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Summary form only given. Highly miniaturized electron beam columns based on a field emission source and microfabricated electron optical components have been developed. A 1 keV microcolumn operating with a miniaturized Zr/O/W Schottky emitter has been successfully evaluated for the first time. This paper will present the results obtained with the new microcolumn and discuss present efforts to further improve column performance with respect to resolution, beam current, and deflection field size.

A fully functional electron beam microcolumn, 3.5 mm in length, demonstrating a probe size of 10 nm and beam current >= 1 nA at 1 keV has been successfully developed. This paper presents its current status and future directions. Potential applications ranging from low cost scanning electron microscopy to arrays of such microcolumns for lithography, metrology, testing etc. will be discussed.

Photoemission has often been proposed as a promising approach for achieving arrays of independently modulated photocathodes for electron-beam lithography applications. In most such proposals the modulation of the photocurrent is assumed to be achieved by controlling the incident light energy reaching each photocathode. For many applications, however, the optical complexity of such a scheme limits the attractiveness of the photocathode approach. In this article we propose a novel gated photocathode structure which resolves this concern. It allows stable and reproducible electrical modulation of the photocurrent from each photocathode in a thin-film array under continuous optical illumination. In addition, by using illumination of the photocathodes through a transparent substrate, the position, the size, and the shape of each photocathode can be accurately determined during fabrication rather than being determined by the size of the optical illumination spot on the photocathode material. A number of structu...

Experimental measurements of emission stability and energy distributions from a Schottky emitter have been conducted at a tip temperature range from 1330 to 1800 K. The changes of emission properties have been observed at reduced tip temperatures. Noise fluctuations of the probe current increase with decrease of the tip temperature at a constant extraction voltage. The work function of the Schottky emitter increases with decrease of tip temperature. The energy distribution measurements show that the energy width at a given temperature increases with increasing angular emission current density. The energy width also increases with decreasing tip temperature at a given angular emission current density. The results indicate that the energy broadening is mainly contributed by electron tunneling. A comparison of the measured energy width with the theoretical predictions is discussed.

Lithography with an array of miniaturized scanning electron‐beam columns presents one of the most promising high‐throughput possibilities for fabrication of devices with feature sizes less than 100 nm. With scanning electron beams no mask is required and the necessary resolution and alignment of overlay structures are realizable. With arrays of microcolumns, the lithography throughput of a single column can be multiplied. The approach can also be used for a number of lithography related applications such as metrology, inspection, testing, etc. We review the status of the microcolumn program and discuss opportunities and challenges of this approach to high‐throughput nanolithography and related applications. Special emphasis is given to lithography in the 100 nm regime.

We have measured the energy distributions of electrons field emitted from tungsten carbide, HfC〈100〉, and ZrC〈100〉 tips, and tungsten field emitters with diamondlike carbon coatings. Multiple‐peaked energy distributions were observed from instability induced emission sites on the carbide tips. Energy distributions of electrons field emitted from the diamondlike carbon coated tungsten tips were broader than those from metal tips. They also showed a shift towards lower energies with increases in the emission current.

We have evaluated the cold‐field‐emission characteristics of HfC〈100〉 and ultrasharp tungsten emitters. We found that proper acetylene treatment improved both the angular current confinement and the emission stability of thermally cleaned HfC〈100〉 tips. Stable emission exceeding 10 μA/sr for over 1 h and angular confinement to a 3° semicone angle have been observed. The improvements are probably related to the modified work function and surface chemical composition induced by the acetylene treatment at the tip apex. Carburization of W〈100〉 and W〈111〉 tips also significantly improved the emission current stability. This study indicates the usefulness of surface processing in the development of cold‐field emitters.

A miniature Schottky electron source has been developed and evaluated for applications in a new generation of scanning tunneling microscope aligned field emission microcolumns. Both the physical dimensions and the heating power of this source have been significantly reduced from a conventional source of the same kind. Operating parameters for such a source in a microcolumn environment in terms of emission characteristics, suppressor operating range, etc., have been evaluated. Test results show that very good emission stability at ≥100 μA emission current over several hours, and axial angular current densities in excess of 100 μA/sr can be obtained. Energy distributions have been measured using a carefully calibrated analyzer, and the results show a full width at half‐maximum of 0.4 to 0.76 eV for a 0.3 μm radius Schottky source operating over an angular current density range of 1 to over 100 μA/sr. A significant change in the shape of the energy distribution was observed over this range of operation, indi...

