Hf layer thickness dependence of resistive switching characteristics of Ti/Hf/HfO₂/Au resistive random access memory device

Abstract

Resistive random access memory (ReRAM) devices with a HfO 2 dielectric layer have been studied extensively owing to the good reproducibility of their SET/RESET switching properties. Furthermore, it was reported that a thin Hf layer next to a HfO 2 layer stabilized switching properties because of the oxygen scavenging effect. In this work, we studied the Hf thickness dependence of the resistance switching characteristics of a Ti/Hf/HfO 2 /Au ReRAM device. It is found that the optimum Hf thickness is approximately 10 nm to obtain good reproducibility of SET/RESET voltages with a small RESET current. However, when the Hf thickness was very small (>2 nm), the device failed after the first RESET process owing to the very large RESET current. In the case of a very thick Hf layer (>20 nm), RESET did not occur owing to the formation of a leaky dielectric layer. We observed the occurrence of multiple resistance states in the RESET process of the device with a Hf thickness of 10 nm by increasing the RESET voltage stepwise.

Effect of Dielectric Thickness on Resistive Switching Polarity in TiN/Ti/HfO2/Pt Stacks

“…Therefore, it is unlikely that resistive switching polarity may present a linear or clear dependence with thickness. Rather, as it is stated by previous studies on resistive switching media, certain RS characteristics may appear at optimal compositions or stoichiometries [45,47,52,53].…”

“…Although it is clear that the HfO 2 thickness and/or the Ti/HfO 2 thickness ratio of the devices is the reason behind the effect that produces the polarity change of the BRS, it should be noted that no clear dependence between dielectric thickness and polarity can be determined. Nonetheless, as precedent research on redox-based RRAM presenting VCM suggests, no clear dependence of RS parameters such as LRS, HRS, LRS/HRS ratio or switching voltages with film thickness should be expected [45][46][47]. Only forming voltage has shown a dependence with thickness [48,49], with some devices even turning formingfree if the dielectric is sufficiently thin [50,51].…”

Structure and Electrical Behavior of Hafnium-Praseodymium Oxide Thin Films Grown by Atomic Layer Deposition

“…Although no direct correlation between the resistance state values and dielectric thickness had been observed in the VCM type RS media, based on HfO 2 [ 59 ] and other media [ 60 ], the dependence of the permittivity and RS performance on the structure development related to the dielectric thickness ( Figure 2 ) could not be neglected. However, the results of electrical measurements presented below were dominantly influenced by the chemical and phase composition rather than by the thickness of the dielectric.…”

Influences of the Temperature on the Electrical Properties of HfO2-Based Resistive Switching Devices

“…However, not many studies on the low-temperature characteristics of HfO 2 devices can be found. A study on Ti/Hf/HfO 2 /Au in the 100-200 K range showed that the resistance increased as the temperature decreased [17]. A report on Cu-doped HfO 2 films showed that the LRS increased with temperature, whereas the HRS decreased as the temperature rose [18].…”