Silicon Micromachining Technology Research Articles

Development and evaluation of a three-component micro-cutting force wireless measurement apparatus and method in turning-milling compound machining

As a supplement to silicon micromachining technology, micro-turning-milling compound machining technology is perceived as a core requirement for non-silicon complex three-dimensional microstructures. In the micro-turning-milling compound machining process, three-component cutting force is the key factor that affects machining accuracy, surface roughness, machining efficiency and processing stability of the component; it is also a prerequisite in determining reasonable cutting parameters and in the machining process. In this study, a new design scheme of ‘direct measurement, wireless transmission’ was proposed to measure the three-component micro-cutting force in a turning-milling-compound machining process. On one hand, the three-component micro-cutting force was measured directly by four sensors installed on the turning spindle. On the other hand, the measured cutting force was sent to a computer indirectly through a Zigbee wireless communication system. Furthermore, a three-component micro-force sensor and wireless measurement apparatus were proposed for the measurement of the three-component micro-cutting force. A series of simulations were conducted to verify the performance of the designed sensor and the wireless measurement apparatus. A calculation method was proposed to extract the three-component cutting force from the 12 channels of signals from four force sensors during static and dynamic measurement. Calibration experiments for the designed sensor, as well as for the whole measuring apparatus, were conducted both statically and dynamically. A series of actual turning-milling compound machining experiments on a turning-milling-lapping compound five-axis NC machine tool was also presented. The results of calibration, and actual machining, experiments indicate that the proposed apparatus and method work well and could measure a three-component cutting force to an uncertainty of ±2‰.

Fabrication of a silicon based vertical sensitive low-g inertial micro-switch for linear acceleration sensing

Most of the MEMS inertial switches developed in recent years are intended for shock and impact sensing with a threshold value above 40 g. These switches were designed as lateral sensitive and were fabricated using either electroplating or silicon micromachining technology. Considering on the other hand the low-g micro-switch (threshold value <10 g), usually consists of a high volume proof mass and a low stiffness spring, were rarely reported because these switches were less practical to be fabricated with lateral sensitive structure design. In this paper, we report on a silicon based vertical sensitive low-g inertial switch designed for linear acceleration sensing. The inertial switch consists of a cylinder shaped proof mass, suspended by circular shaped spiral spring. The fabrication process is based on a customized symmetrical double-buried layer SOI wafer with standard silicon micromachining. The centrifugal experiment results show that the threshold value is around 5.5 g which is close to the designed value.

Force Feedback Control System Dedicated for Robin Heart Surgical Robot

3D contact force sensors were developed and integrated in a demonstration system for testing the feasibility of their application in minimal invasive surgery (MIS). Piezoresistive MEMS based vectorial force sensors were designed and fabricated by 3D silicon micromachining technology and packaged according to their proposed transducer and sensor applications. In this work we demonstrated the integrability and functional applicability of the 3D force sensors in MIS robotic systems to improve their flexibility and reliability by providing real-time force and tactile information during the operation.The final goal is to integrate the new subsystems in the Robin Heart surgery robot of FRK. [1] Three different functions are targeted: 1. Micro-joystick actuator to be integrated in the hilt of the laparoscope to easily control robotic movement during operation. 2. Force sensor inside the laparoscopic jaw to provide feedback to the surgeon by measuring the grasping strength and 3. 3D force/tactile sensor which facilitates palpation for tissue diagnostics during operation. In this paper we demonstrate a feasibility study regarding these proposed applications.

Silicon Micromachined Device Testing by Infrared Low-Coherence Reflectometry

With the development of silicon micromachining technologies, non-contact measurement techniques for in-depth non-destructive inspection of layered and microstructured samples are becoming increasingly relevant. In this paper, we apply optical low-coherence reflectometry (OLCR) to detect the optical path between the interfaces of several silicon devices with characteristic distance in the range 3–17 $\mu \text{m}$ . The implemented configuration is based on a fiberoptic Michelson interferometer that exploits infrared broadband radiation in the wavelength range of 1.2–1.7 $\mu \text{m}$ , with coherence length shorter than 2 $\mu \text{m}$ , for performing spot tomographic measurements. OLCR enabled out-of-plane measurements on a MEMS linear accelerometer and in-plane measurements on vertical periodic silicon/air microstructures. The optical distance between hidden interfaces was found well in agreement with the design parameters. [2015-0108]

