Microwave Annealing Research Articles

Device performances and instabilities of channel engineered amorphous InGaZnO thin film transistors

A channel engineered amorphous InGaZnO thin film transistor which is composed of two active channel layers according to the composition ratio and thickness is suggested to enhance the device performance and the device stability. To investigate the annealing treatment on the device performance and instability, conventional thermal annealing and microwave annealing treatments were conducted. The device performances of channel engineered devices are enhanced due to the increased electron concentrations which result from high In contents in the bottom active layer. The device stability is improved due to the combination effects of passivation with top back channel and the high effective barrier height with bottom active layer. Also, the devices treated by microwave annealing show improved device performances and stability.

Improving Electrical Performance of Few-Layer MoS2 FETs via Microwave Annealing

A few-layer molybdenum disulfide (MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) has attracted great attention because of its novel electrical and optoelectrical properties for devices. In this letter, we perform a systematic study on the evolution of the electrical performance of the few-layer MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> field-effect transistors (FETs) under microwave annealing. As a result, obvious improvements on electrical properties are achieved for the sample annealed in N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ambience between 420 and 840 W. The on/off current ratio of ~8.34 × 108 and the hysteresis of 2.1 V, which are ~150 times higher and ~2.1 times smaller compared with that of fabricated MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> FET, respectively. The proposed technique provides a new method to approach high-performance few-layer MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> FETs with minimized parasitic resistances.

Wearable 1\u2009V operating thin-film transistors with solution-processed metal-oxide semiconductor and dielectric films fabricated by deep ultra-violet photo annealing at low temperature

Amorphous metal-oxide semiconductors (AOSs) such as indium-gallium-zinc-oxide (IGZO) as an active channel have attracted substantial interests with regard to high-performance thin-film transistors (TFTs). Recently, intensive and extensive studies of flexible and/or wearable AOS-based TFTs fabricated by solution-process have been reported for emerging approaches based on device configuration and fabrication process. However, several challenges pertaining to practical and effective solution-process technologies remain to be resolved before low-power consuming AOS-based TFTs for wearable electronics can be realized. In this paper, we investigate the non-thermal annealing processes for sol-gel based metal-oxide semiconductor and dielectric films fabricated by deep ultraviolet (DUV) photo and microwave annealing at low temperature, compared to the conventional thermal annealing at high temperature. A comprehensive investigation including a comparative analysis of the effects of DUV photo and microwave annealing on the degree of metal-oxide-metal networks in amorphous IGZO and high-dielectric-constant (high-k) aluminum oxide (Al2O3) films and device performance of IGZO-TFTs in a comparison with conventional thermal annealing at 400 °C was conducted. We also demonstrate the feasibility of wearable IGZO-TFTs with Al2O3 dielectrics on solution-processed polyimide films exhibiting a high on/off current ratio of 5 × 104 and field effect mobility up to 1.5 cm2/V-s operating at 1 V. In order to reduce the health risk and power consumption during the operation of wearable electronics, the operating voltage of IGZO-TFTs fabricated by non-thermal annealing at low temperature was set below ~1 V. The mechanical stability of wearable IGZO-TFTs fabricated by an all-solution-process except metal electrodes, against cyclic bending tests with diverse radius of curvatures in real-time was investigated. Highly stable and robust flexible IGZO-TFTs without passivation films were achieved even under continuous flexing with a curvature radius of 12 mm.

Characteristics of Amorphous In‐Ga‐Zn‐O Thin Films with Various Compositions Under Microwave Annealing

In this study, the effects of microwave annealing (MWA) on the electrical properties of amorphous In‐Ga‐Zn‐O thin‐film transistors (a‐IGZO TFTs) are evaluated. To measure the transfer and output characteristics of as‐deposited, conventional thermal annealed (CTA), or microwave annealed TFTs, the devices are fabricated by varying the compositional ratios of IGZO films (In2O3:Ga2O3:ZnO = 1:1:1, 1:1:2, and 2:1:2 at%). The reliability is evaluated by measuring the threshold voltage shift under the gate bias stress and by analyzing the charge trapping characteristics according to the operating temperature. In addition, the interface trap density of the a‐IGZO channel/gate insulator and the volume density of the shallow trap of the channel layer are extracted to evaluate the difference in trap density according to the channel composition and the variation in the trap density as a result of the annealing process. Lastly, the sub‐gap density of states (DOS) of the TFTs is investigated to verify the compositional ratio and the annealing effect on the electrical characteristics and reliability of the devices. Based on these results, it is demonstrated that high‐performance a‐IGZO TFTs can be fabricated by using the low thermal budget MWA technique and by controlling the composition of the IGZO channel.

