Silicon microengineering is a rapidly growing subject with real products in the market place and many more in research. This technology is known as Micro Electro-Mechanical Systems or MEMS, examples of MEMS components are pressure transducers, accelerometers and gyroscopes, all used in large numbers by the automotive market. Other sensors in this family are thermal infrared detectors or bolometers, including the QinetiQ FUNTI™ technology. FUNTI™ devices can be made entirely in the silicon foundry using only chemicals and processes already used for the manufacture of standard CMOS chips, making them extremely cheap in large volumes.

Most MEMS devices must be operated in a vacuum for optimum performance and the cost of the vacuum encapsulation can easily dominate the cost of the finished product. Ideally this package will be sealed to the MEMS chip in manufacture, thus saving the complex and delicate handling procedures currently required to prevent damage to the delicate MEMS structures. Infrared detector products present a further challenge in that they must have an infrared transparent window in the package through which the infrared radiation can pass to form the image.

The INTOB project was set up to examine the options for packaging MEMS at the wafer level and to develop techniques for implementing the most promising option. The vehicle chosen for the project is the QinetiQ FUNTI™ microbolometer, currently being developed for airbag control in passenger vehicles by First Technology Ltd., where the production numbers will be very large, and the cost targets extremely tough. This project therefore faces many challenges and will adopt a phased approach to the problem.

In the early stages, the technical options for materials and bonding processes are being examined by GE Aviation with input from the QinetiQ expertise in infrared detectors and materials and the First Technology requirements as the end-Customer. Here GE Aviation’s long experience in packaging semiconductor devices is key to the success of the low-cost assembly of the devices.

In the later stages the project will move on to more and more integrated optical and mechanical parts with the final aim of a simple, robust, high yielding, long-life packaging technology which can meet the environmental and cost challenges of the mass market. This technology will be applicable to many MEMS devices and will help to reduce cost and complexity, opening up new markets for this type of sensor.

The project is supported by the DTI Technology Programme