Chemical mechanical polishing method for wafer

Abstract

The invention provides a chemical mechanical polishing method for a wafer, which comprises the following steps of: sleeving a retaining ring on the periphery of the wafer for fixing, and pressing on a polishing pad for polishing treatment; the surface, close to one side of the grinding pad, of the retaining ring is marked as a first surface, the surface, close to one side of the wafer, of the retaining ring is marked as a second surface, and the transition radius from the first surface to the second surface is 0 < = Rlt; and the thickness is 0.05 mm. The use stability of the retaining ring subjected to grinding treatment is guaranteed, the problem of residue remaining is solved, and the wafer edge grinding rate is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of wafer grinding and relates to a wafer chemical mechanical grinding method. Background Art

[0002] Chemical mechanical polishing is a technology that uses the synergistic effect of chemistry and mechanics to achieve ultra-precision polishing of the wafer surface. The wafer is usually fixed by a retaining ring on the polishing head, and the pressure is evenly distributed on the wafer surface. During the polishing process, the polishing uniformity of the wafer edge is often lower than that of the middle area of ​​the wafer, resulting in performance differences in the devices processed in the wafer edge area. Therefore, improving the polishing effect of the edge area of ​​chemical mechanical polishing is very important for improving the wafer yield.

[0003] CN117484381A discloses a wafer grinding device and a grinding process, comprising the following steps: S10, after a retaining ring is sleeved outside the wafer, the retaining ring is installed on the polishing head, and the position of the polishing head is adjusted so that the wafer is located at an eccentric position of the platform; S20, polishing liquid is injected onto the polishing pad; S30, the platform is started to rotate around its own axis, and the polishing head is started to rotate around its own axis; S40, the polishing liquid enters between the wafer and the polishing pad on the inner circle of the retaining ring from the liquid inlet groove, and then is discharged from the retaining ring from the liquid drain groove; S50, after the grinding is completed, the platform and the polishing head are stopped from rotating, and the injection of polishing liquid is stopped, and the retaining ring and the wafer are removed after the position of the polishing head is adjusted.

[0004] CN213731114U discloses a retaining ring for chemical mechanical grinding, wherein a circular chamfer with a radius R of 0.2-0.6 mm is arranged on the outer circle of the bottom surface of the retaining ring in contact with the grinding pad, and an inclined groove is arranged on the upper surface of the retaining ring.

[0005] CN107052984A discloses a method for optimizing the flatness of the edge area of ​​a wafer in a chemical mechanical flattening process, and the steps are: using a film thickness measuring instrument to measure the surface morphology of the wafer, calculating and comparing the average film thickness of the edge area and the center area; using a step-by-step flattening method that combines adjusting the pressure of the retaining ring and changing the speed difference between the polishing disk and the polishing head on the 1# polishing disk to perform global rough polishing; using a step-by-step flattening method that combines adjusting the pressure of the retaining ring and changing the speed difference between the polishing disk and the polishing head on the 2# polishing disk to perform fine polishing to improve the flatness of the edge area; using low-pressure plasma water on the 3# polishing disk to rinse the wafer surface. The improvement strategy for the edge area of ​​the wafer on the 1# and 2# polishing disks is: according to the film thickness of the wafer edge and the film thickness of the center, adjust the retaining ring pressure and change the speed difference between the polishing disk and the polishing head.

[0006] At present, the main way to improve the wafer edge grinding rate is to adjust the pressure of the retaining ring in chemical mechanical grinding. However, the space for adjusting the pressure parameters of the equipment is limited and there is an upper limit to the specification. When a large pressure is applied to the retaining ring and the wafer edge grinding rate is still very low, it is difficult to adjust the pressure. At the same time, when the pressure applied by the retaining ring is too large, it will accelerate the wear of the grinding pad and the retaining ring. In addition, the retaining ring used in the existing chemical mechanical grinding equipment still has the problem of copper residue in the early stage of use, and the edge is not ground cleanly, and the performance is unstable. It takes more wafer runs to return to normal. If the retaining ring continues to be pressurized, there will be a problem of over-grinding of the edge.

