Fabrication of Circular-Type Microchannel Using Photoresist Reflow and Isotropic Etching for Microfluidic Devices

In this study, we fabricated circular channels using photoresist reflow and isotropic etching. A silicon substrate, using Si 3 N 4 as a mask, was selectively etched using the hydrofluoric acid, nitric acid, acetic acid (HNA) etching system for fabricating the bottom hemisphere of the channels. Photoresist reflow was used to make the top of the channels round. Then Si 3 N 4 was deposited on the reflowed photoresist. Since the deposited Si 3 N 4 was approximately 6000 Å thick, it was possible to observe the inside of the channel. We expect to apply such circular channels to simple bio-systems and microfluidic devices in which optical detection is required.