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Liberation of atomic hydrogen is detected upon photon (hν = 10 eV) irradiation of thermally grown SiO2 on Si followed by neutralization of the created positive charge by electrons. This indicates the formation and trapping of protons in the oxide. Additional evidence for this is provided by an isotopic effect in the positive charge decay observed in samples enriched with 1H and 2D. The most efficient proton generation process is suggested as hole trapping by O3 ≡ SiH centers, leading to the formation of O3 ≡ Si• defects (E' centers) in the oxide.

Characterization of a series of correlated electron-spin resonance (ESR) and photoluminescence (PL) lines in diamond grown by chemical vapor deposition is reported. The series consists of a set of structured PL bands in the range 1.8--2.3 eV, and ESR lines due to an $S=1$ center with $g=2.0039(1)$ and $D=35.8(1) \mathrm{mT}$ at 300 K. PL lines are shown to originate from a defect center with the ground state at 2.24 eV below the conduction band, and with several excited states. The whole set of data can be interpreted in terms of a defect containing a neutral interstitial Ni atom at the center of a divacancy.

The effect of post-deposition anneal in O2 at different temperatures (500-700 °C) on the microstructure and electrical properties of SiOx/ZrO2 gate dielectric stacks is investigated. It is shown that the as-deposited ZrO2 layers are partly amorphous and crystallize after post-deposition anneal. From the analysis of high-frequency capacitance-voltage (C-V) characteristics, positive (negative) fixed charge is found in the as-deposited layer when Al (Au) electrodes are used. Furthermore, positive charge is generated in the gate stack and the density of interface states is increased during post-deposition anneal in O2. Both positive charge and interface state density can be greatly reduced by an additional post-metallization anneal in H2 at low temperature (400 °C). The dielectric constant of the gate stack presents a large increase after O2 post-deposition anneal at 700 °C, which may be attributed to the partial transformation of the silicon oxide interfacial layer into a Zr silicate. The leakage current through the gate stack is reduced by several orders of magnitude after O2 annealing, consistent with the increase in SiOx layer thickness, as well as the reduction in bulk trap density revealed by the reduced hysteresis effect observed in the C-V characteristics. The temperature dependence of the current density through the gate stack is also reduced after the post-deposition anneal in O2, which is attributed to the reduction in the trap-assisted tunnelling contribution to the leakage current.

Ultra-thin (∼2 nm) Si-oxide films, grown by vacuum ultraviolet (VUV) enhanced oxidation of Si at 300 K, were studied using electron spin resonance monitoring of Si dangling bond-type interface defects. As a major impact of VUV photons. large densities (up to ∼ 9 x 10 12 cm -2 ) of P b and P 60 centers (interfacial (Si 3 ≡Si * ) are observed in VUV-grown (1 1 1) and (1 0 0) Si/SiO 2 , respectively. Their features indicate that, as compared to standard thermal Si/SiO 2 , the VUV Si/SiO 2 interface is under much enhanced stress. No Put defects are observed in VUV (100) Si/SiO 2 , ascribed to lack of high temperature oxide relaxation. This may appear pertinent as to the understanding of the defect's specific role in the interface structure. Microscopic understanding is provided for the known inferior electrical interface quality threatening low thermal budget oxide fabrication.

Thermal oxidation of Si intrinsically gives rise to the generation of defects at the Si/SiO 2 interface as a result of mismatch induced stress. In standard thermal (111)Si/SiO 2 , the dominant paramagnetic defect observed by electron spin resonance (ESR) is the P b centre (interfacial ·Si≡Si 3 ). In the present study, the inherently incorporated as-grown P b density (∼4.9×10 12 cm −2 ) was significantly enhanced to various levels, up to 3.1×10 13 cm −2 , by means of the previously unveiled method for P b creation through appropriate postoxidation annealing in H 2 . This resulted, among others, in the observation of a P b dependent anisotropic broadening of the ESR signal, partially arising from dipolar interaction within the essentially two-dimensional spin system. Successful quantitative simulation by a computational model has enabled detailed analysis of the line broadening mechanisms. The simulations reveal concentration related variations in the strain broadening contribution indicating a growing relaxation of the interfacial stress with increasing [ P b ]. The results are discussed in the light of the connection between defect generation and the relaxation of stress.

The electron spin resonance characterization of an undocumented paramagnetic centre in chemical vapour deposited diamond is reported. Successful fitting of the powder pattern-like spectrum characterized the originating defect as an S = 1 centre of spectroscopic splitting factor g = 2.003 86±0.000 05. The zero-field splitting parameters were determined as D = 358±1 G and E = 0±2 G at 294 K. Two hyperfine spectra were resolved, one ascribed to four equivalent C sites. Various suggestions as to the microscopic nature of the defect are explored. The centre is suggested to be an impurity stabilized divacancy-like defect.

