The effect of thermal annealing in a hydrogen atmosphere on tungsten deposited on 6HSiC

Abstract

Tungsten (W) film was deposited on bulk single crystalline 6H-SiC substrate and annealed in H 2 ambient at temperatures of 700 ºC, 800 ºC and 1000 ºC for 1 hour. The resulting solidstate reactions, phase composition and surface morphology were investigated by Rutherford backscattering spectrometry (RBS), grazing incidence X-ray diffraction (GIXRD) and scanning electron microscopy (SEM) analysis techniques. These results are compared with the vacuum annealed results reported in our earlier work. As-deposited RBS results indicated the presence of W and O 2 in the deposited thin film, the GIXRD showed the presence of W, The SEM micrographs of the as-deposited samples indicated the W thin film had a uniform surface with small grains. Annealing at 800 ºC led to the agglomeration of W grains into clusters making the surface rough.

Surface and interface structural analysis of W deposited on 6H–SiC substrates annealed in argon

“…The details on how this was done are available in ref. 24. The samples were subsequently annealed in argon (Ar) of 99.9% purity atmospheres at 700 C, 800 C, 900 C and 1000 C for 1 hour.…”

“…The as-deposited RBS spectrum which was simulated using RUMP is available in ref. 24 ). The oxygen present on the samples might have been attained during deposition in the deposition chamber.…”

“…The W-Si-C system heat of formation for the phases formed is reported in ref. 23 In the study of W-SiC samples annealed in hydrogen ambient, 24 it was observed that phases present were W 5 Si 3 , WC and W, while at 800 C to 1000 C two additional phases appeared, that is, WSi 2 and W 2 C. Aer vacuum annealing, 26 the phases which formed upon annealing at 700 C and 800 C were WO 2 , WC, W and W 3 C, while at 900 C and 1000 C WSi 2 and W 2 C were the additional phases formed. In this study on Ar annealing, phases present aer annealing from 700 C to 1000 C were WO 3 , W 5 Si 3 , SiO 2 , W 2 C and WC.…”

“…The average crystal sizes of the Ar annealed (from 700 C to 1000 C) W-SiC samples are larger and more randomly orientated when compared to vacuum annealed 26 and hydrogen annealed W-SiC samples. 24 A slow crystal growth in the form of grains was observed during annealing in hydrogen. Annealing in vacuum resulted in the formation of grains which changed with an increase in temperature to form crystals in the form of distinct islands (pores between the at crystals).…”

“…removal of oxygen) of the hydrogen. 24 The different morphology of the Ar annealed samples can be explained in terms of a crystal growth model. Some gas atoms present in the annealing system can be physio-sorbed or chemi-sorbed on the crystallite surfaces in the layer and in the reaction zone via cavities/opening in the layer during annealing.…”