Formation of individual holes in amorphous SiO2 by swift heavy-ion bombardment followed by wet and dry etching

Individual holes in amorphous SiO2 were formed from latent tracks which were introduced by bombardment with swift iodine ions. Hole contours strongly depend on the etching method used. Conic holes with the highest aspect ratio were obtained by etching with 48% hydrofluoric acid, The aspect ratio of the holes increased with the acidity of the hydrofluoric acid. Selective etching of the latent tracks was not observed with reactive ion etching, yet 48% hydrofluoric acid etching followed by reactive ion etching formed columnar holes. The etching mechanism is briefly discussed.