New technique improves the monitoring of thin-film stress

17 Jun 2002

Using a low-power laser similar to those at supermarket checkouts together with a half dollar-sized piece of specially coated optical glass, a new technique provides simple, reliable method to determine stresses in thin film materials used in advanced electronic, magnetic and optical devices.

Developed by Sandia physicist Eric Chason and colleague Jerry Floro, the method-- although highly sensitive-- is impervious to vibrations caused by thin-film processing equipment or the rumble of passing trucks, making the technique ideal for use in manufacturing environments. From a single laser beam, the coated glass creates an array of parallel beams aligned like the teeth of a comb. By monitoring small deflections of the beams after they bounce off a target, the warp-- hence stress-- of the material can be measured. Distortions in the material as small as one-hundredth of a micron can be measured by the change in distance between the reflected beams, the researchers reported.