scholarly journals A MEMS Fabrication Process with Thermal-Oxide Releasing Barriers and Polysilicon Sacrificial Layers for AlN Lamb-Wave Resonators to Achieve fs·Qm > 3.42 × 1012

Micromachines ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 892
Author(s):  
Jicong Zhao ◽  
Zheng Zhu ◽  
Haiyan Sun ◽  
Shitao Lv ◽  
Xingyu Wang ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Lamb Wave ◽  
Piezoelectric Layer ◽  
Sacrificial Layer ◽  
High Quality ◽  
Micro Electro Mechanical Systems ◽  
Mems Fabrication ◽  
Thermal Oxide ◽  
Series Resonant ◽  
Releasing Process

This paper presents a micro-electro-mechanical systems (MEMS) processing technology for Aluminum Nitride (AlN) Lamb-wave resonators (LWRs). Two LWRs with different frequencies of 402.1 MHz and 2.097 GHz by varying the top interdigitated (IDT) periods were designed and fabricated. To avoid the shortcomings of the uncontrollable etching of inactive areas during the releasing process and to improve the fabrication yield, a thermal oxide layer was employed below the platted polysilicon sacrificial layer, which could define the miniaturized release cavities well. In addition, the bottom Mo electrode that was manufactured had a gentle inclination angle, which could contribute to the growth of the high-quality AlN piezoelectric layer above the Mo layer and effectively prevent the device from breaking. The measured results show that the IDT-floating resonators with 12 μm and 2 μm electrode periods exhibit a motional quality factor (Qm) as high as 4382 and 1633. The series resonant frequency (fs)·Qm values can reach as high as 1.76 × 1012 and 3.42 × 1012, respectively. Furthermore, Al is more suitable as the top IDT material of the AlN LWRs than Au, and can contribute to achieving an excellent electrical performances due to the smaller density, smaller thermo-elastic damping (TED), and larger acoustic impedance difference between Al and AlN.

Resonant frequency method for monitoring MEMS fabrication

2003 ◽  
Author(s):  
Danelle M. Tanner ◽  
Albert C. Owen, Jr. ◽  
Fredd Rodriguez
Keyword(s):  
Resonant Frequency ◽  
Frequency Method ◽  
Mems Fabrication

A New Design of Large Stroke Micro-Deformable Mirror Actuated by Electrostatic Repulsive Force

2008 ◽  
Author(s):  
Fangrong Hu ◽  
Jun Yao ◽  
Chuankai Qiu ◽  
Dajia Wang
Keyword(s):  
Electric Field ◽  
Resonant Frequency ◽  
Adaptive Optics ◽  
Bottom Electrode ◽  
Sacrificial Layer ◽  
Electrostatic Force ◽  
Repulsive Force ◽  
Deformable Mirror ◽  
Optical Aberrations ◽  
Out Of Plane

In this paper, a MEMS mirror actuated by an electrostatic repulsive force has been proposed and analyzed. The mirror consists of four U-shape springs, a fixed bottom electrode and a movable top electrode, there are many comb fingers on the edges of both electrodes. When the voltage is applied to the top and bottom electrodes, an asymmetric electric field is generated to the top movable fingers and springs, thus a net electrostatic force is produced to move the top plate out of plane. This designed micro-mirror is different from conventional MDM based on electrostatic-attractive-force, which is restricted by one-third thickness of the sacrificial layer for the pull-in phenomenon. The characteristic of this MDM has been analyzed, the result shows that the resonant frequency of the first mode is 8 kHz, and the stroke reaches 10μm at 200V, a MDM with large strokes can be realized for the application of adaptive optics in optical aberrations correction.

scholarly journals Piezoelectric MEMS Acoustic Transducer with Electrically-Tunable Resonant Frequency

Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 96
Author(s):  
Alessandro Nastro ◽  
Marco Ferrari ◽  
Libor Rufer ◽  
Skandar Basrour ◽  
Vittorio Ferrari
Keyword(s):  
Acoustic Emission ◽  
Resonant Frequency ◽  
Piezoelectric Layer ◽  
Flexural Mode ◽  
Resonant Frequencies ◽  
Voltage Mode ◽  
Acoustic Transducer ◽  
Aln Film ◽  
Doped Silicon ◽  
Piezoelectric Mems

