Next Article in Journal
Special Issue: Advances in Dental Bio-Nanomaterials
Next Article in Special Issue
Microstructure and Antimicrobial Properties of Zr-Cu-Ti Thin-Film Metallic Glass Deposited Using High-Power Impulse Magnetron Sputtering
Previous Article in Journal
Enhancing Thermoelectric Properties of (Cu2Te)1−x-(BiCuTeO)x Composites by Optimizing Carrier Concentration
Previous Article in Special Issue
Atypical Properties of a Thin Silver Layer Deposited on a Composite Textile Substrate
 
 
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Temperature- and Frequency-Dependent Ferroelectric Characteristics of Metal-Ferroelectric-Metal Capacitors with Atomic-Layer-Deposited Undoped HfO2 Films

1
School of Electrical and Electronic Engineering, Hongik University, 94 Wausan-ro, Mapo-gu, Seoul 04066, Korea
2
Center for Device Thermography and Reliability (CDTR), University of Bristol, Bristol BS8 1TL, UK
*
Author to whom correspondence should be addressed.
Materials 2022, 15(6), 2097; https://doi.org/10.3390/ma15062097
Submission received: 10 February 2022 / Revised: 3 March 2022 / Accepted: 8 March 2022 / Published: 12 March 2022
(This article belongs to the Special Issue Atomic Layer Deposition: From Fundamentals to Applications)

Abstract

:
In this study, we evaluated the temperature- and frequency-dependent ferroelectric characteristics of TiN/undoped HfO2/TiN metal-ferroelectric-metal (MFM) capacitors in which an undoped HfO2 film was deposited through atomic layer deposition (ALD). Successful ferroelectric characteristics were achieved after postdeposition annealing at 650 °C, which exhibited a remanent polarization of 8 μC/cm2 and a coercive electric field of 1.6 MV/cm at 25 °C (room temperature). The ferroelectric property was maintained at 200 °C and decreased as the temperature increased. The ferroelectric property was completely lost above 320 °C and fully recovered after cooling. The frequency dependency was evaluated by bias-dependent capacitance–voltage and s-parameter measurements, which indicated that the ferroelectric property was maintained up to several hundred MHz. This study reveals the ultimate limitations of the application of an undoped HfO2 MFM capacitor.

1. Introduction

Ferroelectric thin films have promising potential for various applications, including nonvolatile memories, energy-related devices, and negative capacitance field-effect transistors [1,2,3,4,5]. Although various ferroelectric materials, such as P(VDF-TrFE), Pb(Zr,Ti)O3 (PZT), and BaTiO3, have previously been intensively studied [2,5,6,7,8,9], HfO2 thin films have received significant attention recently owing to their excellent properties, such as high dielectric constant (20–25) and wide energy bandgap (~5.68 eV). Moreover, HfO2 thin films can be deposited using a complementary metal–oxide–semiconductor (CMOS) compatible atomic layer deposition (ALD) process [10,11,12,13,14]. Because ALD is based on self-limiting reactions leading to layer-by-layer growth, it exhibits a large-area uniformity and significant conformability, offering atomic-scale controllability [15]. The ferroelectric properties of HfO2 thin films have been reported with doping processes using various dopant elements, such as ZrO, Gd, Si, Al, Y, Sr, and La [4,5,16,17,18,19]. It has also been reported that the ferroelectric property can be achieved in undoped HfO2 films without the doping process [20,21,22,23]. Considering the deposition process, ALD doped HfO2 films require a higher deposition temperature than undoped HfO2 films to achieve the ferroelectric property [12,24]. Therefore, undoped HfO2 films have advantages of a lower temperature process and easy implementation without a delicate doping process [12,24,25].
Because of the mechanical dipole moment of ferroelectric materials, it is useful to determine the maximum temperature and frequency ranges to maintain the ferroelectric property of the MFM capacitor. Although various studies have been reported for different ferroelectric materials in a limited range of temperature and frequency [3,25,26,27,28,29,30,31,32], no study has been conducted with a MFM capacitor based on undoped HfO2. In this study, the ferroelectric property of an ALD-deposited undoped HfO2 thin film was successfully achieved via a postdeposition annealing process. Temperature-dependent polarization and frequency-dependent capacitance characteristics were measured up to >300 °C and GHz range, respectively, to determine the fundamental limitations of the ferroelectricity of TiN/undoped HfO2/TiN MFM capacitors.

