The Role of Reliability Models in Commercializing IntegratedMEMS Technology for Telecom Networks

摘要

Micro-technology/MEMS became an important enabling platform in the late 1990's torncope with the increasing bandwidth demands of optical communications. MEMS werernexplored as an alternative to scale-limited electrical switching and tunability needs withrnthe advent of large scale optical cross connect switches (OXC) and tunable lasers.rnHowever, with the telecom crash of 2001, the demand for exponentially increasingrnbandwidth was diminished and system vendors returned to more classical solutions tornmeet customer requirements. A driving force behind the use of traditional componentsrnwas the well established reliability and ageing standards developed both by industryrnorganizations (e.g. Telcordia) and component vendors (e.g. MSA agreements). MEMSrntechnology does not have an equivalent established lifetime prediction model.rnThis paper will discuss the use of a novel reliability model to characterize the lifetime ofrnMEMS devices used in optical communications. The device under study is an integratedrnvariable optical attenuator (VOA) co-packaged with a high-speed receiver module. Therndevice is fabricated using silicon-on-insulator technology combined with bulk micromachiningrnfor release. The mechanical actuation is effected using thermal expansion andrnJoule heating.rnThe customer base for this device is well established and has a pre-determined model forrnassessing the reliability of a system. For example, in one case: 10-20 years of life, subjectrnto >70℃ temperature shifts, and can be stored and handled in harsh environments (>85%rnRH).rnThe lifetime prediction tool commonly employed is an accelerated ageing model basedrnon an Arrhenius performance decay with the activation energy being determined byrnoverloading devices beyond the conditions that they would see in service. This way, 10-rn20 years of lifetime performance can be determined using several months of acceleratedrntesting. The resulting reliability parameter is the FIT (Failure In Time) rate defined as thernnumber of failures in 109 hr of operation.