Abstract

Volume manufacturing of dense, large-area arrays of small feature size (≅ 100-500 nm) structures is of considerable importance to a range of present and developing technologies including microelectronics and displays. Substantial effort is being expended on improvements in conventional optical lithography (including shorter wavelengths and phase-shift masks), on x-ray lithography, and on alternate patterning techniques, such as e-beam and focused ion-beam lithographies. The optical and x-ray techniques have limitations in terms of depth-of-focus that become more severe as critical dimensions decrease. The particle lithographies, while providing the necessary resolution, are generally more complex serial processes and are ill-suited to volume production. We report on a simple use of multiple exposure interferometric lithography using readily available laser sources to produce large areas of submicrometer structures. This technique has an essentially infinite depth-of-field and is well matched to volume manufacturing constraints. The use of multiple exposures, of zone plates within the optical paths, and the combination of this technique with conventional (but lower resolution) lithography offers the potential of fabricating a wide variety of structures. Multiple exposures result in moire patterns. A simple, but important, example of these moire patterns is a two dimensional array of submicrometer holes on uniform grids in both x and y directions. Another useful structure is a large area interdigitated comb. Linewidths to as small as 100 nm and periods to 250 nm are readily achieved by using a 488 nm Arion laser source.

© 1992 Optical Society of America