Effect Of Post-deposition Annealing Research Articles

Bias–stress-induced threshold voltage shift dependence of negative charge trapping in the amorphous indium tin zinc oxide thin-film transistors

Indium tin zinc oxide (ITZO)-based thin-film transistors (TFTs) were fabricated by dc magnetron sputtering in Ar + O2 reactive gas, at room temperature. We present the effect of post-deposition annealing of ITZO thin films on the oxygen vacancies and on the characteristics of TFT devices. When the annealing temperature was increased from room temperature to 350 °C, the resistivity of ITZO film increased from 2.05 × 101 to 2.60 × 103 Ω cm and the interface trap density (Nt) of the TFTs reduced from 3.18 × 1013 to 4.83 × 1011 cm−2. The TFT with the ITZO film which was annealed at 350 °C showed a very small shift in turn-on voltage, even after applying positive bias stress of +12 V for 104 s. The current–voltage characteristics of 350 °C annealing temperature sample indicated that these TFTs were in an enhanced mode of transistor operation with a high on-to-off current ratio of ∼1.26 × 106, high field-effect mobility of 14.17 cm2 V−1 s−1, and low subthreshold slope of 1.23 V/dec. The trapping time reduced from 3720 to 1546 s as the annealing temperature increased from room temperature to 350 °C. These results suggest that thermal annealing played an important role in reducing defects as well as improvement in stability of the TFTs.

Post-deposition annealing influenced structural and electrical properties of Al/TiO2/Si gate capacitors

Titanium dioxide (TiO2) thin films are deposited on unheated p-Si (100) and quartz substrates by employing DC reactive magnetron sputtering technique. The effect of post-deposition annealing in air at temperatures in the range 673–973K on the structural, electrical, and dielectric properties of the films was investigated. The chemical composition of the TiO2 films was analyzed with X-ray photoelectron spectroscopy. The surface morphology of the films was studied by atomic force microscope. The optical band gap of the as-deposited film was 3.50eV, and it increased to 3.55eV with the increase in annealing temperature to 773K. The films annealed at higher temperature of 973K showed the optical band gap of 3.43eV. Thin film capacitors were fabricated with the MOS configuration of Al/TiO2/p-Si. The leakage current density of the as-deposited films was 1.2×10−6A/cm2, and it decreased to 5.9×10−9A/cm2 with the increase in annealing temperature to 973K. These films showed high dielectric constant value of 36.

Effects of post-deposition annealing on morphology and optical properties of electron beam evaporated Bromoaluminium phthalocyanine thin films

In this paper, effects of post-deposition annealing on morphology and optical properties of electron beam evaporated Bromoaluminium phthalocyanine thin films have been investigated. Surface morphology of the films have been characterized by field emission scanning electron microscopy (FESEM). The FESEM micrographs have shown densely packed nanoparticles and nanorod-like structures for the films annealed at different temperatures. Conditions leading to β-phase have been identified by monitoring post-deposition annealing using optical absorption spectroscopy (UV–Vis). The optical absorption measurements on the as-deposited and annealed films shows that the absorption mechanism is due to direct transition. Also, it is found that the optical band gap decreases with increase in annealing temperature.

Effect of post-deposition annealing on the growth of nanocrystalline TiO2 thin films and elastic anisotropy of rutile phase at different temperatures

Abstract In this work, predominant anatase and rutile nanocrystalline TiO 2 thin films deposited by DC reactive magnetron sputtering are annealed at different temperatures. Raman spectroscopy and XRD experiments suggest phase transformations to rutile at elevated temperatures. A sharp increase of rutile content of the films confirms rutile phase stability above 650 °C. The variations in unit cell parameters are attributed to the changes in microstrain and macrostrain present in the films. The Miller indices dependence of Young’s modulus of rutile nanocrystals is estimated on the basis of the Reuss approximation for polycrystalline aggregates. Young’s modulus shows strong anisotropy. The elastic anisotropy is introduced in the Williamson–Hall (WH) method for the estimation of isotropic stress and uniform deformation energy density. Microstrain decreases with increasing annealing temperature. Lattice microstrain of nanocrystalline rutile is anisotropic. Along a particular crystallographic direction, rutile transformed from anatase rich films exhibit lower microstrain.

