Showing papers on "Electron-beam lithography published in 1986"

Optical spectroscopy of ultrasmall structures etched from quantum wells

Abstract: We have studied the photoluminescence and photoexcitation spectra of ultrasmall structures, of approximately 500 A in dimension, which we refer to as quantum ribbons and quantum disks. These are fabricated from GaAs‐AlGaAs quantum wells grown by molecular beam epitaxy and patterned by electron beam lithography. Contrary to our expectation, photoluminescence from these structures is extremely efficient. The excitation spectra of the two types of small structures differ greatly from each other and from that of the as‐grown quantum wells. These differences may be a result of the confinement of the carriers in these small structures.

Submicron conducting channels defined by shallow mesa etch in GaAs‐AlGaAs heterojunctions

Abstract: A new approach to the lateral confinement of electrons in the two‐dimensional electron gas of GaAs‐AlGaAs heterojunctions has been developed. The electrons are electrostatically confined by a shallow mesa structure etched in the upper n‐doped AlGaAs layer. This structure is fabricated using electron beam lithography and reactive ion etching. The undoped AlGaAs spacer layer is not removed in order to avoid mobility degradation and channel depletion. Long narrow channels have been made for the study of electrical transport properties. The effective channel width in the submicron range is smaller than the width of the mesa structure. Preliminary low‐temperature magnetoresistance data are presented.

Amorphous carbon films as resist masks with high reactive ion etching resistance for nanometer lithography

Abstract: We propose the application of carbon films as resist masks for practical nanometer lithography involving reactive ion etching (RIE). Amorphous carbon films prepared by room‐temperature plasma chemical vapor deposition show a very high resistance against RIE, the etching rates being less than 1/2 of that of a novolak‐based conventional photoresist. The carbon films can be finely patterned by O2 RIE in a bilayer resist process using a high‐resolution silicone‐based negative resist. Nanometer patterns as small as 40 nm are fabricated on a thick solid substrate, and can be transferred into the substrate layer directly by RIE.

Lithographic approach for 100 nm fabrication by focused ion beam

Abstract: A bilevel resist process using P(SiSt90–CMS10) silicon containing resist as a top layer has been developed for Ga+ focused ion beam (FIB) lithography. A 100 nm linewidth pattern with 750 nm thickness has been demonstrated. Lithographic characteristics for 100 kV Ga+ FIB have been studied for PMMA positive resist and P(SiSt90–CMS10) negative resist. The results indicate that backscattering and proximity effects are negligible and that 100 kV Ga+ FIB resist sensitivity is about 100 times larger than that for 20 kV electron beam. Moreover, it has been observed that discontinuous lines, which may be caused by shot noise or by an oscillation at the end of the Taylor cone of Ga ion source, are produced at low dose for both PMMA and P(SiSt90–CMS10) resists.

Fabrication of Small Laterally Patterned Multiple Quantum Wells

Abstract: A technique of high voltage electron beam lithography and BCl3/Ar reactive ion etching for laterally patterning GaAs/Al0.3Ga0.7As multiple quantum wells is described. The resulting structures were analyzed using scanning electron microscopy and a novel reflection electron microscopy technique, and their geometries are shown. Narrow columns 40 nm in diameter etched 230 nm through the quantum wells were reproducibly fabricated.

Deformation-free overgrowth of reactive ion beam etched submicron structures in InP by liquid phase epitaxy

Abstract: Submicron grating patterns written by electron beam lithography are transferred into InP substrates by reactive ion beam etching (RIBE) using an Ar/O2 gas mixture. Trapezoidal grating structures with a depth of 0.15 μm are generated. The influence of the preheating cycle prior to liquid phase epitaxy (LPE) on the grating shape is investigated as a function of different cover materials. We obtain deformation‐free LPE overgrowth of the dry etched corrugations applying the GaAs cover technique. In contrast to wet chemically etched gratings identical grating profiles are formed in different crystallographic directions by RIBE and successfully overgrown by LPE.

