改變能障高度提升穿隧電阻效應之鐵電穿隧元件

Enhanced Tunneling Electro-resistance Ratio for HfZrOx-based Ferroelectric Tunnel Junction by Barrier Height Modulation

許琍雯(Lee-Wen Hsu)

指導教授 ： 巫勇賢

國立清華大學/原子科學院/工程與系統科學系/碩士(2021年)

摘要

具備自發性極化現象之鐵電材料在記憶體的領域中已成為重要研究議題多年，其中以二氧化鉿為基底的鐵電記憶體相較於傳統鐵電材料有諸多優勢，如切換速度較快、可靠度提升，最重要的是可相容於現今標準CMOS製程且利於微縮。鐵電記憶體屬於非揮發式記憶體，而鐵電穿隧接面(FTJ)具備結構簡單、低功耗，並且可以實現非破壞式讀取等優點，成為新興記憶體的研究主題之一。
本篇論文分為MFM和MFIS結構進行實驗，對於MFM結構而言，實驗顯示使用非對稱電極之鐵電穿隧接面元件會具有相較於對稱電極更高的ON /OFF ratio。而MFIS結構的部分，研究發現加入TiAl的上電極，相比起TiN上電極，由於其金屬功函數較低，因此在低阻態的情況下擁有更高的穿隧電流，TER ratio最高能到30左右，而在耐久度的表現上，經過106次脈衝後依然保有良好的特性，未來有望將之運用在神經網絡中並實現神經型態運算。

關鍵字

鐵電性 ； 鐵電穿隧接面 ； 穿隧電阻比 ； 熱離子注入

並列摘要

Ferroelectric materials with spontaneous polarization have become an important research topic in the field of memory. Ferroelectric memory is a nonvolatile memory, and the structure of Ferroelectric Tunnel Junction (FTJ) simply consists of a pair of electrodes. It requires low operation voltage, low power consumption and can achieve a non-destructive read. It has become one of the research topics of emerging memory. Especially, ferroelectric memory based on hafnium dioxide has many advantages over traditional ferroelectric materials. It can achieve a higher switching speed and provide more robust reliability. Most importantly, it is compatible with the current standard CMOS manufacturing process and conducive to scaling.
In this paper, we divided ferroelectric tunnel junctions into MFM and MFIS structures for experiments. For the MFM structure, the observation of the asymmetric electrodes shows a higher on/off ratio than the symmetric electrode. And for the MFIS structure, it is found that the top electrode with TiAl, which has a lower metal work function than the top electrode with TiN, achieves more tunneling current for the condition of a low-resistance state. And the TER ratio can reach about 30. In reliability performance, which still retains good characteristics after 106 times pulse-switching measurements. In the future, it will be hope to use in neural network operations and implement neuromorphic computing.

並列關鍵字

ferroelectricity ； ferroelectric tunnel junction ； TER ratio ； thermionic injection

參考文獻

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