A CHARACTERIZATION OF THE EFFECT OF DEPOSITION TEMPERATURE ON POLYSILICON PROPERTIES - MORPHOLOGY, DOPABILITY, ETCHABILITY, AND POLYCIDE PROPERTIES

Low pressure chemically vapor deposited polysilicon deposition was studied from 525 to 650-degrees-C. The silicon appears to be amorphous with a smooth surface up to 550-degrees-C and completely crystalline above 600-degrees-C. The transition region is found to be from 560 to 590-degrees-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 POCl3 doping and a 1000-degrees-C oxidation. The 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-degrees-C results in large coarse crystals with rough surface morphology and disparate orientation. The smooth morphology of the 550-degrees-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.