JP2015188986A - polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad capable of restraining a scratch without impairing a polishing rate, and also having a high dress characteristic.SOLUTION: A polishing pad 7 is made of polyurethane, and Shore D hardness is 10°-40°, and a difference between a rate of the area of a dress surface in a polishing surface 15 to the area of the polishing surface 15 before dress processing by a dress processing device 11 and a rate of the area of the dress surface in the polishing surface 15 to the area of the polishing surface 15 after the dress processing, is 20-35%.

Description

  The present invention relates to a polishing pad, and more particularly to a polishing pad with high dressability.

  Conventionally, a chemical mechanical polishing method (CMP method) has been used as a method for polishing and flattening the surface of an object to be polished such as a semiconductor wafer, a glass substrate for a liquid crystal display, a glass substrate for a photomask, and a glass substrate for a magnetic disk Is used. When polishing an object to be polished using the CMP method, the polishing pad is pressed against the object to be polished, and the polishing pad and the object to be polished are rotated while supplying the polishing slurry between them. The polishing slurry flows from the center side to the outside by centrifugal force accompanying the rotation of the polishing pad, and is finally discharged to the outside of the polishing pad.

  As the polishing pad, various hardnesses are used according to the requirements at the time of polishing. If you want to achieve a high polishing rate and flatness, use a hard polishing pad to suppress scratches (polishing scratches). If desired, a soft polishing pad is generally used. Also, if the polishing pad is used for a certain period of time, the surface of the polishing pad will be clogged, so it is necessary to apply a dressing (sharpening) treatment to the polishing surface of the polishing pad. Easy to process (high dressing). For example, in Patent Document 1, the polishing rate is recovered by dressing the polishing surface of a polishing pad made of a polyurethane foam resin body having a Shore D hardness of 50 ° to 60 ° to make the polishing surface of the polishing pad conspicuous. ing. On the other hand, Patent Document 2 has found that a polyurethane resin-containing polishing pad having a Shore D hardness of about 30 degrees and a specific tensile breaking strength and tensile breaking elongation has a high dressing speed.

JP 2006-297582 A JP2013-89767

  However, when using a polishing pad made of a polyurethane foam resin body having a Shore D hardness of about 50 ° as in Patent Document 1, a high polishing rate and flatness can be realized, but as described above, There is a high possibility that scratches will occur on objects. Further, as disclosed in Patent Document 2, it is disclosed that a polishing pad having a specific tensile breaking strength and tensile breaking elongation has a high dressing speed, but has low hardness and sufficient flatness is obtained. Is hard to say. There is no mention of dressing in terms of how the dress is applied.

  Accordingly, there is a need for a polishing pad that can suppress scratches and achieve high polishing rate and flatness with high dressability.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide a polishing pad that has high dressability and can suppress scratches without impairing the polishing rate. .

  In order to solve the above-described problems, the present invention is a polishing pad made of polyurethane having a Shore D hardness of 40 ° or less and 10 ° or more, and the dress surface in the polishing surface with respect to the area of the polishing surface before dressing treatment The difference between the ratio of the area and the ratio of the area of the dress surface in the polished surface to the area of the polished surface after dressing is 20 to 35%.

  According to the present invention configured as described above, it is possible to achieve a higher polishing rate than a soft polishing pad while maintaining a dressing property equivalent to a hard polishing pad having a Shore D hardness of 50 ° or more that has been conventionally used. it can.

  Moreover, it is preferable that the said polishing pad is shape | molded by reaction of the prepolymer containing a polyurethane bond containing isocyanate compound, and a hardening | curing agent.

  As described above, according to the present invention, scratches can be suppressed by setting the Shore D hardness of the polishing pad to 40 ° or less and 10 ° or more. A high dressing property is obtained by setting the difference between the ratio of the area of the undressed surface and the ratio of the area of the undressed surface within the polished surface to the area of the polished surface after the dressing treatment is 20 to 35%. Thus, a polishing pad that can ensure a high polishing rate can be provided.

1 is a cross-sectional view showing a double-side polishing apparatus to which a polishing pad according to an embodiment of the present invention is applied. 2 shows photographs of polishing surfaces of polishing pads according to examples and comparative examples of the present invention and images obtained by binarizing them. It is a graph which shows the polishing rate of the polishing pad by the Example and comparative example of this invention.

  Hereinafter, a polishing pad according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a polishing apparatus to which a polishing pad according to an embodiment of the present invention is applied.

