Reactive RF Magnetron Sputtering Method Research Articles

Growth mechanism and field emission of B doped AlN films

This paper highlights the effect of boron dopant on the field emission and growth mechanism of AlN films. The films have been grown by reactive RF magnetron sputtering method. For undoped films, columnar AlN structure was obtained. In the case of boron doped AlN films, the structure growth proceeded gradually through four layers of different thicknesses and structures. It was found that boron favors the formation of an amorphous layer within which oxygen and boron based precipitates develops, retarding the growth of columnar morphology. Depth profiling X-ray photoelectron spectroscopy analyses confirm the presence of B-O, B-N, Al-B and Al-O groups.The study on the field emission (FE) properties of undoped and B doped AlN films on Si substrates indicates that the addition of boron allow to improve FE properties with low turn on field of 2.6 V/μm and low threshold filed of 3.07 V/μm. Such good field emission properties can be attributed to the formation of densely nanograined surface and the appearance of boron based groups.

Reactive RF magnetron sputtering epitaxy of NiO thin films on (0001) sapphire and (100) MgO substrates

Epitaxial growths of NiO thin films were realized on (0001) sapphire and (100) MgO substrates by using a reactive RF magnetron sputtering method. The NiO epilayers grown on a (0001) sapphire exhibited the (111)-oriented double-domain structure, which comprised of a triangular and its inverted triangular grains. Meanwhile, the NiO epilayers on a (100) MgO exhibited the (100)-oriented single-domain structure, which comprised of quadrangular grains. The observed grain structures most likely reflect the growth planes of respective NiO epilayers, and, mixed crystals of NiO and MgO were present near the interface. Therefore, a (100) MgO substrate is suitable for obtaining a single-domain NiO epilayer, whereas a (0001) sapphire substrate is suitable for obtaining a NiO epilayer without interdiffusion between NiO and sapphire. These NiO epilayers will be expected for applying the physical properties evaluation using photoluminescence or Hall measurements, and the fabrication of electrical or optical devices.

Electrical and optical characterization of AgxO films deposited by RF reactive magnetron sputtering

Silver oxide (AgxO) has huge potential in the catalysts and semiconductor devices applications and thus it is of great significance to characterize its semiconductor properties. Here, by using the RF reactive magnetron sputtering method under different substrate temperatures, 40, 100, and 200°C, respectively, three AgxO films were prepared and their semiconductor properties were carefully investigated through X-ray diffraction, Hall measurement, transmittance and photoluminescence spectrum. The main phase of the AgxO films sputtered at 40 and 100°C is found to be AgO, while that sputtered at 200°C is Ag2O. The resistivity of the AgxO films increases with the substrate temperature and the mobility of the AgO films are about 21 and 15cm2/V·s for the 40 and 100°C deposited films, respectively. Photoluminescence measurement results suggest that the band gaps of Ag2O and AgO films are both 3.4eV, and the emission bands in the visual light region indicate the existence of amount of defects in the AgxO films. Moreover, the defect levels in the band gap deduced from the transmittance spectra are consistent with that from the photoluminescence spectra analysis. Besides, a metal-metal-semiconductor-metal structured X-ray detector was fabricated using the high-resistivity Ag2O film to explore its photoconductive response to the X-ray. The signal to noise ratio is 65 and the sensitivity is 4.2nC/Gy at 5V bias voltage using the 30kV X-ray source with the dose rate of 1.53Gy/s.

ZnO thin film synthesis by reactive radio frequency magnetron sputtering

In this study, ZnO thin films were deposited on glass substrates by reactive RF magnetron sputtering method at argon–oxygen gas mixing (1:1) atmosphere. Some properties of the synthesized films were investigated by interferometry, UV–vis spectrophotometer, atomic force microscopy, and tensiometer. Tauc method was adopted to estimate the optical band gaps. The band gaps of the deposited films were affected by film thickness. We concluded that the surface composition plays a substantial role in the values of the band gaps. Nanocrystalline structures were detected in all produced samples.

Nitrogen Concentrations on Structural and Optical Properties of Aluminum Nitride Films Deposited by Reactive RF-Magnetron Sputtering

We have fabricated Aluminum Nitride (AlN) films on the quartz substrates using RF-reactive magnetron sputtering method. The conditions of the films have been performed under different concentration ratios between nitrogen and argon. We have found that all obtained films were transparent in visible wavelength. By using X-ray diffraction (XRD) technique, it was found that the (002), (102) and (103) orientations were shown in XRD patterns. The (002) orientation was dominant when nitrogen concentration (CN) was at 40%. On the other hand, the refractive index and optical band gap energy of the films were determined as a function of CN. We have found that the refractive index weakly depended on CN, while optical band gap energy did not.

