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

Abstract

Embodiments of the present disclosure provide a polishing method, a polishing head, a final polishing apparatus, and a silicon wafer. The polishing method comprises: adsorbing a first surface of a silicon wafer by means of adsorption units of a polishing head, so that the silicon wafer is elastically deformed from a first shape to a second shape; and polishing a second surface of the silicon wafer opposite to the first surface while maintaining the silicon wafer in the second shape, so as to process the shape of the silicon wafer into a desired third shape.

Description

Polishing methods, polishing heads, final polishing equipment, and silicon wafers

[0001] Cross-reference of related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 202411929322.4, filed in China on December 25, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of silicon wafer processing technology, and more particularly to polishing methods, polishing heads, final polishing equipment, and silicon wafers. Background Technology

[0004] With the rapid development of semiconductor technology, the surface flatness requirements for silicon wafers, as the basic material for chip manufacturing, are becoming increasingly stringent. The flatness of the silicon wafer surface directly affects chip performance and production yield; therefore, improving flatness has become a crucial step in the silicon wafer manufacturing process. To achieve the required high flatness standards, polishing processes are widely used, and quality control of the polishing process has become a key step in silicon wafer manufacturing.

[0005] In the polishing process of related technologies, there are usually two-sided polishing processes, which polish both sides of the silicon wafer, and a final polishing process that is performed only on the front side of the silicon wafer. In the final polishing process, the silicon wafer is held by a polishing head and pressed onto a polishing pad arranged below the polishing head by the rotation of the polishing head, thereby polishing the front side of the silicon wafer.

[0006] However, when using the final polishing equipment of the relevant technology, there is a problem that the uneven distribution of silicon removal amount is caused by the uneven distribution of the force exerted by the polishing head on the silicon wafer. In addition, there is a risk that the silicon wafer may separate from the polishing head during the processing due to the unstable holding force of the polishing head on the silicon wafer. Summary of the Invention

[0007] In view of this, embodiments of the present disclosure aim to provide a polishing method, a polishing head, a final polishing apparatus, and a silicon wafer. By using this polishing method, the silicon wafer can be deformed before polishing and polished while maintaining the silicon wafer in that deformed state, thereby significantly improving polishing accuracy and meeting the polishing requirements of silicon wafers with specific shapes.

[0008] The technical solution of this disclosure embodiment is implemented as follows:

[0009] In a first aspect, embodiments of this disclosure provide a polishing method, the polishing method comprising:

[0010] The first surface of the silicon wafer is adsorbed by the adsorption unit of the polishing head, so that the silicon wafer is elastically deformed from a first shape to a second shape;

[0011] While maintaining the silicon wafer in the second shape, the second surface of the silicon wafer, which is opposite to the first surface, is polished to process the silicon wafer into a desired third shape.

[0012] In some optional examples, the adsorption unit of the polishing head adsorbs the first surface of the silicon wafer to elastically deform the silicon wafer from a first shape to a second shape, including:

[0013] The multiple adsorption units of the polishing head adsorb different regions on the first surface of the silicon wafer, so that at least a portion of the regions of the silicon wafer adsorbed by the multiple adsorption units undergo elastic deformation, thereby causing the held silicon wafer to elastically deform from a first shape to a second shape.

[0014] In some optional examples, the adsorption unit of the polishing head adsorbs the first surface of the silicon wafer to elastically deform the silicon wafer from a first shape to a second shape, including:

[0015] The polishing head uses multiple adsorption units to adsorb different areas on the first surface of the silicon wafer.

[0016] At least a portion of the adsorption units are moved along a direction perpendicular to the first surface of the held silicon wafer, so that at least a portion of the region of the silicon wafer adsorbed by the at least a portion of the adsorption units undergoes elastic deformation, thereby causing the held silicon wafer to elastically deform from a first shape to a second shape.

[0017] In some alternative examples, the plurality of adsorption units are disposed at different positions in the radial direction of the adsorbed silicon wafer.

[0018] In some alternative examples, the plurality of adsorption units are arranged in a plurality of annular shapes concentrically with the adsorbed silicon wafer.

