Impact of mask blank and mirror surface roughness on actinic EUVL mask blank inspection signal

Takeshi Yamane; Toshihiko Tanaka; Tsuneo Terasawa; Osamu Suga; Toshihisa Tomie

doi:10.1117/12.793070

19 May 2008 Impact of mask blank and mirror surface roughness on actinic EUVL mask blank inspection signal

Takeshi Yamane, Toshihiko Tanaka, Tsuneo Terasawa, Osamu Suga, Toshihisa Tomie

Proceedings Volume 7028, Photomask and Next-Generation Lithography Mask Technology XV; 70281S (2008) https://doi.org/10.1117/12.793070
Event: Photomask and NGL Mask Technology XV, 2008, Yokohama, Japan

Abstract

The impact of mask blank surface roughness and mirror surface roughness on the defect inspection signal is presented. The power spectrum density (PSD) of the roughness is assumed to be inversely proportional to the square of the spatial frequency. The PSD was estimated based on the mask blank surface roughness (rms), and then the background intensity was calculated using the PSD of the spatial frequencies between the inner and outer NA. The results indicate that the larger outer NA leads to an increase in the background intensity, and that a mask blank roughness of 0.15 nm generates a background intensity of 0.15 - 0.23 %. We also analyzed the effect of the mirror surface roughness on the background intensity and on the defect signal contrast. A point spread function (PSF) of scattered light from the mirror surface was calculated using the estimated PSD, and the defect images were simulated for the inspection optics by employing Fourier technique. The degradation of defect images caused by the mirror roughness was calculated by using the convolution of the PSF with the simulated images. Based on the results, it is concluded that the roughness has a large impact on the maximum intensity of the defect signal but has little effect on the background intensity. It was also learned that the degradation rate of the defect signal contrast is approximately proportional to the square of the mirror roughness.

Citation Download Citation

Takeshi Yamane, Toshihiko Tanaka, Tsuneo Terasawa, Osamu Suga, and Toshihisa Tomie "Impact of mask blank and mirror surface roughness on actinic EUVL mask blank inspection signal", Proc. SPIE 7028, Photomask and Next-Generation Lithography Mask Technology XV, 70281S (19 May 2008); https://doi.org/10.1117/12.793070

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