Showing papers on "Lithography published in 1985"

Modeling of Lithography Related Yield Losses for CAD of VLSI Circuits

Abstract: In this paper, a modeling technique, describing IC manufacturing yield losses in terms of parameters characterizing lithography related point defects and line registration errors, is presented. Optimization of geometrical design rules, evaluation of VLSI IC artwork, and maximization of the wafer yield are discussed as examples illustrating applications and advantages of the proposed modeling technique.

Micron-spaced platinum interdigitated array electrode: Fabrication, theory and initial use

Abstract: Abstract : An interdigitated array (IDA) electrode composed of 40 pairs of 0.3 micrometers thick Pt fingers 3.5 micrometers wide and separated by 2.5 micrometer gaps of insulating borosilicate glass substrate has been fashioned by a modified microlithographic technique. The two IDA is applied to measurement of redox electron conduction through films of poly-Os(bpy)2 (vpy)2 (C1O4)2, poly-CRu(bpy)2 (vpy)2 (C104)2, and Prussian Blue that had been electrochemically deposited over the Pt fingers and in te insulating gaps. Appropriate theory for using the IDA for this purpose is developed. Electrochemically generated luminescence from solutions of Ru(bpy)3 (2+) is also observed with the IDA. (Author)

Electron Beam Fabrication Of Computer-Generated Holograms

Abstract: We report here the development of an integrated capability for writing computer-generated holograms (CGHs) using either of two commercially available electron-beam lithography systems. These binary, chrome-on-glass holograms have been used extensively for aspheric optical testing and also have applications to the interferometric recording of holograms. Algorithms are described for encoding CGHs for drawing by e-beam systems. Limitations of e-beam CGH fabrication are discussed. A self-contact lithography and ion milling process is described for con-verting chrome-on-glass holograms into 40% efficient, environmentally durable all-glass holograms.

Electron-beam fabrication of GaAs low-noise MESFET's using a new trilayer resist technique

Abstract: A LO/HI/LO resist system has been developed to produce sub-half-micrometer T-shaped cross section metal lines using e-beam lithography. The system provides T-shaped resist cavities with undercut profiles. T-shaped metal lines as narrow as 0.15 µm have been produced. GaAs MESFET's with 0.25-µm T-shaped Ti/Pt/Au gates have also been fabricated on MBE wafers using this resist technique. Measured end-to, end 0.25-µm gate resistance was 80 ω/mm, dc transconductance g m as high as 300 mS/mm was observed. At 18 GHz, a noise figure as low as 1.4 dB with an associated gain of 7.9 dB has also been measured. This is the lowest noise figure ever reported for conventional GaAs MESFET's at this frequency. These superior results are mainly attributed to the high-quality MBE material and the advanced T-gate fabrication technique employing e-beam lithography.

Absolute two-dimensional sub-micron metrology for electron beam lithography: A calibration theory with applications☆

Abstract: A mathematical theory is presented along with some simple resulting procedures that permit an electron beam lithography machine to be calibrated by using it to make multiple observations of an imprecisely defined but stable planar object The calibration thus obtained yields a degree of accuracy that is approximately equal to the reproducibility of the machine For this purpose a rigid, movable grid plate is used, with grid points placed at arbitrary but more-or-less evenly distributed, fixed positions on its surface An e-beam lithography machine with a high precision X-Y stage has been used to measure such a grid plate Two interferometer beams, nominally parallel to the X- and Y-axes, measure stage displacements No geometric assumptions are made concerning the stage, other than repeatability Although the assumptions are very general, it is possible to observe the grid in just three orientations to determine both an inverse distortion function (calibration) and accurate, absolute rectangular coordinates for the grid points, providing that the absolute distance between a pair of points on the grid is known A calibration program has been written applying the theory to the practical problem of calibrating an e-beam lithography system Simulations based upon actual e-beam measurements confirm the theory for the practical situation The paper concludes with suggestions for applictions to three other areas of science and technology: astronomy, optometry, and satellite geodesy

Infrared mesh filters fabricated by electron‐beam lithography

Abstract: Capacitive and inductive infrared mesh filters have been fabricated using electron‐beam lithography combined with a lift‐off procedure. A single level of PMMA was used to create positive tone patterns while a two‐level metal‐on‐polymer process was used to create negative tone patterns. Resonant structures consisting of arrays of crossed metal dipoles and arrays of crossed slots in otherwise continuous metal films have been fabricated that have linewidths less than 0.25 μm, and which exhibit bandstop and bandpass transmissive properties, respectively.

