Argon Sputtering Gas Research Articles

Thin film sputter-deposition of AlN crystals in oxygenated chamber: A pilot study

Abstract Aluminium nitride (AIN) is a promising thin film electrical insulation material layer in electronic devices. The magnetron sputtering method is usually employed to sputter-deposit AlN thin film on silicon (Si) substrate using a pure aluminium (Al) metallic target in a low base pressure vacuum condition. In many cases, the thin film deposition of high quality AlN crystals requires the application of heat and bias to the substrate, highly pure nitrogen reactant gas, argon sputtering gas and Al target, low sputtering pressure, high sputtering power, post-deposition AlN annealing, ultra-low base pressure of the sputtering chamber and a distinctive crystal orientation of the nucleation layer or substrate underneath. In our work, the utilisation of AlN ceramic target instead of pure Al metallic target has allegedly facilitated the growth of AlN crystals without the need to conform to these requirements. Non-amorphous AlN〈100〉 and AlN〈002〉 thin film crystals have been successfully sputtered from AlN ceramic target on Si〈100〉 substrate in a relatively high sputtering chamber base pressure and at a moderate 200 W - 250 W of sputtering power. Additionally, 250 W of sputtering power has been observed to assist in the growth of AlN〈002〉 crystals. The presence of AlN〈002〉 may have reduced the leakage/tunnel current density in AlN thin film layer to 46.33 pA/cm2 and modified the small-scale surface height characteristics. A high degree of AlN〈002〉 crystallisation may suggest good electrical insulating properties in AlN thin film layer, which can be applied in electronic devices that critically require a low leakage current specification.

Influence of Ar:O2 Mixing Ratio on Characteristics of Tio2 Nanostructured Thin Films Deposited by DC Reactive Magnetron Sputtering Method

Abstract: In this paper, titanium dioxide nanostructured thin films TiO2 were deposited on unheated glass substrates by applying the DC reactive magnetron sputtering method. Three TiO2 films were deposited using argon sputtering gas with different oxygen ratios: 10%, 25%, and 50%. The resulting films had thicknesses of 200, 184, and 140 nm, respectively. The structural, morphological, optical, and electrical properties of deposited thin films were studied. X-ray diffraction (XRD) data showed that the samples exhibited an amorphous phase. It was found from atomic force microscopy (AFM) that the deposited thin films had a nanostructure, and the heights of their nanograins were 16, 24, and 30 nm, respectively. It was observed from the root-mean-square height RMS values that the films had low roughness. The UV-Vis-NIR spectroscopy showed that the films become more transparent with the increase in oxygen content. The direct band gap ranged between 3.68 and 3.88 eV, while the indirect band gap ranged from 3.3 to 3.66 eV. The highest intensity photoluminescence emission was obtained for the film deposited at 50% O2. In addition, the impedance spectroscopy showed that the films’ resistance did not change with changing oxygen content. Keywords: Magnetron sputtering, Titanium dioxide, X-ray diffraction, Absorption spectra, Atomic Force Microscopy, Photoluminescence, Impedance.

Effects of argon/nitrogen sputtering gas on the microstructural, crystallographic and piezoelectric properties of AlN thin films

The growth of highly crystalline c-plane AlN ‹002› is extremely difficult, entailing high temperature and ultra-high vacuum condition. In sputtering technique, the addition of nitrogen into argon sputtering gas can significantly assist the formation of AlN ‹002› at low temperature. We incorporated purified nitrogen gas and observed the consistent formation of single crystal ‹002› AlN thin film layer sputter-deposited on Mo/Si substrate from the AlN ceramic target. Small presence of oxygen content within AlN crystal relates to the preferential growth of AlN ‹002›. High oxygen content in AlN thin film due to the use of unpurified nitrogen and argon only sputtering gas prefers the formation of AlN ‹100›. Different AlN crystal structure has shown distinct thin film properties and piezoelectric response. This work provides a method to control the crystal structure of the sputter-deposited AlN thin film layer, either c-plane AlN ‹002›, a-plane AlN ‹100› or polycrystalline AlN.

