Showing papers on "Resist published in 1978"

250‐Å linewidths with PMMA electron resist

Abstract: 25‐nm‐wide lines and spaces have been fabricated in 22.5‐nm‐thick films of PdAu (40 : 60) using electron‐beam exposure and polymethylmethacrylate (PMMA) resist. A high‐resolution scanning transmission electron microscopy (STEM) was used to expose the resist and the samples were mounted on 60‐nm‐thick Si3N4 membrane substrates. Previously, the smallest metal structures formed with a resist process were 60 nm wide with spaces between the lines several times larger than the lines. The results presented here show that 25‐nm lines can be fabricated with a center to center spacing of 50 nm.

Self‐consistent proximity effect correction technique for resist exposure (SPECTRE)

Abstract: Submicron electron‐beam lithography for the direct exposure of wafers and for the fabrication of masks cannot be successful until the incident electron exposure can be properly adjusted to compensate the proximity effects. A self‐consistent proximity effect correction technique for resist exposure (SPECTRE) has been developed to compute, for any given pattern, the corrections to the incident electron exposure which must be applied in order to obtain ’’uniform’’ absorbed (incident plus backscattered) exposure in the resist. Mathematically, the solution is unique for any given proximity function. SPECTRE has been successfully implemented on practical pattern data. Experimentally, simultaneous delineation of pattern geometries from 1/4 to 2 μm has been achieved by an automatic application of SPECTRE.

Method of forming thin film interconnection systems

Abstract: A method for forming thin film interconnection patterns atop substrates, particularly semiconductor substrates. It features the use of the passivation layer itself, typically glass, as a stable masking material to etch the conductive lines. Conversely, the metal conductor is used as a stable mask in etching the glass to form via holes. The process provides a practical resist system which is compatible with reactive ion etching or other dry etching process.

Resist development control system

Abstract: RESIST DEVELOPMENT CONTROL SYSTEM Abstract of the Disclosure In the process of developing exposed photoresist on a substrate, the endpoint in developing away all of the exposed positive photoresist or any other positive resist is detected by exposing a wafer with a predetermined pattern including an optical grating or other special pattern formed in the photoresist upon a test area. In a system employing this concept, a beam is diffracted by the optics of the grating only at a first angle until the resist forming the grating is removed by development. Then a sensor is activated when an angle of reflection is unblocked when the grating dis-appears. The system is then turned off to stop development by the sensor in an automatic system or, by the operator in a manual system. A double exposure technique is employed to produce the grating or other special pattern.

High Dose Ion Implantation into Photoresist

Abstract: The characteristics of heavily ion‐implanted photoresist films were studied in relation to types of photoresist, ion species, accelerating energies, and dose levels. By high energy, high dose ion implantation it was observed that the optical transmission of the resist film was exceedingly decreased and the resist becomes more mechanically, thermally, and chemically resistant. Several experimental data indicated that these results are due to the change of photoresist to disordered graphite. As an application of this ion‐implanted resist, a new photomask fabrication process is developed.

Fabrication based on radiation sensitive resists and related products

Abstract: Radiation sensitive negative resists with requisite stability for dry processing of integrated circuits are polymerized from aromatic moieties containing halogen atoms. Halogen-aryl bridging, generally carbonaceous, increases sensitivity to radiation. Exemplary materials, copolymers prepared from aromatic and glycidyl methacrylate (GMA) comonomers, are suitable for direct processing of large-scale integrated circuits. While electron beam patterning is contemplated both for direct processing and mask making, radiation such as X-ray and deep u.v. may be used.

Fabrication of integrated circuits utilizing thick high-resolution patterns

Abstract: In an integrated circuit fabrication sequence, a relatively thick sacrificial layer (18) is deposited on a nonplanar surface of a device wafer in which high-resolution features are to be defined. The thick layer is characterized by a conforming lower surface and an essentially planar top surface and by the capability of being patterned in a high-resolution way. An intermediate masking layer (22) and then a thin resist layer (20) are deposited on the top surface of the sacrificial layer, the thickness of the resist layer being insufficient by itself to provide adequate step coverage if the resist layer were applied directly on the nonplanar surface. A high-resolution pattern defined in the resist layer is transferred into the intermediate masking layer. Subsequently, a dry processing technique is utilized to replicate the pattern in the sacrificial layer. A high-resolution pattern with near-vertical sidewalls is thereby produced in the sacrificial layer. By means of the patterned sacrificial layer, high-resolution features are then defined in the underlying nonplanar surface.

