Elastic stiffness and thermal expansion coefficients of various refractory silicides and silicon nitride films

The elestic stiffness parameter E_f/(1−ν_f) and the thermal expansion coefficient _f were obtained for four different silicides (TiSi₂, TaSi₂, MoSi₂ and WSi₂) and for two different nitrides (chemically vapor-deposited Nitrox Si₃N₄ and r.f. plasma SiN) from stress-temperature measurements on identical films deposited on two different substrate materials. The values determined for _f and E_f/(1−ν_f) were quite similar for all silicides and averaged 15 ppm °C⁻¹ and 1.1 × 10¹² dyncm⁻² respectively. The thermal mismatch of these silicides is such that, once safely formed, the silicide film should be able to withstand high temperature processing steps without cracking. For the nitrides the values were essentially the same (approximately 1.5 ppm°C^-1), although the larger value of E_f/(1−ν_f) chemically vapor-deposited Si₃N₄ film (3.7 × 10¹² as opposed to 1.1 × 10¹² dyn cm^-2) indicates that it is somewhat stiffer than the SiN film.