Properties of large CaF2 crystals grown by CZ method for lens materials

Hiroyuki Yanagi; T. Nawata; Yoji Inui; Y. Hatanaka; E. Nishijima; Tsuguo Fukuda

doi:10.1117/12.556614

28 May 2004 Properties of large CaF₂ crystals grown by CZ method for lens materials

Hiroyuki Yanagi, T. Nawata, Yoji Inui, Y. Hatanaka, E. Nishijima, Tsuguo Fukuda

Proceedings Volume 5377, Optical Microlithography XVII; (2004) https://doi.org/10.1117/12.556614
Event: Microlithography 2004, 2004, Santa Clara, California, United States

Abstract

CaF₂ (Calcium fluoride) lens materials are required for the composition of F₂ laser lithography stepper. Recently, it is reported that both <111> crystal and <100> crystal are necessary for the lens blanks, which can resolve the intrinsic birefringence of CaF₂. Although CaF₂ single crystal has been produced by Bridgman method, some problems are pointed out on the optical properties and production yield especially on <100> crystal with large diameter. So it is worried that the amount of the supply of CaF₂ will be short when F₂ stepper will start on a large scale. To resolve the above mentioned problems, we tried to grow a large CaF₂ single crystal by Czochralski (CZ) technique, because we expected that CZ technique could provide higher productivity and higher quality which mean lower residual stress than conventional method. CZ technique can also easily control the growing crystal axis by the selection of seed crystal. Consequently we succeeded in growth both <111> and <100> direction single crystal which has 210mm diameter and 150mm length. The obtained crystal is a single crystal over a whole boule and it shows high transparency in vacuum ultraviolet region. Moreover it shows very low birefringence value and good homogeneity after annealing process. We hope our challenge should prompt the development of F₂ lithography.

Citation Download Citation

Hiroyuki Yanagi, T. Nawata, Yoji Inui, Y. Hatanaka, E. Nishijima, and Tsuguo Fukuda "Properties of large CaF₂ crystals grown by CZ method for lens materials", Proc. SPIE 5377, Optical Microlithography XVII, (28 May 2004); https://doi.org/10.1117/12.556614

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