Conventional Sputtering Process Research Articles

Y3Fe5O12 film with multi-domain epitaxy on single-crystalline LiNbO3 substrate

Y3Fe5O12 is one of the magnetic insulators that can realize high-speed and low-power-consuming spintronics devices. However, it is hard to prepare a high-quality Y3Fe5O12 film via a conventional sputtering process owing to its low crystalline texture, which leads to a crucial increase in the Gilbert damping constant. Moreover, a single crystalline Gd3Ga5O12 substrate, whose lattice constant is well matched with Y3Fe5O12, is indispensable to improve the crystallinity of the Y3Fe5O12 film. In this article, we demonstrated an epitaxial growth of multiple domains for a 30-nm-thick Y3Fe5O12 film by means of magnetron sputtering on a single crystalline 128° Y–X LiNbO3 substrate , which has been widely utilized in surface acoustic wave devices. From the pole figure of x-ray diffraction, an oblique epitaxial growth of Y3Fe5O12(400) is successfully observed on the 128° Y–X LiNbO3 substrate after a high-temperature post-annealing. The saturation magnetization is equivalent to the value of the epitaxial Y3Fe5O12 film on the Gd3Ga5O12 substrate. The relatively low effective Gilbert damping constant of 0.0039 also supports the high crystalline texture of the Y3Fe5O12 film. The developed growth technique will pave the way for the application of the Y3Fe5O12 film on magneto-acoustic devices.

Exploiting the dodecane and ozone sensing capabilities of nanostructured tungsten oxide films

Tungsten oxide thin films are grown by DC reactive magnetron sputtering combining glancing angle deposition (GLAD) and reactive gas pulsing process (RGPP). Inclined, zigzag and spiral columnar architectures are produced with various oxygen injections during the growth. The dodecane and ozone sensing properties of these tungsten oxide nanostructured active layers are comparatively studied with that of films deposited by conventional sputtering process. Microstructure, morphologies and electrical behaviors are characterized as a function of the growing conditions. As-deposited films systematically exhibit an amorphous crystal structure with a porous microstructure, which depends on the GLAD architecture. Annealing at 300 °C in air for 12 h leads to a polycrystalline structure keeping voided networks. Dodecane and ozone sensing performances are the most significant for inclined columnar architectures but they also depend on the RGPP sputtering conditions. As a result, the GLAD + RGPP combination proves to be a relevant strategy for the fabricating tungsten oxide nanostructured films as active layers with an attractive potential for gas sensors.

Surface characterization of magnesium fluoride thin films prepared by a fluorine trapping based non-reactive sputtering technique

Successful deposition of magnesium fluoride thin films by a non-conventional magnetron sputtering technique is reported here followed by the analysis of their optical, morphological and structural properties. The drawback in the external supply of health hazardous fluorinated gases in the context of fabricating fluoride films by conventional sputtering processes was completely eliminated by trapping the dissociated fluorine gas inside the chamber during deposition. The dependencies of basic thin film properties stated above on magnetron energizing power were investigated. Qualities of surface structures were analyzed on the basis of surface roughness and surface correlation function parameters. A qualitative correlation of film morphology with optical properties of such fluoride films was observed in the present study. Film growth rates were found to have great importance in deciding the surface topography of the films. Careful investigation of film structure clearly revealed a remarkable increase in crystallite size with the increase in sputtering power. The composition of the film is maintained throughout the studied power range as seen by X-ray photoelectron spectroscopy. Finally, optimum sputtering power for film deposition was decided by taking into consideration the quality in surface structure together with optical quality of the films.

Visible-light active thin-film WO3 photocatalyst with controlled high-rate deposition by low-damage reactive-gas-flow sputtering

A process based on reactive gas flow sputtering (GFS) for depositing visible-light active photocatalytic WO3 films at high deposition rates and with high film quality was successfully demonstrated. The deposition rate for this process was over 10 times higher than that achieved by the conventional sputtering process and the process was highly stable. Furthermore, Pt nanoparticle-loaded WO3 films deposited by the GFS process exhibited much higher photocatalytic activity than those deposited by conventional sputtering, where the photocatalytic activity was evaluated by the extent of decomposition of CH3CHO under visible light irradiation. The decomposition time for 60 ppm of CH3CHO was 7.5 times more rapid on the films deposited by the GFS process than on the films deposited by the conventional process. During GFS deposition, there are no high-energy particles bombarding the growing film surface, whereas the bombardment of the surface with high-energy particles is a key feature of conventional sputtering. Hence, the WO3 films deposited by GFS should be of higher quality, with fewer structural defects, which would lead to a decrease in the number of centers for electron-hole recombination and to the efficient use of photogenerated holes for the decomposition of CH3CHO.

