The anisotropy of the thermal oxidation of 6H‐SiC has been investigated. Spheres of Acheson and modified Lely single crystals were prepared and subsequently oxidized under wet oxidation conditions. Afterwards the spheres showed an impressive image of interference colors in different crystal orientations due to different oxide thicknesses. The star‐shaped structure on the (0001) Si face and the regular structure in the plane perpendicular to thecaxis with six maxima and six minima is remarkable. The orientation of one maximum of oxide thickness could be assigned from Laue diffraction patterns to the (11¯00) and the orientation of one minimum of oxide thickness to the (112¯0) orientation. The oxide thicknesses were determined by Rutherford backscattering spectrometry and subsequently fitting of the measured Rutherford backscattering spectra by a spectrometry simulation program on various points on the spheres. The oxide thickness was determined as a function of the azimuth angle of the sphere. Different behavior at the interface SiC/SiO2for the (0001) Si face and the (0001¯) C face was observed and is discussed. ©1996 American Institute of Physics.