B. L. Yang

XPS Study of the Bonding Properties of Lanthanum Oxide/Silicon Interface with a Trace Amount of Nitrogen Incorporation

Recently, both electrical and material properties of lanthanum oxide (La 2 O 3 ) have been found to significantly improve with a trace amount of nitrogen doping. This work conducted a detailed investigation on the nitrogen incorporation at the La 2 O 3 /Si interface by using X-ray photoelectron spectroscopy (XPS) and capacitance-voltage measurements. The process-dependent chemical bonding structures of Si, O, and La atoms at the interface were studied in detail. For samples annealed at 500°C and above, the interfacial metallic La-Si bonds were converted into La-N bonds, and some Si-O bonds were found at the interface. These effects resulted in a significant reduction in the interface trap density. The bulk properties of La 2 O 3 were also improved with the proposed technique as a result of the filling of oxygen vacancies with nitrogen atoms.

Study of process-dependent electron-trapping characteristics of thin nitrided oxides

A detailed investigation on the process dependent characteristics of electronic traps in thin nitrided oxide films is presented. By monitoring the field shift in the Fowler-Nordheim (FN) plots and the flatband voltage of metal-insulator-semiconductor (MIS) structures, the trap centroid of the nitrided oxide film was found to be process dependent. Turnaround behaviour in the location of the trapped charge centroid (X0, measured from the oxide/silicon interface) and trap density were found. The centroid moves to the surface for light nitridation and then moves as close as X0/L = 0.48 (L is the thickness of the dielectric) to the silicon/oxide interface. On the other hand, the current conduction of the nitrided film is found to be enhanced remarkably by shallow traps (∼ 1.0 eV) for electric field strengths less than 8.5 MV/cm. A shallow trap-assisted electronic conduction mechanism in the nitrided oxides is proposed. For electric fields in the range of 8.5–11 MV/cm, a quasi-saturation region due to electron-trapping is observed. In the high electric field region (> 11 MV/cm), the conduction current is governed mainly by the FN mechanism. Detrapping, either by two-step tunnelling or Schottky emission, is also obvious in the high field region.

Effects and mechanisms of nitrogen incorporation into hafnium oxide by plasma immersion implantation

The physics and effects of nitrogen incorporation into HfO2 films were studied in detail. The authors found that only a trace amount (∼5%) of nitrogen can be introduced into the HfO2 films using plasma immersion ion-implantation technique, regardless of implantation dose. They proposed that the nitrogen incorporation is due to the filling of O vacancies (VO) and replacement of VO O neighbors in the bulk with nitrogen atoms. At the interface, the nitrogen atoms exist in the form of Hf–N and Si–N bonding, which significantly improve the interface properties of the HfO2∕Si structure. Temperature-dependent capacitance-voltage characteristics measurements indicate that both interface and oxide trap densities were greatly reduced with the incorporation of trace amount of nitrogen atoms.

Effects of aluminum incorporation on hafnium oxide film using plasma immersion ion implantation

The effects of aluminum implantation on HfO2 thin films using plasma immersion ion implantation (Al– PIII samples) are investigated. X-ray photoelectron spectroscopy measurements reveal that most of the implanted aluminum atoms accumulated near the surface region of the oxide film. The greatly reduced leakage current, smaller flatband shift and steep transition from the accumulation to the depletion region in the capacitance–voltage characteristics for Al–PIII samples indicate that both bulk oxide and interface traps are significantly reduced by aluminum incorporation. Even though the aluminum concentration at the Si/HfO2 interface is very low the results indicate that trace amount of aluminum at the interface leads to significant improvements in both material and electrical characteristics of the thin HfO2 films.

Modelling of trap-assisted electronic conduction in thin thermally nitrided oxide films

The current-voltage characteristics of thin thermally nitrided oxide films have been investigated in detail at temperatures ranging from 100 to 298 K. Considering the fact that shallow traps do not capture any electrons but contribute to the current conduction, a trap-assisted conduction model for dielectric films is developed. The theoretical results are in good agreement with the experimental data. For electric fields in the range of 6–8 MV cm−1, we found that at room temperature the transport current in the nitrided oxide is governed mainly by shallow trap-assisted tunnelling, and by deep trap-assisted tunnelling at low temperatures (<150 K). The energy level of shallow traps is found to be between 0.033 and 0.118 eV, while the deep trap levels are between 2.89 and 3.08 eV.

