Displacement criterion for amorphization of silicon during ion implantation

Results of Boltzmann transport equation calculations are used to estimate what fraction of a crystalline silicon lattice must be displaced to cause a crystalline-to-amorphous transition during ion implantation. Comparison of these calculations with experimental MeV He channeling and backscattering results for 150-keV boron implantation at 77 °K indicates that the displacement of about 10% of the lattice will cause amorphization provided the substrate is at a temperature which inhibits self-annealing processes and defect diffusion. The calculations also indicate that the number of atoms displaced is proportional to the deposited energy density, one displacement occurring on average for each 200 eV of deposited energy. Experimental results for room-temperature silicon implantation confirm the fact that higher temperature substrates require a greater fractional displacement of the lattice before amorphization occurs.