Nanofabrication techniques allow us to carve out narrow (40 nm) conducting channels and multiple voltage probes inside a submicron portion of a “conventional” silicon MOSFET. The repeated capture and emission of single electrons at a particular interface trap can be observed, because this changes the number of scatterers, producing sudden switching of the conductance. The dependence of capture and emission rates on lattice temperature, electron temperature, and gate voltage are consistent with a simple “configuration coordinate” model of the coupling between the trapped electron and the surrounding lattice. At low temperatures, the electrons being scattered diffuse considerable distances Lϕ before losing quantum phase information. When measured at scale Lϕ, random quantum interference causes a typical (rms) conductance change of e 2/h = (25.8 kΩ)−1 (“universal conductance fluctuations”). From this, the resistance fluctions at longer and shorter voltage probe spacings can be predicted. Each scatterer substantially affects the quantum interference throughout a region of size Lϕ.

The low-temperature magnetoresistance of PtSi thin wires of varying width, prepared with different mask elements (Cu and Ni) in the reactive ion beam etching, has been studied, to determine the width dependence of the physical parameters in the weak localization. A drastic decrease of the magnetic impurity scattering time τs and that of the superconducting transition temperature Tc have been found for the wires prepared by Ni mask with narrowing width, which suggests that the phase coherence of diffusing electrons responsible for the weak localization and the superconductivity are strongly affected by the presence of a small amount of Ni impurities recoil implanted into the surface region of the sidewalls of wires.

Our experimental results about aperiodic magnetoconductance in narrow n+-GaAs wire are described. These wires are fabricated in an MOCVD grown n+-GaAs film by electron beam lithography and the dry etching technique. It is found that the aperiodic structure arises from the quantum interference which is important in small structures (<1in). The experimental results are compared to the recent theory.

In this paper we will discuss a new type of field effect transistor, a vacuum FET, where the usual channel material is the vacuum rather than a semiconductor. This new device is based on Field Emitter Arrays (FEA) which are inherently submicron structures. That is, the field emitters themselves must have dimensions less that 0.1 micrometers in order to generate the high electrostatic fields necessary for electron tunneling, and the control gate (or extraction electrode) must be very close to the field emitter tip in order to generate these high fields with reasonable voltages. Consequently, this new “FET” is the first of a new class of vaccum electronic switching devices based on microfabrication techniques, and susceptible to circuit integration.

We have investigated molecular confinement in materials with nanometer sized pores, fabricated from amorphous superlattices of a-Si:H/a-SiOx:H, using 1,10-bis(1-pyrenyl)decane as a fluorescent probe. In large (46 Å) pores, the emission and excitation spectra and their time dependence are similar to microcrystalline material, showing the presence of molecules aggregated in the ground state. This dimer emission decreases sharply as the pore size is decreased, showing that the minimum size for aggregate formation is about 20 Å.

Recent progress in microfabrication technologies for advanced VLSI devices, such as 16M and 64MDRAM, is presented. First, an EB delineator with a vector-scanned VSB on a moving stage has been developed for printing 0.25 μm patterns employing PMMA, high dose exposure, and 50 KeV EB. Optical lithography also has been extended toward lower submicron geometry. A Krf excimer laser reduction projection system, using a quartz/CaF2 lens, resolves successfully 0.35 μm patterns. Ga field ion beam technology has been developed with new applications in fuse-cutting of redundancy and in optimizing sense amplifier by cutting transistor gates in the SRAM device. For fine line etching technology, collimated reactive ions produced by 10−3 Torr magnetron discharge achieves deep Si trench etching and tapered Al etching by using a polymer deposition process in addition to the original thin sidewall film. Finally, a damage-free excimer laser etching process has been developed which can etch n+ poly-Si with resist mask and with pattern transfer using an optics down to 0.5 μm and 0.9 μm resolutions respectively.

Lithographic fabrication techniques have been extended to the molecular dimension by using the layer pattern in deposited amorphous superlattices as an etching template for the creation of slot structures. Fabrication considerations are discussed for the formation of 10–50Å slots structures suitable for studying shape selective chemistry with fluoresence spectroscopy.

