The OPE signature of a lithographic stepper or scanner has become a very important characteristic of the tool, as it determines the OPC correction to be applied to reticles exposed on that tool. The signature depends on a variety of detailed information about the scanner lens and illuminator, which in turn depend on the characteristics of the illumination light from the laser.Specifically, changes in the laser bandwidth should impact OPE as the lens exhibits some chromatic aberration. Tool-totool differences and time fluctuation of the laser bandwidth could cause variations in OPE tool matching and stability.To assess this, a detailed study of laser bandwidth effects on OPE was performed. A sensitive spectrometer was connected to a litho laser, allowing careful measurements of both the FWHM and E 95 parameters of the laser spectral profile.Lithographic modeling using the chromatic response of the lens was run in order to predict effects. Exposures of CD through pitch were made to test the modeling. Finally, the bandwidth data was correlated with litho sensitivity to create a "bandwidth effect", put in context with the other common scanner parameters affecting OPE.

Nikon has developed an illuminator with special options for RET (Resolution Enhancement Technique). For one of the solutions of RET, Nikon has pursued the development of a loss-less polarized illumination system. When the polarization direction is the same as the direction of the printed pattern, this technique improves image contrast and extends the process margin. We have simulated the impact of the RET with polarized illumination, in the case of dipole illumination and phase-shift masks, and we have estimated the dominant parameters for high performance polarized illumination. In addition, we have constructed a polarized-light illuminator and installed it in an ArF full-field scanner. We have measured and optimized the degree and distribution of polarization at the wafer plane with a special tool, and we have investigated image performance with polarized dipole illumination. Results show that the new polarized-light illuminator has extended the process margin, especially with respect to dose latitude. The results of the image simulations and experiments will be reported.

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