Etching characteristics of high-k dielectric HfO2 thin films in inductively coupled fluorocarbon plasmas

Abstract

Inductively coupled fluorocarbon (CF4∕Ar and C4F8∕Ar) 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 in CF4∕Ar plasmas exceeded those in C4F8∕Ar plasmas. The tendency for etch rates to become higher in fluorine-rich (high F∕C ratio) conditions indicates that HfO2 can be chemically etched by fluorine-containing species. In C4F8∕Ar plasmas with a high Ar dilution ratio, the etch rate of HfO2 increased with increasing bias power. The etch rate of Si, however, decreasd with bias power, suggesting that the deposition of carbon-containing species increased with increasing the power and inhibited the etching of Si. The HfO2∕Si selectivity monotonically increased with increasing power, then became more than 5 at the highest tested bias power. The carbon-containing species to inhibit etching of Si play an important role in enhancing the HfO2∕Si selectivity in C4F8∕Ar plasmas.