JP2014188647A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad which suppresses polishing characteristic change over time due to water absorption and obtains a polishing characteristic that is stable for a long time while suppressing scratches generated on the surface of an article to be polished, and achieving both a high leveling characteristic and excellent in-plane uniformity.SOLUTION: Provided is a polishing pad which comprises a polishing layer constituted by plural sheets, the polishing layer includes at least a first sheet which includes a polishing surface contacting to an article to be polished and a second sheet which is adhered to the opposite surface side to the polishing surface of the first sheet, and a polyethylene terephthalate film of thickness equal to 10 μm or more and equal to 125 μm or less is adhered by an adhesive agent between the first sheet and the second sheet. Values of a type D durometer hardness (D1) of the first sheet and a type D durometer hardness (D2) of the second sheet are equal to 30 or more and equal to 60 or less, and D1<D2.

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.

  Large scale integrated circuits (LSIs) typified by semiconductor memories have been integrated year by year, and accordingly, the manufacturing technology of large scale integrated circuits has also been increased in density. Furthermore, with this increase in density, the number of stacked semiconductor device manufacturing locations has also increased. Due to the increase in the number of stacked layers, unevenness of the main surface of the wafer caused by stacking, which has not been a problem in the past, has become a problem. For this reason, chemical mechanical polishing (CMP) technology is used to compensate for insufficient depth of focus at the time of exposure due to unevenness caused by lamination or to improve wiring density by flattening the through-hole portion. The planarization of the used wafer is used in semiconductor manufacturing.

  In general, a CMP apparatus includes a polishing head that holds a wafer that is an object to be polished, a polishing pad that performs polishing of the object to be polished, and a polishing surface plate that holds the polishing pad. Then, the wafer polishing process uses a polishing slurry composed of an abrasive (abrasive grains) and a chemical solution to move the wafer and the polishing pad relative to each other, thereby removing the protruding portion of the wafer surface layer. Is flattened.

  It is effective that the polishing pad is hard to flatten the wafer surface, but if the polishing pad is hard, the polishing pad does not follow the waviness of the wafer and the wafer surface cannot be uniformly polished. In order to make the polishing pad follow the waviness of the wafer, a technique of a polishing pad in which a soft cushion layer is provided under the polishing layer is disclosed, and both flatness and uniformity are achieved (see Patent Document 1 and Patent Document 2). ).

  However, in such a polishing pad, the surface of the polishing layer is too hard, and polishing scratches called scratches are generated on the object to be polished, resulting in a problem that the yield of products is lowered. Furthermore, as the polishing pad is used for a long time, the polishing slurry and the cleaning water penetrate into the polishing layer, so that the elastic characteristics of the polishing pad change, and a target polishing result cannot be obtained.

  Disclosed is a technology that places a low hardness material on the polishing surface side of the polishing layer and a high hardness material on the opposite side of the polishing surface as a technology to suppress scratching while achieving both flatness and uniformity. (See Patent Document 3).

  As a technique for suppressing the water absorption of the polishing pad, a technique is disclosed in which a water stop layer for preventing liquid penetration is provided between the layers of the polishing pad (see Patent Document 4 and Patent Document 5). As another technique, a technique of providing a waterproof material in a part of the polishing layer in order to prevent liquid from penetrating into the polishing layer is also disclosed (see Patent Document 6). Furthermore, a technique for providing an intermediate layer having a low water absorption between the polishing layer and the cushion layer is also disclosed (see Patent Document 7).

JP 10-138123 A JP 2004-106177 A JP 2012-89599 A JP 2009-95944 A JP 2009-95945 A Japanese Patent Laid-Open No. 11-156701 JP 2011-200904 A

  Although the technique described in Patent Document 3 exhibits the intended effect in the initial use of the polishing pad, the polishing slurry and cleaning water penetrate into the polishing layer as the usage time accumulates, and the polishing pad machine over time. The problem that the characteristics change and the polishing characteristics change cannot be solved.

  Although the techniques described in Patent Document 4 and Patent Document 5 focus on prevention of liquid penetration between layers, they do not consider penetration into the polishing layer, and prevent changes in polishing characteristics over time. I couldn't.

