Multi-technology measurements of nitrided oxide and high-K gate stacks

We demonstrate that by using a multi-technology optical metrology platform, accurate and precise measurements may be obtained for both thickness and stoichiometry of advanced Gate materials, including in particular Nitrided Oxide and Hafnium Silicate. The method combines an ultra-stable single-wavelength ellipsometer (Therma-Wave's Absolute Ellipsometere) with a spectral technique to measure the reflectance of the sample in the Deep Ultra-Violet (DUV) part of the spectrum (down to 190nm). This exploits the fact that the non-SiO2 components of these advanced Gate films, namely Silicon Nitride and Hafnium Oxide, are much more strongly absorbing in the DUV range than is SiO2 itself. Thus, by combining a DUV absorption measurement with a film-thickness measurement made in the visible part of the spectrum, it is possible to decouple efficiently the thickness and stoichiometry measurements even for very thin (< 15 angstrom) Gate films.