[0019] In some optional examples, polishing a second surface of the silicon wafer opposite to the first surface while maintaining the silicon wafer in the second shape to process the silicon wafer into a desired third shape includes:

[0020] Fluid is sprayed onto the silicon wafer while polishing the second surface of the silicon wafer that is opposite to the first surface.

[0021] Secondly, embodiments of this disclosure provide a polishing head including an adsorption unit for holding a silicon wafer. The adsorption unit is configured to adsorb a first surface of the silicon wafer 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 opposite to the first surface while holding the silicon wafer in the second shape.

[0022] In some optional examples, the polishing head includes a plurality of adsorption units, wherein the plurality of adsorption units adsorb different regions on the first surface of the silicon wafer, such that at least a portion of the regions 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.

[0023] In some alternative examples, at least a portion of the plurality of adsorption units are configured to move in a direction perpendicular to the first surface of the held silicon wafer while adsorbing different regions on the first surface of the silicon wafer, so that at least a portion of the regions of the silicon wafer adsorbed by the at least a portion of the adsorption units undergo elastic deformation, thereby causing the held silicon wafer to elastically deform from a first shape to a second shape.

[0024] In some alternative examples, the plurality of adsorption units are disposed at different positions in the radial direction of the adsorbed silicon wafer.

[0025] In some alternative examples, the plurality of adsorption units are arranged in a plurality of annular shapes concentrically with the adsorbed silicon wafer.

[0026] In some optional examples, the polishing head also includes a nozzle for jetting fluid onto the held silicon wafer.

[0027] Thirdly, embodiments of this disclosure provide a final polishing apparatus, the final polishing apparatus including a polishing head according to the second aspect.

[0028] Fourthly, embodiments of this disclosure provide a silicon wafer obtained by the polishing method according to the first aspect, wherein the total thickness variation (TTV) of the silicon wafer is less than 500 nanometers, and the site front quotient range (SFQR) of the silicon wafer is less than 50 nanometers.

[0029] Some embodiments of this disclosure provide a polishing method, a polishing head, a final polishing apparatus, and a silicon wafer. Using the polishing head and polishing method provided in these embodiments, the silicon wafer can be locally or entirely elastically deformed 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 amount of material removed by polishing the target area can be greater than the amount removed by polishing other areas. In other words, the amount of material removed by polishing can be different in different areas of the same surface of the same silicon wafer. Therefore, uneven polishing caused by other process factors can be specifically compensated for, thereby obtaining a desired morphology on the polished silicon wafer. Attached Figure Description

[0030] Figure 1 is a schematic diagram of a conventional final polishing equipment;

[0031] Figure 2 is a schematic diagram of the polishing head provided in an embodiment of this disclosure;

[0032] Figure 3 is another schematic diagram of the polishing head shown in Figure 2;

[0033] Figure 4 is another schematic diagram of the polishing head shown in Figure 2;

[0034] Figure 5 is a flowchart of the polishing method provided in an embodiment of this disclosure;

[0035] Figure 6 is a partial bottom view of the polishing head provided in an embodiment of this disclosure;

[0036] Figure 7 is a partial bottom view of a polishing head provided in another embodiment of this disclosure;

[0037] Figure 8 is a schematic diagram of a polishing head provided in another embodiment of this disclosure;

[0038] Figure 9 is a schematic diagram of a polishing head provided in another embodiment of this disclosure;

[0039] Figure 10 is a schematic diagram of the final polishing apparatus provided in an embodiment of this disclosure. Detailed Implementation

[0040] The technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings.

[0041] Figure 1 shows a conventional final polishing apparatus 10. This final polishing apparatus 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 together with the polishing table 11 via the drive shaft 13. For example, when the polishing table 11 rotates counterclockwise under the drive of the drive shaft 13, the polishing pad 12 also rotates clockwise.

