Forming Gas Atmosphere Research Articles

Effects of Oxygen and Forming Gas Annealing on ZnO TFTs

ABSTRACTZnO TFTs with bottom gate top S/D contact architecture were fabricated by sputtering of ZnO with layer thicknesses from 30 nm to 100 nm. The effect of post deposition annealing in oxygen and forming gas atmospheres at 400°C to 500°C on the devices was investigated. The tendencies of a lower threshold voltage Vth and a higher saturation mobility μsat for higher annealing temperature can be observed for both oxygen and forming gas annealing. Reduction of trap density in oxygen annealing and additional hydrogen incorporation in forming gas annealing play an important role for these electrical parameters. Morphological changes of increased grain size and fewer grain boundaries in the channel also contribute to tendencies in electrical characteristics of ZnO TFTs.

Ultra Rapid Sintering of Ceramics

The paper presents some preliminary investigations on the sintering of alumina ceramics to translucency in a low thermal mass furnace. It is found that extremely fast sintering occurs in a forming gas atmosphere. Rapid densification occurs in minutes rather than hours normally encountered in conventional sintering of ceramics.

Flash-lamp-crystallized polycrystalline silicon films with remarkably long minority carrier lifetimes

Polycrystalline silicon (poly-Si) films formed by flash lamp annealing (FLA) of precursor a-Si films are found to hardly lose hydrogen (H) atoms during crystallization and keep the initial H concentration on the order of 10 21/cm 3. Short annealing duration and sufficient Si film thickness would lead to the suppression of H desorption. A characteristic lateral crystallization mechanism, referred to as explosive crystallization (EC), may also contribute to the prevention of H desorption due to rapid lateral heat diffusion into neighboring a-Si. Poly-Si films after annealing under N 2 or forming gas ambient shows remarkably long minority carrier lifetime compared to untreated films, indicating effective defect termination by H atoms remaining in the poly-Si films.

Mobility analysis of highly conducting thin films: Application to ZnO

Hall-effect measurements have been performed on a series of highly conductive thin films of Ga-doped ZnO grown by pulsed laser deposition and annealed in a forming-gas atmosphere (5% H2 in Ar). The mobility as a function of thickness d is analyzed by a simple formula involving only ionized-impurity and boundary scattering and having a single fitting parameter, the acceptor/donor concentration ratio K=NA/ND. For samples with d=3–100 nm, Kavg=0.41, giving ND=4.7×1020 and NA=1.9×1020 cm−3. Thicker samples require a two-layer formulation due to inhomogeneous annealing.

Conductivity and adhesion enhancement in low-temperature processed indium tin oxide/polymer nanocomposites

We report on the conductivity and adhesion enhancement of indium tin oxide (In 2O 3:Sn; ITO) nanoparticle films by the application of polymers as matrix material. We fabricated ITO layers at a maximum process temperature of 130 °C by modifying and spin-coating nanoparticulate ITO dispersions. Dispersions containing the organic film-forming agent polyvinylpyrrolidone (PVP) and the organofunctional coupling agent 3-methacryloxypropyltrimethoxysilane (MPTS) have been developed to obtain transparent and conducting coatings on substrates which do not withstand high process temperatures like polymers or already processed glasses. The layers were cured by UV-irradiation as well as by low-temperature heat treatment ( T = 130 °C) in air and under forming gas atmosphere (N 2/H 2). The influence of the additives on the electrical, optical, morphological and mechanical layer properties is reported. Compared to best pure ITO layers (3.1 Ω − 1 cm − 1 ), the ITO–MPTS–PVP nanocomposite coatings exhibit a conductance of 9.8 Ω − 1 cm − 1 . Stable sheet resistances of 750 Ω/□ at a coexistent transmittance of 86% at 550 nm for a layer thickness of about 1.3 µm were achieved. The conductance enhancement is a consequence of the consolidation of the ITO nanoparticle network due to the acting shrinkage forces caused either by drying in the case of PVP or UV-irradiation induced condensation and polymerization reactions in the case of MPTS.

Wet chemical deposited ITO coatings on flexible substrates for organic photodiodes

ITO (tin doped indium oxide) coatings were produced by gravure printing process on PET and PEN foils. The printing paste consists of ITO nanoparticles, which are dispersed in a solvent and mixed with a binder. By modification of the printing paste, the sheet resistance ( R/sq) of the ITO coatings after hardening under UV-irradiation at low temperatures (< 130 °C) could be decreased to 1 kΩ/sq. R/sq could be further reduced down to 0.5 kΩ/sq by heat treatment under forming gas atmosphere (N 2/H 2), the transmission of the ITO coated foils still being more than 80% in the visible range. The application of these ITO films as a bottom electrode in organic photodiodes (OPDs) is shown, and the current density–voltage characteristics of the OPDs are presented.

