Catálogo de publicaciones - libros

A proposed EU regulation requires the automotive industry to develop technologies that will substantially decrease the risk for vulnerable road users such as pedestrians when hit by a vehicle. Automatic brake assist systems, activated by a suitable sensor, will reduce the speed of the vehicle before the impact. Far InfraRed (FIR) detectors are ideal candidates for such sensing systems. In order to enable high volume serial installation, the main development must be focused on cost reduction. Optimizing all aspects of the system, including sensor size, production yield and 3D wafer level vacuum packaging will lower today’s “high end” FIR product costs by an order of magnitude. A low-cost FIR infrared bolometer is developed in the Eureka labeled PIMS (Pedestrian Injury Mitigation System) project. In the paper the background and the actual design of the first demonstrator to be finished in 2008 are described in detail.

Microelectromechanical Systems (MEMS) resonators have been investigated for over forty years but have never delivered the high performance and low cost required of commercial oscillators. Limiting factors have been temperature drift, long term stability, susceptibility to vibration, manufacturability, and low cost back end packaging. These requirements have now been met by SiTime’s MEMS First™ wafer-level encapsulation technology combined with a system architecture using modern phase lock loop (PLL) technology combined with a high performance CMOS signal conditioning chip with integral temperature sensor to compensate for frequency offset and temperature drift. SiTime’s MEMS and CMOS chips are manufactured in state of the art CMOS fabrication facilities and can be packaged with any semiconductor packaging technology such as plastic molding, flip chip, MCM and SIP. The resulting silicon MEMS oscillators outperform existing quartz solutions in various aspects such as reliability, robustness, small size, and system integration; and are suitable for most automotive and commercial applications.

This paper reviews the product lines for automotive MEMS gyroscopes for the applications ESP®, roll-over detection for airbag systems, and navigation systems by describing their silicon micromachining technology, working principle, and packaging technology. In each of these technology areas, important progress has been made in the past decade which enabled a very broad market acceptance for MEMS gyroscope sensors. Additionally, we discuss important future trends of MEMS gyroscopes that arise due to changing system requirements and due to the impact of upcoming non-automotive applications.

Rapidly developing silicon-based sensor technology also necessitates new material solutions in the field of silicon wafers. Combined with the constantly accelerating product cycles, this means that new sensors need to be launched cost-effectively and quickly. Collaboration between the material supplier and the customer must be seamless and continuous in order to be able to avoid unnecessary business risks. Traditional sensor technologies are now joined by high aspect ratio (HAR) structures that enable the products’ cost-effectiveness to be improved even further, as the method makes allowances for small sensors and large wafer sizes, and is mostly compatible with the technology used in the manufacture of semiconductors. HAR technology also enables full advantage to be taken of the possibilities presented by SOI: in the manufacture of SOI wafers, it is possible to introduce tailored buried structures in the wafer. This opens up new vistas in terms of manufacturing high-performance sensors that integrate multiple functions. This presentation focuses on SOI technology that enables HAR structures with DRIE processing.

Bulk micromachining from VTI Technologies Oy is well known for excellent performance especially for low-g measurements. The latest development of VTI 3D - MEMS has combined higher aspect ratios reached with deep reactive ion etching with those bulk structures. This has allowed shrinking the die size of sensing elements in combination with even better performance than earlier generation of accelerometers and inclinometers. Parallel to this dedicated integrated circuits have been developed in a way that better and more precise signal conditioning and highly advanced safety features were possible in the same die. This has provided an excellent tool box for failure detection that enables latest automotive application to come along with a minimum amount of physical sensors; so called sensor fusion.

Accurate inclination measurement opens various possibilities for improved or new functionality and applications in a vehicle from Hill Start Aid through headlamp levelling to improved navigation. Improved performance of sensors facilitates usage of higher range sensors also as a high performance inclinometer, enabling sensor fusion, adding new applications without increased system cost.