Nitrogen Depth Profiles Research Articles

Annealing effects on the nanoscale indium and nitrogen distribution in Ga(NAs) and (GaIn)(NAs) quantum wells

III∕V semiconductors containing dilute amounts of nitrogen are metastable and need to be thermally treated after growth to optimize optoelectronic properties. The influence of thermal annealing on the nitrogen depth profile in metal organic vapor phase epitaxygrown Ga(NAs)∕GaAs as well as (GaIn)(NAs)∕GaAs heterostructures is examined on a nanometer scale by combining several high resolution transmission electron microscopy techniques, also with Rutherford backscattering spectrometry. Annealing conditions, which are optimized for quaternary alloys with respect to photoluminescence intensity, do not result in element redistribution for the In containing material. Contrary to the quaternary material, the result of annealing the ternary Ga(NAs) is a pronounced pileup of the nitrogen profile without any out diffusion of nitrogen. These findings have important influence on device structures, which often contain Ga(NAs) barriers for strain-compensation purposes together with (GaIn)(NAs) active regions. In the light of metastability considerations for the ternary and quaternary alloy, one can conclude that the In contained in the quaternary material stabilizes the material and suppresses phase separation. Consequently (GaIn)(NAs) is more stable than its ternary counterpart Ga(NAs).

Modeling and Characterization of Nitrogen-Enhanced Negative-Bias Temperature Instability in p-Channel MOSFETs

Negative-bias temperature instability (NBTI) of nitrided gate oxides prepared with different nitridation processes was characterized and the NBTI results can be well described by an analytical reaction-dispersive-diffusion model in the diffusion-limited regime. The activation energies were recalculated by eliminating the non-Arrhenius part, and this confirms that both the interfacial nitrogen concentration and the nitrogen depth profile in the nitrided oxides play important roles in the nitrogen-enhanced NBTI. Furthermore, first-principles calculations were carried out to examine the effects of nitrogen as either the reaction site or the neighboring atoms at the interface. Lower reaction energies due to the incorporation of nitrogen suggest that nitrogen is a more effective hydrogen-originated hole-trapping center than oxygen and hence enhances NBTI. It was also found that hydrogen-originated hole trapping at vacancy defects has the strongest dependence on the nitrogen neighboring effect. Moreover, the role of nitrogen in NBTI was also investigated in terms of its influence on the electronegativity and atomic-charge distribution.

Atomic scale nitrogen depth profile control during plasma enhanced atomic layer deposition of high k dielectrics

Nitrogen incorporation produces several benefits in the performance of high k gate oxides. However, since too much nitrogen incorporation at the interface of gate dielectric can result in device degradation, the atomic scale control of nitrogen depth profile is desirable. In this study, the authors have improved electrical properties and interface properties by depth profile control of in situ nitrogen incorporation during plasma enhanced atomic layer deposition. The best electrical properties in terms of hysteresis, equivalent oxide thickness, and interface states were obtained when the nitrogen is incorporated in the middle of the thin film, which has not been achievable by other techniques.

Surface cavities produced by high‐dose nitrogen ion implantation into silicon

AbstractNitrogen ion implantation (24 keV, 4.6 × 1017 cm−2) into (100) a p‐type silicon wafer material and a subsequent electron beam annealing at 1100 °C for 15 s under high vacuum conditions leads to the formation of an uneven surface in the implanted region caused by nitrogen bubbles beneath the surface. Annealing at 1200 °C for 300 s results in surface cavities with a mean diameter of 350 nm and a surface coverage of 3–4% and an average depth of ∼60 nm. Nuclear reaction analysis reveals that the nitrogen concentration in the as‐implanted state exceeds 57 at%, the value of stoichiometric Si3N4. Annealing at 1100 °C for 15 s slightly reduces the nitrogen peak concentration, whereas annealing at 1200 °C for 300 s induces a significant alteration to the shape of the nitrogen depth profile coupled with the lowering of the concentration close to the stoichiometry of Si3N4. The results present a new method of producing sub‐micrometre cavities embedded in a thin silicon nitride film on wafer silicon which may lead to novel micro‐electronic and biotechnology applications. Copyright © 2007 John Wiley & Sons, Ltd.

