Tae-Hyeon Kim

Nano-cone resistive memory for ultralow power operation

SiN x -based nano-structure resistive memory is fabricated by fully silicon CMOS compatible process integration including particularly designed anisotropic etching for the construction of a nano-cone silicon bottom electrode (BE). Bipolar resistive switching characteristics have significantly reduced switching current and voltage and are demonstrated in a nano-cone BE structure, as compared with those in a flat BE one. We have verified by systematic device simulations that the main cause of reduction in the performance parameters is the high electric field being more effectively concentrated at the tip of the cone-shaped BE. The greatly improved nonlinearity of the nano-cone resistive memory cell will be beneficial in the ultra-high-density crossbar array.

Self-Compliant Bipolar Resistive Switching in SiN-Based Resistive Switching Memory

Here, we present evidence of self-compliant and self-rectifying bipolar resistive switching behavior in Ni/SiNx/n+ Si and Ni/SiNx/n++ Si resistive-switching random access memory devices. The Ni/SiNx/n++ Si device’s Si bottom electrode had a higher dopant concentration (As ion > 1019 cm−3) than the Ni/SiNx/n+ Si device; both unipolar and bipolar resistive switching behaviors were observed for the higher dopant concentration device owing to a large current overshoot. Conversely, for the device with the lower dopant concentration (As ion < 1018 cm−3), self-rectification and self-compliance were achieved owing to the series resistance of the Si bottom electrode.

Concurrent events of memory and threshold switching in Ag/SiNx/Si devices

In this work, the simultaneous detection of threshold switching and bipolar memory switching in Ag/SiNx/p++-Si devices is investigated. In the DC sweep mode, threshold switching is observed with low compliance current limit (CCL) of 1 μA while memory switching is dominant when high CCL (1 mA) is applied. It is found that in the pulse switching mode, pulse amplitude is an important factor in determining the nature of switching. It has been proven that the strength of the Ag filament formed in the SiNx determines the nonvolatile property of the switching. The undirectional threshold switching behavior in low currents of Ag/SiNx/p++-Si devices could be used as a selector for a low-power unipolar memory. Moreover, operating in two modes in one device will provide more flexibility in device design.