Chao Chen

University of Electronic Science and Technology of China, Hua-yang, Sichuan, China

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Publications (19)16.76 Total impact

  • Chao Chen · YaDong Jiang · Long Zhang · Yun Zhou · Xing Zheng
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    ABSTRACT: A method for system-level simulation between microbolometer designing and Read-Out Integrated Circuit (ROIC) was studied. Three-dimensional (3D) structure modeling of the microbolometer was built. Thermal capacity, thermal conductivity and resistance of the model were obtained from thermoelectric coupling Finite Element Method (FEM) based on the model. An electrical equipment circuit of microbolometer which contains these three parameters was established. By using Verilog-AMS language, the electrical equipment circuit was described as a reduced-order macro-model. Then, the reduced-order macro-model was compiled in cadence to form IP unit of microbolometer, which could be used and identified in cadence. System-level simulation between microbolometer and ROIC was accomplished. Key performances of the device, including input and output characteristics, were obtained in simulation and verified by experimental results.
    No preview · Article · May 2015 · Science China Technological Sciences
  • Tao Wang · He Yu · Chao Chen · Yang Wang · Yadong Jiang
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    ABSTRACT: In this work, a modeling for reactive sputtering has been presented where the non-uniform current density is taken into account. The model in this paper can be used to understand the process of reactive magnetron sputtering. The results are compared with those that assume uniform discharge current density distributed on the target. It can be concluded that the process with the non-uniform discharge density shows a higher flow of gas reactive when occurring the hysteresis behavior. In addition, a study of the radial variation of the target composition in metallic and compound mode is also performed.
    No preview · Conference Paper · Sep 2014
  • Chao Chen · Xing Zhao Liu
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    ABSTRACT: The effects of low energy (1.8 MeV) electron irradiation on enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs) have been reported. When the dose up to 1.1×1016 cm-2, the saturation drain current and maximal transconductance of E-mode AlGaN/GaN HEMTs increase after irradiation. However, almost no change of threshold voltage and gate leakage current is observed. The results are explained by the creation of positive charges in the AlGaN layer by ionizing energy loss, especially the creation of N vacancies and Ga vacancies by non-ionizing energy loss. Moreover, low-energy electron irradiation could recover the electron mobility.
    No preview · Article · Sep 2013
  • Xingzhao Liu · Chao Chen · Jun Zhu · Wanli Zhang · Yanrong Li
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    ABSTRACT: This paper presents the modulation effects of charged dielectrics on performance of AlGaN/GaN metal-insulator-semiconductor high-electron mobility transistors (MIS HEMTs). Using fluorinated Al2O3 as gate dielectrics, the threshold voltage of the devices shifted from conventional depletion-mode (D-mode) MIS HEMTs to enhancement-mode (E-mode) MIS HEMTs. And the threshold voltage (Vth) increased more positively by using a successive deposition of Al2O3 layer on the fluorinated Al2O3 as a blocking oxide layer. It was found that not the surface potential but rather the negative charges in the Al2O3 gate dielectrics are primary factors responsible for conversion from D-mode MIS HEMTs to E-mode MIS HEMTs by using fluorinated Al2O3 as gate dielectrics. The positive Vth modulation was attributed to the built-in electric field which was introduced by the charged dielectrics.
    No preview · Article · Jul 2013 · Journal of Applied Physics
  • Chao Chen · Ya Dong Jiang · Hong Xi Zhou
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    ABSTRACT: Thermal conductance of microbolometer has a directly impact on Noise Equivalent Temperature Difference (NETD) and thermal time constant which are the key indicators of uncooled IR detector. It is of great significance to calculate and evaluate thermal conductance. A calculate approach of thermal conductance for uncooled microbolometer detectors is introduced in this paper. Accurate three-dimensional modeling of microbolometer is found by using MEMS analysis software Intellisuite. Dynamic thermal analysis of this model is solved and then thermal time constant can be read from thermal time curve of the analysis mentioned above. Combined with the calculation of thermal capacitance, more precisely thermal conductance value can be reached which is more accurate than theoretical calculations result and meaningful for design and fabrication of the device.
