Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-08-05
2001-05-29
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S056000, C521S137000, C521S155000, C521S170000, C521S174000
Reexamination Certificate
active
06239188
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to method for making urethane molded products for polishing pad which are provided for polishing articles to be polished such as semiconductor devices, and also to urethane molded products for polishing pad.
2. Description of the Prior Art
Polishing pads used for semiconductor devices and glasses are known, including those pads of the porous non-woven fabric type obtained by applying a polyurethane solution to a non-woven fabric as set out in Japanese Laid-open Patent No. 64-58475 and of the foamed polyurethane type which is obtained by wet molding of a polyurethane solution. Both types of pads have a structure which is provided with cellular holes on the surface thereof, and thus, are a good property of holding an article to be polished at the time of polishing and are able to favorably retain a supplied grain solution (polishing slurry) therein. However, these pads are disadvantageous in that they are too soft to cause compressive deformation on use, poor in flatness of the surface of a polished article obtained by polishing, and short in life of the polishing pad.
In recent years, as semiconductor devices are highly integrated, an interconnection pattern on a substrate is more densified, under which there is a strong demand for flatness on a substrate surface as influencing the transfer of a pattern. In order to provide a more flattened wafer surface of a semiconductor substrate, there has been adopted a chemical mechanical polishing process (abbreviated as CMP process) wherein a chemical function and a mechanical function are combined. It has been demanded to develop a polishing pad which is suitably applicable to such CMP process.
For instance, Japanese Laid-open Patent No. Hei 8-500622 discloses a polishing pad which comprises a plurality of polymeric fine elements, such as expanded microballoons, in a polyurethane matrix. The pad has a high surface hardness, so that it is more unlikely to cause compressive deformation than such a non-woven or foamed polyurethane-type polishing pad as mentioned above, thereby ensuring a high polishing rate and a good flatness. However, only one type of the expanded microballoons are mentioned as the polymeric fine elements used. When used as a polishing pad, the cells derived from the microballoons are allowed to open at the surface of the polishing pad, and abrasive grains are held at the opened cells to ensure high polishing rate. Nevertheless, a good flatness of a polished article can not be obtained by this prior invention in which only one type of the microballoons is used.
BRIEF SUMMARY OF THE INVENTION
An object of this invention is to provide urethane molded products for use as polishing pads. The urethane molded products of the present invention comprise two type of expanded microballoons having different sizes uniformly dispersed in and throughout the urethane molded products, whereby polishing pads obtained by slicing the urethane molded products are improved in polishing characteristics. Moreover, in accordance with the present invention, variation of polishing characteristics among polishing pads is small.
According to the present invention, there is provided method for making urethane molded products for polishing pad, which comprises adding expanded microballons (C) having a size of 10 to 50 &mgr;m and expanded microballoons (D) having a size of 80 to 100 &mgr;m to an isocyanate-terminated urethane prepolymer (A) and an active hydrogen-containing compound (B) in a total amount of 0.1 to 20 parts by weight per 100 parts by weight, in total, of said isocyanate-terminated urethane prepolymer (A) and said active hydrogen-containing compound (B), and mixing the resultant mixture, wherein said expanded microballoons (C) having a size of 10 to 50 &mgr;m and/or said expanded microballoons (D) having a size of 80 to 100 &mgr;m is pre-mixed with said isocyanate-terminated urethane prepolymer (A) and/or said active hydrogen-containing compound (B). It Is preferred that the mixing ratio by weight of said expanded microballoons (C) having a size of 10 to 50 &mgr;m and said expanded microballoons (D) having a size of 80 to 100 &mgr;m is in the range of 1:0.5 to 2.0. The active hydrogen-containing compound (B) should preferably consists of a diamine compound (B-1) or a mixture of the diamine compound (B-1) and a diol (B-2) having a molecular weight of 500 to 1000. The urethane molded products for polishing pad obtained according to the present invention includes 0.1 to 20 parts by weight, in total, of expanded microballoons (C) having a size of 10 to 50 &mgr;m and microballoons (D) having a size of 80 to 100 &mgr;m per 100 parts by weight of urethane molded product.
DETAILED DESCRIPTION OF THE INVENTION
As disclosed in Japanese Laid-open Patent No. Sho 57-137323 and the like, the two types of the expanded microballoons having different sizes (C) and (D) used in the present invention are obtained by thermal expansion of non-expanded, thermally expandable microspheres which individually have a low boiling hydrocarbon, such as, for example, isobutane, pentane, isopentane, petroleum ether or the like, at a center thereof and a shell encapsulating the hydrocarbon therein and made of a thermoplastic resin such as, for example, an acrylonitrile-vinylidene chloride copolymer, an acrylonitrile-methyl methacrylate copolymer, a vinyl chloride-ethylene copolymer or the like. When heated, the low boiling hydrocarbon existing at the center of each microsphere is vaporized and gasified to cause the shell portion to be softened thereby providing a microballoon having a gas encapsulated therein.
In the present invention, two types of microballoons having different sizes are used. The expanded microballoons (C) having a size of 10 to 50 &mgr;m are obtained by expanding non-expanded, thermally expandable microspheres having a smaller size. Likewise, non-expanded, thermally expandable microspheres having a larger size are expanded to obtain expanded microballoons (D) having a size of 80 to 100 &mgr;m. Of these two types of microballoons, the expanded microballoons (C) having a smaller size contribute to the improvement in flatness of articles to be polished when applied as the polishing pad. The expanded microballoons (D) having a larger size contributes to the improvement in polishing rate of articles to be polished when applied as the polishing pad. In order to achieve an improved flatness of articles to be polished and an improved polishing rate by use of two types of microballoons having different sizes, it is necessary to control a mixing ratio between these two types of microballoons as will be described later. A preferred combination consists of the expanded microballoons (C) having a size of 10 to 50 &mgr;m and the expanded microballoons (D) having a size of 80 to 100 &mgr;m. If the size of the expanded microballoons (C) is smaller than 10 &mgr;m, a polishing effect is not shown. On the other hand, when the size is larger than 50 &mgr;m, such microballoons are likely to contribute to the improvement of the polishing rate, but the effect of improving the flatness of articles to be polished unfavorably lowers. Moreover, when the expanded microballoons (D) have a size smaller than 80 &mgr;m, the polishing rate is not effectively improved. In contrast, when the size is larger than 100 &mgr;m, physical properties of the resultant polishing pad unfavorably lower.
The isocyanate-terminated urethane prepolymer (A) used in the invention is a reaction product obtained from a polyol or a mixture of a polyol and a low molecular weight diol and an organic diisocyanate compound under ordinarily employed reaction conditions. Examples of the organic diisocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, tolidine diisocyanate, para-phenylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate and the like. These may be used singly or in combination of two or more.
The polyol for rea
Kihara Katushi
Mochizuki Yoshimi
Birch & Stewart Kolasch & Birch, LLP
Cooney Jr. John M.
Fuji Spinning Co., Ltd.
LandOfFree
Urethane molded products for polishing pad and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Urethane molded products for polishing pad and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Urethane molded products for polishing pad and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2470553