Plan-view transmission electron diffraction measurement of roughness at buried Si/SiO2 interfaces

We have developed a novel technique for determining interfacial roughness from plan-view transmission electron diffraction. Certain bulk forbidden Bragg reflections can occur due to crystal termination at surfaces and are very sensitive to steps on crystal boundaries. We demonstrate the technique in the study of Si/SiO2 interfaces and observe that interfaces appear to be significantly flatter than previously found, especially after post-oxidation annealing. The technique is simply quantified and is more reliable than those which require stripping of the oxide to expose the interface.