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Browse Prior Art Database

Etch Rate Monitor

IP.com Disclosure Number: IPCOM000062149D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Dhong, SH: AUTHOR [+2]

Abstract

This article relates generally to a device for monitoring the etching rate during integrated circuit construction and, more particularly, the etching rate of metals during reactive ion etching or plasma etching. Etching of metals can be more precisely and reliably controlled with a dual beam interferometer. Referring to the figure, beam splitter 1 reflects light in two beams 2,3 from laser source 4 toward a work surface. One of the beams 2 is directed to impinge on photoresist 5 having a known index of refraction, and reflect from that surface or the surface 6 beneath it. The other beam 3 impinges directly on workpiece 7 and reflects therefrom. Shutter 8 is selectively movable to block beam 3. The interference pattern is detected at the output of photocell 9.

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Etch Rate Monitor

This article relates generally to a device for monitoring the etching rate during integrated circuit construction and, more particularly, the etching rate of metals during reactive ion etching or plasma etching. Etching of metals can be more precisely and reliably controlled with a dual beam interferometer. Referring to the figure, beam splitter 1 reflects light in two beams 2,3 from laser source 4 toward a work surface. One of the beams 2 is directed to impinge on photoresist 5 having a known index of refraction, and reflect from that surface or the surface 6 beneath it. The other beam 3 impinges directly on workpiece 7 and reflects therefrom. Shutter 8 is selectively movable to block beam 3. The interference pattern is detected at the output of photocell 9. The reflected beams interfere with each other to produce an interference pattern. This pattern enables the relative etched depth of the photoresist and workpiece surface to be determined. If the shutter is closed, a single beam interferometer results. From the known index of refraction, the absolute depth of photoresist can be found. Etch rate is provided by differentiating the etched depth with respect to time. A small computer can be used to aid analysis of the interference patterns.

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