Electrochemical formation process of Si macropore and metal filling for high aspect ratio metal microstructure using single electrolyte system

Array of macropores filled with electrodeposited Ni was formed on Si substrate applying the novel process, which consists of Si electrochemical etching and Ni electrodeposition using single electrolyte. This electrolyte contained HF as Si dissolution agent and Ni(OSO₂NH₂) ₂ 4H₂O as Ni²⁺ source for Ni electrodeposition. First, array of macropores was formed on Si (100) substrate by applying anodic current. The formation was carried out area-selectively by applying Au/Cr micropatterns formed at the back side surface of the substrate as the shade mask, which enables to control the illumination condition for hole generation condition. Subsequently, the applied bias was switched to cathodic current, and Ni was filled into c.a. 200 μm depth Si macropores without void-like defects. Array of Ni needles with smooth surface was formed area-selectively by removal of the Si region of the Ni filled specimen with 25 wt% tetramethylammonium hydroxide (TMAH) aqueous solution at 90°C.