Polishing device for improving edge grinding uniformity

Abstract

Disclosed in the present invention is a polishing device for improving edge grinding uniformity, the device comprising: a polishing head provided with a retaining ring; a porous disc located within the retaining ring; and a suction film wrapping the porous disc, and suctioning or releasing a wafer by means of an air bag assembly, an extension being provided on an outer ring of the porous disc, at least part of the extension being in limiting fit with the retaining ring and cooperating with an inner wall of the retaining ring to clamp the suction film, and an accommodating gap being formed on the periphery of the extension so as to provide a deformation space for the suction film. In the present invention, the extension is in limiting fit with the retaining ring, and when the polishing head rotates to conduct a planarization process, the wafer is still uniformly pressed against by the porous disc when the wafer undergoes slight displacement, thereby ensuring uniform polishing at an edge of the wafer; and the accommodating gap is formed on the periphery of the extension, and micro-area deformation or wrinkles of the suction film at an edge area can be within the accommodating gap, so that the edge-pressing force is more uniform during the polishing process, and thus the polishing uniformity at the edge of the wafer is improved.

Description

A polishing device for improving edge grinding uniformity Technical Field

[0001] The invention belongs to the technical field of semiconductor integrated circuit chip manufacturing, and in particular relates to a polishing device for improving edge grinding uniformity. Background Art

[0002] Planarization technology has become an indispensable key technology in semiconductor integrated circuit chip manufacturing. Chemical Mechanical Planarization (CMP) is currently the only process technology that achieves global planarization. CMP equipment is fully automated, ensuring the safety of every module and every step in the wafer production process. This is crucial for safe production, reducing losses, and improving production efficiency. CMP equipment primarily uses a polishing head to attract and carry wafers onto a polishing pad for polishing. After polishing, the polishing head returns the wafer to the wafer loading rack for unloading. During the polishing process, the edge of the adsorption film is subjected to the combined effects of airbag pressure and clamping components. Polishing uniformity at the edge is often poorer than in the center, resulting in performance differences in devices processed at the wafer edge. Generally speaking, the larger the controllable area of ​​the CMP edge, the larger the effective area within the wafer where devices can be produced. Therefore, improving the CMP edge polishing effect is a key task in improving wafer yield.

[0003] Patent CN2712547Y discloses a "Polishing Head Structure for Chemical Mechanical Polishing." This design improves polishing uniformity by redesigning the polishing head's pressurized airbag structure, separating the single airbag into multiple independent pressurized chambers. However, this adjustment aims to better control uniformity within the polishing wafer and along its edges, and does not specifically improve polishing uniformity at the edges.

[0004] Patent TW481597B discloses "Improvements in Chemical Mechanical Polishing Head Apparatus," which addresses the problem of over-polishing of wafer edges. However, combined with FIG5A and FIG5B, it does not address the problem of wafer polishing uniformity.

[0005] Patent CN214054860U discloses "A polishing head for chemical mechanical polishing", in which the curvature of the lower edge of the adsorption film is close to a right angle, thereby improving the polishing rate of the wafer edge, making the wafer edge polishing rate closer to the wafer center polishing rate, thereby improving the overall uniformity of the wafer polishing surface, that is, the obtained wafer uniformity is better. However, even if the polishing rates of the wafer center and edge are closer, the problem of uniformity of wafer edge polishing is not paid attention to. In addition, it points out that in comparative example 1, when the curvature of the adsorption film edge is large as shown in Figure 3 of the document, the polishing rate of the wafer edge is small, resulting in a poor polishing rate of the wafer edge. It should be pointed out that the curvature of the lower edge close to a right angle in Figure 2 of the document may produce micro-wrinkles when the space for pressurized expansion of the adsorption film is limited, thereby causing the uniformity of the edge area to deteriorate.

[0006] Summary of the Invention

[0007] In order to overcome the deficiencies of the prior art, the present invention provides a polishing device for improving edge grinding uniformity, which improves the polishing uniformity of the wafer edge, thereby increasing the effective area within the wafer where devices can be actually produced.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a polishing device for improving edge grinding uniformity, comprising:

[0009] polishing head with retaining ring;

[0010] a porous disk positioned within the retaining ring;

[0011] An adsorption film is coated on the porous disk and realizes adsorption or release of the wafer through the airbag assembly;

[0012] The outer ring of the porous disk has an extension portion, at least a portion of which is limitedly engaged with the retaining ring and cooperates with the inner wall of the retaining ring to clamp the adsorption film;

[0013] An accommodating gap is formed on the outer periphery of the extension portion to provide a deformation space for the adsorption film.

