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A MICRO/NANO SENSORS & SYSTEMS COMPANY
|   Mask Making Processes   |

GENERAL STEPS INVOLVED IN MAKING A SET OF MASKS

  • AltIneg Device Design and Layout
  • Artwork File (DXF) or 10X or 100X plots
  • Data Generation for the mask:
    Step and repeat device patterns whithin the wafer size;
    Insertion of Alignment Structures for the double sided alignments, if any
    Insertion of Alignment Structures for the same side successive alignments;
    Insertion of critical etch depth and dimension bar patterns;
  • Application of Process DesignAltCombo for exposure and development for various type structures in close proximity
    (e.g. alternating opaque and clear strips);
  • Verification;
  • Mask Layout preparation;
  • 10X or 100X Black and clear Transparency plots using HP printer
  • (If the artwork is hand drafted, we can still use Rubylith or Amberlith to make the film for the mask);
  • (Gerber Autoprep 2000 is employed for digitizing and laser preparation of large format mask film)
    Inkjet transparencies are commonly employed;
  • A 48"X48" light board (with high UV content fluorescent lights mounted in a reflective chamber
    with a diffuser in front) is used to backlit the transparency. The transparency is aligned with
    marks on the light board so as the center of the layout approximately coincides with the center of
    the mask blank;
  • A large format camera is used to capture the transparency image directly on to a photomask blank.
    AltMASKIOM The set-up has been designed to produce a 1/10 inverted image of the transparency layout.
    A special lens is used that provides uniform reduction of the illuminated object devices from the edges and corners to the center of the layout. The large format film cassettes have been modified to accept mask blanks with  photoresist side facing the lens. For best reproduction,  the exposure time, aperture and f-stops are pre-determined based upon type of photoresist and its softbake time.
  • A 48"X48" light board (with high UV content fluorescent lights mounted in a reflective chamber with a diffuser in front) is used to backlit the transparency. The transparency is aligned with
    marks on the light board so as the center of the layout approximately coincides with the center of
    the mask blank;
  • Development of imaged pattern, hardbake, and fixing of the masks.