JP2013018056A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad by which a yield of a product is improved by reducing occurrence of a scratch and defect on a surface of a material to be polished by suppressing a polishing waste from attaching on a surface of the polishing pad, and high flatness and an appropriate polishing speed can be achieved in view of a background of a conventional technology.SOLUTION: The polishing pad is characterized by that a zeta potential of a polishing surface opposite to the material to be polished has a value as: -100 mV≤the zeta potential value<-55 mV.

Description

  The present invention relates to a polishing pad used to form a flat surface in semiconductors, dielectric / metal composites, integrated circuits, and the like.

  As the density of semiconductor devices increases, the importance of multilayer wiring and the accompanying interlayer insulation film formation, electrode formation of plugs, damascene, and the like is increasing. Along with this, the importance of the flattening process of these interlayer insulating films and electrode metal films has increased, and a polishing technique called CMP (Chemical Mechanical Polishing) has become widespread as an efficient technique for this flattening process. doing.

  In this polishing technique called CMP, a surface plate to which a polishing pad is attached and a polishing head for holding an object to be polished, such as a semiconductor substrate, have a polishing surface of the polishing pad and a surface to be polished of the object to be polished. In a polishing apparatus arranged to face each other, an object to be polished is brought into contact with a polishing pad, and both are relatively moved while supplying slurry as a polishing liquid.

  The main characteristics required for CMP are high flatness of the surface of the object to be polished, moderate polishing speed to increase the production efficiency, and few defects such as polishing scratches and adhesion of foreign substances on the surface of the object to be polished. Can be given. In order to polish an object to be polished with high flatness and an appropriate polishing rate, it is necessary that the slurry be uniformly distributed between the polishing pad and the object to be polished.

  As a means for achieving this, Patent Document 1 proposes a technique for setting the zeta potential of the polishing pad polishing surface to -50 mV or more and less than 0 mV so that the familiarity between the polishing pad surface and the slurry is improved. Such a polishing pad improves the familiarity between the abrasive grains contained in the slurry and the surface of the polishing pad, but also improves the familiarity between the polishing debris generated during polishing and the surface of the polishing pad. As a result, the surface of the object to be polished may be subject to polishing scratches called scratches and foreign substances called defects, which may cause the product yield to drop by cutting or shorting the wiring. There was a problem to do.

Japanese Patent No. 4326587

  In view of the background of such a conventional technique, the present invention reduces the generation of scratches and defects on the surface of an object to be polished by suppressing the adhesion of polishing debris to the surface of the polishing pad, thereby improving the yield of the product and high. An object of the present invention is to provide a polishing pad capable of obtaining flatness and an appropriate polishing rate.

  The present invention is a polishing pad characterized in that the zeta potential of the polishing surface facing the object to be polished is smaller than −55 mv and not smaller than −100 mv.

  According to the present invention, when polishing an object to be polished such as glass, a semiconductor, a dielectric / metal composite and an integrated circuit, which is called CMP, it suppresses the accumulation of polishing debris on the surface of the polishing pad, It is possible to obtain a polishing pad that reduces scratches and defects and exhibits high flatness and an appropriate polishing rate.

  According to the present invention, as a result of diligent research on a polishing pad that has reduced scratches and defects on the surface of the object to be polished and has high flatness and an appropriate polishing speed, the zeta potential of the polishing surface facing the object to be polished is -55 mV. It has been clarified that the problem can be solved by being smaller than −100 mv.

  In the present invention, it is important that the zeta potential on the surface of the polishing pad is smaller than −55 mV and not lower than −100 mV.

  When the zeta potential on the surface of the polishing pad is greater than −55 mV, the familiarity with the abrasive grains in the slurry is improved and the polishing rate is increased, while the familiarity with the polishing debris is improved. An object in which abrasive grains are entangled may be easily deposited on the surface of the polishing layer. As a result of polishing debris accumulated on the polishing pad surface, polishing scratches called scratches and foreign substances called defects occur on the surface of the object to be polished, and the wiring of the semiconductor circuit is cut or short-circuited. This is not preferable because the yield may be reduced.

