Maskless zone-plate-array lithography (ZPAL): for enhanced creativity in nanostructures fabrication and research

Abstract

Summary form only given, as follows. We report on our development of a maskless lithography system that uses an array of Fresnel phase zone plates to bring CW laser radiation to an array of onaxis focal spots. A Grating Light Valve (GLVm') device from Silicon Light Machines modulates the intensity of the spots as the stage is moved, enabling the creation of patterns of arbitrary geometry, with excellent control of linewidth. Placement accuracy -1nm is ensured by fabricating the zone plates with spatialphase-locked e-beam lithography, We have demonstrated multilevel alignment, fully multiplexed writing, and lithographic performance near theoretical limits with zone plates of 0.85 numerical aperture. Although our ZPAL prototype employs 400 nm wavelength, 150nm dense lines and spaces (Le,, k, = 0.32) are achieved with little difficulty. Throughput is limited primarily by the speed of beam modulation. We are proceeding toward commercial manufacturing of ZPAL tools for research and development. Diffractive optics has significant advantages over refractive approaches since near-ideal performance is achieved on axis, costs are low, and the approach can be readily scaled to shorter wavelengths. Maskless lithography, such as we will describe, should enable circuit designers to more fully exploit their creativity, unencumbered by the constraints of mask-based lithography. Ths may revolutionize custom circuit design as well as research in electronics, NEMS, microphotonics, nanomagnetics and nanoscale science and engineering.