I've seen the same thing before when using Cr as a mask for LPCVD oxide.
In my case, it appeared that some of the oxide was sputtered off and coated
the Cr.
A quick HF or BHF dip removed the oxide, and the Cr could then be stripped
in CR-14 or CR-7.
    --Kirt Williams

----- Original Message -----
From: "Ho Yin Chan" 
To: 
Sent: Sunday, April 27, 2008 9:49 PM
Subject: [mems-talk] Chromium removal

> Hi all,
>
> Currently, I am etching PECVD oxide using standard RIE and Cr is the
> masking layer. However, I found that I cannot remove the Cr mask using
> Cr etch after going through the RIE process. I am wondering if there
> is anything happened on the Cr surface. I'd like to see if you could
> give me some suggestions on how to remove the top Cr layer. Thanks