Polishing method, polishing head, final polishing equipment and silicon wafer

Abstract

The embodiment of the invention provides a polishing method, a polishing head, final polishing equipment and a silicon wafer, and the polishing method comprises the steps that the first surface of the silicon wafer is adsorbed through an adsorption unit of the polishing head, so that the silicon wafer is elastically deformed into a second shape from a first shape; and under the condition that the silicon wafer is kept in the second shape, polishing a second surface, opposite to the first surface, of the silicon wafer so as to process the shape of the silicon wafer into an expected third shape.

Description

Technical Field

[0001] The disclosed embodiments relate to the field of silicon wafer processing technology, and in particular to a polishing method, a polishing head, a final polishing device and a silicon wafer. Background Art

[0002] With the rapid development of semiconductor technology, silicon wafers, as the basic material for chip manufacturing, have increasingly higher requirements for surface flatness. The flatness of the silicon wafer surface directly affects the performance and production yield of the chip, so in the manufacturing process of silicon wafers, the improvement of flatness has become a crucial link. In order to achieve the required high flatness standards, polishing processes are widely used, and the quality control of polishing processes has become a key step in silicon wafer manufacturing.

[0003] The existing polishing process generally includes a double-sided polishing process for polishing both the front and back sides of the silicon wafer and a final polishing process for performing only the front side of the silicon wafer. In the final polishing process, the silicon wafer is held by a polishing head and pressed against a polishing pad arranged under the polishing head under the rotation of the polishing head, thereby polishing the front side of the silicon wafer.

[0004] However, when using existing final polishing equipment, there is a problem of uneven distribution of silicon wafer removal due to the uneven distribution of the force exerted by the polishing head on the silicon wafer. There is also a risk that the silicon wafer will separate from the polishing head during processing due to the unstable holding force of the polishing head on the silicon wafer. Summary of the invention

[0005] In view of this, the embodiments of the present disclosure are intended to provide a polishing method, a polishing head, a final polishing device, and a silicon wafer. By using the polishing method, the silicon wafer can be deformed before polishing, and the silicon wafer can be polished while being kept in the deformation, thereby significantly improving the polishing accuracy and meeting the polishing requirements of silicon wafers of specific shapes.

[0006] The technical solution of the embodiment of the present disclosure is implemented as follows: In a first aspect, an embodiment of the present disclosure provides a polishing method, the polishing method comprising: Adsorbing a first surface of the silicon wafer by an adsorption unit of the polishing head so that the silicon wafer is elastically deformed from a first shape to a second shape; While the silicon wafer is maintained in the second shape, a second surface of the silicon wafer opposite to the first surface is polished to process the shape of the silicon wafer into a desired third shape.

[0007] In some optional examples, adsorbing the first surface of the silicon wafer by the adsorption unit of the polishing head so that the silicon wafer is elastically deformed from the first shape to the second shape includes: The multiple adsorption units of the polishing head respectively adsorb different areas on the first surface of the silicon wafer, so that at least a part of the areas of the silicon wafer adsorbed by the multiple adsorption units undergoes elastic deformation, thereby causing the retained silicon wafer to elastically deform from a first shape to a second shape.

[0008] In some optional examples, adsorbing the first surface of the silicon wafer by the adsorption unit of the polishing head so that the silicon wafer is elastically deformed from the first shape to the second shape includes: Adsorbing different areas on the first surface of the silicon wafer respectively by using a plurality of adsorption units of the polishing head; At least a part of the multiple adsorption units is moved in a direction perpendicular to the first surface of the held silicon wafer, so that at least a part of the area of ​​the silicon wafer adsorbed by the at least a part of the adsorption units undergoes elastic deformation, thereby elastically deforming the held silicon wafer from a first shape to a second shape.

[0009] In some optional examples, the plurality of adsorption units are disposed at different positions in a radial direction of the adsorbed silicon wafer.

[0010] In some optional examples, the plurality of adsorption units are configured to be in a plurality of annular shapes arranged concentrically with the adsorbed silicon wafer.

[0011] In some optional examples, while keeping the silicon wafer in the second shape, polishing a second surface of the silicon wafer opposite to the first surface to process the shape of the silicon wafer into a desired third shape includes: A fluid is sprayed onto the silicon wafer while polishing a second surface of the silicon wafer opposite to the first surface.

[0012] In a second aspect, an embodiment of the present disclosure provides a polishing head, comprising an adsorption unit for holding a silicon wafer, wherein the adsorption unit is configured to adsorb a first surface of the silicon wafer so as to elastically deform the silicon wafer from a first shape to a second shape, thereby allowing the silicon wafer to be processed into a desired third shape by polishing a second surface of the silicon wafer opposite to the first surface while maintaining the silicon wafer in the second shape.