Design and Analysis of a Micromechanical Three-Component Force Sensor for Characterizing and Quantifying Surface Roughness

Abstract Roughness, which can represent the trade-off between manufacturing cost and performance of mechanical components, is a critical predictor of cracks, corrosion and fatigue damage. In order to measure polished or super-finished surfaces, a novel touch probe based on three-component force sensor for characterizing and quantifying surface roughness is proposed by using silicon micromachining technology. The sensor design is based on a cross-beam structure, which ensures that the system possesses high sensitivity and low coupling. The results show that the proposed sensor possesses high sensitivity, low coupling error, and temperature compensation function. The proposed system can be used to investigate micromechanical structures with nanometer accuracy.

Out-of-plane electret-based MEMS energy harvester with the combined nonlinear effect from electrostatic force and a mechanical elastic stopper

This paper presents the fabrication, modeling and characterization of an out-of-plane electret-based vibrational energy harvester (e-VEH) that has both positive and negative charged electret plates integrated into a single seismic mass system. Strong electrostatic spring-softening effect is induced due to the electric field provided by the double-charged electret plates. An elastic stopper is introduced for reliability concern by limiting the motion of seismic mass and meanwhile serves as a functional element to realize spring-hardening effect. The device has an overall volume of about 0.14 cm3 and is fabricated based on MEMS compatible silicon micromachining technology. When subject to weak excitations, the device exhibits an approximately linear frequency response but changes to a significantly larger broadband when strongly excited due to the combined nonlinear effect from electrostatic force and a mechanical elastic stopper. At a high excitation level of 0.48 g, the experimental results show that the device has 3 dB bandwidths of 3.7 Hz for frequency-up sweep and 2.8 Hz for frequency-down sweep, respectively, which demonstrate a large enhancement compared to the linear response (1.3 Hz). An optimal output power of 0.95 μW is also achieved with a low resonance of 95 Hz. This corresponds to a normalized power density of 37.4 μW cm−3 g−2.

A high performance micro-pressure sensor based on a double-ended quartz tuning fork and silicon diaphragm in atmospheric packaging

A resonant micro-pressure sensor based on a double-ended quartz tuning fork (DEQTF) and bossed silicon diaphragm in atmospheric packaging is presented. To achieve vacuum-free packaging with a high quality factor, the DEQTF is designed to resonate in an anti-phase vibration mode in a plane that is under the effect of slide-film damping. The feasibility is demonstrated by theoretical analysis and a finite element simulation. The dimensions of the DEQTF and diaphragm are optimized in accordance with the principles of improving sensitivity and minimizing energy dissipation. The sensor chip is fabricated using quartz and silicon micromachining technologies, and simply packaged in a stainless steel shell with standard atmosphere. The experimental setup is established for the calibration, where an additional sensor prototype without a pressure port is introduced as a frequency reference. By detecting the frequency difference of the tested sensor and reference sensor, the influences of environmental factors such as temperature and shocks on measuring accuracy are eliminated effectively. Under the action of a self-excitation circuit, static performance is obtained. The sensitivity of the sensor is 299 kHz kPa−1 in the operating range of 0–10 kPa at room temperature. Testing results shows a nonlinearity of 0.0278%FS, a hysteresis of 0.0207%FS and a repeatability of 0.0375%FS. The results indicate that the proposed sensor has favorable features, which provides a cost-effective and high-performance approach for low pressure measurement.

Design and implementation of an out-of-plane electrostatic vibration energy harvester with dual-charged electret plates

This paper presents the design, simulation and implementation of an out-of-plane electrostatic power generator with dual-charged electret plates for low-level ambient kinetic energy harvesting. The rotational symmetrical resonator includes one movable disk-shaped circular mass and a series of spiral springs for suspension. The whole device is fabricated by CMOS compatible silicon micromachining technology with an overall volume of about 0.12cm3. The two-plate device has both positive and negative charged electret plates. Experimental analysis shows that the present prototype is able to achieve an output power of 0.34μW at a low resonance of 66Hz at 0.5g, which corresponds to a normalized power density of 11.67μWcm−3g−2. With an acceleration changing from 0.1 to 0.5g, it is observed the operating half-power bandwidth increases by 2.6 times from 2.5 to 6.5Hz. This may be attributed to the spring softening nonlinearity induced by the strong electrostatic force. The results could potentially provide an intriguing design methodology for developing nonlinear MEMS devices for broadband random energy harvesting.