  If the zeta potential on the polishing pad surface is less than −100 mV, accumulation of polishing debris and the like can be suppressed on the polishing pad surface, but the familiarity with the abrasive grains contained in the slurry may deteriorate, and the surface of the object to be polished This is not preferable because the flatness of the inside may deteriorate and the polishing rate may decrease. The preferred zeta potential on the polishing pad surface is −65 mV or less, and −90 mV or more can prevent deposition of polishing debris on the polishing pad surface, while obtaining an appropriate polishing rate. This is preferable.

  In addition, the zeta potential of the polishing pad of the present invention refers to a value measured under the following conditions using an electrophoretic light scattering photometer ELS-800 manufactured by Otsuka Electronics Co., Ltd.

Light source: He-Ne laser Measurement mode: Heterodyne method Cell: Cell for flat sample Measurement angle: 20 °
Voltage: 80V
Temperature: 25 ± 2 ° C
Measurement room atmosphere: 23 ± 2 ° C, 50 ± 5% RH
Measurement solution: 0.001 M NaCl aqueous solution The lower the zeta potential on the polishing pad surface, the more the adhesion of polishing debris and the like, and as a result, the generation of scratches and defects on the surface of the object to be polished can be suppressed. On the other hand, the familiarity between the abrasive grains of the slurry and the surface of the polishing pad also deteriorates, and the polishing rate tends to decrease.

  When the polishing layer of the polishing pad has a foam structure, the open bubbles on the surface of the polishing pad can hold the slurry and contribute to the improvement of the polishing rate. It is preferable that the foam is a closed cell because the slurry can be prevented from flowing out and retained.

  The average cell diameter is preferably 20 μm or more and 150 μm from the viewpoints of slurry retention, flatness of the object to be polished, and polishing rate. When the average cell diameter is less than 20 μm, the holding ability of the slurry is lowered, and an appropriate polishing rate cannot be obtained. When the average bubble diameter exceeds 150 μm, the flatness of the object to be polished is deteriorated, which is not preferable. More preferably, they are 30 micrometers or more and 100 micrometers or less, More preferably, they are 40 micrometers or more and 80 micrometers or less.

  The average bubble diameter was observed in a circular shape that was missing at the edge of the field among the bubbles observed in one field of view when the sample cross section was observed with a VK-8500 ultra-deep microscope manufactured by Keyence at a magnification of 400 times. The circular bubbles excluding the generated bubbles are obtained by measuring the equivalent circle diameter from the cross-sectional area with an image processing apparatus and calculating the number average value.

  The hardness of the polishing layer is preferably 45 to 65 degrees with an Asker D hardness meter. When the Asker D hardness is less than 45 degrees, the planarity of the object to be polished is reduced. When the Asker D hardness is more than 65 degrees, the planarity is good, but the uniformity of the object to be polished is decreased. There is a tendency.

  Although not particularly limited, materials for forming such a structure include polyethylene, polypropylene, polyester, polyurethane, polyurea, polyamide, polyvinyl chloride, polyacetal, polycarbonate, polymethyl methacrylate, polytetrafluoroethylene, epoxy resin, ABS resin, AS resin, phenol resin, melamine resin, “neoprene (registered trademark)” rubber, butadiene rubber, styrene butadiene rubber, ethylene propylene rubber, silicon rubber, fluororubber, and resins mainly composed of these. Two or more of these may be used. Even in such a resin, a material mainly composed of polyurethane is more preferable in that the closed cell diameter can be controlled relatively easily.

  Polyurethane is a polymer synthesized by polyaddition reaction or polymerization reaction of polyisocyanate. The compound used as the symmetry of the polyisocyanate is an active hydrogen-containing compound, that is, a compound containing two or more polyhydroxy groups or amino groups. Examples of the polyisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, but are not limited thereto. Two or more of these may be used.

