Sounds like a similar problem as Aluminum oxide.  The white ceramic
plates used for hybrids go yellow over time.  An Oxygen plasma restores
the white color.  The theory is it a moisture problem.  Bill Moffat

________________________________

From: [email protected] on behalf of Evelyn B
Sent: Sat 2/7/2009 7:53 AM
To: General MEMS discussion; Evelyn Benabe
Subject: [mems-talk] MgO Cleaning

I have been using MgO wafers for some time and have noticed that if you
leave them unused for a while they no longer look clean.  I have tried
cleaning them in an ultrasound bath using acetone and methanol but that does
not remove whatever is on the surface.  Since the wafers have not been
processed I am assuming that what I see is oxidation on the surface and not
resist.  Does anyone know of a way of cleaning what seems to be a native
oxide on MgO?  I tried dipping the wafer on 10:1 BOE for ~ 2 minutes but
that did not make a difference.

EVELYN BENABE