  Although the technology described in Patent Document 6 prevents changes in mechanical properties due to water absorption over time, the polyethylene sheet described in the document has poor adhesive properties of double-sided tape and adhesive, and the polishing pad is delaminated during polishing. Then there was a problem that made it unusable. Furthermore, the influence of the mechanical properties of the polishing layer material and waterproof material on the polishing pad is not taken into account, and there are satisfactory polishing properties for scratches generated on the surface of the object to be polished and the flatness of the object to be polished. It was not obtained.

  The technique described in Patent Document 7 requires the use of a material having a low water absorption rate that is different from that of the polishing layer, and narrows the range of material selection, making it difficult to design a polishing pad according to the required polishing characteristics. It was.

  The present invention has been made in view of such circumstances, and while suppressing scratches generated on the surface of an object to be polished and achieving high planarization characteristics and good in-plane uniformity, polishing characteristics change over time due to water absorption. It is an object of the present invention to provide a polishing pad that can suppress and obtain stable polishing characteristics over a long period of time. Furthermore, the present invention provides a technique that can be applied even when the polishing layer is a water-absorbing material, and that facilitates the design of a polishing pad according to the required polishing characteristics.

The present invention employs the following means in order to solve the above problems. That is, a polishing pad comprising a polishing layer formed from a plurality of sheets,
The polishing layer has at least a first sheet having a polishing surface that comes into contact with an object to be polished, and a second sheet laminated on a surface opposite to the polishing surface of the first sheet,
A polyethylene terephthalate film having a thickness of 10 μm or more and 125 μm or less is bonded with an adhesive between the first sheet and the second sheet,
The values of the type D durometer hardness (D1) of the first sheet and the type D durometer hardness (D2) of the second sheet are 30 or more and 60 or less, and D1 <D2.

  According to the present invention, in the process of flattening the wafer, the surface of the insulating layer formed on the wafer and the surface of the metal wiring, suppression of scratches generated on the surface of the object to be polished, high flattening characteristics and good While achieving in-plane uniformity, it is possible to provide a polishing pad that suppresses changes in polishing characteristics over time due to water absorption and can obtain stable polishing characteristics over a long period of time.

Sectional drawing of the polishing pad which concerns on this invention

  In the polishing pad of the present invention, the polishing layer is formed of a plurality of sheets, the first sheet having a polishing surface that comes into contact with the object to be polished, and the second layer laminated on the surface side opposite to the polishing surface of the first sheet. And at least a sheet.

  The type D durometer hardness (D1) of the first sheet and the type D durometer hardness (D2) of the second sheet are 30 or more and 60 or less, and D1 <D2. If the hardness of the first sheet in contact with the object to be polished exceeds 60, many scratches are generated on the object to be polished, which is not preferable. If it is less than 30, although there is an effect in suppressing scratches, it is not preferable because the level difference elimination property of the workpiece is deteriorated. When the hardness D2 of the second sheet is less than 30, it is not preferable because the step resolving property is deteriorated, and when it exceeds 60, the followability to waviness of the object to be polished is deteriorated and uniform polishing cannot be performed. The hardness of the surface in contact with the object to be polished is low, and the higher the hardness on the side not in contact with the object to be polished can flatten the unevenness of the surface of the object to be polished while suppressing scratching of the object to be polished. The relationship between the hardness D1 and the hardness D2 is preferably D1 <D2. D1> D2 is not preferable because the effect of suppressing scratches on the surface of the object to be polished is small and the planarization characteristics are also deteriorated.

  In the present invention, type D durometer hardness was measured according to JIS K6253-1997. The test piece was cut into a size of 3 cm × 3 cm (thickness: arbitrary) and allowed to stand for 24 hours in an environment of a temperature of 23 ° C. ± 2 ° C. and a humidity of 50% ± 5%. At the time of measurement, the test pieces were overlapped to a thickness of 6 mm or more. Using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D-type hardness meter), three different locations of the same test piece were measured, and the average value was defined as Type D durometer hardness.

