Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-08-03
2001-10-23
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S043000, C451S168000
Reexamination Certificate
active
06306016
ABSTRACT:
This invention relates to a wafer notch polishing machine and method of polishing an orientation notch in a wafer.
As is known, various types of wafers, such silicon wafers, have been employed in the manufacture semi-conductor chips. Typically, the wafers have been obtained by the slicing of a solid cylindrical ingot into individual wafers. Once cut, the wafers are processed in various manners and particularly to provide a peripheral edge of a predetermined contour. Various type of grinding and polishing machines have also been employed for this purpose.
As is also known, ingots have been provided with a groove to serve for orientation of the crystalline structure of the ingot so that the wafers which are obtained have a notch in the periphery. This notch serves as a reference point for the further processing of the wafers into semi-conductor chips.
During the processing of a wafer into semi-conductor chips, small subsurface cracks or fractures on the peripheral edge of the wafer have been found to have a tendency of migrating into the wafer to such an extent that a significant portion of the wafer becomes unusable for the manufacture of the semi-conductor chips. Hence, the reason for polishing the peripheral edge of the wafer is to avoid such cracks or fractures. However, one of the problems attendant with the polishing of the peripheral edge of the wafer is the need to polish the notch. To date, the techniques which have been available have been cumbersome or not used at all.
Accordingly, it is an object of the invention to provide a relatively simple polishing machine for polishing a notch in a wafer.
It is another object of the invention to be able to polish the orientation notch of a silicon wafer in a simple economical manner.
It is another object of the invention to provide a wafer notch polishing machine that can be employed as a stand-alone unit or as a station in a wafering grinding and polishing machine.
Briefly, the invention provides a wafer notch polishing machine which employs a chuck for holding a wafer having a peripheral notch thereon, means for moving the chuck in two mutually perpendicular directions on a common plane, and a polishing unit for moving a polishing medium within the notch along an axis perpendicular to the common plane and angularly within a plane perpendicular to the common plane.
The polishing unit is constructed to move the polishing medium relative to the wafer so that the polishing medium is able to polish the peripheral edge of the wafer within the notch as well as both sides of the wafer within the notch. Depending upon the cross-sectional shape of the wafer within the notch, the polishing unit is programmed to follow the contour of the notch during the polishing operation. In particular, the polishing unit includes a means for oscillating the polishing medium during movement between the two angular positions relative to the wafer. The oscillation of the polishing medium effects a polishing of the exposed surfaces of the wafer within the notch.
In one embodiment, the polishing medium is in the form of a polishing tape mounted on a rounded nose surface of a resilient backing and , in particular, in the form of a length of polishing tape that is supplied to and around the nose surface of the backing by a suitable means so that fresh surfaces of the tape may be used for polishing. For example, this means includes a supply reel disposed on an axis parallel to the common plane of movement of the chuck for feeding the polishing tape to the backing and a take-up reel disposed on an axis parallel to the same plane for winding-up of the polishing tape from the backing. In addition, the rounded nose surface has a forward portion on a radius less than a radiused portion of the notch in the wafer.
In order to move the polishing medium within a notch of a wafer, the polishing unit has a means for pivoting the backing about an axis parallel to the common plane between a first position with the backing disposed angularly of one surface of the wafer and a second position with the backing disposed angularly of the opposite surface of the wafer.
The polishing unit may be constructed to have a plurality of polishing media disposed in spaced apart parallel relation. In this way, polishing media having different grades of grit may be employed from a course grade to a fine grade. To this end, the chuck on which the wafer is mounted is indexed to move laterally from one polishing medium to another in order to conduct a notch polishing operation.
REFERENCES:
patent: 5185965 (1993-02-01), Ozaki
patent: 5289661 (1994-03-01), Jones et al.
patent: 5445554 (1995-08-01), Hosokawa
patent: 5458529 (1995-10-01), Hasegawa et al.
patent: 5733181 (1998-03-01), Hasegawa et al.
Steere, III Robert E.
Steere, Jr. Robert E.
Carella Byrne Bain Gilfillan Cecchi Stewart & Olstein
Eley Timothy V.
Hand Francis C.
Nguyen Dung Van
TSK America, Inc.
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