Stress analysis in Si membranes for open stencil masks and mini-reticles using double bulging and resonance methods

Abstract

This paper presents two measurement methods for stress determination of Si-membranes. The first one is based on the bulging method. This method was modified by the deflecting of the membrane in both direction, the so-called double bulging technique. A novel improved least-square fitting technique to double bulging data allows to increase the accuracy of the method especially for the membranes with stresses lower than 2 MPa. Additionally it is possible to verify the set up alignment for the diffraction-image method. This method we have used for measurement of membrane deflection. The second method — resonance frequency method — is based on the classical theory of membrane vibration. It uses the dependency of the membrane resonance frequency on membrane residual stress. This novel technique applies a soft piezoresistive cantilever in contact mode for the detection of membrane vibration. The influence of the cantilever on the vibration of the membrane was studied. Initial results show the small lowering of the resonance frequency in measurements with the cantilever in comparison with the optical measurements.