COPRECIPITATION OF CARBON AND OXYGEN IN SILICON - THE DOMINANT FLUX CRITERION

Due to the need of relieving the strain associated with the formation Of SiO2 precipitates in silicon, co-precipitation of carbon with oxyge n in silicon wafers may involve a large number of atomic and point def ect species: oxygen, carbon, vacancies, and silicon self-interstitials . This allows many parallel mechanisms for strain relief to occur. In the present paper we first reason that this complex system may be redu ced to that involving only three species: oxygen, carbon, and self-int erstitials; and the strain relief mechanisms may be limited to two: th at via self-interstitials and that involving carbon. We then propose a dominant (strain relief species) flux criteria to explain the behavio r of carbon and oxygen co-precipitation in silicon. When the carbon fl ux is dominant, carbon should co-precipitate with oxygen. When the sil icon self-interstitial flux is dominant, carbon should not co-precipit ate with oxygen, even at high concentrations. Available data, spanning the temperature range of 450-1000-degrees-C and a carbon concentratio n range of from less than 0.5 X 10(16) to 1 X 10(18) cm-3, can be expl ained using this criterion.