  The thickness of the first sheet and the second sheet of the polishing layer of the present invention is preferably 0.5 mm or more and 3.0 mm or less. A thickness of less than 0.5 mm is not preferable because the life of the polishing pad is shortened. A thickness of 3.0 mm or more is not preferable because the change in mechanical properties due to water absorption by the first sheet of the polishing layer becomes large, and the effects of the present invention may not be obtained.

  In the polishing pad of the present invention, a polyethylene terephthalate film (hereinafter referred to as PET film) having a thickness of 10 μm or more and 125 μm or less is bonded between the first sheet and the second sheet of the polishing layer with an adhesive. The PET film can prevent the penetration of liquid such as polishing slurry and washing water, and can prevent the liquid that has penetrated the first sheet of the polishing layer from penetrating into the second sheet of the polishing layer. Further, since the PET film has a low water absorption rate, the PET film itself does not change the mechanical properties of the polishing pad due to water absorption. Furthermore, since the adhesiveness with an adhesive agent is also favorable, it is a preferable material.

  The thickness of the PET film is 10 μm or more and 125 μm or less. If the thickness of the PET film is less than 10 μm, it is not preferable because air is easily taken in at the time of bonding to the polishing layer. If it exceeds 125 μm, the influence of the PET film on the mechanical properties of the polishing pad becomes too great, and it becomes difficult for the polishing pad to follow the waviness of the object to be polished, and it becomes impossible to uniformly polish the surface of the object to be polished. . A more preferable thickness of the PET film is 20 μm or more and 50 μm or less.

  In order to improve the adhesion between the PET film and the adhesive, it is also possible to use a PET film whose surface is easily adhered. Examples of the easy adhesion treatment include, but are not limited to, corona treatment and easy adhesion coating.

  For bonding the PET film to the first sheet and the second sheet of the polishing layer, a double-sided tape can be used in addition to the adhesive. For reasons such as elution of components due to water permeation and the influence of the adhesive of the double-sided tape on the mechanical properties of the polishing pad, it is preferable to use an adhesive.

  Adhesives include water-soluble adhesives, rubber adhesives, epoxy adhesives, cyanoacrylic adhesives, vinyl adhesives, silicone rubber adhesives, urethane resin adhesives, hot melt adhesives, etc. However, a urethane resin-based reactive hot melt adhesive is preferably used from the viewpoints of adhesive strength, coatability, and mechanical properties after curing.

  A preferable thickness of the adhesive is 30 μm or more and 100 μm or less. If it is less than 30 μm, sufficient adhesion may not be obtained due to the influence of irregularities due to bubbles or the like on the surface of the polishing layer. If the thickness exceeds 100 μm, uneven coating tends to occur, which may affect the thickness uniformity of the polishing pad, which is not preferable. The method of applying the adhesive is preferable because the roll coater can uniformly apply a wide area. After adhering the adherends to each other with an adhesive, it is preferable to pressurize the adherends in order to sufficiently bond them, and pressurization by a roll press is preferable from the viewpoint of productivity and uniform pressurization.

  In the polishing pad of the present invention, as a specific example of the bonding procedure of the first sheet and the second sheet of the polishing layer and the PET film, an adhesive is applied to the surface opposite to the polishing surface of the first sheet of the polishing layer, There is a procedure in which a PET film is bonded, an adhesive is applied to the surface of the PET film, and a second sheet of the polishing layer is bonded.

  The polishing pad of this invention can grind | polish a to-be-polished object uniformly by laminating | stacking a cushion layer on the surface opposite to the polishing surface of a polishing layer. By laminating a softer cushion layer than the polishing layer, the polishing pad can easily follow the waviness of the object to be polished, and the entire object can be polished more uniformly. Examples of the material of the cushion layer include foam resins represented by polyurethane foam, elastomers represented by neoprene rubber and urethane rubber, nonwoven fabrics and felts, and nonwoven fabrics and felts impregnated with resins. It is not limited. Among these, a material containing a urethane resin is particularly preferably used because of its excellent durability. It is preferable that the hardness of the cushion layer is smaller than that of the first sheet and the second sheet of the polishing layer because the followability to the object to be polished is improved.

