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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...
Waveguiding layer acoustic waves (WLAW) technology is considered as a packageless solution for extreme miniaturization of acoustic wave devices. WLAW solution is also original and suitable for high-temperature applications. Indeed, the achievement of a stable high-temperature packaging still constitutes a technological lock, in particular regarding sealing performance. In this context, we consider...
To prevent unauthorized access to ICs, encryption can be enabled via extremely small and practically invisible microscale chips that are embedded inside the packaging of ICs. The authors lately demonstrated an acoustic power link based on AlN HBAR-like structures operating at 500 MHz [1]. Enormous acoustic losses introduced by air at such large frequencies necessitate tight coupling between the transducers...
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...
Aluminium scandium nitride (ASN) exhibits a largely enhanced piezoelectric response as compared to aluminium nitride (AlN), which makes it an upcoming piezoelectric material for next generation RF filters, sensors, actuators and energy harvesting devices. In this work, process-microstructure-property relationships of such ASN films containing up to 40 at% Sc were investigated. Hereby, the influence...
The production and the characterization of high-quality ScAlN films, whose electromechanical coupling and bandwidth are larger than those of traditional AlN films, is attracting interest to develop the next generation of bulk acoustic wave resonators for telecommunication devices operating above 5 GHz.
AlN MEMS CMRs offer high Q and kt2, and a center frequency (f0) that can be primarily set by lithography. They also have direct 50 Ω matching capability. These properties make AlN CMRs an ideal candidate to synthesize multi-frequency bandpass filters on a single chip with low insertion loss (IL). However, their practical implementation is hindered by fabrication induced variations. To address this...
Recently, it was shown that heavily doped AlN film possess the high piezoelectricity by Akiyama et al [1]. On the other hand, SAW devices were widely used as filters and sensors. Among them, SAW in ScAlN film is attracting a lot of attention because this SAW devices have high electromechanical coupling coefficient K2. We analyzed the K2 value in Sc0.4Al0.6N was increased by c-axis tilted angle θ becoming...
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...
Resonator based S0 Lamb wave mode in AlN thin films plate has drawn great attentions thanks to its high phase velocity up to 10 km/s and large electromechanical coupling coefficient (K2). Moreover, this structure allows operation at high temperature conditions. Although several significant research efforts are ongoing to enable AlN-based piezoelectric devices for high temperature applications, an...
Leaky surface acoustic waves (LSAWs) and longitudinal-type LSAWs (LLSAWs) have a number of beneficial characteristics such as a larger electromechanical coupling factor K2 and higher phase velocity than those of Rayleigh-type SAWs. However, LSAWs and LLSAWs have inherent attenuation because they lose energy by continuously radiating bulk waves into the substrate. To solve this problem, the authors...
Filters operated at high power levels and comprising BAW resonators produce 2nd harmonic emissions. To model the emissions of a BAW resonator, Feld and Shim constructed a nonlinear Mason model, which implements an “extended” pair of piezoelectric constitutive equations containing arbitrary 2nd order terms: T = cES − eE + [1/2δ3cES2 − δ1eSE + 1/2δ2εSE2] D = eS + εSE + [1/2δ1eS2 − δ2εSSE +1/2δ4εSeE2...
There is a need for wireless sensors, able to withstand temperatures above 900°C. Promising solutions based on SAW technology have been developed, addressing various technical problems. Material stability, dewetting of the electrodes and damaging of the sensor's housing are some of the main issues that have been tackled over the years. However, there is still no SAW sensor able to withstand very high...
High frequency bands such as LTE band 42 and band 43 require resonators and filters that can operate at frequencies higher than 3 GHz. However, existing lithium niobate fundamental symmetric (S0) lamb mode resonators and surface acoustic wave (SAW) resonators have operating frequency limitations (<2 GHz) due to their low phase velocities. High frequency AlN film bulk acoustic resonators (FBARs)...
Reactively sputtered aluminum nitride (AlN) thin films are widely used in fabrication of various micro devices requiring piezoelectric actuation, such as FBAR, SMR, and Piezo MEMS. Due to recently discovered effect of scandium addition to AlN enabling enhanced electromechanical coupling coefficient, ScAlN is considered now as extremely attractive material for implementation in mass production. In...
Recent literature has focused on improving piezoelectric coupling coefficients by alloying aluminum nitride (AlN) with scandium (Sc). Akiyama et al. showed the highest d_33 piezoelectric coefficient increase of >4x at a 41% Sc substitution for Al. Thus far, studies mainly focus on material measurements such as x-ray diffraction or piezoelectric constants to assess the material quality. Although...
SH-polarized plate modes propagating in thin membranes of 42°-48°LT cuts can combine high Q-factors with electromechanical coupling up to 20% and zero TCF. For high frequency applications the main challenge is fabrication of thin membranes, less than 1 micron at GHz frequencies. Thin LT plates solidly mounted on supporting substrates can help avoid fabrication of fragile membranes. The nature of plate...
Surface acoustic wave (SAW) devices are widely used as filters or resonators for mobile communications or radars applications. However, the velocity of the wave can be very sensitive to physical parameters of the environment (temperature, strain…), which allows the device to be used as a sensor. SAW devices are passive (batteryless) and wireless, but are often bulky due to the package. To dramatically...
Wake-up receivers have been proposed to provide continuous sensing in a wide variety of Internet of Things applications. To achieve impedance transformation and passive amplification between the antenna and rectifier node, current wake-up receivers employ large magnetic transformers that exhibit both low Q and inductance per unit area in planar CMOS technology. The adoption of piezoelectric MEMS resonators...
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