MEASUREMENT OF THERMAL-EXPANSION COEFFICIENTS OF W, WSI, WN, AND WSIN THIN-FILM METALLIZATIONS

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.