Measurement of thermal expansion coefficients of W, WSi, WN, and WSiN thin film metallizations

Abstract

Thermal expansion coefficients and biaxial elastic moduli of the sputtered W, WNx, WSi0.45, and WSi0.67N0.10 thin films, used as refractory gate in the self-aligned metal-semiconductor field effect transistors on GaAs, were determined by insitu stress measurements during heating and cooling of the films on GaAs and Si substrates in the temperature range of 20–450 °C. For the WNx films the average values of thermal expansion coefficients increased with the nitrogen content, and varied from 4.5×10−6 °C−1 for tungsten to 5.80×10−6 °C−1 for WN0.43. For the WSi0.45 and WSi0.67N0.10 films, the measured values of coefficients of thermal expansion (6.55×10−6 and 6.37×10−6 °C−1, respectively) were close to that of GaAs (6.40×10−6 °C−1, respectively). Thus by using these films as refractory gates, the stress-induced interdiffusion and interaction at the interface with GaAs can be substantially reduced.