Edge Bead Removal via Photolithography for 4-inch Wafers

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This method significantly lowers the risk of breaking a wafer in clamped systems such as the DSEiii or Fluorine Etcher.

This process only removes the outermost photoresist for Positive PR's. For Negative PR's, your should design you litho so there is no exposure on the outer 7mm, so the PR is removed during develop.

The metal edge-bead removal masks are in the Suss MA-6 Contact Aligner drawers, and I recommend the "4mm recessed".

Location of our edge-bead removal mask
Edge bead Removal on MA6 - IMG 5623 - vidmar drawers.jpg Edge bead Removal on MA6 - IMG 5624 - cassette location.jpg
Using the mask on the MA-6 with Flood Exposure mode.
Edge bead Removal on MA6 - IMG 5626 - place on wafer.jpg Edge bead Removal on MA6 - IMG 5625 - placed on wafer.jpg

I-Line Photo-EBR Process

  • Spin/cure an I-Line photoresist using your standard photolith. params (for example SPR 220-3).
  • Don't load a mask plate.
  • Turn off "Load Mask" mode - you will likely need to confirm that no mask is present.
  • Place the wafer on the MA-6 Contact Aligner with the metal mask in place.  
  • You will use [Lamp Test] for the exposure. You can also use "Flood Expose" program and type in an exposure time.
  • Expose for about 3-2x longer than your normal exposure time.
  • Load wafer into your I-Line exposure tool & Expose your process
  • Run your PEB and Develop as per your normal process.
    • (If you did not develop the EBR yet, it should go away in this step.)

DUV Photo-EBR Process

  • Spin/cure a DUV photoresist using your standard photolith. params (for example UV6).
  • Place the wafer on the DUV Flood Exposer with the metal mask in place.  
  • Turn on rotation on slow (so mask doesn't move), lamp warmup is not required.
  • Expose for 13 sec, with slow rotation.
  • Optionally: PEB 135°C, 60sec, Develop, dry (in SRD), then proceed.  This did not affect my primary lithography when I did this step separately.  I've also done photo-EBR where I combined this EBR exposure with the primary Imaging litho. and only did a single develop.
  • Load wafer into ASML & Expose your process
  • PEB 135°C, 90sec
  • 300MiF develop as per your normal process.
    • (If you did not develop the EBR yet, it should go away in this step.)
Demis D. John, 2018-10-22; Updated 2025-04-12.
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