N-InAs/GaAs heterostructure superconducting weak links with Nb electrodes

Abstract: We report on the fabrication and characterization of planar superconductor‐normal‐superconductor (SNS) weak links in which the normal region is deposited n‐InAs. The InAs is part of a heterostructure consisting of 100 nm of n‐InAs grown on an undoped GaAs buffer layer on a semi‐insulating GaAs substrate. The superconductor is Nb, patterned by electron beam lithography with interelectrode spacings as small as 260 nm. Device behavior is well explained by SNS weak link theory, with coherence lengths calculated from measured material parameters. These heterostructure weak links can be the basis for superconducting field‐effect devices. They have the significant advantage of allowing simple device isolation compared with bulk InAs, which has been used in previous attempts to make such devices.

Method for producing deep-etch, X-ray lithography masks

Abstract: A method for producing a mask for deep-etch x-ray lithography in which the mask pattern of a thin-film mask having thin absorber structures is transferred by recopying with soft X-ray radiation to an X-ray resist layer whose layer thickness corresponds to the thickness of the absorber structures of the mask to be subsequently produced. Transfer errors during recopying are avoided by producing the thin-film mask directly on one side of a carrier membrane; applying a positive X-ray resist layer on the other side of the carrier membrane; irradiating the positive X-ray resist layer with approximately parallel X-ray radiation through the thin-film mask to produce irradiated portions in the positive X-ray resist layer; removing the irradiated portions of the positive X-ray resist layer to expose portions of the carrier membrane; electrolytically depositing elements having a high atomic number, e.g., heavy metals, onto the exposed portions of the carrier membrane, removing the remaining resist material and etching away the thin-film mask.

Polysiloxane, resist for ion beam and electron beam lithography

Abstract: A method for providing a high temperature imaging resist layer for use in a multilayer resist system. A relatively thick planarizing resist layer is coated onto a suitable substrate to provide a planarizing resist layer having a planar surface. A relatively thin layer of a solvent soluble polysilsesquioxane polymer resist is applied to the planar surface to form an imaging resist which remains solvent soluble at temperatures up to 250° C. The hydroxyl or alkoxy content of the polysilsesquioxane must be 0.05 weight percent or less in order to prevent cross linking of the polysilsesquioxane. The polysiloxane polymer resist is prepared by hydrolizing and polymerizing trichlorosilanes having the formula RSiCl 3 where R is methyl, phenyl, vinyl, n-butyl, t-butyl, chlorophenyl, or chloromethyl-phenyl. The hydroxyl content of the polysilsesquioxane is reduced to 0.05 weight percent by capping the polymer with monoreactive silanes. The polysiloxane imaging resist is designed for use in high temperature electron beam and ion beam lithography.

Resolution limits in x‐ray lithography calculated by means of x‐ray lithography simulator XMAS

Abstract: Resolution in x‐ray lithography is influenced mainly by the exposure geometry, the resist’s behavior, and by the Fresnel diffraction as well. The range of photoelectrons created by the soft x rays, which can also effect the resolution, has been investigated theoretically and experimentally. The effective range remains below 20 nm depending on the resist material and on the exposure wavelength. As the photoelectrons do not limit the resolution in synchrotron lithography under practical conditions (proximity gap≥20 μm), this effect is not considered explicitly in the x‐ray lithography simulator xmas which enables the three‐dimensional simulation of resist profiles. The application of xmas to synchrotron lithography and the related one‐layer resist systems reveals a Fresnel‐limited resolution somewhere between 0.1 and 0.2 μm, depending on the actual resist parameters.

Unique resist profiles with Be and Si focused ion beam lithography

Abstract: The delineation of resist patterns has been investigated for two kinds of ions, Be and Si. Patterns consisting of 0.2 μm lines and spaces were fabricated in 0.7 μm thick resist with good repeatability and accuracy. This shows that the influence of proximity effects can be disregarded. The broadening of patterns was observed for Si exposure because of the more significant influence of recoil atoms. As a special application of focused ion beam lithography, a new process for fabricating a mushroom gate electrode for a GaAs microwave field‐effect transistor (FET) was demonstrated utilizing the particular exposure characteristics of the different ion species.

