Plasmatherm #2

2025 0416 by Yuqi Meng

The operation of the plasmatherm #2 is even simpler than Oxford 80.  You see two chambers the left chamber is Plasmatherm #1 and the right chamber is Plasmatherm #2, the 

left chamber is used for CVD and right chamber is RIE, the only difference between CVD and RIE is if the reaction product is volatile or not, if it is volatile the reaction etches material and the product is pumped out from the chamber. If the reaction product is nonvolatile, the product from the reaction is deposited onto the surface forming a film, that is CVD.

Also, the direction of the electric field is different for CVD compared to RIE, where the anisotrpy is created by ions accelerating towards the surface beacuse of the electric field points downward towards the surface.  For CVD the electric field is pointed upward, so the reaction happens above and the product falls onto the surface. So if one were to use CVD machine to do RIE expect etching to have reduced anisotropy.

If you have seen the previous post of Oxford RIE, since the Plasmatherm #2 does not have fluorine based gases, it does not necessarily need extra protection. You therefore does not see the big plastic hood like the one in Oxford RIE. So the operation of the tools is much more convenient.

1. login to the tool.

2. click "vent"

3. after you see there is a big slit of gap in the processing chamber. It means the pressure inside the chamber reached atmosphere.

4. open the chamber and put your sample on the carrier wafer into the chamber.

5. close the chamber, press it down while clicking 'Evacuate' (because the pump is not as powerful as the other one you need to physically press it).

6. Load your recipe. there is a recipe named "YQSIOLPL" which has been used by Yuqi to etch SiO2 with etch rate of 17nm/min.

A few tips:

The tool has a hard time getting to 30mTorr process pressure. So you may want to set the process pressure at a minimum of 40mTorr.

If you create your own recipe, you will notice when you add"purge" step(which is the step that pumping in nitrogen to substitude the residue air that cannot be pumped out of the chamber). The default pressure is quite low which the machine CANNOT reach. So you need to adjust the purge step pressure to around 212mTorr for it to run.

The process step setting of Yuqi's recipe