[labnetwork] on the deposition of copper indium diselenide

[Pramod C Karulkar]

The odors in plasma systems that use sulfur compounds are well known and 
have been analyzed.  Back-streaming from pumps combined with chamber 
processes can also result in odors. It is not surprising that you smell 
something in a sputtering system that uses selenium.   The trace 
chemicals may be harmful and one should avoid breathing them.   If you 
smell it, then you have it.Your local safety officer should be able help 
you seek solutions.  There are mature protocols in the industry 
for opening, operating, and cleaning reactive systems such as evaporator 
chambers, plasma chambers, implant sources, and even ovens.   You may 
find that the boxes used to store the deposited substrates and vacuum 
system parts might develop the same odor after a few days of storage.

Some possibilities are: (1) Improve protocol: Delay opening of the 
chamber after a deposition and go through repeated vent/pump cycles 
before opening the chamber.  Require operators to wear appropriate 
personal protection equipment e.g., gloves, sleeve covers, masks etc.  
Avoid opening the chamber when the area is crowded with people.

(2) Enhance installation for safety: Place the entire equipment in a 
exhausted enclosure,  environmental chamber, a hood, or a glove box such 
that there is enough exhaust to carry the odor away and airflow is 
always away (and not towards) the operator.  What to do with the exhaust 
will depend on the size of your operation and local 
policies/regulations.  Prevent back-streaming from the pumping station. 
Pump oils, even in trace amounts, lead to serious problems when added to 
the chamber chemistry.

(3) Selenium and many of its compounds are considered toxic.  At some 
point,  the odor causing compound will have to identified.   In sulfur, 
fluorine, oxygen  based plasma systems,  oxyfluorides  are believed to 
cause the odors.


(4) You will have many particles.  They will get worse as the system is 
used.  Your results will be dominated by particle contamination if you 
keep making depositions without any cleaning.  You may choose to cover 
surfaces that are in the direct line of deposition with a disposable 
liner such as a custom made shield or a clean Al foil.  Protocols to 
change the shield often and to vacuum out the chamber after every 
deposition run will have to be developed.  You have to use a vacuum 
cleaner with a HEPA filter designed for such a laboratory use and 
dispose bags appropriately.  A scraping tool made by pinching flat and 
sharpening a stainless steel tube to custom fit the vacuum cleaner hose 
will help.  You can make smaller vacuum tools from smaller tubes by 
using a Teflon plug (cork) to fit them into the vacuum hose.

Good luck and please do send info about the closure of thisissue to the 
microelectronics community.

Pramod Karulkar

Pramod C Karulkar
1470  Goshawk Lane
Fairbanks AK 99709

907 457 4123

On 3/26/2011 8:27 AM, Mark M Crain wrote:
> Hello Everyone,
>
> We have just started some sputter deposition of copper indium
> diselenide.  This deposition has started some questioning both its
> safety and contamination.  I did the obvious before even purchasing the
> target; reviewing the MSDS, speaking with target suppliers, and
> "googling" the topic of CIS and CIGS deposition.
>
> 1) Earlier this week there were concerns regarding the smell coming
> from the chamber after sputter deposition. I did have the opportunity to
> smell this.  Is this harmful?  Would it be advisable to add some pump
> and purge process to the venting sequence?
>
> 2)  There are claims of particulate in the chamber.  I have not seen
> this yet but would be interested in comments regarding the use of a
> target like this and its possible contamination to other deposition
> processes.  The sources have lids so this material should be landing on
> the lids and not the targets.  I can imagine that heated areas of the
> chamber could off gas contamination.
>
>
> Best Regards
>
> Mark
>
> Mark Crain
> Cleanroom Manager
> University of Louisville
> SRB room 233
> 2210 South Brook Street
> Louisville KY 40208
> Phone 502/852-1572
> Fax 502/852-8128
>
>
>
>
>
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