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In order to realize the measurement of three-axis acceleration, pressure, and magnetic field, monolithic integrated three-axis acceleration/pressure/magnetic field sensors are proposed in this paper. The proposed sensors were constructed with an acceleration sensor consisting of four L-shaped double beams, two masses, middle double-beams, and twelve piezoresistors, a pressure sensor made of a square silicon membrane, and four piezoresistors, as well as a magnetic field sensor composed of five Hall elements. COMSOL software and TCAD-Atlas software were used to simulate characteristics of integrated sensors, and analyze the working principles of the sensors in measuring acceleration, pressure, and magnetic field. The integrated sensors were fabricated by using micro-electro-mechanical systems (MEMS) technology and packaged by using inner lead bonding technology. When applying a working voltage of 5 V at room temperature, it is possible for the proposed sensors to achieve the acceleration sensitivities of 3.58 mV/g, 2.68 mV/g, and 9.45 mV/g along the x-axis, y-axis, and z-axis (through an amplifying circuit), and the sensitivities towards pressure and magnetic field are 0.28 mV/kPa and 22.44 mV/T, respectively. It is shown that the proposed sensors can measure three-axis acceleration, pressure, and magnetic field. [ABSTRACT FROM AUTHOR]

A micro-pressure sensor with an isosceles trapezoidal beam-membrane (ITBM) is proposed in this paper, consisting of a square silicon membrane, four isosceles trapezoidal beams (ITBs) and four piezoresistors. To investigate how the elastic silicon membrane affects pressure sensitive characteristics, simulation models based on ANSYS 15.0 software were used to analyze the effect of structural dimension on the characteristics of pressure sensor. According to that, the chips of micro-pressure sensors were fabricated by micro-electro-mechanical system (MEMS) technology on a silicon wafer with 〈 1 0 0 〉 orientation. The experimental results show that the proposed sensor achieves a better sensitivity of 9.64 mV/kPa and an excellent linearity of 0.09%F.S. in the range of 0–3.0 kPa at room temperature and a supply voltage of 5.0 V, with a super temperature coefficient of sensitivity (TCS) about - 2180 ppm/ ∘ C from −40 ∘ C to 85 ∘ C and low pressure measurement less than 3.0 kPa. [ABSTRACT FROM AUTHOR]

To research the piezoresistive properties of SiC thin films, a testing structure consisting of a cantilever beam, SiC thin films piezoresistors and a Cr/Pt electrode is proposed in this paper. The chips of testing structure were fabricated by micro-electro-mechanical system (MEMS) technology on a silicon wafer with 〈 100 〉 orientation, in which SiC thin films were deposited by using radio-frequency (13.56 MHz) magnetron sputtering method. The effect of sputtering power, annealing temperature and time on the microstructure and morphology of the SiC thin films were investigated by the X-ray diffraction (XRD) and scanning electron microscopy (SEM). It indicates that a good continuity and uniform particles on the SiC thin film surface can be achieved at sputtering power of 160 W after annealing. To verify the existence of Si–C bonds in the thin films, X-ray photoelectron spectroscopy (XPS) was used. Meanwhile, the piezoresistive properties of SiC thin films piezoresistors were measured using the proposed cantilever beam. The test result shows that it is possible to achieve a gauge factor of 35.1. [ABSTRACT FROM AUTHOR]

A silicon magnetic sensitive transistor (SMST) with the negative resistance oscillation phenomenon is presented in this paper. The SMST of cubic structure is composed of three regions and three electrodes (E, C and B). Two of the regions (collector region and base region) are designed on the top surface of the SMST, and the emitter region is designed at the bottom of the SMST. Using microelectromechanical system (MEMS) technology, the chip is fabricated on 〈 1 0 0 〉 orientation p-type silicon (near intrinsic) wafer and packaged on printed circuit board (PCB). When collector voltage (V ce ) and the base injecting current (I b ) are a certain value, the experimental results show that the collector current (I c ) attains negative resistance oscillation phenomenon and it is influenced by the external magnetic field (B) and temperature (T). Based on the effect of deep-level impurities on the carrier net recombination rate, theoretical analysis demonstrates that the deep-level impurities are the main factors of the appearance for oscillations phenomenon. [ABSTRACT FROM AUTHOR]