Annealing induced compositional changes in SmCo5/Fe/SmCo5 exchange spring trilayers and its impact on magnetic properties

SmCo5/Fe/SmCo5 sandwich configurations have gained renewed interest when compared to the conventional SmCo5/Fe bilayers, as they exhibit enormous scope to impart high energy product values with strong magnetization reversal behavior. The compositional changes that occur in the intermediate soft layer upon annealing play a critical role in determining the phase chemistry, as well as magnetic performance of the trilayers and herein we address such a study. SmCo5/Fe/SmCo5 sandwich films with fixed layer thicknesses of SmCo5 (25nm) and Fe (8nm) were grown by sputtering on Cr buffered Si (100) substrates and subsequently, annealed at different temperatures: 673, 773 and 873K. The effect of post-deposition annealing on the structure, composition and magnetic properties of the trilayer architecture was investigated by X-ray diffraction (XRD), Rutherford back-scattering (RBS) and super-conducting quantum interference device (SQUID), respectively. The XRD studies showed significant decrease in the lattice parameter values with increasing annealing temperature, which suggests an increase in the diffused Co-content in the Fe-intermediate layer. The XRD results were further validated by RBS measurements, which confirmed that both composition and thickness of the Fe-intermediate layer were strongly affected by the annealing temperature. The SQUID measurements demonstrated the existence of in-plane anisotropy and strong exchange coupling between the hard and soft layers for all the annealed sandwich films. The trilayer stack annealed at 773K showed the best magnetic performance such as high coercivity (814kA/m), remanence (944kA/m) and energy product (243kJ/m3).

Effect of oxygen species on the positive flat-band voltage shift in Al2O3/GaN metal–insulator–semiconductor capacitors with post-deposition annealing

The electrical characteristics of the Al2O3/GaN metal–insulator–semiconductor capacitors are investigated focusing on the effect of post-deposition annealing (PDA) in O2 ambient. X-ray photoelectron spectroscopy analyses reveal that gallium oxynitride (GaOx Ny) interfacial layer is formed at Al2O3/GaN interface even in non-annealed sample due to incorporation of the released oxygen from Al2O3. After PDA in O2 ambient, the GaOx Ny interfacial layer becomes oxygen-rich which plays a role in increasing negative effective oxide charge at the Al2O3/GaN interface and hence positively shifting the flat band voltage (VFB) for the capacitors.

Effects of postdeposition annealing on a high-k-last/gate-last integration scheme for 20 nm nMOS and pMOS

The authors report the use of postdeposition annealing (PDA) to improve the performance of a high-k (HK)-last/gate-last integration scheme involving the use of a chemical oxide interfacial layer (IL). They find that the chemical oxide IL can form Hf-silicate at the HK/IL interface to provide a larger effective k value and a smaller equivalent oxide thickness. They also find that they can achieve a small gate leakage current density (Jg) and minimal flat-band voltage (Vfb) degradation by PDA in O2 atmosphere. Furthermore, they find that Jg and Vfb can be further improved by optimizing the metal gate stack.

Novel encapsulated ITO/arc-ZnO:TiO2 antireflective passivating layer for TCO conducting substrate prepared by simultaneous radio frequency-magnetron sputtering

Graphical abstractDisplay Omitted Highlights? We fabricated ITO/arc-ZnO:TiO2 antireflective TCO with blocking layer capability for DSSCs. ? Step-down interference structure based on double layer antireflection coating was used. ? Two maximum transmittance peaks around 440nm and 760nm could be seen. ? About 11% and 3% reduction in reflectance compared to bare ITO alone were achieved. ? Stable properties of antireflective TCO against annealing temperature achieved. A thermally stable multilayered transparent conducting oxide utilizing nanocomposite ZnO:TiO2 antireflection thin film (arc-ZnO:TiO2) on an indium-tin oxide (ITO) substrate has been prepared by radio frequency-magnetron sputtering. The effects of post-deposition annealing on the morphological, structural, optical and electrical properties were investigated with the aim to find the best conditions for the antireflection substrate. The X-ray diffraction behaviors of mixed type crystalline structures preferred at 222] and 101] between ITO and ZnO were observed, respectively. The grain size increased from 37.9nm to 46.9nm due to the aggregation of smaller grain during the annealing process. Average transmittances of approximately 82% were observed for all the samples in the range between 440nm and 760nm. A corresponding reduction in the reflectance of about 11% and 3% compared to bare ITO was achieved. The refractive index increased from 1.82 up to 2.0 due to the change in the packing density. For all ranges of annealing conditions, the arc-ZnO:TiO2 layers conserved the low resistivity of ITO at 1.96i?10-4?. In other words, the oxygen consumed in the annealing process improved the crystallinity of the film without much change to the resistivity of the ITO-based substrate. The increment of the root mean square roughness from 2.12nm to 3.21nm evidenced by the atomic force microscopy analysis was supported by the increment of grain growth.

