Wafer peripheral polishing device

Abstract

The polishing device (1) for the outer periphery of a wafer of the present invention comprises: a worktable (11) for holding a disk-shaped wafer (31) horizontally; a rotation drive unit (12) for rotating the worktable (11) with its central axis as the rotation axis; a polishing head (13, 14, 15 and 16) having a polishing pad (21, 22, 23, 24, 25, 26, 27 and 28) mounted on the inner periphery; and a polishing head drive mechanism (30) for making the polishing pad (21-28) contact the outer periphery (41) of the wafer (31) and applying a predetermined polishing pressure to the outer periphery (41) of the wafer (31) while sliding the polishing head (13-16) in a direction inclined or vertical to the central axis of the wafer (31). Two or more polishing pads (21-28) having different physical parameters are mounted on the inner periphery of the polishing head (13-16) in the vertical direction.

Description

Technical Field

[0001] The present invention relates to a polishing device for polishing the outer periphery of a rotating disk-shaped wafer by bringing a polishing pad into contact with the outer periphery of the wafer. Background Art

[0002] Generally, a disc-shaped wafer such as a semiconductor wafer is mirror-polished on its upper and lower surfaces as well as its outer periphery. Figure 4 As shown, the outer peripheral portion of the wafer is formed in a trapezoidal or arc shape at the outer edge of the disk-shaped wafer 31. The outer peripheral portion 41 of the wafer 31 is also called a chamfered portion or an edge portion.

[0003] Figure 4 The outer peripheral portion 41 of the wafer 31 shown is trapezoidal and is composed of an upper slope 51, a lower slope 52, and an end surface 53. In the outer edge of the wafer 31, the upper slope 51 is formed to be inclined toward the lower surface 31B relative to the upper surface 31A of the wafer 31.

[0004] At the outer edge of the wafer 31, a lower slope 52 is formed to be inclined toward the upper surface 31A side relative to the lower surface 31B of the wafer 31. An end surface 53 is formed between the upper slope 51 and the lower slope 52 in a direction parallel to the central axis of the wafer 31. The grinding of the outer peripheral portion 41 refers to grinding the upper slope 51, the lower slope 52, and the end surface 53.

[0005] Among conventional wafer peripheral polishing devices, there is a wafer peripheral polishing device that includes: a wafer holding mechanism that holds a wafer; a wafer rotating mechanism that rotates the held wafer; a polishing head that has a polishing surface on which a polishing pad is mounted; and a polishing liquid impregnation mechanism that impregnates the polishing pad with a polishing liquid (slurry). In the wafer peripheral polishing device, the polishing pad mounted on the polishing head and impregnated with slurry is arranged to be in relative contact with the wafer peripheral portion (for example, refer to Patent Document 1).

[0006] In addition, among the conventional wafer peripheral polishing devices, there is a wafer peripheral polishing device as follows: it includes: a chuck mechanism that clamps the wafer and rotates it with the wafer center axis as the rotation axis; a pair of upper bevel polishing members that polish the upper bevel of the wafer; a lower bevel polishing member that polishes the lower bevel of the wafer; and an end face polishing member that polishes the end face of the wafer. The pair of upper bevel polishing members are arranged at opposing positions with the chuck mechanism clamped, the lower bevel polishing member is arranged between the pair of upper bevel polishing members to face the chuck mechanism, and the end face polishing member is arranged between the pair of upper bevel polishing members to face the chuck mechanism. In addition, the wafer peripheral polishing device includes a load mechanism that applies polishing pressure toward the upper bevel, lower bevel, and end face of the wafer to each polishing member (for example, refer to Patent Document 2).

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2015-207658

[0010] Patent document 2: Japanese Patent Application Publication No. 2003-257901. Summary of the invention

[0011] Technical problem to be solved by the invention

[0012] The outer periphery of the wafer is polished using a polishing pad to adjust the outer periphery of the wafer to a predetermined surface roughness Ra. The surface roughness Ra of the outer periphery of the wafer varies depending on the hardness and compression rate of the polishing pad used. The surface roughness Ra of the outer periphery of the wafer, for example, becomes smaller when a polishing pad with a low hardness is used, and also becomes smaller when a polishing pad with a high compression rate is used.

[0013] Generally, when polishing the upper and lower surfaces of a wafer, a polishing pad having high hardness (hardness) is used in a polishing apparatus for rough polishing, and a polishing pad having low hardness (softness) is used in a polishing apparatus for fine polishing.

