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24 May 2004 Characterization and control of sub-100-nm etch and lithography processes using atomic force metrology
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We discuss the aspects of three-dimensional AFM metrology relevant to 90 nm node processes, with extensions to 65 nm node and beyond. Important advances have been made, including deployment of silicon tips with diameter less than 70 nm as well as development of a novel algorithm for tip shape deconvolution. As primary case studies, we present detailed analyses of process and materials issues encountered during poly silicon etch and during 193 nm photolithography. Etched poly silicon shows shape details at the bottom of the line that are known to impact device performance both directly (by defining the physical gate length) and indirectly (by screening ion implantation). Our data from one particular process show that etch shape (CD and sidewall angle) varies strongly as the line pitch decreases from 500 nm to 260 nm, with sidewall angle changing by approximately 0.8 degrees per 100 nm pitch change. We also present data for a different etch process in which both CD and sidewall angle vary systematically across the wafer from center to edge, with the range of sidewall angles being ~2 degrees and CD varying by 20 nm. Resist is seen to have height and sidewall angle variation with pattern density and with linewidth at a given focus-exposure process point. In addition, resist profiles before resist trim show footing, standing waves and 3-dimensional sidewall roughness that are readily visualized and quantified with AFM measurements.
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Kirk Miller, Vincent Geiszler, and Dean Dawson "Characterization and control of sub-100-nm etch and lithography processes using atomic force metrology", Proc. SPIE 5375, Metrology, Inspection, and Process Control for Microlithography XVIII, (24 May 2004);

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