[0042] Furthermore, a polishing head 14 is disposed above the polishing table 11. The polishing head 14 may include at least: a head body 141, a rotary drive 142 connected to the head body 141, an assembly mold 143 disposed below the head body 141, and an adsorption pad 144 connected to the head body 141. The adsorption pad 144 is housed within a first receiving cavity CS1 formed by the assembly mold 143. The silicon wafer S to be polished is also housed within the first receiving cavity CS1.

[0043] The head body 141 can be driven by the rotary drive 142 to rotate, so that the head body 141 and the silicon wafer S housed in the first receiving cavity CS1 of the assembly mold 143 can also rotate with the rotation of the head body 141. For example, when the rotary drive 142 rotates counterclockwise, the head body 141 and the silicon wafer S to be polished also rotate counterclockwise.

[0044] The adsorption pad 144 is used to adsorb the silicon wafer onto the polishing head 14 so that the silicon wafer can rotate together with the polishing head 14. At the same time, the adsorption pad 144 can transmit the pressure from the head body 141 to the silicon wafer S, thereby achieving physical and chemical polishing of the silicon wafer surface.

[0045] A conventional adsorption pad 144 can be configured to adsorb silicon wafers via water. Specifically, when the back of the silicon wafer comes into contact with the adsorption pad 144, a water film can be formed between them. Due to the surface tension of water, a certain degree of adsorption occurs between the silicon wafer and the adsorption pad 144, causing the silicon wafer to adhere 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 both surfaces.

[0046] 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 rate of the polishing liquid may be controlled by a valve.

[0047] During the polishing operation, the rotating polishing head 14 presses the silicon wafer onto the rotating polishing pad 12 under a certain working pressure. A polishing slurry, composed of submicron or nano-abrasive particles and a chemical solution, drips onto the polishing pad 12 through nozzle 15. The polishing slurry is then uniformly distributed on the polishing pad 12 under the influence of transport and centrifugal force. During distribution, the polishing slurry flows between the surface of the silicon wafer S and the polishing pad 12, forming a thin film of polishing slurry between them. The chemical components in the polishing slurry can react with the surface material of the silicon wafer, converting insoluble substances into soluble substances or softening hard substances. These chemical reactants are then removed from the silicon wafer surface by the micromechanical friction of the abrasive particles, dissolved in the flowing slurry and carried away. This alternating process of chemical film formation and mechanical film removal achieves planarization.

[0048] However, the inventors discovered during experiments and actual production that the quality of silicon wafers processed using the aforementioned final polishing equipment 10 could no longer meet the ever-increasing requirements. Furthermore, the aforementioned final polishing equipment 10 could also cause damage to the silicon wafers and the wafers themselves.

[0049] After research and repeated demonstrations, the inventors believe that the above problems are caused by the unreasonable structure of the polishing head 14 of the final polishing device 10.

[0050] Specifically, firstly, before final polishing, silicon wafers often undergo multiple manufacturing steps, and different areas of the same wafer may exhibit varying surface roughness and thickness due to uneven distribution of processing forces. These initial morphological differences result in irregular shapes such as localized warping and unevenness when the silicon wafer is placed on the adsorption pad 144. These initial morphological differences affect the adhesion between the silicon wafer and the adsorption pad 144. During polishing, when the polishing head 14 applies pressure, some areas of the silicon wafer, due to morphological differences, will contact the polishing pad 12 earlier than other areas, thus experiencing greater contact pressure. Other areas that are not fully adhered require greater deformation of the adsorption pad 144 to contact the polishing pad 12, resulting in lower pressure on these areas during polishing, thus creating uneven initial pressure conditions.

[0051] Furthermore, when the final polishing equipment 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 undergoes uneven deformation under external force. This uneven deformation causes the adsorption pad 144 to generate different supporting forces in different areas of the silicon wafer, further deteriorating the stress state of each area of ​​the silicon wafer during polishing. Ultimately, during polishing, the contact pressure in different areas of the silicon wafer cannot be kept uniform, resulting in significant differences in the amount of material removed from the front side of the silicon wafer, making it difficult to achieve the required flatness after polishing.

