1
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Guido R, Lu H, Lomenzo PD, Mikolajick T, Gruverman A, Schroeder U. Kinetics of N- to M-Polar Switching in Ferroelectric Al 1-xSc xN Capacitors. Adv Sci (Weinh) 2024; 11:e2308797. [PMID: 38355302 DOI: 10.1002/advs.202308797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Indexed: 02/16/2024]
Abstract
Ferroelectric wurtzite-type aluminum scandium nitride (Al1-xScxN) presents unique properties that can enhance the performance of non-volatile memory technologies. The realization of the full potential of Al1-xScxN requires a comprehensive understanding of the mechanism of polarization reversal and domain structure dynamics involved in the ferroelectric switching process. In this work, transient current integration measurements performed by a pulse switching method are combined with domain imaging by piezoresponse force microscopy (PFM) to investigate the kinetics of domain nucleation and wall motion during polarization reversal in Al0.85Sc0.15N capacitors. In the studied electric field range (from 4.4 to 5.6 MV cm-1), ferroelectric switching proceeds via domain nucleation and wall movement. The currently available phenomenological models are shown to not fully capture all the details of the complex dynamics of polarization reversal in Al0.85Sc0.15N. PFM reveals a non-linear increase of both domain nucleation rate and lateral wall velocity during the switching process, as well as the dependency of the domain pattern on the polarization reversal direction. A continuously faster N- to M-polar switching upon cycling is reported and ascribed to an increasing number of M-polar nucleation sites and density of domain walls.
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Affiliation(s)
- Roberto Guido
- NaMLab gGmbH, Noethnizer Strasse 64a, 01187, Dresden, Germany
- Chair of Nanoelectronics, Technische Universität Dresden, Noethnizer Strasse 64, 01187, Dresden, Germany
| | - Haidong Lu
- Department of Physics and Astronomy, University of Nebraska, Lincoln, NE, 68588, USA
| | | | - Thomas Mikolajick
- NaMLab gGmbH, Noethnizer Strasse 64a, 01187, Dresden, Germany
- Chair of Nanoelectronics, Technische Universität Dresden, Noethnizer Strasse 64, 01187, Dresden, Germany
| | - Alexei Gruverman
- Department of Physics and Astronomy, University of Nebraska, Lincoln, NE, 68588, USA
| | - Uwe Schroeder
- NaMLab gGmbH, Noethnizer Strasse 64a, 01187, Dresden, Germany
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2
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Cohen A, Li J, Cohen H, Kaplan-Ashiri I, Khodorov S, Wachtel EJ, Lubomirsky I, Frenkel AI, Ehre D. Local Environment of Sc and Y Dopant Ions in Aluminum Nitride Thin Films. ACS Appl Electron Mater 2024; 6:853-861. [PMID: 38435801 PMCID: PMC10902843 DOI: 10.1021/acsaelm.3c01390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 01/04/2024] [Accepted: 01/04/2024] [Indexed: 03/05/2024]
Abstract
The local environments of Sc and Y in predominantly ⟨002⟩ textured, Al1-xDoxN (Do = Sc, x = 0.25, 0.30 or Y, x = 0.25) sputtered thin films with wurtzite symmetry were investigated using X-ray absorption (XAS) and photoelectron (XPS) spectroscopies. We present evidence from the X-ray absorption fine structure (XAFS) spectra that, when x = 0.25, both Sc3+ and Y3+ ions are able to substitute for Al3+, thereby acquiring four tetrahedrally coordinated nitrogen ligands, i.e., coordination number (CN) of 4. On this basis, the crystal radius of the dopant species in the wurtzite lattice, not available heretofore, could be calculated. By modeling the scandium local environment, extended XAFS (EXAFS) analysis suggests that when x increases from 0.25 to 0.30, CN for a fraction of the Sc ions increases from 4 to 6, signaling octahedral coordination. This change occurs at a dopant concentration significantly lower than the reported maximum concentration of Sc (42 mol % Sc) in wurtzite (Al, Sc)N. XPS spectra provide support for our observation that the local environment of Sc in (Al, Sc)N may include more than one type of coordination.
