Cermet as an inorganic resist for ion lithography

Abstract

Al/O cermet has been found to act as a high‐resolution resist for ion lithography. The change in chemical etching produced by the ions appears to be similar to that produced by excimer laser irradiation. Both a focused Ga‐ion beam and collimated Ar ion or proton beams with stencil masks have been used for exposure. Cermet films 500 Å thick were e‐beam evaporated in an atmosphere of O2 and were exposed to ion doses of 5×1014 to 1.6×1016 cm−2 at energies ranging from 800 eV to 75 keV. The etch rate in a phosphoric acid based, Al etch falls rapidly to about 1/2 of the rate for unexposed material after exposure to 70 keVAr+ ions with a dose of 1×1015 cm−2 and is near zero for doses above 8×1015 cm−2. The etch rate in BCl3 plasma is less sensitive to dose and decreases by 30% for a dose of 8×1015 cm−2. Although comparison of Auger analysis of exposed and unexposed cermet indicates that ion bombardment increases the concentration of Al bound in Al2O3 on the surface compared to Al in the metallic state, the mechanism of the ion induced etch resistance is at this point unclear. A film of SiO2 on Si was patterned using the exposed cermet as a mask to reactive ion etch in CHF3. Linewidths down to 0.1 μm were produced.