[0052] Furthermore, the adsorption of silicon wafers by the adsorption pad 144 is easily affected by various factors such as water film thickness, contact area, ambient temperature, and humidity, resulting in instability in the adsorption process. In particular, when the polishing head rotates at high speed, the water film may deform or break due to centrifugal force, significantly reducing the adsorption effect. Especially when the silicon wafer deforms or the adsorption pad 144 deforms, the water film may not uniformly cover the entire contact surface, thus reducing the adsorption effect and making it insufficient to resist external forces on the silicon wafer. In this case, the silicon wafer may slide radially due to centrifugal force, or even detach from the adsorption pad 144. A silicon wafer detached from the polishing head is likely to collide with other components of the final polishing equipment 10, causing damage to both and severely affecting the stability and safety of the polishing operation.

[0053] In view of the above, embodiments of this disclosure aim to provide a polishing method, a polishing head, a final polishing apparatus, and a silicon wafer. By using this polishing method, the silicon wafer can be deformed before polishing and polished while maintaining the silicon wafer in that deformed state, thereby significantly improving polishing accuracy and meeting the polishing requirements of silicon wafers with specific shapes.

[0054] The embodiments of this disclosure are described in detail below with reference to the accompanying drawings.

[0055] Referring to Figure 2, some embodiments of this disclosure provide a polishing head 2. The polishing head 2 may include an adsorption unit 21 for holding a silicon wafer S. The adsorption unit 21 may be configured to adsorb a first surface S1 of the silicon wafer S, causing the silicon wafer S to elastically deform 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 holding the silicon wafer S in the second shape.

[0056] As shown in Figure 2, the polishing head 2 may include a body 22 and a retaining portion 23 extending from one surface of the body 22. When the polishing head 2 is in use, the retaining portion 23 is located on the lower surface of the body 22 and may be generally annular to form a downwardly open chamber 24 with the body 22 to accommodate the silicon wafer S therein.

[0057] In various embodiments of this 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 housed in the chamber 24, the first surface S1 faces the body 22, while the second surface S2 to be polished is exposed to the surrounding environment.

[0058] The adsorption unit 21 is disposed within the chamber 24 of the body 22 and on the surface of the body 22 facing the first surface S1 of the silicon wafer S. The adsorption unit 21 can adsorb the entire first surface S1 of the silicon wafer S by means of, for example, negative pressure, so that the silicon wafer S can be held by the polishing head 2. Furthermore, the adsorption unit 21 can be configured to apply different adsorption effects to different areas of the first surface S1, so that the silicon wafer S undergoes at least partial elastic deformation, thereby changing from a first shape to a second shape.

[0059] In other words, while the silicon wafer S is held in place by the polishing head 2, the adsorption unit 21 has already deformed the silicon wafer S from its original first shape to a second shape. The adsorption effect of the adsorption unit 21 on the silicon wafer S can be controlled so that the silicon wafer S only undergoes elastic deformation, thereby avoiding breakage due to excessive deformation. In some embodiments of this disclosure, the adsorption unit 21 can be designed as a single unit, but with the ability to apply different adsorption effects to different areas of the silicon wafer S. For example, by applying adsorption to the central area of ​​the first surface S1 of the silicon wafer S, while not applying adsorption to other areas, the silicon wafer S can undergo local elastic deformation. In this case, the central area of ​​the silicon wafer S will deform towards the polishing head 2, thereby being 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 alternative embodiments, the polishing head 2 may include multiple independently operating adsorption units 21. These adsorption units can apply independent adsorption effects to different areas of the silicon wafer S. This will be specifically described below in conjunction with embodiments.

[0060] The polishing head 2 can hold the silicon wafer S in a second shape through the stable and continuous adsorption of the adsorption unit 21, and polish the silicon wafer S in the second shape until a silicon wafer S with a third shape is obtained, such as a silicon wafer S with a flat surface and uniform thickness. The polishing head 2 can allow customized polishing schemes to be performed on the silicon wafer. This will be further explained below with reference to examples.