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Affiliation(s)
- Asaf Cohen
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Junying Li
- Department
of Materials Science and Chemical Engineering, Stony Brook University, Stony
Brook, New York 11794, United States
| | - Hagai Cohen
- Department
of Chemical Research Support, Weizmann Institute
of Science, Rehovot 7610001, Israel
| | - Ifat Kaplan-Ashiri
- Department
of Chemical Research Support, Weizmann Institute
of Science, Rehovot 7610001, Israel
| | - Sergey Khodorov
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Ellen J. Wachtel
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Igor Lubomirsky
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Anatoly I. Frenkel
- Department
of Materials Science and Chemical Engineering, Stony Brook University, Stony
Brook, New York 11794, United States
| | - David Ehre
- Department
of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
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3
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Dou W, Zhou C, Qin R, Yang Y, Guo H, Mu Z, Yu W. Super-High-Frequency Bulk Acoustic Resonators Based on Aluminum Scandium Nitride for Wideband Applications. Nanomaterials (Basel) 2023; 13:2737. [PMID: 37887888 PMCID: PMC10608804 DOI: 10.3390/nano13202737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 10/02/2023] [Accepted: 10/07/2023] [Indexed: 10/28/2023]
Abstract
Despite the dominance of bulk acoustic wave (BAW) filters in the high-frequency market due to their superior performance and compatible integration process, the advent of the 5G era brings up new challenges to meet the ever-growing demands on high-frequency and large bandwidth. Al1-xScxN piezoelectric films with high Sc concentration are particularly desirable to achieve an increased electromechanical coupling (Kt2) for BAW resonators and also a larger bandwidth for filters. In this paper, we designed and fabricated the Al1-xScxN-based BAW resonators with Sc concentrations as high as 30%. The symmetry of the resonance region, border frame structure and thickness ratio of the piezoelectric stack are thoroughly examined for lateral modes suppression and resonant performance optimization. Benefiting from the 30% Sc doping, the fabricated BAW resonators demonstrate a large effective electromechanical coupling (Keff2) of 17.8% at 4.75 GHz parallel resonant frequency. Moreover, the temperature coefficient of frequency (TCF) of the device is obtained as -22.9 ppm/°C, indicating reasonable temperature stability. Our results show that BAW resonators based on highly doped Al1-xScxN piezoelectric film have great potential for high-frequency and large bandwidth applications.
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Affiliation(s)
- Wentong Dou
- School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Congquan Zhou
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ruidong Qin
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yumeng Yang
- Shanghai Engineering Research Center of Energy Efficient and Custom AI IC, School of Information Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Huihui Guo
- School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China
| | - Zhiqiang Mu
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
| | - Wenjie Yu
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
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4
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Guido R, Mikolajick T, Schroeder U, Lomenzo PD. Role of Defects in the Breakdown Phenomenon of Al 1-xSc xN: From Ferroelectric to Filamentary Resistive Switching. Nano Lett 2023; 23:7213-7220. [PMID: 37523481 DOI: 10.1021/acs.nanolett.3c02351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/02/2023]
Abstract
Aluminum scandium nitride (Al1-xScxN), with its large remanent polarization, is an attractive material for high-density ferroelectric random-access memories. However, the cycling endurance of Al1-xScxN ferroelectric capacitors is far below what can be achieved in other ferroelectric materials. Understanding the nature and dynamics of the breakdown mechanism is of the utmost importance for improving memory reliability. The breakdown phenomenon in ferroelectric Al1-xScxN is proposed to be an impulse thermal filamentary-driven process along preferential defective pathways. For the first time, stable and robust bipolar filamentary resistive switching in ferroelectric Al1-xScxN is reported. A hot atom damage defect generation model illustrates how filament formation and ferroelectric switching are connected. The model reveals the tendency of the ferroelectric wurtzite-type Al1-xScxN system to reach internal symmetry with bipolar electric field cycling. Defects generated from bipolar electric field cycling influence both the energy barrier between the polarization states and that required for the filament formation.
