摘要:

We have constructed a hydrogen field ionization ion source which includes focusing optics. Both the ion source and a three‐electrode accelerating lens are cooled to cryogenic temperatures. The source and lens are designed to operate at 50 kV and the lens characteristics are optimized for an ionization voltage of 5 kV, such as would be used with ion milled emitters. This source and lens are part of a hydrogen ion beam lithography system currently under construction. The design of the source and lens, their operating characteristics, and the results and problems encountered in using them are presented.

ISSN:1071-1023    

DOI:10.1116/1.583360

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Extraction of a stable, high brightness ion beam from an apertured field ion emitter surface requires microfabrication procedures to sculpture the surface topography on both microscopic (100 –1000 nm) and near atomic (10 –100 nm) length scales. Structuring on a near atomic scale is required to confine and stabilize the ion beam by local enhancement of the surface electrostatic field and to orient that emission on the optical axis. Control of the emitter contour on a microscopic scale is required for manipulating the supply of neutral molecules to the ionization site and also affects beam stability. We have developed a method using ion milling for configuring surface contour on microscopic and near atomic length scales which utilizes the morphological changes occurring at ion bombarded surfaces as a result of erosion by sputtering. A SEM study of the microscopic emitter topographical development is compared to computer simulations of the kinematical wave equation which depicts the erosion process. In this way, prediction of configuration on a length scale large compared to the ion penetration depth has been established. TEM observations show the surface development on the length scale of ion penetration depth. Preliminary results using this microfabricated emitter in a gaseous field ion source to produce a hydrogen ion beam with high angular beam confinement are given. Requirements for surface topography that are essential to obtain stable high brightness ion beams are discussed.

ISSN:1071-1023    

DOI:10.1116/1.583361

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Many applications requiring high beam currents and operation with chemically active gases impose lifetime and operational requirements on the discharge electrodes in conventional ion sources. Despite the development of specially designed hot filaments and hollow cathodes, the presence of these electrodes in the discharge zone still limits the practical application of ion and plasma sources. Thus, the development of an efficient, simple, electrodeless discharge would result in an important improvement in ion beam and plasma processing technology. Recently, an electrodeless microwave ion source and plasma source have been developed. An improvement of this ion source is discussed. This is the redesign to surround the discharge zone with many closely spaced rare earth magnets producing a confining and cyclotron resonant multicusp static magnetic field. The experimental performance of this ‘‘modified’’ ion source using argon gas is presented. Experimental measurements of extracted ion beam current versus accelerating voltage and discharge electron and ion densities, etc. are presented over a range of gas flow rates and operating pressures.

ISSN:1071-1023    

DOI:10.1116/1.583362

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Chromatically limited electron‐microprobe systems are quite common in low‐voltage scanning microscopy. The non‐Gaussian blur disk and the asymmetric focal properties of the system are explained by considering the relation between source electron energy distributions and the spatial distribution of the current density in the vicinity of the image plane.

ISSN:1071-1023    

DOI:10.1116/1.583363

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Using an expression of the local space‐charge force derived in a previous paper, we analyze the broadening of axial energy distribution of beam particles in the acceleration region and calculate an upper bound of the energy broadening 〈‖ΔE‖〉UB. Assuming that the emitter is a sphere of radiusRwith potentialV, we obtain the expression 〈‖ΔE‖〉UB ∼∝ m1/4I1/2e V−1/4T1/2eff α−1e R0, wheremis the particle mass,Ieis the total emission current,Vis the acceleration voltage,Teffis an effective temperature showing the kinetic energy of particles at the emitter surface, and αeis the beam semiangle at the emitter. Theory gives 〈‖ΔE‖〉UB∼several eV for typical electron guns operating in space‐charge unlimited conditions. The result is compared with experiments and a discussion is given of the problem we have to solve to calculate the magnitude of 〈‖ΔE‖〉.

