How about dipping the substrate in HF (1:100) for few seconds to remove the
top oxide layer just before it goes to deposition. Then deposit Ti/Au. Did
you try it??

Regards,
Pavan

On Fri, Jun 19, 2009 at 4:19 PM, 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).