Inductively coupled plasma etching of high-k dielectric HfSiO4 film

Abstract

Hafnium silicate (HfSiO4) is one of the leading high-k dielectrics for advanced complementary metal oxide semiconductorfield-effect transistors (CMOSFETs) since it can provide the reduced leakage current characteristics while maintaining thesame gate capacitance in sub-2 nm equivalent oxide thickness regime. High resolution pattern transfer of the HfSiO4-basedgate structure is important to achieve a good device performance. High density plasma etching of the HfSiO4 thin film wasperformed in Cl2/Ar and SF6/Ar inductively coupled plasmas (ICPs) and the effect of plasma composition, ICP source powerand rf chuck power on the HfSiO4 etch characteristics was studied. As the concentration of fluorine in the SF6/Ar ICPdischarges increases, a steady increase of the HfSiO4 etch rate was observed while the HfSiO4 etch rate in the Cl2/Ar dischargesdecreased at the chlorine content beyond ~33%. For both plasma chemistries, the HfSiO4 etch rate generally increased as theICP source power or rf chuck power increased under most of the conditions examined and maximum etch rates of ~921 Å/min and ~776 Å/min were obtained in the 5SF6/10Ar and 5Cl2/10Ar ICP discharges, respectively. The 5Cl2/10Ar ICPdischarges produced better surface morphology with the normalized roughness values in the rage of 0.72-1.32 compared tothe 5SF6/10Ar plasmas. Highly anisotropic pattern transfer was performed with the 5SF6/10Ar ICP discharges.