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

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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.

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