Semiconductor wafer for providing a plurality of semiconductor chips through electron-beam lithography

Abstract: A semiconductor wafer to be processed with the electron-beam lithography and provided with a registration mark is disclosed. The registration mark is comprised of a plurality of patterns having the same shape and arranged in one direction with a constant interval. The pattern may be protruded or grooved from the part surrounding the pattern.

Critical Koehler illumination for shaped beam lithography

Abstract: The crossover of a thermionic electron gun acts as the virtual source in conventional electron beam lithography systems employing critical illumination as well as those employing Koehler illumination [Broers, SEM (IIT Research Institute, Chicago, 1979)]. The concept of critical Koehler illumination [Essig, IBM Tech. Discl. Bull. 27, 1224 (1985)] combines critical illumination and Koehler illumination to image the cathode surface as the real source of the electrons into the probe shaping aperture and finally onto the target plane (window ray trace). Further on, the crossover as the virtual exit pupil of the gun lens is imaged into the entrance pupil of the final lens (pupil ray trace). Thus, in critical Koehler illumination, the linked beam concept consequently correlates conjugate planes of a probe forming system to those of the electron gun. The implementation of critical Koehler illumination in shaped beam lithography systems requires a special imaging mode of the electron gun. A typical triode gun can ...

Diffractive Infrared Filters Fabricated by Electron-beam Lithography

Abstract: With the increasing number of optical systems for use in the near- and middle-infrared spectral regions, the demand for optical elements that exhibit predetermined spectral and polarizing characteristics has increased also. Although continuous thin films are capable of producing a wide variety of optical characteristics, the use of metal meshes adds another dimension to spectral and polarization selectivity. Metal meshes are essentially amplitude diffraction gratings whose periodicity is less than the wavelength of the incident radiation. As such, only a single propagating mode exists, all others being evanescent. Diffractive structures of this type have been shown to produce spectral and polarizing properties that depend on the geometry of the mesh. Microlithographic techniques were used to fabricate diffractive patterns of aluminum and gold, with minimum feature sizes less than 0.25 p,m for use as mesh filters with near and middle-infrared.

Development of nanometric electron-beam lithography system (JBX-5D II)

Abstract: The production of VHSIC and microwave devices has shown that submicron lithography by e‐beam, optical, or x‐ray systems is rapidly becoming feasible. There is, however, a demand developing for a nanolithography tool for producing GaAs devices and for investigating the physics of scaling of silicon semiconductor devices. We have developed an electron beam lithography system, the JBX‐5D II, which is effective in fabricating both submicron and nanometric devices. The system employs a high brightness single crystal (100) LaB6 cathode and an in‐lens octupole deflector. The JBX‐5D II is fully computer controlled which permits automatic switching of the accelerating voltage between 50 and 25 kV, of writing modes between large and small currents, and of different scanning fields. The ability to switch writing modes permits rapid writing of devices with geometries as small as 10 nm with a fine beam and a coarser beam to be used on larger geometries. The present paper deals with some of the characteristics occurrin...

Lithographic fabrication of transmission electron microscopy cross sections in III–V materials

Abstract: A procedure for forming specifically located transmission electron microscopy (TEM) cross section specimens of III–V semiconductor materials is described. By electron‐beam lithography in a TEM/STEM followed by a lift‐off technique, 40–100 nm wide metal lines were formed on the sample surface. Anisotropic reactive ion etching in a BCl3 and Ar plasma removed the material unprotected by metal lines to leave uniform thickness vertical sections of material. Details of the procedure and the TEM analysis of a sectioned GaAs/AlAs superlattice structure will be described. The ability to form a cross section from a specifically desired region of the sample and the ability to form long uniform sections makes this technique particularly applicable to analysis of devices in brittle semiconductor materials.

