MEMS and technology gap
NTT Microsystem Integration Laboratories has the mission of creating key hardware-oriented technologies to achieve a network environment that can provide safe, secure, and enjoyable broadband and ubiquitous services, as promoted by the NTT Group. At these laboratories, MEMS is positioned as a platform technology for creating ubiquitous services.
The graph in Fig. 1 shows device design rule on the horizontal axis and film thickness on the vertical axis. RF-MEMS and optical-MEMS devices lie in the intermediate region between miniature devices like LSIs (large-scale integrated circuits) and Jisso technologies*1 like multichip modules and printed wired boards. Jisso technologies have an important role in enabling MEMS devices with microscopic movable mechanical elements to interface with the outside world. Existing technologies used for Jisso, however, target elements with sizes of several micrometers to several millimeters or more, and they cannot by themselves be used to fabricate tiny MEMS devices.
Fig. 1.Device technology and dimensions.
If, however, submicrometer LSIs and MEMS devices using LSI fabrication technology can be fabricated and integrated on a silicon substrate, we can expect even greater downsizing and greater functionality including enhanced intelligence in MEMS devices. Yet, technology for fabricating LSIs is specialized for ultramicrofabrication, and it too is not necessarily applicable to the fabrication of MEMS devices. This leaves MEMS devices lying in a technology gap between LSIs and Jisso technologies. Consequently, despite the great expectations that MEMS has been generating, only a few MEMS devices have been successful in business, such as inkjet printer heads.