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Affiliation(s)
- Roberto Guido
- Namlab gGmbH, Nöthnitzer Strasse 64a, 01187 Dresden, Germany
| | - Thomas Mikolajick
- Namlab gGmbH, Nöthnitzer Strasse 64a, 01187 Dresden, Germany
- Chair of Nanoelectronics, TU Dresden, 01187 Dresden, Germany
| | - Uwe Schroeder
- Namlab gGmbH, Nöthnitzer Strasse 64a, 01187 Dresden, Germany
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Jiang W, Zhu L, Chen L, Yang Y, Yu X, Li X, Mu Z, Yu W. In Situ Synchrotron XRD Characterization of Piezoelectric Al 1-xSc xN Thin Films for MEMS Applications. Materials (Basel) 2023; 16:1781. [PMID: 36902897 PMCID: PMC10004546 DOI: 10.3390/ma16051781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 02/18/2023] [Accepted: 02/20/2023] [Indexed: 06/18/2023]
Abstract
Aluminum scandium nitride (Al1-xScxN) film has drawn considerable attention owing to its enhanced piezoelectric response for micro-electromechanical system (MEMS) applications. Understanding the fundamentals of piezoelectricity would require a precise characterization of the piezoelectric coefficient, which is also crucial for MEMS device design. In this study, we proposed an in situ method based on a synchrotron X-ray diffraction (XRD) system to characterize the longitudinal piezoelectric constant d33 of Al1-xScxN film. The measurement results quantitatively demonstrated the piezoelectric effect of Al1-xScxN films by lattice spacing variation upon applied external voltage. The as-extracted d33 had a reasonable accuracy compared with the conventional high over-tone bulk acoustic resonators (HBAR) devices and Berlincourt methods. It was also found that the substrate clamping effect, leading to underestimation of d33 from in situ synchrotron XRD measurement while overestimation using Berlincourt method, should be thoroughly corrected in the data extraction process. The d33 of AlN and Al0.9Sc0.1N obtained by synchronous XRD method were 4.76 pC/N and 7.79 pC/N, respectively, matching well with traditional HBAR and Berlincourt methods. Our findings prove the in situ synchrotron XRD measurement as an effective method for precise piezoelectric coefficient d33 characterization.
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Affiliation(s)
- Wenzheng Jiang
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lei Zhu
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lingli Chen
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yumeng Yang
- Shanghai Engineering Research Center of Energy Efficient and Custom AI IC, School of Information Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Xi Yu
- School of Microelectronics, Shanghai University, Shanghai 200444, China
| | - Xiaolong Li
- Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China
| | - Zhiqiang Mu
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wenjie Yu
- State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
- College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
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6
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Guido R, Lomenzo PD, Islam MR, Wolff N, Gremmel M, Schönweger G, Kohlstedt H, Kienle L, Mikolajick T, Fichtner S, Schroeder U. Thermal Stability of the Ferroelectric Properties in 100 nm-Thick Al 0.72Sc 0.28N. ACS Appl Mater Interfaces 2023; 15:7030-7043. [PMID: 36715613 DOI: 10.1021/acsami.2c18313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The discovery of ferroelectricity in aluminum scandium nitride (Al1-xScxN) opens technological perspectives for harsh environments and space-related memory applications, considering the high-temperature stability of piezoelectricity in aluminum nitride. The ferroelectric and material properties of 100 nm-thick Al0.72Sc0.28N are studied up to 873 K, combining both electrical and in situ X-ray diffraction measurements as well as transmission electron microscopy and energy-dispersive X-ray spectroscopy. The present work demonstrates that Al0.72Sc0.28N can achieve high switching polarization and tunable coercive fields in a 375 K temperature range from room temperature up to 673 K. The degradation of the ferroelectric properties in the capacitors is observed above this temperature. Reduction of the effective top electrode area and consequent oxidation of the Al0.72Sc0.28N film are mainly responsible for this degradation. A slight variation of the Sc concentration is quantified across grain boundaries, even though its impact on the ferroelectric properties cannot be isolated from those brought by the top electrode deterioration and Al0.72Sc0.28N oxidation. The Curie temperature of Al0.72Sc0.28N is confirmed to be above 873 K, thus corroborating the promising thermal stability of this ferroelectric material. The present results further support the future adoption of Al1-xScxN in memory technologies for harsh environments like applications in space missions.
