Surface flattening of 4H-SiC (0001) epitaxial wafers by high temperature oxidation

Due to the special 'step-controlled epitaxy' mode of 4H-SiC, it is easy to generate step bunching on the surface. Although the flatness of epitaxial wafers has been greatly improved with the advancement of epitaxy technology, there are still localized steps on the surface of some certain wafers. The presence of localized steps can affect the performance of the subsequently fabricated devices. Therefore, minimizing or even eliminating the local steps of the epitaxial surface to obtain an atomically smooth surface is very important. Here, we utilize a high-temperature oxidation process to reduce the size of the giant steps and obtain a flatter epitaxial surface. We found that oxidation parameters such as temperature, pressure, and time play an important role in the surface planarization, and the degree of planarization can be further improved by multiple oxidation processes. In addition, although the oxidation rate under low pressure is lower than that under atmospheric pressure, a smoother epitaxial surface can be obtained. Our results demonstrate the possibility of obtaining atomically smooth surfaces through a high-temperature oxidation process.