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Endpoint Detection Method for Ion Etching of Material Having A Titaniun Nitride Underlayer

IP.com Disclosure Number: IPCOM000124026D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-06
Document File: 1 page(s) / 46K

Publishing Venue

IBM

Related People

Rutten, M: AUTHOR

Abstract

By using a grounded substrate mode of ion etching at low pressure (reactive ion etching pressure) and setting an optical detector to pick up emission from nitrogen (N2), endpoint of etching, e.g., for a stud filling process, is detected when underlying titanium nitride (TiN) is etched. This endpoint detection method avoids overetching W in a stud process wherein material underlying the W deposit is TiN.

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Endpoint Detection Method for Ion Etching of Material Having A Titaniun
Nitride Underlayer

      By using a grounded substrate mode of ion etching at low
pressure (reactive ion etching pressure) and setting an optical
detector to pick up emission from nitrogen (N2), endpoint of etching,
e.g., for a stud filling process, is detected when underlying
titanium nitride (TiN) is etched. This endpoint detection method
avoids overetching W in a stud process wherein material underlying
the W deposit is TiN.

      Referring to the figure, TiN 2 is deposited on exposed surfaces
of insulator 4 having a hole which is then filled with W 6 in a
conventional process.  Ion etching is then performed to remove W 6
and TiN 2 from all surfaces external to the hole.  Etching is stopped
when intensity of a nitrogen emission line, e.g., the line at a
wavelength of 337 nm, drops sharply from its peak following removal
of TiN 2.  As a result, W 6 and TiN are removed to a level
indicated by dashed line 8.

      This etching process is performed at low pressure, as is usual
in a reactive ion etching process, but with silicon wafers having W 6
on their top surface on a grounded pedestal.  This electrode
configuration, which is usual in plasma etching, avoids optical
emission from the plasma near wafer surfaces which would create a
high background light level interfering with detection of
characteristic N2 optical emission.

      Disclosed anonymously.