ON THE MECHANISM OF ITO ETCHING IN HALOGEN ACIDS - THE INFLUENCE OF OXIDIZING-AGENTS

The etching process of polycrystalline tin-doped indium oxide (ITO) fi lms in HCl solutions is investigated by kinetic and electrochemical ex periments and the patterning characteristics are examined by scanning electron microscopy. The influence of oxidizing agents on the etching behavior is studied. A model is proposed in which ITO is first attacke d by undissociated HCl molecules, forming a surface intermediate which is mobile on the surface. This intermediate can react with HCL molecu les or with the oxidizing agent. The competition between these two rea ctions determines the kinetics and the patterning characteristics of t he dissolution process. A kinetic rate law is derived that predicts th e etch rate in FeCL(3)/HCl solutions. A good agreement between experim ental and calculated values is obtained in a wide range of HCl and FeC l3 concentrations.