Wafer Polishing Method

Abstract

To provide a polishing pad which hardly causes polishing failure and is excellent in washability of a wafer after polishing in a case in which an outer peripheral edge part of a disk-shaped wafer is polished.SOLUTION: A polishing pad 13 polishes an outer peripheral edge part of a disk-shaped wafer. The polishing pad 13 constitutes a polishing surface, has a polishing layer containing a binder resin, innumerable polishing particles and a fiber, and has durometer hardness of 18.5 to 36.5, a density of 0.50 to 0.63 g / cm3, and an elastic modulus of 0.9 to 2.0 kgf / mm2, and thickness thereof is reduced by 0.73-1.02 mm by a load of 2 kPa.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention Yes The present invention relates to a wafer polishing method. [Background technology]

[0002] Conventional polishing pads are disclosed in Patent Documents 1 to 4. The polishing pads in Patent Documents 1 to 3 are obtained by impregnating a nonwoven fabric with a paste and removing the solvent in the paste. The paste in Patent Document 1 is a mixture of urethane, a solvent such as dimethylformamide, and SiO 2 and alkaline fine particles such as sodium carbonate. The paste in Patent Document 2 is made of an ether-based urethane and a solvent such as N,N-dimethylformamide. The paste in Patent Document 3 is made of a urethane, a solvent, and a water repellent. By removing the solvent by drying or the like, the urethane is solidified in a state bonded to the nonwoven fabric. The polishing pad in Patent Document 4 is manufactured using a paste made by mixing a binder resin, abrasive particles, and a solvent.

[0003] The polishing pad of Patent Document 1 is used to polish the outer peripheral edge of a disk-shaped wafer. That is, the wafer is held on a rotating table that can rotate around the center of rotation. At this time, the center of the wafer is positioned at the center of rotation of the rotating table. Meanwhile, a polishing pad is provided on the upper end of a spindle so that the outer peripheral end face of the polishing pad abuts against the outer peripheral edge of the wafer. Then, a polishing liquid is supplied between the outer peripheral edge of the wafer and the outer peripheral end face of the polishing pad, and the rotating table and spindle are rotated while applying a predetermined load. This allows the outer peripheral edge of the wafer to be polished. This makes it possible to suppress the occurrence of defects in semiconductor devices due to the outer peripheral edge of the wafer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-46838 A [Patent Document 2] JP 2019-118981 A [Patent Document 3] JP 2020-49639 A [Patent Document 4] Patent No. 5511266 Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to the inventors' tests, when polishing the outer peripheral portion of a disk-shaped wafer, the conventional polishing pad has low flexibility and low recovery rate after compression, and has poor followability when pressed against the wafer. This may cause polishing defects. In addition, since the polishing pad does not contain abrasive grains, when a polishing liquid containing abrasive grains is used for free abrasive grain polishing, it is necessary to clean the particles, which are abrasive grains remaining on the wafer after polishing, which causes a problem in cleanability.

[0006] The present invention has been made in consideration of the above-mentioned conventional situation. ,circle The problem to be solved is to provide a method for polishing a wafer, which can polish the outer peripheral edge of a disk-shaped wafer with high efficiency and has excellent cleanability for the wafer after polishing. [Means for solving the problem]

[0009] The wafer polishing method of the present invention includes a first step of preparing a wafer, a polishing pad, and a polishing liquid; a second step of polishing the wafer with the polishing pad while supplying the polishing liquid between the wafer and the polishing pad; the wafer has a central axis, a first surface extending in a direction perpendicular to the central axis, a second surface located opposite to the first surface and extending in a direction perpendicular to the central axis, an outer circumferential surface connecting an outer circumferential edge of the first surface and an outer circumferential edge of the second surface, and an outer circumferential edge portion formed by the first surface or the second surface and the outer circumferential surface, The polishing pad has an abrasive layer that constitutes a polishing surface and contains a binder resin and countless abrasive particles and fibers, and has a durometer hardness of 18.5 to 36.5 and a density of 0.50 to 0.63 g / cm3 The elastic modulus is 0.9 to 2.0 kgf / mm 2 The thickness is reduced by 0.73 to 1.02 mm under a load of 2 kPa. The polishing liquid does not contain the abrasive particles, The second step is characterized in that the polishing surface is pressed against the outer circumferential edge portion with a predetermined pressing force, and at least one of the wafer and the polishing pad is rotated relatively around the central axis.

