Co-gas impact of B2H6 plasma diluted with helium on the plasma doping process in a pulsed glow-discharge system

Abstract

It has been reported that helium dilution of B2H6 in the plasma doping (PLAD) process can be used to control and minimize deposition phenomenon. In this article we quantify the impact of such dilution on boron doping and deposition under PLAD conditions appropriate for ultrashallow junction formation. The sheet resistance (RS) of the implanted wafers remains nearly constant when B2H6 is diluted with He up to 95%, although the retained B dose is reduced. Secondary ion mass spectroscopy profiles indicate that B profiles are deeper for higher dilution than for lower dilution due to less B deposition. The deeper B profiles contribute to a higher activation fraction during annealing due to the B solid solubility limit. This higher activation compensates for the reduction of the retained B dose. The plasma doping process of a pulsed glow-discharge system by using B2H6 diluted with 95% provides optimal conditions for minimizing deposition. This results in a higher doping rate and then higher throughput.