Fabrication of 2-D Capacitive Micromachined Ultrasonic Transducer (CMUT) Array through Silicon Wafer Bonding

Capacitive micromachined ultrasound transducers (CMUTs) have broad application prospects in medical imaging, flow monitoring, and nondestructive testing. CMUT arrays are limited by their fabrication process, which seriously restricts their further development and application. In this paper, a vacuum-sealed device for medical applications is introduced, which has the advantages of simple manufacturing process, no static friction, repeatability, and high reliability. The CMUT array suitable for medical imaging frequency band was fabricated by a silicon wafer bonding technology, and the adjacent array devices were isolated by an isolation slot, which was cut through the silicon film. The CMUT device fabricated following this process is a 4 × 16 array with a single element size of 1 mm × 1 mm. Device performance tests were conducted, where the center frequency of the transducer was 3.8 MHz, and the 6 dB fractional bandwidth was 110%. The static capacitance (29.4 pF) and center frequency (3.78 MHz) of each element of the array were tested, and the results revealed that the array has good consistency. Moreover, the transmitting and receiving performance of the transducer was evaluated by acoustic tests, and the receiving sensitivity was −211 dB @ 3 MHz, −213 dB @ 4 MHz. Finally, reflection imaging was performed using the array, which provides certain technical support for the research of two-dimensional CMUT arrays in the field of 3D ultrasound imaging.

A Capacitive MEMS Inclinometer Sensor with Wide Dynamic Range and Improved Sensitivity

This paper proposes a novel capacitive liquid metal microelectromechanical system (MEMS) inclinometer sensor and introduces its design, fabrication, and signal measurement. The sensor was constructed using three-layer substrates. A conductive liquid droplet was rolled along an annular groove of the intermediate substrate to reflect angular displacement, and capacitors were used to detect the position of the droplet. The numerical simulation work provides the working principle and structural design of the sensor, and the fabrication process of the sensor was proposed. Furthermore, the static capacitance test and the dynamic signal test were designed. The sensor had a wide measurement range from ±2.12° to ±360°, and the resolution of the sensor was 0.4°. This sensor further expands the measurement range of the previous liquid droplet MEMS inclinometer sensors.

Extraction of Equivalent Circuit Parameter of the GIS Pipe Spacer

In Gas Insulated Switchgear (GIS) substation, the spacer used for supporting conductor, isolating air chamber and insulation is a very important insulation component in GIS pipe, and it is important to study the spacer to ensure the insulation performance and quality of GIS. Local distortion of electric field distribution will be produced when electromagnetic wave propagates to spacers. In this article, the static capacitance calculated by electromagnetic simulation is used to model spacers.

Effect of Grinding-Induced Stress on Interface State Density of SiC/SiO2

Back-grinding process was applied to the 4H-SiC (0001) epitaxial wafers. We found that the parameters about stress increased after back-grinding process. In our work, the characterization of stress on interface state density (Dit) of SiC/SiO2 was investigated. Furthermore, the absorption of peak frequencies was also observed by fourier transform infrared spectroscopy attenuated total reflection (ATR-FTIR) analysis, and the Dit of SiC/SiO2 was obtained by quasi-static capacitance voltage (QSCV) measurement as well as C-φs method. The above results suggested that the Dit increased with the increasing grinding-induced stress.