The simultaneous action of passivation and dissociation during thermochemical interaction of trivalent interfacial Si traps (Pb’s;Si3≡Si⋅) with molecular hydrogen has been analyzed. A unified description is attained through solution of the simultaneous set of the first-order rate equations describing passivation and dissociation, under the restriction that the H2 concentrations at the interface and in the ambient are continuously equal. The analysis is given allowance by the recently attained physically consistent pictures for each of the separate steps of passivation in H2 and dissociation in vacuum, incorporating the existence of distinct spreads σEf and σEd in the respective activation energies. The assessment of heat treatment in H2 shows that, as compared to the fictitious case σEf=σEd=0, the effect of the existence of the spreads, for usual anneal times of 10–60 min in 1 atm H2, is to reduce the passivation efficiency by two orders of magnitude, while enhancing the optimum anneal temperature Tan fro...

The electrical characteristics of SiOx/ZrO2 and SiOx/Ta2O5 gate dielectric stacks are investigated. The current–density JG in these dielectric stacks is shown to be strongly temperature dependent at low voltage (below about 2 V), the more so in the ZrO2 stack. On the other hand, JG is much less temperature dependent at higher voltage. These results are consistent with a model which takes into account the direct tunneling of electrons across the SiOx layer and the trap-assisted tunneling of electrons through traps with energy levels below the conduction band of the high permittivity dielectric layer. The energy levels and densities of these electron trapping centers are estimated by fitting this trap-assisted tunneling model to the experimental results.

An electron spin resonance (ESR) study has been carried out on the ${P}_{b}$ centers (interfacial $\ensuremath{\cdot}{\mathrm{Si}\mathrm{\ensuremath{\equiv}}\mathrm{Si}}_{3})$ in standard thermal $(111){\mathrm{S}\mathrm{i}/\mathrm{S}\mathrm{i}\mathrm{O}}_{2},$ of which, in the as-grown state, a density $4.9\ifmmode\times\else\texttimes\fi{}{10}^{12}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ is inherently incorporated. The ${P}_{b}$ density was significantly enhanced to various levels through post oxidation annealing in ${\mathrm{H}}_{2}$ ambient at elevated temperatures. This resulted in the observation of distinct ${P}_{b}$ density-dependent magnetic field angle anisotropy in the ESR spectra, herewith definitely establishing the importance of the magnetic dipolar interactions within the two-dimensional ${P}_{b}$ defect system. Field angle dependence of dipolar origin is observed in linewidth, line shape, and resonance position. The data are interpreted within the framework of a computational model based on the magnetostatic approximation of the local magnetic field, which resulted in a detailed analysis of the line broadening mechanisms. The successful simulation provides evidence for ${P}_{b}$ density-dependent variations in the strain broadening contribution, indicating a growing relaxation of the interfacial strain with increasing ${P}_{b}$ density. Additionally, the spatial ${P}_{b}$ defect distribution is found to exhibit a self-avoiding behavior, with apparently no ${P}_{b}$ pairs occurring within third nearest-neighbor distance. These results are interpreted within a picture connecting defect generation with relaxation of interfacial strain. Magnetic susceptibility measurements reveal an almost purely Curie-type behavior of the ${P}_{b}$ system with Curie temperature ${T}_{c}l1.3\ifmmode\pm\else\textpm\fi{}0.8\mathrm{K}.$

The suppression of thermally induced generation of hole traps in SiO2 layers of Si/SiO2 and poly-Si/SiO2/Si structures by He ambient is analyzed as a function of the gas pressure p. The pressure dependence of the suppression efficiency is found close to p2/3. This pressure dependence and the observed reduced suppression efficiency of heavier noble gases (Ne, Ar) are interpreted as indications that the gas atom dissolved in SiO2 should approach close to the degradation-prone site in order to prevent the thermally induced bond break. This result suggests that a short-range interaction between noble gas atoms and the Si/SiO2 network atoms is at the basis of the degradation blockage effect.

Characterization of the structure and defects in detonation synthesis, ultradisperse diamond (UDD) is reported. X-ray and proton nuclear magnetic resonance results on UDD powders are interpreted in terms of the different structure of the shell of UDD particles, produced under different conditions. In spite of the comparable contents of carbon and nitrogen atoms in the precursor, no (

