Polishing pad and wafer polishing system

Abstract

The utility model discloses a polishing pad which is laid on a polishing table, the polishing pad is provided with a through hole penetrating through the thickness direction of the polishing pad and a groove body arranged on the upper surface of the polishing pad, polishing liquid is accumulated in the through hole and the groove body, and the total cross sectional area of the through hole and the groove body is increased in a gradient mode from the inner ring of the polishing pad to the outer ring in the radial direction. The utility model further discloses a wafer polishing system. According to the polishing pad, the through hole penetrates through the thickness direction of the polishing pad, and during polishing operation, the through hole is filled with conductive polishing liquid, so that a wafer and a polishing table are communicated, a current path is formed, and the polishing pad has good conductivity; when the polishing table drives the polishing pad to rotate, the rotating speed of the outer ring is high, the rotating speed of the center is low, when the wafer is polished, the contact time of the outer ring of the polishing pad and the wafer is shorter, the total cross sectional area of the outer ring through hole and the groove body in the polishing pad is designed to be larger, more polishing liquid can be filled, the uniformity of current passing through the wafer can also be ensured, and the wafer is uniformly polished.

Description

Technical Field

[0001] The utility model belongs to the technical field of semiconductor integrated circuit chip manufacturing and processing, in particular to a polishing pad and a wafer polishing system. Background Art

[0002] In the semiconductor field, chemical mechanical polishing (CMP) is one of the key technologies for wafer surface processing. With the development of the third-generation semiconductor technology, the original CMP polishing pad can no longer meet the polishing requirements of silicon carbide wafers.

[0003] The surface of the existing polishing pad generally has regular circular or divergent grooves, which are used to carry the polishing liquid during the wafer polishing process. However, for silicon carbide wafers with extremely high surface hardness, the silicon carbide wafer needs to be energized to oxidize the wafer surface to achieve a good polishing effect, and the existing polishing pad has poor conductivity and cannot form an effective current path, so a new polishing pad is urgently needed to achieve the polishing of silicon carbide wafers. Utility Model Content

[0004] In order to overcome the deficiencies of the prior art, the utility model provides a polishing pad and a wafer polishing system, which have good conductivity and high current uniformity when working, and are beneficial to the polishing of silicon carbide wafers.

[0005] The technical solution adopted by the utility model to solve its technical problems is: a polishing pad is laid on a polishing table, the polishing pad has a through hole running through the thickness direction thereof, and a groove body is arranged on the upper surface thereof, polishing liquid is accumulated in the through hole and the groove body, and the total cross-sectional area of ​​the through hole and the groove body increases gradually from the inner circle of the polishing pad radially to the outer circle.

[0006] Furthermore, the cross-sectional area of ​​the through hole accounts for 15-30% of the upper surface area of ​​the polishing pad.

[0007] Furthermore, the cross-sectional area of ​​the groove body accounts for 15-30% of the upper surface area of ​​the polishing pad.

[0008] Furthermore, the cross-sectional area gradient of the through hole increases in the radial direction extending from the inner ring of the polishing pad to the outer ring.

[0009] Furthermore, in the radial extension direction from the inner ring of the polishing pad to the outer ring, the total cross-sectional area of ​​the through holes is the same as the proportion of the upper surface area of ​​the polishing pad.

[0010] Furthermore, the sizes of the individual through holes are equal; or, the sizes of the individual through holes gradually decrease from the outer circle to the inner circle of the polishing pad; or, the sizes of the individual through holes gradually increase from the outer circle to the inner circle of the polishing pad.

[0011] Furthermore, the through holes extend in the circumferential direction to form an arc-shaped racetrack, and the circumferential through holes are arranged at intervals; the groove bodies extend in the circumferential direction to form an arc-shaped racetrack, and the circumferential groove bodies are arranged at intervals.

[0012] Furthermore, the through holes include a plurality of through hole groups distributed along the radial direction, each through hole group includes a plurality of through holes arranged at intervals along the circumferential direction, and the plurality of through holes in the same radial direction of each through hole group are radially distributed; the slot bodies include a plurality of slot body groups distributed along the radial direction, each slot body group includes a plurality of slot bodies arranged at intervals along the circumferential direction; radially adjacent through hole groups and slot body groups are staggered, and the plurality of slot bodies in the same radial direction of each slot body group are radially distributed.

[0013] Furthermore, radially adjacent through holes and slot ends have overlapping sections.

