Microstructures of Tungsten Suicide Films Deposited by CVD and by Sputtering

Microstructure changes, after annealing, of tungsten suicide (WSi ϰ ) films formed on the polysilicon films by CVD (chemical vapor deposition) and by sputtering were compared. For both CVD and sputtered WSi ϰ films, microstructural evolutions during annealing were caused by three mechanisms; crystallization from amorphous phase, stoichiometrical change, and grain growth. The microstructures and the electrical resistances of WSi ϰ films after annealing were depended on the deposition method. The movement of excess Si in WSi ϰ film to poly-silicon during annealing was faster in case of sputtering than in case of CVD. At annealing temperature below 850°C, CVD films showed higher resistivity and smaller grain size than sputtered films. On the other hand, at anneal temperature above 850°C, the grain growth rate of the CVD film was higher than that of the sputtered film, and the CVD film resulted in lower resistivity than the sputtered film. The retardation of grain growth for the sputter-WSi ϰ film is thought to be caused by impurity contamination such as argon added into the film during sputtering.