Showing papers on "Lithography published in 1975"

Proximity effect in electron-beam lithography

Abstract: A simple technique for the computation of the proximity effect in electron‐beam lithography is presented. The calculations give results of the exposure intensity received at any given point in a pattern area using a reciprocity principle. Good agreement between the computed results and experimental data was achieved.

Fabrication of a miniature 8K‐bit memory chip using electron‐beam exposure

Abstract: A fully‐ion‐implanted miniature 8192‐bit random‐access memory chip has been fabricated using electron‐beam lithography with minimum linewidth between 1 and 1.5 μm and advanced Si FET technology. Device structure, processing steps, mask transfer, and reactive ion etching processes capable of fabricating device structures in the micrometer and submicrometer dimensions are described. With a minimum linewidth of 1.25 μm, the memory chip occupies an area of 1.1×1.6 mm with an array density of 5 million bits/in.2 (0.8 million bits/cm2). A typical readout access time of 90 ns was measured on a functional chip.

High speed replication of submicron features on large areas by X-ray lithography

Abstract: To achieve the high throughput necessary for a practical X-ray lithographic system, we have devised a new overall approach to X-ray lithography based on the use of X-rays with wavelengths of 4-6 A rather than the 8.34-A wavelength used in previous work. The principal advantage of the shorter wavelengths is that they allow a system to have X-ray windows so that large area patterns can be replicated under ambient conditions. In addition, the shorter wavelengths simplify the selection of mask substrate materials; thus we have developed a new X-ray mask structure using an optically transparent Mylar substrate. This permits realignment to be done by optical means. We also report results obtained with a new negative resist with high sensitivity to the shorter wavelength X-rays. We have achieved the replication of submicron size features using a 4.6-A rhodium X-ray source, a Mylar mask with 7000-A thick gold patterns, and the new resist, and have demonstrated the practicality of this system by the fabrication of propagating magnetic bubble structures with small features.

Laser imaging a lanographic printing plate

Abstract: A planographic printing plate which is imaged by means of a laser beam in combination with overall exposure to ultraviolet light and developed by means which are conventional in lithographic art

Electron‐beam lithography using vector‐scan techniques

Abstract: A computer‐controlled electron‐beam microfabrication system has been developed for evaluation of micron and submicron lithographic technologies. Direct large‐field‐device exposures of complex patterns have been processed for FET and bubble memory fabrication. Experimental exposures have also been made to allow mask fabrication for alternative exposure apparatus. The system exposes the electron‐sensitive resist by sequentially filling in pattern elements (cells), whose geometry and size are determined by an off‐line pattern data processor. Abutting line scans, using a round electron probe, are used to expose each cell. The system normally exposes fields up to 4 mm square. Deflection resolution is 14 bits per axis. Exposure rate, pattern registration, pattern field adjustments (size, position offset, rotation, and orthogonality), and workstage position are among the functions which have been automated.

Preparation of thin windows in silicon masks for x‐ray lithography

Abstract: Soft x‐ray lithography requires the fabrication of thin windows in a material which is relatively transparent at the wavelength of the x rays used. A system under evaluation employs Al Kα radiation, thin window silicon masks, and pattern written in gold on the thin silicon membrane. Windows of uniform 1–5 μ thicknesses up to ∼4 cm in diameter have been made. A description is given of the procedures we now use for producing the complete masks. The etching itself takes 15–45 min. The procedures are uncritical and lend themselves to semiautomated operation. The yield for the etching procedure alone is close to 100%.

Fabrication of silicon MOS devices using X-ray lithography

Abstract: This paper reports on the high-yield fabrication of silicon MOS transistors using X-ray lithography, measurements and annealing of fast surface states and oxide charges created by X-ray irradiation, and design considerations for submicrometer linewidth X-ray lithography on 7.5-cm diameter silicon wafers.

Spurious effects caused by the continuous radiation and ejected electrons in x‐ray lithography

Abstract: X‐ray lithography replication using characteristic and continuous x radiation is studied and compared with exposure results obtained using only characteristic radiation. Several spurious effects that affect the mask contrast and system resolution are discussed.