[0013] In some optional examples, the polishing head includes a plurality of the adsorption units, wherein the plurality of adsorption units respectively adsorb different areas on the first surface of the silicon wafer, so that at least a portion of the areas of the silicon wafer adsorbed by the plurality of adsorption units undergoes elastic deformation, thereby causing the retained silicon wafer to elastically deform from a first shape to a second shape.

[0014] In some optional examples, at least a portion of the multiple adsorption units are configured to move in a direction perpendicular to the first surface of the silicon wafer being held while respectively adsorbing different areas on the first surface of the silicon wafer, so that at least a portion of the areas of the silicon wafer adsorbed by at least a portion of the adsorption units undergoes elastic deformation, thereby elastically deforming the held silicon wafer from a first shape to a second shape.

[0015] In some optional examples, the plurality of adsorption units are disposed at different positions in a radial direction of the adsorbed silicon wafer.

[0016] In some optional examples, the plurality of adsorption units are configured to be in a plurality of annular shapes arranged concentrically with the adsorbed silicon wafer.

[0017] In some optional examples, the polishing head further includes a nozzle for spraying a fluid toward the held silicon wafer.

[0018] In a third aspect, an embodiment of the present disclosure provides a final polishing device, comprising the polishing head according to the second aspect.

[0019] In a fourth aspect, an embodiment of the present disclosure provides a silicon wafer, which is obtained by the polishing method according to the first aspect, wherein the TTV of the silicon wafer is less than 500 nanometers, and the SFQR of the silicon wafer is less than 50 nanometers.

[0020] Some embodiments of the present disclosure provide a polishing method, a polishing head, a final polishing device, and a silicon wafer. Using the polishing head and the polishing method provided by the embodiments of the present disclosure, the silicon wafer can be subjected to partial or overall elastic deformation by adsorption before polishing. By polishing the silicon wafer while maintaining this elastic deformation, only the target area on the silicon wafer can be polished, or the polishing removal amount of the target area can be made greater than the polishing removal amount of other areas, that is, the polishing removal amount of different areas on the same surface of the same silicon wafer can be different. In this way, the uneven polishing caused by other process factors can be compensated in a targeted manner, so that the polished silicon wafer has a desired morphology. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of a conventional final polishing device; Figure 2 A schematic diagram of a polishing head provided for an embodiment of the present disclosure; Figure 3 for Figure 2 Another schematic diagram of the polishing head shown; Figure 4 for Figure 2 Another schematic diagram of the polishing head shown; Figure 5 A flow chart of a polishing method provided in an embodiment of the present disclosure; Figure 6 A partial bottom view of a polishing head provided in an embodiment of the present disclosure; Figure 7 A partial bottom view of a polishing head provided for another embodiment of the present disclosure; Figure 8 A schematic diagram of a polishing head provided for another embodiment of the present disclosure; Fig. 9 A schematic diagram of a polishing head provided for yet another embodiment of the present disclosure; Fig.10 Schematic diagram of a final polishing apparatus provided for embodiments of the present disclosure. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure.

[0023] Figure 1 , a conventional final polishing device 10 is shown. The final polishing device 10 may include: a polishing table 11, a polishing pad 12 disposed on the upper surface of the polishing table 11, and a drive shaft 13 disposed below the polishing table 11. The polishing pad 12 can rotate along with the polishing table 11 through the drive of the drive shaft 13. For example, when the polishing table 11 rotates in the counterclockwise direction under the drive of the drive shaft 13, the polishing pad 12 also rotates in the clockwise direction.

[0024] In addition, a polishing head 14 is arranged in the space above the polishing table 11, and the polishing head 14 may at least include: a head body 141, a rotating driving member 142 connected to the head body 141, an assembly mold 143 arranged below the head body 141, and an adsorption pad 144 connected to the head body 141. The adsorption pad 144 is accommodated in a first accommodation cavity CS1 formed by the assembly mold 143. The silicon wafer S to be polished is also accommodated in the first accommodation cavity CS1.

[0025] The head body 141 can be driven by the rotary drive member 142 to rotate, so that the head body 141 and the silicon wafer S accommodated in the first accommodation cavity CS1 of the assembly mold 143 can also rotate with the rotation of the head body 141. For example, when the rotary drive member 142 rotates in the counterclockwise direction, the head body 141 and the silicon wafer S to be polished also rotate in the counterclockwise direction.

