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.

Good luck.

Kagan TOPALLI, Ph. D.
Senior Research Engineer
MEMS-VLSI and EMT Group
Middle East Technical University
Dept. of Electrical & Electronics Eng.
TR-06531 Ankara Turkey
Phone: +90 312 210 44 09 or +90 312 210 23 40
Fax: +90 312 210 23 04
http://www.mems.eee.metu.edu.tr/~topalli/
--

Michael Larsson wrote:
> Hi Florian,
>
> You can remove the organic residues using an SC1 solution, consisting
> of NH4OH, H202 and H20 in the ratio:1:1:5. The SC1 solution (in
> various mixing ratios) is really the IC industry standard for wet
> removal of organic surface contamination.
>
> I am not sure how this will react with the TiO2 layer, but the absence
> of H2SO4 should improve things. The Pirahna solution is a very
> aggressive cleaning step, aimed at removing general surface
> contamination (metal or organic) as a preliminary step to SC1 and SC2
> cleans. The SC2 clean contains HCl (in substitution of NH4OH in SC1),
> aimed at eliminating metallic contamination.
>
> If you find that your TiO2 is still being etched, alter the mixing
> ratio (add DI) or reduce the reaction time.