[labnetwork] Filtering Setup and Documentation Request for Technics Planar Etch II Plasma Etcher

[Stefan Schönleitner]

Hello Steve,

On 08/07/2014 12:56 AM, Paolini, Steven wrote:
> Stefan, Where is CO being generated?

if CF4 and O2 is used to etch silicon dioxide or polyimide, CO
is generated as by-product [1].
The reason is that the C and O radicals can bind with each other.
On the other side, those molecules will split up again in the plasma.
As with all of those products I would believe that it is also a question of
the concentration.

> CF4 and O2 are widely used and
> are not necessary to abate in most localities (check yours). In most
> applications, general exhaust will suffice for the pump effluent. If
> you are processing something that will form or release CO, no type of
> filter that I know of will trap it, it must be mitigated downstream
> of the pump in compliance to your lab safety folks and local codes.

Thank you for this information. We already talked to a few other people
operating plasma etchers at a regular basis and most of them are saying that
they either directly vent the pump exhaust or they use an inline
trap (to protect the pump from corrosive species).
Besides, the amount of exhaust generated also depends on the gas flow rates.
For my understanding, we have a very small process chamber (tabletop plasma etcher)
and instead of processing full wafers, we would like to process single dies with a surface
of less than 1 sq. cm. I would expect the amount of exhaust gas generated from that to
be rather low.

> What concerns me is that you MAY have a pump that uses hydrocarbon
> oil and that is a potential time bomb(literally) for any system
> running O2, you just can't and shouldn't do it. You can send the pump
> to a reputable rebuilder and they can clean it and prep it for inert
> oil such as Krytox or Fomblin which can be used with O2 service.

I did not mention that in my last mail, but in order to comply with O2
safety standards we will use an inert pump oil (e.g. PFPE based) and
follow the pump manufacturers guidelines for the oil change from hydrocarbon
to inert pump oil (which typically involves a pump service).

> Most
> dry pumps will suffice as well. I don't know where you can get
> manuals for that system but I can tell you that they are very simple
> and I have repaired dozens of them. If there is a particular question
> on this unit, I would be happy to help you with it.

Thank you !
We opened up the unit already and it appears to be pretty simple.
However, before we can test it for the first time we would like to have
the vacuum and exhaust setup working properly to have a practically safe
working environment.

This would comprise:

	(1) vacuum inlet trap with activated aluminia filter medium
	(2) inert PFPE based pump oil
	(3) oil mist filter at exhaust
	(4) activated carbon filter after oil mist filter at exhaust
	(5) exhaust gas analyzer after last filter
	(6) exhaust outlet

Components (4) and (5) are maybe already a bit of an overkill considering
the small size of the unit.

> 
> Steve Paolini Equipment Dood Harvard University Center for Nanoscale
> Systems spaolini at cns.fas.harvard.edu


Thank you and best regards,
Stefan


Sources:

[1] http://www.triontech.com/pdfs/Plasma%20Delayering%20of%20Integrated%20Circuits%20V4%20080%E2%80%A6.pdf