Paper
7 August 2015 Analysis of the pinhole array illumination source for high precision wavefront error metrology
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Abstract
Rapid inspection of a projection optics incorporated to 193 nm excimer-exposure system is important for 90 nm node and beyond IC manufacturing. To overcome the problems of the collimator lens presented in high NA high accuracy wavefront error metrology with Shack-Hartmann wavefront sensor, a pinhole array is used as the illumination source, which produces an array of high NA and high accuracy spherical waves, and form a high brightness source. In this paper, the diffraction of the pinhole array is calculated by using finite-difference time domain method and the theory of partial coherence. The distribution of the pinhole array considered here includes square, hexagonal and random distribution. The results shown that, pinhole diameter and separation in pinhole array have significant influence on the intensity contrast of the diffracted light, and the light intensity diffracted by the random pinhole array is smoother than that diffracted by the square or hexagonal distribution pinhole array, and is preferential in high precision wavefront error metrology.
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Zengxiong Lu, Yuejing Qi, Qingbin Meng, Jiani Su, and Guangyi Liu "Analysis of the pinhole array illumination source for high precision wavefront error metrology", Proc. SPIE 9623, 2015 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Systems, 962302 (7 August 2015); https://doi.org/10.1117/12.2191100
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KEYWORDS
Spherical lenses

Wavefronts

Metrology

Diffraction

Collimators

Error analysis

Wavefront sensors

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