We have developed the following formula for Cu etching and we have not had
any problem with Ni pitting.  The etching process is well behaved with a
very smooth Cu-surface morphology maintained throughout the etching process.


HNO3:H3PO4:CH3COOH = 0.5:50.0:49.5 (volume)
Application condition: room temperature
Etching rate: ~ 10 to 20 Å/sec


Good luck.


Xiaochuan Zhou
Xeotron Corporation
Xczhou@email.msn.com

-----Original Message-----
From:   Adam Cohen [mailto:acohen@ISI.EDU]
Sent:   Friday, September 18, 1998 7:10 PM
To:     MEMS@ISI.EDU
Subject:        Ni-compatible Cu etchants

Dear Colleagues,

We are seeking a Cu etchant that doesn't cause any pitting or other damage
to Ni. A commercial product we have tried, Enthone's Enstrip C38, seems to
pit the Ni, at least sometimes.

Does anyone have any suggestions on what we might try? They would be greatly
appreciated.

Sincerely,

Adam Cohen
USC/ISI