Showing papers on "Resist published in 1988"

Resolution limits for electron-beam lithography

Abstract: This paper discusses resolution limits for electron-beam fabrication. Electron beams have been used to produce structures 1 nm in size and useful devices with minimum features of about 20 nm. In all cases the resolution is set primarily by the range of the electron interaction phenomena that form the structures, and not by the size of the electron beam used to write the patterns. The beam can be as small as 0.5 nm. All useful devices built to date have been fabricated with conventional resist processes; these have an ultimate resolution of about 10 nm. Experimental data for PMMA, the highest-resolution electron resist, show that resolution is independent of molecular weight and is therefore not a function of the molecular size. The most promising of the methods offering resolution below 10 nm is the direct sublimation of materials such as AIF3 and Al2O3; 1-nm structures have been fabricated, but it has not been possible to convert the structures into useful devices. In addition to the processes which use intermediate patterned layers, there is the possibility of making devices by direct modification of the electrical properties of conductors, semiconductors, or superconductors by means of high-energy electron bombardment. In these cases no intermediate fabrication process would be used, and it might be possible to reach dimensions comparable to the beam diameter.

Dispenser for multiple rolls of sheet material

Abstract: A multiple roll towel dispenser The dispenser cabinet has a pair of feed rollers forming a feed roll nip, means for driving one of the feed rollers to dispense web from the cabinet, means in the cabinet for supporting a first roll of web material with its web extended between the feed roll nip, and means for supporting a second roll of web material with its web extended adjacent to the feed roll nip The dispenser also includes means, contacting the edge of the first roll, having a first position for sensing the diameter of the first roll; means, connected to the sensing means, for biasing the sensing means against the edge of the first roll; biased transfer means for introducing the extended web of the second roll into the feed roll nip; and stop means, connected to the sensing means, the stop means being located to resist motion of the transfer means at a ready position when the edge of the first roll resists movement of the sensing means When the edge of the first roll no longer resists movement of the sensing means, the sensing means and connected stop means moves to a second position which allows the biased transfer means to move to a transfer position where the extended web of the second roll is introduced into the feed roll nip

Trilayer microlithographic process using a silicon-based resist as the middle layer

Abstract: A method for patterning an integrated circuit workpiece (10) includes forming a first layer (16) of organic material on the workpiece surface to a depth sufficient to allow a substantially planar outer surface (36) thereof. A second, polysilane-based resist layer (22) is spin-deposited on the first layer (16). A third resolution layer (24) is deposited on the second layer (22). The resolution layer (24) is selectively exposed and developed using standard techniques. The pattern in the resolution layer (24) is transferred to the polysilane layer (22) by either using exposure to deep ultraviolet or by a fluorine-base RIE etch. This is followed by an oxygen-based RIE etch to transfer the pattern to the surface (18) of the workpiece (10).

X‐ray lithography

Abstract: X‐ray lithography with wavelengths between 0.2 and 5 nm provides both high‐structural resolution as good as 0.1 μm and a wide scope of advantages for the application in circuit production. Examples for this better process performance compared to optical techniques are: lower particle and dust sensitivity, applicability of simple single‐layer resist technique, high depth of focus without any influence of substrate material and chip topography, and presumably, the highest throughput of all lithography methods which are able to go into the submicron range. However, the introduction of x‐ray lithography into the semiconductor production means a revolutionary change of production technology. This begins with a completely different mask technology which makes, for example, the classical separation of mask substrate fabrication from pattern generation by different manufacturers very problematical and ends with the necessity to introduce x‐ray lithography in relatively large production capacity units consisting of a larger number of x‐ray steppers. The latter is caused by the fact that a storage ring—even in the smallest version, e.g., COSY (Kompakt Speicherring fur Synchrotronstrahlung)—has to supply up to 10 x‐ray steppers with light in order to clearly beat the optical techniques with respect to throughput and lower cost level. To prove such statements in pilot production lines, the necessary tools and components for x‐ray lithography are already or will be available for the first time on a commercial basis in the very near future. Especially steppers, sources, and resists with satisfying specifications have been announced by a growing number of vendors. The most critical problem at present is the mask technology and the tools for defect elimination. However, with the existing technologies, the requirements for 0.5‐μm‐design rules will be met very soon on a pilot scale.