    No preview · Article · Dec 2012 · Key Engineering Materials
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    ABSTRACT: The purpose of extracting Macro-model of macro sensor is to find out the mathematical model representing system characteristics of behavior efficiently and accurately. A good understanding of the whole system, collaborative simulation with circuit and optimize system design are meaningful. Whether the extraction of device level Macro- model is truly effective or not, it directly influences the simulation results of system level. Therefore, an effective extraction method of Macro-model is crucial to system simulation. Meanwhile, fast and effective extraction approach for MEMS devices Macro-model will continue to be the main future development of technology. This paper presents a fast automatic extraction technology for Macro-model. Coordinating physical level and system level is to meet the demands of system level fast modeling and simulation.
    No preview · Article · Dec 2012 · Key Engineering Materials
  • Hong Xi Zhou · Chao Chen · Tao Wang
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    ABSTRACT: In this paper a high-performance single level uncooled microbolometer detectors with a unit cell size of 25um×25um is introduced. An efficient detectors requires low Noise Equivalent Temperature Difference(NETD) (<80mK,f/1,60Hz)and low thermal time constant (<8.3ms). The trade-offs between physical parameters are studied to attain the optimum design parameters including the thermal conductance, the thermal time constant and the active area, consequently, optimum design parameters such as the width and the length of the support arms, which can satisfy the demand of an efficient detectors is achieved.
    No preview · Article · Dec 2012
  • Shu Min Ma · Chao Chen · Tao Wang · Huan Zhang · Hong Xi Zhou
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    ABSTRACT: An accelerometer is a micro- electromechanical device which can sensitive to acceleration . The sensing mechanism of accelerometer is that when accelerated , the mass moves in Z-axis, and the gap between parallel plates changed with the loads, which causes vary of the capacitance of the estimation. This paper presents a newly devel oped sensor for the conventional capacitive MEMS accelerometer in Z-axis . The principle of capacitive acceleration is based on the detection the change of capacitance which results from acceleration changes. The sensor is used for estimation of the size a nd loads variations for accelerometer. This paper has been focused on the design of the MEMS accelerometer and calculation of the major parameters of the sensor.
    No preview · Article · Dec 2012 · Key Engineering Materials
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    ABSTRACT: With the development of MEMS devices, the design requirements to MEMS devices are more and more high. Computer Aided design of MEMS devices have been from the simple structure, fabrication process design to the development of the system design. The corresponding design pattern originally used to be to function and performance, which is called Bottom-Up, is developing to such a pattern named Top-Down to meet demands as the final purpose, and it is more reasonable. According to the current situation of MEMS technology, this paper presents a timely system design method of micro devices based on Top-Down, and further discuss the design process of Top-Down of micro devices.
    No preview · Article · Nov 2012
  • Shu Min Ma · Chao Chen · Tao Wang · Huan Zhang · Hong Xi Zhou
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    ABSTRACT: MEMS are the manufacturing of a wide variety of items that are mechanical and electronic in nature. This paper describes a capacitive accelerometer technology using sense element structures. The sense element consists of a symmetrically flat plate of mass supported by four L shaped cantilevers, beams and frameworks. Capacitor plates located on the surface are used to detect the displacement. By using the finite element analysis method to build a model, analyzing the maximal displacement of mass, resonant frequency and stress of cantilever beam with different length, width and thickness.
