Optimizing process conditions for improved Hf1 - ZrxO2 ferroelectric capacitor performance

The recently reported ferroelectric phase in doped hafnium oxide films enabled various devices ranging from non-volatile applications to negative capacitance field effect transistors. This study analyses the structural and electrical changes in ferroelectric Hf-1 - xZrxO2 based metal-insulator-metal capacitors. Planar metal-ferroelectric-metal stacks of different composition, thickness and purge times were prepared by atomic layer deposition for the Hf-1 - xZrxO2 films with metal organic precursors, water as oxygen source and reactive physical vapor deposition of TiN electrodes. With the optimization of the process route it was possible to improve the endurance and the remanent polarization of the ferroelectric capacitor. The analysis proved that the reduction of the impurities in the film is decreasing the non-ferroelectric monoclinic phase fraction with increasing purge time. An increase of the annealing temperature from 500 to 800 degrees C resulted in a higher amount of the ferroelectric orthorhombic phase fraction, but also caused a reduced endurance. Impedance spectroscopy indicated the existence of an interfacial dead layer and its widening with higher anneal temperatures. (C) 2017 Elsevier B.V. All rights reserved.