Specific Process Knowledge/Thin film deposition/Deposition of Aluminium
Aluminium can be deposited by e-beam evaporation, by sputter and by thermal evaporation. In the chart below you can compare the different methods on the different deposition equipment.
| E-beam evaporation (Alcatel) | E-beam evaporation (Leybold) | E-beam evaporation (Wordentec) | Sputter deposition (Wordentec) | Thermal evaporation (Wordentec) | |
|---|---|---|---|---|---|
| Batch size |
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| Pre-clean | RF Ar clean | Ar ion bombartment | RF Ar clean | RF Ar clean | RF Ar clean |
| Layer thickness | 10Å to 1µm | 10Å to 1500 Å | 10Å to 1 µm | 10Å to ~0.5µm (very time consuming ) | 10Å to 0.5 µm (this uses all Al in the boat) |
| Deposition rate | 2Å/s to 15Å/s | 1Å/s to 5Å/s | 10Å/s to 15Å/s | Depending on process parameters (see here), up to ~2.5 Å/s | ~8Å/s to 15Å/s |
Aluminium deposition on ZEP520A for lift-off
This is a small study of which aluminium deposition that is best for aluminium lift-off on ZEP520A resist and a very thin layer of aluminium (~20nm).
The conclusion was that e-beam evaporation of aluminium in the Alcatel at 15Å/s gave the best result.
See details of the study here.
Comparison of roughness and other surface characteristics for different methods of Aluminium deposition
Studies by AFM was performed to examine differences in characteristics of the Al films, deposited with the differnt methods (sputter, e-beam, thermal). See details of the study here.
Aluminium deposition on AZ5214 for lift-off
Negative photolithographi process is recomende.
Positive photolithographi process from 1,5µ is possible especially for thin layers of metal.
The more patern the easyer lift.
It was tried(jan09) to lift 2,5µ Al on 4,2µ negative resist on top of 11µ Apox SiO2 in acetone sonic-bath. This proces was done by steps evaporating only 5000Å a time with 5min pause and pressure down to at least 2E-6.