Optical MEMS for Telecommunications: Some Reliability Issues

Abstract

Constant demand for mobility, interconnectivity and bandwidth is causing rapid expansion of the telecommunication infrastructure across the world. World-wide installation of optical fibre-based telecommunication systems has given rise to a promising optically-related sub segment of MEMS technology called micro-opto-electro-mechanical systems (MOEMS), commonly known as optical MEMS. MEMS telecommunications applications can be roughly divided into two key classes: optoelectronic packaging and functional optical devices. When functional optical devices are in question, optical MEMS devices that integrate optical, mechanical, and electrical components on a single wafer are allowing the implementation of various key optical-network elements in a compact, low-cost form. They usually involve small moving optical parts in order to obtain more advanced functionality. In optoelectronic packaging, MEMS are providing low-cost accurate optical alignment. At the moment, fabri‐ cation of complex optical MEMS devices and micro-electro-mechanical alignment devices is based on micromachining techniques combined with IC-based processing methods. Such manufacturing techniques have enabled low cost, mass production of optical MEMS compo‐ nents and devices. However, successful commercialization of optical MEMS technology that is being driven by the progress in optical communications strongly depends on device reliability. Optical MEMS device reliability is significantly more complex than silicon IC reliability, partly because optical MEMS failures can be either electrical or mechanical, and partly because there is a vast diversity of device designs, materials and functions. It is of the greatest importance that design and realization of optical MEMS device must include all levels of reliability issues from the onset of the project. For that reason, this chapter focuses on the identification and understanding of main mechanisms that cause failure of optical MEMS devices that are being used in telecommunications. First, the commonly used MEMS process‐