[0026] The adsorption pad 144 is used to adsorb the silicon wafer to the polishing head 14 to allow the silicon wafer to rotate with the polishing head 14. At the same time, the adsorption pad 144 can transfer the pressure from the head body 141 to the silicon wafer S, thereby achieving physical and chemical polishing of the silicon wafer surface.

[0027] The conventional adsorption pad 144 can be configured to adsorb the silicon wafer through water. Specifically, when the back side of the silicon wafer contacts the adsorption pad 144, a water film can be formed between the two. Due to the surface tension of water, a certain adsorption effect will be formed between the silicon wafer and the adsorption pad 144, so that the silicon wafer is attached to the adsorption pad 144. The magnitude of the adsorption effect can depend on the thickness of the water film, the contact area, and the hydrophilicity of the surfaces of the two.

[0028] The final polishing device 10 may also include a nozzle 15 disposed in the space above the polishing pad 12 and close to the center of the polishing pad 12. The nozzle 15 may be connected to a storage tank (not shown) for storing polishing liquid, and the dripping flow of the polishing liquid may be controlled by a valve.

[0029] When performing the polishing operation, the rotating polishing head 14 presses the silicon wafer onto the rotating polishing pad 12 at a certain working pressure, and the polishing liquid composed of submicron or nano abrasive particles and chemical solution drips onto the polishing pad 12 through the nozzle 15. Then, the polishing liquid can be evenly distributed on the polishing pad 12 under the transmission of the polishing pad 12 and the action of centrifugal force. During the distribution process, the polishing liquid can flow between the surface of the silicon wafer S and the polishing pad 12 to form a thin film of polishing liquid between the two. The chemical components in the polishing liquid can react chemically with the surface material of the silicon wafer, converting insoluble substances into soluble substances, or softening substances with high hardness. Then, these chemical reactants are removed from the surface of the silicon wafer through the micromechanical friction of the abrasive particles, dissolved into the flowing liquid and taken away, that is, the purpose of flattening is achieved in the alternating process of chemical film formation and mechanical film removal.

[0030] However, the inventors have found in experiments and actual production that the quality of silicon wafers processed using the final polishing device 10 can no longer meet the current increasing requirements. In addition, the final polishing device 10 may also cause damage to the silicon wafer and the device itself.

[0031] After research and repeated demonstration, the inventor believes that the above problem is caused by the unreasonable structure of the polishing head 14 of the final polishing device 10.

[0032] Specifically, first, before the final polishing, the silicon wafer has often gone through multiple manufacturing steps, and different areas of the same silicon wafer may present different surface roughness and thickness differences due to uneven distribution of processing forces. These initial morphological differences cause the silicon wafer to have irregular shapes such as local warping and bumps when placed on the adsorption pad 144. These initial morphological differences will affect the fit state of the silicon wafer when it contacts the adsorption pad 144. During the polishing process, when the polishing head 14 applies pressure, some areas of the silicon wafer will contact the polishing pad 12 earlier than other areas due to morphological differences, thereby being subjected to greater contact pressure. Other areas that are not fully fitted require a larger deformation of the adsorption pad 144 to contact the polishing pad 12, resulting in less pressure on these areas during the polishing process, thereby forming an initial condition of uneven pressure.

[0033] In addition, when the final polishing device 10 applies pressure to the silicon wafer through the polishing head 14, the silicon wafer is transferred through the adsorption pad 144. Due to the morphological differences in different areas of the silicon wafer, the adsorption pad 144 will deform unevenly when subjected to external force. This uneven deformation phenomenon causes the adsorption pad 144 to generate different supporting forces in different areas of the silicon wafer, thereby causing the stress state of each area of ​​the silicon wafer to further deteriorate during the polishing process. Ultimately, when the silicon wafer is polished, the contact pressure in different areas cannot be kept uniform, resulting in significant differences in the amount of material removed from the front of the silicon wafer, making it difficult to meet the flatness requirements after polishing.

[0034] Furthermore, since the adsorption effect of the adsorption pad 144 on the silicon wafer is easily affected by various factors such as the thickness of the water film, the contact area, the ambient temperature and humidity, the adsorption effect is unstable. In particular, when the polishing head rotates at a high speed, the water film may be deformed or broken due to the centrifugal force, resulting in a significant reduction in the adsorption effect. In particular, when the silicon wafer is deformed or the adsorption pad 144 is deformed, the water film may not be able to evenly cover the entire contact surface, thereby reducing the adsorption effect, making the adsorption effect insufficient to resist the external force on the silicon wafer. In this case, the silicon wafer may slide radially due to the centrifugal force, or even fall off the adsorption pad 144. The silicon wafer that has detached from the polishing head is likely to collide with other components of the final polishing equipment 10, causing damage to both, seriously affecting the stability and safety of the polishing operation.