[0010] According to the inventors' tests, in the wafer polishing method of the present invention, the polishing pad has excellent conformability when pressed against the wafer, so that polishing defects are unlikely to occur. Also, in the wafer polishing method of the present invention, the polishing layer of the polishing pad contains countless abrasive particles, so that a polishing liquid that does not contain abrasive grains can be used, and since there are few particles, which are abrasive particles, remaining on the wafer after polishing, the wafer after polishing has excellent cleaning properties. Effect of the Invention

[0011] Books The wafer polishing method of the invention can polish the outer peripheral edge of a disk-shaped wafer with high efficiency, and is excellent in terms of the cleanability of the wafer after polishing. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a method for producing the polishing pads of Examples 1 to 10. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a method for producing the polishing pads of Examples 1 to 10. [Diagram 3] FIG. 3 is a schematic cross-sectional view showing a method for producing the polishing pads of Examples 1 to 10. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a method for producing the polishing pads of Examples 1 to 10. [Diagram 5] FIG. 5 is a schematic cross-sectional view of the polishing pads of Examples 1 to 10. [Figure 6] FIG. 6 is a schematic cross-sectional view showing a test method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The polishing pad of the present invention has an abrasive layer containing a binder resin and numerous abrasive particles and fibers. This abrasive layer constitutes the polishing surface.

[0014] As the binder resin, polyethersulfone (PES), polyvinylidene fluoride (PVDF), polyvinyl fluoride, vinyl fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, polyethylene, polymethyl methacrylate, etc. may be used alone or in combination of two or more.

[0015] As the abrasive particles, silica, ceria, alumina, diamond, zirconia, titania, manganese oxide, barium carbonate, chromium oxide, boron carbide, iron oxide, etc. can be used alone or in combination of two or more.

[0016] The fibers may be aramid fibers, glass fibers, cellulose fibers, nylon fibers, vinylon fibers, polyester fibers, polyethylene fibers, polypropylene fibers, polyolefin fibers, rayon fibers, low-density polyethylene resins, ethylene vinyl acetate resins, synthetic rubbers, copolymerized polyamide resins, copolymerized polyester resins, etc. These may be used alone or in combination of two or more. It is also possible to select the shape, such as the fiber length and thickness.

[0017] The fibers of the polishing pad may be based on a preformed fiber web or may be non-preformed. A fiber web is a layer of fibers arranged in a longitudinal direction, crossed fiber arrangement, or random fiber arrangement. A nonwoven fabric is a layer of fibers of a fiber web bonded together.

[0018] The polishing pad of the present invention can be manufactured by the following manufacturing method. This manufacturing method includes a preparation step of preparing a paste containing a binder resin, a solvent for dissolving the binder resin, and a countless number of abrasive particles, and a fiber web; an impregnation step of impregnating the fiber web with the paste to form an impregnated body; and a solidification step of removing the solvent from the impregnated body to solidify the binder resin.

[0019] The polishing layer of the polishing pad obtained by this manufacturing method includes a fiber web that constitutes the fibers, and a binder resin and abrasive particles contained in the fiber web. In this case, since the fibers are formed in advance as a fiber web, the productivity of the polishing pad is high.

[0020] The paste contains a binder resin, numerous abrasive particles, and a solvent. As the solvent, dimethylformamide, dimethylsulfoxide, acetone, ethyl acetate, methyl ethyl ketone, etc. can be used. These may be used alone or in combination of two or more. The solvent is selected from various types according to the binder resin.

