ZnO/SiO2-diaphragm composite resonator on a silicon wafer

Nakamura, Kazuo; Sasaki, H.; Shimizu, Hiroshi

doi:10.1049/el:19810355

Cited by 91 publications

(22 citation statements)

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“…It is necessary to lower phase noise of Si-CMOS oscillators. In this paper, to improve the phase noise of oscillators, we used film bulk acoustic resonator (FBAR) [5,6,7] instead of conventional LC resonant circuit. FBAR have great advantages of high Q value, low insertion loss and small size over 2 GHz.…”

Section: Introductionmentioning

confidence: 99%

5GHz band low phase noise Si-CMOS oscillator using FBAR

Tanifuji

Kameda

et al. 2010

IEICE Electron. Express

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Section: Introductionmentioning

confidence: 99%

5GHz band low phase noise Si-CMOS oscillator using FBAR

Tanifuji

Kameda

et al. 2010

IEICE Electron. Express

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“…Besides electro-acoustic applications, optical applications [4] were also investigated. The potential of these films for RF filtering with bulk acoustic waves (BAWs) was soon discovered [5][6][7]. Such devices are composed of several electromechanical resonators, commonly called thin-film bulk acoustic resonators (TFBARs), which are based on standing bulk waves trapped in a film slab, as sketched in Fig.…”

Section: Introductionmentioning

confidence: 99%

Piezoelectric materials parameters for piezoelectric thin films in GHz applications

Muralt

Conde

Artieda

et al. 2009

Int. j. microw. wirel. technol.

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Piezoelectric thin films have existing and promising new applications in microwave filter technologies. The final performance depends on many parameters, and very specifically on the materials properties of each involved material. In this article, materials and properties for thin-film bulk acoustic wave resonators are discussed on some selected issues: the piezoelectric coefficients and acoustic losses of AlN, the relation of the first one with microstructural parameters, the inclusion of parasitic elements, and the merits of and problems with ferroelectric materials. I . I N T R O D U C T I O NThe wurtzite materials AlN and ZnO are currently the only piezoelectrics that are used in thin-film form for microwave applications in the 1-10 GHz range. They combine good piezoelectric properties with excellent acoustic qualities, and grow most easily in the optimal film orientation for RF filter applications. In addition, they can be synthesized by sputter deposition, a plasma method allowing for low processing temperatures. According to Hickernell [1], efforts to grow ZnO thin films go back to around 1965; good-quality films were obtained in the mid-to late 1970s, mostly by sputtering [2,3], but also by CVD [4]. Besides electro-acoustic applications, optical applications [4] were also investigated. The potential of these films for RF filtering with bulk acoustic waves (BAWs) was soon discovered [5][6][7]. Such devices are composed of several electromechanical resonators, commonly called thin-film bulk acoustic resonators (TFBARs), which are based on standing bulk waves trapped in a film slab, as sketched in Fig. 1, whereby film thickness defines the frequency of resonance. In these early years, ZnO was much more frequently investigated than AlN. Insufficient vacuum in the deposition tools at this time is certainly one of the reasons, because nitrides require much better vacuum conditions than oxides. In addition, the target applications had frequencies in the ultra-high frequency range (television), requiring a film thickness of several micrometers. This is not ideal for a material such as AlN that tends to create immense mechanical stresses, and also exhibits a very high sound velocity requiring almost twice as thick layers as with ZnO. Anyhow, the time was not yet ripe for TFBARs. Surface acoustic wave (SAW) devices based on piezoelectric single crystals such as quartz, LiNbO 3 , and LiTaO 3 were and are much more practical in the frequency range below 1 GHz. SAW filter production was much less demanding, once single-crystal wafers of these materials were available. TFBARs had to wait until the mid-1990s for the first industrial activities [8,9]. Sputter sources and industrial-type vacuum systems were considerably improved in the meantime, MEMS technology was already at a suitable development stage, and then the application was ready as well: mobile communication. Especially the second generation with carrier frequencies around 2 GHz was and still is ideal for TFBARs, because the required thin-film thickness is in...

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“…electrodes, support layers, etc) building the TF-BAR. Nakumura et al [13] modeled the dependence of the k 2 ef f on the ratio of the thicknesses of the piezoelectric layer and the TFBAR device. For the fundamental mode resonance (λ/2) it was found that k 2 ef f decreases with increasing mechanical load.…”

Section: Introductionmentioning

confidence: 99%

Effect of mechanical loading on the tuning of acoustic resonances in Ba x Sr1−x TiO3 thin films

et al. 2009

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The effect of mechanical loading on the tuning performance of a tunable Thin Film Bulk Acoustic Wave Resonator (TFBAR) based on a Ba 0.3 Sr 0.7 TiO 3 (BST) thin film has been investigated experimentally and theoretically. A membrane-type TFBAR was fabricated by means of micromachining. The mechanical load on the device was increased stepwise by evaporating SiO 2 on the backside of the membrane. The device was electrically characterized after each evaporation step and the results were compared to those obtained from modeling. The device with the smallest mechanical load exhibited a tuning of −2.4% and −0.6% for the resonance and antiresonance frequencies at a dc electric field of 615 kV/cm, respectively. With increasing mechanical load a decrease in the tuning performance was observed. This decrease was rather weak if the thickness of the mechanical load was smaller or comparable to the thickness of the active BST film. If the thickness of the mechanical load was larger than the thickness of the active BST layer, a significant reduction in the tuning performance was observed. The weaker tuning of the antiresonance frequency was due to a reduced tuning of the sound velocity of the BST layer with increasing dc bias. The resonance frequency showed a reduced tuning due to a decrease in the effective electromechanical coupling factor of the device with increasing mechanical load. With the help of the modeling we could de-embed the intrinsic tuning performance of a single, non-loaded BST thin film. We show that the tuning performance of the device with the smallest mechanical load we fabricated is close to the intrinsic tuning characteristics of the BST layer.

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ZnO/SiO2-diaphragm composite resonator on a silicon wafer

Cited by 91 publications

References 0 publications

5GHz band low phase noise Si-CMOS oscillator using FBAR

5GHz band low phase noise Si-CMOS oscillator using FBAR

Piezoelectric materials parameters for piezoelectric thin films in GHz applications

Effect of mechanical loading on the tuning of acoustic resonances in Ba x Sr1−x TiO3 thin films

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