13 September 1982 Analysis Of Image Field Placement Deviations Of A 5x Microlithographic Reduction Lens
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Abstract
A simple model of the deviations in position between an ideal grid and a corresponding grid imaged through a photolithographic projection lens is presented. The model describes the dependence within the image field of origin translation, rotation, lens magnification, lens trapezoid, and lens distortion. The model has been used to analyze the image placement behavior of a Zeiss reduction lens mounted in a David Mann wafer stepper. The method of measurement of image field placement deviations relies upon the overlay of optical position verniers. One vernier half is arrayed by step-and-repeat to form an ideal grid in the image plane, while the other vernier half derives from an ideal vernier array in the object plane projected through the reduction lens. Vernier readings then yield placement deviations throughout the image field of the lens. A single reticle is used to generate this data, and its design will be briefly discussed. These measurements have been made utilizing a GCA 4800 DSWtm wafer stepper to construct the ideal grid. The lens evaluated was a Zeiss 10 78 06 5X reduction lens. The results of these measurements are then fit to the model in a least squares fashion. This allows separation of the mechanisms leading to placement deviations and assesses their relative importance. The overall measurement and fitting procedure is capable of detecting changes in the model coefficients which correspond to image field deviations as small as .03pm at the image field edge. Image field deviation values for a single lens will be shown along with the data fit coefficients and residuals. Systematic errors relating to generation of the ideal grid, as well as lens behavior outside the scope of the model will be discussed.
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Don MacMillen, Don MacMillen, W. D. Ryden, W. D. Ryden, } "Analysis Of Image Field Placement Deviations Of A 5x Microlithographic Reduction Lens", Proc. SPIE 0334, Optical Microlithography I: Technology for the Mid-1980s, (13 September 1982); doi: 10.1117/12.933563; https://doi.org/10.1117/12.933563
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