Specific Process Knowledge/Thin film deposition/ALD Picosun R200: Difference between revisions

The Picosun R200 ALD (atomic layer deposition) tool is used to deposit a very thin layer of Al₂O₃ or TiO₂ (amorphous or anatase) on different samples.  

Each process is using two different precurcors. 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 precurcor 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 eveywhere, it has a dual chamber structure. The inner chamber is the ALD reactor with the 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 connected to a nitrogen carrier gas line.  

When the reactor chamber is heated up or cooled down, it will take some time before the sample holder and the sample reach 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 percursors pulse time is controlled using special ALD valves, that allow very short precursors pulses to be introduced into the ALD reactor and a at the same time allow a constant nitrogen purge.

The liquid precursors (TMA, TiCl₄ and H₂O) are located in the cabinet below the ALD chamber. When the TMA 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.