Hello Evelyn,

I just happen to know what happened. Oxygen plasma oxidizes platinum.
You're likely measuring Pt-Ox. You can reduce the oxygen in a hydrogen
atmosphere. There are a number of references in a paper I recently wrote
(shameless plug):

Hydrogen Detection by Polyaniline Nanofibers on Gold and Platinum
Electrodes
Jesse D. Fowler, Shabnam Virji, Richard B. Kaner, Bruce H. Weiller
The Journal of Physical Chemistry C 2009 113 (16), 6444-6449

Jesse Fowler


>From Evelyn B 
To General MEMS discussion 
Subject [mems-talk] Ashing effects


To all,

I measured the average thickness of a Ti/Pt stack-up on a Si wafer at
three different locations as summarized below:

                  *  Before ashing        After ashing      Delta*
Structure #1: 139.7 nm              219.00 nm         79.30 nm
Structure #2: 122.5 nm              199.75 nm         77.25 nm
Structure #3: 117.0 nm              200.00 nm         83.00 nm

After doing the ashing I did not observe any damage to the Pt layer but
can't explain the increase in thickness above, especially when I had
already
calculated an etch rate of 11 nm/min and had only etched for 3 minutes.
The
ashing recipe is 150 W, 44 sccm, 250 mT for 3 minutes in O2 plasma (PE
mode).

Can anyone think of anything that could cause a change of 80 nm in
thickness?

--
EVELYN BENABE