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

Paper PS2-TuM9
Ion-Radical Synergy in HfO@sub 2@ Etching Studied in a Beam Experiment

Tuesday, November 14, 2006, 10:40 am, Room 2011

Session: Plasma Surface Interactions I: Joint AVS-AIChE Session
Presenter: P.M. Gevers, Eindhoven University of Technology, The Netherlands
Authors: P.M. Gevers, Eindhoven University of Technology, The Netherlands
H.C.W. Beijerinck, Eindhoven University of Technology, The Netherlands
M.C.M. Van De Sanden, Eindhoven University of Technology, The Netherlands
W.M.M. Kessels, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
The material HfO@SUB 2@ is one of the leading candidates to replace SiO@SUB 2@ as the dielectric material in gate stacks. Etching of HfO@SUB 2@ is currently under research, but mainly under actual plasma conditions. To get a more fundamental understanding of the etching properties, we studied Atomic Layer Deposited HfO@SUB 2@ under well-defined conditions in a multiple-beam experiment. The experiment consists of a thermal XeF@SUB 2@ beam and a low energy (50-1000 eV) Ar@super +@ beam. Real-time ellipsometry and mass spectrometry are used to measure etch rates, layer composition and etch products. The HfO@SUB 2@ etch rate is determined as a function of ion-to-radical flux ratios, ion energy and substrate temperature. Physical etching (sputtering) proves to be the main etching mechanism for HfO@SUB 2@ in the XeF@SUB 2@/Ar@super +@ chemistry. The F-radical does not etch HfO@SUB 2@ spontaneously, as can expected from the high boiling point of HfF@SUB 4@. The Ar@super +@ ion etch rate, however, can be increased by at least a factor of two in an F-chemistry, under specific temperature and ion-energy conditions. The ion-radical synergy varies from ion-dominated at room temperature/high ion energy to more chemically enhanced at elevated temperatures/low ion energy. Furthermore, during ion-etching, oxygen is preferentially sputtered which results in a non-stochiometric top layer. This is confirmed by an ex situ analysis of the atomic composition of the top layer. Based on these results we will present a simple model to describe the etching mechanism of HfO@SUB 2@ and discuss the promises of the F/Ar@super +@ chemistry for HfO@SUB 2@ etching.