CN214771284U

CN214771284U - Polishing pad

Info

Publication number: CN214771284U
Application number: CN202120217077.XU
Authority: CN
Inventors: 矢岛利康; 二宫大辅; 龙野慎平
Original assignee: Maruishi Sangyo Co Ltd
Current assignee: Maruishi Sangyo Co Ltd
Priority date: 2020-01-27
Filing date: 2021-01-26
Publication date: 2021-11-19
Anticipated expiration: 2031-01-26
Also published as: KR200497189Y1; JP3225815U; KR20210001793U; TWM617168U

Abstract

The utility model relates to a grinding pad, for the grinding pad of non-woven fabrics type, can show more preferred planarization at present, can restrain the damage simultaneously and produce and the grinding precision is excellent. The utility model relates to a grinding pad, for make have the grinding layer of abrasive surface, with have the grinding pad that forms of the buffer layer laminating of fixing the stationary plane at the platform. In this structure, the polishing layer is composed of a nonwoven fabric having an Askel C-type hardness of 70 to 90, and the cushion layer is composed of a nonwoven fabric having an Askel C-type hardness of 40 to less than 70. The non-woven fabric of the utility model is formed by impregnating resin into the resin, wherein the resin fiber is polyethylene terephthalate fiber, nylon fiber or polypropylene fiber.

Description

Polishing pad

Technical Field

The utility model relates to a grinding pad used in the grinding steps of semiconductor wafers, glass substrates for displays, substrates for hard disks and the like. More particularly, the present invention relates to a polishing pad made of a nonwoven fabric, which is improved in flatness of an object to be polished and processing accuracy of surface roughness.

Background

In the manufacturing process of semiconductor components and electronic components such as semiconductor wafers, glass substrates for displays, machine boards for hard disks, etc., polishing steps for planarizing and mirroring the surfaces are generally combined. In this polishing step, after the polishing pad is fixed to the polishing apparatus, a member to be polished, such as a wafer, is pressed against the polishing pad, and polishing slurry is supplied thereto while the polishing pad and the member are relatively slid to polish them. The polishing step includes a plurality of polishing steps including a primary polishing step and a secondary polishing step for mainly planarizing the surface to be polished, and a finishing polishing step for mainly mirror-polishing the surface to be polished.

In the polishing step, various polishing pads are used depending on the material of the material to be polished or the purpose of each step. Known examples of such polishing pads include a foamed polyurethane type polishing pad, a suede type polishing pad, and a nonwoven fabric type polishing pad.

The polishing pad of the foamed polyurethane type is produced by foaming and curing a two-pack type curable polyurethane, and then slicing the cured product into a suitable size. The foamed polyurethane type polishing pad is relatively hard and is often used for primary polishing because it can be used for flattening a surface to be polished.

A suede-type polishing pad is produced by impregnating a nonwoven fabric such as polyester with a resin such as polyurethane to grow a foam layer, and then removing the surface portion of the substrate to form an opening in the foam layer. The surface of the suede-shaped polishing pad is soft, and mirror finishing without polishing scratches can be performed by the retaining action of the polishing material of the foamed layer. Therefore, the polishing composition is mainly used for finish polishing.

The nonwoven fabric type polishing pad is produced by impregnating a resin such as polyurethane with randomly stacked resin fibers. Since the nonwoven fabric type polishing pad has low hardness and appropriate elasticity and flexibility, the shape of the surface to be polished can be made to follow well. Therefore, the nonwoven fabric type polishing pad has a lower polishing rate than the foamed polyurethane type polishing pad, and can perform polishing while suppressing polishing scratches, and therefore, it is mainly used for primary polishing and secondary polishing, but is also used for finish polishing.

In recent years, the semiconductor components and electronic components have been further improved in accuracy and deposition. Further, the diameter and area of the wafer and the display panel have been increased. Under these circumstances, the efficiency of the polishing step is important and the formation of a highly accurate polished surface is also required. In order to meet these demands, various improvements have been proposed for polishing pads in addition to improvements in polishing apparatuses and polishing materials.

The inventors of the present application have focused on a nonwoven fabric type polishing pad from among the above-described various polishing pads. As described above, the nonwoven fabric type polishing pad has appropriate hardness and elasticity, and can be used in a wide range of polishing steps from primary polishing and secondary polishing to finish polishing, and is expected to be a polishing pad which will be required to be improved more in the future. Here, as an improvement of a nonwoven fabric type polishing pad, for example, there is a polishing pad using ultrafine polyester fibers having a predetermined average fineness as fibers constituting a nonwoven fabric (patent document 1).

