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

摘要

Inductively coupled hydrogen-added fluorocarbon (CF[4]∕Ar∕H[2] and C[4]F[8]∕Ar∕H[2]) plasmas were used to etch HfO[2], which is a promising high-dielectric-constant material for the gate of complementary metal-oxide-semiconductor devices. The etch rates of HfO[2] and Si were drastically changed depending on the additive-H[2] flow rate in C[4]F[8]∕Ar∕H[2] plasmas. The highly selective etching of HfO[2] 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 HfO[2] surface was extremely low compared with the preetched surface contaminated by adventitious hydrocarbon in atmosphere. In the gas phase of the C[4]F[8]∕Ar∕H[2] 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 HfO[2] and that the carbon species also plays an important role in selective etching of HfO[2] over Si.