  First, as shown in FIG. 1, a polishing apparatus 1 is for flattening a surface of an object to be polished 3 by a CMP method. The polishing apparatus 1 includes a polishing surface plate 5 that rotates about a rotation axis, a polishing pad 7 that is fixed to the upper surface of the polishing surface plate 5, and a holding surface plate 9 that holds the workpiece 3. . In the polishing apparatus 1, the polishing pad 7 is set on the surface of the polishing surface plate 5, and the workpiece 3 is disposed between the polishing pad 7 and the holding surface plate 9. Further, the polishing apparatus 1 includes a dressing apparatus 11 for modifying the polishing surface of the polishing pad 7.

  In such a polishing apparatus 1, the holding surface plate 9 is rotated while rotating the polishing surface plate 5 around the shaft 17 while supplying the polishing slurry from the polishing slurry supply device 13 to the vicinity of the center of the polishing surface 15 of the polishing pad 7. By rotating around the center, the surface of the workpiece 3 held by the holding surface plate 9 that is in contact with the polishing pad 7 is flattened.

  The polishing surface plate 5 is made of metal (or made of ceramic) and has a disk shape. One surface of the polishing surface plate 5 constitutes an affixing surface to which the polishing pad 7 is affixed, and this affixing surface is substantially flat. The polishing surface plate 5 is fixed to a single shaft 17 passing through the center thereof, and rotates around the shaft 17 by rotating the shaft 17.

  The holding surface plate 9 has a diameter larger than that of the workpiece 3 and is configured by attaching a holding pad made of, for example, soft plastic to a hard surface plate. The holding surface plate 9 is fixed to a single shaft 19 passing through the center thereof, and rotates around the shaft 17 on the polishing surface 15 by rotating the shaft 19.

  The polishing pad 7 is made of a polyurethane having a Shore D hardness of 10 ° or more and 40 ° or less, which is manufactured by a prepolymer method in which a curing is performed by a reaction between a prepolymer containing an isocyanate group-containing compound and a curing agent, for example. It is a pad and has countless bubbles inside. The bubbles are opened toward the polishing surface 15 of the polishing pad 7. Further, the polishing pad 7 is a circle having substantially the same outer diameter as the polishing surface plate 5. One surface of the polishing pad 7 constitutes a polishing surface 15. The polishing pad 7 is detachably attached to the polishing surface plate 5.

  The method for producing such a polishing pad 7 includes, for example, a preparation step of preparing at least a urethane bond-containing isocyanate compound and an active hydrogen compound (chain extender); at least a polyurethane bond-containing isocyanate compound and an active hydrogen compound are mixed to form a molded body A mixing step for obtaining a liquid mixture for molding; a molding step for molding a polyurethane polyurea resin molded body from the liquid mixture for molding; and a polishing surface for polishing an object to be polished from the polyurethane polyurea resin molded body. A polishing layer forming step of forming a polishing layer.

<Preparation process>
In order to manufacture the polishing pad according to the present embodiment, at least a urethane bond-containing isocyanate compound and an active hydrogen compound are used as raw materials for the polyurethane polyurea resin molded article. Further, different active hydrogen compounds may be used together with the above components, and for the purpose of including a foamed product in the resin molded body, a fine hollow sphere, water, or the like may be used. In addition to the components described above, various additives such as fillers, softeners, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, foam stabilizers, and catalysts may be added.

  Hereinafter, each component will be described.

[Urethane bond-containing isocyanate compound]
As a urethane bond containing isocyanate compound, what is marketed may be used and what was synthesize | combined by making a polyisocyanate compound and a polyol compound react may be used. The NCO equivalent of the urethane bond-containing isocyanate compound used in the present invention is preferably 500 to 600.

[Active hydrogen compounds]
Examples of the active hydrogen compound used for manufacturing the polishing pad 7 include a polyamine compound. The polyamine compound means a compound having two or more amino groups in the molecule. The polyamine compound acts as a chain extender, partly reacts with the polyisocyanate compound to form a hard segment, and partly binds to the main chain terminal side of the urethane bond-containing isocyanate compound (soft segment part). The polymer chain can be further extended. Thereby, the polyurethane polyurea resin which has the block copolymer of a hard segment and a soft segment is produced | generated. As the polyamine compound, an aliphatic or aromatic polyamine compound, in particular, a diamine compound can be used. For example, ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4′-diamine, 3 , 3′-dichloro-4,4′-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA), polyamine compounds having the same structure as MOCA, and the like. Further, the polyamine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, and di-2-hydroxy. Examples include ethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine. As the polyamine compound, a diamine compound is preferably used, MOCA, diaminodiphenylmethane, diaminodiphenylsulfone is more preferably used, and MOCA is particularly preferably used.