[ Prior art documents ]

[ patent document ]

Japanese patent laid-open No. 2007-54910.

SUMMERY OF THE UTILITY MODEL

[ problems to be solved by the utility model ]

The nonwoven fabric type polishing pad described in patent document 1 mentioned above can form a highly accurate polishing surface, although it is referred to a predetermined fiber composition and surface properties. However, the polishing pad requires flatness together with polishing precision. It is not clear whether the above-mentioned conventional polishing pad can have these properties in a balanced manner.

In addition, as for the improvement of the polishing pad, the foamed polyurethane type polishing pad is still abundant, but the report on the improvement of the nonwoven fabric type polishing pad is few. In view of these points, an object of the present invention is to provide a polishing pad of a nonwoven fabric type, which can exhibit more preferable flatness than ever before, and can suppress the occurrence of scratches to thereby achieve excellent polishing accuracy.

[ means for solving problems ]

The polishing pad is not limited to a nonwoven fabric type polishing pad, and the mechanical interaction between the polishing pad and the material to be polished during polishing work is mutually influenced. That is, the polishing pad exerts a polishing action on the material to be polished together with the polishing material particles, and the material to be polished receives vertical and horizontal micro-vibrations generated by the polishing device on the material to be polished, and transmits them to the polishing pad. In addition, the micro-vibration generated by the polishing device on the inner surface side (platen side) of the polishing pad is also transmitted to the polishing pad. The influence of these micro-vibrations is considered to be generated in various types of polishing pads, and the inventors of the present invention speculate that the influence of the micro-vibrations is particularly large in the nonwoven fabric type polishing pad. Since the nonwoven fabric type polishing pad has low hardness, abrasion and deformation in the thickness direction may occur due to micro-vibration. In particular, in a nonwoven fabric-type polishing pad containing a resin unevenly distributed by impregnating random resin fibers, deformation due to micro-vibration is likely to be uneven. It is also presumed that the polishing flatness is lowered.

Based on these findings, the inventors of the present invention attempted to reduce the influence of the micro-vibration as an improvement in the directionality of the nonwoven fabric-type polishing pad. Specifically, a polishing pad formed of a conventional single-layer nonwoven fabric is formed of two types of nonwoven fabrics having different hardness. Further, it was found that a polishing pad having excellent flatness can be obtained by absorbing micro-vibration with a nonwoven fabric layer on the side of the material to be polished (polishing apparatus side) and reducing the influence of micro-vibration.

The polishing pad of the present invention is a polishing pad in which a polishing layer having a polishing surface and a cushion layer having a fixing surface fixed to a platen are laminated, wherein the polishing layer is composed of a nonwoven fabric having an astco C-type hardness of 70 or more and 90 or less, and the cushion layer is composed of a nonwoven fabric having an astco C-type hardness of 40 or more and less than 70.

As described above, the present invention is a nonwoven fabric type polishing pad having a double-layer structure of nonwoven fabrics having different aspeck C-type hardness. The use of such a bilayer structure is known per se in the art of polishing pads. However, these polishing pads are of a type using foamed polyurethane for any one layer, and a two-layer structure using a nonwoven fabric type polishing pad has not been known before. The nonwoven fabric type polishing pad of the present invention will be described in detail below.

(A) Polishing layer

As described above, the polishing layer is composed of a nonwoven fabric having an assc type C hardness of 70 or more and 90 or less. The polishing layer is a layer for polishing by contacting with a material to be polished. The nonwoven fabric of the polishing layer should have a hardness that can maintain flatness even when an effective polishing force is exerted. Further, the ASKER C hardness (ASKER C) is a well-known index of hardness of a rubber material, a sponge material, or the like. The asick type C hardness can be measured by an appropriate hardness meter such as a durometer.

Other physical properties of the nonwoven fabric constituting the polishing layer are preferably a nonwoven fabric having a compression elastic modulus of 40% to 80%. This is because the polishing layer is preferably used to maintain flatness and suppress deformation. In addition, the compression elastic modulus represents a value of difficulty in deformation of a material. The compression modulus of elasticity can be measured, for example, according to JIS (japanese industrial standards) L1913 (general nonwoven fabric test method).

