Data averaging effect on roughness measurement using phase-shifting interferometry for a few-ten-angstrom and sub-angstrom rough surfaces

The phase and intensity data averaging effect on roughness measurement usin g phase-shifting interferometry was investigated for a few-ten-A and sub-A rough surfaces. For a few-ten-A rough surface, the roughness value did not depend on the data average. In contrast, the sub-A rough surface determinat ion was strongly influenced by the data average so that measurement error w as significantly improved as the number of data averages increased. As an o ptimal data average condition that die measurement noise was minimized, 30 phase data and 20 intensity data averages were experimentally determined. S ub-A roughness measurement under the optimal data average condition had hig h measurement accuracy of the absolute roughness and small measurement repr oducibility error.