[0007] Therefore, how to ensure the stability of use in the initial stage of grinding and improve the grinding rate of the wafer edge is very important for improving the wafer processing yield. Summary of the invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a wafer chemical mechanical polishing method, which changes the interactive mechanical force between the wafer, the retaining ring and the polishing pad so that the deformation of the polishing pad in the edge area of ​​the wafer remains consistent, thereby solving the problem of poor stability of the retaining ring in the initial stage of use and the generation of residues.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] The present invention provides a wafer chemical mechanical polishing method, which comprises: a retaining ring is sleeved on the outer circumference of a wafer to fix it, and is pressed on a polishing pad to perform a polishing process; a surface of the retaining ring close to the polishing pad is recorded as a first surface, and a surface of the retaining ring close to the wafer is recorded as a second surface, and a transition radius from the first surface to the second surface is 0≤R<0.05mm.

[0011] The transition radius R from the first surface to the second surface may be 0, 0.001, 0.002, 0.004, 0.005, 0.008, 0.01, 0.012, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04 or 0.045, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0012] The present invention improves the mechanical force between the wafer, the retaining ring and the grinding pad in the transition area by improving the chamfer design of the retaining ring, so that the deformation of the grinding pad in the edge area of ​​the wafer remains consistent, avoiding the problem of unstable grinding rate at the edge of the wafer caused by residues in the initial stage of grinding, and ensuring the uniformity of wafer grinding.

[0013] As a preferred technical solution of the present invention, the first surface transitions to the second surface at a right angle.

[0014] The retaining ring of the present invention adopts a non-chamfered design, that is, the transition radius R from the first surface to the second surface is 0, and there is no need to change the grinding parameters, thereby ensuring stable performance in the initial stage of grinding and improving the wafer edge grinding rate.

[0015] As a preferred technical solution of the present invention, before fixing the wafer, the retaining ring is deburred to remove burrs on the first surface, the second surface, and the transition area between the first surface and the second surface.

[0016] As a preferred technical solution of the present invention, the deburring process includes: using dry ice to blow the retaining ring.

[0017] As a preferred technical solution of the present invention, the purging pressure is 0.25-0.55 MPa, for example, it can be 0.25 MPa, 0.28 MPa, 0.30 MPa, 0.32 MPa, 0.35 MPa, 0.40 MPa, 0.45 MPa, 0.48 MPa, 0.50 MPa, 0.52 MPa or 0.55 MPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] As a preferred technical solution of the present invention, the density of the dry ice is 0.4-0.7 g / cm 3 , for example, it can be 0.4 g / cm 3 , 0.43g / cm 3 , 0.45g / cm 3 , 0.5g / cm 3 , 0.52g / cm 3 , 0.55g / cm 3 , 0.6g / cm 3 、0.63g / cm 3 , 0.65g / cm 3 , 0.67g / cm 3 or 0.7g / cm 3 , but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] Preferably, the particle size of the dry ice is 1 to 3 mm, for example, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.6 mm, 2.8 mm or 3 mm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] As a preferred technical solution of the present invention, after the deburring treatment, the roughness of the first surface is less than 0.01 μm.

[0021] The roughness of the second surface is 0.6-0.7 μm, for example, it can be 0.6 μm, 0.61 μm, 0.62 μm, 0.63 μm, 0.64 μm, 0.65 μm, 0.66 μm, 0.67 μm, 0.68 μm, 0.69 μm or 0.7 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] The present invention adopts a retaining ring without chamfer design and optimizes the deburring process of the retaining ring to avoid residues caused by wear of the retaining ring chamfer, which affects the stability of wafer grinding and effectively improves the wafer edge grinding rate.

[0023] As a preferred technical solution of the present invention, the grinding treatment pressure is 5 to 6.2 psi, for example, it can be 5psi, 5.1psi, 5.2psi, 5.3psi, 5.4psi, 5.5psi, 5.6psi, 5.7psi, 5.8psi, 5.9psi, 6psi, 6.1psi or 6.2psi, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] It should be noted that the pressure of the grinding process described in the present invention refers to the pressure applied to the retaining ring.

