Thermal Expansion and Atomic Structure of Amorphous Silicon Nitride Thin Films

Abstract

Thermal expansion and atomic structure of amorphous silicon nitride (SiNx) thin films were investigated. SiNx films of different Si/N compositions were formed by changing the SiH4/NH3 source gas ratio in plasma enhanced chemical vapor deposition (PE-CVD). The measurements of high temperature stress and hydrogen desorption demonstrated that the more Si-rich composition of SiNx led to less thermal expansion and more hydrogen desorption from Si-H bonds between 650°C and 800°C. In case the SiNx is Si-rich and contains both Si-H and N-H bonds, the Si and N atoms bond together after the hydrogen desorption. The increase of Si-N bonds should shrink the SiNx film and suppress the thermal expansion.