Built-in interface in high-κ gate stacks

Abstract The advantage of using the Al 2 O 3 gate dielectric is discussed from thermodynamic and kinetic standpoints. We fabricated n -field effect transistors with Al 2 O 3 dielectrics and built-in interfacial SiO 2 having thicknesses of 0.6–2.0 nm to investigate the effect on electron mobility and gate leakage current. The mobility was reduced and the shift in flat-band voltage was increased with decreases of the thickness of the interfacial SiO 2 . We propose that a fixed charge is generated at the interface of Al 2 O 3 /interfacial SiO 2 , it induced Coulomb scattering to the surface channel, and that the electron mobility is consequently reduced. The plot of gate leakage current against the total physical thickness, which includes Al 2 O 3 and interfacial SiO 2 dielectrics, showed the enhanced leakage current. This suggests that the band offset may be lowered at the interface of ultra-thin SiO 2 /Si beneath the Al 2 O 3 dielectric.