Magneto-transport study of magnetite (Fe3O4) nanoparticles between Au nanogap electrodes on surface-oxidized Si substrate

We have studied the magneto-transport of magnetite (Fe3O4) nanoparticles (MNPs) between Au nanogap electrodes (ANGEs) on surface-oxidized Si substrate. The MNP sizes are approximately 40nm and the 100nm thick magnetite thin film (which is formed of the MNP aggregation) was prepared between and around the ANGEs by use of the RF reactive magnetron sputtering method. The distance between the ANGEs and the bridge width of the ANGEs are approximately 50nm and 1.5μm, respectively. The ANGEs were produced by the tilted-angle-deposition method. The optical microscope, scanning electron microscope and atomic force microscope were used to observe the sample surface structure and morphology. To investigate the crystal structure and crystallinity of the MNPs, the X-ray diffraction measurement was performed. The electrical resistance and magneto-resistance ratio of the MNPs between the ANGEs were measured as a function of temperature. The magneto-transport mechanism is discussed on the basis of the spin dependent transport.

Influence of Chemical Bonding States on Electrical Properties of Amorphous Carbon Nitride Films

The electrical properties of amorphous carbon nitride (a-CNx) films have been investigated in terms of the nitrogen concentration (N/C) and chemical bonding states in the films. The films were deposited by the reactive rf magnetron sputtering method. Nitrogen concentration and chemical bonding states in the films were controlled by regulating the deposition temperature. C–C networks in the films changed to those having a graphite like structure with decreasing N/C, as deduced by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). In addition, the N–sp2C bonding state becomes more predominant. These results indicate the contributions of the N–sp2C component to the decrease in electrical resistivity and increase in photoconductivity.

Effect of ion treatment on the structure and optical properties of nanocrystalline In2O3:Sn films

Transparent conductive films of indium oxide doped with tin have been obtained by the reactive RF-magnetron sputtering method with ion treatment of the specimen during film condensation. Ion treatment of the oxide surface during the sputtering process leads to the formation of a preferred crystallite orientation, a decrease in the size of the coherent reflection areas and an increase in the optical transparency window.

Measurements of Microwave Dielectric Properties of (1-x)TiO2-xCaTiO3 and (1-x)TiO2-xSrTiO3 thin Films By The Cavity Perturbation Method

This research studies the measurements of dielectric properties of thin films at microwave frequencies by the cavity perturbation method. The measured frequency is in X-band (8.2–12.4 GHz). The titanium dioxide based (1-x)TiO2-xCaTiO3 and (1-x)TiO2-xSrTiO3 thin films deposited by the RF reactive magnetron sputtering method are adopted for the measurements. It was found that the dielectric constants of the films are increased as the compositions of CaTiO3 or SrTiO3 are increased. The microwave dielectric constants and loss tangents of films are measured. The accuracy of measurements is discussed.

Detection of carcinoembryonic antigen using AlN FBAR

In this study, we investigated AlN-based film bulk acoustic resonator (FBAR) for the detection of carcinoembryonic antigen(CEA). CEA is a glycoprotein most often associated with breast, colorectal and lung cancer and used to monitor patients with this type of cancer. AlN thin film was deposited on Mo (200 nm)/Ti (10 nm)/Si 3N 4 (300 nm)/Si (300 µm)/Si 3N 4 (300 nm) substrate by reactive RF magnetron sputtering method. Deposited AlN films showed strongly c-axis preferred orientation with main (002) peak as well as the high intensity of 2.50° for FWHM in rocking curve. The FBAR has a resonant frequency of 2.477 GHz and a sensitivity of 3514 Hz cm 2/ng. To investigate optimal condition of self-assembled monolayer (SAM) and anti-CEA concentration for detecting CEA, protein A and protein G as SAM and anti-CEA concentration from 0.2 to 1.0 mg/ml were adopted.