An electron-spin-resonance study has been carried out, both isothermally and isochronically, of the recovery under vacuum annealing from the hydrogen passivated state (symbolized as $\mathrm{H}{P}_{b})$ of paramagnetic ${P}_{b}$ centers $({\mathrm{Si}}_{3}{\mathrm{\ensuremath{\equiv}}\mathrm{Si}}^{\ifmmode\bullet\else\textbullet\fi{}})$ at the ${(111)\mathrm{S}\mathrm{i}/\mathrm{S}\mathrm{i}\mathrm{O}}_{2}$ interface. Previous work had reported simple exponential decay of $[{P}_{b}\mathrm{H}]$ vs time, taken as key evidence for the process obeying the first-order rate equation $d[{P}_{b}\mathrm{H}]/dt=\ensuremath{-}{k}_{d}[{P}_{b}\mathrm{H}],$ where ${k}_{d}{=k}_{\mathrm{do}}\mathrm{exp}(\ensuremath{-}{E}_{d}/\mathrm{kT})$ and ${E}_{d}$ the single-valued activation energy. This inference, however, suffered from inadequate data. In contrast, experimental upgrading reveals manifest nonsimple exponential decay, which, within the simple thermal model, reveals the existence of a distinct spread ${\ensuremath{\sigma}}_{{E}_{d}}$ in ${E}_{d}.$ Incorporation of Gaussian spread in ${E}_{d}$ leads to a consistent generalized simple thermal model, that matches physical insight. The broad range of data enabled unbiased determination of the physical parameters involved, giving ${E}_{d}=2.83\ifmmode\pm\else\textpm\fi{}0.02\mathrm{eV},$ ${\ensuremath{\sigma}}_{{E}_{d}}=0.08\ifmmode\pm\else\textpm\fi{}0.03\mathrm{eV},$ and attempt frequency ${k}_{\mathrm{do}}=(1.6\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}{10}^{13}{\mathrm{s}}^{\mathrm{\ensuremath{-}}1},$ close to the Si-H waging mode frequency, which provides a clue to the atomic dissociation mechanism. The spread ${\ensuremath{\sigma}}_{{E}_{d}}$ results from the interfacial stress-induced variations in ${P}_{b}$ defect morphology. The body of data is found incompatible with second-order kinetics, thus exposing ${P}_{b}\mathrm{H}$ dissociation as an individual process. Combination with the previous generalized thermal model for ${P}_{b}$ passivation with ${\mathrm{H}}_{2}$ culminates in a consistent unified picture of the ${P}_{b}$-hydrogen interaction kinetics.

Comparison between the densities of positive charge and paramagnetic E´ centres (O3 Si defects) generated in thermal SiO2 layers on Si by 10 eV photons at different electric field strengths in the oxide demonstrates that the paramagnetic states cannot be associated with positively charged centres, i.e., the E´ centre is neutral. The variation in E´ density results from the balance between activation by irradiation and passivation with radiolytic hydrogen. Therefore, the neutral diamagnetic state of the defect is ascribed to the O3 Si-H fragment in the SiO2 network, which is converted into an E´ centre by radiation-induced hydrogen cracking.

Generation of electrically active defects at the interfaces between hexagonal SiC polytypes and thermally grown oxide was studied under conditions of electron injection, which simulates the SiC/oxide interface damage induced by plasma processing or hot-carrier injection in SiC device structures. The injection-induced degradation of 4H, 6H–SiC(0001)/SiO 2 interfaces is found to be enhanced significantly when compared with the structurally isomorphic (111)Si/SiO 2 interface, particularly in terms of the generation of interface acceptor-type defects. Moreover, a much higher density of these defects is generated in the oxidized 4H–SiC as compared to 6H–SiC. Most of these interface states are resistant against passivation with hydrogen up to 500°C, which suggests these to be related to some stable bonding configuration created at the SiC/SiO 2 interface during electron injection. The observed enhancement of the SiC/oxide interface degradation with increasing amount of carbon at the semiconductor surface points to a relationship between the degradation process and formation of some carbon-related defect states. The sensitivity of the degradation to the SiC polytype suggests that the crystal surface imperfections may also be part of the defect generation (activation) process.

Degradation of ultrathin ( d ox =3–6 nm) oxides on (100)Si under irradiation with deep-UV ( hν =10 eV) photons was studied in order to evaluate the possible oxide damage by deep-UV lithography. The irradiation was found to lead to a significant enhancement in electrical conduction of the ultrathin oxides. The leakage current observed after irradiation correlates with the concentration of radiolytic atomic hydrogen in the oxide and includes two components. A first transient one is related to thermally unstable defects similar to the H-related donor interface states observed after irradiation of thicker oxides. The second, stable component correlates with the enhanced density of Si dangling bond defects in the oxide ( E ′ center) which points to the H-assisted rupture of Si O bonds. It is also found that the leakage currents observed after electrical stress and after deep-UV irradiation exhibit similar annealing behavior. The two revealed sources of the degradation-induced leakage current may account for the enhanced electron transport across ultrathin Si oxides under various circumstances.