Modeling and Characterization of Negative Bias Temperature Instability in p-Channel MOSFETs

Negative bias temperature instability (NBTI) of nitrided gate oxides prepared with different nitridation process is characterized and the NBTI results can be well described by an analytical reaction-dispersive-diffusion model in the diffusion-limited regime. The activation energies are re- calculated by eliminating the non-Arrhenius part, and it confirms that both the interfacial nitrogen concentration and the nitrogen depth profile in the nitrided oxides play important roles in the nitrogen-enhanced NBTI. Furthermore, first-principles calculations are carried out to examine the effects of nitrogen as either the reaction site or the neighboring atoms at the interface. Lower reaction energies due to the incorporation of nitrogen suggest that nitrogen is a more effective hydrogen-originated hole trapping center than oxygen, and hence enhances NBTI. It is also found that hydrogen-originated hole trapping at vacancy defect has the strongest dependence on the nitrogen neighboring effect. Moreover, the role of nitrogen in NBTI is also investigated in terms of its influence on the electro-negativity and atomic charge distribution.

Application of ion beams in the study of depth profiling of nitrogen

In recent days there has been considerable interest in the analysis of nitrogen concentration in Si3N4, GaN, TiN and TaN films. The analysis of these films using Rutherford Back Scattering Analysis (RBS) suffers from poor sensitivity to nitrogen. This work presents two resonance reactions for depth profiling of nitrogen: 14N(p,γ)15O at 278keV and 15N(p,αγ)12C at 897keV. The technique is non-destructive and can be used for both conductive and non-conductive films. Both the techniques were tried on different films and their sensitivity, accuracy and repeatability are reported in this work.

Nitrogen Ion Beam Irradiation on Amorphous Carbon

Both bulk and thin film amorphous carbon were irradiated using a nitrogen ion beam and changes in surface roughness and composition after ion beam irradiation have been studied. Amorphous carbon thin films were prepared from toluene vapor using plasma enhanced chemical vapor deposition. Ion irradiation was performed at room temperature using a nitrogen ion beam and the ion beam energy was varied from 0.2 to 1.5 keV under the constant ion current density. Surface morphology was observed with atomic force microscopy (AFM). Depth profiles of nitrogen in the irradiated specimens were analyzed by X-ray photoelectron spectroscopy (XPS). AFM observations reveal that after the ion beam irradiation the surface of the bulk amorphous carbon becomes rough, while the surface of the amorphous carbon films becomes smooth. However, the notable difference in the surface roughness is hardly observed between low- and high-energy ion irradiation. From XPS studies, it is found that the nitrogen concentration near the surface increases after the ion irradiation for both bulk and thin films and irradiated nitrogen ions are combined with carbon, resulting in formation of carbon nitride layers. Depth profiles of nitrogen show that for the bulk specimen low-energy ion irradiation is more effective for the carbon nitride formation than high-energy ion irradiation, while for the thin films high-energy ions are implanted more deeply than low-energy ions.

Photocatalytic Properties of Plasma-Nitrided TiO2 Films

Nitrogen-doped films were prepared by plasma-nitridation using nitrogen gas of sol-gel derived films. Obvious difference of nitrogen depth profile is observed between the films plasma-nitrided before and after densification by postannealing. In the films plasma-nitrided after the densification of the films, the nitridation takes place around the surface (about ). In the films for which the plasma-nitridation was carried out prior to densification of the films, the nitridation proceeds into the films. The nitrogen content in the latter case is more than that in the former case. Higher photocatalytic activity for visible light was observed in the latter film.

Parametric study of nitrided AISI 304 austenite stainless steel prepared by plasma immersion ion implantation

This paper investigates the characteristics of plasma immersion nitrogen-ion implanted AISI 304 austenite stainless steel against such processing parameters as bias voltage (5–20 kV), substrate temperature (300–500 °C), and implantation fluence (1.4 × 10 18–4.2 × 10 18 cm − 2 ). Characteristics of the as-implanted specimens under investigation included elemental depth profile, hardness depth profile, crystallographic structure, and corrosion behavior and were determined using glow discharge spectrometry (GDS), the Vickers hardness tester, X-ray diffractometry (XRD), and the potentiodynamic polarization test, respectively. The results show that nitrogen depth profiles strongly depend on these processing parameters and closely relate to the corresponding chromium depth profiles. The hardness depth profiles increase and widen as substrate temperature, bias voltage, and implantation fluence increase. In particular, an improvement in hardness is accompanied by a reduction in corrosion resistance when substrate temperature reaches 500 °C. The corrosion-resistance degrader, CrN, precipitates as substrate temperature exceeds 450 °C, a phenomenon which is clearly evident in the chromium depth profiles as well as the XRD results.

Significance of Nitrogen and Aluminum Depth Profile Control in HfAlON Gate Insulators

Aluminum and nitrogen depth-profile dependences of the electron mobility are examined. We show that the electron mobility for MOSFETs with HfAlON gate dielectrics in which nitrogen and aluminum depth profiles are controlled is strongly affected by the nitrogen profile rather than the aluminum one, although the nitrogen profile does not affect the VFB shift. These results suggest that additional scattering due to nitrogen incorporation cannot be explained by only the Coulombic components such as the fixed charges. Thus, an appropriate profile control of the nitrogen to suppress the mobility degradation is a key for obtaining high performance MOSFETs with HfAlON dielectrics.

