Corrosion mechanism and surface passivation strategies of polycrystalline silicon electrodes

We present a detailed study of the effect of geometry and surface termination on the morphological and chemical evolution of polycrystalline silicon electrodes at high relative humidity (RH) and applied bias. The corrosion test structures consist of two poly-silicon electrodes isolated from the substrate by a silicon nitride layer. Anodic oxidation is observed on electrodes with native oxide layers. Damage to the cathode is observed within 20 h under RH value ≥89% when the anode to cathode area ratio is higher than unity. The unusual phenomenon is attributed to the surface electrolyte-driven electrochemical reactions in the system. Understanding of the corrosion mechanism has enabled the selection of surface passivation pretreatments to reduce the observed corrosion. In particular, the effects of hydrogen-terminating and alkyltrichlorosilane-based self-assembled monolayer coatings have been investigated. It is found that although both approaches help reduce the rate of corrosion at both electrodes, SAMs have a longer lasting impact. This is attributed to the greater stability of SAMs and their ability to form on silicon nitride isolation layers.