Effect of Gas Flow Ratio in PE-CVD on Elastic Properties of Sub-Micron Thick Silicon Nitride Films for MEMS

摘要

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 0.1μm to 0.7μm are deposited on single crystal silicon (SCS) specimens of 10 um 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. Young's modulus of SiN{sub}x films ranges from 102 GPa to 143 GPa, independent of film thickness. 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.