30 July 2002 Assessment of OPC effectiveness using two-dimensional metrics
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Abstract
A complete evaluation of the optical proximity effects (OPE) and of their corrections (OPC) requires a quantitative description of two-dimensional (2D) parameters, both at resist- and at reticle-level. Because the 2D behaviour at line-ends and at line-corners can become a limiting factor for the yield, it should be taken into account when characterising a process, just as the CD- and pitch-linearity are already kept under control. This implies the measurement of 2D-metrics in a precise way. We used an SEM Image Analysis tool (ProDATA SIAM) to define and measure various OPC-relevant metrics for a C013 process. For the METAL (M1) process, we show that the overlap between line-ends of M1-trenches and underlying nominal contacts is a relevant metric to describe the effectiveness of hammerheads. Moreover, it is an interesting metric to combine with the CD process window. For the GATE process, we demonstrate that for a given set of metrics there is a degree of OPC aggressiveness beyond which it is not worth to go. We considered both line-end shortening (LES) and corner rounding affecting the poly linewidth close to a contact pad, and this on various logic circuits having received different degrees of fragmentation. Finally the knowledge of the actual line-end contour on the reticle allows one to simulate separately the printing effect of that area loss at reticle line-ends. The area loss measured by comparing the extracted contour to the target one is regarded as a combination of pull-back and area loss at corners. For our C013 gate process, and for the 130nm lines at a 1:1.25 duty cycle, those two parameters contribute together to approximetely 40% of the measured LES in the resist. This fact raises the question of specifications on 2D reticle parameters. We also find a linear correlation between the area loss at reticle line-end corners and the corresponding increase of LES on the wafer, which suggests a way towards putting specifications on the reticle line-ends.
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Vincent Wiaux, Vincent Wiaux, Vicky Philipsen, Vicky Philipsen, Rik M. Jonckheere, Rik M. Jonckheere, Geert Vandenberghe, Geert Vandenberghe, Staf Verhaegen, Staf Verhaegen, Thomas Hoffmann, Thomas Hoffmann, Kurt G. Ronse, Kurt G. Ronse, William B. Howard, William B. Howard, Wilhelm Maurer, Wilhelm Maurer, Moshe E. Preil, Moshe E. Preil, } "Assessment of OPC effectiveness using two-dimensional metrics", Proc. SPIE 4691, Optical Microlithography XV, (30 July 2002); doi: 10.1117/12.474588; https://doi.org/10.1117/12.474588
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