Thermal optimization of CZ bulk growth and wafer annealing for crystalline dislocation-free silicon

In this article, we consider a number of questions related to the thermal optimization of 200 mm diameter Si Czochralski (CZ) single-crystal growth process using the new “Redmet-90M” puller and the rapid thermal annealing (RTA) of Si wafers cut from single crystals. The article includes results of the CZ numerical modeling of heat transfer, which takes into account the special thermal shield assemblies (with and without water cooling). The influences of various crucible rotation rates on the distribution of the azimuthal velocity of the melt and on the liquid-solid interface were also investigated. Differences in axial temperature profiles of the growing crystal were analyzed depending on whether the thermal shield was used with or without its water-cooling system and depending on the various crucible rotation rates. A numerical diffusion-recombination model of intrinsic point defects (vacancies and interstitial Si atoms), which takes into account the vacancy cluster formation, was applied for RTA optimization. Vacancy concentration, density and sizes of vacancy clusters were calculated along the thickness of a wafer. An experimental study on the defect structure in the annealed Si wafers was carried out by the light microscopy and the transmission electron microscopy. The type, density and morphology of defects in the thickness of a wafer were also analyzed. The experimental distribution of total defect density in the thickness of a wafer was compared with the calculated vacancy cluster density.