Effect of gas flow ratio in PE-CVD on elastic properties of sub-micron thick silicon nitride films for MEMS

This paper focuses on revealing the effect of gas flow ratio in PE-CVD on elastic properties of sub micron-thick silicon nitride (SiN/sub x/) films for surface-micromachined MEMS. SiN/sub x/ films having a thickness of 0.1 /spl mu/m to 0.7 /spl mu/m are deposited on single crystal silicon (SCS) specimens of 10 /spl mu/m in thickness by changing the gas flow ratio of NH/sub 3/' to SiH/sub 4/ in PE-CVD. The atomic force microscope (AFM) tensile testing technique is employed to characterize Young's modulus and Poisson's ratio of SiN/sub x/ films. The Young's modulus of SiN/sub x/ films range from 102 GPa to 143 GPa, independent of film thickness. A Poisson's ratio ranging from 0.2 to 0.26 is also obtained from tensile and nano-indentation combined tests. Auger spectroscopy makes it clear that an increase of the atomic content ratio of nitrogen to silicon in SiN/sub x/ film yields its higher elastic mechanical properties.