Effect Of Post-deposition Annealing Research Articles

Postdeposition annealing effect on the reliability of atomic-layer-deposited Al2O3 films on GaN

Atomic-layer-deposited (ALD) Al2O3 is a promising gate insulation material for wide-bandgap semiconductor devices of increasing importance for high-speed and high-power switching operation. This study comprehensively reports on postdeposition annealing (PDA) effects on the reliability of ALD-Al2O3/GaN metal-insulator-semiconductor capacitors. High-temperature (450 °C) ALD for the Al2O3 growth was effective for reducing the bias instability (BI) of the capacitors and for suppressing the blisters caused by PDA in the Al2O3 films. The BI of the high-temperature Al2O3 capacitors was reduced more remarkably by PDA at high temperatures. The conduction current in the capacitors was also reduced by PDA at 800 °C and higher by 2 orders of magnitude. The high-temperature PDA, however, caused a positive flat-band voltage shift and increased the distribution of times to breakdown of the capacitors and the interface-state density from 1 × 1011 to 3 × 1012 cm−2 eV−1, causing the large frequency dispersion of C–V characteristics. This increase in the interface-state density was found to be the major cause of the aforementioned flat-band voltage shift by PDA, whereas the stress-induced flat-band voltage shift was mostly due to the negative Al2O3 charging. In agreement with the literature, transmission electron microscope observations demonstrated the crystallization of Al2O3 films by annealing at 800 °C and higher, ascribing the increased distribution of times to breakdown to some crystalline defects in the Al2O3 films. Hence, the best PDA effect was achieved at 700 °C, reducing BI by half in 200 °C operation. For this PDA, the breakdown lifetimes of capacitors were confirmed to be the same, if not longer, as those of unannealed samples even at an elevated temperature of 200 °C, achieving 300 years at the rating of 3 MV/cm, well over the reliability target of 20 years. To put the ALD-Al2O3/GaN capacitors into practical use, PDA possibly needs to be performed before contact formation and their BI should preferably be further improved, simultaneously carrying out its long-term projections.

Polarization-Charge Inversion at Al2O3/GaN Interfaces through Post-Deposition Annealing

The effects of post-deposition annealing (PDA) on the formation of polarization-charge inversion at ultrathin Al2O3/Ga-polar GaN interfaces are assessed by the analysis of energy band bending and measurement of electrical conduction. The PDA-induced positive interface charges form downward energy band bending at the Al2O3/GaN interfaces with polarization-charge inversion, which is analyzed using X-ray photoelectron spectroscopy. Net charge and interface charge densities at the Al2O3/GaN interfaces are estimated after PDA at 500 °C, 700 °C, and 900 °C. The PDA temperatures affect the formation of charge densities. That is, the charge density increases up to 700 °C and then decreases at 900 °C. Electrical characteristics of GaN Schottky diodes with ultrathin Al2O3 layers exhibit the passivation ability of the Al2O3 surface layer and the effects of polarization-charge inversion through PDA. This result can be applied to improvement in GaN-based electronic devices where surface states and process temperature work important role in device performance.

Deep UV-assisted capacitance–voltage characterization of post-deposition annealed Al2O3/ β -Ga2O3 (001) MOSCAPs

In this Letter, the interface state density (Dit) and bulk trap density (nbulk) in post-deposition annealed Al2O3/β-Ga2O3 (001) metal–oxide–semiconductor capacitors (MOSCAPs) are extracted using the deep UV-assisted capacitance–voltage method and an improved physical analytical model. The effects of atomic layer deposition (ALD) temperature and post-deposition annealing (PDA) conditions are also studied. Increasing the deposition temperature and PDA at 500 °C in O2 seems to be an effective way to improve the forward breakdown voltage (BV) and suppress capacitance–voltage hysteresis in Al2O3/β-Ga2O3 (001) MOSCAPs. These results are useful for future high performance Ga2O3-based metal-oxide-semiconductor field effect transistors (MOSFETs) and Fin-FETs.

Effects of Post-Deposition Annealing Time in Forming Gas Ambient on Y2O3 Films Deposited on Silicon Substrate

Effects of post-deposition annealing (PDA) time (15, 30, and 45 min) at 800°C in forming gas (95% N2-5% H2) ambient was systematically studied for RF-magnetron sputtered Y2O3 films on n-type Si(100) substrate. X-ray diffraction characterization has revealed the detection of Y2O3 phase oriented in (400), (440), (541), and (543) planes for all of the investigated samples. In addition, capacitance-voltage characteristics of the investigated Al/Y2O3/Si-based metal-oxide-semiconductor capacitors were also presented in this work.

