Hi Kagan,

My suggestion was to use SC1, rather than Piranha to wet-clean the TiO2
layer. I have no practical experience to back-up my comments unfortunately,
but I am unaware of any wet etchants capable of high etch rates in Ti that
don't either include HF or -Cl groups. With regard to TiO2, this is
the product formed when Ti oxidises under galvanic attack. Once grown, the
oxide acts as a barrier, inhibiting further chemical attack. The ability to
protect underlying Ti from oxidation can obviously be reduced when
considering a deposited layer (with defects) relative to pure, bulk
material. Nevertheless, theory would suggest that an SC1 clean
(NH4OH:H2O2:H20) should not attack Ti, and certainly not it's chemically
inert oxide; even if this is indeed formed during the SC1 clean.

Florian: is the layer sputtered or evaporated?

Regards,

Michael


>
> ---------- Forwarded message ----------
> From: Kagan Topalli 
> To: General MEMS discussion 
> Date: Mon, 07 Apr 2008 20:34:33 +0300
> Subject: Re: [mems-talk] Pirahna attack of TiO2
> Dear Florian,
>
> Ti (probably also TiO2) is attacked by Piranha solution (actually H2O2
> attacks Ti, hence Michael's suggestion might be dangerous). you may try
> SVC-175 or PRS2000  (a photoresist stripper) overnight swirling the
> chemical.