[0014] When grinding the periphery of a wafer, for example, when using a soft grinding pad, sometimes the grinding pad not only grinds the periphery of the wafer to be ground, but also grinds the surface side (upper surface side, lower surface side) of the wafer. When over-polishing occurs, the flatness of the upper and lower surfaces of the wafer deteriorates due to defects such as edge roll off where the thickness of the periphery of the wafer becomes thinner. In addition, when using a soft grinding pad, the productivity is poor due to the slow grinding speed, but the surface roughness Ra can be reduced.

[0015] On the other hand, when grinding the periphery of the wafer, when using a hard grinding pad, the grinding speed is fast, so the productivity is excellent, and the grinding pad can be suppressed from wrapping around the surface side of the wafer, which can reduce the occurrence of over-polishing. However, when using a hard grinding pad, the surface of the periphery of the wafer has a larger surface roughness Ra than when using a soft grinding pad.

[0016] In this regard, when using a grinding device for rough grinding and fine grinding, after using a hard grinding pad for rough grinding, the hard grinding pad is removed from the grinding head, and a soft grinding pad is installed on the grinding head to perform fine grinding. However, the operation of replacing the grinding pad is required, resulting in a decrease in productivity.

[0017] In addition, it is considered to separately set up a grinding device dedicated to rough grinding and a grinding device dedicated to fine grinding. However, in this case, since a wafer conveying mechanism is required for transferring wafers between the two devices, the manufacturing cost is consumed, the operating efficiency (cycle time) is reduced, and the productivity is also reduced.

[0018] The present invention takes solving the above-mentioned various problems as an example of a subject, and an object of the present invention is to provide a polishing device for the outer periphery of a wafer that can solve these problems.

[0019] Solutions for solving technical problems

[0020] The grinding device for the outer periphery of a wafer of the present invention is characterized in that it includes: a disc-shaped worktable for keeping the disc-shaped wafer horizontal; a rotation drive unit for rotating the worktable with its central axis as the rotation axis; one or more grinding heads with a grinding pad installed on the inner peripheral surface; and a grinding head driving mechanism for making the grinding pad abut against the outer periphery of the wafer, applying a specified grinding pressure to the outer periphery of the wafer, and sliding the grinding head in a direction inclined or vertical to the central axis of the wafer, wherein two or more grinding pads having different physical parameters are installed on the inner peripheral surface of the grinding head along the vertical direction of the grinding head.

[0021] The wafer outer periphery polishing device of the present invention is characterized in that the polishing head driving mechanism slides the polishing head within the polishing pad having the same physical parameters in one polishing step.

[0022] The wafer outer periphery polishing device of the present invention is characterized in that the inner peripheral surface of the polishing head can approach and move away from the outer periphery of the wafer and is in an arc shape along the circumferential direction of the outer periphery.

[0023] The grinding device for the outer periphery of a wafer of the present invention is characterized in that the grinding heads include: a first grinding head for grinding a lower inclined surface constituting the outer periphery of the wafer; a second grinding head for grinding an upper inclined surface constituting the outer periphery of the wafer; and a third and a fourth grinding head for grinding end surfaces constituting the outer periphery of the wafer, wherein the grinding head driving mechanism causes the first to fourth grinding heads to abut against the outer periphery of the wafer, applies a prescribed grinding pressure to the outer periphery of the wafer, and simultaneously slides the first grinding head in a direction along the lower inclined surface, the second grinding head in a direction along the upper inclined surface, and the third and fourth grinding heads in a vertical direction of the wafer.

[0024] The grinding device for the outer periphery of a wafer of the present invention is characterized in that the grinding pad is composed of a grinding pad installed on the upper part of the inner peripheral surface and a grinding pad installed on the lower part of the inner peripheral surface, and the compression rate of the grinding pad installed on the lower part of the inner peripheral surface is greater than the compression rate of the grinding pad installed on the upper part of the inner peripheral surface.

[0025] The grinding device for the outer periphery of a wafer of the present invention is characterized in that the grinding pad is composed of a grinding pad installed on the upper part of the inner peripheral surface and a grinding pad installed on the lower part of the inner peripheral surface, and the hardness of the grinding pad installed on the lower part of the inner peripheral surface is lower than the hardness of the grinding pad installed on the upper part of the inner peripheral surface.

