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EDGE ROUGHNESS DETECTOR FOR SEMICONDUCTOR WAFERS

IP.com Disclosure Number: IPCOM000005720D
Original Publication Date: 1988-Oct-01
Included in the Prior Art Database: 2001-Oct-30
Document File: 1 page(s) / 54K

Publishing Venue

Motorola

Related People

George Wayne Hawkins: AUTHOR

Abstract

This device detects local rough spots in a semiconductor wafer edge by recording the noise created by rubbing the edge with a piece of plastic. Edge roughness on wafers frequently is due to flaws or cracks in the wafer edge. Such flaws reduce the strength of wafers. This detector system locates the flaws quickly, without damaging the wafer, and makes a permanent record of location and approximate magnitude.

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MOTOROLA Technical Developments Volume a October 1988

EDGE ROUGHNESS DETECTOR FOR SEMICONDUCTOR WAFERS

by George Wayne Hawkins

   This device detects local rough spots in a semiconductor wafer edge by recording the noise created by rubbing the edge with a piece of plastic. Edge roughness on wafers frequently is due to flaws or cracks in the wafer edge. Such flaws reduce the strength of wafers. This detector system locates the flaws quickly, without damaging the wafer, and makes a permanent record of location and approximate magnitude.

   In operation, a motorized rotating vacuum chuck holds the wafer, with the wafer edge extending beyond the chuck edge. The edge of a plastic tape rubs against the wafer edge as the wafer rotates about its center. The tape is pulled through the machine by a slow drive motor, to avoid wear of the tape edge by the wafer roughness. Any flaws in the wafer edge make the tape vibrate, which generates noise. The noise is picked up by a microphone, high pass filtered, rectified, and low pass filtered. The noise level is recorded on a strip chart recorder, and the location of a noise burst on the chart can be correlated with the location of the flaw on the wafer edge.

   Compared to previous methods of finding and recording flaws by operators using optical microscopes, this system is faster, more objective and more certain to pick up isolated flaws. Compared to stylus roughness gages, this system does not damage the wafers and separates sharp ro...