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Aluminum nitride (AlN) Lamb wave resonators (LWRs) utilizing the lowest symmetric (S0) mode have attracted much interests since they have high frequencies, low motional impedances, and capability of multiple frequencies on a single chip. However, the transverse spurious modes are often strong in AlN LWR, and largely degrade the performance in application, so suppression the transverse mode is highly...
Diamond has the highest sound velocity among all materials and has been applied in high frequency surface acoustic wave (SAW) devices in the gigahertz range. To date, numerous researches have reported that the SAW devices built on a diamond wafer can work in the frequency range from 2 GHz to 10 GHz. S. Fujii et al. reported that the one-port resonator with an interdigital transducer (IDT)/AlN/single...
Amorphous thin films are used as components of acoustic resonators because they could control temperature coefficient of resonator. Because elastic constants of thin films are often different from those of bulk materials, the direct measurement of sound velocity and temperature coefficient of velocity (TCV) for individual thin films becomes important in designing resonators. Because The TCV of amorphous...
The constantly rising demand for higher data rates is addressed by advanced communication standards like carrier aggregation (CA) in combination with LTE. The increased complexity of the RF frontend has put tremendous pressure on improving linear performance of BAW filters over the last years. On top of that a large number of intermodulation (IMD) specification have been added to safeguard all CA...
Partial substitution of Al by Sc in AlN wurtzite films leads to a strong enhancement of the piezoelectric properties as long as the wurtzite phase is maintained. This is very promising for improving piezoelectric MEMS devices and enlarging their application range. Nucleation of (0001)-AlScN works particularly well on Pt (111) thin films. However, in some applications, the growth on insulating substrates...
Coupling between surface acoustic waves (SAW) and arrays of mechanical resonators has appeared early in SAW history as a potential means to slow down wave propagation through mass-loading, in particular by creating corrugations on the substrate surface. This concept has been revisited over the past few years in the context of locally-resonant phononic crystals where pillars deposited on a homogeneous...
This paper reports on the investigation of 1 μm thick films of 20% Scandium-doped Aluminum Nitride (ScAlN) for the making of piezoelectric MEMS laterally vibrating resonators (LVRs). The ScAlN films, which can be sputter-deposited such as undoped Aluminum Nitride (AlN) films, were used to demonstrate high performance resonators. These devices showed quality factor (Qs) in excess of 1000 in air centered...
This paper introduces the use of artificial neural networks (ANNs) as a method to guide the design of high-performance MEMS resonators and applies it to the prediction of spurious modes (SMs) in the proximity of the series resonance of aluminum nitride (AlN) contour-mode MEMS resonators (CMRs). ANN enables both fast and accurate prediction of spurious modes, hence facilitating the MEMS designer in...
Driven by the need for high data-rates and improved cell coverage, mobile phone filters are required to process increasingly high RF power levels. The simultaneous demand for smaller filter footprints makes designing a filter for high-power performance a challenge. We report a method for simulating the self-heating effects of high input powers on a surface acoustic wave (SAW) filter. We also report...
As an application of ultrasonic motors becomes widespread, an efficient ultrasound transmission line becomes important. We are developing a puncture type ultrasonic microscope that uses our miniature ultrasonic motor to scan the acoustic mirror placed at the tip of the probe. In order to efficiently supply ultrasound energy from the outside of the body to drive the motor, we are studying an ultrasound...
Over the course of accelerated failure testing of 2-port SAW delay line resonators on quartz, periodic acoustomigration damage patterns with acoustic apertures of less than 6 wavelengths were observed across the fully metalized region between the transducers, while typical electrode stress damage was observed over the acoustic aperture in the transducer gratings. This suggested the power density had...
Lithium niobate (LN) based thin film piezoelectrics have being extensively explored [1-3] for the making of high coupling and high performance resonators. The most important bottleneck for the use of LN film is related to fabrication process and it is particularly challenging when a bottom electrode is included in the stack to increase the film capacitance per unit area. We have explored Y-cut LN...
The most important bottleneck for the use of lithium niobate (LN) films for making MEMS resonators is related to the fabrication process and it is particularly challenging when a bottom electrode needs to be included in the film stack to increase the resonator's capacitance per unit area. In this work, we propose to access the bottom electrode by using capacitive coupling rather than a direct resistive...
Temperature stability is critical for commercial oscillators and many methods have been explored such as: a) constant-resistance-based control methods; b) DTCMs with look-up tables; c) phase-lock-loop based control methods. Whereas exemplary results have been attained with these techniques, to be effective they require: a) accurate knowledge of the source of temperature fluctuations; (b) the use of...
It is more difficult to nucleate AlN-ScN alloy thin films (AlScN) in pure (0001)-texture than it is with pure AlN thin films. AlN thus can serve as seed layer for AlScN. Equipment limitations may lead to the problem of a vacuum break between AlN and AlScN deposition, as it leads to oxidation of the AlN surface. This issue was studied with high resolution TEM and electron diffraction. The formed oxide...
We demonstrated the statistical element selection (SES) technique with an array of 1.15 GHz AlN MEMS subfilters fabricated in an 8” Si fabrication facility by A∗STAR, Institute of Microelectronics (IME), Singapore. The chip integration is achieved through a split-fab process where the hermetically thin-film-encapsulated (TFE) MEMS resonators are solder-bump bonded to a CMOS chip fabricated in a Samsung...
A general purpose finite element model that yielded directly the nonlinear frequency response of the second harmonic generation in SAW IDT resonators was developed. The model enabled us to study the effects of the nonlinear material constants, voltage drive, duty factor, and IDT geometry on f-2f nonlinear interactions. Specifically we have applied our model to the study of nonlinear frequency response...
Type I Lamb wave modes exhibit a strong affinity toward multimode behavior, especially the high-transduction-efficiency modes: S0 and S1 mode. Apodization, the standard technique to suppress the transverse modes for IDT-excited resonators, suffers from drawbacks such as additional loss and reduction of the effective coupling coefficient (k2eff). Most Lamb wave modes in AlN show a positive slope in...
RF filtering technologies based on piezoelectric MEMS resonators have been successfully developed and commercialized in the past decade thanks to their size and outstanding performance. The challenge to enhance filter's performance in terms of lower insertion losses and wider bandwidth still makes for an active research topic, especially spurring the interest for new classes of materials such as doped-AlN...
Multilayered structures with LT plates bonded to silicon or glass substrates via AlN, isotropic SiO2 or their combinations, were theoretically investigated as potential materials for resonators with high Q-factors required for the 5th generation of mobile communication systems. Characteristics of SH-waves propagating under Al grating in such structures, including electromechanical coupling and propagation...
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