Self-developing polysilane deep-uv resists - photochemistry, photophysics, and submicron lithography

Abstract: A new class of alkyl silane copolymers with relatively facile self-developing behavior under deep UV exposure has been examined. These materials can reproduce 0.8 μ features by projection lithography with a KrF excimer light source. The mechanism of material removal is primarily photochemical in nature and yields chemically inert volatile siloxanes as the major photoproducts, via a high quantum yield silylene expulsion/oxidation process.

Multiple channel electron beam optical column lithography system and method of operation

Abstract: The invention provides an improved direct-write/read charged particle beam lithography/readout system employing multiple channel charged particle beam optical columns wherein a plurality of individually controlled, single deflector stage charged particle beam optical columns are operated in parallel to simultaneously write or read the same or complementary semiconductor device microcircuit patterns on a plurality of different target areas of a semiconductor target wafer whereby considerably increased thru-put of a microcircuit fabrication facility is achieved.

Soft x-ray lithography using radiation from laser-produced plasmas

Abstract: Plasmas formed by focusing 0.6-J pulses from a 10-Hz Nd:YAG laser onto solid targets were used as soft x-ray sources for lithographic studies. Results of exposing masked photoresists to plasma radiation produced using steel, copper, and tungsten as targets are presented.

Application of a focused ion beam system to defect repair of VLSI masks

Abstract: A scanning ion beam lithography system has been used for the rework of chromium‐on‐glass mask plates to repair defects in the VLSI circuit pattern. By using submicrometer diameter beams of gallium and of gold ions to sputter selected areas of the mask, both clear and opaque areas have been generated on the substrate.

Optical single layer lift-off process

Abstract: The lithography of the metal wiring layers is becoming the most confining technology in the era of VLSI (very large-scale integration), as more and more circuits have to be wired on the chip itself. The two competing technologies are subtractive etch (wet or dry), and additive metal lift-off. As lift-off needs no etching, it inherently offers cost and density advantages. It, however, requires an undercut photoresist profile. These undercuts can be achieved with an image-reversal process. The paper describes such a reversal process, especially tuned for lift-off applications. The result is a simple single-layer lift-off technology with excellent image quality.

Method and apparatus for in-situ plasma cleaning of electron beam optical systems

Abstract: A method and apparatus for in-situ cleaning of charged particle beam optical systems such as electron microscopes, electron beam lithography systems, ion beam microscopes or lithography systems, through the use of a specially introduced plasma forming gas such as hydrogen that is excited by applying a high voltage, high frequency excitation potential between various optical elements of the electron beam optical column. Alternately, specially constructed separate plasma forming electrodes can be built into the electron beam optical system for this purpose. During the cleaning operation the plasma reacts chemically with the contaminants previously formed on the surface of the electron beam column optical elements to form gaseous reactants which then are pumped out of the electron beam column system.

Mask structure for lithography, method for preparation thereof and lithographic method

Abstract: A mask structure for lithography has a ring frame holding the peripheral portion of a thin film for holding a mask material, the mask material holding thin film comprising a layer of aluminum nitride.

Electron lithography for the fabrication of microelectronic devices

Abstract: Electron lithography is a technique which is in widespread use for making masks and reticles for the manufacture of integrated circuits. It is also commonly used in research laboratories for exposing micron or sub-micron patterns directly on wafers. In addition, direct exposure is used, to a limited extent, in manufacturing plants, although generally at coarser resolutions. The reasons for using electron lithography in these applications are explained, and a history of the technique's evolution is given. The two major types of instrument-the scanning instrument and the projection instrument-are described and their limitations are pointed out. Interactions between electrons with energies of tens of keV (the energies typically used in electron lithography), the substrate (wafer or mask plate) and the resist material (in which a latent image is formed) are discussed. It is shown how these interactions affect the quality of the resist image before and after development.

