On the Depth Profiling of the Traps in MOSFET's with High-k Gate Dielectrics

Abstract

A general and reliable model for charge pumping (CP) proposed recently has been extended to trap depth distributions towards oxides depth. The fundamental features concerning the energy and depth region probed at the Si-SiO2 interface and in the direction of oxides depth are presented in the case of the different basic CP curves. The effect of the electric field is accounted for and its impact on the results is discussed. Then, MOSFET's with HfO2 gate dielectric are studied. Trap depth concentration profiles recorded from devices after different technological processes are presented and discussed.

Advances in La-Based High-k Dielectrics for MOS Applications

“…It has been reported that doping La into other high-k materials can also achieve improvements, and the most important effect of La doping is to passivate the oxygen vacancies in other high-k binary oxides. After several reports showing that La incorporated in HfO 2 could significantly improve the device performance [53][54][55][56][57][58][59][60][61][62][63][64][65][66], X. P. Wang et al proposed that this improvement should be ascribed to the reduction of oxygen vacancies (V O ) in HfLaO [66]. Therefore, several studies on the physics of this phenomenon have been made and confirmed the V O passivation role of La as discussed below.…”

“…After several reports showing that La incorporated in HfO2 could significantly improve the device performance [53-66], X. P. Wang et al proposed that this improvement should be ascribed to the reduction of oxygen vacancies (VO) in HfLaO [66]. Therefore, several studies on the physics of this phenomenon have been made and confirmed the VO passivation [60], (e) Si 1s spectrum at the La 2 O 3 /Si interface for different annealing temperatures [57], and (f) XRD patterns of La 2 O 3 and LaON films after annealing [61].…”

“…It is known that La 2 O 3 has an ionic bonding nature while the bond in the La-silicate layer is more covalent, thus creating a larger amount of oxygen vacancies at the La 2 O 3 /Si interface [59]. It has been reported that charge-pumping measurement can be used to detect the interface traps between ionic HfO 2 and covalent SiO 2 , and so the traps located at the La 2 O 3 /La-silicate interface can be considered as slow states [60]. Figure 10c shows the density of this slow state (D slow ) together with D it calculated based on the measured conductance of the La 2 O 3 -gated MOS capacitor, with D slow much higher than D it and almost distributed uniformly in the Si band gap [58].…”

“…Figure 10c shows the density of this slow state (D slow ) together with D it calculated based on the measured conductance of the La 2 O 3 -gated MOS capacitor, with D slow much higher than D it and almost distributed uniformly in the Si band gap [58]. [60], (e) Si 1s spectrum at the La2O3/Si interface for different annealing temperatures [57], and (f) XRD patterns of La2O3 and LaON films after annealing [61].…”

“…Therefore, in this case, the oxidation of Si drives this substitution without releasing electrons, and the VB holes are filled by the electrons in the conduction band to prevent the formation of VO states in the band gap. For HfO2 and HfLaO: (a) relaxed structure of oxygen vacancies VO[60], (b) contour plot of wave function corresponding to the VO-related gap states[60], and (c) schematic band diagram showing oxygen vacancies[68].…”