A 100-kV, 100-A/cm2 Electron Optical System for the EB-X3 X-Ray Mask Writer
In order to increase the throughput of the EB-X3 variably shaped electron beam writing system, a method of increasing the current density with a zoom lens was introduced into the electron optical system. The electron optical characteristics were measured at current densities of 50 and 100 A/cm2 under various zoom-lens conditions, and the results show that this method can increase the current density to 100 A/cm2 without any change in the major electron optical characteristics. At this current density, the patterning resolution was estimated to be 55 nm, and no melting of the first shaping aperture and no microdischarges in the 100-kV electron gun were observed. This confirms that the current density of the EB-X3 can in fact be extended to 100 A/cm2 for the fabrication of X-ray masks with a minimum feature size of 100 nm and below.
Electron optical system for the x-ray mask writer EB-X2
An electron optical system that yields a beam voltage of 100 kV and a beam edge resolution of 20 nm was developed for a variably shaped electron beam writing system, the EB-X2. In order to improve the beam edge resolution, the objective lens and main deflector were designed on the basis of the uniform field concept, and the optimum beam half-angle was determined by beam profile calculations. The optimized design provides a beam edge resolution of 20 nm for a 650-μm-square deflection field and a beam current of 250 nA. Given the high acceleration voltage, it is possible that the electron optical column could be too high to fit into a clean room. To shorten the height of the electron optical column, the lens configuration was carefully examined. The results show that the height of the column is a minimum when the first shaping aperture is placed in the principal plane of the illumination lens. This finding enabled us to reduce the height of the column to 880 mm. The electron optical column was constructed a...
Geomagnetic micropulsations due to the motion of ocean waves
When sea waves move in the magnetic field of the earth, electric currents are generated in the water volume. These currents give rise to a small magnetic field which perturbs the earth's field. For plane trochoidal waves, this perturbing field decays exponentially with altitude and lies in a vertical plane which is oriented in the direction of wave propagation. The magnitude of the perturbing field also depends upon the magnitude and dip angle of the earth's field, and upon the height, wavelength, and propagation direction of the sea waves. For north-south waves, sea state 5, and an altitude of 100 feet, the perturbation is of the order of 0.1 gamma.