Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Interferometric Testing of Photomask Blank Flatness



Christopher J. Evans, R E. Parks, L Z. Shao, Tony L. Schmitz, Angela Davies


Conventional interferometric testing of the flatness of photomask blanks is rendered difficult by the long coherence length of the HeNe laser sources typically used in commercially available phase measuring interferometers appropriate for flatness testing.  The Ritchey-Common configuration allows testing of flats in spherical wavefront; this paper shows that, under appropriate conditions, high resolution surface flatness maps of photomask blanks may be obtained using instrumentation currently available in many optical shops.
Proceedings Title
SPIE International Symposium on Microlithography
Conference Dates
February 26-28, 2001
Conference Location
Santa Clara, CA
Conference Title
International Symposium on Microlithography


flatness, interfermetry, photomasks, Ritchey-Common test


Evans, C. , Parks, R. , Shao, L. , Schmitz, T. and Davies, A. (2001), Interferometric Testing of Photomask Blank Flatness, SPIE International Symposium on Microlithography, Santa Clara, CA (Accessed April 21, 2024)
Created February 28, 2001, Updated February 19, 2017