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Tergeo plasma cleaner operator’s manual
Revision: B3, Year 2020
8.10 How to reduce the venting time?
Plasma cleaner chamber is vented through a solenoid valve with a small orifice. If the pressure on the
venting port is at the atmospheric pressure, it will takes a long time for the chamber to be fully vented
to the atmospheric pressure. The venting time can be significantly reduced if the user can connect the
venting port to a pressurized gas source and set the pressure to 5~15 psi above the atmospheric
pressure.
8.11 How to set the right gas flow rate for hydrogen gas.
The pumping speed of mechanical pump for hydrogen is usually not very stable. Hydrogen tends to
accumulate inside the vacuum systems. The pressure will gradually increase for pure hydrogen gas. If
the pure hydrogen gas has been used for a long time, it’s will be very hard to pump down the chamber
even when all the MFCs are closed. To make the process more stable, it’s recommended to mix the
hydrogen with argon gas. If it’s hard to pump down the chamber after using the hydrogen, please use
10~100 sccm of argon as the carrier gas to flush the chamber for 30 seconds to 100 seconds. The
vacuum will be recovered much faster.
To make the hydrogen plasma more stable, it’s recommended to mix hydrogen with >10sccm argon. The
hydrogen gas flow rate can be increased to >10sccm if it is used together with enough argon carrier gas.
For pure hydrogen, please keep gas flow rate below 1.0sccm. Otherwise, the vacuum pressure may not
be stable.
8.12 How to create extremely weak oxygen plasma for some critical
biopolymer processing applications
For some biopolymer coating and bonding applications, it’s very important not to over-etch the polymer
sample such as PDMS in the oxygen plasma. For those applications, only extremely weak oxygen plasma
is required. Two potential recipes are: 1) high pressure, rf power 35W, pulse 255/255, O2 gas flow
25~45 sccm, time 30 seconds; 2) low pressure, rf power 20W, pulse 255/255, O2 gas flow rate 3~5sccm.
The oxygen plasma emission is usually very weak. If the plasma emission is too weak to be detected by
the plasma sensor in a weak O2 recipe (low rf power, high O2 flow), the user can change the setting in
the system screen to “count down the timer when rf ON” instead of “count down the timer when
plasma ON”. If the system will only be used to generate the extremely weak plasma, user can disable the
auto-impedance matching function by setting the autotune to be “disabled”. Then manually set the
position of the auto tuner to a value that is about 100 counts less than the maximum range of the auto-
tuner (usually around 10,000 or so). If low flow O2 recipe (<5sccm) is used, process time may need to be
as less as 10 seconds. If the O2 flow rate is higher than 25sccm, the processing time can be increased to
40 seconds or more. Usually water moisture in the plasma chamber can improve the bonding or coating
adhesion because of the enhanced hydroxyl functional group production.