[0026] The grinding device for the outer periphery of a wafer of the present invention is characterized in that the length in the vertical direction of the grinding pad installed on the upper part of the inner peripheral surface or the length along the inclined surface of the inner peripheral surface of the grinding head is longer than the length in the vertical direction of the grinding pad installed on the lower part of the inner peripheral surface or the length along the inclined surface of the inner peripheral surface of the grinding head.

[0027] According to the present invention, the roughness of the surface of the outer peripheral portion of the wafer can be improved while suppressing the occurrence of over-polishing without reducing the operating efficiency (cycle time). BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a conceptual diagram showing an example of the structure of a wafer outer peripheral portion polishing device according to one embodiment of the present invention.

[0029] Figure 2 yes Figure 1 A-A' cross-sectional view.

[0030] Figure 3 yes Figure 1 B-B' cross-sectional view.

[0031] Figure 4 This is a partial cross-sectional view showing an example of the shape of the outer peripheral portion of the wafer. DETAILED DESCRIPTION

[0032] Hereinafter, a mode for carrying out the present invention will be described with reference to the drawings.

[0033] [Structure of the polishing device for the outer periphery of the wafer]

[0034] Figure 1 1 is a conceptual diagram showing an example of the structure of a wafer peripheral portion polishing device 1 according to an embodiment of the present invention. Figure 2 yes Figure 1 A-A' section view, Figure 3 yes Figure 1 B-B' cross-sectional view.

[0035] The polishing device 1 for polishing the outer periphery of a wafer includes a table 11, a rotation drive unit 12, polishing heads 13, 14, 15 and 16, first polishing pads 21, 22, 23 and 24, second polishing pads 25, 26, 27 and 28, a nozzle 29 and a polishing head driving mechanism 30. Figure 1 In the figure, the table 11, the rotation drive unit 12, the second polishing pads 27 and 28, the nozzle 29, and the polishing head drive mechanism 30 are not shown.

[0036] Figure 2 and Figure 3 The workbench 11 shown is roughly disk-shaped. The workbench 11 holds the wafer 31 horizontally by vacuum adsorbing the lower surface 31B of the wafer 31 or by electrostatically adhering the lower surface 31B of the wafer 31. The diameter of the workbench 11 is not particularly limited, but can be set to about 280±10mm when grinding the outer peripheral portion 41 of the wafer 31 with a diameter of 300mm, and can be set to about 430±10mm when grinding the outer peripheral portion 41 of the wafer 31 with a diameter of 450mm. The rotation drive unit 12 is mounted on the lower part of the center portion of the workbench 11 to rotate the workbench 11 with its center axis as the rotation axis.

[0037] The grinding head 13 can approach and move away from the outer peripheral portion 41 of the wafer 31, and has an inner peripheral surface in an arc shape along the circumferential direction of the outer peripheral portion 41. The first grinding pad 21 is installed on the upper part of the inner peripheral surface, and the second grinding pad 25 is installed on the lower part of the inner peripheral surface to grind the lower inclined surface 52 (refer to Figure 4 ).

[0038] The grinding head 14 can approach and move away from the outer peripheral portion 41 of the wafer 31, and has an inner peripheral surface in an arc shape along the circumferential direction of the outer peripheral portion 41. The first grinding pad 22 is installed on the upper part of the inner peripheral surface, and the second grinding pad 26 is installed on the lower part of the inner peripheral surface. The upper inclined surface 51 (refer to Figure 4 ).

[0039] The grinding head 15 can approach and move away from the outer peripheral portion 41 of the wafer 31, and has an inner peripheral surface in an arc shape along the circumferential direction of the outer peripheral portion 41. A first grinding pad 23 is installed on the upper part of the inner peripheral surface, and a second grinding pad 27 is installed on the lower part of the inner peripheral surface. The end surface 53 (refer to Figure 4 ).

[0040] The grinding head 16 can approach and move away from the outer peripheral portion 41 of the wafer 31, and has an inner peripheral surface in an arc shape along the circumferential direction of the outer peripheral portion 41. A first grinding pad 24 is mounted on the upper part of the inner peripheral surface, and a second grinding pad 28 is mounted on the lower part of the inner peripheral surface. The end surface 53 (refer to Figure 4 ).

[0041] The polishing heads 13 , 14 , 15 , and 16 are arranged along the outer peripheral portion 41 in order to maximize the contact area with the outer peripheral portion 41 of the wafer 31 .

