Specific Process Knowledge/Etch/Wet Aluminium Etch
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Wet ething of aluminium can be done using many different acids and bases. Using dilute phosphoric acid gives reasonably good control and compatibility with photoresists. Etching with dilute phosphoric acid is suitable for etching pure aluminium. If the aluminium is alloyed with other metals, other etchants may be better suited. Previously, aluminium with 1,5% silicon was used at DTU Danchip. This alloy is no longer in use at DTU Danchip but a suitable etchant (PES 77-19-04) for this alloy is included below.
Wet Aluminium Etch
Wet etching of aluminium is done with two different solutions:
- H2O:H3PO4 1:2 at 50 oC
- Pre-mixed etch solution: PES 77-19-04 at 20 oC
Both solutions are used in the Aluminium etch bath shown to the right. It must be written on which one is in. Solution no. 1 is the most used solution for etching aluminium. Solution no. 2 is primarily for etching aluminium mixed with a small percentage of silicon.
The user manual and contact information can be found in LabManager:
Al-etch info page in LabManager
Comparing the two solutions
| Aluminium Etch | Etch with PES 77-19-4 | |
|---|---|---|
| General description | Etch of pure aluminium | Etch of aluminium + 1.5% Si |
| Location | Aluminium Etch bath inside Wet Bench 05 in D-3 | Beaker in Fumehood 01 or 02 in D-3 |
| Link to SDS | ||
| Chemical solution | H2O:H3PO4 1:2 | PES 77-19-04
77 vol% H3PO4 85% 19 vol% CH3COOH 100% 4 vol% HNO3 70% |
| Process temperature | 50oC | 20oC |
| Possible masking materials! | Photoresist (1.5 µm AZ5214E) | Photoresist (1.5 µm AZ5214E) |
| Etch rate | ~100 nm/min (Pure Al) | ~60 nm/min |
| Batch size | 1-25 wafers at a time | 1-25 wafer at a time |
| Size of substrate | 4" wafers
6" wafers |
Any size that fits in beaker |
| Allowed materials |
See the Cross Contamination Sheet for Aluminium Etch bath |
Any material allowed in cleanroom |