A novel technique for the measurement of stress in thin metallic films

A novel interferometric method for determining mechanical stress in vacuum-deposited thin metallic layers on glass substrates is described. Stress in the glass - metal structure affects the curvature and hence the resonant frequencies of the substrate. Thus, by measuring variations of the resonant frequencies, the curvature and hence the stress can be determined. The technique of photo-thermoelastic bending has been adapted to this measurement. Measuring the variation in resonant frequency is a very sensitive method of determining the substrate curvature. Tests of the new technique using thin Cr films on glass demonstrate its effectiveness.