Author

Sangki Hong

Abstract

In the rapidly developing semiconductor industry, sputter deposition is the most widely used metallization (metal coating) process in chip manufacturing and packaging. Since most sputtered coatings are in a state of stress, understanding the origin of stress is very important. High stress can lead to electrical shorts and mechanical instability in a microelectronic circuit pattern.

The purpose of this thesis is to investigate the parameters which can be used to control stress in sputtered metal films. We worked with sputtered copper on polyimide (Kapton H) as a film-substrate combination which occurs frequently in the microelectronic packaging industry.

Stress and film growth in sputtered films were studied as a fuction of: (1) argon gas pressure, (2) deposition rate, and (3) film-thickness. Two types of stress were observed: (1) compression (the film is trying to expand on the substrate) and (2) tension (the film is trying to contract on the substrate). As argon pressure is increased for a fixed deposition rate of 2.0 Å/s, stress changes from compression to tension at a transition pressure of 2.5 mTorr. As deposition rate is increased for a fixed pressure of 5.0 mTorr, stress changes from tension to compression at a deposition rate of 4.8 Å/s. In both cases, in the initial stages of film growth, stress increases rapidly until a "critical thickness" is reached; above this thickness, stress decreases gradually.

Our results suggest that stress (and thus mechanical and electrical film properties) may be controlled with deposition conditions. The study of stress as a function of film thickness leads to a better understanding of how internal stress originates in the film-substrate system.

Library of Congress Subject Headings

Thin films--Testing--Analysis; Metal coating--Testing--Analysis; Strains and stresses; Microelectronic packaging--Materials

Publication Date

1-1-1988

Document Type

Thesis

Student Type

Graduate

Degree Name

Materials Science and Engineering (MS)

Department, Program, or Center

School of Chemistry and Materials Science (COS)

Advisor

Alan B. Entenberg

Advisor/Committee Member

Robert A. Clark

Advisor/Committee Member

Vern Lindberg

Comments

Physical copy available from RIT's Wallace Library at TK7871.5.F5 H664 1988

Campus

RIT – Main Campus

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