[0014] Furthermore, the length of the through holes of the radially adjacent through hole groups decreases gradually from the outside to the inside; and the length of the slot bodies of the radially adjacent slot body groups decreases gradually from the outside to the inside.

[0015] Furthermore, it has through hole areas and slot body areas alternately distributed along the circumferential direction, wherein the through hole area has a plurality of through holes arranged at intervals along the radial direction, and the cross-sectional area of ​​the through holes increases gradually from the inner circle to the outer circle; the slot body area has a plurality of slot bodies arranged at intervals along the radial direction, and the cross-sectional area of ​​the slot bodies increases gradually from the inner circle to the outer circle.

[0016] Furthermore, the through hole area and the slot area are evenly distributed.

[0017] The utility model also discloses a wafer polishing system, comprising:

[0018] Polishing head, rotatable in circumferential direction;

[0019] a rotating unit through which the circuit passes;

[0020] A polishing pad as described above;

[0021] A polishing table, used to support the polishing pad and drive the polishing pad to rotate;

[0022] The polishing head, the wafer, the polishing liquid in the through hole of the polishing pad, and the polishing table form an electric circuit.

[0023] Furthermore, the current in the power-on circuit flows to the polishing head, the back side of the wafer, the front side of the wafer, and the polishing liquid in the through-holes of the polishing pad; or, the current in the power-on circuit flows to the polishing liquid in the through-holes of the polishing pad, the front side of the wafer, the back side of the wafer, and the polishing head.

[0024] The beneficial effects of the utility model are as follows: the through hole runs through the thickness direction of the polishing pad, and when the polishing operation is performed, the through hole is filled with conductive polishing liquid, thereby connecting the wafer and the polishing table to form a current path, so that the polishing pad has good conductivity; when the polishing table drives the polishing pad to rotate, the outer ring speed is high and the center speed is low. During the wafer polishing operation, the contact time between the outer ring of the polishing pad and the wafer is shorter, and the total cross-sectional area of ​​the outer ring through hole and the groove body on the polishing pad is designed to be larger, which can be filled with more polishing liquid, and can also ensure the uniformity of the current passing through the wafer, so that the wafer is evenly polished; the production is simple and the processing cost is saved; from the inner ring to the outer ring of the polishing pad, the area of ​​the through hole and the groove body for accommodating the polishing liquid gradually increases, which is conducive to the uniform distribution of the polishing liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A partial cross-sectional view of the polishing pad provided by the utility model.

[0026] Figure 2 It is a partial cross-sectional view of the polishing head with the wafer against the polishing pad in the utility model.

[0027] Figure 3 A top view of the polishing pad provided in the first embodiment of the utility model.

[0028] Figure 4 for Figure 3 A magnified view of the structure in Figure 2.

[0029] Figure 5 A top view of the polishing pad provided in the second embodiment of the present invention.

[0030] Figure 6 A top view of the polishing pad provided in the third embodiment of the present invention.

[0031] Figure 7 A top view of the polishing pad provided in the fourth embodiment of the present utility model.

[0032] Figure 8 A simplified diagram of a wafer polishing system is provided for the utility model.

[0033] Among them, 1-polishing table, 2-polishing pad, 21-through hole, 211-through hole group, 22-trough body, 23-overlapping section, 24-through hole area, 25-trough body area, 26-mixing area, 3-polishing liquid, 4-wafer, 5-polishing head, 6-rotation unit. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the solution of the utility model, the following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the utility model.

[0035] like Figure 1 , Figure 2 As shown, a polishing pad is laid on a polishing table 1, and the polishing pad 2 has a through hole 21 and a groove 22. The through hole 21 passes through the upper and lower surfaces of the polishing pad 2 in the thickness direction, and the groove 22 is located on the upper surface of the polishing pad 2. In other words, the bottom of the groove 22 does not pass through the lower surface of the polishing pad 2. Polishing liquid 3 is accumulated in both the through hole 21 and the groove 22, and the total cross-sectional area of ​​the through hole 21 and the groove 22 increases gradually from the inner circle of the polishing pad 2 to the outer circle of the polishing pad 2 along the radial direction.

[0036] The polishing pad 2 in the utility model is a conductive polishing pad, which utilizes the polishing liquid 3 in the through hole 21 to realize the conductive function, utilizes the polishing liquid 3 in the groove body 22, or utilizes the polishing liquid 3 in the groove body 22 and the through hole 21 at the same time, to react chemically with the surface of the wafer 4, thereby realizing the electrochemical polishing effect on the surface of the wafer 4.

