Nanoscale two-dimensional patterning on Si(001) by large-area interferometric lithography and anisotropic wet etching

Abstract

A fabrication technique for nanoscale two-dimensional (2D) patterning by large-area interferometric lithography (IL) and anisotropic wet etching (AWE) is reported. On a Si(001) substrate corrugated by one-dimensional (1D) periodic V-grooves in a first IL/AWE step, an additional 1D IL/AWE patterning perpendicular to the groove direction is performed. In this process, {111} facets—the sidewalls of a V-groove having an extremely low etch rate in AWE—are utilized as an etch barrier to confine AWE to a nanoscale-wide (001) stripe facet between V-grooves. IL on the corrugated Si surface results in an array of photoresist (PR) lines localized on each (001) stripe. The subsequent AWE with a Cr etch mask fabricated from this unusual PR pattern thus begins from the inner side of (001) stripe but slows down as it reaches the (001)-{111} facet intersection of the V-groove. The {111} planes at each facet intersection play the important role of an etch barrier laterally confining the etch area within each (001) stripe. The direction along the stripe is also confined with the formation of 2D {111} inverted pyramids. A 355 nm period, 2D array of Si mesas having a rectangular top (001) facet of area ∼150 nm×110 nm and surrounded by various (111) facets in a unit period is fabricated on a Si(001) substrate.