Conventional RF Magnetron Sputtering Research Articles

Piezoelectric Properties of ZnO Films on a Sapphire Substrate Deposited by an RF-Magnetron-Mode ECR Sputtering System

Compared to conventional RF magnetron sputtering systems, electron cyclotron resonance (ECR) sputtering systems are characterized by the ability to generate high-density plasma under low gas pressure. (1120)-plane oriented epitaxial ZnO films were deposited on an R-plane sapphire substrate using the RF-magnetron-mode ECR sputtering equipment. As the results of the measurement, the films showed a good orientation and excellent effective electromechanical coupling factors (keff) for the Rayleigh surface acoustic wave (SAW) and its high-order SAW waves. These coupling factors were equal to or higher than the theoretical values keff obtained by the finite element method (FEM) analysis using a single crystal material constant.

Microstructure dependence of electrical properties of (Ba0.5Sr0.5)TiO3 thin films deposited on Pt/SiO2/Si

Stoichiometric (Ba0.5Sr0.5)TiO3 (BST) thin films with various thicknesses have been prepared on Pt/SiO2/Si substrates using conventional rf magnetron sputtering method with a ceramic target containing excess BaO and SrO. With increasing film thickness, the grain size of the BST films gradually increased. It was observed that the dielectric constant increased from 348 to 758 when grain size increased from 32 to 82 nm in BST films deposited at 600 °C. The decrease of dielectric constant in thinner BST films was attributed to the initial low dielectric constant layer and small grain size. In the current–voltage curves for BST films, higher leakage current densities and narrower flat regions (hopping conduction region) in the low bias field were obtained with increasing grain size.

C-Axis Oriented PbTiO 3 Thin Films on MgO and Their Microstructure

PbTiO3 thin films were prepared on MgO(100) substrates using a conventional rf magnetron sputtering system with a powder target. By optimizing the deposition conditions, highly c-axis oriented PbTiO3 epitaxial films were obtained. The c-axes of the domains in the films were normal to the substrate, but some a-axes were tilted from the normal towards <100> directions with a particular angle and fourfold symmetry. From the tilt angle and the tilt directions, it is concluded that 90° domain structures were formed by twins, the domain walls of which were {101} twin boundaries.

Oxygen plasma effects on electrical properties of barium strontium titanate (BST) thin films

Abstract (Ba0.5Sr0.5)TiO3 thin films have been prepared on Pt/Ta/SiO2/Si substrates by means of a conventional rf magnetron sputtering method with ceramic target and excess BaO, SrO target under various Ar/O2 plasma conditions. Electric properties of the films have been studied. Increase of O2 plasma content improve dielectric and insulating properties of the films. An 80nm-BST thin film deposited with 50% O2 plasma content has a dielectric constant of 446 and a leakage current density of 1.5 × 10−7A/cm2 at 3V. In the current-voltage curve of BST film deposited with higher O2 plasma content, a wider saturated region of hopping conduction appeares.

Electrical Properties and Crystal Structure of (Ba0.5Sr0.5)TiO3 Thin Films Prepared on Pt/SiO2/Si by RF Magnetron Sputtering

( Ba0.5Sr0.5)TiO3 (BST) thin films have been prepared on Pt/SiO2/Si substrates under various Ar/O2 plasma conditions by the conventional rf magnetron sputtering method using a ceramic target containing excess BaO and SrO. With increasing deposition temperature, the crystallinity of the BST films abruptly increased and change of the preferred orientation was observed. At 650° C, (100)-preferred orientation was obtained. The increase of the crystallinity of films improved the dielectric constant. A 100 nm BST thin film deposited at 650° C with 50% O2 plasma content has a dielectric constant of 725 and a leakage current density of 2.3×10-7 A/cm2 at 2.5 V. In the current-voltage curve of BST film deposited at higher substrate temperature, lower leakage current density in the low bias region and narrower flat region (hopping conduction region) were obtained.

Preferred orientation and microstructure of Ni-Zn-Cu ferrite thin films deposited by rf magnetron sputtering

We have investigated the effects of process parameters such as rf power, substrate, and gas pressure PAr on preferred orientation, microstructure, and magnetic properties of Ni-Zn-Cu ferrite thin films deposited by conventional rf magnetron sputtering. The texture structure was developed in the ferrite films deposited on the SiO2/Si(100) substrate at low rf power conditions. The ferrite film on the Si(111) substrate always had (111) texture irrespective of process parameters due to lattice matching, but the texture of the ferrite film on SiO2/Si(100) changed from (111) to (100) and finally returned to (111) orientation again with decreasing PAr. Such behavior would occur presumably due to the characteristic atomic stacking sequence corresponding to a given condition of the ion bombardment. The ferrite films deposited at low PAr had a denser microstructure consisting of tightly packed columnar grains with a smoother surface, better adhesion to the substrate, and better crystallinity than those at high PAr. Hc‖ of ferrite film deposited at low PAr was larger than that at high PAr and also larger than Hc⊥ of that deposited at the same PAr because larger compressive stress was induced at low PAr than at high PAr.

