E. Castán

Deposition of SiNx : H thin films by the electron cyclotron resonance and its application to Al/SiNx : H/Si structures

We have analyzed the electrical properties and bonding characteristics of SiNx:H thin films deposited at 200 °C by the electron cyclotron resonance plasma method. The films show the presence of hydrogen bonded to silicon (at the films with the ratio N/Si<1.33) or to nitrogen (for films where the ratio N/Si is higher than 1.33). In the films with the N/Si ratio of 1.38, the hydrogen content is 6 at. %. For compositions which are comprised of between N/Si=1.1 and 1.4, hydrogen concentration remains below 10 at. %. The films with N/Si=1.38 exhibited the better values of the electrical properties (resistivity, 6×1013 Ω cm; and electric breakdown field, 3 MV/cm). We have used these films to make metal-insulator-semiconductor (MIS) devices on n-type silicon wafers. C–V measurements accomplished on the structures indicate that the interface trap density is kept in the range (3–5)×1011 cm−2 eV−1 for films with the N/Si ratio below 1.38. For films where the N/Si ratio is higher than 1.4, the trap density suddenly ...

Experimental observation of conductance transients in Al/SiNx:H/Si metal-insulator-semiconductor structures

Room temperature conductance transients in the SiNx:H/Si interface are reported. Silicon nitride thin films were directly deposited on silicon by the low temperature electron-cyclotron-resonance plasma method. The shape of the conductance transients varies with the frequency at which they are obtained. This behavior is explained in terms of a disorder-induced gap-state continuum model for the interfacial defects. A perfect agreement between experiment and theory is obtained proving the validity of the model.

Good quality Al/SiNx:H/InP metal-insulator-semiconductor devices obtained with electron cyclotron resonance plasma method

We have obtained Al/SiNx:H/InP metal-insulator-semiconductor devices depositing SiNx:H thin films by the electron cyclotron resonance plasma method at 200 °C. The electrical properties of the structures were analyzed according to capacitance–voltage and deep level transient spectroscopy measurements. We deduce an inverse correlation between the insulator composition—the N/Si ratio—and the density of interface traps: those films with the maximum N/Si ratio (1.49) produce devices with the minimum trap density—2×1012 cm−2 eV−1 at 0.42 eV. above the midgap. We explain the influence of film composition on the interface trap density in terms of a substitution of phosphorous vacancies at the InP surface, Vp, by N atoms coming from the insulator, NVp. The values obtained in our research for the interface trap distribution were similar to other published results for devices that use chemical and/or physical passivation processes of the InP surface prior to the deposition of the insulator.

Deep‐level transient spectroscopy and electrical characterization of ion‐implanted p‐n junctions into undoped InP

Current‐voltage, small‐signal measurements, and deep‐level transient spectroscopy (DLTS) spectra of p‐n junctions made by Mg implantation into undoped InP are described. The I‐V characteristics show that the dominant conduction mechanism at forward bias is recombination in the space‐charge zone, whereas a thermally activated tunneling mechanism involving a trap at 0.32 eV dominates at reverse bias. Five deep levels located in the upper‐half of the band gap were detected in the junctions by DLTS measurements, three of which (at 0.6, 0.45, and 0.425 eV) were found to appear due to rapid thermal annealing. The origin of the other two levels, at 0.31 and 0.285 eV, can be ascribed to implantation damage. Admittance spectroscopy measurements showed the presence of three levels at 0.44, 0.415, and 0.30 eV, all in agreement with those found by DLTS. The DLTS measurements showed that the concentration of deep levels decreased after longer annealing times, and that the concentration of deep levels due to the implan...

Characterization of the damage induced in boron-implanted and RTA annealed silicon by the capacitance-voltage transient technique

The electrically active profiles and the induced defects in boron-implanted silicon under different implantation conditions were measured. The implantation profiles were derived from conventional capacitance-voltage measurements. Deep-level defects induced by the technological process have been characterized. Deep-level transient spectroscopy (DLTS) seems not to be sufficient to study the variations of the deep-level properties along the space-charge region of the junctions. In order to achieve a more complete deep-level characterization we have set up a new technique, named the capacitance-voltage transient technique (CVTT), which allows us to determine the spatial variation of the concentration and of the emission rates of the deep levels. The results obtained from the application of these techniques to the study of the influences of the different implantation parameters are presented.

