Hi Natsuki

You should sandwich the another glass wafer between the glass and the
electrode plate. Probably the anther wafer should absorb most sodium ions
during the bonding process.

Regards,

Yoshi Sakata

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org]
On Behalf Of Miyakawa, Natsuki
Sent: Tuesday, November 03, 2009 11:18 PM
To: General MEMS discussion
Subject: [mems-talk] Anodic bonding

Dear all,

When I bond glass wafer (Borofloat33, Schott) with silicon wafer anodically,
then I observe lot of small spots on the back side of the glass wafer which
make the glass to appear rather cloudy. So far as I understand  this
phenomenon is due to locally concentrated sodium ions.

My question: Is there any method to avoid this happens so that the glass
wafer remains clear and transparent after the anodic bonding?

Thanks!

Regards

Natsuki