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This paper presents a pair of trapezoid microcantilever probes with a monolithic micromachined thermocouple for inspecting the electrical and thermal properties of Micro-LED. To meet testing requirements, one of the microcantilevers was designed as a single-layer Ni structure for electrical conduction, while the other one, which consists of n-type poly-Si, SiO₂ and Ni layers, was used for temperature sensing. Both microcantilevers were fabricated by using Si bulk micromachining, thin film deposition, and electroplating processes. Fabrication result shows the length of each probe is about 78 μm and 118 μm, and the thicknesses of the microcantilevers and probe tip are 7.2 μm and 5.5 μm. Experiment results depict that the thermocouple junction between Ni layer and poly-Si achieves a good ohmic contact, and the measured sheet resistances for poly-Si and electroplated Ni are 150 Ω /sq and 0.01 Ω /sq. This suggests that the induced thermoelectric voltage can be generated and detected in response to a temperature difference. Mechanical tests verified that the probes provide an available elastic deflection to guarantee that the probe tips can exactly contact the Micro-LED electrodes, with a low contact force. The thermoelectric characteristics of the device have been further confirmed and calibrated on the basis of the measurement results of a commercial mm-sized LED in cooperation with an infrared camera. For the subject of the Micro-LED chip with a square size of 75 μm, its electrical and thermal properties were successfully determined, as the measured chip temperature is 52 °C at the applied current of 100 μA. [2021-0053]

This study presents the design and realization of a piezoelectric MEMS microspeaker for high-frequency enhancement. Based on piezoelectric thin film actuation, designs of cantilever diaphragms are conducted by modal analysis. Under a die size of 2.5 mm (w) × 5 mm (l) × 0.4 mm (t), the diaphragms are designed to include mid-range and tweeter units with regard to the balance of radiation area and sound pressure contribution. Furthermore, the out-of-phase driving of the proposed device can ensure that the superposition of the sound pressure level (SPL) is within the target frequency range (8–13 kHz) while reducing the SPL outside the target range. In pressure-field measurements, the proposed multi-shape cantilever array can produce high average SPL (91.6 dB) in the target frequency range from 8 kHz to 13 kHz and has a low total harmonic distortion (THD) of rms input signal. The performance can be further improved by biasing the input signal. With a 9 V bias, the average SPL of the proposed microspeaker in the target frequency range is enhanced to 99.4 dB, and the average THD is reduced to

This study presents the design and implementation of a MEMS capacitive tactile force sensor with polydimethylsiloxane (PDMS) filler for in-process and in-use modulation of the sensing range and sensitivity performance. The presented MEMS tactile force sensor consists of a loading unit with driving electrodes, PDMS filler, and a sensing unit. By varying input voltages on the driving electrodes (either in curing process or in-use), the stiffness of the PDMS filler as well as the loading unit can be modulated. Thus, the sensitivity and sensing range of the presented tactile force sensor was modulated accordingly. Since each sensor has its own driving electrodes and electrical routings, different input voltages can be applied to modulate the PDMS for each individual sensor. As a result, tactile sensors of different sensitivities and sensing ranges can be simultaneously fabricated and monolithically integrated on the same chip using the presented approach. The tactile sensors were implemented using TSMC $0.18~\mu \text{m}$ 1P6M standard CMOS process together with the in-house post-CMOS releasing and the polymer filling processes. Experiments demonstrate the capabilities of implementing various tactile sensors with different sensing ranges and sensitivities on a single chip by the in-process and in-use modulation techniques. Through the in-process and in-use modulation, the presented CMOS-MEMS tactile sensors show the sensing window: (1) for sensitivity modulation: 8.6 fF/N to 219.1 fF/N, and (2) for sensing range modulation: 30 mN to 270 mN.

This article proposed a novel design for the monolithic micro-LED array, directly integrated with a sapphire microreflector. Its resolution was 300 dpi. Theoretically, each micro-LED pixel owns an individual sapphire microreflector which can directly concentrate rays from an emitting source. Therefore, this study proposed that the optical crosstalk between neighboring micro-LED pixels could be suppressed and the contrast of the micro-LED array improved; as this would be especially beneficial for display. The simulation results showed that the increased thickness of the sapphire microreflector could further improve the optical performance of the micro-LED array. For the fabrication process, the key technology was an integrated process involving the inductively coupled plasma (ICP) etching technology for sapphire and micro-LED fabrication, which was used to fulfill the proposed and reference micro-LED arrays. The measurement results showed that the sapphire microreflector could effectively concentrate the emitting rays and increase the contrast of the micro-LED array. In addition, it also indicated that the inclination angle of the microreflector could further improve optical performance. Therefore, this approach was verified to be capable of improving the performance of the micro-LED display.

This study demonstrates the integration of thermoelectric type MEMS infrared (IR) sensor with plasmonic metamaterial absorber (PMA) through a standard CMOS process platform to improve the responsivity of MEMS IR sensor in a specific range of wavelength. Based on an existing thermoelectric IR sensor with the serpentine film structure, the proposed device further combines with a Metal-Insulator-Metal (MIM) type PMA. The absorber consists of a top antenna layer, a middle dielectric spacer, and a bottom reflector, and the metal and dielectric films in the standard CMOS process are exploited in this study to implement the MIM design. The advantage of narrow linewidth in CMOS process can meet the need of critical dimensions for MIM antennas. The absorption wavelength can be adjusted by varying the pattern and dimension of antennas. The MIM PMAs are designed in the coupling regime, and hence the shifting of absorbed wavelength caused by the variation of antenna dimensions from fabrication can be prevented. The feasibility of the presented MIM PMA is demonstrated by simulations and experiments. The absorption spectra measured by FTIR show the capability of proposed MIM PMAs in extending the absorption range of far-infrared. Measurement results also indicate that under the same sensor footprint and the equal number of thermocouples, the device integrated with the proposed MIM PMA has a 20 percent improvement in responsivity as well as detectivity.

