ADVANCED HIGH K DIELECTRICS FOR NANO-ELECTRONICS —SCIENCE AND TECHNOLOGIES

摘要

Some of our research activities on high κ gate dielectrics on GaAs (and its related compound semiconductors), Si, and GaN are reviewed. Ga_2O_3(Gd_2O_3), the novel oxide, which was electron-beam evaporated from a gallium-gadolinium-garnet target in UHV, has unpinned the GaAs Fermi level for the first time. Systematic heat treatments under various gases and temperatures were studied to achieve low leakage currents of 10~(-8) - 10~(-9) A/cm~2 and low D_(it)'s in the range of 4-9 x 10~(10) cm~(-2)V~(-1). By removing moisture from the oxide, thermodynamic stability of the Ga_2O_3(Gd_2O_3)/GaAs hetero-structures and the interfaces were achieved with high temperature annealing, which is needed for fabricating inversion-channel MOSFET's. More importantly, Ga_2O_3(Gd_2O_3) remains amorphous and the interface remains intact with atomic smoothness and sharpness. The mechanism of Fermi-level unpinning in atomic layer deposition (ALD)-Al_2O_3 ex-situ deposited on GaAs (InGaAs) was studied and unveiled. Single crystal Gd203 was found to grow epitaxially on GaAs and unpin its Fermi level, the first time for a single crystal oxide on semiconductor. We have also reviewed the work of inversion-channel, depletion-mode, and power GaAs MOSFET's using Ga_2O_3(Gd_2O_3) as the gate dielectric. The recent advances in HfO_2 gate oxides grown by MBE on Si and the device results of the MOSFET with metal gate of TiN and gate dielectric of HfO_2 were discussed. The work of GaN passivation is reviewed, which will play an important role in high temperature and high power electronic device application. Finally, recent work of high-quality nano-thick single crystal oxides of gamma-Al_2O_3 and Sc_2O_3 epitaxially grown on Si (111) is discussed.