1T1C FeRAM Memory Array Based on Ferroelectric HZO With Capacitor Under Bitline

• Published in: IEEE journal of the Electron Devices Society Vol. 10; pp. 29 - 34
• Main Authors: Okuno, Jun, Kunihiro, Takafumi, Konishi, Kenta, Materano, Monica, Ali, Tarek, Kuehnel, Kati, Seidel, Konrad, Mikolajick, Thomas, Schroeder, Uwe, Tsukamoto, Masanori, Umebayashi, Taku
• Format: Journal Article
• Language: English
• Published: New York IEEE 2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Arrays; capacitor under bitline; Capacitors; CUB; Electric potential; FeRAM; Ferroelectric films; Ferroelectric materials; Ferroelectric random-access memory; Ferroelectricity; hafnium oxide; Metallizing; Nonvolatile memory; post-metallization annealing; Random access memory; Semiconductor devices; Sense amplifiers; System on chip; Tin; Transistors; Voltage; zirconium oxide
• ISSN: 2168-6734; 2168-6734
• DOI: 10.1109/JEDS.2021.3129279

A novel system-on-a-chip compatible one-transistor one-capacitor ferroelectric random-access memory array (1T1C FeRAM) based on ferroelectric Hf 0.5 Zr 0.5 O 2 with a capacitor under bitline (CUB) structure was experimentally demonstrated. The CUB structure facilitates the application of post-metallization annealing on metal/ferroelectric/metal capacitors above 500 °C because they are fabricated before the back-end-of-line process. A large remanent polarization of 2Pr <inline-formula> <tex-math notation="LaTeX"> {>}40~\mu \text{C} </tex-math></inline-formula>/cm 2 , projected endurance <inline-formula> <tex-math notation="LaTeX">{>}10^{11} </tex-math></inline-formula> cycles, and ten years of data retention at 85 °C were obtained at 500 °C, after metallization using a single large capacitor. Furthermore, a large memory window of the 64 kbit 1T1C FeRAM array with 500 °C post-metallization was comprehensively demonstrated without degradation of the underlying CMOS logic transistors. The operation voltage and speed dependence were extensively investigated using a dedicated sense amplifier for the 1T1C FeRAM. Furthermore, the perfect bit functionality at an operation voltage of 2.5 V and a read/write speed < 10 ns were obtained. Therefore, superior properties of CUB-structured 1T1C FeRAM can be achieved by flexible process engineering of crystallization annealing for metal/ferroelectric/metal fabrication.