Measurement of roughness at buried Si/SiO2interfaces by transmission electron diffraction

We use surface-sensitive reflections to observe roughness at Si/${\mathrm{SiO}}_2$ interfaces formed under conditions used in metal-oxide-semiconductor device fabrication. On specially prepared samples, both imaging and diffrac- tion 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)/${\mathrm{SiO}}_2$ samples, but the method can also be applied to Si(100)/${\mathrm{SiO}}_2$ samples. The algorithms will also be useful for the interpretation of x-ray and optical scattering. © 1996 The American Physical Society.