Investigation of Electrical Characteristics on LaAlO₃/ZrO₂/IGZO TFTs with Microwave Annealing.

Conventional thin film transistor suffered from high threshold voltage, poor subthreshold swing, and high operation voltage. These shortcomings make the traditional thin film transistor does not meet the needs with the high-performance, high-resolution, low temperature and energy conservation nowadays. Due to the good selectivity of energy transformation and rapid heating rate, microwave annealing is promising to replace conventional furnace annealing and applied in the investigation. LaAlO₃/ZrO₂ is employed as gate electrode and gate dielectric layer for a-IGZO TFTs, under the premise that performance of a-IGZO TFTs without decreasing. With adjusting the power/time of microwave annealing, the effect on electrical characteristics of a-IGZO TFTs is investigated.

Study on lattice constant and magnetic properties of bismuth substituted YIG polycrystal thin film on different substrates prepared by rf magnetron sputtering

In this study, we investigated the magnetic and magneto-optical properties of Bi1.5Y1.5Fe5O12 (Bi:YIG) films prepared on quartz and silicon substrates, respectively, by radio frequency magnetron sputtering and disposed by microwave annealing. The results indicated that the lattice constant and magnetic properties were significantly different on different substrates. First, the lattice constant of film on quartz substrate was found to be 9% greater than that on silicon substrate because of larger residual stress. Second, the grain size of film on silicon substrate was smaller than that on quartz substrate at same annealing temperature, which led to its magnetization being 70% smaller than that on quartz substrate and coercive force was 50% less. Finally, the transmittance of the Bi:YIG film and pure YIG was studied and the Faraday angle of Bi1.5Y1.5Fe5O12 film on quartz substrate was found to be − 8°/µm at λ = 544 nm and − 1.8°/µm at λ = 677 nm.

The Effect of Microwave Annealing of Reliability Characteristics on Amorphous IGZO Thin Film Transistors.

Amorphous oxide semiconductors (AOSs) are attracted much attention due to high mobility, low temperature deposition, flexible, transmission, and uniformity. The thin film transistors (TFTs) with a-IGZO thin film as active layer perform higher field-effect mobility (>10 cm²/V·S), larger Ion/Ioff ratio (106), smaller subthreshold swing and better stability against electrical stress. LaAlO₃/ZrO₂ is employed as gate electrode and gate dielectric layer for a-IGZO TFTs, under the premise that performance of a-IGZO TFTs without decreasing. Due to the good selectivity of energy transformation and rapid heating rate, microwave annealing is applied to improve the device reliability in the investigation. With adjusting the parameter of microwave annealing, the effect on reliability characteristics of a-IGZO TFTs is studied.

Effects of Annealing on Ferroelectric Hafnium–Zirconium–Oxide-Based Transistor Technology

In this letter, we investigate annealing effects in ferroelectric HfZrO x dielectric in metal–insulator–metal devices and metal–oxide–semiconductor capacitors by comparing two annealing methods: rapid thermal annealing (RTA) and microwave annealing (MWA). The tradeoff characteristics between the annealing conditions, polarization–electric field characteristics, gate leakage current, and interface state density ( ${D} _{\textsf {it}}$ ) are discussed. We show that: 1) a positive correlation between the remanent polarization (Pr), the gate leakage current, and ${D}_{\textsf {it}}$ as the annealing temperature (RTA) and the annealing power (MWA) increase and 2) the MWA is promising for ferroelectric transistors technology, since its low thermal budget can minimize ${D}_{\textsf {it}}$ and avoid increase in the gate leakage current.

