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5 - effects depth of focus and stray radiation there is...

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EE440, Prof. Sanjay Bannerjee Prateek Choudhary 5.1) According to our simple calculations, an ArF source will have a resolution to 193nm and a depth of focus of 134nm. So, it will not be adequate for 130nm and 100nm technologies. 5.7) Contemporary photoresists are opaque to UV light. So when they are exposed to it, only the top layers get exposed and change their chemistry. However, the photoresist after reacting is transparent to UV light, and so the consecutive layer of photoresist gets exposed to UV light. Therefore, when the underlying topography is very rough, then in the deep regions it takes longer for all the photoresist layers to be exposed to UV radiation, and in the meantime, other shallower regions get exposed to more radiation. Due to diffraction
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Unformatted text preview: effects, depth of focus, and stray radiation, there is wider exposure of photoresist in the shallower regions, thus affecting resolution. 5.10) As lithography moves to shorter wavelengths, people will also need to use wider lens apertures to maintain resolution. This, along with a smaller length will greatly reduce the Depth of Focus. Depth of Focus causes great problems in underexposure and over exposure and these problems arise due to an uneven topography. Therefore, to reduce the over and exposure problems associated with photoresist, the wafers would have to be planarized before being exposed to radiation....
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