离子注入硅退火过程中平面形核和结晶问题研究

According to the thermodynamic and kinectic theory, considering variation of bulk free energy and superficial energy after nucleation as well as migration of atom, we study deeply planar nucleation and crystallization that relate to two possible transition mechanism in the process of annealing of ion implanted Si. 1） Liquid/Solid transition: critical nucleation work is a half of increased superficial energy and inversely proportional to the supercooling . Compared with bulk nucleation, the radius of critical nucleus decrease by a half, nucleation rate attain its maximum at T=1/2Tm; 2） Amorphous/Crystal transition: atoms containing in critical nucleus and on its surface, as well as critical nucleation work are all directly proportional to the height of nucleus, nucleation barrier is a half of superficial energy too. Taking SiGe semiconductor as an example, we calculate that the value of its elastic strain energy is 0.03eV/atom, and get more reasonable result after taking its effect to transition into account. In one word, we reach such a conclusion through calculation: for annealing of ion implanted Si, no matter what transition way—liquid or solid, the planar nucleation and recrystallization process is actually carried out layer by layer on crystal substrate, probability forming “rod-like”nucleus is much larger than probability of “plate-like”nucleus.

Planar nucleation and crystallization in the annealing processof ion implanted silicon