Katsuhiro Kuroda

Numerical analysis of electron orbits in a compact high-current circular microtron

The performance of a compact high-current circular microtron is investigated by means of computer simulation. The microtron investigated here is operated with the Russian second type of acceleration and has an electron gun, composed of a cathode and an anode, located outside the accelerating cavity. The simulation results enable us to see the possibility of stable acceleration, to estimate the capture coefficient, and to predict the initial conditions necessary for stable acceleration.

Analysis of magnetic induction distribution by scanning Lorentz/interference electron microscopy

A new observation technique of magnetic induction base on the combination of differential phase contrast and interface electron microscopy has been developed. This technique can be used to clearly to visualize the magnetic induction distribution in and around the specimen. Furthermore, the quantitative determination of induction strength with a unit of h/e (h: Plancks constant, e: electron charge) can also be made possible.

Novel Technique for Observing Three-Dimensional Magnetic Head Field Using Electron Beam Apparatus

31 steel and Cr-Mo steels, not only were the magnetic properties found to change with fatigue damage dynamically, but also a linear relationship between measured remanence and fatigue crack area was observed. A model equation was developed in this study which shows agreement with the observed linear relationship between crack area and magnetic remanence. On the other hand, the coercivity and its relationship to crack area were found to depend upon the sensor position relative to the crack. 3D finite element analysis of the leakage field above a crack showed agreement with the coercivity results. Using the remanence measurement method presented in this paper, therefore, fatigue damage and crack area in steel components can be evaluated nondestructively. This work was sponsored by National Science Foundation under grant number CMS-9532056. AP-05. AUTOMATED LONGITUDINAL RECORDING MEDIA CHARACTERIZATION USING OPERATIVE FIELD HYSTERESIS MEASUREMENTS. Ferenc Vajda, Erik Samwel, and Dennis Speliotis (Digital Measurement Systems, Inc., 8 Ray Ave, Burlington, MA 01 803) Appropriately interpreted, moving Preisach-based hysteresis models provide physical insight into the hysteretic behavior of interacting systems consisting of a large number of “particles.” Experimental analysis of various longitudinal recording media has verified that the medium perceives an operative field, h=H+aM, where a is the material-dependent moving constant.’ Hence, in order to correctly measure the hysteresis parameters of recording media, the operative field has to be accurately controlled. Using a computer controlled DMS vibrating sample magnetometer an automated data acquisition technique was implemented that uses operative field measurements. The program first measures the moving parameter and then iteratively searches for the applied field, H. that results in the required operative field, h. The algorithm ensures that the target operative field is approached asymptotically, making the technique suitable for the measurement of operative minor loops. Using this technique the operative anhysteretic susceptibility curve of a and a CO modified recording sample was measured and was verified to be always Gaussian. Using the automated technique to measure operative minor loops a specific magnetizing process was experimentally verified that maximizes the accommodation in media. These results, together with the general framework of using the operative field rather than the applied field provides a physically derived set of hysteresis parameters to be measured when characterizing longitudinal recording media ‘F. Vajda and E. Della Torre, IEEE Trans. Magn. 31 (1995). pp. 18091812. AP-06. MEASUREMENT OF OXYGEN PRESSURE INCREASE IN MAGNETIC FIELD. Noriyuki Hirota, Jun Nakagawa, Koichi Kitazawa (Dept. of Appl. Chem Univ. of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113,Japan). Hiroyuki Yokoi, Ryuzi Katoh, Yozo Kakudate, and Syuzo Fujiwara (NIMC, 1-1 Higashi, Tsukuba 305, Japan) We are investigating surface and interface shape changes of liquids under high magnetic fields. It was observed that the water surface falls under high field. In this study we also consider susceptibility of a gas on the surface. It is already known that oxygen has relatively huge susceptibility among gases. A superconducting magnet, which produce 8 T at the center, was used. A water vessel was set in a horizontal bore and the surface shape was observed. When nitrogen gas, which is nearly non-magnetic, was passed on water, surface level under the field center was lowered 24.7 mm than outside the field. On the other hand, in case of oxygen, the surface difference was 29.2 mm. This increment was introduced by magnetism of oxygen and reveals that oxygen gas pressure is higher in the field. Theoretically calculated increment of oxygen pressure under 8 T was 46 Pa. Experimentally obtained value was 44 Pa and it agreed with the calculated one. If we try to measure gas pressure increment in a field by other methods, it would be quite difficult. Because magnetic field and its gradient may affect the pressure detector. The method for observing gas pressure change under a field proposed in this work is as follows. First we observe some liquid surface under gradient field with nitrogen, we can get a magnetic force influence on the liquid. Secondly, observing surface shape under the same condition with sample gas, the surface shows field influence on both the liquid and the sample gas. By subtracting the value of surface level change with small magnetic gas from the value of the sample gas, we can get the surface level change introduced by sample gas pressure. This method could be a general way to measure gas pressure in

