Observation of silicon front surface topographs of an ultralarge-scale-integrated wafer by synchrotron x-ray plane wave

Surface roughness and undulation of unpatterned silicon wafers are serious issues for ultralarge-scale-integrated circuit devices, even after fine mechanochemical polishing. It has never been clarified whether the undulations exist only on the surface or also exist inside the bulk crystal. We produced grazing incident diffraction topographs at three x-ray photon energies, with penetration depths estimated to be 3.85 nm, 4.78 nm, and 1.28 µm. All the topographs contained striation. We also obtained clear total reflection images using synchrotron x-ray plane waves, which also showed striation patterns at penetration depths from 3.85 nm to 1.28 µm. These results indicate that the origin of the patterns is not at the surface but is inside the Si wafer. The origin of striation patterns, observed in the topographs, was found not to be due to mechanochemical polishing processes but to crystal growth