Abstract
A method to measure directly the aerial image of arbitrary patterns, imaged by a stepper optics in a very thin layer of photoresist, is presented. Using this technique we characterised the optical properties of an advanced Deep UV stepper. Measured and simulated aerial images differ significantly, which can be attributed to imperfections of the projection optics. The major goal of this study was to find out the aerial image related limitations of lithographic process windows for patterns with 0.35 μm and 0.25 μm ground rule. Experimental data for several types of illumination (conventional and oblique illumination techniques) were obtained., and the aerial image induced offsets between the widths of isolated and grouped lines studied.
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