隨著科技進步，數據量急速增長，記憶單元與邏輯單元之間的數據傳輸面臨嚴重的功耗和訊號延遲問題，因此，結合記憶與邏輯單元的邏輯記憶元件(Logic in Memory)應運而生，其中鐵電記憶體(FeRAM)因高集成密度、低功耗、高讀寫速度而備受矚目。然而，受到製程條件與電場循環等因素影響，金屬-鐵電-金屬(Metal-Ferroelectric-Metal)鐵電電容在電極與鐵電層之間容易產生介面層缺陷，導致元件漏電流增加、極化特性降低與可靠度衰退等問題。因此，本研究調變氮化鈦的材料性質與厚度，將其作為下電極緩衝層、中間阻障層、上電極介面層與金屬介面層，應用於氧化鋯鉿鐵電電容之中，並通過量測分析，探討氮化鈦是否能穩定面品質、優化元件性能。
實驗結果顯示，2奈米的氮化鈦作為下電極緩衝層與中間阻障層不僅未能增強鐵電極化特性，反而導致漏電流大幅提升，推測氮化鈦已經發生氧化反應。在氮化鈦金屬介面層電容結構中，通過調變氮化鈦金屬介面層厚度，可以在極化特性、漏電流與可靠度之間取得參數最佳化。經過450°C的金屬沉積後退火處理，氮化鈦金屬介面層電容結構展現最佳兩倍殘餘極化量24.83 µC/cm2，比起氮化鈦上電極介面層電容結構高出約16%~45%，氮化鈦金屬介面層電容結構在-3 V時的漏電流值為1.72×10-10A，顯著低於無氮化鈦金屬介面層電容結構約3個數量級。在可靠度測試中，無氮化鈦金屬介面層電容結構在較小的定電壓應力下便發生永久性崩潰，氮化鈦金屬介面層電容結構則需要更大的定電壓應力才會發生電洞生成現象，展現卓越的抗電應力，並且氮化鈦金屬介面層電容結構經過108次耐久度循環後仍維持兩倍殘餘極化量7.13 µC/cm2，表現出最低的疲勞現象，證實氮化鈦金屬介面層可以穩定氮化鉭上電極與氧化鋯鉿薄膜間的介面品質，減少介面缺陷的產生，有助於維持優異的極化特性、降低漏電流與優化元件可靠度。

With rapid technological advancement, increasing data volumes have caused significant power consumption and signal delay issues in data transmission between memory and logic units. Logic-in-Memory devices, which integrate logic and memory units, have emerged as a solution. Ferroelectric Random Access Memory is notable for its high density, low power consumption, and fast read/write speeds. However, process conditions and electric field cycling will lead to interface layer defects in Metal-Ferroelectric-Metal capacitors, resulting in increased leakage current, reduced polarization, and decreased reliability. Therefore, this study modifies the material properties and thickness of titanium nitride (TiN) for use as a bottom electrode buffer layer, inserting barrier layer, top electrode interface layer, and interface metal layer in hafnium zirconium oxide (HfZrO) ferroelectric capacitors to stabilize interface quality and optimize device performance.
The results show that using 2 nm TiN as a bottom electrode buffer layer and inserting barrier layer did not enhance polarization but increased leakage current, likely due to TiN oxidation. However, optimizing the thickness of the TiN interface metal layer improved polarization characteristics, decreased leakage current, and enhanced reliability. After post-metal annealing at 450°C, the TiN interface metal layer capacitor achieved a double remanent polarization of 24.83 µC/cm², 16% to 45% higher than the TiN top electrode interface layer capacitor. Additionally, its leakage current at -3 V is 1.72×10-10A, three orders of magnitude lower than the capacitor without a TiN interface metal layer. In reliability tests, the TiN interface metal layer capacitor did not occur early breakdown, it showed superior resistance to constant voltage stress and maintained double remanent polarization of 7.13 µC/cm² with the lowest fatigue after 108 endurance cycles. These results confirm the TiN interface metal layer stabilizes the interface between the Tantalum nitride top electrode and HfZrO, reducing defect generation. At the same time, it optimizes device polarization, leakage current, and reliability.