  The bonding of the polishing layer and the cushion layer can be performed with a double-sided tape or an adhesive, but as with the bonding of the PET film and the polishing layer, it is possible to use a urethane resin-based reactive hot-melt adhesive. It is preferable from the viewpoints of coatability and mechanical properties after curing.

  It is preferable that the first sheet and the second sheet of the polishing layer of the polishing pad of the present invention are composed of materials having the same components because the characteristics as the polishing layer are easily obtained. As long as the materials have the same components, the content ratio of each component may be different. For example, by appropriately adjusting the content ratio of each component, the hardness of the material can be adjusted according to the required polishing characteristics.

  What is preferable as a polishing layer of the polishing pad of the present invention is a pad containing a polymer polymerized from polyurethane and a vinyl compound and having closed cells. Polyurethane is easy to form closed cells and has high toughness, but the hardness cannot be increased. Moreover, although the hardness can be increased only with the polymer from the vinyl compound, it has been difficult to obtain a homogeneous polishing pad having closed cells. By containing a polymer polymerized from polyurethane and a vinyl compound, it was possible to obtain a polishing pad containing closed cells and having high toughness and hardness. Furthermore, the hardness of the polishing layer can be adjusted by appropriately adjusting the content ratio of the polyurethane and the vinyl compound.

  The vinyl compound in the present invention 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. These monomers can be used alone or in combination of two or more.

  Among the vinyl compounds described above, CH2 = CR1COOR2 (R1: methyl group, ethyl group, R2: methyl group, ethyl group, propyl group, butyl group) is preferable. Among them, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate are easy to form closed cells in polyurethane, good in impregnation of monomers, easy to cure by polymerization, A foamed structure containing a polymer polymerized from a vinyl compound is preferable in that it has high hardness and good flattening characteristics.

  Examples of polymerization initiators for these vinyl compounds include azobisisobutyronitrile, azobis (2,4-dimethylvaleronitrile), azobiscyclohexanecarbonitrile, benzoyl peroxide, lauroyl peroxide, isopropyl peroxydicarbonate, and the like. A radical initiator can be used. A redox polymerization initiator, for example, a combination of a peroxide and an amine can also be used. These polymerization initiators can be used not only alone but also by mixing two or more.

  As a method for impregnating a vinyl compound into polyurethane, a method in which polyurethane is immersed in a container containing a monomer and impregnated can be mentioned. 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 monomer 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 polymerized and cured foam structure and polyurethane is preferably 30/70 to 80/20 by weight. When the content ratio of the polymer obtained from the vinyl compound is less than 30/70 by weight, the hardness of the polishing layer becomes too low, which may not be preferable. On the other hand, when the content ratio exceeds 80/20, the hardness of the polishing layer becomes too high, which may not be preferable.

  In addition, the polymer obtained from the vinyl compound in the polymerization-cured polyurethane and the polyurethane content 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, the polyurethane and the vinyl polymer are preferably not contained in a state where the polyurethane phase and the polymer phase polymerized from the vinyl compound are 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 polyurethane and an infrared absorption peak of a polymer polymerized from a vinyl compound. In other words, the infrared spectra at various points are almost the same. As a micro-infrared spectrometer used here, IRμs manufactured by SPECTRA-TECH can be mentioned.

  Various additives such as abrasives, antistatic agents, lubricants, stabilizers, and dyes may be added for the purpose of improving the characteristics of the manufactured polishing pad.

The polishing layer of the present invention preferably has a density in the range of 0.3 to 1.1 g / cm ³ . When the density is less than 0.3 g / cm ³ , local level difference resolution may be poor. When the density exceeds 1.1 g / cm ³ , scratches are likely to occur. A more preferable density is 0.6 to 0.9 g / cm ³ , and a more preferable density is 0.65 to 0.85 g / cm ³ .

  The density of the polishing layer of the present invention is a value measured using a Harvard pycnometer (JIS R-3503 standard) and water as a medium.

