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

Abstract

The etching characteristics of indium zinc oxide (IZO) films were investigated using a high-density plasma in Ar, Ar∕Cl2, and Ar∕CH4∕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 Ar∕CH4∕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 Ar∕CH4∕H2 plasma plays an important role in the evolution of the IZO etch rate with the In concentration fraction.