Development of an experimental EUV interferometer for benchmarking several EUV wavefront metrology schemes

Murakami, Katsuhiko; Saito, Jun; Ota, Ken‐ichiro; Kondo, Hiroyuki; Ishii, Mikihiko; Kawakami, Jun; Oshino, Tetsuya; Sugisaki, Katsumi; Zhu, Yongtian; Hasegawa, Masanobu; Sekine, Yoshiyuki; Takeuchi, Shigeyuki; Ouchi, Chidane; Kakuchi, Osamu; Watanabe, Yutaka; Hasegawa, Takayuki; Hara, Shinichi; Suzuki, Atsushi

doi:10.1117/12.484935

Cited by 11 publications

(3 citation statements)

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“…(1) The high NA, 6-mirror PO has several challenging items. The high NA PO needs a very small pinhole, in order to produce an ideal spherical wavefront used as a reference wavefront.…”

Section: Intoroductionmentioning

confidence: 99%

EUV wavefront metrology system in EUVA

Hasegawa¹,

Ouchi²,

Hasegawa³

et al. 2004

SPIE Proceedings

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ABSTRUCTAn Experimental extreme ultraviolet (EUV) interferometer (EEI) using an undulator as a light source was installed in New SUBARU synchrotron facility at Himeji Institute of Technology (HIT). The EEI can evaluate the five metrology methods reported before. (1) A purpose of the EEI is to determine the most suitable method for measuring the projection optics of EUV lithography systems for mass production tools. INTORODUCTIONWe started a new EUV wavefront metrology project at the Association of Super-Advanced Electronics Technology (ASET) in 2002. And in 2003 the management of the project has been transferred to the Extreme Ultra-violet Lithography System Development Association (EUVA). The objective of the project is to develop an EUV wavefront metrology system for EUV projection optics with precision of 0.1nm RMS. We are planning to construct an EUV wavefront metrology system (EWMS) for full-field 6-mirror EUV projection optics with high numerical aperture (NA). Before developing the EWMS, we developed an EUV Experimental Interferometer (EEI) with a simple composition. A test optics (PO) for the EEI is 0.2 numerical aperture (NA) Schwarzchild optics with two spherical reflection mirrors. The requirements of the PO for the EEI are large NA (up to 0.25) and low wavefront error (less than 1nm RMS). A wavefront of this PO was measured using a visible-light (633nm) PDI system, which had been developed at the ASET EUV laboratory. The wavefront error was 1.06nm RMS, which almost satisfies the requirement of the test optics of the EEI.We are now evaluating the following five metrology methods using the EEI: point diffraction interferometer (PDI), line diffraction interferometer (LDI), lateral shearing interferometer (LSI), slit shearing interferometer (SSI), and doublegrating lateral shearing interferometer (DLSI). (1) The high NA, 6-mirror PO has several challenging items. The high NA PO needs a very small pinhole, in order to produce an ideal spherical wavefront used as a reference wavefront. In addition, EUV intensity becomes low because of the 6-times refrection of the mirrors. Therefore in the EEI, it becomes important that the small pinhole is producible and that it is measurable with low intensity.

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“…(1) The high NA, 6-mirror PO has several challenging items. The high NA PO needs a very small pinhole, in order to produce an ideal spherical wavefront used as a reference wavefront.…”

Section: Intoroductionmentioning

confidence: 99%

EUV wavefront metrology system in EUVA

Hasegawa¹,

Ouchi²,

Hasegawa³

et al. 2004

SPIE Proceedings

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“…The wavefront of this test optic, when measured with a visible (633nm) interferometer before installation, was 1.06nmRMS. The following 6 measurement methods can be evaluated with the EEI: two (2) diffraction-type methods, namely, point diffraction interferometer (PDI) and line diffraction interferometer (LDI), and four (4) shearing-type methods, namely, conventional lateral shearing interferometer (LSI), slit-type lateral shearing interferometer (SLSI), double-grating lateral shearing interferometer (DLSI) [2], and cross-grating lateral shearing interferometer (CGLSI).…”

Section: Introductionmentioning

confidence: 99%

Comparison of EUV interferometry methods in EUVA project

et al. 2005

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We are developing an at-wavelength interferometer for EUV lithography systems. The goal is the measurement of the wavefront aberration for a six-aspherical mirror projection optic. Among the six methods that EEI can measure, we selected CGLSI and PDI for comparison. PDI is a method well-known for its high accuracy, while CGLSI is a simple measurement method. Our comparison of PDI and CGLSI methods, verified the precision of the CGLSI method. The results show a difference between the methods of 0.33nm RMS for terms Z5-36. CGLSI measurement wavefronts agree well with PDI for terms Z5-36, and it is thought of as a promising method. Using FFT analysis, we estimated and then removed the impact of flare on the wavefront. As a result of having removed the influence of flare, the difference between CGLSI and PDI improved to only 0.26nm RMS in Zernike 5-36 terms. We executed PDI wavefront retrieval with FFT, which has not been used till now. By confirming that the difference between methods using FFT and Phase shift is 0.035nm RMS for terms Z5-36, we have proven that PDI wavefront analysis with FFT is possible.

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“…Modern microelectronic technologies provide manufacturing high-quality, low-edge roughness pin-holes with diameters down to 40-50 nm. Such pin-holes are applied in diffraction interferometers operating at the working wavelength of a EUV nano-lithographer, λ=13.5 nm, which are installed on undulators of the last generation synchrotrons in USA and Japan (Naulleau et al, 2000;Murakami et al, 2003). An interferometer circuit installed on ALS (Berkeley, USA) is given in Fig.…”

Section: Interferometers With a Diffraction Reference Wavementioning

confidence: 99%