AVS 50th International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS2-WeM

Paper PS2-WeM3
Plasma Etching of High Dielectric Constant Materials on Silicon

Wednesday, November 5, 2003, 9:00 am, Room 315

Session: Etching Difficult Materials
Presenter: L. Sha, University of California, Los Angeles
Authors: L. Sha, University of California, Los Angeles
D.L. Ramirez, University of California, Los Angeles
J.P. Chang, University of California, Los Angeles
Correspondent: Click to Email
Novel plasma etching chemistries are needed to pattern high dielectric constant materials, such as ZrO@sub 2@ and HfO@sub 2@, to enable their integration in sub-100 nm complementary metal oxide semiconductor (CMOS) devices. In the paper we discuss the study of the reaction kinetics of etching ZrO@sub 2@ and HfO@sub 2@ in chlorine and boron trichloride chemistry in an Electron Cyclotron Resonance (ECR) high-density plasma reactor. The BCl@sub 3@/Cl@sub 2@ plasma was characterized by Langmuir probe, optical emission spectroscopy (OES), and quadrupole mass spectroscopy (QMS). The etch rate of ZrO@sub 2@ and HfO@sub 2@ were determined to scale linearly with the square root of ion energy in Cl@sub 2@ plasma, indicating that the etching reactions are limited by the momentum transfer to the etched film. The etching products in Cl@sub 2@ plasma were determined to be highly chlorinated metal chlorides and chlorine oxides. The relative abundances of metal tetrachlorides were increased at higher ion energy due to the enhanced surface chlorination. Addition of BCl@sub 3@ reduced the ion densities, but significant enhanced the metal oxides etch rate, due to the enhanced removal of oxygen. Silicon etch rate was suppressed with formation of the passivation layer of B-Si, resulting in the improved metal oxide etching selectivity with respect to silicon. The etching threshold energy for ZrO@sub 2@ and Si in BCl@sub 3@ were determined to be 21 eV and 28 eV, respectively, providing a range of operating conditions with very high etching selectivity. Increasing the electron temperature and ion density in BCl@sub 3@ plasma could further increase the etching selectivity. Under the same operating conditions, the HfO@sub 2@ etch rate is lower than ZrO@sub 2@ etch rate, due to the stronger Hf-O bonds.