°-1° smaller than the first preset angle, and the fourth preset angle should be 0.5°-1° larger than the second preset angle, so as to facilitate chip removal and prevent the wear debris of the fine grinding wheel and wafer particles from causing secondary damage to the processed surface.

[0068] S7: Fine thinning the wafer.

[0069] Specifically, fine thinning is divided into three stages: the fine grinding wheel speed is 1250-1350 rpm, the platform speed is 301-401 rpm, the F1 feed rate is 0.4-0.6 μm / s, the removal amount is 7 μm, the F2 removal rate is 0.2-0.4 μm / s, the removal amount is 2 μm, and the F3 removal rate is 0.1-0.3 μm / s, the removal amount is 1 μm. The mesh number of the fine grinding wheel here can be 6000-8000.

[0070] Furthermore, after fine thinning, it is necessary to press and grind the wafer for the first preset time, and then slowly lift the fine grinding wheel after idling and grinding the wafer for the second preset time, wherein the first preset time is 2-3s and the second preset time is 5-10s. In actual operation, after fine thinning, the fine grinding wheel is pressed and ground, and after idling and removing a certain thickness, it is slowly lifted. Specifically, after fine thinning, the position of the fine grinding wheel is maintained and the wafer is idling and ground at a fine grinding wheel speed of 1750-1850rpm and a platform speed of 301-401rpm. Press and grind for 2-3s, the idling time is 5-10s, the slow lifting rate is 0.2-0.4μm / s, and the slow lifting height is 2-3μm.

[0071] It should be noted that pressure grinding and idle grinding for a period of time can further reduce defects such as grinding wheel marks on the wafer surface and repair the wafer surface shape. Combined with adjusting the grinding wheel angle during thinning, it can reduce wafer surface defects caused by poor thinning processing and avoid abnormalities such as excessive wear during subsequent wafer tape-out.

[0072] S8: Detecting the fine-grinding surface data of the wafer after fine-thinning.

[0073] Specifically, after the fine thinning is completed, the surface shape of the wafer after fine thinning can be inspected again. The fine grinding surface shape data includes the TTV value, film thickness value and LTV value (Local Thickness Variation) of the wafer after fine thinning, which can effectively detect the thinning quality and provide corresponding feedback for the thinning program.

[0074] The thinning method provided by the embodiment of the present invention can effectively reduce surface defects such as grinding wheel marks. First, by adjusting the angles of the coarse grinding wheel and the fine grinding wheel to fit the surface shape of the wafer to be thinned, the thinning quality is better and the warping can be reduced. Then, by press grinding and increasing the idling time, surface defects such as wafer grinding wheel marks are reduced. The surface defects of the wafer caused by poor thinning processing are reduced, and abnormalities such as excessive insertion loss in the subsequent wafer flow process are avoided. After repairing the surface shape of the wafer, the present invention avoids abnormalities such as PrPeeling of the wafer edge and frequency offset of the Saw device in the subsequent process. In addition, because there is a sorting process for the wafers according to the surface shape, and batch processing is carried out according to the sorting results, the consistency of data between wafers is greatly improved, and the stability of the batch processing wafer process is guaranteed.

[0075] An embodiment of the present invention also provides a thinning device for lithium tantalate bonded wafers, which is suitable for the aforementioned thinning method. The thinning device includes a surface detection device, a thinning machine platform, a coarse grinding wheel and a fine grinding wheel. The surface detection device is used to detect the initial surface shape data of the wafer after cleaning, the coarse grinding surface shape data of the wafer after coarse thinning, and the fine grinding surface shape data of the wafer after fine thinning; the thinning machine platform is used to carry the wafer; the coarse grinding wheel is used to perform coarse thinning on the wafer; and the fine grinding wheel is used to perform fine thinning on the wafer; wherein, the initial surface shape data includes an initial BOW value, the coarse grinding surface shape data includes a coarse grinding BOW value, and the thinning machine platform is further used to adjust the inclination angle of the coarse grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the initial BOW value, and to adjust the inclination angle of the fine grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the coarse grinding BOW value.

[0076] It should be noted that the thinning machine platform here is capable of adjusting the relative inclination angles of the coarse and fine grinding wheels. The thinning equipment also includes other components such as a drive device. Its basic operating principle and structure can refer to existing thinning equipment. The prior art also uses ICP etching instead of fine grinding to grind the damaged layer on the back of the wafer. This method removes the deeper damage caused by the rough grinding process, reduces wafer warpage, and avoids mechanical damage caused by the fine grinding process. However, this process uses ICP etching, which is more expensive and complex than fine grinding. The efficiency is significantly lower than direct fine grinding, making it unsuitable for batch processing requirements of production lines. Conventional technology also has solutions for adjusting the grinding angle during grinding for other materials. However, this adjustment is usually made directly based on the wafer slope specification requirements. Compared with softer materials with fragile cleavage surfaces such as lithium tantalate, this grinding device cannot perform targeted processing on batch wafers, and the possibility of edge chipping and fragmentation during such processing also increases. The embodiments of the present invention can effectively solve the above problems.

