Flash-Lamp Annealing for Manufacturing of Reduced Thermal Budget Self-Aligned LTPS TFTs

Flash lamp annealing is explored as a replacement process for crystallization of amorphous silicon and activation of boron introduced subsequently by ion implantation. Single-stage crystallization/activation and two-stage crystallization + activation flash-lamp anneal processes were investigated for evaluation of boron activation. The two-stage process had an initial high intensity pre-implant crystallization treatment, followed by a lower intensity post-implant activation treatment which avoided a melt phase. The single-stage process included only the latter post-implant treatment which served to solid-phase crystallize amorphous silicon and activate boron simultaneously. The two-stage process was found to be superior in supporting highly conductive source/drain regions, with further enhancement in boron activation achieved via silicon mesa pre-patterning, reliably attaining sheet resistances less than 1 kΩ/□. This process was used to produce self-aligned PMOS TFTs on glass with reduced thermal budget, reinforcing the feasibility of flash lamp annealing in display manufacturing.