A combined objective lens for electrons and ions

Nanofabrication is possible using focused ion beam technology, but the observation of these structures with the same ion beam is not possible because of its erosion effect. Therefore a general purpose instrument for nanotechnology based on particle optics has to combine an ion and an electron beam. The objective lens, the final lens above the specimen, has to focus both beams on the specimen. An objective lens that combines magnetic and electrostatic fields has been designed for this purpose. Its aberration coefficients allow a 1 nm ion beam and a 0.3 nm electron beam.     

Focused ion beams for lithography and direct doping in VLSI device fabrication

We review the possible applications of focused ion beams to the lithography and doping stages in the fabrication of microelectronic devices. Topics discussed include ion sources, system performance, ion beam lithography and direct implantation doping. Emphasis is placed on a comparison between electron and ion beams for direct write lithography. Wafer throughput for both techniques is analysed in terms of equipment limitations and resist properties. For direct implantation doping, the effects of the ion beam profile are discussed and wafer throughput is considered. We conclude that, due to throughput limitations, ion beams are not appropriate for either lithography or direct doping for VLSI device fabrication.     

A comparison of focused ion beam and electron beam induced deposition processes

Focused ion and electron beams are used for local deposition of conducting or insulating films. Major applications are integrated circuit design edit, prototype modification, repair of masks, and machining of microsystems. In this paper, the dependence of the deposition rates versus the beam parameters for both, ion beam and electron beam induced deposition were investigated and compared with each other. At the same time, a more precise consideration of the influence of secondary electrons on the deposition process was accomplished.     

Estimation of wave fields of incident beams in a transmission electron microscope by using a small selected-area aperture

The direction of an electron beam in a nanometer-sized area is measured directly by utilizing a selected-area aperture. By the measurements at several areas in a beam, the wavefront curvature and thus the defocus value of the beam are detected. From the defocus value, the wave field at the specimen plane is also reproduced in consideration of the influences of the condenser aperture and spherical aberration of the illumination lens. The result shows that phase deviation of 2π is caused only at about 10?nm apart from the beam center in a beam with a typical diameter for high-resolution transmission electron microscopy. Based on the defocus value, the convergence angle of the beam is also estimated to be about 6?mrad without being influenced by the partial coherence, that is, independently of the type of the electron gun. Measuring the defocus values for only two beam diameters enables us to determine geometrical parameters peculiar to the illumination system, based on which wave fields of any beam diameters by any condenser aperture sizes can be estimated. The technique proposed in this paper is effective in evaluating the influence of wavefront curvature of incident beams on various kinds of precise measurements conducted in transmission electron microscopes.     

Intense Sheet Electron Beam Transport in a Uniform Solenoidal Magnetic Field

In this paper, the transport of intense sheet electron beams in a uniform solenoidal magnetic field in high-power vacuum electronic devices is theoretically examined with the 3-D beam optics code MICHELLE. It is shown that a solenoidal magnetic field can be an effective transport mechanism for sheet electron beams, provided the beam tunnel is matched to the beam shape, and vice versa. The advantage of solenoidal magnetic field transport relative to periodic magnetic transport resides in the feasibility of transporting higher current density beams due to the higher average field strength achievable in practice and the lower susceptibility to field errors from mechanical misalignments. In addition, a solenoidally transported electron beam is not susceptible to voltage cutoff as in a periodic magnetic focusing system; hence, device efficiency is potentially higher.     

Performance of magnetically compressed O-type electron beams emitted from nonshielded cathodes

The theory pertaining to the behavior of a cylindrical electron beam emitted from a nonshielded cathode in an axial, monotonically increasing magnetic field is experimentally verified. A convenient technique of measuring the scalloping of electron beams in sealed-off tubes by varying the beam voltage is described. Experimental results include the study of the beam compression and percentage scalloping in several configurations of increasing magnetic fields. It is shown that for such beams the percentage scalloping is fairly independent of the amount of compression.     

Positive ion oscillations in long electron beams

Positive ion oscillations occurring in a long electron beam were investigated experimentally. The predominant direction of oscillation was found to be transverse to the direction of electron flow, and the frequency of oscillation was found to be three times higher than existing theory predicts. In pulsed beams the onset time of irregularities in current flow due to positive ion formation was found to be inversely proportional to current, and in some cases positive ion effects were observed to take place within four microseconds of the beginning of the pulse.     

