Composite TaSi2/n+poly-Si formation by rapid thermal annealing

Composite TaSi2/n+ poly-Si structures have been formed by rapid thermal annealing (RTA). Polysilicon films 0.2 µm thick were deposited on oxidized Si wafers by LPCVD and heavily doped with phosphorus by diffusion. A layer of TaSix0.22 µm thick was then cosputtered on polysilicon from separate targets. The as-deposited samples were annealed by RTA using high-intensity tungsten lamps. Uniform stoichiometric low-resistivity tantalum disilicide was formed by RTA in 1 s at 1000°C. The sheet resistance and grain size of the silicide layers are comparable to those formed by conventional furnace anneals. The surface morphology of the RTA samples is superior to that obtained by furnace annealing. These results show that RTA technique has a great potential for low-resistivity tantalum silicide formation in VLSI circuits.