2. Device Structure and Fabrication

TiN/undoped HfO2/TiN MFM capacitors were fabricated on a quartz substrate to eliminate the dielectric loss during high-frequency measurements. TiN electrodes play an important role in undoped HfO2 films. Unlike doped HfO2 films, the N impurity provided by metal nitrides is responsible for achieving the ferroelectric properties of undoped HfO2 films [33]. Figure 1a,b shows the top and cross-sectional schematics of the MFM capacitor, respectively, where a ground–signal–ground (GSG) pattern was employed for the s-parameter measurement.
The fabrication process of the device was as follows. After cleaning the substrates, a TiN bottom electrode with a thickness of 100 nm was deposited via RF sputtering. The films were deposited at a process pressure of 1 mTorr and an RF power of 600 W in Ar/N2 (10/25 sccm) ambient at two different temperatures, namely 25 °C (room temperature) and 250 °C. The sheet resistance of the TiN films deposited at room temperature and 250 °C were 9.89 and 9.33 Ω/sq, respectively. After patterning the bottom electrode, the TiN layer was etched using a fluorine-based plasma etching process. A 10 nm thick undoped HfO2 film was deposited via ALD at 220 °C with a TEMA-Hf precursor and O3 at a concentration of 100 gm−3. The deposition cycle consisted of a TEMA-Hf pulse time of 1 s, purge time of 20 s, O3 pulse time of 0.5 s, and purge time of 15 s. The growth per cycle was 1 Å/cycle, and the refractive index (RI) was 2.01. A TiN top electrode with a thickness of 100 nm was deposited on the undoped HfO2 film using RF sputtering. The top electrode was patterned and etched to complete the device structure. The diameter of the active region of the MFM capacitor was 100 μm. The fabricated MFM capacitors were annealed via rapid thermal annealing (RTA) at 650 °C for 1 min in a N2 atmosphere to achieve ferroelectric property. It was observed in our previous experiments that the optimum RTA temperature was 650 °C; the ferroelectric property was slightly weaker with RTA at 600 °C and noticeably reduced with RTA at 700 °C.

