Resistless fabrication of embedded nanochannels by FIB patterning, wet etching and atomic layer deposition

Self-supported SiO2 structures were fabricated from thermal SiO2/Si substrates by combining FIB direct writing and selective and anisotropic chemical wet etching of silicon. These structures, such as SiO2 overhangs on the edges of Si trenches, were then used as templates for ALD of Ta2O5 to form sealed nanochannels and cavities. The size of trenches formed by etching through openings in the SiO2 increases with FIB patterning ion dose as well as KOH etching time. Channel formation results from sealing the trenches by the conformal ALD of Ta2O5. The KOH etching time determines the channel size while the ion dose determines final wall thickness after ALD. The fabricated hollow nanochannels are embedded under SiO2 and surrounded by Ta2O5 on crystalline Si. The channel size reaches 50 nm by this fabrication approach with a 60 min KOH etching time.