Drytek4 RF tuning notes
10-16-09
RF tuning on Drytek4 is done by manually adjusting the “Coil” and “Cap” 10 turn pots.
All 3 “Process” pairs are the same, the system just uses the settings selected for the “lit” Process button .
Most recipes should be close to the tuning for Oxygen, with some variation due to power or pressure (SF6
is very different). The numbers as of 10-15-09 are about 0.55 for “Coil” (upper) and 10.00 for “Cap”
(lower).
Start with these numbers if you can’t get the plasma to light up. Reflected power goes back to the RF
generator and can cause damage. If the plasma is not lighting right away, reduce power to between 50 and
75 watts until you can get it to light. Pressures less than about 100 mTorr are more difficult. Raise
pressure to make striking easier.
As a last resort if you are having trouble striking “your” recipe, try staring with Oxygen to verify striking,
then gradually add your gasses and reduce O2 until it is working for your gasses, power and pressure.
As always, re-tune to get minimum reflected power for your recipe.
Be aware that the RF level potentiometers are not linear: you get no RF until the pot is 3.50 or so, and the
max allowed RF (150 watts) at about 5.80.
Sometimes you might find the RF pots set to zero to enable a “pump-down , gas only”, step in e.g. Process
1 for 1 or 2 minutes ahead of the etch in Process 2. If multiple Process buttons are lit, the system will
proceed from step to step with a pump-down but no vent in between. This can be used to reduce the affect
of air or of water vapor on sensitive etch recipes in this non-load-locked etcher.
On 10-15-09, the pressure “zero” ( throttle wide open, no gas flow) was 0006 mTorr and the leak up rate
was very good at less than about 1 mTorr per minute.
jimkruger