A compact high-current circular microtron

A compact high-current circular microtron has been developed. This microtron is operated with the Russian second type of acceleration to reduce its size and has an electron gun outside the accelerating cavity to increase the beam current. The uniform magnetic field is about 0.19 T, and the energy gain per orbit is about 0.9 MeV. The beam current at a microwave power of 2.2 MW is 200 mA at 4 MeV and 80 mA at 9.5 MeV.

Optimized secondary electron collection in in-lens-type objective lens

Secondary Electron (SE) trajectories were numerically simulated for an ultra-high resolution Hitachi S-900 SEM with an in-lens type objective lens in order to optimize the SE detector position. The trajectories of SEs emitted from the sample were computed as follows. The electrostatic field of SE detector was calculated by a 2D rectangular finite element method (FEM). On the other hand, the magnetic field of the objective lens was calculated by a 2D axially symmetrical FEM. SE trajectories were then 3D simulated by Runge-Kutta method. The SE detector angle relative to the electron optical axis was changed from 45 degree(s) to 60 degree(s) and the SE trajectories were calculated for a various SE positions on the sample at 1 kV to 30 kV accelerating voltage. As a result, the position of the SE detector was optimized so that it gave no variation of brightness even in a low magnification of 250.

A simplified focusing and deflection system with vertical beam landing

A focusing and deflection system with vertical beam landing and reduced aberrations was developed for direct electron beam lithography. The system consists of two magnetic lenses and a magnetic deflector. The excitations between the lenses are inverse to each other. The deflector, which has saddle‐type coils, is set inside the first lens. The pivot point introduced by the deflector and the first lens coincides with the focal point of the second lens to achieve a vertical beam landing. These arrangements and the operating conditions also enable minimized aberrations, especially elimination of transverse chromatic aberration. In computer simulation, the system gives a 2 mrad/mm landing angle coefficient and a 0.1 μm aberration disk after refocusing at each deflective point, when a converging semiangle of 2.5 mrad is used in a 3.2×3.2 mm2 deflection area at a 30 kV beam energy. The converging angle gives a current density of 10 A/cm2 using the LaB6 electron gun with 5×105A/cm2sr brightness. In the simulation...

Resonant tunneling electron beam source using GaAs/AlAs/GaAs field emitter

In order to realize a new type of monochromatic electron beam source which incorporates the resonant tunneling effect, methods to form GaAs/AlAs/GaAs field emitters and extract electron beams from them were examined. An undoped GaAs/AlAs/GaAs field emitter showed narrow (0.2 eV) energy distributions almost irrespective with extraction voltages. A δ-doped GaAs/AlAs/GaAs field emitter showed a shoulder. The energy difference between the shoulder and the main peak coincides with that among calculated quantum well subbands. These results suggest the existence of resonant tunneling electron emission in the GaAs/AlAs/GaAs field emitter systems.

A nondestructive analysis technique for residual thin films in deep-submicron contact holes

Abstract A new type of scanning electron microscope has been developed to check for residual materials in deep-submicron contact holes without cracking the wafer. To detect the characteristic X-rays emitted from resudues, the microscope has an energy-dispersive X-ray detector located near the electron beam axis between the condenser and objective lenses. When the residual materials are irradiated with a focused low energy (2 keV) electron beam, we can easily identify materials and determine their amount from the observed X-ray energy and intensity. The analysis technique can detect a 20 nm thick SiO2 film remaining at the bottom of a 0.2 μm diameter contact hole (2 μm deep) patterned on a SiO2 layer. This technique is a key tool to speed up the development of semiconductor devices and improve production yield in its fabrication process.