Specific Process Knowledge/Etch/Wet Aluminium Etch
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Wet etching 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 Nanolab. This alloy is no longer in use at DTU Nanolab but a suitable etchant (Aluminum etch 80-15-3-2) 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°C
- Pre-mixed etch solution: Aluminum etch 80-15-3-2 at 20°C
The first solution is always available ready made in the Aluminium Etch bath. The second solution can be mixed manually or bought pre-mixed and ready for use. Please contact DTU Nanolab if you need to use the Aluminum etch 80-15-3-2 etch mixture. Since it is used only very rarely it will probably have to be ordered when needed. The table below summarizes possibilities and parameter for the two etch mixtures.
contact Wetchem if change off bath or want to use it in a beaker.
Comparing the two solutions
| Aluminium Etch | Etch with Aluminum etch 80-15-3-2 | |
|---|---|---|
| General description | Etch of pure aluminium | Etch of aluminium with 1.5% Si |
| Location | Bath inside Wet Bench 05 in D-3 | Bath inside Wet Bench 05 in D-3 |
| Link to SDS | ||
| Chemical solution | H2O:H3PO4 1:2 | Aluminum etch 80-15-3-2:
60-90 vol% H3PO4 85% 5-20 vol% CH3COOH 100% 1-5 vol% HNO3 70% |
| Process temperature | 50°C | 20°C |
| 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 wafers at a time |
| Size of substrate | 4" wafers
6" wafers |
4" wafers
6" wafers |
| Allowed materials |
See the Cross Contamination Sheet for Aluminium Etch bath |
See the Cross Contamination Sheet for Aluminium Etch bath |