[0035] In view of the above situation, the embodiments of the present disclosure are expected to provide a polishing method, a polishing head, a final polishing device and a silicon wafer. By using the polishing method, the silicon wafer can be deformed before polishing, and the silicon wafer can be polished while being kept in the deformation, thereby significantly improving the polishing accuracy and meeting the polishing requirements of silicon wafers of specific shapes.

[0036] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0037] See also Figure 2 Some embodiments of the present disclosure provide a polishing head 2. The polishing head 2 may include a suction unit 21 for holding a silicon wafer S. The suction unit 21 may be configured to be able to suction a first surface S1 of the silicon wafer S so that the silicon wafer S is elastically deformed from a first shape to a second shape, thereby allowing the shape of the silicon wafer S to be processed into a desired third shape by polishing a second surface S2 of the silicon wafer S opposite to the first surface S1 while the silicon wafer S is kept in the second shape.

[0038] like Figure 2 As shown, the polishing head 2 may include a body 22 and a holding portion 23 extending from one surface of the body 22. When the polishing head 2 is in use, the holding portion 23 is located on the lower surface of the body 22 and may be substantially annular to form a downwardly open chamber 24 with the body 22 so as to accommodate the silicon wafer S therein.

[0039] In various embodiments of the present disclosure, one of the first surface S1 and the second surface S2 of the silicon wafer refers to the front side of the silicon wafer, and the other refers to the back side of the silicon wafer. When the silicon wafer S is accommodated in the chamber 24, the first surface S1 faces the direction of the body 22, and the second surface S2 to be polished is exposed to the surrounding environment.

[0040] The adsorption unit 21 is disposed in the chamber 24 of the body 22 and is disposed on the surface of the body 22 facing the first surface S1 of the silicon wafer S. The adsorption unit 21 may adsorb the entire first surface S1 of the silicon wafer S by, for example, negative pressure, so that the silicon wafer S can be held by the polishing head 2. Further, the adsorption unit 21 may be configured to elastically deform the silicon wafer S at least partially by applying different adsorption effects to different regions of the first surface S1, thereby changing from a first shape to a second shape.

[0041] That is to say, when the silicon wafer S is held in place by the polishing head 2, the adsorption unit 21 has deformed the silicon wafer S from the original first shape to the second shape. The adsorption effect of the adsorption unit 21 on the silicon wafer S can be controlled to cause the silicon wafer S to only undergo elastic deformation, thereby avoiding the silicon wafer S from breaking due to excessive deformation. In some embodiments of the present disclosure, the adsorption unit 21 can be designed as a whole, but has the ability to apply different adsorption effects to different regions of the silicon wafer S. For example, by applying an adsorption effect to the central region of the first surface S1 of the silicon wafer S, while not applying an adsorption effect to other regions, the silicon wafer S can be locally elastically deformed. In this case, the central region of the silicon wafer S will deform toward the polishing head 2, so that it is stably held by the polishing head 2. In this way, for the silicon wafer S with a "bowl-shaped" protrusion on the second surface S2, the adsorption unit 21 can deform it into a flat shape, thereby providing an ideal shape for subsequent polishing. In an alternative embodiment, the polishing head 2 may include a plurality of independently working adsorption units 21. These adsorption units can respectively apply independent adsorption effects to different regions of the silicon wafer S. This will be specifically described in conjunction with the embodiments below.

[0042] The polishing head 2 can maintain the silicon wafer S in the second shape by the stable and continuous adsorption of the adsorption unit 21 on the silicon wafer S, and polish the silicon wafer S in the second shape until a silicon wafer S having a third shape is obtained, for example, a silicon wafer S having a flat surface and a uniform thickness is obtained. The polishing head 2 can allow a customized polishing scheme to be performed on the silicon wafer. This is further described below with reference to examples.

[0043] Example 1 In the final polishing process, the polishing liquid tends to accumulate at the edge of the silicon wafer under the action of centrifugal force, resulting in over-polishing of the edge of the silicon wafer. In other words, although the entire front surface of the silicon wafer is polished at the same time, the amount of removal at the edge of the silicon wafer is greater than that at the center. In this regard, the adsorption unit 21 of the polishing head 2 can be used to elastically deform the originally roughly flat silicon wafer S into Figure 2 The shape of the downward protrusion shown in FIG. In this way, the central area of ​​the silicon wafer S can be polished first. When the removal amount of the central area reaches the expected value, the silicon wafer S can be re-adsorbed by the adsorption unit 21 to restore it to Figure 3 The flat shape shown in the figure is obtained, and the silicon wafer S is subjected to subsequent polishing operations in this state until the end.