Electrical Properties of TaOx Thin Films for ReRAM Prepared by Reactive RF Magnetron Sputtering Method

AbstractRecently the Flash Memory is scaling limit, Thus the Memory of various types is now under study for the next generation large capacity nonvolatile memory. Resistance random access memory (ReRAM) is attracts much attention due to its advantage for integration in the next generation nonvolatile memory, because it is depend on scaling by lithography compared with the Flash Memory of capacity type. The material for ReRAM is classified roughly into binary oxides and perovskite oxides. Several binary oxides such as a TaOx have the advantage for low-temperature process and low-cost materials compared with perovskite oxides such as a (Pr,Ca)MnO3 (PCMO). In this study, TaOx film with the thickness of 10nm were prepared by reactive RF magnetron sputtering on 8inch-Pt/Si substrate using a Ta metal target in oxygen ambient. The sputtering system was the multi chamber type mass production tool. The TaOx thin film was amorphous phase as a result of measurement by X-ray diffraction meter. Ta top electrodes with 50 um diameters were deposited on the surface of TaOx layer by the DC sputtering method using a shadow mask. The “Forming” voltage of TaOx-ReRAM was 5.0V. After “Forming” process, the “Set” and “Reset” voltage were 3.0V and –3.0V respectively. It has good switching properties with large on/off resistance ratio above 1,000.

Measurements of dielectric properties of TiO2 thin films at microwave frequencies using an extended cavity perturbation technique

This research provides a simple method to measure the dielectric properties of thin films at microwave frequencies. The cavity perturbation theory is applied to the measurement method. The measured frequency is in X-band (8.2–12.4 GHz). The titanium dioxide thin films are deposited by the RF reactive magnetron sputtering method onto borosilicate glass substrates. The microwave complex permittivity of films is then measured by the extended cavity perturbation technique. It was found the dielectric constants of titanium dioxide thin films strongly depend on the partial pressure of oxygen. The dielectric constant maximized at a value of 95 with 30% O2. This is the first report that confirms the high dielectric constant of TiO2 thin films at microwave frequencies which shows its potential for high-K related microwave devices.

Effects of silicon nitride diffusion barrier on germanium MOS capacitors with HfON gate dielectrics

MOS capacitors with hafnium oxynitride (HfON) gate dielectrics were fabricated on Ge and Si substrates using the RF reactive magnetron sputtering method. A large amount of fixed charges and interface traps exist at the Ge/HfON interface. HRTEM and XPS analyses show that Ge oxides were grown and diffused into HfON after post metal annealing. A Si nitride interfacial layer was inserted between Ge and HfON as diffusion barrier. Using this method, well behaved capacitance-voltage and current-voltage characteristics were obtained. Finally hystereses are compared under different process conditions and possible causes are discussed.

Relation between the plasma characteristics and physical properties of functional zinc oxide thin film prepared by radio frequency magnetron sputtering process

The ZnO thin film was deposited on a glass substrate by a RF reactive magnetron sputtering method. Results showed that plasma density, electron temperature, deposition rate and estimated ion bombardment energy increase with increasing applied RF power. Three distinct power regimes were observed, which are strongly correlated with plasma properties. In the low-power regime, the largest grain size was observed due to slow deposition rate. In the medium-power regime, the smallest grain size was found, which is attributed to insufficient time for the adatoms to migrate on substrate surface. In the high-power regime, relatively larger grain size was found due to very large ion bombardment energy which enhances the thermal migration of adatoms. Regardless of pure ZnO thin film or ZnO on glass, high transmittance (> 80%) in the visible region can be generally observed. However, the film thickness plays a more important role for controlling optical properties, especially in the UV region, than the applied RF power. In general, with properly coated ZnO thin film, we can obtain a glass substrate which is highly transparent in the visible region, is of good anti-UV characteristics, and is highly hydrophobic, which is highly suitable for applications in the glass industry.

Investigation of Characteristics of Multi-Function ZnO Thin Film Deposited with Various Argon and Oxygen Ratios

AbstractThe ZnO thin film was successfully deposited on a glass substrate at RT by a RF reactive magnetron sputtering method. Structural, chemical, optical, and hydrophilic/hydrophobic properties are measured by using a surface profilometer, an x-ray diffractometry (XRD), an x-ray photoelectron spectroscopy (XPS), a UV-VIS spectrophotometer, and a contact angle system, respectively. Results show that the deposition rate decreases with increasing O2/(Ar+O2) ratio. Otherwise, the best stoichiometric and quality of ZnO thin film was observed at 0.30 of O2/(Ar+O2) ratio by the smallest FWHM and the strong O-Zn bonds. Regardless of O2/(Ar+O2) ratio effect or thickness effect, high transmittance (> 86%) in the visible region is observed, while the UV-shielding characteristics depend upon both the magnitude of film thickness. The film thickness plays a more prominent role in controlling optical properties, especially in the UV-shielding characteristics, than the O2/(Ar+O2) ratio. However, the hydrophobic characteristics can be obtained when the glass coating with ZnO thin films. In general, with properly coated ZnO thin film, we can obtain a glass substrate which is highly transparent in the visible region, has good UV-shielding characteristics, and possesses highly hydrophobic characteristics (self-clean capability), which is highly suitable for applications in the glass industries.