Application of solar cell using II‐III‐VI compound thin film fabricated by conventional sputtering process

AbstractIn order to achieve low cost solar cells, a novel type multinary compound thin film solar cell using ZnInS (II‐III‐VI) thin film as n‐type layer and other layer fabricated by the conventional sputtering process were realized. An AgInTe/ZnInS thin film solar cell fabricated by the conventional sputtering process showed the conversion efficiency is 1.1%. In this study, p‐type materials suitable for ZnInS and doping ZnInS with additive elements such as IIa (Ca,Sr) and VIb (O) group elements were investigated to improve the characteristics of ZnInS thin film solar cell. As the results, the best conversion efficiency of 2.8% was obtained CuInGaSe/CaZnInS thin film solar cell. This value is superior to that of AgInTe/ZnInS thin film solar cell by 2.5 times. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Substrate temperature dependence of electrical and structural properties of Ru films

Microstructures and resistivities of sputtered Ru films were investigated as a function of substrate temperature to obtain a single-layered Ru barrier without a Ta/TaN under layer. High resistivity Ru films with a high density of crevices, which enhances Cu diffusion along the crevices, were formed by the conventional sputtering process, i.e., sputtering at room temperature and annealing at 400 °C–700 °C for 30 min in Ar + 3%H 2. But, crevice-free and smooth Ru films with low resistivity, the same as that for the bulk phase, were formed when substrate temperature add sputtering was raised to 700 °C. Ru films formed by this process had (002) preferred orientation and then Cu (111) was formed by plating. This result corresponded to the tendency predicted by ab initio calculations.

In Situ Epitaxial Growth of Lead Zirconate Titanate Films by Bias Sputtering at High RF Power

High-quality epitaxial lead zirconate titanate (PZT) films with high growth rate were successfully grown by bias sputtering on (001) MgO single crystal substrates using a composite ceramic target. The composite ceramic target composed of a PbO pellet on the center of Pb1.2(Zr0.4Ti0.6)O3 ceramics was necessary to stably obtain perovskite-phase PZT films under high RF power by sputtering. At high RF power, the application of DC bias voltages to the growing PZT films increased the growth rate and changed the Ti/Zr composition. In particular, the optimum negative bias voltage considerably improved the crystallinity and surface morphology of the films compared with the conventional sputtering process. The optimum negative bias voltage plays a role in suppressing the bombardments of the energetic negative oxygen ions on growing films and also in making low-energy positive ions assist help in crystallization.

Evaluating the Large Electromigration Resistance of Copper Interconnects Employing a Newly Developed Accelerated Life‐Test Method

An accelerated electromigration life‐test method has been developed to evaluate the large electromigration resistance of Cu interconnects in a very short period of test time. The essence of the acceleration technique employed here is to use stress current more than 107 A/cm2 and to utilize the self‐heating of the test interconnect for giving temperature stress. Moreover, to avoid uncontrollable thermal runaway and resultant interconnect melting, we adopted an efficient cooling technique that immediately removes the joule heat and keeps the interconnect temperature constant. As a result, it has been demonstrated that large grain copper interconnects created by a low‐kinetic‐energy particle process and the thermal annealing that follows exhibit approximately three orders of magnitude larger electromigration lifetime at 300 K than Al‐alloy interconnects formed by a conventional sputtering process. Additionally, a new expression for electromigration lifetime was proposed based on Black's equation through the comparative studies of electromigration endurance of various materials.

Properties of Superconducting Niobium Films Made by Asymmetric ac Sputtering

Superconducting films of niobium can be made by asymmetrical ac sputtering. This modification of the conventional sputtering process uses a reverse sputtering current to bombard the film as it deposits, thus dislodging gaseous impurities to obtain pure films. The deposition conditions to yield the purest films have been established using cylindrical geometry, that is, Vycor tubing substrates which are heated internally and surrounded by a large niobium cathode. At substrate temperatures of 500°C and with a sputtering to reverse sputtering current density ratio of 4:1, films with β=R300°K/R10°K as large as 4.7 have been obtained from bulk material of β=14. Films so made have critical temperatures between 8.9° and 9.2°K; the bulk material critical temperature is 9.25°K. The critical temperature of the films is a strong function of β, falling below 4.2°K for β<1.25.