[0042] When the first polishing pads 21 , 22 , 23 , and 24 and the second polishing pads 25 , 26 , 27 , and 28 are collectively referred to as polishing pads in short.

[0043] The types of polishing pads include, for example, non-woven fabrics, foamed polyurethanes, and suede. For example, non-woven fabrics are obtained by impregnating polyurethane resin in polyester felt. For example, suede is obtained by growing a foamed layer in a base material of polyurethane impregnated in polyester felt, removing the surface portion, and providing an opening in the foamed layer (this layer is called a velvet layer). The polishing liquid is stored in the velvet layer.

[0044] The physical parameters of the polishing pad include hardness, compressibility, thickness, etc. The so-called compressibility refers to the ratio of shrinkage when a constant load is applied to a molded body of a predetermined shape. The main measurement methods for the hardness of the polishing pad are (1) and (2) shown below, and the main measurement method for the compressibility is (3) shown below.

[0045] (1) Hardness (JIS)

[0046] Hardness (JIS) is measured according to the Type A hardness test based on Japanese Industrial Standards (JIS K7312-1996).

[0047] (2) Hardness (ASKER)

[0048] The hardness was measured with an Asker C hardness tester (Asker).

[0049] (3) Compression ratio (JIS)

[0050] The compression rate (JIS) is measured in accordance with Japanese Industrial Standards (JIS L 1021) using a shopper-type thickness gauge (pressing surface: circular with a diameter of 1 cm). Specifically, the thickness t0 is measured after 30 seconds of pressure application with the initial load, and then the thickness t1 is measured after 5 minutes of placement under the final pressure. The compression rate is calculated using these measurement data according to formula (1). At this time, the initial load is 100 g / cm 2 , the final load is 1120g / cm 2 .

[0051] Compression ratio (%) = (t0-t1) / t0×100…(1)

[0052] Table 1 shows specific examples of the polishing pad.

[0053] [Table 1]

[0054] type hardness Compression Non-woven fabrics 50~92(ASKER) 3.5～11 Polyurethane foam 80~88(JIS) 1.4～3.4 Suede 50~80(JIS) 8.5～40

[0055] In this embodiment, one polishing device is used to perform rough polishing to finish polishing of the outer peripheral portion 41 of the wafer 31. The first polishing pads 21, 22, 23, and 24 use polishing pads having the same physical parameters. In addition, the second polishing pads 25, 26, 27, and 28 use polishing pads having the same physical parameters.

[0056] On the other hand, the first polishing pad 21 and the second polishing pad 25 use polishing pads having different physical parameters. Similarly, the first polishing pad 22 and the second polishing pad 26, the first polishing pad 23 and the second polishing pad 27, and the first polishing pad 24 and the second polishing pad 28 use polishing pads having different physical parameters.

[0057] Regarding the combination of the first polishing pads 21, 22, 23 and 24 and the corresponding second polishing pads 25, 26, 27 and 28, they can be selected from polishing pads having the physical parameters shown in Table 1 according to the user's required specifications for the surface roughness Ra of the outer peripheral portion 41 of the chip 31 after polishing.

[0058] When hardness is used as a reference, the first polishing pads 21, 22, 23, and 24 are selected to have a higher hardness than the second polishing pads 25, 26, 27, and 28. Moreover, when compressibility is used as a reference, the first polishing pads 21, 22, 23, and 24 are selected to have a lower compressibility than the second polishing pads 25, 26, 27, and 28. The combination of the first polishing pads 21, 22, 23, and 24 and the second polishing pads 25, 26, 27, and 28 may be selected from the same type of polishing pads but with different physical parameters.

[0059] The reasons for adopting the above-mentioned polishing pad mounting method are described below: A polishing pad having low hardness or high compressibility is easily deteriorated, and thus, during polishing of the outer peripheral portion 41 of the wafer 31 , separation debris is easily generated from the polishing pad body.

[0060] Therefore, when a grinding pad with low hardness or high compression rate is installed on the upper part of the inner peripheral surface of the grinding heads 13, 14, 15 and 16, when grinding the peripheral portion 41 of the next chip 31, the above-mentioned separation chips may become one of the reasons for deteriorating the grinding accuracy of the peripheral portion 41 of the chip 31.

