Spin-coatable Al2O3 resists in electron beam nanolithography

Inorganic resists such as amorphous alumina are projected as potential candidates for high resolution electron beam nanolithography; the drawbacks being its low sensitivity and tedious deposition process such as sputtering. Therefore, a spin-coatable Al2O3 resist with higher sensitivity is strongly desirable to overcome these drawbacks. In this paper, we describe the electron beam exposure characteristics of spin-coatable Al2O3 gel films prepared by reacting aluminium tri-sec-butoxide, AI(OBuS)(3), with chelating agents like ethylacetoacetate (EAcAc). The electron beam sensitivity of similar to 70nm thick Al2O3 gel films baked at 40 degrees C as well as in the no-bake condition is similar to 4mCcm(-2), which is similar to 10(6) times higher than the sputtered alumina films. Baking at 70 degrees C seems to produce little change in the sensitivity. The Fourier transformed infrared (FTIR) spectroscopy studies indicate that the increased sensitivity of these films is due to the rapid breakdown of chelate rings under the electron beam. This rapid breakdown of organic bonds could have resulted in the appearance of inorganic Al-O bonds which are insoluble in acetone. Indeed the spin-coatable Al2O3 resist provides high resolution negative line patterns of linewidth of about 20nm.