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A Novel Method to Protect Metallization from Mechanical Damage During Lift-off

IP.com Disclosure Number: IPCOM000044729D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gati, GS: AUTHOR [+2]

Abstract

A method is provided to protect metallization from mechanical damage during lift-off. This is achieved by the use of a protective layer or cap which allows the use of ultrasonics to reduce lift-off process time without endangering yield or reliability.

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A Novel Method to Protect Metallization from Mechanical Damage During Lift-off

A method is provided to protect metallization from mechanical damage during lift-off. This is achieved by the use of a protective layer or cap which allows the use of ultrasonics to reduce lift-off process time without endangering yield or reliability.

When additive type metallization is used to create metal interconnection lines in microcircuits, the unwanted metal is usually lifted off using an appropriate lift- off structure and solvent or other suitable liquid. The time period needed to complete this lift-off can be shortened considerably by using ultrasonics to agitate the liquid. Unfortunately, ultrasonic agitation, and its associated mechanical action, also frequently results in scratched or smeared metallization patterns. This is most likely caused by dangling or floating metal particles rubbing against the pattern which is rather soft (95% Aluminum).

This problem can be considerably alleviated by using the following process:

.IN 5 1. Deposit Al-Cu metallurgy according to established

procedures, as shown in Figure 1;

2. Deposit a thin layer (300-400AOE, for example) of

metal

with hardness known to be well above that for

Aluminum (Ta, Ti, or TiW, for example);

3. Proceed with conventional lift-off.

As can be seen, the thin layer of hard metal provides a scratch resistant surface for the metallization pattern.

The introduction of the protective layer allows the use of ultrasonics...