[0014] Furthermore, at least a portion of the accommodating gap faces the side where the wafer is located, so as to prevent the outer circle of the adsorption film from forming micro-area deformation or wrinkles.

[0015] Furthermore, the maximum radial width of one side of the extension portion is 0.5-2 mm.

[0016] Furthermore, the extension portions are continuously arranged in the circumferential direction; or, the extension portions are evenly spaced in the circumferential direction.

[0017] Furthermore, the radial width of one side of the extension portion decreases from top to bottom, and the upper portion of the outer ring of the extension portion is limitedly engaged with the retaining ring, and the accommodating gap is formed between the lower portion of the outer ring and the inner wall of the retaining ring.

[0018] Furthermore, the side wall thickness of the adsorption film is H, and the difference between the maximum single-side radial width and the minimum single-side radial width of the extension portion is 1H-10H.

[0019] Furthermore, the side wall of the outer ring of the extension part smoothly transitions to the bottom wall of the porous disk; the side wall of the outer ring of the extension part smoothly transitions to the top wall of the extension part.

[0020] Furthermore, the extension portion includes at least two arc-shaped protrusions, and the side of the arc-shaped protrusion facing the retaining ring is an arc surface, and the accommodating gap is formed between adjacent arc-shaped protrusions.

[0021] Furthermore, there are multiple arc-shaped protrusions, and they are evenly arranged on the outer circumference of the porous disk.

[0022] Furthermore, the sum of the outer diameter of the extension portion and the double thickness of the adsorption film is equivalent to the inner diameter of the retaining ring; the sum of the outer diameter of the extension portion and the double thickness of the adsorption film is equivalent to the inner diameter of the wafer.

[0023] Furthermore, the extension portion and the porous disk are separately provided; or, the extension portion and the porous disk are integrally provided.

[0024] The present invention proposes to ensure that the pressure applied to the wafer surface remains consistent by increasing the size of the porous disk, and to reduce the formation of micro-area wrinkles in the adsorption film by optimizing the edge spatial distribution, thereby optimizing the uniformity of the edge area while ensuring the overall uniformity of the wafer surface.

[0025] The technical solution proposed in the present invention is to ensure the area of ​​the wafer covered by the adsorption film by optimizing the size of the porous disk coated with the adsorption film, and at the same time optimize the edge structure of the porous disk to ensure the deformation space of the adsorption film during the pressurized expansion process, so as to ensure that the adsorption film can be spread relatively smoothly on the back of the wafer to participate in grinding, thereby improving the pressurization uniformity of the wafer edge, and then improving the uniformity of the wafer edge polishing.

[0026] The beneficial effects of the present invention are: 1) the extension part is limited in cooperation with the retaining ring, and when the polishing head rotates to perform the flattening process, the wafer is still evenly pressurized by the porous disk when it has a slight offset, thereby ensuring that the edge of the wafer is polished evenly; 2) a receiving gap is formed on the periphery of the extension part, and the micro-area deformation or wrinkles produced by the adsorption film in the edge area can be within the receiving gap, so that the edge pressure force is more uniform during the polishing process, thereby improving the polishing uniformity of the wafer edge; 3) the area of ​​the outer ring of the extension part and the retaining ring is reduced accordingly, thereby reducing the micro-area deformation or wrinkles produced in the edge area of ​​the adsorption film. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a cross-sectional view of the polishing head of the present invention in a polishing state.

[0028] FIG2 is a cross-sectional view of the polishing head in the present invention when it absorbs the wafer.

[0029] FIG3 is a schematic diagram of the three-dimensional structure of the porous disk in Example 1 of the present invention.

[0030] FIG4 is a cross-sectional view of the porous disk in the first embodiment of the present invention.

[0031] FIG5 is an enlarged view of the structure at point C in FIG4 .

[0032] FIG6 is a schematic diagram of the matching structure of the retaining ring and the extension portion in the first embodiment of the present invention.

[0033] FIG7 is a schematic diagram of the three-dimensional structure of the porous disk in the second embodiment of the present invention.

[0034] FIG8 is a cross-sectional view of the porous disk in the second embodiment of the present invention.

[0035] FIG9 is an enlarged view of the structure at point D in FIG8 .

