A simple thermal oxidation technique and KOH wet etching process for fuel cell flow field fabrication

The relatively inexpensive SiO2 layer was studied as the silicon etch mask in a KOH etching process for the fabrication of a flow field pattern that consists of channels as well as through-holes on the substrate of a fuel cell. The SiO2 layer was grown in a wet thermal oxidation process to obtain a thickness of up to 6.5 μm and the growth was predicted using the Deal–Grove model. The flow fields on the cathode and anode sides were done using a wet etch process with KOH as etchant. Etching time was utilized to control the depth of the required pattern and the pattern shape was found to have an influence over the etch rate. With constant monitoring of the conditions and parameters used throughout the micro-fabrication process, the thick SiO2 layer was found to be a reliable masking material for a long KOH etching.