Fabrication technology of Si microfluidic devices for microbial cell trapping

We report fabrication technology for micro fluidic filter device with fine and high aspect ratio filtration gap using single-mask and CMOS compatible process flow. Advantage of Si based Microfabrication platform technology has been fully exploited by adopting manufacture-able process flow. A novel approach of combining silicon deep reactive ion etch (RIE) capability with subsequent gap-fill engineering enabled achieve wide range of filtration gaps of deep sub-micron size with high aspect ratios of >200. This approach eliminated the need to use high-end lithography techniques in order to achieve deep sub-micron gaps after pattern transfer. Si deep RIE etch process was optimized by applying dual passivation technique which enabled to realize sub-micron gap pillar-type filter structures and large reaction chambers simultaneously using single-mask process. Wide range of filtration gap sizes demonstrated in this work offer versatile applications for fine cell trapping such as protozoa and bacteria. Fluid injection channels for the device were realized through wafer backside Si wet etch processing to complete the filter device chip fabrication.