鐵電記憶元件特性量測與電路模擬

Abstract

由於可攜式電子器材如行動電話，個人數位助理(PDA)以及個人辨識卡(smart card)的廣泛應用，可與固態積體電路相容的非揮發性記憶體之市場在最近幾年持續成長。現今該市場無疑由快閃式記憶體主導，然而對於速度與可靠度的高度需求驅使工程師尋求可取而代之的新記憶體。以鐵電材料作為記憶元件的非揮發性記憶體於焉成為數種選擇之一。鐵電記憶體歷經長時間的研究，薄膜生長技術的改進與可靠度的控制對於成功生產有決定性影響力，唯有清楚定義元件特性，準確的電路模式建立和記憶體電路設計方能實現。 本篇論文的主旨在於探討鐵電電容器的特性量測和模式建立，各種薄膜衰退現象的物理機制和他們對記憶體可靠性的影響皆列入討論。另外針對過去所發表過的鐵電電容模式建立方法簡短整理後，以零轉換時間暫態模式(ZSTT)為出發點，建立該模式並驗證其電性，與實驗數據比較，模擬結果顯示與實驗數據相容。最後將零轉換時間暫態模式與記憶體電路結合，其中包括2T/2C、1T/1C和1T/2C結構。文中並對感應放大器的靈敏度作基礎的分析，總結模擬結果，若能對於薄膜特性充分的了解並將其可靠度控制在最佳狀態便掌握了鐵電記憶體的可行性。

The market for non-volatile memories integrated with solid-state circuits has been growing in recent years due to wide spread of various kinds of portable devices including cell phones, PDAs, and smart cards. Flash memories dominate this market today. However, the need for higher speed and reliability is pushing engineers to search for better replacement. Non-volatile memory using ferroelectric materials to form the memory element is a strong candidate. This product has been under development for years. Improved process technology and better control of long-term reliability are vital for introducing commercial devices. With well-defined ferroelectric film characteristics, accurate modeling and circuit design are therefore feasible. The main concern of this work will focus on the characterization of ferroelectric capacitor and its modeling. Each degradation mechanism is reviewed; their physical concept and impact on device reliability are discussed. Several effective modeling approaches have been proposed. In this thesis, the behavioral modeling method of ZSTT is implemented and demonstrated. The results of simulation match the experimental data quantitatively. The model is also integrated into FRAM cells of 2T/2C, 1T/1C and 1T/2C architecture. The sense amplifier is also analyzed, too. HSPICE simulation proves the viability of FRAM cells with the well-controlled film characteristics.