Jian-She Liu

Tsinghua University, Beijing, Beijing Shi, China

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Publications (19)6.69 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: A monolithic MEMS triaxial accelerometer based on piezoelectric lead zirconate titanate (PZT) thin films with highly symmetric quad-beams and a seismic mass, has been designed and simulated. Theoretical and numerical models for this structure are presented. The dynamic response and the trade-off between several design considerations are discussed. Static and modal simulations with FEM (Finite Element Method) simulator have been performed to analyze the mechanical response. It shows that the sensitivities of the three axes (X, Y, Z) are respectively 27, 27, and 29 mv/g, and there is almost no transverse sensitivity for the accelerometer. Also, the device is expected to have good temperature performance.
    Integrated Ferroelectrics 11/2003; 56(1):1115-1122. · 0.38 Impact Factor
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    ABSTRACT: The present paper proposes a simple fabrication technique of high quality PZT thick films that call for silicon mold technique. The fabrication process adopts the silicon with back window obtained from silicon anisotropic etching as the silicon mold, and the improved PZT sol is dispensed in the silicon mold. The PZT films obtained using single spin coating with the thickness of l00 μ m or higher, which is over the depth of back window of the silicon substrate, are crack-free and have good morphology. The PZT films with perfect perovskite structure have excellent piezoelectric property and the d<sub>33</sub> is about 170pC/N. Ferroelectric hysteresis loops are measured, and the remnant polarization (P<sub>r</sub>) of the PZT ceramics pellet is about 25 μC/cm<sup>2</sup> and the coercive field (E<sub>C</sub>) is about 27kV/cm. In the radio-frequency (RF) region, the dielectric constant is about 350 and the dielectric loss is less than 0.01.
    TRANSDUCERS, Solid-State Sensors, Actuators and Microsystems, 12th International Conference on, 2003; 07/2003
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    ABSTRACT: This paper proposes a novel lead-zirconate-titanate (PZT)-based structure used for the integrated microphone. The performance of the PZT thin films and the devices were improved due to adoption of the lead-titanate (PT) layer as the seeding layer. The PZT-based piezoelectric microphones with conductor-piezoelectric-conductor sandwich structure were fabricated. The size of the finished microphone ranged from 600×600 μ m<sup>2</sup> to 1000×1000 μ m<sup>2</sup>. A high sensitivity of 38 mV/Pa can be obtained. This quality was prominent in the existed microphones. The frequency response of the microphone was very flat in the audio frequency range. The novel piezoelectric microphones should be very promising for acoustic applications.
    TRANSDUCERS, Solid-State Sensors, Actuators and Microsystems, 12th International Conference on, 2003; 07/2003
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    ABSTRACT: Fabrication and properties of lead zirconate titanate (PZT) thin films have been studied for Metal-Ferroelectric-Semiconductor FET (MFSFET) devices. PZT based MFS capacitors using lead titanate (PT) as seeding layers have been respectively prepared on p-type ⟨111⟩ and n-type ⟨100⟩ silicon wafers directly by a sol-gel method. PZT/PT films are final annealed at 650°C for 1 min in oxygen ambient using rapid thermal annealing (RTA). The measured memory windows of the MFS capacitors are about 1.8 V and 5 V under the polarization voltages of ±5 V and ±10 V correspondingly. The MFS structure can be valuable for MFSFET applications.
    Integrated Ferroelectrics - INTEGR FERROELECTRICS. 01/2003; 57(1):1241-1248.
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    ABSTRACT: A novel ferroelectric based microphone with lead zirconate titanate [Pb(Zr,Ti)O3, PZT] coated silicon cantilever has been proposed in this paper. The cantilever structure is composed of a Pt/PZT/Pt/Ti/SiO2/Si3N4/SiO2/Si multilayer and is designed using a multimorph model. Optimum fabrication process of the PZT thin films and the cantilever has been developed. The acoustic outputs of the fabricated microphones have been measured with a standard microphone and a high sensitivity of 40 mV/Pa can be obtained. The frequency response of the microphone is very flat in the audio frequency range.
    Microelectronic Engineering 01/2003; 66:683-687. · 1.22 Impact Factor
