High-quality aluminum oxide gate dielectrics by ultra-high-vacuum reactive atomic-beam deposition

We demonstrate the potential for ultrathin aluminum-oxide films as alternate gate dielectrics for Si complementary metal–oxide–semiconductor technology. Films are deposited in ultrahigh vacuum utilizing atomic beams of aluminum and oxygen on Si(100) surfaces. We show device-quality ${\mathrm{Si(100)/Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ interfaces with interfacial trap densities in the ${10}^{10} {\mathrm{cm}}^{\text{−2}} {\mathrm{eV}}^{\mathrm{-1}}$ range, and with leakage current densities five orders of magnitude lower than what is observed in ${\mathrm{SiO}}_{\mathrm{2}}$ insulators at the same equivalent electrical thickness. As-grown films possess an amorphous-to-microcrystalline structure, depending upon the deposition temperature, and any interfacial layers between the Si(100) and ${\mathrm{Al}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ layer are $\text{<∼0.5\hspace{0.5em}}\mathrm{nm}.$