DEFECTS PRODUCED IN SI P-NITROGEN TEMPERATURE OR -60-DEGREES-C(N DIODES BY B+ IMPLANTATION AT LIQUID)

Defects induced by B+ implantation (35 keV) at liquid-nitrogen (LN) te mperature and -60-degrees-C are examined using transmission electron m icroscopy (TEM), secondary-ion-mass spectroscopy, and electrical chara cterization of p+n diodes. B+ implantation at LN temperature produces a 120-nm-thick amorphous layer with a residual surface crystalline reg ion. B+ implantation at -60-degrees-C does not produce an amorphous la yer, but damage can be observed as a dark band at the depth of B+ proj ected range R(p). For RT implantation, cross-sectional transmission el ectron microscopy reveals no visible damage in contrast to implantatio n at -60-degrees-C. Frenkel-pair diffusion and annihilation is suppres sed during implantation at the low temperature. The damage accumulates to form an amorphous layer for LN temperature. At -60-degrees-C, the defects are confined near R(p). After annealing at 1000-degrees-C for 10 min, near-surface and depth-encountering solid-phase-epitaxy disloc ation-loop defects are observed in the sample implanted at LN temperat ure. The density of these is about several 10(8) cm-2, which is 10 or 100 times smaller than samples implanted at higher temperature. The an nealed samples implanted at -60-degrees-C and RT are mainly [111]-plan e directed defects and dislocation loops, respectively. Corresponding to the degree of as-implanted damage, the defects distributed at a sha llower depth in the sample implanted at -60-degrees-C than at RT, and have about 10 times higher density. The leakage current characteristic s of p+n diodes indicate that the LN temperature and -60-degrees-C imp lanted samples have lower leakage than RT samples at all annealing con ditions. Notably, at 1000-degrees-C for 10 min the leakage current is reduced to 56%. This is consistent with the result of TEM analysis; th us, the defect confinement to shallow layer by cooling contributes to lower the leakage current. Implantation at -60-degrees-C is suitable f or modern high-current implanters, due to practical coolant and less m echanical stress by thermoplasticity.