Abrading – Flexible-member tool – per se
Reexamination Certificate
1999-10-26
2001-04-10
Eley, Timothy V. (Department: 3723)
Abrading
Flexible-member tool, per se
C451S527000, C451S529000, C451S533000, C451S539000
Reexamination Certificate
active
06213858
ABSTRACT:
BACKGROUND OF THE INVENTION
The purpose of this invention is to produce seamless, composite belts for improved polishing of semiconductor wafers as a result of the belts lying flat, without cupping up or down, while in contact with a semiconductor wafer.
Chemical mechanical polishing (CMP) of semiconductor wafers is a relatively new technology used in the manufacture of integrated circuits. Conventional CMP technology involves holding a wafer face down in contact with a flat polishing pad mounted on a rotating turntable. This arrangement derived from traditional glass polishing technology. More recently a new type of CMP polishing tool has been invented by Ontrak Systems, later acquired by Lam Research. The new tool, as described in U.S. Pat. No. 5,692,947, uses a linear polishing member comprising a conventional, flat polishing pad adhered to a supporting endless metal belt. Currently there are no one-piece belts available either for use in polishing semiconductor wafers or for use on Lam's tool.
A division of Scapa Group has been developing a seamless, composite belt for use on Lam's proprietary polishing tool. There are many difficulties and constraints involved with developing such a belt that integrally combines sufficient strength and a precision polishing surface and that can be manufactured efficiently and consistently. One unexpected problem in particular was that the prototype belts would not maintain a flat surface, i. e., the edges of the belt would curl up or down in the span between the mounting rollers, which resulted in poor polishing performance because of uneven contact with the surface of the semiconductor wafer. The present invention overcomes this critical problem.
SUMMARY OF THE INVENTION
The present invention comprises a seamless, composite belt that is designed, constructed, or manufactured to maintain a substantially flat surface in the span between two rollers. The belts of the present invention typically have one or more polymer layers, including the polishing layer, and one or more supporting woven or non-woven layers. The present invention is accomplished by achieving the necessary balance between down-cupping and up-cupping forces using one or more of the following approaches: 1) varying the relative thickness of the different polymer and supporting layers in the belt, 2) varying the relative hardness or rigidity of the different layers in the belt, 3) varying the temperatures at which the different layers are formed, 4) varying the compositions of supporting layers, and 5) prestressing one or more of the composite layers.
Belts of the present invention are particularly useful in chemical mechanical polishing of semiconductor wafers, where it is critical to maintain even contact with the entire surface of the flat wafer. In addition, belts of the present invention would be useful in other applications, including other polishing applications, printing applications, and material handling applications, for example, where uniform contact between the belt and the workpiece is necessary.
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Berry Jr. Willie
Eley Timothy V.
Lyon & Lyon LLP
Scapa Group PLC
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