Featured in Nanophotonics – Scaling up multispectral color filters with binary lithography and reflow (BLR)

Professor Joel Yang is a corresponding author in the research on using binary lithography and reflow (BLR) will be featured in online journal Nanophotonics.

Spectral sensors are an integral part in digital cameras and mobile phones. To exhibit color sensitivity, color filters are fabricated above photodiodes. However, processes that rely on the sequential fabrication of each filter are cost ineffective. In collaboration with LiteOn Semiconductor, we introduce an approach to produce at least 16 distinct filters based on a single low-resolution lithographic step with a minimum feature size of 0.6 μm. Distinct from grayscale lithography that requires multiple steps for fabrication, we employ standard binary lithography but achieve height variations in polymeric resist through a post-development reflow process. The resulting transparent polymeric films were incorporated in Fabry–Perot cavity structures with cavity thickness ranging 90–230nm to produce transmittance across the visible spectrum. This process demonstrates control of the dielectric layer thickness down to ∼15nm. This new process provides a cost-effective alternative to traditional techniques but not limited to fabricating transmission and reflective spectral filters.

SUTD Authors: Md Abdur Rahman, Soroosh Daqiqeh Rezaei, Deepshikha Arora, Wang Hao, Chia Ser Chern, Chan John You En, Uddin Siam, Pan Cheng-Feng, Zhang Wang, Wang Hongtao, Yang Joel K. W