Kiyoshi Kuwahara

Ceramics inner coating of narrow tubes by a coaxial magnetron pulsed plasma

Abstract We have developed a double-ended anode coaxial magnetron pulsed plasma (DCMPP) for the purpose of coating fine ceramics with, for example, titanium nitride (TiN) on the inner surface of a narrow insulated tube by reactive sputtering. In the magnetron pulsed plasma, the magnetron effect and J × B plasma transport by a pulsed discharge occurred simultaneously. Discharge characteristics and optimum conditions for uniform and high-rate sputter-coating were investigated. By using DCMPP, goldcolored TiN films could be deposited on the inner surfaces of narrow glass tubes of 8 mm in inner diameter and 400 mm in length. The deposition rate was about 20 nm min −1 for a deposition time of 600 s. By using a light absorption method, it was found that axial uniformity of the prepared films was within 25% over 400 mm.

Application of the Child-Langmuir law to magnetron discharge plasmas

In order to investigate the influence of magnetic field on magnetron plasmas, the dependence of discharge-current density (J/sub d/) on magnetic flux densities (B) perpendicular to the electric field over the whole discharge space in a magnetron apparatus with flat multi-targets has been studied. The dependencies on working gas pressures (P) and voltages (V) have been also studied in the configuration. From the experimental results, it was found that J/sub d/ was approximately proportional to B/sup 2/, P/sup 2/ and V/sup 3/2/. The sheath structure in the apparatus has been investigated as a function of B by both a probe method and a spectroscopic one. The cathode-fall thickness was roughly proportional to B/sup -1/. From a numerical analysis on kinetics of /spl gamma/ electrons emitted from the cathode surface, it was found that the dependence of J/sub d/ on B could be explained by the Child-Langmuir law, in which the sheath thickness was replaced by the equivalent electron Larmor radius. >

Preparation of iron nitride thin films by magnetron sputtering under surface magnetic field on substrates

Abstract Newly developed magnetron sputtering apparatus has been employed to control surface magnetic field on substrate independent of external magnetic field. Iron and iron nitride thin films were deposited by DC magnetron sputtering under various surface magnetic fields on substrates. The X-ray diffraction patterns indicated that the orientation of iron thin films changed from {110} to {100} with the increase in surface magnetic field; the (110) pole figure indicated that iron {100} thin films had a little anisotropy with the easy axis parallel to the direction of applied magnetic field during deposition. Furthermore, iron nitride thin films deposited on the iron {100} thin films showed larger saturation magnetization than iron nitride thin films deposited on glass plates. In this way, multilayer iron and iron nitride thin films by orientation control could enhance magnetic properties.

Titanium coating of the inner of a 1 m long narrow tube by double-ended anode coaxial magnetron-pulsed plasmas

In order to reveal the potential of a coaxial magnetron-pulsed plasma (CMPP) reactor for the deposition of thin films on the internal walls of narrow tubes, discharge characteristics and an extended-anode effect were investigated. The extended-anode effect is quite unique in CMPP, and appears due to the deposition of a conductive film onto the surface of an insulator. Three discharge regions corresponding to a plasma breakdown, a steady state and an afterglow were observed and characterized. The breakdown region was extremely dependent on the repetition frequency of the pulsed voltage. Titanium thin films were sputter-deposited onto the inner surface of a narrow glass tube (1000 mm long and 8 mm inner diameter) using double-ended anode coaxial magnetron-pulsed plasmas (DCMPP), to which CMPP was applied for the internal coating of narrow tubes with high aspect ratios of length to inner diameter.

Development of a large area sputter-coating method using a new magnetron discharge

Abstract Two-dimensional structures produced by a new magnetron discharge—a transversely magnetized a.c. discharge using completely inclined targets—are investigated by means of optical emission spectroscopy. When the transverse magnetic field is increased, a considerable increase in the argon line emission intensity and a spatial modification of the line emission profiles are observed. From these observations it is found that when the cathode sheath width becomes less than the gap distance between the electrodes, electrons go around the target with infinite orbital motion, forming a high density electron ring. These new magnetron effects are available for increasing the deposition rate of large area sputter coating and/ or chemical vapour deposition. Further, by modulating the transverse magnetic field, the uniformity of the deposited copper films is confirmed to be much improved.

