Effect of Thickness on the Resistive Switching Characteristics of Pt/Ag/HfO2/W MIMStacks
Please login to view abstract download link
In this work, we compare the resistive switching (RS) characteristics of two Pt/Ag/HfO2/W/Ti RRAM devices differing only in the HfO₂ thickness: one consisting of a 5.6 nm layer and another consisting of a 21 nm layer. We present a thorough electrical characterization in order to understand the role of the thickness in these differences of their electrical response. Both samples delivered excellent RS characteristics, which can be seen by the 100 I-V cycles shown for both devices in Fig. 1. Nevertheless, it is clear just by observing the I-V curves that the currents are much higher in the thinner sample, thus consuming more power. Moreover, looking at the cumulative probabilities of set and reset voltages on Fig. 2, both switching voltages are higher for the thinner device, further increasing its power consumption. Meanwhile, the LRS/HRS ratio is far greater in the thicker device (Fig. 3). Additionally, variability in I-V curves (Fig. 1) and set/reset voltages (Fig. 2) is lower in the thicker device, pointing to more stable switching conditions, which can also be seen on the pulsed RS characteristics of Fig. 4. Nevertheless, multilevel switching performance was superior in the thinner sample (Fig. 6). These findings suggest that the dielectric thickness critically influences device performance. In the thicker sample, conductive filaments are more confined and form in well-defined regions, reducing variability and leading to more stable switching. In contrast, in the thinner sample multiple conductive filaments can contribute to conduction, making the switching process more stochastic due to the increased probability of multiple filamentary paths. This randomness also results in higher set/reset voltage variability. The thinner sample consumes more power because higher leakage currents increase overall conduction, also requiring larger voltages to induce the switching. However, the presence of multiple filaments enhances its multilevel switching capability, allowing for more gradual resistance control.