Plasma characterization of a plasma doping system for semiconductor device fabrication

Plasma characterization in a pulsed plasma doping system for semiconductor ion implantation has been carried out. The wafer to be implanted is placed directly on a platen in the pulsed plasma and then biased to a negative potential to accelerate the positive ion, from the plasma into the wafer. A wafer bias between 0 V and -4.5 kV with BF₃ source gas was used to implant boron ions into 200 mm-diameter silicon wafers. An ion mass and energy analyzer was used to measure the ion species and ion energy distribution during the plasma doping. The time-resolved Langmuir probe measurement technique was also used to determine the doping plasma conditions such as plasma density and electron temperature. The ion mass analysis result shows that BF₂⁺ is the dominant ion species in the BF₃ bulk plasma and BF⁺ is the second important dopant species. The time-resolved Langmuir probe measurement shows the presence of energetic primary electrons, and the fast decay of electron temperature during the afterglow period is observed