Research

NANOPANTOGRPAHY

Introduction

The goal of this project is to fabricate orderly arrays of nanofeatures (few nm length scale) with pre-defined shapes and patterns over large areas (10s of cm2). These can find application in growth of orderly arrays of singe wall carbon nanotubes, nanoelectronics, and nanocatalysis. Simulations of ion extraction from a plasma and ion beam focusing on the wafer to form nanofeatures by etching or deposition are used to guide experimentation.

In nanopantography, standard photolithography, thin film deposition, and etching are used to fabricate arrays of ion-focusing micro-lenses (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 “nano-pantography” 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 Cl2 effusive beam on an array of 950 nm dia. lenses can be used to etch 10 nm dia. 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 ~1 nm should be possible with 90 nm dia. lenses. We expect nano-pantography 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. (please click here for PDF file onNanopantography)

Figure 1. Side views: Depiction of nanopantography, a new method for massively parallel writing of nanopatterns. Top view: AFM and SEM images of Ni nanodots deposits by nanopantography. 45° View:SEM image of a cleaved edge of a lens array with ~100 nm long, 44 nm deep trenches etched at the center of each lens by nanopantography.

 

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