  The polishing layer surface of the polishing pad of the present invention is a normal polishing pad having a lattice shape, a dimple shape, a spiral shape, a concentric shape, etc. for the purpose of supplying and discharging slurry and preventing adsorption of an object to be polished to the polishing pad. A groove that can be removed is formed and used.

  The polishing layer of the present invention preferably has an average cell diameter of 20 to 100 μm. When the average cell diameter is less than 20 μm, the retention of the polishing slurry on the surface of the polishing layer is lowered, which is not preferable. When the average bubble diameter exceeds 100 μm, foreign substances are likely to be accumulated in the bubbles, and scratches may be easily generated on the object to be polished, which is not preferable. A more preferable average bubble diameter is 30 μm or more and 60 μm or less.

  The average bubble diameter is a bubble observed in a circular shape lacking at the edge of the field among the bubbles observed in one field of view when the sample cross section is observed with a VK-8500 ultra-deep microscope made by Keyence at a magnification of 400 times. The circle-equivalent diameter was measured from the cross-sectional area of the circular bubbles excluding, and the calculated number average value was defined as the average bubble diameter.

  Using the polishing pad of the present invention, the unevenness of the insulating film and the unevenness of the metal wiring on the semiconductor wafer are locally planarized using silica-based slurry, aluminum oxide-based slurry, cerium oxide-based slurry, etc. as the slurry. Can be reduced, global steps can be reduced, and dishing can be suppressed. As specific examples of the slurry, CAB-O-SPERSE (registered trademark) SC-1 for CMP, CAB-O-SPERSE (registered trademark) SC-112 for CMP, SEMI-SPERSE (registered trademark) AM100 for CMP manufactured by Cabot Corporation. , SEMI-SPERSE (registered trademark) AM100C for CMP, SEMI-SPERSE (registered trademark) 12 for CMP, SEMI-SPERSE (registered trademark) 25 for CMP, SEMI-SPERSE (registered trademark) W2000 for CMP, SEMI-SPERSE for CMP (Registered trademark) W-A400 and the like can be mentioned, but are not limited thereto.

  The object of the polishing pad of the present invention is, for example, the surface of an insulating layer or metal wiring formed on a semiconductor wafer. As the insulating layer, an interlayer insulating film of metal wiring, a lower insulating film of metal wiring or element isolation The metal wiring is aluminum, tungsten, copper or the like, and there are structurally damascene, dual damascene, plug, and the like. 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 mainly used at present, but a low dielectric constant insulating film is used due to the problem of delay time. With the polishing pad of the present invention, it is possible to satisfactorily measure the polishing state while polishing in a state where scratches are difficult to enter. In addition to semiconductor wafers, it can also be used for polishing magnetic heads, hard disks, sapphire, and the like.

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

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.
<Measurement of in-plane uniformity>
The wafer thickness before and after polishing was measured at intervals of 1 mm in the diameter direction except for the outermost circumference of 2 mm, and the polishing rate at each point was calculated by dividing by the polishing time. In-plane uniformity was calculated from the determined polishing rate according to the following formula.

In-plane uniformity (%) = {(maximum in-plane polishing rate) − (minimum in-plane polishing rate)} / (average polishing rate) × 100.
<Measurement of scratch>
A scratch of 0.18 μm or more was measured with a product name “SP-1” manufactured by KLA-Tencol. 50 or less was regarded as acceptable.
<Measurement of step resolution>
When the polishing amount of the 300 μm-wide concave portion of the wafer with a test pattern having an initial step of 800 nm was 400 nm, the remaining steps of the 300 μm-wide concave portion and the 300 μm-wide convex portion were measured. 450 nm or less was regarded as acceptable.
<Micro rubber A hardness measurement>
A test piece cut into a size of 3 cm × 3 cm was left to stand for 24 hours in an environment of a temperature of 23 ° C. ± 2 ° C. and a humidity of 50% ± 5%. Using a micro rubber hardness meter MD-1 manufactured by Kobunshi Keiki Co., Ltd., three different points were measured in one sample, and the calculated average value was defined as micro rubber A hardness.
Example 1
30 parts by weight of polypropylene glycol, 40 parts by weight of diphenylmethane diisocyanate, 0.5 parts by weight of water, 0.3 parts by weight of triethylamine, 1.7 parts by weight of a silicone foam stabilizer and 0.09 parts by weight of tin octylate are mixed in a RIM molding machine. The foamed polyurethane sheet having a thickness of 2.6 mm (micro rubber A hardness: 42, density: 0.76 g / cm ³ , average cell diameter of closed cells: 34 μm).

