Simulation of focused ion beam induced damage formation in crystalline silicon

Application of focused ion beams (FIB) to circuit modification during design and debugging of integrated circuits is limited by the degradation of active devices due to beam induced crystal damage. In order to investigate FIB induced damage formation theoretically, we have extended our 1-D/2-D binary collision (BC) code IMSIL to allow surface movement due to sputtering. In contrast to other dynamic BC codes, the crystal structure of the target and damage generation during implantation may be taken into account. Using this tool we simulate the milling of trenches in the gate stack of MOSFETs and compare the results with transmission electron microscopy cross sections and charge pumping data. The simulations confirm that damage tails are generated that are a factor of two (per at relevant defect concentrations than expected by conventional BC simulations. This result is shown to be due to recoil channeling in spite of the fact that a beam-induced surface amorphous layer is present throughout the implant. In addition, we, discuss the accuracy of the experimental results and the simulations.