  The polyhydroxy group-containing compound is typically a polyol, and examples thereof include polyether polyol, polytetramethylene ether glycol, epoxy resin-modified polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and silicone polyol. Two or more of these may be used. It is preferable to determine the combination and optimum amount of polyisocyanate and polyol, catalyst, foaming agent, and foam stabilizer depending on the hardness, the cell diameter and the expansion ratio.

  As a method of forming closed cells in these polyurethanes, the chemical foaming method is generally used by blending various foaming agents into the resin during polyurethane production, but it is cured after foaming the resin by mechanical stirring. The method of making it can also be used preferably.

  A preferred embodiment of the polishing pad in the present invention is a pad containing a polymer of a vinyl compound and polyurethane and having closed cells. Toughness and hardness can be increased only with a polymer from a vinyl compound, but it is difficult to obtain a homogeneous polishing pad having closed cells, and polyurethane becomes brittle when the hardness is increased. By impregnating a polyurethane with a vinyl compound, a polishing pad containing closed cells and having high toughness and hardness can be obtained.

  A vinyl compound is a compound having a polymerizable carbon-carbon double bond. Specifically, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl Methacrylate, 2-hydroxybutyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, ethylene glycol dimethacrylate, acrylic acid, methacrylic acid, fumaric acid, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, maleic acid, maleic Dimethyl acid, diethyl maleate, dipropyl maleate, phenylmaleimide, Hexyl maleimide, isopropyl maleimide, acrylonitrile, acrylamide, vinyl chloride, vinylidene chloride, styrene, alpha-methyl styrene, divinylbenzene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and the like. Two or more of these may be used.

Among the vinyl compounds described above, CH ₂ = CR ¹ COOR ² (R ¹ : methyl group or ethyl group, R ² : methyl group, ethyl group, propyl group or butyl group) is preferable. Among them, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate are easy to form closed cells in polyurethane, good in impregnation of monomers, easy to polymerize, vinyl compound that has been polymerized and cured The foamed structure containing the polymer and polyurethane is preferred because of its high hardness and good flattening characteristics.

  Polymerization initiators preferably used for obtaining polymers of these vinyl compounds include azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile), azobiscyclohexanecarbonitrile, benzoyl peroxide, lauroyl peroxide. Examples thereof include radical initiators such as oxide and isopropyl peroxydicarbonate. Two or more of these may be used. A redox polymerization initiator, for example, a combination of a peroxide and an amine can also be used.

  Examples of the method for impregnating the polyurethane with the vinyl compound include a method of immersing the polyurethane in a container containing the vinyl compound. In this case, it is also preferable to perform treatments such as heating, pressurization, decompression, stirring, shaking, and ultrasonic vibration for the purpose of increasing the impregnation rate.

  The amount of vinyl compound impregnated in polyurethane should be determined by the type of vinyl compound and polyurethane used and the characteristics of the polishing pad to be produced. The content ratio of the polymer obtained from the vinyl compound in the body and the polyurethane is preferably 30/70 to 55/45 by weight ratio. Within this range, the hardness of the polishing pad can be made sufficiently high, and the zeta potential on the surface of the polishing pad can be made smaller than −55 mV and made −100 mV or higher.

  The content of the polymer obtained from the polymerized and cured vinyl compound in polyurethane and the content of polyurethane can be measured by a pyrolysis gas chromatography / mass spectrometry method. As an apparatus that can be used in this method, a double shot pyrolyzer “PY-2010D” (manufactured by Frontier Laboratories) is used as a thermal decomposition apparatus, and “TRIO-1” (manufactured by VG) is used as a gas chromatograph / mass spectrometer. Can be mentioned.

  In the present invention, from the viewpoint of flatness of local irregularities of the semiconductor substrate, it is preferable that the polymer phase obtained from the vinyl compound and the polyurethane phase are contained without being separated. Expressed quantitatively, the infrared spectrum of the polishing pad observed with a micro-infrared spectrometer having a spot size of 50 μm has an infrared absorption peak of a polymer polymerized from a vinyl compound and an infrared absorption peak of polyurethane. In other words, the infrared spectra at various points are almost the same. As a micro-infrared spectrometer used here, IRμs manufactured by SPECTRA-TEC can be mentioned.

