STRUCTURAL AND ELECTRICAL-PROPERTIES OF P(-ENERGY GA+ IMPLANTATION()NJUNCTIONS IN SI BY LOW)

Ultrashallow p(+)n junctions have been formed in silicon by low energy (5.5 keV) Ga+ implantation into n-type substrates. This avoids the us e implantation of molecular species such as BF2+ or preamorphization w ith Ge+ or Si+, which degrade the integrity of p(+)n junctions in meta stably strained SixGe1-x layers. High resolution secondary ion mass sp ectroscopy measurements indicate an implant peak at less than 10 nm, e xcept for postanneal temperatures above 800 degrees C, for which sever e loss of profile control was observed. Electrical characteristics of the implanted junctions were determined from diode current-voltage mea surements and Hall data. At low anneal temperatures, these showed good rectification behavior, with an ideality factor of 1.1+/-0.1 and a re verse bias leakage of approximate to 3 mu A cm(-2) in a relatively lar ge junction area of 5 x 10(-2) cm(2). The electrical properties of the p(+)n junctions were found to be sensitive to implant dose, improving with increasing dose. At 580degrees>C, implant doses were achieved th at were completely activated at levels above previously published Ga e quilibrium solubility data. For temperatures of 800 degrees C, reverse annealing occurred, observed as a reduction in carrier concentration with increasing anneal time and severe profile broadening. (C) 1997 Am erican Institute of Physics.