Browse Prior Art Database

Etch End Point Detector

IP.com Disclosure Number: IPCOM000079030D
Original Publication Date: 1973-Apr-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Price, RN: AUTHOR

Abstract

Shown is an etch end-point detector system to automatically detect the completion of etch while etching metal and oxide films. The problem of overetching and underetching due to variance in film parameters, etchant temperature and etchant concentration are eliminated.

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Etch End Point Detector

Shown is an etch end-point detector system to automatically detect the completion of etch while etching metal and oxide films. The problem of overetching and underetching due to variance in film parameters, etchant temperature and etchant concentration are eliminated.

The system comprises a laser 1, a light pipe 2, an etch tank 4, a phototransistor detector and a detector electronics package 5. The etch tank consists of an etching chamber 6 surrounded by a constant temperature water chamber 7. One end of the light pipe 2 is inserted in the etch tank flush with the transparent wall 8 of the etch chamber 6, with a sleeve 9 isolating the light pipe from the water. The fibers in the light pipe 2 are randomly orientated and are divided in two bundles at the other end. The laser light 1 is directed to the end of one bundle 10 and the phototransistor electronics is coupled to the end of the other bundle 11.

When etching oxide films, monochromatic light is transmitted from the laser 1 to the surface of a wafer (inserted in the tank 4) via half of the randomly orientated fibers of the light pipe 10-2, and reflected light from the wafer is transmitted to the photo-detector electronics system 5 via the other half of the light pipe bundle 2-11. Because of interference phenomena, the reflected signal will vary in a sinusoidal manner as the film thickness changes during etch. The detector electronics filters and differentiates the reflected signal, whic...