Soft x‐ray projection lithography using an x‐ray reduction camera

Abstract: Soft x‐ray projection lithography can now be realized with recent developments in x‐ray optics. Using new x‐ray optical components and spherical imaging optics, we have designed an x‐ray reduction camera which is capable of projecting with soft x‐ray radiation, a 5× demagnified image of a mask onto a resist coated wafer. The resolution of this design is ∼100 nm with a depth of focus of ±5.6 μm and a 0.5‐cm‐diam image field. We use x‐ray reflecting masks (patterned x‐ray multilayer mirrors) which are fabricated on thick substrates and can be made relatively distortion free. Our design uses a laser produced plasma for the x‐ray source. Better resolution and/or larger areas are possible with improvements in optic figures and source characteristics.

Lift‐off metallization using poly(methyl methacrylate) exposed with a scanning tunneling microscope

Abstract: The scanning tunneling microscope (STM) is a unique tool for ultrahigh resolution, ultralow voltage electron beam lithography. In a previous paper we described the formation of metallic patterns by a ‘‘contamination’’ process followed by sputter etching. Here we report the formation of 22‐nm‐wide metal lines by STM exposure of poly(methyl methacrylate) (PMMA) resist followed by liftoff. Resist exposure and liftoff have also been achieved with reverse polarity, where the electrons are emitted from the resist sample and accelerated towards the tip. Results include the first working device made with a STM, a thin‐film resistor 2 μ long and 120 nm in width. In addition to lithographic applications, studying resists in this regime may offer new insights on the chemical process of resist exposure and the role played by secondary electrons in exposing resist. Our results indicate that PMMA only works as a negative resist for energies above 25 eV; below this value it appears that the electrons cannot cause suffic...

Resist ink composition

Abstract: A photosetting liquid ink composition developable with a dilute alkaline aqueous solution and comprising (A) a resin curable with an activated energy ray, obtained by the reaction of a saturated or unsaturated polybasic acid anhydride with a product of the reaction of a novolak type epoxy compound and an unsaturated monocarboxylic acid, (B) a photopolymerization initiator, and (C) a diluent can be used for the production of an etching resist or a solder resist in the manufacture of a printed circuit This composition, when combined with a thermosetting component, produces a photosetting and thermosetting liquid ink composition

Excimer laser patterning of a novel resist

Abstract: A dual layer resist configuration is employed for photopatterning high resolution conductive patterns on underlying polymeric or ceramic substrates, particularly substrates exhibiting surface roughness and non-planar design features such as channels, bosses and ridges. More particularly, a thin underlayer of ablatable photoabsorptive polymer is disposed on a metal coated substrate, after which a thicker layer of substantially transparent material is disposed over the polymer. A beam of laser energy, such as that produced by an ultraviolet excimer laser, is directed through the upper layer and is absorbed by the lower layer which is ablated and simultaneously removes the thick layer above it. This results in the ability to etch high resolution features on polymeric and other substrates, particularly copper coated polyetherimide circuit boards. The resist system is also applicable to VLSI wafers even though such wafers usually do not exhibit surface roughness on the scale generally considered herein. It is also equally applicable in various high density interconnect systems used for the direct connection of chip devices. A mask for patterning and a method for making it are also seen to be desirable because of the high laser energy densities generally desired for thorough ablation.