The thermal interaction kinetics of interfacial Si dangling bond P b defects (Si 3 ≡Si·) in (1 1 1)Si/SiO 2 , including passivation in molecular hydrogen (pictured as P b H formation) and dissociation in vacuum, is readdressed. An initial simple thermal model had concluded simple exponential decay for both processes characterised by single-valued activation energies E f and E d , respectively. The picture, however, is found inadequate. In the first part, the results are reviewed of a previous expanded electron spin resonance (ESR) study of the passivation step, leading to a consistent model for passivation, in which the existence of a significant spread σ E f in E f was exposed. In the present work, the results are presented of a similar study on the dissociation kinetics, providing distinct extension of the data set based on proper ESR defect density probing. Unlike previous conclusion, manifest non-simple exponential decay is exposed, which within the simple thermal model reveals the existence of a distinct spread σ E d in E d . Incorporation of this results in a consistent generalised thermal model, the solid set of data enabling unbiased extraction of the pertinent physical parameters, such as the attempt frequency k d0 =(1.6±0.5)×10 13 s −1 , close to the Si–H bending mode. The spreads in E d and E f are the natural manifestation of the stress-induced non-uniformity in atomic P b morphology. The combination of both studies leads to a consistent unified picture of the P b -(molecular) hydrogen interaction kinetics that matches underlying physical insight, based on the rate limiting reactions P b +H 2 →P b +H and P b H→P b +H. It is evidenced that the model also applies to the interfacial Si dangling bond defects in (1 0 0)Si/SiO 2 .

Defects generated by 10 eV photons in ultrathin (3‐6 nm) layers on Si are studied using electron spin resonance and laser photoionization spectroscopy in relation to the observed enhancement of electrical conduction of the oxide. The leakage current is found to include two components: a transient one, related to thermally unstable defect states, and a thermally stable portion. The former current behavior strongly resembles that of the donor interface states observed in structures with thick oxides and is associated with bonding of atomic H in the oxide layer. The stable component correlates with the H‐assisted oxide damage resulting in Si‒O bond rupture. The exposed similarity between leakage currents observed after irradiation and after electrical stress suggests the hydrogen bonding in these two states to be responsible for the dielectric failure of under stress conditions. © 1999 The Electrochemical Society. All rights reserved.

Observation by electron spin resonance of the full angular dependence of the hyperfine (hf) interaction spectrum associated with the interfacial Pb1 defect in thermal (100)Si SiO 2 shows that the dominant interaction arises from a single 29Si atom. The hf tensor displays weakly monoclinic I (nearly axial) symmetry, with the principal axes of the g and hf tensors coinciding. Observation of an identical hf structure consolidates the presence of the Pb1 defect in porous Si. A molecular orbital analysis indicates that the unpaired electron resides for ∼58% in a single unpaired Si hybrid orbital, found to be 14% s-like and 86% p-like, with the p-orbital pointing closely along a 〈211〉 direction at 35.26° with the [100] interface normal. Excluding oxygen as an immediate part of the defect, the results establish the Pb1 core as a tilted (∼20° about 〈011〉) Si3Si• unit. The moiety is pictured as part of a strained SiSi dimer near the interface.

SiO2 films were grown in dry oxygen on Si (100) substrates at various temperatures, then annealed for various times and temperatures. The density of the oxides was found to depend on the growth temperature, and on the anneal time and temperature. The amount of positive charge trapped in these oxides during vacuum ultraviolet hole injection was found to be inversely related to the oxide density, regardless of how the oxide was prepared. Comparison of the density of trapped holes with the density of E' centers detected by electron spin resonance indicates that E' centers cannot account for most of the trapped positive charge. A model to explain these observations is proposed.

Annealing-induced degradation of Si SiO 2 has been studied in noble gas ambients (He, Ne, Ar). The vacuum postoxidation annealing induced interface degradation in (111) Si SiO 2 , previously identified as intense creation of interfacial Si dangling bond defects (P b s: Si 3 Si•) from ∼640 °C on, is found remarkably impeded, inversely proportional to the gas atomic diameter: He fully blocks the process up to ∼800 °C, Ne suppresses partially, while the effect of Ar is marginal. This is attendant with a significant reduction of oxide degradation, including suppression of the degradation of the insulating properties of ultrathin SiO 2 layers and generation of hole trapping centers. The data support the degradation model based on interfacial SiO(g) release, showing that the degradation mechanism may just occur as the result of the existence of a typical interstice/channel structure in thermal SiO 2 . The observed process represents blocking of a chemical reaction in a physical way.

Positive charge created at the ${\mathrm{S}\mathrm{i}/\mathrm{S}\mathrm{i}\mathrm{O}}_{2}$ interface by lithium diffused through the substrate silicon is compared with the charge produced at this interface by hydrogen exposure. The charged centers created in both cases are thermally stable up to 400 \ifmmode^\circ\else\textdegree\fi{}C, show no correlation with the presence of dangling-bond defects at the ${\mathrm{S}\mathrm{i}/\mathrm{S}\mathrm{i}\mathrm{O}}_{2}$ interface, and are spatially located in the oxide at $2\ifmmode\pm\else\textpm\fi{}1\AA{}$ above the Si substrate plane. The impurity atoms (H, Li) are suggested to be bonded to the first layer of bridging oxygens in impurity-induced valence-alternation states, i.e., $[{\mathrm{Si}}_{2}\mathrm{=}\mathrm{OH}{]}^{+}$ and $[{\mathrm{Si}}_{2}\mathrm{=}\mathrm{OLi}{]}^{+}.$ It is hypothesized that the decomposition of the positively charged state at elevated temperatures is involved in the observed impurity-assisted bond breaking at the ${\mathrm{S}\mathrm{i}/\mathrm{S}\mathrm{i}\mathrm{O}}_{2}$ interface.

