OXYGEN IN CZOCHRALSKI SILICON FOR ULSI

Complementary analytical techniques based on infrared absorption of electron irradiated samples and gamma activation analyses have been applied to study the incorporation and disposition of oxygen in heavily doped (5 × 10 17 to 1 × 1019 cm-3) n+ (Sb) and p+ (B) Czochralski silicon crystals of the type which will be used as substrates for epitaxy in CMOS ULSI. As in lightly doped (5 × 1016 cm -3) p- and n- type control crystals, oxygen resides predominantly in interstitial sites in as-grown n+ CZ-Si, but the levels are anomalously low due to enhanced oxygen evaporation from the antimony-rich melt. Even when the interstitial oxygen concentration is the same as lightly doped silicon, oxide precipitation is retarded in n+ crystals. The total concentration of oxygen incorporated into p+ silicon is the same as lightly doped control material for the same growth process, but measureable amounts of oxygen clustering take place during cooling. The results are interpreted in terms of the effect of the electron-hole equilibrium on the formation of thermal donors which are assumed to be the embryos for homogeneous nucleation in Czochralski silicon. © 1990, Elsevier Science Publishers B.V. (North-Holland). All rights reserved.