raith clip #4 is very dirty

James Conway jwc at snf.stanford.edu
Tue Jun 27 09:27:24 PDT 2006

Hello Raith Users:

Once again we have had the return to a single user, or group of Users, 
whom have some material on the back of their wafer pieces.  This 
material is incompatible with the Aluminum pallet and it is rapidly 
anodically corroding its surface where they are clipping down their 
samples.  Often they are working with multiple very small samples on 
several clips in the system. 
It is difficult if not impossible to remove as it smears when you 
mechanically attempt to clean it off, and is not affected by solvents.
Likely this is Gallium or Indium metal that a MBE or MOCVD system User 
may have used to attach his wafer to the growth mount in those system. 
These are all small pieces of substrate often smaller than 4 x 3 mm.

The end result is that it contaminates the Std. sample holder, roughens 
and corrodes the surface and then renders the Std. Sample holder 
unsuitable for EBL because the holder cannot make suitable electrical 
contact to the sample nor allow it to lay flat onto it.


All Users working with any material on the back sides of the wafers are 
instructed to completely remove all material before placing the sample 
into the RAITH.
  This includes resist and PMMA residues as well as all residues from 
previous processing and mounting of your samples on the backside of your 
chips and wafers.

Users having concerns or needing assistance in cleaning their samples 
are requested to contact James Conway for help.

Thank you for your support!

James Conway

Andrei Faraon wrote:

> Hi James,
> Today around 9:30 when I came to do my Raith lithography and I noticed 
> a big grey-colored stain under clip number 4. It looks like the same 
> material that made the other clips dirty. However, this stain is very 
> large, on the order of ~1cm/1cm. Maybe you could re polish the stage 
> during the Raith shutdown next week because all the clips are in 
> pretty bad condition, especially for people working with small pieces.
> Andrei
> -- 
> Andrei Faraon
> Stanford University, Applied Physics
> 316 Via Pueblo Mall
> Stanford, CA, 94305
> Mobile: 650 714 7881
> Office: 650 723 2279 

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