Specific Process Knowledge/Etch/Wet Aluminium Etch
THIS PAGE IS UNDER CONSTRUCTION
Feedback to this page: click here
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 50oC
- Pre-mixed etch solution: PES 77-19-04 at 20oC
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 Danchip if you need to use the PES 77-19-04 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.
Comparing the two solutions
| Aluminium Etch | Etch with PES 77-19-4 | |
|---|---|---|
| General description | Etch of pure aluminium | Etch of aluminium with 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 | Flexible |
| 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 |