  The polishing pad may contain various additives such as an abrasive, an antistatic agent, a lubricant, a stabilizer, and a dye for the purpose of improving characteristics.

In the present invention, the density of the polishing layer is preferably 0.3 g / cm ³ or more, more preferably 0.6 g / cm ³ or more, and 0.65 g / cm ³ from the viewpoint of reducing local flatness defects and global steps. More preferably, it is cm ³ or more. On the other hand, from the viewpoint of reducing scratches, 1.1 g / cm ³ or less is preferable, 0.9 g / cm ³ or less is more preferable, and 0.85 g / cm ³ or less is more preferable. The density of the polishing layer in the present invention is a value measured using water as a medium using a Harvard pycnometer (JIS R-3503 standard).

  Examples of the material to be polished in the present invention include the surface of an insulating layer or metal wiring formed on a semiconductor wafer. Examples of the insulating layer include an interlayer insulating film of metal wiring, a lower insulating film of metal wiring, and shallow trench isolation used for element isolation. Examples of the metal wiring include aluminum, tungsten, and copper, and structurally include damascene, dual damascene, and plug. When copper is used as the metal wiring, a barrier metal such as silicon nitride is also subject to polishing. As the insulating film, silicon oxide is currently mainstream, but a low dielectric constant insulating film is also used. In addition to semiconductor wafers, it can also be used for polishing magnetic heads, hard disks, sapphire, and the like.

  The polishing method of the present invention is suitably used for forming a flat surface on glass, semiconductors, dielectric / metal composites, integrated circuits and the like.

  The polishing layer of the polishing pad can be ground for the purpose of adjusting the roughness of the surface and the zeta potential in addition to eliminating the thickness unevenness. The zeta potential on the pad surface increases on the surface adjusted with the coarse sandpaper, and the zeta potential on the pad surface decreases on the surface adjusted with the fine sandpaper. The zeta potential is further reduced on the unground surface. In order to eliminate the thickness unevenness of the polishing pad, only the surface opposite to the polishing surface of the polishing layer may be ground and the polishing surface may be an unground surface.

  Depending on the performance of the required polishing pad, the surface to be ground and the sandpaper count used for grinding can be selected as appropriate, and the arithmetic average surface roughness Ra of the polishing surface is from 0 μm to 5 μm. The surface roughness is preferable in order to make the zeta potential of −100 mV smaller than −55 mV.

  In addition, arithmetic mean surface roughness Ra of the polishing pad of this invention says the value measured on condition of the following using HANDYSURF E-35B by Tokyo Seimitsu Co., Ltd.

Cut-off type: Gaussian
Cut-off wavelength: 2.50 mm
Measurement length: 12.5mm

  Hereinafter, the details of the present invention will be described with reference to examples. However, the present invention is not construed as being limited by this embodiment. The measurement was performed as follows.

Micro rubber A hardness:
It is measured with a micro rubber hardness meter “MD-1” manufactured by Kobunshi Keiki Co., Ltd. The configuration of the micro rubber hardness tester “MD-1” is as follows.
1.1 Sensor part (1) Load method: cantilever leaf spring (2) Spring load: 0 point / 2.24 gf. 100 points / 33.85 gf
(3) Spring load error: ± 0.32 gf
(4) Needle size: Diameter: 0.16 mm cylindrical shape. 0.5mm height
(5) Displacement detection method: Strain gauge type (6) Pressure leg size: Outer diameter 4 mm Inner diameter 1.5 mm
1.2 Sensor driving unit (1) Driving method: Vertical driving by a stepping motor. Descent speed control by air damper (2) Vertical movement stroke: 12mm
(3) Descent speed: 10-30mm / sec
(4) Height adjustment range: 0 to 67 mm (distance between sample table and sensor pressing surface)
1.3 Sample stage (1) Sample stage size: Diameter 80mm
(2) Fine movement mechanism: Fine movement by an XY table and a micrometer head. Stroke: 15mm for both X and Y axes
(3) Level adjuster: Level adjustment body legs and round level.

