Metal Oxide Chemical Vapor Deposition Research Articles

Nextchem's MyRechemical and Johnson Matthey team up to commercially develop waste-to-methanol technology

Nanostructures of TiO2 were grown using the metal oxide chemical vapor deposition (MOCVD) technique. The procedure used induction heating on a graphite susceptor. This specific feature and the use of cobalt and ferrocene catalysts resulted in nanomembranes never obtained by common MOCVD reactors. The present study discusses the preparation of TiO2 nanomembranes and the dependence of nanomembrane structure and morphology on growth parameters.

A Temperature Stable Amplifier Characteristics of AlGaN/GaN HEMTs on 3C-SiC/Si

A high temperature stable amplifier characteristics for L-band or 2 GHz was studied using AlGaN/GaN high electron mobility transistors (HEMTs) on 3C-SiC/Si substrate. A crack free, high quality AlGaN/GaN heterostructure on a 6-inch Czochralski (Cz)-Si substrate was realized by metal oxide chemical vapor deposition (MOCVD). The epitaxial structure comprises an $8~\mu \text{m}$ thick nitride layer and a $1~\mu \text{m}$ thick 3C-SiC intermediate layer. The fabricated AlGaN/GaN HEMT achieved excellent electron transport characteristics along with a comparable cutoff frequency ( ${f}~_{\text {T}}$ ) of 4.8 GHz for $2~\mu \text{m}$ gate length device. Temperature dependent S-parameter measurement of open pad structures achieved outstanding temperature stability up to $125~^\circ \text{C}$ . Continuous wave power measurements showed a 2 GHz continuous wave power density of 2 W/mm, a maximum power added efficiency (PAE) of 47% along with a linear gain of 17.2 dB for class A amplifier operation. Moreover, at elevated temperature of up to $125~^\circ \text{C}$ , the minimal power performance degradation was mainly attributed to the intrinsic property of the device, thus elimination of RF leakage from the buffer or epitaxial layers at high temperatures was confirmed.

Elimination of the Low Resistivity of Si Substrates in GaN HEMTs by Introducing a SiC Intermediate and a Thick Nitride Layer

We report the effect of a thick nitride layer on the high-frequency performance of AlGaN/GaN highelectron-mobility transistors (HEMTs) grown by metal oxide chemical vapor deposition (MOCVD) on a 6-inch Czochralski (Cz)-Si substrate. The thick nitride layer was grown via a 3C-SiC intermediate layer. A significantly low parasitic pad capacitance and a comparable cutoff frequency of 4.5 GHz for 2-μm gate length devices were achieved along with excellent electron transport characteristics, such as a mobility of ~2200 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /V-s and a drain current density of 520 mA/mm. The extracted small-signal equivalentcircuit parameters also verified the accuracy of the measured cutoff frequency and parasitic capacitances.

Linearity Improvement With AlGaN Polarization- Graded Field Effect Transistors With Low Pressure Chemical Vapor Deposition Grown SiNx Passivation

In this letter, we discuss the application of low pressure chemical vapor deposition (LPCVD) grown SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> passivation-first process to improve the power density and linearity performance of a metal oxide chemical vapor deposition (MOCVD) grown AlGaN channel polarization-graded field-effect transistor (PolFET). Significantly improved dispersion behavior was observed compared to plasma enhanced chemical vapor deposition (PECVD) grown SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> passivation. The Current collapse at 30 V drain quiescent condition for pulsed I-V was reduced to 8% (LPCVD) from 25% (PECVD). 10 GHz load-pull measurement showed a maximum output power density of 3.4 W/mm with a peak power added efficiency (PAE) of 40%. Two-tone intermodulation distortion measurement at 10 GHz for devices with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$150\boldsymbol {\mu }\text{m}$ </tex-math></inline-formula> width revealed an OIP3 of 39 dBm and an excellent corresponding linearity figure of merit OIP3/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{P}_{{\textit {DC}}}$ </tex-math></inline-formula> of 13.3 dB. This is the best device level OIP3/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{P}_{{\textit {DC}}}$ </tex-math></inline-formula> reported to date at X-band for III-Nitride microwave transistors.