[0077] The thinning method and device for lithium tantalate bonded wafers provided by the embodiments of the present invention can achieve thinning of lithium tantalate bonded wafers. The method includes: first detecting the initial surface shape data of the wafer after cleaning, the initial surface shape data at least including the initial BOW value, then adjusting the inclination angle of the coarse grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the initial BOW value, so that the coarse grinding wheel can match the initial surface shape of the wafer, and then performing rough thinning on the wafer. Since the inclination angle of the coarse grinding wheel is changed according to the positive and negative BOW value, the wafer warping can be preliminarily corrected during the rough thinning process. Then, the rough grinding surface shape data of the wafer after thinning is detected again, the rough grinding surface shape data at least including the rough grinding BOW value, and then adjusting the inclination angle of the fine grinding wheel relative to the thinning machine according to the positive and negative values ​​of the rough grinding BOW value, so that the fine grinding wheel can match the surface shape of the wafer after rough thinning, and then performing fine thinning on the wafer. Finally, the fine grinding surface shape data of the wafer after fine thinning is detected again. Compared to the prior art, the present invention uses a graded process of coarse and fine thinning to achieve thinning of lithium tantalate bonded wafers. Before thinning, the inclination angle of the coarse or fine grinding wheel is adjusted based on the BOW value, allowing the grinding wheel to better conform to the wafer during thinning. This reduces the risk of brittle fractures such as edge chipping and mitigates the development of subsurface damage. Furthermore, the BOW value of the wafer can be adaptively corrected, addressing the severe warping caused by thinning. Furthermore, by increasing press grinding and idle time, surface defects such as wafer grinding wheel marks are reduced. This reduces wafer surface defects caused by poor thinning processing and avoids abnormalities such as excessive insertion loss during subsequent wafer fabrication. After repairing the wafer surface profile, the present invention avoids abnormalities such as wafer edge PrPeeling and Saw device frequency offset in subsequent processes. Furthermore, because wafers are sorted according to their surface profile and batch processed based on the sorting results, data consistency between wafers is greatly improved, ensuring the stability of the batch wafer processing process. Therefore, the quality of ultra-thin lithium tantalate bonded wafers after thinning can be effectively improved.

[0078] Example 1

[0079] S1: Use a single-sided scrubber to scrub a 6-inch lithium tantalate bonded wafer. After cleaning, inspect the wafer's TTV, BOW, and film thickness data.

[0080] S2: Level the thinning machine platform so that the horizontal deviation of the thinning machine platform in the X and Y axis directions is 1μm.

[0081] S3: The cleaned lithium tantalate bonded wafers are divided into two categories according to the positive and negative BOW values ​​and processed separately. When the Bow value of the wafer to be processed is positive, it indicates that the center of the wafer is convex warping. At this time, the grinding wheel is tilted toward the inside of the wafer and the adjustment angle is 1°. When the Bow value of the wafer to be processed is negative, it indicates that the center of the wafer is concave warping. At this time, the grinding wheel is tilted toward the outside of the wafer and the adjustment angle is 1°.

[0082] S4: Then, the lithium tantalate bonded wafer is placed into the thinning machine, and the thinning machine program is set for rough thinning. The rough thinning grinding wheel speed is 1750 rpm, the platform speed is 301 rpm, the F1 feed rate is 1 μm / s, the removal thickness is 50 μm, the F2 feed rate is 0.5 μm / s, the removal amount is 3 μm, and rough thinning begins;

[0083] S5: Detect wafer surface data TTV, BOW, and film thickness data after rough thinning.

[0084] S6: Set the thinning machine program and adjust the grinding wheel tilt angle. When the Bow value of the wafer to be processed is positive, it indicates that the center of the wafer is convex warping. At this time, the grinding wheel is tilted toward the inside of the wafer and the adjustment angle is 0.5°. When the Bow value of the wafer to be processed is negative, it indicates that the center of the wafer is concave warping. At this time, the grinding wheel is tilted toward the outside of the wafer and the adjustment angle is 1.5°.

[0085] S7: Set the thinning machine program for fine thinning, the fine thinning wheel speed is 1250rpm, the platform speed is 301rpm, the F1 feed rate is 0.4μm / s, the removal amount is 7μm, the F2 removal rate is 0.2μm / s, the removal amount is 2μm, the F3 removal rate is 0.1μm / s, the removal amount is 1μm, and fine thinning begins. After fine thinning, the fine grinding wheel is pressed and ground for 2s, and then slowly lifted after idling. After fine thinning, the grinding wheel position is maintained and the wafer is idlingly ground at a grinding wheel speed of 1750rpm and a platform speed of 301rpm. The idling time is 5s, the slow lifting rate is 0.2μm / s, and the slow lifting height is 2μm.

