Study on the Nano-topography of the Electrode Surface and the Breakdown Voltage in RF MEMS Switches

Study on the relationship between the breakdown voltage and the nano-topography of electrode surface is presented. The bottom electrode is electroplated with three different current densities. The measured RMS roughness for the obtained electrodes is 27.4nm, 16.0nm and 5.4nm correspondingly. PECVD 300degC Si₃N₄ is deposited onto the electrodes as dielectric layer. After measuring the surface nano-topography of both the metallic surface and the dielectric surface, it is founded that the RMS roughness of Si₃N₄ layer is determined by that of the bottom electrode. Applying a ramping DC voltage between the up- and bottom- electrode, different breakdown voltages are obtained. For the switches with electrode roughness of 27.4nm, 16.0nm and 5.4nm, the breakdown event maximum is in the voltage ranges of 20-40V, 30-60V and 80-110V respectively