Three dimensional bimetallic phosphides nanoneedle arrays as electrode materials for symmetric all-solid-state supercapacitor

Because of the rapid development of wearable electronic devices, energy storage devices with thin, lightweight and flexible have attracted much attention. Hybrid materials consisting of bimetallic phosphides nanoneedle arrays supporting on carbon cloth are successfully synthesized by a single-mode microwave and thermal annealing treatment followed by a low temperature phosphorization. For evaluating as electrode materials of supercapacitor, electrochemical performances of all samples are manipulated by a three-electrode system in 1 mol KOH solution. The results indicate that appropriate amount of Ni substitution could improve the electrochemical performance of NixCo1-xPy nanoneedle arrays as electrode of supercapacitor. Cyclic voltammetry, Galvanostatic charge/discharge curve, specific capacitance and electrochemical impedance spectroscopy display that NiCo2Py nanoneedle arrays as electrode materials of supercapacitor exhibits excellent electrochemical performance. A symmetric all-solid-state supercapacitor is assembled via using NiCo2Py nanoneedle arrays supported on carbon cloth as electrodes. The as-assembled symmetric all-solid-state supercapacitors exhibit an excellent electrochemical performance with a specific capacitance of 236.2 F/g at a scan rate of 10 mV/s. Good cycling stability of NiCo2Py has been demonstrated and 87.13% of the initial capacitance can be remained after 15000 cycles under a scan rate 3 V/s. This result indicates that NiCo2Py nanoneedle arrays/Carbon cloth hybrids are a good potential candidate as electrode materials for all-solid-state supercapacitor.

Effect of annealing conditions on dopants activation and stress conservation in silicon-germanium

As the miniaturization of the size of semiconductor components, the silicon-based transistor has reached its material limitations, so that researching the new materials (silicon-germanium compound) to replace silicon is more important. The ion implantation technology is conducted to discuss the activation issue of p-type dopants, due to silicon-germanium epitaxial layer has the stress effect to enhance the carrier mobility, it is in a conflict of high-temperature annealing. In order to maintain the stress of the epitaxial silicon germanium layer and achieve the activation level of the carrier at the same time, this paper explores a new annealing method - microwave annealing (MWA) with the low thermal budget. In this study, we have investigated that using one-step microwave annealing energy in 3P (1P = 600W), which can make boron implanted into 30% Ge content of silicon germanium layer has the lowest sheet resistance (170 ohm/sq), the best epitaxial layer quality and the better residual stress index (1.48%). However, using two-step microwave annealing energy in 3P+1P over 100s, it can further achieve higher activation level for Si0.7Ge0.3: B sample without stress relaxation. (Sheet resistance as low as 134.6 ohm/sq, Hall measurement mobility of 302.7 cm2/Vs.).

Dynamic Behavior Improvement of Normally-Off p-GaN High-Electron-Mobility Transistor Through a Low-Temperature Microwave Annealing Process

The surface morphology optimization of ohmic contacts and the Mg out-diffusion suppression of normally off p-GaN gate high-electron-mobility transistors (HEMTs) continue to be challenges in the power electronics industry in terms of the high-frequency switching efficiency. In this study, better current density and reliable dynamic behaviors of p-GaN gate HEMTs were obtained simultaneously by adopting low-temperature microwave annealing (MWA) for the first time. Moreover, HEMTs fabricated using MWA have a higher ION/IOF ratio and lower gate leakage current than the HEMTs fabricated using rapid thermal annealing. Due to the local heating effect, a direct path for electron flow can be formed between the two-dimensional electron gas and the ohmic metals with low bulges surface. Moreover, the Mg out-diffusion of p-GaN gate layer was also suppressed to maintain good current density and low interface traps.

Reusable surface-enhanced Raman substrates using microwave annealing

In this work, we report the fabrication of large-scale homogeneous surface-enhanced Raman scattering (SERS) substrates using a microwave annealing (MWA) process on Ag thin films on silicon, using a typical low-cost domestic microwave oven, avoiding the use of chemicals and stabilizing agents, or time-consuming and expensive approaches. We provide evidence that in 5–15 s, uniform and reproducible SERS substrates of several centimeter squares can be grown, providing a Raman signal enhancement of five orders of magnitude, for an incident Raman laser with an intensity as low as ~ 0.035 mW, against the characterization of Rhodamine 6G, which is a standard test molecule for SERS. Moreover, we tested the reusability of the fabricated MWA SERS substrates under conditions as tough as ultrasonic sonication in isopropyl alcohol and acetone for 15 min, respectively, and we demonstrate that our SERS substrates can be efficiently reused for more than six times after sonication, which is quite critical since it minimizes the cost of the procedure to minimum.