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Affiliation(s)
- Roberto Guido
- Namlab gGmbH, Nöthnitzer Strasse 64a, 01187Dresden, Germany
| | | | - Md Redwanul Islam
- Technical Faculty, Kiel University, Kaiserstraße 2, 24143Kiel, Germany
| | - Niklas Wolff
- Technical Faculty, Kiel University, Kaiserstraße 2, 24143Kiel, Germany
| | - Maike Gremmel
- Technical Faculty, Kiel University, Kaiserstraße 2, 24143Kiel, Germany
| | - Georg Schönweger
- Technical Faculty, Kiel University, Kaiserstraße 2, 24143Kiel, Germany
| | - Hermann Kohlstedt
- Technical Faculty, Kiel University, Kaiserstraße 2, 24143Kiel, Germany
| | - Lorenz Kienle
- Technical Faculty, Kiel University, Kaiserstraße 2, 24143Kiel, Germany
| | - Thomas Mikolajick
- Namlab gGmbH, Nöthnitzer Strasse 64a, 01187Dresden, Germany
- Chair of Nanoelectronics, TU Dresden, 01187Dresden, Germany
| | - Simon Fichtner
- Technical Faculty, Kiel University, Kaiserstraße 2, 24143Kiel, Germany
| | - Uwe Schroeder
- Namlab gGmbH, Nöthnitzer Strasse 64a, 01187Dresden, Germany
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7
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Nian L, Zou Y, Gao C, Zhou Y, Fan Y, Wang J, Liu W, Liu Y, Soon JB, Cai Y, Sun C. Demonstration of Thin Film Bulk Acoustic Resonator Based on AlN/AlScN Composite Film with a Feasible Keff2. Micromachines (Basel) 2022; 13:2044. [PMID: 36557343 PMCID: PMC9781223 DOI: 10.3390/mi13122044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 11/01/2022] [Accepted: 11/07/2022] [Indexed: 06/17/2023]
Abstract
Film bulk acoustic resonators (FBARs) with a desired effective electromechanical coupling coefficient (Keff2) are essential for designing filter devices. Using AlN/AlScN composite film with the adjustable thickness ratio can be a feasible approach to obtain the required Keff2. In this work, we research the resonant characteristics of FBARs based on AlN/AlScN composite films with different thickness ratios by finite element method and fabricate FBAR devices in a micro-electromechanical systems process. Benefiting from the large piezoelectric constants, with a 1 μm-thick Al0.8Sc0.2N film, Keff2 can be twice compared with that of FBAR based on pure AlN films. For the composite films with different thickness ratios, Keff2 can be adjusted in a relatively wide range. In this case, a filter with the specific N77 sub-band is demonstrated using AlN/Al0.8Sc0.2N composite film, which verifies the enormous potential for AlN/AlScN composite film in design filters.