[1] Z. Fan, J. Chen, and J. Wang, “Ferroelectric HfO2-based materials for next-generation ferroelectric memories,” Journal of Advanced Dielectrics, vol. 06, no. 02, p. 1630003, Jun. 2016.
[2] M. S. Park et al., “Ferroelectricity and Antiferroelectricity of Doped Thin HfO2-Based Films,” Advanced Materials, vol. 27, no. 11, pp. 1811–1831, Feb. 2015.
[3] T. S. Böscke et al., “Phase transitions in ferroelectric silicon doped hafnium oxide,” Applied Physics Letters, vol. 99, no. 11, p. 112904, Sep. 2011.
[4] W. Banerjee, “Challenges and Applications of Emerging Nonvolatile Memory Devices,” Electronics, vol. 9, no. 6, p. 1029, Jun. 2020.
[5] A. Chen, “A review of emerging non-volatile memory (NVM) technologies and applications,” Solid-State Electronics, vol. 125, pp. 25–38, Nov. 2016.
[6] S. Bertolazzi et al., “Nonvolatile Memories Based on Graphene and Related 2D Materials,” Advanced Materials, vol. 31, no. 10, p. 1806663, Jan. 2019.
[7] X. Liu, Y. Liu, W. Chen, J. Li, and L. Liao, “Ferroelectric memory based on nanostructures,” Nanoscale Research Letters, vol. 7, no. 1, Jun. 2012.
[8] R. C. G. Naber, Bart de Boer, Paul, and M. de, “Low-voltage polymer field-effect transistors for nonvolatile memories,” Applied Physics Letters, vol. 87, no. 20, Nov. 2005.
[9] J. Müller, Polakowski P, S. Mueller, and T. Mikolajick, “Ferroelectric Hafnium Oxide Based Materials and Devices: Assessment of Current Status and Future Prospects,” Journal of Solid State Science and Technology, vol. 4, no. 5, pp. 30–35, Jan. 2015.
[10] J. Cao, S. Shi, Y. Zhu, and J. Chen, “An Overview of Ferroelectric Hafnia and Epitaxial Growth,” physica status solidi (RRL) – Rapid Research Letters, vol. 15, no. 5, p. 2100025, Apr. 2021.
[11] “技術文章-閎康科技-MA-tek 閎康科技,” www.matek.com. https://www.matek.com/zh-TW/Tech_Article/detail/specialist-column/all/202202-IAR (accessed Jun. 24, 2024).
[12] T. Shimizu, “Ferroelectricity in HfO2 and related ferroelectrics,” Journal of the Ceramic Society of Japan, vol. 126, no. 9, pp. 667–674, Sep. 2018.
[13] M. Kobayashi, J. Wu, Yoshiki Sawabe, Saraya Takuya, and T. Hiramoto, “Mesoscopic-scale grain formation in HfO2-based ferroelectric thin films and its impact on electrical characteristics,” Nano convergence, vol. 9, no. 1, Nov. 2022.
[14] D. Zhang et al., “Grain Size Reduction of Ferroelectric HZO Enabled by a Novel Solid Phase Epitaxy (SPE) Approach: Working Principle, Experimental Demonstration, and Theoretical Understanding,” Jun. 2023.
[15] Y. Matveyev, D. Negrov, A. Chernikova, Y. Lebedinskii, R. Kirtaev, S. Zarubin, E. Suvorova, A. Gloskovskii, and A. Zenkevich, “Effect of polarization reversal in ferroelectric TiN/Hf0.5Zr0.5O2/TiN devices on electronic conditions at interfaces studied in operando by hard x-ray photoemission spectroscopy,” ACS applied materials & interfaces, vol. 9, no. 49, pp. 43370-43376, 2017.
[16] U. Schroeder et al., “Impact of different dopants on the switching properties of ferroelectric hafnium oxide,” Japanese Journal of Applied Physics, vol. 53, no. 8S1, pp. 08LE02–08LE02, Jul. 2014.
