Preparation of Aluminum Nitride Substrates for Device Fabrication

We propose to prepare AlN substrates from single-crystal boules of AlN. When properly prepared, these AlN substrates should be superior to all substrates currently available commercially. In particular, the AlN substrates have significantly superior chemical compatibility, lattice/crystal structure match, thermal expansion match, and thermal conductivity when compared to sapphire substrates that are currently being extensively used for eptixial growth. In addition, the higher thermal conductivity, larger band-gap energy and higher thermal stability of AlN will be attractive for many nitride applications. However, two key technical issues need to be overcome before AlN substrates can be used for epitaxial layer growth for device application. These key obstacles are: (1) the extreme hardness of the AlN makes it easy to propagate microscopic defects into the surface of the substrate when mechanical polishing is used; and (2) the removal of the oxide layer on the AlN surface prior to epitaxial growth. We will determine wafer grinding, polishing and chemical cleaning techniques that can be scaled up into an AlN wafer production facility.