activation anneal

Activation annealing is a high-temperature thermal process that moves implanted dopant atoms from interstitial positions to substitutional sites in the silicon crystal lattice where they become electrically active. Ion implantation creates crystal damage and leaves most dopants in electrically inactive positions. Annealing at 900-1100°C provides energy for dopants to diffuse to substitutional sites and for the crystal to repair damage through solid-phase epitaxial regrowth. Activation efficiency (percentage of dopants that become electrically active) depends on temperature, time, and dopant concentration. Higher temperatures increase activation but also cause unwanted dopant diffusion that degrades junction abruptness. Advanced activation techniques like spike annealing, flash annealing, and laser annealing use rapid heating to minimize diffusion while achieving high activation. Activation annealing must balance competing requirements of high activation, minimal diffusion, and complete damage repair. Incomplete activation increases sheet resistance and degrades transistor performance.