Wafer Polishing Method

Abstract

To provide a polishing pad which is excellent in followability when pushed against a wafer.SOLUTION: A polishing pad 13 polishes an outer peripheral edge part of a wafer 15. The polishing pad 13 constitutes a polishing surface, is composed of a resin containing a plasticizer, and has a base material formed with a plurality of air bubbles, and polishing particles held in the base material or a pore. The polishing pad 13 is plastically deformable.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent Documents 1 to 4 disclose conventional polishing pads. The polishing pads of Patent Documents 1 to 3 are made by impregnating a nonwoven fabric with a paste and removing the solvent in the paste. The paste of Patent Document 1 is made of urethane, a solvent such as dimethylformamide, abrasive particles such as SiO2, and alkaline fine particles such as sodium carbonate. The paste of Patent Document 2 is made of an ether-based urethane and a solvent such as N,N-dimethylformamide. The paste of Patent Document 3 is made of urethane, a solvent, and a water repellent. By removing the solvent by drying or the like, the urethane is hardened in a state bonded to the nonwoven fabric. The polishing pad of Patent Document 4 is manufactured using a paste in which a binder resin, abrasive particles, and a solvent are mixed.

[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 view of the above-mentioned conventional situation. ,circle The peripheral edge of a disk-shaped wafer can be polished with high efficiency. Polishing defects are unlikely to occur, Another object of the present invention is to provide a method for polishing a wafer which is excellent in cleaning the wafer after polishing. [Means for solving the problem]

[0008] According to the inventors' tests, when the outer peripheral edge of a disk-shaped wafer is polished with the polishing pad of the present invention, the pad has excellent tracking properties when pressed against the wafer, and polishing defects are unlikely to occur. In addition, since the polishing surface of the polishing pad of the present invention contains countless abrasive particles, 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 polishing pad has excellent cleaning properties for the wafer after polishing.

[0009] Binder The resin is preferably polyethersulfone containing orthophthalic acid or terephthalic acid as a plasticizer, and the polishing pad is preferably plastically deformable. The inventors have confirmed the effect of the present invention with this combination.

[0010] The polishing pad of the present invention is , dense Strength: 0.52~0.81g / cm 3 and the elastic modulus is 7 to 10 kgf / mm 2 in be According to tests conducted by the inventors, in this case, polishing defects are less likely to occur when polishing the outer peripheral edge of a disk-shaped wafer.

[0011] The wafer polishing method of the present invention comprises the steps of: Polishing equipment 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 polishing apparatus includes a drum capable of rotating the wafer around a rotation center, and a bracket that holds the polishing pad and presses the polishing surface against the surface of the wafer at a displaceable angle and with a predetermined pressing force; The wafer is Rotation Center And the above Rotation Center a first surface extending in a direction perpendicular to the first surface; Rotation Center a second surface extending in a direction perpendicular to the first surface, 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 constitutes a polishing surface, The polishing pad is Contains plasticizers Binder The polishing tool has a base material made of resin and having a plurality of pores formed therein, and abrasive particles held within the base material or the pores. 、 the binder resin is polyethersulfone containing orthophthalic acid or terephthalic acid as the plasticizer, The polishing pad is It is plastically deformable, The polishing liquid does not contain the abrasive particles, In the second step, The polishing surface is moved at a displaceable angle relative to the first surface or the second surface of the wafer. The polishing surface is pressed against the outer peripheral portion with a predetermined pressing force, and at least one of the wafer and the polishing pad is Rotation Center The present invention is characterized in that the rotor is rotated relatively around the rotor.

[0012] 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

[0013] Books The wafer polishing method of the invention can polish the outer peripheral edge of a disk-shaped wafer with high efficiency, Polishing defects are unlikely to occur, In addition, the cleaning properties of the wafer after polishing are excellent. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating the test method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The polishing pad of the present invention comprises a polishing surface. The polishing pad is Contains plasticizers Binder The polishing pad of the present invention has a base material made of resin and having a plurality of pores formed therein, and abrasive particles held in the base material or in the pores. Shape possible It is possible to perform plastic deformation. Shape The degree and thickness are appropriately selected depending on the object to be polished, the part to be polished, the polishing conditions, etc.

[0016] Binder The resin is polyethersulfone (PES )of It is possible to adopt 。

[0017] Plasticizers include orthophthalic acid and terephthalic acid. Acid These may be used alone or in combination of two or more. The plasticizer is Binder Various options are selected depending on the resin.

[0018] 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.

[0019] The paste that constitutes the base material is Binder In addition to resin, plasticizer, and numerous abrasive particles, it contains 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 according to the binder resin.

[0020] 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.

[0021] 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.

[0022] (Examples and Comparative Examples) Examples 1 to 4 embodying the present invention and Comparative Examples 1 to 8 will be described below.

[0023] As shown in Table 1, the plasticizer was changed in various ways, and polishing pads 13 of Examples 1 to 4 and Comparative Examples 1 to 4 were manufactured by the manufacturing method described below.

[0024] [Table 1]

[0025] In the first step, the following resin ( Binder Resin ), a solvent and abrasive particles were prepared. (binder resin) PES (Polyethersulfone) (solvent) N-Methyl-2-pyrrolidone (abrasive particles) Silica (SiO2) (average particle size: 0.2 μm)

[0026] Binder 12% by mass of resin, 39% by mass of abrasive particles, 44% by mass of solvent, and 5% by mass of plasticizer were mixed together to prepare a paste.

