Showing papers on "Resist published in 1976"

Electron‐beam fabrication of 80‐Å metal structures

Abstract: Metal structures 100 A high with sharply defined linewidths of 80 A have been produced using an electron‐beam fabrication process. A contamination resist pattern is written with a 5‐A 45‐keV scanning electron beam in a 100‐A‐thick Au‐Pd film supported by a 100‐A carbon foil. The unprotected Au‐Pd is removed by dc ion etching with 1‐keV Ar ions. Unlike most electron‐beam microfabrication processes, the resolution of the resulting structure is not limited by electron scattering, but by the grain size of the metal films. These structures should have direct application in a large number of device fabrication problems in electron and x‐ray beam technology and they should provide masks for other microfabrication processes such as x‐ray lithography.

Application of synchrotron radiation to x‐ray lithography

Abstract: Synchrotron radiation from the German electron synchrotron DESY in Hamburg has been used for x‐ray lithography. Replications of different master patterns (for magnetic bubble devices, Fresnel zone plates, etc.) were made using various wavelengths and exposures. High‐quality lines down to 500 A wide have been reproduced using very soft x rays. The sensitivities of x‐ray resists have been evaluated over a wide range of exposures. Various critical factors (heating, radiation damage, etc.) involved with x‐ray lithography using synchrotron radiation have been studied. General considerations of storage ring sources designed as radiation sources for x‐ray lithography are discussed, together with a comparison with x‐ray tube sources. The general conclusion is that x‐ray lithography using synchrotron radiation offers considerable promise as a process for forming high‐quality‐submicron images with exposure times as short as a few seconds.

Polymer Resist Systems for Photo- And Electron Lithography

Abstract: Modcrn technology is dependent on solid state electronics. Computers, communica­ tion equipment, medical instruments, and transportation systems all require complex electronic devices. The complexity of these devices is increasing each year, thus placing more demand on the materials and processes used in their fabrication. Manufacture of silicon integrated circuits (SIC) requires as many as 90 processing steps; a completed device is a complex structure containing five or more different materials, including dielectrics, conductors, and semiconductors. These materials, except the substrate semiconductor, are low-defect thin films ( < 3 JIm in most cases) deposited using a variety of techniques. The thin films must be patterned to form individual elements of an integrated circuit or other device. Shape and size of individual elements determine size, ultimate complexity, and operating parameters of a finished device. Increasing the scale of integration (device complexity) may reduce fabrication costs and increase performance; however, it requires a reduction in element geometry. Conventional pattern delineation is accomplished by etching a thin conductor or dielectric film through a polymer resist film that has been selectively patterned. The pattern conventionally is transferred to a resist by exposing to UV radiation through a mask. The polymer's solubility is altered by this exposure, and the pattern is developed by immersion in a solvent (developer), which removes the more soluble material. Resolution of photolithography is limited to 1·-3 JIm mainly as a result of the wavelength (300-40.0. nm) of radiation employed and mask technology. Exposure with short wavelength electrons is currently being developed at several laboratories for pattern generation of features less than I pm. This technique is used to fabricate master masks and complex integrated circuits. For either photo­ lithography or electron beam lithography to be useful, high-quality resist materials are required. This review attempts to cover materials and processing considerations for both photoresists and electron resists.

Process in the production of a multilayer printed board

Abstract: In a process for the production of a multilayer printed board built up by starting from a desired number of insulating bases clad on both sides with an unpatterned metal layer, the improvement consisting in that the metal layers, whereout conductive patterns are to be etched and which layers are to be hidden inside the finished multilayer printed board, are coated with a plating resist in the shape of a negative of the desired conductive pattern, that the remaining visible parts of the metal layers, which are to form the conductive patterns, are coated by electroplating with a thin, rough, adhesion-promoting metal layer comprising copper, zinc, nickel, tin or any one of their alloys, that an etch resist layer of nickel, tin or any one of their alloys is electroplated on top of the adhesion-promoting layer, if the latter consists of copper, zinc or any one of their alloys, that the negative plating resist is removed, that the parts of the metal layers thus uncovered are etched away and that the insulating bases provided with conductive patterns are laminated to a multilayer printed board.

