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Image Reversal Lift-Off Process

IP.com Disclosure Number: IPCOM000048743D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Hamel, CJ: AUTHOR [+3]

Abstract

This photolithographic process provides a negative image lift-off structure using Shipley AZ-type positive photoresist. Image reversal is accomplished by causing decarboxylation of the photoactive compound decomposition products in initially exposed areas in order to render these areas less soluble in an alkaline developer than the originally unexposed areas which are subsequently rendered soluble by a blanket exposure prior to development. Decarboxylation is accomplished by subjecting image-exposed photoresist to a basic environment, preferably gaseous ammonia, either in the presence of heat, or followed by a heating step.

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Image Reversal Lift-Off Process

This photolithographic process provides a negative image lift-off structure using Shipley AZ-type positive photoresist. Image reversal is accomplished by causing decarboxylation of the photoactive compound decomposition products in initially exposed areas in order to render these areas less soluble in an alkaline developer than the originally unexposed areas which are subsequently rendered soluble by a blanket exposure prior to development. Decarboxylation is accomplished by subjecting image-exposed photoresist to a basic environment, preferably gaseous ammonia, either in the presence of heat, or followed by a heating step.

A specific process includes the steps of:
1. Applying standard Shipley AZ-1350J positive photoresist to a

desired thickness.
2. Drying at 75 degrees C for about five minutes on a hot plate.
3. Exposing through a correct positive mask.
4. Exposing to ammonia vapor at ambient conditions for about five

minutes.
5. Baking at 95 degrees to 100 degrees C for about ten minutes.
6. Blanket exposing.
7. Developing in an aqueous KOH solution in order to form a

negative image of the originally exposed areas.

Steps 4 and 5 may be combined in an alternative version of the process.

A proposed mechanism for this process is based on the decarboxylation of the diazonapthoquinone sensitizer decomposition products in the initially exposed areas in the presence of a base.

This is followed by normal exposure and development of the p...