Fabrication and characteristics of a Pt/MgxZn1–xO Schottky photodiode on a ZnO single crystal

AbstractThe photoresponse of a Pt/MgxZn1–xO Schottky photodiode using a (0001) ZnO single crystal substrate grown by the hydrothermal growth method is described in this report. MgxZn1–xO thin films were prepared by a reactive RF magnetron sputtering method on the Zn‐face of the ZnO single crystal substrate. The prepared MgxZn1–xO thin films had a band gap of 4.1 eV. The fabricated Schottky photodiode had high responsivity of 0.034 A/W at the wavelength of 250 nm, and the responsivity ratio at wavelength of 250 nm and 550 nm was of the order of 4. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

기판 온도 변화에 따른 AlN 박막 성장에 잔류 산소가 미치는 영향

Aluminum nitride (AlN) thin films have been deposited on Au electrodes by using reactive RF magnetron sputtering method in a gas mixture of Ar and <TEX>$N_2$</TEX> at different substrate temperature. It was found that substrate temperature was varied in the range up to <TEX>$400^{\circ}C$</TEX>, highly c-axis oriented film can be obtained at <TEX>$300^{\circ}C$</TEX> with full width at half maximum (FWHM) <TEX>$3.1^{\circ}$</TEX>. Increase in surface roughness from 3.8 nm to 5.9 nm found to be associated with increase in grain size, with substrate temperature; however, the AlN film fabricated at <TEX>$400^{\circ}C$</TEX> exhibited a granular type of structure with non-uniform grains. The Al 2p and N 1s peak in the X-ray photoelectron spectroscopy (XPS) spectrum confirmed the formation of Al-N bonds. The XPS spectrum also indicated the presence of oxynitrides and oxides, resulting from the presence of residual oxygen in the vacuum chamber. It is concluded that the AlN film deposited at substrate temperature of <TEX>$300^{\circ}C$</TEX> exhibited the most desirable properties for the application of high-frequency surface acoustic devices.

CMOS Humidity Sensor System Using Carbon Nitride Film as Sensing Materials.

An integrated humidity sensor system with nano-structured carbon nitride film as humidity sensing material is fabricated by a 0.8 μm analog mixed CMOS process. The integrated sensor system consists of differential humidity sensitive field effect transistors (HUSFET), temperature sensor, and operational amplifier. The process contains two poly, two metal and twin well technology. To form CNx film on Si₃N₄/Si substrate, plasma etching is performed to the gate area as well as trenches. CNx film is deposited by reactive RF magnetron sputtering method and patterned by the lift-off technique. The drain current is proportional to the dielectric constant, and the sensitivity is 2.8 ㎂/%RH.

Microcrystalline Silicon Germanium Thin Films Prepared by Reactive Sputtering

Microcrystalline silicon-germanium (μc-SiGe) films were fabricated on glass substrates by the RF reactive magnetron sputtering method using Ar and H2 mixtures. We could reduce the crystallization temperature to 100°C and obtained the photosensitivity in the μc-SiGe films with any Ge content from 0 to 100%. These results indicate that the H2 introduction into the sputtering gases has two important effects to decrease the crystallization temperature of the μc-SiGe films and to improve the film properties by the hydrogen termination of defects.

Surface Acoustic Wave Device on (AlN/LGS) Substrate

Langasite (La3Ga5SiO14 or abbreviated as LGS) single crystal is an attractive substrate for surface acoustic wave (SAW) devices requiring good temperature stability and higher electromechanical coupling constant than quartz. AlN thin films are attractive materials that have some excellent characteristics, such as high SAW velocity, piezoelectricity, high-temperature stability, and stable chemical properties. In this study, AlN thin films were deposited on LGS to be a new composite SAW substrate (AlN/LGS) by reactive RF magnetron sputtering method. SAW delay-line device was manufactured on this substrate. The performance of the device was measured by network analyzer (Agilent 8753E).The results exhibited the composite substrate (AlN/LGS) increased the Rayleigh wave velocity, decreased the insertion loss of SAW devices, and suppressed the harmonic response.