The mapping theorem of two-dimensional electron beam trajectories

Two-dimensional electron beams in certain electrostatic fields are dealt with, ignoring space-charge effects. The central trajectories of electron beams were previously given. The electron beam in a suitable electrostatic field fluctuates near the given trajectory just as a paraxial electron beam fluctuates near the axis. If both fluctuations agree completely, the electron beam considered can be regarded as a projection of the paraxial electron beam. This situation is called here the mapping of electron beams and is verified in the mapping theorem.     

L波段相对论速调管束流实验研究

介绍在L波段强流相对论速调管研究中,强流相对论短脉冲空心电子束的产生、传输、束流调制及其诊断等方面的初步实验研究情况。在直线感应加速器上,利用66mm、壁厚3mm的石墨空心阴极,加上约5kGs的准直流引导磁场,引出了约500kV、4.5kA、脉宽100ns、54.5mm、厚度4.5mm的空心电子束。注入500kW的微波调制,束流经过输入腔后,得到了约6％的最大基波电流调制深度,经过中间腔后,得到了约23％的基波电流调制深度。     

Analog computer solutions for correction of ripple in magnetically-collimated electron beams

Analysis of the dynamics of an electron beam in a magnetic collimating field leads to formulas which can be processed conveniently in an analog computer to obtain individual solutions. This technique is applied to the problem of correcting the ripple which is generally imposed upon the envelope of the beam after passage through a spatial variation or reversal of the collimating field. However, a relatively general viewpoint is retained in developing methods and formulas for studying the motion of an outermost electron of a relatively uniform, round, straight electron beam. Fer this reason the results can be applied to beams from shielded or unshielded cathodes, passing through uniform, periodic, or nonperiodic reversing magnetic collimating fields. A simplified development of the mathematical theory of magnetically confined electron beams is presented, including the effects of spatial variations and reversals in the collimating magnetic fields. Formulas are developed for the equilibrium electron beam radius, and for the ripple frequency, axial wavelength, amplitude, and phase of the outermost electrons, in terms of the field parameters and the initial beam conditions. Analog computer solutions for an electron beam with various collimating magnetic fields serve to illustrate and confirm the developed formulas. From these computer solutions, suggestions are derived for guidance in shaping collimating magnetic fields so that electron beam ripple will be prevented or reduced.     

Synthesis of systems formation of converging sheet electron beams at partial magnetic shielding of the cathode

The synthesis method of electro-optical systems forming converging sheet electron beams at partial magnetic shielding of the cathode is developed. Equations of the inerior and exterior problems of the synthesis method and an equation for estimation of the deformation of the configuration of the sheet electron beam in the transit channel are obtained in the paraxial approximation. The proposed method is used to simulate electron guns forming converging sheet electron beams with the electrical parameters similar to the parameters of the uncompressed electron beam for terahertz radiation sources.     

Resolution, overlay, and field size for lithography systems

Resolution, overlay, and field size limits for UV, X-ray, electron beam, and ion beam lithography are described. The following conclusions emerge in the discussion. 1) At 1-µm linewidth, contrast for optical projection can be higher than that for electron beam. 2) Optical cameras using mirror optics and deep UV radiation can potentially produce linewidths approaching 0.5 µm. 3) For the purpose of comparing the resolution of electron beam and optical exposure, it is useful to define the minimum linewidth as twice the linewidth at which the contrast of the exposure system has fallen to 30 percent. 4) X-ray lithography offers the highest contrast and resist aspect ratio for linewidths above about 0.1 µm, but for dimensions below 0.1 µm, highest aspect ratio is obtained with electron beam. 5) With electron beam exposure on a bulk sample, contrast for a 50-nm linewidth is the same as that for 1-µm linewidth, provided the resist is thin. Higher accelerating voltages make it easier to correct for proximity effects and to maintain resolution with thick resist. 6) Ultimately the range of secondary electrons limits resolution in electron beam lithography, just as the range of photoelectrons limits resolution in X-ray lithography. In both cases, minimum linewidth and spacing in dense patterns is about 20 nm. Resolution with ion beams will probably be about the same because the interaction range of the ions will be similar to the electrons.     

