MONTE-CARLO SIMULATION OF 2-DIMENSIONAL IMPLANTED DOPANT DISTRIBUTIONS AT MASK EDGES

Two-dimensional implanted dopant distributions at mask edges are studied using the Monte Carlo code IMSIL. The models implemented in the program are reviewed. An empirical model of electronic stopping describes correctly the range of channeled B, P, and As ions in a wide energy range. The damage model takes defect recombination into account but does not require the simulation of recoil cascades. Two-dimensional dopant distributions are calculated by randomly selecting the starting points of the ions between two positions defining a mask opening. The simulation results show that the penetration below the mask is larger than expected and that a Gaussian function is inappropriate to describe the lateral distribution function. The discrepancy increases with decreasing implantation energy. The dependence of the two-dimensional profiles on mask edge orientation, tilt angle, and ion species, and the influence of a screening oxide are investigated.