The study of quantum interference effects in metallic structures requires the lithographic resolution of electron-beam lithography. Resolution and reproducibility can be greatly enhanced by the use of a multilayer resist. We have implemented a polymethylmethacrylate (PMMA) bilayer resist which avoids the typical problem of intermixing of the layers. This is accomplished by an expedient choice of the solvent, xylene, for the upper resist layer. Metal lines 30 nm wide have been fabricated. We also describe an additional deep ultraviolet (DUV) exposure method which facilitates making electrical contact to these ultrasmall structures. Quantum interference, localization effects, and the electron phase-coherence time have been studied.

Electron-beam lithography that has the capability of writing high-resolution nanometer features in semiconductors will be required to fabricate next-generation quantum scale devices, such as nanometer gate mini-FET's, lateral quantum-well arrays, or metal grid radiators,which have feature sizes from 100 nm (1000 A) to 15 nm (150 A). A Philips EM 420T scanning transmission, electron microscope (STEM) has been modified to write nanometersize features in gallium arsenide. For this STEM we have developed a high-speed beam blanker and pattern generator (PG) that is resist speed limited. The maximum writing field size is 100 by 100 micrometers; within this field size, the smallest addressable step is approximately 1.8 nm (18 A). A HP-9845 is used to supply data for the PG and for computer-aided design of the devices to be written. Pattern transfer from the resist to GaAs is completed by using the liftoff method. As a result of this capability, we have patterned more than one million dots in a prototype 80 by 80 micrometer solid state radiator. The dots have diameters down to 15 nm (150 A), which requires an e-beam writing time of less than 30 minutes.

Vacuum integrated circuits and field emission (FE) devices with geometries on the micron and submicron scale have been discussed as alternatives to solid state devices for high speed and hostile environment application as well as for miniature electron sources for CRTs. These miniaturized vacuum devices have been developed on the basis of the advances in micromachining technology, i.e. orientation-dependent etching (ODE) of lithographically patterned silicon. This paper describes the ODE methods used to fabricate pyramidal electron emitter points 1.5 μm high, with radius of curvature of 20 to 100 nm from <100> silicon. In order to reduce operating voltages, an integral extraction electrode (grid) was fabricated by a self-aligned technique. With a single gate mask level the extraction and planar collector structures were fabricated on chip, to form a planar vacuum triode. The final mask step provided the flexibility for fabricating a variety of planar vacuum integrated circuit elements.

Ion projection lithography (IPL) has demonstrated the ability to replicate high resolution patterns with very short exposure times. Computer modeling of masks used in a hypothetical IPL system Is accomplished to estimate mask distortion during fabrication and exposure. Radiation cooling is shown to play an important role in temperature control. Two different methods of mask temperature control are examined. Results suggest a high degree of pattern stability can be expected from this type of mask.

Maskless patterning of Mo and Si was done by implanting 50 keV focused Ga+ ion beam and by plasma etching using CF4 gas. The implantation is done to modify the chemical properties of the sample surface. It was found that Mo films became etch-resistant for the plasma etching after implantation at a dose higher than 4×1015 /cm2. Si crystals showed a positive tone pattern due to a radiation enhanced etching at a dose lower than 5x1016/cm2. At higher doses, the etching rate decreased and above 8 x 1016/cm2, no etching was observed in the implanted region. Patterns with a thickness of a several hundred nanometers were formed by the present maskless patterning technique.

We describe the fabrication of submicron, multiprobe thin indium film conductors for electrical measurments above their melting transition. Problems unique to handling liquid films were overcome by using tri-level Si3N4/In/W structures. Tungsten (W) leads made good electrical contact to, yet did not alloy With the liquid indium (In). A silicon-nitride (Si3N4 ) encapsulating layer deposited over the In/W devices prevented the indium from forming islands when liquid. Indium wires were fabricated using e-beam lithography and liftoff. Low temperature reactive sputtering technique was used to deposit the Si3N4 without melting the indium. The technique could be easily adapted to use with other low melting point materials.