Micro fabrication of stainless steel micro components using soft moulding and aqueous slurry

Presented is a fabrication process of stainless steel micro components. The fabrication process is divided into two main parts. In the first part, high quality SU-8 master moulds and their negative replicas from soft moulds are produced using photolithography and soft moulding techniques, respectively. The second part includes preparation of stainless steel slurry, filling the soft mould, obtaining the green parts, de-binding and sintering to the finial parts. The metallic slurry is investigated in details and the optimum dispersant and binder are obtained. Two different sintering conditions are investigated, vacuum and forming gas atmospheres. The effect of sintering atmospheres and temperatures on both density and linear shrinkage of the micro components are studied in details. The results show high quality micro components the same quality as the master moulds. The maximum sintered density and linear shrinkage are obtained when the samples are sintered in vacuum at 1350 °C and found to be 98.1% and 17.97%, respectively. The surface roughness of the sintered micro components is also investigated.

Electrochemical Synthesis of Nanocrystalline In&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;:Sn (ITO) in an Aqueous System with Ammonium Acetate as Conducting Salt

Nanoscaled so called indium tin oxide In2O3:Sn (ITO) with a specific BET surface area of 50 m2/g to 60 m2/g was prepared via an electrochemical method in an aqueous system containing ammonium acetate as conductive salt. As an intermediate product of the synthesis nanocrystalline In(OH)3 is obtained which serves as a precursor for the subsequent calcinations accompanied by tin doping resulting in ITO powders with various tin concentrations. Its phase transitions and the reduction behaviour of hydroxide to oxide during the calcination process in air flow and forming gas atmosphere of N2 to H2 ratio of 95 to 5 respectively, have been investigated by high temperature X-ray diffraction, TG/DSC/MS, HRTEM and SEM analysis. Depending on the atmosphere dehydration of tin doped In(OH)3 started at 150 degrees C, cubic ITO solid solution formed between 190 degrees C and 300 degrees C. The total weight loss of the hydroxide of approx. 21% occurred mainly below 360 degrees C and the burn-out of organic components mainly between 308 degrees C and 316 degrees C. The results of DSC and MS analyses were in good agreement with the results of the X-ray diffraction. In addition, the products have been characterized by EDX associated with TEM, XPS, ICP-AES, BET analysis and 119Sn Mössbauer spectroscopy. Completely reacted samples of ITO have been processed to pellets, calcined and sintered in the temperature range between 900 degrees C and 1100 degrees C and characterized by measurements of the electrical conductivities of bulk and surface in the reduced as well as in the oxidized state giving values up to 1400 Scm(-1).

A Soft Molding Process for Fabrication of Micromachine Parts from Stainless Steel Powder

This work introduces a valid approach to fabricate high quality micromachine parts from stainless steel powder using soft molding and powder metallurgy techniques. In soft molding, SU-8 and negative replicas micromolds are produced. A mixture of Duramax B-10007 and B-1000 is successfully used as a binder in the preparation of stainless steel slurry. Sintering in forming gas atmosphere is very effective of preventing the oxidation of the stainless.

The influence of annealing conditions on the growth and structure of embedded Pt nanocrystals

The growth and structure of Pt nanocrystals (NCs) formed by ion implantation in a-SiO2 has been investigated as a function of the annealing conditions. Transmission electron microscopy and small-angle x-ray scattering measurements demonstrate that the annealing ambient has a significant influence on NC size. Samples annealed in either Ar, O2, or forming gas (95% N2: 5% H2) at temperatures ranging from 500 °C–1300 °C form spherical NCs with mean diameters ranging from 1–14 nm. For a given temperature, annealing in Ar yields the smallest NCs. O2 and forming gas ambients produce NCs of comparable size though the latter induces H chemisorption at 1100 °C and above, as verified with x-ray absorption spectroscopy. This H intake is accompanied by a bond-length expansion and increased structural disorder in NCs of diameter &amp;gt;3 nm.