Deposition and piezoelectric characteristics of ZnO films by using an ECR sputtering system

Piezoelectric properties of ZnO films, were investigated by using an Electron Cyclotron Resonance (ECR) sputtering system. It was confirmed that this system was capable of depositing a ZnO film with a large specific resistance, and good c-axis orientation on an interdigital transducer (IDT)/glass substrate at a low temperature (less than 200/spl deg/C) and in a low gas pressure (/spl sim/10/sup -4/ torr). Furthermore, these ZnO films exhibited excellent SAW characteristics (insertion losses) and effective electromechanical coupling factors (k/sub eff/) compared with ZnO films deposited by a conventional RF magnetron sputtering system. Further, this ECR sputtering system was capable of depositing a ZnO film, without heating the substrate, that was capable of propagating a Rayleigh SAW at 700 MHz for the first time.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Formation of TiB 2 films and BFe interdiffused layers by dynamic mixing

Steel specimens were treated by B ion implantation combined with simultaneous Ti evaporation (dynamic mixing), and the structure of the synthesized films and the formation of BFe interdiffused layer were investigated. B ion beam current density and Ti deposition rate were varied, 15–130 μA/cm 2, and 0.03–0.27 nm/s, respectively. The ion energy was maintained at 40 keV. The phase of the synthesized film was found to change from αTi to αTi + TiB 2 and then to TiB 2 by decreasing the Ti deposition rate or increasing the B ion current density. The TiB phase was not observed in any condition. The formation of a BFe interdiffused layer beneath the synthesized film was found to be enhanced by decreasing the Ti deposition rate. The thickness of the BFe interdiffused layer reached up to 3 μm, which was about 30 times the thickness of the 40 keV B ion implanted layer in steel as predicted by the TRIM simulation program. These thin films synthesized by the dynamic mixing showed higher adhesion compared with those deposited by the conventional rf magnetron sputtering.

Piezoelectric Characteristics of ZnO Films Deposited Using an Electron Cyclotron Resonance Sputtering System

Piezoelectric properties of ZnO films were investigated for the first time by means of an electron cyclotron resonance (ECR) sputtering system. It is confirmed that this system is capable of depositing a ZnO film with a large specific resistance, a good piezoelectric property and good c-axis orientation on an interdigital transducer (IDT)/glass substrate at a low temperature (less than 200°C) and under low gas pressure (∼10-4 Torr). These ZnO films exhibited excellent surface acoustic wave (SAW) characteristics (insertion losses) and effective electromechanical coupling factors (keff) compared with ZnO films deposited by a conventional RF magnetron sputtering system. Furthermore this ECR sputtering system was capable of depositing a ZnO film capable of driving a Rayleigh SAW of 700 MHz, without heating the substrate (room temperature), while it was impossible to drive such a wave conventionally, using other sputtering systems.

Electric Properties of SrTiO3 Thin Films Prepared by RF Sputtering

Dielectric SrTiO3 thin films have been prepared on Pt/SiO2/Si-wafer by means of a conventional rf-magnetron sputtering technique. Electric and dielectric properties of the films have been studied. It is demonstrated that the leakage current of the films is strongly dependent on the atmosphere during deposition. The SrTiO3 film 75 nm in thickness fabricated in pure O2 of 26.6 Pa at 600°C obtained the lowest leakage current density of 4.0×10-9 A/cm2 at 2 V. Analysis of the leakage current vs applied voltage characteristic indicated that the conduction in the higher electric field was due to the Pool-Frenkel emission.

Microscopic observation of interface structures of YBaCuO/MgO/YBaCuO double-heteroepitaxial thin films by TEM

The YBaCuO/MgO/YBaCuO double-heterostructure (DHS) was fabricated using conventional RF magnetron sputtering. The formation of [110]YBaCuO/[100]MgO/[110]YBaCuO on [110]SrTiO/sub 3/ substrate, and [001]YBaCuO/[100]MgO/[100]YBaCuO and [001]YBaCuO/[100]MgO/[001]YBaCuO on [100]MgO substrate are demonstrated. According to RHEED (refraction high-energy electron diffraction) observations, each layer of the DHS was grown epitaxially. The cross-sectional TEM (transmission electron microscope) observation of the [001]YBaCuO/[100]MgO(2 nm)/[001]YBaCuO structure was carried out in order to characterize the heterostructure. The ultrathin MgO layer grew in an island shape. The MgO shape deposited on YBaCuO film is island-like because of the low absorption energy of Mg on the YBaCuO surface and/or large value of MgO/YBaCuO interface free energy. The YBaCuO atomic arrangement shape implied that the YBaCuO growth mechanism was atomic layer epitaxy.

Studies of MZS and MZOS Structures with Zinc Oxide Deposited by Conventional Rf Diode and Magnetron Sputtering Techniques

ABSTRACTHighly crystalline and c-axis oriented zinc oxide thin films were sputter deposited from a ceramic target using rf diode and magnetron sputtering techniques. A comparative evaluation of structure and electrical characteristics of ZnO films in the MZS and MZOS configurations is presented and the results are discussed. The physical and electrical properties were significantly influenced by highly energetic particles originating from the presence of oxygen neutrals in the plasma during the growth process and the behavior differed between the diode and magnetron sputtering processes.

Piezoelectric thin films of zinc oxide for saw devices

Abstract Fabrication processes of piezoelectric ZnO films utilizing sputtering deposition technique and properties of the sputtered films are described mainly in view of their application to surface-acoustic-wave (SAW) devices. Both polycrystalline films with c-axis orientation and single-crystal films on sapphire are treated in this paper. As for the polycrystalline films, it is emphasized that an improved sputtering system with a hemispherical electrode configuration provides excellent uniformity of film thickness and c-axis orientation. The single-crystal films have been successfully grown by conventional rf-sputtering and rf magnetron sputtering. The rf magnetron sputtering is found to be superior over the conventional method with respect to SAW properties of the films. Fundamental SAW properties have been measured for the films and the results are compared with theoretical predictions. Several SAW devices in a wide variety of operating frequency (30–2200 MHz) have been realized using the ZnO films. Some of them are now in practical use. It is noted that the polycrystalline films have the advantages that various substrate materials are allowed and good temperature-stability is obtained. On the other hand, the single-crystal films on sapphire are suitable for high-frequency SAW devices owing to their high phase velocity and low propagation loss.