Probing the oxygen vacancy related defect states in HfO$_{\mathrm{2}}$ gate dielectric using DLTS

Large numbers of theoretical works are present to understand the oxygen vacancy related traps (V$_{\mathrm{O}})$ in technologically relevant HfO$_{\mathrm{2}}$.$_{\mathrm{\thinspace }}$Most of these calculations are based on the atomistic models and typically ideal, hence, cannot provide the realistic device parameters. Here, we applied the Deep Level Transient Spectroscopy (DLTS): a sensitive tool; to study the deep level defects presents in high-k HfO$_{\mathrm{2}}$. DLTS signal is originating from the segregated oxygen vacancy at the interface, tunneling/hopping between bulk and interface traps and communication of interface defects with respective bands. We observed four prominent deep levels; the estimated activation energies are Ec$_{\mathrm{\thinspace }}$- 1.22, Ec - 1.36, Ec - 1.76 and Ec$_{\mathrm{\thinspace }}$- 2.03 eV, below the HfO$_{\mathrm{2}}$ conduction band. These trap states are related to V$_{\mathrm{O}}$ in different charge states as suggested theoretically. We also measured the capture cross-sections ($\sigma )$ of these states and found it is quite low (\textasciitilde 10$^{\mathrm{-18}}$ - 10$^{\mathrm{-21\thinspace }}$cm$^{\mathrm{2}})$, which indicate a negligible influence on the device performance. This study will be helpful to disclose the numerous fascinating facts witnessed in HfO$_{\mathrm{2}}$.