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C1 was introduced into SiO2 films by thermally oxidizing (100) Si in either OJHC1 or O2/C12 gas mixtures at llO0~ C1 concentration vs. depth profiles in these oxide films were determined by SIMS (secondary ion mass spectrometry). Analysis of the C1 distributions shows that, after incorporation into the SiO2 network at the interface, in the bulk of the growing oxide the bonded C1 is removed from the network. This process is analyzed quantitatively as a chemical reaction in which H20 reacts to replace C1 with OH. The kinetics of this replacement reaction and of the oxide film growth determine the C1 concentration vs. depth profiles in the grown films. The replacement reaction kinetics are faster when H20 is present than when only O2 is present. This accounts for the significantly different CI profiles in HCI oxides and Cl2 oxides. These observations are consistent with previous studies of the redistribution of implanted CI in oxide films during a second oxidation step.Oxidation of Si in chlorine-containing ambients is a widely used process in preparing gate oxide films for Si devices (1). In this process C1 is incorporated into the SIO2, and is found to be segregated primarily near the Si/SiO2 interface (2-4). Recent C1 concentration vs. depth profiles determined by secondary ion mass spectrometry (SIMS) show a significant amount of C1 distributed in the oxide with increasing concentration toward the Si/SiO2 interface (5-9). One interpretation of these profiles was that the measured C1 was determined by the high temperature distribution of a mobile, diffusing C1 species (7). The authors suggested that the C1 transport was by a "field-aided" diffusion process, against the concentration gradient. However, the origin of such a field was not established. In contrast, the C1 profile was suggested to be determined by a reaction-controlled process (9, 10). This difference has not been resolved. The question will be addressed in this paper.In a previous paper, we presented a semiquantitative analysis of C1 concentration profiles measured by SIMS (11). The profiles were obtained in the course of high temperature (900~ reoxidation of thermal oxide films implanted with C1; the analysis indicated that redistribution of the implanted C1 during the reoxidation step can be controlled by either reaction or diffusion. Which process dominates depends on the concentration of mobile molecular species (H~O or O2) capable of displacing chlorine species bonded into the SiO2 network (=-Si-C1) and on the relative magnitude of forward and reverse reaction rates in the displacement reaction. In fact, the redistribution process is slow and reaction limited in dry reoxidizing ambients (of order 1 ppm H20). It is fast and possibly diffusion limited in wet ambients (more than 1% H20).Similar processes should determine the distribution of chlorine within oxide films fabricated by thermal oxidation of silicon in ambients containing HC1. Because of the gas-phase reaction of HC1 and O2, the molecular species HC1, C12, 02, and H20 will be present in ...

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