Browse Prior Art Database

Localized Emission Signal Collection Technique for Process End-Point Detection

IP.com Disclosure Number: IPCOM000120024D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 84K

Publishing Venue

IBM

Related People

Chen, L: AUTHOR [+3]

Abstract

Emission spectroscopy techniques are widely used for the detection and monitoring of plasma etching process end points when fabricating semiconductor chips. Their sensitivity is limited, however, by the pattern factor of chips present on the wafer during single reactor etching. The technique disclosed in this article overcomes this limitation by employing interferometric fringe counts, from light generated by the plasma itself, to determine the etching end point and the etch rate.

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Localized Emission Signal Collection Technique for Process End-Point
Detection

      Emission spectroscopy techniques are widely used for the
detection and monitoring of plasma etching process end points when
fabricating semiconductor chips.  Their sensitivity is limited,
however, by the pattern factor of chips present on the wafer during
single reactor etching. The technique disclosed in this article
overcomes this limitation by employing interferometric fringe counts,
from light generated by the plasma itself, to determine the etching
end point and the etch rate.

      Emission signal strength at process end point has been
determined to be a function of the pattern factor of chips on a
wafer.  When the pattern factor (the ratio of area etched to area
masked) is small, the emission signal does not change to a detectable
level at end point.  The disclosed end point detection scheme employs
an End Point Detection (EPD) site on the wafer to monitor the
emission intensity of a particular spectral line, making use of the
interference of the light generated in the plasma itself (as
reflected from the films being etched).  It thereby eliminates the
need for an external monochromatic light source.  This light is
sufficiently coherent to generate an interference pattern when
reflected from the top and bottom surfaces of the film.  By filtering
this signal with an optical filter, a graph of the interference can
be generated and the etching rate monitored.

      The disclosed technique is made opera...