A Temperature-Compensated Gallium Nitride Micromechanical Resonator

Ansari, Azadeh; Rais‐Zadeh, Mina

doi:10.1109/led.2014.2358577

Cited by 23 publications

(15 citation statements)

References 13 publications

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“…It is shown in [ 14 ] that placing embedded SiO 2 structures at the location of maximum stress is most effective in reducing TCF values. In [ 13 ], we have shown GaN micromechanical resonators with a 400 nm thick blanket SiO 2 on the top surface to reduce the value of TCF to ~−15 of ppm/K. Using the structure in this work, even with a thinner SiO 2 layer, which is placed at high stress locations, significantly higher levels of temperature compensation can be achieved ( Figure 8 ).…”

Section: Placement Of the W/sio 2 Meshed Bottommentioning

confidence: 86%

“…Most materials (e.g., Si, AlN, GaN) have a negative TCE, and therefore their resonance frequency decreases with an increase in temperature. SiO 2 , unlike GaN, has a positive TCE (TCE of SiO 2 : ~+160 ppm/K, TCE of GaN: ~−60 ppm/K) and can be used to cancel the temperature-induced frequency drift in GaN resonators [ 13 ]. Both the volume and location of SiO 2 structures play a critical role in determining the TCF of a resonator.…”

Section: Placement Of the W/sio 2 Meshed Bottommentioning

confidence: 99%

“…120 nm thick embedded oxide layer is placed within the stack, fully compensating the temperature-induced frequency shifts of the fundamental thickness-mode resonance of the GaN piezoelectric resonator. Assuming a TCE value of -60 ppm/K for GaN, and TCE of +160 ppm/K for SiO 2 [ 13 ], TCF of the resonator is simulated to be ~−5 ppm/K for the stack shown above.…”

Section: Placement Of the W/sio 2 Meshed Bottommentioning

confidence: 99%

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GaN Micromechanical Resonators with Meshed Metal Bottom Electrode

et al. 2015

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This work describes a novel architecture to realize high-performance gallium nitride (GaN) bulk acoustic wave (BAW) resonators. The method is based on the growth of a thick GaN layer on a metal electrode grid. The fabrication process starts with the growth of a thin GaN buffer layer on a Si (111) substrate. The GaN buffer layer is patterned and trenches are made and refilled with sputtered tungsten (W)/silicon dioxide (SiO2) forming passivated metal electrode grids. GaN is then regrown, nucleating from the exposed GaN seed layer and coalescing to form a thick GaN device layer. A metal electrode can be deposited and patterned on top of the GaN layer. This method enables vertical piezoelectric actuation of the GaN layer using its largest piezoelectric coefficient (d33) for thickness-mode resonance. Having a bottom electrode also results in a higher coupling coefficient, useful for the implementation of acoustic filters. Growth of GaN on Si enables releasing the device from the frontside using isotropic xenon difluoride (XeF2) etch and therefore eliminating the need for backside lithography and etching.

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Section: Placement Of the W/sio 2 Meshed Bottommentioning

confidence: 86%

Section: Placement Of the W/sio 2 Meshed Bottommentioning

confidence: 99%

Section: Placement Of the W/sio 2 Meshed Bottommentioning

confidence: 99%

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GaN Micromechanical Resonators with Meshed Metal Bottom Electrode

et al. 2015

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“…Several piezoelectric devices fabricated with materials such as langasite (La 3 Ga 5 SiO 14 ), aluminum nitride (AlN), and gallium nitride (GaN) have been examined for high-temperature RF applications [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Yet, the effective electromechanical coupling of the devices reported in these demonstrations is limited ( k t 2 < 1.4%), due to the inherently low piezoelectric coupling coefficients ( K 2 ) in the selected materials.…”

Section: Introductionmentioning

confidence: 99%

A Laterally Vibrating Lithium Niobate MEMS Resonator Array Operating at 500 °C in Air

Eisner

Chapin

et al. 2020

Sensors

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This paper reports the high-temperature characteristics of a laterally vibrating piezoelectric lithium niobate (LiNbO3; LN) MEMS resonator array up to 500 °C in air. After a high-temperature burn-in treatment, device quality factor (Q) was enhanced to 508 and the resonance shifted to a lower frequency and remained stable up to 500 °C. During subsequent in situ high-temperature testing, the resonant frequencies of two coupled shear horizontal (SH0) modes in the array were 87.36 MHz and 87.21 MHz at 25 °C and 84.56 MHz and 84.39 MHz at 500 °C, correspondingly, representing a −3% shift in frequency over the temperature range. Upon cooling to room temperature, the resonant frequency returned to 87.36 MHz, demonstrating the recoverability of device performance. The first- and second-order temperature coefficient of frequency (TCF) were found to be −95.27 ppm/°C and 57.5 ppb/°C2 for resonant mode A, and −95.43 ppm/°C and 55.8 ppb/°C2 for resonant mode B, respectively. The temperature-dependent quality factor and electromechanical coupling coefficient (kt2) were extracted and are reported. Device Q decreased to 334 and total kt2 increased to 12.40% after high-temperature exposure. This work supports the use of piezoelectric LN as a material platform for harsh environment radio-frequency (RF) resonant sensors (e.g., temperature and infrared) incorporated with high coupling acoustic readout.

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“…It is defined as the ratio of the temperature-induced frequency shift to the reference frequency. Traditional MEMS-based temperature sensors that employ CMOS-compatible materials (e.g., silicon, AlN, and GaN) typically suffer from a low TCF value of <35 ppm/°Ϲ [11,12]. Various techniques have been developed to improve the sensitivity of these temperature sensors, which can be classified into three main categories: material composition, mode tuning, and stress controlling methods (either by geometry optimization or by stress engineering during device fabrication).…”

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confidence: 99%

High-Sensitivity Thermal Sensing Based on a Single Strain-Assisted Resonator

et al. 2022

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Microresonator-based temperature sensors offer stable and high-resolution temperature detection. However, typical temperaturesensing techniques based on resonators suffer from design complexity and low sensitivity. In this study, we present a simple high-sensitivity temperature sensor that comprises a sealed electrostatically actuated clamped-clamped silicon microbeam resonator. The sensor's high sensitivity is attributed to the thermal-strain effects due to the mismatch between the thermal expansion coefficients of the composite materials. And the sensitivity is further enhanced by operating the resonator near the buckling zone via in situ Joule heating. In addition, The sensor operates at a single drive frequency that corresponds to the resonant frequency at the maximum temperature. A change in temperature induces a thermal strain that shifts the resonant frequency, which changes the output voltage. This considerably simplifies the readout system from the typical frequency-tracking method to the proposed amplitude tracking method. The encapsulated sensor achieves a minimum detectable temperature of 0.0196 °Ϲ and an absolute temperature coefficient of frequency of 1757 ppm/°Ϲ. These results demonstrate the great potential of the proposed sensor for efficient resonant thermal sensing with high resolution, enhanced sensitivity and a simplified readout scheme.

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A Temperature-Compensated Gallium Nitride Micromechanical Resonator

Cited by 23 publications

References 13 publications

GaN Micromechanical Resonators with Meshed Metal Bottom Electrode

GaN Micromechanical Resonators with Meshed Metal Bottom Electrode

A Laterally Vibrating Lithium Niobate MEMS Resonator Array Operating at 500 °C in Air

High-Sensitivity Thermal Sensing Based on a Single Strain-Assisted Resonator

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