Analysis of Cadmium and Cadmium Oxide by Inductively Coupled Plasma Atomic Emission Spectrometry

A procedure of the multielement analysis of cadmium and cadmium oxide by inductively coupled plasma atomic emission spectrometry is proposed. The effect of the concentration of the matrix component on the analytical signals of impurity elements is studied and the analytical lines of the analytes are chosen. For the chosen concentration of the matrix component, the optimum conditions of analysis are selected, i.e., power delivered to the plasma and the flow rate of sputtering argon gas. The accuracy of the developed procedure, ensuring the determination of up to 41 impurity elements with limits of detection in the range from n × 10–7 to n × 10–4 wt %, is estimated.

Effect of nitrogen doping on structural, morphological, optical and electrical properties of radio frequency magnetron sputtered zinc oxide thin films

Zinc oxide receives remarkable attention due to its several attractive physical properties. Zinc oxide thin films doped with nitrogen were grown by employing RF magnetron sputtering method at room temperature. Doping was accomplished in gaseous medium by mixing high purity nitrogen gas along with argon sputtering gas. Structural studies confirmed the high crystalline nature with c-axis oriented growth of the nitrogen doped zinc oxide thin films. The tensile strain was developed due to the incorporation of the nitrogen into the ZnO crystal lattice. Surface roughness of the grown films was found to be decreased with increasing doping level was identified through atomic force microscope analysis. The presenting phonon modes of each film were confirmed through FTIR spectral analysis. The increasing doping level leads towards red-shifting of the cut-off wavelength due to decrement of the band gap was identified through UV–vis spectroscopy. All the doped films exhibited p-type conductivity was ascertained using Hall measurements and the obtained results were presented.

EFFECTS OF DEPOSITION PARAMETERS AND OXYGEN ADDITION ON PROPERTIES OF SPUTTERED INDIUM TIN OXIDE FILMS

Indium tin oxide (ITO) films were sputtered on corning glass substrate. Oxygen admixture and sputtering deposition parameters were optimized to obtain the highest transparency as well as lowest resistivity. Structural, electrical and optical properties of the films were then examined. Increasing deposition rate and film thickness changed the crystallographic orientation from (222) to (400) and (440), as well as higher surface roughness. It was necessary to apply substrate heating during reposition to get films with better crystallinity. The lowest resistivity of 5.36 x 10-4 Ω•cm was obtained at 750 nm film thickness. The films’ resistivity was increased by addition of oxygen up to 2% in the argon sputtering gas. All films showed over 85% transmittance in the visible wavelength range, possible for applications in photovoltaic and display devices.

Effect of Hydrogen on Vacancy Formation in Sputtered Cu Films Studied by Positron Annihilation Spectroscopy

As a part of the LSI interconnect fabrication process, a post-deposition high-pressure annealing process is proposed for embedding copper into trench structures. The embedding property of sputtered Cu films has been recognized to be improved by adding hydrogen to the sputtering argon gas. In this study, to elucidate the effect of hydrogen on vacancy formation in sputtered Cu films, normal argon-sputtered and argon–hydrogen-sputtered Cu films were evaluated by positron annihilation spectroscopy. As a result, monovacancies with a concentration of more than 10-4 were observed in the argon–hydrogen-sputtered Cu films, whereas only one positron lifetime component corresponding to the grain boundary was detected in the normal argon-sputtered Cu films. This result means monovacancies are stabilized by adding hydrogen to sputtering gas. In the annealing process, the stabilized monovacancies began clustering at around 300 °C, which indicates the dissociation of monovacancy-hydrogen bonds. The introduced monovacancies may promote creep deformation during high-pressure annealing.

