Study of end of range loop interactions with B+ implant damage using a boron doped diffusion layer

Abstract

A boron doped epilayer was used to investigate the interaction between end of range dislocation loops (formed from Ge+ implantation) and excess point defects generated from a low dose 1014/cm2 B+ implant into silicon. The boron doping spike was grown in by chemical vapor deposition at a depth of 8000 Å below the surface. The intrinsic diffusivity of the boron in the doped epilayer was determined by simply annealing the as-grown layer. The end of range (type II) dislocation loops were created using two overlapping room-temperature Ge+ implants of 75 and 190 keV each at a dose of 1×1015/cm2. Upon annealing the amorphous layer regrew and a layer of type II dislocation loops formed ∼2300 Å deep at a density of ∼8×1010/cm2. The enhancement in the buried boron layer diffusivity due to the type II loop forming Ge+ implant was observed to increase approximately between 2.5 and 5 min from 1500× to a value 2500× above the intrinsic diffusivity before dropping back to intrinsic levels after 30 min at 800 °C. A low-energy (8 keV) 1×1014/cm2 B+ (Rp=320 Å) implant into material without loops resulted in an average enhancement of 1540× in boron epilayer diffusivity after 2.5 min at 800 °C. The enhancement dropped down to intrinsic diffusivity levels after 5 min at 800 °C. When a layer of loops was introduced and annealed prior to and deeper than a subsequent low-energy B+ implant, annealing of the B+ implant produced no measurable enhancement in the buried B layer diffusivity. Taken together this imples that the interaction kinetics between the dislocation loop layer and the damage induced interstitials are primarily diffusion limited and the loops are absorbing a significant fraction of the interstitials produced by the low-energy B+ implant.