鐵電二氧化鉿鋯(Hf1-xZrxO2)材料因具有雙穩態(Bi-stable)的特性，使其能在外加偏壓為零時仍具有兩個穩定的極化狀態，此特性使得它具備成為新興非揮發性記憶體(Non-volatile memory, NVM)的潛力，預期在未來人工智慧(Artificial intelligence, AI)和類神經運算(Neuromorphic computation)的應用中扮演至關重要的角色。截至現今已經有相當多關於鐵電材料於記憶體的研究，而本論文主要探討調變HZO中摻雜鉿(Hf)與鋯(Zr)的比例，並成功開發反鐵電(Anti-ferroelectric)材料應用於電阻式記憶體元件，且在記憶體特性上皆優於正鐵電(Ferroelectric)材料。
本論文第二章研究結果為反鐵電介面二極體(Anti-ferroelectric junction diode)的記憶體具備單極性操作的能力，且記憶體的開關比例(On/Off ratio)達到100倍和耐受性(Endurance)可達到109次；而第三、四章則展示雙層反鐵電穿隧式記憶體(Bi-layer anti-ferroelectric tunneling junction)具有大於100倍的On/Off ratio和大於50倍的穿隧電阻比(Tunneling electro-resistance, TER)，耐受性與資料保存性(Retention)分別可達到108次與大於104秒，並且在調控不同寫入的脈衝電壓下，顯示具有多階儲存單元的能力（Multi-level cell）與深度學習(Deep Learning)的特性，使其具備成為高密度且低功耗的非揮發性記憶體應用於類神經運算的潛力(Neuromorphic computation)。

Ferroelectric (FE) material Hf1-xZrxO2 is one of the most promising candidates for emerging non-volatile memory (NVM) in artificial intelligence (AI) and neuromorphic computation due to its two stable polarization states at zero electrical field for data storage with natural bi-stable characteristics. A variety of prototypes utilizing ferroelectricity in different storage mechanisms have been proposed. In this work, we demonstrate the FE and antiferroelectric (AFE) material properties, which are modulated from doped Zr incorporated into the HfO2-system. The result shows AFE material enhances the capacity to modulate the current ratio/TER.
We demonstrate two resistive switching memory devices, (anti-)ferroelectric junction diode((A)FE Diode) and bilayer-based (anti-)ferroelectric Tunneling Junction (Bilayer (A)FTJ) in chapter 2, 3 and 4 respectively. The proposed AFE diode shows memory On/Off ratio >100 and the switching endurance reaches > 109 cycles under unipolar operations. Bilayer (A)FTJ demonstrates >100x current ratio, >50x TER, leading to possible multi-level information storage (MLC) and neuromorphic computing. The endurance behavior shows 108 switching cycles with low energy consumption and data retention>104 seconds.

[1] C. Matsui, K. Takeuchi, ” Step-by-Step Design of memory hierarchy for heterogeneously-integrated SCM/NAND flash storage, ” ScienceDirect, vol. 69, pp. 62-74, 2019.
[2] Shimeng Yu and Pai-Yu Chen, ” Emerging Memory Technologies Recent Trends and Prospects , ” IEEE Solid-State Circuits Magazine ,Date of publication, 21 June 2016.
[3] M. Marinella, "The future of memory," 2013 IEEE Aerospace Conference, 2013, pp. 1-11
[4] A. Sebastian, "In-memory computing for AI," Short Course, 2019 IEDM, Dec. 8 2019
[5] T. S. Bösckea, J. Müllerb, D. Bräuhausc, U. Schröderd, and U. Böttgerc, “Ferroelectricity in Hafnium Oxide: CMOS Compatible Ferroelectric Field Effect Transistors, ” in IEDM, 2011, pp. 547-550.
