xi Yu

Wireless passive polymer-derived SiCN ceramic sensor with integrated resonator/antenna

This paper presents a passive wireless polymer-derived silicon carbonitride (SiCN) ceramic sensor based on cavity radio frequency resonator together with integrated slot antenna. The effect of the cavity sensor dimensions on the Q-factor and resonant frequency is investigated by numerical simulation. A sensor with optimal dimensions is designed and fabricated. It is demonstrated that the sensor signal can be wirelessly detected at distances up to 20 mm. Given the high-temperature stability of the SiCN, the sensor is very promising for high-temperature wireless sensing applications.

Design and simulation of betavoltaic battery using large-grain polysilicon

In this paper, we present the design and simulation of a p-n junction betavoltaic battery based on large-grain polysilicon. By the Monte Carlo simulation, the average penetration depth were obtained, according to which the optimal depletion region width was designed. The carriers transport model of large-grain polysilicon is used to determine the diffusion length of minority carrier. By optimizing the doping concentration, the maximum power conversion efficiency can be achieved to be 0.90% with a 10 mCi/cm(2) Ni-63 source radiation.

Self-Packaging Fabrication of Silicon–Glass-Based Piezoresistive Pressure Sensor

A self-packaged piezoresistive pressure sensor was fabricated using a silicon-glass anodic bonding technique. The Wheatstone bridge piezoresistive sensing configuration was located on the lower surface of the silicon diaphragm and was vacuum sealed in a Si-glass cavity, and the embedded Al feedthrough lines at the Si-glass interface were used to realize the electrical connections between the piezoresistive sensing elements and hybrid metal electrode pads through Al vias and heavily doped diffusion zones. The pressure sensors demonstrate comparable performance characteristics, but a more simple process and low cost in comparison with the commercial Si-based piezoresistive pressure sensor. Due to the self-packaging protection, the pressure sensors are capable of handling harsh environments.

Silicon-glass-based single piezoresistive pressure sensors for harsh environment applications

National Natural Science Foundation of China [51075344, 61274120, 51175444]; Fujian Province Major Projects on University-Industry Cooperation in Science and Technology [2013H6023]; Science and Technology Program of Xiamen [3502Z20123008, 3502Z20126006]

Study on dielectric charging in low-stress silicon nitride with the MIS structure for reliable MEMS applications

Charge-induced failure has been recognized as a primary reliability issue in capacitive micro-actuators. In this paper, we present a simple method to assess the effect of dielectric charging on reliability of a capacitive micro-actuator. By capacitance–voltage measurements for a metal–insulator–semiconductor (MIS) structure, the characteristics of dielectric charging can be investigated, and the obtained results can be used to study the charging behavior of a capacitive micro-actuator. An analytical model based on this method has been established. The silicon-rich nitride film was deposited by low-pressure chemical vapor deposition on silicon substrate. The current–voltage and capacitance–voltage measurements exhibit an asymmetric electrical characteristic under different polarity of stress voltage. The charging parameters of the silicon-rich nitride were extracted by the stretched exponential curve fitting method. This charging behavior suggests that silicon-rich nitride can be negatively or positively charged, and the injection and transport of holes are more favored than the injection and transport of electrons. The charge injection from movable electrode plays a dominant role in the dielectric charging of a capacitive micro-actuator. It is expected that the charge accumulation in dielectrics can be eliminated by employing the bipolar square-wave voltage to actuate a capacitive micro-actuator.

A Si-Glass based pressure sensor with a single piezoresistive element for harsh environment applications

A Si-Glass based MEMS piezoresistive pressure sensor is designed for harsh environment applications, such as vibration, shock and environment conditions with humidity, alkalescence or acidity, electrostatic particles and so on. The sensor chips were fabricated using SOI wafer-glass anodic bonding technology, which enables a single boron-implanted piezoresistor to be on lower surface of silicon diaphragm and be vacuum-sealed in glass cavity. The sensing signals were led out by using the embedded Al electrode structure at the bonding interface of Si-glass to connect single piezoresistor, and two large-area Ni-Au pads are used to electrically connect to the print circuit board (PCB) by using the drag soldering technology instead of gold wire bonding. The characteristics of voltage-pressure were measured with constant current under different temperature conditions. A temperature compensation technology is used to calibrate the measured results, by which the sensitivity of 116 mV/ (mA·MPa) and accuracy of 5.8% F.S. are obtained.

GHz surface acoustic wave ultraviolet sensor based on photo-conductive lamellar Molybdenum Disulfide

This article reports the fabrication and characterization of a highly sensitive ultraviolet (UV) sensor based on Zinc Oxide (ZnO)/glass surface acoustic wave resonator (SAWR) with lamellar Molybdenum Disulfide (MoS2) as photo-conductive layer. The interdigital transducers (IDTs) with a periodicity of 2.4 μm were fabricated on SAWR by Electron Beam Lithography (EBL) technique, enabling a resonant frequency of 1.019 GHz in the SAWR. The SAWR UV sensor exhibited a linear up-shift in the frequency with UV intensity and a high sensitivity of 4.15 ppm/μW/cm2. The significant frequency-shift is attributed to high resonant frequency and excellent photoelectric properties of lamellar MoS2. The experimental results show the MoS2 coated ZnO/glass-based SAWR have great promise for wireless ultraviolet sensor applications.

Fabrication of silicon piezoresistive pressure sensor using a reliable wet etching process

Silicon-based piezoresistive pressure sensors are generally fabricated as a piezo-sensitive diaphragm by using MEMS technology and SOI wafer. Lots of innovations and improvements have been made for silicon pressure sensor to increase its performance and reliability. It is found that the quality of Si-Si bonding will directly affect the performing of SOI substrate removing processes. The main problem is that the etching liquid infiltrate into bonding interface from the defect position of bonding wafer edge, resulting in the damage and corrosion of bonding wafer. To solve this problem, the paper presents an etching fixture design for effectively protecting the bonding wafer edge. Experimentally, a SOI-Si bonding wafer with poor quality in bonding edge was used to fabricate the piezoresistive pressure sensors by using the etching fixture. The experimental results show the use of etching fixture did not damage the bonding wafer and made a nice removal of SOI substrate. The fabricated pressure sensors wafers are also presented.

Piezoresistive pressure sensors for harsh environments

To increase the stabilization and reliability of piezoresistive pressure sensors working in harsh environments with harsh acids,alkalis,corrosive salts,and other destructive substances such as electrostatic particles and damp,a novel piezoresistive pressure sensor was presented.The innovation of the sensor was that the sensing elements of the sensor were fabricated in the lower surface of a silicon diaphragm and were sealed in a vacuum pressure cavity by silicon-glass bonding process.The work principle of this pressure sensor was introduced.Then,Finite Element Method and ANSYS soft were used to simulate the stress distribution of the diaphragm.Finally,the micro-electro-mechanical System(MEMS) technology was used to fabricate a pressure sensor with the dimension of 1.5mm×1.5mm×500 μ m.The measurement results by apressure test platform show that the sensitivity of the sensor is about 20mV / V-MPa,and its maximum nonlinearity is 2.73% FSS,which meets the requirements of the modern industrial applications.