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Method for photolithographic definition of recessed features on a semiconductor wafer utilizing auto-focusing alignment

  • US 5,783,340 A
  • Filed: 07/31/1997
  • Issued: 07/21/1998
  • Est. Priority Date: 09/06/1995
  • Status: Expired due to Term
First Claim
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1. A method for photolithographically defining device features recessed below a surface of a semiconductor wafer using an auto-focusing photolithographic stepper exposure system comprising steps for:

  • (a) forming a plurality of equal-depth cavities within a die field on a top surface of the semiconductor wafer, including a focusing cavity formed at a predetermined position of a focusing light beam from the auto-focusing photolithographic stepper exposure system and at least one device cavity proximate to the focusing cavity;

    (b) forming a material layer within each cavity, thereby raising a bottom surface of each cavity by a thickness of the material layer;

    (c) covering the material layer with a photoresist layer;

    (d) focusing the photolithographic stepper exposure system by reflecting the focusing light beam off the material layer in the focusing cavity and generating a detected light signal for vertically positioning the bottom surface of each cavity at a focal plane of the stepper exposure system; and

    (e) exposing the photoresist layer for photolithographically defining the recessed device features to be formed in the material layer within the device cavity.

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