Multidimensional process optimization of a negative e-beam photoresist for silicon-waveguide manufacturing

Current applications of silicon photonic devices are strongly limited by waveguide performance. Rough sidewalls scatter electromagnetic radiation and lead to significant losses. Prototyping of state-of-the-art silicon photonic devices on full wafer scale requires maskless manufacturing. Therefore, variable shaped electron-beam lithography in chemically amplified photoresists and anisotropic etching processes are used. As a result, size and roughness errors in the photoresist structures are directly transferred to the silicon-waveguides. In this study a high-resolution chemically amplified negative photoresist for electron-beam writing was run in and optimized for photonic device manufacturing successfully. The investigation of the photoresist contrast and critical dimensions enabled the production of smooth and critical dimension stable lines in photoresist, which exhibit vertical sidewalls as well as a resolution limit far below 100 nm.