    No preview · Article · Jun 2012 · Applied Mechanics and Materials
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    ABSTRACT: The enhancement-mode (E-mode) AlGaN/GaN metal-insulator-semiconductor high-electron mobility transistors (MISHEMTs) were realized by using fluorinated Al2O3 as gate dielectrics. The variations in binding-energy spectrum and valance-band spectrum in fluorinated-Al2O3/AlGaN/GaN are studied in this Letter, providing insights to mechanism underlying drastic threshold voltage (Vth) modulation of AlGaN/GaN MISHEMTs with fluorinated Al2O3 gate dielectrics. It was found that not the surface potential but rather the negative charges in Al2O3 gate dielectrics are the primary factor responsible for conversion from depletion-mode (D-mode) to E-mode AlGaN/GaN MISHEMTs by using fluorinated Al2O3 as gate dielectrics.
    No preview · Article · Mar 2012 · Applied Physics Letters
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    ABSTRACT: High-performance enhancement-mode (E-mode) AlGaN/GaN metal-insulator-semiconductor HEMTs (MISHEMTs) were realized by using fluorinated Al<sub>2</sub>O<sub>3</sub> thin films as gate dielectrics. The depth profile of Fluoride atoms determined by X-ray photoelectron spectroscopy showed that the fluorine (F) ions were incorporated into the surface (approximately 2 nm) of the Al<sub>2</sub>O<sub>3</sub> gate dielectrics. With proper amount of F-ion incorporation, the threshold voltage of MISHEMTs shifted from - 4.8 to 0.11 V, converting depletion-mode (D-mode) MISHEMTs to E-mode ones. The E-mode MISHEMTs exhibited high performances including a high transconductance value of 153 mS/mm and a large saturated drain-current value I <sub>ds</sub> of 547 mA/mm. This paves a new way to fabricate E-mode AlGaN/GaN MISHEMTs and allows the monolithic integration of E/D-mode MISHEMTs for analog integrated circuits.
    No preview · Article · Nov 2011 · IEEE Electron Device Letters
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    ABSTRACT: An AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistor (MISHFET) with about 40 nm Al2O3 for both surface passivation and gate dielectric has been investigated and compared with the regular metal-semiconductor heterostructure field-effect transistor (MESHFET). The output characteristic measurements have shown that the MISHFET yielded 34% increase of the saturation drain current compared to the MESHFET. The Hall effect measurements of AlGaN/GaN two-dimensional electron gas (2DEG) coated with Al2O3 thin films indicated an increase of mobility and density of 2DEG, and thus a decrease of the parasitic series resistance. The XRD analysis of the AlGaN/GaN heterostructure showed that strain was introduced into the AlGaN barrier layer with Al2O3 coating. The energy band calculations showed that the biaxial tensile stress should possibly be the main mechanism for the performance improvement of the MISHFET.
    No preview · Article · May 2011 · Semiconductor Science and Technology
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    ABSTRACT: Uncooled infrared detectors are applied widely in both civilian and military. Recently, novel microbolometers composing of two planes located at diffeent levels were proposed to improve the performance of the detectors. In this paper, such two-layer microbolometers were simulated by finite element analysis. Results reveal that when SiO2 film is utilized as the isolating and supporting material located at the lower bridge plane, the temperature rise of the pixel reaches 3∼5 times higher than those in the conventional one-layer microbolometers, and the maximum IR absorptance increases for about 40%. Therefore, these two-layer microbolometers are helpful for significantly improving the thermal and optical properties. However, their structural stability turns poor. Consequently, the mechanical properties for such two-layer microbolometers should be enhanced in practical applications.
    No preview · Article · Mar 2011
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    ABSTRACT: A nearly square-like ferroelectric hysteretic loop of spin-coated and crystallized poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) with a remnant polarization 2 Pr of 20 µC cm−2 was obtained. The electrical transport properties of the P(VDF-TrFE)/AlGaN/GaN structure were investigated. The results show that the carrier density Ns, mobility μ, and resistivity ρ of AlGaN/GaN 2DEG can be directly and strongly modulated by an external electric field via the ferroelectric polymer P(VDF-TrFE): the Ns, μ, and ρ of AlGaN/GaN 2DEG exhibit closed hysteretic loops under a closed external electric field and the carrier density can be tuned as large as 235% only by changing the external electric field.
