Mechanical property measurements of thin films using load-deflection of composite rectangular membrane

Abstract

The internal stress and Young's modulus of thin films are determined by measuring the deflection versus pressure of the rectangular membranes of materials. In order to reduce the measurement error for the Young's modulus due to an unknown Poisson's ratio, a 2 mm*8 mm rectangular membrane is adopted. Measurements are made by using a computerized measurement system. Low-pressure chemical-vapor-deposited (LPCVD) silicon nitride films are characterized and found to have an internal stress of 1.0 GPa and a Young's modulus of 290 GPa. By using this composite membrane technique, an LPCVD polysilicon film and a plasma-CVD silicon nitride film are characterized. The internal stress and Young's modulus were found to be -0.18 GPa and 160 GPa for the LPCVD polysilicon film and 0.11 GPa and 210 GPa for the plasma-CVD silicon nitride film. >