Browse Prior Art Database

Single-Step Lift-Off Process

IP.com Disclosure Number: IPCOM000047528D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Bergeron, RJ: AUTHOR [+3]

Abstract

The lift-off process forms a reproducible, uniform and well-defined structure of a material, such as photoresist, by the addition of a basic soak step prior to image exposure to harden the surface of the photoresist. The soak step forms a less soluble barrier layer which eliminates or at least minimizes the formation of round edges at the openings in the photoresist during the development of the photoresist. As indicated in the figure, a layer 10 of photoresist is deposited on a semiconductor substrate 12. After photoresist layer 10 is baked, it is soaked in, e.g., any suitable basic (alkaline) developer such as a potassium hydroxide (KOH) solution, to produce a barrier layer 10' which is less soluble than the remaining portion of layer 10.

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Single-Step Lift-Off Process

The lift-off process forms a reproducible, uniform and well-defined structure of a material, such as photoresist, by the addition of a basic soak step prior to image exposure to harden the surface of the photoresist. The soak step forms a less soluble barrier layer which eliminates or at least minimizes the formation of round edges at the openings in the photoresist during the development of the photoresist. As indicated in the figure, a layer 10 of photoresist is deposited on a semiconductor substrate 12. After photoresist layer 10 is baked, it is soaked in, e.g., any suitable basic (alkaline) developer such as a potassium hydroxide (KOH) solution, to produce a barrier layer 10' which is less soluble than the remaining portion of layer 10. The thickness of barrier layer 10' may be controlled by the developer concentration, type and immersion time. An opening 14 is formed in layer 10, including layer 10', by known techniques wherein the width of opening 14 is larger at the bottom than at the top thereof. As can be seen in the figure, a sharp edge 16 is produced in opening 14 in barrier layer 10' which improves metal image control and tolerance when depositing, e.g., aluminum 18, to form an interconnecting metal segment 18' on semiconductor substrate 12. Photoresist layer 10, including barrier layer 10', is then readily removed along with aluminum 18 formed thereon with the use of a suitable solvent by known lift-off techniques.

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