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Affiliation(s)
- Laixia Nian
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
| | - Yang Zou
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
| | - Chao Gao
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
| | - Yu Zhou
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
| | - Yuchen Fan
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
| | - Jian Wang
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
| | - Wenjuan Liu
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
| | - Yan Liu
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
| | | | - Yao Cai
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
- School of Microelectronics, Wuhan University, Wuhan 430072, China
| | - Chengliang Sun
- The Institute of Technological Sciences, Wuhan University, Wuhan 430072, China
- School of Microelectronics, Wuhan University, Wuhan 430072, China
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Barth S, Schreiber T, Cornelius S, Zywitzki O, Modes T, Bartzsch H. High Rate Deposition of Piezoelectric AlScN Films by Reactive Magnetron Sputtering from AlSc Alloy Targets on Large Area. Micromachines (Basel) 2022; 13:mi13101561. [PMID: 36295914 PMCID: PMC9610784 DOI: 10.3390/mi13101561] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 09/07/2022] [Accepted: 09/13/2022] [Indexed: 06/01/2023]
Abstract
This paper reports on the deposition and characterization of piezoelectric AlXSc1-XN (further: AlScN) films on Si substrates using AlSc alloy targets with 30 at.% Sc. Films were deposited on a Ø200 mm area with deposition rates of 200 nm/min using a reactive magnetron sputtering process with a unipolar-bipolar hybrid pulse mode of FEP. The homogeneity of film composition, structural properties and piezoelectric properties were investigated depending on process parameters, especially the pulse mode of powering in unipolar-bipolar hybrid pulse mode operation. Characterization methods include energy-dispersive spectrometry of X-ray (EDS), X-ray diffraction (XRD), piezoresponse force microscopy (PFM) and double-beam laser interferometry (DBLI). The film composition was Al0.695Sc0.295N. The films showed good homogeneity of film structure with full width at half maximum (FWHM) of AlScN(002) rocking curves at 2.2 ± 0.1° over the whole coating area when deposited with higher share of unipolar pulse mode during film growth. For a higher share of bipolar pulse mode, the films showed a much larger c-lattice parameter in the center of the coating area, indicating high in-plane compressive stress in the films. Rocking curve FWHM also showed similar values of 1.5° at the center to 3° at outer edge. The piezoelectric characterization method revealed homogenous d33,f of 11-12 pm/V for films deposited at a high share of unipolar pulse mode and distribution of 7-10 pm/V for a lower share of unipolar pulse mode. The films exhibited ferroelectric switching behavior with coercive fields of around 3-3.5 MV/cm and polarization of 80-120 µC/cm².
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Cohen A, Cohen H, Cohen SR, Khodorov S, Feldman Y, Kossoy A, Kaplan-Ashiri I, Frenkel A, Wachtel E, Lubomirsky I, Ehre D. C-Axis Textured, 2-3 μm Thick Al 0.75Sc 0.25N Films Grown on Chemically Formed TiN/Ti Seeding Layers for MEMS Applications. Sensors (Basel) 2022; 22:7041. [PMID: 36146391 PMCID: PMC9504120 DOI: 10.3390/s22187041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Revised: 07/05/2022] [Accepted: 09/13/2022] [Indexed: 06/16/2023]
Abstract
A protocol for successfully depositing [001] textured, 2−3 µm thick films of Al0.75Sc0.25N, is proposed. The procedure relies on the fact that sputtered Ti is [001]-textured α-phase (hcp). Diffusion of nitrogen ions into the α-Ti film during reactive sputtering of Al0.75,Sc0.25N likely forms a [111]-oriented TiN intermediate layer. The lattice mismatch of this very thin film with Al0.75Sc0.25N is ~3.7%, providing excellent conditions for epitaxial growth. In contrast to earlier reports, the Al0.75Sc0.25N films prepared in the current study are Al-terminated. Low growth stress (<100 MPa) allows films up to 3 µm thick to be deposited without loss of orientation or decrease in piezoelectric coefficient. An advantage of the proposed technique is that it is compatible with a variety of substrates commonly used for actuators or MEMS, as demonstrated here for both Si wafers and D263 borosilicate glass. Additionally, thicker films can potentially lead to increased piezoelectric stress/strain by supporting application of higher voltage, but without increase in the magnitude of the electric field.
