Local critical dimension variation from shot-noise related line edge roughness
Mean free path between the creation of secondary electrons in PMMA, comparable to most other polymers.
Comparison of the interaction in resist of the electrons and EUV photons. Each cross indicates an interaction process that creates a secondary electron.
Example of Monte Carlo simulated line segments for different doses at two different length scales (0.92 and ). Probe size is , acid diffusion length is . No background and no other dose variations are taken into account. The bold black lines give the 50% exposure level, where one would expect to develop the resist. The indicated CDu values are for a short segment.
CD uniformity plotted vs the CDu averaging length with doses of 2, 8, and for a spot size of , a background of 0.4, an acid diffusion length of , other dose variations of 1% (1 sigma) and is 1.9. Local CD variation resulting only from shot noise, as a function of line length over which the line width is averaged. Optimized diffusion parameter of . Note that the ITRS roadmap for half pitch specifies a CD control of .
CD uniformity of a single line plotted versus the probe size for different acid diffusion lengths with a dose of , a background of 0.4, other dose variations of 1% (1 sigma) and a constant of 1.9. The averaging length is taken to be . Also the CD uniformity is plotted for the optimized acid diffusion length per probe size.
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