Optical lithography is rapidly becoming very complex. As the limits of resolution are pushed to achieve feature sizes on the order of the wavelength of light or smaller, many phenomena must be understood. Technology innovation to extend optical lithography is also introducing many implementation options that must be assessed. Together, the increased concern for physical effects and the introduction of innovations have greatly increased the number of parameters whose effects must be characterized and balanced. Modeling offers a solid foundation for efficient characterization and a way to systematically quantify relationships and quickly investigate new innovations. The ultimate test is, of course, producing the desired features on product wafers. Yet a little time spent in understanding the models or in making a few simulation runs at a computer terminal can make working in the fabrication facility much more effective. It is also true that observational feedback from the fabrication facility can make modeling and simulation much more effective.
This chapter is designed to provide information about modeling and simulation at four distinct levels. It begins with an overview of the phases and nature of modeling and simulation. Then the underlying basic physical models and phenomena of optical imaging, substrate interactions, and resist dissolution are considered. The usefulness of modeling and simulation in concert with conventional characterization methods for determining the practical performance of lithography is then illustrated. Uses of modeling and simulation in assessing technology innovation in materials, exposure tools, masks, etc., are considered. Finally, a summary of available simulators is provided.
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