Redox buffered hydrofluoric acid etchant for the reduction...

Compositions – Etching or brightening compositions

Reexamination Certificate

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C216S002000, C216S102000, C438S048000, C438S052000

Reexamination Certificate

active

07597819

ABSTRACT:
Etchant solutions comprising a redox buffer can be used during the release etch step to reduce damage to the structural layers of a MEMS device that has noble material films. A preferred redox buffer comprises a soluble thiophosphoric acid, ester, or salt that maintains the electrochemical potential of the etchant solution at a level that prevents oxidation of the structural material. Therefore, the redox buffer preferentially oxidizes in place of the structural material. The sacrificial redox buffer thereby protects the exposed structural layers while permitting the dissolution of sacrificial oxide layers during the release etch.

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