Hi Jay,

The peeling depends on the relative film thicknesses of the trilayers. How
thick is your Au layer in comparision to device layer? Perhaps you may try
increasing the Cr layer thickness a bit more. There are other adhesion
layers such as titanium, tungsten which are normally preferred to overcome
the diffusion effects. However, in your case, it may not be
required. Getting an estimate of the pre-stress as you go along the
processing steps would be of help.

Regards,
Prasanna

On Fri, Apr 30, 2010 at 6:33 AM, Jie Zou  wrote:

> Hi folks,
>
> I defined a gold pattern by e-beam lithography and lift-off. The gold was
> evaporated on the SOI with ~8nm Cr as the adhesion. After several other
> fabrications (mainly DRIE), I had some free-standing gold structures
> sitting
> on a silicon structure made by the device layer of a SOI wafer. My last
> step
> was to release the whole structure by HF etching the buried oxide layer. I
> used 49% HF for 3min to achieve the necessary undercutting to make sure my
> structure was free. However part of the gold structure was peeled off.
>
> How can I improve it? Is there another adhesion layer that can resist HF
> better? I tried BOE instead of 49% HF. It didn't help much.
>
> Thanks a lot.
>
> Jay