Using the Pirani Gauge on the MRC
Using the Pirani Gauge on the MRC Etcher
What is the Pirani Gauge?
The Pirani gauge gives the user another more accurate way to measure the chamber pressure of the tool. The manometer readings are in mT and the Pirani reads in T. A typical Pirani reading is 5e-6 or 0.5mT.
Why would I want to use it?
Users may want to know with more precision what the base pressure the system can attain. Users may also want to do a rate-of-rise test on the system. And users who are doing O2 sensitive etches, for example Ar sputter etching of metals, may want to make sure the system has reached a low base pressure before starting to set up the etch.
How do I use it?
- Go through the normal pumpdown procedure to opening the gate valve.
- Open the gas inlet valve. This removes the chance of a burst of gas going into the chamber.
- Open the Pirani gauge valve and monitor the chamber pressure by looking at the black box on the wall behind the tool.
- Monitor the pressure for at least 8 minutes.
- Close the Pirani gauge valve before striking the plasma. The plasma may harm the Pirani sensor.
- To perform a rate-of-rise start a timer for one minute after closing the Pirani gauge valve. The pressure shown on the Pirani gauge readout at the end of the minute is the rate-of-rise. Please note it in coral. It should be less than 10mT/min.
- Continue with the standard operating instructions starting with ‘Toggle on selected gases’ in the Section Pumping Down the Chamber.
Pirani gauge do’s and don’t’s;
- Do not have the gauge open while running the plasma. This will harm the sensor and eventually render the gauge useless.
- The gauge may be exposed to atmosphere. Unlike the manometer, the Pirani is fine in a vented condition on the tool.