Effect of post-deposition annealing on charge distribution of metal-oxide-semiconductor capacitor with TiN/HfO2/SiO2/Si gate structure

We experimentally investigate the effect of post-deposition annealing on the charge distribution of a metal-oxide-semiconductor capacitor with a TiN/HfO2/SiO2/Si gate structure. We decoupled interfacial charges at the SiO2/Si and HfO2/SiO2 interfaces; bulk charges in HfO2; and the dipole formation at the HfO2/SiO2 interface. The interfacial charges at the HfO2/SiO2 interface decreased and the dipole increased after H2 or N2 annealing. Oxygen dangling bonds are the physical origin of the charges at the HfO2/SiO2 interface. The interfacial charges at the SiO2/Si interface and the bulk charges in HfO2 are almost unchanged.

Effect of high-temperature post-deposition annealing on cesium lead bromide thin films deposited by vacuum evaporation

The effects of high-temperature (500 °C) post-deposition annealing (PDA) on the properties of cesium lead bromide (CsPbBr3) films deposited by vacuum evaporation were studied. The PDA effectively improved the grain size of the CsPbBr3 films. This improvement of the grain size leads to the improvement of carrier diffusion length from 0.1 µm to 0.5 μm. A CsPbBr3 solar cell fabricated using a CsPbBr3 layer with PDA at 500 °C for 60 min showed a conversion efficiency of 6.62% (VOC = 1.465 V, JSC = 6.57 mA/cm2, and FF = 0.688). Our CsPbB3 solar cell also showed a conversion efficiency of 22.5% (VOC = 1.502 V, JSC = 53.7 mA/cm2, and FF = 0.574) for blue LED light (peak wavelength of 453 nm) with an intensity of 206 mW/cm2.

Role of temperature on structure and electrical properties of titanium nitride films grown by low pressure plasma enhanced atomic layer deposition

Film crystallinity is one of the key factors determining the resistivity of thin conductive nitride films. In the process of plasma enhanced atomic layer deposition (PEALD), the film crystallinity can be significantly improved by the ion bombardment effect taking place at a low pressure. At a low plasma pressure, ion bombardment supplies additional energy for adatom rearrangement and ligand desorption which significantly enhances the film crystallinity. The deposition of low resistive (∼300 μΩ cm) TiN films is demonstrated here at a temperature as low as 100 °C. The role of deposition temperature on TiN PEALD structure and electrical properties, such as resistivity and temperature coefficient of resistivity, is investigated. The effect of postdeposition annealing is discussed as well. The resistivity can be further reduced (to ∼60 μΩ cm) by increasing deposition temperature up to 250 °C or by postdeposition annealing. The increased temperature results in larger grain size, which is the dominant factor in determining the electrical properties of the film.

Influence of Ultra-Thin Ge₃N₄ Passivation Layer on Structural, Interfacial, and Electrical Properties of HfO₂/Ge Metal-Oxide-Semiconductor Devices.

We report the effects of the nitride passivation layer on the structural, electrical, and interfacial properties of Ge metal-oxide-semiconductor (MOS) devices with a hafnium oxide (HfO₂) gate dielectric layer deposited on p-type 〈100〉 Ge substrates. X-ray photoelectron spectroscopy analysis confirmed the chemical states and formation of HfO₂/Ge₃N₄ on Ge. The interfacial quality and thickness of the layers grown on Ge were confirmed by high-resolution transmission electron microscopy. In addition, the effects of post-deposition annealing (PDA) on the HfO₂/Ge₃N₄/Ge and HfO₂/Ge samples at 400 °C in an (FG+O₂) ambient atmosphere for 30 min were studied. After PDA, the HfO₂/Ge₃N₄/Ge MOS device showed a higher dielectric constant (k) of ~21.48 and accumulation capacitance of 1.2 nF, smaller equivalent oxide thickness (EOT) of 1.2 nm, and lower interface trap density (Dit) of 4.9×1011 cm-2 eV-1 and oxide charges (Qeff) of 7.8×1012 cm-2 than the non-annealed sample. The I-V analysis showed that the gate leakage current density of the HfO₂/Ge₃N₄/Ge sample (0.3-1 nA cm-2 at Vg = 1 V) was half of that of the HfO₂/Ge sample. Moreover, the barrier heights of the samples were extracted from the Fowler-Nordheim plots. These results indicated that nitride passivation is crucial to improving the structural, interfacial, and electrical properties of Ge-based MOS devices.