Electron Beam Nanolithography

Abstract: Lithography plays a central role in the fabrication of electronic devices, and is essential in the preparation of samples for studies of transport in 1-D. The minimum feature size required in the device is important in the choice of lithographic method. Generally for linewidths above 1μm 1inewidth optical lithography is used whilst for smaller dimensions it is necessary to use electron, ion beam or X-ray lithography. The linewidths in current production VLSI circuits range between 1 and 3μm; there are programs in the U.S and the U.K to reduce the linewidth to 0.5μm over the next few years [1]. Single conventional semiconducting electronic devices have been made with gates as small as O.1μm, and some experimental superconducting devices employ features with sizes in the 10–30nm range.

Electron‐beam investigation and use of Ge–Se inorganic resist

Abstract: Electron‐beam exposure and computer simulation are used to characterize the performance of Ge0.1Se0.9 inorganic resist and examine the fundamental mechanisms of resist action. A first‐order model based on the energy density of electrons deposited in the active region along the interface of the sensitized layer and the resist is developed. Resist sensitivity as a function of sensitized‐layer thickness and accelerating voltage are calculated with the Monte Carlo method and compared with experimental results. Special test patterns including multiscanning are designed to explore lateral diffusion of silver in the sensitized layer and proximity effect due to backscattering. With Ge0.1Se0.9 resist and e‐beam direct writing sub‐half‐micrometer working lithography can be achieved on silicon substrate at incident doses comparable with that needed for polymethylmethacrylate (PMMA) polymer resists.

Improved Bilayer Resist System Using Contrast-Enhanced Lithography With Water-Soluble Photopolymer

Abstract: A new water-soluble contract enhanced material, WSP (Water-soluble Photopolymer), has been developed. The WSP is composed of a mainpolymer and a photobleachable reagents. The mainpolymer is a water-soluble polymer mixed with pullulan (refined through biotechnological process) and polyvinyl-pyrolidone (PVP). The photo-bleachable reagent is of a diazonium compound gorup. The introduction of the mainpolymer and photobleach-able reagent mixture has improved filmity, gas transparency, photobleaching characteristics and solubility in alkaline which are essential to the device fabrication. Submicron photoresist patterns are successfully fabricated by a simple sequence of photolithography process. The WSP layer has been applied to the bilayer resist system--deep-UV portable conformable masking (PCM)--that is not affected by VLSI's topography, and is able to fabricate highly accurate pattern. The aqueous developable layer, PMGI, with high organic solvent resistance is used in the bottom layer. Therefore, no interfacial mixing with conventional positive resist top layer is observed. Furthermore, deep-UV exposure method has been used for the KrF excimer laser optical system in order to increase high throughput. From the experiments, it has been confirmed that good resist transfer profile can be realized by the use of WSP, and that the submicron resist patterns with high aspect-ratio can be developed on the nonplaner wafer with steps of up to 41m by the combination of the WSP with the PCM system. By this technology, has been improved the weak point: variation in the line width due to the thickness of contrast-enhanced layer when the CEL technology is applied, and dependency of both the finished resist profile and the line-width accuracy on the thickness of the top layer resist when the PCM system is adopted.

A fine emitter transistor fabricated by electron-beam lithography for high-speed bipolar LSI's

Abstract: A highly stable, high-performance bipolar transistor with a 1/4-µm emitter is developed. This is accomplished by using advanced electron-beam (EB) lithography and polysilicon reactive ion etching (RIE). Results show that the minimum emitter width is only 0.2 µm and the emitter width accuracy is ±0.06 µm. In addition, the gate delay is reduced from 190 to 100 ps/gate for 25-stage, three-input ECL circuits. The effects of an ultra-narrow emitter on transistor characteristics are also studied.

