Specific Process Knowledge/Thin film deposition/thermalevaporator

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This page is written by DTU Nanolab staff

Thermal evaporator for metal deposition

Positioned in cleanroom A-1.

This instrument is NANO 36 Thermal evaporator from Kurt J. Lesker. Instrument specifications below. It takes around 1 hour for a round of deposition (depending on thickness and rate of course). The small chamber means that the deposited thickness may vary quite a bit across large samples, as further described in the specifications table.

The main purpose of this evaporator is to deposit Al for dissipation of charge when doing electron beam lithography on insulating substrates. It can also be used for Cr evaporation for the same purpose. 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.

Additionally we have processes for evaporation of Ag, Au, Cu, and Ge. We have also attempted to evaporate Zn, but this resulted in heavy contamination of the chamber. You are always welcome to ask for other metals in the machine.

Up to two sources can be present at the same time (metals in a boat, crucible or rod for evaporation) but there is only one power supply, so only one material can be evaporated at a time.

The user manual, APV, technical information, cross-contamination sheet and contact information can be found in LabManager:

Thermal Evaporator in LabManager

Process information

Materials evaporated in the Lesker Thermal Evaporator

• Aluminium
• Silver
• Chromium
• Germanium
• Gold
• Copper
• (Zinc - we don't like to evaporate this material)

We can develop processes for other materials if requested.

Equipment performance and process related parameters

Purpose	Deposition of metals	Thermal evaporation of metals
Performance	Film thickness	10Å - 1µm (Al) 10Å - 0.5µm (Ag) up to 100 nm (Cr) ask the Thin Film group if in doubt or if you wish to exceed the limits
	Deposition rate	0.5-2 Å/s (Al), 5 Å/s (Ag), 1 Å/s (Cr) In general, 0.5-10 Å/s is possible We need to develop a new process for each rate
	Thickness uniformity (no rotation, wafer centered above source)*	Approx. 6-9 % variation on a 4" wafer with 100 nm Al (crucible source) Approx. 8-13 % variation on a 6" wafer with 100 nm Al (crucible source) Approx. 23 % variation on a 4" wafer with 100 nm Ag (boat source) - expect better result with rotation Approx. 10 % variation on a 6" wafer with 100 nm Cr (rod source)
	Thickness uniformity (with rotation)	Approx. 6-9 % Wafer-in-Wafer variation on 4" wafers with Al (crucible source) using 3-wafer holder (4 % variation wafer-to-wafer) Approx. 6 % variation for 6" wafers with Al (crucible source) with wafer off-center on holder Approx. 7 % variation for 6" wafers with Al (crucible source) with wafer centered on holder
	Pumpdown time	about 15-25 min
Process parameter range	Process Temperature	Approximately room temperature
	Process pressure	Below 4*10-6 mbar
Substrates	Batch size	Up to 1 x 6 " or 8" wafer Up to 3 x 4" wafers Many smaller pieces Deposition on one side of the substrate
	Substrate material allowed	Silicon wafers Quartz wafers Pyrex wafers
	Material allowed on the substrate	Silicon oxide Silicon (oxy)nitride Photoresist PMMA Mylar Metals

* The variation is defined as (Max-Min)/Average for the various points measured on the wafer. The max. point was around the center and the min. somewhere along the edge. The exact location of the maximum thickness depends how the sample is placed relative to the point of maximum material flux.

Number for Al 4" no rotation based on QC measurements 2018-2023.

Other measurements by Rebecca Ettlinger, Evgeniy Shkondin and Patama Pholprasit 2018-2023