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Non-intrusive Real-time Fluorocarbon Film RIE Chamber Contamination Monitor

IP.com Disclosure Number: IPCOM000108910D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 3 page(s) / 106K

Publishing Venue

IBM

Related People

Angell, D: AUTHOR [+6]

Abstract

Selective reactive ion etching of silicon dioxide using fluorocarbon-based etching gases, e.g., CHFs O2 or CHF3 Hs, is a standard pattern transfer step in Si technology. Selectivity of etching SiO2 over Si, silicides, photoresist and other materials is due to the selective deposition of a thin fluorocarbon film on the underlayers, but not on the SiO2 film as long as it is placed on the RF powered electrode. Deposition of the fluorocarbon film will take place onto SiO2 surfaces on grounded electrodes, e.g., onto a window in the chamber wall. Massive deposition of fluorocarbon film takes place onto the walls of the chamber and this effect changes significantly the chemistry of the discharge. The fluorocarbon film on the chamber walls needs to be periodically removed, e.g.

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Non-intrusive Real-time Fluorocarbon Film RIE Chamber Contamination Monitor

       Selective reactive ion etching of silicon dioxide using
fluorocarbon-based etching gases, e.g., CHFs O2 or CHF3 Hs, is a
standard pattern transfer step in Si technology.  Selectivity of
etching SiO2 over Si, silicides, photoresist and other materials is
due to the selective deposition of a thin fluorocarbon film on the
underlayers, but not on the SiO2 film as long as it is placed on the
RF powered electrode.  Deposition of the fluorocarbon film will take
place onto SiO2 surfaces on grounded electrodes, e.g., onto a window
in the chamber wall.  Massive deposition of fluorocarbon film takes
place onto the walls of the chamber and this effect changes
significantly  the chemistry of the discharge.  The fluorocarbon film
on the chamber walls needs to be periodically removed, e.g., using
oxygen plasma cleaning, since otherwise it would build up to large
thicknesses, peel off and cause a particulate problem.  Tool-cleaning
is based on a somewhat arbitrary schedule but not on the actual
contamination state of the tool.  Presently there is no reliable
method which enables the non-intrusive, in situ measurement of the
fluorocarbon film thickness.  Knowledge of the fluorocarbon film
thickness would enable scheduling tool cleaning periods based on the
actual contamination state of the tool and improve tool up-time and
avoid product loss in cases where the degree of fluorocarbon film
contamination exceeds the specification.

      A method of determining the fluorocarbon film thickness on the
chamber walls non-intrusively and in real-time is demonstrated here.
The fluorocarbon film is deposited on the metallic walls of the
process chamber and any optical windows present in the chamber walls.
X-ray photoemission studies of the deposited films have shown that
the structure of the films and the film thickness is independent of
the substrate.  The fluorocarbon film which is deposited onto an
optical window during reactive ion etching of oxide using
fluorocarbon gases attenuates the optical emission of the plasma in
the ultraviolet (250 to 320 nm) in a characteristic fashion and
varies linearly with the thickness of the film.  The dependence of...