  The polyamine compound used as the active hydrogen compound may be used alone, or a plurality of polyamine compounds may be combined. Moreover, when the equivalent ratio of the active hydrogen compound to the equivalent of the urethane bond-containing isocyanate compound used when the polishing pad 7 is produced is defined as an R value, the R value is preferably 0.8 to 1.1.

  The polyamine compound is preferably degassed under reduced pressure in a heated state as necessary in order to facilitate mixing with other components and / or to improve the uniformity of the bubble diameter in the subsequent molding step. As a defoaming method under reduced pressure, a known method may be used in the production of polyurethane polyurea. For example, defoaming can be performed at a vacuum degree of 0.1 MPa or less using a vacuum pump. When a solid compound is used as the chain extender, it can be degassed under reduced pressure while being melted by heating.

<Mixing process>
In the mixing step, the urethane bond-containing isocyanate compound (prepolymer) and the active hydrogen compound obtained in the preparation step are supplied into the mixer and stirred and mixed. A mixing process is performed in the state which can ensure the fluidity | liquidity of said each component.

<Molded body forming process>
In the molded body molding step, the polyurethane polyurea resin molded body is molded by pouring the molded body molding mixed solution prepared in the mixing step into a mold at 50 to 100 ° C. and curing the mixture. At this time, the prepolymer and the active hydrogen compound react to form a polyurethane polyurea resin, whereby the mixed solution is cured.

<Polishing layer forming step>
The polyurethane polyurea resin molded body obtained by the molded body molding step is sliced into a sheet to form a polyurethane polyurea sheet.

  The polishing layer having the polyurethane polyurea sheet thus obtained is then affixed with a double-sided tape on the surface opposite to the polishing surface of the polishing layer, and is cut into a predetermined shape, preferably a disc shape, A polishing pad 7 can be obtained. As the double-sided tape, one arbitrarily selected from double-sided tapes known in the art can be used.

  The polishing pad 7 may have a single-layer structure composed of only the polishing layer, and is composed of a multilayer in which another layer (lower layer, support layer) is bonded to the surface opposite to the polishing surface of the polishing layer. It may be. Although the characteristics of the other layers are not particularly limited, it is preferable that a layer softer than the polishing layer is bonded to the opposite surface of the polishing layer. By providing a softer layer than the polishing layer, polishing flatness is further improved.

  When the polishing pad 7 has a multilayer structure, a plurality of layers may be bonded and fixed using a double-sided tape, an adhesive, or the like while being pressurized as necessary. There is no restriction | limiting in particular in the double-sided tape and adhesive used at this time, It can select and use arbitrarily from what is known in this technical field.

  Furthermore, the polishing pad of the present invention may be ground and / or grooved or punched on the surface and / or the back surface of the polishing layer as necessary. May be bonded to the polishing layer, and a light transmission part may be provided. There is no restriction | limiting in particular in the method of a grinding process, It can grind by a well-known method. Specifically, grinding with sandpaper or a diamond electrodeposition roll can be mentioned. There is no particular limitation on the shape of the groove or hole formed by the groove processing and punching processing, and examples thereof include a lattice shape, a concentric circular shape, and a radial shape.

  The polishing pad 7 thus manufactured has a dressing property within a specific range, and the dressing property is not inferior to that of the hard polishing pad even though the Shore D hardness is not as high as that of the hard polishing pad. It is. Here, the dressing property refers to the amount of change in the ratio of the area occupied by the dress surface, that is, the surface subjected to the dressing process, with respect to the polished surface before and after performing the dressing process. In general, the harder the polishing pad, the higher the dressing property, that is, the more the dress surface increases when the dressing process is performed, and the softer the polishing pad, the lower the dressing property, ie, the dressing process. The amount of increase in the dressing surface is small. On the other hand, although the polishing pad 7 according to the present embodiment is softer than the generally known hard polishing pad having a Shore D hardness of 50 ° or more, the dressability is not inferior to that of the hard polishing pad. It is.

  Various methods are conceivable as a method for measuring the dressing property. For example, there is a method of binarizing the CCD image of the polished surface before and after the dressing process. For example, a polishing pad that is not new and used as an example will be described. Taking a CCD image of a polishing surface of a polishing pad that is in use and binarizing the captured image, the polishing surface in the image is It can be classified into two colors: a portion worn until just before use, and a portion not corresponding to this, for example, a portion that was dressed before the last use and did not contribute to wear after the last use. In the present specification, the former is referred to as “wear surface” and the latter is referred to as “dress surface”. And in order to measure the dressing property of the polishing pad, each of the images of the polished surface before and after the dressing process is binarized, and the images of the polished surface before and after the binarized dressing process are compared, Measure the increase in dressing surface.