Deep-submicrometer MOS device fabrication using a photoresist-ashing technique

Abstract: A photoresist-ashing process has been developed which, when used in conjunction with conventional g-line optical lithography, permits the controlled definition of deep-submicrometer features. The ultrafine lines were obtained by calibrated ashing of the lithographically defined features in oxygen plasma. The technique has been successfully used to fabricate MOSFETs with effective channel length as small as 0.15 mu m that show excellent characteristics. An NMOS ring oscillator with 0.2- mu m devices has been fabricated with a room-temperature propagation delay of 22 ps/stage. Studies indicate that the thinning is both reproducible and uniform so that it should be usable in circuit as well as device fabrication. Since most polymer-based resist materials are etchable with an oxygen plasma, the basic technique could be extended to supplement other lithographic processes, including e-beam and X-ray processes, for fabricating both silicon and nonsilicon devices and circuits. >

A review of excimer laser projection lithography

Abstract: Excimer‐laser projection lithography now appears to be in a position to extend production optical techniques to dimensions approaching 0.25 μm. Such methods could well be the basis for the bulk of the advanced manufacturing capability in microelectronics over the next decade. This technology is reviewed with an eye to the state of the art and to the optical‐, resist‐, and materials‐engineering issues that it presents.

Method of connecting electronic element to base plate

Abstract: An electronic element is connected to a base plate provided with a metallic pattern and a conductive resist layer superposed thereon by a thermal compression process with an adhesive layer sandwiched between the element and the base plate The adhesive layer contains many metallic particles which are larger than the layer thickness of the resist such that these metallic particles penetrate the resist layer and invade the metallic pattern by the thermal compression process

Method of manufacturing molds for molding optical glass elements and diffraction gratings

Abstract: A base material excellent in heat resistance and high-temperature strength is processed into a desired configuration. The processed base material is coated with a heat-resistant film having excellent strength at high temperatures and low reactivity with a glass material to be molded. A resist is applied on the heat resistant film and a desired pattern is drawn thereon by means of electron beam, ion beam, hologram exposure, or ordinary photolithography. Or if a mold having deep unevenness of the pressing surface is required, the resist is applied after an intermediate layer which permits selective etching is formed on the heat resistant film, and the required pattern is drawn thereon by means of electron beam, ion beam, hologram exposure, or ordinary photolithography. The intermediate layer is removed by wet etching or dry etching to emphasize unevenness of the mask. The resist film or the resist film and intermediate layer film are completely removed and a part of the heat-resistant film is removed to obtain a mold having the desired configuration of the molding surface.

Laser plasma x‐ray sources for microlithography

Abstract: A plasma produced by laser irradiation of solid targets is a promising candidate as an efficient x‐ray lithography source. In order to design a practical laser created x‐ray source, it is necessary to study the factors affecting the x‐ray emission. For this purpose, we investigate both theoretically and experimentally the influence of the laser target parameters on the x‐ray emission in different spectral ranges for two laser wavelengths (λ=1.06 μm, λ=0.26 μm). From these results and considering mask transmission, resist sensitivities, and wafer throughput, we establish the characteristics of the laser required as an x‐ray lithography source with performance acceptable for industrial applications.

Requirements on resist layers in deep‐etch synchrotron radiation lithography

Abstract: To fabricate microstructures with heights of several hundred micrometers and great aspect ratios by the LIGA (German acronym for LIthographie, Galvanoformung, Abformtechnik) process thick poly(methylmethacrylate) (PMMA) resist layers are produced on a metallic base plate. The requirements these resist layers must fulfill are reported. It is shown that it is possible to achieve defect‐free structuring with high accuracy using cross‐linked PMMA with little content of residual monomer. Good adherence of microstructures with extremely small diameters, even on polished surfaces, is achieved by using an internal coupling agent which establishes a chemical bond between the substrate surface and the PMMA layer. By modifying the resist composition requirements dependent on product specifications can be fulfilled.