X-ray lithography: Part I—Design criteria for optimizing resist energy absorption; part II—Pattern replication with polymer masks

Abstract: An X-ray lithography system is analyzed in terms of maximizing the absorbed energy density in the resist. The individual factors, such as X-ray quantum efficiency, electron-beam energy, wavelength, power dissipated in the anode, and the possible use of an X-ray window are discussed. It is shown that K-line radiation from an Al or Si source is the most efficient for mask membranes of either Si or a thin polymer film without an X-ray window and for a thin Be window. For thick Be windows, L-line radiation sources become more efficient. Fabrication procedures have been developed in our Laboratories for polymer film X-ray masks using both photo and electron-beam lithography. The advantages and disadvantages of such masks are discussed. Etched SiO 2 patterns made using polymer film masks show excellent replication of the mask patterns.

Control system design and alignment methods for electron lithography

Abstract: The electron‐beam exposure system (EBES) was designed to economically expose integrated circuit masks on a production basis and to directly pattern semiconductor substrates for special applications where a limited number of devices are required. The machine was designed to assure absolute pattern accuracy over the entire substrate so that masks made by EBES will be interchangable with those made by our optical mask shop or those made by later electron‐beam pattern generators. This has been achieved by a combination of control system design and by automated periodic system alignment. The control system design utilizes a laser interferometer to determine precise table position and a feedback system that continuously corrects the writing‐beam location for errors in table location. This combination, coupled with a small‐angle electron‐beam deflection system using an ultrastable sawtooth‐scan generator to achieve repeatable beam positioning over a small writing area, allows exposure rates of 107 addresses per ...

Electron‐beam fabrication of chromium master masks

Abstract: Conventional photolithographic methods of mask manufacture in the semiconductor industry have limitations which can be overcome using electron lithography. This paper describes application of the electron‐beam exposure system (EBES) to the fabrication of chromium master masks using the negative electron resist poly(glycidyl methacrylate‐co‐ethyl acrylate). Lithographic characterization methods developed specifically for this application include the variation of feature size and develped resist thickness with exposure and have led to the choice of correct operating conditions for EBES. Writing time for a typical 2.5‐in. (6.35‐cm) mask is 30–60 min, and processing time is about 70 min (excluding inspection and handling). Linewidth control is better than ±0.5 μm and chip yields typically exceed 90% per mask level for LSI circuits. Masks with chip sizes up to 20×16 mm have been processed. One‐micrometer feature sizes are obtained routinely.

Instrumentation for conformable photomask lithography

Abstract: A vacuum frame and a multiple mask alignment system for conformable photomask lithography are described. These instruments greatly improve the convenience and adaptability of conformable photomask lithography and may permit the advantages of improved resolution, dimensional control, photoresist profile control, and reduced mask damage to be realized in routine photolithographic production.

Pathways in device lithography

Abstract: A brief review is given of approaches to lithography for microdevice fabrication. Exposure systems in common use, as well as those in development, are described and assessed. These include contact and proximity printing, stationary and scanning projection printing, step-and-repeat reduction printing, scanning electron beam systems, electron imaging systems, and X-ray systems.

Applications of the electron beam exposure system

Abstract: Successful application of high-speed scanning electron lithography machines such as the electron beam exposure system (EBES) requires the development of suitable materials and processes. We describe how electron resists with improved sensitivity have been used to make high-quality photolithographic master masks in which 1-µm lines and spaces are resolved and also to make MOS integrated circuits with improved packing density and performance.