    No preview · Article · Dec 2010 · Semiconductor Science and Technology
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    ABSTRACT: The way of improving the thickness uniformity of the thin film deposited by magnetron sputtering system is presented in this paper. A simple model for the magnetron sputtering system with a baffle between cathode target and substrate is described. Based on this model, it is possible to predict the relative deviation of film thickness with this baffle-model by taking the shape and size of baffle into the consideration. The purpose of this article is to explain how different baffle parameters affect the uniformity of thin film using the method of finite element with rectangle target in this magnetron system. It is found that there may exist optimum baffle conditions where the relative deviation of thin film thickness is less than 3 % with a diameter of Phi 150 mm substrate.
    No preview · Article · May 2010 · Proceedings of SPIE - The International Society for Optical Engineering
  • Henan Zhao · Tao Wang · He Yu · Chao Chen · Yadong Jiang
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    ABSTRACT: In this article, the practical structure of two-color microbolometers for uncooled infrared detection was considered, a mathematical model to calculate infrared absorptance was described. The optical characteristic of multilayer structure consisting of Nitride (SiNx) infrared absorber film/ Vanadium (VOx) heat sensitive film/ SiNx support film/ the first optical resonant cavity/ a tunable reflecting Al micromirror/ the second optical resonant cavity /a bottom electrode made up of Al was investigated. According to optical admittance matrix theory, relation between infrared absorber film thickness, the first optical resonant cavity of two-color microbolometer and infrared absorptivity was simulated by MATLAB software.
    No preview · Article · May 2010 · Proceedings of SPIE - The International Society for Optical Engineering
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    ABSTRACT: A tunable reflecting micro-optoelectromechanical systems (MOEMS) micromirror is designed for measuring the actual temperature and color of an object based on comparison of two wavelength response windows, 3-5 and 8-12 μm. The MOEMS micromirror with switching between two positions by an applied electrostatic voltage provides a response to two wavelength windows by tuning the optical resonant cavity. Three different structural models of the tunable micromirror, which are made up of single Al layer with type I legs, single Al layer with type L legs, and double Al/Si3N4 layers with type I legs, are designed and simulated accurately using ANSYS tools on a 35-μm pixel-pitch array. On the basis of the comparsion, the third model, made up of double Al/Si3N4 layers with type I legs, is chosen. With different distances between the MOEMS micromirror and the bottom electrode, the total capacitance of the tunable micromirror is gained based on electromagnetic analysis and theoretical equation. The pull-in voltage is calculated as 8.21 V by electrostatic-mechanical coupling analysis, and the maximum stress is 368.744 MPa, which is less than the yield strength of Si3N4 thin film. But if the voltage is increased to ∼9.73 V, the micromirror will touch the bottom electrode by pull-in behavior.
    No preview · Article · Jan 2010 · Journal of Micro/ Nanolithography, MEMS, and MOEMS
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    ABSTRACT: A tunable reflecting micromirror made up of two layers of Al and Si3N4 is designed to suspend between the silicon substrate and the heat sensitive membrane for measuring the actual temperature and color of an object based on comparison of two wavelength response windows, 3-5 mum and 8-12 mum. The micromirror, switching between two positions by an applied electrostatic voltage, provides a response to two wavelength windows by tuning the optical tunable resonant cavity. With different distances between the micromirror and the bottom electrode, the total capacitance of the tunable micromirror is gained based on electromagnetic analysis and theoretical equation. The pull-in voltage is calculated as 8.21 V by electrostatic-mechanical coupling analysis. But if the voltage is increased to about 9.73 V, the micromirror will touch the bottom electrode by pull-in behavior. At last, the vibration modes of the tunable micromirror are simulated using ANSYS, and the fabrication process flow of the two-color microbolometer is theoretically demonstrated.
    No preview · Article · Nov 2009 · Proceedings of SPIE - The International Society for Optical Engineering