[0027] In the second step, the paste is molded into a sheet on a base to form a sheet-like molded body. This sheet-like molded body is then immersed in water together with the base to obtain a sheet body in which the solvent has been replaced with water. The sheet body is then removed from the water together with the base, and is then dried. The parts of the sheet body other than the solvent become the base material, and the parts where the solvent has been replaced with water and dried become pores. The surface of the sheet body is then polished to make the polishing surface smooth, and a polishing pad 13 is obtained. This polishing pad 13 contains a plasticizer. Binder It has a base material made of resin with a plurality of pores formed therein, and abrasive particles held within the base material or within the pores.

[0028] The durometer hardness and density (g / cm) of the polishing surface of the polishing pads 13 thus obtained in Examples 1 to 4 and Comparative Examples 1 to 4 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.

[0029] The deformation behavior of the polishing pads 13 of Examples 1 to 4 is plastic deformation, while the deformation behavior of the polishing pads 13 of Comparative Examples 1 to 4 is elastic deformation.

[0030] The polishing pad of Comparative Example 5 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.

[0031] The polishing pad of Comparative Example 6 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.

[0032] The polishing pad of Comparative Example 7 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.

[0033] The polishing pad of Comparative Example 8 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.

[0034] The durometer hardness, density, elastic modulus, compression displacement and deformation behavior of the polishing surfaces of the polishing pads of Comparative Examples 5 to 8 are also shown in Table 1.

[0035] (test) A polishing apparatus shown in Fig. 1 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 a wafer 15 around a rotation center O, and a bracket 17. The bracket 17 holds the polishing pads 13, 19 of Examples 1 to 4 or Comparative Examples 1 to 8, 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.

[0036] (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: A piperazine aqueous solution containing 0% silica (SiO2) (average particle size: 0.2 μm) was used in Examples 1 to 4 and Comparative Examples 7 and 8. A polishing slurry containing 10,000 ppm or less of silica (SiO2) (average particle size: 0.05 μm) was used in Comparative Examples 5 and 6.

[0037] 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. In the polishing liquid, if the concentration of abrasive particles was 0 ppm and polishing was possible, it was evaluated as ◯; if the concentration of abrasive particles was not 1 ppm or more and less than 5000 ppm, polishing was not possible; if the concentration of abrasive particles was not 5000 ppm or more and 10000 ppm or less, polishing was not possible; it was evaluated as ×. Overall, if the shape after polishing, surface roughness, polishing rate, particles, and polishing liquid were all ◯, it was evaluated as ◯; if any one of them was △, it was evaluated as ◯; and if any one or two of them was ×, it was evaluated as △. The results are shown in Table 2. From Table 2, it can be seen that Example 1 received an ◯ overall, and Examples 2 to 4 received an ◯ overall.

[0038] [Table 2]

[0039] From Table 2, BinderThe resin is polyethersulfone containing orthophthalic acid or terephthalic acid as a plasticizer, and is plastically modified. Shape possible It can be seen that no.

[0040] The durometer hardness is 30 to 34, and the density is 0.52 to 0.81 g / cm 3 and the elastic modulus is 7 to 10 kgf / mm 2 It can be seen that if the compression displacement is 0.23 to 0.35 mm, polishing defects are unlikely to occur when polishing the outer peripheral edge of the wafer 15 made of Si or SiC.

[0041] In addition, since the polishing surface of the polishing pads of Examples 1 to 4 contains countless abrasive particles, 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.

[0042] Therefore, when polishing the outer peripheral edge of the disk-shaped wafer 15, the polishing pads of Examples 1 to 4 are less likely to cause polishing defects and provide excellent cleaning properties for the polished wafer 15. Furthermore, the wafer polishing methods of Examples 1 to 4 can polish the outer peripheral edge of the disk-shaped wafer 15 with high efficiency and provide excellent cleaning properties for the polished wafer 15.

[0043] 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.

[0044] 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]

[0045] The present invention can be used in an apparatus for manufacturing semiconductor devices. [Explanation of symbols]

[0046] 13...Polishing pad

Claims

1. A first step of preparing a polishing device, 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 polishing apparatus includes a drum capable of rotating the wafer around a rotation center, and a bracket that holds the polishing pad and presses the polishing surface against the surface of the wafer at a displaceable angle and with a predetermined pressing force; the wafer has a rotation center, a first surface extending in a direction perpendicular to the rotation center, a second surface located opposite to the first surface and extending in a direction perpendicular to the rotation center, an outer peripheral surface connecting an outer peripheral edge of the first surface and an outer peripheral edge of the second surface, and an outer peripheral edge portion formed by the first surface or the second surface and the outer peripheral surface, The polishing pad constitutes a polishing surface, The polishing pad is made of a binder resin containing a plasticizer, and has a base material having a plurality of pores formed therein, and abrasive particles held in the base material or in the pores; the binder resin is polyethersulfone containing orthophthalic acid or terephthalic acid as the plasticizer, The polishing pad is plastically deformable, 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 at an angle that is displaceable relative to the first surface or the second surface of the wafer, and at least one of the wafer and the polishing pad is rotated relatively around the center of rotation.

2. A wafer polishing method as described in claim 1, wherein the angle is 0 to 180 degrees.

3. The polishing pad has a density of 0.52 to 0.81 g / cm 3 , 3. The method for polishing a wafer according to claim 1, wherein the elastic modulus is 7 to 10 kgf / mm 2 .

Images