Patents by Inventor Tadao Yasuzato

Tadao Yasuzato has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 6150059
    Abstract: A photomask has a plurality of main holes which pass a prescribed light beam that is shone onto positions that make up a plurality of pattern parts, at locations that are opposite a plurality of pattern parts for said semiconductor device, this photomask also having a plurality of minute auxiliary holes, which pass a light beam of a degree that is not transferred at the time of exposure, these auxiliary holes being disposed between the main holes.
    Type: Grant
    Filed: October 29, 1998
    Date of Patent: November 21, 2000
    Assignee: NEC Corporation
    Inventors: Hiroyoshi Tanabe, Shinji Ishida, Tadao Yasuzato
  • Patent number: 6004699
    Abstract: A photomask used for a projection exposure equipment comprises a transparent substrate and a light intercepting film provided on the transparent substrate. The transparent substrate comprises a main pattern region and an auxiliary pattern region provided in a periphery of the main pattern region. The auxiliary pattern region is etched to a depth at which a phase difference arises between light transmitted through the main pattern and light transmitted through the auxiliary pattern. The phase difference is of substantially an integral number of times as large as 360 degrees, wherein the integral number is one selected from the group consisting of integral numbers of one or more and integral numbers of minus one or less. The light intercepting film comprises openings on the main pattern region and the auxiliary pattern region.
    Type: Grant
    Filed: February 26, 1998
    Date of Patent: December 21, 1999
    Assignee: NEC Corporation
    Inventors: Tadao Yasuzato, Shinji Ishida
  • Patent number: 5935738
    Abstract: To a projection lens system is added spherical aberration of 0.1.lambda., and the exposure is performed by using a phase-shifting mask having a phase difference of 200 degrees which is provided with a phase error of 20 degrees corresponding to the spherical aberration amount. Therefore, the focus characteristic can be more remarkably flattened as compared with the prior art in which the phase difference of the mask is set to 180 degrees and the spherical aberration of the projection lens system is set to zero, so that the depth of focus can be enlarged by about 0.2 micron and the precision of the pattern dimension of semiconductor devices manufactured by using the exposure method can be enhanced.
    Type: Grant
    Filed: February 18, 1998
    Date of Patent: August 10, 1999
    Assignee: NEC Corporation
    Inventors: Tadao Yasuzato, Shinji Ishida
  • Patent number: 5908718
    Abstract: Disclosed is a photomask, which has: a transparent substrate; and masking film which is selectively formed on the transparent substrate to provide a predetermined pattern composed of a transparent region and a masking region; wherein the transparent region comprises a first transparent region which is formed adjacent to the masking region and extends like a belt along the masking region and a second transparent region which lies sandwiching the first transparent region with the masking region, whereby a phase of exposure light through the first transparent region is advanced prior to that through the second transparent region.
    Type: Grant
    Filed: March 31, 1997
    Date of Patent: June 1, 1999
    Assignee: NEC Corporation
    Inventors: Shinji Ishida, Tadao Yasuzato
  • Patent number: 5827623
    Abstract: In a halftone type phase shift photomask, a patterned halftone layer is formed on a transparent substrate, and a light screen layer is formed on the halftone layer. A part of a mask pattern is changed from opaque to halftone, thus improving the resist pattern fidelity.
    Type: Grant
    Filed: October 30, 1996
    Date of Patent: October 27, 1998
    Assignee: NEC Corporation
    Inventors: Shinji Ishida, Tadao Yasuzato
  • Patent number: 5792596
    Abstract: In a method of forming a pattern, a photo-mask including a desired pattern is provided. A photo-sensitive resin film is spin-coated on a semiconductor substrate. Subsequently, the surface of the photo-sensitive resin film is changed to have a resistivity against a development solution. Next, light is illuminated to transmit the photo-mask. As a result, the resistivity of only the surface portion of the photo-sensitive resin film corresponding to the desired pattern is decreased based on the property of photo-sensitive resin film by the light having transmitted the photo-mask. Last, the photo-sensitive layer is developed with the development solution.
    Type: Grant
    Filed: February 6, 1996
    Date of Patent: August 11, 1998
    Assignee: NEC Corporation
    Inventors: Tadao Yasuzato, Shinji Ishida, Kunihiko Kasama, Yoko Iwabuchi
  • Patent number: 5750290
    Abstract: After forming a light shielding layer 2 of ruthenium in a thickness of 70 nm and a reflection preventing layer 3 of a ruthenium oxide in thickness of 30 nm, and a photosensitive resin layer, a sililated layer is formed by electron beam lithography and sililation. Etching is performed for the photosensitive resin layer, and the reflection preventing layer and the light shielding layer are dry etched using oxygen gas with taking the sililated layer as a mask. By this, dimensional precision of a pattern of a photo mask can be improved.
