Submicrometer lithography of a silicon substrate by machining of photoresist using atomic force microscopy followed by wet chemical etching

Abstract

In this paper, the atomic force microscope (AFM) is used as a powerful technique for the machining and imaging of a nonconducting, 1.0 μm thick, photoresist. A systematic approach is adopted to determine the minimum number of passes of the AFM probe tip and the optimized maximum force that could be applied by a Si cantilever (∼ 50 N m-1) on a photoresist to achieve the desired modifications. Linear relationships are established for the number of passes to achieve the corresponding attainable depth. V-grooves are fabricated in the photoresist using high normal forces of 5 and 10 μN with a transverse speed of 10 μm s-1. With a higher manoeuvring speed of 200 μm s-1, a window is created in the photoresist without significant irregular undulation at its base. A regular window of 20.4 μm × 36.2 μm with depth 60 nm and a line window of width 1.08 μm and depth 12 nm are successfully fabricated in silicon using the photoresist machined pattern as a mask for wet preferential Si etching.