Tungsten Deposition by Metal-Chloride-Reduction Chemical Vapor Deposition

Abstract

We successfully developed a fluorine-free tungsten deposition technique on a Si substrate at a substrate temperature in the range from 450 to 520°C by metal chloride reduction chemical vapor deposition (MCR-CVD). In this process, we first prepared a tungsten coil as a source material that can be heated by passing a current directly in itself at a temperature of 800°C. In a reaction chamber, the heated tungsten coil is exposed to RF excited Cl radicals to produce W chlorides to be delivered to the Si substrate. The adsorbed W chlorides are reduced to W by the Cl radical and a W film is grown on the Si surface. The residual Cl and F levels in the deposited W film were measured under the detection limit by x-ray photoelectron spectroscopy. The deposited W exhibited very low resistivity in the order of 10−5 Ω cm. The film conformality was examined using a trench-filling experiment, which suggests the suitability of the present process for the plug filling in VLSI production.