Wei-Cheng Lai

Design and Implementation of a Capacitive-Type Microphone With Rigid Diaphragm and Flexible Spring Using the Two Poly Silicon Micromachining Processes

This study reports the design and implementation of a novel capacitive-type micromachined microphone. The design of the microphone is based on the well-known two poly-Si layers micromachining processes. The microphone consists of a rigid diaphragm (the 2nd poly-Si layer), flexible springs (the 1st ply-Si layer), and rigid back plate (the 1st poly-Si layer). In short, the proposed microphone design has four merits, (1) the rigid diaphragm acting as the acoustic wave receiver and moving electrode is realized using the rib-reinforced poly-Si layer, (2) the flexible spring acting as the electrical routing as well as supporter for diaphragm is implemented using the thin poly-Si film, (3) the electrical routing of rigid diaphragm (moving electrode) is through the central poly-via and the flexible spring, and (4) the rigid plate acting as the stationary electrodes and back plate is fabricated using the high-aspect-ratio (HARM) trench-refilled poly-Si. To demonstrate the feasibility, the two poly-Si microphone has been implemented and tested. Typical measurement results show that the open-circuit sensitivity of the microphone was 12.63 mV/Pa ( -37.97 dBV/Pa) at 1 kHz. (the reference sound-level is 94 dB).

Implementation of a New Capacitive Touch Sensor Using the Nanoporous Anodic Aluminum Oxide (np-AAO) Structure

This study reports the implementation of a high-performance capacitive-type touch sensor by using the nanoporous anodic aluminum oxide (np-AAO) layer. The np-AAO layer is batch fabricated as the template to enable the direct formation of nanotexture metal film after deposition. The np-AAO is also exploited as the dielectric layer. Thus, the integration of np-AAO layer and the nanotexture metal film is employed to realize a metal-insulator-metal parallel-plate capacitance sensor. The sensitivity of the capacitive-type touch sensor is enhanced by the nanostructures. In application, the Au and Al metal layers and np-AAO are fabricated on Si substrate to form the parallel-plate capacitor. The testing demonstrates the np-AAO-based touch sensor has higher sensitivity. In addition, the detection of small object such as Drosophila using the fabricated np-AAO-based touch sensor is also demonstrated.

Micro devices integration with large-area 2D chip-network using stretchable electroplating copper spring

This study presents a large-area multi-devices integration scheme using stretchable electroplated copper spring. Each device is located on the silicon-node of a 2D chip-network distributed, which are mechanically and electrically connected to surrounding devices by stretchable copper spring. The springs stretch and expand the functional devices by several orders of magnitude area forming a variable-density network of interconnected devices. Advantages of this approach include: (1) using existing process technologies and materials for semiconductor in large-area applications, compatible with foundry fabrication processes; (2) stretchable electroplated copper springs with large maximum strain act as both mechanical and electrical connections between devices; (3) silicon-nodes act as hubs for device implementation and integration; and (4) the chip-network can be applied to 2D-curved (spherical) surfaces. The proposed expandable network using stretchable springs integrated with multiple devices has been implemented and tested.

A normally closed MEMS micro reed switch with fill in liquid metal micro hinge structure

This study has successfully designed and implemented the first normally-closed (NC) micro reed switch (Fig.1). The NC-type reed switch consists three separate metal structures (hinge, movable pad/spring, and fixed-pad) and is assembled by an attractive magnetic force exerted by an out-of-plane magnetic field. Furthermore, as applying a strong enough in-plane magnetic field, the spring is deformed by repulsive magnetic force to separate the pads and turn-off the switch (Fig.2). Merits of this NC reed switch: (1) liquid-metal to ensure electrical connection at hinge, (2) UV-gel fixed hinge structure, and (3) magnetized repulsive actuating mechanism. Experiment demonstrates a typical fabricated NC reed switch with driving magnetic field of near 160Gauss (G), and releasing at near 150G. The contact resistance is between 0.2-5Ω. The contact resistance variation is near 13% under a 20G excitation.

Novel two-stage CMOS-MEMS capacitive-type tactile-sensor with ER-fluid fill-in for sensitivity and sensing range enhancement

This study has presented a novel two-stage CMOS-MEMS capacitance-type tactile sensor with ER-fluid fill-in to extend the sensing range. Merits of the sensor are: (1) small tactile force (mN) is detected by first-stage sensing-unit with sensing range modulated by driving-voltage through ER-fluid; (2) larger tactile force (N) is detected by the second-stage sensing-unit. Moreover, sensing range and sensitivity can be further modulated using different ER-fluid. This tactile-sensor is implemented using TSMC 0.18μm 1P6M CMOS process, in-house post-CMOS releasing, ER-fluid filling, and parylene sealing process. Measurement results demonstrate the modulation of sensing ranges are 0~50mN (as the bias-voltage for ER-fluid is 0-1V), and 0~90mN (as the bias-voltage for ER-fluid is 10V); sensitivities are 0.15fF/mN (bias-voltage for ER-fluid is 0-1V) and 0.1fF/mN (bias-voltage for ER-fluid is 10V) for first-stage. Moreover, the second-stage has a larger sensing range (0~2.5N) and the sensitivity can also be modulated by bias voltage (3.55fF/N for 0.5V and 3fF/N for 5V).

Design and implementation of a novel double-poly microphone with rigid acoustic receiver, flexible spring supporter, and harm backplate

This study reports the design and implementation of a novel micromachined microphone. The design of the microphone is based on the well-known two-poly processes. The design as shown in Fig.1 has four merits, (1) rigid-diaphragm formed by the rib-reinforced poly-Si as acoustic wave receiver and moving-electrodes, (2) flexible-spring formed by thin poly-Si as diaphragm supporter, (3) rigid-diaphragm anchored to flexible-spring by central poly-via, and (4) very rigid plate formed by high-aspect-ratio (HARM) trench-refilled poly-Si as stationary-electrodes and back-plate. To demonstrate the feasibility, the two-poly microphone has been implemented and tested. Typical measurement results show that the sensitivity of microphone is 12.63 mV/Pa (−37.97 dB/Pa) measured at the sound level of 94 dB.