Ube Industries, Inc.

National Institute of Advanced Industrial Science and Technology

Keigo Nagao

Tetsuo Yamada

Chisen Hashimoto

Kosuke Nishimura

Eiji Masui

Morito Akiyama

Naohiro Ueno

Hiroshi Tateyama

Kazuki Iwashita

Shinji Fukuda

Tetsuro Kunisawa

Hirofumi Kimura

A thin film piezoelectric resonator suppresses deterioration of impedance at antiresonant frequency and has a high Q value. The thin film piezoelectric resonator is provided with a semiconductor substrate (); an insulating layer () formed on the semiconductor substrate () in contact with the surface of the semiconductor substrate; and a piezoelectric resonator stack () formed above the insulating layer and having a lower electrode (), a piezoelectric layer () and an upper electrode () in this order from the insulating layer side. An oscillation space () is formed corresponding to an oscillation region where the lower electrode () and the upper electrode () of the piezoelectric resonator stack () overlap each other in the thickness direction. The fixed charge density in the insulating layer () is 1&#xd7;10cmor less. At the time of manufacturing the thin film piezoelectric resonator, the insulating layer is formed in contact with the semiconductor substrate and then, heat treatment at 300&#xb0; C. or higher is performed under non-oxygenated atmosphere.

Thin film piezoelectric resonator and method for manufacturing the same

A piezoelectric thin film resonator has a substrate and a piezoelectric layered structure including a lower electrode, piezoelectric aluminum nitride thin film with c-axis orientation and upper electrode formed on the substrate in this order. The lower electrode are made of a metal thin film including a layer containing ruthenium as a major component having a full-width half maximum (FWHM) of a rocking curve of a (0002) diffraction peak of ruthenium of 3.0&#xb0; or less. The piezoelectric aluminum nitride thin film formed on the lower electrode has a full-width half maximum (FWHM) of a rocking curve of a (0002) diffraction peak of 2.0&#xb0; or less.

Aluminum nitride thin film, composite film containing the same and piezoelectric thin film resonator using the same

A thin film piezoelectric device includes a substrate () having via holes () and a piezoelectric laminated structure () consisting of a lower electrode (), a piezoelectric film (), and an upper electrode () formed on the substrate () via an insulation layer (). A plurality of thin film piezoelectric resonators () are formed for the via holes (). The piezoelectric laminated structure () includes diaphragms () located to face the via holes () and a support area other than those. The thin film piezoelectric resonators () are electrically connected by the lower electrode (). When the straight line in the substrate plane passing through the centers () of the diaphragms () of the thin film piezoelectric resonators () has the length Dof the segment passing through the support area and the distance between the centers of the diaphragms of the thin film piezoelectric resonators () is Dthe ratio D/Dis 0.1 to 0.5. The via hole () is fabricated by the deep graving type reactive ion etching method.

Thin film piezoelectric resonator, thin film piezoelectric device, and manufacturing method thereof

Method of producing a piezoelectric thin film device comprises a step of forming an insulating layer () capable of being etched by a specific chemical substance on the upper surface of a substrate (); a step of forming a sacrificial layer () made of a substance having a higher etching rate by the specific chemical substance than the insulating layer on a partial region of the insulating layer; a step of forming a lower electrode () on a region including the sacrificial layer; a step of forming the piezoelectric thin film () on a region including a part of the lower electrode; a step of forming an upper electrode () on a region including a part of the piezoelectric thin film; a step of forming via hole (), which penetrates the piezoelectric thin film and lower electrode, so as to expose a part of the sacrificial layer; and a step of forming a space () for oscillation by etching both the sacrificial layer and the insulating layer with the same specific chemical substance by introducing the specific chemical substance through the via hole.

Method of manufacturing piezoelectric thin film device and piezoelectric thin film device

A method of producing a thin film bulk acoustic resonator having a piezoelectric layer, a first electrode joined to a first surface of the piezoelectric layer, and a second electrode joined to a second surface of the piezoelectric layer, which is located at the opposite side to the first surface, including the steps of forming a pit on a surface of a substrate; filling the pit with a sacrificial layer; polishing a surface of the sacrificial layer so that the RMS variation of a height of the surface of the sacrificial layer is equal to 25 nm or less; forming the first electrode over a partial area of the surface of the sacrificial layer and a partial area of the surface of the substrate; forming the piezoelectric layer on the first electrode so that RMS variation of a height of the second surface of the piezoelectric layer is equal to 5% or less of a thickness of the piezoelectric layer; forming the second electrode on the piezoelectric layer; and removing the sacrificial layer from the inside of the pit by etching.

Method of producing thin film bulk acoustic resonator

A thin film bulk acoustic resonator comprises a substrate () of a silicon single crystal, a base film () formed on the substrate () and composed of a dielectric film mainly containing silicon oxide, and a piezoelectric stacked structure () formed on the base film (). A vibratory section () composed of a part of the base film () and a part of the piezoelectric stacked structure (). The piezoelectric stacked structure () includes a lower electrode (), a piezoelectric film (), and an upper electrode () formed in this order from below. The substrate () had a via hole () in the region corresponding to the vibratory section (). The via hole forms a space for allowing vibration of the vibratory section (). The piezoelectric film () is an aluminum nitride thin film containing 0.2 to 3.0 atom % of alkaline earth metal and/or a rare earth metal. Thus, the thin film bulk acoustic resonator has a high performance such as a large electromechanical coupling coefficient, an excellent acoustic quality factor (Q) and an excellent frequency-temperature characteristic.

Film bulk acoustic resonator

A transmission band filter () having a series of elements () each composed of a film bulk acoustic resonator and grounded shunt elements () each composed of a film bulk acoustic resonator is connected between a transmission port () and an antenna port (). A reception band filter () having a series of elements () each composed of a film bulk acoustic resonator and grounded shunt elements () each composed of a film bulk acoustic resonator is connected between a reception port () and the antenna port (). A film bulk acoustic resonator () for adjustment is connected between the antenna port () and the ground. The resonance frequency of the adjusting film bulk acoustic resonator () lies between the upper limit frequency of the transmission frequency pass band of the transmission band filter () and the lower limit frequency of the reception frequency pass band of the reception band filter (). Therefore a duplexer such that it can be a monolithic element, the power handling capability is good, the size is small, and the cost is low is provided.

Filter using film bulk acoustic resonator and transmission/reception switch

A pit () is formed in a substrate comprising a silicon wafer () on a surface of which a silicon oxide thin layer () is formed. A sandwich structure () comprising a piezoelectric layer () and lower and upper electrodes () joined to both surfaces of the piezoelectric layer is disposed so as to stride over the pit (). The upper surface of the lower electrode () and the lower surface of the piezoelectric layer () joined to the upper surface of the lower electrode are treated so that the RMS variation of the height thereof is equal to 25 nm or less. The thickness of the lower electrode () is set to 150 nm or less. According to such a structure, there is provided a high-performance thin film bulk acoustic resonator which are excellent in electromechanical coupling coefficient and acoustic quality factor.

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Ube, Japan

Keigo Nagao