Specific Process Knowledge/Thermal Process/C4 Aluminium Anneal furnace

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Aluminium Anneal furnace (C4)

Aluminium Anneal furnace (C4). Positioned in cleanroom B-1. /Photo: DTU Nanolab internal

The Aluminium Anneal or Al-Anneal furnace (C4) is a Tempress horizontal furnace for annealing and oxidation of different samples.

The samples can for instance be silicon and quartz wafers or small samples with aluminium or ALD deposited Al2O3 and TiO2. Other materials might be allowed in the furnace, but this requires a permision from the Thin Film group. Also please check the cross contamination information in LabManager, before you use the furnace.

The furnace is the lowest of the C-stack furnaces positioned in cleanroom B-1. .

The user manual, technical information and contact information can be found in LabManager:

Aluminium Anneal furnace (C4)

Process knowledge

Overview of the performance of the Aluminium Anneal furnace and some process related parameters

Purpose
  • Annealing in N2
  • Dry oxidation with O2
Process parameter range Process Temperature
  • Normally 350-500 oC for wafers and samples with aluminium
  • Up to 1150 oC for wafers and samples with other materials
Process pressure
  • 1 atm (no vacuum)
Gas flows
  • N2 (nitrogen): 0-10 SLM
  • O2 (oxygen): 0-10 SLM
Substrates Batch size
  • 1-30 4" wafers (or 2" wafers)
  • 1 6" wafer (2 6" wafers with less good uniformity) - Requires training
  • Small samples placed on a 6" dummy wafer - Requires traning
Substrate materials allowed
  • Silicon and quartz samples with
    • SiO2 and Si3N4
    • Aluminium. Wafers are allowed to enter the furnace after aluminium lift-off or aluminium etch and resist strip in acetone
    • Al2O3 and TiO2 deposited by ALD
  • Other materials might be allowed, but it requires a permission from the Thin Film group


Oxidation uniformity for 6" wafers

In November 2023 an oxygen (O2) mass flow controller was connected to the furnace, so that it became possible to oxidize different wafers and samples in the furnace.

The C4 furnace is made for processing of 4" wafers placed vertically in a quartz boat. However, it is possible to process 6" wafers (or small sample placed on a 6" wafer), if they are placed horizontally on the boat.

Normally only one 6" wafer is be processed, because the temperature flat zone, i.e. the area where the temperature is uniform, it only a little longer than one quartz boat. The teh


It was tried to oxidize two 6" wafers at the same time in the furnace.


Process parameters:

  • Recipe: "DRY1050"
  • Oxidation temperature: 1050 oC
  • Oxidation time: 1 h 40 min


Two 6" wafer loaded in the C4 furnace. Two 4" dummy wafers are placed in the end of each boat.
Oxide thickness measured on the two 6" wafers
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