Fabrication of Vertical Electrodes on Channel Sidewall for Picoliter Liquid Measurement

This paper presents an IC-compatible 3D fabrication technology for silicon-based vertical electrodes on channel sidewall, aiming at liquid measurement up to picoliter level. The developed process uses bulk silicon as vertical electrodes and employs deep buried oxide (50 mum deep) as electrical insulation in between. Several challenges are discussed, and many key process steps are optimized. This technology is successfully used to make capacitive sensors, with electrodes up to 25 mum high, on a microfluidic dispenser nozzle for monitoring the movement of the liquid meniscus.