CMOS-based sealed membranes for medical tactile sensor arrays

We present a novel method for producing capacitive membrane structures using an industrial CMOS (Complementary Metal Oxide Semiconductor) process combined with bulk and surface micromachining. The membranes are released with a sacrificial metal etching step from the backside of the sensor chip. This way, no sealing step to protect the small cavities is required. The aluminum metallization is assessed from the back of the wafer using an anisotropic silicon etching step. First structures have been processed and tested, showing a deflection sensitivity of 390 nm/bar. A pressure of 1 bar corresponds to a static force of about 100 mN acting on the sensor surface. An array configuration of these membranes will be used to equip a robotic assistant performing minimally invasive coronary bypass surgery on a beating heart. The goal is to provide haptic feedback to the operating surgeon.