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, WN sub x, WSi sub 0.45, and WSi sub 0.67 N sub 0.10 thin films, used as refractory gate in the self-aligned MESFETs on GaAs, were determined by in-situ stress measurements during heating and cooling of the films on GaAs and Si substrates in the temperature range of 20-450C. For the WN sub x films the average values of thermal expansion coefficients increased with the nitrogen content, and varied from 4.5x10 sup (-6) C sup (-1) for tungsten to 5.80x10 sup (-6) C sup (-1) for WN sub 0.43. For the WSi sub 0.45. and WSi sub 0.67 N sub 0.10 films, the measured values of coefficients of thermal expansion. films, the measured values of coefficients of thermal expansion (6.55x10 sup (-6) and 6.37x10 sup (-6) C sup (-1), respectively) were close to that of GaAs (6.40x10 sup (-6) C sup (-1)). Thus by using these films as refractory gates, the stress-induced interdiffusion and interaction at the interface with GaAs can be substantially reduced.