Browse Prior Art Database

Laser Customized Liftoff Stencils for Circuit Repair and Engineering Changes

IP.com Disclosure Number: IPCOM000106018D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Donelon, JJ: AUTHOR [+3]

Abstract

Disclosed is a method for locally depositing high quality metal with high resolution on any substrate for the efficient repair of metal circuits supported on such substrates.

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This is the abbreviated version, containing approximately 52% of the total text.

Laser Customized Liftoff Stencils for Circuit Repair and Engineering Changes

      Disclosed is a method for locally depositing high quality metal
with high resolution on any substrate for the efficient repair of
metal circuits supported on such substrates.

      Many methods for the repair of metal circuits supported on
insulating polymer substrates have been described in the prior art,
some utilizing an excimer laser.  The disclosed method also use an
excimer laser to create a liftoff stencil but either create a good
overhang at the top surface of the polyimide or make nearly vertical
walls.

      The methods diagrammed in the drawing consist of a first
blanket coating ~  5 &mu.m of soluble polymer (polyimide or
equivalent), then coating a thin ~  1 &mu.m of AZ resist
which is then silylated to produce an oxygen reactive ion etch (RIE)
barrier.  The open circuit which has previously been located by
optical or electron beam inspection techniques, is visible through
the silylated resist only.  The laser tool used may be the same as is
used to delete shorts but the fluence is chosen to etch the silylated
resist in a smooth controlled fashion.  The laser is used to image a
variable size aperture which is projected onto the part by an
objective lens.

      Once the pattern is created in the silylated resist, the rest
of the stencil can be created in either of two ways.  The first
method is to use RIE with an oxygen plasma.  This produces a good
overhang and the etch rate is slow and well known so that a precisely
etched depth is easily produced.  If the metal line contains a top
chromium adhesion layer it can be easily removed in a RIE process.
This step is necessary to produce low contact resistance between the
original metal and the repair.  The part is then placed in a metal
evaporator and high quality vacuum deposited metal is blanket coated
on the part.  The liftoff stencil is then removed in standard
solvents.

      The second method for completing the liftoff stencil once the
silylated resist has been op...