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

Keywords: HfSiO4 thin film, Inductively coupled plasma etching, Cl2/Ar and SF6/Ar inductively coupled plasmas, Etch rate, anisotropy