Stencil technique for the preparation of thin-film Josephson devices

Abstract: We describe a photoresist stencil technique that has proven to be quite reliable in the preparation of thin‐film Josephson logic and memory devices. The method employs multiple layers of resist with the top layer providing patterning and the bottom layer spacing the top layer from the substrate and providing an undercut under the top layer. This method has consistently produced uniform undercuts over ∠1 in. (∠2.54 cm) sample dimensions and has been used to produce micron‐sized patterns.

Two layer resist system

Abstract: A resist mask comprising two layers of resist, one of which is saturated with a dilutant which does not dissolve the other. In one embodiment, the two layers of resist are applied upon a substrate, the first layer of which is more soluble in a developer. The second layer is said saturated resist and the first layer is non-saturated. This composite is preferably used to form a relief mask with recessed sidewalls used in lift-off processes.

Method of modifying the development profile of photoresists

Abstract: The cross-sectional profile which is produced upon development of a layer of alkali soluble resin-diazo ketone photoresist is modified by treating the layer with a solvent or solvent mixture which is different from but miscible with the solvent or solvent mixture used to form the resist layer. The treating solvent is believed to dilute the resist solvent in a surface layer portion of the resist thereby modifying the alkaline developer solubility of this portion. Undercut resist profiles may be obtained by this method with normal optical exposure of the resist.

Performance characteristics of diazo-type photoresists under e-beam and optical exposure

Abstract: The performance characteristics of three different diazotype positive photoresists such as Shipley AZ2400, Kodak 809, and Polychrome PC129, are compared after optical exposure and electron-beam exposure. The development rates for both e-beam and optically exposed resists are measured by an in-situ automated technique using the IBM Film Thickness Analyzer. The optical exposure parameters are obtained at three wavelengths (4358, 4047, and 3650) by computer-controlled transmission measurements. The optical exposure and development parameters permit direct quantitative comparisons for these photoresists. The development rates of e-beam and optically exposed resists are compared. Also a comparison of e-beam sensitivity between the three resist systems is made by studying the resist profile shape after development in the scanning-electron microscope (SEM).

A dry‐etched inorganic resist

Abstract: An as‐deposited As2S3 thin film is employed as a negative working inorganic resist in lithographic applications. A CF4 plasma is used to etch differentially for pattern delineation. A maximum etch rate ratio of 1.8 between the unexposed and exposed films is obtained. Ag‐photodoped As2S3 is found to have a much slower etch rate in the CF4 plasma. Grating patterns have been obtained using this dry process. The extension of this concept to conventional organic polymer resists is considered.

Production of semiconductor device

Abstract: PURPOSE:To improve the reliability of the device preventing damage to the surface of the semiconductor substrate when the protective film is formed by forming an inorganic insulating protective film formed through a precoat by polyimide resin CONSTITUTION:A resist film 6a is applied on the source and the drain electrodes 3 and 4 of FET of GaAs with the gate region exposed Then, it is coated with a precoat for a polymide resin and treated at a specified temperature With the lift-off of the resist film 6a and the precoat 9, an oxidation is performed at a given temperature, and an insulating protective film 10 made of inorganic substance such as SiO2 is formed by sputtering Then, an opening is given on the film over the electrodes 3 and 4 In this method, the formation of the inorganic protective film protects the surface of the semiconductor from damage thereby improving the reliability of the device Thus, production of a good yield is possible

Pulsed X-ray lithography

Abstract: A method and means for x-ray lithography which utilizes means for producingn a vacuum system a high-temperature plasma from which soft x-rays are emitted. The x-rays pass through a mask exposing an x-ray resist on a substrate to produce the desired pattern on the substrate. The x-ray spectrum has a significant energy in the 1-5 keV range. These x-rays pass through the support layer of the mask, stop in the pattern material (gold) of the mask or, where the pattern material is lacking, are absorbed adequately by the x-ray resist. Since there is very little energy above 5 keV, there is little if any substrate damage due to the x-rays.