[0086] S8: Detect TTV, LTV, BOW, film thickness and other data of the wafer after thinning, and provide feedback for program adjustment.

[0087] See also Figure 2 and Figure 3 , Figure 2 This is the wafer surface shape before thinning. It can be seen that it has a concave warpage in the middle. Figure 3 The figure shows the wafer surface shape after thinning, and it can be seen that the warpage has been effectively improved. After testing, after thinning the lithium tantalate bonded wafer using the thinning method of Example 1 of the present invention, the wafer TTV is less than 1.5μm, the BOW is less than 2μm, the thickness between wafers in the batch is ≤1μm, and the surface roughness of the wafer after thinning is ≤10nm. The wafer thickness range before thinning is 2640-3889μm, and the wafer thickness range after thinning using the method of the present invention is 1732-2246μm. The wafer thickness difference is improved from 1249μm to 514μm.

[0088] Comparative Example 1

[0089] S1: Use a single-sided scrubber to scrub a 6-inch lithium tantalate bonded wafer. After cleaning, inspect the wafer's TTV, BOW, and film thickness data.

[0090] S2: Level the thinning machine platform so that the horizontal deviation of the thinning machine platform in the X and Y axis directions is 1μm.

[0091] S3: Place the lithium tantalate bonded wafer into the thinning machine, set the thinning machine program, the rough thinning wheel speed is 1750rpm, the platform speed is 301rpm, the F1 feed rate is 1μm / s, the removal thickness is 50μm, the F2 feed rate is 0.5μm / s, the removal amount is 3μm, and start rough thinning.

[0092] S4: Detect wafer surface data TTV, BOW, and film thickness data after rough thinning.

[0093] S5: Set the thinning machine program for fine thinning, with the fine thinning wheel speed of 1250rpm, the platform speed of 301rpm, the F1 feed rate of 0.4μm / s, the removal amount of 7μm, the F2 removal rate of 0.2μm / s, the removal amount of 2μm, the F3 removal rate of 0.1μm / s, the removal amount of 1μm, and start fine thinning. After fine thinning, the fine grinding wheel is idling and then slowly lifted. After fine thinning, the grinding wheel position is maintained and the wafer is idling at a grinding wheel speed of 1750rpm and a platform speed of 301rpm. The idling time is 5s, the slow lifting rate is 0.2μm / s, and the slow lifting height is 2μm.

[0094] S6: Detect TTV, LTV, BOW, film thickness and other data of the wafer after thinning, and provide feedback for program adjustment;

[0095] See also Figure 4 and Figure 5 , Figure 4 This is the wafer surface shape before thinning. It can be seen that it has a concave warpage in the middle. Figure 5 The wafer surface shape after thinning shows that the warpage has not been improved. After testing, after thinning the lithium tantalate bonded wafer using the thinning method of Comparative Example 1, the wafer TTV is less than 1.5μm, the BOW is 9-10μm, the thickness difference between wafers in a batch is less than 2μm, and the surface roughness of the wafer after thinning is ≤10nm. The wafer thickness range before thinning is 3207-3886μm, and the wafer thickness range after thinning using the thinning method in Comparative Example 1 is 1664-2444μm. The wafer thickness difference changes from 679μm to 780μm, showing no improvement. The BOW value is too large, and the wafer is warped.

[0096] Comparative Example 2

[0097] S1: Use a single-sided scrubber to scrub a 6-inch lithium tantalate bonded wafer. After cleaning, inspect the wafer's TTV, BOW, and film thickness data.

[0098] S2: Level the thinning machine platform so that the horizontal deviation of the thinning machine platform in the X and Y axis directions is 1μm.

[0099] S3: Place the lithium tantalate bonded wafer into the thinning machine, set the thinning machine program, the rough thinning wheel speed is 1750rpm, the platform speed is 301rpm, the F1 feed rate is 1μm / s, the removal thickness is 50μm, the F2 feed rate is 0.5μm / s, the removal amount is 3μm, and start rough thinning.

[0100] S4: Detect wafer surface data TTV, BOW, and film thickness data after rough thinning.

[0101] S5: Set the thinning machine program for fine thinning, the fine thinning wheel speed is 1250rpm, the platform speed is 301rpm, the F1 feed rate is 0.4μm / s, the removal amount is 7μm, the F2 removal rate is 0.2μm / s, the removal amount is 2μm, the F3 removal rate is 0.1μm / s, the removal amount is 1μm, and fine thinning begins.