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    ABSTRACT: A miniature microphone with silicon-based lead zirconate titanate (PZT) thin films has been fabricated and tested. The main structure of the device is composed of Al/Pt/PZT/Pt/Ti/SiO2/Si3N4/SiO2/Si multi-layer diaphragm. The PZT thin films have been prepared using an improved sol-gel method. Optimized fabrication process of the device has been developed, especially, RIE (reactive ion etching) and IBE (ion beam etching) processes have been used to etch the PZT thin film and electrode metal successfully. The sensitivity of microphone is 16 mV/Pa at 1 KHz and 158 mV/Pa at the resonant frequency of 17.3 KHz. The electrical and thermal reliability of the microphone is satisfactory. This miniature microphone can be widely used in hearing aids, mobile phones, and many other applications.
    Integrated Ferroelectrics 01/2003; 52(1):229-235. · 0.38 Impact Factor
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    ABSTRACT: Silicon-based BaxSr1-xTiO3 (BST) thin films have been prepared by a sol-gel method with rapid thermal annealing (RTA) processes. Phase structure of the films has been investigated by x-ray diffraction. Atomic force microscopy studies reveal a dense and smooth surface of the sol-gel prepared films. Microstructure and electrical properties of the BST films can be affected by the substrate and the annealing process. RTA method is found to be very efficient to improve the electrical properties of the films. Dielectric constant and dielectric loss of the BST films at 100 kHz are 230 and 0.02, respectively. Leakage current density of the BST capacitors is 1.6×10-7A cm-2 at 3 V.
    Journal of Physics D Applied Physics 04/2002; 35(9):923. · 2.53 Impact Factor
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    ABSTRACT: Lead-zirconate-titanate (PZT) and ZnO thin films on silicon substrates were prepared by a sol-gel method. Phase characterization and crystal orientation of the films were investigated by X-ray diffraction analysis (XRD). It was shown that the PZT thin films had a perfect perovskite structure after annealed at a low temperature of 600 ¯ , and the ZnO thin films were well crystallized with (002) preferred orientation at a low annealing temperature of 400 ¯ . PZT thin films were chemically etched using HCl/HF solution through typical semiconductor lithographic process, and ZnO thin films were wet etched using acidic and alkaline etchants. The etching conditions were optimized. The etching precision can be higher than 1 w m.
    Integrated Ferroelectrics 01/2002; 48(1):271-279. · 0.38 Impact Factor
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    ABSTRACT: In this paper, a novel piezoelectric microphone based on a lead zirconate titanate [Pb(Zr, Ti)O3, PZT]-coated silicon cantilever is presented. The main structure of the cantilever is composed of the Pt/PZT/Pt/Ti/SiO2/Si3N4/SiO2/Si multilayer structure. An optimum fabrication process of the PZT thin films and the cantilever has been developed. The acoustic outputs of the fabricated microphones have been measured with a standard microphone and a high sensitivity of 40 mV/Pa can be obtained. The frequency response of the microphone is very flat in the audio frequency range.
    Japanese Journal of Applied Physics 01/2002; 41:7158-7159. · 1.07 Impact Factor
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    ABSTRACT: High quality silicon-based PZT thin films were prepared using an improved sol-gel process. PT thin film was adopted as the seeding layer. The fabrication technique and the growth mechanism of the PZT thin films crystallized with (100) preferred orientation were studied through changing the pre-annealing temperatures, the annealing temperatures and the thickness of the PT seeding layer. It was shown that the PZT thin films with the suitable seeding layer had a more highly (100) preferred orientation. The dielectric response and dielectric loss of the PZT thin films were also measured. In the radio-frequency (RF) region, the dielectric constant was about 150 and the dielectric loss was less than 0.01, respectively.
    Integrated Ferroelectrics - INTEGR FERROELECTRICS. 01/2002; 46(1):79-86.
  • Integrated Ferroelectrics - INTEGR FERROELECTRICS. 01/2002; 50(1):81-89.
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    ABSTRACT: RF-MEMS bulk acoustic wave (BAW) filter using surface micromachining is successfully achieved using PZT as the piezoelectric layer. The resonant frequency is adjusted by changing the thickness of the SiO 2 film on the top of the upper electrode. By etching the sacrificial porous silicon (PS) layer, the suspended structure is formed. This structure is able to eliminate the influence of the thick support film to the filter, and to improve the IC process compatibility and quality of the filter. Each resonator forms a self-supporting structure, so that the cross-talk between resonators with different frequencies will be dramatically reduced. In addition, dry-etching processes are used to improve the quality of the device. It is found that reactive ion etching (RIE) can be used to etch PZT/PT and platinum with a rate of 200 and 100 Å/min respectively using HCFC-124 as the etching gas.
    Integrated Ferroelectrics - INTEGR FERROELECTRICS. 01/2002; 50(1):71-79.