[0025] As a preferred technical solution of the present invention, in the grinding process, the rotation speed of the wafer is 78-90rpm / min, for example, it can be 78rpm / min, 80rpm / min, 81rpm / min, 82rpm / min, 83rpm / min, 84rpm / min, 85rpm / min, 86rpm / min, 87rpm / min, 88rpm / min, 89rpm / min or 90rpm / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] The rotation speed of the polishing pad is 92-102 rpm / min, for example, it can be 92 rpm / min, 93 rpm / min, 94 rpm / min, 95 rpm / min, 96 rpm / min, 97 rpm / min, 98 rpm / min, 99 rpm / min, 100 rpm / min, 101 rpm / min or 102 rpm / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] The present invention optimizes the grinding process, which not only ensures the grinding rate of the wafer edge, but also alleviates the wear of the grinding pad and the retaining ring, prolongs the service life, and further reduces the production cost.

[0028] As a preferred technical solution of the present invention, the hardness of the retaining ring is 75-85SHD, for example, it can be 75SHD, 76SHD, 77SHD, 78SHD, 79SHD, 80SHD, 81SHD, 82SHD, 83SHD, 84SHD or 85SHD, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, the hardness of the polishing pad is 60-70 SHD, for example, it can be 60 SHD, 61 SHD, 62 SHD, 63 SHD, 64 SHD, 65 SHD, 66 SHD, 67 SHD, 68 SHD, 69 SHD or 70 SHD, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] The invention reduces wear during use by adjusting the hardness of the retaining ring and the grinding pad, thereby reducing deformation of the retaining ring, the grinding pad and the edge of the wafer during grinding, thereby ensuring grinding uniformity.

[0031] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The invention provides a wafer chemical mechanical polishing method, which is simple to operate, does not require changing polishing parameters, improves the stability in the initial stage of polishing, ensures the uniformity of wafer polishing, and solves the problem of residue retention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of a retaining ring, a grinding pad and a wafer edge during a grinding process provided in Example 1 of the present invention;

[0035] Figure 2 A schematic diagram of the transition between the first surface and the second surface of the retaining ring provided in Example 1 of the present invention;

[0036] Figure 3 This is a schematic diagram of the chamfering of the retaining ring provided in Comparative Example 1 of the present invention.

[0037] Among them, 10 is a retaining ring; 20 is a grinding pad; 30 is a wafer; 1 is a first surface; 2 is a second surface. DETAILED DESCRIPTION

[0038] It should be understood that in the description of the present invention, the terms "center", "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features.

[0039] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0040] The present invention provides a wafer chemical mechanical polishing method, comprising: setting a retaining ring on the outer circumference of the wafer to fix it, and pressing it on the grinding pad to perform a grinding process. Specifically, a chemical mechanical polishing device commonly used in the art is used for the grinding process. Among them, the chemical mechanical polishing device usually includes a grinding head and a polishing table well known to those skilled in the art, the retaining ring is arranged in the grinding head, the grinding pad is located on the polishing table, the grinding head is placed above the polishing table, so that the wafer contacts the grinding pad, and a certain pressure is applied to the wafer surface by using an adsorption film, and pressure is applied to the retaining ring. Through relative rotation, a certain amount of film thickness on the wafer surface is ground off, so as to achieve the purpose of flattening the wafer surface. The surface of the retaining ring close to the grinding pad is recorded as the first surface, and the surface of the retaining ring close to the wafer is recorded as the second surface. The transition radius from the first surface to the second surface is 0≤R<0.05mm.

[0041] Furthermore, the first surface transitions to the second surface at a right angle. Due to the mechanical force interacting between the wafer, the retaining ring and the grinding pad during the grinding process, the grinding pad will be deformed to a certain extent in the edge area of ​​the wafer, thereby affecting the grinding rate of this area. Traditionally, a C0.2mm chamfer is made on the inner side of the retaining ring before grinding. The C0.2mm chamfer there is inconsistent in size, resulting in differences in the interaction forces among the three, causing the initial wafer edge grinding rate to be unstable, and after a certain number of wafers have been ground, the chamfer is worn away, and it is also easy to cause residual problems. The present invention improves the design of the retaining ring, changes the chamfer design of the retaining ring itself, ensures the consistency of the deformation of the wafer edge, the retaining ring and the grinding pad during the grinding process, and does not need to change the parameter settings of the chemical mechanical grinding equipment to achieve the effect of improving the wafer edge grinding rate.

