Defects and Impurities in Silicon Materials

This chapter reviews the defects and impurities in Si materials. Most of the defects in Si crystal originate from point defects, which can be divided into intrinsic and extrinsic categories. The intrinsic point defects include self-interstitial atoms and vacancies, and the extrinsic point defects refer to foreign impurity atoms. These point defects can form bulk defects and micro-defects, among which oxygen precipitates, voids (COPs), and oxidation-induced stacking faults are the most important ones. The line defects named after dislocations and planar defects only exist in some special cases, which often occur during Si epitaxial and wafer thermal cycles. The important impurity in Czochralski (CZ) Si crystal is oxygen, which should be as low as possible. The oxygen impurities can form SiO2 precipitates as the intrinsic gettering sites for metal contaminants. Meanwhile, the nitrogen doping enhances the formation of oxygen-related SiO2 precipitates and reduces the thermal stability of voids (COPs), and therefore has been widely used in microelectronics industry.