Low temperature wafer-level packaging of MEMS using selective laser bonding

In recent years there has been significant interest in the development of new types of Micro-Electro-Mechanical-Systems (MEMS) and related microdevices but the issue of packaging remains a problem in many cases, and is indeed a particular challenge for their commercialisation. Current hermetic bonding techniques involve heating the whole device to high temperatures, in some cases combined with strong electric fields. This prevents the use of temperature-sensitive materials within the package (e.g. polymer and magnetic materials). We have therefore been developing alternative solutions based on the use of a laser as a truly localised heat source to drive an intermediate layer bonding process. In this paper we describe laser-based packaging of silicon to glass - materials commonly used in MEMS fabrication - on a wafer-level, where multiple devices are packaged on a single silicon wafer. The bonding is achieved by using a Benzocyclobutene intermediate layer. Previously we have demonstrated bonding of a simplified pattern of 5 individual packages on the same chip as a proof of principle. In this work we present packaging of more complex and more closely spaced patterns and the issues involved in such processes when using laser bonding.