Postdeposition annealing of NiOx thin films: A transition from n-type to p-type conductivity for short wave length optoelectronic devices

Abstract

Improvement in carrier transport properties by mild thermal annealing of PbS quantum dot solar cells

We studied the effect of post-deposition thermal annealing in the preparation of PbS quantum dot (QD) solar cells. We find an optimal annealing temperature that improves the power conversion efficiency by a factor of 1.5 for different sized QDs with bandgaps of 1.65 and 1.27 eV. We examined the onset of the photocurrent response and correlated that with domain grain growth and find that annealing the PbS QD array at 120 °C causes little change in the PbS QD size, bandgap, and open-circuit voltage and yet leads to an increase in the carrier transport as realized by an improved current response. We also find a decrease in the activation energy of a shallow trap, which also likely contributes to the improvement in the solar cell efficiency.

Influence of post-deposition heat treatment on electrical transport properties of In2S3-buffered Cu(In,Ga)Se2 cells

The electrical characteristics of Cu(In,Ga)Se2-based solar cells with In2S3 buffer were investigated. The effects of post-deposition annealing in helium or in air on current–voltage characteristics, net acceptor density profiles and admittance spectra were studied. Analysis of the current–voltage characteristics showed that interface recombination dominated transport in the as-deposited devices was reduced after annealing and partially replaced by bulk recombination. This was accompanied by a decrease in the saturation current and diode ideality factor. The influence of the heat treatment on the buffer/hetero-interface region as determined by capacitance measurements was minor. We conclude that a reduction in the interface states density and in the p+ layer doping caused by the chemical modification of the hetero-interface region is the major source of the improvement.

Electrical characterization of atomic-layer-deposited hafnium oxide films from hafnium tetrakis(dimethylamide) and water/ozone: Effects of growth temperature, oxygen source, and postdeposition annealing

The electrical properties of HfO2-based metal–insulator–semiconductor capacitors have been systematically investigated by means of I–V and C–V characteristics, admittance spectroscopy, deep level transient spectroscopy, conductance transient, and flat band voltage transient techniques. Attention is also given to the study of the temperature dependence of the leakage current. HfO2 films were grown on p-type silicon substrates by atomic layer deposition using hafnium tetrakis(dimethylamide) as hafnium precursor, and ozone or water as oxygen precursors. The growth temperature ranged from 150 to 350 °C. Low growth temperatures prevent decomposition and high growth rate, as well as high contamination levels. As a result, the leakage current is lower for lower deposition temperatures. Some of the deposited samples were submitted to a postdeposition annealing at 650 °C in N2 atmosphere, showing a decrease in the leakage current and an increase in the equivalent oxide thickness (EOT), whereas interfacial state density increases and defect density inside the dielectric bulk decreases. Regarding dielectric reliability, in our experimental conditions, HfO2 layers grown at 150 °C exhibit the largest EOT and breakdown voltage. The electrical behaviour is clearly linked with structural properties, and especially with the formation of an interfacial layer between the HfO2 layer and the silicon substrate, as well as with the presence of several impurities.

Effects of annealing and deposition temperature on the structural and optical properties of AZO thin films

Al-doped ZnO (AZO) thin films were deposited on p- type Si(100) substrate by r.f magnetron sputtering at 200, 300 and 400 °C substrate temperatures. The deposited films were annealed in air atmosphere for 1 h at temperatures of 700, 800 and 900 °C. The deposition temperature and post-deposition annealing effects on structural and optical properties of the AZO samples were analyzed using X-ray diffraction, atomic force microscope and photoluminescence (PL). After annealing, the value of full width half maximum of the diffraction peaks was decreased as well as, the intensity of visible and strong UV PL emission peaks were increased with temperature. However, the deep-level emission related with zinc point defects was removed by annealing of the samples. Results revealed that all of the as-deposited and annealed AZO films have hexagonal structure along (002) direction and their crystallinity were improved with the increased deposition and post-growth annealing temperatures. In addition, the surface roughness and the particle size of the films were increased with increased deposition and annealing temperatures.