We have built and tested a 1 keV electron‐beam microcolumn that focuses 1 nA of beam current into a 10 nm full width half‐maximum beam diameter at a working distance of 1 mm. The electron source is a miniaturized Zr/O/W Schottky field emitter with 150 μA/sr angular emission current density operating at about 1800 K at a distance of only 100 μm from a silicon membrane extractor electrode. The actual microcolumn is 3.5 mm long assembled mainly from silicon membrane electrodes. Improved einzel lens design and fabrication allowed the operation of this beam focusing element in the accelerating mode. Spherical and chromatic aberrations were reduced by factors of about 2–3, respectively, as compared to the retarding lens mode. Excellent beam current stability with less than 1% variation over several hours has been observed.

Schottky emission tips have been evaluated with microlenses for applications in scanning tunneling microscope aligned field emission microcolumns. Operation of Zr/O/W 〈100〉 Schottky emission tips at 1800 K with an axial separation of 50–100 μm between the tip and a microlens has been successfully tested. The microlens consists of an extraction electrode with a 5‐μm‐diam hole in a 1‐μm‐thick silicon membrane. The preliminary results of this study show that thermal field emission tips can be operated continuously in close proximity to a microlens over a long period of time, and that good emission stability of less than 1% noise fluctuation over 10 h is achieved with emission currents up to at least 100 μA.

We have examined the field emission characteristics of oxygen‐processed and thermal‐field buildup W 〈111〉 tips. Good emission angular confinement was found to correlate with the global geometry of the tip. Emission stability was related to the atomic arrangement at the apex. This phenomenon is described by the different driving forces for atomic surface diffusion. We also showed that tip apexes can be engineered to form flat (111) facets at the tip end for improved stability.

An oxygen induced sharpening process of field emitter tips, W〈111〉, for use in a scanning tunneling microscope aligned field emission microcolumn system has been developed. The sharpening process which depends on processing temperature and oxygen pressure can be used to control tip radius accurately with reliability and reproducibility. The measured tungsten removal rate was ∼13 A/min at a processing temperature of ≂1650 K and at an oxygen pressure of ≂4×10−5 Torr. The process is primarily intended for more accurate control of the tip radius and hence performance of newly etched tips, although damaged or blunt tips can also be resharpened in situ with this process. Favorable emission characteristics of the oxygen processed tips have been observed with microcolumn operation: (1) reasonably stable emission current, (2) low extraction voltage, (3) reproducible threefold symmetric emission patterns, and (4) small emission angle.

A three-dimensional close-packed array of Josephson junctions was successfully produced in the form of a bulk granular superconductor. The granular system is a tightly compressed solid of oxide coated small tin particles in the thousand A range. The three-dimensional array of Josephson junctions thus formed showed coherent Josephson oscillations when external rf radiation was imposed, rf induced constant voltage steps were observed on its I-V characteristics at voltages a few thousand times the Josephson voltage hv/2e. The external rf radiation also induced Stable dc voltages on unbiased bulk samples, suggesting a practical mode of microwave detection. The analogy of this bulk superconducting system with a magnetic spin system will be discussed.

Measurements have been made within a few micrometers of a current-carrying superconducting-normal boundary, which indicate that an electric potential exists in the superconductor in this region. Near the transition temperature the experimental results are consistent in magnitude and temperature dependence with a theory recently proposed by Rieger, Scalapino, and Mercereau.

Normalized ionization probabilities α+ are reported for binary Fe‐Ni alloys under O+2 bombardment at a 45° incidence angle. It is shown that the dependence of α+ on the composition is much smaller than at normal incidence. Photoemission spectroscopy reveals that both nickel and iron remain essentially metallic under oblique‐incidence bombardment, whereas almost complete oxidation occurs at normal incidence. This is attributed to our observation that sputter yields under oxygen bombardment increase much faster than cos α−1.

Secondary ion emission during sputtering depends very much on the local atomic environments of the sputtered atoms. For example, sputtering with 02 + significantly enhances positive ion formation [1]. This enhancement is attributed to the incorporation of oxygen atoms in the target. The formation of the oxide bonds intensifies the secondary ion yields. In this experiment we moved a step further and tried to see whether the presence of a second metallic component in the sample could influence this oxygen enhancement effect. We also tried to look for any corresponding changes in the oxide bonds with X-ray photoemission (XPS). We examined two alloy systems: CrNi and AgPd. Both Cr and Ni form strong oxides, while both Ag and Pd form weak ones.