The thickness of the polishing layer is preferably 1.0mm to 1.8 mm. Since the polishing layer is essential for its polishing action on the surface, it is ineffective even if it is excessively thickened. However, since abrasion is generated as the polishing progresses, a certain thickness is required. Therefore, the thickness in the above range is preferable.

As described above, the nonwoven fabric is a cloth-like material formed by impregnating resin with resin fibers randomly stacked. The resin fiber of the nonwoven fabric constituting the polishing layer is not particularly limited as long as it has the above physical properties. Specific examples of the resin fibers include polyethylene terephthalate fibers (PET), nylon fibers, and polypropylene fibers. The resin to be impregnated into the stacked resin fibers is not particularly limited. Specifically, ester-based urethane resins, ether-based urethane resins, polycarbonate-based urethane resins, and the like can be used.

(B) Buffer layer

As described above, the cushion layer is composed of a nonwoven fabric having an Askel C-type hardness of 40 or more and less than 70. The buffer layer is a layer for absorbing micro-vibrations from the polishing apparatus to minimize the influence on the polishing layer. The hardness of the nonwoven fabric of the cushion layer is a hardness that is considered to be effective for the function of the cushion layer. The same meaning as for the polishing layer is applied to the hardness of type C of Ascker.

Other physical properties of the nonwoven fabric constituting the cushion layer are preferably 80% to 90% in the compressive modulus of elasticity. This is because the buffer layer is intended to absorb the micro-vibration and to be easily deformed. In addition, the compressive modulus of elasticity is the same as that of the polishing layer.

The thickness of the buffer layer is preferably 1.0mm to 5.0 mm. The buffer layer is a functional layer for absorbing micro-vibration, and the absorption capacity of vibration is about the thickness of the buffer layer. Therefore, a thickness of a certain value or more is preferable. However, the utility model discloses the micro-vibration that foresees is the unavoidable micro-vibration of the normal operating of grinder, so need not excessive bodiness buffer layer. In addition, if the buffer layer is excessively thickened, the entire polishing pad may become thicker, which may affect the polishing operation. Therefore, the buffer layer is preferably as thick as the above range.

The polyester fiber constituting the nonwoven fabric of the cushion layer is not particularly limited as long as it has the above physical properties. As the resin fiber constituting the cushion layer, polyethylene terephthalate fiber (PET), nylon fiber, polypropylene fiber, or the like can be used. The resin impregnation is also the same as the nonwoven fabric of the polishing layer. The nonwoven fabric constituting the polishing layer and the cushion layer has an Askel C-type hardness adjusted depending on the bulk density of the resin fibers, the impregnated resin, and the like.

(C) Other constructions of polishing pads

The utility model discloses a grinding pad accessible laminating constitutes the non-woven fabrics of grinding layer and constitutes the non-woven fabrics of buffer layer and make. For joining the two nonwoven fabrics, a known adhesive or adhesive tape may be used. For example, an acrylic adhesive, a rubber adhesive, a silicone adhesive, an epoxy adhesive, or the like can be used. By bonding the nonwoven fabrics in this manner, the polishing pad has an adhesive layer made of an adhesive or a pressure-sensitive adhesive tape between the polishing layer and the cushion layer. The thickness of the adhesive layer is not particularly limited. The adhesive may be used in an amount that can reliably bond the polishing layer and the buffer layer, and the thickness of the adhesive layer is not limited in consideration of the function of the polishing pad.

In addition, the polishing pad of the present invention can form a bonding layer or an adsorption layer for fixing to the inner surface of the buffer layer fixed to the fixing surface of the platen. The polishing pad may be fixed to the platen by using an adhesive material such as an adhesive tape. The adhesive material may be composed of an acrylic adhesive, a rubber adhesive, a silicone adhesive, or an epoxy adhesive. The adhesive layer made of these adhesive materials may be formed on the inner surface of the polishing pad in advance.

In addition, a predetermined adsorbent composed of a silicone composition can be used as a method for fixing the polishing pad. The adsorbent is a composition obtained by crosslinking at least one silicone selected from the group consisting of a silicone comprising a linear polyorganosiloxane having a vinyl group at both ends, a silicone comprising a linear polyorganosiloxane having a vinyl group at both ends and at a side chain, a silicone comprising a branched polyorganosiloxane having a vinyl group at only the ends, and a silicone comprising a branched polyorganosiloxane having a vinyl group at both ends and at a side chain. The adsorption layer composed of the adsorbent may be formed on the inner surface of the polishing pad in advance.

