E-Beam Evaportion of Gold -- Features Wash Away in Lift Off

Fabrication Q&A
1

I have a question about e-beam evaporation. I’m trying to fabricate an array of gold electrodes. I used EBL to define the pattern in PMMA, then evaporated 100nm of Au. After lift-off, most of the structures get washed away. Any idea how to make them stick to the substrate?

2

What substrate are you using? Gold doesn’t adhere well to glass or fused silica. Also, do you perform lift-off at room temperature? Any sonication involved?

3

Yes, I’m using fused silica. No sonication, and lift-off at room temperature. Is there a way to improve adhesion?

4

Try adding a thin adhesion layer before gold — typically 3–5 nm of chromium (Cr) or titanium (Ti). That should help

5

Thanks! I added 3 nm Cr before Au, and adhesion improved, but some regions still peel off.

6

Try descumming your developed resist with a short low-power O₂ plasma (around 200 W, ~20-40 s). You can use an RIE or plasma asher. It removes organic residue left behind from the developer and the resist and improves adhesion.

7

Thanks @Vikachu That worked!