NASA’s Langley Research Center has developed a new way to reduce the high-temperature heating requirement of sapphire substrates in wafer production. The growth of high-quality and single-crystal epitaxy layers on sapphires requires uniform and high-temperature heating to accommodate restructuring of the sapphire surface to be aluminum-terminated. These requirements (uniform heating and re-structuring of sapphire substrates) are challenging for high-yield and high-quality production. This innovation offers a new way to reduce the high-temperature heating requirement of sapphire substrates and at the same time create the morphological restructure of sapphire surface required.
The process utilizes an electron beam flood gun to irradiate the sapphire surface as a means of raising the surface temperature. As the electrons collide with the top layers of surface atoms, the substrate absorbs much of the energy through thermalization losses from the electrons. Subsequently, the surface temperature rises and this modifies the atomic surface structure into a form conducive to single-crystal SiGe epitaxy. Moreover, while tested on sapphire, this method applies to any other wafer material, providing a broad new means of changing surface temperature and atomic structure independently of the substrate heater.