Design, fabrication and testing of a piezoelectric energy microgenerator

This article presents the design, fabrication and characterization of a micromachined energy harvester utilizing aluminium nitride (AlN) as a piezoelectric thin film material for energy conversion of random vibrational excitations. The harvester was designed and fabricated using silicon micromachining technology where AlN is sandwiched between two electrodes on top of a silicon cantilever beam which is terminated by a silicon seismic mass. The harvester generates electric power when subjected to mechanical vibrations. The generated electrical response of the device was experimentally evaluated at various acceleration levels. A maximum power of 34.78 μW was obtained for the device with a seismic mass of 5.6 × 5.6 mm2 at an acceleration value of 2 g. Various fabricated devices were tested and evaluated in terms of the generated electrical power as well as the resonant frequency.

Ultra-small micro pressure sensor chip design and fabrication featuring high-sensitivity and good-linearity

Ultra-small micro pressure sensors are demanded in dynamic performance research of airplanes, missiles and other mechanical movements in aerodynamics. In this study, a novel two island-beam-diaphragm structural sensor chip is designed to improve the sensitivity and linearity simultaneously. Two islands are introduced into the back side of the chip to fulfill the requirement of stress concentration. The chip is fabricated with silicon micromachining technology and calibrated after packaging into a pressure sensor. The resulting sensors perform well. The sensitivity of the sensor is 1.60 mV/V/100 Pa, higher than the designed 1.48 mV/V/100 Pa. Nonlinearity values at 0.04 %FS and repeatability and hysteresis uncertainty value at 0.01 %FSO and 0.05 %FSO, respectively. The temperature coefficient of sensitivity and temperature coefficient of offset is ?0.93 × 10?3/°C FSO and 0.86 × 10?3/°C FSO. The accuracy is 0.04 %FSO. Extremely high over-pressure capability is achieved due to the small island for over-range protection.

A Broadband, Micromachined Rectangular Waveguide to Cavity-Backed Coplanar Waveguide Transition Using Impedance-Taper Technique

This paper presents a broadband fully micromachined transition from rectangular waveguide to cavity-backed CPW line for submillimeter-wave (sub-MMW) and terahertz applications. A cavity-backed CPW line (CBCBW) is a planar transmission line that is designed and optimized for minimum loss while providing 50- Ω characteristic impedance. This line is shown to provide less than 0.12 dB/mm loss over the entire J-band (220-325 GHz). The transition from CBCPW to waveguide is realized in three steps to achieve a broadband response with a topology amenable to silicon micromachining. The first step is a tapered transition from the CBCPW line to a 50- Ω reduced-height waveguide. The next two steps utilize a novel in-plane impedance tapering technique to transition from the reduced-height waveguide to the on-wafer regular height waveguide. The full transition has less than 0.9 dB of insertion loss and more than 13 dB of return loss over the entire J-band (39% bandwidth). Silicon micromachining technology is used to fabricate prototypes of back-to-back CBCPW line-to-waveguide transitions. A novel waveguide-probe measurement setup is introduced and utilized to evaluate the performance of the transitions and the CBCPW lines.

Effects of Micropatterning and Surface Modification of Microfluidic Channels on Capillary Water Transport

Abstract This work is intended to characterize the fluid conducting behaviour of microcapillary systems containing various 3D microstructures and surface modifying molecular layers. The microchannels are patterned by secondary structures mimicking the natural water-conducting tissue (xylem) of dry-habitat plants. The complex microstructure of the microcapillary system was developed by bulk silicon micromachining technology, applying multistep Deep Reactive Ion Etching (DRIE) to fabricate and pattern the microfluidic channels subsequently. The inner surfaces of the capillary systems were covered by Atomic Layer Deposition (ALD) of different oxide layers to control their wetting properties. We demonstrated that the fluid conducting behaviour of the fabricated capillary systems can be systematically controlled by structural patterning and surface modification of the channels.

