Ultrathin TiN membranes as a technology platform for CMOS-integrated MEMS and BioMEMS devices

Abstract

A standard complementary metal-oxide-semiconductor (CMOS) process is successfully modified to encompass the preparation of suspended TiN membranes of only 50 nm thickness from one of the metal layer stacks of the back-end fl ow. The layers' elastomechanical constants are determined with high precision by laser Doppler vibrometry. Residual stress gradients are compensated and a state of moderate tensile strain is introduced into the membranes. Test systems of TiN beams and bridges operating in a capacitive coupling scheme are optimized for the low voltage range attainable with CMOS devices. TiN actuators are particularly suited for applications in biotechnology like sensing of pressure or viscosity in microfl uidic devices due to their high corrosion resistance in liquid electrolyte surroundings. The established inclusion of the process in a CMOS pilot line enables the production of cheap and monolithically integrated microelectromechanical systems (MEMS) and bio-microelectromechanical systems (BioMEMS) devices. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.