Programmable aperture plate for maskless high-throughput nanolithography

One of the most serious challenges to extending lithography (by whatever radiation) into the sub-100 nm regime is mask manufacturing technology. We propose and analyze a pattern writing concept somewhat like a dot matrix printer that can expose resist with 25 nm pixels at rates needed for production lithography. It consists of a programmable aperture plate which defines an array of 3000x3000, 5 mu mx5 mu m apertures on 20 mu m centers which is illuminated by a collimated beam of either ions or electrons. Each aperture can be blanked off by suitable electrodes and is individually addressed. The image of the array is demagnified on the wafer by 200x. The pattern is entered into the array from one edge only and is toggled across the array by shift registers. The wafer is moved in synchronism. Each pixel on the wafer is exposed 750 times by 750 different pixels to accumulate the total dose. If ions are used (e.g., H+) and a total maximum current of 3 mu A is passed down the ion optical column, consistent with space charge limits, then the writing speed with 25 nmx25 nm pixels on the wafer is 1 cm(2)/s for an ion resist sensitivity of 3 mu C/cm(2). The aperture plate can be fabricated from a sandwich of 3 Si membranes and will exploit the high aspect ratio etching of [110] Si to achieve the structures that hold the blanking plates. The aperture array will measure 6 cmx6 cm. The shift register circuits clocking at about 10 MHz will be built in the spaces between the apertures and are feasible with state of the art devices. (C) 1997 American Vacuum Society.