Hey Kyle,
I have struggled with this problem for many years and have been unsuccessful in coming up with a wet or dry etch that selectively removes cobalt silicide. The method we use is to polish into the polysilicon layer using 0.05um alumina. You can use coloration under an optical microscope to know that you're into the poly layer. The 'colors' you will have to 'learn' for the given fabrication technology. It is important that the silicide layer is completely gone. Then we use a hydroxide wet etch to selectively remove the polysilicon, leaving the gate dielectric exposed. This has been our standard POR for years. It is an acquired skill but it does work quite nicely.
- Phil Kaszuba
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Phil Kaszuba
Senior Member Technical Staff
Globalfoundries
Essex Junction VT
(802) 769-1043
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Original Message:
Sent: 04-22-2020 16:00
From: Kyle Murphy
Subject: Cobalt-Silicide Layer Removal from Poly
Hello All,
I am deprocessing a part that uses cobalt silicide on top of the poly. I am trying to remove the cobalt silicide from the poly that would allow for the poly silicon to be removed to view the gate oxide for anomalies. I am having issues with this step and have tried wet and dry etch approaches. Does anyone have some insight into an etching recipe wet or dry, or a deprocessing technique that has success in removing this layer?
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Kyle Murphy
FA Engineer
Microchip Technology
Colorado Springs CO
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