[0036] FIG10 is a schematic diagram of the matching structure of the retaining ring and the extension portion in the second embodiment of the present invention.

[0037] FIG11 is a schematic diagram of the three-dimensional structure of the porous disk in the third embodiment of the present invention.

[0038] FIG12 is a cross-sectional view of the porous disk in the third embodiment of the present invention.

[0039] FIG13 is an enlarged view of the structure at point E in FIG12 .

[0040] FIG14 is a schematic diagram of the matching structure of the retaining ring and the extension portion in the third embodiment of the present invention.

[0041] FIG15 is a schematic diagram of the three-dimensional structure of the porous disk in the fourth embodiment of the present invention.

[0042] FIG16 is a cross-sectional view of the porous disk in the fourth embodiment of the present invention.

[0043] FIG17 is an enlarged view of the structure at point F in FIG16 .

[0044] FIG18 is a schematic diagram of the matching structure of the retaining ring and the extension portion in the fourth embodiment of the present invention.

[0045] FIG19 is a schematic diagram of the three-dimensional structure of the porous disk in the fifth embodiment of the present invention.

[0046] FIG20 is a top view of the porous disk in the fifth embodiment of the present invention.

[0047] FIG21 is a cross-sectional view taken along the AA and BB perspectives in FIG20 .

[0048] FIG22 is a schematic diagram of the matching structure of the retaining ring and the extension portion in the fifth embodiment of the present invention.

[0049] FIG23 is a numerical curve of the removal rate at various locations on the wafer before and after the improvement of the porous disk in the present invention.

[0050] Among them, 1-polishing head, 11-retaining ring, 2-porous disk, 21-extension part, 211-arc-shaped protrusion, 22-porous disk top wall, 23-porous disk bottom wall, 3-adsorption film, 4-airbag assembly, 5-wafer, 6-accommodation gap. DETAILED DESCRIPTION

[0051] In order to enable those skilled in the art to better understand the solutions of the present invention, the following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0052] A polishing device for improving edge grinding uniformity includes a polishing head 1 with a retaining ring 11, a porous disk 2 located within the retaining ring 11, and an adsorption film 3 coated on the porous disk 2. The adsorption film 3 can adsorb or release the wafer 5 through an airbag assembly 4. The function of the airbag assembly 4 is realized by existing technology and will not be repeated here.

[0053] The outer ring of the porous disk 2 has an extension 21, at least part of which is engaged with the retaining ring 11 and the inner wall of the retaining ring 11 to clamp the adsorption membrane 3. At the same time, the outer periphery of the extension 21 is formed with an accommodation gap 6, thereby providing space for the adsorption membrane 3 to deform.

[0054] The extension portion 21 and the porous disk 2 can be separate components, and the two can be detachably connected. The adsorption membrane 3 applies pressure to the extension portion 21 toward the inside of the porous disk 2, so that the two can remain stably connected. Of course, the extension portion 21 and the porous disk 2 can also be integrally provided, and there is no specific limitation.

[0055] Figure 1 shows a cross-sectional view of the polishing head 1 during polishing, while Figure 2 shows a cross-sectional view of the polishing head 1 with wafer 5 adsorbed. The porous disc 2 secures the adsorption membrane 3, which is typically made of soft, elastic rubber or silicone. In its static state, the membrane 3 adheres to the porous disc 2. During operation, an external mechanism introduces air into the air cavity through an airway. The air pressure expands the membrane 3, applying pressure to the surface of the wafer 5. The polishing pad and polishing fluid then flatten the wafer 5 through chemical and mechanical interactions.

[0056] When the adsorption film 3 is deformed, the gas is evenly introduced through the holes of the porous disk 2 and filled into the air cavity. There are no other hardware mechanisms in the middle area of ​​the adsorption film 3, and the pressure is relatively uniform, so the polishing uniformity is better. In the edge area, due to the presence of the part where the porous disk 2 and the adsorption film 3 are in contact, the adsorption film 3 may have micro-area deformation or wrinkles, resulting in poor uniformity. On the other hand, there is a small gap between the wafer 5 and the retaining ring 11 during the polishing process. If the wafer 5 has a flat-edge configuration, the gap between the wafer 5 and the retaining ring 11 will be greatly increased. When the polishing head 1 rotates to perform the flattening process, the wafer 5 may deviate in a certain direction under the action of centrifugal force, resulting in uneven edge polishing.