Correlation between the shape of Raman, photoluminescence (PL) and Electron Spin Resonance (ESR) signals in CVD diamond films was examined for both undoped and nitrogen-doped films. No correlation was observed between the shift of the diamond Raman line and its linewidth, even for the films produced under essentially the same growth conditions. It was found that the increase in the width of the diamond Raman peak interrelates with the broadening of zero-phonon PL lines and the changes in the structure of the ESR signal from the substitutional nitrogen (P1) center. Observed changes in the ESR spectra are interpreted in terms of reduction of the symmetry of the P1 center induced by internal stress.

Spectroscopic ellipsometry was used to determine the density of oxides thermally grown on Si substrates as a function of the oxidation temperature, and the time and temperature of postoxidation anneals. All the oxides were found to be denser than fused silica. The density of the as-grown oxides was found to decrease as the growth temperature was increased. Postoxidation anneals were found to reduce the oxide density; high temperature or long-time anneals caused the greatest reduction in density. Holes alone, or holes and electrons, were injected into the oxides by irradiating with vacuum ultraviolet light or x rays under electric field bias. Using capacitance–voltage measurements, it was found that low-density oxides trap charge more efficiently than high-density oxides. Electron spin resonance measurements indicated that, for most of these oxides, the number of paramagnetic defects was substantially smaller than the number of trapped charges. It is hypothesized that the additional, nonparamagnetic, charge is in the form of protons trapped near network oxygen atoms that have large Si–O–Si bond angles. The number of these large-angle bonds in the near-interfacial oxide increases as the oxide density decreases, explaining the observed correlation between the charge trapping and the oxide density.

Annealing of interfaces between SiO 2 and (111)Si, (100)Si in H 2 in the temperature range 450–800°C is found to introduce a considerable density (up to 10 13 cm −2 ) of positively charged centres. There is no comparable density of dangling bonds initially present nor generated during the annealing at the Si/SiO 2 interfaces or in the SiO 2 layer that could account for the observed hydrogen bonding. Therefore, the hydrogen is suggested to be trapped in the positively charged valence alternation state 3-fold coordinated oxygen resembling the well known hydronium ion (H 3 O) + .

The process of interface degradation induced in (111)Si/SiO2 by postoxidation annealing (POA) in vacuum, previously identified by electron spin resonance (ESR) as creation of persistent Pb (Si/Si3) interface defects, is found to be strongly enhanced (≈6 times) when performed in H2 ambient, and additionally, as sensed by ESR, the treshold temperature for creation is lowered from ≈640°C for vacuum to ≈550°C. It thus appears that POA in H2 rich ambient, such as routinely applied to passivate interface states (preexisting Pbs) naturally introduced during oxidation, effectively creates extra defect entities, which then have to be passivated additionally. The results point to the key role of the POA ambient in interface degradation. The data reveal the atomic nature of one of the mechanisms of the electrically long known H-induced POA generation of detrimental interface states. PACS numbers: 85.30.De; 68.35.Dv; 73.40.Ty; 76.30.Mi

Direct experimental evidence for the dipolar interactions within the two-dimensional P b defect system at the Si/SiO 2 interface is provided by the observation of anisotropy in the electron spin resonance spectra. This observation was enabled through distinct interface degradation by post-oxidation annealing in H 2 , leading to enhanced P b density. The data are interpreted within the framework of a computational model based on the magnetostatic approximation of the local field. The results suggest P b defects to exhibit a self-avoiding behaviour and confirm their occurrence as related to the release of interface stress.

In order to explore the possibility of bandgap engineering in binary oxide insulators we studied photoconductivity of nanometer-thin Hf oxide layers containing different fractions of cations of another sort (Si, Al, Sr, or Ce) deposited on (100)Si. The smallest bandgaps of the Hf:Al and Hf:Ce oxides are close to the values found in elemental Al"2O"3 (6-6.2eV) and HfO"2 (5.6eV), respectively, and show little sensitivity to the concentration of Al or Ce. This result suggests that the oxide sub-network with the largest bandgap preserves its gap energy, while development of a narrower gap is prevented, likely, by dilution of the second cation sub-network. In Hf:Si oxide samples photoconductivity thresholds of 5.6-5.9eV, corresponding to the bandgap of HfO"2, were observed for all studied Si concentrations, suggesting phaseseparation to occur during deposition. Photoconductivity of SrHfO"3 exhibits two thresholds, at 4.4 and 5.7eV, which are close to the bandgaps of elemental SrO"2 and HfO"2, respectively. These gap values indicate the phase separation also to occur in this binary oxide. Through this work photoconductivity is demonstrated to be a feasible method to trace phase separation in binary oxides, even in nanometer-thin layers.