Projection electron lithography using aperture lenses

Abstract: Methods are presented for using two-dimensional (axially symmetric) aperture lenses of both the single- and multiaperture (fly's-eye) kind and one-dimensional (planar-symmetric) aperture lenses in image-projection systems for electron lithography. The basic electron-optical properties of such aperture lenses are derived. The ancillary film technology is discussed, including pre-exposure and postexposure resist processes in use and the techniques developed for fabricating electron-transmission object masks that can withstand the requisite electron bombardment during image projection. The image-projection systems developed for use in fabricating arrays of thin-film field emitters, electron-beam-addressed memory planes, optical waveguides, and interdigital transducers (unapodized and apodized) for surface-acoustic-wave devices are described, and representative examples of each device produced are shown.

Abstract: New x‐ray mask of Al–Al2O3 structure

Abstract: This paper describes the fabrication and performance of a newly developed x‐ray lithography mask consisting of an aluminum substrate and an Al2O3 film which was grown on the aluminum substrate by anodization. Transparent membranes of Al2O3 film were made by chemically etching parts of the aluminum substrate beneath the film on which gold absorber patterns were fabricated. Gold micropatterns were replicated successfully by Al Kα (8.34 A) x rays. Properties of this mask include ease of fabrication, transparency, feasibility of realignment by optical means, and high mechanical strength allowing the capability of larger window size.

Application of moiré techniques in scanning‐electron‐beam lithography and microscopy

Abstract: When a grating is viewed by scanning electron microscopy, a moire pattern is observed. Applications of the moire phenomenon in scanning‐electron‐beam lithography and microscopy are discussed, including adjustment of the spatial period and angle of a scan raster, analysis of distortion in a scan raster, analysis of stray‐field beam deflection and measurement errors, and registration of a scan field relative to coded patterns on a substrate.

Printing plate water sensing means and method

Abstract: The amount of water present on a lithographic printing plate during printing is determined by measuring the amount of water present on a surface which is other than that of the printing plate but which carries an amount of water related to the amount of water present on the printing plate. The surface upon which the measurement is made may be the surface of a control pad mounted on the printing roller in the gap between opposite ends of the printing plate, the surface of one of the rollers of the damp train applying water to the printing plate, or the surface of an auxiliary roller contacting one of the rollers of the damp train applying water to the printing plate. The amount of water subsequently applied to the printing plate may be regulated in dependence upon the amount of water determined as being already present on the printing plate.

Electron‐beam‐delineated X‐band silicon transistor

Abstract: An X‐band silicon power transistor has been used to develop and demonstrate electron‐beam lithography in a multilevel device with submicron geometries. The importance of an automatic registration system capable of submicron precision will be discussed. The difficulties of processing submicron geometries once they have been defined in resist and the means of addressing these problems will be reported. Dry etch processes such as plasma etch and ion milling have definite advantages. The benefits in resolution and registration of direct slice writing with an electron beam are, of course, offset in some degree by the reduced throughput caused by serial patterning. Therefore, a hybrid approach was taken, using the e beam only for the three levels in which its superior resolution and registration are critical. Photomasks are used for three noncritical levels. Comparison with a completely photolithography‐defined device will be made to show the advantages in performance and yield of the e‐beam device. A single‐cell e‐beam‐generated transistor with 1/2‐μm emitters has demonstrated a significant advancement in the state of the art: 230 mW cw amplifier output power with 6.7 dB gain and 25% collector efficiency (20% power added efficiency) at 10 GHz.

Single lithography for multiple-layer bubble domain devices

Abstract: A fabrication process for fabricating multiple layer magnetic bubble domain devices using only a single masking step. As a specific example, a thin conductor film (which could be a magnetic material, such as NiFe) is deposited on a substrate comprising a magnetic bubble domain material. This conductor film is coated with a resist which is exposed with an electron beam or an X-ray beam. The exposure density in a first area of the resist is different than that in a second area of the resist. Subsequent development of the resist will uncover the thin film only in the area which has received the greater exposure density. This area can then be used as a plating base for electro-plating another conductive layer, such as a thick gold film. Further development of the resist is used to uncover the second area (which initially received a lower exposure density). Another layer then can be plated which will plate onto the thin conductive base film which is now uncovered and onto the second conductive layer which was formed in the previous electro-plating step. After this, the remaining resist and the unwanted remaining thin film is etched away to leave a final circuit structure.