3. Results and Discussion

3.1. Ferroelectric Characteristics of TiN/Undoped HfO2/TiN MFM Capacitor

The polarization–electric field (P–E) characteristics of fabricated TiN/undoped HfO2/TiN MFM capacitors measured at 100 kHz before and after RTA are shown in Figure 2a,b, respectively. Although no hysteresis in the P–E characteristics was observed before RTA, successful ferroelectric property was achieved after RTA. No significant difference was observed in the P–E characteristics as a function of the deposition temperature for the TiN electrodes. When both the top and bottom electrodes were deposited at room temperature, the remanent polarization (Pr) was 6.8 μC/cm2, and the coercive field (Ec) was 1.46 MV/cm. When the electrodes were deposited at 250 °C, the values slightly decreased: Pr = 6.15 μC/cm2 and Ec = 1.2 MV/cm.
The permittivity–voltage characteristics of fabricated MFM capacitors were derived from the capacitance–voltage (C–V) characteristics measured at different frequencies. Figure 3 shows the frequency-dependent permittivity versus voltage characteristics for different samples; Figure 3d compares the maximum permittivity values as a function of the measurement frequency. The permittivity decreased as the frequency increased for all samples. The permittivity is determined by free dipoles oscillating in the presence of an alternating electric field. As the frequency increases, the dipoles begin to lag behind the electric field change, which decreases the permittivity [32]. As shown in Figure 3, the MFM capacitor with only the top electrode deposited at 250 °C exhibited relatively higher permittivity over the entire range of frequencies evaluated in this study. We speculate that the difference in permittivity was associated with unbalanced strains caused by the bottom and top TiN electrodes. Figure 4a,b shows the grazing-angle incident X-ray diffraction (GIXRD) patterns measured for two samples prepared with different TiN electrode deposition temperatures of room temperature and 250 °C, respectively. It was observed that a TiN (111) peak was dominant for the sample deposited at room temperature, whereas a TiN (200) peak was dominant for the sample deposited at 250 °C. Because of the different grain sizes and strains between TiN (111) and TiN (200) [34], the HfO2 film experienced unbalanced strains when the top TiN electrode was deposited at 250 °C, whereas the bottom TiN electrode was deposited at room temperature, which was responsible for the higher permittivity. It was reported that the strain increased the permittivity of the dielectric thin films [35,36]. It should be noted that new peaks appeared after the RTA process for both samples, which corresponded to the noncentrosymmetric o-phases that are responsible for the ferroelectric property [37].
The MFM capacitor with the bottom electrode deposited at room temperature and the top electrode deposited at 250 °C was chosen for the following study.

3.2. Temperature-Dependent Ferroelectric Property of TiN/Undoped HfO2/TiN MFM Capacitor

The temperature-dependent P–E characteristics of the MFM capacitor were evaluated in the temperature range from room temperature to 320 °C. As shown in Figure 4a, the ferroelectric hysteresis was maintained at 150 °C with a slight decrease in Ec and a slight increase in the saturation polarization (Ps). The increased Ps is owing to the relaxation of oxygen vacancies, which can significantly contribute to their recombination, improving the ferroelectricity of the HfO2 film [28]. As shown in Figure 5a–c, significant deformation in the polarization characteristics occurred at 200 °C and significant degradation was observed at higher temperatures. The decreased Pr value at 200 °C is attributed to weaker spontaneous polarization caused by partial transition from the ferroelectric phase to the antiferroelectric phase and/or more defect formation at higher temperatures [28]. The hysteresis disappeared at temperatures higher than ~310 °C. Notably, this is the highest temperature at which an HfO2 MFM capacitor exhibits ferroelectric properties, although special composite materials, such as BaTiO3:Sm2O3, can achieve even higher operation temperature [3,28,29,30,31,38,39].

3.3. Frequency-Dependent Ferroelectric Characteristics of TiN/Undoped HfO2/TiN MFM Capacitor

To determine the frequency-dependent ferroelectric property of the fabricated MFM capacitor, C–V and s-parameter measurements were employed. The butterfly-shaped capacitance characteristics were measured at frequencies ranging from 10 kHz to 1 MHz, as shown in Figure 6a. The maximum capacitance value (CMAX) was obtained at a bias voltage of −0.5 V, whereas the minimum capacitance value (CMIN) was obtained at −3 V, and the capacitance tunability was defined by CMAX − CMIN [25]. Because conventional C–V measurements cannot be used at very high frequencies, the equivalent circuit of the MFM capacitor was extracted by s-parameter measurements; for high frequencies, it is convenient to describe a given network in terms of waves rather than voltages or currents [40]. The s-parameter measurements for the GSG pattern were performed in a frequency ranging from 100 MHz to 10 GHz using a network analyzer with the bias voltage conditions obtained for CMAX and CMIN at C–V measurements. The GSG-type MFM structure shown in Figure 1a can be modeled as capacitors connected in series, and the intrinsic ferroelectric capacitance can be extracted by converting the s-parameter into ABCD parameters [25,27]. Zo in Equation (1) was 50 Ω in the s-parameter measurement.
Capacitance = 1 j ω × imag ( B ) ,   where   B = Z o ( 1 + S 11 ) ( 1 + S 22 ) S 12 S 21 2 S 21
The CMAX and CMIN values extracted from the C–V and s-parameter measurements are plotted as functions of frequency in Figure 5b. Both the CMAX and CMIN values decreased as the frequency increased, reducing the capacitance tunability. Nevertheless, a capacitance tunability of up to several hundred MHz was achieved in this work. It is inferred that fabricated TiN/undoped HfO2/TiN MFM capacitor can be utilized as a variable capacitor up to hundreds of MHz, which can be used to explore a new field of undoped HfO2 MFM capacitors in microwave applications [41]. It is speculated that the rapid increase in capacitance at frequencies near 10 GHz is attributed to the series LC resonance.