Improving Retention Properties of ALD-AlxOy Charge Trapping Layer for Non-Volatile Memory Application

In this work, the charge retention properties of the thermal ALD-Al2O3 trapping layer with metal-oxide-oxide-oxide-silicon (MOOOS) gate stack have been investigated for non-volatile memory application. The precursor gas concentrations were changed to engineer the band gap of the AlxOy trapping layer and the effect of AlxOy post-deposition annealing on charge retention properties was studied. The Al2O3 layer with trimethyl aluminum (TMA): H2O gas flow ratio of 1:1 and deposition pulse time of 1 s per each cycle showed the band gap of 4.49 eV , which is suitable for charge trapping layer. The memory retention properties of the ALD-Al2O3 MOOOS device was investigated by performing high-frequency capacitance-voltage measurement and compared to the device having a SiNx charge trapping layer. The 10 nm AlxOy trapping layer showed the improvement in charge retention properties after low-temperature post-deposition annealing in N2 ambient as compared to that of SiNx trapping layer with relatively large flat band voltage shift of 2.79 V. The multilayer Al2O3-MOOOS gate stack is suitable for the non-volatile memory application with good retention properties as compared to different oxides non-volatile memory devices.

The effect of precursor concentration and post-deposition annealing on the optical and micro-structural properties of SILAR deposited SnO2 films

Uniform and well-adherent SnO2 thin films, with thickness ranging from 60 nm to 6 μm, were deposited on borosilicate glass substrate by Successive Ionic Layer Adsorption and Reaction (SILAR) technique. A micro-controlled SILAR unit was employed to precisely monitor the deposition conditions. The effect of precursor concentration and post-deposition annealing on the micro-structural and optical properties of SnO2 thin films were studied in detail. The films were found to possess tetragonal rutile structure. The crystallite size of the films increased with solution molarity. Microstructural properties were analyzed using Scherrer, Modified Scherrer, Williamsons-Hall and Size-Strain plot techniques. Different optical properties such as band gap, skin depth, extinction coefficient, Urbach energy etc were determined. The post-deposition annealing at a moderate temperature of 573 K was found to enhance the crystallite size of the films while the density of the defect energy states reduced.

Impact of Surface Treatments and Post-Deposition Annealing Upon Interfacial Property of ALD-Al₂O₃ on a-Plane GaN

Optimization of interface characteristics between dielectric and non-polar GaN surface is very important and urgent for vertical GaN MOS device whose channel is perpendicular to the conventional cplane. In this work, the effects of piranha cleaning and N2 post deposition annealing (PDA) to the interface between atomic-layer-deposited (ALD)-Al 2 O 3 and a-plane GaN samples were comprehensively investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and photo-assisted capacitance-voltage (C-V) measurements. The piranha cleaning and N2 annealing can improve interface characteristics through the reduction in surface roughness and Ga-O bonds, respectively. Therefore, the frequency dispersion and hysteresis are nearly suppressed with a low interface trap quantity (Qit) of 4.1 x 10 11 cm -2 and a low average interface state density (Dit) of 2.04 x 10 11 cm -2 ·eV -1 from photoassisted C-V measurements, showing the great promise of utilizing piranha pretreatment, buffered oxide etch (BOE) dip, and N 2 annealing as an effective route to improve the vertical GaN MOS interface properties.

Effect of post-deposition annealing on electrical properties and structures of aluminum oxide passivation film on a crystalline silicon substrate

We studied the effect of post-deposition annealing (PDA) on the electrical property and the structure of aluminum oxide (AlOx) passivation films prepared by atomic layer deposition with various temperatures. Surface recombination velocity (Smax), interface trap density (Dit), and fixed charge density (Qeff/q) before and after the PDA were evaluated employing lifetime and capacitance–voltage measurements. The structural change by the PDA was investigated by a Stokes ellipsometer and X-ray reflectivity (XRR) measurements at SPring-8. The Smax of all samples was improved by the PDA. The improvement of Smax in the samples deposited at the temperature of 200 °C and 300 °C was due to the Dit decrease, but that in the sample deposited at the temperature of 25 °C was due to both the Dit decrease and the Qeff/q increase. From the XRR measurements, it revealed that the formation of the interfacial thin layer is essential for the appearance of negative fixed charges.

