Sensors strip off their packaging with VTI Chip-on-MEMS
VTI Technologies has developed manufacturing concepts that offer better ways of combining MEMS and ASIC technology to create smaller, smarter and dramatically lower cost sensing devices suitable for large volume production. The work being carried out by VTI, a leader in MEMS sensing applications could open up a raft of new sensing applications for a wide range of handheld devices.
One of the challenges in sensing technology is to combine the very different requirements of microelectromechanical systems with that of conventional electronic circuitry at the wafer level. In the first phase of its development work, VTI has been able to demonstrate one approach that uses currently available manufacturing techniques, to make smaller, lower cost devices. In the second phase, VTI is looking at new manufacturing technologies which will allow more complex sensing devices to be made using wafer-level integrations with the benefits of lower cost volume production and small size.
In its successful first phase, completed this year, VTI has demonstrated the potential of heterogeneous integration. Its approach has been to maintain the benefits of manufacturing the MEMS devices and ASICs on separate wafers to allow full testing of both types of before wafer level integration takes place. For this Chip-on-MEMS concept, thinned ASICs chips are flip-chipped onto the MEMS wafer in known good locations. Redistribution and isolation layers are applied to the MEMS wafer, solder points are provided for external connection before the ASICs are added and the MEMS and ASICs chips are then isolated using a passivation layer.
“This is an important step in bringing down the cost and size of sensing technology for volume production,” points out Heikki Kuisma, Vice President of Research at VTI. “The concept has been proven in the successful construction and testing of a demonstration component having a foot print of only 4mm2 and a height of less than 1mm. This Chip-on-MEMS is a radical step away from conventional packaging as it is simply an extension of wafer-fab processes. Even the final testing and calibration are now wafer processes.” The potential of these new integration concepts is that the size of MEMS devices could be cut to one third their current sizes.
Taking the next step
Having proven the benefits of better integration, VTI is now moving to develop novel manufacturing concepts and processes that will allow for the production of more complex sensing components that can combine a MEMS sensing elements with several ASICs chips. The goal is to offer smarter sensing designs with more input/output features, on-board micro processing and radio communications, for example. This ambitious research programme would involve stacking several ASICs chips, around 20 microns thick, on top of the MEMS device using heterogeneous integration techniques. These new manufacturing concepts will eventually provide the foundation for new generations of small size sensing devices for use in high volume, low cost applications.
Heikki Kuisma, Vice President, Research, tel. +358 50 568 1253, heikki [dot] kuisma [at] vti [dot] fi
Tiina Olkkonen, Vice President, Corporate Communications, tel. +358 40 827 8844, tiina [dot] olkkonen [at] vti [dot] fi
VTI in Brief
VTI Technologies is a global market leader of low-g acceleration sensors for automotive industry applications and Cardiac Rhythm Management (CRM). Application areas for the company's motion and pressure sensors include the automotive industry, medical, instruments, as well as sports and handheld terminals. VTI develops and produces silicon-based capacitive sensors using its proprietary 3D MEMS (MicroElectroMechanicalSystem) technology, with application areas in acceleration, inclination, shock, vibration, angular rate and pressure measurement. VTI is owned by EQT III private equity fund. VTI's net sales in 2006 totalled €72,4 million and the company has approx. 700 employees. Along with the head office in Finland and the global partner network, VTI's international sales and marketing network includes offices in Germany, USA, Japan and China. Besides Finland, VTI also has manufacturing operations in Mexico. More than 99% of the company's products are sold on international markets.