Development of Electrolytic Etching Process Simulator for Molybdenum MEMS

This paper addresses development of electrolytic etching process simulator for molybdenum MEMS. We investigated the effects of process parameters such as processing time, applied voltage, ethanol concentration in the electrolyte, and electrolyte temperature on the processability of electrolytic etching of molybdenum. As processing time increased, the etch rate remained constant, but the etch factor decreased. Increasing the applied voltage and heating the electrolyte significantly increased the etch rate. In particular, heating the electrolyte has no measurable impact of the etch factor, and thus serves as an effective strategy when a high etch rate is required. An increase in the ethanol concentration of the electrolyte led to a decrease in both the etch rate and the etch factor. This was also accompanied by a reduction in the error bars, which may contribute to achieving more uniform processing. Based on the accumulated experimental data, electrolytic etching process simulator for molybdenum was developed. By specifying arbitrary processing conditions, the simulator enables prediction of the required processing time as well as the resulting cross-sectional profile. The developed simulator is highly effective in the step of photomask design.