MATERIAL AND ELECTRICAL-PROPERTIES OF ULTRA-SHALLOW P+-N JUNCTIONS FORMED BY LOW-ENERGY ION-IMPLANTATION AND RAPID THERMAL ANNEALING

Ultra shallow p+-n junctions were formed by 1.35-keV B and 6-keV BF2 implantation into preamorphized and nonpreamorphized silicon substrates. Dopant activation and implantation damage removal were achieved via rapid thermal annealing (RTA). Junctions shallower than 0.11 mu-m and complete activation of the implanted boron were obtained after a 1050-degrees-C, 10-s RTA anneal. Reverse activation was observed for BF2 implanted samples for both Ge preamorphized and nonpreamorphized substrates with the minimum activation temperature increasing with increasing Ge premorphization energy. The minimum activation temperature was correlated with the formation of dislocation loops from the end-of-range damage. Cross-sectional transmission electron microscopy (TEM) was performed on B, BF2, Ge + B, or Ge + BF2 implanted samples to study the implantation damage removal process with respect to RTA annealing conditions. Results indicated that both Ge preamorphization and F implantation (via BF2) retard defect annihilation. Complete damage removal was observed for all implantation conditions after a 1050-degrees-C, 10-s RTA. Reverse leakage current measurement performed on B, BF2, Ge + B, or Ge + BF2 implanted diodes showed reasonable correlation with residual defects. Leakage current densities below 1 nA/cm2 were obtained for 500-mu-m x 500-mu-m diodes. Leakage current measuremnts on diodes of different sizes were used to determine areal and peripheral components of leakage current. Scaling of the results of micrometer-sized junctions indicates that the peripheral leakage current component is the dominant component for such shallow implanted junctions.