[0021] The paste may also contain alkaline fine particles such as sodium carbonate, piperazine, potassium hydroxide, sodium hydroxide, calcium oxide, potassium carbonate, and magnesium oxide. The paste may also contain a water repellent such as a fluorine-based water repellent, a silicon-based water repellent, a hydrocarbon-based water repellent, and a metal compound-based water repellent. The paste may also contain a pigment such as an inorganic pigment such as titanium dioxide, calcium carbonate, and carbon black, and an organic pigment such as an azo pigment and a polycyclic pigment. These may be used alone or in a mixture of two or more.

[0022] When a polishing liquid is used, the polishing liquid may be pure water, may be oil-based, or may contain an acidic or alkaline chemical.

[0023] (Examples and Comparative Examples) Examples 1 to 10 embodying the present invention and Comparative Examples 1 to 4 will be described below.

[0024] As shown in Table 1, the combinations of the fiber web, binder resin, and abrasive particles were changed, and the polishing pads 13 of Examples 1 to 20 were manufactured by the manufacturing method described below.

[0025] [Table 1]

[0026] As a preparation step, the following binder resin, solvent, abrasive particles, and fiber web were prepared. (binder resin) PVDF (Polyvinylidene Fluoride) PES (Polyethersulfone) (solvent) N-Methyl-2-pyrrolidone (abrasive particles) Silica (SiO 2 )(Average particle size: 0.2μm) (fiber web) A: 100% PET (polyethylene terephthalate) fiber, fiber diameter 25 μm, thickness 3.0 mm, basis weight 500 g / m 2 B: 100% PP (polypropylene) fiber, fiber diameter 40μm and 30μm, 3.0mm thickness, basis weight 200g / m 2 C: PP (polypropylene) fiber 100%, fiber diameter 27μm, 3.0mm thickness, basis weight 300g / m 2 D: 100% PP (polypropylene) fiber, fiber diameter 40μm and 30μm, 3.0mm thickness, basis weight 400g / m 2 E: 100% PP (polypropylene) fiber, fiber diameter 26 μm, 1.5 mm thickness, basis weight 275 g / m 2

[0027] A paste was prepared by mixing 11% by mass of binder resin, 34% by mass of abrasive particles, and 56% by mass of solvent.

[0028] In the impregnation step, as shown in Fig. 1, the paste is formed into a sheet on a base 1 to form a first sheet-like formed body 3. Then, a fiber web 5 is placed on the first sheet-like formed body 3. As a result, the paste of the first sheet-like formed body 3 impregnates the lower part of the fiber web 5 as shown in Fig. 2. As a result, a first layer 71 consisting of only the paste, a second layer 72 consisting of the paste and the fiber web 5, and a third layer 73 consisting of only the fiber web 5 are formed.

[0029] The paste is formed into a sheet on the fibrous web 5 to form a second sheet-like formed body 3. As a result, as shown in Fig. 3, the paste of the second sheet-like formed body 3 is impregnated into the upper part of the fibrous web 5. As a result, a laminate 9 is formed which is composed of a first layer 71 composed of only the paste, a second layer 72 composed of the paste and the fibrous web 5, a third layer 73 composed of only the fibrous web 5, a fourth layer 74 composed of the paste and the fibrous web 5, and a fifth layer 75 composed of only the paste.

[0030] Furthermore, the laminate 9 is vacuum-pressurized in the lamination direction. As a result, the first layer 71 and the fifth layer 75 are incorporated into the fiber web 5, forming the pressurized laminate 11 as an impregnated body. That is, as shown in Fig. 4, the pressurized molded body 11 is composed of a second layer 72 made of the paste and the fiber web 5, a third layer 73 made of only the fiber web 5, and a fourth layer 74 made of the paste and the fiber web 5. In this case, the thickness of each layer is appropriately selected depending on the object to be polished, the part to be polished, the polishing conditions, etc.