    Type: Grant
    Filed: April 19, 1996
    Date of Patent: May 12, 1998
    Assignee: NEC Corporation
    Inventors: Tadao Yasuzato, Shinji Ishida
  • Patent number: 5644390
    Abstract: In an intensity distribution simulation method for a demagnification projection aligner, the light intensity distribution due to each of unit lenses constituting an integrator is approximated with a Gaussian-distribution approximate equation to thereby model the integrator, and the light intensity distribution of a reticle pattern (mask pattern) on an image plane is calculated on the basis of the calculated light intensity distribution of the modeled integrator.
    Type: Grant
    Filed: January 31, 1995
    Date of Patent: July 1, 1997
    Assignee: NEC Corporation
    Inventor: Tadao Yasuzato
  • Patent number: 5636005
    Abstract: A projection aligner is equipped with a diaphragm having four sectoral openings arranged in symmetry with respect to orthogonal symmetrical lines respectively aligned with two orthogonal directions of a reticle pattern, and a rotating system is provided for a fly-eye lens so as to align two orthogonal symmetrical lines of the fly-eye lens with the two orthogonal symmetrical lines of the diaphragm, thereby improving a resolution of the reticle pattern on a photo-resist layer.
    Type: Grant
    Filed: January 31, 1995
    Date of Patent: June 3, 1997
    Assignee: NEC Corporation
    Inventor: Tadao Yasuzato
  • Patent number: 5619304
    Abstract: Rays of light from a super-high pressure mercury lamp are collected by an oval mirror, reflected by a cold mirror and additionally rendered parallel. The parallel light is passed through an interference filter and enters as incident light to individual lens units of a fly-eye lens. The individual lens units improve uniformity of intensity distribution and coherency of the light and act as isolated light sources. Right after the fly-eye lens is placed an aperture member that determines the form of an effective light source. The light passes through the aperture member, a cold mirror and a condenser lens to illuminate a reticle. A pattern of the reticle is projected on a semiconductor substrate coated with a photosensitive resin, by a projection lens system. The resolution property and exposure intensity of a reduction exposure apparatus is improved and aperture member positioning is facilitated. The throughput of the system can also be improved.
    Type: Grant
    Filed: November 29, 1994
    Date of Patent: April 8, 1997
    Assignee: NEC Corporation
    Inventor: Tadao Yasuzato
  • Patent number: 5532497
    Abstract: A projection aligner transfers a pattern image of a reticle by using a light radiated from a light source through a diaphragm to a photo-resist layer, and the position of the light source is automatically regulated on the basis of pieces of illuminance data simultaneously measured on an image forming plane so that the regulation is exact and completed within a short time period.
    Type: Grant
    Filed: December 20, 1994
    Date of Patent: July 2, 1996
    Assignee: NEC Corporation
    Inventors: Tadao Yasuzato, Hiroshi Nozue, Seiichi Shiraki
  • Patent number: 5439767
    Abstract: A periodic line and space pattern made of chromium film is formed on a glass substrate, and a phase shifter is arranged on every other transparent portion of the line and space pattern. Using a stepper and the phase shift mask, photoresist film coated on a wafer is exposed several times to light of i-line by varying the focus, then developed. Next, the width Ws of the photoresist pattern formed by the exposure to the light through the phase shifter, and the width Wo of the photoresist pattern formed by the exposure to the light without passing through the phase shifter are measured. Based on the relation between Ws and Wo for defocusing, the transmittance error and the phase shift angle error of the phase shifter are obtained.
    Type: Grant
    Filed: February 17, 1994
    Date of Patent: August 8, 1995
    Assignee: NEC Corporation
    Inventors: Hiroshi Yamashita, Tadao Yasuzato
  • Patent number: 5060843
    Abstract: A process of forming bumps on respective electrodes of a semiconductor chip comprises the steps of a) preparing a bonding apparatus equipped with a bonding tool three-dimensionally movable, b) forming a small ball at the leading end of a wire passing through the bonding tool, c) causing the bonding tool to press the small ball against the upper surface of one of the electrodes for bonding thereto, d) moving the bonding tool in a direction leaving from the upper surface of the electrode by a distance, e) moving the bonding tool in a horizontal direction substantially parallel to the upper surface of the electrode so that the wire is cut from the small ball with the leading end of the bonding tool, and f) repeating the steps b) to e) for producing bumps on the respective upper surfaces of the other electrodes, in which the horizontal direction is different depending upon the location of the electrode.
    Type: Grant
    Filed: June 1, 1990
    Date of Patent: October 29, 1991
    Assignee: NEC Corporation
    Inventors: Tadao Yasuzato, Keizo Sakurai