Electrode flatness requirements for cathode projection microfabrication systems

Abstract: One of the most promising techniques for large-area submicron electron-beam lithography is the Cathode Projection Microfabrication System. According to published reports, these systems suffer from excessive image distortion. This distortion is partly caused by nonflat photocathodes and silicon wafer anodes. In this paper, a universal curve is obtained which quantitatively predicts and explains the image distortions which result from surface topography. Apparently, the practicality of multilayer submicron lithography in such systems is presently threatened by a requirement that nonreproducible wafer surface waviness be less than 2-3 microns.

Super high contrast silver halide photographic emulsion

Abstract: PURPOSE: To provide a super high contrast image especially on developing in a lithographic type processing by making a specific cyanine dye and a specific polyalkyleneoxide compound contained. COPYRIGHT: (C)1977,JPO&Japio

Electron-beam fabrication of high-density amorphous bubble film devices

Abstract: A low-temperature, all-vacuum process combined with electron-beam lithography suitable for single-level masking devices using 2-μm diameter amorphous bubble films has been developed. A test vehicle which uses 0.75-μm wide chevrons and 1-μm wide T.I bars in an 8,000- bit chip configuration, resulting in an areal density of 1×107bits/in2, was used. Important process features are found to be: (1) laminated NiFe films to obtain low H c and high magneto-resistive effect when deposited at low substrate temperature, (2) maintenance of low surface temperature during metallization to preserve the integrity of exposed and developed electron-beam resist pattern, and (3) proper resist profile for ease of the lift-off process. Excellent bubble device operating characteristics have been obtained as a result of uniformity in materials and structure resulting from careful control of fabrication parameters.

Liquid of forming protection film for lithographic press plate

Abstract: A protective coating material for lithographic printing plate, which comprises pullulan or pullulan derivatives. Said material is superior to hitherto used gum arabic solution in the protection of the surface of lithographic printing plate against oxidation and scumming as well as in the ability to enhance the hydrophilic character of metallic surface of a non-image area.

Abstract: Fabrication of microelectronic devices with electron‐beam lithography

Abstract: A variety of semiconductor devices have been fabricated by scanning‐electron‐beam lithography to demonstrate not only high resolution lithography but also to show that adequate associated processes exist for making properly functioning devices. The resist used was poly‐methyl‐methacoylate (PMMA) (DuPont, Elvacite 2010) developed in methyl iso‐butyl ketone. The devices include npn bipolar transistors with As emitters,1 n‐ and p‐channel MOS FET’s with gate lengths from 1.25 to 7.5 μm,2–4 n‐channel ring oscillators with 1‐μm gate lengths,5 CMOS ring oscillators with minimum linewidths of 1.25 μm, and a three‐phase CCD with 3‐μm‐long electrodes and 1‐μm gaps. By combining state of the art electron optics6,7 with newly developed electron resists, scanning‐electron‐beam lithography could be an attractive technique for making devices and circuits.

Positive optical lithography

Abstract: New techniques for characterizing and modeling the positive photoresist process have led to a quantitative understanding of the optical lithographic process. The model treats nonlinear exposure and development processes and resolved optical interference effects within the resist, permitting a new ability to understand and control lithography, and enabling the replacement of black magic by engineering.

Image Mechanisms in Screenless Lithography

Abstract: 1 Chapter

Techniques for Making Gap-Coupled Acoustoelectric Devices

Abstract: : The techniques recently developed for fabricating, inspecting, assembling and packaging silicon-on-LiNbO3 acoustoelectric devices, such as amplifiers, convolvers and memory correlators, will be presented. This will include: description of the lithographic and ion beam etching techniques employed in making the spacer posts, demonstration of the techniques used for eliminating dust and achieving uniform gaps, inspection methods, and several examples of packages. Experience to date indicates that the techniques for making gap-coupled structures are reliable, and lend themselves to widespread application. (Author)