Rapid thermal annealing of co-sputtered tantalum silicide films

Abstract

A rapid thermal annealing (RTA) technique has been used to produce uniform low resistivity composite TaSi 2/n +-poly-Si layers (where poly-Si is polycrystalline silicon). Poly-Si films 0.2 μm thick were deposited onto oxidized silicon wafers by low pressure chemical vapor deposition and were doped with phosphorus by diffusion. A layer of TaSi x 0.22 μm thick was then co-sputtered onto the poly-Si from separate targets. The as-deposited samples were annealed by using radiation from a bank of tungsten-halogen lamps. Electrical and structural measurements indicate that uniform stoichiometric low resistivity TaSi 2 layers with a hexagonal crystal structure were formed in 1 s at 1000 °C. The sheet resistance and grain size of the silicide layers are comparable with those of samples formed with conventional furnace anneals. The surface morphology of the samples produced by RTA is superior to that of samples produced by furnace annealing. These results show that the RTA technique has a great potential for low resistivity tantalum silicide formation in very-large-scale integrated circuits.