Study on Gallium Nitride-Based Metal–Oxide–Semiconductor Capacitors With RF Magnetron Sputtered $\hbox{Y}_{2}\hbox{O}_{3}$ Gate

Effects of postdeposition annealing (PDA) temperatures (200°C-1000°C) in argon ambient on radio-frequency magnetron sputtered Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> film on n-type GaN substrate were studied. As-deposited Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> film was amorphous as no Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> phase was detected by X-ray diffraction. A transformation of the amorphous to polycrystalline phase happened when PDA (≥ 200°C) was carried out. The detection of β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> phase for samples annealed beyond 400°C denoted the formation of interfacial layer (IL) consisting of an Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> mixture. The formation of IL was revealed by cross-sectional energy-filtered transmission electron microscopy images. Metal-oxide-semiconductor characteristics of Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /GaN structure annealed at different temperatures were correlated with structural and surface morphology analysis. The 400-°C-annealed sample demonstrated the highest electric breakdown field (~ 10.7 MV/cm) due to the attainment of the lowest effective oxide charge, semiconductor-oxide interface-trap density, and total interface-trap density.

Effect of postdeposition annealing on the structure, composition, and the mechanical and optical characteristics of niobium and tantalum oxide films

Optical, mechanical, and thermal properties of optical thin films are very important for a reliable device performance. In the present work, the effect of annealing on the stability and the characteristics of niobium and tantalum oxide films grown at room temperature (RT) by dual ion beam sputtering were studied. The refractive index (n(λ)), extinction coefficient (k(λ)), hardness (H), reduced Young's modulus (E(r)), and film stress (σ) were investigated as a function of the annealing temperature (T(A)). X-ray diffraction analysis showed that all as-deposited films were amorphous, and crystallization was observed only after annealing at 700°C. Compositional analyses confirmed that the atomic ratio of oxygen to metal in as-deposited and annealed films was close to 2.5, indicating that the films were stoichiometric pentoxides of Nb and Ta. The properties of Nb(2)O(5) and Ta(2)O(5) films were, respectively, affected by postdeposition annealing: n(λ) values (at 550 nm) decreased from 2.30 to 2.20 and from 2.14 to 2.08, the average H and E(r) values increased from 5.6 to 7.4 GPa, and from 121 to 132 GPa for Nb(2)O(5), and from 6.5 to 8.3 GPa, and from 132 to 144 GPa for Ta(2)O(5), and the initial low compressive stress for both materials changed to tensile. We explain the variation of the coating material properties in terms of film stoichiometry, crystallinity, electronic structure, and possible reactions at the film-substrate interface.

Influence of capping layers on CoFeB anisotropy and damping

Magnetic behavior of CoFeB at various thicknesses ranging from 2 nm to 8 nm capped with different materials, such as MgO, Ta, Ru, and V have been studied. The films were sputter-deposited and subsequently characterized by magnetometry and broadband ferromagnetic resonance (FMR). There are magnetically dead layers at the interface observed with Ru and Ta capping layers, while MgO and V have almost no effect on the magnetization of the CoFeB. As the ferromagnetic layer is made thinner, the effective magnetization decreases, indicating an interfacial perpendicular anisotropy. Particularly in the case of MgO, V/Ru, and V/Ta capping layers, interfacial perpendicular anisotropy is induced in CoFeB, and the Gilbert damping parameter is also reduced. The origin of this perpendicular magnetic anisotropy (PMA) is understood to be caused by the interface anisotropy between the free layer and the capping layer. The effect of post-deposition annealing and CoFeB thickness on the anisotropy and damping of V/Ta capped samples are reported. Doping CoFeB with vanadium (V) greatly reduced the 4πMs and 4πMeff values, resulting in an effective increase in the PMA.

