Study of critical modulation transfer function by UV-vis spectroscopy

Ping Linda Zhang; Song Hu; Lu Chuan Zhang; Zhong Yuan Jin; Hai Liang Yu; Le Wang; Yong Yang

doi:10.1117/12.782963

21 November 2007 Study of critical modulation transfer function by UV-vis spectroscopy

Ping Linda Zhang, Song Hu, Lu Chuan Zhang, Zhong Yuan Jin, Hai Liang Yu, Le Wang, Yong Yang

Proceedings Volume 6724, 3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems; 67241T (2007) https://doi.org/10.1117/12.782963
Event: 3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes, 2007, Chengdu, China

Abstract

Modulation Transfer Function (MTF) for the aerial image formation and Critical Modulation Transfer Function (CMTF) from the image formation system are two most important parameters for the photolithography processes. In this paper, we studied CMTF, or to be precise, we studied the contrast γ of the photoresist. γ is essential to the photolithography processes. New method to measure contrast γ is proposed and studied on DNQ/novolac photoresist. We provided the UV-vis absorption spectroscopic figures of the DNQ/novolac photoresist with sequentially increased exposure energy. In the figures the exposure energy from the i-line (365 nm) contact aligner is from 100 mJ/cm² to 220 mJ/cm². Higher amount of exposure dose was also applied to the resist. The UV-vis wavelength range is between 300 to 450 nm and 250 to 550 nm. Based on our UV-vis spectra, the contrast value for the resist is retrieved. We also provided a table that does the contrast comparison of the photography science, the photolithography and our UV-vis method. Our simplified CMTF measurement method yields the contrast of 1.11 and the CMTF of 0.8 for AZ 1500 at 365 nm. The CMTF measurement from the semiconductor fab requires 20-60 data points on one complete wafer to achieve the contrast value and the process latitude. Here CMTF from UV-vis requires two complete spectra. Because of the latent image, this new CMTF measurement is different from the old ways by applying UV-vis method. In the table, we compared the new method with the existing method of the photography and the semiconductor photolithography. Whether in the photography and the photolithography area, contrast is the baseline for the quality specification.

Citation Download Citation

Ping Linda Zhang, Song Hu, Lu Chuan Zhang, Zhong Yuan Jin, Hai Liang Yu, Le Wang, and Yong Yang "Study of critical modulation transfer function by UV-vis spectroscopy", Proc. SPIE 6724, 3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Micro- and Nano-Optical Devices and Systems, 67241T (21 November 2007); https://doi.org/10.1117/12.782963

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KEYWORDS

Modulation transfer functions

Optical lithography

Absorbance

Photography

UV-Vis spectroscopy

Photoresist processing

Photoresist materials

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