Boron diffusion upon annealing of laser thermal processed silicon

In order to investigate the role of the end of range damage on dopant motion during post-laser thermal processing (LTP) anneals, a 15 keV, 1×10¹⁵ ions/cm² Si⁺ implant was used to amorphize the silicon surface. Low energy implantation was used to introduce 1 keV B⁺ at a dose of 4×10¹⁵ ions/cm² into the amorphous region. LTP was performed at energies from 0.625 to 0.825 J/cm². After LTP, conventional RTA was performed for 30 sec at temperatures between 700°C and 1000°C. SIMS analysis showed a significant pile-up of boron in the end of range region of the implant, as well as dose loss and enhanced diffusion of the boron. Qualitative agreement between the defect location and the gettered peak was observed but strong quantitative agreement between the density of the extended defects and the dose of gettered boron was not observed. At higher LTP powers (>0.75 J/cm²) over-melting of the amorphous layer occurs, the density of EOR defects and the gettered boron dose decreases. In addition to gettering, post LTP annealing results in enhanced diffusion of the boron. It is unclear if this is transient enhanced diffusion (TED) but the enhancement is comparable to TED. The enhanced diffusion may result from the EOR damage however it is observed even for the highest LTP power. At this power the melting of the crystalline Si is observed and thus a significant fraction of the EOR region is removed. Thus the enhanced diffusion may be associated with quenched in interstitials after the laser melting process