Abstract
Resistive random-access memory (RRAM) devices are fabricated by utilizing silicon oxynitride (SiOxNy) thin film as a resistive switching layer. A SiOxNy layer is deposited on a p+-Si substrate and capped with a top electrode consisting of Au/Ni. The SiOxNy-based memory device demonstrates bipolar multilevel operation. It can switch interchangeably between all resistance states, including direct SET switching from a high-resistance state (HRS) to an intermediate-resistance state (IRS) or low-resistance state (LRS), direct RESET switching process from LRS to IRS or HRS, and SET/RESET switching from IRS to LRS or HRS by controlling the magnitude of the applied write voltage signal. The device also shows electroforming-free ternary nonvolatile resistive switching characteristics having RHRS/RIRS > 10, RIRS/RLRS > 5, RHRS/RLRS > 103, and retention over 1.8 × 104 s. The resistive switching mechanism in the devices is found to be combinatory processes of hopping conduction by charge trapping/detrapping in the bulk SiOxNy layer and filamentary switching mode at the interface between the SiOxNy and Ni layers.
Highlights
As complementary metal-oxide-semiconductor (CMOS) technology is reaching its size limit, the traditional flash memory used in the present electronics industry is facing physical and technological difficulty in retaining charges in the reduced dimension [1,2]
The effect of copper diffusion on the performance of SiOx Ny -based resistive random-access memory (RRAM) was investigated by Yang et al, who observed that the devices exhibit bistable resistive switching with an on/off current ratio of about 101.5 with the aid of diffused copper after a two-step electroforming process
The composition of the PECVD-deposited silicon oxynitride films depends on four major factors, (1) the N2O gas flow rate, (2) the presence of N2 gas, (3) the ratio of NH3 in the gas mixture, and (4)
Summary
As complementary metal-oxide-semiconductor (CMOS) technology is reaching its size limit, the traditional flash memory used in the present electronics industry is facing physical and technological difficulty in retaining charges in the reduced dimension [1,2]. The effect of copper diffusion on the performance of SiOx Ny -based RRAMs was investigated by Yang et al, who observed that the devices exhibit bistable resistive switching with an on/off current ratio of about 101.5 with the aid of diffused copper after a two-step electroforming process. With the combination of the Ni layer and the defect-rich SiOx Ny layer, we successfully incorporate an intermediate resistance state (IRS) between the HRS and low-resistance state (LRS) and eliminate the electroforming process, which requires a high activation voltage [18]. The device exhibits bipolar electroforming-free SET/RESET operational characteristics as well as multilevel digital memory characteristics with an HRS/LRS resistance ratio over 103 , which is better than that of the SiOx Ny -based devices introduced in previous reports [17,18]. A feasible resistive switching model is proposed to describe the conduction mechanism of the device
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