The electronic structure of silicon nanocrystals (~2-6nm in size) embedded in cubic Gd"2O"3 epi-layers grown on (111) Si was analyzed using spectroscopic ellipsometry and photocharging methods. With decreasing nanocrystal size down to the 2nm range, the optical absorption exhibits a spectacular shift in spectral threshold to 2.9+/-0.1eV, as compared to the 1.12eV absorption edge of the bulk Si crystal. This shift suggests a significant influence of quantum confinement on the Si nanocrystal/oxide interface band diagram, which effect is shown to be predominantly caused by an upshift of the nanocrystal conduction band.

An optimized electron spin resonance study has resulted in the observation of the full angular dependence of the hyperfine interaction spectrum associated with the unpaired electron of the ${P}_{b1}$ point defect at the thermal $(100){\mathrm{S}\mathrm{i}/\mathrm{S}\mathrm{i}\mathrm{O}}_{2}$ interface, showing that the dominant interaction arises from a single ${}^{29}\mathrm{Si}$ isotope. The hyperfine tensor exhibits nearly axial (weakly monoclinic I) symmetry with ${A}_{\ensuremath{\parallel}}$ $(\ensuremath{\parallel}〈211〉)=167\ifmmode\pm\else\textpm\fi{}3\mathrm{G}$ and ${A}_{\ensuremath{\perp}}=107\ifmmode\pm\else\textpm\fi{}4\mathrm{G}.$ Molecular-orbital analysis indicates that the unpaired electron resides for \ensuremath{\sim}58% in a single unpaired Si hybrid orbital, found to be 14% s like and 86% p like, with the p orbital pointing closely along a 〈211〉 direction at 35.26\ifmmode^\circ\else\textdegree\fi{} with the [100] interface normal. If O is excluded as an immediate part of the defect, the results establish the kernel of the ${P}_{b1}$ defect as a tilted (\ensuremath{\sim}22\ifmmode^\circ\else\textdegree\fi{} about 〈01\ifmmode\bar\else\textasciimacron\fi{}1〉) asymmetric, likely strained, ${\mathrm{Si}}_{3}{\mathrm{\ensuremath{\equiv}}\mathrm{Si}}_{\mathrm{\ifmmode\bullet\else\textbullet\fi{}}}$ unit. Like ${P}_{b}$ and ${P}_{b0},$ ${P}_{b1}$ is a prototype Si dangling bond defect. All available structural information may, in principle, be compatible with the moiety being incorporated as part of a defected strained Si-Si dimer configuration at slightly subinterfacial position. The dimer has previously been advanced as a natural building block in matching ${\mathrm{SiO}}_{2}$ to (100)Si.

A systematic study of the flat-band voltage (Vfb) shift of Ru gated metal-oxide-semiconductor (MOS) capacitors subjected to thermal treatment in O2 has been performed. The dependence of the Vfb shift on the thickness of Ru, anneal temperature and time is studied. The Vfb shift is ascribed to the shift of metal gates’ work function (WF), and is not significantly dependent on the type of dielectric (HfO2 or SiO2). From time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurement, it was found that after thermal treatment in 18O2, 18O penetrated through Ru and was incorporated in the Ru/dielectric interface region. We believe that the formation of the thin interfacial RuOx layer is responsible for the Vfb shift.

Oxygen vacancy centers in buried oxide (BOX) layers of Si/SiO 2 /Si structures produced by implantation of oxygen ions into silicon and subsequent internal thermal oxidation (ITOX) were studied by monitoring hole trapping and paramagnetic properties. During the ITOX process the BOX layer is augmented by thermally grown oxide. We have found that this additional buried thermal oxide layer has nearly the same density of O vacancies as the initial buried oxide, and an even higher number of oxygen vacancy clusters (E' δ centers), even though the superficial Si layer was saturated by oxygen. This result suggests the generation of oxygen vacancies in Si-confined SiO 2 to be due to temperature driven interaction between Si and SiO 2 . The clustering of the oxygen vacancies observed in all the high temperature oxides (both buried and unconfined), and the inverted relationship between the vacancy charge and its paramagnetic state point toward changes in the SiO 2 network structure as compared to the conventional oxides.

The observation of the electron spin resonance hyperfine (hf) spectra associated with the unpaired electron of the interface defect in thermal shows that the dominant interaction arises from a single isotope. The hf tensor displays weakly monoclinic I (nearly axial) symmetry, with the principal axes of the g and hf tensors coinciding. A molecular orbital analysis indicates that the unpaired electron resides for in a single unpaired Si hybrid orbital, found to be 14% s-like and 86% p-like, with the p-orbital markedly pointing closely along a direction at with the [100] interface normal. With oxygen not constituting an immediate part of the defect, the results firmly establish the key part of the defect as a tilted ( about ) unit.

