RF Bulk Acoustic Wave Research Articles

Ion-beam-induced in-plane a-axis oriented (0001) AlN and ScAlN thin film BAW resonators

High-Q RF bulk acoustic wave filters are still required for mobile communication applications. However, the in-plane orientation of commercial AlN films is random, despite their excellent out-of-plane c-axis orientation. We proposed combining two different orientation control techniques: self-texture for out-of-plane alignment and ion beam irradiation for in-plane alignment. To demonstrate the effectiveness of this approach, both in-plane a-axis and out-of-plane c-axis aligned AlN and ScAlN films were grown on Ti/silica glass substrates using 0.3–0.5 keV grazing ion-beam-assisted RF sputtering technique without using epitaxial growth. The clear six symmetry in the pole-figure observed in AlN and ScAlN thin films indicates the single-crystal-like in-plane a-axis orientation. The ion beam direction corresponded to the in-plane 〈101̄0〉 axis. In-plane x-ray diffraction ϕ-scan curve and ω-scan curve FWHM were measured to be 25° and 2.2°.

Enhancing RF Bulk Acoustic Wave Devices: Multiphysical Modeling and Performance

The rapid proliferation of smartphones, tablets, and intelligent wearables is proof of the global success of high-performance RF acoustic devices based on bulk acoustic wave (BAW) and surface acoustic wave (SAW) technologies. Advanced wireless communication standards, such as 4G/LTE and the upcoming 5G, make the implementation of new RF features (power handling, wider bandwidth, and reconfigurability) mandatory in modern end-user equipment for mobile communications. This leads to an increasing demand for SAW and BAW components due to their compatibility with higher frequencies. In the year 2020, shipments of RF filters will exceed 68 billion (Figure 1), of which about 40 billion will be high-performance filters, such as film bulk acoustic resonators (FBARs), high quality factor (Q) BAW components, temperature-compensated (TC) SAW components, and thin-film SAW components [1]-[3].

Study on the Frequency Dependence of Lateral Energy Leakage in RF Bulk Acoustic Wave Device by Fast-Scanning Laser Probe System

This paper describes the application of the developed fast-scanning laser probe system to the diagnosis of frequency dependence of lateral energy leakage occurring in RF bulk acoustic wave (BAW) devices. According to wavenumber domain analyses, dispersion relation for the device under test is derived, the leakage behaviors at different frequencies are shown as images, and energy of each lateral mode is evaluated quantitatively. The cause of the lateral energy leakage and its frequency dependence are discussed. It is shown that the cause of lateral energy leakage is the higher order transverse modes which are not excited at frequency higher than a cut-off frequency ( fc) for the longitudinal extension mode. It is demonstrated that by using this laser probe system, the lateral energy leakage variation upon frequency can be seen intuitively, and the underlying mechanism for the leakage can be analyzed and explained clearly.

RF Bulk Acoustic Wave Resonators and Filters

RF Bulk Acoustic Wave Resonators and Filters

A novel piezoelectric-based RF BAW filter

A novel structure of piezoelectric-based RF passband bulk acoustic wave (BAW) filter is fabricated using surface micromachining. The solutions of the wave equation for the electrode–piezoelectrics–electrode sandwich structure on support film in the BAW RF resonators are presented. Based on the solutions, a new method to adjust the frequency of the filter is given.