[0044] By dividing the polishing operation into two stages, the edge region of the silicon wafer S undergoes less polishing than the central region, thereby compensating for over-polishing of the edge region caused by the accumulation of polishing liquid at the edge region of the silicon wafer S. The silicon wafer polished in this way instead has a relatively flat surface and uniform thickness.

[0045] Example 2 In actual production, due to the influence of the previous process, the silicon wafer arriving at the final polishing station may not have a substantially flat shape. For example, the silicon wafer is thin in the center area and thick in the edge area before the final polishing. When this thickness difference cannot be eliminated by conventional polishing strategies, a customized polishing removal strategy can be implemented using the polishing head 2.

[0046] Specifically, the adsorption unit 21 of the polishing head 2 can be used to elastically deform the silicon wafer S into Figure 4 The upward protruding shape shown in FIG. 1 can be polished first on the edge area of ​​the silicon wafer S. When the removal amount of the edge area reaches the expected value, the silicon wafer S can be re-adsorbed by the adsorption unit 21 to restore it to Figure 3 The flat shape shown in the figure is obtained, and the silicon wafer S is subjected to subsequent polishing operations in this state until the end.

[0047] By dividing the polishing operation into two stages, the thicker areas of the silicon wafer S undergo more polishing than the thinner areas, thereby reducing the thickness difference of the silicon wafer before polishing, so that the polished silicon wafer has a flatter surface and uniform thickness.

[0048] Based on the above polishing head 2, see Figure 5 Some embodiments of the present disclosure also provide a polishing method, which includes steps S101 and S102.

[0049] In step S101, the first surface S1 of the silicon wafer S is adsorbed by the adsorption unit 21 of the polishing head 2, so that the silicon wafer S is elastically deformed from the first shape to the second shape; In step S102 , while the silicon wafer S is kept in the second shape, a second surface S2 of the silicon wafer S opposite to the first surface S1 is polished to process the shape of the silicon wafer S into a desired third shape.

[0050] By using the polishing head 2 and the polishing method provided by the embodiment of the present disclosure, the silicon wafer can be subjected to partial or overall elastic deformation by adsorption before polishing. By polishing the silicon wafer while maintaining such elastic deformation, only the target area on the silicon wafer can be polished, or the polishing removal amount of the target area can be made greater than the polishing removal amount of other areas, that is, the polishing removal amount of different areas on the same surface of the same silicon wafer can be different. Thus, the uneven polishing caused by other process factors can be compensated in a targeted manner, so that the polished silicon wafer has a desired morphology.

[0051] In order to achieve precise elastic deformation of the silicon wafer before polishing, in some embodiments of the present disclosure, see Figures 2 to 4The polishing head 2 may include a plurality of adsorption units 21. The plurality of adsorption units 21 may respectively adsorb different regions on the first surface S1 of the silicon wafer S, so that at least a portion of the regions adsorbed by the adsorption units 21 of the silicon wafer undergoes elastic deformation, thereby causing the held silicon wafer S to be elastically deformed from a first shape to a second shape.

[0052] Correspondingly, in the polishing method provided in the embodiment of the present disclosure, the adsorption unit 21 of the polishing head 2 adsorbs the first surface S1 of the silicon wafer S so that the silicon wafer S is elastically deformed from the first shape to the second shape, including: The multiple adsorption units 21 of the polishing head 2 respectively adsorb different areas on the first surface S1 of the silicon wafer S, so that at least a part of the areas of the silicon wafer adsorbed by the multiple adsorption units 21 undergoes elastic deformation, thereby elastically deforming the held silicon wafer S from the first shape to the second shape.

[0053] like Figures 2 to 4 As shown in , a plurality of adsorption units 21 may be disposed in a chamber 24 of a body 22 and disposed on a surface of the body 22 facing a first surface S1 of the silicon wafer S. The plurality of adsorption units 21 are arranged spaced apart from each other and are capable of applying independent and controllable adsorption to different regions of the first surface S1 of the silicon wafer S. The size and distribution of the adsorption may be dynamically adjusted according to the initial shape of the silicon wafer and the polishing target, thereby achieving targeted shape adjustment.

