help with evaporating tungsten

Deji A. dejia at stanford.edu
Mon Dec 11 21:02:34 PST 2006


Charis,
I and many other users have done tungsten liftoff successfully 
routinely. How thick is your metal and how thick is your resist?

Many Cheerz
Deji A.
EE rocks
-------------------------------------
Nature is the teacher of all things



Charis Quay Huei Li wrote:
> Dear all,
>
>      Recently we have been trying in our lab to evaporate tungsten as 
> e-beam alignment marks. We are encountering some problems with poor 
> adhesion during liftoff and we were wondering if ay of you who do a 
> similar process would mind sharing your steps?
>      Our smallest feature size is about 100nm and we are using either 
> 200K/950K or 495K/950K PMMA bilayer.
>      Initially, after just soaking in acetone, squirting and heating up 
> the acetone (and squirting again) one chip came out with extra metal all 
> over the place. I then tried sonicating in larger and larger time 
> increments, starting with 10s and finally going up to minutes at a time. 
> It looked like the metal wouldn't come off and wouldn't come off, and then 
> suddenly a lot of it came off at once at t = 20 minutes roughly.
>      Please let me know if you have any insight into this.
>      Thanks very much.
>
> Cheers,
> Charis.
>
>   



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