Damage resistant and low-stress Si-based multilayer mirrors

Torsten Feigl; Sergey A. Yulin; Thomas Kuhlmann; Norbert Kaiser

doi:10.1117/12.450958

20 December 2001 Damage resistant and low-stress Si-based multilayer mirrors

Torsten Feigl, Sergey A. Yulin, Thomas Kuhlmann, Norbert Kaiser

Author Affiliations +

Proceedings Volume 4506, Soft X-Ray and EUV Imaging Systems II; (2001) https://doi.org/10.1117/12.450958
Event: International Symposium on Optical Science and Technology, 2001, San Diego, CA, United States

Abstract

Applications of multilayer mirrors for extreme ultraviolet lithography (EUVL) require not only a high normal incidence reflectivity but also a long lifetime and minimal residual stress. A serious problem of Mo-Si multilayers is the structural instability in the case of localized absorption of in- and outband radiation from the EUV source followed by the degradation of the multilayer. A number os solutions have been envisaged in the past, including the use of compound materials (MoSi₂Si) as well as the use of C barrier layers. We focused our interest on two Si-based systems: Mo/Si and Mo₂C/Si multilayer mirrors. The mirrors were designed for normal incidence reflectivity at about 13 nm wavelength and were deposited by dc magnetron sputtering. Maximum normal incidence reflectivities of 68.4%12.8 nm for Mo/Si multilayer mirrors and 66.8%12.8 nm for Mo₂C/Si have been achieved. Investigating the thermal stability of the multilayers in the temperature range from 300 degree(s)C to 500 degree(s)C we found that the reflectivity of Mo/Si mirrors is drastically decreasing after annealing above 300 degree(s)C, whereas the Mo₂C/Si multilayers show a superior stability up to 400 degree(s)C...500 degree(s)C. Another problem of EUV multilayer mirrors is the large residual compressive stress (-400 to - 500 MPa), which causes undesirable distortion of the substrate figure. The reduction of residual stress of Mo/Si and Mo₂C/Si multilayers with annealing has been investigated. Using a slow thermal annealing (1 degree(s)C/min), it is possible to reduce the stress from -520 MPa to zero by heating the Mo/Si samples up to 310 degree(s)C. However, this results ina reflectivity drop of about 3...4%. On the other hand one can reduce the stress of a Mo₂C/Si multilayer from -490 MPa to zero by annealing without a considerable reflectivity drop.

Citation Download Citation

Torsten Feigl, Sergey A. Yulin, Thomas Kuhlmann, and Norbert Kaiser "Damage resistant and low-stress Si-based multilayer mirrors", Proc. SPIE 4506, Soft X-Ray and EUV Imaging Systems II, (20 December 2001); https://doi.org/10.1117/12.450958

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