Simulation of the influence of mechanical stresses on the kinetics of crystallization of ion-implanted silicon layers under pulse heating

The method of numerical simulation on two-layer structures such as a-Si-Si and a-Si-SiO2 is used to study the influence of mechanical stresses on the start temperature of self-sustaining crystallization of an amorphous film, on the waiting time for the start of crystallization (or melting) t0, and on the expected time of film crystallization t/sub eta/ which is compared to the duration of a heating pulse. In case of simulation of the transformation kinetics the energy of strain field of a lattice during the doping is estimated for the substitutional position of impurity atoms by the difference of their size from that of silicon atoms. Isotropy of the stress field, the local action of an impurity, the possibility of incorporation into a lattice and of excess over equilirium solubility are included. Numerical calculations are made for the degree of deformation of 0.1 and variations of a free energy by 56 meV and of an activation energy of transformation by 1 eV typical of amorphous silicon obtained by ion implantation. It is shown that t0 and t/sub eta/ decrease by 103 to 104 times for A → C and by 10 to 103 for A → L transformations, the melting being most likely as usual. The proposed way of taking into account the influence of mechanical stresses can be used in simulation of the crystallization process by the method of finite differences. (author)