High temperature lift-off technique

Abstract: A layer of resist is applied to a metal substrate, and a matrix is formed in the resist. A metal or dielectric mask having overhanging upper edges is formed by electroplating metal into the resist matrix which has preformed openings for defining the mask. The resist matrix is then removed from the substrate. A film is then deposited upon the substrate, where it is exposed, and the mask with the overhanging upper edges protecting the side walls of the mask from being covered. Then a chemical, such as an etchant, is applied to the side walls of the mask to remove it, lifting off the material deposited upon it. The mask is made by plating metal through apertures or coating of tapered holes.

Negative electron resists for direct fabrication of devices

Abstract: The Bell Laboratories electron‐beam exposure system (EBES) is currently being used to fabricate master masks and experimental devices using a negative resist based on poly(glycidyl methacrylate‐co‐ethyl acrylate) (COP) and a positive resist, poly(butene‐1‐sulfone) (PBS). COP was designed to have a sensitivity of 2–4×10−7 C cm−2 and good wet chemical etching resistance for a variety of thin‐film conductors and insulators. The resolution obtained with a 0.6‐μm initial COP film exposed with EBES and processed on a routine line is 2.0 μm. These characteristics are satisfactory for current requirements; soon however, machine improvements, smaller device geometries, and new processing procedures are going to place increasing demands on resist systems. In addition to resolution requirements, it is desirable to have a resist which is resistant to ion beam milling, plasma etching, or other dry etching techniques. Each of these requirements will be discussed in detail. This paper summarizes the results of the synth...

Process for providing self-aligned doping regions by ion-implantation and lift-off

Abstract: A process for providing ion-implanted regions in a substrate such as silicon beneath an existing layer such as silicon dioxide and being self-aligned to subsequently fabricated regions of said layer which includes providing a resist masking pattern above the existing layer wherein the resist masking pattern has vertical sidewalls (i.e., perpendicular to the upper surface of the substrate) or is undercut; ion-implanting impurities such as boron ions through the layer but not through the resist and portions of the layer beneath the resist; and depositing a layer of lift-off material such as aluminum on the existing layer and on the resist. The implantation step must be performed after providing the undercut resist masking pattern, but before depositing the layer of lift-off material in order to achieve the desired self-alignment feature. Because of the resist profile (i.e., vertical walls or being undercut) no lift-off material is deposited on the sidewalls of the resist and a gap is formed between the resist and that portion of the lift-off material which is above the existing layer. The resist pattern is removed along with the portion of the lift-off material layer deposited thereon. The now-exposed portion of the existing layer located beneath the previous resist pattern is then removed. Finally, the remaining regions of lift-off material are removed from above the regions of the existing layer. The ion-implanted regions occur in the substrate beneath the remaining portions of the existing layer, are self-aligned to the boundaries of said portions, and correspond to a negative image of the original undercut resist masking pattern.

Electron beam exposure method

Abstract: PURPOSE:To reduce the damages that the substrate to be treated receives during rediation and eliminate the need for special annealing process by rediating an electron beam to the resist film while maintaining the substrate to be greated which is deposited with the resist film for electron beam at a high temperature.

Process and mask for ion beam etching of fine patterns

Abstract: The specification describes a process for ion beam etching fine patterns in a substrate using a protected resist mask which prevents erosion of the mask. First, a resist pattern is formed on the surface of a substrate to expose pre-selected areas of the substrate. Next, a selected material is deposited on the resist mask at a predetermined controlled angle of incidence with respect to the surface of the mask to form a relatively thin protective layer on the resist mask, having edges and patterns replicated from the edges and patterns of the resist mask and a negligible amount of the selected material deposited on the exposed substrate. Then, a beam of ions at a chosen energy is directed through openings in the protected mask to the substrate to etch the pre-selected areas. During etching, the protective layer on the resist prevents erosion of the resist mask and provides improved pattern definition for the etched region. In a preferred embodiment, metal contacts to the etched regions are subsequently formed by depositing a selected metal from a directional source and then lifting off the resist and the undesired metal.