[0031] Next, in the solidification step, the pressurized laminate 11 is dried to remove the solvent from the pressurized laminate 11. Thus, the binder resin is solidified. Thus, the polishing pad 13 shown in FIG. 5 is obtained. This polishing pad 13 is composed of a lower polishing layer 92 in which the paste is solidified at the bottom of the fiber web 5, a base 93 consisting of only the fiber web 5, and an upper polishing layer 94 in which the paste is solidified at the top of the fiber web 5. That is, the lower polishing layer 92 and the upper polishing layer 94 include the fiber web 5 constituting the fibers, and the binder resin and abrasive particles contained in the fiber web 5. In this case, since the fibers are formed in advance as the fiber web 5, the productivity of the polishing pad 13 is high. The surface of the lower polishing layer 92 or the upper polishing layer 94 is ground to form an abrasive surface.

[0032] The durometer hardness and density (g / cm) of the polishing surface of the polishing pads 13 thus obtained in Examples 1 to 10 were 3 ), elastic modulus (kgf / mm 2 ), compression displacement (mm) and deformation behavior are also shown in Table 1. The compression displacement is the thickness reduction caused by a load of 2 kPa.

[0033] The polishing pad of Comparative Example 1 is a soft pad used for free abrasive polishing. This polishing pad is made of nonwoven fabric (100% polyester fiber, fiber diameter 14 μm, thickness 3.0 mm) impregnated with polyurethane and does not contain abrasive grains.

[0034] The polishing pad of Comparative Example 2 is a hard pad used for free abrasive polishing. This polishing pad is made of nonwoven fabric (100% polyester fiber, fiber diameter 14 μm, thickness 3.0 mm) impregnated with polyurethane and does not contain abrasive grains.

[0035] The polishing pad of Comparative Example 3 was manufactured by the manufacturing method described in Japanese Patent No. 5511266 using a paste containing 11 mass % binder resin (PVDF), 34 mass % abrasive particles, and 56 mass % solvent.

[0036] The polishing pad of Comparative Example 4 was manufactured by the manufacturing method described in Japanese Patent No. 5511266 using a paste containing 11 mass % binder resin (PES), 34 mass % abrasive particles, and 56 mass % solvent.

[0037] The durometer hardness, density, elastic modulus, compression displacement and deformation behavior of the polishing surfaces of the polishing pads of Comparative Examples 1 to 4 are also shown in Table 1.

[0038] (test) A polishing apparatus shown in Fig. 6 was prepared. The polishing apparatus was a "FINE SURFACE E-200" manufactured by BBS Kinmei, and was equipped with a drum (not shown) capable of rotating the wafer 15 around a rotation center O, and a bracket 17. The bracket 17 holds the polishing pads 13, 19 of Examples 1 to 10 or Comparative Examples 1 to 4, and is capable of pressing the polishing surfaces of the polishing pads 13, 19 against the surface of the wafer 15 at a displaceable angle θ and with a predetermined pressing force.

[0039] (Test 1) In Test 1, the outer peripheral edge of a wafer 15 made of Si was polished under the following conditions. Rotation speed of wafer 15: 10.0 (rpm) Drum rotation speed: 250 rpm (pressed by centrifugal force) Up and down speed: 3.00mm / sec Angle θ: 0~180° Polishing liquid: In Examples 1 to 10 and Comparative Examples 3 to 4, silica (SiO 2 In Comparative Examples 1 and 2, a piperazine aqueous solution containing 0% silica (SiO 2 The polishing slurry used contained 10,000 ppm or less of ferromagnetic powder (average particle size: 0.05 μm).