[0057] To improve the above two situations, the present invention provides an extension 21 on the outer ring of the porous disk 2. At least a portion of the extension 21 is in positional engagement with the retaining ring 11, so that even if the wafer 5 deviates slightly during polishing, it is still uniformly pressurized by the porous disk, ensuring uniform polishing of the edge of the wafer 5. The positional engagement here refers to the sum of the outer diameter of the extension 21 and the double-layer thickness of the adsorption film 3, which is equivalent to the inner diameter of the retaining ring 11 and the inner diameter of the wafer 5. As a result, there is no large gap, or even no gap, between the wafer 5 and the retaining ring 11. During the rotation of the polishing head 1 for flattening, the porous disk can achieve uniform pressure within this area.

[0058] At the same time, a containment gap 6 is formed on the periphery of the extension 21. Micro-deformations or wrinkles generated by the adsorption film 3 at the edge region can be accommodated within this containment gap 6. In other words, the containment gap 6 provides room for the adsorption film 3 to deform, making the edge pressure more uniform during the polishing process, thereby improving the polishing uniformity of the wafer 5 edge. Furthermore, when the containment gap 6 is formed on the periphery of the extension 21, the area of ​​the restraining fit between the outer ring of the extension 21 and the retaining ring 11 is correspondingly reduced. In other words, the contact surface between the extension 21 and the retaining ring 11 on the adsorption film 3 is reduced, which also helps to reduce micro-deformations or wrinkles generated at the edge region of the adsorption film 3.

[0059] Example 1

[0060] As shown in Figures 3-4, the extension portion 21 is continuously arranged in the circumferential direction, the single-side radial width of the extension portion 21 decreases from top to bottom, and the upper part of the outer ring of the extension portion 21 is limitedly engaged with the retaining ring 11, and an accommodating gap 6 is formed between the lower part of the outer ring and the inner wall of the retaining ring 11, as shown in Figure 6.

[0061] In other words, the width of the upper outer ring of the extension portion 21 is larger, and the sum of its width and the double-layer thickness of the adsorption film 3 is equivalent to the inner diameter of the retaining ring 11 and the inner diameter of the wafer 5. That is, the position of the porous disk 2 is relatively limited by the retaining ring 11, ensuring that the porous disk 2 will not deviate from the edge under the action of centrifugal force, and its pressurized coverage area is slightly larger than the area of ​​the wafer 5, which can ensure that even if the wafer 5 has a slight slip, it can still be ground within the coverage area of ​​the porous disk 2.

[0062] The lower portion of the outer ring of the extension 21 has a smaller width, forming a receiving gap 6 between the upper and lower portions of the outer ring of the extension 21, with this receiving gap 6 facing the side of the wafer 5. When the inner wall of the retaining ring 11 and the upper portion of the outer ring of the extension 21 cooperate to clamp the adsorption film 3, the presence of the receiving gap 6 allows the adsorption film 3 to fit more loosely against the porous disk 2, preventing micro-deformation or wrinkling of the outer ring of the adsorption film 3. This allows for more uniform pressure applied to the edge during polishing, thereby improving polishing uniformity of the wafer 5 edge. During polishing, gas is introduced into the adsorption film cavity, causing the adsorption film to expand and press the wafer against the polishing disk. Surface material is removed under the action of the polishing fluid and mechanical force. During this process, the more uniform the pressure applied by the adsorption film to the back of the wafer, the better the uniformity of the wafer polishing removal rate. At the edge of the adsorption film, due to the pull of the porous disk and the space in the receiving gap, a smaller receiving gap can easily cause micro-bending or wrinkling. In the slightly curved or wrinkled area, the downward pressure will be different from that in the smooth area, resulting in a difference in the polishing removal rate in the wafer edge area.

[0063] In this embodiment, the width gradient of the upper and lower outer rings of the extension portion 21 decreases, that is, the outer ring sidewall of the extension portion 21 is an inclined surface, which tilts from top to bottom toward the center of the porous disk 2.

[0064] Define the sidewall thickness of the adsorption film 3 as H, then the difference between the maximum unilateral radial width and the minimum unilateral radial width of the extension 21 is 1H-10H. If the difference between the maximum unilateral radial width and the minimum unilateral radial width of the extension 21 is too large, the size of the porous disk 2 is too small and cannot cover the processing surface of the wafer 5, resulting in a low edge removal rate, reducing the overall uniformity of the wafer and causing a decrease in yield. If the width difference is too small, firstly, the deformation space of the adsorption film 3 is limited, which is prone to wrinkles, resulting in reduced edge uniformity. Secondly, when the adsorption film 3 is deformed and squeezed, resulting in excessive wear on the retaining ring 11 or the back of the wafer 5, the debris generated by the wear will fall onto the polishing pad and participate in the process grinding of the front side of the wafer, causing defects or scratches on the front side of the wafer, and in severe cases, the wafer may be scrapped.

