Hello,

Developing a stable gold layer over different substrate materials has been
the topic of discussion in the field of microelectronics for years. I don't
know why you prefer to have a layer of gold over titanium. Is there any
specific reason for choosing titanium and gold combination? Thin film Nickel
over titanium layer before depositing Gold can be one of the options.
Nickel is a good barrier layer to prevent gold diffusion and gold film was
found to be stable over nickel layers. Besides Nickel is a resonably good
electrical conductor as well.

Regards,
Prasanna

On Fri, Jun 19, 2009 at 9:19 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).