Excimer laser patterning of a novel resist using masked and maskless process steps

Abstract: A dual layer resist configuration is employed for photopatterning high resolution conductive patterns on underlying polymeric or ceramic substrates, particularly substrates exhibiting surface roughness and non-planar design features such as channels, bosses and ridges. More particularly, a thin underlayer of ablatable photoabsorptive polymer is disposed on a metal coated substrate, after which a thicker layer of substantially transparent material is disposed over the polymer. A beam of laser energy, such as that produced by an ultraviolet excimer layer, is directed through the upper layer and is absorbed by the lower layer which is ablated and simultaneously removes the thick layer above it. This results in the ability to etch high resolution features on polymeric and other substrates, particularly copper coated polyetherimide circuit boards. The resist system is also applicable to VLSI wafers even though such wafers usually do not exhibit surface roughness on the scale generally considered herein. It is also equally applicable in various high density interconnect systems used for the direct connection of chip devices. A mask for patterning and a method for making it are also seen to be desirable because of the high laser energy densities generally desired for thorough ablation. An alternate method is also disclosed which employs two laser exposure steps with the first step being a masked operation on only an ablatable layer and with the second step being an unmasked operation on a dual layer material.

Apparatus for photoresist stripping

Abstract: An apparatus for rapidly stripping a photoresist which utilizes an oxidizing fluid such as ozone. A very thin layer of oxidizing fluid of four millimeters or less is flowed over the photoresist. The fluid flows at high velocity over the resist, while the resist is heated. Additionally, the resist may be irradiated with ultraviolet radiation at an irradiance of at least about 800 milliwatts/cm 2 .

Progress in deep‐etch synchrotron radiation lithography

Abstract: The recent progress in the development of the lithographic processes within the LIGA technique is reported, which is based on deep‐etch synchrotron radiation lithography, electroforming, and molding processes (in German: lithografie, galvanoformung, abformung). Mask blanks for high‐contrast x‐ray masks for 0.2 nm wavelength are fabricated from titanium and beryllium membranes produced by physical vapor deposition techniques. Absorber patterns on these masks can be produced by 50‐keV electron‐beam pattern generation in 3–5‐μm‐thick polymethylmethacrylate (PMMA) resists, because the use of beryllium strongly reduces the otherwise marked influence of electrons backscattered from the substrates on the resist profiles. To comply with the requirements of deep‐etch lithography cross‐linked PMMA resists and suitable multicomponent developers have been formulated. The casting resin‐based resists are polymerized directly on the substrate which results in extremely low internal stresses to prevent stress corrosion of the resist structure during development.

Manufacture of semiconductor device

Abstract: PURPOSE:To stabilize a transistor in characteristics by a method wherein a first gate electrode is formed, a second N.type impurity layer is formed by diffusion on the entirety or a prescribed region of a semiconductor substrate, and, in a second gate channel region, unnecessary portions of the second N-type impurity layer and the semiconductor substrate are subjected to etching. CONSTITUTION:A first N-type diffusion layer 3 is formed on a silicon substrate 1. Next, a first gate oxide film 4 is formed and, thereon, a first polycrystalline silicon 5 is formed. The first polycrystalline silicon 5 and the first gate oxide film 4 are patterned, which is accomplished according to the geometry of a second resist mask 6. An N-type impurity is diffused into the primary surface of the silicon substrate 1, and then a second N-type diffusion layer 7 is formed. A process follows wherein a third resist mask 8 is formed and the silicon substrate 1 is etched through the second and third resist masks 6 and 8. In this process, etching is so accomplished as to remove only the portions of the first N-type diffusion layer 3 and the second N-type diffusion layer 7 located not under the second and third resist masks 6 and 8. This method realizes a transistor with its characteristics stabilized.

Plasma etching using a bilayer mask

Abstract: A bilayer mask is utilized for etching a primary layer, which may be either an aluminum metallization layer or a dielectric layer. The bilayer mask includes both a thin resist layer and a metal imaging layer. The thin resist layer provides for high resolution patterning of the metal imaging layer. The metal imaging layer, in turn, provides for durability to withstand subsequent plasma etching of the underlying primary layer.

