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 mainly dependent on the microcrystallinity of the films. Amorphous ITO dissolved with an extremely high rate, while the etch rate of polycrystalline ITO was in a technologically interesting range. Amorphous ITO which was crystallized after annealing was stress free and its etch rate was 11 nm min(-1). ITO which was already polycrystalline after deposition showed the same rate when the films were stress free. Under conditions where the films became stressed, the etch rate decreased. The compressive stress is expected to hinder the penetration of the etchant between the crystallites, thereby reducing the etch rate when the stress is increased, and vice versa. For a good pattern definition after etching, films deposited at high temperature are preferable over films that are deposited at low temperature and annealed afterwards.