Electronic surface, optical and electrical properties of p – GaN activated via in-situ MOCVD and ex-situ thermal annealing in InGaN/GaN LED

Electronic surface properties, optical and electrical characteristics of p-type Mg-doped Gallium Nitride (p-GaN) activated under different thermal annealing condition were investigated. In this work, p-GaN samples were subjected to in-situ and ex-situ thermal annealing process at 650 °C in Nitrogen (N2) rich condition. In-situ annealing process took place in Metal Oxide Chemical Vapor Deposition (MOCVD) chamber while ex-situ annealing process was carried out in the conventional oven. X-Ray and Ultraviolet Photoemission Spectroscopy (XPS/UPS) were used to observe the energy alignment of the p-GaN surface. From PES spectra, the sample subjected to in-situ thermal annealing shown to exhibit lower surface bend bending of 0.28 eV as compared to ex-situ thermal annealing activation with 0.45 eV band bending. This result is in agreement with specific contact resistance measurement that shows in-situ sample exhibits lower resistance resulted in better carrier injection from metal to p-GaN. Photoluminescence (PL) spectra elucidates that in-situ sample has a good surface quality with less nitrogen related vacancies (VN) formed on the p-GaN surface. All these results are further proved with the higher output power from LED with in-situ annealing. At 20 mA, in-situ sample shown an increment of ~14% light output power compared to ex-situ sample. Results obtained in this work suggest that the thermal activation condition for p-GaN activation process plays an active role on the surface quality as well as the energy alignment of the film surface and shows the potential of in-situ p-GaN activation for tunnel junction structure.

Structure and photoluminescence properties of InN films grown on porous silicon by MOCVD

In this work, indium nitride (InN) films were successfully grown on porous silicon (PS) using metal oxide chemical vapor deposition (MOCVD) method. Room temperature photoluminescence (PL) and field emission scanning electron microscopy (FESEM) analyses are performed to investigate the optical, structural and morphological properties of the InN/PS nanocomposites. FESEM images show that the pore size of InN/PS nanocomposites is usually less than 4 μm in diameter, and the overall thickness is approximately 40 μm. The InN nanoparticles penetrate uniformly into PS layer and adhere to them very well. Nitrogen (N) and indium (In) can be detected by energy dispersive spectrometer (EDS). An important gradual decrease of the PL intensity for PS occurs with the increase of oxidation time, and the PL intensity of PS is quenched after 24 h oxidization. However, there is a strong PL intensity of InN/PS nanocomposites at 430 nm (2.88 eV), which means that PS substrate can influence the structural and optical properties of the InN, and the grown InN on PS substrate has good optical quality.

Transport properties and electroresistance of a manganite based heterostructure: role of the manganite-manganite interface.

In this paper, we report the results of the investigations on the transport properties performed across the manganite-manganite interface in the LaMnO3-δ/La0.7Ca0.3MnO3/LaAlO3 (LMO/LCMO/LAO) heterostructure. The bilayered heterostructure was synthesized by a low cost and simple chemical solution deposition (CSD) method by employing the acetate precursor route. The same LMO/LCMO/LAO heterostructure was also grown using the dry metal oxide chemical vapor deposition (CVD) method and the results of transport characterization have been compared on the basis of wet and dry chemical methods used. XRD Φ-scan measurements were carried out to verify the structural quality and crystallographic orientations of LMO and LCMO manganite layers, for both wet and dry chemical method grown heterostructures. For wet and dry chemical methods, the temperature dependent resistance of the LMO/LCMO interface suggests the metallic nature. The asymmetric I-V curves collected at different temperatures show normal diode characteristics which get transformed to backward diode characteristics at high temperatures under high applied voltages at Vtr for both the methods. The values of Vtr are strongly dependent on the chemical method used. I-V data have been fitted using the Simmons model at different temperatures and discussed in terms of the spin-flip scattering mechanism for both wet and dry chemical method grown heterostructures. The electric field dependent electroresistance (ER) behavior of the presently studied LMO/LCMO manganite-manganite interface, grown using wet and dry chemical methods, has been understood on the basis of complex mechanisms including charge injection, formation of the depletion region, the tunneling effect, thermal processes and junction breakdown and their dependence on the applied electric field, field polarity and temperature studied.