  According to the experiments by the inventors, the dressing property of a polyurethane hard polishing pad having a Shore D hardness of 50 °, which has been conventionally used, was measured based on the above dressing measurement method. The amount of surface increase was about 30%. On the other hand, when the dressability of a polyurethane soft polishing pad having a Shore D hardness of 35 ° was measured under the same measurement conditions, the amount of increase in the dress surface before and after the dressing was about 9%. On the other hand, by manufacturing a polishing pad by the above-described method, a polishing pad having a Shore D hardness in the range of 10 ° to 40 ° and an increase in the dress surface of 20 to 35% can be obtained. .

  Therefore, according to the embodiment of the present invention, it is possible to provide a polishing pad having a Shore D hardness lower than that of the hard polishing pad while having dressability equivalent to that of the hard polishing pad. And such a polishing pad does not impair the polishing rate, can suppress scratches, and is excellent in dressability.

  Examples of the present invention will be described in detail below.

  In Examples, four types of prepolymers shown in Table 1 below (Examples 1 and 2, and Comparative Examples 1 and 2) were prepared, and each prepolymer and curing agent (MOCA (trade name: Pandex E ( DIC)))) was mixed, poured into a predetermined mold and cured, and then the resulting molded body was sliced to produce a sheet to obtain a polishing pad. The resulting polishing pad was dressed for 10 minutes, and the polished surface before and after the dressing was imaged with a laser CCD. For the laser CCD image, VK-X200 (magnification: eye × 10 eyepiece × 20, measurement pitch: 6 μm, brightness: 6207) manufactured by KEYENCE was used. Thereafter, the picked-up image was binarized and the amount of increase in the dress surface was measured. For binarization processing, analysis software WinRof ver 6.5 (measurement range: 1 mm × 1.4 mm, median: filter 5 * 5, contrast: 75, automatic binarization: discriminant analysis threshold value 88) was used.

  In the scratch evaluation, 25 substrates were polished, and the 21st to 25th substrates after polishing were measured in a high-sensitivity measurement mode of a wafer surface inspection apparatus (Surfscan SP1DLS, manufactured by KLA Tencor). The presence or absence of scratches on the substrate surface was evaluated. Table 1 shows the measurement results of the dressing property of the polishing pad in each Example and each Comparative Example, and FIG. 2 shows the captured images of the polishing surface of the polishing pad according to Examples 1 and 2 and Comparative Examples 1 and 2, and the results. This is a binarized image.

*スクラッチの有無は、無（０枚）を○、有（１枚以上）を×として評価した。

* The presence or absence of scratches was evaluated as “No” (0 sheets) and “Yes” (1 sheet or more) as “X”.

FIG. 3 shows the measurement results of the respective polishing rates for the polishing pad showing the dressability shown in Table 1 above. The measurement conditions for the polishing rate are as follows.
-Polishing machine used: F-REX300 manufactured by Ebara Corporation
・ Rotation speed: (Surface plate) 70 rpm, (Top ring) 71 rpm
・ Polishing pressure: 220 hPa
・ Abrasive: manufactured by Cabot, product number: SS25 (SS25 undiluted solution: pure water = 1: 1 mixture)
・ Abrasive temperature: 30 ℃
・ Abrasive discharge rate: 200ml / min
Workpiece (object to be polished): Substrate in which tetraethoxysilane is formed on a 12-inch φ silicon wafer by CVD to a thickness of 1 μm of insulating film Polishing time: 60 seconds / each time Dress: 10 minutes

  As is apparent from Table 1 above, the dressability of the polishing pads of Examples 1 and 2 is almost the same as that of the hard polishing pad according to Comparative Example 1, and is superior to the soft polishing pad of Comparative Example 2. . As is apparent from FIG. 3, the polishing pads of Examples 1 and 2 having excellent dressing properties have a polishing rate superior to that of Comparative Example 2 having low dressing properties.

1 Polishing device 3 Object 7 Polishing pad

Claims (2)

A polishing pad made of polyurethane having a Shore D hardness of 40 ° or less and 10 ° or more, and the ratio of the area of the dress surface in the polishing surface to the area of the polishing surface before the dressing, and the polishing surface after the dressing The polishing pad whose difference with the ratio of the area of the dress surface in a polishing surface with respect to an area is 20 to 35%.   The said polishing pad is a polishing pad of Claim 1 shape | molded by reaction of the prepolymer containing urethane bond containing isocyanate and an active hydrogen compound.

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