Analysis of local lattice strain around oxygen precipitates in silicon crystals using CBED technique

Abstract

Oxygen precipitates (SiO x ) in Czochralski-grown silicon single crystals (CZ-Si) have been used for the `getter' sink for impurities introduced during the LSI wafer manufacturing process. In order to understand the `gettering' phenomena, lattice strain fields around the precipitates have been measured quantitatively using convergent beam electron diffraction (CBED). The local lattice strain can be measured from higher order Laue zone (HOLZ) patterns since the HOLZ pattern in the bright field disk is sensitive to the lattice displacement. As a result, a tetragonal distortion of silicon lattices was found in the vicinity of a platelet of an oxygen precipitate. That is, the strain due to the displacement of (001) Si planes is compressive along the direction normal to [001] Si and is tensile along the direction parallel to [001] Si. The normal strain is estimated to be about 0.3% near the flat plane of the platelet and 0.1% near the edge of the platelet whose edge length is about 500 nm. The results are discussed and compared to those from the finite element method (FEM) simulation.