A microstructure for in situ determination of residual strain

This work presents a new strain sensor with a compact structure. The strain sensor comprises of a pair of cantilever beams with different lengths conn ected by a short tip. The residual strain causes two beams to deflect each other, thereby magnifying the deflection, which is measured by the tip. The displacement is independent of both Young's modulus and the film's thickne ss. An analytical model is derived to relate the measured displacement to r esidual strain. Finite-element modeling is also used to analyze the model. This work also thoroughly considers other factors that influence the design s and the implicit limitations of the strain sensors. Experimental results with an SiO2 film as well as undoped LPCVD polysilicon films are used to de monstrate the effectiveness of the proposed structure.