Silicon microfluidic channels and microstructures in single photolithography step

In this paper, a fabrication method of suspended silicon microfluidic channels and various shapes of microstructures of desired thickness in (100)-Si wafers using single photolithography step is presented. The fabrication method uses wafer bonding with silicon nitride (Si₃N₄) as intermediate layer, local oxidation of silicon (LOCOS), and complementary metal oxide semiconductor (CMOS) process compatible wet anisotropic etching. The etching process is performed in two steps in non-ionic surfactant Triton-X-100 [C₁₄H₂₂O(C₂H₄O)_n] added and pure tetramethyl ammonium hydroxide (TMAH) solutions. The surfactant added TMAH is used to define the shape of the structures, whereas pure TMAH is employed for their release.