Effect of chelating agents on high resolution electron beam nanolithography of spin-coatable A1₂O₃ gel films

The effect of chelating agents on the electron beam exposure characteristics as well as environmental stability of the spin-coatable A1₂O₃ gel films is discussed. It was found that the A1₂O₃ gel films prepared by reacting aluminium tri-sec-butoxide, Al(OBu⁵)₃, with acetylacetone (AcAc), AcAc/Al₂O₃, gave better environmental stability and patterning characteristic than the gel films prepared by reacting the Al(OBu₅)₃ with ethylacetoacetate (EAcAc), EAcAc/Al₂O₃. The latter suffered from a faster moisture attack in the laboratory atmosphere. Both EAcAc/Al₂O₃ and AcAc/Al₂O₃ films are ∼10⁶ times more electron beam sensitive than sputtered AlO_x films, thus bringing the formers' sensitivity very close to some of the organic electron beam resists. It was seen that the baking temperature up to 70°C has almost no effect on either the sensitivity or the contrast in both the films; but it has a significant effect on the developing characteristics. Electron beam nanolithography gave 20nm linewidth with a rectangular cross-section in both EAcAc/Al₂O₃ and AcAc/Al₂O₃ films. It was observed that the etching characteristics of Al₂O₃ films in the electron cyclotron resonance (ECR) plasma are dependent upon the final baking temperature of the developed pattern. Preliminary plasma etching studies show that 15 nm lines on polysilicon can be etched.