[0037] When the polishing head 5 drives the wafer 4 to perform electrochemical polishing on the polishing pad 2, since the outer ring of the polishing table 1 rotates at a higher speed and the center of the polishing table 1 rotates at a relatively lower speed, a certain area of ​​the outer ring of the polishing pad 2 is in contact with the wafer 4 for a shorter time during the polishing operation. In order to ensure the uniformity of the current, the total cross-sectional area of ​​the through hole 21 and the groove body 22 of the outer ring of the polishing pad 2 is designed to be larger than that of the inner ring, so that more polishing liquid can be filled in the through hole 21 and the groove body 22, so that the wafer 4 can be polished uniformly. The inner ring of the polishing pad 2 here refers to the position close to the center of the polishing pad 2, and the outer ring of the polishing pad 2 refers to the position close to the edge of the polishing pad 2.

[0038] The total cross-sectional area of ​​the through holes 21 and the grooves 22 increases gradually from the inner circle of the polishing pad 2 radially to the outer circle. The specific implementation method may be to increase the area of ​​the through holes 21 and the grooves 22, or to increase the number of the through holes 21 and the grooves 22, and there is no specific limitation.

[0039] In this embodiment, the cross-sectional area gradient of the through hole 21 increases in the radial extension direction from the inner circle of the polishing pad 2 to the outer circle, and the total cross-sectional area of ​​the through hole 21 accounts for the same proportion as the upper surface area of ​​the polishing pad 2. In other words, taking one circumferential circle of the polishing pad 2 as an area unit, the ratio of the total cross-sectional area of ​​the through holes 21 in the area unit to the total surface area of ​​the area unit is X, and the ratio of the total cross-sectional area of ​​the through holes 21 in an area unit in any radial direction of the polishing pad 2 to the total surface area of ​​the area unit is X, thereby ensuring the uniformity of the current on the surface of the wafer 4 per unit time, and the wafer 4 is uniformly polished.

[0040] The above compares the total cross-sectional areas of the through holes 21 and the groove body 22 of the inner and outer circles of the polishing pad 2, but the respective proportions of the through holes 21 and the groove body 22 are not limited and can be selected according to actual process requirements. For example, if the intensity of the electrochemical reaction needs to be increased, the proportion of the through holes 21 is increased; if the electrochemical reaction needs to be slowed down, the proportion of the groove body 22 is increased.

[0041] Specifically, the cross-sectional area of ​​the through hole 21 accounts for 15-30% of the upper surface area of ​​the polishing pad 2; the cross-sectional area of ​​the groove body 22 accounts for 15-30% of the upper surface area of ​​the polishing pad 2. The specific shapes of the through hole 21 and the groove body 22 are not limited.

[0042] Based on the above structure, the specific structure of the polishing pad 2 is described through three embodiments.

[0043] Embodiment 1

[0044] like Figure 3 , Figure 4 As shown, a single through hole 21 extends along the circumference of the polishing pad 2 to form an arc-shaped racetrack, with a relatively narrow width, arc-shaped ends, and circumferentially adjacent through holes 21 are arranged at intervals. Similarly, a single groove body 22 extends along the circumference of the polishing pad 2 to form an arc-shaped racetrack, with a relatively narrow width, arc-shaped ends, and circumferentially adjacent groove bodies 22 are arranged at intervals. In this embodiment, the cross-sectional shapes of the through hole 21 and the groove body 22 are the same.

[0045] The through hole 21 includes a plurality of through hole groups 211 distributed in the radial direction, and each through hole group 211 includes a plurality of through holes 21 spaced apart in the circumferential direction, that is, Figure 3The multiple through holes 21 in the dotted circle are a through hole group 211. The lengths of the through holes 21 of radially adjacent through hole groups 211 decrease gradually from the outside to the inside, and the multiple through holes 21 in the same radial direction of each through hole group 211 are radially distributed. In other words, the through holes 21 on the polishing pad 2 can be divided into multiple columns, each column is evenly spaced along the radial direction of the polishing pad 2, and the size of each column of through holes 21 gradually increases from the inside to the outside, that is, the size of a single through hole 21 gradually decreases from the outer circle of the polishing pad 2 to the inner circle. Of course, near the center of the polishing pad 2, the shape of the through hole 21 can also be close to a circle.

