Paper AS-TuP13
A Mutual Calibration Method to Certify the Thickness of Nanometer Oxide Films

Tuesday, October 21, 2008, 6:30 pm, Room Hall D

The reliable measurement of ultra-thin gate oxide thickness below 1 nm is one of the most important analysis issues for the next generation semiconductor devices as shown in the recent international technology roadmap (ITRS). X-ray photoelectron spectroscopy (XPS) is an ideal candidate for the thickness measurement of ultra-thin films because of the surface sensitivity due to the shallow detection depth of low energy photoelectrons. However, XPS needs a standard film to determine the electron attenuation length because XPS is not an absolute method to determine the original thickness of overlayer films. In a recent study on the measurement of SiO2 film thickness on a silicon substrate, the thicknesses measured by various methods showed large offset values, giving an apparent thickness when the real thickness is extrapolated to zero. Compensation of these offset values is a key solution for the establishment of the traceability in the measurement of SiO2 film thickness. In this study, a mutual calibration method is suggested as a new method to certify the thickness of SiO2 films on Si by compensating for the offset values. In a linear plot of the thicknesses measured by x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) of a series of SiO2 films with different thicknesses, the offset value of TEM and the thickness scale of XPS can be mutually calibrated. Using this method, the XPS photoelectron attenuation length can be well defined and XPS becomes traceable in the measurement of the thickness of SiO2 films.