STRUCTURE AND STABILITY STUDIES ON W, WSI, WSIN GAAS SYSTEMS BY XRD/

The microstructural properties of tungsten, tungsten silicide and tung sten silicide nitride layers on GaAs were studied by thin film x-ray d iffraction and correlated with deposition parameters, target compositi on and residual contamination during deposition. The x-ray diffractogr ams were used as 'fingerprints' for the existing phases in such contac t layer/III-V semiconductor systems. It was found that in the as-depos ited case of sputtered tungsten and WSIx the beta-W phase can coexist, whereas in the case of reactively sputtered WSixNy no other phases we re found. After a series of rapid thermal annealing treatments diffrac tograms were measured showing W and/or W5Si3 as dominating phases. The recrystallization temperatures of WSixNy are found to be near 850 deg rees C and 50 K higher than for the optimum WSi0.45. In contrast to WS IN, the recrystallization behaviour of WSi is strongly dependent on co mposition and contamination.