[6] P. Polakowski, S. Riedel, W. Weinreich, M. Rudolf, J. Sundqvist, K. Seidel, and J. Müller, “Ferroelectric Deep Trench Capacitors based on Al:HfO2 for 3D Nonvolatile Memory Applications, ” in International Memory Workshop (IMW), 2014, pp. 1-4.
[7] C. H. Cheng and A. Chin, “Low-Leakage-Current DRAM-Like Memory Using a One-Transistor Ferroelectric MOSFET With a Hf-Based Gate Dielectric, ” Electron Device Letter, vol. 35, pp. 138-140, 2014.
[8] C. H. Cheng and A. Chin, “Low-Voltage Steep Turn-on PMOSFET Using Ferroelectric High-k Gate Dielectric, ” IEEE Electron Device Letter, vol. 35, pp. 274-276, 2014.
[9] M. H. Park, H. J. Kim, Y. J. Kim, T. Moon,K. D. Kim, and C. S. Hwangn, “Toward a Multifunctional Monolithic Device Based on Pyroelectricity and the Electrocaloric Effect of Thin Antiferroelectric HfxZr1-xO2 Films, ” Nano Energy, vol. 12, pp. 131-140, 2015.
[10] Y. C. Chiu, C. H. Cheng, C. Y. Chang, M. H. Lee, H. H. Hsuand, and S. S. Yen, “Low Power 1T DRAM/NVM Versatile Memory Featuring Steep Sub-60-mV/decade Operation, Fast 20-ns Speed, and Robust 85oC-Extrapolated 1016 Endurance, ” in VLSI Technology Symp., 2015, pp. 184-185.
[11] S. Fujii, Y. Kamimuta, T. Ino, Y. Nakasaki, R. Takaishi, and M. Saitoh, “First Demonstration and Performance Improvement of Ferroelectric HfO2-Based Resistive Switch With Low Operation Current and Intrinsic Diode Property, ” in VLSI Technology Symp., 2016, pp. 978-979.
[12] H. Mulaosmanovic, J. Ocker, S. Müller, M. Noack, J. Müller, P. Polakowski, T. Mikolajick, and S. Slesazeck, “Novel Ferroelectric FET based Synapse for Neuromorphic Systems, ” in VLSI Technology Symp., 2017, pp. 176-177.
[13] R. Eskandari, X. Zhang, and L. M. Malkinski, “Polarization-Dependent Photovoltaic Effect in Ferroelectric-Semiconductor System, ” Applied Physics Letters, vol. 110, pp. 121105, 2017.
[14] M. Dragoman, M. Aldrigo, M. Modreanu, and D. Dragoman, “Extraordinary Tunability of High-Frequency Devices Using Hf0.3Zr0.7O2 Ferroelectric at Very Low Applied Voltages, ” Applied Physics Letters, vol. 110, pp. 103104, 2017.
[15] J. V. Houdt, “Memory Technology for the Terabit Era: from 2D to 3D, ” in VLSI Technology Symp., 2017, pp. 978-979.
[16] S. W. Smith, A. R. Kitahara, M. A. Rodriguez, M. D. Henry, and M. T. Brumbach, and J. F. Ihlefeld, “Pyroelectric Response in Crystalline Hafnium Zirconium Oxide (Hf1-xZrxO2) Thin Films, ” Applied Physics Letters, vol. 110, pp. 072901, 2017.
[17] F. Huang, Y. Wang, X. Liang, J. Qin, Y. Zhang, X. Yuan, Z. Wang, B. Peng,L. Deng, and Q. Liu, “HfO2-Based Highly Stable Radiation-Immune Ferroelectric Memory, ” IEEE Electron Device Letter, vol. 38, pp. 330-333, 2017.
[18] A. Chen, “Nanoelectronic Device Research for beyond - CMOS Technologies, ” in “Emerging Technologies for the post 14nm Node Area, ” in IEDM short course, Dec. 8, 2012.
