Contour lithography methods for DRIE fabrication of nanometre–millimetre-scale coexisting microsystems

Abstract

This paper proposes a nanometrically precise fabrication method for nanometric and millimetric structures on the same wafer. The advancement in deep reactive ion etching (DRIE) is enabling a number of applications of high aspect ratio nanostructures. However, DRIE conditions optimized for nano-size openings are often incompatible with large area etching due to the aspect-ratio dependence of optimum conditions. This paper proposes to solve the problem by a two-step etching method: the etching of nanostructures plus contours of large area openings followed by the etching of the rest. Both masking layers for nano+contour and the rest of the area are embedded prior to the first deep etching. This ‘embedded masking method’ ensures fine lithography on the flat surface. The second masking for the rest of the area is created by LOCOS. Following LOCOS the process created a uniform passivation to large area etching. Its capability has been shown by successful fabrication of 1.3 µm wide optical filters coexisting with millimetre-scale (0.15 mm × 2.7 mm) trenches.