Properties of selective low pressure chemically vapor deposited tungsten films produced by hydrogen reduction in a cold wall system

Abstract

The properties of selective low pressure chemically vapor deposited tungsten films deposited on silicon by hydrogen reduction of tungsten hexafluoride in a cold wall system and the interaction of tungsten and silicon on subsequent annealing are presented. The hydrogen reduction process produces pure films with resistivities around 9-10 μΩ cm for film thicknesses below 500-600 nm. These selectively deposited tungsten blanket films have large columnar grains whose size increases linearly with film thickness. Selectivity of the films can be excellent with careful wafer and chamber cleaning. High growth rates (more than 50 nm min-1) can be achieved at turret temperatures above 550 °C. Subsequent annealing of W-Si structures in forming gas results in uniform tungsten and silicon reactions to produce silicides. As a result of enhanced silicide formation above 800°C, films turn cloudy with increase in resistivity. © 1980.