Exposure of $\mathrm{Si}/{\mathrm{SiO}}_{2}$ and $\mathrm{SiC}/{\mathrm{SiO}}_{2}$ interfaces to hydrogen in the temperature range of $450\char21{}800\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ is found to produce a considerable density (up to ${10}^{13}\mathrm{cm}{}^{\ensuremath{-}2}$) of positively charged centers. The absence of any correlation between the charging process and the presence of Si dangling bond centers in ${\mathrm{SiO}}_{2}$ or at the $\mathrm{Si}/{\mathrm{SiO}}_{2}$ interface indicates hydrogen bonding in a valence alternation state which is suggested to be an over-coordinated oxygen center $[{\mathrm{Si}}_{2}=\mathrm{OH}{]}^{+}$ stabilized by ${\mathrm{SiO}}_{2}$ network rearrangement at the interface.

The interface degradation induced in (111) by postoxidation annealing in vacuum, previously identified by electron spin resonance as intense creation of interfacial Si dangling bond defects from on, is found to be remarkably suppressed when annealing in He ambient. On the time scale of , He firmly blocks the degradation up to , from which temperature on creation gradually rises, though much suppressed as compared to the vacuum case. At , the density drops abruptly to a value ( about one-third that of the as-oxidized state density, indicating an electrically much improved interface. The transition results from the known thermal cooperative restructuring of the layer, completed at . The data support the degradation model based on interfacial SiO(g) release, where He is seen as rapidly occupying the SiO accessible sites in the oxide thus inhibiting the degradation mechanism through impeding SiO removal - a prerequisite for the degradation to occur.

The correlation between the detrimental electrically active interface traps and the electron-spin-resonance-active point defects ${P}_{b0}$ and ${P}_{b1}$ (unpaired Si orbitals) was studied through controlled variation, both relatively and absolutely, of the defect bath densities. Unlike previous inference, no electrical activity of ${P}_{b1}$ as an interface state could be traced, thus questioning its relevance for device fabrication, while all ${P}_{b0}$'s appear active. A fundamental reason is inferred as to why the (100) Si surface dominates device fabrication.

Electron spin resonance (ESR) on thermal (100)Si/SiO2 predominantly exhibiting either the Pb0 or Pb1 interface defect confirms the Pb1 point symmetry as monoclinic-I with g1=2.0058, g2=2.00 735±0.00 010, and g3=2.0022, where the g2 direction is at 3°±1° (towards the interface) with a 〈111〉 direction at 35.3° with the interface plane. Its line width is found weakly dependent on magnet angle, exhibiting a strain induced spread σg⊥∼0.00 035 in g⊥ about 2–3 times less than typical for Pb in (111)Si/SiO2. For Pb0, an axially symmetric g matrix is observed, with g∥=2.0018 and g⊥=2.0081, and σg⊥∼0.0009. From comparison of salient ESR data, it is concluded that Pb and Pb0 are chemically identical; however, systematic fabrication-induced variations in defect environment will lead to second order systematic shifts in average properties. The Pb1 defect is provisionally pictured as an unpaired Si bond on a defect Si atom at slightly subinterface plane position in the Si substrate, possibly facing an oxygen atom.

Annealing of thermal in hydrogen in the temperature range is found to introduce a considerable density (up to ) of positively charged centres, ascribed to H bonding. However, there is no comparable density of dangling bonds initially present nor generated at the interface that could account for the observed hydrogen bonding. The hydrogen is suggested to be trapped in the positively charged valence-alternation state - threefold-coordinated oxygen - resembling the well known hydronium ion . The activation energy of dissociation of this state was found to be about 2.4 eV.

The microstructure and electrical properties of buried SiO2 layers produced in silicon by the implantation of oxygen ions are analyzed in terms of implantation parameters and supplemental incorporation of oxygen. The buried oxides show inhomogeneous etching in aqueous HF, revealing the presence of a crystalline oxide phase and Si-enriched regions. Silicon enrichment in SiO2 is found in the form of Si inclusions and oxygen deficient network defects. The former are found to be sensitive to the oxygen implantation profile, and may arise as a result of a blockage of Si outdiffusion by crystalline oxide inclusions. The network defects, in turn, are predominantly generated during high temperature postimplantation annealing, caused possibly by some mechanism of silicon transport from the interfaces into the bulk of oxide. The electron trapping and electrical conduction characteristics of buried oxides are found to correlate with the density and size of the inhomogeneities. By contrast, hole trapping and the gene...

The interaction of fused silica (SiO2) with gaseous SiO during annealing at ∼1140 °C has been studied by electron spin resonance (ESR). In contrast with annealing in vacuum, this results in the generation of an isotropic defect in SiO2 of g=2.0028 and peak-to-peak width 3.6 – 6 G. These spectroscopic properties are similar to those of the signal found generated in the oxide layer of standard thermal Si SiO 2 structures upon postoxidation annealing in vacuum a ≳ 960 °C, assigned to S centers, tentatively ascribed previously to E'-like defects of the type O2SiSi· or OSi2Si·. An attendant observation is enhanced sensitivity of the SiO2 network to photogeneration (VUV) of E'γ defects (O-vacancy center O3Si·). The results suggest that interaction of interface generated SiO with the SiO2 network may explain the degradation of the thermal Si SiO 2 structure during postoxidation annealing in vacuum.