The paper presents a technique to obtain an electrically-tunable matching between the series and parallel resonant frequencies of a piezoelectric MEMS acoustic transducer to increase the effectiveness of acoustic emission/detection in voltage-mode driving and sensing. The piezoelectric MEMS transducer has been fabricated using the PiezoMUMPs technology, and it operates in a plate flexural mode exploiting a 6 × 6 mm doped silicon diaphragm with an aluminum nitride (AlN) piezoelectric layer deposited on top. The piezoelectric layer can be actuated by means of electrodes placed at the edges of the diaphragm above the AlN film. By applying an adjustable bias voltage Vb between two properly-connected electrodes and the doped silicon, the d31 mode in the AlN film has been exploited to electrically induce a planar static compressive or tensile stress in the diaphragm, depending on the sign of Vb, thus shifting its resonant frequency. The working principle has been first validated through an eigenfrequency analysis with an electrically induced prestress by means of 3D finite element modelling in COMSOL Multiphysics®. The first flexural mode of the unstressed diaphragm results at around 5.1 kHz. Then, the piezoelectric MEMS transducer has been experimentally tested in both receiver and transmitter modes. Experimental results have shown that the resonance can be electrically tuned in the range Vb = ±8 V with estimated tuning sensitivities of 8.7 ± 0.5 Hz/V and 7.8 ± 0.9 Hz/V in transmitter and receiver modes, respectively. A matching of the series and parallel resonant frequencies has been experimentally demonstrated in voltage-mode driving and sensing by applying Vb = 0 in transmission and Vb = −1.9 V in receiving, respectively, thereby obtaining the optimal acoustic emission and detection effectiveness at the same operating frequency.

scholarly journals On the Practical Evaluation of the Switching Loss in the Secondary Side Rectifiers of LLC Converters

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5915
Author(s):  
Manuel Escudero ◽  
Matteo-Alessandro Kutschak ◽  
Francesco Pulsinelli ◽  
Noel Rodriguez ◽  
Diego Pedro Morales
Keyword(s):  
Resonant Frequency ◽  
High Voltage ◽  
Low Voltage ◽  
Hysteresis Loss ◽  
Resonant Converters ◽  
Switching Loss ◽  
Operating Modes ◽  
Switching Losses ◽  
Series Resonant ◽  
Secondary Side

The switching loss of the secondary side rectifiers in LLC resonant converters can have a noticeable impact on the overall efficiency of the complete power supply and constrain the upper limit of the optimum switching frequencies of the converter. Two are the main contributions to the switching loss in the secondary side rectifiers: on the one hand, the reverse recovery loss (Qrr), most noticeably while operating above the series resonant frequency; and on the other hand, the output capacitance (Coss) hysteresis loss, not previously reported elsewhere, but present in all the operating modes of the converter (under and above the series resonant frequency). In this paper, a new technique is proposed for the measurement of the switching losses in the rectifiers of the LLC and other isolated converters. Moreover, two new circuits are introduced for the isolation and measurement of the Coss hysteresis loss, which can be applied to both high-voltage and low-voltage semiconductor devices. Finally, the analysis is experimentally demonstrated, characterizing the switching loss of the rectifiers in a 3 kW LLC converter (410 V input to 50 V output). Furthermore, the Coss hysteresis loss of several high-voltage and low-voltage devices is experimentally verified in the newly proposed measurement circuits.

Behaviour of the series resonant frequency in electrolyte solutions

2006 ◽  
Vol 115 (2) ◽  
pp. 567-574 ◽  
Author(s):  
Pedro J. Lamas-Ardisana ◽  
A. Costa-García
Keyword(s):  
Resonant Frequency ◽  
Electrolyte Solutions ◽  
Series Resonant

High Quality Ultrathin Gate Dielectrics Prepared by In-Situ RTP

1995 ◽  
Vol 387 ◽  
Author(s):  
L. K. Han ◽  
M. Bhat ◽  
J. Yan ◽  
D. Wristers ◽  
D. L. Kwong
Keyword(s):  
Gate Dielectric ◽  
Defect Density ◽  
Gate Dielectrics ◽  
Charge Trapping ◽  
Interface State ◽  
High Quality ◽  
Hot Carrier ◽  
Thermal Oxide ◽  
State Generation

