A Generic Surface Micromachining Module for Mems Hermetic Packaging at Temperatures Below 200 degrees C

TL;DR

This paper introduces a versatile surface micromachining process for MEMS hermetic packaging at temperatures below 200°C, utilizing nickel plating and photoresist sacrificial layers for low-cost, efficient sealing and release.

Contribution

It presents a new generic process for MEMS hermetic packaging that reduces costs and complexity through thin film caps, reflow sealing, and innovative etch hole techniques.

Findings

Successful sealing with reflow technique at 180°C

Small etch holes enable efficient release and block sealing material

Process reduces thickness, area, and cost of MEMS packaging

Abstract

This paper presents the different processing steps of a new generic surface micromachining module for MEMS hermetic packaging at temperatures around 180 degrees C based on nickel plating and photoresist sacrificial layers. The advantages of thin film caps are the reduced thickness and area consumption and the promise of being a low-cost batch process. Moreover, sealing happens by a reflow technique, giving the freedom of choosing the pressure and atmosphere inside the cavity. Sacrificial etch holes are situated above the device allowing shorter release times compared to the state-of-the-art. With the so-called over-plating process, small etch holes can be created in the membrane without the need of expensive lithography tools. The etch holes in the membrane have been shown to be sufficiently small to block the sealing material to pass through, but still large enough to enable an efficient release.