[0061] In this regard, when a polishing pad having high hardness or low compression rate is installed on the upper part of the inner peripheral surface of the polishing heads 13 , 14 , 15 and 16 , during the polishing of the outer peripheral portion 41 of the wafer 31 , polishing chips are separated from the outer peripheral portion 41 of the wafer 31 itself.

[0062] However, during the grinding of the outer peripheral portion 41 of the chip 31, most of the aforementioned grinding chips are removed by the grinding liquid that is constantly supplied from above the chip 31, and the remaining aforementioned grinding chips are fine and made of the same material as the chip 31. Therefore, it is considered that the influence of the aforementioned grinding chips during the grinding of the outer peripheral portion 41 of the chip 31 can be ignored.

[0063] On the other hand, the above-mentioned separation debris of the polishing pad having low hardness or high compressibility is made of a material different from that of the wafer 31 , and therefore it is considered that it has a greater influence on the polishing of the outer peripheral portion 41 of the wafer 31 than the above-mentioned polishing debris.

[0064] Next, the dimensions of the first polishing pads 21, 22, 23, and 24 and the second polishing pads 25, 26, 27, and 28 are described. The length of the first polishing pads 23 and 24 for polishing the end surface 53 is preferably set within a range of 60% to 90% of the length of the inner circumference of the corresponding polishing heads 15 and 16 in the vertical direction. The length of the first polishing pad 21 for polishing the lower inclined surface 52 and the length of the first polishing pad 22 for polishing the upper inclined surface 51 are preferably set within a range of 60% to 90% of the inclined surface length of the inner circumference of the corresponding polishing heads 13 and 14.

[0065] Here, the length of the first polishing pads 23, 24 and the second polishing pads 27, 28 refers to the length in the vertical direction. On the other hand, the length of the first polishing pads 21, 22 and the second polishing pads 25, 26 refers to the length of the inclined surface along the inner peripheral surface of the corresponding polishing heads 13, 14.

[0066] The lower limit of the aforementioned length range considers the first polishing workload, and the upper limit of the aforementioned length range is used to consider the second polishing workload in order to extend the life of a polishing pad having high hardness or low compressibility.

[0067] The length of the second polishing pads 27 and 28 for polishing the end surface 53 is preferably set within a range of 40% to 10% of the length in the vertical direction of the inner circumference of the corresponding polishing heads 15 and 16. The length of the second polishing pad 25 for polishing the lower inclined surface 52 and the second polishing pad 26 for polishing the upper inclined surface 51 are preferably set within a range of 40% to 10% of the length of the inclined surface of the inner circumference of the corresponding polishing heads 13 and 14. The lower limit of the aforementioned length range is used to consider the workload of the second polishing, and the upper limit of the aforementioned length range is used to consider the workload balance between the first polishing and the second polishing.

[0068] like Figure 2 and Figure 3As shown, a nozzle 29 for supplying abrasive liquid (slurry) to the approximate center of the wafer 31 is provided above the substantially central portion of the worktable 11. As the worktable 11 on which the wafer 31 is mounted is rotated by the rotation drive unit 12 with its central axis as the rotation axis, the abrasive liquid supplied from the nozzle 29 flows toward the outer peripheral portion 41 on the upper surface 31A of the wafer 31 due to centrifugal force, and is thus supplied to the outer peripheral portion 41 of the wafer 31 to be polished.

[0069] When the first polishing pads 21, 22, 23, and 24 are used, an alkaline aqueous solution containing abrasive grains is preferably used as the polishing liquid. Among them, it is particularly preferred to use colloidal silica (SiO2) with an average particle size of 50 nm as the abrasive grains and to use a potassium hydroxide (KOH) aqueous solution with a pH of about 10 to 11 as the alkaline aqueous solution.

[0070] On the other hand, when the second polishing pads 25, 26, 27, and 28 are used, an alkaline aqueous solution containing no abrasive is preferably used as the polishing liquid. Among them, a potassium hydroxide (KOH) aqueous solution with a pH of about 10 to 11 is particularly preferably used as the alkaline aqueous solution. In addition, a polymer is preferably added to the polishing liquid.

[0071] Figure 2 and Figure 3 The grinding head driving mechanism 30 shown in the figure moves the grinding heads 13, 14, 15 and 16 horizontally in the direction toward the central axis of the worktable 11 and in the direction away from the central axis of the worktable 11, and also moves the grinding heads 13, 14, 15 and 16 vertically up and down. When grinding the upper inclined surface 51 and the lower inclined surface 52 constituting the outer peripheral portion 41 of the wafer 31, the grinding head driving mechanism 30 causes the grinding heads 13 and 14 to move horizontally and vertically in a linked manner so that the upper inclined surface 51 and the lower inclined surface 52 form a desired angle with the upper surface 31A and the lower surface 31B of the wafer 31 (see FIG. 1 ). Figure 2 slanted arrow).