Influence of bias and in situ cleaning on through cage (TC) or active screen plasma nitrided (ASPN) steels

The effect of a substrate bias and prenitride plasma etching on the nitriding response of four steel substrates is investigated in a two factor two level full factorial experimental design. The steels investigated were P20 (M200, plastic mould steel), H13 (W302, hot work tool steel – as received), 4140 (preheat treated nitriding steel) and 1020 (CS1020, bright mild steel). The nitriding response was determined from surface and cross-sectional hardness measurements. Nitrogen depth profile measurements were obtained using glow discharge optical emission spectroscopy. Considering the main effects, the results show that without a worktable bias during the nitriding step there is effectively little or no nitriding response in most of the materials. The prenitride plasma etch did not produce a significant surface hardness response in all steels except H13, where a prior etch substantially increased surface hardness and influenced the hardness depth profile. The bias also significantly increased the nitrogen wt-%. The plasma etch also influenced the near surface nitrogen wt-% concentrations, however the practical implications of this require further investigation.

Control of Nitrogen Depth Profile near Silicon Oxynitride/Si(100) Interface Formed by Radical Nitridation

Depth profiles of composition and chemical structures in radical nitrided silicon oxynitride films formed with Ar/N2, Xe/N2, or Ar/NH3 plasma excited by microwave have been investigated by X-ray photoelectron spectroscopy combined with step etching in HF solution. The relationship between the intensities of emission from N2+ radical in these plasmas and the concentration of nitrogen atoms forming Si3≡N configuration near the silicon oxynitride film/Si substrate interface nitrided using these plasmas was studied. The emission intensities from N2+ radical generated in Xe/N2 or Ar/NH3 plasma are a quarter or one-sixth of that from N2+ radical generated in Ar/N2 plasma respectively. However, the emission from NH radical is also detected in Ar/NH3 plasma. Although the nitrogen concentration of Xe/N2 plasma is smaller than that of Ar/N2 plasma at the film/substrate interface, that of Ar/NH3 plasma is larger than that of Ar/N2 plasma at the interface. It is important for the reduction of the nitrogen concentration near the film/substrate interface to use Xe/N2 plasma in which both of the generation efficiencies of N2+ and NH radicals are low.

Significance of Nitrogen and Aluminum Depth Profile Control in HfAlON Gate Insulators

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Depth profiling of carbon and nitrogen in copper using nuclear reactions

Simultaneous implantations of 12C and 15N were performed into copper using the non-deviated beam line of a 2MV Tandetron accelerator. The atomic composition of the implanted layer was measured using appropriate nuclear reactions with a 1.05MeV deuteron beam. 12C(d,p0)13C and 15N(d,α0)13C nuclear reactions were used to depth profile simultaneously 12C and 15N and to determine the relative contribution of multi-ionised 12C and 15N ions to the carbon and nitrogen distribution. We also used the narrow resonance at 429keV of the 15N(p,αγ)12C nuclear reaction to check the validity of our results. The depth distributions obtained with this resonant nuclear reaction confirmed that (d,p) and (d,α) reactions are well suited to profile both carbon and nitrogen elements with a quite good resolution. Moreover, using these reactions makes possible to profile 12C and 15N atoms with a single and relatively rapid measurement.

Compositional and structural changes in ZrOxNy films depending on growth condition

The present work focuses on the analysis of ZrOxNy thin films, the composition evolution with changing growth conditions and its relation with the structural and morphological properties of the films. The films were prepared by rf reactive magnetron sputtering, using different reactive gas flows. Composition and structure were measured combining ion beam analysis (IBA) and X-ray diffraction (XRD) techniques. The depth profiles of nitrogen and oxygen have been obtained by elastic recoil detection analysis (ERDA).Results showed that the oxygen fraction in the films increases with gas flow, reaching a value of x∼0.33 for a reactive gas flow mixture of 6.25sccm. During growth mixed zirconium nitride and oxide phases form. Furthermore, the deposition rate correlates with the oxygen content variations, showing a continuous decrease with reactive gas flow.

Nitrogen depth profiling in thin oxynitride layers on silicon

AbstractThis paper describes the results of nitrogen depth profiling in nanometer oxynitride layers on silicon, employing dynamic SIMS and time‐of‐flight SIMS. The surface transient effect was studied using surface encapsulation method, and the attractive possibility of time‐of‐flight SIMS profiling with low energy Cs sputtering was demonstrated. Quantification of the nitrogen profiles was performed after a detailed study of the matrix effect in order to correct for the ion yield difference at the oxynitride/silicon interface. Copyright © 2006 John Wiley & Sons, Ltd.

