Migrated from the old Google Sites wiki (Nov 2026). Text and numbers were carried over; photos and screenshots were not. If you have them, add them to assets/wiki/ and link them here. Check numbers against your own run before relying on them.
When to use it
The group mainly uses the Oxford 80 to etch silicon oxide or aluminum oxide. Two RIE tools can do this job, Plasmatherm #2 and the Oxford. The Oxford is preferred because its pump reaches a lower process pressure (about 30 mTorr, versus about 40 mTorr on Plasmatherm #2).
Safety: fluorine-based process gases are hazardous. Newer RIE tools isolate the process chamber behind a load lock. The Oxford 80 has a single chamber, so a large plastic shield takes the place of that protection. A manual is kept beside the tool.
Operating procedure
- Log in to LabSentry and enable the tool.
- In the control software: Pump → Stop → Vent.
- Wait 3–4 min. When the yellow warning message appears, click Accept.
- Press the two buttons together to open the chamber.
- Load your wafer, or pieces mounted on a carrier wafer.
- Press the buttons to close the chamber.
- Click Stop → Evacuate.
- Wait until the Penning gauge reads about 1 × 10⁻⁴.
- Load your recipe and click Run.
- When finished, vent and remove your sample.
- Pump the system back down.
Recipe
- The base recipe was written by group alumnus “DK”.
- Measured etch rate (Yuqi, March 2025): about 17 nm/min.
- The tool drifts over time and many factors change etch rate, so calibrate with your own test piece.
- The recipe includes Ar. Ar ion bombardment speeds up the etch and makes it more anisotropic, but on long etches it can crack a photoresist mask. For long etches, consider dropping the Ar step.
Pressure and polymer ⚠️
- APC pressure: 30 mTorr standard. Do not exceed 40 mTorr. Above that, carbon from CHF₃ forms a Teflon-like polymer that stops the etch.
- Adding about 1 sccm O₂ reacts away the polymer.
| Condition (tested by Yuqi) | Result |
|---|---|
| 40 mTorr, 20 sccm CHF₃, 1 sccm O₂ | Etches normally, no polymer |
| 50 mTorr, 20 sccm CHF₃, no O₂ | Etch stops completely; heavy Teflon deposition |
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