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    ABSTRACT: Lead zirconate titanate (PZT) based ferroelectric capacitor using lead titanate (PT) as seeding layers has been prepared on silicon wafer by an improved sol-gel method. The novel ferroelectric capacitor has high dielectric constant of about 1200, ultralow leakage current density of 0.1nA/cm 2 , high remanent polarization of 20 w C/cm 2 at coercive field of about 30kV/cm, and almost fatigue free properties. The capacitor structure can be valuable for FeRAM applications.
    Integrated Ferroelectrics 01/2002; 46(1):47-53. · 0.38 Impact Factor
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    ABSTRACT: Undoped and Mn(II)-doped barium strontium titanate (BST) thin films have been prepared by a "water based" sol-gel method. With this method, BST stock solution can be easily doped with any concentration of aqueous metal ion solution and can be stocked for 34 days at room temperature. The crystallization temperature of 650 ¯ 750 ¯ is suitable for the films from traded-off of both the X-ray diffraction (XRD) patterns and the surface topography. The Mn 2p 3/2 X-ray photoelectron spectra (XPS) pattern is given for the first time in the thin film and shows the valence state of the Mn-doped BST has a same valance with the Mn(II) dopant. Considering the peak shift of the binding energy, it is proposed that the Fermi level of the Mn-doped BST has been shifted down by 0.7 eV.
    Integrated Ferroelectrics 01/2002; 45(1):31-38. · 0.38 Impact Factor
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    ABSTRACT: A PZT-based cantilever structure for microphone and microspeaker applications is designed using a multimorph model. The use of zirconate titanate (PZT) greatly improves the characteristics of the microphone and microspeaker. The sensitivity and the sound pressure level (SPL) of the integrated microphone and microspeaker are calculated. It is found that the sensitivity of the microphone and the SPL of the microspeaker are higher than those using normal piezoelectric materials.
    Solid-State and Integrated-Circuit Technology, 2001. Proceedings. 6th International Conference on; 11/2001
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    ABSTRACT: Analytical solutions of the wave equation for the electrode-piezoelectric-electrode sandwich structure in film bulk acoustic resonators (FBARs) are presented. The impedance for PZT based FBAR is derived utilizing proper boundary conditions and their material parameters. A novel method to adjust the resonant frequency is proposed corresponding to the process feasibility and material properties. Ferroelectric-based RF filters composed of FBARs are designed
    Solid-State and Integrated-Circuit Technology, 2001. Proceedings. 6th International Conference on; 02/2001
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    ABSTRACT: High quality ferroelectric capacitor with a PT/PZT/PT sandwich structure prepared by an improved sol-gel method is proposed for FeRAM applications. This novel ferroelectric capacitor has high dielectric constant of about 1200, ultra-low leakage current density of 0.1 nA/cm, high remanent polarization of 20 μC/cm2 at coercive field of about 30 kV/cm, and almost fatigue free properties
    01/2001;
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    ABSTRACT: The analytical solutions of the wave equation for the electrode-piezoelectrics-electrode sandwich structure in film bulk acoustic resonators(FBARs) are presented. The impedance for PZT, PT based FBAR is derived utilizing appropriate boundary conditions and their material parameters. A novel method to adjust the resonant frequency is proposed corresponding to the process feasibility and material properties. Ferroelectrics-based RF filters composed of FBARs are designed.
    Integrated Ferroelectrics - INTEGR FERROELECTRICS. 01/2001; 41:73-80.
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    ABSTRACT: A SAW filter with ZnO/Al/SiO2/Si structure was designed and fabricated. An image-impedance connection electrode structure was adopted to depress the insert loss and improve the stop-band rejection. A ZnO film was deposited by DC magnetron sputtering. The sputtering parameters, such as substrate temperature, sputtering gas pressure and deposition rate were extensively investigated. The film showed good c-axis normal orientation through x-ray analysis. The thickness of the ZnO film was designed to work at Rayleigh and Sezawa wave mode, and the center frequencies of the filters reached to 1.05 GHz and 1.48 GHz respectively.
    Integrated Ferroelectrics - INTEGR FERROELECTRICS. 01/2001; 41:137-144.

Publication Stats

27 Citations
635 Views
6.69 Total Impact Points

Institutions

  • 2001–2003
    • Tsinghua University
      • • Institute of Microelectron
      • • Department of Microelectronics and Nanoelectronics
      Beijing, Beijing Shi, China