Correlations between microstructure and Q-factor of tunable thin film bulk acoustic wave resonators

Abstract

Correlations between microstructure and Q-factor of tunable solidly mounted Ba 0.25 Sr 0.75 TiO 3 (BSTO) thin film bulk acoustic wave resonators are studied using analysis of test structures prepared at different growth temperatures of the BSTO films varying in the range 450-650 C. The observed changes in the Q-factor with growth temperature are correlated with related changes in microstructure, including the grain size, texture misalignment, interfacial amorphous layer, surface roughness, and deterioration of the Bragg reflector layers. The correlations are established through analysis of corresponding extrinsic acoustic loss mechanisms, including Rayleigh scattering at localized defects, acoustic attenuation by amorphous layer, generation of the shear waves leaking into the substrate, waves scattering by surface roughness, and resonance broadening by local thickness variations. It is shown that the waves scattering by surface roughness at the BSTO film interfaces is the main loss mechanism limiting the Q-factor of the BSTO thin film bulk acoustic wave resonators.

Characterization of Al2O3 gate dielectric for graphene electronics on flexible substrates

“…Furthermore, we have fabricated GFETs with Al 2 O 3 as gate dielectric with the growth processes as mentioned above on PET substrate. The loss tangent of GFETs was calculated using the reflective coefficient measured by an Agilent N5230A vector network analyzer without drain bias [9]. The measured loss tangent of a GFET versus frequency is shown in Fig.…”

“…Thus, a possible path to improve performance of high frequency GFETs is to reduce the series resistance based on perfecting the design and fabrication process. The series resistance can be extracted from the real part of the measured input impedance [9]. Hence, the corresponding loss tangent of series resistance can be subtracted from the total loss tangent.…”

“…a and b are inner electrode radius and ring radius, respectively. The equivalent circuit of the structure based on the parallel capacitance model [9] is shown in Fig. 1 (c).…”

Switching reliability of tunable ferroelectric resonators and filters

“…Ferroelectrics with the composition of Ba (x) Sr (1-x) TiO 3 (BST) have been utilized in the design of film bulk acoustic resonators (FBARs) and solidly mounted resonators (SMRs) and have recently been demonstrated with dramatically improved quality factors [1] and tunabilities [2]. The performance of BST thin film resonators is expected to further improve by reducing the surface roughness of the device [3] and optimizing the Ba/Sr ratio of the BST [2].…”

Effect of ferroelectric substrate on carrier mobility in graphene field-effect transistors

“…The R s can be found as the real part of the input impedance at the high frequency limit and corresponding loss can be de-embedded from the total input losses. 32 The de-embedded loss tangents tand de are shown in Fig. 5.…”