AbstractThis paper reports on the formation of high quality ultrathin oxynitride gate dielectric by in-situ rapid thermal multiprocessing. Four such gate dielectrics are discussed here; (i) in-situ NO-annealed SiO2, (ii) N2O- or NO- or O2-grown bottom oxide/RTCVD SiO2/thermal oxide, (iii) N2O-grown bottom oxide/Si3N4/N2O-oxide (ONO) and (iv) N2O-grown bottom oxide/RTCVD SiO2/N2O-oxide. Results show that capacitors with NO-based oxynitride gate dielectrics, stacked oxynitride gate dielectrics with varying quality of bottom oxide (O2/N2O/NO), and the ONO structures show high endurance to interface degradation, low defect-density and high charge-to-breakdown compared to thermal oxide. The N2O-last reoxidation step used in the stacked dielectrics and ONO structures is seen to suppress charge trapping and interface state generation under Fowler-Nordheim injection. The stacked oxynitride gate dielectrics also show excellent MOSFET performance in terms of transconductance and mobility. While the current drivability and mobilities are found to be comparable to thermal oxide for N-channel MOSFET's, the hot-carrier immunity of N-channel MOSFET's with the N2O-oxide/CVD-SiO2/N2O-oxide gate dielectrics is found to be significantly enhanced over that of conventional thermal oxide.

A fabrication process based on structural layer formation using Au–Au thermocompression bonding for RF MEMS capacitive switches and their performance

2014 ◽  
Vol 6 (5) ◽  
pp. 473-480 ◽  
Author(s):  
Cagri Cetintepe ◽  
Ebru Sagiroglu Topalli ◽  
Simsek Demir ◽  
Ozlem Aydin Civi ◽  
Tayfun Akin
Keyword(s):  
Transmission Lines ◽  
Rf Mems ◽  
Mechanical Design ◽  
Sacrificial Layer ◽  
Fabrication Process ◽  
Worst Case ◽  
Micro Electro Mechanical Systems ◽  
Wave Measurements ◽  
Thermocompression Bonding ◽  
Structural Layer

This paper presents a radio frequency micro-electro-mechanical-systems (RF MEMS) fabrication process based on a stacked structural layer and Au–Au thermocompression bonding, and reports on the performance of a sample RF MEMS switch design implemented with this process. The structural layer consists of 0.1 µm SiO2/0.2 µm SixNy/1 µm Cr–Au layers with a tensile stress less than 50 MPa deposited on a silicon handle wafer. The stacked layer is bonded to a base wafer where the transmission lines and the isolation dielectric of the capacitive switch are patterned. The process flow does not include a sacrificial layer; a recess etched in the base wafer provides the air gap instead. The switches are released by thinning and complete etching of the silicon handle wafer by deep reactive ion etching (DRIE) and tetramethylammonium hydroxide (TMAH) solution, respectively. Millimeter-wave measurements of the fabricated RF MEMS switches demonstrate satisfactory up-state performance with the worst-case return and insertion losses of 13.7 and 0.38 dB, respectively; but the limited isolation at the down-state indicates a systematic problem with these first-generation devices. Optical profile inspections and retrospective electromechanical analyses not only confirm those measurement results; but also identify the problem as the curling of the MEMS bridges along their width, which can be alleviated in the later fabrication runs through proper mechanical design.

Improved Prediction of Electrodes’ Mass Loading Effect on MEMS FBAR Structure in Longitudinal Resonance

2008 ◽  
Author(s):  
Annie Ruimi ◽  
Yueming Liang ◽  
Robert M. McMeeking
Keyword(s):  
Finite Elements ◽  
Aluminum Nitride ◽  
Resonant Frequency ◽  
Layer Thickness ◽  
Piezoelectric Layer ◽  
Numerical Scheme ◽  
Three Dimensional ◽  
Mass Loading ◽  
Loading Effect ◽  
One Dimensional

In this paper, we derive an exact one-dimensional rule for predicting mass loading effect due to electrodes by analyzing a FBAR structure consisting of a piezoelectric layer and two electrodes in longitudinal resonance. We validate the numerical scheme using aluminum nitride as the piezoelectric material and gold and aluminum for the top and bottom electrodes respectively. Results are compared with three-dimensional finite elements simulations obtained earlier. It is seen that the new rule predicts higher values of the resonant frequency and constitutes an improvement over an elementary rule particularly for electrodes thicknesses greater than 20% of the piezoelectric layer thickness.

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