Research on Micro Twin-Bridges Catalytic Combustion Type Kerosene Gas Sensor Technology

Based on the principle of catalytic combustion type gas sensor, a kerosene gas sensor with micro twin-bridge structure is fabricated using silicon micromachining technology. A pair of platinum film resistor is fabricated by film processing, and its nominal resistance is 20Ω at 0°C. The nano-alumina catalytic carrier and noble metal catalyst are coated on the surface of sensitive resistance in order to form the sensitive bridge and compensating bridge. The monolithic integration of catalytic element and compensating element is achieved on the silicon micro twin-bridge for fabrication of kerosene sensor. The simulation result shows that once temperature of one bridge rises to 650K, the other bridge may increases about 10°C. The test on kerosene sensor by calibration device indicates that the sensor can detect the kerosene volume fraction ranging from 0 to 7000×10-6 and the sensor output property is linear.

Design and fabrication of a micromachined gyroscope with high shock resistance

In this paper, a tuning fork gyroscope designed for high-g shock environments is presented. This micro gyroscope with 10 kHz designed working frequency is composed of double symmetrical frame structures that are connected by middle coupling beams. Two level elastic stoppers were designed in order to improve the shock resistance of the gyroscope. Slots were etched to reduce damping in the inner bonding regions. By bulk silicon micromachining technology, the gyroscope was fabricated on a 300 μm thickness silicon wafer. The working frequencies of the gyroscope on the driving and sensing modes are 10,240 and 11,160 Hz, respectively. Shock experiments to bare chips indicate that the shock resistance of the gyroscope along X-axis is 15,000 g, Y-axis is 14,000 g and Z-axis is 11,000 g.

Sensitivity Improvement of Micromachined Convective Accelerometers

The sensitivity of a micromachined convective accelerometer filled with different gases at various conditions is theoretically and experimentally investigated. It is shown that the sensitivity of the accelerometer is proportional to the Rayleigh number for the contained gas. The Rayleigh numbers for nine gases are calculated, and the corresponding sensitivity improvements are predicted. To test our predictions, bulk silicon micromachining technology is used to fabricate and package several thermal accelerometers. A precision rotary stage is set up enclosing a packaged device into a gas chamber and rotating its sensitive axis against gravity. Data acquisition is done by a high-precision digital multimeter over full cycle rotations for seven candidate gases: nitrogen (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), argon (Ar), carbon dioxide (CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), sulfur hexafluoride (SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> ), hexafluoroethane (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> ), octafluoropropane ( C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> ), and octafluorocyclobutane ( C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> ). The measured sensitivities are in good agreement with the theoretical predictions. An upper limit to the sensitivity improvement by boosting the Rayleigh number for the contained gas is measured. Sensitivity decline beyond a critical Rayleigh number is reported for the first time since the advent of the convective accelerometers without proof mass.

Monolithic Integration of Pressure Plus Acceleration Composite TPMS Sensors With a Single-Sided Micromachining Technology

This paper concerns the development of a single-side micromachined tire-pressure monitoring system (TPMS) sensor for automobiles, which is with a piezoresistive pressure sensor and a cantilever-mass piezoresistive accelerometer monolithically integrated in a 1.6 mm × 1.5 mm sized (111)-silicon chip. Single-wafer-based front-side silicon micromachining and metal electroplating technologies are employed to fabricate the device. Specially designed releasing trenches along (111) orientation are constructed to form the hexagonal pressure-sensitive diaphragm and the postsealed vacuum reference cavity. The fabrication of the accelerometer is also based on a hexagonal diaphragm that is latterly cut into suspended cantilevers and seismic mass. To achieve a high sensitivity, a high-density copper thick film is selectively electroplated to significantly increase the mass. The performance of the 115-g-ranged accelerometer is measured, exhibiting a sensitivity of 99.9 μV/g (under 3.3-V supply), nonlinearity of ±0.45% FS, and the noise floor of better than 0.2 g. The 750-kPa-ranged pressure-sensor sensitivity is measured as 0.108 mV/kPa (under 3.3-V supply), with the nonlinearity error smaller than ±0.1% FS and the temperature coefficient of sensitivity as -0.19%/°C FS before compensation. The noise floor of the pressure-sensor out- put signal is 0.15 kPa. The zero-point temperature coefficient is tested as -0.11%/°C FS and -0.024%/°C FS for the accelerometer and the pressure sensor, respectively. Fabricated with the low-cost front-side micromachining technique, the small-sized TPMS sensors are promising in practical applications and volume production.