[ effects of the utility model ]

The nonwoven fabric type polishing pad of the present invention is different from conventional ones in that it is composed of a double-layered nonwoven fabric having a cushion layer. The utility model can absorb the micro-vibration from the grinding device and restrain the uneven deformation caused by the grinding operation. Thus, a polished surface having excellent flatness can be obtained. Further, the polishing precision is improved by the absorption of the micro-vibration. Although the nonwoven fabric type polishing pad is expected to be used from primary polishing to secondary polishing, the present invention can widen the range of use of the nonwoven fabric type polishing pad.

Drawings

Fig. 1 shows an appearance and a cross section of a polishing pad of example 1, which is an example of a polishing pad of the present invention.

Fig. 2 is a schematic view of a polishing apparatus used in the present invention.

Description of the reference numerals

None.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described. In this embodiment, a polishing pad of a nonwoven fabric type having a two-layer structure in which two kinds of nonwoven fabrics are laminated is manufactured. In addition, although the reference example is a nonwoven fabric type polishing pad having a two-layer structure, the polishing pad of the present invention is produced so that the hardness of the polishing layer is lower than that of the cushion layer. In addition, a conventional nonwoven fabric-type polishing pad having a single-layer structure was also produced.

Example 1: a nonwoven fabric (thickness: 1.13mm) containing PET resin fibers impregnated with a polyurethane resin was prepared, and the nonwoven fabric was cut into a circular shape having a diameter of 810mm to prepare a nonwoven fabric constituting a polishing layer. The nonwoven fabric had an Ascker C-type hardness of 78 and a compression modulus of elasticity of 60%. Further, a nonwoven fabric (thickness: 2.0mm) in which nylon resin fibers were impregnated with a urethane resin was prepared, and the nonwoven fabric was cut into a circular shape having a diameter of 810mm in the same manner as the polishing layer to form a cushioning layer. The nonwoven fabric had an Ashock C-type hardness of 65 and a compressive modulus of elasticity of 86%. The two nonwoven fabrics were bonded together with an acrylic adhesive, and adhesive tapes (acrylic adhesive) of the same size were bonded to the inner surfaces of the two nonwoven fabrics to prepare the polishing pad of the present example. The polishing pad manufactured in example 1 is shown in fig. 1.

Reference example: the two nonwoven fabrics prepared above were bonded in reverse to those of the examples, and an adhesive tape of an acrylic adhesive was bonded to the inner surface of the lower nonwoven fabric (having an asker C hardness of 78), to prepare a polishing pad of the reference example.

Comparative example: the nonwoven fabric (Ascker C-type hardness 78, thickness 1.13mm) produced in example as the polishing layer was attached to the inner surface thereofThe polishing pad of the comparative example was a single layer of the pressure-sensitive adhesive tape with an acrylic pressure-sensitive adhesive.

Grinding test: polishing tests were conducted on the polishing pads of examples, reference examples, and comparative examples produced as described above, using a silicon wafer (Φ 300mm) having a 1 μm thermal oxide film deposited thereon as a member to be polished. In the polishing test, the polishing pad was bonded and fixed to the platen to polish the silicon wafer as shown in fig. 2. In the polishing step, the polishing slurry is dropped onto the polishing pad, and the polishing pad (platen) and the silicon wafer (head) are rotated to polish the silicon wafer. The polishing conditions at this time are as follows.

Abrasive slurry: glanzox (manufactured by Fujimi Co., Ltd.) was diluted 30-fold with pure water to obtain a slurry.

Dropping speed of polishing slurry: 2L/min

Grinding pressure: 0175kgf/cm²

Polishing pad (platen) rotation speed: 45rpm

Wafer (head) rotation speed: 50rpm

Wafer (head) rocking speed: 100mm/min

Grinding time: 3min

After polishing in the polishing test, the polished surface of the wafer was washed with pure water and dried in a dust-free state, and then the polishing accuracy and flatness of the polished surface by each polishing head were evaluated.

The polishing precision was evaluated by a 100 point full-scale subtraction method in which the polished surface was observed and the size and number of scratches were counted. In this case, the large damage is reduced more. As for the evaluation results, 95 to 100 points were evaluated as "very excellent", 90 to 95 points were evaluated as "o", 85 to 90 points were evaluated as "Δ", and 85 to 85 points were evaluated as "x".