[0040] The shape after polishing was evaluated as ◯ if the radius of curvature was less than 1500 (mm), △ if the radius of curvature was 1500 (mm) or more and less than 2000 (mm), and × if the radius of curvature was 2000 (mm) or more. The surface roughness was evaluated as ◯ if the surface roughness Sa was less than 8 (Å), △ if the surface roughness Sa was 8 (Å) or more and less than 10 (Å), and × if the surface roughness Sa was 10 (Å) or more. The polishing rate was evaluated as ◯ if the polishing amount X was 2 (mg / min) or more, △ if the polishing amount X was 1.5 (mg / min) or more and less than 2 (mg / min), and × if the polishing amount X was less than 1.5 (mg / min). The particles were evaluated by observation with an electron microscope as ◯ if the number of particles was 5 or less within a 5 μm x 5 μm surface, △ if 5 to 10, and × if 10 or more. For the polishing liquid, if polishing was possible with a concentration of 0 ppm of abrasive particles, it was evaluated as ◯, if polishing was not possible unless the concentration of abrasive particles was 1 ppm or more and less than 5000 ppm, it was evaluated as △, and if polishing was not possible unless the concentration of abrasive particles was 5000 ppm or more and 10000 ppm or less, it was evaluated as ×. In the overall evaluation, if the shape after polishing, surface roughness, polishing rate, particles, and polishing liquid were all ◯, it was evaluated as ◯. The results are shown in Table 2. From Table 2, it can be seen that, overall, Examples 1 to 5 were rated as ◎, and Examples 6 to 10 were rated as ◯.

[0041] [Table 2]

[0042] From Table 2, the durometer hardness is 18.5 to 36.5, and the density is 0.50 to 0.63 g / cm 3 The elastic modulus is 0.9 to 2.0 kgf / mm 2 It can be seen that if the compression displacement is 0.73 to 1.02 mm, polishing defects are unlikely to occur when polishing the outer peripheral edge of the Si wafer 15.

[0043] In addition, the polishing pads of Examples 1 to 10 have an abrasive layer that constitutes the polishing surface that contains countless abrasive particles, so that a polishing liquid that does not contain abrasive grains can be used, and since fewer abrasive particle particles remain on the wafer after polishing, the wafer has excellent cleaning properties after polishing.

[0044] Therefore, the polishing pads of Examples 1 to 10 are less likely to cause polishing defects when polishing the outer peripheral edge of a disk-shaped wafer 15, and are excellent in cleanability of the polished wafer 5. Furthermore, the wafer polishing methods of the Examples can polish the outer peripheral edge of a disk-shaped wafer 15 with high efficiency, and are excellent in cleanability of the polished wafer 15.

[0045] Although the present invention has been described above with reference to the embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified as appropriate without departing from the spirit of the present invention.

[0046] For example, in the embodiment, the outer peripheral edge of the wafer 15 made of Si is polished, but the polishing pad and wafer polishing method of the present invention can also be applied to polishing the outer peripheral edge of the wafer 15 made of SiC. [Industrial Applicability]

[0047] The present invention can be used in an apparatus for manufacturing semiconductor devices. [Explanation of symbols]

[0048] 5…Fiber web 92, 94...Polishing layer (92...Lower polishing layer, 94...Upper polishing layer) 13...Polishing pad 15…Wafer

Claims

1. A first step of preparing a wafer, a polishing pad, and a polishing liquid; a second step of polishing the wafer with the polishing pad while supplying the polishing liquid between the wafer and the polishing pad; the wafer has a central axis, a first surface extending in a direction perpendicular to the central axis, a second surface located opposite to the first surface and extending in a direction perpendicular to the central axis, an outer circumferential surface connecting an outer circumferential edge of the first surface and an outer circumferential edge of the second surface, and an outer circumferential edge portion formed by the first surface or the second surface and the outer circumferential surface, The polishing pad has a polishing layer that constitutes a polishing surface and contains a binder resin and countless abrasive particles and fibers, and has a durometer hardness of 18.5 to 36.5 and a density of 0.50 to 0.63 g / cm 3 and the elastic modulus is 0.9 to 2.0 kgf / mm 2 The thickness is reduced by 0.73 to 1.02 mm under a load of 2 kPa. The polishing liquid does not contain the abrasive particles, A wafer polishing method, characterized in that in the second step, the polishing surface is pressed against the outer peripheral edge portion with a predetermined pressing force, and at least one of the wafer and the polishing pad is rotated relatively around the central axis.

2. 2. The method for polishing a wafer according to claim 1, wherein the polishing layer includes a fiber web that constitutes the fibers, and the binder resin and the abrasive particles that are contained within the fiber web.

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