A New Way to Form Three-Dimensional Microstructures by Electrochemical Etching of Silicon
2001 (English)In: Materials Research Society Symposium Proceedings, ISSN 0272-9172, Vol. 638, F821-F826 p.Article in journal (Refereed) Published
A new technique of bulk micromachining using anodic etching of (100)-oriented n-type silicon is presented. For particular conditions the transition regime between porous silicon formation and electropolishing enables the formation of high aspect ratio microtips which correspond to inverted macropore structures. This unusual property can be explained by the distortion of currant lines near the basis of formed structures. The distortion, which prevents the tip dissolution, is due to the electrical field in the space charge region at the silicon-electrolyte interface. The same property can be used to form three-dimensional microstructures. The position and shape of the structures can be defined by forming steps of a few microns depth, prior to the electrochemical etching. Then the etching parameters (HF concentration, light intensity, etching current density) are adjusted in order to electropolish the sample except where vertical walls are needed. This enables to form microstructures without a periodic pattern. The feasibility of this technique is demonstrated by forming 100 μm wide pores, free-standing beams as well as high aspect ratio micro-needles and micro-tubes.
Place, publisher, year, edition, pages
2001. Vol. 638, F821-F826 p.
Anodes, Current density, Electric currents, Electric distortion, Electric fields, Electric space charge, Electrochemistry, Electrolytes, Electrolytic polishing, Etching, Micromachining, Microstructure, Electrochemical etching
Condensed Matter Physics
IdentifiersURN: urn:nbn:se:kth:diva-6470ISBN: -OAI: oai:DiVA.org:kth-6470DiVA: diva2:11192
QC 201011012005-09-152005-09-152010-11-01Bibliographically approved