4. Conclusions

In this study, the ferroelectric properties of TiN/undoped HfO2/TiN MFM capacitors were evaluated over a wide range of temperatures and frequencies. A 10 nm thick undoped HfO2 film was deposited via ALD, which was annealed at 650 °C after forming the electrodes. The fabricated MFM capacitor exhibited stable ferroelectric properties up to 150 °C with negligible degradation. Although the ferroelectric property weakened at temperatures higher than 200 °C, the hysteresis characteristics were maintained up to ~300 °C, which is the highest temperature reported for ferroelectric films. The frequency limitation was examined using C–V and s-parameter measurements, from which the capacitance tunability was achieved up to several hundred MHz. This study reveals the ultimate application conditions for a ferroelectric undoped HfO2 MFM capacitor.

Author Contributions

Device fabrication, data curation, visualization, and writing—original draft preparation, C.-H.J.; formal analysis and validation, H.-S.K.; review and editing, H.K.; resources, supervision, project administration, conceptualization, writing—review and editing, and funding acquisition, H.-Y.C.; All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Civil–Military Technology Cooperation Program (17-CM-MA-03), the Basic Science Research Program (2015R1A6A1A03031833, 2022R1A2C1003723).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Li, S.; Zhou, D.; Shi, Z.; Hoffmann, M.; Mikolajick, T.; Schroeder, U. Involvement of unsaturated switching in the endurance cycling of Si-doped HfO2 ferroelectric thin films. Adv. Electron. Mater. 2020, 6, 2000264. [Google Scholar] [CrossRef]
  2. Kim, H.J.; An, Y.; Jung, Y.C.; Mohan, J.; Yoo, J.G.; Kim, Y.I.; Hernandez-Arriaga, H.; Kim, H.S.; Kim, J.; Kim, S.J. Low-thermal-budget fluorite-structure ferroelectrics for future electronic device applications. Phys. Status Solidi 2021, 15, 2100028. [Google Scholar]
  3. Bhargavi, G.N.; Khare, A.; Badapanda, T.; Anwar, M.S.; Brahme, N. Analysis of temperature and frequency dependent dielectric properties, dynamic hysteresis loop and thermal energy conversion in BaZr0.05Ti0.95O3 ceramic. J. Mater. Sci. Mater. Electron. 2018, 29, 11439–11448. [Google Scholar] [CrossRef]
  4. Fan, Z.; Chen, J.; Wang, J. Ferroelectric HfO2-based materials for next-generation ferroelectric memories. J. Adv. Dielectr. 2016, 6, 1630003. [Google Scholar] [CrossRef] [Green Version]
  5. Kim, S.J.; Mohan, M.J.; Summerfelt, S.R.; Kim, J. Ferroelectric Hf0.5Zr0.5O2 thin films: A review of recent advances. JOM 2019, 71, 246–255. [Google Scholar] [CrossRef]
  6. Jo, J.; Choi, W.Y.; Park, J.D.; Shim, J.W.; Yu, H.Y.; Shin, C. Negative capacitance in organic/ferroelectric capacitor to implement steep switching MOS devices. Nano Lett. 2015, 15, 4553. [Google Scholar] [CrossRef] [PubMed]
  7. Khan, A.I.; Chatterjee, K.; Wang, B.; Drapcho, S.; You, L.; Serrao, C.; Bakaul, S.R.; Ramesh, R.; Salahuddin, S. Negative capacitance in a ferroelectric capacitor. Nat. Mater. 2015, 14, 182–186. [Google Scholar] [CrossRef] [PubMed]