Manufacture of semiconductor device

Abstract: PURPOSE:To promote the microminiaturization of the patterns in a semiconductor device and to contrive to enhance the integration thereof by a method wherein parts of a film, such as an Al film, to be formed on the substrate are removed, an etching is performed by a reactive ion-etching method and the residual film is removed by performing a wet etching via an oxygen gas plasma process. CONSTITUTION:An Al film 3 or an Al alloy film is formed on a semiconductor substrate 1 and after the desired patterns are formed of a photo resist utilizing a photolithography technique, a reactive ion-etching is performed using the patterns as masks. Then, phosphoric acid etching liquid, such as mixed liquid of phosphoric acid, acetic acid and anitric acid; from which organic attachments being constituted with a resist, which is generated during a time when a reactive ion-etching is being performed using oxygen gas and high-frequency voltage, such as voltage of 13.56MHz, in a state that the pressure in the interior of the same sealed container is brought to low pressure, as its main component are ashing-removed; is heated, the etching liquid is foggily formed and is sprayed and an etching is applied on the residual Al film.

Thermally stable photoresists with high sensitivity

Abstract: The present invention discloses particular lithographic polymeric materials and methods of using these materials, wherein the polymeric materials have acid labile or photolabile groups pendant to the polymer backbone. The polymeric materials are sufficiently transparent to deep UV radiation to permit deep UV imaging, can be used to produce resist structures having thermal stability at temperatures greater than about 160° C., and are sufficiently resistant to excessive crosslinking when heated to temperatures ranging from about 160° C. to about 250° C. that they remain soluble in common lithographic developers and strippers. The present invention also discloses resists comprising substituted polyvinyl benzoates which, after imaging, exhibit unexpectedly high thermal stability, in terms of plastic flow. These resists cannot be imaged using deep UV because they exhibit such a high degree of opacity below 280 nm; however, they are useful as the top, imaging layer in a bilayer resist process wherein the top layer acts as a mask during deep UV exposure of the bottom layer.

Ultrathin polymer films for microlithography

Abstract: Ultrathin (14–22 nm) poly(methylmethacrylate) (PMMA) films prepared by both spin casting and Langmuir–Blodgett (LB) techniques and novolac films prepared by spin casting have been explored as high‐resolution electron beam resists. One‐eighth micron lines‐and‐spaces patterns (equal to the smallest beam diameter available) have been achieved by using a Perkin Elmer MEBES I pattern generation system as the exposure tool, and the definition of 45‐nm features has recently been achieved by using a high‐resolution electron beam lithography system. [J. H. Newman, K. E. Williams, and R. F. W. Pease, J. Vac. Sci. Technol. B 5, 88 (1987)]. The etch resistance of such films is sufficiently good to allow patterning of a chromium film suitable for photomask fabrication. The most surprising result has been that the pinhole densities in 14.3‐nm LB PMMA film and 22‐nm spin‐cast novolac film are only a few per cm2, considerably lower than the density in spin‐cast PMMA films of comparable thicknesses.

Fabricating T-gate MESFETS employing double exposure, double develop techniques

Abstract: A method for forming a T-gate for a MESFET device comprises a double exposure, double develop process. In a first exposure employing lithography a layer of PMMA is applied first to a substrate and spun to a desired thickness and then baked for a predetermined period. The gate pattern was aligned to the ohmic level and either E-beam written or exposed to deep UV radiation through a quartz mask. The wafer as treated was then spray developed using a mixture of MIBK and alcohol. After coating with a Novolak resist, the same gate mask was either realigned to the Ohmic level and exposed to mid-range UV radiation in the 400 nm range or alternatively E-beam written with a modified gate pattern to eliminate the T at the gate pad. The wafer was then spray developed again, this time using LSI developer. The second photo was overexposed in order to form a large opening through the top of the T while the first photo was underexposed to make the stem of the T as narrow as possible. After an oxygen plasma descum, the wafer was spray etched with a suitable solution and then rinsed. The resultant wafer possessed a T-shaped recess for the gate configuration which then was conventionally metallized to form MESFETS.

