AVS 53rd International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuM

Paper PS2-TuM5
Surface Reactions in Plasma Etching of Nitrided Hafnium Silicates

Tuesday, November 14, 2006, 9:20 am, Room 2011

Session: Plasma Surface Interactions I: Joint AVS-AIChE Session
Presenter: J. Liu, University of California, Los Angeles
Authors: R.M. Martin, University of California, Los Angeles
J. Liu, University of California, Los Angeles
B. Xia, Air Liquide
A. Misra, Air Liquide
J.P. Chang, University of California, Los Angeles
Correspondent: Click to Email
The development of plasma etching chemistries is necessary to pattern new gate dielectric materials, such as hafnium-based oxides, for sub-65nm CMOS devices. Nitrided hafnium silicates (HfSiON) are promising since they combine the high dielectric constant and improved interface state density of hafnium silicates with the beneficial properties of silicon oxynitrides. In this work, chlorine-based chemistries are used in an electron cyclotron resonance high density plasma reactor to etch Hf-rich and Si-rich nitrided hafnium silicates, with 0 to 15 at.% of nitrogen. The plasma density, electron temperature, and gas phase species are characterized by a Langmuir probe, optical emission spectroscopy, and quadrupole mass spectrometry. The etching of SiO@sub 2@ and HfO@sub 2@ was first studied in Cl@sub 2@ and BCl@sub 3@ plasmas, to allow for studies of the etching of HfSiON with well controlled and varying compositions of Si and N in HfO@sub 2@. The etch rates of nitrided hafnium silicates were found to increase with the square root of ion energy, and the etching rate of films with 15 at.% of nitrogen is the highest. The surface chlorination was enhanced with increasing ion energy, ranging from 1 to 4 at.% of chlorine on the etched surfaces, demonstrating that the etching reaction is limited by the momentum transfer from the ions to the film surface. The measured etching threshold energies were higher than that of pure HfO@sub 2@, suggesting that Si and N incorporation modifies film structure/density. In addition, while physical sputtering is the dominant mechanism in removing nitrogen as it was the lightest element of the four composing the film, more nitrogen remains on the surface of the Hf-rich films than the Si-rich films. This suggests that the removal of N is still related to its bonding within the film. The identity and distribution of the etch products will also be presented to elucidate the effect of Si and N on the removal of HfO@sub 2@.