约束刻蚀剂层技术对金属铝的微结构加工研究

Investigation of Microstructure-machining on Aluminium Surface by Confined Etchant Layer Technique

采用约束刻蚀剂层技术,以亚硝酸钠为先驱物,通过电化学氧化产生刻蚀剂(硝酸)刻蚀铝,并以NaOH为捕捉剂,在电极模板上形成约束刻蚀剂层.在金属铝表面加工出梯型槽微结构,加工分辨率约为500 nm.通过测量表面氢离子浓度,对捕捉剂的约束效果进行了分析.

This work aims to develop confined etchant layer technique （CELT） to fabricate three-dimensional （3D） microstructures of aluminum substrate for microelectromechanical systems （MEMS）. In spite of the fact that LIGA technique is current method for metal bulk micromachining with a high aspect ratio, it is extremely difficult to be applied to aluminum because the electrodeposition as one of the process for LIGA is not suitable for using molten salt at a high temperature. The important feature of CELT is to use a scavenger in solution to efficiently consume the etchant so as to confine the etchant as an ultrathin layer on the working electrode surface （ mold electrode）. The outer boundary of the diffusion layer of the etchant can retain the three-dimensional fine micro-pattern of the mold electrode. The key issue to successful fabrication of microstrnctures with CELT is the design of an appropriate ＂generating-scavenging＂ system for etchant. In the present study, NaNO2 was electrochemically oxidized into HNO3 so as to etch the aluminum workpiece. The thickness of H^＋ diffusion layer was confined by reacting with NaOH as the scavenger. The etched pattern of aluminum was observed to be approximately the negative copy of the mold with the precision of 504 nm. The chemical and electrochemical processes were analyzed. The influences of processing parameters, such as current density and scavenger concentration, were discussed. Our preliminary result demonstrates that CELT has a potential to be developed as an effective technique for micromachining for fabrication of micro electromechanical systems. 3D microstructures of aluminum, which can be applied