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Microlithography for IC Production

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It is a form of printmaking in the micron range, ... Pictures courtesy of www.charfaq.umn.edu. Other Lithography Processes. Optical Proximity Printing ... – PowerPoint PPT presentation

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Title: Microlithography for IC Production


1
Microlithography for IC Production
  • by John Broky
  • OPTI 422
  • 9/22/03

2
What is Microlithography?
It is a form of printmaking in the micron range,
predominantly used for circuits on silicon
wafers.
It creates highly accurate 2-D patterns in
photosensitive resist material, which is used to
build integrated circuits.

3
Integrated Circuits
  • Complex circuitry that fits on semiconductor
    microchips the size of a fingernail. The
    circuitry consists of several layers stacked upon
    each other where each layer contains an elaborate
    network of connections just microns in size.

4
Components of the Exposure System of a Typical
Stepper
  • Lithographic Projection Lens
  • Illumination Subsystem
  • Wafer Positioning Subsystem

5
Lithographic Projection Lens
  • Contains many simple lens
    elements
  • Images photomask with
    demagnification 5x
  • Wavefront aberration must be
    less than 1/10 the source
    wavelength
  • Corrected for chromatic
    aberration at 365nm

6
Illumination Subsystem
  • 1000 watt mercury arc lamp
  • Layers of dielectric filters allow only
    365nm light
    through
  • Light passes through relay optics and is
    projected through the
    photomask and onto
    the entrance pupil of the lithographic lens
  • Non-uniformity must be less than 1
  • Photoresist is exposed to the image
    for only a few
    hundredths of a second

light
photomask
7
Wafer Positioning Subsystem
  • The position of the silicon wafer must be as
    precise as the optics
  • Each wafer contains around 100 semiconductor
    devices, or chips
  • Less than one second to move between successive
    exposure sites
  • It detects and corrects tilt errors because the
    wafer surface is not flat enough to guarantee
    focus everywhere
  • A stepper can expose about 60 wafers in one hour

8
Close-ups of Integrated Circuits
Pictures courtesy of www.charfaq.umn.edu
9
Other Lithography Processes
  • Optical Proximity Printing
  • X-Ray Proximity Lithography
  • Scanners
  • Step-and-Scan
  • Immersion Lithography

10
References
  • Sheats, James R., and Bruce W. Smith.
    Microlithography Science and Technology. New
    York Marcel Dekker, Inc, 1998.
  • http//www.charfac.umn.edu/MMS/ProjectMicro/Explor
    ations/Jun1998.html
  • http//www.geocities.com/beatles_forever_plus_some
    /Silicon_information.html
  • http//www.siliconstrategies.com/story/OEG20030422
    S0052
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