ISSN:1071-1023    

DOI:10.1116/1.583364

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

An aberration theory has been developed for analyzing the effects of machining errors of electrostatic ion‐optical systems comprising round lenses and octupole deflectors. The relationship has been investigated between the machining error and the induced perturbation, or the difference between the perturbed potential and the ideal one. The aberration formulas based on Sturrock’s perturbation characteristic function are shown. A computer program has been developed for analyzing electrostatic beam‐scanning systems and a submicron ion‐probe system is analyzed. The results show that lens errors may be corrected by a stigmator and that beam blurring by deflector error is negligible.

ISSN:1071-1023    

DOI:10.1116/1.583365

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Optical characteristics of a new submicron ion probe system capable of covering a wide area have been investigated; the system is composed of two cylindrical gap lenses, dual octupole deflectors, and a liquid metal ion source. We qualitatively measured the focusing characteristics of this focused ion beam system equipped with a liquid Ga ion source, through scanning ion microscope image of Cu mesh, and through scanning electron microscope observation of the ion etched crater formed in a gold film deposited on silicon. We obtained the on‐axis probe size of about 0.2 μm diam under the condition of an accelerating voltage of 15 kV and acceptance half‐angle of 1 mrad, leading to a current density of about 1 A/cm2. We also measured deflection characteristics of the system, and from the scanning ion microscope image we confirmed that the on‐axis probe size is almost unchanged even at a point 1 mm away from the axis by correcting astigmatism and field curvature. A microcomputer system has been developed for controlling the dual octupole deflector (including dynamic correction) and the ion dose by monitoring probe or source current.

ISSN:1071-1023    

DOI:10.1116/1.583366

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

We analyze photo, x‐ray, e‐beam, and ion‐beam lithographies from a statistical point of view in order to relate linewidth control to the contrast provided by the exposure technique, the resist contrast, and the resist sensitivity. Assuming a linewidth control of 20% at a minimum linewidth of 0.5  μm, we compare UV and x‐ray lithographies and find that the former is practical only with very high contrast resists (δN/N̄<0.16). We derive a simple expression for the minimum number of photons or charged particles required per pixel, and compare the pixel‐transfer rates of various lithographies. We find that beyond UV photolithography, synchrotron and pulsed‐plasma x‐ray sources offer the highest pixel‐transfer rates and appear most attractive for submicron lithography.

ISSN:1071-1023    

DOI:10.1116/1.583367

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

Monte Carlo computer simulations of e‐beam systems have proven quite successful in determining the contribution of mutual particle repulsion to critical beam parameters such as spot size and energy spread. For similar simulations on ion beams, the small charge‐to‐mass ratio of ions results in significant numerical problems which do not occur in the simulation of electron beams. New techniques are introduced which extend the application of this Monte Carlo technique to higher perveance beams. These techniques include the use of a periodic boundary condition on the simulation charge packet, a dynamic sphere of influence which reduces the number of interactions to be evaluated, and a dynamic time step which accounts for varying ion densities and random ion collisions. The resulting program is used to simulate a focused 50 kV Ga+beam, with a source divergence angle of 2 mrad and currents of up to 1 μA. Significant beam broadening was observed at currents in excess of 10 nA and the broadening was observed to increase with the application of a retarding field. Finally, arrival time distributions at the target plane were analyzed and no reduction in the statistical noise was observed as a result of space charge smoothing.

ISSN:1071-1023    

DOI:10.1116/1.583368

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

The task of successfully dealing with the proximity effect problem involves many aspects, all of which must be dealt with in a reasonably satisfactory manner. If one chooses to correct for the proximity effect by doing dose compensation, one major task is the solution of the integral equation which describes the resultant exposure in terms of the incident flux of electrons. One well known method is the self‐consistent method. This paper describes a method which provides a relatively accurate approximate solution to the integral equation which is easy to calculate and which provides information on where features should be fractured to obtain good dose compensation. Although the relationship between the incident flux and the resultant exposure is linear, the development process itself is not. This means that the usual integral equation should be modified slightly so that the resultant exposure is defined in a manner which more closely matches the real problem. This paper will attempt to describe how information from the development process can be used to define the exposure problem in a manner which provides more desirable solutions.

ISSN:1071-1023    

DOI:10.1116/1.583369

出版商:American Vacuum Society    

年代:1986

数据来源: AIP