Evaluating the accuracy of a calibrated Rigorous Physical resist Model under various process and illumination conditions

If RET selection by simulation is to be successful for the deep sub-wavelength technologies of today, then the predictions of the simulator must be quantitatively accurate over the parameter space of interest. The Rigorous Physical resist Model (RPM) within PROLITH and Lithoware is separable from the illumination conditions and the reflection behavior of the wafer stack, and thus should be an excellent candidate for such projects. In this work, the RPM is calibrated for a commercially available ArF photoresist using top-down CD-SEM data, including focus-exposure matrices and CD vs. mask pitch data, under fixed process conditions. It will be shown that this RPM is able to predict the performance of line, trench and contact features, with quantitative accuracy, under different numerical aperture and illumination conditions, even when the wafer stack is altered significantly. The stack alterations include resist thickness change, the presence or absence of an immersion topcoat, substitution of different underlying substrate materials and the use of a single or double layer anti-reflection coating. The resist model accurately describes both the experimental calibration data and two separate experimental validation datasets. The RMS error seen in the extrapolative predictions is comparable to that observed between the model and the original calibration dataset.