(A) study on the material, electrical and reliability properties of $Hf_{0.5}Zr_{0.5}O_2$ based ferroelectric devices with $RuO_2$ electrodes by atomic layer deposition

Abstract

The purpose of this research is to analyze the material, electrical and reliability properties of hafnium-zirconium oxide($Hf_{0.5}Zr_{0.5}O_2$) based ferroelectric devices based on ruthenium oxide electrodes using atomic layer deposition(ALD). The ruthenium oxide electrode deposited by ALD method was applied to the metal-ferroelectric-metal(MFM) devices to suppress the oxygen vacancy in the hafnium thin films which cause the wake-up effect and the degradation of reliability. The difference in material, electrical and reliability characteristics was analyzed by applying titanium nitride(TiN) which are typical electrode materials and ruthenium oxide($RuO_2$) thin films to the top electrode(TE), respectively. The device with $RuO_2$ electrode at the TE has less oxygen vacancy at the interface with the upper hafnium - zirconium oxide than the device with the TiN TE. Less oxygen vacancy occurred at the upper interface between $RuO_2$ and $Hf_{0.5}Zr_{0.5}O_2$, resulting in less wake-up effect and improved electrical properties. However, another improvement goal, reliability, did not improve. Through electrical analysis, it was confirmed that the work function of the electrode changed at the interface, and indirectly found that the $RuO_2$ was reduced to ruthenium(Ru) through materials property analysis. During rapid thermal annealing(RTA) process, the reduction to Ru led to a decrease in work function, which in turn resulted in poorer leakage properties.