Fabrication of thin periodic structures in photoresist: a model

Abstract: We present a technique for designing holo-graphically fabricated structures in photoresist. A method is given for obtaining a suitable initial resist thickness. The etch depth (Deltat) vs exposure (E) characteristic is determined experimentally for a fixed development time (T). The characteristics for other values of T are found using the linearity of Deltat with T. Whole families of grating profiles can then be generated by using a polynomial fit to the exposure characteristics. For example, using a single holographic exposure plus an optional uniform preexposure, a family of grating profiles is obtained by varying the parameter T. A desired profile can thus be realized by a suitable combination of initial resist thickness, exposure, and development time. Residual resist layers may be eliminated by this method thereby minimizing scattering and other losses. Experimental verification of the various features of the model is given.

Profile and groove‐depth control in GaAs diffraction gratings fabricated by preferential chemical etching in H2SO4‐H2O2‐H2O system

Abstract: We studied in detail the fabrication of diffraction gratings in GaAs by preferential chemical etching and demonstrated that different grating profiles can be obtained by proper choice of substrate orientation and direction of grating‐mask groove openings or by controlling the width of these groove openings and/or etching time. We have also obtained experimental curves relating the etched groove depth to etching time for gratings with different periodicities at different etchant temperatures. In our experiments, the H2SO4‐H2O2‐H2O system was used as the preferential etchant together with Shipley AZ‐1350J as the resist. This combination enables us to use the resist grating directly as a protective mask during chemical etching.

Method of depositing thin films utilizing a polyimide mask

Abstract: A polyimide mask is used as an undercoat for a standard resist material during the patterning of an underlying thin film layer by plasma etching. The polyimide mask can withstand the conditions of reactive ion (plasma) etching so that it can be used as a protective coating when the thin film is subtractively etched by the plasma etching. The polyimide is particularly useful in processes using either positive or negative electron beam lithography which require sensitive resists.

New Type Thermal Printing Head Using Thin Film

Abstract: This paper describes the development of a new type thermal printing head. The main features of this paper are as follows. 1) The heating element is a Ta 2 N thin-film resistor coated with a SiO 2 -Ta 2 O 5 double layer. The SiO 2 layer prevents oxidation of Ta 2 N; the Ta 2 O 5 layer, which rubs directly against the heat-sensitive paper, is hard enough to resist abrasion. 2) A theoretical calculation revealed that the thermal time constant can be controlled by changing the thickness of the heat insulating layer. It was found that a glazed alumina ceramic substrate has the most suitable thermal properties. 3) A beam-lead diode array and a crossover structure have been developed to satisfy the electrical interface requirements of both the thermal printing head and the external logic.

X-ray lithography mask

Abstract: An X-ray mask for variable resist exposure for use with X-ray lithography so that multi-level devices, using a single exposure of X-rays, can be made.

Negative resist for X-ray and electron beam lithography and method of using same

Abstract: A class of chlorinated or brominated polymeric negative resists for high resolution X-ray or electron lithographic processes is described. Chlorine and bromine atoms have a generally high mass absorption coefficient for X-rays and can be incorporated into the polymer in high weight percents. The chlorinated resists are especially sensitive to the 4.37 Angstrom characteristic X-rays from a Pd target.

Photoresist O-quinone diazide containing composition and resist mask formation process

Abstract: A resist composition includes an alkali soluble resin, a light sensitive diazo compound, and a thermally activated free radical initiator. Resist masks are formed from the above composition by providing a layer of resist on a substrate, exposing the layer patternwise to radiation, removing portions of the layer with a developing solution, and heating the remaining portions of the layer at a temperature which activates the initiator and cross-links the resist to improve the physical characteristics of the resist layer and minimize pattern distortion.

