Selective etching of high-k HfO2 films over Si in hydrogen-added fluorocarbon (CF4∕Ar∕H2 and C4F8∕Ar∕H2) plasmas

Abstract

Inductively coupled hydrogen-added fluorocarbon (CF4∕Ar∕H2 and C4F8∕Ar∕H2) plasmas were used to etch HfO2, which is a promising high-dielectric-constant material for the gate of complementary metal-oxide-semiconductor devices. The etch rates of HfO2 and Si were drastically changed depending on the additive-H2 flow rate in C4F8∕Ar∕H2 plasmas. The highly selective etching of HfO2 over Si was done in the condition with an additive-H2 flow rate, where the Si surface was covered with the fluorocarbon polymer. The results of x-ray photoelectron spectroscopy indicated that the carbon content of the selectively etched HfO2 surface was extremely low compared with the preetched surface contaminated by adventitious hydrocarbon in atmosphere. In the gas phase of the C4F8∕Ar∕H2 plasmas, Hf hydrocarbide molecules such as metal-organic compounds and Hf hydrofluoride were detected by a quadrupole mass analyzer. These findings indicate that the fluorine species, carbon, and hydrogen can work to etch HfO2 and that the carbon species also plays an important role in selective etching of HfO2 over Si.