  8. Gene, H. Haertling. Ferroelectric ceramics: History and technology. J. Am. Ceram. Soc. 1999, 82, 797. [Google Scholar]
  9. Park, M.H.; Lee, Y.H.; Kim, H.J.; Kim, Y.J.; Moon, T.; Kim, K.D.; Müller, J.; Kersch, A.; Schroeder, U.; Mikolajick, T.; et al. Ferroelectricity and antiferroelectricity of doped thin HfO2-based films. Adv. Mater. 2015, 27, 1811. [Google Scholar] [CrossRef] [PubMed]
  10. Cheynet, M.C.; Pokrant, S.; Tichelaar, F.D.; Rouvière, J.-L. Crystal structure and band gap determination of HfO2 thin films. J. Appl. Phys. 2007, 101, 054101. [Google Scholar] [CrossRef] [Green Version]
  11. Bae, K.; Do, S.; Lee, J.; Lee, Y. Electrical and material characteristics of HfO2 film in HfO2/Hf/Si MOS structure. J. Korean Inst. Electr. Electron. Mater. Eng. 2009, 22, 101–106. [Google Scholar]
  12. Kim, K.D.; Park, M.H.; Kim, H.J.; Kim, Y.J.; Moon, T.; Lee, Y.H.; Hyun, S.D.; Gwon, T.; Hwang, C.S. Ferroelectricity in undoped-HfO2 thin films induced by deposition temperature control during atomic layer deposition. J. Mater. Chem. C 2016, 4, 6864–6872. [Google Scholar] [CrossRef]
  13. Kwon, Y.; Lee, M.; Oh, J. Deposition and electrical properties of Al2O3 and HfO2 films deposited by a new technique of proximity-scan ALD (PS-ALD). Korean J. Mater. Res. 2008, 18, 148–152. [Google Scholar] [CrossRef] [Green Version]
  14. Gaskins, J.T.; Hopkins, P.E.; Merrill, D.R.; Bauers, S.R.; Hadland, E.; Johnson, D.C.; Koh, D.; Yum, J.H.; Banerjee, S.; Nordell, B.J.; et al. Review—Investigation and review of the thermal, mechanical, electrical, optical, and structural properties of atomic layer deposited high-k dielectrics: Beryllium oxide, aluminum oxide, hafnium oxide, and aluminum nitride. ECS J. Solid State Sci. Technol. 2017, 6, N189. [Google Scholar] [CrossRef] [Green Version]
  15. Jang, Y.; Lee, S.M.; Jung, D.H.; Yum, J.H.; Larsen, E.S.; Bielawski, C.W.; Oh, J. Improved dielectric properties of BeO thin films grown by plasma enhanced atomic layer deposition. Solid-State Electron. 2020, 163, 107661. [Google Scholar] [CrossRef]
  16. Müller, J.; Polakowski, P.; Riedel, S.; Mueller, S.; Yurchuk, E.; Mikolajick, T. Ferroelectric hafnium oxide A game changer to FRAM? In Proceedings of the 14th Annual Non-Volatile Memory Technology Symposium (NVMTS), Jeju, Korea, 27–29 October 2014. [Google Scholar]
  17. Yin, Y.; Shen, Y.; Wang, H.; Chen, X.; Shao, L.; Hua, W.; Wang, J.; Cui, Y. In situ growth and characterization of TiN/HfxZr1−xO2/TiN ferroelectric capacitors. Acta Phys. Chim. Sin. 2022, 38, 2006016. [Google Scholar]
  18. Shin, W.; Bae, J.H.; Kim, S.; Lee, K.; Kwon, D.; Park, B.G.; Kwon, D.; Lee, J.H. Effects of high-pressure annealing on the low-frequency noise characteristics in ferroelectric FET. IEEE Electron. Device Lett. 2022, 43, 13–16. [Google Scholar] [CrossRef]
