help with evaporating tungsten

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

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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