Nitrogen Incorporation into Hafnium Oxide Films by Plasma Immersion Ion Implantation

The physics and effects of nitrogen incorporation into hafnium oxide (HfO2) films were studied in detail. We found that only a trace amount (~5%) of nitrogen can be introduced into the HfO2 films by plasma immersion ion-implantation, regardless of implantation dose. We proposed that the nitrogen incorporation is mainly due to the filling of O vacancies in the as-deposited HfO2 films and the nitridation of silicide bonds at the HfO2/Si interface. Temperature-dependent capacitance–voltage and current–voltage characteristics measurements indicate that both interface and oxide trap densities were greatly reduced as the results of the nitrogen filling of the O-vacancies and the nitridation of interfacial hafnium silicide bonds.

Study of shallow bulk traps in thin nitrided oxide films by thermal re-emission of electrons trapped at high field

Abstract The temperature and field dependence of high-field electron trapping and thermal re-emission of trapped electrons in thin nitrided oxide films at temperatures ranging from 100 to 423 K are investigated. It is found that, when the temperature decreases, the effective surface density of electron traps in nitrided oxide films increases, while for thin SiO2 film it decreases. The electron trap capture cross-section of thermal oxide and nitrided oxide films is about 10−19 and 10−16 cm2, respectively. Discrete shallow bulk traps in the nitrided oxide are identified. It is suggested that traps with activation energies between 0.046 and 0.072 eV are related to nitrogen. On the other hand, traps having activation energies larger than 0.1 eV are due to hydrogen and Si dangling bonds. Depending on the nitridation duration, the shallow trap density varies from a few percent to over 30% of the total trap density and the energy levels become shallower as the nitridation continues.

Off-state drain breakdown mechanisms of VDMOS with anti-JFET implantation

Abstract Efficiency, reliability, and cost are the important design considerations of a vertical double diffused MOSFET (VDMOS) because of its high-voltage applications in consumer electronics. To minimize the cost, the devices were normally fabricated on an epitaxial layer which was grown on a highly-doped substrate. Meanwhile, it was proposed that the efficiency of a VDMOS can be enhanced by conducting an anti-JFET implant to reduce the “ON” resistance of the transistor. This paper reports the effects of anti-JFET implant on the reliability and the blocking capability of the VDMOS. Experimental results show that the anti-JFET implant can reduce the ON resistance by suppressing the channel depletion due to the parasitic JFET and enhance the breakdown voltage by moving the high-field region to the surface channel region. However, it deteriorates the device reliability greatly because the oxide quality was deteriorated and the hot holes generated in the surface high-field region could be easily injected into the gate oxide and hence caused larger subthreshold conduction and drain breakdown at lower voltage.

Electrical Stability Improvement for Lanthanum Oxide Films by Nitrogen Incorporation using Plasma Immersion Ion Implantation

The effect of nitrogen implantation on thin lanthanum oxide (La2O3) films grown by e-beam evaporation are investigated using X-ray photoelectron spectroscopy (XPS), current-voltage (I-V) and capacitance-voltage (C-V) measurements. The amount of nitrogen incorporation in the oxide film by plasma immersion ion-implantation (PII) is found to be quite low (about 3% near the surface). However, the introduction of nitrogen atoms into the La2O3 network results in a significant reduction in the oxide traps and leads to a notable improvement in both material and electrical properties of the dielectric.

Electrical characteristics and reliability of hafnium oxide films with nitrogen doping

The effects of trace amount of nitrogen doping on the electrical characteristics of thin hafnium oxide have been studied. The chemical compositions and bonding structure of the dielectric film have been explored with x-ray photoelectron spectroscopy (XPS) measurements. Current-voltage (I-V) and capacitance-voltage (C-V) measurements have been conducted on nitrogen-doped hafnium oxide samples and to study the reliability of the film constant-voltage stressing has been performed. The trapping characteristics have been further revealed by conducting the I-V and C-V measurements at different temperatures ranging from 100 to 400 K. We have found that although the deep trap level due to oxygen vacancy and interface trap density due to Hf-Si bonding can be significantly suppressed with nitrogen doping; large amount of shallow traps are still present.