In-Situ Isotropic and Anisotropic DRIE Sequence for Massive Parallel Multistage Brownian Ratchets

In this paper an in-situ isotropic and anisotropic deep reactive ion etching (DRIE) sequence process is presented to obtain a periodic asymmetric variation along the z-axis in pore diameter on silicon wafers, which can act as massively parallel and multiply stacked Brownian ratchets. The etch rates of isotropic and anisotropic etching process depends strongly on the size and the shape of structures. The undercut phenomenon for small size structure (less than 2 mum) is investigated. Exposure into NH₃ plasma after etching to smoothen the surface of silicon is discussed as well.