Application for Strategic Equipment: Wafer Bonder at LCN

Wafer processing originated in microelectronics, for mass production of integrated circuits, a technology that has transformed the world in the past generation. The wafers are usually cut from single crystals of silicon. In the past twenty five years, the technology has spawned many new areas of microengineering, such as MEMs, micro-fluidics, lab-on-a-chip and micropackaging. In these areas, small three-dimensional structures are built on wafers; often this is done by bonding two or more wafers together. There are many methods for forming the bonds: adhesive, anodic, direct, eutectic, glass, solder and thermo-compression. Which method is best depends on the materials, allowable temperatures and other many considerations; usually, successful bonding is crucial to the success of the device that is being fabricated.

This grant will enable a versatile wafer bonding machine to be bought for the London Centre for Nanotechnology (LCN) that can be used for all these types of bonding. It will be made available for researchers in universities and for product development by companies. The applicants have projects to develop very small surgically-implanted electronic devices that can only be made by these techniques. Supporters of the application include those working on flexible displays, micro chemical reactors, energy harvesting, wireless sensors, and many others.

The grant will pay for the machine, maintenance for five years and for a member of LCN staff to look after it. Good management will ensure that it is kept in good working order, and that operating experience is passed between users. The LCN will advertise its presence so that as many people as possible benefit from it.

The bonder will be available to university researchers and others, such as small companies who are developing products or doing small production runs.

Wafer bonders are basic tools in microengineering which covers a huge range of applications from implantable sensors and devices, through body-worn sensors and energy harvesting, lab-on-a-chip for small scale manufacturing, metabolite analysis, environmental monitoring, and so on. Given how much progress is now being made in microengineered devices, it is strategically important that researchers can implement their ideas at wafer scale to show that manufacturing is feasible and so that these devices can be incorporated into prototype products.

This grant will allow a versatile wafer bonder to be installed at the LCN. This is advantageous in several ways. The versatility and availability of the bonder will mean that researchers can readily compare more than one method, which may be possible in their application, and they can optimise the processes by making series of bonds, all at reasonable cost per session. Once trained, they can use the machine themselves which will allow a full understanding of the process on which the success of their device will depend. LCN has a wide range of analytic apparatus on site to help with inspection and quality control. Furthermore, the location of LCN is very convenient for researchers in London and, because of the proximity of many mainline stations, can be easily be reached from many other universities and from the rest of the county. The fact that LCN is also used by companies is important, particularly it means that devices that have emerged from university research projects can be taken on by development companies, which might be spun off or in technology transfer, and they can use the same bonder for product development and perhaps early commercial manufacturing.

For implanted devices and sensors, small packaging is vital yet the unit cost must be low and the quality control good. In our opinion, the new generation of devices that increases functionality by having more electrodes, will only be possible by using microengineering methods, and wafer bonding appears to be the most promising. The materials needed are not always easily joined and thus the versatility of this bonder is bound to be important. The presence of the bonder should inspire researchers to be more imaginative in looking for solutions to their problems.