Prebreakdown and breakdown characteristics of micrometer gap in micro-electro-mechanical system device

To carefully predict and evaluate the insulation characteristics for providing the guidelines of insulation design in micro-electro-mechanical system (MEMS) devices, the samples were prepared by etching insulation gaps measured from 5 μm to 40 μm. The pre-breakdown current-voltage curve and relationships between breakdown voltages and electrode gaps were measured on the test samples fabricated with aluminium film electrodes in standard MEMS processes. The electrode surface after breakdown was analyzed by scanning electron microscopy (SEM). The results show that the pre-breakdown current-voltage curve can be divided into three stages: free charged particles directionally migrate along electric field; the current density gets saturated; the impact ionization develops into electron avalanche continuously. Fowler-Nordheim plot verifies that for larger scale (>5 μm), the breakdown characters agree with Paschen curve and are consistent with the previous studies. However, the breakdown thresholds between micro-electrodes are greater than those between macroscopic metal electrodes. SEM analysis shows that anode surface becomes crater-like and the cathode surface is sputtered with metal.