A Characterization of the Effect of Deposition Temperature on Polysilicon Properties

Low pressure chemically vapor deposited polysilicon deposition was studied from 525 to 650 ~ The silicon appears to be amorphous with a smooth surface up to 550 ~ and completely crystalline above 600 ~ The transition region is found to be from 560 to 590 ~ This transition is marked by sharp crystallographic and resistivity changes. The smooth surface morphology of the amorphous silicon is found to be preserved after POC13 doping and a 1000 ~ 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 ~ results in large coarse crystals with rough surface morphology and disparate orientation. The smooth morphology of the 550 ~ 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. Doped polysilicon is widely used in very large scale inte-grated (VLSI) device fabrication as gate electrodes, inter-connect material, and as resistors in static memory circuits. As gate electrodes, the surface morphology is an important factor in device reliability, as the presence of asperities o