Hi Gabriel,

I build structures of similar geometry (2-3 µm tall, lateral dimensions varying
from 4 - 12 µm) using RIE of a uniform layer of SiO2 with a hardbaked
photoresist mask, with an SF6/C4F8/H2 based chemistry that's been carefully
tuned for high anisotropy.  (Alternatively, if you don't specifically need SiO2,
for rapid prototyping I've also been successful in building these structures
directly out of SU-8 - the SU-8 2002 formulation can easily be spun to 2 µm
thick and patterned directly.)

Good luck,
Mike Whitson


On Nov 20, 2012, at 11:37, Gabriel Puebla-Hellmann wrote:

>
> Hi,
>
> I need 2 micron high dielectric pillars with somewhat sloped sidewalls for a
> project involving post deposition, lateral dimensions are 6 by 8 microns.
> I'm currently using PECVD silicon oxide, which gives good slopes, but due to
> the conformal nature of the deposition, also flags (see SEM image), even
> with an undercut of more than 5 microns.
> Does anyone have an alternative suggestion? Or a way of getting rid of the
> flags/making the PECVD more directional? Unfortunately, a post deposition
> wet-etching does not really work, 10 s in 20:1 BHF already removes the
> entire structure. The oxide quality is low as the PECVD is running at a low
> temp (120 deg) process to avoid resist melting/glass transition.
> Thanks for your input,
> Gabriel
>
> **************************************************************
> Gabriel Puebla-Hellmann
> ETH Zuerich
> Laboratory for Solid State Physics
> Quantum Device Lab
> HPF D5
> Schafmattstr.  16
> 8093 Zurich
> Switzerland
>
> Tel: +41 44 633 71 24
>
> www.qudev.ethz.ch
> **************************************************************
>
>
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