Browse Prior Art Database

Dry/Wet Lift-Off Process

IP.com Disclosure Number: IPCOM000043194D
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Logan, JS: AUTHOR [+2]

Abstract

In patterning thin film by the lift-off process, unwanted material is removed by dissolving or swelling the underlying polymer with a suitable solvent. When this polymer has been heated or irradiated during processing, this requires aggressive solvents used at high temperatures for long times. The disclosed process avoids this by etching the underlying polymer in an active, selective atmosphere and subsequently washing away the loosened metal in a mild liquid rinse. As an example of this process, aluminum-copper (AlCu) was evaporated over polysulfone photoresist patterned in a lift-off configuration. The wafers were then ashed for five minutes in 1.5 Torr oxygen at 300 watts. The chamber was preheated to 80ŒC.

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Dry/Wet Lift-Off Process

In patterning thin film by the lift-off process, unwanted material is removed by dissolving or swelling the underlying polymer with a suitable solvent. When this polymer has been heated or irradiated during processing, this requires aggressive solvents used at high temperatures for long times. The disclosed process avoids this by etching the underlying polymer in an active, selective atmosphere and subsequently washing away the loosened metal in a mild liquid rinse. As an example of this process, aluminum-copper (AlCu) was evaporated over polysulfone photoresist patterned in a lift-off configuration. The wafers were then ashed for five minutes in 1.5 Torr oxygen at 300 watts. The chamber was preheated to 80OEC. The wafers were then immersed in 7:1 buffered HF for 10 seconds to remove any back-sputtered coating (from a previous sputter clean step) from along the underlying sidewall. The wafers were again ashed at 300 watts in 1.2 to 2.0 Torr O2 for 30 minutes. This largely removed the polysulfone underlay. A soak for 5-10 minutes in n-methyl-2pyrrolidone (NMP) at 80OEC causes the unwanted AlCu to float off. A final ashing under the above conditions for 10 minutes removes any polysulfone residues.

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