Showing papers on "Resist published in 1974"

Fabrication techniques for surface-acoustic-wave and thin-film optical devices

Abstract: The techniques of photolithography, electron lithography, X-ray lithography, ion bombardment etching, and liftoff are reviewed, and their advantages and disadvantages assessed from the point of view of fabricating surface-acoustic-wave and thin-film optical devices.

An exposure model for electron-sensitive resists

Abstract: We present a mathematical model for the exposure of electron-sensitive resists where an electron beam is incident normal to a substrate coated with a thin layer of resist. We include both the scattering of the incident electrons as they penetrate the resist and the electrons backscattered from within the resist and from the substrate. The calculations yield contours of equal absorbed energy density, and these are interpreted as the contours which bound the resist after development. The absorbed energy density is found as the sum, for all electrons, of the product of the energy absorbed per unit length of trajectory and the flux density of electrons at the point in question. We first calculate the absorbed energy density for an electron beam of vanishingly small cross section (an incident delta function) and then convolve that result with a beam of Gaussian current-density distribution to obtain the reSult for a single beam location. For poly(methyl methacrylate) resist, we study the achievable dot resolution, as a function of the incident charge, for various incident energies-and substrates. Since our main interest is in computer-controlled resist exposures in which patterns are generated as a succession of dots, we calculate the absorbed energy density contours for a line generated in that manner. Detailed comparison is made with the experimental results of Wolf et al., by fitting a single point on one contour at one beam energy to account for the unknown developer sensitivity. The resulting contours predict the undercutting effect experimentally observed for the 5-20-keV beam energies studied. The developed shape and linewidth are found to be nonlinear functions of the incident charge per unit length. Experimental data for the linewidth at 20 keV are presented and compared with theory.

Lithography and radiation chemistry of epoxy containing negative electron resists

Abstract: A class of negative electron-beam resists is described which have excellent lithographic characteristics. The resists are copolymers of glycidyl methacrylate and ethyl acrylate. Their molecular weights, epoxy contents, and polydispersivities can be controlled to give an adjustable range of electron sensitivity and contrast. The copolymers are compared to other epoxy containing, negative electron-beam resists. Micrography of resist profiles generated from a single line scan of the electron beam have been used to illustrate the complex interaction of accelerating voltage of the electron beam and resist contrast on resolution. Optical gratings made from single line scans of the beam have feature sizes less than 300 nm in the resist, etched metals, and dielectrics.

Method for forming regions of predetermined thickness in silicon

Abstract: A method for forming thin regions of predetermined thickness in a silicon wafer which comprises the steps of applying an etchant resist mask on the faces of the wafer, opening a slot of predetermined width in the mask on one face to expose the underlying silicon, removing the mask from all areas of the other face where the thin regions are to be formed including removal opposite said slot, etching the wafer until the back surface of the thin region reaches the groove etched at the slot and then quenching the etch.

High sensitivity positive resist layers and mask formation process

Abstract: A high sensitivity resist layer structure for high energy radiation exposure is formed by coating plural layers of radiation degradable polymers on a substrate which layers are successively slower dissolving in the resist developer. Upon exposure and solvent development, a resist edge profile is obtained which is particularly useful for metal lift-off.

Etching process for accurately making small holes in thick materials

Abstract: A sheet of metallic material having a thickness T is covered on one side by an etchant resist and on the opposite side by an etchant resist and a removable shield. Etching is first performed on the side with only the etchant resist layer. Next, the shield is removed and the material is etched from both sides to produce an opening having a minimum dimension less than the thickness T of the material.

Process for fabricating small geometry semiconductor devices

Abstract: A process for fabricating small geometry semiconductor devices wherein an active region or regions are formed in a semiconductive layer and metalization patterns are formed on the surface thereof, while a resist pattern used to define the geometry of these regions and patterns is left temporarily in place between metal and semiconductor. Then, the resist is lifted off the surface of the oxide located between the metal and the semiconductive layer and whose geometry it controlled carrying with it the metalization lying on the resist surface and leaving very narrow strips of metalization in contact with the active regions.

