Microtensile Testing of Thin Films in the Optical and Scanning Electron Microscopes

Because thin films are formed by processes different from those used to produce bulk materials, their microstructures, and hence their mechanical properties, are quite different from those of bulk materials of the same chemical composition. While the general principles of conventional mechanical testing are applicable to thin films, special test equipment and techniques are required. These are briefly described here. Present specimen sizes are near the limit of what can be tested in the optical microscope, so techniques useful in the scanning electron microscope are of interest. Test techniques adapted for use in the SEM are presented. These test methods have been applied to pure aluminum films deposited in our laboratory, aluminum films made in a commercial CMOS fab facility, electrodeposited copper, polyimide films, and polysilicon films. The differences among the stress‐strain curves for these very different materials were as dramatic as would be expected. Now that some experience with these test techn...