Interface state density measurement in MOS structures by analysis of the thermally stimulated conductance

Abstract The analysis of thermally stimulated conductance is a modification of the Nicollian-Goetzberger conductance technique for interface state density measurement in MOS structures. This technique relies on the measurement of the MOS structure conductance as a function of temperature, at a constant frequency. The conductance as a function of temperature shows a maximum which allows the interface state density to be determined. It is a simple method for measuring the interface state density because it is carried out at a constant frequency. In addition, the frequency can be taken low enough to prevent side effects, like those due to possible resistances in series with the MOS structures. The results obtained by this technique agree with those obtained by standard techniques like DLTS.

Tantalum pentoxide obtained from TaNx and TaSi2 anodisation: an inexpensive and thermally stable high k dielectric

Abstract We summarise the main performances of tantalum oxide films fabricated by anodic oxidation of tantalum nitride and tantalum silicide with thickness ranging from 100 to 4500 A. These films exhibit greatly improved leakage currents, breakdown voltage and very low defect density, thus allowing the fabrication of large area capacitors. Thermal treatments at temperatures up to 400°C do not degrade the insulator. We have proposed a set of selection guides to select the more appropriate process parameter values and electrode materials for a given application of these capacitors. Leakage currents in the insulator under thermal stress have been carefully studied in order to determine the nature and physical origin of the dominant conduction mechanisms in the insulator. We have found noticeable differences in the dominant conduction mechanisms for thin and thick anodic tantalum pentoxide films. These differences are explained in terms of the thickness dependence of the insulator layer structure. We have characterised the physical nature of the conduction mechanisms in the dielectric films. Poole–Frenkel effect and modified Poole–Frenkel effect from defect in the insulator are suggested. Finally, we report on conductance transient measurements ( G – t ) carried out on films of tantalum oxide fabricated by anodic oxidation of tantalum nitride and tantalum silicide with thickness ranging from 100 to 4500 A. One of the causes of the good properties of anodic tantalum pentoxide is the presence of nitrogen atoms in the dielectric. The influence of the nitrogen content on the anodisation precursor is showed up along the paper.

Characterization of the EL2 center in GaAs by optical admittance spectroscopy

We have measured the electron optical capture cross section, σ0n(hν), of EL2 (the most important native center in GaAs) using a new technique which we have recently developed: optical admittance spectroscopy. This is a spectroscopic technique based on the measurement of the capacitance and conductance of a junction under monochromatic light of energy hν. This technique allows the measurement of the spectrum σ0n(hν) of each center located in the band gap. We have measured the electron photoionization cross section of the EL2 center, σ0n(hν), at three different temperatures within a range limited at high temperature by thermal emission and at low temperature by photoquenching (a feature characteristic of EL2 below 140 K). The study of the experimental data reveals that this center has a more complex nature than that of a simple defect. It seems to behave like a family of very close levels corresponding to similar atomic structures and located near the midgap. These results also reveal the existence of a sha...

A study of metal‐oxide‐semiconductor capacitors fabricated on SF6 and SF6+Cl2 reactive‐ion‐etched Si

Metal‐oxide‐semiconductor capacitors have been fabricated on SF6 and SF6+Cl2 reactive‐ion‐etched silicon in order to study the resulting defects at the Si‐SiO2 interface and in the bulk of the silicon substrate. The reactive‐ion‐etching (RIE) induced damage reveals itself by the presence of positive charge in the oxide, by interfacial states, and by two deep levels in the silicon bulk located at 300 and 335 meV above the valence band and probably related to fluorine atoms. We have studied the effect of the chamber pressure and the plasma composition on the resulting damage. This damage is more important when the chamber pressure is low because of the higher free‐mean path of the plasma ions. On the other hand, when the Cl2 concentration in the plasma is raised the densities of interface states and of the deep levels decrease while the positive charge in the oxide increases. Finally, we have shown that a post‐RIE thermal annealing can be used to restore the electrical properties of the RIE‐damaged silicon ...

Deep levels in p(+)-n junctions fabricated by rapid thermal annealing of Mg or Mg/P implanted InP

In this work, we investigate the deep levels present in ion implanted and rapid thermal annealed (RTA) InP p+-n junctions. The samples were implanted with magnesium or coimplanted with magnesium and phosphorus. These levels were characterized using deep level transient spectroscopy (DLTS) and capacitance–voltage transient technique (CVTT). Seven majority deep levels located in the upper half of the band gap were detected in the junctions by using DLTS measurements, four of which (at 0.6, 0.45, 0.425, and 0.2 eV below the conduction band) result from RTA, while the origin of the other three levels (at 0.46, 0.25, and 0.27 eV below the conduction band) can be ascribed to implantation damage. An RTA-induced origin was assigned to a minority deep level at 1.33 eV above the valence band. From CVTT measurements, several characteristics of each trap were derived. Tentative assignments have been proposed for the physical nature of all deep levels.