In this paper, a force sensor based on piezoelectric effect of Li-doped ZnO (LZO) thin films was presented, which constituted by Pt/LZO/Pt/Ti functional layers and Si cantilever beam. The chips were designed and fabricated by micro electro-mechanical system (MEMS) technology on silicon wafer with 〈100〉 orientation. In this sandwich structure, the top electrode (TE) was Pt and bottom electrode (BE) was Pt/Ti, LZO piezoelectric thin films were prepared by radio frequency (RF) magnetron sputtering method. The microstructure and morphology were analyzed through X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM), analysis results shows that the LZO thin films with highly c-axis orientation and uniform grain size distribution under sputtering power of 220 W. The experimental results show, when external force loaded on the tip of the beam, the output voltage (Vpp) was 280.3 mV at external force of 5 N, the sensitivity of the proposed sensor was 46.1 mV/N in the range of 1–5 N. [ABSTRACT FROM AUTHOR]

To further improve the sensitivity temperature characteristics of pressure sensor, a kind of pressure sensor taking nanopolysilicon thin films as piezoresistors is proposed in this paper. On the basis of the microstructure analysis by X-ray diffraction (XRD) and scanning electron microscope (SEM) tests, the preparing process of nanopolysilicon thin films is optimized. The effects of film thickness and annealing temperature on the micro-structure of nanopolysilicon thin films were studied, respectively. In order to realize the measurement of external pressure, four nanopolysilicon thin films resistors were arranged at the edges of square silicon diaphragm connected to a Wheatstone bridge, and the chip of the sensor was designed and fabricated on a orientation silicon wafer by microelectromechanical system (MEMS) technology. Experimental result shows that when = 6.80 mA, the sensitivity of the sensor PS-1 is 0.308 mV/kPa, and the temperature coefficient of sensitivity (TCS) is about −1742 ppm/C in the range of −40-140C. It is possible to obviously improve the sensitivity temperature characteristics of pressure sensor by the proposed sensors. [ABSTRACT FROM AUTHOR]

A monolithic-integrated 3-D magnetic field sensor is proposed in this paper, which is composed of four silicon magnetic sensitive transistors and a Hall magnetic field sensor. Using microelectromechanical system (MEMS) technology, the chip of the sensor was designed and fabricated on a p-type silicon wafer with a higher resistivity. At the room temperature, the magnetic sensitivities Sxx and Syy on the x - and y -directions are 77.5 and 78.6 mV/T at power supply VDD= 5.0 V and base injection current Ib= 1.0 mA, respectively. In addition, the magnetic sensitivity Szz on the z -axis is 77.4 mV/T at V_{DD}= 5.0 V. The experimental results show that the proposed sensor has a good uniformity of magnetic sensitivity, besides achieving the measurement to 3-D magnetic fields and the cross sensitivities are less than 3% at B\le 0.8$ T. [ABSTRACT FROM PUBLISHER]

A three-axis accelerometer with a double L-shaped beams structure was designed and fabricated in this paper, consisting of a supporting body, four double L-shaped beams and intermediate double beams connected to two mass blocks. When applying acceleration to the accelerometer chip, according to the output voltage changes of three Wheatstone bridges constituted by twelve piezoresistors on the roots of the beams, the corresponding acceleration along three axes can be measured based on the elastic force theory and piezoresistive effect. To improve the characteristics of the three-axis accelerometer, we simulated how the width of the intermediate double beams affected the characteristics. Through optimizing the structure size, six chips with different widths of intermediate double beams were fabricated on silicon-on-insulator (SOI) wafers using micro-electromechanical systems (MEMS) technology and were packaged on printed circuit boards (PCB) by using an electrostatic bonding process and inner lead bonding technology. At room temperature and VDD = 5.0 V, the resulting accelerometer with an optimized size (w = 500 μm) realized sensitivities of 0.302 mV/g, 0.235 mV/g and 0.347 mV/g along three axes, with a low cross-axis sensitivity. This result provides a new strategy to further improve the characteristics of the three-axis accelerometer. [ABSTRACT FROM AUTHOR]

In this paper, a double piezoelectric layer acceleration sensor based on Li-doped ZnO (LZO) thin film is presented. It is constituted by Pt/LZO/Pt/LZO/Pt/Ti functional layers and a Si cantilever beam with a proof mass. The LZO thin films were prepared by radio frequency (RF) magnetron sputtering. The composition, chemical structure, surface morphology, and thickness of the LZO thin film were analyzed. In order to study the effect of double piezoelectric layers on the sensitivity of the acceleration sensor, we designed two structural models (single and double piezoelectric layers) and fabricated them by using micro-electro-mechanical system (MEMS) technology. The test results show that the resonance frequency of the acceleration sensor was 1363 Hz. The sensitivity of the double piezoelectric layer was 33.1 mV/g, which is higher than the 26.1 mV/g of single piezoelectric layer sensitivity, both at a resonance frequency of 1363 Hz. [ABSTRACT FROM AUTHOR]