High-speed low-power x-ray lithography

Abstract: High‐speed low‐power x‐ray lithography has been accomplished using 834‐A radiation excited by a 75‐W electron beam Incident x‐ray flux at the polymer film was 50 μW/cm2 Exposure was through a 34‐μm‐thick silicon mask substrate with patterns in a 4000‐A‐thick gold film Resist thickness was 4000–5000 A Both positive and negative resists have been used Exposure times were 4 min for both poly(diallyl orthophthalate) and poly(butene‐1 sulfone), 100 sec for poly(glycidyl methacrylate‐co‐ethyl acrylate), and 15 sec for epoxidized polybutadiene

Method of manufacture of additive printed circuitboards using permanent resist mask

Abstract: Circuit boards for electronic equipment are produced in which the circuit-forming conductor metal is deposited on a suitably catalyzed and masked resin substrate by all-electroless deposition techniques, wherein the characterizing feature of the invention is the use of a separate acceleration step after catalyzing and prior to application of a resist mask, supplementary of the usual post-masking accelerating step. Improved surface resistivity or insulation resistance in the printed circuit board and improved adhesion of the electrolessly deposited metal are achieved.

Fabrication of integrated optical elements using a computer-controlled electron beam.

Abstract: A computer-controlled electron beam has been used to fabricate complex thin film waveguide structures in an electron resist (polyphenylsiloxane). The machine uses an interferometric substrate positioning technique to enable covering macroscopic distances. Elements fabricated include straight and curved guides, triangular transition elements, directional couplers, and resonant ring structures between straight guides. Typical guide widths are 5 or 10 micro with lengths ranging up to several centimeters. Losses (2 to 5 dB/cm at 6328 A) are primarily due to scattering by localized proturberances, which should be possible to eliminate.

Gratings for integrated optics by electron lithography.

Abstract: The electron lithographic fabrication of high quality diffraction gratings with periods in the 0.25-microm < a(o) < 1.5-microm range is reported. The negative electron resist employed is a copolymer of glycidyl methacrylate and ethyl acrylate with a sensitivity about 15 times better than that of poly(methyl methacrylate), a positive resist. A new scan generator with linearity accurate to 1 part in 10(4) and locked onto the 60-Hz power supplies is described. Gratings with up to 3000 lines were fabricated with long range order deltaa(o)/a(o)

Resist mask formation process

Abstract: A resist mask is formed by coating on a substrate a layer of a polymer, such as polymethyl methacrylate, which is degradable by high energy radiation, such as a scanning electron beam. The layer is exposed to high energy radiation in a patternwise manner so as to lower the molecular weight of the polymer in the exposed portions. The layer is developed to remove the exposed portions by immersing the layer in a developer which consists of alkyl acetates and ketones having between 7 and 9 carbon atoms and mixtures thereof at a temperature of at least about 40° C.

Platinum oxide lithographic masks

Abstract: Because of the advantages it offers over wet chemical processing, sputter etching is an attractive process for making dimensionally-controlled high-resolution lithographic masks. This process needs a mask material that sputter etches rapidly in relation to the sputter etch resist. We have found that platinum oxide (Pt3O4) films sputter etch 15 X faster than iron oxide films, and are at least as durable and adherent. Because of the relatively high atomic number of platinum, platinum oxide masks are useful in electron beam and X-ray lithography.

Method for developing electron beam sensitive resist films

Abstract: The effective sensitivity of a photo- or electron beam resist is improved by contacting the resist film with developer solution and water prior to exposure.

Process for improved development of electron-beam-sensitive resist films

Abstract: The development of an exposed electron beam sensitive resist film in a two-stage process, rather than in a single stage, with a water wash between stages, improves the sensitivity and resolution that can be achieved for the resist.

Method of making a semi-transparent photomask

Abstract: A method of making a semi-transparent photomask of the iron oxide type comprising depositing a thin film of nickel or of a nickel alloy on a glass substrate, forming on the nickel or nickel alloy film a pattern of a resist which is the negative of the desired photomask, electrolytically depositing a layer of iron on the areas of the alloy film not covered by the resist, removing the resist and heating the assembly in an oxidizing atmosphere to convert the iron layer to iron oxide and also to convert the nickel or nickel alloy film to transparent oxides, at the same time providing improved adherence.

Computer-controlled electron beam microfabrication machine with a new registration system

Abstract: A direct fabrication system has been developed for semiconductor devices. It allows the recording of submicrometre patterns by an electron resist on a semiconductor wafer, using a fine electron beam controlled by a digital computer. The accelerating voltage, incident current and beam diameter are 15 kV, 100 pA and less than 0.2 mu m, respectively. The beam scans the unit field of 0.5 mm square, and an area of 25 mm square on the wafer can be irradiated by means of mechanical stepping and repeating. Four kinds of distortions (amplitude, rotation, trapezoid and shift) can be eliminated so that a registration accuracy of +or-0.2 mu m can be obtained over the whole area. Some microelectronic devices have been fabricated by using this system.

Thermally stable positive polycarbonate electron beam resists

Abstract: Electron beam positive resists which are sensitive to electron beam radiation and simultaneously thermally stable are prepared using polycarbonates.