Submicron pattern fabrication by focused ion beams

Abstract: A focused ion beam (FIB) technology has many advantages for submicron structure fabrication and other maskless processes. In order to develop 4–16 M(D) RAM, the FIB technology is strongly desired for its capability of submicron lithography without proximity effects.

8 nm Wide Line Fabrication in PMMA on Si Wafers by Electron Beam Exposure

Abstract: The ultimate limit of electron beam lithography in practical samples, e.g., thick PMMA on bulk Si substrate, was investigated in both experiment and theory. For this, the nanometer electron beam lithography system (NSF-1) was used to perform nanometer structure patterning. Monte Carlo calculation with secondary electron generation included was done to simulate the experiment. Eight nanometer wide lines with 100 nm period were delineated in 230 nm thick PMMA on a bulk Si, probably attaining the ultimate limit of electron beam fabrication. This has also been supported by evaluation based on the Monte Carlo simulation.

Silicon-containing novolak resin and resist material and pattern forming method using same

Abstract: Disclosed is a novel novolak resin comprising structural units having a trimethylsilyl group. A resist material highly resistive to dry etching is obtained by adding a photosensitive diazo compound to this novolak resin. The resist material is useful in various lithography methods to form a positive resist pattern. This resist material is used in a pattern forming method of a two-layer type, in which a fine pattern is formed in a thin film of the resist material by lithography and then transferred into an underlying thick organic polymer layer by dry etching of the underlying layer with the resist pattern as mask. Curing of the resist pattern by irradiation with deep UV rays is effective for further improvement in the precision of the transferred pattern.

0.1 μ scale lithography using a conventional electron beam system

Abstract: A commercial electron beam machine has been used in conjunction with high contrast resists to define patterns with dimensions close to the minimum beam diameter of 0.1 μ on a range of solid substrates. This has required a detailed knowledge of the beam‐substrate interactions in order to control linewidth. The electron scattering profiles in thin resist layers have been experimentally determined for substrates of Si, GaAs, InP, and Au on Si, and for beam voltages between 10 and 50 kV. These experimental results have been correlated with empirical models of electron scattering. It has been found that the simple double Gaussian model is inadequate at these dimensions, and the addition of an exponential term is necessary to fit data adjacent to the primary beam. Exposures have been modeled using this three term approximation, and the resultant lithography predicted by taking account of resist contrast. Routine fabrication of asymmetric 0.46 μm period gratings on InGaAsP substrates, used in the manufacture of distributed feedback lasers, has been possible, while experimental nonperiodic structures of 0.1–0.2 μ dimensions have been made on Si and InP. The reduction of backscattering by a multilevel resist system on Si has been studied with planarizing layer thicknesses up to 2 μm, and beam voltages of 20 and 30 kV.

Contamination Lithography For The Fabrication Of Zone Plate X-Ray Lenses

Abstract: A VG HB5 STEM has been modified to allow computer controlled contamination writing on thin Carbon substrates. Line widths of 20 nM and height to width aspect ratios of better than 5:1 can be drawn. This writing has been used to fabricate Fresnel zone plates. A patching process is involved with registration to an accuracy of 2.5 nM. Methods and techniques have been developed to compensate for non-linearity of the field scans together with specimen drift. Zone plates of 50 NM diameter and outer zone widths of 40 nM have been con-structed.

Self‐developing photoresist using a vacuum ultraviolet F2 excimer laser exposure

Abstract: An F2 excimer laser at 157 nm has been used for the first time as an exposure source for high resolution photolithography with the self‐developing resist nitrocellulose. Ablative development of the nitrocellulose was observed for 157‐nm energy densities greater than 0.025 J/cm2. Stencil masks fabricated using electron beam lithography were used for contact photolithography, and mask features to 200 nm were reproduced. These are the smallest features yet reproduced from a mask with an optical, self‐developing resist technology.

Submicrometer-resolution etching of integrated circuit materials with laser-generated atomic fluorine

Abstract: We have demonstrated submicrometer‐resolution lithography by ultraviolet laser‐induced radical etching. We previously showed that this method can provide highly specific and efficient etching of various refractory metal/insulator and semiconductor/insulator substrate combinations.