Post-deposition annealing effect on the structural, morphological, and photoluminescence properties of β-Ga2O3 nanowires deposited on silicon by glancing angle deposition

β-Ga2O3 nanowire (NW) was fabricated on a Si-substrate using glancing angle deposition (GLAD) technique. To study the structural, morphological, and optical properties of the as-deposited β-Ga2O3 NW, thermal annealing was done at different temperatures ranging from 600 to 1000 °C and the corresponding results were analyzed. XRD analysis shows an increase in crystallinity of the as-deposited sample upon annealing. The average crystallite size was found to be increased from 13.72 to 20.19 nm after annealing at 900 °C. Annealed β-Ga2O3 NW contains more concentration of oxygen due to absorption of O2 molecules. The lattice strain and dislocation density of the as-deposited β-Ga2O3 NW were found to reduce significantly after thermal annealing. The FEG-SEM image confirms the growth of vertically aligned β-Ga2O3 NW. An enhancement in the UV region was observed in the photoluminescence spectra after annealing at 900 °C.

Evolution of physical properties of diamond nanoparticles deposited by DC-PECVD method after post deposition annealing

High quality diamond nanoparticles were synthesized by plasma enhanced chemical vapor deposition (PECVD) method on steal 304 substrates. Effects of post deposition annealing in the vacuum at temperature of 100 °C, 200 °C, and 300 °C was studied. Investigations of phase structures and surface morphology of diamond materials were examined by X-ray diffraction (XRD), atomic force microscopy, scanning electron microscopy (SEM) and Raman spectroscopy. The XRD spectrum of the annealed samples showed the well-defined crystalline structure of the diamond nanoparticles with a more intense peak at 100 °C. Post annealing of the samples at higher temperature transforms the diamond structure to graphite phase with is reduced of the film’s crystalline quality. A shift in preferred diamond growth orientation at higher annealing temperature from (111) to (220) was happened. Remarkable differences in the morphology were evident in the SEM images of annealed samples. The high concentration and distribution of the diamond nanocrystals with crystallite size of lower than 50 nm were obtained on the surfaces of the annealed sample at 100 °C. Raman spectra showed a more intense diamond peak for annealed sample at 100 °C and graphitic and non-diamond components for annealed sample at higher temperature.

Effect of substrate temperature, laser energy and post-deposition annealing on the structural, morphological and optical properties of laser-ablated perovskite BaSnO3 films

Perovskite BaSnO3 thin films suitable for excitonic solar cell applications were deposited on quartz substrate by pulsed-laser ablation method. The effect of various deposition parameters on the structural, morphological and optical properties is systematically studied by various characterization techniques. Phase-pure films with cubic crystalline nature were evolved at a substrate temperature of 600 °C with a laser energy of 60 mJ and post-deposition annealing further improved the structural purity and optical quality of the films. An exponential growth in film thickness was observed with increasing laser energy in which Stranski–Krastnov growth mechanism dominated. Chemical states of BaSnO3 were confirmed from XPS analysis. The deposited films present luminescence in the visible region at 452 nm, 480 nm and 580 nm wavelength.

Effects of post-deposition annealing and copper inclusion in superstrate Sb2Se3 based solar cells by thermal evaporation

Earth-abundancy, nontoxic constituent, along with excellent stability and optoelectronic properties make antimony selenide (Sb2Se3) one of the potential candidate for low cost photovoltaics. In this work, antimony selenide (Sb2Se3) thin films were prepared by low temperature thermal evaporation method and characterized. Solar cells were fabricated in the superstrate configuration of Glass/ITO/ZnO/CdS/Sb2Se3/Au. It was found that annealing in vacuum after Sb2Se3 deposition played a significant role in the device performance. One-dimensional crystal structure of Sb2Se3 with a preferred grain orientation was found to be beneficial for the higher performance of the solar cells with vacuum annealing at 300 °C. Furthermore, Cu addition after the deposition of Sb2Se3 was introduced to improve the back contact and the device performance. In particular, Cu addition as a back contact leads to a significant increase in the Voc and the fill factor (FF). Moreover, aging of the finished cells during accelerated stability tests revealed a light soaking effect without degradation even in case of copper insertion. Our best solar cell showed a conversion efficiency of 3.5% without selenization.

Improving Charge Trapping/Detrapping Characteristics of Amorphous In-Ga-ZnO Thin-Film-Transistors Using Microwave Irradiation.

We investigated the effect of post-deposition annealing (PDA) on the gate-bias-stress-induced charge trapping/detrapping phenomenon in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). To evaluate device reliability, we used the microwave irradiation (MWI), rapid thermal annealing (RTA), and conventional thermal annealing (CTA) methods for PDA of the TFTs and compared the resulting device performances. Fabricated devices were measured in the dark and under light illumination under positive and negative gate-bias-temperature stress (PBTS and NBTS, respectively). Because microwave energy was transferred directly to the substrate in a short time of 2 min in the MWI device, defects were removed more effectively. The obtained results indicated that the threshold voltage (Vth) shift of the MWI-treated a-IGZO TFT with different temperatures and gate bias stresses in the dark and under light illumination was the smallest and the most reliable. Further, comparisons of the Vth recovery characteristics in the dark and under light illumination indicated that charge detrapping behaviors were enhanced under the latter condition. Furthermore, the average effective energy barrier based on Arrhenius plots was extracted. Therefore, the MWI method is considered promising for fabricating next-generation displays on various substrates.

