Research in the Improvement of Wettability of Micro-Structure in Patterned Electrodeposition

Problem statement: The high aspect-ratio electrodeposition was widely used in the manufacture of non-silicon MEMS devices. The wetting of high aspect-ratio micro-structure in electrolyte was important to the uniformity of micro-structure. Approach: In this study, to enhance the wettability of micro-structures in electrolyte, the effect of Sodium Dodecyl Sulfate (SDS) and O₂ plasma surface modification were discussed. Contact Angles (CA) between nickel sulfamate and the micro-structure were investigated to test the effect of two ways mentioned above. We employ the plasma photoresist-removal machine to modify micro-structure made of photoresist and the effects of different modification time were also discussed. The mechanism of O₂ plasma treatment was investigated. According to Cassie’s law, a new method was proposed to follow the wetting progress of micro-structure. Results: The contact angles between the electrolytes with SDS and smooth photoresist surfaces exposed to O₂ plasma surface modification decreased from 90-5.2° continuously. The maximum SDS concentration was 1g L⁻¹ and the longest modification time was 60s. After 30min’s quiescence, the micro-structure was completely filled by electrolyte, with the size of 50×50×50 µm (width×width×height×). Conclusion/Recommendation: It was possible to promote the wettability by introduction of SDS as wetter and the employment of O₂ plasma surface modification. The effect of O₂ plasma surface modification could be attributed to the introduction of free and associated hydroxyl.