Mechanical strength of silicon crystals as a function of the oxygen concentration

Abstract

Mechanical strengths of silicon crystals involving oxygen at various concentrations up to 10¹⁸ atoms/cm³ are investigated with the use of crystals grown by the Czochralski technique in magnetic field. Oxygen atoms dispersed on interstitial sites at any concentration have almost no influence on the dislocation processes that control the mechanical behavior of a dislocation‐free crystal. Oxygen atoms in a dislocated crystal lock dislocations effectively and result in the strengthening of the crystal. Locking of dislocations becomes more effective as the concentration of oxygen in the crystal increases. Softening of crystals due to precipitation of oxygen at elevated temperature occurs rapidly in highly concentrated crystals with oxygen, but is almost absent or takes place slowly in crystals of oxygen concentrations lower than about 5×10¹⁷ atoms/cm³.