Measurement of roughness at buried Si/SiO2 interfaces by transmission electron diffraction

We use surface-sensitive reflections to observe roughness at Si/SiO2 interfaces formed under conditions used in metal-oxide-semiconductor device fabrication. On specially prepared samples, both imaging and diffraction analysis are possible in the same area. We develop a theoretical approach to estimate roughness from diffraction patterns, and validate the approach from a comparison with direct images. The results are for Si(111)/SiO2 samples, but the method can also be applied to Si(100)/SiO2 samples. The algorithms will also be useful for the interpretation of x-ray and optical scattering.