[0072] The polishing head driving mechanism 30 is composed of a sliding member that can freely move in the vertical and horizontal directions, a ball screw that drives these, and other linear driving mechanisms. The linear driving mechanism can control the driving amount using a stepping motor or the like.

[0073] The above-mentioned grinding head driving mechanism 30 causes the grinding heads 13, 14, 15 and 16 to move horizontally in the direction toward the central axis of the worktable 11 at the same time, so that the first grinding pads 21, 22, 23 and 24 or the second grinding pads 25, 26, 27 and 28 abut against the outer periphery 41 of the wafer 31 held on the rotating worktable 11, and applies a predetermined grinding pressure to the outer periphery 41 of the wafer 31 while sliding in a direction inclined or vertical to the central axis of the wafer 31 to grind the outer periphery 41 of the wafer 31.

[0074] [Wafer periphery polishing method]

[0075] Next, an example of a method for polishing the outer periphery of a wafer using the wafer outer periphery polishing apparatus 1 having the above-described structure will be described. First, the table 11 is made to hold the lower surface 31B of the wafer 31 horizontally.

[0076] Next, while polishing liquid is supplied from the nozzle 29 to the approximate center of the wafer 31, the rotation drive unit 12 rotates the worktable 11 and the wafer 31 at a specified rotation speed (for example, 10 rpm), and the polishing head drive mechanism 30 causes the first polishing pads 21, 22, 23 and 24 of the polishing heads 13, 14, 15 and 16 to simultaneously abut against corresponding positions of the outer peripheral portion 41 of the wafer 31 with a specified processing load, thereby performing the first polishing process on the outer peripheral portion 41 of the wafer 31.

[0077] At this time, the polishing head driving mechanism 30 slides the polishing heads 13, 14, 15, and 16 in the length direction of each polishing pad 21, 22 along the inner circumferential surface inclined surface and the length of the first polishing pad 23, 24 in the vertical direction. In other words, the polishing head driving mechanism 30 slides the polishing heads 13, 14, 15, and 16 in the first polishing pads 21, 22, 23, and 24 having the same physical parameters during the first polishing. In this way, the life of the first polishing pads 21, 22, 23, and 24 can be extended.

[0078] The processing time of the first grinding is, for example, about 40 to 50 seconds. Furthermore, the number of sliding movements of the grinding heads 13, 14, 15, and 16 is, for example, 2 to 3 times.

[0079] Thus, the first polishing pad 21 polishes the lower inclined surface 52 of the outer peripheral portion 41 of the wafer 31 , the first polishing pad 22 polishes the upper inclined surface 51 of the outer peripheral portion 41 , and the first polishing pads 23 and 24 polish the end surface 53 of the outer peripheral portion 41 .

[0080] Next, while polishing liquid is supplied from the nozzle 29 to the approximate center of the wafer 31, the rotation drive unit 12 rotates the worktable 11 and the wafer 31 at a specified rotation speed (for example, 10 rpm), and the polishing head drive mechanism 30 causes the second polishing pads 25, 26, 27 and 28 of the polishing heads 13, 14, 15 and 16 to simultaneously abut against corresponding positions of the outer peripheral portion 41 of the wafer 31 with a specified processing load, thereby performing the second polishing process on the outer peripheral portion 41 of the wafer 31.

[0081] At this time, the polishing head driving mechanism 30 slides the polishing heads 13, 14, 15, and 16 in the length direction of each of the second polishing pads 25 and 26 along the inner circumferential surface inclined surface and the length of the second polishing pads 27 and 28 in the vertical direction. In other words, the polishing head driving mechanism 30 slides the polishing heads 13, 14, 15, and 16 in the second polishing pads 25, 26, 27, and 28 having the same physical parameters during the second polishing. In this way, the life of the second polishing pads 25, 26, 27, and 28 can be extended.

[0082] The processing time of the second grinding is, for example, about 5 to 10 seconds. Also, the number of sliding movements of the grinding heads 13, 14, 15, and 16 is, for example, 1 to 2 times.

