Chun-You Liu

A Sub-150-

This letter presents the design of a low power, low phase noise monolithic oscillator with a back-end-of-line-embedded CMOS-MEMS resonator. The proposed CMOS-MEMS oscillator consists of a double-ended tuning fork resonator and a high gain (>138 dBQ) ultra-low input-referred current noise (<;25 fA/√Hz) integrator-differentiator transimpedance amplifier (TIA) with sub-150-μW power consumption. The 1.2-MHz CMOS-MEMS oscillator prototype shows the phase noise better than -120 dBc/Hz at 1-kHz offset and -122 dBc/Hz at 10-kHz offset with moderate dc-bias (VP = 22 V). The proposed oscillator can be operated with reduced MEMS dc bias (VP <; 7 V) and TIA power supply (VDD <; 1.3 V, 65 μW) while maintaining satisfactory performance. The frequency-power-normalized oscillator phase noise figure-of-merit (will be defined later) of 190 dB is achieved at 1-kHz offset with a resonator Q of 1900, which is comparable with the state-of-the-art using bulk-mode resonators possessing Q > 100 k.

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We report the design of a 50 μW 1.2 MHz monolithic MEMS oscillator embedded in a standard 0.35 μm CMOS with dc-bias lower than 8V. This is the first-time demonstration for a sub-100 μW single-chip CMOS-MEMS oscillator operated in MHz range. To overcome the motional impedance R m > 8 MΩ under sub-10V dc-bias (VP), an ultra-low input referred noise (<; 25 fA/rtHz), high gain integrator-differentiator transimpedance amplifier (ID-TIA) is designed with only 50-150 μW power consumption. With Vp of 8V and 11V, the phase noise (PN) FOM of 146 dB and 177 dB is attained at 1-kHz offset, respectively, for sub-100μW operations. Moreover, the power FOM of 40.6 nW/kHz (Vp = 8V) and 52.8 nW/kHz (Vp = 11V) is also comparable with state-of-the-art low power CMOS and MEMS oscillators.

BEOL-Embedded CMOS-MEMS Oscillator With a 138-dB

This work reports an ultra-low-power temperature-compensated CMOS-MEMS oscillator based on an uniform temperature design that ensures low temperature gradient of the proposed resonator to attain high frequency stability. The oven heating efficiency greater than 140°C/mW is achieved in this work by a proper thermal isolation design. In addition, the lowest temperature coefficient of frequency (TCf) of 2.84 ppm/°C is also accomplished through a passive temperature compensation scheme. The performance of the ovenized oscillator is evaluated by Allan deviation where the frequency instability of 95 ppb / 32 ppb is characterized for the oven on/off conditions, respectively, which is on par with state-of-the-art silicon-based MEMS oscillators.

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A degenerate mode 130-kHz ring-coupled gyroscope with auxiliary transducer array is designed to enhance the sensitivity as well as the mode-matching feature. The proof-of-concept device with 3 μm transducers gap is fabricated using a conventional (100) silicon-on-insulator (SOI) wafer process with only two lithography steps. The auxiliary parallel-plate transducer array is located at the maximum displacement of the vibrating ring to enhance the electromechanical coupling while reducing the sensing noise. The in-plane trefoil mode (n=3) is adopted to alleviate the initial frequency splitting in (100) crystalline silicon device layer. The average frequency split for the drive/sense modes over multiple tested devices is only 225 ppm with the mean resonance frequency of 130 kHz. The measured Q-factor is 50 in atmospheric pressure and up to 10,000 in vacuum. Owing to the larger transduction area benefitting from the transducer array design, a low dc-bias voltage (VP) of 3 V in vacuum (21 V in air) is sufficient to sustain the driving loop oscillation. As integrated with the sensing circuits to operate the proposed gyroscope, a scale factor of 2.2 mV/°/s and resolution of 0.26 °/s, respectively, are characterized in atmospheric pressure.

Ultra-Low-Noise TIA

We present a precise cell trapping platform, structure-confined electrophoresis, which utilize microchannel with lateral cavity to bend the electric field for generating positive dielectrophoresis (DEP) force. A revealed metal electrode, 10µm × 20µm, is placed inside the deep place of cavity. Providing stronger DEP force to trap mobile cells and reducing the flow shear stress acting on the trapped cell are two advantages of the cavity design. The cells trapping efficiency are increased by the multi-channel design. Five microchannels provide 400 cells trapping locations. Finally, we calibrate the relationship between flow velocity, applied ac voltage and the trapped cells number. This application utilizing structure to confine the electric field distribution is not only to provide the accurate cells trapping function, but to be a platform for electrical fusion approach of trapped cells.

