Microstructural characterization of molybdenum films deposited by LPCVD.

Molybdenum films have been deposited by Low Pressure Chemical Vapor Deposition (LPCVD) on silicon substrates by the reduction of molybdenum hexafluoride in hydrogen and argon atomospheres. The deposition is extremely selective, with no Mo observed on silicon dioxide surfaces over the temperature range 200- 400C. Reduction by both hydrogen and silicon contribute to the deposition, with approximately equal, extremely high deposition rates; no self-limiting thickness was observed. Extensive TEM and SEM studies were conducted in order to characterize the microstructure of the deposited films. The main feature of the films is their extreme porosity - about 30%, which can explain many specific properties of the process and the films. On the basis of our experiments we propose a model to explain the porosity of deposited films.