Subthreshold Characteristics of MOS Transistors With $ \hbox{CeO}_{2}/\hbox{La}_{2}\hbox{O}_{3}$ Stacked Gate Dielectric

Abstract

This letter reports the subthreshold characteristics of MOS transistors with the novel CeO 2 /La 2 O 3 stacked gate dielectric. We found that the top CeO 2 capping layer does not only improve the bulk properties of La 2 O 3 by reducing the oxygen vacancies as a result of the reduction reaction of CeO 2 but also reduces the La 2 O 3 /Si interface trap pronouncedly. We further identify the energy level of the interface traps by conducting temperature-dependent subthreshold slope measurements.Index Terms-High-k gate dielectric, La 2 O 3 , MOS, temperature dependence.

Improving the electrical characteristics of MOS transistors with CeO2/La2O3 stacked gate dielectric

“…The improvement of subthreshold slope for shorter devices was because of the better electrostatic integrity. The subthreshold slope is mainly governed by the interface trap density [12]. A larger S value indicates a higher amount of interface trap density.…”

“…Using certain alloy forms or complex oxides where the desirable electrical properties can be tailored is a promising technique [1,[7][8][9]. Meanwhile, a special measure for overcoming the high oxygen vacancies of high-k materials based on the oxygen chemical potential control to the film was proposed recently [10][11][12][13]. It was recently found that multivalent cerium (Ce) can significantly improve the characteristics of MOS devices using La 2 O 3 as gate dielectric film [10,12].…”

“…Meanwhile, a special measure for overcoming the high oxygen vacancies of high-k materials based on the oxygen chemical potential control to the film was proposed recently [10][11][12][13]. It was recently found that multivalent cerium (Ce) can significantly improve the characteristics of MOS devices using La 2 O 3 as gate dielectric film [10,12]. These materials can be self-adapted to supply extra-oxygen atoms to the La 2 O 3 film and reduce the amount of oxygen vacancy therein.…”

Beneficial Lattice Strain in Heterogeneously Doped Ceria

“…The space charge regions created by the spatially dependent defect formation provide a counteracting Coulombic energy to limit the extent of the above reaction. Similar reactions across La 2 O 3 /CeO 2 interfaces have been examined as a means of reducing oxygen vacancies in La 2 O 3 gate dielectrics. − …”

Current conduction and stability of CeO2/La2O3 stacked gate dielectric

“…1,2 It was found recently that the electrical properties of La 2 O 3 can be significantly improved by introducing oxygen chemical potential control with the multivalent cerium oxides (CeO 2 and Ce 2 O 3 ). [3][4][5] Cerium dioxide has a smaller value of oxygen chemical potential and thus can reduce the oxygen vacancy formation in the La 2 O 3 film of the stack. 3,6 However, since the final oxygen chemical potential relies on the thermal equilibrium and the diffusivity of the oxygen, it may be unstable at high temperatures or upon a high-electric field stress.…”