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As the popularity of photonic devices and their uses increases, reliable manufacturing processes will need to be developed to make them more cost effective. Many companies still utilize i-line lithography, with very robust processes. Photonic devices require feature sizes often too small to be fabricated on i-line tools, especially for TE mode devices. In order to fabricate these devices, a form of double patterning will need to be developed.

Proposed is a Litho-Freeze-Litho-Etch (LFLE) process that can achieve the feature sizes capable of fabricating TE mode photonic devices. This project encompasses design, development, and characterization of a LFLE process that can achieve sub 300 nm spacing and feature widths of 300 nm. The LFLE process will pattern a positive resist (OiR-620), which will be cured using a UV source (250 nm). A negative resist (NLOF-2020) will be patterned over top the cured positive resist, resulting in a compound photoresist image that can be etched. A development mask design was created and utilized to successfully pattern a compound image, feature sizes were resolved down to 150 nm with the negative resist and 200 nm in positive resist, gaps were shown to be in the sub 200 nm range.

Future work will be needed to refine the process to be usable for TE mode devices, however the process has been successfully tested and shows significant promise.

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