Fabrication of high-aspect-ratio silicon nanostructures using near-field scanning optical lithography and silicon anisotropic wet-etching process

摘要

A new process in which near-field scanning optical lithography (NSOL) is combined with anisotropic wet-etching of (110) silicon is developed for the fabrication of high-aspect-ratio (HAR) nanochannels. In the proposed process, NSOL is applied to produce nanopatterns on a commercial positive photoresist as in an optical lithography. The use of a commercial photoresist is an advantage of this process because it allows the direct application of many photoresists currently available without pretreat-ment, saving cost and time. A bare (110) silicon wafer coated with a thin Si_3N_4 layer, of approximately 10 nm thickness, is used as the sample and the, photoresist is spin-coated on the Si_3N_4 layer to a thickness of about 50-80 nm. Nanopatterning of the photoresist using a contact mode NSOL, transfer of the photoresist pattern onto the Si_3N_4 layer by reactive ion etching, and anisotropic wet etching of the silicon wafer using the patterned Si_3N_4 layer as an etch mask, lead to the intended HAR nanostructures. Fabrication of silicon nanochannels with a channel width below 150 nm and an aspect ratio greater than 3 is demonstrated.