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Proceedings Paper

Micro-optics: enabling technology for illumination shaping in optical lithography
Author(s): Reinhard Voelkel
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Paper Abstract

Optical lithography has been the engine that has empowered semiconductor industry to continually reduce the half-pitch for over 50 years. In early mask aligners a simple movie lamp was enough to illuminate the photomask. Illumination started to play a more decisive role when proximity mask aligners appeared in the mid-1970s. Off-axis illumination was introduced to reduce diffraction effects. For early projection lithography systems (wafer steppers), the only challenge was to collect the light efficiently to ensure short exposure time. When projection optics reached highest level of perfection, further improvement was achieved by optimizing illumination. Shaping the illumination light, also referred as pupil shaping, allows the optical path from reticle to wafer to be optimized and thus has a major impact on aberrations and diffraction effects. Highly-efficient micro-optical components are perfectly suited for this task. Micro-optics for illumination evolved from simple flat-top (fly’s-eye) to annular, dipole, quadrupole, multipole and freeform illumination. Today, programmable micro-mirror arrays allow illumination to be changed on the fly. The impact of refractive, diffractive and reflective microoptics for photolithography will be discussed.

Paper Details

Date Published: 31 March 2014
PDF: 11 pages
Proc. SPIE 9052, Optical Microlithography XXVII, 90521U (31 March 2014); doi: 10.1117/12.2046116
Show Author Affiliations
Reinhard Voelkel, SUSS MicroOptics SA (Switzerland)

Published in SPIE Proceedings Vol. 9052:
Optical Microlithography XXVII
Kafai Lai; Andreas Erdmann, Editor(s)

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