An 8V 50μW 1.2MHz CMOS-MEMS oscillator

In this work, a high-performance mass sensor utilizing CMOS-MEMS thermal-piezoresistive resonator (TPR) sustained by an instrumental Lock-in and PLL circuit for oscillation is demonstrated. Under a low dc power consumption of the device with only 1.75 mW, the motional transconductance (gm) of the proposed TPR reaches record-high values both in vacuum (118.4 μA/V) and air (16.96 μA/V) among all reported CMOS-MEMS TPRs [1] and even on par with single crystal silicon (SCS) TPRs [2]. The unique design of a butterfly-shaped TPR with its low thermal capacitance (Cth) actuator beams is the key to improve the transduction efficiency and sensor sensitivity. The mass resolution of the proposed thermal-piezoresistive oscillator (TPO) attains 29.8 fg, which is extracted from the measured Allan deviation of 89 ppb. To verify the mass sensing capability, a pico-liter ink jet printing setup was used to demonstrate the real time response and frequency shifts corresponding to a number of droplets printed onto the proof-masses of the TPO with a high sensitivity of 1.946 Hz/pg, well suited for future aerosol detection.

An ovenized CMOS-MEMS oscillator with isothermal resonator and sub-mW heating power

A 3-D mechanically-coupled resonator array has been demonstrated for the first time using CMOS-MEMS technology. A high-performance vertically-coupled (VC) CMOS-MEMS resonator pair was utilized to extend the array topology into 3-D configuration with an on-chip interfaced circuit through a TSMC 0.35 μm 2P4M CMOS-MEMS platform. An array design of 9 VC pairs (N = 18 where N is the number of constituent resonators of an array) was fabricated and characterized with resonance frequency of 5.64 MHz and 0-factor of 1,092. As compared to a single VC pair (N = 2), the Saddle (SA) mode (undesired mode) was eliminated in the array design by the use of electrode phasing at the cost of weak spurious modes around the desired resonance. The 3-D array oscillator was also realized by using an instrumental Lock-in + PLL system. Under same dc biasing, the proposed 3-D array achieves better power handling and phase noise performance over the single VC pair. This technology is expected to bring more functionalities towards medium-scale integrated (MSI) micromechanical circuits.

A mode-matching 130-kHz ring-coupled gyroscope with 225 ppm initial driving/sensing mode frequency splitting

A 1 MHz 4 ppm temperature-stable micro-oven μOven) controlled monolithic CMOS-MEMS oscillator has been demonstrated in this work, exhibiting heating power in sub-mW across the 100°C temperature span. The proposed novel isothermal μOven platform consists of dual heaters, one of which stabilizes the resonator temperature while the other of which serves as built-in self-test (BIST) to mimic ambient temperature, and a resistive temperature detector (RTD) for local resonator temperature monitoring. By adapting the constant-resistance (CR) feedback temperature control scheme, the integrated 1 MHz CMOS-MEMS oscillator shows a maximum frequency inaccuracy of only 4 ppm during a fast temperature ramp across the 94°C testing span (i.e., < 43 ppb/°C). The oscillator circuit shows a worst-case bias instability of 60 ppb and phase noise (PN) of −105 dBc/Hz at 1-kHz offset (Q = 1,700).

Precise cell trapping with structure-confined dielectrophoresis

The light-driven optoelectronic vortex concept is firstly reported in this article. Utilizing illuminating light image to manipulate the liquid flow direction without any mechanic components is the feature of this design, named as optoelectroosmosis flow (OEOF). With the simple spin-coating process to form a thin organic photoconductive material, TiOPc, on the designed ITO pattern, the projected light pattern is able to generate dynamic virtual electrode on the substrate surface. Besides, the non-uniform electric field distribution would drive the ions moving with slip velocity. Furthermore, two light driven flows with different directions are able to form a clockwise or counter clockwise for microparticles concentration from non-illuminating toward illuminating region. This convenient approach of light-driven flow and microparticle concentration without any mechanical component enlarge the scope of liquid manipulation field.