Spacer-less, decoupled granular L1 FePt magnetic media using Ar–He sputtering gas

Spacer materials are often used to fabricate granular L10 FePt media and reduce the grain size, however, at the expense of reduced out-of-plane coercivity. Here, we demonstrate a spacer-less method in which adding 1% helium to argon sputtering gas leads to a substantial improvement in the chemical ordering, as well as the magnetic and microstructural properties of FePt. This change is attributed to the modification in the ion current density of the plasma caused by the excited metastable helium species. Helium plays a pivotal role in providing the Fe and Pt atoms optimal adatom mobility, thereby, producing well-ordered L10 FePt media. This leads to an enhancement of the out-of-plane coercivity from 15 to 22 kOe. Furthermore, exchange decoupled grains with a twofold reduction in their diameter to ∼24 nm are also achieved. These properties are crucial for magnetic media of the future for data storage recording densities beyond 1 Tb/in2.

Effect of O2 gas partial pressure on mechanical properties of Al2O3 films deposited by inductively coupled plasma-assisted radio frequency magnetron sputtering

The effect of O2 partial pressure on the mechanical properties of Al2O3 films is studied. Using films prepared by inductively coupled plasma-assisted radio frequency magnetron sputtering, the deposition rate of Al2O3 decreases rapidly when oxygen is added to the argon sputtering gas. The internal stresses in the films are compressive, with magnitude decreasing steeply from 1.6 GPa for films sputtered in pure argon gas to 0.5 GPa for films sputtered in argon gas at an O2 partial pressure of 0.89 × 10−2 Pa. Stress increases gradually with increasing O2 partial pressure. Using a nanoindentation tester with a Berkovich indenter, film hardness was measured to be about 14 GPa for films sputtered in pure argon gas. Hardness decreases rapidly on the addition of O2 gas, but increases when the O2 partial pressure is increased. Adhesion, measured using a Vickers microhardness tester, increases with increasing O2 partial pressure. Electron probe microanalyzer measurements reveal that the argon content of films decreases with increasing O2 partial pressure, whereas the O to Al composition ratio increases from 1.15 for films sputtered in pure argon gas to 1.5 for films sputtered in argon gas at O2 partial pressures over 2.4 × 10−2 Pa. X-ray diffraction measurements reveal that films sputtered in pure argon gas have an amorphous crystal structure, whereas γ-Al2O3 is produced for films sputtered in argon gas with added O2 gas. Atomic force microscopy observations reveal that the surface topography of sputtered Al2O3 films changes from spherical to needlelike as O2 partial pressure is increased. Fracture cross sections of the films observed by scanning electron microscopy reveal that the film morphology exhibits no discernible features at all O2 partial pressures.

Conductivity and transparency in amorphous In-Zn-O transparent conductors

Amorphous indium zinc oxide (a-IZO) is an increasingly important material both as a transparent conductor or semiconductor in transparent electronics and as an archetype amorphous electronic mixed metal oxide in itself. Here, a co-sputtering composition spread combinatorial approach was used to examine the conductivity and optical transparency in a-IZO thin films as a function of both In : Zn metals stoichiometry and the amount of oxygen added to the argon sputter gas. For optimising the conductivity, the percent oxygen in the sputter gas and the metals composition were found to have a strongly coupled effect. In particular, a-IZO films with conductivity σ > 2000 S/cm can be grown for a broad range of metals compositions, In content from ∼60 to ∼85 cation%, as long as the corresponding optimal oxygen level is used in the deposition. The amount of oxygen required increases with increasing indium content. When too much oxygen is used, the conductivity is reduced due to a decreased carrier concentration whereas when too little oxygen is used, the conductivity is reduced due to decreased electron mobility. Concurrent with the decrease in electron mobility, there is increasing optical absorption from 400 nm to 1000 nm which renders the oxygen deficient a IZO samples grey.

Effects of processing parameters on electroluminescence of rf magnetron sputter deposited ZnS:ErF3

Zn S : Er F 3 alternating current thin film electroluminescent (ACTFEL) devices are fabricated by rf plasma magnetron sputtering. In a full factorial design-of-experiment study, increasing deposition temperature, duty cycle on the doped target, and sputter gas pressure all result in increases in the 1.55μm near infrared (NIR) electroluminescence (EL) irradiance at 20V above threshold (B20). An increase in the EL threshold voltage (Vth) upon increasing the duty cycle of the undoped target is also reported. Postdeposition annealing of ACTFEL devices at 425°C for 1h improves the NIR EL irradiance by decreasing the F concentrations in the ZnS:Er films. The origins of these effects are discussed in terms of negative ion resputtering, surface mobility of sputtered species, crystallinity, and the effects of atomic concentration on the EL and radiative relaxation processes. A maximum irradiance, B20, of 147μW∕cm2 is measured for the 1.55μm NIR EL peak from ZnS:Er ACTFEL devices produced using a deposition temperature of 150°C, a duty cycle of 75%, an argon sputtering gas pressure of 24mTorr, and postdeposition annealing at 425°C for 1h in nitrogen.