[0083] Thus, the second polishing pad 25 polishes the lower inclined surface 52 of the outer peripheral portion 41 of the wafer 31 , the second polishing pad 26 polishes the upper inclined surface 51 of the outer peripheral portion 41 , and the second polishing pads 27 and 28 polish the end surface 53 of the outer peripheral portion 41 .

[0084] [Effects of this embodiment]

[0085] As described above, in the above-mentioned embodiment, the following effects can be achieved.

[0086] 1) In the first polishing, polishing pads having high hardness or low compressibility are used as the first polishing pads 21 , 22 , 23 , and 24 , so that the polishing pads 21 , 22 , 23 , and 24 can be reduced from sinking into the wafer 31 during the first polishing.

[0087] Therefore, it is possible to prevent the first polishing pads 21, 22, 23, and 24 from wrapping around the upper surface 31A side or the lower surface 31B side of the wafer 31. As a result, in the first polishing, the occurrence of over-polishing can be reduced, and damage and indentations generated in the previous process can be removed. In addition, since the polishing speed is high, the productivity is excellent.

[0088] 2) In the second polishing, immediately after the first polishing is completed, the outer peripheral portion 41 of the wafer 31 is polished by the second polishing pads 25, 26, 27, and 28 attached to the lower portion of the inner peripheral surface of the polishing heads 13, 14, 15, and 16. That is, in the present embodiment, it is not necessary to remove the first polishing pads 21, 22, 23, and 24 from the polishing heads 13, 14, 15, and 16, attach the second polishing pads 25, 26, 27, and 28 to the polishing heads 13, 14, 15, and 16, or to transport the wafer after the first polishing is completed to the polishing device dedicated to the second polishing by the wafer transport mechanism. Therefore, the manufacturing cost can be reduced, and the productivity is improved because the operation efficiency (cycle time) is improved.

[0089] 3) In the present embodiment, the processing time of the first grinding is about 40 to 50 seconds, and the processing time of the second grinding is about 5 to 10 seconds. The surface roughness Ra of the outer peripheral portion 41 of the chip 31 can be set to less than 0.4, and the occurrence of over-polishing can be minimized, and the reduction in productivity can be suppressed.

[0090] 4) In the present embodiment, since a polymer is added to the polishing liquid during the second polishing, the wettability of the outer peripheral portion 41 of the wafer 31 can be improved during the second polishing.

[0091] [Other embodiments]

[0092] Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and design changes and the like that do not depart from the gist of the present invention are also included in the present invention.

[0093] In the above-mentioned embodiment, the rotation direction of the wafer 31 is not particularly described, but the wafer 31 may be rotated clockwise or counterclockwise during the first polishing and the second polishing.

[0094] In the above embodiment, an example of two kinds of polishing pads is shown, but it is not limited to this, and it can also be three or more kinds. When this structure is adopted, for example, when the user requires a more stringent condition than the current one regarding the surface roughness Ra of the outer peripheral portion 41 of the wafer 31, it can be dealt with by performing the second polishing multiple times using two or more kinds of second polishing pads.

[0095] In the above embodiment, the nozzle 29 for supplying the polishing liquid to the center of the wafer 31 is provided above the substantially central portion of the worktable 11, but the present invention is not limited thereto. For example, the nozzle 29 may be provided above each of the polishing heads 13, 14, 15, and 16, respectively, and the polishing liquid may be supplied to and impregnated only to the first polishing pads 21, 22, 23, 24 and the second polishing pads 25, 26, 27, and 28 before polishing the outer peripheral portion 41.

[0096] In the above-mentioned embodiment, an example is shown in which one grinding head 13 for grinding the lower inclined surface 52 of the outer peripheral portion 41 and one grinding head 14 for grinding the upper inclined surface 51 of the outer peripheral portion 41 are provided, and a pair of grinding heads 15 and 16 for grinding the end surface 53 of the outer peripheral portion 41 are provided, but the present invention is not limited thereto. For example, a plurality of grinding heads 13 and 14 may be provided, and a plurality of pairs of grinding heads 15 and 16 may be provided.

[0097] In the above-mentioned embodiment, an example in which a polymer is added to the polishing liquid during the second polishing is shown, but a polymer may be added to the polishing liquid during the second polishing.

[0098] In the foregoing embodiments, the present invention is applied to Figure 1 to Figure 3 The present invention is an example of a polishing device shown in the figure, but is not limited thereto. The present invention can also be applied to a polishing device described in, for example, Japanese Patent Application Laid-Open No. 2003-257901 (Patent Document 2).

