SUBMICROMETER LITHOGRAPHY OF A SILICON SUBSTRATE BY MACHINING OF PHOTORESIST USING ATOMIC-FORCE MICROSCOPY FOLLOWED BY WET CHEMICAL ETCHING

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