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Affiliation(s)
- Asaf Cohen
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Hagai Cohen
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sidney R. Cohen
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sergey Khodorov
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Yishay Feldman
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Anna Kossoy
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Ifat Kaplan-Ashiri
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Anatoly Frenkel
- Department of Materials Science and Chemical Engineering, Stony Brook University, Stony Brook, NY 11794, USA
| | - Ellen Wachtel
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Igor Lubomirsky
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - David Ehre
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
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10
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Wolff N, Islam MR, Kirste L, Fichtner S, Lofink F, Žukauskaitė A, Kienle L. Al 1-xSc xN Thin Films at High Temperatures: Sc-Dependent Instability and Anomalous Thermal Expansion. Micromachines (Basel) 2022; 13:mi13081282. [PMID: 36014204 PMCID: PMC9412885 DOI: 10.3390/mi13081282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 07/29/2022] [Accepted: 08/04/2022] [Indexed: 05/13/2023]
Abstract
Ferroelectric thin films of wurtzite-type aluminum scandium nitride (Al1−xScxN) are promising candidates for non-volatile memory applications and high-temperature sensors due to their outstanding functional and thermal stability exceeding most other ferroelectric thin film materials. In this work, the thermal expansion along with the temperature stability and its interrelated effects have been investigated for Al1−xScxN thin films on sapphire Al2O3(0001) with Sc concentrations x (x = 0, 0.09, 0.23, 0.32, 0.40) using in situ X-ray diffraction analyses up to 1100 °C. The selected Al1−xScxN thin films were grown with epitaxial and fiber textured microstructures of high crystal quality, dependent on the choice of growth template, e.g., epitaxial on Al2O3(0001) and fiber texture on Mo(110)/AlN(0001)/Si(100). The presented studies expose an anomalous regime of thermal expansion at high temperatures >~600 °C, which is described as an isotropic expansion of a and c lattice parameters during annealing. The collected high-temperature data suggest differentiation of the observed thermal expansion behavior into defect-coupled intrinsic and oxygen-impurity-coupled extrinsic contributions. In our hypothesis, intrinsic effects are denoted to the thermal activation, migration and curing of defect structures in the material, whereas extrinsic effects describe the interaction of available oxygen species with these activated defect structures. Their interaction is the dominant process at high temperatures >800 °C resulting in the stabilization of larger modifications of the unit cell parameters than under exclusion of oxygen. The described phenomena are relevant for manufacturing and operation of new Al1−xScxN-based devices, e.g., in the fields of high-temperature resistant memory or power electronic applications.
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Affiliation(s)
- Niklas Wolff
- Department of Material Science, Faculty of Engineering, Kiel University, Kaiserstr. 2, D-24143 Kiel, Germany
- Correspondence: (N.W.); (A.Ž.); (L.K.); Tel.: +49-431-880-6179 (N.W.); +49-351-2586-167 (A.Ž.); +49-431-880-6176 (L.K.)
| | - Md Redwanul Islam
- Department of Material Science, Faculty of Engineering, Kiel University, Kaiserstr. 2, D-24143 Kiel, Germany
| | - Lutz Kirste
- Fraunhofer Institute for Applied Solid State Physics, IAF, Tullastr. 72, D-79108 Freiburg, Germany
| | - Simon Fichtner
- Department of Material Science, Faculty of Engineering, Kiel University, Kaiserstr. 2, D-24143 Kiel, Germany
- Fraunhofer Institute for Silicon Technology ISIT, Fraunhoferstr. 1, D-25524 Itzehoe, Germany
| | - Fabian Lofink
- Fraunhofer Institute for Silicon Technology ISIT, Fraunhoferstr. 1, D-25524 Itzehoe, Germany
| | - Agnė Žukauskaitė
- Fraunhofer Institute for Applied Solid State Physics, IAF, Tullastr. 72, D-79108 Freiburg, Germany
- Correspondence: (N.W.); (A.Ž.); (L.K.); Tel.: +49-431-880-6179 (N.W.); +49-351-2586-167 (A.Ž.); +49-431-880-6176 (L.K.)
| | - Lorenz Kienle
- Department of Material Science, Faculty of Engineering, Kiel University, Kaiserstr. 2, D-24143 Kiel, Germany
- Correspondence: (N.W.); (A.Ž.); (L.K.); Tel.: +49-431-880-6179 (N.W.); +49-351-2586-167 (A.Ž.); +49-431-880-6176 (L.K.)