[0042] In some embodiments, before the wafer is fixed, the retaining ring is subjected to a deburring process to remove burrs on the first surface, the second surface, and a transition region between the first surface and the second surface.

[0043] Specifically, the deburring process is performed by using dry ice to blow the retaining ring.

[0044] The purge pressure is 0.25-0.55 MPa, and the density of dry ice is 0.4-0.7 g / cm 3 The particle size of the dry ice is 1-3 mm. After the deburring treatment, the roughness of the first surface is less than 0.01 μm, and the roughness of the second surface is 0.6-0.7 μm.

[0045] Due to the limitations of parameter adjustment of mechanical grinding equipment, when a retaining ring with a chamfer is used for grinding, as the chamfer is gradually worn away, the edge grinding rate will gradually become faster, resulting in poor performance stability of the retaining ring in the initial use. The present invention adopts a retaining ring without chamfer design and optimizes the deburring process of the retaining ring, which can well solve the problem of residue in the initial use, ensure stable performance, and improve the uniformity of wafer surface grinding.

[0046] In some embodiments, the pressure of the grinding process is 5-6.2 psi. The pressure in the present invention refers to the pressure applied by the chemical mechanical grinding equipment to the retaining ring.

[0047] Furthermore, during the grinding process, the rotation speed of the wafer is 78-90 rpm / min, and the rotation speed of the grinding pad is 92-102 rpm / min.

[0048] The poor uniformity of wafer grinding rate is mainly due to the uneven removal of thin film on the wafer surface, which is reflected in the low removal of wafer edge. By improving the wafer edge grinding rate, the margin at the wafer edge can be widened, the utilization rate of the wafer can be increased, and the yield rate can be improved. The present invention optimizes the pressure applied to the retaining ring and the rotation speed of the wafer and the grinding pad to avoid accelerated wear of the grinding pad and the retaining ring, shorten the service life, and at the same time ensure a high wafer edge grinding rate.

[0049] In some embodiments, the hardness of the retaining ring is 75-85 SHD. The hardness of the grinding pad is 60-70 SHD. During the grinding process, the edge of the wafer contacts the first surface of the retaining ring and the grinding pad respectively, and the grinding pad contacts the second surface of the retaining ring. By optimizing the hardness of the retaining ring and the grinding pad, the deformation of each component during the grinding process can be reduced, the interaction mechanical force can be enhanced, and the wafer edge grinding rate can be improved.

[0050] Example 1

[0051] The present embodiment provides a wafer chemical mechanical polishing method, comprising: sleeve-mounting a retaining ring 10 on the outer circumference of a wafer 30 to fix it, and pressing the retaining ring 10 on a polishing pad 20 to perform a polishing process.

[0052] like Figure 1 and Figure 2 As shown, the surface of the retaining ring 10 close to the grinding pad 20 is recorded as the first surface 1, and the surface of the retaining ring 10 close to the wafer 30 is recorded as the second surface 2. The transition radius from the first surface 1 to the second surface 2 is R=0.02 mm.

[0053] Before fixing the wafer 30, the retaining ring 10 is deburred by blowing dry ice to remove the burrs on the first surface 1, the second surface 2, and the transition area between the first surface 1 and the second surface 2. The blowing pressure is (0.45Mpa), and the density of dry ice is 0.6g / cm 3 The particle size of the dry ice is 2 mm. After deburring, the roughness of the first surface 1 is less than 0.01 μm, and the roughness of the second surface 2 is 0.6 μm.

[0054] During the polishing process, the polishing pressure was 5.8 psi, the rotation speed of the wafer 30 was 87 rpm / min, and the rotation speed of the polishing pad 20 was 93 rpm / min.