[17] D.R. Hsieh, C.C. Lee, and T.S. Chao, “Role of Nitrogen in Ferroelectricity of Hf x Zr1-x O2-Based Capacitors With Metal-Ferroelectric-Insulator-Metal Structure,” I.E.E.E. transactions on electron devices/IEEE transactions on electron devices, vol. 69, no. 4, pp. 2074–2079, Apr. 2022.
[18] L. Xu, T. Nishimura, S. Shibayama, T. Yajima, S. Migita, and A. Toriumi, “Kinetic pathway of the ferroelectric phase formation in doped HfO2 films,” Journal of Applied Physics, vol. 122, no. 12, p. 124104, Sep. 2017.
[19] D. Fischer and A. Kersch, “The effect of dopants on the dielectric constant of HfO2 and ZrO2 from first principles,” Applied Physics Letters, vol. 92, no. 1, Jan. 2008.
[20] Si Wouk Kim, J. Mohan, S. R. Summerfelt, and J.-Y. Kim, “Ferroelectric Hf0.5Zr0.5O2 Thin Films: A Review of Recent Advances,” The Journal of The Minerals, Metals & Materials Society, vol. 71, no. 1, pp. 246–255, Sep. 2018.
[21] J. Müller et al., “Ferroelectricity in Simple Binary ZrO2 and HfO2,” Nano Letters, vol. 12, no. 8, pp. 4318–4323, Jul. 2012.
[22] M. S. Park, Han Jo Kim, Yu Seun Kim, W. Lee, T. Moon, and Cheol Seong Hwang, “Evolution of phases and ferroelectric properties of thin Hf0.5Zr0.5O2 films according to the thickness and annealing temperature,” Applied Physics Letters, vol. 102, no. 24, Jun. 2013.
[23] Si Wouk Kim et al., “Large ferroelectric polarization of TiN/Hf0.5Zr0.5O2/TiN capacitors due to stress-induced crystallization at low thermal budget,” Applied Physics Letters, vol. 111, no. 24, pp. 242901–242901, Dec. 2017.
[24] Y. H. Yeh et al., “Degradation mechanism differences between TiN- and TaN-electrode HZO-based FeRAMs analyzed by current mechanism fitting,” Semiconductor science and technology, vol. 38, no. 8, pp. 085004–085004, Jun. 2023.
[25] M. Hoffmann et al., “Stabilizing the ferroelectric phase in doped hafnium oxide,” Journal of Applied Physics, vol. 118, no. 7, p. 072006, Aug. 2015.
[26] S. Li, D. Zhou, Z. Shi, M. R. Hoffmann, T. Mikolajick, and U. Schroeder, “Involvement of Unsaturated Switching in the Endurance Cycling of Si‐doped HfO2 Ferroelectric Thin Films,” Advanced Electronic Materials, vol. 6, no. 8, pp. 2000264–2000264, Jul. 2020.
[27] F. Zhang et al., “Evolution of the Interfacial Layer and Its Impact on Electric-Field-Cycling Behaviors in Ferroelectric Hf1–xZrxO2,” ACS applied materials & interfaces, vol. 14, no. 8, pp. 11028–11037, Feb. 2022.
[28] P. D. Lomenzo et al., “Ferroelectric Hf1-xZrxO2 memories: device reliability and depolarization fields,” Qucosa (Saxon State and University Library Dresden), Oct. 2019.
[29] Takashi Onaya et al., “Improvement in ferroelectricity of HfxZr1−xO2 thin films using ZrO2 seed layer,” Applied Physics Express, vol. 10, no. 8, pp. 081501–081501, Jul. 2017.
[30] H. Chen et al., “Significant improvement of ferroelectricity and reliability in Hf0.5Zr0.5O2 films by inserting an ultrathin Al2O3 buffer layer,” Applied surface science, vol. 542, pp. 148737–148737, Mar. 2021.
[31] A. A. Koroleva et al., “Retention Improvement of HZO-Based Ferroelectric Capacitors with TiO2 Insets,” ACS omega, vol. 7, no. 50, pp. 47084–47095, Dec. 2022.
