A Characterization of the Effect of Deposition Temperature on Polysilicon Properties: Morphology, Dopability, Etchability, and Polycide Properties

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Abstract
Low pressure chemically vapor deposited polysilicon deposition was studied from 525 to 650°C. The silicon appears to be amorphous with a smooth surface up to 550°C and completely crystalline above 600°C. The transition region is found to be from 560 to 590°C. This transition is marked by sharp crystallographic and resistivity changes. The smooth surface morphology of the amorphous silicon is found to be preserved after doping and a 1000°C oxidation. The preservation of this smooth morphology is demonstrated to be due to the presence of a native oxide on the surface of the silicon upon exposure to atmosphere. However, an in situ anneal of amorphous silicon at 610°C results in large coarse crystals with rough surface morphology and disparate orientation. The smooth morphology of the 550°C silicon is found to be transmitted through subsequent polycide structure layers. The impact on device reliability is discussed. The amorphous silicon is found to have a higher plasma etch rate than the polysilicon.

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