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

A fully.three-dimensional simulation tool for modeling the ion implantation in arbitrarily complex three-dimensional structures is described. The calculation is based on the Monte Carlo (MC) method. For MC simulations of realistic three-dimensional structures the key problem is the 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 location 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 applied. For the point location (geometry checks) different possibilities are presented. Advantages and disadvantages of the conventional intersection method and a newly introduced octree method are discussed. The octree method was found to be suited best for three-dimensional simulation. Using the octree the CPU-time required for the simulation of one ion trajectory could be reduced so that it only needs approximately the same time as the intersection method in the two-dimensional case. Additionally, the data structure of the octree simplifies the coupling of this simulation tool with topography simulators based on a cellular method. Simulation results for a three-dimensional trench structure are presented.