IWLPC (Wafer-Level Packaging) Conference Proceedings


Authors: M. Bartek and T. Zoumpoulidis et al.
Company: Delft University of Technology
Date Published: 9/17/2007   Conference: IWLPC (Wafer-Level Packaging)

Abstract: Possibility to conform microelectronic circuits onto non-planar or even highly-curved surfaces is of increasing interest in many applications, e.g. medical instrumentation, implantable micro-systems, sensory skin, wearable electronics, electronics in paper, etc. Such applications generally require that the active electronics layer remains operational under bending or even limited stretching. In this contribution, our progress in developing processing modules for realization of deformable single-crystalline-silicon electronics is presented. Our approach is based on the previously reported ultra-thin and flexible Circonflex technology [1] intended for RF-ID tags. To achieve extended flexibility or even stretchability while maintaining full electrical functionality, the fragile silicon and dielectric layers are laterally segmented into small islands that are electrically interconnected by deformable metal lines. In the current study, segment thickness (silicon/silicon oxide) of ~1 µm, segment size between 150 and 450 µm, spacing of 20-200 µm and meander-shaped aluminum interconnect transferred onto 8-10 µm thick polyimide film are characterized by bending and tensile stretching to find out the reliability limits. Compared to our previous report [2], next to the processing issues also new electrical integrity results obtained from passive electrical test structures implemented on fully segmented polymer-embedded silicon islands are presented. The developed processing modules to achieve extended deformability/reliability are implemented as post-processing modules allowing sensors and/or electronics to be built with proven technologies before they are rendered flexible.

Key words: stretchable electronics, flexible substrate, substrate transfer technology, ultra-thin substrate.

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