With the development of 3D integration technology, microsystems with vertical interconnects are attracting attention from researchers and industry applications. Basic elements of integrated passive devices (IPDs), including inductors, capacitors, and resistors, could dramatically save the footprint of the system, optimize the form factor, and improve the performance of radio frequency (RF) systems. In this paper, IPDs using thin film built-up technology are introduced, and the design and characterization of coplanar waveguides (CPWs), inductors, and capacitors are presented.

Manufacturing and integration of micro-electro-mechanical systems (MEMS) devices and integrated circuits (ICs) by wafer bonding often generate problems caused by thermal properties of materials. This paper presents a low temperature wafer direct bonding process assisted by O₂ plasma. Silicon wafers were treated with wet chemical cleaning and subsequently activated by O₂ plasma in the etch element of a sputtering system. Then, two wafers were brought into contact in the bonder followed by annealing in N₂ atmosphere for several hours. An infrared imaging system was used to detect bonding defects and a razor blade test was carried out to determine surface energy. The bonding yield reaches 90%–95% and the achieved surface energy is 1.76 J/m² when the bonded wafers are annealed at 350 °C in N₂ atmosphere for 2 h. Void formation was systematically observed and elimination methods were proposed. The size and density of voids greatly depend on the annealing temperature. Short O₂ plasma treatment for 60 s can alleviate void formation and enhance surface energy. A pulling test reveals that the bonding strength is more than 11.0 MPa. This low temperature wafer direct bonding process provides an efficient and reliable method for 3D integration, system on chip, and MEMS packaging.

 

A planar capacitive sensor (PCS) capable of 2D large-scale measurement is presented in this paper. Displacement interpretation depends on independently measuring the periodic variation in capacitance caused by the change in the overlapping area of sensing electrodes on a moving plate and a fixed plate. By accumulating the number of quarters in each direction and the specific position in the final quarter, the large-scale measurement is fulfilled. Displacements in X- and Y-direction can be measured independently and simultaneously. Simulation shows that a shorter gap distance and a longer electrode guarantee better sensitivity. Experiments based on a PCS test bench demonstrate that the PCS has a sensitivity of 0.198 mV/μm and a resolution of 0.308 μm. An electric fringe effect and other possible measurement errors on displacement interpretation accuracy are discussed. The study confirms the high potential of PCSs as innovative 2D long-range displacement sensors.

High temperature co-fired ceramics (HTCCs) have wide applications with stable mechanical properties, but they have not yet been used to fabricate sensors. By introducing the wireless telemetric sensor system and ceramic structure embedding a pressure-deformable cavity, the designed sensors made from HTCC materials (zirconia and 96% alumina) are fabricated, and their capacities for the pressure measurement are tested using a wireless interrogation method. Using the fabricated sensor, a study is conducted to measure the atmospheric pressure in a sealed vessel. The experimental sensitivity of the device is 2 Hz/Pa of zirconia and 1.08 Hz/Pa of alumina below 0.5 MPa with a readout distance of 2.5 cm. The described sensor technology can be applied for monitoring of atmospheric pressure to evaluate important component parameters in harsh environments.

This paper presents the design, fabrication, and characterization of a quartz tuning fork temperature sensor based on a new ZY-cut quartz crystal bulk acoustic wave resonator vibrating in a flexural mode. Design and performance analysis of the quartz tuning fork temperature sensor were conducted and the thermal sensing characteristics were examined by measuring the resonance frequency shift of this sensor caused by an external temperature. Finite element method is used to analyze the vibratory modes and optimize the structure of the sensor. The sensor prototype was successfully fabricated and calibrated in operation from 0 to 100 °C with the thermo-sensitivity of 70×10^?6/°C. Experimental results show that the sensor has high thermo-sensitivity, good stability, and good reproducibility. This work presents a high-precision low-power temperature sensor using the comprehensive thermal characterization of the ZY-cut quartz tuning fork resonator.

