鐵電電容式記憶體增強開關比之技術

Abstract

鐵電記憶體（Ferroelectric Memory）是一種基於鐵電材料特性的非揮發性記憶體技術。鐵電材料具有自發極化的特性，即在沒有外加電場的情況下，材料內部會形成電偶極，並且這種極化可以被外加電場反轉，當施加一個電場時，鐵電材料內部的電偶極會隨電場方向翻轉，形成兩種穩定狀態，分別代表二進制的「1」和「0」，這種特性使得鐵電材料成為儲存訊號的理想材料。而鐵電電容式記憶體（Ferroelectric Capacitive Memory，FCM）包含在其中。此次研究首次展示具有SOI（Silicon-On-Insulator）基板和雙層HfZrO2（Double HZO，DHZO）的鐵電電容式記憶體其電容的開關比（Capacitive on/off Ratio，CHCS/CLCS）超過500倍。這一比率是FCM中的關鍵參數，表示記憶體可靠的儲存和檢索數據的能力。由於SOI在垂直方向上的空間限制，使得調控的空乏區域能夠在橫向方向上擴張以減少CLCS；此外，由於DHZO中高正交相（orthorhombic phase，o-phase）的比例，進一步增強CHCS，實現基於低電壓的飽和電容。對於DHZO-SOI FCM，實驗展示卓越的非破壞性讀取操作（Nondestructive Read Operation，NDRO），元件和讀取方案的操作週期均大於109次，並且在多階操作的4種狀態相比單層HfZrO2（Single HZO，SHZO）-SOI顯示錯誤率（Error Rates，ER）的改善。此技術包括DHZO和SOI的FCM是一個有前途的概念，具有潛在的非揮發性記憶體（Non-Volatile Memory，NVM）應用。Ferroelectric memory is a type of non-volatile memory technology based on the properties of ferroelectric materials. Ferroelectric materials possess spontaneous polarization, meaning that in the absence of an external electric field, electric dipoles form within the material. This polarization can be reversed by an external electric field. When an electric field is applied, the electric dipoles inside the ferroelectric material align with the direction of the field, creating two stable states representing the binary"1" and "0". This characteristic makes ferroelectric materials ideal for storing information. Ferroelectric capacitive memory is included within this category. For the first time, we have demonstrated a CHCS/CLCS ratio greater than 500× for a ferroelectric capacitive memory with an SOI substrate and double-HfZrO2 (DHZO). This ratio is a crucial parameter in FCM as it indicates the ability of the memory to store and retrieve data reliably. The modulated depletion region could be expanded laterally due to the spatial limitations in the vertical direction by the SOI to reduce CLCS; moreover, a low-voltage-based saturation capacitance by a high orthorhombic phase (o-phase) fraction of DHZO further enhanced CHCS. For DHZO-SOI FCM, the outstanding nondestructive read operation (NDRO) was experimentally exhibited with>10⁹ cycles by both devices and readout scheme, and the multilevel operation with 4-state also showed error-rate improvement compared to that of SHZO-SOI. The proposed technique involving DHZO and SOI for FCM is a promising concept and has potential NVM applications.