Specific Process Knowledge/Thin film deposition/Deposition of Aluminium

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Deposition of Aluminium

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

Sputtering of Aluminium

Aluminium may be sputter deposited in either the single-chamber sputter-system ("Sputter System Lesker") or the cluster-based sputter system ("Sputter-System Metal-Oxide(PC1)" and "Sputter-System Metal-Nitride(PC3)"). See more in links here and the chart below.

E-beam evaporation of Aluminium

Aluminium can be deposited by e-beam assisted evaporation in the two Temescal e-beam evaporators.

E-beam evaporation of Al in Temescal

Notes on low oxygen content in e-beam prepared Al thin films (Temescal)

Thermal deposition of Aluminium

In the Lesker Thermal evaporator aluminium can be deposited by thermal deposition. Some properties of the evaporated films are described on the following page:

Thermal deposition of Aluminium

Comparison of Al deposition options

	E-beam evaporation (E-beam evaporator (Temescal))	E-beam evaporation (E-beam evaporator (10-pockets))	Sputter deposition (Sputter-System (Lesker))	Sputter deposition (Sputter-system Metal-Oxide (PC1) and Sputter-system Metal-Nitride (PC3))	Thermal evaporation (Thermal Evaporator)
General description	E-beam deposition of Aluminium. Option to tilt substrate.	E-beam deposition of Aluminium. Option to tilt substrate.	Sputter deposition of Aluminium (DC)	Sputter deposition of Aluminium (DC, Pulsed DC, HIPIMS)	Aluminum deposition onto unexposed e-beam resist
Pre-clean	Ar ion etch			RF Ar clean
Layer thickness	10Å to 1 µm*	10Å to 1 µm*	10Å to ~0.5µm (very time consuming )	10Å to ~0.5µm	10Å to 1 µm*
Deposition rate	1Å/s to 10Å/s	1Å/s to 5Å/s	Depending on process parameters at least up to 0.7 Å/s	Depending on process parameters at least up to 1.3 Å/s. See conditions here	0.5, 1, or 2 Å/s
Batch size	Up to 4x6" or 3x8" wafers smaller pieces	Up to 4x6" or 3x8" wafers smaller pieces	1x4" wafer or 1x6" wafer or several small samples	up to 10x4" wafers or up to 10x6" wafers or many smaller samples	Up to 3 x 4" wafers or one 6" or 8" wafer (limited uniformity on large substrates) Many small chips
Pumping time from wafer load	Approx. 20-30 min	Approx. 20-30 min	Approx. 10 min	Approx. 5 min plus 6 min transfer time	Approx. 15-20 min
Allowed materials	Almost any that does not degas. See the cross-contamination sheet.	Almost any that does not degas. See the cross-contamination sheet.	Silicon wafers and almost any	Almost that does not degas - see cross contamination sheets for PC1 and PC3 Special carrier for III-V materials.	Almost any that does not degas. See the cross-contamination sheet.

* For cumulative deposition above 600 nm please write to metal@nanolab.dtu.dk to make sure there will be enough Al for your deposition

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 recommended.

Positive photolithography process from 1.5 µm is possible especially for thin layers of metal.

The more pattern the easier the lift-off.

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