Contact Properties of Titanium Nitride Sidewall Coating for Nanoelectromechanical Electronics

M. Shavezipur, K.L. Harrison, W.S. Lee, B. Espinosa, J. Provine, S. Mitra, H.-S.P. Wong, R.T. Howe
The Ohio State University, US

Keywords: nanoelectromechanical relay, titanium nitride (TiN), atomic layer deposition (ALD), adhesion force, contact resistance

Summary:

The performance of hybrid NEM-CMOS low power electronics and logic gates highly depends on the source-drain contact resistance and adhesion force, which affect the power consumption and the pull-in/pull-out hysteresis, respectively. In the present work, these surface properties are characterized for titanium nitride coated, laterally actuated polysilicon nanoelectromechanical relays, using actual devices in operation. The adhesion force is determined using a combination of finite element simulations and measured I-V responses. The measured responses are also used to determine the on-state (contact) resistance. The test results show that the adhesion force increases with gate and drain voltages. The on-state resistance also depends on the gate and drain voltages and is improved as drain voltage and gate voltage increase. Comparing the results of adhesion force and contact resistance measurements shows a slight correlation between lower contact resistance and higher adhesion force. The endurance of sidewall TiN contact was also studied with accelerated life-time tests. Cold and hot switching tests were performed and the test results show rapid increase in the on-state resistance of the tested relays. Although higher contact force (implemented by overdrive gate voltage) may decrease the initial contact resistance, the surface degradation over cyclic switching may not be prevented.