Current issues in the physics of heavily doped semiconductors at the metal–insulator transition

Abstract
The adhesion of thin polycrystalline metallic Ta films to Si wafer substrates was studied in situ under real–time conditions using white–beam synchrotron Laue transmission diffraction topography with simultaneous radiographic imaging. The observations were carried out using a newly developed experimental apparatus, which consisted of a computer–controlled mini–tensile stage, an 800°C ancillary furnace, and a CCD X–ray imaging system. The stress and imaging data were collected simultaneously via a video recorder and also at selected intervals by frame–grabbing/storage technology on a microcomputer. This allowed direct correlation between the stress, temperature and film–failure processes. The results for sputtered Ta polycrystalline thin films deposited onto Si wafers indicated that induced stresses led to buckling delaminations along well–defined directions. These observations can be readily extended to study a variety of film–adhesion and cycle–failure problems.