ON THE HOMOGENEITY OF SPUTTER-DEPOSITED ITO FILMS .2. ETCHING BEHAVIOR

The etching behaviour of sputter-deposited tin-doped indium oxide (ITO ) films in 8 M HCl solutions was investigated. The etch rate was mainl y dependent on the microcrystallinity of the films. Amorphous ITO diss olved with an extremely high rate, while the etch rate of polycrystall ine ITO was in a technologically interesting range. Amorphous ITO whic h was crystallized after annealing was stress free and its etch rate w as 11 nm min(-1). ITO which was already polycrystalline after depositi on showed the same rate when the films were stress free. Under conditi ons where the films became stressed, the etch rate decreased. The comp ressive stress is expected to hinder the penetration of the etchant be tween the crystallites, thereby reducing the etch rate when the stress is increased, and vice versa. For a good pattern definition after etc hing, films deposited at high temperature are preferable over films th at are deposited at low temperature and annealed afterwards.