ALD1

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ALD - Atomic layer deposition

The ALD1 (Picosun R200 ALD) tool is used to deposit a very thin layer of Al₂O₃, TiO₂ (amorphous or anatase), HfO₂, ZnO and AZO (Al-doped ZnO) on different samples.

Each process is using two (or three for AZO) different precursors. The reaction takes place in cycles. During each cycle, a very short pulse of each precursor is introduced into the ALD reaction chamber in turns, and in-between each precursor pulse the chamber is purged with nitrogen. All reactions have to take place on the sample surface, thus it is very important that each precursor is removed from the chamber before the next one is introduced. In that way, materials can be deposited atomic layer by atomic layer by ALD.

In order to ensure that the ALD reactor has the same temperature everywhere, it has a dual chamber structure. The inner chamber is the reactor chamber, and the outer chamber is a vacuum chamber that is isolating the reactor from room air. The space between the two chambers is called an intermediate space (IMS), and this is constantly purged with nitrogen. A sample holder is placed in the reactor chamber.

When the reactor chamber is heated up or cooled down, it will take some time before the sample holder and the sample reaches the desired temperature. Thus, it is important to include a temperature stabilization time in the process recipes.

The ALD deposition takes place in the reactor chamber. All precursor and nitrogen carrier gas lines are connected to the reactor chamber through separate gas lines. The precursor pulse time is controlled using special ALD valves, that allow very short precursors pulses to be introduced into the ALD reactor and at the same time allow a constant nitrogen purge.

The ALD reaction takes place under vacuum, thus a vacuum pump is connected to the bottom of the ALD reactor chamber. The pump is located in the basement.

The liquid precursors (H₂O, TMA, TiCl₄, DEZ and TEMAHf) are located in the cabinet below the ALD chamber. When these precursors are not in use, the manual valves have to be closed. Only four of the precursors (normally H₂O, TMA, TEMAHf and either TiCl₄ or DEZ) can be connected at the same time. Ozone is generated by use of an ozone generator that is located on the side of the machine.

It is possible to change the sample holder, so that ALD deposition can take place on different samples, e.g. a small wafer batch (up to five wafers at a time) or a number of smaller samples. Samples are loaded manually into the sample holder by use of a tweezer. However, for some materials the uniformity will only be good for the top sample(s) in a minibatch holder.

A short presentation with some information about the ALD tool can be found here.

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

ALD1 info page in LabManager,

Process information

Equipment performance and process related parameters

Equipment		ALD1
Purpose	ALD (atomic layer deposition) of	Al₂O₃ TiO₂ (amorphous or anatase) HfO₂ ZnO AZO (Al-doped ZnO)
Performance	Deposition rates	Al₂O₃: ~ 0.075 - 0.097 nm/cycle (Using the "Al2O3" recipe, depending on temperature) TiO₂: 0.041 - 0.061 nm/cycle (Using the "TiO2" recipe, depending on temperature) ZnO: 0.11 - 0.18 nm/cycle (Using ZnOT recipe, depending on temperature) HfO₂: 0.827 nm/cycle
Performance	Thickness	Al₂O₃: 0 - 100 nm TiO₂: 0 - 100 nm ZnO: 0 - 100 nm HfO₂: 0 - 50 nm
Process parameter range	Temperature window	Al₂O₃: 150 - 300 ^oC Amorphous TiO₂: 100 - 150 ^oC Anatase TiO₂: 300 - 350 ^oC ZnO: 100 - 250 ^oC HfO₂: 150 - 350 ^oC
Process parameter range	Precursors	TMA DEZ TiCl₄ H₂O O₃ O₂ TEMAHf
Substrates	Batch size	1 200 mm wafer 1-5 100 mm wafers 1-5 150 mm wafers Several smaller samples
	Allowed materials	Silicon Silicon oxide, silicon nitride Quartz/fused silica Al, Al₂O₃ Ti, TiO₂ Other metals (use dedicated carrier wafers) III-V materials (use dedicated carrier wafers) Polymers (depending on the melting point/deposition temperature, use carrier wafers)