[labnetwork] Cadmium Telluride sputtering target exchange problems

[Pramod Karulkar]

Explosive oxidation of very pure thin films in a vacuum chamber is 
known.   Popping sounds can be heard if a chamber used for depositing 
titanium or  aluminum is suddenly exposed to room air.  Flash of light 
can also be seen if the chamber is full of dust or peeling matter.  Both 
can be dangerous.  You have to set up protocols for slow venting, 
waiting for a long time ( hour or hours)  to allow for slow passivation 
of unoxidized materials, and then opening the chamber.  Vent and pump 
cycles may help too.  Check with your vendor.

Slow venting may reduce peeling and release of particles.  You have to 
allow the whole system to reach room temperature (or slightly above RT) 
before venting it.  However, some peeling of material will occur and the 
chimney and chamber walls/parts will have to be cleaned thoroughly using 
a dedicated  vacuum cleaner.  Again  protocols for this will have to be 
set up. You may follow processes/precautions used to clean similar 
equipment such as CVD chambers or ion implant source chambers.  Color of 
the flakes depends on the composition and surface finish.  "Black" may 
not mean anything.  It may be an off stoichiometric deposition with 
residual gas contamination that may vary with position in the chamber. 

Smells are hard to track down unless you sample the gas and analyze.  
Complex species are formed if you are doing anything reactive in the 
chamber.  Smells can arise from back streaming of some vapors from a 
pumping station.  Check with the vendor.  Repeated cycles of venting and 
rough pump down without opening the door will help to reduce the 
concentration of smelly components.  (Plasma etch chambers tend to have 
unusual odors. Well exhausted bench, hood, enclosure etc has to be used 
to clean such chambers. A mask is needed to.)

Vendor websites used to have info on such topics.  If you did not 
download and save it,  most of it is gone because of the newer style of 
websites.  
http://www.asm.com/index.php?option=com_content&task=view&id=51&Itemid=67

Hope this helps. 

Pramod C Karulkar
Fairbanks Alaska
907 457 4123
443 622 4425

Keith Bradshaw wrote:
>
> We are getting a strong smell from the chamber and instant oxidation 
> and flaking of product deposited on the chimney of our Sputtering 
> system when changing the Cad-Tel target.
>
>  
>
> What is done to avoid this?
>
>  
>
> Is this smell harmful?
>
>  
>
> The flakes are very dark and seem to form when we open the system up 
> to atmosphere.  It is load locked so normally it doesn't see air.
>
>  
>
> Keith Bradshaw
>
> 972-883-2099
>
> RL 10
>
> University of Texas at Dallas Clean Room
>
> NSERL building
>
>  
>
> ------------------------------------------------------------------------
>
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