  19. Bae, J.H.; Kwon, D.; Jeon, N.; Cheema, S.; Tan, A.J.; Hu, C.; Salahuddin, S. Highly Scaled, High Endurance, Ω-Gate, Nanowire Ferroelectric FET Memory Transistors. IEEE Electron. Device Lett. 2020, 41, 1637–1640. [Google Scholar] [CrossRef]
  20. Awadhiya, B.; Kondekar, P.N.; Meshram, D.M. Investigating Undoped HfO2 as Ferroelectric Oxide in Leaky and Non-Leaky FE–DE Heterostructure. Trans. Electr. Electron. Mater. 2019, 20, 467–472. [Google Scholar] [CrossRef]
  21. Polakowski, P.; Muller, J. Ferroelectricity in undoped hafnium oxide. Appl. Phys. Lett. 2015, 106, 232905. [Google Scholar] [CrossRef]
  22. Pa, A.; Narasimhan, V.K.; Weeks, S.; Littau, K.; Pramanik, D.; Chiang, T. Enhancing ferroelectricity in dopant-free hafnium oxide. Appl. Phys. Lett. 2017, 110, 022903. [Google Scholar]
  23. Kim, G.M.; Ohmi, S.-i. Ferroelectric properties of undoped HfO2 directly deposited on Si substrates by RF magnetron sputtering. Jpn. J. Appl. Phys. 2018, 57, 11UF09. [Google Scholar] [CrossRef]
  24. Kim, K.D.; Lee, Y.H.; Gwon, T.h.; Kim, Y.J.; Kim, H.J.; Moon, T.h.; Hyun, S.D.; Park, H.W.; Park, M.H.; Hwang, C.S. Scale-up and optimization of HfO2-ZrO2 solid solution thin films for the electrostatic supercapacitors. Nano Energy 2017, 39, 390–399. [Google Scholar] [CrossRef]
  25. Han, S.; Lee, C.; Lee, J.; Cha, H. Study on the ferroelectric properties of ALD-HfO2 in microwave band for tunable RF apparatus. j. inst. Korean Electr. Electron. Eng. 2018, 22, 780–785. [Google Scholar]
  26. Nishimura, T.; Xu, L.; Shibayama, S.; Yajima, T.; Migita, S.; Toriumi, A. Ferroelectricity of nondoped thin HfO2 films in TiN/HfO2/TiN stacks. Jpn. J. Appl. Phys. 2016, 55, 08PB01. [Google Scholar] [CrossRef]
  27. Han, S.; Lee, C.; Shin, H.; Lee, J.; Cha, H. Investigation of frequency-dependent permittivity tenability of P(VDF−TrFE) metal-ferroelectric-metal capacitor. Results Phys. 2019, 12, 469–470. [Google Scholar] [CrossRef]
  28. Chen, H.; Tang, L.; Liu, L.; Chen, Y.; Luo, H.; Yuan, X.; Zhang, D. Temperature dependent polarization-switching behavior in Hf0.5Zr0.5O2 ferroelectric film. Materialia 2020, 14, 100919. [Google Scholar] [CrossRef]
  29. Zhang, Y.; Chen, Z.; Cao, W.; Zhang, Z. Temperature and frequency dependence of the coercive field of 0.71PbMb1/3Nb2/3O3–0.29PbTiO3 relaxor-based ferroelectric single crystal. Appl. Phys. Lett. 2017, 111, 172902. [Google Scholar] [CrossRef]
  30. Qiao, H.; He, C.; Wang, Z.; Pang, D.; Li, X.; Liu, Y.; Long, X. Influence of Mn dopants on the electrical properties of Pb(In0.5Nb0.5)O3–PbTiO3 ferroelectric single crystals. RSC Adv. 2017, 7, 32607. [Google Scholar] [CrossRef] [Green Version]
  31. Chen, X.; Qiao, X.; Zhang, L.; Zhang, J.; Zhang, Q.; He, J.; Mu, J.; Hou, X.; Chou, X.; Geng, W. Temperature dependence of ferroelectricity and domain switching behavior in Pb(Zr0·3Ti0.7)O3 ferroelectric thin films. Ceram. Int. 2019, 45, 18030. [Google Scholar] [CrossRef]
  32. Saif, A.A.; Saif, Z.A.Z.; Jamal, Z.S.; Poopalan, P. Frequency dependent electrical properties of ferroelectric Ba0.8Sr0.2TiO3 Thin Film. Mater. Sci. 2011, 17, 2. [Google Scholar] [CrossRef]