Single mask, simple structure micro rotational motor driven by electrostatic comb-drive actuators

We report a design and fabrication of a new micro rotational motor (MRM) using silicon micromachining technology with the overall diameter of 2.4 mm. This motor utilizes four silicon electrostatic comb-drive actuators to drive the outer ring (or rotor) through ratchet teeth. The novel design of the anti-reverse structure helps us to overcome the gap problem after deep reactive ion etching of silicon. The MRM was fabricated by using silicon on insulator wafer with the thickness of the device layer being 30 µm and one mask only. The motor was successfully tested for performance. It was driven by periodic voltage with different frequencies ranging from 1 to 50 Hz. The angular velocity of the outer ratchet ring was proportional to the frequency. Moreover, when the driving frequency is lower than 30 Hz, the experiment results perfectly match the theoretical calculation.

Multimodule Micro Transportation System Based on Electrostatic Comb-Drive Actuator and Ratchet Mechanism

We present a novel multimodule micro transportation system (MTS), which can drive micro containers in straight, curved, and T-junction paths based on electrostatic comb-drive actuator and ratchet mechanism. The transported objects are micro containers, which have two pairs of driving wings and anti-reverse wings attached to a body. Their movement is like a water strider, i.e., its driving wings rotate backward to generate reaction force to push the containers forward, while the anti-reverse wings act as a ratchet mechanism to prevent the container from moving backward. By developing three basic modules, i.e., straight, turning, and T-junction modules, the different configurations of the MTS can be built from these modules conveniently. Each module consists of ratchet racks driven by electrostatic comb-drive actuators. Containers having length, width, and thickness of 500, 250, and 30 μm, respectively, were driven to move with a changeable velocity up to 1000 μm/sec in straight, turning, and T-junction modules. The velocity of the container was proportional to the frequency of driving voltage. By utilizing silicon micromachining technology, a prototype of MTS was fabricated from silicon-on-insulator wafer with only one mask.

电容读出式非制冷红外焦平面阵列设计

With the aim to improve the performance of an infrared detector and to enhance the characteristics of a Focal Plane Array(FPA),a capacitive-read infrared FPA with the structure of cantilever element in a fold-line leg and a long-line leg was designed.The thermal conductivity,thermo-mechanical sensitivity and the thermal time constant of the structure were discussed and optimized,then these parameters were set to be 3×10-7 W/K,162 nm/K and 35 ms,respectively.The sensitivity of design is fast enough to satisfy the requirements of human eyes.Furthermore,the Noise Equivalent Temperature Difference(NETD) which is key for the FPA detection was discussed,and calculated result shows that the NETD of the designed FPA is 6 mK.A simulation for the NETD was also performed,which shows the NETD is 5 mK.Experiments indicate that the simulation result agrees with that of the calculation well and show that the NETD is small enough to satisfy the resolution for signal read-out.Finally,the capacitive-read FPA was fabricated based on silicon micromachining technology successfully.

A novel micro transportation system with fast movement of a micro container based on electrostatic actuation and a ratchet mechanism

This paper presents a novel micro transportation system (MTS), which can drive micro containers in both straight and curved paths based on an electrostatic comb actuator and a ratchet mechanism. The micro container, which has four driving wings and four anti-reverse wings attached to its central ‘backbone’, is driven to move forward only by an electrostatic actuator. While the driving wings act as the legs of a water strider to push the container forward, the anti-reverse wings work as a ratchet mechanism to prevent the container from moving backward. The container with a length, width and thickness of 500 µm, 250 µm and 30 µm, respectively, moves unidirectionally with a desirable velocity up to 1000 µm s−1 in straight and curved paths. The velocity can be changed by varying the frequency and/or amplitude of the driving voltage. The MTS has been fabricated from SOI (silicon on insulator) wafer utilizing silicon micromachining technology with only one mask.