Abrading – Abrading process
Reexamination Certificate
1999-12-28
2002-04-23
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
C451S533000, C451S534000, C051S294000, C051S295000
Reexamination Certificate
active
06375543
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a manganese oxide-based abrasive molding, an abrasive disc provided with the abrasive molding, and a process for polishing a material to be polished by using the abrasive disc.
The abrasive disc of the invention is useful for polishing or chemicomechanically polishing substrate materials such as a silicon wafer, oxide substrate materials, compound semiconductor substrates and glass substrates, and optical materials.
More particularly, the invention relates to an abrasive molding made by molding a powdery manganese oxide raw material, and firing or sintering the molded manganese oxide product; an abrasive disc made by fixing the abrasive manganese oxide molding to a supporting auxiliary; and a process for polishing a material to be polished by using the abrasive disc.
(2) Description of the Related Art
The progress recently made in the optical and electronic industries imposes severe requirements for surface finish of materials such as, for example, magnetic discs, semiconductor substrates and single crystal materials. In processes for polishing substrate materials used in the electronic industry, a loose abrasive polishing process has heretofore been employed wherein substrate materials are polished with a polishing pad made of nonwoven fabric or suede cloth, while a polishing liquid comprising loose grains is continuously applied onto the substrate materials. As examples of the loose grains, there can be mentioned alumina, silica, ceria and zirconia. For example, a chemicomechanical polishing process for selectively polishing an insulating film such as a SiO
2
film and an electrically conductive layer such as a tungsten layer by using manganese oxide as loose abrasive grains is described in Japanese Unexamined Patent Publication (hereinafter abbreviated to “JP-A”) H9-22888 and JP-A H10-72578. In the conventional loose grain polishing process, a polishing liquid containing a large amount of loose grains is used, and thus, a considerable amount of a waste polishing liquid containing loose grains is produced during polishing. Therefore, the efficiency of the polishing process, and equipment for the waste disposal and the environmental pollution with the waste polishing liquid must be considered. The polishing pad such as a polishing cloth tends to be clogged and the polishing performance is deteriorated, and, thus, the polishing pad must be exchanged with considerable frequency and the polishing efficiency is decreased.
Further, the conventional polishing process using a polishing pad has a problem such that the surface of the polishing pad is pliable and therefore the entire surface of the material to be polished is not uniformly abraded, i.e., the corner portions of the material surface are excessively abraded upon polishing.
SUMMARY OF THE INVENTION
In order to solve the foregoing problems, the inventors have made researches to utilize an abrasive manganese oxide molding, made by molding a powdery manganese oxide, for polishing or chemicomechanically polishing substrate materials such as a silicon wafer, oxide substrate materials, compound semiconductor substrates and glass substrates, and optical materials, and found that a specific abrasive manganese oxide molding has the following benefits.
(1) The abrasive manganese oxide molding has a rough surface due to finely divided manganese oxide particles, and manganese oxide particles are brought in direct contact with a substrate material to be polished, and thus, polishing can be effected by using a polishing liquid containing no loose grain. Further, manganese oxide particles fall off from the abrasive molding only to a minimized extent, and the problem of waste disposal can be mitigated.
(2) The abrasive manganese oxide molding has a high tenacity and thus exhibits a good durability. Therefore polishing operation can be continued over a long period without exchange of the abrasive molding.
(3) A surface finish equal to those of the conventional polishing processes can be obtained. At a polishing rate equal to or higher than those of the conventional processes, a surface finish of the same quality can be obtained. Further, decrease of the polishing performance with time is minor.
(4) Even when a polishing liquid comprising a loose abrasive grain is used, a high polishing rate can be employed at an abrasive grain concentration lower than that in the conventional polishing processes.
(5) Where interconnecting minute pores of the abrasive manganese oxide molding are filled with a solid soluble in a polishing liquid, the durability of the abrasive molding and the fitness of the abrasion molding to a supporting auxiliary can be enhanced.
Thus, a primary object of the invention is to provide an abrasive manganese oxide molding, an abrasive disc having the abrasive molding, and a polishing process using the abrasive disc, wherein the abrasive manganese oxide molding is characterized as having the above-mentioned benefits.
In one aspect of the present invention, there is provided an abrasive molding predominantly comprised of manganese oxide, and having a bulk density of 0.4 to 4.0 g/cm
3
, a BET specific surface area of 0.2 to 250 m
2
/g and an average particle diameter of 0.005 to 10 &mgr;m.
In another aspect of the invention, there is provided an abrasive disc comprising an abrasive molding and a supporting auxiliary, to which the abrasive molding is fixed; said abrasive molding characterized in that it is predominantly comprised of manganese oxide, and having the above-mentioned properties.
In still another aspect of the present invention, there is provided a process for polishing a material to be polished, which comprises rubbing the material to be polished with an abrasive disc while at least one of the abrasive disc and the material to be polished is moved; said abrasive disc comprising an abrasive molding and a supporting auxiliary, to which the abrasive molding is fixed; said abrasive molding being characterized in that it is predominantly comprised of manganese oxide, and having the above-mentioned properties.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The abrasive molding of the invention is predominantly comprised of manganese oxide, and has a bulk density of 0.4 to 4.0 g/cm
3
a BET specific surface area of 0.2 to 250 m
2
/g and an average particle diameter of 0.005 to 10 &mgr;m.
By the term “manganese oxide” used herein we mean oxides of manganese usually having an oxidation number of +2 to +4. The oxidation number of manganese in manganese oxide contained in an abrasive molding can be identified, for example, by X-ray diffractometry. The oxidation number of manganese is not particularly limited provided that it is in the range of +2 to +4. According to Powder Diffraction File published by ICDD in 1991, as examples of manganese oxides having an oxidation number of +2 to +4, there can be mentioned MnO
2
Mn
2
O
3
, Mn
3
O
4
, Mn
5
O
8
and others. The oxidation number used herein is that as determined with a precision to an extent as determined by X-ray diffractometry. For example, assuming that manganese of certain manganese oxide is identified as having a chemical formula MnO
1.98
by an analyzing method other than X-ray diffractometry, for example, an oxidation number of +3.96, but, identified as having an oxidation number of 4 by X-ray diffractometry, then this should be construed to be manganese oxide with an oxidation number falling within the above-specified range in the invention.
By the term “predominantly” used herein, we mean that the abrasive manganese oxide molding comprises at least 90% by weight of manganese based on the weight of the abrasive molding. The content of manganese oxide can be expressed as a manganese oxide content as measured on a powdery manganese oxide material which has been prepared by heat-treating a powdery manganese oxide raw material. The powdery manganese oxide raw material contains moisture, and therefore, the content of manganese oxide in the molding is express
Kubota Yoshitaka
Kuramochi Hideto
Berry Jr. Willie
Hail III Joseph J.
Tosoh Corporation
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