20 March 2018 Mask-aligner Talbot lithography using a 193nm CW light source
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Abstract
We present and discuss Talbot mask-aligner lithography, relying on a continuous wave laser emitting at 193nm for the illumination. In this source, a diode laser at 772nm is amplified by a tapered amplifier in master-oscillator power-amplifier configuration and frequency-quadrupled in two subsequent enhancement cavities using lithium triborate and potassium fluoro-beryllo-borate nonlinear crystals to generate the emission at 193 nm. The high coherence and brilliance of such an illumination source is predestined for plane wave mask-aligner illumination, crucial in particular for high-resolution lithographic techniques such as Talbot lithography and phase-shift masks. Talbot lithography takes advantage of the diffraction effect to image periodic mask features via self-replication in multiples of the Talbot distance behind the photomask when exposed by a plane wave. By placing a photoresistcoated wafer in one of the Talbot planes, the mask pattern is replicated in the resist. Periodic patterns with diverse shapes are required for wire grid polarizers, diffraction gratings, and hole arrays in photonic applications as well as for filters and membranes. Using an amplitude mask with periodic structures, we demonstrate here with such a technique sub-micron feature sizes for various designs at a proximity gap of 20 µm.
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Andreas Vetter, Raoul Kirner, Dmitrijs Opalevs, Matthias Scholz, Patrick Leisching, Toralf Scharf, Wilfried Noell, Carsten Rockstuhl, Reinhard Voelkel, "Mask-aligner Talbot lithography using a 193nm CW light source", Proc. SPIE 10587, Optical Microlithography XXXI, 105870W (20 March 2018); doi: 10.1117/12.2296503; https://doi.org/10.1117/12.2296503
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