Stresses in TaSix films sputter deposited on polycrystalline silicon

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Abstract
Stress in thin TaSix films sputtered on polycrystalline silicon was studied as a function of temperature. A dual laser‐beam apparatus was used to measure wafer curvature in situ. Stress was studied in the TaSi2/undoped polysilicon structure, in TaSi2 on polysilicon doped with either phosphorus, arsenic, or boron, and in films with a deposited Si/Ta ratio of more than 2. Several observations of stress‐temperature behavior in TaSi2 were made. Tensile stress in TaSi2/undoped polysilicon increases to 1.2×1010 dyn/cm2 at 450 °C during the postdeposition anneal, decreases to near 0 at 900 °C, and linearly increases as temperature is subsequently lowered. Both doping and stoichiometry affected the stress‐temperature behavior. N‐type dopants decreased tensile stress and boron did not. Raising the Si/Ta ratio increased tensile stress at high temperatures. The stress‐temperature measurements were combined with results from other characterization techniques to draw conclusions about the influence of temperature on the film. TaSi2 compound formation was found to occur at less than 400 °C in these films.