Hard X-ray and fluorescent X-ray detection of alignment marks for precision mask alignment

Abstract: The specification describes a process wherein short wavelength or "hard" x-rays (less than about 4 Angstroms) are used to align a semiconductor processing mask with a semiconductor wafer without the requirement for thinning the wafer to permit the x-rays to pass through. These short wavelength x-rays may be obtained from either the continuum x-rays which accompany the "soft" (longer wavelength) characteristic x-rays used for resist exposure, or from a specialized source of hard x-rays. Alternatively, alignment marks may be provided on the surface of the wafer to project alignment-indicative fluorescent x-rays onto an x-ray detector without passing through the underlying semiconductor wafer. A null condition in the intensity of the "hard" x-rays, or the fluorescent x-rays in the alternative embodiment of the invention, which are received at an x-ray detector is indicative of an alignment between a reference mark on the mask and either a reference mark or an opening on the wafer.

Utilization of a substrate alignment marker in epitaxial deposition processes

Abstract: An alignment marker on a substrate surface is covered with polycrystalline semiconductor material during the growth of an epitaxial layer on the monocrystalline substrate. This polycrystalline material is then removed with a selective etchant to re-expose the marker for use in defining an area for processing at the epitaxial layer surface. Permits accurate alignment between buried layers and regions formed from the epitaxial layer surface. Permits provision of the marker on the substrate when it is undesirable to provide the marker on the epitaxial layer surface. Particularly advantageous for electron image projection exposure of electron-sensitive resists.

Gel Formation in Negative Electron Resists

Abstract: Exposure characteristics of negative electron resists are described on the basis of Charlesby's theory on gel formation by a chain reaction. By use of the theory, the important resist parameters, contrast and sensitivity, can be related to the chemical properties of the resist materials. Applicability of the theory to exposure curves of Kodak thin film resist (KTFR), polymethylvinylsiloxane (PMVS), and epoxidized polybutadiene (EPB) is experimentally verified. The radiation yield for the reaction initiated directly by the electron irradiation and that for the over-all reaction propagated via radicals is separately estimated. It is found that the sensitivity of styrene-butadiene copolymers (SB) is increased by an introduction of ..cap alpha..-phenylmaleimide. This increase in sensitivity is also explained by the theory. The observed lowering in contrast associating the improvement in sensitivity by ..cap alpha..-phenylmaleimidation in SB, by epoxidation in polybutadiene, and by introduction of vinyl groups in polysiloxanes is in good agreement with the theoretical results. It is concluded that if a resist with higher contrast than 1.0 is required, the chain reaction must be inhibited so that the inhibition factor is larger than about 0.5.

Determination of wavelength and excitation voltage for X-ray lithography

Abstract: The exposure time of an X-ray lithography system is minimized by the appropriate choice of X-ray wavelength and target excitation voltage, within the constraints of a specified resolution and contrast in the exposed resist pattern The factors that must be considered in making this choice are the X-ray source brightness of various target materials, the continuum emission spectrum of the target, the wavelength-dependent transmission of the X-ray mask and the vacuum window, and the wavelength-dependent absorption in the resist The relative exposure time, as a function of wavelength, is predicted for a system using a 25-µm-thick beryllium window and PMMA resist with three choices of mask substrate: 125- µm-thick Mylar, 40-µm-thick silicon, and 85-µm-thick beryllium A new mask substrate, 02-µm-thick aluminum oxide, is presented and shown to be suitable for exposure in vacuum with a 25-µm-thick aluminum filter at 133-A wavelength (copper target) X-ray emission spectra from an aluminum target were measured at electron energies of 45, 79, 104, 125, 155, 195, and 285 keV These spectra showed that the continuum radiation contributes little to the degradation of contrast with a gold-on-silicon X-ray mask Thus a 20-kV electron beam may be used for maximum X-ray production efficiency

Forming method for fine resist patterns

Abstract: PURPOSE: To fine resist patterns of high resolution using high energy beams by using a specific alkyl ester methacrylate halogenide polymer as a photo resist layer. COPYRIGHT: (C)1977,JPO&Japio

Actinic radiation emissive pattern defining masks for fine line lithography and lithography utilizing such masks

Abstract: An actinic radiation emissive mask for a high resolution lithography emits actinic radiation which originates within the mask. The mask patterns the actinic radiation to expose resist in accordance with a desired pattern. The actinic radiation originating in the mask may be produced by radioactivity, stimulated emission or combinations thereof.

