Stress and doping impact on intrinsic point defect behavior in growing single crystal silicon

Abstract

For the mass‐production of 450 mm‐diameter defect‐free Si crystals, one has to take into account the impact of thermal stress on intrinsic point defect properties and behavior during single crystal growth from a melt. Very recently, first experimental evidence was published that the compressive thermal stress near the melt/solid interface makes a growing 300 mm diameter Czochralski Si crystal more vacancy‐rich. In order to explain these experimental results quantitatively, the dependence of the formation enthalpies of the vacancy (V) and the self‐interstitial (I) on compressive plane stress was determined using density functional theory (DFT) based calculations. It is found that compressive plane stress gives a higher stress dependence of the so‐called “Voronkov criterion” compared to isotropic stress. The calculated plane stress dependence is in excellent agreement with the published experimental values and should be taken into account in the development of pulling processes for 450 mm diameter defect‐free Si crystals. Also, the mechanisms behind the experimentally observed impact of the type and concentration of substitutional dopants on intrinsic point defect behavior and formation of grown‐in defects are clarified. On the basis of the DFT calculated results, an appropriate model of intrinsic point defect behavior in heavily doped Si is proposed. (i) The incorporated total V and I concentrations at the melting point depend on the types and concentrations of dopants. (ii) Most of the total V and I concentrations contribute to Frenkel pair recombination during Si crystal growth at temperatures much higher than those to form grown‐in intrinsic point defect clusters. The Voronkov model, while taking into account the present improvements, clearly explains all reported experimental results on grown‐in defects for heavily doped Si. The most important remaining problems with respect to intrinsic point defect behavior and properties during single crystal growth from a melt are also discussed.