Chemical Vapor Deposition of Epitaxial Silicon from Silane at Low Temperatures I. Very Low Pressure Deposition

The deposition of epitaxial silicon films at temperatures from 600~176 by both very low-pressure chemical vapor deposition (VLPCVD) and plasma-enhanced chemical vapor deposition (PECVD) has been examined. The VLPCVD dep-osition process is first order in silane partial pressure, zero order in hydrogen partial pressure, and exhibits a low, 8-12 kcal/ mole, activation energy for temperatures from 700~176 with 1-15 mtorr silane and hydrogen. For temperatures below 700 ~ an activation energy of 40 kcal/mole is observed. The growth rate depends upon surface orientation, decreasing in the order (100), (111), polycrystalline, indicating surface processes are rate controlling. The low activation energy regime is associated with a process controlled by silane adsorption and decomposition on a sparsely covered silicon surface. The higher activation energy regime is thought o reflect growth under conditions of high surface coverage with silane frag-ments and the transition temperature is thought o be pressure dependent. Conditions for the deposition of device quality epitaxial silicon at low temperatures are defined and iscussed. Plasma enhancement of the VLPCVD process is dis-cussed in a companion paper. This paper and a companion paper examine the epitaxial deposition process under very low-pressure chemical vapor deposition (VLPCVD) and plasma-enhanced chemi