Influences of Process Condition of Magnetron Sputtering on Magnetostrictive Susceptibility of Fe<SUB>2.2</SUB>Sm Alloy Film

Since morphological interface of iron-samarium alloy thin film prepared by direct current magnetron sputtering process is controlled by substrate temperature, sputtering argon gas pressure and residual gas pressure, influences of changes of morphology and its interface on compressive (negative) magnetostrictive susceptibility of Fe 2.2 Sm alloy films are investigated. Decreasing the pressures of sputtering argon gas enhances the magnetostrictive susceptibility. The high susceptibility is also found under the low pressures of residual (impurity) gas at each substrate temperatures (T s ) from 423 to 523 K. The clear interface cannot be observed in the densely packed amorphous phase, when the high magnetostrictive susceptibility is obtained. Since the decreasing in impurity atoms at the unclear interface easily changes the domain direction and then doesn't prevent to move the magnetic domain wall in the amorphous phase, influences of the residual gas pressure on magnetostrictive susceptibility are explained by not only morphological interface but also its oxidation.

Stress anisotropy in circular planar magnetron sputter deposited molybdenum films and its annealing effect

As part of the program to develop a free-standing thin-film filter for soft X-ray optics application, stress anisotropy in the molybdenum films deposited by dc circular planar magnetron sputtering were studied by X-ray diffraction (XRD) as a function of sputtering argon gas pressure over a range of 0.8–1.5 Pa. Surface morphology of the films has been investigated by optical microscopy and scanning tunneling microscopy (STM). It is found that, for the film deposited at 0.8 Pa pressure, the stresses are more compressive in the tangential than in the radial direction; the highest compressive stress exists in the center area. The film deposited at 1.5 Pa pressure has the highest stress anisotropy, and the stresses are less tensile in the tangential than in the radial direction. Annealing in vacuum is more effective in reducing tensile stress and stress anisotropy in the tensile stressed film than in the compressively stressed film.

Doping Experiments in ZNO

ABSTRACTThis paper reports on attempts to fabricate transparent electrically conductive p-type ZnO by pulsed laser deposition (PLD) and sputtering using N2, N2O and NO gases. Expanding on the work of Kawai and coworkers [1,2], we used an ion source, rather than an ECR source in the PLD chamber to dissociate N2O gas, and explored the use of aluminum in addition to gallium as potential co-dopants. The most promising results have been obtained with DC reactive sputtering of gallium-doped zinc metal targets. A three to six order of magnitude reduction in n-type carrier density was observed when 2% of the argon sputtering gas was replaced with NO.

Directly sputtered stress-compensated carbon protective layer for silicon stencil masks

Silicon stencil masks for ion beam projection lithography have a protective layer stopping the ions and thus preventing a change in the Si membrane stress. This is needed to maintain extremely tight pattern placement specifications even when they are irradiated with high exposure doses. The fabrication of carbon protective layers by indirect sputter coating which are suitable for helium ion beam exposure has already been reported. This article describes a method of forming very low stress carbon protective layers based on direct radio frequency sputter coating with nitrogen added to the argon sputter gas and in situ thermal treatment using commercially available equipment. The carbon layers thus produced are stable in conventional environments. The article deals also with the physical characterization of carbon layers and the protection performances of these coatings under helium ion beam exposure using accelerated lifetime testing.

