Ultra-low-energy BF/sub 3/ plasma doping characterization by ion mass and energy spectrometry

Summary form only given. Pulsed plasma doping (P/sup 2/LAD) provides controllable and cost effective solutions to dopant delivery in semiconductor device fabrication. In the P/sup 2/LAD system under investigation here, plasma is ignited with each negative voltage pulse applied to the cathode electrodes, including the silicon wafer. During the pulse-on period, positive ions are accelerated across the sheath and implanted within the wafer. This process has been studied using a Hiden EQP mass spectrometer installed within the pulsed electrode for in-situ detection of implant process parameters. Previous work, employing time-averaged mass spectrometry, indicated that BF/sub 2//sup +/ is the dominant ion species in the BF/sub 3/ plasmas, with BF/sup +/ as the second most abundant ion species. In this paper, we report time-resolved ion mass and energy distributions for various BF/sub 3/ doping voltage in the sub kilovolt range, at constant gas pressure, pulse frequency and duty ratio. These experiments have led to the better understanding of the gas phase phenomena, resulting in an improved optimization of the boron doping process.