  Bubble diameter measurement: Using a SEM2400 scanning electron microscope manufactured by Hitachi, Ltd. and analyzing the photograph observed at a magnification of 200 times with an image analysis device, in the photograph excluding bubbles on the field frame of the photograph All the bubble diameters present in were measured, and the average value was taken as the average bubble diameter.

  Defect inspection: A defect of 0.18 μm or more was measured using SP-1 manufactured by KLA-Tencol. If the number of defects was 30 or less, it was considered acceptable.

D hardness measurement:
This was performed in accordance with JIS K6253-1997. 3cm of the produced polyurethane resin
X3 cm (thickness: arbitrary) cut out into a sample for hardness measurement, temperature 23 ° C. ±
It was allowed to stand for 24 hours in an environment of 2 ° C. and humidity of 50% ± 5%. At the time of measurement, the samples were overlapped to a thickness of 6 mm or more. The hardness was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D type hardness meter).

Average polishing rate:
Polishing was performed using Mirror 3400 from Applied Materials, Inc. while performing end point detection under predetermined polishing conditions. The polishing characteristics were measured in the diametrical direction excluding the outermost 2 mm of the 8-inch wafer. An average polishing rate (nm / min) was calculated by measuring 37 points within a radius of 90 mm from the center every 5 mm and 16 points within a radius of 91 mm or more from the center every 1 mm. If the average polishing rate was 190 to 230 nm / min, the test was accepted.

Example 1
Polyether polyol maintained at a liquid temperature of 40 ° C .: “Sanix (registered trademark) FA-909” (manufactured by Sanyo Chemical Industries, Ltd.) 100 parts by weight, chain extender: 8 parts by weight of ethylene glycol, amine catalyst: 1 part by weight of “Dabco (registered trademark) 33LV” (produced by Air Products Japan), amine catalyst: 0.1 part by weight of “Toyocat (registered trademark) ET” (produced by Tosoh Corporation), silicone foam stabilizer: "TEGOSTAB (registered trademark) B8462" (manufactured by Th. Goldschmidt AG) 0.5 part by weight, foaming agent: A liquid obtained by mixing 0.2 part by weight of water, and isocyanate maintaining the liquid temperature at 40 ° C: "Sunform (registered trademark) NC-703" 95 parts by weight of B liquid was collided with a RIM molding machine at a discharge pressure of 15 MPa, and then kept at 60 ° C. A foamed polyurethane block having a size of 700 × 700 mm and a thickness of 10 mm (micro rubber A hardness: 47 degrees, density: 0.77 g / cm 3, average cell diameter) : 37 μm). Thereafter, the foamed polyurethane block was sliced with a slicer to a thickness of 3 mm.

  Next, the foamed polyurethane sheet was immersed in methyl methacrylate to which 0.1 part by weight of azobisisobutyronitrile was added, and the foamed polyurethane sheet impregnated with methacrylate having a methyl methacrylate content of 48% by weight was treated with vinyl chloride. It was sandwiched between two glass plates via a gasket made and polymerized and cured by heating at 60 ° C. for 10 hours and at 120 ° C. for 3 hours. After releasing from between the glass plates, vacuum drying was performed at 50 ° C. The hard foam sheet thus obtained was sliced with a slicer so as to have a thickness of 2.5 mm, and a surface opposite to the sliced surface was ground to produce a polishing layer having a thickness of 2.0 mm.

  The methyl methacrylate content in the obtained polishing layer was 48% by weight. The D hardness of the polishing layer was 54 degrees, the density was 0.80 g / cm 3, and the average cell diameter of closed cells was 45 μm.

  Next, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) was bonded to the ground surface of the polishing layer using a laminator, and then the release paper was peeled off. A laminator was used for bonding onto a cushion layer made of a urethane rubber sheet (A hardness: 84 degrees). Furthermore, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) was bonded under the cushion layer using a laminator. This laminate was cut into a circle having a diameter of 508 mm, and grooves having a width of 1 mm, a pitch of 15 mm, and a depth of 0.9 mm were formed on the surface of the polishing layer to obtain a polishing pad.

