Characterization of Thin-Film Decoupling and High-Frequency (Ba,Sr)TiO₃ Capacitors on Al₂O₃ Ceramic Substrates

Abstract

In this paper we present the results of the characterization of parallel-plate thin-film (Ba1-x ,Sr x )TiO3 (BST) capacitors, to demonstrate their suitability for use as decoupling capacitors (a capacitance as high as 0.34 µF and a capacitance density of up to 70 fF/µm2) and as tunable RF components (a small capacitance from 0.5 pF to 16 pF, a high tunability of 4.22:1 at 10 V and a capacitance density of up to 34 fF/µm2). BST films of different compositions, (Ba0.7Sr0.3)TiO3 and (Ba0.5Sr0.5)TiO3, were grown by metal-organic decomposition (MOD) and RF magnetron reactive sputtering on Pt/TiO x /SiO2/Al2O3 ceramic substrates. For large capacitors (2.25 mm2), capacitance and tan δ were measured at low frequencies (1 kHz) using an LCR meter. Smaller capacitors (16 µm2 to 961 µm2) were characterized in the frequency range of 0.01–20 GHz. Capacitance, tan δ and equivalent series resistance (ESR) were extracted from two port scattering parameters obtained using a vector network analyzer (VNA). The relationships between dielectric loss, tunability and commutation quality factor (CQF) vs BST composition and deposition conditions were outlined.

Microwave properties of epitaxial (111)-oriented Ba0.6Sr0.4TiO3 thin films on Al2O3(0001) up to 40 GHz

“…The application as tunable devices for telecommunications which are operated in the microwave range ͑300 MHz to 300 GHz͒ requires detailed knowledge of the microwave properties in the high-frequency domain. 7,8 Although ferroelectric materials in thin-film form often show inferior properties as compared to bulk ceramics, it has been demonstrated that high quality epitaxial films generally have much better properties than polycrystalline films. [9][10][11] Very recently, it was shown that by depositing epitaxial ͑111͒-oriented BST films on Al 2 O 3 ͑0001͒ substrates, it is possible to obtain higher tunability while keeping the microwave loss low compared to polycrystalline BST films.…”

Orientation Dependence of Epitaxial and One-Axis-Oriented (Ba0.5Sr0.5)TiO3 Films Prepared by RF Magnetron Sputtering

“…The films obtained were annealed at 500 C in atmospheric O 2 flow for 30 min. Epitaxial SrRuO 3 films 100 nm thick were deposited on (100) and 111 7,13) The crystal structure of the films was characterized by X-ray diffraction (XRD). The composition of the films was ascertained using a wavelength dispersion X-ray fluorescence (XRF) spectrometer.…”

High-Throughput Synthesis and Characterization of (BaxSr1–x)1+yTi1–yO3−δ and (BaxSr1–x)1+yTi1–yO3–zNz Perovskite Thin Films

“…Barium strontium titanate perovskites along the barium to strontium solid solution have been extensively studied due to their interesting electrical properties. − In the case of thin films, studies have focused on material compositions, synthetic routes, and the influence of the substrate. The main applications of such materials are decoupling capacitors, as well as their potential use in tunable microwave applications.…”