[0054] These distributed adsorption units 21 can accurately control the elastic deformation state of the silicon wafer S, so that the silicon wafer S can better match the polishing requirements, and can also adapt to different initial shapes and target shapes of the silicon wafer, especially some complex shapes, to create favorable conditions for subsequent polishing operations. In addition, when multiple adsorption units 21 act synchronously, the shape adjustment of the silicon wafer can be completed quickly.

[0055] In some embodiments of the present disclosure, at least a portion of the multiple adsorption units 21 are configured to be able to move in a direction perpendicular to the first surface S1 of the held silicon wafer S while respectively adsorbing different areas on the first surface S1 of the silicon wafer S, so that at least a portion of the areas of the silicon wafer adsorbed by the at least a portion of the adsorption units undergoes elastic deformation, thereby causing the held silicon wafer S to elastically deform from a first shape to a second shape.

[0056] Correspondingly, in the polishing method provided in the embodiment of the present disclosure, the first surface S1 of the silicon wafer S is adsorbed by the adsorption unit 21 of the polishing head 2 so that the silicon wafer S is elastically deformed from the first shape to the second shape, including: The multiple adsorption units 21 of the polishing head 2 respectively adsorb different areas on the first surface S1 of the silicon wafer S; At least a portion of the multiple adsorption units 21 is moved in a direction perpendicular to the first surface S1 of the held silicon wafer S, so that at least a portion of the area of ​​the silicon wafer S adsorbed by at least a portion of the adsorption units 21 undergoes elastic deformation, thereby elastically deforming the held silicon wafer from a first shape to a second shape.

[0057] exist Figures 2 to 4 In the illustrated embodiment, the adsorption unit 21 may be formed in a rod shape and may be capable of telescopic movement. One end of the adsorption unit 21 may be vertically fixed to the body 22, and the other end may vertically adsorb the first surface S1 of the silicon wafer S. For example, a negative pressure pipeline may be provided in the adsorption unit 21 to adsorb the first surface S1 of the silicon wafer S by negative pressure.

[0058] Since the adsorption unit 21 has a retractable characteristic, the end portion thereof for adsorbing the silicon wafer S can move along the extension direction of the adsorption unit 21. When the adsorption unit 21 performs a retractable movement while adsorbing the silicon wafer S, the movement of the end portion of the adsorption unit 21 may affect the adsorbed area of ​​the silicon wafer S, thereby causing local elastic deformation of the silicon wafer.

[0059] As mentioned above, the plurality of adsorption units 21 are designed to be able to exert independent and controllable adsorption forces on different regions of the silicon wafer S. In this embodiment, the extension and contraction degrees of different adsorption units 21 can be individually adjusted according to the requirements of the polishing strategy, so that different regions of the silicon wafer S produce different degrees of elastic deformation, wherein the silicon wafer region adsorbed by the adsorption unit 21 with a larger extension and contraction degree will have a larger degree of elastic deformation, while the silicon wafer region adsorbed by the adsorption unit 21 with a smaller extension and contraction degree will have a smaller degree of elastic deformation, or may not even deform.

[0060] Through the synergistic effect of multiple adsorption units 21, the silicon wafer S can be elastically deformed from its initial shape to a target shape that meets the requirements of a specific polishing strategy. At the same time, the adsorption unit 21 can stably keep the silicon wafer S in this shape to support subsequent polishing operations. This design significantly improves the adaptability of the polishing head 2, enabling it to cope with the processing requirements of silicon wafers with different initial shapes and target shapes. In particular, for silicon wafers with complex shapes, a solution is provided that can achieve precise shape adjustment and optimize the polishing effect.

[0061] In some embodiments of the present disclosure, the plurality of adsorption units 21 are disposed at different positions in the radial direction of the adsorbed silicon wafer S.

[0062] See also Figure 6 ,exist Figure 6In the embodiment shown in FIG. 1 , the adsorption unit 21 is roughly in the form of an arc segment. Six groups of adsorption units 21 can be arranged circumferentially spaced apart from each other around the center of the body, wherein each group includes a plurality of adsorption units 21 spaced apart in the radial direction of the body. It should be noted that this arrangement of the adsorption units 21 is only exemplary and not restrictive. In other embodiments not shown, the adsorption units 21 may also be arranged in other ways, which will not be described one by one.

