Effect of negatively charged species on the growth behavior of silicon films in hot wire chemical vapor deposition

The deposition behavior of silicon in hot wire chemical vapor deposition was investigated, focusing on the generation of negatively charged species in the gas phase using a gas mixture of 20% SiH4 and 80% H-2 at a 450 degrees C substrate temperature under a working pressure of 66.7 Pa. A negative current of 6-21 mu A/cm(2) was measured on the substrate at all processing conditions, and its absolute value increased with increasing wire temperature in the range of 1400 degrees C-1900 degrees C. The surface roughness of the films deposited on the silicon wafers increased with increasing wire temperature in the range of 1510 degrees C-1800 degrees C. The film growth rate on the positively biased substrates (+100 V, +200 V) was higher than that on the neutral (0 V) and negatively biased substrates (-100 V, -200 V, -300 V). These results indicate that the negatively charged species are generated in the gas phase and contribute to deposition. The surface roughness evolved during deposition was attributed to the electrostatic interaction between these negatively charged species and the negatively charged growing surface. (C) 2008 Elsevier B.V. All rights reserved.