EPR characterization of defects in m-HfO₂

Abstract

Electron Paramagnetic Resonance (EPR) measurements have been made on a variety of commercially available samples of powdered monoclinic HfO₂. The high relative permittivity of HfO₂ is one reason that it is being considered as a replacement for SiO₂ as the gate dielectric in Si CMOS devices. The aim of the current measurements is to characterize the defects in HfO₂. All EPR spectra were taken at a microwave frequency of about 9.5GHz and at room temperature. An axially symmetric spectrum with g_// = 1.940 ± 0.003, g_⊥ = 1.970 ± 0.002 is seen for all but one of the HfO₂ samples; it is attributed to centres involving Hf³⁺ or Ti³⁺. Their average volume concentration varies from about 10¹⁷ cm⁻³ to less than 10¹⁴ cm⁻³ depending on the product specification and it is unaffected by γ-irradiation. Grinding granules to powder and/or γ-irradiation yields further EPR spectra that are likely to be associated with defects at or near the surface.