Reactive Ion Beam Etching of Aluminum - 4% Copper Thin Films and Diamond

Reactive ion beam etching of aluminum-4% copper thin film alloys and diamond were studied. The dependence of argon and oxygen ion beam etching yield of diamond as a function of angle of ion incidence was measured. Etching mechanisms of chlorine ion beam etching of aluminum-4% copper thin films were investigated. Along the 110 crystallographic direction the etching yield with argon ions was observed to decrease by more than a factor of 2 due to channeling along that axis. The etching yield as a function of angle of incidence of 500 eV oxygen ions was observed to be strikingly different than that for argon ions. In addition to a large gain in yield at normal incidence, the etching yield of diamond with 500 eV oxygen ions is almost constant as a function of angle of incidence. The etching yield of diamond with 1000 eV oxygen ions is actually less than that for 500 eV. The 1000 eV etching yield increases with angle of incidence in a similar manner to argon ion beam etching. Chlorine etching of thin film alloys of aluminum -4% copper was studied as a function of ion energy, ion flux, background gas pressure and temperature. The deleterious effects of small amounts of residual water vapor present in the vacuum system were significantly less for 1000 eV chlorine ions than for 500 eV ions. At a residual water vapor pressure of 10('-6) torr, the etching rate was observed to be limited by the availability of reactant for 500 eV chlorine etching of aluminum-4% copper alloys. The etching rate at 1000 eV was observed to be independent of ion flux or pressure. The etching rate at 500 eV and 1000 eV was observed to be independent on temperature from 5(DEGREES)C to 65(DEGREES)C with 10('-7) torr residual water vapor pressure. Precipitation of CuAl(,2) during etching was observed if the film temperature was allowed to rise above 125(DEGREES)C. This precipitation results in a rough etch surface since the copper rich precipitate etches more slowly than the surrounding aluminum matrix. The amount of chlorine incorporated into the thin film during etching was found to be proportional to the inverse of the etching yield. This chlorine remaining in the near surface layer was responsible for extremely rapid oxidation on contact with air. Oxidation followed a parabolic growth law.