Specific Process Knowledge/Thin film deposition/thermalevaporator

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This page is written by DTU Nanolab staff

Thermal evaporator- A system for deposition of metals

This evaporator is intuitive to operate and does not have a lot of bells and whistles. You can see the instrument specifications below.

The main purpose of the thermal evaporator is to deposit Al for removing charging of the resist when doing EBL on isolating substrate. It can also be used for Cr evaporation for the same purpose, and evaporation of Ag, Au, Cu, and Ge. We have also attempted to evaporate Zn, but this resulted in heavy contamination of the chamber that required a lot of effort to clean and the process was not stable.

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 and Ag) up to 100 nm (Cr) (ask if you wish to deposit more) for other metals ask if in doubt
	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 parameter range	Process pressure	Below 4*10^-6 mbar
Substrates	Batch size	Up to 8" wafer Or several 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