Mary Tang mtang at
Thu Jan 26 17:10:17 PST 2006

Hi everyone --

I think I'm a bit concerned about allowing nanoparticle suspensions in 
the litho area.  I really have no data, but it seems to me that when you 
spin coat a material, you get an aerosol dispersion from the edges.  So, 
it seems to me that you'd probably get floating bits of nanoparticles in 
the area.  These particles are likely to stick really, really well to a 
surface, once they hit.  Therefore, I don't think I could in good 
conscience recommend allowing this -- particularly when it appears that 
there is no compelling reason to do this in the litho area.

I understand Mahnaz has a spare little laurel spin coater -- maybe we 
could set this up in another area of the lab (outside the lab?) for 
nanoparticle work?  Along with a programmable hot plate?

Again, I have no data -- just this gut feeling that this wouldn't be a 
good idea.  I guess this is based on once working in a lab where we made 
nanoparticles out of biopolymers and polymers -- these used to get 
everywhere and stick to everything -- not that you could see them, but 
you'd see them in the test results, due to cross-contamination.  
Granted, working in a filtered laminar flow hood improved things, but it 
appeared to be largely depending on whether the researcher had "good 
hands".  Somehow, I'd feel better if any processes we approved weren't 
quite so dependent on one's good lab technique...

I think after the wafer has been spun dry and then baked dry, that the 
nanoparticles aren't likely to come off with anything short of a metal 
etch or RCA clean and that subsequent processing in innotec or metalica 
wouldn't be a problem.


Yuan Zhang wrote:

> Dear community members,
> Some students in our group are going to work with several kinds of 
> nanoparticles. We are not sure if the materials or processes are safe 
> enough to be allowed inside snf. Here are our processes.
> 1. FePt nanoparticles (3~4nm or 5~6nm in size)
>     Purpose: make ohmic contact with nanoparticles in between metal 
> and heavily doped Si
>     Chemical include:  n.p. are in a oleylamine/oleic acid/hexane 
> solution, where oleylamine/oleic acid act as surfactants that surround 
> each nanoparticle
>     Process: 1. HF clean Si surface
>                   2. ion implantation to form n-type doped Si
>                   3. dilute FePt solution by hexane and spin coat 
> using headway
>                   4. remove hexane using hot plate
>                   5. remove oleic acid under Ne/vacuum heating, use 
> blue oven
>                   6. evaporate or sputter Al, use innotec or metalic
>                   7. lithography: headway2, karlsuss/evaline, develop
>                   8. etch Al
> 2. Au nanoparticles (~10nm in size)
>     Purpose: form nice ordered Au nanoparticles on Si surface
>     Chemical included: Au nanoparticles in PSP4VP/toluene solution
>                                  PSP4VP: poly(styrene-b-4-vinylpyridine)
>     Process: 1. clean the Si surface
>                   2. spin coat the solution using headway
>                   3. remove toluene by hot plate
>                   4. remove polymer by annealing under Ar or etching 
> by O2 (drytek1)
>                   5. afm or SEM imaging
> Please let me know if they are allowed. Thank you very much for your 
> attention and help.
> Best,
> Yuan       

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
mtang at

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