Takashi Ikehata

Sheath formation and ion flux distribution inside the trench in plasma-based ion implantation

Abstract Geometrical effects of a three-dimensional workpiece on the plasma-based ion implantation have been studied using trench-shape and L-shape workpieces. Temporal and spatial evolution of the sheath and the ion flux on the workpiece are measured for a negative voltage pulse of −1.8 to −7.0 kV, 40 μs: (1) The trench is occupied by the ion sheath quickly due to the sheath overlapping from both side walls; this effect is not seen in the L-shape workpiece with only one side wall. (2) Electrons are detected inside the trench even after the ion sheath fills the trench, which is attributed to secondary electrons emitted from the surface of the workpiece by ion impact and trapped electrostatically between the side walls. (3) The ion flux incident upon the inner surface of the trench is strongly enhanced because trapped secondary electrons ionize the filling gas as in the hollow-cathode discharge. The enhanced ionization is therefore not seen in L-shape and planar workpieces.

Effect of Axially Symmetric Magnetic Fields for Dynamics of Low-Current DC Vacuum Arc Plasma

In this paper, effects of four types of axially symmetric magnetic fields on the dynamics of low-current dc vacuum arc plasma, which is less than 30 A, were examined. Arcs were ignited by the opening of the butt contacts made of zinc. In the axial magnetic field, the arc plasma was restricted within a column, and the arc voltage rose with increasing gap length. When a magnet was arranged behind the cathode, the cathode spot rotated in the opposite direction to the Lorentz force (-J times B) on the edge of the circular-rod cathode. On the other hand, when a magnet was arranged behind the anode, the arc plasma was constricted on the anode side, and the lifetimes of the arcs became longer, although the arc voltage rose with increasing gap length. The compression effect of the axial component of the magnetic field was analyzed by introducing a simple magnetic piston model, and the experimental diameters of the arc column showed a good agreement with the model.

Performance of the undulator for JAERI FEL project

Abstract A newly designed hybrid undulator (DFTH-1), whose field termination parts are a novel implementation of the displacement-free termination scheme, has been constructed for the JAERI FEL project. The field termination part of the undulator was designed to minimize the electron trajectory walkoff by using the 3D magnetic field computational code named ELF/Magic. The DFTH-1 undulator could reduce the walkoff by one third of that of the conventional hybrid undulator with non-steering termination.

Positive pulse bias method in plasma-based ion implantation

A novel scheme of the plasma-based ion implantation (PBII), the positive pulse bias (PPB) method has been proposed, in which a workpiece to be treated is at the ground potential while the plasma surrounding it is biased to a positive high voltage; thus the ion sheath same as the one in the conventional negative pulse bias (NPB) method is formed on the workpiece. Principal merit of the PPB method over the NPB method is that it possesses a mechanism of suppressing X-rays from the wall by impact of secondary electrons and it enables to manipulate the workpiece during PBII processing. The latter merit will serve to realize an efficient continuous processing system. The principle of the PPB method is discussed based on the asymmetric double probe theory and results of the proof-of-principle experiment are presented.

Ion current on the inner surface of a pipe by plasma-based ion implantation and deposition

Four ring-probes were pasted on the inner surface of a pipe via an insulator sheet and the ion current was separately measured at each position by applying a negative pulse voltage in order to obtain the current distribution on the inner wall of the pipe, which was immersed in a cathodic arc plasma with a current of 80 A dc produced in a nitrogen gas at a pressure of 8 Pa. The probe current inside the pipe decreases rapidly, because the ion sheath thickness increases with time to arrive at the center of the pipe, which causes extinction of the plasma during the application of the pulse voltage to the pipe. Not only multiple setting of the arc sources but also the operation of a high frequency with a short pulse duration are necessary to realize a uniform treatment by a cathodic arc plasma-based ion implantation and deposition.

Control of Ion Energy for Low-Damage Plasma Processing in RF Discharge

A new control technique for ion energy is based on the external electron injection into the capacitively coupled rf plasma using an auxiliary plasma source. The externally injected electrons replace the plasma electrons carrying the rf current and then reconstruct the rf sheath in which ions are accelerated. The experiment is carried out by using a parallel-plate rf plasma device with a magnetron discharge plasma source mounted behind the mesh grounded electrode. The experimental results show that the energies of ions are continuously controlled by varying the amount of injected electrons in a wide range from ≃(1 /2)eV rf to ≃T e ; and this result agrees with that derived from our simple model.

Static Elimination Performance of a Corona Ionizer in Nitrogen-Based Electronegative Gases

Corona ionizers are widely used in metal-oxide-semiconductor (MOS) device manufacturing processes to mitigate electrostatic hazards, such as the destruction of ultrathin-gate insulators that decreases production rates. However, unbalanced corona ionizers may deposit charges increasing electrostatic hazards. In this study, static neutralization characteristics of an ac corona ionizer in oxygen-free gas atmospheres, such as mixed

Scaling Relations for the Production and Acceleration of a J × B Driven Rotating Plasma

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A novel laser technique for constructing a plasma micro-undulator and a compact X-ray source

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Plasma centrifuge for separation of metal elements and isotopes

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