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11
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Stoeckel C, Meinel K, Melzer M, Žukauskaitė A, Zimmermann S, Forke R, Hiller K, Kuhn H. Static High Voltage Actuation of Piezoelectric AlN and AlScN Based Scanning Micromirrors. Micromachines (Basel) 2022; 13:mi13040625. [PMID: 35457927 PMCID: PMC9025745 DOI: 10.3390/mi13040625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 04/06/2022] [Accepted: 04/07/2022] [Indexed: 11/16/2022]
Abstract
Piezoelectric micromirrors with aluminum nitride (AlN) and aluminum scandium nitride (Al0.68Sc0.32N) are presented and compared regarding their static deflection. Two chip designs with 2 × 3 mm2 (Design 1) and 4 × 6 mm2 (Design 2) footprint with 600 nm AlN or 2000 nm Al0.68Sc0.32N as piezoelectric transducer material are investigated. The chip with Design 1 and Al0.68Sc0.32N has a resonance frequency of 1.8 kHz and a static scan angle of 38.4° at 400 V DC was measured. Design 2 has its resonance at 2.1 kHz. The maximum static scan angle is 55.6° at 220 V DC, which is the maximum deflection measurable with the experimental setup. The static deflection per electric field is increased by a factor of 10, due to the optimization of the design and the research and development of high-performance piezoelectric transducer materials with large piezoelectric coefficient and high electrical breakthrough voltage.
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Affiliation(s)
- Chris Stoeckel
- Fraunhofer Institute for Electronic Nano Systems ENAS, 09126 Chemnitz, Germany; (S.Z.); (R.F.); (K.H.); (H.K.)
- Center for Microtechnologies, Chemnitz University of Technology, 09111 Chemnitz, Germany; (K.M.); (M.M.)
- Correspondence:
| | - Katja Meinel
- Center for Microtechnologies, Chemnitz University of Technology, 09111 Chemnitz, Germany; (K.M.); (M.M.)
| | - Marcel Melzer
- Center for Microtechnologies, Chemnitz University of Technology, 09111 Chemnitz, Germany; (K.M.); (M.M.)
| | - Agnė Žukauskaitė
- Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, 01277 Dresden, Germany;
| | - Sven Zimmermann
- Fraunhofer Institute for Electronic Nano Systems ENAS, 09126 Chemnitz, Germany; (S.Z.); (R.F.); (K.H.); (H.K.)
- Center for Microtechnologies, Chemnitz University of Technology, 09111 Chemnitz, Germany; (K.M.); (M.M.)
| | - Roman Forke
- Fraunhofer Institute for Electronic Nano Systems ENAS, 09126 Chemnitz, Germany; (S.Z.); (R.F.); (K.H.); (H.K.)
| | - Karla Hiller
- Fraunhofer Institute for Electronic Nano Systems ENAS, 09126 Chemnitz, Germany; (S.Z.); (R.F.); (K.H.); (H.K.)
- Center for Microtechnologies, Chemnitz University of Technology, 09111 Chemnitz, Germany; (K.M.); (M.M.)
| | - Harald Kuhn
- Fraunhofer Institute for Electronic Nano Systems ENAS, 09126 Chemnitz, Germany; (S.Z.); (R.F.); (K.H.); (H.K.)
- Center for Microtechnologies, Chemnitz University of Technology, 09111 Chemnitz, Germany; (K.M.); (M.M.)
