Abrading – Machine – Rotary tool
Reexamination Certificate
1999-12-21
2001-08-14
Rose, Robert A. (Department: 3723)
Abrading
Machine
Rotary tool
C451S388000, C451S398000
Reexamination Certificate
active
06273804
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for polishing wafers and, particularly, to an apparatus for polishing semiconductor wafers relying upon a chemical-mechanical polishing (CMP) method.
2. Description of the Related Art
In recent years, ICs have been finely machined and IC patterns have been formed in a multiplicity of layers. Some degree of roughness is inevitably formed in the surfaces of the layers on which the patterns are formed. According to the prior art, the pattern of the next layer has been formed without any treatment. As the number of the layers increases and as the widths of the lines and holes decrease, however, it has become difficult to favorably form patterns and defects occur easily. Therefore, it has been attempted to form the pattern of the next layer after the surface of the layer on which the pattern is formed is flattened by polishing. The wafer-polishing apparatus (CMP apparatus) based on the CMP method is employed to polish the wafer in the step of forming the IC patterns.
There has been widely employed a wafer-polishing apparatus comprising a disk-like polishing table having a polishing pad stuck on the surface thereof, a plurality of wafer-holder heads that hold the surfaces on one side of the wafers to be polished and bring the other surfaces of the wafers into contact with the polishing pad, and a holder head drive mechanism for turning the wafer-holder heads relative to the polishing table, and wherein a slurry, which is a polishing agent, is supplied between the polishing pad and the wafers to polish the wafers.
As a wafer-holder mechanism in a wafer-holder head, there have heretofore been known one by which a wafer is adhered to a carrier via a wafer-adhering sheet (Japanese Unexamined Patent Publication (Kokai) No. 8-229808) and one by which a very finely porous insert having elasticity is adhered to the carrier and the wafer is held by being adhered thereto (Japanese Unexamined Patent Publication (Kokai) No. 6-79618).
According to the above-mentioned conventional wafer-holder mechanisms, however, a so-called packing sheet must be stuck to the surface of the carrier, and bubbles evolve at the time of sticking the packing sheet requiring skill for sticking, the degree of flatness on the surface on which the packing sheet is stuck affects the wafer-machining surface, and the wafer-holder head must be removed for sticking the packing sheet.
The applicant therefore has proposed an apparatus for polishing wafers in which an air-blowing member is provided under the lower surface of the carrier that is loosely supported in a wafer-holder head body so as to move up and down, in order to blow the air toward the back surface of the wafer thereby to form a pressurized fluid layer between the carrier and the wafer, and the wafer is held being pushed onto the polishing table via the pressurized fluid layer, as taught in Japanese Patent Application No. 10-92030 filed by the applicant.
Even in the wafer-holder mechanism in the above-mentioned apparatus for polishing wafers, however, the back surface of the wafer is likely to come into direct contact with the hard surface of the carrier and is scratched while the wafer is held by adsorption and is polished.
SUMMARY OF THE INVENTION
In view of the above-mentioned problem, the object of the present invention is to provide a wafer-holder mechanism which does not permit the back surface of the wafer to come into contact with the hard surface of a ceramic carrier and be scratched, and to facilitate the removal of the retainer ring so that the protection sheet can be easily attached.
As a means for solving the above-mentioned problem, the present invention provides an apparatus for polishing wafers as described in the claims.
In the apparatus for polishing wafers according to an embodiment of the present invention, a retainer ring is held by a carrier using an O-ring, enabling the retainer ring to be pulled down so as to be easily removed from the carrier and further enabling the retainer ring to be easily attached by simply pushing it. This facilitates the operation for exchanging the protection sheet and an exchange unit of the retainer ring within a short period of time, without permitting the slurry to dry that could cause scratching, and decreasing the time in which the retainer ring is immersed in water for preventing the slurry from drying.
When fitted to the carrier, further, the centering of the retainer ring is easily accomplished relying on the O-ring.
In the apparatus for polishing wafers according to another embodiment of the present invention, an air-blow member is provided on the lower surface of the carrier and a protection sheet is provided on the outer surface thereof, in order to prevent the back surface of the wafer from coming in contact with the surface of the hard carrier and being scratched.
In the apparatus for polishing wafers according to a further embodiment of the present invention, the peripheral edges of the protection sheet are held by the retainer ring, so that the protection sheet can be easily attached.
In the apparatus for polishing wafers according to a still further embodiment of the present invention, the retainer ring is constituted by three members, i.e., a retainer body, an exchange unit and a fall-stop fitting, in a manner that it can be assembled and disassembled, enabling the exchange unit to be quickly and easily exchanged, the exchange unit being subject to abrasion caused by being in contact with the polishing pad at all times and being likely to be exchanged relatively frequently. Further, the peripheral edges of the protection sheet can be held by the retainer body and by the exchange unit, and can be easily attached and detached.
In the apparatus for polishing wafers according to a yet further embodiment of the present invention, a ring-like groove is formed on the inside in the lower surface of the retainer body or on the inside in the upper surface of the exchange unit, to impart a margin for the elongation of the protection sheet. This permits the protection sheet to easily elongate.
In the apparatus for polishing wafers according to a further embodiment of the present invention, a ring-like thick portion is formed along the outer periphery of the protection sheet to prevent the protection sheet from escaping.
In the apparatus for polishing wafers according to another embodiment of the present invention, a disk-like recess is formed in the protection sheet, in order to absorb irregularity in the pushing force caused by the protection sheet having irregular thickness. Further, the air gap is maintained to a sufficient degree to maintain a favorable flow of air.
In the apparatus for polishing wafers according to a further embodiment of the present invention, the protection sheet is provided with holes for adsorption to reliably hold the wafer by adsorption.
Even when the air is blown out from the air-blow member of the carrier while the wafer is being polished, the protection sheet is pushed onto the back surface of the wafer, and the holes for adsorption are closed and no air is permitted to escape through the holes for adsorption.
The present invention may be more fully understood from the description of preferred embodiments of the invention set forth below, together with the accompanying drawings.
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patent: 0861706 A1 (1998-02-01), None
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patent: 6-79618 (1994-03-01), None
patent: 8-229808 (1996-09-01), None
patent: 10-012578 (1998-01-01), None
patent: 10-270538 (1998-10-01), None
patent: 10-92030 (1999-03-01), None
patent: 11090820 (1999-11-01), None
patent: WO 98/210
Christie Parker & Hale LLP
Rose Robert A.
Tokyo Seimitsu Co. Ltd.
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