Thin‐film transistors based on wide bandgap Ga 2 O 3 films grown by aqueous‐solution spin‐coating method

Ga2O3 is a wide bandgap oxide semiconductor material with the bandgap value only second in magnitude to diamond among known semiconductors. As a wide-bandgap semiconductor, Ga2O3 has emerged as a new competitor to silicon carbide and III-nitrides in various applications of ultraviolet optoelectronics and high power electronics. However, almost all the devices are based on the Ga2O3 grown by molecular-beam epitaxy or chemical vapour deposition, which is time-consuming and expensive. In this work, the authors report on thin-film transistors based on wide bandgap Ga2O3 films grown by aqueous-solution spin-coating method. The morphological, optical and electrical properties of the films and devices are investigated using a range of characterisation techniques, whilst the effects of post-deposition annealing are also investigated. Both as fabricated and post-annealed Ga2O3 films are found to be very smooth and exhibit wide energy bandgaps of around 4.8 and 4.9 eV, respectively. Thin-film transistors based on the grown Ga2O3 films show n-type conductivity with the maximum electron mobility of 0.1 cm2/Vs.

Effects of Rapid Thermal Annealing on the Structural, Optical, and Electrical Properties of ZnO/Ag/SnO2 Tri-Layer Films

ZnO 50 nm/Ag 10 nm/SnO2 50 nm (ZAS) tri-layer films were deposited on a glass substrate by RF and DC magnetron sputtering and then underwent rapid thermal annealing in a low vacuum of 1×10-3 Torr to investigate the effects of post-deposition annealing on the optical and electrical properties of the films. The peak intensity of the XRD pattern related to the ZnO (002) peak of the annealed films was higher than that of the as-deposited film and the full width at half-maximum of the ZnO (002) diffraction peak of the annealed films was smaller than that of the as-deposited film. Therefore, the crystallinity of ZnO was improved by rapid annealing. However, crystallization of the Ag interlayer and SnO2 surface layer were not significantly affected by the annealing temperature, compared with the ZnO bottom layer. From the observed electrical properties and optical band gap, it was concluded that the blue shift in the optical band gap is related to the carrier density of the films. The band gap increased from 4.19 eV to 4.24 eV, with the carrier density increasing from 7.09 × 1021 cm-3 to 7.77 × 1021 cm-3. However, the film annealed at 450 °C showed a decreased band gap energy of 4.17 eV due to the decreased carrier density of 6.80 × 1021 cm-3. The as-deposited ZAS films showed a sheet resistance of 11.0 Ω/□ and a visible transmittance of 80.8%, whereas the films annealed at 450 °C had a higher visible transmittance of 82.3% and a lower sheet resistance of 6.55 Ω/□. The results indicate that ZAS thin films may be possible substitutes for conventional Sn-doped In2O3 transparent electrodes in various optoelectronic devices. Key words: ZnO/Ag/SnO2, magnetron sputtering, annealing, AFM, XRD

Effect of Post Deposition Annealing on the Structural and Electrical Properties of NbTiN Thin Films Deposited by Reactive Bias Target Ion Beam Deposition Technique

Nb-based superconducting alloys, such as NbN and NbTiN, can have a superconducting energy gap near twice that of elemental Nb, thus, being ideal candidates for low-loss superconducting circuits operating above the gap frequency of Nb. We are particularly interested in these materials for THz-frequency superconducting-insulating-superconducting (SIS) mixers, kinetic inductance detectors, and traveling wave kinetic inductance parametric amplifier devices. We recently reported the use of an alternative synthesis technique, reactive bias target ion beam deposition (RBTIBD), used to realize high-quality NbTiN films and high-energy gap NbTiN/AlN/NbTiN SIS heterostructures. In this paper, the effect of post-deposition annealing on the electrical and structural properties of room temperature deposited RBTIBD NbTiN was investigated. Our room temperature RBTIBD NbTiN films were annealed using rapid thermal annealing from 200 to 1000 °C. The change in structural and electrical properties was characterized by X-ray diffraction, atomic force microscopy, and four-point probe measurements. The annealed films demonstrated an enhancement in transition temperature (T c ), increased crystallinity, larger grain size, and significantly reduced intrinsic stress.