Development of large area sputter-coating method using magnetized a.c. plasmas with inclined electrodes

Abstract A novel sputter coating method has been developed for preparing large area thin films. Plasmas are generated with a number of long plate electrodes by an a.c. discharge; thus all the electrodes operate as sputtering targets. Two large substrates are sustained outside the discharge region, and deposited simultaneously. To increase the deposition rate and to improve the uniformity of the deposited films, an external magnetic field is applied transverse to the discharge electric field; further, the electrodes are inclined at a proper angle. When the magnetic flux density is more than 38 Gauss, a strong increase in the deposition rate is observed. From the viewpoint of both deposition rate and uniformity, the use of completely inclined targets is shown to be promising for high rate and uniform sputter coating of large area substrates.

Numerical Simulation of Electron Transport in Electric and Magnetic Fields for Analysis of Electron Temperature and Number Density Profiles Measured in Argon Magnetic Neutral Loop Discharge Plasma

A Monte Carlo simulation of electron transport in electric and magnetic fields was performed to analyze experimental data of the electron temperature Te and electron number density ne measured in a magnetic neutral loop discharge (NLD) plasma driven in Ar at 0.13 Pa. Te and ne in the vicinity of the substrate holder were measured with a triple probe, and their radial profiles had peaks at different radial positions. The simulation reproduced these peak positions well under the chosen boundary condition that the electron reflectivity of the side wall was lower than that of the reactor ceiling and the substrate holder. It was explained that the Te peak was formed by high-energy electrons transported from the neutral loop along a separatrix of the quadrupole magnetic field and that the ne peak consisted of electrons undergoing reciprocating motion between the reactor ceiling and the substrate.

EXTENDED ANODE EFFECT IN COAXIAL MAGNETRON PULSED PLASMAS FOR COATING THE INSIDE SURFACE OF NARROW TUBES

In order to coat functional thin films onto the inside surface of narrow tubes, a coaxial magnetron pulsed plasma (CMPP) device has been developed. The feature of this device is that deposited conductive films play the role of an anode. Consequently, plasmas are generated away from the anode located at one end of the tube and the distribution of film thickness widens with increasing deposition time. This is called the extended anode effect. The shifting velocity of the main position for plasma generation was dependent on the properties of the target materials. The shifting velocity increased with sputtering yield and decreased with the electrical resistivity of target materials.

Magnetron plasmas for large-area uniform sputtering

Abstract A new magnetron plasma with multi-targets has been investigated for large-area uniform sputter-coating with uniform erosion of all targets. When the electron Hall parameter was larger than unity and the length of the cathode dark thickness was shorter than the gap length for the applied magnetic flux density B > B c ( mT )= 150 d( mm ) , the discharge was transferred to magnetron mode. In the magnetron mode, it was found that the current density Jd on the target was approximately proportional to B2, P2 and V 3 2 , respectively. Here P and V are gas pressure and discharge voltage, respectively. The cathode fall depth was roughly proportional to B−1. From these experimental results and from the numerical analysis for the secondary electrons emitted from the targets, a new expression for the Child-Langmuir law in a magnetized plasma was obtained, in which the sheath thickness was replaced by the equivalent electron Larmor radius.

SiO2 etching characteristics in DC magnetron plasmas by using an external magnetic field

Abstract In order to create a crystal resonator with a high clock frequency, a new magnetron plasma etching method has been developed. Generation of a stable plasma over a wide range of plasma characteristics was achieved for an external magnetic field type magnetron plasma apparatus based on investigation of the relationship of discharge current and voltage of CF 4 plasmas with and without Ar and O 2 as additive gases. By using such plasmas, the etching characteristics of cultured quartz crystals (SiO 2 ) were studied. The etching rates were approximately 80 nm/min for CF 4 plasmas and 14 nm/min for Ar plasmas. By mixing Ar and CF 4 gases, it was confirmed that ion-assist-etching took place by both chemical and physical means. Furthermore, it was found that etching rates increased up to a maximum of 105 nm/min in a plasma mixture containing 20% O 2 Etched crystal blanks (resonators) were obtained with a thickness of less than 10 μm and with a resonant frequency with a fundamental mode of about 187 MHz.