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Free Polishing Apparatus

IP.com Disclosure Number: IPCOM000088236D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Markovits, G: AUTHOR [+2]

Abstract

In the free polishing apparatus a workpiece, such as a semiconductor wafer, fits in a nest which is then sandwiched between two counter-rotating polishing pads. This produces a smooth backside as well as a polished frontside. A new design for the wafer nest is provided which has the advantages of doubling the output of the free polisher and retaining a rough backside where desired. Normal free polishing wafer nests are like that labeled "top nest" in Fig. 2B.

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Free Polishing Apparatus

In the free polishing apparatus a workpiece, such as a semiconductor wafer, fits in a nest which is then sandwiched between two counter-rotating polishing pads. This produces a smooth backside as well as a polished frontside. A new design for the wafer nest is provided which has the advantages of doubling the output of the free polisher and retaining a rough backside where desired. Normal free polishing wafer nests are like that labeled "top nest" in Fig. 2B.

Nest 1 (Figs. 1A and 1B) is made of a flexible material just slightly thinner than the incoming wafer. Wafers are placed in nest holes 2 and they are then sandwiched between two large counter-rotating polishing rings (not shown). The edge of the nest has teeth 3 which engage in a free-wheeling central gear to maintain spacing between the nest assemblies. In addition the upper and lower pads are chosen with different coefficients of friction so that there will be forces on the wafer causing it to rotate itself within nest 1.

The improved nest illustrated in Figs. 2A and 2B consists of three parts including upper and lower nests 1. Between the upper and lower nests is a separator 4, which is the same diameter and edge design as the upper and lower nests, but it may be thicker and does not have any holes in it. The material for the separator is selected to have a different coefficient of friction than the polishing pads which are now identical for top and bottom rings.

The bottom nest i...