23 March 2009 Inspection and metrology tools benefit from free-form refractive micro-lens and micro-lens arrays
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Abstract
LIMO's unique production technology based on computer-aided design enables the manufacture of high precision asphere single lenses and arrays, where every single lens can be individually shaped. These free form micro-optical cylindrical lens and lens arrays find their application in various types of metrology systems. Due to the high precise manufacturing of specially designed surface, single lenses can be bond directly onto sensor or sensor arrays, performing efficient projection of signal onto detector. Optical modules based on micro-lenses arrays enable special intensity distribution, as well as highly homogeneous illumination with inhomogeneity less then 1% (peak to valley) used in illumination parts of inspection tools. Due to the special free form profile, a special case of asymmetric lens arrays can offer extreme uniformity illumination at the target non orthogonal to the illumination path. The feature under inspection can be uniformly illuminated even if it lies at a specific angle to the illumination. This allows better conditions for measurement devices arranged orthogonal to the mask or wafer. Furthermore the use of micro-optics enables more sufficient inspection of laser beam parameters for excimer or CO2 lasers. Additionally very accurate metal patterns can be applied on the optics and used as alignment marks, apertures or bonding features.
© (2009) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Tanja Bizjak, Thomas Mitra, and Lutz Aschke "Inspection and metrology tools benefit from free-form refractive micro-lens and micro-lens arrays", Proc. SPIE 7272, Metrology, Inspection, and Process Control for Microlithography XXIII, 72723Q (23 March 2009); doi: 10.1117/12.814264; https://doi.org/10.1117/12.814264
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