[0055] The hardness of the retaining ring 10 used in this embodiment is 79 SHD, and the hardness of the polishing pad 20 is 62 SHD.

[0056] Example 2

[0057] This embodiment provides a wafer chemical mechanical polishing method, including: setting a retaining ring on the outer circumference of the wafer to fix it, and pressing it on a polishing pad to perform a polishing process.

[0058] The surface of the retaining ring close to the grinding pad is recorded as the first surface, and the surface of the retaining ring close to the wafer is recorded as the second surface. The transition radius from the first surface to the second surface is R=0.005 mm.

[0059] Before the wafer is fixed, the retaining ring is deburred by blowing dry ice to remove the burrs on the first surface, the second surface, and the transition area between the first surface and the second surface. The blowing pressure is 0.55Mpa and the density of dry ice is 0.45g / cm 3 The particle size of the dry ice is 1 mm. After deburring, the roughness of the first surface is less than 0.01 μm, and the roughness of the second surface is 0.6 μm.

[0060] During the grinding process, the grinding pressure was 6.2 psi, the rotation speed of the wafer was 82 rpm / min, and the rotation speed of the grinding pad was 92 rpm / min.

[0061] The hardness of the retaining ring used in this embodiment is 82 SHD, and the hardness of the grinding pad is 68 SHD.

[0062] Example 3

[0063] This embodiment provides a wafer chemical mechanical polishing method, including: setting a retaining ring on the outer circumference of the wafer to fix it, and pressing it on a polishing pad to perform a polishing process.

[0064] The surface of the retaining ring close to the grinding pad is recorded as the first surface, and the surface of the retaining ring close to the wafer is recorded as the second surface. The transition radius from the first surface to the second surface is R=0.01 mm.

[0065] Before the wafer is fixed, the retaining ring is deburred by blowing dry ice to remove the burrs on the first surface, the second surface, and the transition area between the first surface and the second surface. The blowing pressure is 0.3Mpa and the density of dry ice is 0.5g / cm 3 The particle size of the dry ice is 1.5 mm. After deburring, the roughness of the first surface is less than 0.01 μm, and the roughness of the second surface is 0.7 μm.

[0066] During the grinding process, the grinding pressure was 5.5 psi, the rotation speed of the wafer was 84 rpm / min, and the rotation speed of the grinding pad was 95 rpm / min.

[0067] The hardness of the retaining ring used in this embodiment is 82 SHD, and the hardness of the grinding pad is 65 SHD.

[0068] Example 4

[0069] This embodiment provides a wafer chemical mechanical polishing method, including: setting a retaining ring on the outer circumference of the wafer to fix it, and pressing it on a polishing pad to perform a polishing process.

[0070] The surface of the retaining ring close to the grinding pad is recorded as the first surface, and the surface of the retaining ring close to the wafer is recorded as the second surface. The first surface and the second surface transition at a right angle, that is, the retaining ring adopts a non-chamfered design.

[0071] Before fixing the wafer, a dry ice purge holding ring is used to perform a deburring process to remove burrs on the first surface and the second surface. The purge pressure is 0.50 MPa, and the density of dry ice is 0.4 g / cm 3The particle size of the dry ice is 3 mm. After deburring, the roughness of the first surface is less than 0.01 μm, and the roughness of the second surface is 0.65 μm.

[0072] During the grinding process, the grinding pressure was 5 psi, the rotation speed of the wafer was 80 rpm / min, and the rotation speed of the grinding pad was 93 rpm / min.

[0073] The hardness of the retaining ring used in this embodiment is 78 SHD, and the hardness of the grinding pad is 62 SHD.

[0074] Example 5

[0075] This embodiment provides a wafer chemical mechanical polishing method, including: setting a retaining ring on the outer circumference of the wafer to fix it, and pressing it on a polishing pad to perform a polishing process.

[0076] The surface of the retaining ring close to the grinding pad is recorded as the first surface, and the surface of the retaining ring close to the wafer is recorded as the second surface. The first surface and the second surface transition at a right angle, that is, the retaining ring adopts a non-chamfered design.