[0046] Similarly, the groove body group is located inside the through hole group 211, and each groove body group includes a plurality of groove bodies 22 arranged at intervals along the circumferential direction, and all the groove bodies 22 are divided into a plurality of groove body groups distributed along the radial direction. The groove body lengths of radially adjacent groove body groups decrease gradually from the outside to the inside, and the plurality of groove bodies in the same radial direction of each groove body group are radially distributed. In other words, the groove bodies 22 on the polishing pad 2 can be divided into a plurality of columns, and each column is evenly spaced along the radial direction of the polishing pad 2, and the size of each column of groove bodies 22 gradually increases from the inside to the outside. Of course, near the center of the polishing pad 2, the shape of the groove body 22 can also be close to a circle.

[0047] From the outer ring to the inner ring of the polishing pad 2, the through hole groups 211 and the groove groups are arranged alternately, and the radially adjacent through hole groups 211 and groove groups are staggered, and the staggered arrangement here means that the two are not completely opposite. Specifically, the ends of the radially adjacent through holes 21 and grooves 22 have overlapping sections 23 in the radial direction.

[0048] Embodiment 2

[0049] like Figure 5 As shown, the polishing pad 2 has through hole areas 24 and groove areas 25 (areas circled by dotted lines) alternately distributed along the circumferential direction, and a plurality of through holes 21 are radially spaced apart in the through hole area 24, and the cross-sectional area of ​​the through holes 21 increases gradually from the inner circle to the outer circle of the polishing pad 2; similarly, a plurality of grooves 22 are radially spaced apart in the groove area 25, and the cross-sectional area of ​​the grooves 22 increases gradually from the inner circle to the outer circle.

[0050] In this embodiment, two opposite side walls of the through hole 21 and the groove body 22 in the length direction are arc-shaped, and two opposite side walls in the width direction are straight-line-shaped.

[0051] In this embodiment, the through hole region 24 and the slot region 25 are evenly distributed, that is, the areas of the through hole region 24 and the slot region 25 are substantially equal.

[0052] Embodiment 3

[0053] like Figure 6As shown, the size of a single through hole 21 on the polishing pad 2 gradually increases from the outer circle to the inner circle of the polishing pad 2 , and of course, the size of the groove body 22 gradually increases from the outer circle to the inner circle of the polishing pad 2 .

[0054] Specifically, the polishing pad 2 is divided into a plurality of mixed regions 26 along the radial direction, namely Figure 6 The dotted circle is a mixing area 26, each of which has both a through hole 21 and a slot 22. The cross-sectional areas of the through holes 21 and the slot 22 in each mixing area 26 are equal. The sizes of the through holes 21 and the slot 22 in adjacent mixing areas 26 are different, and the overall distribution density of the through holes 21 and the slot 22 in adjacent mixing areas 26 is different. Specifically, the outer circle is denser.

[0055] Embodiment 3

[0056] like Figure 7 As shown, the size of each through hole 21 on the polishing pad 2 is equal, the size of each groove body 22 is equal, and the size of the through hole 21 and the groove body 22 is also equal, but their distribution density is different, and the distribution of the outer circle through holes 21 and the groove body 22 is denser.

[0057] Embodiment 4

[0058] like Figure 8 As shown, a wafer polishing system includes a circumferentially rotatable polishing head 5, a rotating unit 6, a polishing pad 2 such as any of the above structures, and a polishing table 1 for supporting the polishing pad 2. The polishing table 1 drives the polishing pad 2 to rotate. In order to prevent the circuit from being entangled, the circuit passes through the rotating unit 6, the above-mentioned polishing head 5, the wafer 4, the polishing liquid 3 in the through hole 21 of the polishing pad 2, and the polishing table 1 to form an energized circuit, thereby realizing electrochemical polishing of the wafer 4.

[0059] The current of the power-on circuit flows to the polishing head 5, the back of the wafer 4, the front of the wafer 4, and the polishing liquid 3 in the through hole 21 of the polishing pad 2, that is, the current directly passes through the wafer 4. In this embodiment, the above-mentioned power-on circuit is used. Specifically, when polishing the silicon carbide wafer 4, the current enters the polishing head 5 from the rotating unit 6, and then flows in from the upper surface of the wafer 4. At this time, the through hole 21 and the groove body 22 of the polishing pad 2 are full of conductive polishing liquid 3, and the lower surface of the wafer 4 contacts the upper surface of the polishing pad 2. The current flows from the polishing liquid 3 on the polishing pad 2 into the polishing table 1, thereby forming a current path, so that the surface of the wafer 4 is electrolytically oxidized and softened, and the polishing head 5 and the polishing table 1 rotate separately to form friction, the direction is the same direction or the opposite direction, clockwise or counterclockwise, and the silicon carbide wafer 4 is polished under the action of the polishing liquid 3.