Study of TiO2 nanomembranes obtained by an induction heated MOCVD reactor

Nanostructures of TiO2 were grown using the metal oxide chemical vapor deposition (MOCVD) technique. The procedure used induction heating on a graphite susceptor. This specific feature and the use of cobalt and ferrocene catalysts resulted in nanomembranes never obtained by common MOCVD reactors. The present study discusses the preparation of TiO2 nanomembranes and the dependence of nanomembrane structure and morphology on growth parameters.

High resolution medium energy ion scattering analysis for the quantitative depth profiling of ultrathin high-k layers

Ultrathin high-k layers such as hafnium oxide (HfO2) in combination with a subnanometer SiO2 or Hf silicate have emerged as Si compatible gate dielectric materials. Medium energy ion scattering (MEIS) analysis has been carried out on a range of such metal oxide chemical vapor deposition grown HfO2∕SiO2 and HfSiOx(60%Hf)∕SiO2 gate oxide films of thickness between 1 and 2nm on Si(100), before and after decoupled plasma nitridation (DPN). The ability of MEIS in combination with energy spectrum simulation to provide quantitative layer information with subnanometer resolution is illustrated and the effect of the DPN process is shown. Excellent agreement on the deduced layer structures and atomic composition with the as grown layer parameters, as well as with those obtained from cross section electron microscopy and other studies, is demonstrated. MEIS analysis of a high-k, metal gate TiN∕Al2O3∕HfO2∕SiO2∕Si stack shows the interdiffusion, after thermal treatment, of Hf and Al from the caplayer, inserted to modify the metal gate workfunction.

수열합성 법으로 성장된 산화 아연 나노로드의 전구체 농도에 따른 구조적, 광학적 특성 연구

Zinc Oxide (ZnO) nanorods arrays were deposited on ZnO buffered p-Si(100) substrates by hydrothermal method. The ZnO buffer layer with a thickness of 30 nm was deposited by metal oxide chemical vapor deposition at . The structural and optical properties of ZnO nanorods arrays controlled by precursor concentrations from 0.06 to 0.5 M were studied by FE-SEM(field emission scanning electron microscopy), XRD(X-ray diffraction), and PL(photoluminescence), respectively. It was found that the structural and optical properties of ZnO nanorods arrays are changed significantly with increase of precursor concentration. The sizes of diameter and length of nanorods were increased as the concentration increase, and good optical property was shown with the concentration of 0.3 M.

Nanoscopic versus macroscopic C– V characterization of high- κ metal-oxide chemical vapor deposition ZrO 2 thin films

In this paper we compare macroscopic C– V-measurements with (local) scanning capacitance (SCM) measurements to extract electrical parameters. In future microelectronic CMOS devices, high- κ dielectrics, primarily as gate oxides, will play an important role. The characterization of their electrical behaviour is one key issue to evaluate their suitability. We deposited zirconium dioxide (ZrO 2) thin films by metal–organic chemical vapor deposition (MOCVD) on (1 0 0)-silicon substrates to fabricate metal oxide semiconductor gate stacks. These devices were evaluated by conventional C( V) characterization using a probing station. Additionally, we applied a new C( V)-characterization method, allowing to determine electrical characteristics of nm-thick dielectric films on a nanoscopic scale. This method enabled us to directly compare the nanoscopic and macroscopic measurements. As a result, local and global measurements turned out to be consistent. A comparison of our ZrO 2high- κ layers with thermal SiO 2 films indicate a superior behaviour of MOCVD grown ZrsO 2 film.

