EQUILIBRIUM OF CARBON AND OXYGEN IN SILICON WITH CARBON-MONOXIDE IN AMBIENT ATMOSPHERE

The pressure of CO in equilibrium with Si saturated with both C and O was measured by the transportation method from 1683°K (mp of Si) to about 1800°K, and was found to be as Pco = exp [-54900/T + 24.7]. This equation, when combined with the known solubilities of C and O in Si, gives the following relationship among C and O concentrations in Si ([C]si and [O]Si in ppma) and ambient CO pressure ([CO] in atm) at the mp of Si: [CO]/ ([C]si[O]si) = 9.6 × 10-8 for liquid Si and 1.1 × 10-6 for solid Si. This equilibrium constant for solid Si has been compared with the corresponding (nonequilibrium) values actually observed in our silicon factory. Also, some thermochemical constants of solid SiO were derived from the experimental result. © 1979, The Electrochemical Society, Inc. All rights reserved.