[0060] Alternatively, the current of the energized circuit flows to the polishing liquid 3 in the through hole 21 of the polishing pad 2 , the front side of the wafer 4 , the back side of the wafer 4 , and the polishing head 5 .

[0061] The above specific implementation modes are used to explain the present invention rather than to limit the present invention. Any modification and change 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 pad, laid on a polishing table, characterized in that: The polishing pad has a through hole running through its thickness direction and a groove body arranged on its upper surface. Polishing liquid is accumulated in the through hole and the groove body, and the total cross-sectional area of ​​the through hole and the groove body increases gradually from the inner circle of the polishing pad to the outer circle along the radial direction.

2. The polishing pad according to claim 1, characterized in that: The cross-sectional area of ​​the through-holes accounts for 15-30% of the upper surface area of ​​the polishing pad.

3. The polishing pad according to claim 1, characterized in that: The cross-sectional area of ​​the groove body accounts for 15-30% of the upper surface area of ​​the polishing pad.

4. The polishing pad according to claim 1, characterized in that: The cross-sectional area gradient of the through hole increases in the radial direction extending from the inner ring of the polishing pad to the outer ring.

5. The polishing pad according to claim 4, characterized in that: In the radial extension direction from the inner ring of the polishing pad to the outer ring, the total cross-sectional area of ​​the through holes is the same as the proportion of the upper surface area of ​​the polishing pad.

6. The polishing pad according to claim 1, characterized in that: The sizes of the individual through holes are equal; or, the sizes of the individual through holes gradually decrease from the outer circle to the inner circle of the polishing pad; or, the sizes of the individual through holes gradually increase from the outer circle to the inner circle of the polishing pad.

7. The polishing pad according to claim 1, characterized in that: The through holes extend in the circumferential direction to form an arc-shaped racetrack, and the circumferential through holes are arranged at intervals; the groove bodies extend in the circumferential direction to form an arc-shaped racetrack, and the circumferential groove bodies are arranged at intervals.

8. The polishing pad according to claim 7, characterized in that: The through holes include a plurality of through hole groups distributed along the radial direction, each through hole group includes a plurality of through holes arranged at intervals along the circumferential direction, and the plurality of through holes in the same radial direction of each through hole group are radially distributed; the slot bodies include a plurality of slot body groups distributed along the radial direction, each slot body group includes a plurality of slot bodies arranged at intervals along the circumferential direction; radially adjacent through hole groups and slot body groups are staggered, and the plurality of slot bodies in the same radial direction of each slot body group are radially distributed.

9. The polishing pad according to claim 8, characterized in that: Radially adjacent through holes and slot body ends have overlapping sections.

10. The polishing pad according to claim 8, characterized in that: The lengths of the through holes of the radially adjacent through hole groups decrease gradually from the outside to the inside; and the lengths of the slot bodies of the radially adjacent slot body groups decrease gradually from the outside to the inside.

11. The polishing pad according to claim 1, characterized in that: It has through hole areas and slot body areas alternately distributed along the circumferential direction, wherein the through hole area has a plurality of through holes arranged at intervals along the radial direction, and the cross-sectional area of ​​the through holes increases gradually from the inner circle to the outer circle; the slot body area has a plurality of slot bodies arranged at intervals along the radial direction, and the cross-sectional area of ​​the slot bodies increases gradually from the inner circle to the outer circle.

12. The polishing pad according to claim 11, characterized in that: The through hole area and the slot body area are evenly distributed.

13. A wafer polishing system, characterized in that: include: Polishing head, rotatable in circumferential direction; a rotating unit through which the circuit passes; The polishing pad according to any one of claims 1 to 12; A polishing table, used to support the polishing pad and drive the polishing pad to rotate; The polishing head, the wafer, the polishing liquid in the through hole of the polishing pad, and the polishing table form an electric circuit.

14. The wafer polishing system according to claim 13, characterized in that: The current of the power-on circuit flows to the polishing head, the back side of the wafer, the front side of the wafer, and the polishing liquid in the through-holes of the polishing pad; or, the current of the power-on circuit flows to the polishing liquid in the through-holes of the polishing pad, the front side of the wafer, the back side of the wafer, and the polishing head.

Images