D. P. Kern

High-Resolution Imaging by Fourier Transform X-ray Holography.

Fourier transform x-ray holography has been used to image gold test objects with submicrometer structure, resolving features as small as 60 nanometers. The hologram-recording instrument uses coherent 3.4-nanometer radiation from the soft x-ray undulator beamline X1A at the National Synchrotron Light Source. The specimen to be imaged is placed near the first-order focal spot produced by a Fresnel zone plate; the other orders, chiefly the zeroth, illuminate the specimen. The wave scattered by the specimen interferes with the spherical reference wave from the focal spot, forming a hologram with fringes of low spatial frequency. The hologram is recorded in digital form by a charge-coupled device camera, and the specimen image is obtained by numerical reconstruction.

Diffraction-limited imaging in a scanning transmission x-ray microscope

Abstract We report the characterization of a scanning transmission X-ray microscope which makes use of an undulator X-ray source, a high resolution scanning stage, and a 45 nm outer zone width, > 10% diffraction efficiency Fresnel zone plate as the probe-forming optic at soft X-ray wavelengths (typically 3.64 nm). The modulation transfer function of the instrument is in good agreement with theory; it remains above 0.1 to spatial frequencies corresponding to structures as small as 25 nm. This spatial frequency limit is the best obtained in any soft X-ray microscope, and is about a factor of ten better than what is attained in conventional or confocal visible light microscopes. By deconvolving the zone plate point spread function from the image, the microscope has been used to resolve 36 nm features in a gold test object. The microscope is used primarily for the study of thick, hydrated biological specimens with minimal radiation dose.

Direct deposition of 10‐nm metallic features with the scanning tunneling microscope

In this preliminary study we have used a modified scanning tunneling microscope (STM) to directly deposit metallic features as small as 10 nm by decomposing organometallic gases containing tungsten and gold. Dots as well as lines have been formed. Tungsen deposits analyzed by Auger electron spectroscopy contained 48% tungsten, 40% carbon, and 12% oxygen. A resistivity of 0.01 Ω/cm for the deposits was measured by aligning the STM to a metal contact pattern. This is the first reported combination of STM lithography with conventional lithography. A discussion of several interesting physical and chemical mechanisms involved in the deposition process is also presented.

X‐ray spectromicroscopy with a zone plate generated microprobe

The scanning photoelectron microscope at the National Synchrotron Light Source (NSLS) has recently recorded micrographs with a resolution below half a micron. To demonstrate elemental and chemical sensitivity at the submicron level, an artificial structure consisting of Al and SiO2 lines on a boron‐doped silicon substrate was examined. Al 2p and Si 2p primary photoelectrons as well as O KVV Auger electrons were used for image formation. Contrast reversal between the the Si and SiO2 areas was observed in images formed from Si 2p and oxide‐shifted Si 2p photoelectrons. The soft x‐ray undulator at the NSLS provides coherent illumination of a zone plate to produce the microprobe. The sample is mechanically scanned through the beam allowing the formation of images from photoelectrons detected by a single‐pass cylindrical mirror analyzer, or a more complete spectroscopic examination of a selected area of the sample.

Arrayed miniature electron beam columns for high throughput sub‐100 nm lithography

In recent years, considerable progress has been made on an approach based on a novel concept which combines scanning tunneling microscope, microfabricated lenses, and field emission technologies to achieve microminiaturized low‐voltage electron beam columns with performance surpassing the conventional column. High throughput lithography is a potentially very important application for these microfabricated columns which measure only millimeters in dimensions. This is to be achieved using an array of these minicolumns in parallel in a multibeam mode with one or more columns per chip. The low‐voltage operation is attractive because proximity effect corrections may not need to be applied. In addition, an arrayed microcolumn system also has the potential of reducing the cost of the overall system through the compaction of the mechanical system. The throughout advantages for such an arrayed system based on different beam forming optics and pattern generation approaches will be discussed. In addition to lithogra...

Microminiaturization of electron optical systems

The performance of miniaturized electron optical systems comprising a field emission microsource and a microlens for probe forming has been studied. A complete system measuring millimeters in length and diameter with performance exceeding that of a conventional system over a wide range of potentials (100 V–10 kV) and working distances (up to 10 mm) appears to be feasible. A scanning tunneling microscope aligned field emission microsource offers performance well suited for this application and a selective scaling approach has been developed to allow a wide range of potentials to be applied. Such miniaturized systems can be of significant importance to many areas of electron‐beam applications.

Scanning x‐ray microscope with 75‐nm resolution

A scanning soft x‐ray microscope has been built and operated at the National Synchrotron Light Source. It makes use of a mini‐undulator as a bright source of 3.2‐nm photons. An electron beam fabricated Fresnel zone plate focuses the beam onto the specimen, which is scanned under computer control. The scanning stage can be moved by both piezoelectric transducers and stepping motors, and the location is monitored by a high‐speed laser interferometer. X rays transmitted through the specimen are detected using a flow proportional counter. Images of biological specimens and of artificial microstructures have been made with resolution in the 75–100‐nm range. Acquisition time for 256×256‐pixel images is about 5 min.

Experimental high performance sub-0.1 /spl mu/m channel nMOSFET's

Very high performance sub-0.1 /spl mu/m channel nMOSFETs are fabricated with 35 /spl Aring/ gate oxide and shallow source-drain extensions. An 8.8-ps/stage delay at V/sub dd/=1.5 V is recorded from a 0.08 /spl mu/m channel nMOS ring oscillator at 85 K. The room temperature delay is 11.3 ps/stage. These are the fastest switching speeds reported to date for any silicon devices at these temperatures. Cutoff frequencies (f/sub T/) of a 0.08 /spl mu/m channel device are 93 GHz at 300 K, and 119 GHz at 85 K, respectively. Record saturation transconductances, 740 mS/mm at 300 K and 1040 mS/mm at 85 K, are obtained from a 0.05 /spl mu/m channel device. Good subthreshold characteristics are achieved for 0.09 /spl mu/m channel devices with a source-drain halo process.<<ETX>>

Spatial-phase-locked electron-beam lithography : initial test results

Earlier spatial‐phase‐locked e‐beam lithography (SPLEBL) was proposed as a means of eliminating the well‐known problem of feature placement precision in scanning electron‐beam lithography. In SPLEBL, a grid with long‐range spatial‐phase coherence is created on a substrate (or on top of its resist coating) and this grid is used to feedback information on beam location to the control system. In initial tests a standard deviation (σ) of 0.3 nm for phase‐locking precision in one dimension was demonstrated, which represents the finest field stitching ever obtained with any lithographic method. In two dimensions (2D), σx, σy=0.6, 0.4 nm was obtained. Moire spatial‐phase locking was also demonstrated in 2D. Two strategies for the global‐fiducial grid appear feasible: plating base modulation and a thin film of holographically exposed photoresist on thin‐film Al above the e‐beam resist. Either would permit spatial‐phase locking without exposure of resist.

Spectroscopy, electron-electron interaction, and level statistics in a disordered quantum dot

A novel spectrometer is employed to study the spectrum of heavily doped quantum dots. A single-particle discrete spectrum is found to exist only in close vicinity to the Fermi energy. Levels further away are broadened beyond the average level spacing and merge to form a quasi-continuous spectrum. The broadening is traced to electron-electron interaction in the dot. For the discrete part of the spectrum, level statistics is studied as a function of magnetic field and found to agree remarkably well with recent calculations.