Nanopantography: A New Method for Massively Parallel Nanopatterning over Large Areas

Abstract

We report a radically different approach to the versatile fabrication of nanometer-scale preselected patterns over large areas. Standard lithography, thin film deposition, and etching are used to fabricate arrays of ion-focusing microlenses (e.g., small round holes through a metal/insulator structure) on a substrate such as a silicon wafer. The substrate is then placed in a vacuum chamber, a broad-area collimated beam of ions is directed at the substrate, and electric potentials are applied to the lens arrays such that the ions focus at the bottoms of the holes (e.g., on the wafer surface). When the wafer is tilted off normal (with respect to the ion beam axis), the focal points in each hole are laterally displaced, allowing the focused beamlets to be rastered across the hole bottoms. In this "nanopantography" process, the desired pattern is replicated simultaneously in many closely spaced holes over an area limited only by the size of the broad-area ion beam. With the proper choice of ions and downstream gaseous ambient, the method can be used to deposit or etch materials. Data show that simultaneous impingement of an Ar(+) beam and a Cl(2) effusive beam on an array of 950-nm-diam lenses can be used to etch 10-nm-diam features into a Si substrate, a reduction of 95x. Simulations indicate that the focused "beamlet" diameters scale directly with lens diameter, thus a minimum feature size of approximately 1 nm should be possible with 90-nm-diam lenses that are at the limit of current photolithography. We expect nanopantography to become a viable method for overcoming one of the main obstacles in practical nanoscale fabrication: rapid, large-scale fabrication of virtually any shape and material nanostructure. Unlike all other focused ion or electron beam writing techniques, this self-aligned method is virtually unaffected by vibrations, thermal expansion, and other alignment problems that usually plague standard nanofabrication methods. This is because the ion focusing optics are built on the wafer.