Browse Prior Art Database

Protective Coating for Photolithographic Masks

IP.com Disclosure Number: IPCOM000120015D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

Bassous, E: AUTHOR [+5]

Abstract

Disclosed is a method to improve the performance and extend the useful life of a photolithographic mask (photomask). The method involves the deposition of a thin transparent coating of diamond-like carbon (DLC) on the patterned surface of the photomask. The DLC coating protects the chromium pattern from physical damage and allows frequent cleaning of the patterned surface, thereby extending the useful life of the mask.

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Protective Coating for Photolithographic Masks

      Disclosed is a method to improve the performance and
extend the useful life of a photolithographic mask (photomask). The
method involves the deposition of a thin transparent coating of
diamond-like carbon (DLC) on the patterned surface of the photomask.
The DLC coating protects the chromium pattern from physical damage
and allows frequent cleaning of the patterned surface, thereby
extending the useful life of the mask.

      A typical photomask is an optically transparent glass plate
which supports a circuit pattern on one of its surfaces.  The pattern
is typically defined in a thin chromium film which is opaque to
ultraviolet light.  The photomask pattern is subject to frequent
contact with resist-coated substrates which lead to contamination and
physical damage to the opaque pattern.

      DLC films can be deposited on photomask glass plates at
relatively low temperature and under conditions which do not affect
the physical and chemical properties of the chromium pattern and the
glass surface.  For this purpose, a DLC film is typically obtained by
plasma- assisted chemical vapor deposition (PACVD) of acetylene at a
substrate temperature of 30 to 200o C and substrate bias of -80 to
-150 V DC (1,2)  An interfacial layer of amorphous silicon 2 to 4 nm
thick is first deposited, followed by deposition of the DLC film.
The silicon film promotes adhesion of the DLC layer to the metal
pattern on the glass phot...