Proceedings Article | 21 March 2007
KEYWORDS: Optical proximity correction, Scanners, Apodization, Reticles, Polarization, Error analysis, Resolution enhancement technologies, Lithography, Lenses, SRAF
The imaging power of microlithographic lenses, normalized to minimum feature size, has become lower and lower for
each generation, even with the progress of high-NA lithography. The rate of increase of NA has not kept pace with
Moore's law. Therefore, low k1 lithography techniques such as RET (Resolution Enhancement Technology) have been
applied for more than a decade. RET, however, is a technique to increase the imaging contrast only for dedicated pattern
types/sizes, and may decrease the imaging power for other than dedicated patterns.
To fill this gap between actual imaging power and required imaging power, OPC (Optical Proximity Correction)
technologies are becoming more and more important for leading edge lithography. The accuracy of OPC is important
for high performance quality chips. On the other hand, due to low relative imaging power and high NA of the current
projection lens, imaging performance is very sensitive to various kinds of errors such as defocus, dose error, aberration,
apodization, flare, polarization aberration, polarization status, etc.
In order to solve this, scanner parameters, which can be obtained even before the scanner itself has been completed,
should be embedded in the imaging simulation in OPC design and verification to improve the accuracy. In addition,
OPE (Optical Proximity Effect) data simulated with the scanner parameters may be useful for early stage reticle design
before actual exposure using first lot scanners.
We have studied the sensitivity of OPE to scanner parameters and prioritized parameters to be input to the OPC design
and/or verification process for improving the accuracy without significant increase in the amount of calculation.
