Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18
The Photoelastic/Topographic Analyzer (PTA) allows screening of wafers for internal stresses prior to further processing. The analyzer simultaneously performs two functions: it examines the wafer surface topography by means of a 2-beam interferometer, and it detects stresses within the wafer by viewing it in the near infrared between crossed polarizers. By this technique, bad wafers can be discarded before undergoing extensive processing. The tester is comprised of the following three optical systems: Michelson Interferometer IR Illumination System Polariscope IR Imaging System For clarity, the interferometer and the polariscope will be described separately, although in actual use both functions are implemented in one unit, sharing common components.