Low-temperature epitaxy of phosphorus doped Si and Si/sub 1-x/Ge/sub x/ films by RTP/VLP-CVD

Abstract

In situ phosphorus doped Si and Si/sub 1-x/Ge/sub x/ epitaxial layers have been grown at 600/spl deg/C in a very low pressure chemical vapor deposition system using SiH/sub 4/ and 1800 ppm PH/sub 3/ diluted in H/sub 2/. The epitaxial growth rates were found to decrease with phosphorus doping and input of the diluent H/sub 2/. The constant phosphorus concentration with depth for a steady flow of PH/sub 3/ was achieved. Dopant concentration is a function of gas phase dopant concentration. Chemical concentrations as high as 2.5/spl times/10/sup 20/ P/cm/sup 3/ were obtained in Si epitaxial layers. The doping level can be modulated between 1.2/spl times/10/sup 20/ and 1.5/spl times/10/sup 17/ P/cm/sup 3/. There is no evidence of a time-dependent accumulation of phosphorus on the growth surface or the reactor wall.