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Excimer Laser Etch Stop for Thin Film Module Fabrication

IP.com Disclosure Number: IPCOM000121680D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 3 page(s) / 59K

Publishing Venue

IBM

Related People

Donelon, JJ: AUTHOR [+2]

Abstract

A technique is described whereby an etch depth stop for polymer ablation is achieved by means of excimer laser radiation.

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This is the abbreviated version, containing approximately 79% of the total text.

Excimer Laser Etch Stop for Thin Film Module Fabrication

      A technique is described whereby an etch depth stop for
polymer ablation is achieved by means of excimer laser radiation.

      It has been demonstrated that a thin layer of Al2O3 (Z1500 o)
imbedded between two layers of polyimide acts as an excimer laser
etch stop.  The fluence levels must be chosen so as not to exceed the
etching threshold of the oxide.

      A feature has been ablated into a (Z5.6 m thick) polyimide
film, using an excimer laser at 248 nm at a 1 Hz repetition rate.
The laser fluence used, as shown in Fig. 1, was Z 145 mJ/cm2 .  Under
the polyimide film is the Al2O3 layer, under which is a 10 m
polyimide film.  This film structure is on a Si wafer that has a thin
Cr adhesion layer, as shown in Fig. 2.  The Al2O3 is sputtered to
assure the repeatability of the stoichiometry between samples.  It is
evident from the knee in the curve in Fig. 1, that no additional
polyimide etching occurred after the aluminum oxide film was reached.

      When this method of fabrication is combined with a proximity or
projection mask, it provides trenches of a specific depth.  The
trenches are then filled with Mo, or other suitable metal, to form
the required circuitry.  The polymer can be overcoated, prior to this
process, with a lift-off polymer, or a non-baked photoresist.  After
the trenches are ablated, a vapor deposited metallic layer of the
same thickness as the trench depth will b...