Etching of high-k dielectric Zr1−xAlxOy films in chlorine-containing plasmas

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Abstract
As new, advanced high-kdielectrics are being developed to replace SiO 2 in future generations of microelectronicsdevices, understanding their etchcharacteristics becomes vital for integration into the manufacturing process. We report on the etch rates and possible mechanisms for one such dielectric, Zr 1−x Al x O y (x≈0.2), in plasmas containing a mixture of Cl 2 and BCl 3 , as a function of gas composition and ion impact energy. Higher concentrations of BCl 3 enhance the etch rate as well as selectivity of Zr 1−x Al x O y etching as compared to the etching of α-Si, whereas increasing ion energy increases the etching rates but decreases selectivity. In a high density helical resonator plasma,etching rates on the order of 700 Å/min and 1:1 selectivity are typical. Angle-resolved x-ray photoelectron spectroscopy was used to study the composition of the upper ∼30 Å of the film, before and at the end of the etching process. We found that the etching rate of Zr 1−x Al x O y does not change with time for the range of Cl 2 /BCl 3 ratios and ion energies investigated, whereas the α-Si etching rate in pure BCl 3 plasma and at zero substrate bias decreases with time, due to the formation of a B–Si film on the surface.