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12
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Liu X, Wang D, Kim KH, Katti K, Zheng J, Musavigharavi P, Miao J, Stach EA, Olsson RH, Jariwala D. Post-CMOS Compatible Aluminum Scandium Nitride/2D Channel Ferroelectric Field-Effect-Transistor Memory. Nano Lett 2021; 21:3753-3761. [PMID: 33881884 DOI: 10.1021/acs.nanolett.0c05051] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Recent advances in oxide ferroelectric (FE) materials have rejuvenated the field of low-power, nonvolatile memories and made FE memories a commercial reality. Despite these advances, progress on commercial FE-RAM based on lead zirconium titanate has stalled due to process challenges. The recent discovery of ferroelectricity in scandium-doped aluminum nitride (AlScN) presents new opportunities for direct memory integration with logic transistors due to the low temperature of AlScN deposition (approximately 350 °C), making it compatible with back end of the line integration on silicon logic. Here, we present a FE-FET device composed of an FE-AlScN dielectric layer integrated with a two-dimensional MoS2 channel. Our devices show an ON/OFF ratio of ∼106, concurrent with a normalized memory window of 0.3 V/nm. The devices also demonstrate stable memory states up to 104 cycles and state retention up to 105 s. Our results suggest that the FE-AlScN/2D combination is ideal for embedded memory and memory-based computing architectures.
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Affiliation(s)
- Xiwen Liu
- Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Dixiong Wang
- Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Kwan-Ho Kim
- Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Keshava Katti
- Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Jeffrey Zheng
- Material Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Pariasadat Musavigharavi
- Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
- Material Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Jinshui Miao
- Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Eric A Stach
- Material Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
- Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Roy H Olsson
- Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Deep Jariwala
- Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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13
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Song Y, Perez C, Esteves G, Lundh JS, Saltonstall CB, Beechem TE, Yang JI, Ferri K, Brown JE, Tang Z, Maria JP, Snyder DW, Olsson RH, Griffin BA, Trolier-McKinstry SE, Foley BM, Choi S. Thermal Conductivity of Aluminum Scandium Nitride for 5G Mobile Applications and Beyond. ACS Appl Mater Interfaces 2021; 13:19031-19041. [PMID: 33851815 DOI: 10.1021/acsami.1c02912] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Radio frequency (RF) microelectromechanical systems (MEMS) based on Al1-xScxN are replacing AlN-based devices because of their higher achievable bandwidths, suitable for the fifth-generation (5G) mobile network. However, overheating of Al1-xScxN film bulk acoustic resonators (FBARs) used in RF MEMS filters limits power handling and thus the phone's ability to operate in an increasingly congested RF environment while maintaining its maximum data transmission rate. In this work, the ramifications of tailoring of the piezoelectric response and microstructure of Al1-xScxN films on the thermal transport have been studied. The thermal conductivity of Al1-xScxN films (3-8 W m-1 K-1) grown by reactive sputter deposition was found to be orders of magnitude lower than that for c-axis-textured AlN films due to alloying effects. The film thickness dependence of the thermal conductivity suggests that higher frequency FBAR structures may suffer from limited power handling due to exacerbated overheating concerns. The reduction of the abnormally oriented grain (AOG) density was found to have a modest effect on the measured thermal conductivity. However, the use of low AOG density films resulted in lower insertion loss and thus less power dissipated within the resonator, which will lead to an overall enhancement of the device thermal performance.
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Affiliation(s)
- Yiwen Song
- Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Carlos Perez
- Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Giovanni Esteves
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - James Spencer Lundh
- Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | | | - Thomas E Beechem
- Center for Integrated Nanotechnologies, Albuquerque, New Mexico 87185, United States
| | - Jung In Yang
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Kevin Ferri
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Joseph E Brown
- Electronic Materials and Devices Department, Applied Research Laboratory, University Park, University Park, Pennsylvania 16802, United States
| | - Zichen Tang
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Jon-Paul Maria
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - David W Snyder
- Electronic Materials and Devices Department, Applied Research Laboratory, University Park, University Park, Pennsylvania 16802, United States
| | - Roy H Olsson
- Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Benjamin A Griffin
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Susan E Trolier-McKinstry
- Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Brian M Foley
- Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Sukwon Choi
- Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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