laser anneal

Laser annealing uses pulsed or scanned laser beams to rapidly heat and activate implanted dopants in a very thin surface layer with minimal thermal budget to the bulk wafer. Nanosecond or microsecond laser pulses melt the silicon surface to depths of 100-300nm, allowing dopants to move to substitutional sites and the crystal to regrow epitaxially from the underlying substrate. The extremely short heating time prevents dopant diffusion, enabling ultra-shallow junctions below 10nm critical for advanced transistors. Laser annealing can achieve near-complete dopant activation even at very high concentrations that would be limited by solid solubility in conventional furnace annealing. The process requires careful control of laser energy density, pulse duration, and beam uniformity to avoid surface damage or incomplete melting. Laser annealing is particularly valuable for source-drain activation in advanced CMOS where junction depth must be minimized. Challenges include equipment cost, throughput, and achieving uniform results across the wafer.