[0077] Before fixing the wafer, a dry ice purge holding ring is used to perform a deburring process to remove burrs on the first surface and the second surface. The purge pressure is 0.52 Mpa, and the density of dry ice is 0.6 g / cm 3 The particle size of the dry ice is 2.5 mm. After deburring, the roughness of the first surface is less than 0.01 μm, and the roughness of the second surface is 0.7 μm.

[0078] In the grinding process, the grinding process pressure was 5.3 psi, the rotation speed of the wafer was 87 rpm / min, and the rotation speed of the grinding pad was 100 rpm / min.

[0079] The hardness of the retaining ring used in this embodiment is 79 SHD, and the hardness of the grinding pad is 65 SHD.

[0080] Example 6

[0081] This embodiment provides a wafer chemical mechanical polishing method, which is different from Example 1 in that the pressure of dry ice blowing is 0.2 MPa, and the remaining process steps and parameters are the same as those in Example 1.

[0082] Example 7

[0083] This embodiment provides a wafer chemical mechanical polishing method, which differs from Embodiment 1 in that the pressure of dry ice blowing is 0.7 MPa, and the remaining process steps and parameters are the same as those in Embodiment 1.

[0084] Example 8

[0085] This embodiment provides a wafer chemical mechanical polishing method, which is different from the embodiment 1 in that the density of dry ice is 0.3 g / cm 3 , the remaining process steps and parameters are the same as those in Example 1.

[0086] Example 9

[0087] This embodiment provides a wafer chemical mechanical polishing method, which is different from the embodiment 1 in that the density of dry ice is 0.9 g / cm 3 , the remaining process steps and parameters are the same as those in Example 1.

[0088] Example 10

[0089] This embodiment provides a wafer chemical mechanical polishing method, which differs from Embodiment 1 in that the polishing pressure is 4.6 psi, and the remaining process steps and parameters are the same as those in Embodiment 1.

[0090] Embodiment 11

[0091] This embodiment provides a wafer chemical mechanical polishing method, which differs from Embodiment 1 in that the polishing pressure is 6.5 psi, and the remaining process steps and parameters are the same as those in Embodiment 1.

[0092] Example 12

[0093] This embodiment provides a wafer chemical mechanical polishing method, which is different from Embodiment 1 in that the hardness of the retaining ring used is 74SHD, and the remaining process steps and parameters are the same as those of Embodiment 1.

[0094] Embodiment 13

[0095] This embodiment provides a wafer chemical mechanical polishing method, which is different from Embodiment 1 in that the hardness of the retaining ring used is 92SHD, and the remaining process steps and parameters are the same as those of Embodiment 1.

[0096] Embodiment 14

[0097] This embodiment provides a wafer chemical mechanical polishing method, which differs from Embodiment 1 in that the retaining ring is not deburred, and the remaining process steps and parameters are the same as those in Embodiment 1.

[0098] The present invention adopts the methods provided in Examples 1 to 14 to grind wafers with a diameter of 75 mm, and detects the edge grinding rate of the wafer and the relative standard deviation between the center and the edge of the wafer. The results are shown in Table 1.

[0099] Table 1

[0100]

[0101]

