Gas-phase and surface reactions in plasma enhanced chemical etching of high-K dielectrics

Chlorine based plasmas were found to chemically etch ZrO 2 and HfO 2 thin films in a high density electron cyclotron resonance reactor, and the etch rates scaled linearly with the square root of ion energy at high ion energies with threshold energies between 12-20 eV. Optical emission spectroscopy and quadruple mass spectrometry were used to identify the reaction etching products. No pure metal, O, or metal monochlorides were detected as etching products, but highly chlorinated metal compounds (ZrCl 2 , ZrCl 3 , ZrCl 4 , HfCl 3 , HfCl 4 ) and ClO were found to be the dominant etching products. Metal trichlorides were the dominant etching products at low ion energies, while metal tetrachlorides became dominant at higher ion energies. The addition of BCl 3 was found to be able increase the etching selectivity of ZrO 2 to Si. The main ZrO 2 etching products in BCl 3 /Cl 2 plasma were found to be ZrCl x and B 2 OCl 3 + and B 3 O 2 Cl 4 + .