Low Temperature Tungsten Deposition by Arf-Laser Induced Photo-CVD

Abstract

ABSTRACTLaser-induced Chemical Vapor Deposition of tungsten on Si(100) using WF6 and H2 has been investigated using a high-vacuum system comprising a cold-wall reactor. The activation source is a pulsed ArF-excimer laser. The deposition rate depends linearly on the repetition rate, when H2 is used as a reducing agent. When no H2 is used the laser radiation suppresses deposition.At deposition temperatures down to 200 °C laser deposited layers have resistivities better than 20 μΩ cm. Thick layers have resistivities down to 8 μΩ cm. There is a direct relation between layer thickness and resistivity. X-ray diffraction revealed the layers to consist of α-tungsten. β-tungsten was only obtained for those thermally deposited layers where growth was slower than expected.Nuclear reaction analysis of fluorine showed that most fluorine is present near the W-Si interface, and that the amount of fluorine relative to the amount of tungsten in the layer decreases markedly with deposition temperature.