Characterization of ultra-shallow p + -n junctions formed by plasma doping with BF 3 and N 2 plasmas

Abstract

Plasma doping (PLAD) is a promising alternative to conventional ion implantation for the formation of ultra-shallow p + -n junctions. In the PLAD process, a silicon wafer is placed directly in a plasma containing the desired dopant ions and then pulse-biased to a negative potential to accelerate positive dopant ions into the silicon surface. Most of Varian's work to date has used BF 3 source gas and wafer biases of −0.5 to −5 kV to implant boron into 150 and 200 mm wafers. Data will be presented showing successful formation of ultra-shallow junctions, good sheet resistance uniformity and repeatability, and excellent structural quality of the silicon after rapid annealing. Very good device characteristics obtained from deep sub-half micron MOSFETs fabricated using PLAD will also be shown. Finally, the combination of PLAD with an N 2 plasma followed by ultra-low energy B + implantation to produce ultra-shallow junctions with low sheet resistances will be discussed.