FORMATION OF SHALLOW P(+)N JUNCTIONS BY BF2+ IMPLANTATION INTO THIN POLYCRYSTALLINE SI FILMS

Excellent shallow p(+)n junctions have been formed by implanting BF2ions into thin polycrystalline Si films and subsequent annealing. The samples implanted with 5X10(15) cm(-2) at 50 keV show a leakage of 1 n A/cm(2) and a junction depth of about 0.05 mu m after a 800 degrees C annealing. Various implant and annealing cases were examined to determ ine and characterize their effects on the resultant junctions. High en ergy implantations (125 and 150 keV) exhibit poor characteristics at a ll annealing temperatures because the Si substrates are severely damag ed. However, the specimens implanted below 100 keV result in excellent diode characteristics for all implantation doses after an 800 degrees C annealing since the implantation defects are confined in the poly-S i layer. The major factors affecting the junction depth were found to be the implantation energy and annealing temperature, while a minor fo r the implantation dosage. Furthermore, the effects of the subsequent silicidation on the resultant junction characteristics were also inves tigated.