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Etch Stop for Polymer Machining With an Excimer Laser

IP.com Disclosure Number: IPCOM000036927D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Doany, FE: AUTHOR [+2]

Abstract

Disclosed is a method of trench making in polyimide to a specific, repeatable depth using a XeCl excimer laser. This method of circuit patterning polyimide can be followed by a suitable form of metallurgy application.

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Etch Stop for Polymer Machining With an Excimer Laser

Disclosed is a method of trench making in polyimide to a specific, repeatable depth using a XeCl excimer laser. This method of circuit patterning polyimide can be followed by a suitable form of metallurgy application.

An excimer laser is used as the heat source to micromachine polyimide. Energy fluences of 0.2 joule/cm2 are sufficient to ablate .02 micron of polyimide with each laser shot. It is possible to etch the polyimide down to a metal which acts as an etch stop. However, many processes of interest would be possible if we could stop at an insulator which was easily removed in another step.

For example, a few thousand-angstrom-thick layer of polymethyl methacrylate (PMMA), SiO2, or a polymer which is transparent to the 308 nm excimer laser light and scatters the laser light would be deposited at the depth where the etching is to stop. The polyimide layer could then be spun on leaving the etch stop film imbedded in the polymer film at the depth that we wish the etching to cease. The SiO2 film can be formed by several methods. Deposition by downstream microwave technique CVD or sputtering are two of the possible SiO2 deposition techniques. Polymer films could best be spun on.

When the polymer has been etched to the etch stop layer, no further etching occurs. The power window of the laser must be chosen to be high enough to machine the polymer and below the damage threshold of the SiO2 or the ablation thresh...