Cost-effective assembly of three-dimensional microstructures using a wirebonder

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Almost all integrated circuits are fabricated using planar technology. As a result, integrated circuits components occupy only the top 5-20 microns of the silicon substrate.Microelectromechanical Systems (MEMS) research often uses well-established integrated circuit processes. Unfortunately, the planar structure limits MEMS devices performance, and expanding to the third dimension is necessary. One approach is to elevate planar structures out-of-plane to form three-dimensional (3-D) microstructures. Generally a mechanical force is required to carry out the lifting. Researchers have used thin film stress, magnetic force, electrostatic force, centrifugal force, and surface tension to lift 3-D microstructures out of the silicon surface plane. While these approaches have different levels of success, their applications are limited to the research laboratories in a small scale. Applying them in the production environment remains a major challenge. In this research, we will develop a cost-effective means of elevating 3-D microstructures. Specifically we will develop techniques and device structures which can exploit the mechanical motion and force of an automatic wire bonder in the assembly of 3-D microstructures. Automatic wire bonding is a standard integrated circuits packaging operation which provides electrical connection to the silicon chip. It is a mechanical process in which gold or aluminum wires are welded onto the bond pads of the silicon chip and the package. The wire bonding machine moves the package and silicon chip in the X and Y directions to align the bond wire to the bond pad, and provides a vertical bond head motion and force to complete the welding process. Utilizing this motion and force capabilities to lift the 3-D microstructures has the advantage that only standard equipment (automatic wire bonder) compatible with volume production is required. Applications of this cost-effective 3-D microstructure include accelerometer, optical components, anemometer, magnetometer, low-cost radio frequency coil structure etc.