A Wafer Level Chip Size Package for Micromechanical and Microlenses Applications

ABSTRACT While package developers struggle to keep pace with the shrinking I/O pitch of the latest ICs, another challenge is being added by a new wave of micro-electro-mechanical systems (MEMS). These devices combine standard IC circuitry with micro-moving silicon structures. MEMS are micron-sized structures such as beams, cantilevers, diaphragms, valves, plates, and switches that can function as tiny sensors and actuators. They are fabricated by integrated circuit (IC) manufacturing processes; that is, by bulk and surface micromachining. Like ICs, thousands of micromachines can be fabricated on a single wafer with supporting circuits integrated on the chip. They can be mass-produced in the millions at low prices, which is their main appeal. One of the biggest challenges is how MEMS chips will be packaged. While the devices share many of the same features of conventional ICs, they also present a host of differences. Since the whole point of MEMS is to utilize the micro-moving parts, the package must have feedthroughs from these structures to the environment, while protecting - but not impeding - the moving parts. The packaging of MEMS devices and systems needs to improve considerably from its current primitive state. MEMS packaging present unique challenges compared to IC packaging due to the diversity of MEMS devices and the requirement that many of these devices are in continuous and intimate contact with their environment. Presently, nearly all MEMS development efforts must develop a new and specialized package each time a new device is designed. Consequently, most companies find that packaging is the single most expensive and time-consuming task in their overall MEMS product development program. As with the actual components themselves. The packaging issue for micromechanical devices is currently one of the most problematic technologies in this emerging field. The available packages are often large and expensive, thereby limiting the applications of micromechanical devices.