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Variable transmission focal mask for lens heating compensation

  • US 20030095243A1
  • Filed: 11/19/2001
  • Published: 05/22/2003
  • Est. Priority Date: 11/19/2001
  • Status: Active Grant
First Claim
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1. A semiconductor fabrication alignment and exposure equipment comprising:

  • an exposure and alignment unit including a light source and a lens;

    a variable transmission mask under the lens to at least indirectly measure focus and adjust the focus in real time in response to determining that the focus is out of specification; and

    a stage on which a wafer is placed for exposure to the light source through one of a mask and a reticle.

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