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Lateral Passivation by Double Lift-Off

IP.com Disclosure Number: IPCOM000042619D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Iyer, SS: AUTHOR [+2]

Abstract

This article relates generally to passivation techniques used in integrated circuit fabrication and more particularly to the passivation of a corrodible material including the edges thereof with a non-corrodible material. Metallization films on electronic circuits (semiconductor or otherwise) are subjected to various ambient gases, such as moisture, etc., which act to corrode the metal film both during processing and during their lifetime. Some metals have the ability for self-passiva- tion whereby a native oxide forms rapidly in a self-limiting manner and acts as a protective layer. This is most desirable, and is seen in metals such as Ti and A1. Metals such as copper, however, do not exhibit such a protective mechanism and need to be coated to passivate them.

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Lateral Passivation by Double Lift-Off

This article relates generally to passivation techniques used in integrated circuit fabrication and more particularly to the passivation of a corrodible material including the edges thereof with a non-corrodible material. Metallization films on electronic circuits (semiconductor or otherwise) are subjected to various ambient gases, such as moisture, etc., which act to corrode the metal film both during processing and during their lifetime. Some metals have the ability for self- passiva- tion whereby a native oxide forms rapidly in a self-limiting manner and acts as a protective layer. This is most desirable, and is seen in metals such as Ti and A1. Metals such as copper, however, do not exhibit such a protective mechanism and need to be coated to passivate them. Coating is accomplished by evaporating a self-passivating protective film over the metal, as shown in Fig.
1. When such films are patterned, however, a problem arises. The pattern may be defined either subtractively or by lift-off. As seen in Fig. 2, the edges of the pattern are not passivated and are easily corroded. This article shows a method by which the edges of a defined pattern may be passivated along with the top without any increase in lithographic complexity. This is done in the manner described below. As shown in Fig. 3, a thin film A of thickness tA is spun onto a substrate. Another film B of thickness tB is spun on top of film A. Film B is photosensitive and may be patterned using lithographic techniques to achieve a desired lift-off profile. Next, layer A is etched using the pattern developed in B. A slight, controlled over-etch is performed so that layer A is etched back and an und...