On the design of lithographic interferometers and their application

Abstract

Interference lithography is presented as an ideal technique for fabricating large-area periodic structures with sub-100nm dimensions. A variety of interferometer designs are discussed and implemented, each of which emphasizes a different attribute. Curvature of the substrate during exposures in a Mach-Zender interferometer is demonstrated as a method for reducing periodicity variations in the printed pattern down to the level of picometers. A robust Lloyd's-mirror interferometer is developed as a simple and flexible lithography system capable of sub-100nm features. Prospects and designs for the use of grating interferometers for the fabrication of structures with 50nm spatial-periodicity are discussed. A novel, integrated, thin-film interferometer exploiting solid immersion is introduced for the fabrication of features below the diffraction-limit. Using 193nm illumination, 45nm dense features are demonstrated. Aspects of sub-wavelength diffraction and thin-film resonance are discussed in relation to the fabrication of structures with sub-50nm periodicity. A selection of applications are discussed which take advantage of the unique capabilities of interference lithography, including patterned magnetic media, DFB lasers and the templated self-assembly of nano-particles. A novel technique for ion-beam etching, applicable to any material system, is shown to improve the patterning of nanoscale magnetic elements.