Browse Prior Art Database

Etching End-Point-Detection Technique

IP.com Disclosure Number: IPCOM000061286D
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Dhong, SH: AUTHOR [+2]

Abstract

This article relates generally to integrated circuit fabrication and, more particularly, to a method for end-point detection during wafer etching. Etching end-points on each of the wafers in a batch can be detected with a laser interferometer system by including a rotating mirror to repeatedly scan the wafers in succession. Referring to Fig.1, light from laser 1, that includes an adjacent detector 2, is reflected by either an oscillating or rotating mirror 3 to reflect light in succession to individual mirrors (not shown) each directing its beam to one of the wafers 4 and returning reflected light to detector 2. A quarter-wave retardation plate is inserted in the scanning beam to establish the necessary delay. Mirror 3 can be operated by a synchronous motor to provide desired sampling frequency.

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Etching End-Point-Detection Technique

This article relates generally to integrated circuit fabrication and, more particularly, to a method for end-point detection during wafer etching. Etching end-points on each of the wafers in a batch can be detected with a laser interferometer system by including a rotating mirror to repeatedly scan the wafers in succession. Referring to Fig.1, light from laser 1, that includes an adjacent detector 2, is reflected by either an oscillating or rotating mirror 3 to reflect light in succession to individual mirrors (not shown) each directing its beam to one of the wafers 4 and returning reflected light to detector 2. A quarter-wave retardation plate is inserted in the scanning beam to establish the necessary delay. Mirror 3 can be operated by a synchronous motor to provide desired sampling frequency. An alternative rotating mirror for directing light to and receiving light from the individual wafer mirrors is shown in Fig.2. This device rotates about axis 5 and uses front side mirrors 6 and 7 to scan the wafers and mirror 8 to return light to detector 2. Detector 2 output is fed to a sample-and-hold circuit, then sent to a comparator. An attached computer makes a determination of the etching status from the signal level. Sampling is done after a predetermined delay of the signal from each wafer to assure reflection from a flat portion of the detector output.

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