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.

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According to the ITRS Roadmap, for 45nm Node (as 65nm Half Pitch), the requirement of Gate CD Control is defined as 2.6nm. One of the most challenging CD errors is Iso-Dense Bias (IDB). Assuming 40% of CD errors are dominated by IDB, IDB should be less than 1nm. In general, the majority of IDB is due to: primarily, exposure toolrelated factors such as aberrations, flare, and sigma fluctuation, and secondly, the change in photoresist characteristics.However, due to the rapidly increasing usage of ArF exposure tools, Band Width (BW) characteristics of the laser source is an additional factor whose contribution is becoming more critical.Ideally, BW is monochromatic, thereby not affected by chromatic aberration change. However, in reality, the BW exhibits a shape of spectral distribution with a finite width.This study describes experimental and simulation results for E95%, and how performance of both CDs and Laser is dependent on E95% in order to meet 1nm of IDB towards 45nm Node. -IDB vs. E95% -CD at through pitch vs. E95% -Process Latitude vs. E95% -D O F -EL -Pattern shortening vs. E95%