  33. Lee, D.H.; Yang, K.; Park, J.Y.; Park, M.H. A brief review on the effect of impurities on the atomic layer deposited fluorite-structure ferroelectrics. J. Korean Inst. Surf. Eng. 2020, 53, 169–181. [Google Scholar]
  34. Valipour, M.; Aman, M.; Singh, M.R. Rawat. Increasing of hardness of titanium using energetic nitrogen ions from sahand as a filippov type plasma focus facility. J. Fusion Energ. 2012, 31, 65–72. [Google Scholar] [CrossRef]
  35. Suzuki, K.; Imasaki, K.; Ito, Y.; Miura, H. Strain dependence of dielectric properties and reliability of high-k thin films. In Proceedings of the International Conference on Simulation of Semiconductor Processes and Devices, San Diego, CA, USA, 9–11 September 2009. [Google Scholar]
  36. Antons, A.; Neaton, J.B.; Rabe, K.M.; Vanderbilt, D. Tunability of the dielectric response of epitaxially strained SrTiO3 from first principles. Phys. Rev. B 2005, 71, 024102. [Google Scholar] [CrossRef] [Green Version]
  37. Wang, J.; Wang, D.; Li, Q.; Zhang, A.; Gao, D.; Guo, M.; Feng, J.; Fan, Z.; Chen, D.; Qin, M.; et al. Excellent ferroelectric properties of Hf0.5Zr0.5O2 thin films induced by Al2O3 dielectric layer. IEEE Electron. Device Lett. 2019, 40, 1937–1940. [Google Scholar] [CrossRef]
  38. Liu, Y.; Aziguli, H.; Zhang, B.; Xu, W.; Lu, W.; Bernholc, J.; Wang, Q. Ferroelectric polymers exhibiting behaviour reminiscent of a morphotropic phase boundary. Nature 2018, 562, 96–100. [Google Scholar] [CrossRef] [PubMed]
  39. Harrington, S.A.; Zhai, J.; Denev, S.; Gopalan, V.; Wang, H.; Bi, Z.; Redfern, S.A.T.; Baek, S.H.; Bark, C.W.; Eom, C.B.; et al. Thick lead-free ferroelectric films with high Curie temperatures through nanocomposite-induced strain. Nat. Nanotechnol. 2011, 6, 491–495. [Google Scholar] [CrossRef] [PubMed]
  40. Pozar, D.M. Microwave Engineering; John Wiley & Sons: Hoboken, NJ, USA, 2021. [Google Scholar]
  41. Ren, Y.; Huang, Z.; Guo, L.-F. A electrically tunable patch antenna with P(VDF-TrFE) thin film. In Material Engineering and Mechanical Engineering (MEME2015); World Scientific: Hangzhou, China, 2015; pp. 239–245. [Google Scholar]
Figure 1. (a) Top view and (b) cross-sectional schematic along a–a’ of TiN/undoped HfO2/TiN MFM capacitor fabricated on a quartz substrate.
Figure 1. (a) Top view and (b) cross-sectional schematic along a–a’ of TiN/undoped HfO2/TiN MFM capacitor fabricated on a quartz substrate.
Materials 15 02097 g001
Figure 2. Polarization–electric field (P–E) characteristics of TiN/undoped HfO2/TiN MFM capacitors before (a) and after (b) RTA with different TiN deposition temperature conditions.
Figure 2. Polarization–electric field (P–E) characteristics of TiN/undoped HfO2/TiN MFM capacitors before (a) and after (b) RTA with different TiN deposition temperature conditions.
Materials 15 02097 g002
