Silicon oxynitride blanket films approximately 2 nm in thickness were characterized in cross section using a 300 keV TEM/STEM. High resolution imaging was used to investigate the accuracy and precision of TEM film thickness measurements and their comparability to other techniques such as spectroscopic ellipsometry, secondary ion mass spectrometry, x-ray reflectivity, x-ray photoelectron spectroscopy, and medium energy ion scattering. Silicon oxynitride films were grown by SEMATECH and were characterized by several techniques in a SEMATECH-sponsored round robin. Cross sectional TEM samples were prepared by dimpling/ion milling and HRTEM micrographs were acquired at 297 keV using an imaging energy filter and a multiscan CCD camera. Thickness measurements were performed after calibrating the magnification using a phase contrast image of the silicon substrate. Approximately 10 measurements were performed for each film, including measurements on both sides of the cross section glue line and both sides of the dimple/ion mill perforation. Statistical analysis of the HRTEM thickness measurements reveals that the expanded uncertainty of the technique (with coverage factor designed to estimate a 95% confidence interval) can be larger than 0.33 nm.
- Transmission electron microscopy
- X-ray photoelectron spectroscopy
- Dielectric thin films
- Elemental semiconductors
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