MONTE-CARLO SIMULATION OF ION-IMPLANTATION FOR 3-DIMENSIONAL STRUCTURES USING AN OCTREE

A fully.three-dimensional simulation tool for modeling the ion implant ation in arbitrarily complex three-dimensional structures is described . The calculation is based on the Monte Carlo (MC) method. For MC simu lations of realistic three-dimensional structures the key problem is t he CPU-time consumption which is primarily caused by two facts. (1) A large number of ion trajectories (about 10(7)) has to be simulated to get results with reasonable low statistical noise. (2) The point locat ion problem is very complex in the three-dimensional space. Solutions for these problems are given in this paper. To reduce the CPU-time for calculating the numerous ion trajectories a superposition method is a pplied. For the point location (geometry checks) different possibiliti es are presented. Advantages and disadvantages of the conventional int ersection method and a newly introduced octree method are discussed. T he octree method was found to be suited best for three-dimensional sim ulation. Using the octree the CPU-time required for the simulation of one ion trajectory could be reduced so that it only needs approximatel y the same time as the intersection method in the two-dimensional case . Additionally, the data structure of the octree simplifies the coupli ng of this simulation tool with topography simulators based on a cellu lar method. Simulation results for a three-dimensional trench structur e are presented.