聚焦离子束(Focused Ion Beam)原理与其在半导体工业之应用

聚焦离子束被广泛应用于芯片电路修改、研磨、沉积和二次电子/离子成像。FIB对于新原型电路设计的修改以及离子间交互作用的基础研究具有独特之性能。使用极细的聚焦离子束,FIB技术可以进行比从前更加精确的产品失效分析。操作者可以快速地、选择性地去除绝缘层或金属层,以便进行集成电路下层信号的点针探测或材质分析。集成电路的断面切割还可以达到亚微米的精度。     

Electron beams in axially-symmetric crossed fields

M-type traveling-wave tubes use electron beams that drift in crossed electric and magnetic fields. One such tube, the axiotron described by Warnecke and Doehler in 1950, used a hollow beam drifting parallel to the tube axis in a radial electric field crossed by an azimuthal magnetic field. The addition of an axial magnetic field to the azimuthal one adds another degree of complication and flexibility to the beam equations, yet maintains their symmetry about the tube axis. It gives, in effect, a helical magnetic field crossed by a radial electric field. This report examines the behavior of hollow electron beams drifting in laminar flow through fields of the latter configuration. It defines a stability index for electron paths, and four fairly general types of beam. It determines the stability index and the distribution of space charge obtainable in each type as functions of the amplitudes and directions of the fields and drift velocities. In general, the density tends to be greatest at the inner beam radius, but it is possible to approach uniform density in stable beams. This report does not consider beam launching nor the "gun" problem; nor does it consider over-all beam instabilities such as scalloping.     

A time-dependent non-linear theory of ion channel electron cyclotron maser

A time-dependent non-linear theory is developed for ion channel electron cyclotron maser (ICECM), and the corresponding numerical calculation results are given for the first time. The theoretical analysis shows that the longitudinal plasma wave tends to enhance the energy exchange between the beam and wave. Using the numerical calculation of the self-consistent time evolution of scattering wave growth, the non-linear effect of ion density on the beam-wave interaction efficiency has been studied. The time norm, which must be satisfied in the operation of ICECM, is verified. Taking 6.8?×?10¹³?cm^?3 ion density, 1?MV accelerated voltage and 1.5?KA beam current, the present numeric calculation results show that the pulse scattering wave power and the frequency can achieve about 200?MW and 284?G?rad/s respectively.     

Eigenvalues of characteristic noise matrix of an electron beam with half-Maxwellian velocity distribution

A method is devised for determining the eigenvalue spectra of the characteristic noise matrix of electron beams with continuous velocity distributions. It is found that for an electron beam with a half-Maxwellian velocity distribution, all positive eigenvalues are equal to kTΔf while all negative eigenvalues approach zero. This finding is in agreement with the phenomenon of noise reduction in an electron beam drifting at a low average velocity (an average velocity comparable to the velocity spread).     

离轴高斯光束经光学系统变换后特性研究

以广义衍射理论为基础,通过collins 公式,分析了离轴高斯光束经过矩阵元为ABCD 的光学系统的变换特性,得到的出射激光束是偏心高斯光束,并研究了离轴高斯光束聚焦和准直的特点。     

Production of electron vortex beams carrying large orbital angular momentum using spiral zone plates

We report the production of electron vortex beams carrying large orbital angular momentum (OAM) using micro-fabricated spiral zone plates. A series of the spherical waves, focussing onto different positions along the propagating direction of the electron beam, were observed. The nth order vortex beam has an OAM n times larger than that of the first-order vortex beam. We observed an electron vortex with an OAM up to in a high-order diffracted wave. A linear dependence of the diameter of the vortex beam on the OAM was observed, being consistent to numerical simulations.     

均匀磁场聚焦部分屏蔽流电子注的一种设计方法

本文叙述了适用于轴对称强流电子光学系统各种磁结构的部分屏蔽流过渡区的设计方法。通过综合选取磁系统和电子枪参数,实现了磁系统与电子枪的最佳匹配,获得了屏蔽系数大于0.8,波动小于1％的电子注。     

Gridded electron guns for high average power

The design and performance of electron guns producing high-average-power beams which are controlled by an intercepting-type grid are described. The design consists of a modification of the design of Pierce-type electron guns to allow for the effect of grid insertion, and calculation of the amplification factors based on the potential distribution. The performance is evaluated in terms of the beam shapes and average beam powers obtainable. Measured amplification factors are compared with calculated values. Factors influencing the measured beam shapes are discussed. Trajectories of electrons emitted as secondaries from the grid and those of electrons deflected by the lens effect of the grid wires were plotted using an analog computer and electrolytic tank. The shapes and focusing properties of electron beams from similar gridded and nongridded guns are compared. Expressions relating the average beam power capability to the gun and grid dimensions are developed. The calculated average beam power capabilities are compared with measured values. Average beam power as high as 8 kw has been obtained with electron guns of a size suitable for use in X-band twt's.