  The foamed polyurethane sheet was immersed in methyl methacrylate to which 0.2 parts by weight of azobisisobutyronitrile was added, and the foamed polyurethane sheet was 1.7 times the weight before immersion at 65 ° C. for 6 hours. The polymer was cured by heating at 120 ° C. for 3 hours. The hard foam sheet thus obtained was processed into a thickness of 1.00 mm to produce a first sheet of the polishing layer.

The methyl methacrylate content in the first sheet was 41% by weight. The type D durometer hardness of the first sheet was 48, the density was 0.77 g / cm ³ , and the average cell diameter of closed cells was 42 μm.

Similarly, the foamed polyurethane sheet was immersed in methyl methacrylate to which 0.2 parts by weight of azobisisobutyronitrile was added, and the foamed polyurethane sheet was 1.9 times the weight before immersion at 65 ° C. For 6 hours at 120 ° C. for 3 hours for polymerization and curing. The hard foam sheet thus obtained was processed into a thickness of 1.00 mm to produce a second sheet of the polishing layer. The methyl methacrylate content in the second sheet was 46% by weight. The type D durometer hardness of the second sheet was 54, the density was 0.77 g / cm ³ , and the average cell diameter of closed cells was 42 μm.

  After applying the urethane resin reactive hot melt adhesive to the surface of the prepared polishing layer opposite to the polishing surface of the first sheet using a roll coater so as to have a thickness of 50 μm, polyester having a thickness of 50 μm A terephthalate film (PET film) was bonded and pressed with a roll press to form a laminate. After the laminated body of the first sheet of the bonded abrasive sheet and the PET film is allowed to stand for 24 hours, a roll coater is used so that the urethane resin reactive hot melt adhesive has a thickness of 50 μm on the surface of the PET film. After the application, the second sheet of the polishing layer was bonded and pressed with a roll press to obtain a laminate. The laminated body of the first sheet, the PET film, and the second sheet of the bonded abrasive sheet is allowed to stand for 24 hours, and then the urethane sheet-based reactive hot melt adhesive is rolled on the second sheet so as to have a thickness of 50 μm. After coating using a coater, a urethane rubber sheet having a thickness of 0.3 mm and a type D durometer hardness of 40 was attached and pressed with a roll press to form a laminate. The prepared laminate was further left for 24 hours, and then a double-sided tape # 5604TDX manufactured by Sekisui Chemical Co., Ltd. was applied as a back surface tape to the urethane rubber sheet to produce the laminate shown in FIG. An XY lattice groove (groove width of 1.0 mm, groove pitch of 15 mm, groove depth of 0.8 mm) was processed on the surface of the laminate, and processed into a circular shape having a diameter of 508 mm to obtain a polishing pad.

  The polishing pad produced in this way was attached to a surface plate of a polishing machine (“Mirra 3400 (registered trademark)” manufactured by Applied Materials). After a break-in with Kinik dresser for 20 minutes under conditions of disk load 4 lbf, platen rotation speed 76 rpm, disk rotation speed 85 rpm, pure water 200 ml / min, retainer ring pressure = 4.0 psi, inner tube pressure = 6.0 psi, Membrane pressure = 4.0 psi, platen rotation speed = 76 rpm, polishing head rotation speed = 78 rpm, slurry (Cabot Corp., SS-25) diluted twice with pure water is flowed at a flow rate of 150 ml / min, polishing time 300 8-inch wafers of oxide films were continuously polished under the conditions of 1 minute.

  As the polishing characteristics at the initial stage of using the polishing pad, the in-plane uniformity of the 15th wafer, the scratch of the 16th wafer, and the step resolution of the 17th wafer were measured. In order to confirm the change with time due to water absorption of the polishing pad, the in-plane uniformity of the 299th wafer and the level difference elimination property of the 300th wafer were measured as polishing characteristics at the end of use.