[0102] S6: Detect TTV, LTV, BOW, film thickness and other data of the wafer after thinning, and provide feedback for program adjustment;

[0103] See also Figure 6 , Figure 6 The figure is a schematic diagram of the wafer surface after thinning. It can be seen that there are a large number of surface defects such as grinding wheel marks on its surface. After inspection, after thinning the lithium tantalate bonded wafer using the thinning method of this comparative example 2, the wafer TTV is <1.5μm, the BOW is 9-10μm, the thickness difference between wafers in the batch is <2μm, and the surface roughness of the wafer after thinning is ≥20nm. Surface defects such as grinding wheel marks on the wafer surface have not been repaired. The wafer thickness range before thinning is 3207-3886μm, and the wafer thickness range after thinning using the method of the present invention is 1668-2448μm. The wafer thickness difference changes from 679μm to 780μm, and there is no improvement. In addition, the BOW value is too large, and the wafer is warped.

[0104] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for thinning a lithium tantalate bonded wafer, characterized in that: include: Detecting initial surface data of the cleaned wafer, wherein the initial surface data includes an initial BOW value; Adjusting the inclination angle of the coarse grinding wheel relative to the thinning machine platform according to the positive or negative value of the initial BOW value so that the coarse grinding wheel fits the initial surface shape of the wafer; performing rough thinning on the wafer; detecting rough-grinding surface data of the wafer after rough thinning, wherein the rough-grinding surface data includes a rough-grinding BOW value; Adjusting the inclination angle of the fine grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the rough grinding BOW value, so that the fine grinding wheel fits the surface shape of the wafer after rough thinning; performing fine thinning on the wafer; Detecting the fine grinding surface data of the wafer after fine thinning; After the step of fine thinning the wafer, the method further comprises: Pressing and grinding the wafer for a first preset time; The wafer is idling and polished for a second preset time.

2. The method for thinning a lithium tantalate bonded wafer according to claim 1, wherein: The step of adjusting the inclination angle of the coarse grinding wheel relative to the thinning machine platform according to the initial BOW value comprises: If the initial BOW value is positive, the coarse grinding wheel is tilted toward the inside of the wafer to adjust a first preset angle; If the initial BOW value is negative, the coarse grinding wheel is tilted toward the outside of the wafer to adjust a second preset angle.

3. The method for thinning a lithium tantalate bonded wafer according to claim 2, wherein: The first preset angle is 0.5°-2°, and the second preset angle is 0.5°-2°.

4. The method for thinning a lithium tantalate bonded wafer according to claim 2, wherein: The step of adjusting the inclination angle of the fine grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the rough grinding BOW value comprises: If the rough grinding BOW value is positive, the fine grinding wheel is tilted toward the inner side of the wafer to adjust a third preset angle; If the rough grinding BOW value is negative, the fine grinding wheel is tilted toward the outside of the wafer to adjust a fourth preset angle.

5. The method for thinning a lithium tantalate bonded wafer according to claim 4, wherein: The third preset angle is less than 1°, and the fourth preset angle is 1°-3°.

6. The method for thinning a lithium tantalate bonded wafer according to claim 1, wherein: Before the step of adjusting the inclination angle of the grinding wheel relative to the thinning machine platform according to the positive or negative value of the initial BOW value, the method further includes: The thinning machine platform is leveled so that the horizontal deviation of the thinning machine platform is less than or equal to 1 μm.

7. The method for thinning a lithium tantalate bonded wafer according to claim 1, wherein: The first preset time is 2-3 seconds, and the second preset time is 5-10 seconds.

8. The method for thinning a lithium tantalate bonded wafer according to claim 1, wherein: The initial surface shape data also includes the TTV value and film thickness value of the wafer before thinning; the rough grinding surface shape data also includes the TTV value and film thickness value of the wafer after rough thinning; the fine grinding surface shape data includes the TTV value, film thickness value and LTV value of the wafer after fine thinning.

9. A thinning device for lithium tantalate bonded wafers, suitable for the thinning method for lithium tantalate bonded wafers according to claim 1, characterized in that: The thinning equipment for the lithium tantalate bonded wafer includes: A surface shape detection device, the surface shape detection device is used to detect the initial surface shape data of the wafer after cleaning, the rough-ground surface shape data of the wafer after rough thinning, and the fine-ground surface shape data of the wafer after fine thinning; A thinning machine platform, the thinning machine platform is used to carry the wafer; a coarse grinding wheel, the coarse grinding wheel being used for roughly thinning the wafer; A fine grinding wheel, used for fine thinning the wafer; Among them, the initial surface shape data includes an initial BOW value, the rough grinding surface shape data includes a rough grinding BOW value, and the thinning machine platform is also used to adjust the inclination angle of the rough grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the initial BOW value, and to adjust the inclination angle of the fine grinding wheel relative to the thinning machine platform according to the positive and negative values ​​of the rough grinding BOW value.

Images