Specific Process Knowledge/Thin film deposition/Deposition of Aluminium

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Deposition of Aluminium

Aluminium can be deposited by e-beam evaporation, by sputtering and by thermal evaporation. In the chart below you can compare the different methods on the different deposition equipment.

Sputtering of Aluminium

Aluminium may be sputter deposited in either the Wordentec, the Sputter-system (Lesker) or the Cluster-based sputter system.

• Sputtering of Aluminium in the Wordentec

E-beam evaporation of Aluminium

Aluminium can be deposited by e-beam assisted evaporation in the Wordentec, Physimeca and Temescal tools.

• E-beam evaporation of Al in Temescal

Thermal deposition of Aluminium

In the Wordentec and the Thermal evaporator aluminium can be deposited by thermal deposition. The two instruments are compared on the following page:

• Thermal deposition of Aluminium

Comparison of Al deposition options

	E-beam evaporation (Temescal)	E-beam evaporation (Physimeca)	E-beam evaporation (Wordentec)	Sputter deposition (Wordentec)	Sputter deposition (Sputter-System (Lesker))	Sputter deposition (Cluster-based sputter system )	Thermal evaporation (Wordentec)	Thermal evaporation (Thermal Evaporator)
General description	E-beam deposition of Aluminium	E-beam deposition of Aluminium	E-beam deposition of Aluminium	Sputter deposition of Aluminium	Sputter deposition of Aluminium	Sputter deposition of Aluminium	Aluminum deposition onto unexposed e-beam resist	Aluminum deposition onto unexposed e-beam resist
Pre-clean	Ar ion etch	None	RF Ar clean	RF Ar clean	RF Ar clean	RF Ar clean	RF Ar clean	None
Layer thickness	10Å to 1 µm*	10Å to 0.5 µm **	10Å to 1 µm*	10Å to ~0.5µm	10Å to ~0.5µm (very time consuming )	10Å to ~0.5µm	10Å to 0.2 µm*** (this uses all Al in the boat)	10Å to 1 µm**
Deposition rate	0.5Å/s to 15Å/s	0.5Å/s to 15Å/s	10Å/s to 15Å/s	Depending on process parameters, up to ~2.5 Å/s	Depending on process parameters at least up to ~0.5 Å/s	Depending on process parameters at least up to ~3 Å/s	~1.5Å/s to 2Å/s	0.5, 1, or 2 Å/s
Batch size	Up to 4x6" or 3x8" wafers smaller pieces	Up to 1x4" wafers smaller pieces	24x2" wafers or 6x4" wafers or 6x6" wafers	24x2" wafers or 6x4" wafers or 6x6" wafers	1x4" wafer or 1x6" wafer or several small samples	up to 10x4" wafers or up to 10x6" wafers or many smaller samples	24x2" wafers or 6x4" wafers or 6x6" wafers	Up to one 8" wafer (limited uniformity on large substrates)
Pumping time from wafer load	Approx. 20 min	Approx. 10 min	Approx. 1 hour	Approx. 1 hour	Approx. 10 min	Approx. 5 min plus 6 min transfer time	Approx. 1 hour	Approx. 15 min
Allowed substrates	Silicon wafers Quartz wafers Pyrex wafers	Silicon wafers Quartz wafers Pyrex wafers	Silicon wafers Quartz wafers Pyrex wafers	Silicon wafers Quartz wafers Pyrex wafers	Silicon wafers and almost any	Silicon wafers And almost any that does not degas. Special carrier for III-V materials.	Silicon wafers Quartz wafers Pyrex wafers	Silicon wafers Quartz wafers Pyrex wafers
Allowed materials	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Almost any	Almost any - ask!	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar SU-8 Metals
Comment	* Thickness above 600 nm: ask for permission It is possible to tilt the substrate. Pumpdown approx. 20 min.	** Thickness above 200 nm: ask for permission.	* Thickness above 600 nm: ask for permission. Pumpdown approx. 1 hour.	Pumpdown approx. 1 hour.	***Thickness above 120 nm: ask for permission Pumpdown approx. 1 hour.	**Thickness above 200 nm: ask for permission. Pumpdown approx. 10 min.

* For thicknesses above 600 nm please get permission from ThinFilm group by writing to metal@danchip.dtu.dk

** For thicknesses above 200 nm please get permission from ThinFilm group by writing to metal@danchip.dtu.dk

*** For thicknesses above 120 nm please get permission from ThinFilm group by writing to thinfilm@danchip.dtu.dk

Aluminium deposition on ZEP520A for lift-off - comparison of thermal and e-beam evaporation

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 grain size is compared for the different methods.

The conclusion was that e-beam evaporation of aluminium at 15 Å/s gave the best result.

See details of the study here.

Aluminium deposition on AZ5214 for lift-off

Negative photolithography process is recomended.

Positive photolithography process from 1,5 µm is possible especially for thin layers of metal.

The more pattern the easyer lift.

It was tried (jan09) to lift 2.5 µm Al on 4.2µ negative resist on top of 11 µm Apox SiO2 in an acetone sonic-bath. The Al deposition process was done in steps evaporating 500 nm a time with 5 min pause and pressure down to at least 2E-6.

Roughness of thermally evaporated aluminium

A study by AFM was performed to examine Al films deposited with thermal evaporation in the Wordentec. See details here.