[19] S. Müller, H. Mulaosmanovic, S. Slesazeck, J. Müller, and T. Mikolajick, “CMOS Compatible Ferroelectric Devices for Beyond 1X nm Technology Nodes, ” in Solid State Device and Materials(SSDM), 2017, pp. 539-540.
[20] F. P. G. Fengler, M. Pešić, S. Starschich, T. Schneller, U. Böttger, T. Schenk, M. H. Park, T. Mikolajick and U. Schroeder, "Comparison of hafnia and PZT based ferroelectrics for future non-volatile FRAM applications," in European Solid-State Device Research Conference (ESSDERC), 2016
[21] Boescke,T.S.,Mueller,J.,Braeuhaus,D.,Schroeder,U.,Boettger,U.,2011.Ferroelectricityinhafniumoxidethin films. Appl. Phys. Lett. 99,102903.
[22] J. Muller et al., “Ferroelectricity in simple binary ZrO2 and HfO2,” Nano Lett., vol. 12, no. 8, pp. 4318–4323, 2012.
[23] H. H. Huang, T. Y. Wu, Y. H. Chu, M. H. Wu, C. H. Hsu, H. Y. Lee, S. S. Sheu, W. C. Lo, and T. H. Hou, “A Comprehensive Modeling Framework for Ferroelectric Tunnel Junctions, ” in IEDM Tech. Dig., Dec. 2019, pp. 298-301.
[24] M. Kobayashi, Y. Tagawa, F. Mo, T. Saraya, and T. Hiramoto, “Ferroelectric HfO2 Tunnel Junction Memory with High TER and Multi-Level Operation Feat uring metal replacement process,” IEEE Journal of the Electron Devices Society, 2019, 7, 134-139.
[25] V. Garcia and M. Bibes, “Ferroelectric tunnel junctions for information
storage and processing,” Nat. Comm., vol. 5, p. 4289, Jul. 2014
[26] T. Mikolajick, “Ferroelectric nonvolatile memories,” in Reference Module
in Materials Science and Materials Engineering. Amsterdam,
The Netherlands: Elsevier, 2016.
[27] V. Garcia, S. Fusil, K. Bouzehouane, S. Enouz-Vedrenne, N. D. Mathur, A. Barthelemy, and M. Bibes, “Giant tunnel electroresistance for non-destructive readout of ferroelectric states,” Nature, 2009, 460, (7251), 81-84.
[28] S. Boyn, A. Chanthbouala, S. Girod, C. Carre´te´ro, A. Barthe´le´my, M. Bibes, J. Grollier, S. Fusil, and V. Garcia, “Real-time switching dynamics of ferroelectric tunnel junctions under single-shot voltage pulses,” Applied Physics Letters, 2018, 113, (23), 232902.
[29] X. Lyu, M. Si, X. Sun, M. A. Capano, H. Wang, and P. D. Ye, “Ferroelectric and anti-ferroelectric Hafnium Zirconium oxide: Scaling limit, switching speed and record high polarization density,” in VLSI Technology Symp., 2019, T44-T45.
[30] X. J. Lou, “Why do antiferroelectrics show higher fatigue resistance than ferroelectrics under bipolar electrical cycling?” Applied Physics Letters, 2009, 94, (7), 072901.
[31] M. Gao, X. Tang, C. M. Leung, S. Dai, J. Li, and D. D. Viehland, “Phase transition and energy storage behavior of antiferroelectric PLZT thin films epitaxially deposited on SRO buffered STO single crystal substrates,” Journal of the American Ceramic Society, 2019, 102, (9), 5180-5191.
[32] B. Max, M. Hoffmann, S. Slesazeck, and T. Mikolajick, “Direct correlation of ferroelectric properties and memory characteristics in ferroelectric tunnel junctions,” IEEE J. Electron Devices Soc., vol. 7.
[33] S. Fujii, Y. Kamimuta, T. Ino, Y. Nakasaki, R. Takaishi, and M. Saitoh, “First demonstration and performance improvement of ferroelectric HfO2-based resistive switch with low operation currentand intrinsic diode property,” in Proc. IEEE Symp. VLSI Technol.,Jun. 2016, pp. 1–2.