[0063] Due to the circular geometric characteristics of the silicon wafer S, that is, the circular first surface S1 and the second surface S2, the silicon wafer is usually processed in a rotating state during the grinding, etching, polishing and other processes. Due to the unevenness of the processing conditions during the rotation process, the silicon wafer is prone to thickness deviation in the radial direction. Therefore, in the shape adjustment and polishing process, the thickness and morphological characteristics in the radial direction, that is, the direction from the center of the silicon wafer to the edge, have an important influence. To this end, multiple adsorption units 21 can be distributed according to the radial thickness change of the silicon wafer S to achieve precise shape adjustment of the silicon wafer in its radial direction, compensate for thickness differences and optimize the polishing process, so that the polished silicon wafer has a flatter surface and uniform thickness.

[0064] In further embodiments, see Figure 7 The plurality of adsorption units 21 may be arranged in a plurality of annular shapes concentrically with the adsorbed silicon wafer S. Such an annular distribution design can maximize the coverage of the adsorption units on different radial regions of the silicon wafer, so that the polishing head 2 can more evenly control the deformation of the silicon wafer.

[0065] More specifically, the multiple adsorption units 21 arranged concentrically in an annular shape are highly matched to the circular geometric characteristics of the silicon wafer S. This arrangement optimizes the mechanical distribution of adsorption force and shape adjustment, enabling the adsorption unit 21 to more efficiently adjust the shape of the silicon wafer, especially in the radial direction. In addition, the adsorption units distributed in an annular shape can work together to apply precise adsorption force to different radial regions, meet the diverse needs of silicon wafer shape adjustment, and provide reliable technical support for the high-precision polishing process.

[0066] Furthermore, if Figure 7 As shown, each ring shape can be divided into multiple arc segments. For example, each ring is composed of 12 arc-shaped adsorption units 21. This division method refines each ring into multiple independent adsorption unit areas, thereby enhancing the fine control capability of adjusting the shape of the silicon wafer.

[0067] Specifically, the more arc segments the adsorption unit 21 is divided into, the more accurate the adjustment of the shape of the silicon wafer is. By increasing the number of adsorption units, independent and accurate adsorption forces can be applied to different radial and angular regions of the silicon wafer, so that its deformation is more in line with the requirements of the polishing strategy. This design not only optimizes the overall shape adjustment effect of the silicon wafer, but also improves the adaptability to silicon wafers with complex shapes.

[0068] According to the above content, the adsorption unit 21 optimizes the polishing process in terms of mechanics by providing a shape adjustment function. The inventor believes through research and experiments that on this basis, chemical improvement measures can be further combined by introducing chemical liquids such as , deionized water ( )、 , The spraying action of the surfactant and the mechanical shape adjustment function work together. Chemical liquid can be used to increase material removal rate, improve edge flatness and optimize overall surface quality. The synergistic effect of mechanics and chemistry can provide higher accuracy and efficiency in the polishing process of silicon wafers, and realize regional precise adjustment and optimization.

[0069] Specifically, in some embodiments of the present disclosure, see Figure 8 The polishing head 2 may further include a first nozzle 25 for spraying a fluid toward the held silicon wafer S.

[0070] The first nozzle 25 may be disposed outside the polishing head 2, or may be disposed in the holding portion 23 of the polishing head 2. Figure 8 The first nozzle 25 may be disposed on the lower surface of the holding portion 23 and located radially outside the silicon wafer S held by the polishing head 2 .

[0071] The first nozzle 25 may be configured to spray the chemical solution toward the silicon wafer S, for example , , , and surfactants. These chemical solutions can be used to adjust the material removal rate and, in conjunction with the elastic deformation of the silicon wafer, can optimize the surface flatness for specific areas. Since different chemical solutions can play different roles, the specific selection of chemical solutions should be determined according to the process requirements. For example, etc. can accelerate the removal of silicon wafer surface materials; surfactants and The use of can refine the processing of edges and local areas to avoid over-throwing or concave.

[0072] In some embodiments of the present disclosure, a second nozzle 26 may be provided for spraying chemical liquid onto the silicon wafer after the silicon wafer is polished, so as to further improve the surface state of the silicon wafer and increase the particle level.

[0073] Specifically, see Fig. 9 , a second nozzle 26 may be provided on the surface of the holding portion 23 of the polishing head 2 facing the held silicon wafer. After the polishing operation is completed, the position of the silicon wafer S in the chamber 24 may be lifted by the suction unit 21 so that the second nozzle 26 is exposed below the silicon wafer. Then, the second nozzle 26 may be used to spray the following on the silicon wafer in sequence: , , , , surfactants. This chemical liquid treatment method can further clean the surface of the silicon wafer, remove residual microparticles or pollutants, optimize the flatness and cleanliness of the silicon wafer, and provide high-quality silicon wafer surface conditions for subsequent processes.