As for the polishing characteristics at the initial stage of use, in-plane uniformity was 18%, 25 scratches, and step resolution was 400 nm. As for the polishing characteristics at the end of use, in-plane uniformity was 18%, and the level difference elimination property was 390 nm.
Examples 2-6, Comparative Examples 1-11
Using the sheet in which the amount of methyl methacrylate impregnated into the polyurethane foam sheet was adjusted so that the hardness of the first sheet and the second sheet of the polishing layer was as shown in Table 1, the first sheet and the second sheet of the polishing layer were used. A polishing pad was prepared and evaluated in the same manner as in Example 1 except that the material and thickness described in Table 1 were used for the sheet provided therebetween. In each of Examples 1 to 6, since the hardness of the first sheet and the second sheet of the polishing layer is 30 or more and 60 or less, and hardness D1 <hardness D2, scratches and level difference elimination are values with no problem. It was. Further, since the space between the first sheet and the second sheet of the polishing layer is a PET film having a thickness of 10 μm or more and 125 μm or less, the in-plane uniformity is also acceptable, and the change in the polishing characteristics due to the effect of water absorption until the end of use is observed. I couldn't. Also, the adhesiveness with the adhesive was good, and polishing was possible without delamination during use.

  On the other hand, in Comparative Example 1, since the polishing layer was formed with a single sheet, there was no problem in the initial stage of use, but moisture penetrated the entire polishing layer over time, and the polishing characteristics changed. The property was rejected.

  The polishing pad produced in Comparative Example 2 had a problem in step resolution since the hardness of the first sheet and the second sheet of the polishing layer was the same.

  The polishing pad produced in Comparative Example 3 had a problem in the step resolution because the relationship between the hardness of the first sheet and the second sheet of the polishing layer was hardness D1> hardness D2.

  The polishing pad produced in Comparative Example 4 had very many scratches because the hardness of the first sheet and the second sheet of the polishing layer was 60 or more.

  The polishing pad produced in Comparative Example 5 failed in step resolution because the hardness of the first sheet and the second sheet of the polishing layer was 30 or less.

  Since the polishing pad produced in Comparative Example 6 had a PET film that was too thick, the followability of the polishing pad to the object to be polished was deteriorated and the in-plane uniformity was unacceptable.

  In the polishing pad produced in Comparative Example 7, since the PET film was too thin, air was often caught during bonding, resulting in unevenness on the polishing pad surface, resulting in an increase in scratches.

  In the polishing pads prepared in Comparative Examples 8 and 11, a polyethylene sheet having a thickness of 100 μm and a fluororesin sheet were provided between the first sheet and the second sheet of the polishing layer. Delamination occurred at the polyethylene sheet, and the planned polishing evaluation could not be completed.

  In the polishing pads prepared in Comparative Examples 9 and 10, when a sheet other than the PET film was provided between the first sheet and the second sheet of the polishing layer, the mechanical properties of the polishing pad became inappropriate, and the initial stage of use was In-plane uniformity and level difference elimination were unacceptable.

1: First sheet of polishing layer 2: Second sheet of polishing layer 3: Polyester terephthalate film 4: Cushion layer 5: Adhesive 6: Back tape 7: Polishing layer 8: Polishing pad

Claims (2)

A polishing pad comprising a polishing layer formed from a plurality of sheets,
The polishing layer has at least a first sheet having a polishing surface that comes into contact with an object to be polished, and a second sheet laminated on a surface opposite to the polishing surface of the first sheet,
A polyethylene terephthalate film having a thickness of 10 μm or more and 125 μm or less is bonded with an adhesive between the first sheet and the second sheet,
A polishing pad, wherein the value of the type D durometer hardness (D1) of the first sheet and the type D durometer hardness (D2) of the second sheet is 30 or more and 60 or less, and D1 <D2. The polishing pad according to claim 1, wherein a cushion layer is laminated on a surface of the polishing layer opposite to the polishing surface.

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