Low-Frequency Noise Performance of HfO2-Based Gate Stacks

The low-frequency noise characteristics of -based dielectrics have been investigated. Attention is given to the deposition technique (metal oxide chemical vapor deposition or atomic layer deposition) used, the film thickness, and the use of a interface layer. n-Type metal oxide semiconductor devices with equivalent oxide thicknesses (EOTs) of 1.5, 2, 3, and 5.5 nm were studied. It is shown that the LF noise of such high- transistors is like. The behavior of the normalized current spectral density vs the drain current points out that for relative thin interfacial layers and at high gate voltages carrier trapping in the layer governs the current fluctuations. The trap densities extracted from the noise are up to 200 times higher than in a thermal oxide reference wafer (5.5 nm EOT). The deposition technique has no strong impact on the density of traps in the high- layer, which is in the range of . However, a strong difference was observed in the noise contribution, which is dominated by carrier scattering at charged traps. For , the scattering coefficient derived from the noise is smaller than for , which can be interpreted in terms of the suppression of the coulomb scattering by the high dielectric constant.

In situ fabrication of metal gate/high-κ dielectric gate stacks using a potential lower cost front-end process for the sub-90nm CMOS technology node

In this article we discuss the advantages of in situ fabrication of metal gate/high-κ gate stacks using single wafer processing. The aim was to develop an in situ process for the sub-90nm CMOS regime, which allows for a reduction in the number of processing steps and consequently the number of processing tools, while also providing for improved device performance, yield and reliability. In this work, we demonstrate improved electrical characteristics of ultrathin high dielectric constant films processed by rapid thermal processing (RTP) assisted metal-oxide chemical vapor deposition (MOCVD), where the silicon wafer underwent an in situ precleaning treatment followed by an in situ oxide deposition, in situ oxide anneal, and an in situ metallization step. Gate leakage currents on the order of 10−11A∕cm2 at a gate voltage of 1V and an EOT of 1.5nm were measured across the Al2O3 gate oxide of the gate stacks. These results present an improvement of two orders of magnitude over gate leakage currents measured across Al2O3 gate oxides with comparable EOT values reported in literature.

Electrical Evaluation of Defects at the Si ( 100 ) / HfO2 Interface

This work examines the electrical activity of defects at the interface with Si(100) for thin films (10-20 nm) deposited by injection metal oxide chemical vapor deposition. Based on an analysis of the capacitance-voltage response of structures, two clear peaks are detected in the interface state density profiles, at specific energies in the lower eV) and upper eV) bandgap. The densities of defects responsible for these peaks have been calculated as and respectively. These defects are present when the films were deposited at sufficiently low temperatures to prevent hydrogen passivation. The density of interface defects was not significantly different for films deposited on native oxide or hydrogen-terminated silicon surfaces. The position of these defects in the silicon bandgap corresponds to the location of dangling bond defects in the thermally oxidized system. films deposited at 450°C did not exhibit the prominent interface defects observed on films deposited at indicating hydrogen passivation during deposition. © 2004 The Electrochemical Society. All rights reserved.

Growth of the dilute magnetic semiconductor GaMnN by molecular-beam epitaxy

Growth by molecular-beam epitaxy (MBE) of the dilute-magnetic alloy GaMnN is reported. The Mn concentration, as determined by Auger electron spectroscopy (AES), is found to be linear with increasing Mn-cell temperature up to ∼43at.%Mn. No second phases are observed for Mn levels below 9 at.%. The cubic-phase Mn4N is found to be the thermodynamically stable phase at the growth conditions used to produce GaMnN. Hysteresis in M versus H is observed in both GaMnN and GaMnN:C grown on both sapphire and metal-oxide chemical-vapor deposition (MOCVD) GaN at several growth temperatures. Magnetotransport results show the anomalous Hall effect, negative magnetoresistance, and magnetic hysteresis, indicating that Mn is incorporating into the GaN and forming the ferromagnetic-semiconductor GaMNN. Room-temperature hysteresis is obtained in magnetization measurements with an optimum Mn concentration of ∼3 at.%.

