PROCEEDINGS ARTICLE | May 10, 2005
Proc. SPIE. 5752, Metrology, Inspection, and Process Control for Microlithography XIX
KEYWORDS: Lithography, Cadmium, Inspection, Monte Carlo methods, Photomasks, Line width roughness, Transistors, Critical dimension metrology, Line edge roughness, Semiconducting wafers
The influence of long-period line-edge roughness (LER) on measured critical-dimension (CD) values is identified, and a guideline for LER-impact-free CD measurement is introduced. There are two kinds of meanings of CD, one is the average pattern-size calculated in a limited area (i.e., local CD), and the other is the representative pattern-size (average CD). The width of a line pattern measured by CD-SEM is a local CD, which deviates from the average CD because of long-period LER. This LER impact on the CD measurement is investigated in two typical measurements of CD-SEM, evaluation of across-wafer CD-variation and dynamic repeatability of the equipment. It is shown that both results strongly depend upon the height of the inspection area along the line-edge (L) because of long-period LER. It is found that a large L can reduce the LER-impact, and a 2-μm inspection-area or more is recommended for CD measurements. Furthermore, the validity and limitation of the patchwork method, in which several inspection areas are connected to obtain one large area, is examined.