Semiconductor/insulator interface states with energy levels above the semiconductor bandgap have so far escaped direct detection. From experiments on the photon stimulated tunneling of electrons at the interfaces of SiO 2 with Si and SiC, direct evidence is provided for the presence of defects with electron binding energy of 2.8 eV relative to the SiO 2 conduction band edge - well above the silicon bandgap. The defects are located in the near interfacial oxide layer, their density being sensitive to the silicon enrichment of SiO 2 . A remarkable correlation is observed between the optically stimulated tunneling transitions and the dark conductivity for various oxide layers, revealing the defects discovered as the common origin of trap-assisted electron injection phenomena in SiO 2 .

Experiments on the photon stimulated tunneling of electrons at the interfaces of Si${\mathrm{O}}_{2}$ with Si and SiC demonstrate the presence of defects with electron binding energy of 2.8 eV relative to the Si${\mathrm{O}}_{2}$ conduction band, well above the semiconductor band gap. These defects, which so far escaped direct detection, are located near interfacial oxide layers, their density being sensitive to the silicon enrichment of Si${\mathrm{O}}_{2}$. The discovered defects appear to be the origin of the trap-assisted electron injection phenomena in Si${\mathrm{O}}_{2}$.

The generation of defects in buried oxide layers in silicon-on-insulator structures by vacuum ultraviolet radiation is studied using electron/hole trapping measurements and electron spin resonance. The oxide layers produced by oxygen implantation show trap generation near the irradiated oxide surface, in contrast to thermally grown and bonded oxides, in which the defects are produced over the entire oxide volume. Spatially confined trap production is associated with the limited length of radiolytic hydrogen diffusion in the oxide during irradiation due to the enhanced interaction of hydrogen with the oxide network.

This chapter overviews charge properties of oxide and interface paramagnetic defects in semiconductor/oxide entities, primarily Si/SiO2, as revealed by correlative analysis of electron spin resonance data and electrical analysis. The role of dangling bond defects in electrical degradation phenomena induced by bias-temperature stress or irradiation is discussed. In particular, the importance of hydrogen/proton-mediated interactions is underlined on the basis of the available experimental evidence.

Selected physical and electrical characterization of gate-oxide defects is reviewed. Interfacial dangling bond defects at interfaces of Si and SiGe are characterized electrically and compared to the electron spin resonance data. It is found that additional silicon dangling bonds (Pb0-ceters) acting as amphoteric interface traps are generated upon oxygen scavenging anneal. A close density of Pb0 centers is also found in Si/SiGe/Si/HfO2 stack. The Ge dangling bond defects (Ge Pb1 centers) found at interfaces of SiGe with thermal SiO2 are shown to behave as acceptor centers. The properties of individual gate-oxide defects in FETs are studied with Time-Dependent Defect Spectroscopy (TDDS), an electrical characterization technique. The primary properties of a defect are its capture and emission time constants, both dependent on the local electric gate field and the temperature. Considering the wide distributions of these defect properties, complete characterization of many defects is required over the full gate and drain voltage range from 0 to VDD at different temperatures. This is desirable in order to model degradation for large, “analog” FETs and to model the ΔVth-variability of deeply-scaled FETs. The impact of individual charged defects on transistor properties is then discussed. It is shown that the shift in the threshold voltage is exponentially distributed, with a small fraction of defects causing significant shifts of tens of mV. The average impact per charged defect is experimentally confirmed to be increasing with the gate oxide thickness, the substrate doping, and with the decreasing FET area. The average impact per charged defect is found to be reduced in SiGe substrates, contributing to lower degradation of SiGe-based FETs. In low-doped substrates, other sources of variability, such as interface states, are shown to take over. The impact of a single charged gate-oxide defect on the full I-V characteristic is measured and corroborated by atomistic device simulations, thus enabling the path to compact modeling of degraded deeply-scaled FET devices. Finally, the model explaining the correlation between drain and gate current RTN is discussed.

The interaction of silicene, the silicon counterpart of graphene, with (0001) ZnS surfaces is investigated theoretically, using first-principles simulations. The charge transfer occurring at the silicene/(0001) ZnS interface leads to the opening of an indirect energy band gap of about 0.7 eV in silicene. Remarkably, the nature (indirect or direct) and magnitude of the energy band gap of silicene can be controlled by an external electric field: the energy gap is predicted to become direct for electric fields larger than about 0.5 V Å-1, and the direct energy gap decreases approximately linearly with the applied electric field. The predicted electric field tunable energy band gap of the silicene/(0001) ZnS interface is very promising for its potential use in nanoelectronic devices. © the Owner Societies 2013