Inspection and metrology tools benefit from free-form refractive micro-lens and micro-lens arrays
2009
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
CO 2 lasers. Additionally very accurate metal patterns can
be applied on the optics and used as alignment marks, apertures or bonding features.
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