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Expired photoresist is still usable, but it gets more viscous, so spun films come out thicker than the datasheet says.
AZ5214 as a positive resist
Reference: AZ 5200 series datasheet.
| Step | Setting | Notes |
|---|---|---|
| 1. Clean | Piranha or AMI clean | Choose based on what is already on the wafer. |
| 2. HMDS prime (optional) | 2 min prime, about 18 min 20 s total cycle | Recommended for small features. Improves adhesion so the resist survives dicing. |
| 3. Spin | 3000 rpm, 30 s | About 1.6 µm of AZ5214. |
| 4. Pre-bake | 110 °C, 50 s, hotplate | Check the hotplate temperature first. |
| 5. Expose (MA8) | 75–100 mJ/cm² | Recipe files are in the “Zihuan Liu” folder on the tool. |
| 6. Develop | AZ400K : water = 1 : 4 (50 ml : 200 ml), 25–35 s | Adjust time until the pattern is clearly visible. |
AZ5214 as an image-reversal (negative) resist
Follow steps 1 to 5 above, then:
- Reversal bake: after exposure and before developing, bake at 110–120 °C for 45 s.
- Flood expose: more than 300 mJ. The exact dose is not critical, just make it enough.
- Develop as in step 6 above.
SU-8 3005 as a negative resist
References: Kayaku Advanced Materials SU-8 3000 datasheet and Omnicoat datasheet.
Omnicoat release layer
Omnicoat lets you strip SU-8 cleanly later.
- Spin at 1000 rpm for 40 s, then bake at 200 °C for 1 min.
- Apply 3 coats (about 17 nm each, roughly 40 nm total). Let the wafer cool to room temperature between coats.
SU-8 process
| Step | 3 µm film | 10 µm film | Notes |
|---|---|---|---|
| 1. Spin | 4000 rpm, 40 s | 1000 rpm, 40 s | |
| 2. Soft bake, 95 °C | 3 min | 6 min | |
| 3. Expose (MA8) | 100–200 mJ/cm² | 100–200 mJ/cm² | Pattern is not visible yet. Recipes in the “Zihuan Liu” folder. |
| 4. Post-exposure bake | 95 °C, 3 min | 95 °C, 3 min | Pattern appears after this step. |
| 5. Develop | SU-8 developer, 1 min | same | |
| 6. Rinse and dry | IPA, then N₂ gun | same | Use IPA, not DI water. |
| 7. Remove exposed Omnicoat | Oxford RIE, recipe “YS Omniremoval” | same | 90 s is enough for 3 coats; the saved recipe runs 4 min. |
Stack summary: Omnicoat on Al₂O₃ → SU-8 on Omnicoat → PEB → develop → RIE to clear the Omnicoat. See Oxford 80 RIE.
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