Fabrication of ultra-high aspect ratio silicon nanopores by electrochemical etching
2014 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 12, 123111- p.Article in journal (Refereed) Published
We report on the formation of ultra-high aspect ratio nanopores in silicon bulk material using photo-assisted electrochemical etching. Here, n-type silicon is used as anode in contact with hydrofluoric acid. Based on the local dissolution of surface atoms in pre-defined etching pits, pore growth and pore diameter are, respectively, driven and controlled by the supply of minority charge carriers generated by backside illumination. Thus, arrays with sub-100 nm wide pores were fabricated. Similar to macropore etching, it was found that the pore diameter is proportional to the etching current, i.e., smaller etching currents result in smaller pore diameters. To find the limits under which nanopores with controllable diameter still can be obtained, etching was performed at very low current densities (several mu A cm(-2)). By local etching, straight nanopores with aspect ratios above 1000 (similar to 19 mu m deep and similar to 15 nm pore tip diameter) were achieved. However, inherent to the formation of such narrow pores is a radius of curvature of a few nanometers at the pore tip, which favors electrical breakdown resulting in rough pore wall morphologies. Lowering the applied bias is adequate to reduce spiking pores but in most cases also causes etch stop. Our findings on bulk silicon provide a realistic chance towards sub-10 nm pore arrays on silicon membranes, which are of great interest for molecular filtering and possibly DNA sequencing.
Place, publisher, year, edition, pages
2014. Vol. 105, no 12, 123111- p.
N-Type Silicon, Formation Mechanism, Macroporous Silicon, Array Fabrication, Porous Silicon, Pore Arrays, Limits
Other Physics Topics
IdentifiersURN: urn:nbn:se:kth:diva-155801DOI: 10.1063/1.4896524ISI: 000343004400073ScopusID: 2-s2.0-84908300823OAI: oai:DiVA.org:kth-155801DiVA: diva2:763083
FunderSwedish Foundation for Strategic Research , RMA08-0090
QC 201411132014-11-132014-11-132014-11-13Bibliographically approved