Ken Numata

Characteristics of post-annealed SrTiO3 thin films prepared by mirror-confinement-type ECR plasma sputtering

Abstract SrTiO3 films were synthesized on Pt/Ti/SiO2/Si multilayer substrates by mirror-confinement-type ECR plasma sputtering without substrate heating. All films were found to be well crystallized at a substrate temperature below 450 K. A low temperature post-annealing of the films by electromagnetic-wave radiation drastically improved the crystallographic and electric properties of Pt/SrTiO3/Pt/Ti/SiO2/Si capacitors. The crystallinity of the films indicated little variation by post-annealing, but irradiation of electromagnetic wave was confirmed to be effective for decreasing the post-annealing time and temperature. The electric properties of films annealed without Pt upper electrodes were better than those with them, and the film dielectric constant reached a value of 260, which is nearly equal to thebulk one, at an annealing temperature of 573 K.

Preparation of high quality strontium titanate based thin films by ECR plasma sputtering

Abstract Strontium titanate based thin films were prepared using a mirror-confinement-type electron-cyclotron-resonance plasma sputtering method. Typically films were deposited Ar/O 2 gas mixture with a thickness of approximately 100 nm on Si wafers and Pt/Ti/SiO 2 /Si multilayer substrates at floating potential and at a temperature below 473 K. Films on Si substrates were found to be amorphous-like both in the preparation of SrTiO 3 (STO) films and (Ba, Sr)TiO 3 (BST) ones. While on Pt-multilayer substrates STO films could be crystallized well even at as-deposited condition, but BST films were poorly crystallized. As for the post-annealing of these films, 28 GHz millimeter-wave radiation could drastically lower their crystallization temperature. STO films on Si substrates were crystallized at 673 K and BST at 923 K by the conventional method, while by the millimeter-wave method the crystallization temperature of STO films decreased to 573 K and that of BST to 673 K. The millimeter-wave irradiation to STO on Pt-multilayer substrates did not give remarkable contribution to further crystallization, since they were already crystallized well at as-deposited condition. While for BST on Pt-multilayer substrates the temperature again decreased to 673 K by the millimeter-wave irradiation. The dielectric constant of as-deposited STO films on the Pt-multilayer substrates was approximately 70, and it increased drastically to a value of approximately 260, which was comparable with the bulk value, by the millimeter-wave annealing at 573 K.

Preparation of strontium titanate thin films by mirror-confinement-type electron cyclotron resonance plasma sputtering

Abstract Using mirror-confinement-type electron cyclotron resonance (ECR) plasma sputtering method, strontium titanate (SrTiO 3 ) thin films have been prepared on Si and Pt/Ti/SiO 2 /Si substrates at a low substrate temperature (below 450 K) in a low pressure (2.7×10 −2 Pa) environment of pure Ar and Ar/O 2 mixture. Prepared film surfaces were very smooth regardless of high deposition rate (∼8.5 nm/min). The composition ratio Sr/Ti of Sr to Ti in the films varied with the distance between the target and the substrate. All as-deposited films on Si substrates were found to be amorphous and were crystallized by post-deposition annealing using an electric furnace at 650 K, i.e. approximately 250 K lower than annealing for films obtained by conventional RF magnetron sputtering. Post-deposition annealing of these films using millimeter-wave radiation decreased the crystallization temperature to a value of 550 K. Furthermore, all as-deposited films on Pt/Ti/SiO 2 /Si substrates by a plasma of Ar and O 2 gas mixture were found to be crystallized regardless of no substrate heating.

Coating and ion implantation to the inner surface of a pipe by metal plasma-based ion implantation and deposition

This article describes the characteristics of the coating of the inner surface of a pipe using plasma-based ion implantation and deposition method with a d.c. titanium-cathodic-arc in nitrogen gas. It was confirmed that the coating of the inner surface of the pipe with titanium nitride film was possible by using this method. The film structure and preferential orientation can be controlled by the applied voltage to the pipe. The film on the inner surface of a pipe in its entrance region showed an oriented columnar grain structure oblique to the substrate. The surface morphology changed with the waveform of the applied voltage. These characteristics were closely related to the dynamic behavior of the ions.

Macroparticles on titanium nitiride thin film prepared by cathodic-arc plasma-based ion implantation and deposition

This article describes particles formed on a substrate when a cathodic arc is generated in nitrogen at pressure of 0.27 Pa for plasma-based ion implantation and deposition (PBII-D). After a titanium nitride (TiN) film was deposited and titanium and nitrogen ions were simultaneously implanted into the silicon substrate, macroparticles of TiN were observed on/in the deposited film. Most of these were less than 1 μm in size and were classified as spherical or non-spherical particles. The spherical particles were so-called droplets, while non-spherical particles were formed by crystal growth from the near-surface of the substrate. The latter was inferred to originate from nucleus precipitation due to the high-energy ion implantation. The number density and the shape of the non-spherical macroparticles changed to a great extent with the applied voltage and its waveform.

Low temperature preparation of perovskite oxide films by ECR sputtering assisted with microwave treatment

Abstract SrTiO 3 (STO) and (Ba,Sr)TiO 3 (BST) films were prepared on unheated substrates by mirror-confinement-type electron cyclotron resonance (MCECR) plasma sputtering. STO films deposited on Si substrates by Ar plasma were amorphous, whereas those on Pt/Ti/SiO 2 /Si substrates by Ar/O 2 plasma were sufficiently crystallized in spite of a low substrate temperature below 450 K. Annealing by 28 GHz microwave irradiation was applied to amorphous STO films on Si substrates and amorphous BST films on Pt/Ti/SiO 2 /Si substrates to crystallize these films. With microwave annealing, these films were crystallized at lower temperatures than with electric furnace annealing. The dielectric constant of STO films on Pt/Ti/SiO 2 /Si substrates annealed by microwave irradiation at 573 K was approximately 260, which was nearly equal to the bulk value of STO. Microwave irradiation to these films is considered to be useful since it can reduce the annealing temperatures and improve the electrical property.

Effects of target voltage on the structure of the film prepared by plasma-based ion implantation and deposition method

Abstract This article describes the characteristics of titanium nitride film prepared by the plasma-based ion implantation and deposition method using a titanium cathodic arc of d.c. 80 A. The surface morphology and structure of the film were affected by the voltage applied to the target. With increasing the negative voltage, the surface became smoother with a lesser number of particles. The grain structure varied from the stratified one at 0 kV to the columnar one at −5 to −20 kV, and further to the densely packed columnar one at −40 kV. These facts strongly suggested that the ions in the sheath played an important role in the deposition of the film.