Modeling for temperature compensation and temperature characterizations of BAW resonators at GHz frequencies

Abstract

This paper deals with the temperature dependence of electrical and physical features of various kinds of solidly mounted resonators (SMR). The presented bulk acoustic wave (BAW) devices are designed for the 2 GHz application. The temperature coefficient of frequency (TCF) is determined from measurements well above the temperature range defined for wireless telecommunication system specifications. Therefore, evolution of electromechanical coupling factors and quality factors at resonance and antiresonance are also monitored. Results of characterizations show the trend for a subsequent theoretical temperature compensation study by using analytical modeling. To improve accuracy of modeling, an attempt to extract temperature dependence of dielectric permittivity epsilon(33) and piezoelectric coefficient e(33) is made. Finally, a well-known analytical model is modified to take into account the temperature dependence of length, density, stiffness coefficient, dielectric permittivity, and piezoelectric coefficient. Modeling highlights the need to deposit a material with positive temperature coefficient of stiffness on the top electrode. Realistic thickness of such a layer is determined. At the same time, it is necessary to adjust piezoelectric and electrode thin film thicknesses for simultaneously keeping a constant antiresonance frequency, reaching a zero temperature coefficient of frequency for antiresonance, and minimizing the decrease in the coupling factor because of the mass-loading deposition.

Synthesis of c-Axis Inclined AlN Films in an Off-Center System for Shear Wave Devices

“…It is worth noting that the roughness of the layers is critical for the acoustic wave scattering loss, since a rough surface or interface leads to energy scattering and induces dissipation loss in microwave applications. 17 In the SAED pattern (Fig. 5b), the electron beam was parallel to the [100] direction of the silicon substrate, and the diffraction was taken from an area in close proximity to the film interface.…”

Sources of Third–Order Intermodulation Distortion in Bulk Acoustic Wave Devices: A Phenomenological Approach

“…In addition to being able to calculate the temperature oscillations, we also need to determine how these oscillations influence the device performance. For the specific case of BAW devices, there is consensus in assuming that the detuning of BAW devices with temperature is due to the variation of multiple material properties with temperature (Lakin et al, 2000;Ivira et al, 2008;Petit et al, 2007). We reflect this in our model by adding a temperaturedependent term to the stiffened elasticity in (1)…”

Surface and Bulk Acoustic Waves in Multilayer Structures

“…A temperature dependence of a layer thickness -TCF h A temperature dependence of material constants is described by temperature coefficients of these constants, a temperature dependence of a mass density is described by three linear expansion coefficients or by a single bulk expansion coefficient, a temperature dependence of a thickness is described by a linear expansion coefficient along a thickness direction. All these coefficients can be found in a literature, for example, for materials, usually used for FBAR resonators, one can see corresponding values in (Ivira et al, 2008). First we will consider the simplest variant -a membrane type FBAR resonator with a single AlN layer and infinite thin electrodes.…”