Multilayer resists with improved sensitivity and reduced proximity effect

Abstract: The present invention discloses multi-layered resist structures and methods of producing them which can be used in electronic device lithography to produce micrometer and submicrometer geometries. The resist structure comprises two or more layers at least one of which is a metallic material and at least one of which is a radiation-sensitive material. The metallic layer exhibits both a high atomic number and a high density. The metallic material is positioned relative to the radiation-sensitive polymeric material so that it can be used to control reflection and backscatter of radiation used to create a latent image within the radiation-sensitive polymeric material. The thickness of the metallic layer is determined by the amount of reflection desired and the amount of backscatter permitted into the layer of radiation-sensitive polymeric material.

Mask for X-ray lithography

Abstract: The invention relates to a mask for X-ray lithography, in particular, for the manufacture of VLSI semiconductor components, which is economical and reliable in its manufacture. The mask should transfer absorber structures down to the submicron range. Lateral mechanical distortions are avoided by a tension-compensated carrier membrane of simultaneously B and Ge doped silicon. This carrier membrane is also optically more transparent than known Si membranes doped only with B, which facilitates optical alignment of the mask.

Adaptive X-ray lithography mask

Abstract: Provided is an apparatus for improving alignment accuracy by distorting in a controlled manner an X-ray lithographic mask to compensate for mask distortions induced primarily by thermally induced clamping effects in E-beam and X-ray exposure systems. A system of additional alignment sensors is used to provide localized misalignment information. This information is then used to provide feedback to a servo system which in turn activates electromechanically translatable clamps which distort the X-ray mask so as to minimize misalignment over the exposure field.

Ion beam lithography at nanometer dimensions

Abstract: Factors affecting the ultimate resolution of ion beam lithography are discussed. These factors are primary ion scattering, recoil atom scattering, range of secondary electrons, and resist properties (i.e., resist sensitivity and molecule size in the resist). From a consideration of these factors, it is estimated that minimum linewidths of ≲10 nm can be achieved in polymethyl methacrylate (PMMA) using light ions. For heavy ions such as gallium, the resolution limit is estimated to be ∼30 nm with the limitation being due to recoil atom scattering. Fabrication of high resolution silicon nitride stencil masks is described and replication of the masks with protons in PMMA is demonstrated with features as small as 20 nm.

Method and device for lithography

Abstract: PURPOSE:To enhance an operating efficiency in process of lithography, by spraying a water repellent liquid on the hydrophilic surface of a plate. CONSTITUTION:A volatile organic solvent in which a water repellent matter is dissolved is sprayed on a plate for lithography wherein a hydrophilic treatment is applied on the surface thereof by an ink jet method according to an image information. At this time, quick volatilization of the organic solvent allows the water repellent matter to adhere only on the water repellent matter sprayed portion of the water hydrophilic surface of the plate for lithography. In this manner, an image portion having a lipophilic surface and a non-image portion having a hydrophilic surface can be formed on the plate for lithography, which enables an operating efficiency to be enhanced.

Repair of x‐ray lithography masks using UV‐laser photodeposition

Abstract: UV‐laser photodeposition of cadmium has been adapted to the repair of clear defects in fully fabricated polymide membrane x‐ray lithography masks. The spatial resolution of the process has been explored with carbon x‐ray exposures and was found adequate for one‐step repair of 1 μm defects. Repair of smaller features should be possible with photodeposition in combination with ion milling with a focused ion beam. A new photodeposition process has been developed for lead, a material with better x‐ray opacity than Cd for many practical x‐ray wavelengths. Both materials can be deposited with good edge definition and without damage to the fragile x‐ray mask membrane.

Mask-to-wafer alignment utilizing zone plates

Abstract: Mask-to-wafer alignment in X-ray lithography is advantageously carried out utilizing zone plate marks formed on the mask and wafer. In practice, it has been observed that the intensity and in some cases even the location of the centroid of the light spot formed by a zone plate mask can vary during alignment as the mask-to-wafer spacing is changed. In accordance with the invention, the zone plate (18) on the mask (12) is encompassed within an illumination blocking layer (72) for preventing undesired transits and reflections of the illuminating beams.