[0061] Example 1

[0062] In the final polishing process, the polishing slurry tends to accumulate at the edges of the silicon wafer under centrifugal force, resulting in over-polishing of these edges. In other words, even though the entire front side of the silicon wafer is polished simultaneously, the amount of material removed from the edges is greater than that removed from the center. To address this, the adsorption unit 21 of the polishing head 2 can be used to elastically deform the originally roughly flat silicon wafer S into a downwardly protruding shape as shown in Figure 2. This allows for initial polishing of the center area of ​​the silicon wafer S. Once the desired amount of material removed from the center area has been removed, the adsorption unit 21 can be used to re-adsorb the silicon wafer S, restoring it to the flat shape shown in Figure 3. The silicon wafer S can then be subjected to subsequent polishing operations in this state until the process is complete.

[0063] By dividing the polishing operation into two stages, the edge region of silicon wafer S undergoes less polishing than the center region, thus compensating for over-polishing of the edge region caused by polishing slurry accumulation. The silicon wafer polished in this way actually has a flatter surface and more uniform thickness.

[0064] Example 2

[0065] In actual production, due to the influence of preceding processes, the silicon wafers arriving at the final polishing station may not have a generally flat shape. For example, the silicon wafer may be thinner in the central area and thicker at the edges before final polishing. When this thickness difference cannot be eliminated by conventional polishing strategies, a customized polishing removal strategy can be implemented using polishing head 2.

[0066] Specifically, the adsorption unit 21 of the polishing head 2 can be used to elastically deform the silicon wafer S into an upwardly protruding shape as shown in Figure 4. This allows the edge area of ​​the silicon wafer S to be polished first. Once the expected amount of material removed from the edge area has been removed, the adsorption unit 21 can be used to re-adsorb the silicon wafer S, restoring it to the flat shape shown in Figure 3. The silicon wafer S is then subjected to subsequent polishing operations in this state until the process is complete.

[0067] By dividing the polishing operation into two stages, the thicker areas of silicon wafer S undergo more polishing than the thinner areas, thereby reducing the thickness difference of the silicon wafer before polishing, resulting in a flatter surface and more uniform thickness after polishing.

[0068] Based on the polishing head 2 described above, and referring to Figure 5, some embodiments of this disclosure also provide a polishing method, which includes steps S101 and S102.

[0069] 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.

[0070] In step S102, while keeping the silicon wafer S in its second shape, the second surface S2 of the silicon wafer S, which is opposite to the first surface S1, is polished to process the shape of the silicon wafer S into the desired third shape.

[0071] Using the polishing head 2 and polishing method provided in this embodiment, the silicon wafer can be locally or entirely elastically deformed 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 amount of material removed by polishing the target area can be greater than the amount removed by polishing other areas. In other words, the amount of material removed by polishing can be different in different areas of the same surface of the same silicon wafer. Therefore, uneven polishing caused by other process factors can be specifically compensated for, thereby obtaining a desired morphology on the polished silicon wafer.

[0072] To achieve precise elastic deformation of the silicon wafer before polishing, in some embodiments of this disclosure, referring to Figures 2 to 4, the polishing head 2 may include a plurality of adsorption units 21. The plurality of adsorption units 21 may adsorb different regions on the first surface S1 of the silicon wafer S respectively, so that at least a portion of the regions of the silicon wafer adsorbed by these adsorption units 21 undergoes elastic deformation, thereby causing the held silicon wafer S to elastically deform from a first shape to a second shape.

[0073] Correspondingly, in the polishing method provided in this embodiment, the step of adsorbing the first surface S1 of the silicon wafer S through the adsorption unit 21 of the polishing head 2 to elastically deform the silicon wafer S from a first shape to a second shape includes:

[0074] The multiple adsorption units 21 of the polishing head 2 adsorb 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 multiple adsorption units 21 undergo elastic deformation, thereby causing the held silicon wafer S to elastically deform from a first shape to a second shape.