[34] B. Max, T. Mikolajick, M. Hoffmann, S. Slesazeck, and T. Mikolajick, “Retention characteristics of Hf0.5Zr0.5O2-based ferroelectric tunnel junctions,” in Proc. Int. Memory Workshop (IMW), 2019.
[35] Mikolajick, U. Schroeder and S. Slesazeck, "The Past, the Present, and the Future of Ferroelectric Memories,“ in IEEE Transactions on Electron Devices, vol. 67, no. 4, pp. 1434-1443, April 2020
[36] Max B, Hoffmann M, Slesazeck S and Mikolajick,"Ferroelectric tunnel junctions based on ferroelectricdielectricHf0.5Zr0.5.O2/A12O3Capacitor stacks" 2018 48th European Solid-State Device Research Conf. (ESSDERC) (Dresden) pp 142–5
[37] M. Pešić, T. Li, V. D. Lecce, M. Hoffmann, M. Materano, C. Richter, B. Max, S. Slesazeck, U. Schroeder, L. Larcher, and T. Mikolajick, “Built-In Bias Generation in Anti-Ferroelectric Stacks: Methods and Device
Applications, ” IEEE Journal of the Electron Devices Society, vol. 6, pp. 1019-1025, 2018
[38] D. K. Simon, P. M. Jordan, T. Mikolajick, and I. Dirnstorfer, “On the Control of the Fixed Charge Densities in Al2O3‑Based Silicon Surface Passivation Schemes” ACS Appl. Mater. Interfaces, vol. 7, no. 51, pp. 28215–28222, 2015
[39] T T. Y. Wu, H. H. Huang, Y. H. Chu, C. C. Chang, M. H. Wu, C. H. Hsu, C. T. Wu, M. C. Wu, W. W. Wu, T. S. Chang, H. Y. Lee, S. S. Sheu, W. C. Lo, and T. H. Hou, “Sub-nA Low-Current HZO Ferroelectric Tunnel Junction for High-Performance and Accurate Deep Learning Acceleration, ”in IEDM Tech. Dig., Dec. 2019, pp. 118-121
[40] Benjamin Max, Michael Hoffmann, Halid Mulaosmanovic, Stefan Slesazeck, and Thomas Mikolajick, “Hafnia-Based Double-Layer Ferroelectric Tunnel Junctions as Artificial Synapses for Neuromorphic Computing ", ACS Applied Electronic Materials 2020 2 (12), 4023-4033
[41] J. J. Huang, T. H. Hou, C. W. Hsu, Y. M. Tseng, W. H. Chang, W. Y. Jang, and C. H. Lin, "Flexible one diode–one resistor crossbar resistive-switching memory," Japanese Journal of Applied Physics, vol. 51, p. 04DD09, 2012
[42] S. Fujii, M. Yamaguchi, S. Kabuyanagi, K. Ota, and M. Saitoh, “Improved sate stability of HfO2 ferroelectric tunnel junction by template-induced crystallization and remote scavenging for efficient in-memory reinforcement learning, ” in VLSI Symp., June 2020, TF2.3, doi: 10.1109/VLSITechnology18217.2020.9265059.
[43] Z. Chen, L. He, F. Zhang, J. Jiang, J. Meng, B. Zhao, and A. Jiang, “The conduction mechanism of large on/off ferroelectric diode currents in epitaxial (111) BiFeO3 thin film,” Journal of Applied Physics, 2013, 113, 184106.
[44] F. Liu, F. Ji, Y. Lin, S. Huang, X. Lin, and F. Yang, “Ferroresistive Diode Currents in Nanometer-Thick Cobalt-Doped BiFeO3 Films for Memory Applications,” ACS Applied Nano Materials, 2020, 3, 8888-8896