A new illumination source for Shack-Hartmann wavefront sensor

Yuejing Qi; Zengxiong Lu; Gongming Ding; Jiani Su

doi:10.1117/12.2068294

18 September 2014 A new illumination source for Shack-Hartmann wavefront sensor

Yuejing Qi, Zengxiong Lu, Gongming Ding, Jiani Su

Proceedings Volume 9282, 7th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment; 928205 (2014) https://doi.org/10.1117/12.2068294
Event: 7th International Symposium on Advanced Optical Manufacturing and Testing Technologies (AOMATT 2014), 2014, Harbin, China

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.

Citation Download Citation

Yuejing Qi, Zengxiong Lu, Gongming Ding, and Jiani Su "A new illumination source for Shack-Hartmann wavefront sensor", Proc. SPIE 9282, 7th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 928205 (18 September 2014); https://doi.org/10.1117/12.2068294

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