Flatness is a measurement of the thickness of an oxide film on the surface of a polished silicon wafer, and is evaluated by detecting the in-plane uniformity of the film thickness. An interference-type film thickness measuring device (manufactured by tsukawa electronic corporation) was used to measure the thickness of the oxide film. The uniformity of the film thickness was determined by measuring the film thickness at 25 points on the wafer at a specific position after polishing before and after polishing, and calculating the in-plane uniformity from the following equation. As for the evaluation results, 5% or less was evaluated as "very good", more than 5% and 8% or less was evaluated as "good", 10% or less was evaluated as "fair", and more than 10% was evaluated as "poor".

In-plane uniformity (%) (maximum polishing amount-minimum polishing amount) (maximum polishing amount + minimum polishing amount) × 100

The results of evaluation of the polishing accuracy and uniformity of the polished surfaces formed by the polishing pads are shown in table 1.

[ Table 1]

From table 1, it was confirmed that a favorable polishing surface was formed from two viewpoints of polishing accuracy and flatness by the nonwoven fabric-type polishing pad having the two-layer structure of the example. In the polishing test of the present embodiment, the polishing was performed for a long time, and the abrasion of the polishing pad was intentionally generated. The polishing pad of the present embodiment also forms a polishing surface with good flatness under such conditions. In the case of long-time polishing, the vicinity of the outer periphery of the polishing pad tends to be worn by heat sagging or the like, and the polishing amount of the central portion and the outer peripheral portion often differs, thereby deteriorating uniformity. The single-layer nonwoven fabric-type polishing pad of the comparative example had poor uniformity of the polished surface due to heat flow near the outer periphery. The polishing pad of the present embodiment effectively suppresses the uniformity degradation caused by such wear.

The polishing pad of the nonwoven fabric type is not necessarily required to have a two-layer structure. In the polishing pad of the reference example, the nonwoven fabric of the cushion layer is harder than the nonwoven fabric of the polishing layer, and the flatness is deteriorated. In this case, even if the cushion layer is hard, since vibration is absorbed to a small extent, the flatness is better than that of the polishing pad of a single layer, but is clearly inferior to that of the polishing pad of the present embodiment. In the case of a nonwoven fabric type polishing pad having a two-layer structure, it is necessary to dispose a nonwoven fabric having an appropriate hardness in the buffer layer and the polishing layer.

[ industrial applicability ]

As described above, the nonwoven fabric-type polishing pad of the present invention having a two-layer structure can provide a polished surface having a preferable flatness and a high quality. The utility model can be used for the grinding steps of semiconductor wafers, glass substrates for displays, substrates for hard disks and the like. In addition, a high-precision polished surface can be formed even for a wafer or a display panel whose diameter and area are increasing.

Claims

1. A polishing pad is characterized in that a polishing layer having a polishing surface is bonded to a cushion layer having a fixing surface fixed to a platen,

the polishing layer is composed of a nonwoven fabric having an Askel C-type hardness of 70 to 90, and the cushion layer is composed of a nonwoven fabric having an Askel C-type hardness of 40 to less than 70.

2. The polishing pad according to claim 1, wherein the polishing layer is composed of a nonwoven fabric having a compressive elastic modulus of 40% to 80%, and the cushion layer is composed of a nonwoven fabric having a compressive elastic modulus of more than 80% to 90%.

3. The polishing pad according to claim 1 or 2, wherein the polishing layer has a thickness of 1.0mm to 1.8mm, and the cushion layer has a thickness of 1.0mm to 5.0 mm.

4. The polishing pad according to claim 1 or 2, wherein the nonwoven fabric constituting the polishing layer and the cushion layer is formed by impregnating resin with resin fibers randomly stacked,

the resin fiber is a polyethylene terephthalate fiber, a nylon fiber, or a polypropylene fiber.

5. The polishing pad according to claim 3, wherein the nonwoven fabric constituting the polishing layer and the cushion layer is formed by impregnating resin with resin fibers randomly stacked,

6. The polishing pad according to claim 1 or 2, wherein an adhesive layer comprising an adhesive or an adhesive tape is provided between the polishing layer and the cushion layer.

7. The polishing pad according to claim 3, wherein an adhesive layer comprising an adhesive or an adhesive tape is provided between the polishing layer and the cushion layer.

8. The polishing pad according to claim 4, wherein an adhesive layer comprising an adhesive or an adhesive tape is provided between the polishing layer and the cushion layer.

9. The polishing pad according to claim 5, wherein an adhesive layer comprising an adhesive or an adhesive tape is provided between the polishing layer and the cushion layer.