Net shape fabrication of stainless-steel micro machine components from metallic powder

A fabrication process of the net shape 316-L stainless-steel micro machine components is reported. The fabrication process combines softlithography and powder metallurgy to produce microcomponents of complex geometries of high quality. The process starts with softlithography by producing ultra thick SU-8 master moulds and their negative replicas of polydimethylsiloxane (PDMS). Then stainless-steel slurry is prepared by mixing super fine 316-L steel powder and binder to fill the PDMS moulds. The two binders used in the experiments were Duramax D-3005 and a mixture of B1000 and B1007. The PDMS micro moulds are filled with the metallic slurries and green parts are obtained from de-moulding, before going through de-binding and sintering in forming gas atmosphere. The fabrication steps were repeatedly tested. The resultant micro parts show high quality shape retention which is attributed to the quality of the SU-8 master moulds. The hardness property of the sintered microcomponents was tested with a micro indenter and a 200 g load was applied. The Vickers hardness of the sintered components was found to be about 255, which was higher than 225 of annealed 316L stainless steel and the two binders make little difference on the hardness of the sintered samples.

A Study of Deep Energy-Level Traps at the 4H-SiC/SiO&lt;sub&gt;2 &lt;/sub&gt;Interface and Their Passivation by Hydrogen

This study is focused on characterization of deep energy-level interface traps formed during sodium enhanced oxidation of n-type Si face 4H-SiC. The traps are located 0.9 eV below the SiC conduction band edge as revealed by deep level transient spectroscopy. Furthermore these traps are passivated using post-metallization anneal at 400°C in forming gas ambient.

Thermal Stability Study of Pore Sealing Using Parylene N

The thermal stability of chemical vapor deposited (CVD) Parylene N used as a pore sealant has been evaluated. Parylene N pore sealing is shown to have a thermal stability up to in an Ar-3% forming gas ambient. A thin film of Parylene N remains effective at blocking Co precursor penetration into porous methyl silsesquioxane (MSQ) during the CVD of Co, even after being annealed at temperatures up to . The leakage current improvement of pore sealed MSQ with an Al electrode is also maintained after a anneal. In addition, the thermal stability of thin Parylene N films themselves has been verified up to .

Forming Gas Annealing Characteristics of Germanium-on-Insulator Substrates

Large-area layer transfer of germanium-on-insulator (GeOI) substrates has been fabricated by ion-cut processes. Pseudo-MOSFET structure was employed to characterize interface trap density, interface fixed charge density, interface carrier mobility, and bulk carrier mobility of these GeOI substrates with various annealing conditions in forming gas ambient. High-temperature annealing in the vicinity of 500degC-600degC has shown the best carrier mobilities, with the interface trap density and the interface fixed charge density as low as 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> q/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The extracted bulk hole mobility of the annealed GeOI is near 500 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /( V middots), which is higher than that of silicon [300 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /(V middots)] at the same doping concentration level.

Fabrication of 316-L stainless steel micro parts by softlithography and powder metallurgy

This paper presents an approach to fabricate 316-L stainless steel micro parts with complex shapes using soft lithographical and powder metallurgical techniques. The process includes production of high quality deep micro SU-8 master moulds and their negative replicas in polydimethylsiloxane (PDMS). Then the PDMS soft moulds are filled with slurry containing superfine (< 4 um) stainless steel particles and binder. When the slurry is dry, green patterns are removed from the PDMS moulds before the patterns are de-bound and sintered in the tube furnace at 1200 in forming gas atmosphere. The resultant micro parts show high shape retention. The linear shrinkage of the sintered part is measured and found to be 17%.

Structural Evolution and Electrical Properties of Sc2O3-Stabilized ZrO2Aged at 850°C in Air and Wet-Forming Gas Ambients

X-ray diffraction (XRD) and electron microscopy investigations have been performed on Sc2O3-stabilized ZrO2 as-sintered and after aging in air or in wet-forming gas at 850°C for 1000 h. Some tetragonal to monoclinic transformation had occurred in the near-surface regions of 4 mol% Sc2O3 samples after aging; the phase transition was more severe for samples aged in the forming gas ambient. A decrease of ∼20% in electrical conductivity accompanied the aging. In 6 mol% Sc2O3 samples, although no cubic to tetragonal transformation was detected, both the electrical conductivity and the activation energy for ionic conductivity decreased significantly during aging. Ten mole percent Sc2O3 samples did not show appreciable change in electrical conductivity due to aging, although some near-surface cubic to rhombohedral transformation did occur. Sharpening of the (400)t XRD peak of Sc2O3-stabilzed tetragonal ZrO2 accompanies the change(s) in the electrical conductivity.