[0065] Specifically, the maximum radial width of the extension portion 21 on one side is 0.5-2 mm, that is, the left side of the line O in FIG. 5 is the extension portion 21 , and the radial width of the extension portion 21 on one side S=0.5-2 mm.

[0066] The sidewalls of the outer ring of the extension 21 smoothly transition to the bottom wall 23 of the porous disk 2, and the sidewalls of the outer ring of the extension 21 smoothly transition to the top wall 22 of the porous disk 2. Therefore, when the adsorption film 3 covers the porous disk 2 and its extension 21, the adsorption film 3 is not pulled at the connection between the extension 21 and the rest of the porous disk 2, allowing the adsorption film 3 to be smoothly distributed along the circumference of the porous disk 2, preventing the formation of wrinkles.

[0067] Example 2

[0068] As shown in Figures 7 to 10, in this embodiment, the upper portion of the outer ring of the extension portion 21 is limitedly engaged with the retaining ring 11, and an accommodating gap 6 is formed between the lower portion of the outer ring and the inner wall of the retaining ring 11, except that the width of the upper and lower portions of the outer ring of the extension portion 21 does not decrease gradually, and the lower portion of the outer ring of the extension portion 21 forms an arc-shaped depression toward the center of the porous disk 2.

[0069] The other structures are the same as those in the first embodiment and will not be described in detail.

[0070] Example 3

[0071] As shown in Figures 11 to 14, in this embodiment, the upper part of the outer ring of the extension part 21 is limitedly engaged with the retaining ring 11, and an accommodating gap 6 is formed between the lower part of the outer ring and the inner wall of the retaining ring 11, except that the width of the upper and lower parts of the outer ring of the extension part 21 does not decrease gradually, and the lower part of the outer ring of the extension part 21 forms a rectangular depression toward the center of the porous disk 2.

[0072] The other structures are the same as those in the first embodiment and will not be described in detail.

[0073] Example 4

[0074] As shown in Figures 15 to 18, in this embodiment, the cross-section of the extension portion 21 is semicircular with an opening toward the center of the porous disk 2, and the middle part of its outer ring is limitedly engaged with the retaining ring 11, and an accommodating gap 6 is formed between the upper part of the outer ring, the lower part of the outer ring and the inner wall of the retaining ring 11. That is to say, part of the accommodating gap 6 is toward the side where the wafer 5 is located, and part is away from the side where the wafer 5 is located. The upper part and the lower part of the outer ring of the extension portion 21 are formed to prevent the outer ring of the adsorption film 3 from forming micro-area deformation or wrinkles.

[0075] Example 5

[0076] As shown in FIG19 , in this embodiment, the extension portion 21 is evenly spaced circumferentially and includes at least two arc-shaped protrusions 211 , and the side of the arc-shaped protrusion 211 facing the retaining ring 11 is an arc surface, and an accommodating gap 5 is formed between adjacent arc-shaped protrusions 211 .

[0077] In this embodiment, there are multiple arc-shaped protrusions 211, which are evenly arranged on the outer circumference of the porous disk 2. As shown in Figures 20-22, the AA cross-sectional view shows the porous disk 2 with the extension 21, and the BB cross-sectional view shows the porous disk 2 without the extension 21. The extension 21 is to the left of line O.

[0078] To further illustrate the advantages of the present invention, Table 1 shows the removal rates of the wafer 5 along the diameter direction obtained by using the structures of the porous disk 2 in Examples 1 to 5 (improved version 1 and improved version 2) and using the porous disk 2 without the extension portion 21 (unimproved version).

