An instrument for in-situ stress measurement in thin films during growth

An improved stress-measuring technique based on the cantilever bending principle is presented. Any thermal shift of the sample holder position that results in errors in the stress data is minimised by evaluating the difference in the deflection of two laser beams. The film thickness is calculated from the reflected laser intensity, or from ellipsometry data recorded simultaneously during film growth. Without using a lock-in technique or image processing, the resolution in the bending force per unit width is 0.02 N/m for a 50-μm thick cantilever. The system represents an easy, versatile and cheap technique to measure intrinsic and thermal stresses in thin films. The system has been employed to record the instantaneous stress during the ion beam-assisted deposition of BN films, and the global stress during the ion-induced amorphisation of silicon.