E. Ibok et S. Garg, A CHARACTERIZATION OF THE EFFECT OF DEPOSITION TEMPERATURE ON POLYSILICON PROPERTIES - MORPHOLOGY, DOPABILITY, ETCHABILITY, AND POLYCIDE PROPERTIES, Journal of the Electrochemical Society, 140(10), 1993, pp. 2927-2937
Low pressure chemically vapor deposited polysilicon deposition was stu
died from 525 to 650-degrees-C. The silicon appears to be amorphous wi
th a smooth surface up to 550-degrees-C and completely crystalline abo
ve 600-degrees-C. The transition region is found to be from 560 to 590
-degrees-C. This transition is marked by sharp crystallographic and re
sistivity changes. The smooth surface morphology of the amorphous sili
con is found to be preserved after POCl3 doping and a 1000-degrees-C o
xidation. The of this smooth morphology is demonstrated to be due to t
he presence of a native oxide on the surface of the silicon upon expos
ure to atmosphere. However, an in situ anneal of amorphous silicon at
610-degrees-C results in large coarse crystals with rough surface morp
hology and disparate orientation. The smooth morphology of the 550-deg
rees-C silicon is found to be transmitted through subsequent polycide
structure layers. The impact on device reliability is discussed. The a
morphous silicon is found to have a higher plasma etch rate than the p
olysilicon.