Mounting integrated circuit elements

Abstract: A multi layer printed circuit interconnection system together with pillars for mounting integrated circuit components is progressively formed layer by layer by successive sequences for each layer, involving using a photo resist to produce a pattern of apertures defining circuit tracks and the pillar positions, depositing metal to form the tracks and the pillars and replacing the remainder of the resist with insulation material. Openings co-operating with the pillars, for the circuit elements are produced during formation of the outermost insulation layer of the circuit system. The circuit elements are mounted on the pillars and the connections between the elements and the printed circuit system are formed by using a further one of said sequences.

Scanning electron microscope fabrication of optical gratings

Abstract: A method of making optical gratings by the use of a Scanning Electron Microscope wherein (1) a substrate having a thin film of electron resist thereon is exposed in adjacent areas by an electron dosage and the amount of such dosage and the depth of the thin film are selected such that energy deposition in regions between adjacent exposed areas in said electron resist is below the threshold sensitivity of said resist for development, (2) the development time of the resist is made an inverse function of the electron dosage, and/or (3) the period of the grating is controlled by use of a standard scanning format.

Factors affecting the sensitivity of e‐beam resists

Abstract: In order to determine the effects of chemical structure on electron beam resist sensitivities, a series of polymers with different reactive components and additives has been investigated. The results, based on a larger number of exposures varying over five orders of magnitude, point out several interesting facts. The data indicate that the sensitivity of negative resists is not a linear function of molecular weight as previously supposed. Also, the negative electron resists tend to be more sensitive and cover a broader range of sensitivities than positive resists. The results further show that olefin and epoxy groups greatly enhance the crosslinking rate of these exposed polymers. However, additives, which are good energy transferring type sensitizers, have little effect on resist sensitivity. This last result is not surprising considering the nonselectivity of the exciting electrons.

Technique for using solder etch resist in generation of patterns on printed wiring boards

Abstract: A technique is described for the generation of a pattern on printed wiring boards bearing a layer of copper. The technique involves the use of a solder cream as an etch resist, the cream comprising a slurry of solder suspended in a curable resin flux. The use of the cream as an etch resist is similar to the use of either ink or solder plate for such purposes. However, the process described is far more economical than currently used techniques and provides a preferred alternative.

Electron beam processing systems (a state of the art review)

Abstract: This paper presents a review of electron-sensitive resists evaluated for electron beam exposure. This includes positive as well as negative resists and their relative merits and drawbacks. The paper also presents general guidelines that can be used in evaluating any electron resist system for performance and usefulness in electron beam microfabrication.

Pattern‐generators and technique for electron‐beam fabrication of submicron thin‐film bridges for superconductivity studies

Abstract: A low‐cost technique is discussed for fabricating bridges down to 0.12μ in width in aluminum using a conventional scanning electron microscope without a beam‐blanking facility. A detailed discussion is also given of the bridge pattern generators for the rectangular and Anderson‐Dayem geometries. The successful use of Shipley AZ‐1350 as an electron resist is reported.

Photoresist composition useful for making chromium film masks

Abstract: A photopolymerizable composition which acts as a negative etch resist useful in making chrome masks. A water based resist is employed which essentially comprises the polymerizable compound of acrylamide and gelatin to which is added the wetting agent Tergitol NPX. In the preferred method of making the chrome mask, the resist is prepared and processed with aqueous solutions thus eliminating the need for organic solvents.

Method for resist coating of a glass substrate

Abstract: A method for preparing the surface of a glass substrate so that resist maial may be directly applied to the surface and adhere thereto. The invention is particularly useful in the fabrication of relief masks used for pattern generation in planar thin film overlays, which masks are used to provide intimate contact between a photoresist surface and a masking pattern during exposure of the photoresist surface. The present method comprises cleaning of the glass substrate, boiling the substrate in trichloroethylene, and heating the substrate to between 160° and 200°C. Resist material may then be applied directly to the glass substrate.

Fabrication of bubble memory chips

Abstract: Investigations have been made on the fabrication of accurate and uniform T-bar circuits. Chrome masks are preferable to emulsion masks, and furthermore, a minimum exposure and intimate contact have been demonstrated to be necessary for accurate and uniform pattern imaging on the AZ1350 resist. A newly developed chemical etchant, a nitric acid-base solution without ferric chloride, can almost eliminate undercutting of permalloy elements. Application of spin-on-glass prior to Permalloy evaporation can result in excellent step coverage at the places where T-bar circuits overlap conductors. Large memory chips having a capacity of 16 × 103bits and a storage density of 105bits/cm2have successfully been fabricated.