Enhancing the Release Process Yield for CMOS-MEMS Metal Resonators Based on Diffusion-Controlling Structures

This paper presents an effective approach for improving the yield during the wet-release process of CMOS-MEMS metal resonators by covering the devices with diffusion-limiting structures to pinch the diffusion path of the HF-based etchant. Particularly, similar to the work recently published in [1], the introduced diffusion-controlling structure successfully extends the release time window ~9 from 8 min to 70 min, with an expanse of a roughly doubled overall release time. In addition to that in [1], this work further investigates the influence of the design variations of the release holes, providing a guideline in the future adoption to other types of resonator devices based on the same process platform. Although demonstrated on the die level, this approach could be much more useful in wafer batch processes, where the release time window for each individual device becomes much critical as they should be longer enough to cover the variation across the whole batch.