Plasma etching of aluminum

Abstract: Experimental plasma etching apparatus and methods utilizing BCl 3 etch gas have been developed for the accurate patterning of thin Al and Al-Si alloy metallization as used in integrated circuit fabrication. A two micron linewidth capability has been achieved for the patterning of 0.5 micron thick metallization on three inch diameter wafers with positive and negative photoresist etch masks as thin as 2500A. Etchrates of 500 to 1000 A/min. are typical, and there is negligible etching of both the photoresist and the underlying SiO 2 layers. The process is CMOS compatibles, yielding threshold voltage shift and temperature-bias stability specifications of less than ±0.050 volts that are comparable to those for wet chemically etched devices.

Electron beam resist and its usage

Abstract: PURPOSE: Stable resist having sensitivity to radiation of 2 × 10 -7 C/cm 2 , short radiation time and resistance to ion beam etching by using polymethacrylic amide or its compolymer as its main ingredient. COPYRIGHT: (C)1977,JPO&Japio

Thin-Film Microwave Integrated Circuits

Abstract: There has been an increase in the use of thin-film technology for the preparation of microwave circuits since it permits the realization of very complex circuitry with precision, reliability, and economy. The requirements for the realization of such circuits have made it necessary to extend the state of the art of the hybrid technology in many areas. Two new substrate types (fine-grain alumina and fused silica) and low-loss conductor systems that are both solderable and thermocompression (TC) bondable were introduced. Further complications which were overcome included bilevel patterns with laser-drilled plated via-holes, the control and measurement of the alumina substrates dielectric constant, and the use of laser trimming to adjust small geometries of tantalum nitride (Ta 2 N) termination resistors. Precise pattern delineation of conductors by laser machining, sputter etching, and selective plating was evaluated and the latter process was found to be the most economical and reliable, since the selective plating technique depends on good photoresist delineation, resist properties were evaluated with special attention given to the variation of linewidth as a function of exposure conditions and resist adhesion during the plating of the gold conductors to prevent underplating. The line shape of the resist was also determined as a function of exposure, development, mask-to-substrate distance, and postbake conditions. Linewidth tolerances such as ± 2.5 µm on fused silica and ±5.0 µm on alumina were routinely achieved. Microwave integrated circuits (an 18-GHz downconverter, a 1.7-GHz amplifier, a filter, and a demodulator) prepared by this technique are illustrated and their performances are discussed. These circuits are used in a digital transmission system currently under development.

Alignment pattern forming method for mask alignment

Abstract: PURPOSE: To make possible the recognition of pattern serrations definitely despite existence of inteference fringes by etching the metal gloss surface of a wafer according to the alignment patterns on the wafer, then coating thereon a resist film. COPYRIGHT: (C)1977,JPO&Japio

Electron-beam lithography for microcircuit fabrication

Abstract: Electron beams are being used to make new generations of solid-state devices with critical dimensions that are less than 1 μm. Using the technique, device designers are able to overcome many of the performance limits that have been set by the conventional methods of fabrication where ultraviolet light is shone through a mask to define a pattern on photosensitive resist. The minimum practical dimension in light-exposure systems is usually greater than 1 μm although the fundamental limit set by the diffraction of light is somewhat less. In comparison the limit using electron-beam techniques is much less than 1 μm, so that one can expect substantial improvements in the specifications of surface-acoustic-wave devices, microwave transistors, narrow-gate field-effect transistor and high-density large-scale-integration devices once the techniques of electron-beam lithography are fully established

Resist image formation by stripping

Abstract: PURPOSE:To enable a light sensitive material for forming a conventional stripping development type resist image to be rendered highly sensitive without impairing various characteristics of the resist layer, by employing in combination an aromatic carbonyl compound and an amine as a photopolymerization initiator.

Inspecting method of resist pattern

Abstract: PURPOSE:An inspecting method whereby defects in resist patterns can be detected rapidly under an electronic computer control without any human help, using the same pattern data used at the time of exposure.

Manufacturing process of semiconductor device

Abstract: PURPOSE:To improve adhesion property of phosphor glass to the resist by providing a special structure in which the phospher glass and the resist coat are not directly touching This is possible by coating a thin low-temperature oxidized film of a fixed thickness on a high density phosphor glass