鐵電氧化鉿鋯之記憶體及類神經元件應用

Abstract

近年來發現摻雜HfO2在正交晶相中具有鐵電性，鐵電薄膜的殘餘極化和矯頑場可以通過摻雜濃度，退火條件進行調整。重要的是，HfO2與CMOS製程相容，用於記憶體上可以提供隨機存取、高速、低功率、高密度和非揮發性的理想記憶體條件。 本論文中展示了5nm厚度的Hf0.5Zr0.5O2 (HZO)閘極堆疊鐵電電晶體之記憶體元件應用，後閘極製程(gate-last process)使鐵電性隨著結晶溫度的逐漸轉變。元件具備優異的寫入/抹除(P/E)數據保持(retention)，當寫入/抹除電壓為4.8V時，外插到10年之電流開關比~2x104，記憶窗0.67 V。本篇論文第一部分為探討1T1C鐵電電容二極體的讀取耐久性(Endurance)以及高數據保持力(Retention)，第二部分為5奈米厚度的Hf0.5Zr0.5O2 (HZO)閘極堆疊鐵電電晶體之記憶體元件應用，以及探討不同介面層(Interfacial layer)對元件的影響，最後由於近年人工智慧的迅速崛起，我們利用具有鐵電性的元件來進行類神經應用，驗證了超薄鐵電層可做為新興記憶體及物聯網架構的真實性。

In recent years, it has been found that doped HfO2 has ferroelectricity in the orthorhombic phase. Additionally, the remanent polarization and coercive field of the ferroelectric thin film can be adjusted by doping concentration and annealing temperature. Most importantly, HfO2 is fully compatible with current CMOS processes and it also has many advantages for memory application, such as random access, high speed, low power, high density, and non-volatility. The feature of this work is an unaffected coercive-field (~1 MV/cm) with scaling FE-HZO down to 5-nm-thick, which is beneficial for reducing the operation voltage. FeFETs with 5-nm-thick Hf0.5Zr0.5O2 (HZO) have been demonstrated in memory operations. Gradual transition of the ferroelectricity with an increasing crystallization temperature for the gate-last process was presented. The excellent program/erase (P/E) data retention are the ~2x104 ON/OFF ratio and 0.67 V extrapolated to 10 years with VP/E=4.8 V. Comparable performance with previous works on high data retention and endurance with low voltage for read are achieved. The ultrathin ferroelectric layer proposes a realistic emerging memory for 1T architecture.