[0075] As shown in Figures 2 to 4, multiple adsorption units 21 can be disposed within the chamber 24 of the body 22 and on the surface of the body 22 facing the first surface S1 of the silicon wafer S. The multiple adsorption units 21 are arranged spaced apart from each other and can apply independent and controllable adsorption to different areas of the first surface S1 of the silicon wafer S. The magnitude and distribution of the adsorption can be dynamically adjusted according to the initial shape of the silicon wafer and the polishing target, thereby achieving targeted shape adjustment.

[0076] These distributed adsorption units 21 can precisely control the elastic deformation state of the silicon wafer S, enabling the silicon wafer S to better match polishing requirements. They can also adapt to different initial and target shapes of the silicon wafer, especially complex shapes, creating favorable conditions for subsequent polishing operations. Furthermore, with multiple adsorption units 21 operating synchronously, the shape adjustment of the silicon wafer can be completed quickly.

[0077] In some embodiments of this disclosure, at least a portion of the adsorption units 21 are configured to move in a direction perpendicular to the first surface S1 of the held silicon wafer S while adsorbing different regions on the first surface S1 of the silicon wafer S respectively, so that at least a portion of the regions of the silicon wafer adsorbed by the at least a portion of the adsorption units undergo elastic deformation, thereby causing the held silicon wafer S to elastically deform from a first shape to a second shape.

[0078] Correspondingly, in the polishing method provided in this embodiment, 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 elastically deforms from a first shape to a second shape, including:

[0079] The polishing head 2 uses multiple adsorption units 21 to adsorb different areas on the first surface S1 of the silicon wafer S.

[0080] At least a portion of the adsorption units 21 are moved along a direction perpendicular to the first surface S1 of the held silicon wafer S, so that at least a portion of the region of the silicon wafer S adsorbed by at least a portion of the adsorption units 21 undergoes elastic deformation, thereby causing the held silicon wafer to elastically deform from a first shape to a second shape.

[0081] In the embodiments shown in Figures 2 to 4, the adsorption unit 21 can be formed in the shape of a rod and is capable of telescopic movement. One end of the adsorption unit 21 can be vertically fixed to the body 22, and the other end can vertically adsorb the first surface S1 of the silicon wafer S. For example, a negative pressure pipeline can be provided in the adsorption unit 21 to adsorb the first surface S1 of the silicon wafer S by negative pressure.

[0082] Because the adsorption unit 21 has a stretchable characteristic, its end used to adsorb the silicon wafer S can move along the extension direction of the adsorption unit 21. When the adsorption unit 21 performs a stretching motion while adsorbing the silicon wafer S, the movement of the end of the adsorption unit 21 may pull on the area of ​​the silicon wafer S that is adsorbed, thereby causing local elastic deformation of the silicon wafer.

[0083] As mentioned above, the multiple adsorption units 21 are designed to apply independent and controllable adsorption forces to different regions of the silicon wafer S. In this embodiment, the degree of stretching and contraction of different adsorption units 21 can be individually adjusted according to the requirements of the polishing strategy, thereby causing different regions of the silicon wafer S to produce different degrees of elastic deformation. The silicon wafer region adsorbed by the adsorption unit 21 with a larger degree of stretching and contraction will have a larger degree of elastic deformation, while the silicon wafer region adsorbed by the adsorption unit 21 with a smaller degree of stretching and contraction will have a smaller degree of elastic deformation, or may not even deform.

[0084] Through the synergistic action of multiple adsorption units 21, the silicon wafer S can elastically deform from its initial shape into a target shape that meets the requirements of a specific polishing strategy. Simultaneously, the adsorption units 21 can stably maintain 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 handle the processing needs of silicon wafers with different initial and target shapes. Especially for silicon wafers with complex shapes, it provides a solution that enables precise shape adjustment and optimized polishing results.

[0085] In some embodiments of this disclosure, the plurality of adsorption units 21 are disposed at different positions in the radial direction of the adsorbed silicon wafer S.

[0086] Referring to Figure 6, in the embodiment shown in Figure 6, the adsorption unit 21 is generally in the form of an arc segment. The 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 multiple 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 merely exemplary and not limiting. In other embodiments not shown, the adsorption units 21 may also employ other arrangements, which will not be described in detail here.