[0099] In the grinding device described in Patent Document 2, a pair of upper bevel grinding members are arranged at positions facing each other on both sides of the diameter direction of a wafer held by a chuck mechanism, and each central axis is tilted relative to the central axis of the wafer, and the operating surface of each upper bevel grinding member is arranged to completely contact the upper bevel of the wafer. When grinding, the grinding device grinds the upper bevel in a state where the operating surface of the upper bevel grinding member is in line contact with the upper bevel of the wafer. The lower bevel grinding member is arranged between the pair of upper bevel grinding members, and when grinding, the lower bevel is ground in a state where the operating surface of the lower bevel grinding member is in line contact with the lower bevel of the wafer.

[0100] Description of Reference Numerals

[0101] 1-grinding device for the periphery of the wafer, 11-work table, 12-rotation driving part, 13, 14, 15, 16-grinding head, 21, 22, 23, 24-first grinding pad, 25, 26, 27, 28-second grinding pad, 29-nozzle, 30-grinding head driving mechanism, 31-wafer, 31A-upper surface, 31B-lower surface, 41-periphery, 51-upper inclined surface, 52-lower inclined surface, 53-end surface.

Claims

1. A wafer peripheral polishing device, characterized in that: include: A disc-shaped workbench to keep the disc-shaped wafer level; A rotation drive unit, which causes the worktable to rotate with its central axis as the rotation axis; One or more grinding heads having a grinding pad mounted on the inner circumference; and The polishing head driving mechanism causes the polishing pad to contact the outer periphery of the wafer, applies a predetermined polishing pressure to the outer periphery of the wafer, and slides the polishing head in a direction inclined or vertical to the central axis of the wafer. On the inner peripheral surface of the polishing head, two or more polishing pads having different physical parameters are mounted along the vertical direction of the polishing head. The polishing pad is composed of a polishing pad mounted on the upper part of the inner circumferential surface and a polishing pad mounted on the lower part of the inner circumferential surface, and the compression rate of the polishing pad mounted on the lower part of the inner circumferential surface is greater than the compression rate of the polishing pad mounted on the upper part of the inner circumferential surface.

2. The wafer outer periphery polishing device according to claim 1, characterized in that: The polishing head driving mechanism slides the polishing head within the polishing pad having the same physical parameters during one polishing step.

3. The wafer outer periphery polishing device according to claim 1, characterized in that: The inner peripheral surface of the polishing head can approach and move away from the outer peripheral portion of the wafer and is in an arc shape along the circumferential direction of the outer peripheral portion.

4. The wafer outer periphery polishing device according to claim 1, characterized in that: The grinding head comprises: a first grinding head for grinding a lower inclined surface constituting the outer peripheral portion of the wafer; a second grinding head for grinding an upper inclined surface constituting the outer peripheral portion of the wafer; and The third and fourth polishing heads are disposed opposite to each other with the wafer sandwiched therebetween and polish the end surface constituting the outer peripheral portion of the wafer. The grinding head driving mechanism causes the first to fourth grinding heads to abut against the outer periphery of the wafer, applies a specified grinding pressure to the outer periphery of the wafer, and simultaneously slides the first grinding head in a direction along the lower slope, the second grinding head in a direction along the upper slope, and the third and fourth grinding heads in a vertical direction of the wafer.

5. The wafer outer periphery polishing device according to claim 1, characterized in that: The polishing pad driving mechanism slides the polishing pad so that after the outer periphery of the wafer is polished by the polishing pad attached to the upper portion of the inner peripheral surface, the outer periphery of the wafer is polished by the polishing pad attached to the lower portion of the inner peripheral surface.

6. The wafer outer periphery polishing device according to claim 1, characterized in that: The hardness of the polishing pad attached to the lower portion of the inner peripheral surface is lower than the hardness of the polishing pad attached to the upper portion of the inner peripheral surface.

7. The wafer outer periphery polishing device according to any one of claims 1 to 6, characterized in that: The length of the polishing pad installed on the upper part of the inner circumferential surface in the vertical direction or the length of the inclined surface along the inner circumferential surface of the polishing head is longer than the length of the polishing pad installed on the lower part of the inner circumferential surface in the vertical direction or the length of the inclined surface along the inner circumferential surface of the polishing head.

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