[0074] In some embodiments of the present disclosure, the following silicon wafers can be obtained by using the above-mentioned grinding method provided by the embodiments of the present disclosure: the total thickness variation (TTV) of the silicon wafer is less than 500 nanometers, and the local front surface least squares range (SFQR) is less than 50 nanometers. The changes in the TTV value and SFQR value of the silicon wafer before polishing and after polishing using the above-mentioned polishing method provided by the embodiments of the present disclosure are shown in Table 1. Table 1

[0075] See also Fig.10 The embodiment of the present disclosure further provides a final polishing device 3, which includes the polishing head 2 described above.

[0076] It should be noted that the technical solutions described in the embodiments of the present disclosure can be combined arbitrarily without conflict.

[0077] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A polishing method, characterized in that: The polishing method comprises: Adsorbing a first surface of the silicon wafer by an adsorption unit of the polishing head so that the silicon wafer is elastically deformed from a first shape to a second shape; While the silicon wafer is maintained in the second shape, a second surface of the silicon wafer opposite to the first surface is polished to process the shape of the silicon wafer into a desired third shape.

2. The polishing method according to claim 1, characterized in that: The step of adsorbing the first surface of the silicon wafer by the adsorption unit of the polishing head so that the silicon wafer is elastically deformed from the first shape to the second shape comprises: The multiple adsorption units of the polishing head respectively adsorb different areas on the first surface of the silicon wafer, so that at least a part of the areas of the silicon wafer adsorbed by the multiple adsorption units undergoes elastic deformation, thereby causing the retained silicon wafer to elastically deform from a first shape to a second shape.

3. The polishing method according to claim 2, characterized in that: The step of adsorbing the first surface of the silicon wafer by the adsorption unit of the polishing head so that the silicon wafer is elastically deformed from the first shape to the second shape comprises: Adsorbing different areas on the first surface of the silicon wafer respectively by using a plurality of adsorption units of the polishing head; At least a part of the multiple adsorption units is moved in a direction perpendicular to the first surface of the held silicon wafer, so that at least a part of the area of ​​the silicon wafer adsorbed by the at least a part of the adsorption units undergoes elastic deformation, thereby elastically deforming the held silicon wafer from a first shape to a second shape.

4. The polishing method according to claim 2 or 3, characterized in that: The plurality of adsorption units are disposed at different positions in a radial direction of the adsorbed silicon wafer.

5. The polishing method according to claim 4, characterized in that: The plurality of adsorption units are provided in a plurality of annular shapes arranged concentrically with the adsorbed silicon wafer.

6. A polishing head, characterized in that: The polishing head includes an adsorption unit for holding a silicon wafer, and the adsorption unit is configured to be able to adsorb a first surface of the silicon wafer so that the silicon wafer is elastically deformed from a first shape to a second shape, thereby allowing the shape of the silicon wafer to be processed into a desired third shape by polishing a second surface of the silicon wafer opposite to the first surface while the silicon wafer is maintained in the second shape.

7. The polishing head according to claim 6, characterized in that: The polishing head includes a plurality of adsorption units, wherein the plurality of adsorption units respectively adsorb different areas on the first surface of the silicon wafer, so that at least a portion of the areas of the silicon wafer adsorbed by the plurality of adsorption units undergoes elastic deformation, thereby causing the held silicon wafer to elastically deform from a first shape to a second shape.

8. The polishing head according to claim 7, characterized in that: At least a part of the multiple adsorption units are configured to move in a direction perpendicular to the first surface of the silicon wafer being held while respectively adsorbing different areas on the first surface of the silicon wafer, so that at least a part of the areas of the silicon wafer adsorbed by at least a part of the adsorption units undergoes elastic deformation, thereby elastically deforming the held silicon wafer from a first shape to a second shape.

9. The polishing head according to claim 7 or 8, characterized in that: The plurality of adsorption units are disposed at different positions in a radial direction of the adsorbed silicon wafer.

10. The polishing head according to claim 9, characterized in that: The plurality of adsorption units are provided in a plurality of annular shapes arranged concentrically with the adsorbed silicon wafer.

11. The polishing head according to any one of claims 6 to 8, characterized in that The polishing head further includes a nozzle for spraying a fluid toward the held silicon wafer.

12. A final polishing device, characterized in that: The final polishing apparatus comprises a polishing head according to any one of claims 6 to 11.

13. A silicon wafer, characterized in that: The silicon wafer is obtained by the polishing method according to any one of claims 1 to 5, wherein a TTV of the silicon wafer is less than 500 nanometers, and a SFQR of the silicon wafer is less than 50 nanometers.

Images