[0102] As can be seen from Table 1, the wafers were ground using the methods provided in Examples 1 to 5, and a higher wafer edge grinding rate was obtained, and the wafer surface uniformity was good, and the product qualified rate was high. Compared with Example 1, the edge grinding rate and uniformity of the wafer in Example 6 were both deteriorated. This was mainly due to the fact that the purge pressure in Example 6 was too low, resulting in poor deburring effect. When the retaining ring was in contact with the wafer, the wafer edge was scratched, affecting the grinding effect. The difference between Example 1 and Example 7 in the grinding effect of the wafer was not large, but Example 7 used too high a purge pressure, which caused waste and increased production costs. The edge grinding rate and uniformity of the wafers in Examples 8 and 9 were slightly lower than those in Example 1. This was caused by the different dry ice densities used. When the dry ice density was too large or too small, the burr removal effect of the retaining ring would be reduced, thereby affecting the grinding effect of the wafer. The edge grinding rate of the wafer in Example 10 was lower than that in Example 1. This was because the pressure applied to the retaining ring during the grinding process was too low, resulting in a low amount of removal from the edge of the wafer. The wafer edge grinding rate in Example 11 is still lower than that in Example 1. This is because the pressure applied to the holding ring is too high, which accelerates the wear of the holding ring, reduces the force between the wafer edge, the grinding pad and the holding ring, and causes the grinding effect to deteriorate. Compared with Example 1, the grinding effects on the wafer in Examples 12 and 13 are both reduced. This is mainly because the hardness difference of the holding ring brings about the difference in grinding efficiency. When the hardness of the holding ring is too large or too small, it will affect the mechanical force between it and the wafer edge and the grinding pad, resulting in inconsistent deformation and reduced grinding effect. By comparing Example 1 with Example 14, it can be seen that the burrs in the transition area between the first surface and the second surface of the holding ring will not only scratch the edge of the wafer during the grinding process, but also accelerate the wear of the holding ring during the grinding process, thereby affecting the overall wafer grinding efficiency.

[0103] Comparative Example 1

[0104] This comparative example provides a wafer chemical mechanical polishing method, which is different from Example 1 in that: Figure 3 As shown, the transition from the first surface to the second surface is a C0.2mm chamfer, and the remaining process steps and parameters are the same as those in Example 1.

[0105] The present invention adopts the method of Example 1 and Comparative Example 1 to grind the same batch of wafers, and observe the grinding process. In the early stage of grinding of Comparative Example 1, there are residues at the grinding head, and it is necessary to run 100 pieces of wafers before it can return to normal and no residues will appear. This is because the retaining ring used in Comparative Example 1 has a chamfer. After the chamfer contacts the wafer and the grinding pad in the early stage of use, it wears off and forms residues. The transition radius of the retaining ring used in Example 1 is very small, and it will not affect the mechanical force between it and the edge of the wafer and the grinding pad even in the early stage of use, and it also reduces the wear of the retaining ring to avoid the formation of residues.

[0106] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A wafer chemical mechanical polishing method, characterized in that: The wafer chemical mechanical polishing method comprises: setting a retaining ring sleeve on the outer periphery of the wafer to fix it, and pressing it on the polishing pad to perform polishing; The surface of the retaining ring close to the grinding pad is recorded as the first surface, and the surface of the retaining ring close to the wafer is recorded as the second surface. The transition radius from the first surface to the second surface is 0≤R<0.05mm.

2. The wafer chemical mechanical polishing method according to claim 1, characterized in that: The first surface transitions to the second surface at a right angle.

3. The wafer chemical mechanical polishing method according to claim 1 or 2, characterized in that: Before fixing the wafer, the retaining ring is deburred to remove burrs on the first surface, the second surface, and the transition area between the first surface and the second surface.

4. The wafer chemical mechanical polishing method according to claim 3, characterized in that: The deburring process includes: using dry ice to blow the retaining ring.

5. The wafer chemical mechanical polishing method according to claim 4, characterized in that: The purging pressure is 0.25-0.55 MPa.

6. The wafer chemical mechanical polishing method according to claim 4 or 5, characterized in that: The density of the dry ice is 0.4-0.7 g / cm 3 ; Preferably, the particle size of the dry ice is 1 to 3 mm.

7. The wafer chemical mechanical polishing method according to claim 4, characterized in that: After the deburring treatment, the roughness of the first surface is less than 0.01 μm, and the roughness of the second surface is 0.6-0.7 μm.

8. The wafer chemical mechanical polishing method according to claim 1, characterized in that: The grinding process has a pressure of 5 to 6.2 psi.

9. The wafer chemical mechanical polishing method according to claim 1, characterized in that: During the grinding process, the rotation speed of the wafer is 78-90 rpm / min, and the rotation speed of the grinding pad is 92-102 rpm / min.

10. The wafer chemical mechanical polishing method according to claim 1, characterized in that: The hardness of the retaining ring is 75-85 SHD; Preferably, the hardness of the polishing pad is 60-70 SHD.

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