Effect of variable sigma aperture on lens distortion and its pattern size dependence

Takashi Saito; Hisashi Watanabe; Yoshimitsu Okuda

doi:10.1117/12.240102

21 May 1996 Effect of variable sigma aperture on lens distortion and its pattern size dependence

Takashi Saito, Hisashi Watanabe, Yoshimitsu Okuda

Proceedings Volume 2725, Metrology, Inspection, and Process Control for Microlithography X; (1996) https://doi.org/10.1117/12.240102
Event: SPIE's 1996 International Symposium on Microlithography, 1996, Santa Clara, CA, United States

Abstract

While modified illumination with various illumination apertures is the promising method to get finer patterns, there are many problems in putting it into practical use. In particular, the different apertures give different effects on the lens distortion and they cause the pattern displacement. In this paper, we studied the image placement error of fine patterns under 1 micrometer and its pattern pitch dependence using various illumination apertures. The first layer of 0.8 micrometer lines and spaces is patterned using conventional aperture (NA equals 0.57, sigma equals 0.6) and the second layer is exposed on the etched patterns with various apertures such as conventional, annular and small sigma. The patterns of the second layer are 0.4 micrometer lines with various spaces. Pattern displacements of the second layer are measured within the lens field along the X axis. The results show that the displacements are affected by the illumination status. In addition, the displacement varies with the pattern pitch and the placements of the fine patterns are different from those of large overlay patterns such as box-in-box. These results are confirmed by the optical simulator. The simulated results correspond to the experimental results and they point out the third order coma aberration most effects the pattern displacement. The pattern size and pitch dependence of the image displacement reveals that the measurement result of the conventional overlay patterns such as box-in-box with the sizes of 10 - 20 micrometer doesn't represent the overlay of the fine patterns of actual devices.

Citation Download Citation

Takashi Saito, Hisashi Watanabe, and Yoshimitsu Okuda "Effect of variable sigma aperture on lens distortion and its pattern size dependence", Proc. SPIE 2725, Metrology, Inspection, and Process Control for Microlithography X, (21 May 1996); https://doi.org/10.1117/12.240102

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available