Title: Nanomechanical study of amorphous and polycrystalline ALD HfO₂ thin films

Authors: K. Tapily, J.E. Jakes, D. Gu, H. Baumgart, A.A. Elmustafa

Addresses: Department of Electrical Engineering, Old Dominion University, Norfolk, Virginia 23529, USA; Applied Research Center, Newport News, Virginia, 23606, USA. ' Performance Enhanced Biopolymers, USDA Forest Products Laboratory, Madison, Wisconsin, 53726, USA; Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA. ' Department of Electrical Engineering, Old Dominion University, Norfolk, Virginia 23529, USA; Applied Research Center, Newport News, Virginia, 23606, USA. ' Department of Electrical Engineering, Old Dominion University, Norfolk, Virginia 23529, USA; Applied Research Center, Newport News, Virginia, 23606, USA. ' Applied Research Center, Newport News, Virginia, 23606, USA; Department of Mechanical Engineering, Old Dominion University, Norfolk, Virginia 23529, USA

Abstract: Thin films of hafnium oxide (HfO₂) were deposited by atomic layer deposition (ALD). The structural properties of the deposited films were characterised by transmission electron microscopy (TEM) and X-ray diffraction (XRD). We investigated the effect of phase transformations induced by thermal treatments on the mechanical properties of ALD HfO₂ using nanoindentation. The elastic modulus of the amorphous low temperature deposited ALD HfO₂ films was measured to be 370 ± 20 GPa. Subsequent to crystallisation by annealing in a rapid thermal annealing (RTA) chamber, the elastic modulus dropped to 240 ± 20 GPa. Similarly, the Meyer hardness decreased from a value of 18 ± 1 GPa for amorphous HfO₂ to 15 ± 1 GPa following the transition temperature from amorphous to polycrystalline HfO₂.

Keywords: atomic layer deposition; ALD; nanoindentation; high-k dielectrics; elastic modulus; hardness; hafnium oxide; HfO2 thin films; phase transformations.

DOI: 10.1504/IJSURFSE.2011.041402

International Journal of Surface Science and Engineering, 2011 Vol.5 No.2/3, pp.193 - 204

Published online: 14 Oct 2014 *

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