Theoretical and experimental study of the formation of grown-in and as-grown microdefects in dislocation-free silicon single crystals grown by the Czochralski method

Abstract

A complex theoretical and experimental investigation is performed, including the following stages. (i) Simulation of the processes of the recombination of intrinsic point defects and the formation of grown-in microdefects in dislocation-free Si single crystals 200 mm in diameter grown in modern commercial heating units. The simulation takes into account the thermal history of the defect growth. Modified designs of heating units are analyzed to compare the results of the simulation of thermal processes during the growth of Si single crystals 200 mm in diameter with a shield in the crucible region. The thermal history of the crystal is simulated, the recombination of intrinsic point defects near the crystallization front is analyzed, and the formation of vacancy microdefects in the temperature range t = 1200–900°C is modeled. This simulation made it possible to determine the effect of a heat shield on the processes of v-i recombination and microdefect formation. (ii) Microdefects in s-grown crystals and in crystals subjected to thermal treatments are investigated by optical and electron microscopy; specific features of the generation and motion of dislocations are analyzed for Si wafers containing microdefects of different types, formed as a result of the decomposition of the supersaturated solid solution of oxygen during multistep heat treatments of Si wafers. (iii) The three-dimensional problem of determining the field of elastic stresses caused by the wafer weight is solved in the isotropic approximation for 200-and 300-mm Si wafers placed on three or symmetrically arranged point supports of different areas.