The oxygen content of heat4reated and quenched SiO2-Si(1) samples has been analyzed by the SIMS technique in order to investigate the temperature dependence of the equilibrium SiO2]Si(1). A SiO(s) phase was predicted by thermodynamical calculations and also verified experimentally. This phase appears in equilibrium with a melt of lower oxygen content than the SiO2 phase and, when formed, determines the oxygen content of the melt. The existence of the SiO(s) phase in a Czochralski silicon crystal growth system was confirmed and the implications are briefly discussed.The incorporation of oxygen in silicon crystals grown by the Czochralski technique has been thoroughly investigated over the last 10 years. Many topics have been covered both theoretically and experimentally, and a recent review is made by Moody (1). However, no experimental investigations of the solubility of oxygen in liquid silicon in equilibrium with its oxide at elevated temperatures have been carried out, in spite of the importance of such measurement for working out a quantitative model of the crucible dissolution. One of the reasons may be the difficulty in obtaining reliable oxygen measurements from quenched, polycrystalline samples. With the relatively new SIMS technique, however, such measurements can now be carried out with sufficient accuracy.Another relevant aspect in this context is the reactions and mechanisms involved in the dissolution process of SiO2 in contact with liquid silicon. Some observations have been made in conjunction with studies of the dissolution rate (2, 3), and the common opinion seems to be that partial devitrification of the fused quartz to cristobalite occurs without any influence on the dissolution rate.The aim of this work originally was to measure the oxygen content of molten silicon in equilibrium with SiQ above the melting point and compare it to recently published theoretical data (4). As the results however, were clearly linked to phase transitions at the studied interface, further thermodynamic and metallographical investigations had to be made in order to understand the measured solubilities and the reactions involved. ExperimentIn order to investigate the temperature dependence of the solubility of oxygen in molten silicon, in equilibrium with SiO2, silica ampuls were filled with a few grams of polycrystalline, 300 ~cm, CVD-silicon from Wacker Chemitronic GmbH. The ampuls were evacuated, sealed, and heat-treated at different temperatures between 1415 ~ and 1490~ for 45 rain. The temperature was controlled by a Pt-Pt 10% Rh thermocouple and held within _+3~ The collapsed ampuls were subsequently quenched in cold water.The oxygen content in the bulk-of the quenched melt was evaluated by SIMS analysis with a background level of 2 9 10 iv atom/cm ~ measured on FZ St.Samples from the melt/crucible interface of a Czochralski system were examined in optical microscope, together with samples from the ampuls. Differences in composition between different phases were revealed by the use ofa SEM microscope equipped w...

By the application of well-known thermodynamics, growth kinetics, diffusion processes, and experimental results, a reasonable explanation for the behavior of silica in contact with liquid silicon is presented. Decomposition of silica to solid SiO, and diffusion of silicon and oxygen ions through solid SiO, play important parts in the discussion. The consequences for Czochralski growth of silicon crystals are outlined.Oxygen incorporation in Czochralski-grown silicon crystals has been the subject of numerous investigations, particularly over the last 15 years. Most of the investigations have been directed toward studying the influence of different growth parameters on the oxygen distribution in the crystals, e.g., see Moody (1) for a recent review; more fundamental work has been carried out by Kaiser and Breslin (2), Kubaschewski and Alcock (3), and the present authors (4, 5). In spite of these studies, there is no known investigation into the nature of the interaction that takes place at the interface between molten silicon and silica. Some experiments were done by Zulehner and Huber (6), and Chaney and Varker (7), and it was concluded that cristobalite grows on the SiO2/Si(1) interface. This opinion was opposed in Ref. (5), where it was concluded that the phase growing at elevated temperatures is solid SiO. This conclusion was based on thermodynamic calculations and measurements of the solubility of oxygen in molten silicon. However, none of the authors made any serious treatment of the reaction mechanisms involved, which is the subject of the present paper. ExperimentalSilica ampuls were filled with polycrystalline chemical vapor-deposited (CVD) silicon, 300 fl-cm, obtained from Wacker Chemitronic GmbH. The ampuls were evacuated, sealed, and heat-treated at 1420~ for 15 min, 1, 2, and 9h. The temperature was kept within _+ 2~ and measured by a Pt-Pt 10%Rh thermocouple calibrated at the eutectic point of the iron-carbon system. After the heat-treatment, the samples were subsequently quenched in cold water. The samples were mounted, ground, and polished metallographically so that the structure at the interface, Si/SiO2, could be examined. A sample from the bottom of a silica crucible, from which a high-resistivity phosphorus-doped silicon crystal had been grown, was treated in the same way as well as an ampul in which solid CVD silicon had been heat-treated for 8h at 1390~ ResultsIn Fig. 1-5, the results of the metaUographic investigation are presented. No picture from the sample heattreated for 15 min is presented, as it did not contain any information that cannot be obtained from the other micrographs. The very light phase covering the top part of the pictures is silicon, and the gray phase at the bottom is the unaffected SiO2. At the interface between these phases, the reaction products form an irregular pattern. In Fig. 1, lh heat-treatment, an isolated spot of a gray phase, herein called the A phase, has been formed and has grown into the silica. A layer of silicon between the unaffected silica and the edges...

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