A silicon-on-insulator (SOI) piezoresistive three-axis acceleration sensor, consisting of four L-shaped beams, two intermediate double beams, two masses, and twelve piezoresistors, was presented in this work. To detect the acceleration vector (ax, ay, and az) along three directions, twelve piezoresistors were designed on four L-shaped beams and two intermediate beams to form three detecting Wheatstone bridges. A sensitive element simulation model was built using ANSYS finite element simulation software to investigate the cross-interference of sensitivity for the proposed sensor. Based on that, the sensor chip was fabricated on a SOI wafer by using microelectromechanical system (MEMS) technology and packaged on a printed circuit board (PCB). At room temperature and VDD = 5.0 V, the sensitivities of the sensor along x-axis, y-axis, and z-axis were 0.255 mV/g, 0.131 mV/g, and 0.404 mV/g, respectively. The experimental results show that the proposed sensor can realize the detection of acceleration along three directions. [ABSTRACT FROM AUTHOR]

A novel piezoelectric energy harvester with multi-resonant frequencies based on Li-doped ZnO (LZO) thin films is proposed in this paper, consisting of an elastic element with three (or more) different length cantilever beam arrays and a piezoelectric structure (Al/Li-doped ZnO/Pt/Ti). The LZO thin films of piezoelectric structure were prepared on Pt/Ti/SiO2/Si by using a radio frequency (RF) magnetron sputtering method under certain process conditions. When the LZO thin films were deposited with an LZO target concentration of 5 wt%, the piezoelectric coefficient d33 was 9.86 pm/V. Based on this, the energy harvester chips were fabricated on a <100> silicon substrate using micro-electromechanical systems (MEMS) technology, and its performance can be measured by fixing it to a printed circuit board (PCB) test substrate. The experimental results show that, when exerting an external vibration acceleration of 2.2 g and a vibration frequency of 999 Hz, the energy harvester can achieve a big load voltage of 1.02 V at a load resistance of 600 kΩ, and a high load power of 2.3 µW at a load resistance of 200 kΩ. [ABSTRACT FROM AUTHOR]

A monolithically-integrated two-dimensional (2D) magnetic field sensor consisting of two difference structures (DSІ and DSII) is proposed in this paper. The DSІ and DSII are composed of four silicon magnetic sensitive transistors (SMST1, SMST2, SMST3 and SMST4) and four collector load resistors (RL1, RL2, RL3 and RL4). Based on the magnetic sensitive principle of SMST, the integrated difference structure can detect magnetic fields’ component (Bx and By) along the x-axis and y-axis, respectively. By adopting micro-electromechanical systems (MEMS) and packaging technology, the chips were fabricated on a p-type <100> orientation silicon wafer with high resistivity and were packaged on printed circuit boards (PCBs). At room temperature, when the VCE = 5.0 V and IB = 8.0 mA, the magnetic sensitivities (Sxx and Syy) along the x-axis and the y-axis were 223 mV/T and 218 mV/T, respectively. The results show that the proposed sensor can not only detect the 2D magnetic field vector (B) in the xy plane, but also that Sxx and Syy exhibit good uniformity. [ABSTRACT FROM AUTHOR]

An acceleration sensor based on piezoelectric thin films is proposed in this paper, which comprises the elastic element of a silicon cantilever beam and a piezoelectric structure with Li-doped ZnO piezoelectric thin films. The Li-doped ZnO piezoelectric thin films were prepared on SiO2/Si by radio frequency (RF) magnetron sputtering method. The microstructure and micrograph of ZnO piezoelectric thin films is analysed by a X-ray diffractometer (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and piezoresponse force microscopy (PFM), respectively. When the sputtering power of 220 W and Li-doped concentration of 5%, ZnO piezoelectric thin films have a preferred (002) orientation. The chips of the sensor were fabricated on the <100> silicon substrate by micro-electromechanical systems (MEMS) technology, meanwhile, the proposed sensor was packaged on the printed circuit board (PCB). The experimental results show the sensitivity of the proposed sensor is 29.48 mV/g at resonant frequency (1479.8 Hz). [ABSTRACT FROM AUTHOR]