A trapezoidal cantilever density sensor is developed based on micro-electro-mechanical systems (MEMS) technology. The sensor measures fluid density through the relationship between the density and the resonant frequency of the cantilever immersed in the fluid. To improve the sensitivity of the sensor, the modal and harmonic response analyses of trapezoidal and rectangular cantilevers are simulated by ANSYS software. The higher the resonant frequency of the cantilever immersed in the fluid, the higher the sensitivity of the sensor; the higher the resonant strain value, the easier the detection of the output signal of the sensor. Based on the results of simulation, the trapezoidal cantilever is selected to measure the densities of dimethyl silicone and toluene at the temperature ranges of 30 to 55 °C and 26 to 34 °C, respectively. Experimental results show that the trapezoidal cantilever density sensor has a good performance.

Bulk acoustic wave resonators with piezoelectric films have been widely explored for the small size and high quality factor (Q) at GHz. This paper describes a high overtone bulk acoustic resonator (HBAR) based on Al/ZnO/Al sandwich layers and c-axis sapphire substrate. ZnO film with high quality c-axis orientation has been obtained using DC magnetron sputtering. The fabricated HBAR presents high Q at the multiple resonances from a 0.5–4.0 GHz wide band with a total size (including the contact pads) of 0.6 mm×0.3 mm×0.4 mm. The device exhibits the best acoustic coupling at around 2.4 GHz, which agrees with the simulation results based on the one-dimensional Mason equivalent circuit model. The HBAR also demonstrates Q values of 30 000, 25 000, and 6500 at 1.49, 2.43, and 3.40 GHz, respectively. It is indicated that the HBAR has potential applications for the low phase noise high frequency oscillator or microwave signal source.

A micromachining technique is presented for the fabrication of resin-bonded permanent magnets in the microscale. Magnetic paste is prepared from NdFeB powder and an epoxy resin, filled into lithographically defined photoresist molds or metal molds, and formed into resin-bonded magnets after curing at room temperature. A coercivity of 772.4 kA/m, a remanence of 0.27 T, and a maximum energy product of 22.6 kJ/m³ have been achieved in an NdFeB disk micromagnet with dimensions of Ф200 μm×70 μm. Based on the developed micro-patterning of resin-bonded magnets, a fully integrated electromagnetic vibration energy harvester has been designed and fabricated. The dimensions of the energy harvester are only 4.5 mm×4.5 mm×1.0 mm, and those of the micromagnet are 1.5 mm×1.5 mm×0.2 mm. This microfabrication technique can be used for producing permanent magnets tens or hundreds of micrometers in size for use in various magnetic devices.

A Ka-band sub-harmonically pumped resistive mixer (SHPRM) was designed and fabricated using the standard 0.18-μm complementary metal-oxide-semiconductor (CMOS) technology. An area-effective asymmetric broadside coupled spiral Marchand balance-to-unbalance (balun) with magnitude and phase imbalance compensation is used in the mixer to transform local oscillation (LO) signal from single to differential mode. The results showed that the SHPRM achieves the conversion gain of ?15–?12.5 dB at fixed f_IF=0.5 GHz with 8 dBm LO input power for the radio frequency (RF) bandwidth of 28–35 GHz. The in-band LO-intermediate freqency (IF), RF-IF, and LO-RF isolations are better than 31, 34, and 36 dB, respectively. Besides, the 2LO-IF and 2LO-RF isolations are better than 60 and 45 dB, respectively. The measured input referred P1dB and 3rd-order inter-modulation intercept point (IIP3) are 0.5 and 10.5 dBm, respectively. The measurement is performed under a gate bias voltage as low as 0.1 V and the whole chip only occupies an area of 0.33 mm² including pads.

This paper proposes a novel multi-pulse flexible-topology thyristor rectifier (FTTR) that can operate over a large voltage range while maintaining a low total harmonic distortion (THD) in the input current. The proposed multi-pulse FTTR has two operating modes: parallel mode and series mode. Irrespective of the mode in which it operates, the multi-pulse FTTR maintains the same pulses in the load current. To mitigate the harmonic injection into the AC mains, the topology-switching mechanism is then proposed. In addition, predictive current control is employed to achieve fast current response in both the transience and the transitions between modes. To verify the effectiveness of the multi-pulse FTTR as well as the control scheme, performance analysis based on an 18-pulse FTTR is investigated in detail, including fault tolerance evaluation, current THD analysis based on IEEE standard, and potential applications. Finally, a simulation model and the corresponding laboratory setup are developed. The results from both simulation and experiments demonstrate the feasibility of the proposed multi-pulse FTTR as well as the control scheme.