10 April 2013 Critical dimension small angle X-ray scattering measurements of FinFET and 3D memory structures
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We have demonstrated that transmission critical dimension small angle X-ray scattering (CD-SAXS) provides high accuracy and precision CD measurements on advanced 3D microelectronic architectures. The competitive advantage of CD-SAXS over current 3D metrology methods such as optical scatterometry is that CD-SAXS is able to decouple and fit cross-section parameters without any significant parameter cross-correlations. As the industry aggressively scales beyond the 22 nm node, CD-SAXS can be used to quantitatively measure nanoscale deviations in the average crosssections of FinFETs and high-aspect ratio (HAR) memory devices. Fitting the average cross-section of 18:1 isolated HAR contact holes with an effective trapezoid model yielded an average pitch of 796.9 ± 0.4 nm, top diameter of 70.3 ± 0.9 nm, height of 1088 ± 4 nm, and sidewall angle below 0.1°. Simulations of dense 40:1 HAR contact holes and FinFET fin-gate crossbar structures have been analyzed using CD-SAXS to inquire the theoretical precision of the technique to measure important process parameters such as fin CD, height, and sidewall angle; BOX etch recess, thickness of hafnium oxide and titanium nitride layers; gate CD, height, and sidewall angle; and hafnium oxide and titanium nitride etch recess. The simulations of HAR and FinFET structures mimic the characteristics of experimental data collected at a synchrotron x-ray source. Using the CD-SAXS simulator, we estimate the measurement capabilities for smaller similar structures expected at future nodes to predict the applicability of this technique to fulfill important CD metrology needs.
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Charles Settens, Charles Settens, Benjamin Bunday, Benjamin Bunday, Brad Thiel, Brad Thiel, R. Joseph Kline, R. Joseph Kline, Daniel Sunday, Daniel Sunday, Chengqing Wang, Chengqing Wang, Wen-li Wu, Wen-li Wu, Richard Matyi, Richard Matyi, } "Critical dimension small angle X-ray scattering measurements of FinFET and 3D memory structures", Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 86810L (10 April 2013); doi: 10.1117/12.2012019; https://doi.org/10.1117/12.2012019

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