Thermal stability of encapsulated tungsten/carbon multilayer thin films

Tungsten/carbon (W/C) multilayer thin films prepared by sputtering on unheated Si (100) substrates were encapsulated with two types of layers having low x-ray absorption. The encapsulating layers are SiNx and carbon prepared by plasma enhanced chemical vapor deposition and sputtering techniques, respectively. Isochronal annealings for 1 h in the temperature range from 300 to 600 °C and isothermal annealings at 300 and 400 °C were carried out under ambient conditions (in air) on coated and uncoated multilayers. Previous studies have shown that unprotected W/C multilayers annealed in air exhibit oxidation at relatively low temperatures (∼300 °C). In the present study, we have used Raman scattering, Auger depth profiling, and scanning electron microscopy to investigate the effects of thermal treatments on the encapsulated W/C multilayers. The results indicate that oxidation of both W and C layers takes place during annealing at temperatures as high as 600 °C on the SiNx coated multilayer.