ASML DUV: Edge Bead Removal via Photolithography
The metal edge-bead removal masks are in the Suss MA-6 Contact Aligner drawers, and I recommend the "4mm recessed".
It loses a bit more device area, but significantly lowers the risk of breaking a wafer in clamped systems such as the DSEiii.
(This process can easily be transferred to I-Line photoresists, using the Suss MA-6 for flood exposure instead of DUV Flood expose.)
- Spun/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