X-ray exposure mask

Abstract: PURPOSE:To enable a X-ray mask having high accuracy in dimension even in case of fine patterning to be obtained, by making an electrode film for plating composed of a material whose atomic number is smaller than that of a X-ray absorber. CONSTITUTION:In a X-ray exposure mask formed by a plating method of a X-ray absorber pattern 7', an electrode film 4 for plating is composed of an element whose atomic number is smaller than that of the element composing the X-ray absorbar 7'. Al, for example, as the electrode layer 4 for plating is evaporated on a pattern holding film 5 having a Si substrate frame 6, and followed thereon by a resin layer 3, an intermediate layer 2, and an electron-ray resist 1. Electron beam lithography is then performed to form a resist pattern 1', and the intermediate layer 2 is processed by dry etching with this resist serving as a mask, and further the resin layer 3 is processed with this intermediate layer serving as a mask. Successively, electrolytic plating of Au is performed to precipitate an absorber pattern on the exposed part of the electrode layer 4, and the electrode film 4 at the plating recessed part and at its direct lower part is removed to obtain a X-ray mask.

The Physics and fabrication of microstructures and microdevices : proceedings of the winter school, Les Houches, France, March 25-April 5, 1986

Abstract: I Physics and Engineering of Microfabrication.- High Resolution Lithography (Some Comments on Limits and Future Possibilities).- Submicron Lithography Tools.- Electron Beam Nanolithography.- The Spin Coating Process Mechanism.- Resists Patterning.- Dry Etching: Concepts, Methods and Applications.- Overlayers.- Self-Aligned Growth of Microstructures.- Laser-Induced Growth of Microstructures.- Structural Characterization of Superlattices by X-Ray Diffraction.- Recently Developed TEM Approaches for the Characterisation of Semiconductor Heterostructures and Interfaces.- Fabrication of Small Structures of Semiconductors and Metals.- Atomically Controlled Growth in 2, 1 and OD, and Applications.- Microstructure of Organic Mono- and Multilayers.- II Physics of Microstructures.- Fundamentals of Low Dimensional Physics.- Electron States in Semiconductor Microstructures.- Quantum Transport Theory for Small-Geometry Structures.- Noise in Microstructures.- Transport Physics of Multicontact Si MOS Nanostructures.- 1D Structures - Field Confinement Approach.- Excitons in GaAs Quantum Wells: Interface Disorder and Mobility.- Nonlinear Optics and Electro-Optics of Quantum Wells.- Quantum Interference Effects in Small Systems: Normal and Superconducting Networks.- 2D Localisation and Interaction Effects in Semiconductor Structures.- Optical Nonlinearities in Small Particles and Composite Materials.- Tunnel Currents and Electron Tunnelling Times in Semiconductor Heterostructure Barriers inPresenceanMagnetic Field.- III Perspectives in Microfabrication Applications.- Scaling Limits of Silicon VLSI Technology.- Three Part Series on Heterojunction Transistors.- CAD: Overview and Perspectives.- Silicon-on-Insulator Technology Leading Towards Three-Dimensional Integration of Microelectronics.- The Metal Base Transistors.- An Integrated Microfabrication System for Low-Dimensionality Structures and Devices.- Fabrication of Gate Array Interconnect Structures Using Direct-Write Deposition Processes.- Electronic Neural Computing.- IV Poster Session, Abstracts.- Fabrication of Submicron Structures Combining E-Beam and Deep-UV Exposure.- Fabrication of Short-Gate GaAs MESFETs by Electron Beam Lithography.- 2D Josephson Junction Networks.- Electric Field Heating of Supported and Free-Standing AuPd Fine Wires.- High-Frequency Limits of Quantum Noise Detectors Based on Superconducting Tunnel Junction Mixers.- Photoresponse and Transport Properties of a 'Quasi' Graded Gap Superlattice P-I-N Diode.- Disorder and Two-Dimensional Electronic Sub-Bands.- A Model for the Oscillatory Structure in the J(V) Characteristics of GaAs/(AlGa)As Tunneling Structures.- A Minute Metallic Sphere Close to Flat Metal Surface System: A Scanning Tunneling Microscope Problem.- A Calculation of the Effect of Subband Structure on the Thermopower of a Quasi-1D Wire.- The Effect of Electron-Electron Scattering on the Distribution Function in Semiconductors.- Index of Contributors.

Tiny Tale Gets Grand

Abstract: Electron beam lithography reduces a page of Dickens to micrometer size to meet a longstanding challenge from Richard Feynman.