Oxford RIE

Oxford 80 RIE

2025 04/16 Yuqi Meng

Some notes: Oxford RIE is usually used by our group to etch silicon oxide or aluminum oxide

The operation of this RIE is pretty straight forward,  if you forget about it there is always a manual near the machine for you to look at.

For fluorine based gases, it is usually very dangerous, newer versions mayhave two chambers an additional loadlock chambers separating the process chamber from the outside environment. 

Since Oxford 80 have fluorine gases but only has ONE CHAMBER (process chamber), You will see a big plastic shield that supposingly to server as the protetcion of the loadlock chamber.

Remember, there are two RIE etching machine that can be used for our purposes. Plasmatherm #2 and Oxford RIE. But Oxford RIE is a better choice since the pump can pump to lower process pressure ~30mTorr. where 40mTorr is around the limit of Plasmatherm #2

General Operating procedure:

1. Log into the labsentry system and enable the tool.

2. click on the 'Pump'-> 'stop'-> 'vent'

3. Wait for 3-4 mins, after the yellow warning message appears, click 'Accept'

4. Press the two button at the same time to open up the Chamber.

5. Put your wafer(or pieces mounted on carrier wafer) inside the chamber.

6. Press buttons to close the chamber.

7. click 'Stop->Evacuate'

8. wait till the Penning pressure has changed to around 1e-4.

9. load 'Recipe->click Run'.

10. After you are done, 'Vent' and take out your sample.

11. Pump the system afterwards

The above recipe is the recipe developed by DK our Alumni. The etch rate was tested to be around 17nm/min by Yuqi in March 2025, since the machine is likely a time varinat system. There is a lot of contributing factors to etch rate. You may wish to update based on your own experiment. 

Notice the presence of Ar gases in the recipe, the physical bomarbment of the Ar ion is advantageous in increasing the etch rate as well as helping to achieve better anisotropy. However, it sometimes can create some unwanted effects cracks on the PR mask layer because the physical damage caused by Ar ion. So you may wish to remove that from the recipe if the etch time is very long.

There are several parameters:

APC pressure: 30mTorr, this is standard, you do not want to increase it to anything >40mTorr. As the Carbon atoms in CHF3 is more likely to form significant polymer(Teflon) on the surface that forbids further etching if the process pressure is two high. 

 To mitigate this effect, we usually put 1sccm oxygen to react with teflon to eliminate the effect of polymerization.

40mTorr of pressure + 20sccm CHF3 +1sccm O2 has been tested by Yuqi and it has proven to work without polymerization

50mTorr pressure with the same setting without oxygen completely stops the etching and significant teflon demosition has been observed