The influence of bias and in-situ cleaning on Through Cage (TC) or Active Screen Plasma Nitrided (ASPN) steels

The effect of a substrate bias and prenitride plasma etching on the nitriding response of four steel substrates is investigated in a two factor two level full factorial experimental design. The steels investigated were P20 (M200, Plastic mould steel), H13 (W302, Hot-work tool steel, as received), 4140 (Preheat treated nitriding steel) and 1020 (CS1020, Bright mild steel). The nitriding response was determined from surface and cross-sectional hardness measurements. Nitrogen depth profile measurements were obtained using Glow Discharge Optical Emission Spectroscopy. — Considering the main effects, the results show that without worktable bias during the nitriding step there is effectively little or no nitriding response in most of the materials. The prenitride plasma etch did not produce a significant surface hardness response in all steels except H13, where a prior etch substantially increased surface hardness and influenced the hardness depth profile. The bias significantly increased the nitrogen wt%. The plasma etch also influenced the near surface nitrogen wt% concentrations, however, the practical implications of this require further investigation.

Calculation of nitrogen depth profiles in nitrided multi-component ferritic steel

Nitrogen depth profiles in steels that were subjected to a nitriding treatment can be calculated both on the basis of precipitation and on the basis of trapping. Nitrogen depth profiles calculated on the basis of precipitation agree reasonably well with experimentally observed depth profiles, except for the occurrence of a tail advancing the main nitriding front, which is obtained in the calculations, but is not observed in the experiment. In calculations using a trapping model presented in the present paper the tail is absent, which suggests that for an accurate description of nitrogen diffusion in steel during nitriding trapping should be incorporated. Comparison of experimental nitrogen depth profiles in En40B, X38CrMoV5-1 and En19 steel with trapping model calculations shows that in general the trapping model is too simple to accurately describe the diffusion of nitrogen during nitriding, although for some steels already a very good agreement is obtained. The validity of the trapping model is discussed in view of the complicated microstructural changes occurring during the nitriding of steel. A realistic model to calculate nitrogen depth profiles in nitrided steel should incorporate the complicated precipitation sequence during nitriding, including both trapping and precipitation.

Control of Nitrogen Depth Profile and Chemical Bonding State in Silicon Oxynitride Films Formed by Radical Nitridation

Chemical bonding states and depth profiles of nitrogen in radical nitrided silicon oxide film formed in Ar/N2 plasma excited by microwave has been investigated using X-ray photoelectron spectroscopy with HF step etching. The main chemical bonding state of nitrogen atom is Si3≡N configuration, and the other unknown bonding state (termed Nhigh) is observed, whose peak energy shift is about +4.8 eV. The nitrogen atoms forming Si3≡N configuration accumulate only at the film surface and those forming Nhigh configuration are distributed deeper in the films. The Nhigh bond is very weak because it is desorbed completely at low temperature (300–500°C). Although the nitrogen atoms forming Nhigh configuration are removed by post O2-annealing, those forming Si3≡N configuration migrate toward the film/substrate interface and they increase negative bias temperature instability. In the case of ultra thin film, nitriding species forming Nhigh bond reach the film/substrate interface and form Si3≡N bond at the interface. Suppression of the generation of nitriding species forming Nhigh bond in the plasma is very important. It is clear that Nhigh bond is reduced using Ar/NH3 plasma.

Plasma immersion ion implantation of nitrogen into H13 steel under moderate temperatures

Ion implantation of nitrogen into samples of tempered and quenched H13 steel was carried out by plasma immersion technique. A glow discharge plasma of nitrogen species was the ion source and the negative high voltage pulser provided 10–12kV, 60μs duration and 1.0–2.0kHz frequency, flat voltage pulses. The temperatures of the samples remained between 300 and 450°C, sustained solely by the ion bombardment. In some of the discharges, we used a N2+H2 gas mixture with 1:1 ratio. PIII treatments as long as 3, 6, 9 and up to 12h were carried out to achieve as thickest treated layer as possible, and we were able to reach over 20μm treated layers, as a result of ion implantation and thermal (and possibly radiation enhanced) diffusion. The nitrogen depth profiles were obtained by GDOS (Glow Discharge Optical Spectroscopy) and the exact composition profiles by AES (Auger Electron Spectroscopy). The hardness of the treated surface was increased by more than 250%, reaching 18.8GPa. No white layer was seen in this case. A hardness profile was obtained which corroborated a deep hardened layer, confirming the high efficacy of the moderate temperature PIII treatment of steels.