[0087] Due to the circular geometry of the silicon wafer S, specifically the circular first surface S1 and second surface S2, grinding, etching, and polishing processes are typically performed while the wafer is rotating. Because of the inhomogeneity of processing conditions during rotation, thickness deviations easily occur in the radial direction of the silicon wafer. Therefore, the thickness and morphology characteristics in the radial direction—from the center to the edge of the silicon wafer—have a significant impact on shape adjustment and polishing. To address this, multiple adsorption units 21 can be distributed according to the radial thickness variation of the silicon wafer S to achieve precise shape adjustment of the wafer in its radial direction, compensate for thickness differences, and optimize the polishing process, resulting in a smoother surface and more uniform thickness after polishing.

[0088] In a further embodiment, referring to FIG7, the plurality of adsorption units 21 can 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 different radial regions of the silicon wafer by the adsorption units, thereby enabling the polishing head 2 to more uniformly control the deformation of the silicon wafer.

[0089] More specifically, the multiple adsorption units 21 arranged concentrically in a ring are highly matched to the circular geometry of the silicon wafer S. This arrangement optimizes the mechanical distribution of adsorption force and shape adjustment, enabling the adsorption units 21 to adjust the shape of the silicon wafer more efficiently, especially in the radial direction. Furthermore, the ring-shaped adsorption units can work collaboratively to apply precise adsorption force to different radial regions, meeting diverse needs for silicon wafer shape adjustment and providing reliable technical support for high-precision polishing processes.

[0090] Furthermore, as shown in Figure 7, each annular shape can be divided into multiple arc segments. For example, each annular shape consists of 12 arc-shaped adsorption units 21. This division refines each annular shape into multiple independent adsorption unit regions, thereby enhancing the fine control over the shape adjustment of the silicon wafer.

[0091] Specifically, the more arc segments the adsorption unit 21 is divided into, the more precise the adjustment of the silicon wafer shape. By increasing the number of adsorption units, independent and precise adsorption forces can be applied to different radial and angular regions of the silicon wafer, making its deformation 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 its adaptability to complex-shaped silicon wafers.

[0092] As described above, the adsorption unit 21 optimizes the polishing process mechanically by providing a shape adjustment function. Through research and experimentation, the inventors believe that, based on this, chemical improvements can be further combined. This involves introducing chemical solutions such as potassium hydroxide (KOH), deionized water (DIW), hydrogen peroxide (H2O2), hydrogen fluoride (HF), and surfactants through spraying, working synergistically with the mechanical shape adjustment function. These chemical solutions can be used to increase material removal rate, improve edge smoothness, and optimize overall surface quality. The synergistic effect of mechanics and chemistry can provide higher precision and efficiency in the silicon wafer polishing process, enabling precise regional adjustment and optimization.

[0093] Specifically, in some embodiments of this disclosure, referring to FIG8, the polishing head 2 may further include a first nozzle 25 for jetting fluid onto the held silicon wafer S.

[0094] The first nozzle 25 can be disposed outside the polishing head 2 or in the holding portion 23 of the polishing head 2. More specifically, referring to FIG8, the first nozzle 25 can 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.

[0095] The first nozzle 25 can be configured to spray chemical solutions, such as KOH, DIW, H2O2, HF, and surfactants, towards the silicon wafer S. These chemical solutions can be used to adjust the material removal rate and, in conjunction with the elastic deformation of the silicon wafer, optimize surface flatness for specific areas. Since different chemical solutions have different effects, the specific selection of the chemical solution must be determined according to process requirements. For example, KOH can accelerate the removal of material from the silicon wafer surface; the use of surfactants and HF can refine the treatment of edges and localized areas, avoiding over-polishing or depressions.

[0096] In some embodiments of this disclosure, a second nozzle 26 may be provided for spraying chemical solutions onto the silicon wafer after polishing, in order to further improve the surface condition of the silicon wafer and enhance particle levels.

