[en] A new electron beam excited plasma (EBEP) etching system has been developed. This EBEP system can efficiently generate a high density and uniform plasma by introducing a high current low-energy electron beam into an etching gas chamber. The uniformity of the Cl plasma density is within ±2.5% over an 8 in. wafer and the uniformity of the plasma and floating potential across the wafer is within ±2 V. This ultrahigh uniformity of the potentials overcomes the problem of the breakdown of thin gate insulators during etching that originate from the nonuniformity of the potential at the substrate. The selectivity of etching obtained is 40:1 for poly-Si/resist and more than 100:1 for poly-Si/SiO₂. The etch rate is 3600 A/min. 4 refs., 9 figs

[en] Plasma source ion implantation (PSII) with metal plasma results in a qualitatively different kind of surface modification than with gaseous plasma due to the condensable nature of the metal plasma, and a new, PSII-related technique can be defined: metal plasma immersion ion implantation and deposition (MPI). Tailored, high-quality films of any solid metal, metal alloy, or carbon (amorphous diamond) can be formed by MPI using filtered vacuum arc plasma sources, and compounds such as oxides or nitrides can be formed by adding a gas flow to the deposition. Here we describe the plasma formation at cathode spots, macroparticle filtering of the vacuum arc plasma by magnetic ducts, the underlying physics of MPI, and present some examples of MPI applications

[en] Inductively coupled plasma sources are being developed to address the need for high plasma density (10¹¹--10¹² cm^-3), low pressure (a few to 10--20 mTorr) etching of semiconductor materials. One such device uses a flat spiral coil of rectangular cross section to generate radio-frequency (rf) electric fields in a cylindrical plasma chamber, and capacitive rf biasing on the substrate to independently control ion energies incident on the wafer. To investigate these devices we have developed a two-dimensional hybrid model consisting of electromagnetic, electron Monte Carlo, and hydrodynamic modules; and an off line plasma chemistry Monte Carlo simulation. The results from the model for plasma densities, plasma potentials, and ion fluxes for Ar, O₂, Ar/CF₄/O₂ gas mixtures will be presented

[en] Established semiconductor process technologies are demonstrated to be suitable for the fabrication of high temperature superconductor Josephson junctions. Single YBa₂Cu₃O₇ bridges have been modified by local oxygen ion irradiation through a narrow slit in an implantation mask, which was formed by electron-beam lithography and reactive ion etching. The influence of the slit dimension, the mask thickness, and the irradiation dose have been investigated systematically. The critical current and the normal resistance of the modified microbridges were found to be controllable by these parameters achieving a great variety of different I/V curves, i.e., resistive or superconductor/normal/superconductor (SNS) Josephson junction behavior. Further investigations were performed on SNS junctions. Microwave irradiation of the microbridges exhibits Shapiro steps in the I/V characteristics. In dc superconducting quantum interference devices a voltage modulation as a function of an applied magnetic flux is observed. copyright 1996 American Vacuum Society

[en] It is contended that contrarily to the claim of Szilagyi and Cho (Ref. 1), thecoma of deflection as well as field curvature can not be eliminated in the optimized electrostatic deflectors

[en] Using some sophisticated modes of scanning tunneling spectroscopy the local density of states on two superconducting compounds in the superconductive state at 4.2 K were analyzed. On NbSe₂ which is a type-II low-T_c material, the Abrikosov flux line lattice was imaged for various external magnetic fields up to B_C2. The field-induced decrease of the vortex core radius for increasing magnetic field, which was recently predicted by a microscopic theory, could be clearly verified. On sputtered YBa₂Cu₃O_7-δ films the measurements yielded some distinct types of the surface density of states involving gaps, being in accordance to the Bardeen endash Cooper endash Schrieffer theory, unexpectedly large gaps, Coulomb staircases, and zero-bias peaks. copyright 1996 American Vacuum Society

[en] 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, indicating evidence of tunneling currents at the high angular current density regime. copyright 1995 American Vacuum Society

[en] An anisotropic nonselective etch for GaAs/AlGaAs rib waveguides has been developed for use under electron cyclotron resonance conditions. The plasma chemistry features BCl₃ to minimize AlGaAs oxidation effects and small additions of N₂ to induce sidewall protection when using photoresist masks. The fundamental mode attenuation in GaAs/AlGaAs waveguides is sensitive to the choice of both plasma chemistry and making material, but can be reduced to < 1 dB cm^-1 for channel widths of 4-5 μm. 36 refs., 10 figs

[en] The field emission characteristic of a Spindt-type cathode, cleaned extensively in a hydrogen atmosphere while emitting, is considered. The maximum emission reached is about 800 μA. At high current levels the I-V curve clearly deviates from a Fowler-Nordheim behavior. This can be explained by the occurrence of space charge. Several models are considered to simulate the experimental results. The fit to the data is good except at the highest emission levels. In this region the difference between the measured currents and the simulation results is due to the neglect of the variation of the field on top of the tip in the presence of space charge. 15 refs., 14 figs

[en] Scanning tunneling microscopy (STM) has been used to obtain images and current--voltage (I--V) curves of carbon nanotubes produced by arc discharge of carbon electrodes. The STM I--V curves indicate that carbon nanotubes with diameters from 2.0 to 5.1 nm have a metallic density of states. Using STM, we also observe nanometer-size graphene sheets which are four graphite layers thick. The STM images of carbon nanotubes are in good agreement with transmission electron microscope images. copyright 1995 American Vacuum Society