Specific Process Knowledge/Thin film deposition/ALD Picosun R200

ALD1

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ALD - Atomic layer deposition

ALD1, positioned in cleanroom F-2.

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, the ALD layer will be deposited atomic layer by atomic layer.

In order to ensure that the ALD reactor has the same temperature everywhere, it has a dual chamber structure. The inner chamber is the ALD reactor with a sample holder, 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). The IMS is constantly purge with nitrogene.

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. The pump is located in the basement.

The liquid precursors (H₂O, TMA, TiCl₄ and TEMAHF) are located in the cabinet below the ALD chamber. DEZ (diethylzinc) is located in a metallic box outside in the service room. When the DEZ, TMA, TEMAHf and TiCl₄ precursors are not in use, the manual valves have to be closed. 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 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

• Standard recipes on the ALD-1 tool
• Advanced recipes involving fabrication of multilayers
• Al₂O₃ deposition using ALD-1
• TiO₂ deposition using ALD-1
• ZnO deposition using ALD-1
• Al-doped ZnO (AZO) deposition using ALD-1
• HfO₂ deposition using ALD-1

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
	Thickness	Al2O3: 0 - 100 nm TiO2: 0 - 100 nm ZnO: 0 - 100 nm HfO2: 0 - 50 nm
Process parameter range	Temperature	Al2O3: 150 - 300 oC Amorphous TiO2: 100-150 oC Anatase TiO2: 300-350 oC ZnO: 100 - 250 oC HfO2: 150-300 oC
	Precursors	TMA DEZ TiCl4 H2O O3 O2 TMAHf
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 wafer) III-V materials (use dedicated carrier wafer) Polymers (depending on the melting point/deposition temperature, use carrier wafer)