Energy Levels, Electronic Properties, and Rectification in Ultrathin p-NiO Films Synthesized by Atomic Layer Deposition

NiO is an attractive p-type transparent semiconductor that is being explored for a variety of applications. We report a systematic study of the electronic properties, relevant to hole-transporting materials in solar energy conversion applications, of NiO synthesized by atomic layer deposition (ALD). The acceptor concentration, flat band potential, and valence band position were determined by electrochemical Mott–Schottky analysis of impedance data in aqueous electrolytes for films less than 100 nm in thickness on F:SnO2 (FTO)-coated glass substrates. The effects of postdeposition annealing and film thickness were studied. Oxidation of the NiO was observed at temperatures as low as 300 °C in 1 atm of oxygen. Films annealed at 400 °C and above in Ar exhibited signs of thermal decomposition. Thinner films were found to have a higher carrier concentration. F:SnO2 and thermally evaporated Ag were both observed to form ohmic contact to ALD-synthesized TiO2 and NiO. A p/n heterojunction diode was fabricated from...

Atomic layer deposition and characterization of stoichiometric erbium oxide thin dielectrics on Si(1 0 0) using (CpMe)3Er precursor and ozone

Thin stoichiometric erbium oxide films were atomic layer deposited on p-type Si(100) substrates using tris(methylcyclopentadienyl)erbium and ozone. The film growth rate was found to be 0.12±0.01nm/cycle with an atomic layer deposition temperature window of 170–330°C. X-ray photoelectron spectral (XPS) analysis of the resulting Er2O3 films indicated the as-deposited films to be stoichiometric with no evidence of carbon contamination. Studies of post deposition annealing effects on resulting films structures, interfaces, surface morphologies, and electrical properties were done using Fourier transform infrared spectroscopy, XPS, glancing incidence X-ray diffraction, optical surface profilometry, and C–V/I–V measurements. As-deposited Er2O3 films were found to start crystallizing in the cubic structure with dominant (222) orientation; no erbium silicate was found at the interface. After annealing at 800°C in N2, a new XPS feature was found and it was assigned to the formation of erbium silicate. As the annealing temperature was increased, the interfacial erbium silicate content was found to increase in the temperature range studied. Electrical characterization of Er2O3 thin gate dielectrics annealed at 600°C exhibited higher dielectric constant (κ=11.8) than that of as-deposited films (9.8), and a remarkably low hysteresis voltage of less than 50mV along with a leakage current density of 10−7Acm−2 at 1MVcm−1.

Effects of high-temperature O2 annealing on Al2O3 blocking layer and Al2O3/Si3N4 interface for MANOS structures

In this paper, we have investigated the effects of O2 post-deposition annealing (PDA) on metal/Al2O3/Si3N4/SiO2/Si (MANOS) devices. Compared with low-energy plasma oxygen pre-treatment and the N2 PDA process, the O2 PDA process can lead to a significant retention improvement. The improvement is attributed to the removal of oxygen vacancies in Al2O3 block oxide and the oxygen incorporation at the Si3N4/Al2O3 interfacial layer which is determined by x-ray photoelectron spectroscopy (XPS) depth profiling and electrical characteristics. Metal/Al2O3/SiO2/Si (MAOS) devices are also studied to confirm these effects. As a result, we consider that the O2 PDA process is a crucial process for future MANOS-type memory devices.

Effects of post-deposition annealing ambient on Y2O3 gate deposited on silicon by RF magnetron sputtering

Effects of different post-deposition annealing (PDA) ambient [O2, N2O, N2, forming gas (95% N2-5% H2), and Ar] on the physical and metal–oxide–semiconductor (MOS) characteristics of yttrium oxide (Y2O3) films deposited on Si substrate by RF magnetron sputtering had been reported. X-ray diffraction (XRD) had revealed the presence of Y2O3 and yttrium silicate (Y2Si2O7) phases while Fourier transform infrared spectrometer (FTIR) had successfully identified chemical functional groups of Y-O, Si-O, and Si-Si. The detection of Y2Si2O7 phase and Si-O bondings by XRD and FTIR, respectively, had suggested the formation of interfacial layer comprising of Y2Si2O7 and SiO2. The MOS characteristics of annealed Y2O3 gate oxide in different ambient were then correlated with the physical results. It was perceived that O2 annealed sample had demonstrated the highest dielectric breakdown voltage as well as the lowest effective oxide charge, interface trap density, and total interface-trap density. Current conduction mechanisms that governed the leakage current in these gate oxides had also been established using a non-linear curve fitting method.