Simulation of x-ray section topographs due to hydrogen precipitates in silicon

Abstract

Computer simulation of X-ray diffraction section topographs has been used to investigate hydrogen precipitates in silicon crystals. The field of X-ray topography is reviewed, with an account of image formation and the experimental techniques used to obtain topographs. The dynamical theory, for a perfect crystal, and Takagi's theory, for an imperfect crystal, are both presented. Simulation techniques, based on numerical integration of Takagi's equations, are then discussed. A computer program is presented, which is used to simulate the experimental topographs due to hydrogen precipitates in silicon, allowing the positions of precipitates to be located. A second simulation program, to take into account the effects of surface relaxation, is constructed. Simulations with and without surface relaxation are compared, and their differences are discussed. Finally, the effect upon simulations of crystal bending is investigated. This is an important consideration, since the growth of an oxide layer onto a silicon wafer, resulting in wafer curvature, is an integral part of silicon device production technology. Possibilities for future work are discussed.