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

Paper PS2-TuM6
Ion-Enhanced Plasma Etching of Hafnium Aluminates in Chlorine Based Plasmas

Tuesday, November 14, 2006, 9:40 am, Room 2011

Session: Plasma Surface Interactions I: Joint AVS-AIChE Session
Presenter: R.M. Martin, University of California, Los Angeles
Authors: R.M. Martin, University of California, Los Angeles
H.-O. Blom, Uppsala University, Sweden
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. Hafnium aluminates (HfAlO) have arisen as a promising material for gate oxide replacement due to their high dielectric constant, bandgap, and recrystallization temperature. Five compositions of hafnium aluminates were synthesized under this study with the Al@sub 2@O@sub 3@ content varying from 0 to 100%. An electron cyclotron resonance high density plasma reactor is used in this work to study the etching of hafnium aluminates in chlorine-based chemistries. 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 Al@sub 2@O@sub 3@ and HfO@sub 2@ was first studied in Cl@sub 2@ and BCl@sub 3@ plasmas, to allow for studies of the etching of co-sputter-deposited hafnium aluminate with well controlled and varying compositions of Al in HfO@sub 2@. The dominant etch products of Al@sub 2@O@sub 3@ and HfO@sub 2@ in Cl@sub 2@ and BCl@sub 3@ plasmas were metal chlorides and metal boron-oxy-chlorides, respectively. The etch rates of hafnium aluminates were found to increase with the square root of ion energy, and the surface chlorination was enhanced with increasing ion energy, demonstrating that the etching reaction is limited by the momentum transfer from the ions to the film surface. In Cl@sub 2@ plasma, the dominant etch products were HfCl@sub 3@, HfCl@sub 4@, AlCl@sub 2@, and Al@sub 2@OCl, and the amount of chlorine on the etched surface increased with increasing ion energy, ranging from 0-2 at.%. In BCl@sub 3@ plasma, the etching rate was controlled largely by the dominant ion, BCl@sub 2@@super +@, with higher etch rates. The identity and distribution of the etch products in BCl@sub 3@ will also be presented to assess the effect of boron in patterning hafnium aluminates.