Vacancy-type microdefect formation in Czochralski silicon

Abstract

Vacancy-based microdefects in CZ silicon are voids and oxide particles; they are nucleated simultaneously during cooling. The nucleation rate reaches a sharp peak at some `nucleation temperature' since the vacancy loss to the growing microdefects suppresses further nucleation. Normally, the dominant species (those responsible for the loss) are voids; the quantitative model of void formation is considered to provide the nucleation temperature, density and size of voids dependent on the starting vacancy concentration and the cooling rate. Lowering the starting vacancy concentration results in switching of the dominant species from voids to particles. Silicon crystals often consist of the two neighbouring zones, the vacancy one and the interstitial one; the vacancy zone is further subdivided into the inner void region and the marginal particle band identified with the OSF-ring. The vacancy properties – diffusivity and equilibrium concentration – are deduced from the reported data on grown-in voids.