This study presents a backside loading design inductive tactile sensor with the monolithic integration of thermometer. Based on the commercially available standard complementary metal-oxide-semiconductor (CMOS) process (the TSMC $0.35\mu \text{m}$ 2P4M CMOS process) and the in-house post CMOS processes, the sensing chip is designed and implemented. The electrical connection is further achieved by using the flip-chip bonding process, and hence the breakage of bonding wires by the tactile load can be avoided. The CMOS sensing chip consists of the magnetic sensing coil and the polysilicon RTD (resistive thermal detector). Moreover, a cavity is defined on the backside (silicon substrate) of CMOS chip to act as a mold for the polymer filler as well as the housing for the chrome steel ball contact interface. The tactile force will cause the polymer deformation and chrome steel ball displacement, and further lead to the magnetic flux change on the sensing coil. Thus, the tactile force is detected by the inductance variation of magnetic sensing coil on the CMOS chip. Moreover, the temperature variation is detected by the resistance change of RTD thermometer, and the in-situ temperature monitoring during tactile loading is achieved. The force response of the proposed tactile sensor and the temperature response of the thermometer have been characterized. The influence of temperature variation on the tactile sensor has also been calibrated. Moreover, the characteristics of the thermometer on sensing chip at different contact conditions are also investigated.

This study presents the design, implementation, and characterization of 1D resonant type micro-electro-mechanical-systems (MEMS) piezoelectric scanning mirrors with different actuator designs to investigate their influences on the figure of merits (FoMs) for automotive light detection and ranging application. The MEMS scanning mirrors are driven by lead zirconate titanate (PZT) thin film in this study owing to its outstanding piezoelectric properties. Three different beam-type piezoelectric actuators are designed, including the reference meander straight-beam actuator design, and the proposed meander curved-beam and straight-curved tapered beam actuator designs. Simulations show the scan angle enhancement for two proposed designs, yet the resonant scanning frequency of meander curved-beam design dropped to below the 2 kHz requirement. To evaluate the designs, scanning mirrors with two proposed actuators are fabricated and tested. Measurements show that the resonant frequencies for the two proposed MEMS scanning mirrors are 1735 Hz and 2578 Hz, respectively. Two proposed designs respectively have the maximum optical angles of 48.1° and 50.6° at the 20 Vpp driving voltage. Due to the much higher stress on the beam structure induced by the misalignment of PZT film, the actuator could not reach the predicted scanning angle of near 80°. In comparison of the two proposed designs, the straight-curved tapered beam actuator design could enhance the FoM for about 56%. In summary, the performances of piezoelectric MEMS scanning mirror can be improved by varying the designs of length and shape of actuator, and the distribution of PZT film on the suspended actuator is also a critical design concern.

This paper reports on a 1D PZT micromirror integrated with buried piezoresistors for quasi-static feedback position control. The piezoresistors located along or below the PZT actuators could achieve the sensitivity as high as 3.1 mV/°, which was two orders of magnitude higher than the traditional ones located at the torsion springs (8.2 μV/°). This increased the signal-to-noise ratio by 2 orders of magnitude, which could enable the accurate position control. The response of the longitudinal sensors along the beams had a fast settling time less than 1 ms. The average position error was 0.975%, which was much better than that from the conventional shear stress sensor on the torsion bar of 3.1%.

This letter presents a simple approach to implement the inductive-type micro tri-axial tactile sensor by integrating a complementary metal–oxide–semiconductor (CMOS) chip with sensing coils and a stainless steel sheet (as the sensing interface) using polymer encapsulation. In addition to the component integration, the polymer layer is exploited as the spring for the tactile sensor. The proposed CMOS-MEMS inductive tri-axial tactile sensor presents several features and advantages as follows: 1) the gap-closing inductive sensing approach is used for normal force ( ${Z}$ -axis) detection; 2) the area-change inductive sensing method is adopted for shear forces’ ( ${X}$ -axis and ${Y}$ -axis) detection; 3) the compact sensing coil array is implemented using the standard CMOS process; and 4) the polymer is employed as the encapsulation layer to cover and integrate the rigid stainless steel sheet sensing interface and the CMOS chip, while also acting as the spring to avoid the fragile suspended thin-film structure. To demonstrate the concept, a CMOS sensing chip with a $2\times 2$ coil array is fabricated using the Taiwan Semiconductor Manufacturing Company standard process and is further integrated with a stainless steel sheet prepared by laser machining. The measurements indicate that the typical fabricated tri-axial inductive tactile sensor exhibits a normal load sensitivity ( ${Z}$ -axis) of 2.9 nH/N, an ${X}$ -axis shear force sensitivity of 17.4 nH/N, and a ${Y}$ -axis shear force sensitivity of 15.3 nH/N.