Fabrication of thin composite emission filter for high-performance lens-free fluorescent imager

Erus Rustami; Kiyotaka Sasagawa; Thanet Pakpuwadon; Yasumi Ohta; Hironari Takehara; Makito Haruta; Jun Ohta

doi:10.1117/12.2546540

21 February 2020 Fabrication of thin composite emission filter for high-performance lens-free fluorescent imager

Erus Rustami, Kiyotaka Sasagawa, Thanet Pakpuwadon, Yasumi Ohta, Hironari Takehara, Makito Haruta, Jun Ohta

Proceedings Volume 11235, Microfluidics, BioMEMS, and Medical Microsystems XVIII; 112350F (2020) https://doi.org/10.1117/12.2546540
Event: SPIE BiOS, 2020, San Francisco, California, United States

Abstract

The emission filter plays a key role in resolving a modest-quality image of the lens-free fluorescent imager. The complementary structure of an interference filter and absorption filters exhibits a high-rejection ratio, corresponding to the lens-based fluorescence device. However, existing fabrication methods are facing challenges to reach a reasonable filter thickness for low invasiveness. It is difficult to deposit interference filters on the polymer-based absorption filter and CMOS die directly. Conversely, the interference is fragile and easy to crack so that transferring from its substrate to the image sensor is a fatiguing task. Here we report composite filter fabrication using laser lift-off (LLO) and silicon plasma etching. The LLO utilized high energy laser to separate the interference filter from the glass substrate, whereas the plasma etching tailored SiF₆ gas to completely annihilate silicon-substrate whereby the filter was deposited beforehand. As a result, a narrow-size filter is successfully fabricated by LLO, yet a crack issue for a larger sensor size remains unsolved. On the other hand, the plasma etching produced large-size and spotless filters with relatively high reproducibility. Additionally, this method offers multiple device fabrication in a single process, which, we expect, could intensify largescale lens-free fluorescent imager applications in the future.

Conference Presentation

Citation Download Citation

Erus Rustami, Kiyotaka Sasagawa, Thanet Pakpuwadon, Yasumi Ohta, Hironari Takehara, Makito Haruta, and Jun Ohta "Fabrication of thin composite emission filter for high-performance lens-free fluorescent imager", Proc. SPIE 11235, Microfluidics, BioMEMS, and Medical Microsystems XVIII, 112350F (21 February 2020); https://doi.org/10.1117/12.2546540

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