Electrochemical fabrication of nanodimensional multilayer films

A novel method of fabricating nanodimensional multilayer films using electrochemistry is described. A thin layer of tantalum (Ta) is sputtered on a smooth insulating substrate. Ta is partially electrochemically oxidized (anodized) forming a Ta(2)O(5) layer. The rate of Ta consumption, the rate of Ta(2)O(5) expansion, and the dependence of Ta(2)O(5) thickness on anodization conditions have been carefully characterized to enable accurate predictions of the resulting thicknesses of both layers. Due to strong planarization action of the anodization process, the resulting interfaces Ta/Ta(2)O(5) and Ta(2)O(5)/electrolyte are remarkably smooth. The next layer of Ta is deposited on top of Ta(2)O(5), and the process is repeated as many times as needed. The Ta(2)O(5) layers are amorphous and pinhole free. We report fabrication of 10-layer structures with pitches ranging from 200 nm down to 12 nm and with excellent uniformity between the layers. The smallest achieved thickness of Ta layers is only 2.8 +/- 0.1 nm. The edges of such films, after proper polishing and etching, could serve as templates in nanoimprint lithography and in other applications.