Submicrosecond X-ray lithography

Abstract: X-rays from laser-heated plasmas were used to replicate features as fine as 750 nm in the positive resist polybutene-1-sulfone (p.b.s.). The measured sensitivities of p.b.s. to pulsed and d.c. X-rays (≈ 109 ratio in exposure rate) are similar (no reciprocity loss). Laser-plasma X-rays produced only small (0.25 V) flat-band shifts in m.o.s. capacitors at irradiation levels sufficient to expose p.b.s.

Mask apparatus for fine-line lithography

Abstract: There is described a unique apparatus which is especially useful with very thin masks used in X-ray lithography, transmission electron lithography or electron projection lithography. The apparatus includes temperature stabilization means for counteracting the deleterious effects in the mask caused by absorption of energy from the energy source as well as positioning means for precisely spacing thin masks for proximity lithography techniques. The thermal effects are counteracted by providing a chuck which supports the substrate to be acted upon. A thermally conductive layer, for example a fluid or other conformable medium, can be provided between the substrate and the chuck. The mask is similarly spaced from the substrate by a thin layer of thermally conductive material, for example, a low pressure gas which is capable of passing the energy in question. The precise spacing of the mask is controlled by the use of a source which establishes an electrostatic charge between the substrate and the mask. The charge may be provided by a source connected to the substrate and mask or by means of filaments disposed above the mask. Precise spacing is achieved by balancing the attractive force of the electrostatic charge with the repulsive force of the low pressure gas.

Laser-Plasma Source For Pulsed X-Ray Lithography

Abstract: The exposure of an x-ray resist by radiation from laser-heated plasmas was recently demonstrated. Single-shot submicrosecond exposures with a very favorable x-ray spectrum are possible. In order to reduce the cost of a laser-plasma x-ray lithography system, it is desirable to maximize the intensity in the soft (1 to about 3 keV) range. The x-ray output of laser-plasmas depends on laser pulse parameters (wavelength, pulse shape and energy), the focal conditions, and the target composition and geometry. Laser-plasma x-ray characteristics and their sensitivity to experimental parameters are reviewed in this paper. Presently available information indicates that a Nd:glass laser having pulse width in or near the 1-10 nsec range with at least 500 J of energy should be adequate for practical single-shot x-ray lithography.

Fluorine plasma resist image hardening

Abstract: An organic polymer resist image layer, formed on a substrate, is stabilized by placing the substrate with the resist image layer in an electrodeless glow discharge in a low pressure fluorine containing atmosphere, for example, CF4, so as to harden the exposed surface of the layer and then heating the layer.

Method of depositing thin films of small dimensions utilizing silicon nitride lift-off mask

Abstract: A method for depositing thin film patterns of very small and controllable dimensions in the fabrication of integrated circuits which avoids edge tearing of the films. A non-photosensitive organic polymeric first masking layer is deposited on the integrated circuit substrate. Upon this layer is deposited a layer of silicon nitride using plasma deposition techniques employing a gaseous source. The silicon nitride layer is covered by a second masking layer, preferably an organic polymeric resist material, through which apertures are formed in preselected patterns using standard lithographic masking and etching techniques. The silicon nitride layer is then reactive ion etched with CF4 through the apertures formed in the second masking layer. The first masking layer is then etched through the apertures in the second masking layer and silicon nitride layer using reactive ion etching techniques. The etching of the first masking layer continues until the first masking layer is undercut beyond the edges of the aperture in the silicon nitride layer so that the silicon nitride layer forms an overhang of the aperture in the first masking layer. The thin film to be deposited is then applied over the resulting structure including the surface of the silicon nitride layer and the substrate exposed through the apertures. Because of the overhang, a discontinuity is formed between the thin film deposited upon the exposed surface of the substrate and that formed upon the outer surface of the silicon nitride layer so that when the first masking layer is dissolved, the film deposited upon the substrate is left without any edge tearing between it and the removed portions of the film.

