Measuring thicknesses of native oxide, crystalline-silicon, buried oxide layers, and the interface roughnesses of SOI

In this paper we describe a non-destructive technique that characterizes Silicon-On-Insulator (SOI) wafers. With this technique, the thickness of the crystalline silicon (c-Si) and BOX layers, as well as the thickness of the native oxide that naturally forms on SOI are determined. Additionally the degree of smoothness (interface roughness) of SOI interfaces are measured The spectra of optical constants, n and k, of the BOX are also determined. The thicknesses, n and k spectra, and interface roughness are determined simultaneously by analyzing broad-band reflectance with the Forouhi-Bloomer equations for n and k. The reflectance measurement is based on all-reflective optics to generate a highest possible signal-to-noise ratio over the entire measured wavelength range. The total measurement time is about 1 second We show that the results obtained with the present technique are in excellent agreement with cross-section TEM.