Base-line error-free non-TTL alignment system using oblique illumination for wafer steppers

Dohoon Kim; Kag Hyeon Lee; Yong-Ho Oh; Jong-Hyun Lee; Hai Bin Chung; Hyung Joun Yoo

doi:10.1117/12.209318

26 May 1995 Base-line error-free non-TTL alignment system using oblique illumination for wafer steppers

Dohoon Kim, Kag Hyeon Lee, Yong-Ho Oh, Jong-Hyun Lee, Hai Bin Chung, Hyung Joun Yoo

Proceedings Volume 2440, Optical/Laser Microlithography VIII; (1995) https://doi.org/10.1117/12.209318
Event: SPIE's 1995 Symposium on Microlithography, 1995, Santa Clara, CA, United States

Abstract

In this paper, an alignment method with oblique illumination and oblique detection named ZBAS (Zero Base-line Alignment System) is proposed and its characteristics and applications are analyzed. It detects the position error from alignment mark at the exposure position even though it is a non-TTL method. The alignment mark, a diffraction pattern with a 4 micrometers width (8 micrometers pitch), is illuminated with a He-Ne laser beam at an incident angle of 75 degree(s) and the first order diffracted beam at this is detected as an alignment signal at a diffraction angle of 60 degree(s). The peak value of the alignment signal with appropriate electrical system is about 20 mV and the signal sensitivity to the wafer position is 0.5 mV/0.1 micrometers . The theoretical analysis of ZBAS was carried out with respect to the effects of pattern depth and resist thickness. The result shows the stable detection is realized by a 2- wavelength (670,780 nm) illumination, in which the variation of the calculated signal is 27% in the range of 0.6 approximately equals 1.2 micrometers of pattern depth, 37% in the range of 0.6 approximately equals 1.2 micrometers of resist thickness. In conclusion, the ZBAS was verified as a potential alignment system in excimer laser stepper, which has a smaller base-line error than the conventional non-TTL method.

Citation Download Citation

Dohoon Kim, Kag Hyeon Lee, Yong-Ho Oh, Jong-Hyun Lee, Hai Bin Chung, and Hyung Joun Yoo "Base-line error-free non-TTL alignment system using oblique illumination for wafer steppers", Proc. SPIE 2440, Optical/Laser Microlithography VIII, (26 May 1995); https://doi.org/10.1117/12.209318

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KEYWORDS

Optical alignment

Semiconducting wafers

Signal detection

Diffraction

Excimer lasers

Helium neon lasers

Laser systems engineering

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