Shortcomings of growth modelling of silicon carbide
In short: Simulations can provide a better understanding of the chemical vapor deposition process of silicon carbide (SiC) to improve material quality, film thickness, uniformity and the yield. However, the current models have shortcomings prohibiting accurate simulations. In this work we point out that improvements are very much needed in both the chemical species' thermodynamic data and the gas phase reaction models, as well as in the surface reaction descriptions. For example, we show that the current surface reaction models do not provide realistic predictions, and we suggest that several hydrocarbon molecules may have higher reactivities with the SiC surface than previously accepted values.
A better understanding of the chemical vapor deposition (CVD) process of silicon carbide (SiC) is needed if one wants to optimize process conditions and equipment to improve material qualilty, film thickness and doping uniformity and increase the yield. Simulations can provide much information about gas flow characteristics, temperature gradients and gas mix composition in the CVD reactor, but also about chemical reaction rates and products, both in the gas phase and on surfaces. However, when it comes to the models used for simulations of the SiC CVD process there is still much work to be done.
In this paper we point out three important parts of the modeling where improvements are very much needed for accurate simulations of this process: the thermochemical properties of the species involved, the gas phase chemistry reaction mechanism, and the surface reaction rates leading to the actual deposition. We have used accurate quantum chemical computations to calculate the properties of 30 species thought to be part of the gas phase chemistry, and compared with literature values. We show that very different results can be obtained depending on which data are used for the species properties. We compare three different gas phase reaction mechanisms (two from the literature and one new), and show that the predicted gas phase composition and concentrations of different species varies largely depending on the reaction mechanism used. We finally show that the surface reaction models used up to date in fact does not provide realistic predictions. Instead, we suggest that several of the hydrocarbon molecules may have higher reactivities with the SiC surface than previously accepted values.
Details of the research are described in Theoretical Chemistry Accounts 132, 1398 (2013)
- Swedish Foundation for Strategic Research (SSF)
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Last updated: 02/11/14