Orientational dependence of the exchange biasing in Ni–Fe/Mn1−xNix (x=0.11, 0.18, 0.23) bilayers

The correlation between the exchange anisotropy of ferromagnetic (F)/antiferromagnetic (AF) bilayers and the spin alignment of antiferromagnet at the interface is still under question. In the present study, Mn1−xNix (x=0.11,0.18,0.23) alloys, whose spin structure changes with x, were used for Ni–Fe/AF bilayers. The correlation between AF spin alignment at the interface and exchange anisotropy was investigated by controlling the preferred orientation of the bilayers. The crystal orientation of bilayers was changed by adding nitrogen into the sputtering argon gas only during the deposition of the Ni–Fe layer adjacent to the substrate. The preferred orientation was (111) when the nitrogen partial pressure, PN2=0%–1%; (100) when PN2>1%. When PN2<1%, Jk decreased and Hc increased with increasing PN2, because of the decrease of the grain size of γ-Mn–Ni. When PN2 exceeds 1%, Jk increased discontinuously, accompanied by the orientational change of the bilayers.

Effect of helium partial pressure on DC-magnetron sputtering of Co–Cr films

The effect of diluting the argon sputter gas with helium in DC-magnetron sputtering of both CoCr magnetic layers and Cr underlayers was studied. A Co 88Cr 12 target and a PET substrate were used. The addition of helium markedly improved the longitudinal magnetic properties and the magnetic uniformity of the films. It is shown that sputtering of the Cr underlayer with a He/Ar mixture improved the magnetic properties of the CoCr film which was sputtered subsequently; an explanation is that the structure of the Cr film sputtered with He/Ar is better suited to the epitaxial growth of CoCr. The beneficial effects of He are ascribed to an increased ion bombardment on the substrate. This is supported by measurement of the ion current of the substrate and by SEM measurements.

Intercalation of lithium in r.f.-sputtered vanadium oxide film as an electrode material for lithium-ion batteries

Vanadium oxide films were prepared by r.f.-sputtering using an argon sputter gas and a V 2 O 5 target. The films were characterized by scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical techniques. The oxide film as deposited is amorphous; they are heat-treated in the range 300-700 °C in oxygen atmosphere and are composed of orthorhombic V 2 O 5 crystals. At higher heat-treatment temperatures (600-700°C) the crystallization of the oxide proceeded significantly with ab-direction parallel to the substrate. The oxide film undergoes a reversible lithium intercalation and deintercalation process. The kinetics of the intercalation process of lithium into amorphous V 2 O 5 film was studied using an a.c. impedance method. Furthermore, a rocking-chair type V 2 O 5 film/Li x V 2 O 5 film cell could be charge-discharge cycled over 300 times at a current of 10 μA at 25 °C.

Correlation of GMR with texture and interfacial roughness in optimized rf sputtering deposited Co/Cu multilayers

The objectives of the present work were two fold: first to obtain the highest giant magnetoresistance (GMR) ratio in Co/Cu multilayers grown from the unusual process of rf diode sputtering and second, to investigate in detail correlation between GMR and texture and the interfacial roughness deduced from X-ray diffraction and AFM, respectively. Different interface structures have been induced from the change of the sputtering parameters (sputtering argon gas pressure P Ar) which gave the optimal rf sputtering conditions for high GMR. From different results it is concluded that the most important parameter is interface roughness which induces a strong effect on both the GMR and the resistivity of the superlattice. A change in the t 2 Co dependence of the reciprocal resistance near t Co = 25 Å is attributed to an increase of the effect of the layer roughness when the t Co is going from mesoscopic ( t Co > 25 Å) to nanoscopic scale ( t Co < 25 Å).

Low Resistivity Transparent Indium Tin Oxide (Ito) Films Sputtered At Room Temperature With H2O Addition

AbstractA new kind of amorphous indium tin oxide (ITO) film with good pattern delineation properties and mass production capability, as well as low resistivity and high transparency has been developed. The film was prepared by a cluster-type DC magnetron sputtering apparatus at room temperature with H2O addition to the argon sputtering gas. The amorphous ITO film quality was improved by effective termination of oxygen vacancies with -OH species generated by enhanced decomposition from the added H2O in the plasma.