Phosphorus and boron doping effects on solid phase recrystallization of polycrystalline silicon films amorphized by germanium ion implantation

Abstract

Fig. 1 shows the density of grains as a function of annealing time for the undoped, P-doped and Bdoped films that were subjected to Ge + with a dose of 1 x 1015cm -2 and annealed at 600°C. The density of grains was obtained by directly counting the number of grains produced in the amorphized films after annealing through plan-view TEM observation. It is shown that the number of grains was very small at the beginning of the annealing step, but after a certain incubation time, which is the time for nuclei to grow to the critical size, the number of grains increased rapidly. It was found from this figure that the initial generation of nuclei for the doped films is faster than that for the undoped films. This is presumed to be due to the stress effects induced by a mismatch of atomic size between the implanated atoms and Si atoms [5]. Fig. 2 shows the nucleation rate as a function of reciprocal annealing temperature for the same films as shown in Fig. 1. The nucleation rates of these films were estimated from the slope of the line, as shown in Fig. 1. As can be seen from this figure, it was found that the nucleation rate was strongly dependent on the kind of doping, with B doping increasing the nucleation rate and P doping decreasing it. This is presumed to be due to the increase in the local stress for the B-doped films and the increase in the implantation-induced damage for the P-doped films [6].