The etching characteristics of indium zinc oxide (IZO) films were investigated using a high-density plasma in Ar, Ar/Cl, and Ar/CH/H 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/Cl 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 Ar/CH/H 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 Ar/CH/H plasma plays an important role in the evolution of the IZO etch rate with the In concentration fraction.