Hydrogen Etching for Removal of Mechanical Defects from Silicon Carbide Substrates for Epitaxial Film Growth Confirmed with Atomic Force Microscopy

I am a physics major working in a surface physics laboratory with the primary goal of growth of thin films for producing the next generation of semiconductors to be used in the development of new electronic technologies. These films are only a few atoms thick and must be grown on extremely clean and atomically flat substrates. As delivered, the silicon carbide substrates that we use exhibit many scratches and mechanical defects on the microscopic scale from the manufacturing process, namely from polishing procedures. The hydrogen etching procedure removes mechanical defects and scratches from the surface of silicon carbide wafers, and leaves behind a chemically inert surface. This etching procedure entails using a previously established process of resistively heating the wafers to high temperatures on molybdenum sheets with hydrogen gas flowing across the surface for a period of time. After the etching process, the substrate cleanliness and flatness must be confirmed prior to growth of thin films; this is done using atomic force microscopy. In the hydrogen etching procedure, it was found that the parameters of heating must be monitored closely, and adjusted accordingly, due to changes in electrical properties of the molybdenum substrate holder with increasing temperature. Atomic force microscopy comes with its own challenges, including proper adjustment and alignment of machine parameters, as well as dampening of all vibrations due to the sensitivity of the machine. These techniques which I have studied are instrumental in the preparation of silicon carbide substrates for use in other processes, mainly molecular beam epitaxy for the growth of thin films. Based on these studies, the hydrogen etching process is hugely successful in cleaning and preparing silicon carbide substrates for thin film growth. We are currently working on a new system for heating the substrates to provide more even and consistent heating during the etching process. This will allow for a more controlled etching environment resulting in higher quality etching