Electrical Characterization of GaN Metal Oxide Semiconductor Diodes Using MgO as the Gate Oxide

GaN metal oxide semiconductor diodes were demonstrated utilizing MgO as the gate oxide. MgO was grown at 100°C on metal oxide chemical vapor deposition grown n-GaN in a molecular beam epitaxy system using a Mg elemental source and an electron cyclotron resonance oxygen plasma. -based wet-chemical etchant was used to remove MgO to expose the underlying n-GaN for ohmic metal deposition. Electron deposited Ti/Al/Pt/Au and Pt/Au were utilized as ohmic and gate metallization, respectively. An interface trap density of low-to-mid- eV−1 cm−2 was obtained from temperature conductance-voltage measurements. Terman method was also used to estimate the interface trap density, and a slightly lower number was obtained as compared to the conductance method. Results from elevated temperature (up to 300°C) conductance measurements showed an interface state density roughly three times higher eV−1 cm−2) than at 25°C. © 2002 The Electrochemical Society. All rights reserved.

Nitrogen (N2) Implantation to Suppress Growth of Interfacial Oxide in Mocvd Bst and Sputtered Bst Films

ABSTRACTBa0.5Sr0.5TiO3 (BST) is one of the high-k candidates for replacing SiO2 as the gate dielectric in future generation devices. The biggest obstacle to scaling the equivalent oxide thickness (EOT) of BST is an interfacial layer, SixOy, which forms between BST and Si. Nitrogen (N2) implantation into the Si substrate has been proposed to reduce the growth of this interfacial layer. In this study, capacitors (Pt/BST/Si) were fabricated by depositing thin BST films (50Å) onto N2 implanted Si in order to evaluate the effects of implant dose and annealing conditions on EOT. It was found that N2 implantation reduced the EOT of RF magnetron sputtered and Metal Oxide Chemical Vapor Deposition (MOCVD) BST films by ∼20% and ∼33%, respectively. For sputtered BST, an implant dose of 1×1014cm−;2 provided sufficient nitrogen concentration without residual implant damage after annealing. X-ray photoelectron spectroscopy data confirmed that the reduction in EOT is due to a reduction in the interfacial layer growth. X-ray diffraction spectra revealed typical polycrystalline structure with (111) and (200) preferential orientations for both films. Leakage for these 50Å BST films is on the order of 10−8 to 10−5 A/cm2—lower than oxynitrides with comparable EOTs.

Characterization of a GaAs metal–semiconductor–metal low-energy electron detector

In this article we present the preliminary results regarding the performance characterization of a metal–semiconductor–metal low-energy (≤1 keV) electron detector fabricated by electron-beam lithography on metal–oxide chemical vapor deposition grown GaAs. These devices display very low dark currents, ≤3 nA at 1 V and 300 nA at 9 V. Also, under electron-beam irradiation very high gain values (≳1000) have been noted, which could be evidence of avalanche multiplicative effects. In addition, the input/output response of the device shows a high degree of linearity even in the high gain regime. The signal-to-noise response of the devices is well within the acceptable range of operation for low current sensitivity.

Structure of the (100) GaAs on GaP interface

A 55-nm-thick GaAs layer has been grown on a (100) GaP substrate at a temperature of 550 °C by metal–oxide chemical vapor deposition. The morphology and the structure of the interface and the epitaxial GaAs layer has been studied by transmission electron microscopy (TEM). The growth was found to be two-dimensional without any indications of island growth. The 3.7% misfit between GaAs and GaP is partially relaxed by misfit dislocations which are located at the interface. The misfit dislocations are arranged in a regular array along the 〈110〉 directions in the interface plane. Many stacking faults and fewer microtwins are observed in the overgrown GaAs layer, whose generation is discussed. Models for the two dominant misfit dislocation types are proposed, based on high-resolution TEM results.