Browse Prior Art Database

Etch Laser End Point Progress

IP.com Disclosure Number: IPCOM000102741D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 30K

Publishing Venue

IBM

Related People

Tousley, SR: AUTHOR

Abstract

The method taught herein provides an accurate and repeatable method of determining the point at which an oxide layer is etched away even when the oxide overlies a polysilicon substrate.

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Etch Laser End Point Progress

      The method taught herein provides an accurate and repeatable
method of determining the point at which an oxide layer is etched
away even when the oxide overlies a polysilicon substrate.

      Normally laser end point detection requires a flat response at
the point of etch through of the oxide film being monitored and such
occurs when an oxide film overlies a silicon substrate.

      However, when the oxide overlies a polysilicon substrate, no
such flat response can be detected because of signal interference at
the oxide-polysilicon interface.

      To determine the end point in this case it is necessary to
determine when the slope of the curve of the detected signal
(mv/minute) goes through a minimum value and again begins to
increase.  When the slope of the curve again rises to meet the
selected value (usually selected at 500 mv/minute), it is known that
etch through of the oxide has occurred and the process can be
terminated.

      This technique can also be used to guarantee a small amount of
overetch into the polysilicon underlayer.

      Disclosed anonymously.