[32] A. Chouprik et al., “Origin of the retention loss in ferroelectric Hf0.5Zr0.5O2-based memory devices,” Acta Materialia, vol. 204, p. 116515, Feb. 2021.
[33] Y. Qi, X. Xu, Igor Krylov, and M. Eizenberg, “Ferroelectricity of as-deposited HZO fabricated by plasma-enhanced atomic layer deposition at 300 °C by inserting TiO2 interlayers,” Applied Physics Letters, vol. 118, no. 3, Jan. 2021.
[34] H. Joh, T. Jung, and S. Jeon, “Stress Engineering as a Strategy to Achieve High Ferroelectricity in Thick Hafnia Using Interlayer,” IEEE Transactions on Electron Devices, vol. 68, no. 5, pp. 2538–2542, May 2021.
[35] V. Gaddam, D. Das, T. Jung, and S. Jeon, “Ferroelectricity Enhancement in Hf0.5Zr0.5O2 Based Tri-Layer Capacitors at Low-Temperature (350 °C) Annealing Process,” IEEE electron device letters, vol. 42, no. 6, pp. 812–815, Jun. 2021.
[36] M. Kim, Y. Goh, J. Hwang, and S. Jeon, “Enabling large ferroelectricity and excellent reliability for ultra-thin hafnia-based ferroelectrics with a W bottom electrode by inserting a metal-nitride diffusion barrier,” Applied physics letters, vol. 119, no. 26, Dec. 2021.
[37] Asim Senapati et al., “Low Polarization Loss of Long Endurance on Scavenged Ru-Based Electrode Ferroelectric Hf0.5Zr0.5O2 by Optimizing TiN x Interfacial Capping Layer and Its Fatigue Mechanism,” IEEE electron device letters, vol. 45, no. 4, pp. 673–676, Apr. 2024.
[38] “Kurt J. Lesker Company,” www.lesker.com. https://www.lesker.com/blog/challenges-for-non-ideal-atomic-layer-deposition-processes-systems.
[39] J. Gruss-Gifford, V. Mehta, Oscar, G. Rodriguez, M. Lippitt, and D. Canaperi, “Method for improving stability of plasma ignition in a multi-cathode magnetron PVD system,” Aug. 2020.
[40] X. Wang et al., “Enhanced Photoelectrochemical Behavior of H-TiO2 Nanorods Hydrogenated by Controlled and Local Rapid Thermal Annealing,” Nanoscale Research Letters, vol. 12, no. 1, May 2017.
[41] P. Jiang et al., “Wake‐Up Effect in HfO2 ‐Based Ferroelectric Films,” Advanced electronic materials, vol. 7, no. 1, Nov. 2020.
[42] S. Starschich, S. Menzel, and Ulrich Böttger, “Evidence for oxygen vacancies movement during wake-up in ferroelectric hafnium oxide,” Applied Physics Letter, vol. 108, no. 3, pp. 032903–032903, Jan. 2016.
[43] K. Florent et al., “Investigation of the endurance of FE-HfO2 devices by means of TDDB studies,” Mar. 2018.
[44] X. Li et al., “Experimental investigations on ferroelectric dielectric breakdown in sub-10 nm Hf0.5Zr0.5O2 film through comprehensive TDDB characterizations,” Japanese journal of applied physics, vol. 61, no. 10, pp. 101002–101002, Oct. 2022.
[45] D. Wang, Y. Zhang, Y. Guo, Z. Shang, F. Fu, and X. Lu, “Impact of annealing temperature on the ferroelectric properties of W/Hf0.5Zr0.5O2/W capacitor,” Chinese Physics B, vol. 32, no. 9, pp. 097701–097701, Aug. 2023.
[46] P. Cai et al., “Investigation of Coercive Field Shift During Cycling in HfZrOx Ferroelectric Capacitors,” I.E.E.E. transactions on electron devices, vol. 69, no. 5, pp. 2384–2390, May 2022.