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Proceedings Paper

A new illumination source for Shack-Hartmann wavefront sensor
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Paper Abstract

Rapid inspection of a projection optics incorporated to 193 nm excimer-exposure system is important for 90 nm node and beyond IC manufacturing. The measurement accuracy of the projection optics, which comprises of dozens of refractive mirrors and has numerical aperture (NA) of 0.75, should be reach 2.0 nm RMS. The high brightness subnanometer accuracy spherical wave with NA of 0.75 is crucial to realize such high accuracy metrology. In this paper, we introduce a new illumination source for Shack-Hartmann wavefront sensor used to measure the wavefront error of the projection optics. The new illumination source, which contains many randomly distributed pinholes etched on a metal membrane, acts as many incoherent point sources and has high brightness. The diameters of the pinholes are in the same order as the wavelength of the illumination wave. The diffraction of the pinholes is calculated based on finite difference time domain (FDTD) method, the diffractive waves can cover the whole space behind the pinholes, the wavefront error of the diffracted spherical wave is about 10-3λ RMS (λ=193 nm) within NA 0.75. The brightness is improved to N (Number of pinholes) times compared with single pinhole case.

Paper Details

Date Published: 18 September 2014
PDF: 7 pages
Proc. SPIE 9282, 7th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 928205 (18 September 2014); doi: 10.1117/12.2068294
Show Author Affiliations
Yuejing Qi, Academy of Opto-Electronics (China)
Zengxiong Lu, Academy of Opto-electronics (China)
Gongming Ding, Academy of Opto-Electronics (China)
Hefei Univ. of Technology (China)
Jiani Su, Academy of Opto-Electronics (China)


Published in SPIE Proceedings Vol. 9282:
7th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment
Yudong Zhang; Wei Gao, Editor(s)

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