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Measuring Local Stress in Thin Films

IP.com Disclosure Number: IPCOM000074363D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 3 page(s) / 30K

Publishing Venue

IBM

Related People

Lin, SCH: AUTHOR [+2]

Abstract

This method allows measurement of localized compressive or tensile stresses in thin-noncrystaline films at the interface between the film and a substrate.

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Measuring Local Stress in Thin Films

This method allows measurement of localized compressive or tensile stresses in thin-noncrystaline films at the interface between the film and a substrate.

The method consists of determining the stressed and unstressed length of a thin section of film and thereafter determining the stress according to the relationship sigma = (E/1-mu)epsilon where E is Young's Modulus, mu is Poisson's ratio and epsilon (strain) is (L-L(0)/L(0)) where L(0) is the unstressed length of the film. Two methods are illustrated by the following examples.

A. 1) Utilizing a standard photoresist etch technique etch

away film 1 from the surface of substrate 2, as shown

at A, to provide an opening of length "a" leaving a bar

3 of length a/2 and a convenient width "t" in the center

of the opening. Width t should be wide enough to prevent

bending of bar 3 under its own weight or from breaking

away from the remainder of film 1 during processing.

2) Measure the length "L" of bar 3 with a light microscope.

3) Apply additional photoresist and etch away enough of

substrate 2 from under bar 3 to leave it cantilevered,

thereby relieving any film-substrate stress in the

length direction.

4) Measure the unstressed length "L(0)" of

bar 3 as in step 2.

5) The strain is determined as described above. If the

etched dimension of bar 3 is known, step 2 may be

eliminated and step 4 may be accomplished

by photographing the stressed bar and substituting

the photographed lengths of a and L(0) with

L equal to half the photographed

length of a.

B. Where accurate interface compressive

stress...