Mechanism of Electron Trapping and Characteristics of Traps in $\hbox{HfO}_{2}$ Gate Stacks

Theoretical Prediction of Intrinsic Self-Trapping of Electrons and Holes in MonoclinicHfO2

“…We note that an electron migration process exhibiting a very low activation energy of 0.01 eV has recently been identified by simulating temperature dependent threshold voltage shift during constant voltage stress of the HfO 2 gate dielectric MOSFETs using temperatureassisted charge migration model [28]. This low activation energy process might represent the transport of selftrapped electron polarons.…”

The Pulsed Id-Vgmethodology and Its Application to the Electron Trapping Characterization of High-κ gate Dielectrics

“…This effect is caused by substrate electrons injected to and captured by shallow traps (just below the Hf-based dielectric conduction band, Fig. 1) [74], where the trapping may occur within hundreds of nanoseconds to microseconds [50,73]. The charges trapped during this process are well-localized within the dielectric, with their spatial distribution through the dielectric thickness being determined by the Fermi energy of the channel electrons and the trap energy (presumably, a neutral or singlecharged negative oxygen vacancies) [4,7,[9][10][11]16] fast trapping, which is reversible with no residual damage [30,75,76], can contribute significantly to threshold voltage (V t ) instability and degradation of device performance in Hf-based gate stack nMOS transistors.…”

“…Proper analysis techniques can provide information on charge trapping [32, 70-74, 81, 83, 85] and the effect on device performance, separation of fast and slow trapping processes [20,32,50,54,55,74,86], and bias temperature instability [50,[87][88][89][90].…”

“…It has been demonstrated that the fast trapping process, with a characteristic time of about 100 μs, is independent of temperature, implying that the pre-existing traps are filled by the resonant capture of the tunneling electron injected from the substrate [20,74]. The charges trapped by this process are well-localized within the dielectric thickness, with their location being determined by the Fermi energy of the channel electrons and the trap energy, whose value is close to the HfO 2 conduction band edge, Fig.…”

“…1 (presumably, a neutral or single-charged negative oxygen vacancy) [4,7,[9][10][11]16]. Therefore, we assume for simplicity that the traps are characterized by a single energy value that is close to the bottom of the conduction band [4,20,74]. For longer stress times, over 1 second, the trapped charge distribution widens due to slow temperature-activated electron capture processes [50,74].…”