  The arithmetic average roughness Ra of the polishing surface of the obtained polishing pad was 2.8 μm, and the zeta potential was −73.0 mV.

  The polishing pad obtained by the above method was attached to a surface plate of a polishing machine (“MIRRA3400” manufactured by Applied Materials). Retainering pressure = 41 kPa (about 6.0 psi), inner tube pressure = 28 kPa (about 4.0 psi), membrane pressure = 28 kPa (about 4.0 psi), platen rotation speed = 76 rpm, polishing head Rotation speed = 75 rpm, slurry (Cabot, SS-25) is flowed at a flow rate of 150 mL / min, load is 17.6 N (about 4.0 lbf) with a Saesol dresser, polishing time is 1 minute, 30 seconds from the start of polishing. 100 wafers were polished by chewing. The average polishing rate of the 25th oxide film was 216.6 nm / min, and the average polishing rate of the 100th oxide film was 221.5 nm / min. The average polishing rate of the 25th sheet was ± 10% of the average polishing rate of the 100th sheet, and there was no problem.

  When the number of defects of 0.18 μm or more was measured on a polished oxide film 8-inch wafer with a defect inspection apparatus “SP-1” manufactured by KLA-Tencol, the number of defects on the 25th wafer was 8th and 100th. The number of defects of the wafer was as good as 15 pieces.

Example 2
The hard foam sheet produced in the same manner as in Example 1 was sliced with a slicer to a thickness of 2.5 mm, and the surface opposite to the sliced surface was ground to a thickness of 2.01 mm, and then sliced. The surface was ground by 0.01 mm with # 120 count sandpaper to prepare a polishing layer having a thickness of 2.00 mm.

  The methyl methacrylate content in the obtained polishing layer was 48% by weight. The D hardness of the polishing layer was 54 degrees, the density was 0.80 g / cm 3, and the average cell diameter of closed cells was 45 μm.

  Next, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) was bonded to the first ground surface of the polishing layer using a laminator, and then the release paper was peeled off. The laminate was laminated on a cushion layer made of a thermoplastic urethane rubber sheet (A hardness: 84 degrees) using a laminator. Furthermore, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) was bonded under the cushion layer using a laminator. This laminate was cut into a circle having a diameter of 508 mm, and grooves having a width of 1 mm, a pitch of 15 mm, and a depth of 0.9 mm were formed on the surface of the polishing layer to obtain a polishing pad.

  The arithmetic average roughness Ra of the polishing surface of the obtained polishing pad was 4.8 μm, and the zeta potential was −58.5 mV.

  100 wafers were polished in the same manner as in Example 1 with the polishing pad obtained by the above method. The polishing rate of the 25th oxide film was 220.0 nm / min, and the polishing rate of the 100th oxide film was 225.5 nm / min. The polishing rate of the 25th sheet was ± 10% of the polishing rate of the 100th sheet, and there was no problem.

  When the number of defects of 0.18 μm or more was measured on a polished oxide film 8-inch wafer with a defect inspection apparatus “SP-1” manufactured by KLA-Tencol, the number of defects on the 25th wafer was 12th and 100th. The number of defects of this wafer was as good as 14 pieces.

Example 3
The hard foam sheet produced in the same manner as in Example 1 was sliced with a slicer to a thickness of 2.5 mm, and the surface opposite to the sliced surface was ground to a thickness of 2.02 mm, and then sliced. The surface was ground by 0.02 mm with a # 120 count sandpaper to produce a polishing layer having a thickness of 2.00 mm.

  The methyl methacrylate content in the obtained polishing layer was 48% by weight. The D hardness of the polishing layer was 54 degrees, the density was 0.80 g / cm 3, and the average cell diameter of closed cells was 45 μm.

