Influence of the film properties on the plasma etching dynamics of rf-sputtered indium zinc oxide layers

The etching characteristics of indium zinc oxide (IZO) films were investigated using a high-density plasma in Ar, Ar Cl2, and ArC H4 H2 chemistries. The IZO layers were deposited by means of rf magnetron sputtering, in which the target composition and growth temperature were varied to selectively tune the film properties. X-ray diffraction, elastic recoil detection, and Rutherford backscattering spectroscopy were used to determine the crystallization quality, atomic density, and composition of the as-deposited IZO films. As the In (In+Zn) composition ratio in the IZO layer increases, the etch yield in Ar and Ar Cl2 plasmas remains fairly constant, indicating that the etching dynamic is essentially independent of the film properties. In sharp contrast, a strong increase of the IZO etch yield with the In (In+Zn) fraction is observed in ArC H4 H2 plasma due to the preferential desorption of the group-III etch products. By comparing these experimental data to the predictions of a simple rate model accounting for preferential desorption effects, it is concluded that the balance between etching and polymer deposition in the ArC H4 H2 plasma plays an important role in the evolution of the IZO etch rate with the In concentration fraction.