Enhanced electrical properties of Nb-doped a-HfO2 dielectric films for MIM capacitors

Chris Yeajoon Bon,Dami Kim,Insung Park,Kanghyuk Lee,Sungjoon Choi,Sang-Im Yoo

doi:10.1063/5.0024783

Abstract

We report enhanced electrical properties of metal–insulator–metal (MIM) capacitors consisting of Al (100 nm)/Nb-doped a-HfO2 (∼30 nm)/Pt (100 nm) on a p-type silicon wafer, where Nb-doped amorphous HfO2 (a-HfO2) layers were deposited by radio frequency magnetron sputtering in various low oxygen partial pressures at room temperature. Polycrystalline HfO2 targets with three different Nb contents of 0 mol. %, 6 mol. %, and 10 mol. % were used in this study. Compared with the leakage current of the undoped a-HfO2 film (∼1.1 × 10−8 A cm−2 at 1 V), greatly reduced leakage currents (∼3.7 × 10−10 A cm−2 at 1 V) with no significant alteration in the dielectric constants (∼22) were obtainable from the MIM samples composed of Nb-doped a-HfO2 films, which is attributable to the suppression of oxygen vacancy formation based on the XPS analysis results. The Nb-doped a-HfO2 dielectric thin films also exhibited improved voltage nonlinearity compared to undoped HfO2. These results indicate that Nb-doped a-HfO2 has potential application as a high-κ dielectric material in MIM capacitors.

Highlights

Continuing the trend of device miniaturization as set by Moore’s law has led to the scaling down of device dimensions
radio frequency (RF) magnetron sputtering is used as the deposition method in this study since it is more advantageous than atomic layer deposition (ALD) in that thin films can be deposited with low contamination, which will be beneficial for investigating the effects of Nb-doping on HfO2 films, and amorphous HfO2 (a-HfO2) films can be deposited at lower temperatures
To determine the dielectric constants of undoped and Nbdoped HfO2 dielectric thin films, C–V measurements were performed for the MIM samples

Summary

INTRODUCTION

Continuing the trend of device miniaturization as set by Moore’s law has led to the scaling down of device dimensions Such scaling down of memory device technology has cast a serious challenge in materials selection since a dielectric thin layer should have both high dielectric constant and low leakage current. Since the α values of Nb5+ and Hf4+ are reported to be 3.10 and 1.89,33 respectively, Nb-doping was expected to increase the overall polarizability of HfO2 and, thereby, increase the dielectric constant This explanation is based on Nb-doping on crystalline. Nb-doping was employed in order to reduce leakage current by suppressing oxygen vacancy formation This strategy has been utilized for La-doped and Gd-doped HfO2 crystalline films,[16,20] where the suppression of oxygen vacancy formation was suggested to originate from stronger ionic bonding of La–O and Gd–O compared with that of Hf–O. Nb-doping was hypothesized to facilitate the formation of Hf–O bonds and minimize the formation of oxygen vacancies

EXPERIMENT

RESULTS AND DISCUSSION

CONCLUSIONS