Electrical and material characterisation of silicon carbide based resistive memories

Abstract

Resistive memory is widely considered as a promising non-volatile memory to address the demands for high-density data storage, low power consumption, augment the performance of current transistor-based memories or even replace current transistor-based memories. Main advantages of resistive memory include simple Metal/Insulator/Metal device structure, low switching voltage, fast switching speed, and long data retention. Material properties of the insulating layer play important roles in the overall performance of resistive memory. Among a range of insulator materials of resistive memories that have been reported in the literature thus far, Silicon Carbide (SiC) has shown great promise as the insulating layer which leads to resistive memories with desirable performance including large ON/OFF ratios, excellent data retention, and CMOS compatibility in device fabrication. However, there are still many challenges to be solved in the resistive memories using SiC, especially amorphous (a)-SiC as the insulating layer to be superior to other resistive memories. One of these challenges is to reduce the forming voltage which could affect the power consumption and complexity of the peripheral power-supply circuit. Another challenge is to achieving device structure exclusively using native CMOS back-end-of-line materials which would enable low fabrication cost and low development time to embed a-SiC based resistive memories in the CMOS back-end-of-line layer. Moreover, the existing Electrochemical metallisation (ECM) mechanism cannot precisely predict the switching voltage nor resistance state of resistive memories, and there is a lack of knowledge on how the material properties of the insulating layer affect resistive-switching performance and mechanisms. Further exploration of the resistiveswitching characteristics to improve the understanding of switching mechanism and influence of material and electrical properties of the insulating layer on resistive-switching characteristics are needed from a scientific point of view.

This thesis focuses on addressing all the challenges above, highlights the influence of insulator material choice on the performance of resistive memories using SiC as the insulating layer. Amorphous silicon carbide (a-SiC), Cu embedded a-SiC (a-SiC:Cu), CMOS back-end-of-line dielectrics (a-Si(O)C:H), and crystalline SiC (c-SiC) are used as the insulating layer of resistive memories in this thesis. The material and electrical properties of these insulator materials are characterised. Metal/Insulator/Metal resistive memories using these insulator materials as the insulating layer are fabricated and the resistive-switching characteristics of these resistive memories are studied. Ultrahigh ON/OFF ratios up to 109 which enables fast and reliable detection of the states, are achieved. Forming voltage and SET voltage are reduced and endurance is improved by embedding Cu nanoparticles in the a-SiC insulating layer. Non-volatile resistive-switching is observed on resistive memories using exclusively native CMOS back-end-of-line materials including Cu, W, a-SiC:H, aSiOC:H, and a-SiCO:H. The influence of material and electrical properties of the insulating layer on resistive-switching characteristics of resistive memories made exclusively using CMOS back-end-ofline materials is discussed.

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ORCID for Liudi Jiang: orcid.org/0000-0002-3400-825X

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