Aberrations calculated from the electron trajectories are compared with those estimated from the third-order aberration coefficients. Field curvature and radial and azimuthal distortions are consistent with each other for moderate radial value R. In order to optimize lens positions, a method is adopted which makes the lens condition under which the principal ray trajectory from the largest objective radius R o crosses the optical axis at its normal position equal to that under which the trajectories diverging from the same R o focus on the image. For the 50 cm object-to-image distance optics, residual aberrations are calculated through the trajectory calculation after the corrections of lens current, crossover and beam position. When the main and subfield sizes are 20 mm and 0.25 mm square, the residual field curvature, astigmatism, and radial and azimuthal distortions are 13.1 nm, 6.4 nm, 19 nm, and 8.35 nm, respectively, when the beam semiangle is 0.1 mrad, and the beam energy is 100 keV.
Multiple beams are formed around an optical axis and scanned on a specimen. Secondary electrons (SEs) emitted from the scanned points are accelerated by an electrostatic objective lens and deflected by an E cross B (E×B) beam separator to a secondary-electron detector. By scanning over an 80 nm line & space pattern with four beams, Scanning Electron Microscopy (SEM) images are obtained. From these SEM images it is seen that there is no problem with cross-talk from the neighboring beams in multiple-beam SEM where there are plural detectors. The emittance and brightness of the electron gun with a LaB6 spherical cathode are measured to be 163 mrad µm and 1.5×105 A/cm2sr, respectively, for an emission current of 450 µA and a beam energy of 4.5 keV. A simulation is performed for a combination lens, with a lens, the magnetic gap of which is formed at the specimen side, and an electrostatic lens with an electrode to which a positive high voltage is applied. Based on these electron gun characteristics and simulated aberration characteristics, 8-columns by 8-rows multiple beams with a 160 nA total beam current and a 50 nm resolution are expected. A defect inspection with equivalent pixel frequencies of 4 GHz is expected. This pixel frequency is 10 times larger than that of a commercial available system, and then the multiple-beam SEM is a most promising system for a next-generation inspection.
High speed silicon photonic crystal waveguide modulator for low voltage operation Low voltage and high speed operating electrostatic wafer chuck using sputtered tantalum oxide membrane A new electrostatic force expression for the electrostatic wafer chuck with a three layer insulator is introduced. If a few micrometers of air layer is assumed, the expression coincides with the experimental results. An electrostatic wafer chuck with a two layer insulator is designed and evaluated. The bottom layer is a spin coated polyimide and the top layer is a vacuum evaporated alumina. The holding pressure is 35 gf/cm2, when 200 V dc is applied in atmosphere. The pressure is not influenced by the duration of the applied voltage. The residual pressure, after the voltage is turned off, decreases to zero rapidly. The breakdown voltage is from 320 to 700 V. The scratch test shows good results due to a vacuum evaporated alumina layer.
An electron gun for an accelerating voltage of 100 kV to be operated under space charge limited condition is designed, and its emittance and brightness are calculated. To obtain low brightness, a Pierce-type electron gun with a Wehnelt electrode and a control anode is adopted. Choosing a low value of the ratio between anode and cathode curvatures reduces the electric field strength at the cathode. A maximum emittance of 1.8 mm mrad and a minimum brightness of 350 A/(cm2 sr) are obtained under the above conditions with a cathode diameter of 1.66 mm. The radius of the Wehnelt aperture and its axial position are optimized. The effects of deviations of the shapes of the Wehnelt and control electrodes from concentric sphere are studied. It is found that in the space between the anode and the control anode the electrodes must be spherical up to an angle of at least 55°, whereas in the space between the Wehnelt electrode and the control anode the electrodes must be spherical up to an angle of at least 21°.
AbstncL (Fe4i)E'd multilayered films with different layer thickness have k e n oblained by RF sputtering. When the thickness of the Pd layers is k e d . the specific saluration magnetimtion M, of films inercases with dccrcase in lhe thickness of Fe-Si layers. l h i s result is mused by the polariration effecl of Pd atoms. On "lying lhe thickness dp of the Pd layers, with a ked Fe-% layer thicknes, il iF found that for Pd layen thinner than 36 A the polarization effect of Pd is reduced and even disappears at dp = 18 A: lhen magnetic mupling between lhe magnetic layers appean on funher decrease in d,.
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