Pure and Applied Chemistry

Abstract: The hot-wire silicon chemical vapor deposition (CVD) was approached by the new concept of the theory of charged clusters (TCC). The role of a hot wire is to enhance the rate of negative surface ionization producing negative ions. These ions induce nucleation and produce negatively charged silicon clusters, which deposit as polycrystalline films at low temperatures. During the deposition of silicon, an appreciable amount of negative current (~nA/cm²) was measured, and clusters, a few nanometers in size, were captured and observed by transmission electron microscopy (TEM). The effect of bias on the deposition behavior of the clusters indicated that most of the clusters were negatively charged. In order to deposit films with a large grain size with a high mobility, both the generation of neutral clusters and the cluster size should be minimized. A working pressure of 0.3 Torr and a wire temperature of 1800 °C were found to be optimal. Under these conditions, the film with grain size of almost 1 μm could be deposited with a mobility of 175 cm²/Vsec.