Influence of irradiation parameters

During irradiation there is a competence between damage generation and dynamic annealing. Depending on irradiation parameters generated damage may anneal out during the process, or may accumulate leading to the amorphization of the damaged region. The formation of an amorphous layer strongly affects device performance, since it affects dopant activation and residual damage after regrowth. Irradiation fluence and energy define the amount and distribution of generated damage. Particle mass determines the topology of damage (dilute or compact) and therefore its endurance upon anneal. Temperature controls the intensity of annealing, and beam current affects damage accumulation by specifying the time for which a cascade anneals out before the next cascade arrives into the same region.

Combining the Binary Collision approximation and kinetic Monte Carlo techniques we are able to reproduce the complex scenario of damage generation and accumulation, and simulate particular irradiation conditions to obtain the onset of amorphization, the depth of the amorphous layer and the amount of residual damage. In particular, we have studied the influence of commercial implanters on damage accumulation and amorphization, by analyzing the effect of beam diameter, scanning speed or wheel rotation speed.

Damage and implanted ion profiles for a 12keV 8·10¹⁴cm^-2 Si self- implantation performed at two different beam currents. The higher beam current leads to a deeper amorphous layer (modeled by the accumulation of IV-pairs) which results in less residual damage after recrystallization (P. López et al., Materials Science and Engineering B 124–125, 379 (2005) - Amorphous layer depth dependence on implant parameters during Si self-implantation).