Manufacture of semiconductor device

Abstract: PURPOSE:To assure a good contact between Ti silicide and polycrystalline silicon by forming a metal silicide layer on part of a substrate, forming an interlayer insulating film over the whole surface of the substrate, opening partly the metal silicide layer and forming polycrystalline silicon over the whole surface of the metal silicide layer, and rendering an interface between the metal silicide layer and the polycrystalline silicon to ion implantation and mixing. CONSTITUTION:A P type Si substrate 1 includes an oxide film 2, a gate oxide film 3, polycrystalline silicon 4, a N type low concentration diffusion layer 5, an oxide film side wall 6, and a N type high concentration diffusion layer 7 formed in this order thereon. Then, Ti is deposited on the whole surface of the substrate. The resulting substrate is annealed to form Ti silicide 8 on the gate electrode 4 and on the source-drain 7. Non-reacted Ti is thereafter removed. In succession, an interlayer insulating film 9 is formed and a contact hole 10 is formed using a resist pattern. Further, after a polycrystalline silicon 11 is formed, an interface between the Ti silicon 8 and the polycrystalline silicon 11 is subjected to ion-implantation of As 13 using a resist pattern 12 and subjected to mixing. In succession, after the resist pattern 12 is removed, the polycrystalline silicon 11 is etched into a desired pattern. Hereby, a good contact can be assured between the Ti silicide and the polycrystalline silicon.

High-resolution focused ion beam lithography

Abstract: The resolution of focused ion beam (FIB) lithography has been studied by proximity effect measurement and fine pattern fabrication. In the proximity effect measurement, a 0.1 μm line pattern, according to the gap between square and line patterns, could be achieved. Moreover, 0.1 μm line and space poly(methylmethacrylate) patterns and 0.1 μm linewidth novolak based negative resist could be fabricated at 1×1013 and 2×1012 ions/cm2 dose by 260 keV Be++ FIB with 0.1 μm beam diameter, respectively.

Alignment mark system for electron beam/optical mixed lithography

Abstract: A system for making alignment marks in a semiconductor for a wafer etched in alignment with and bordered by an isolation level oxide. A silicon wafer has a film stack of silicon dioxide and silicon nitride. A pattern of data and alignment marks are exposed on the films and the device is processed to define a pattern or alignment mark positions on the silicon substrated bordered by the isolation oxide. The wafer is then patterned with a resist covering the device region and leaving exposed the alignment mark positions. The wafer is then etched to create the alignment mark pattern in the wafer while the device region is protected by the resist. The resist may then be removed and device processing continued.

Achromatic holographic lithography in the deep ultraviolet

Abstract: Holographic lithography, in which the interference pattern of two coherent waves is used to expose a resist film, is the preferred technique for producing large‐area gratings with low distortion. The spatial period of a pattern produced by holographic lithography is directly proportional to the wavelength of the radiation and inversely proportional to the sine of one‐half the angle between the incoming beams. To expose gratings with periods ≊100 nm (50‐nm‐nominal linewidth) the source wavelength must be ≊200 nm. Since coherent deep‐ultraviolet sources are not readily available, we have investigated an achromatic holographic configuration which permits the use of incoherent sources (e.g., CdXe arc lamp) or short‐coherence‐length (≊10 μm) excimer lasers. The configuration consists of two gratings, one acting as a beamsplitter, the other as a recombiner. The beam from the source is split into plus and minus first‐order beams by the beamsplitter grating, and the zero order is subsequently blocked. The plus an...

Angular Etching Correlations from RIE Application to VLSI Fabrication and Process Modeling

Abstract: Etch‐rate dependency as a function of ion angle of incidence on topological features common to VLSI devices is measured under RIE conditions. Investigated are oxide, nitride, Si, poly‐Si, and Kodak micro positive resist 820 (820 resist) using fluoroform, oxygen, and other gaseous ions. Construction of a special cathode electrode allowed samples to be mounted at different angles with respect to the positive ion flux at gas pressures of 10–20 mtorr. Depending on the substrate and ionic species, angular etching correlations resolved three distinct curve shapes: (i) that showing chemisorption followed by desorption of chemical‐induced by‐product, which resembles a cosine function at low ion energy; (ii) a combination of chemical plus high‐angle sputtering produced at increased ion energies; and (iii) that characteristic due to knock‐on bombardment. Incorporation of angular etching data into a modeling program is shown to be useful for two‐dimensional simulation of etched features important to fabrication of microelectronic structures.