[0097] Specifically, referring to Figure 9, a second nozzle 26 can be provided on the surface of the holding part 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 can be raised using the adsorption unit 21, so that the second nozzle 26 is exposed below the silicon wafer. Then, the silicon wafer can be sprayed sequentially with DIW, H2O2, HF, H2O2, and surfactant using the second nozzle 26. This chemical treatment method can further clean the surface of the silicon wafer, remove residual microparticles or contaminants, optimize the flatness and cleanliness of the silicon wafer, and provide high-quality silicon wafer surface conditions for subsequent processes.

[0098] In some embodiments of this disclosure, a silicon wafer with a total thickness variation (TTV) of less than 500 nm and a site front quotient range (SFQR) of less than 50 nm can be obtained by using the polishing method provided in the embodiments of this disclosure. The changes in TTV and SFQR values ​​of the silicon wafer before polishing and after polishing using the polishing method provided in the embodiments of this disclosure are shown in Table 1.

[0099] Table 1

[0100] Referring to Figure 10, embodiments of this disclosure also provide a final polishing apparatus 3, which includes a polishing head 2 as described above.

[0101] It should be noted that the technical solutions described in the embodiments of this disclosure can be combined arbitrarily without conflict.

[0102] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

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

2. The polishing method according to claim 1, wherein, The adsorption unit of the polishing head adsorbs the first surface of the silicon wafer, causing the silicon wafer to elastically deform from a first shape to a second shape, including: The multiple adsorption units of the polishing head adsorb different regions on the first surface of the silicon wafer, so that at least a portion of the regions of the silicon wafer adsorbed by the multiple adsorption units undergo elastic deformation, thereby causing the held silicon wafer to elastically deform from a first shape to a second shape.

3. The polishing method according to claim 2, wherein, The adsorption unit of the polishing head adsorbs the first surface of the silicon wafer, causing the silicon wafer to elastically deform from a first shape to a second shape, including: The polishing head uses multiple adsorption units to adsorb different areas on the first surface of the silicon wafer. At least a portion of the adsorption units are moved along a direction perpendicular to the first surface of the held silicon wafer, so that at least a portion of the region of the silicon wafer adsorbed by the at least a portion of the adsorption units undergoes elastic deformation, thereby causing the held silicon wafer to elastically deform from a first shape to a second shape.

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

5. The polishing method according to claim 4, wherein, The plurality of adsorption units are arranged in a plurality of annular shapes concentrically with the silicon wafers being adsorbed.

6. A polishing head comprising an adsorption unit for holding a silicon wafer, the adsorption unit being configured to adsorb a first surface of the silicon wafer to elastically deform the silicon wafer from a first shape to a second shape, thereby allowing the silicon wafer to be shaped into a desired third shape by polishing a second surface opposite to the first surface while holding the silicon wafer in the second shape.

7. The polishing head according to claim 6, wherein, The polishing head includes a plurality of adsorption units, wherein the plurality of adsorption units adsorb different regions on the first surface of the silicon wafer, so that at least a portion of the regions 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, wherein, At least a portion of the adsorption units are configured to move in a direction perpendicular to the first surface of the held silicon wafer while adsorbing different regions on the first surface of the silicon wafer, so that at least a portion of the regions of the silicon wafer adsorbed by the at least a portion of the adsorption units undergo elastic deformation, thereby causing the held silicon wafer to elastically deform from a first shape to a second shape.

9. The polishing head according to claim 7 or 8, wherein, Multiple adsorption units are disposed at different positions in the radial direction of the adsorbed silicon wafer.

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

11. The polishing head according to any one of claims 6 to 8, wherein, The polishing head also includes a nozzle for spraying fluid onto the held silicon wafer.

12. A final polishing apparatus comprising a polishing head according to any one of claims 6 to 11.

13. A silicon wafer obtained by a polishing method according to any one of claims 1 to 5, wherein, The total thickness deviation (TTV) of the silicon wafer is less than 500 nanometers, and the local front surface least squares range (SFQR) of the silicon wafer is less than 50 nanometers.

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