  Next, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) was bonded to the first ground surface of the polishing layer using a laminator, and then the release paper was peeled off. The laminate was laminated on a cushion layer made of a thermoplastic urethane rubber sheet (A hardness: 84 degrees) using a laminator. Furthermore, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) was bonded under the cushion layer using a laminator. This laminate was cut into a circle having a diameter of 508 mm, and grooves having a width of 1 mm, a pitch of 15 mm, and a depth of 0.9 mm were formed on the surface of the polishing layer to obtain a polishing pad.

  The arithmetic average roughness Ra of the polishing surface of the obtained polishing pad was 5.6 μm, and the zeta potential was −55.5 mV.

  100 wafers were polished in the same manner as in Example 1 with the polishing pad obtained by the above method. The polishing rate of the 25th oxide film was 248.0 nm / min, and the polishing rate of the 100th oxide film was 226.0 nm / min. The polishing rate of the 25th sheet was ± 10% of the polishing rate of the 100th sheet, and there was no problem.

  When the number of defects of 0.18 μm or more was measured on a polished oxide film 8-inch wafer with a defect inspection apparatus “SP-1” manufactured by KLA-Tencol, the number of defects on the 25th wafer was 25, 100th. The number of defects of this wafer was as good as 24.

Comparative Example 1
A foamed polyurethane sheet was prepared in the same manner as in Example 1. Next, the foamed polyurethane sheet was immersed in methyl methacrylate to which 0.1 part by weight of azobisisobutyronitrile was added, and the foamed polyurethane sheet impregnated with methacrylate having a methyl methacrylate content of 48% by weight was treated with vinyl chloride. It was sandwiched between two glass plates via a gasket made and polymerized and cured by heating at 60 ° C. for 10 hours and at 120 ° C. for 3 hours. After releasing from between the glass plates, vacuum drying was performed at 50 ° C. A polishing layer having a thickness of 2.0 mm was prepared by grinding both surfaces of the hard foam sheet thus obtained with a # 100 sandpaper.

  The methyl methacrylate content in the obtained polishing layer was 48% by weight. The D hardness of the polishing layer was 54 degrees, the density was 0.79 g / cm 3, and the average cell diameter of closed cells was 42 μm.

  Next, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) was bonded to the polishing layer using a laminator, and then the release paper was peeled off. The thermoplastic urethane rubber sheet (A A laminate having a hardness of 84 degrees was laminated using a laminator. Furthermore, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) was bonded under the cushion layer using a laminator. This laminate was cut into a circle having a diameter of 508 mm, and grooves having a width of 1 mm, a pitch of 15 mm, and a depth of 0.9 mm were formed on the surface of the polishing layer to obtain a polishing pad.

  The arithmetic average roughness Ra of the polishing surface of the obtained polishing pad was 6.8 μm, and the zeta potential was −28.2 mV.

  100 wafers were polished in the same manner as in Example 1 with the polishing pad obtained by the above method. The polishing rate of the 25th oxide film was 225.1 nm / min, and the polishing rate of the 100th oxide film was 220.8 nm / min, both of which were acceptable values.

  When the number of defects of 0.18 μm or more was measured on a polished oxide film 8-inch wafer with a defect inspection apparatus “SP-1” manufactured by KLA-Tencol, the number of defects on the 25th wafer was 54, 100th. The number of defects in the wafer was 55, which was an unacceptable value.

Comparative Example 2
A foamed polyurethane sheet was prepared in the same manner as in Example 1. Next, the foamed polyurethane sheet was dipped in methyl methacrylate to which 0.1 part by weight of azobisisobutyronitrile was added, and the foamed polyurethane sheet impregnated with methacrylate having a methyl methacrylate content of 57% by weight was treated with vinyl chloride. It was sandwiched between two glass plates via a gasket made and polymerized and cured by heating at 60 ° C. for 10 hours and at 120 ° C. for 3 hours. After releasing from between the glass plates, vacuum drying was performed at 50 ° C. A polishing layer having a thickness of 2.0 mm was prepared by grinding both surfaces of the hard foam sheet thus obtained with a # 100 sandpaper.

