Doping gas effects on plasma enhanced chemical vapor deposition on heavily phosphorus-doped $n+$silicon film

Unusual doping gas effects on the plasma enhanced chemical vapor deposited heavily phosphorus-doped silicon film have been observed. The deposition rate increases linearly with the silane (1% phosphine) feed gas flow rate. However, the film’s resistivity increased abruptly, i.e., more than 2 orders of magnitude, in a narrow range of flow rate. This was inconsistent with the change of the film’s dopant or hydrogen concentration. It was consistent with the variation of the film’s morphology. For example, below the transition flow rate, the film had a large volume fraction of microcrystal; above the transition flow rate, the film was amorphous. The enhancement of the doping efficiency is probably due to the segregation of the dopant at grain boundaries. In addition, the deposition rate was facilitated by the existence of the doping gas. It is possible that the doping gas influences the surface electrical characteristics during the film growing process, which accounts for the increase of the deposition rate and the mechanism of the crystal formation.