Hi Mikas,

We have had similar problems with adhesion between Ti, Au and other
materials that works well for liftoff, but generally does not survive
wirebonding.  What other materials do you have in your e-beam system?
I'm surprised that the Ti did not work, but aluminum or chrome might
also be worth a shot.  Finally, is the substrate treated any after the
oxygen plasma?  A mild acid etch, if possible, might work.

-Alex

mikas remeika wrote:
> Hello,
>
> does anybody have experience dealing with this kind of issue:
>
> I'm trying to deposit a film of gold on top of a thin film of titanium
> (e-beam evaporated), the titanium is exposed to air (and oxygen plasma)
> during previous processing, so its inevitable that there is a thin layer of
> oxide on the surface of the titanium.
>
> A Gold film is e-beam evaporated onto the surface of the Ti (TiO2).
> Resulting film adheres well enough to perform lift-off, however, mechanical
> stress such as wireboding results in large sections of the gold film peeling
> off.  I have tried evaporating a fresh layer of Ti under the gold (in the
> same vacuum), that did not give any improvement in adhesion.  I also have
> access to sputtering machines, however in previous experience evaporated
> gold adhered more reliably to different surfaces.
>
> So my question - is there are way to treat the titanium/TiO2 surface to
> create good adhesion to the gold layer? I have acceess to a range of
> materials for sputtering and evaporation, if there is a specific material
> that adheres well to both gold and TiO2 I would really like to know what it
> is.
>
> Some notes: The sample in this case cannot be heated to more than 100C and
> cannot be exposed to RIE type plasma.  Also, it is necessary to have
> electrical contact between the gold and titanium (the naturally formed oxide
> in this case does not create electrical insulation).
>
> Thank you very much for any advice,
>
> -Mikas
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