Lawrence Berkeley National Laboratory

The physical thickness of silicon oxynitride gate dielectric materials currently in development have dimensions in the range of 15-20 Angstrom (~;;6-8 oxygen atoms), while approaching the dielectric constant equivalent oxide thickness (EOT) of 12 Angstrom silicon dioxide. These structures present serious challenges in meeting stringent requirements within the semiconductor industry for precise determination of thickness, interfacial roughness and chemical distribution. Limitations in conventional HRTEM must be removed that would minimize errors in such measurements. Our approach was to use the National Center for Electron Microscopy (NCEM) One Angstrom Microscope (O Angstrom M), together with focal series acquisition (FSA) and exit wave reconstruction (EWR) techniques to obtain <0.8A interpretable resolution. HRTEM data on the same oxynitride materials from an aberation corrected (Cs=0) microscope were also collected as part of this work, as were scanning TEM (STEM) measurements. The HRTEM characterization provides an absolute calibration and validation for a precise "near-line" metrology to determine gate oxide thickness and nitrogen dose using x-ray photoelectron spectroscopy (XPS).