We describe herein an electron-beam, proximity lithograghic process which operates in soft vacuum (50 mT< p <1 Torr) using highly directed electron emission from a cold cathode. The electron-beam operates with large areas(<10 cm2) and with large total currents (Ipeak< 100A). Using this soft vacuum beam we could replicate feature sizes of ∼0.5 μm on∼3 μm thick PMMA, with a resist layer to stencil mask spacing of 25 to 30 μm. While resist exposed in a helium background showed vertical wall profiles (developed thickness ∼3 ¼m), resists exposed in air showed sloped walls (∼ 60°). Resist behavior also appears to be dependent on the number of pulses used for exposure ranging from simple exposure ( 1 to 5 pulses) to self-development ( >25 pulses).

Now that single crystal silicon has established itself as the preeminent electronic material, increasing applications are being implemented in which silicon's MECHANICAL properties are more important. This paper reviews some of the history behind this trend, explains how and why silicon can be an economical and effective mechanical material, and describes several of the devices which have been demonstrated in this technology.

Refined processing procedures for producing geometrically highly precise silicon structures are described. The structures are fabricated by the high-precision micromachining of silicon utilizing wet chemical orientation and/or concentration dependent, etching techniques. Very exact processing procedures required to reproducibly achieve good high quality structures with excellent large and small scale uniformity are detailed. Relief structures having features as small as 0.2μm have been produced. Some of the structures and devices attainable will be described including: (1) very high Q torsional oscillators useful as powerful probes of the mechanical properties of a variety of physical systems, (2) unstrained focusing x-ray mirrors, and (3) μm dimension mechanical “shadow masks” with multiple slit features having knife-edge acuity of much better than 1μm over an area ˜1cm2 and useful for noncontaminative, in situ patterning of thin films deposited in MBE or other vacuum deposition techniques.

A double-bending-beam technique has been developed to determine the mechanical properties (e.g., the elastic stiffness parameter and the in-plane coefficient of thermal expansion) of thin polymer films during thermal cycling. The mechanical properties of poly(methyl methacrylate) and a polyimide have been determined from the combined stress-temperature relationships of identical polymer films coated on two rigid beams (each with a distinctly different Young's modulus and coefficient of thermal expansion). The measured mechanical properties were found to agree with data obtained using conventional techniques. The double-bending-beam technique can be applied to a wide variety of dry and wet processing situations involving thin polymer films.

Collaborative work between Brookhaven and Los Alamos National Laboratories is developing a new type of linear accelerator that uses a high-power, picosecond pulse CO2 laser to irradiate a specialized form of grating with a pitch of 10.6 microns. The electromagnetic field that results can be used to accelerate electrons at field gradients of several GeV/m with potential efficiencies much better than current accelerators. The grating must be conductive to minimize resistive losses, be able to withstand high fields without damage, and requires dimensional tolerances in the sub-micron range. These requirements focus attention on grating material selection, microfabrication methods, and metrological methods used for quality control. At present, several types of gratings have been manufactured by reactive ion etching of fused silica in CHF 3/Ar or etching silicon with KOH/H 2O or ethylenediamine-pyrocatechol solutions. Metrological analysis of the gratings has begun with a Tracor Northern 5700 digital image analyzer.

The needs of high precision engineering currently call for dimensional tolerances of the order of 0.1μm and surface roughness of order 0.01μm, often in hard, brittle materials or materials of relatively poor machinability. The development of argon ion beam machining for milling, drilling and turning or lathing is reported as a means of satisfying these requirements. Highly controllable material removal is achieved for the fabrication of micromechanical structures, profiling of surfaces and fine surface finishing. Surface evolution at submicron precision is demonstrated, with particular reference to the production of both circular and non-circular sections in an “ion beam lathe”.

This article contains a description of hot jet etching through stencil masks. The dry etching technique does not damage the stencil mask, but anisotropically etches GaAs at rates as high as 10 μm min−1. Resolution less than 50 nm has been demonstrated. At present the etched surfaces are rough, but improvement of the etching technique may result in smooth surfaces.