Self-aligned reduction lithography using backside exposure through embedded masks

Abstract

We demonstrate a novel self-aligned diffraction-based photolithographic technique, that uses embedded masks and backside exposure through transparent substrates, to fabricate sub-wavelength features with conventional photolithography tools. To demonstrate one potential application of this lithography tool, we produce arrays of metallic rings, split rings, and nanowires with feature sizes ranging from 130 nm and above, by modulating the exposure intensity, photoresist thickness, and etch time. The ability to produce both continuous and split rings composed of noble metals over wafer-sized areas has promise in low-cost techniques for fabricating metamaterials and other advanced optical devices.

Lithographically Patterned Electrodeposition of Gold, Silver, and Nickel Nanoring Arrays with Widely Tunable Near-Infrared Plasmonic Resonances

“…Backside exposure has been previously used with a negative photoresist to create micrometer-sized rings structures. 54 A similar fabrication technique was described by Ji et al, who also used a modified LPNE approach with interference lithography and silicon processing to create arrays of micrometer-sized rings. 55 Our combined approach of LPNE and backside exposure allows us to photopattern and electrodeposit on the submicrometer scale without the need for a highresolution photomask.…”

“…The key step in this fabrication process is the backside exposure of the photoresist through the nanohole array. Backside exposure has been previously used with a negative photoresist to create micrometer-sized rings structures . A similar fabrication technique was described by Ji et al ., who also used a modified LPNE approach with interference lithography and silicon processing to create arrays of micrometer-sized rings .…”

Microscale nuclear magnetic resonance gradient chip

“…The curved coil pattern required a refined manufacturing concept to structure the arbitrary shaped coil windings. The use of back-side (BS) exposure through an embedded metallic photomask had enabled self-aligned patterning of polymermetal micro-and nanostructures [22,23]. We employed our previous BS lithography process [24] to extend the capabilities of common PCB structuring.…”

Self-aligned patterning on β-Ga2O3 substrates via backside-exposure photolithography

“…Substrates, transparent to lithography lights, such as the g-, h-, and i-lines (436, 405, and 365 nm, respectively), are the key requirements in BEL as the photo-illumination is applied from the reverse side of the substrate to enable accurate lithographic alignment of the metal pattern. Ultraviolet-transparent glass and plastic substrates with optically flat front and back surfaces have been used in BEL [1][2][3][4][5][6][7][8][9][10] to fabricate various nanostructures, including self-aligned bottom-gates for thin film transistors, [1][2][3][4] nanoscale beam resonators, 5) metal wires 6) and rings, 6,7) and polymer-based nanopillars 8) and complex three-dimensional structures. 9,10) Although monocrystalline wide-bandgap semiconductor substrates are transparent to conventional lithography lights, there have been few attempts to use backside-exposure lithography in the literature.…”