A Three-Dimensional Study of the Absorbed Energy Density in Electron-Resist Films on Substrates

Abstract: A computer program has been developed for the three-dimensional calculation of the absorbed energy density in polymer films on substrates in electron beam lithography. In this calculation the Monte Carlo results have been used for the radial energy intensity distribution for a point source electron beam. The program is based on the reciprocity principle proposed by Chang. Some exposure experiments have been conducted with an electron resist of PMMA (polymethyl methacrylate) for isolated patterns in the from of a line of finite length (8.1 µm) as well as of a rectangle (3.1×8.1 µm2) in order to check the reliability of the calculations. Operating beam voltages used for the investigation are 14 and 20 keV. The electron resist thickness is 8000 A. Relatively good agreement has been obtained between the calculated and the experimental results. This program is applicable to an arbitraty pattern, and therefore it will be useful for investigations of the proximity effect in electron beam lithography.

Production of semiconductor device

Abstract: PURPOSE:To simplify the element production process by making up a pattern of a pair of memory elements comprising a transistor and a capacitor of a resist having a shielding property against parallel beam such as light and X rays and leaving a part of the film utilizing shade developed by sharp projection of the beam. CONSTITUTION:A thick SiO2 is formed at either end of an Si substrate. A thin SiO2 film 3 is allowed to grow on the capacitor-formed region of the substrate surrounded by the film and a polycrystaline Si film 10 is done so on the film 3 covering the film 2. Then, a pattern of a thick resist film 11 is provided and the substrate 1 is exposed by etching in the given area which is entirely coated with an Si3N4 film 12. Parallel ion beam is irradiated slantly to the film 12 so that the area thereof behind the film 11 is left. Subsequently, the film 11 is removed to form a given diffused region 5 and a layer insulation oxidized film 6 is provided. Thus, a transistor is formed by a generally accepted method. This method elminates the need for making contact holes on the memory cell.

Process for channeling ion beams

Abstract: The specification describes a process for minimizing ion scattering and thereby improving resolution in ion beam lithography. First, a substrate coated with a layer of ion beam resist is provided at a chosen spaced distance from an ion beam source. Next, a monocrystalline membrane with a patterned ion absorption region is positioned at a predetermined location between the substrate target and the ion beam source. The patterned ion absorption region may be either an ion absorption mask, such as gold, deposited on the surface of the monocrystalline membrane, or a pattern of ion-damaged regions within the monocrystalline membrane. Finally, a collimated wide area ion beam is passed perpendicular to the surface of the membrane and through crystal lattice channels therein which are exposed by the patterned ion absorption region and which extend perpendicular to the membrane surface. The parallel paths established by the channels in the membrane provide low resistance paths to the passage of ion beams and consequently minimize the angle of deflection of the ions passing from the membrane to the target resist layer.

Positive resist for high energy radiation

Abstract: A film of poly(methacrylamide) is heated to partially form imide bonds with elimination of ammonia, and such imide bonding causes crosslinking in the polymer to form a crosslinked polymer film. This film can be advantageously adapted as a positive resist capable of forming a positive image by exposure to radiation such as electron beams. The minimum incident charge required for such exposure is of the order of 10-7 coulomb/cm2, which is far lower than the level required in the use of conventional resists. The resist provided according to this invention is also capable of forming an excellent heat-resistant positive resist image by short-time exposure to radiation.

Simulation of x‐ray resist line edge profiles

Abstract: X‐ray resist line edge profiles are explored as a function of exposure, mask, and resist properties. The study is based on an exposure‐scission and development‐etching model of positive resists. Development rate curves for two actual and three hypothetical resists are used. The simulation is implemented by using a string of points to follow the contour of the developer–resist interface as a function of development time. Control of the resist profile suitable for liftoff of 0.4‐μm lines is explored in the context of low flux levels for a high throughput production environment. High aspect ratio lines (3:1) and profiles degradation due to mask edge effects for Alkα and CuL exposures are considered.