Specific Process Knowledge/Thin film deposition/Deposition of Aluminium/Thermal deposition of Al

Feedback to this page: click here

All text on this page by DTU Nanolab staff

Thermal evaporation of Aluminum

Aluminum can be thermally evaporated at DTU Nanolab in the Thermal Evaporator.

We recommend depositing a thin layer of thermally evaporated aluminum on top of e-beam resist before e-beam lithography. It is also possible to use Cr, see more info here. The advantage of Al is that it can be removed simultaneously with the e-beam resist. However Cr may allow even better resolution of the lithography.

For deposition onto the unexposed e-beam resist, you need to use thermal evaporation as it will be damaged by e-beam evaporation.

Using the Thermal Evaporator

The Thermal Evaporator (Lesker) is easy to use and (without rotation): File:thermal evap wtec vs lesker nano uniformity and particles.pdf

As usual, you need a training session before using the instrument independently.

Time requirements for Al deposition (approx.)

Vent the chamber (3 min)
Loading samples and adding Al pellets to the crucible as necessary (5 min)
Pump down (15-25 min)
Run the process (soaking/ramping 7 minutes plus time for the deposition rate to stabilize after opening the source shutter, time for the deposition itself and about 1 minute for running down the power afterwards). The deposition rate is 0.5-2 Å/s.

In total set aside at least 45 min PLUS time for the deposition itself.

Quality control (QC) of Al evaporation on the thermal evaporator

Quality control (QC) for the Thermal evaporator

QC Recipe:	Al1_1A/s
Deposition rate	1 Å/s
Thickness	150 nm
Pressure	Below 1*10^-5 Torr

QC limits	Thermal Evaporator
Measured average thickness	± 20 %
Deposition rate deviation	± 50 % after stabilizing
Thickness deviation across a 4" wafer	± 30 %

Thicknesses are measured in 5 points with one of the stylus profilers.
Additionally we monitor the pumpdown time and the state of the Al crucible and ensure that it does not contain too much Al as this can wet the outside and short circuit the heater.

Info about decommissioned equipment (Wordentec)

This file contains some short notes regarding thermal Al evaporation in the Wordentec: Short Tests thermal deposition of Al in Wordentec

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.