基于约束刻蚀原理的电化学微纳加工研究进展

Research advances of electrochemical micro/nanofabrication based on confined etchant layer technique

与机械加工相比,电化学加工技术具有无刀具磨损、无热效应、无机械损伤、加工效率高等优点,而且适用于柔性、脆性及超硬材料,具备传统方法难以实现的复杂结构加工能力,因而在航空航天、汽车、微电子等领域有着重要应用,日益成为一种重要的工业制造技术.随着超大规模集成电路(ULSI)、微机电系统(MEMS)、微全分析系统(μ-TAS)、现代精密光学系统等高技术产业的迅速发展,功能性结构/器件的微型化和集成化的要求越来越高.由于传统电化学只适用于金属材料,为了应对微纳制造的时代要求,拓展电化学加工的材料普适性,1992年田昭武院士提出了具有我国自主知识产权的约束刻蚀剂层技术(CELT).一般的,约束刻蚀包括3个步骤:(1)通过电化学、光化学或光电化学的方法在模板电极表面生成刻蚀剂;(2)通过后续的均相化学反应或自由基衰变反应将刻蚀剂约束在微/纳米厚度的液层内;(3)将模板电极逼近加工基底,当约束刻蚀剂层接触被加工基底时,通过刻蚀反应实现微纳加工.最近,联合课题组通过仪器、原理和方法3个方面的努力,引入外部物理场调制技术,实现一维铣削、二维抛光、三维微/纳结构加工,大幅提升了CELT的技术水平.

Compared with mechanical machining, ECM has several advantages, such as avoiding tool wear, none thermal or mechanical stress on machining surfaces, as well as high removal rate. Moreover, ECM is capable of making complex three-dimensional structures and is appropriate for flexible, fragile, or fissile materials even materials harder than the machining tool. Thus, ECM has been widely used for various industrial applications in the fields of aerospace, automobiles, electronics, etc. ECM methods can be classified usually as electrolytic machining based on anodic dissolution and electroforming based on cathodic deposition of metallic materials. Recently, high technology industry, such as ultralarge scale integration （ULSI） circuits, microelectromechanical systems （MEMS）, miniaturized total analysis systems （la-TAS） and precision optics, has developed more and more rapidly, where miniaturization and integration of functional components are becoming significant. Nowadays, the feature size of intercormectors in ULSI circuits has been down to 20 nanometers, predicted by Moore＇s law. Confined etchant layer technique （CELT） was proposed in 1992 to fabricate three-dimensional micro- and nanostructures （3D-MNS） on different metals and semiconductors, which has been developed an effective machining method with independent intellectual property rights. Generally, there are three procedures in CELT： （I） generating the etchant on the surface of the tool electrode by electrochemical or photoelectrochemical reactions; （2） confining the etchant in a depleted layer with a thickness of micro- or nanometer scale; （3） etching process when the tool electrode is fed to the workpiece, which applicable for 1D milling, 2D polishing, and 3D microfabrication with an accuracy at micro or nanometer scale. External physical-field modulations have recently been introduced into CELT to improve its machining precision. In this review, the advances of CELT in principles, instruments and applications will be addressed as well as the prospects.