應用於FeRAM之鐵電氧化鉿鋯電容特性及穿隧接面元件

Abstract

隨著氧化鉿(HfO2)鐵電(Ferroelectric, FE)特性的發現，可以彌補最新技術節點與鐵電非揮發性記憶體之間的微縮瓶頸。除了非揮發性，新穎的記憶體還應該保證足夠的可靠度並同時具備低延遲及低耗能的特性，與鈣鈦礦鐵電記憶體相比，鐵電鉿基氧化物具備與CMOS製程相容且有利於尺寸微縮的優勢。 本論文第一部份使用氧化鉿鋯(Hf0.5Zr0.5O2)作為元件的鐵電層，以TiN及TaN 分別作為MFM(Metal-Ferroelectric-Metal)的上電極金屬，發現TaN的應力能使鐵電薄膜有著較大的殘餘極化(Remnant Polarization, Pr)，達到更好的記憶體特性。根據文獻，因反鐵電(Antiferroelectric, AFE)材料具有高耐久度的特性，故第二部分以高鋯濃度之氧化鉿鋯(HfxZr1-xO2)為鐵電層之MFM用於記憶體特性研究，並且達到耐久度(Endurance)超過1011次，使反鐵電材料能應用於FeRAM。另外，我們也將高鋯濃度之氧化鉿鋯，作為氧化鉿鋯鐵電穿隧接面(Ferroelectric Tunnel Junction, FTJ)元件之鐵電層，並成功區分出高阻態(High-Resistance State, HRS)與低阻態(Low-Resistance State, LRS)，證實AFTJ具有成為未來新興記憶體的潛力。

With the discovery of ferroelectricity within hafnium-based oxide, the gap between state-of-the-art technology node and non-volatile memory can be addressed by ferroelectric materials. In addition to non-volatility, emerging memory should simultaneously meet the demand of remarkable reliability, low access latency and low power consumption. Contrary to perovskite-type ferroelectric materials, hafnium-based oxide is compatible with current CMOS processes and beneficial for scaling down. The first part of this thesis adopts HfZrO2 as the ferroelectric layer. The TiN and TaN are served as capping electrode of MFM (metal-ferroelectric-metal), respectively. The stress from TaN capping metal brings larger remnant polarization of HZO and excellent memory performance. The excellent endurance of Antiferroelectric materials have been reported in some literature. In the second part, high zirconium concentration HfZrO2 integrated with MFM is studied for memory operation, and a superior 1011 cycles endurance is obtained. Beside, high-resistance state (HRS) and low-Resistance State (LRS) of antiferroelectric FTJ can be clearly distinguished for read-out. AFTJ has potential to be next generation emerging memory.