Surface roughness measurements of low-scatter mirrors and roughness standards

TLDR

Surface roughness of low‑scatter mirrors and roughness standards can be measured mechanically, optically, or electronoptically. The paper presents several useful methods and instruments for measuring surface roughness of low‑scatter mirrors and roughness standards. The study employs total integrated scattering, stylus profilometry, optical heterodyne profilometry, variable‑angle scatterometry, electron‑mirror interference microscopy, Nomarski microscopy, and TEM of surface replicas, with samples prepared at Balzers and measurements performed at multiple laboratories. The measurements are compared across laboratories, revealing differences that are attributed to methodological variations.

Abstract

The surface roughness of low-scatter mirrors and roughness standards can be measured in various ways: mechanically, optically, and electronoptically. In this paper several useful methods and instruments—total integrated scattering, stylus profilometer, optical heterodyne profilometer, variable angle scatterometer, and electron mirror interference microscope—are presented. Qualitative surface roughness assessment is provided by Nomarski microscopy and transmission electron microscopy of surface replicas. Samples were prepared at Balzers, and their surface roughness was measured at several laboratories using the methods given above. The results of these measurements are compared, and reasons for the differences are discussed.