National Semiconductor Corporation

Weidong Chen

Christopher S Blair

A process flow for forming a polysilicon-to-polysilicon capacitor performs the capacitor anneal step in a nitrous oxide ambient. As a result, a nitroxide layer forms over heavily doped polysilicon of the upper electrode of the capacitor. This nitroxide layer acts as a barrier against the diffusion of oxygen, preventing further oxidation of the heavily doped polysilicon electrode layer during the subsequent seal oxidation step. The nitroxide barrier layer is readily removed along with the other seal oxide layers immediately before formation of the silicided capacitor electrode contacts, without any attendant danger of overetching of gate oxide or spacer structures. Where the gate polysilicon layer is doped immediately after its formation, an additional capacitor anneal step in a nitrous oxide ambient is necessary to form an additional nitroxide layer.

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San Jose, CA, United States of America

Weidong Chen