The purpose of paper is to investigate the impact of mask blank flatness on critical
dimension uniformity (CDU) and depth of focus (DOF) in the wafer printing process
with a test pattern designed for 65nm node technology. In this experiment we use 3
test masks with different flatness (0.3T, 0.5T and 1T), and the same test pattern array.
The mask flatness was measured with a Tropel® UltraFlat<sup>TM</sup> 200, and the focus error
is extracted from the CD data of the focus and energy matrix (FEM) analysis.
The goal of the study is to quantify the mask flatness influence on the high-numerical
aperture (NA) lithographic process.