Figure 3. Frequency–dependent permittivity–voltage characteristics of MFM capacitors fabricated with different deposition temperatures for TiN electrodes. (a) Top and bottom electrodes deposited at room temperature, (b) bottom electrode at room temperature and top electrode at 250 °C, and (c) top and bottom electrodes at 250 °C. (d) Comparison of the maximum permittivity values for devices (ac) as a function of measurement frequency.
Figure 3. Frequency–dependent permittivity–voltage characteristics of MFM capacitors fabricated with different deposition temperatures for TiN electrodes. (a) Top and bottom electrodes deposited at room temperature, (b) bottom electrode at room temperature and top electrode at 250 °C, and (c) top and bottom electrodes at 250 °C. (d) Comparison of the maximum permittivity values for devices (ac) as a function of measurement frequency.
Materials 15 02097 g003
Figure 4. GIXRD patterns measured before and after the RTA process for TiN/undoped HfO2/TiN samples with both top and bottom TiN electrodes deposited at (a) room temperature and (b) 250 °C.
Figure 4. GIXRD patterns measured before and after the RTA process for TiN/undoped HfO2/TiN samples with both top and bottom TiN electrodes deposited at (a) room temperature and (b) 250 °C.
Materials 15 02097 g004
Figure 5. P–E characteristics of fabricated TiN/undoped HfO2/TiN MFM capacitor as a function of temperature: (a) from room temperature to 200 °C, (b) from 200 °C to 280 °C, and (c) from 280 °C to 320 °C. (d) Pr and Ec as functions of temperature.
Figure 5. P–E characteristics of fabricated TiN/undoped HfO2/TiN MFM capacitor as a function of temperature: (a) from room temperature to 200 °C, (b) from 200 °C to 280 °C, and (c) from 280 °C to 320 °C. (d) Pr and Ec as functions of temperature.
Materials 15 02097 g005
Figure 6. (a) Capacitance characteristics measured from 10 kHz to 1 MHz and (b) capacitance tunability characteristics versus frequency.
Figure 6. (a) Capacitance characteristics measured from 10 kHz to 1 MHz and (b) capacitance tunability characteristics versus frequency.
Materials 15 02097 g006
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Jang, C.-H.; Kim, H.-S.; Kim, H.; Cha, H.-Y. Temperature- and Frequency-Dependent Ferroelectric Characteristics of Metal-Ferroelectric-Metal Capacitors with Atomic-Layer-Deposited Undoped HfO2 Films. Materials 2022, 15, 2097. https://doi.org/10.3390/ma15062097

AMA Style

Jang C-H, Kim H-S, Kim H, Cha H-Y. Temperature- and Frequency-Dependent Ferroelectric Characteristics of Metal-Ferroelectric-Metal Capacitors with Atomic-Layer-Deposited Undoped HfO2 Films. Materials. 2022; 15(6):2097. https://doi.org/10.3390/ma15062097

Chicago/Turabian Style

Jang, Chan-Hee, Hyun-Seop Kim, Hyungtak Kim, and Ho-Young Cha. 2022. "Temperature- and Frequency-Dependent Ferroelectric Characteristics of Metal-Ferroelectric-Metal Capacitors with Atomic-Layer-Deposited Undoped HfO2 Films" Materials 15, no. 6: 2097. https://doi.org/10.3390/ma15062097

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop