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	Up to 1x4" wafers smaller pieces	8x4" wafers or 5x6" wafers	24x2" wafers or 6x4" wafers or 6x6" wafers	24x2" wafers or 6x4" wafers or 6x6" wafers	24x2" wafers or 6x4" wafers or 6x6" wafers
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.