Hybrid Microwave Annealing for Fabrication of More Efficient Semiconductor Photoanodes for Solar Water Splitting

Hybrid microwave annealing (HMA) is proposed as an alternative to conventional thermal annealing (CTA) in a furnace to fabricate efficient semiconductor photoelectrodes for solar water splitting. Thus, the effects of HMA are investigated in comparison with CTA using spinel zinc ferrite as an example. The ZnFe2O4 photoanodes fabricated by HMA with a graphite susceptor provide less defective surface, better structural ordering and smaller feature size than photoanodes prepared by CTA. Besides, HMA does not impair conductivity of the F:SnO2 glass substrate. All these positive factors of HMA leads to ∼4 times higher photocurrents at 1.23 VRHE and lowered onset potential by ∼100 mV under 1 sun irradiation of an optimized ZnFe2O4 photoanode relative to that fabricated by CTA. The HMA could be an effective generic method to fabricate efficient photoelectrodes based on refractory semiconductors replacing incumbent CTA.

Multi- and single-step in situ microwave annealing as low-thermal-budget techniques for solution-processed indium–gallium–zinc oxide thin films

In this study, low-thermal-budget in situ microwave annealing of solution-processed indium–gallium–zinc oxide (IGZO) thin films was investigated as a potential alternative to the conventional high-thermal-budget annealing process. The low-temperature baking and high-temperature post-deposition annealing of the solution-processed IGZO film were continuously performed using the same microwave equipment, leading to a reduced heat treatment processing time and temperature. We compared the electrical characteristics of IGZO thin film transistors (TFTs) produced using single- and multi-step in situ microwave annealing methods with those of TFTs manufactured via the conventional annealing method and found that the proposed single-step microwave annealing method yielded TFTs with electrical characteristics better than those of the TFTs fabricated using the multi-step and conventional annealing methods. In addition, the reliability was evaluated by conducting positive and negative gate bias stress tests, in which the IGZO TFTs manufactured using the proposed heat treatment method proved superior to those fabricated via the conventional heat treatment method. We investigated the effects of heat treatment on the composition and energy band structures of the IGZO films by performing x-ray photoelectron spectroscopy analysis and found that the proposed in situ microwave annealing method is more effective than the conventional method in solution processing.

The effects of rapid thermal annealing and microwave annealing on the electrical properties of ZrO2 metal-insulator-metal capacitors

The effects of different rapid thermal annealing (RTA) and microwave annealing (MWA) on the electrical behaviors of ZrO2 metal-insulator-metal (MIM) capacitors were studied in detail. The maximum capacitance density was achieved at 1400 W for MWA, i.e. ∼29.29 fF/μm2 increased by ∼40% compared with that of the un-annealed capacitors. For the capacitors under RTA at 370 °C, equivalent to the ambient of the MWA at 1400 W, the capacitance density is ∼28.04 fF/μm2. Moreover, the leakage current density of ZrO2 MIM capacitors for MWA at 1400 W and RTA at 370 °C are determined to be about 3.55 × 10−7A/cm2 and 1.88 × 10-6 A/cm2 at the applied voltage of -1.5 V, respectively. Finally, the possible mechanisms of the improved electrical properties of ZrO2 MIM capacitors through MWA were proposed.

Effect of Microwave Annealing on Transparent In–Ga–ZnO Thin-Film Transistors With Graphene Source and Drain Electrodes

In this letter, we investigated the effects of microwave heat treatment on amorphous In–Ga–ZnO (a-IGZO) thin-film transistors (TFTs) with transparent graphene source and drain (S/D) electrodes. Microwave annealing (MWA) was simultaneously applied to post-deposition annealing of the a-IGZO channel layer and post-metallization annealing of the graphene S/D electrode, and then, the influence of MWA on the a-IGZO channel and graphene S/D electrode was evaluated and compared with conventional thermal annealing. We measured the ${I}$ – ${V}$ characteristics of the a-IGZO TFTs, analyzed the trap density of the channel layer, the interface trap density between the gate oxide and the channel, and the instability of device was evaluated. In addition, the effect of MWA on the contact resistance and process stability of transparent graphene electrodes was analyzed. As a result, we improved the electrical properties of the a-IGZO TFTs, simplified the annealing step, and reduced the thermal budget without damaging the graphene S/D electrode for transparent and flexible displays.