[0079] Table 1

[0080] As can be seen from Table 1, the present invention tests the polishing rates of improved version 1, improved version 2 and unimproved version porous disc while keeping other test conditions consistent. The test wafer is a 6-inch polishing disc (wafer radius 75mm), and the polishing disc surface is SiO2 film. The absolute value of the wafer radius parameter is the position from the center of the wafer circle, and the positive and negative signs represent the left and right directions. It can be seen that the unimproved version porous disc polishing rate data has a relatively uniform removal rate along the wafer diameter direction, with an average removal rate of 1942A / min and a variance data of 125A / min. It is worth noting that in the edge area of ​​the wafer, taking 72mm and -72mm as examples, there is a situation where the polishing rate is high and low, and its polishing rate difference is 960A / min, that is, because the wrinkles at the edge cause the situation where the edge removal rate is uneven.

[0081] The polishing rate data for the improved porous disc, shown in Figure 1, shows a more uniform removal rate across the wafer diameter, with an average removal rate of 1855 A / min and a variance of 59 A / min, significantly lower than the unmodified data, indicating improved uniformity. Specifically, for the 72mm and -72mm discs, the difference in polishing rate is only 163 A / min, significantly lower than the unmodified data, indicating a significant improvement in polishing rate uniformity at the edge. These data demonstrate that the improved porous disc significantly improves edge removal rate uniformity by reducing the likelihood of edge wrinkling.

[0082] In addition, the polishing rate data 2 of the improved porous disk can increase the rate at the edge by adjusting the pressure parameters, which is higher than the polishing rate in the center area. During this process, the polishing rates at -72mm and 72mm are 2515A / min and 2508A / min respectively, which are comparable, indicating that the removal rate at the edge is still very uniform. This data shows that the improved porous disk has a significant improvement on the polishing uniformity of the edge area.

[0083] The above specific embodiments are used to illustrate the present invention rather than to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A polishing device for improving edge grinding uniformity, comprising: A polishing head (1) with a retaining ring (11); A porous disk (2) located inside the retaining ring (11); The adsorption film (3) is coated on the porous disk (2) and realizes adsorption or release of the wafer (5) through the airbag component (4); the characteristics are: The outer ring of the porous disk (2) has an extension portion (21), at least a portion of which is in position-limiting cooperation with the retaining ring (11) and cooperates with the inner wall of the retaining ring (11) to clamp the adsorption film (3); An accommodating gap (6) is formed on the outer periphery of the extension portion (21) to provide a deformation space for the adsorption film (3).

2. The polishing device according to claim 1, characterized in that: At least part of the accommodating gap (6) faces the side where the wafer (5) is located, so as to prevent the outer ring of the adsorption film (3) from forming micro-region deformation or wrinkles.

3. The polishing device according to claim 1, characterized in that: The maximum radial width of the extension portion (21) on one side is 0.5-2 mm.

4. The polishing device according to claim 1, characterized in that: The extension portions (21) are arranged continuously in the circumferential direction; or, the extension portions (21) are arranged at even intervals in the circumferential direction.

5. The polishing device according to claim 1, characterized in that: The radial width of one side of the extension portion (21) decreases from top to bottom, and the upper portion of the outer ring of the extension portion (21) is limitedly matched with the retaining ring (11), and the accommodating gap (5) is formed between the lower portion of the outer ring and the inner wall of the retaining ring (11).

6. The polishing device according to claim 5, characterized in that: The side wall thickness of the adsorption film (3) is H, and the difference between the maximum single-side radial width and the minimum single-side radial width of the extension portion (21) is 1H-10H.

7. The polishing device according to claim 5, characterized in that: The side wall of the outer ring of the extension part (21) smoothly transitions to the bottom wall of the porous disk (2); the side wall of the outer ring of the extension part (21) smoothly transitions to the top wall of the extension part (21).

8. The polishing device according to claim 1, characterized in that: The extension portion (21) comprises at least two arc-shaped protrusions (211), and the side of the arc-shaped protrusion (211) facing the retaining ring (11) is an arc surface, and the accommodating gap (5) is formed between adjacent arc-shaped protrusions (211).

9. The polishing device according to claim 8, characterized in that: The arc-shaped protrusions (211) are multiple in number and are evenly arranged on the outer circumference of the porous disk (2).

10. The polishing device according to claim 1, characterized in that: The sum of the outer diameter of the extension part (21) and the double-layer thickness of the adsorption film (3) is equivalent to the inner diameter of the retaining ring (11); the sum of the outer diameter of the extension part (21) and the double-layer thickness of the adsorption film (3) is equivalent to the inner diameter of the wafer (5).

11. The polishing device according to claim 1, characterized in that: The extension portion (21) and the porous disk (2) are arranged separately; or, the extension portion (21) and the porous disk (2) are arranged integrally.

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