  The methyl methacrylate content in the obtained polishing layer was 57% by weight. The D hardness of the polishing layer was 61 degrees, the density was 0.80 g / cm 3, and the average cell diameter of closed cells was 44 μm.

  Next, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) was bonded to the polishing layer using a laminator, and then the release paper was peeled off. The thermoplastic urethane rubber sheet (A A laminate having a hardness of 84 degrees was laminated using a laminator. Furthermore, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) was bonded under the cushion layer using a laminator. This laminate was cut into a circle having a diameter of 508 mm, and grooves having a width of 1 mm, a pitch of 15 mm, and a depth of 0.9 mm were formed on the surface of the polishing layer to obtain a polishing pad.

  The arithmetic average roughness Ra of the polishing surface of the obtained polishing pad was 6.8 μm, and the zeta potential was −28.2 mV.

  100 wafers were polished in the same manner as in Example 1 with the polishing pad obtained by the above method. The polishing rate of the 25th oxide film was 215.5 nm / min, and the polishing rate of the 100th oxide film was 210.0 nm / min, both of which were acceptable values.

  When the number of defects of 0.18 μm or more was measured on a polished oxide film 8-inch wafer with a defect inspection apparatus “SP-1” manufactured by KLA-Tencol, the number of defects on the 25th wafer was 122, the 100th The number of defects in the wafer was 145, which was an unacceptable value.

Comparative Example 3
A foamed polyurethane sheet was prepared in the same manner as in Example 1. Next, the foamed polyurethane sheet was dipped in methyl methacrylate to which 0.1 part by weight of azobisisobutyronitrile was added, and the foamed polyurethane sheet impregnated with methacrylate having a methyl methacrylate content of 57% by weight was treated with vinyl chloride. It was sandwiched between two glass plates via a gasket made and polymerized and cured by heating at 60 ° C. for 10 hours and at 120 ° C. for 3 hours. After releasing from between the glass plates, vacuum drying was performed at 50 ° C. The hard foam sheet thus obtained was sliced with a slicer so as to have a thickness of 2.5 mm, and a surface opposite to the sliced surface was ground to produce a polishing layer having a thickness of 2.0 mm.

  The methyl methacrylate content in the obtained polishing layer was 57% by weight. The D hardness of the polishing layer was 61 degrees, the density was 0.79 g / cm 3, and the average cell diameter of closed cells was 45 μm.

  Next, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Co., Ltd.) was bonded to the ground surface of the polishing layer using a laminator, and then the release paper was peeled off. A laminator was used for bonding onto a cushion layer made of a urethane rubber sheet (A hardness: 84 degrees). Furthermore, a double-sided adhesive tape “442JS” (manufactured by Sumitomo 3M Limited) was bonded under the cushion layer using a laminator. This laminate was cut into a circle having a diameter of 508 mm, and grooves having a width of 1 mm, a pitch of 15 mm, and a depth of 0.9 mm were formed on the surface of the polishing layer to obtain a polishing pad.

  The arithmetic average roughness Ra of the polishing surface of the obtained polishing pad was 2.5 μm, and the zeta potential was −26.9 mV.

  100 wafers were polished in the same manner as in Example 1 with the polishing pad obtained by the above method. The polishing rate of the 25th oxide film is 178.5 nm / min, the polishing rate of the 100th oxide film is 208.0 nm / min, the polishing rate of the 25th sheet is low, and the reject value is there were.

  When the number of defects of 0.18 μm or more was measured on a polished oxide film 8-inch wafer with a defect inspection apparatus “SP-1” manufactured by KLA-Tencol, the number of defects on the 25th wafer was 162, 100th The number of wafer defects was 150, which was an unacceptable value.

Claims (2)

A polishing pad, wherein a zeta potential of a polishing surface facing an object to be polished is less than −55 mv and −100 mv or more. 2. The polishing pad according to claim 1, wherein an arithmetic average roughness Ra of the polishing surface of the polishing pad is 0 μm or more and 5 μm or less.