ANALYSIS OF LOCAL LATTICE STRAIN AROUND OXYGEN PRECIPITATES IN SILICON-CRYSTALS USING CBED TECHNIQUE

Oxygen precipitates (SiOx) in Czochralski-grown silicon single crystal s (CZ-Si) have been used for the 'getter' sink for impurities introduc ed during the LSI wafer manufacturing process. In order to understand the 'gettering' phenomena, lattice strain fields around the precipitat es have been measured quantitatively using convergent beam electron di ffraction (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 te tragonal distortion of silicon lattices was found in the vicinity of a platelet of an oxygen precipitate. That is, the strain due to the dis placement of (001)(Si) planes is compressive along the direction norma l 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 len gth is about 500 nm. The results are discussed and compared to those f rom the finite element method (FEM) simulation. (C) 1998 Elsevier Scie nce B.V. All rights reserved.