Integration of RF sputtered ZnO film with MEMS based diaphragms

In the present work, we report a modified fabrication process to integrate the ZnO film with bulk-micromachined diaphragms. ZnO films are very sensitive to the chemicals used in the micro-electro-mechanical systems (MEMS) fabrication process which include acids, bases and etchants of different material layers (e.g. SiO₂, chromium, gold etc.). A Si₃N₄ layer is incorporated to protect the ZnO film from the etchants of chromium and gold used for patterning the electrodes. A mechanical jig is used for protecting the front side (ZnO film side) of the wafer from ethylenediamine pyrocatechol water (EPW) during the anisotropic etching of silicon.