The reactive ion etching of transparent electrodes for flat panel displays using Ar/Cl-2 plasmas

Large area flat panel displays require high resolution patterning of transparent and high conductivity metal oxides, but the reliability of standard chemical etch techniques at high resolution is inadequate. Tin oxide (SnO2) is a viable alternative to standard In2O3:Sn (ITO) over large areas but has been ignored due to the lack of a suitable etch process. We have developed an Ar/Cl-2 reactive ion etch process capable of etching 4 mu m feature sizes and resolutions of 300 lines per inch with rates of up to 90 nm min(-1). Emission spectroscopy showed that atomic chlorine is a strong candidate for the active species and that volatile tin chlorides were generated as etch products. Furthermore, the presence of impurity species, particularly hydrogen, was found to be beneficial to the etch rate. Near etch completion, a dramatic decrease in atomic tin emission was observed along with an increase in Cl emission intensity. The etch rate for tin oxide using Ar/Cl-2 was higher than those obtained for ITO using alcohol-based plasmas without the polymer deposition normally associated with organic gas plasmas. Thus the use Ar/Cl-2 etching of SnO2 can provide high resolution transparent conductive electrodes that are uniform over a large area.