Microwave annealing promoted in-situ electrochemical activation of Ni3S2 nanowires for water electrolysis

Microwave is widely used to synthesize advanced nanomaterials for energy storage and conversion, whereas its applications remain limited in water electrolysis. Herein, we qualitatively explore the house-hold microwave annealing in atmosphere as chemical-free oxidation pretreatment strategy on Ni3S2 nanowires for hydrogen evolution reaction (HER). The microwave can induce fast surface oxidation to form metal hydroxides on catalyst which promotes in-situ electrochemical activation (ISEA) to improve the catalytic performance. The microwave annealing is superior to traditional oxidation such as chemical oxidation or Ar gas annealing. Thanks to faster reaction kinetics, better conductivity and larger electrochemical surface area, the formed NiOx/Ni3S2 hybrids by ISEA achieve 7-time higher activity and operate well for 12 h compared with pristine catalyst. The NiOx/Ni3S2 hybrids also perform well in acid (0.5 M H2SO4) and neutral (1.0 M phosphate buffer solution) media to realize all-pH water electrolysis. Moreover, the microwave annealing is found to be applicable for other transition metals such as cobalt sulfide to obtain higher HER properties. Therefore, such chemical-free modulation concept in our work might be a general access for many advanced materials in other electrocatalysis fields.

Enhanced electromagnetic wave absorption properties of NiCo2 nanoparticles interspersed with carbon nanotubes

The NiCo2 nanoparticles and NiCo2/carbon nanotubes (CNTs) nanohybrids were prepared by a single-model microwave heating and annealing treatment. It was found that the NiCo2 nanoparticles were evenly distributed around with CNTs. As a result, the complex permittivity of NiCo2/CNTs nanohybrids could be adjusted effectively, and achieved a well impedance matching for the microwave absorption. The dielectric loss, magnetic loss mechanism and the impedance matching were also investigated systematically. As a result, the reflection loss (RL) less than −20 dB (99% absorption) were observed at 3.7–16.5 GHz with the thickness of 1.2–4.0 mm; moreover, the maximum bandwidth of the RL values less than −10 dB (90% absorption) was 4.4 GHz (12.5–16.9 GHz), and a minimum RL value of −25.5 dB could be observed at 14.7 GHz with the thickness of 1.3 mm. These performances revealed that the NiCo2/10%CNTs nanohybrids have a great potential to be used as the lightweight microwave absorption material.

Improved Electrical Characteristics of ~0.5 nm EOT Ge pMOSFET With GeON Interfacial Layer Formed by NH3 Plasma and Microwave Annealing Treatments

A hole mobility of ~650 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /V-s at N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">inv</sub> = ~ 0.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , a gate leakage current density of ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> = V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FB</sub> + 1 V, and an equivalent oxide thickness of ~0.5 nm in Ge pMOSFETs are simultaneously achieved by using the GeON interfacial layer (IL) formed with NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> plasma and microwave annealing (MWA) treatments. The high performance can be attributed to the O-N polar covalent bonds in GeON, which is efficiently annealed by the MWA to increase the Ge oxidation sate in the IL. Ge out diffusion or GeO desorption can be suppressed by an MWA thanks to less thermal budget.

Simultaneous enhancement in light absorption and charge transportation of bismuth vanadate (BiVO4) photoanode via microwave annealing

We report the crystallization of electrodeposited BiVO4 photoanode by deploying conventional furnace annealing and hybrid microwave annealing, with the latter proving to possess higher crystallinity, charge carrier mobility, light absorption and conduction band level. The crystallization of BiVO4 was improved by microwave annealing, yielding higher charge carrier density. Higher morphological compactness and crystallinity for microwave annealed sample enhanced its light absorption properties. The smaller crystallite sizes upon microwave annealing resulted in band gap augmentation due to quantum confinement effect and manifested itself in its more elevated conduction band. The enhanced intrinsic properties of BiVO4 increased photoelectrochemical performance of microwave annealed sample by approximately two times compared with that of furnace annealed sample. The ultrafast synthesis as well as the possibilities of morphological, optical and electronics tunability motivates further research into devices and photoelectrodes based on microwave-annealed BiVO4.