If ther resist is not to thick you may try an O2 plasma - it's very
slow.
 There are strippers - expensive - to strip negattive resist by several
 manufactures.

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   1. selective negative resist stripper (Javier Crespo)


Message: 1
Date: Mon, 17 Nov 2008 16:42:57 +0100
From: "Javier Crespo" 
Subject: [mems-talk] selective negative resist stripper
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<2320FF588EF2E34AA1F756CB6284ECBD04BDFF8B@srvcorreo.fagorelectronica.es>

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Dear All,

Could anyone tell me how could I remove negative photoresist from a
silicon wafer without affecting metal layer (Ni or AlSi)?

I know that the piranha etching etches the resist in a higher rate than
the metal, but I don't know in which percentage.