Sandia develops thin-film stress sensor

17 Jun 2002

Precision stress monitoring of thin films during processing is possible with a charge-coupled-device (CCD) camera-based system developed by researchers at Sandia National Laboratories. Multiple parallel beams from a single 0.5-mW diode-laser source are scanned onto an etalon that reflects them into a line arrangement on the film being tested.

Spacing between reflections is monitored by the CCD camera, with changes in the spacing indicating surface stress. Distortions on the order of 0.01 mm can be detected. With a second etalon at right angles to the first, a square beam array is generated for detecting stresses across a film area rather than just along a line, researchers say.