Ti/Ni(80%)Cr(20%) Thin-Film Resistor With a Nearly Zero Temperature Coefficient of Resistance for Integration in a Standard CMOS Process

A thin-film resistor out of Ni(80%)Cr(20%) for integration in a standard complementary metal-oxide-semiconductor process with a temperature coefficient of resistance (TCR) below 10 ppm/K was realized by applying a thin Ti layer underneath. The Ti-layer thickness and the temperature and duration of furnace annealing after deposition were optimized in different experiments. The combination of 5-nm Ti + 10-nm NiCr and a 30-min heat treatment at 350degC in a forming gas ambient was found to yield a sheet resistance of about 140 Omega/sq and a TCR of below 10 ppm/K. The long-term drift of the sheet resistance after 1000 h at 200degC was about 0.3%. A transmission electron microscopy analysis was conducted to investigate the structure of the film and a possible change during annealing. An Auger analysis was conducted for film surface analysis.

Transmission Electron Microscopy Observations on the Interfacial Structures of the Pt/SrBi2Ta2O9/Pt Thin-Film Capacitors Prepared by Metallo-Organic Decomposition

Interfacial structures of the Pt/SBT/Pt capacitors prepared by metallo-organic decomposition were examined by transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) as a function of the postannealed time at 750°C to investigate the interfacial evolution developed in the Pt/SBT/Pt capacitors. The results show that after postannealing at 750°C for a short time (e.g., 300 s), a thin amorphous layer was observed at the interfaces of the SBT/Pt-bottom and the SBT/Pt-top electrodes in the Pt/SBT/Pt capacitors, whereas after postannealing for a moderate time (e.g., 20 min), the interfaces of the SBT/Pt-bottom and the SBT/Pt-top electrodes became quite smooth and uniform, and almost free of the interfacial phase. However, after postannealing for a longer time (e.g., 60 min), an interfacial phase consisting of oval-shaped nanocrystallites was developed at both the SBT/Pt-bottom and the SBT/Pt-top electrode interfaces, which resulted in weakly bonded interfaces between the SBT films and Pt electrodes. This is the reason why a Pt electrode peeling phenomenon (similar to that reported in the Pt/SBT/Pt/capacitors annealed in the forming gas atmosphere) is frequently observed in the Pt/SBT/Pt capacitors postannealed for 60 min during the fabrication of cross-sectional TEM samples. Based on two-dimensional lattice fringes of the HRTEM images from the small nanocrystallites and the corresponding fast Fourier transform patterns, the oval-shaped nanocrystallites precipitated at both the SBT/Pt-bottom and the SBT/Pt-top electrode interfaces were determined to be a PtBi2 phase with a cubic structure. The formation of the Pt–Bi-based interfaces in the Pt/SBT/Pt capacitors is due to the reaction of bismuth (out-diffused from the SBT films) with Pt electrodes during the postannealing process. The elliptical morphology of the interfacial PtBi2 phase can be ascribed to its different growth rates in the parallel and vertical directions of the interface, and also the limited space for grain growth perpendicular to the interface.

Low temperature high k dielectric on poly-Si TFTs

In this work, it is demonstrated the application of a high k dielectric, as hafnium oxide (HfO2), in poly-Si thin film transistors (TFTs) obtained by metal induced lateral crystallization (MILC). The dielectric layer was deposited at room temperature by sputtering, using argon and oxygen as process gases. As produced TFTs exhibit field effect mobility around 45cm2V−1s−1and Ion/Ioff ratio of about 2×105. After annealing in a forming gas atmosphere for about 1h at 200°C, the threshold voltage and the sub-threshold slope are reduced, respectively from 4.8 to 2V and from 1.6 to 1.4V/dec. Nevertheless, by doing so, we notice a reduction on the field effect mobility of about 45% and a decrease of about 2.5 times on the Ion/Ioff ratio. Longer annealing time will not improve the TFT’s performance.

Effects of annealing on the electrical properties of highly resistive float zone p-type silicon

This paper reports effects of heat treatment in nitrogen or forming gas ambient on the electrical properties of highly resistive float zone p-type silicon (Si). Capacitance–voltage and Hall Effect measurements were used to examine role of impurities associated with annealing. A reduction in the free carrier density was observed for both the nitrogen and forming gas anneals. In addition, temperature-dependent capacitance measurements revealed the appearance of deep traps with a concentration of 2×10 11 cm −3, following the nitrogen anneal.