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Publication Citation: Critical Dimension small angel X-ray scattering measurements of FinFET and 3D memory structures

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Author(s): Regis J. Kline; Daniel F. Sunday; Chengqing C. Wang; Wen-Li Wu; Charlie Settens; Bunday Benjamin; Brad Thiel; Matyi Richard;
Title: Critical Dimension small angel X-ray scattering measurements of FinFET and 3D memory structures
Published: April 08, 2013
Abstract: Critical dimension small angle X-ray scattering (CD-SAXS) has been identified as a potential solution for measurement of nanoscale lithographic features by interrogating structures with sub-nanometer wavelength radiation in transmission geometry. The most apparent parameters that can be extracted from the SAXS pattern are pitch and pitch variation based on the spacing of diffraction peaks. Furthermore, the envelope function of the diffraction orders provides insight into the geometric form factor of the feature cross section. In this work, we will discuss the subtleties in CD-SAXS data collection, reduction, simulation and fitting with an emphasis on the theoretical framework of small angle X-ray scattering and its application to modeling nanoscale dimensions of advanced architectures such as FinFETs and high-aspect ratio (HAR) features in 3D memory devices. Isolated HAR contact holes are characterized by CD-SAXS to obtain information on the spatial dimensions of nanoscale features such as the average pitch, diameter, height, and sidewall angle. FinFET fin-gate crossbar structures have been analyzed using CD-SAXS to inquire the sensitivity of the technique to measure variations in critical 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. Simulations of HAR and FinFET structures are then used to model the experimental data collected at a synchrotron x-ray source. A nonlinear least squares fitting routine was used to simultaneously fit the scattered intensity as a function of wave-vector qz at discrete positions in qx corresponding to diffraction orders that are induced due to the pitch. 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
Proceedings: SPIE
Location: San Jose, CA
Dates: February 24-28, 2013
Keywords: CD-SAXS; small angle x-ray scattering; transmission; FinFET; 3D memory; high-aspect-ratio; HAR; CD metrology
Research Areas: Semiconductor Materials