Sumitomo Electric Industries, Limited

Seiko Epson Corporation

Shinichi Shikata

Hideaki Nakahata

Akihiro Hachigo

Satoshi Fujii

Naoji Fujimori

Kenjiro Higaki

Katsuhiro Itakura

Yoshiki Nishibayashi

Yuichiro Seki

Tomoki Uemura

Hideo Itozaki

Takahiro Imai

Natsuo Tatsumi

Hiroyuki Kitabayashi

Tadashi Tomikawa

Hideki Hayashi

Hidenori Nakanishi

The present invention provides a surface acoustic wave device comprising a diamond, having operating frequencies in the range of several hundreds of MHz to several tens of GHz, and being capable of operating at high frequencies. The surface acoustic wave device of the present invention comprises a diamond layer or a substrate layer and a diamond layer, a ZnO piezoelectric layer, interdigital transducers and a short-circuit electrode layer, being characterized in that (2&#x3c0;&#xb7;H/&#x3bb;) is in the range of 3.0 to 10.0 where the thickness of the ZnO layer is H and the wavelength of the surface acoustic wave is &#x3bb;.

Saw device

A surface acoustic wave (SAW) device that is suitable for mass production and that has excellent operational performance at the superhigh-frequency range. The SAW device comprises (a) a diamond layer ; (b) a ZnO layer , with a thickness of tz, formed on the diamond layer ; (c) interdigital transducers (IDTs) , which excite and receive a SAW, formed on the ZnO layer ; and (d) an SiO layer , with a thickness of ts, formed on the ZnO layer so that the SiO layer can cover the IDTs . The structure of the SAW device is determined by specific numeric ranges of the parameters kh1 and kh2, which are given in equations kh1&equals;3&middot;2&pgr;&middot;(tz/&lgr;) and kh2&equals;3&middot;2&pgr;&middot;(ts/&lgr;), where &lgr; signifies the wavelength of the fundamental wave of the second Sezawa mode of the SAW. The SAW device uses the third harmonic of the second Sezawa mode of the SAW excited.

Surface acoustic wave element

Surface acoustic wave device and substrate thereof

A surface acoustic wave (SAW) device that is made with diamond, that has high efficiency, and that can be operated at high frequencies, particularly from 9.5 to 10.5 GHz. The SAW device comprises a diamond layer formed singly or formed on a substrate, a ZnO piezoelectric layer, interdigital transducers (IDTs), and a short-circuiting electrode as required. The SAW device has a structure in which the thickness of the ZnO layer, the wavelength of a harmonic of the SAW, and the line width of the IDTs fall in a specified range. With this structure, a large electromechanical coupling coefficient is obtained in a high-frequency range of 10 GHz band by utilizing the third or fifth harmonic of the SAW.

Surface acoustic wave device utilizing a ZnO layer and a diamond layer

A surface acoustic wave (SAW) device is provided that is suitable for mass production and that has excellent operational performance at the superhigh-frequency range. The SAW device comprises (a) a diamond layer 3; (b) a ZnO layer 4, with a thickness of tz, formed on the diamond layer 3; (c) interdigital transducers (IDTs) 5, which excite and receive a SAW, formed on the ZnO layer 4; and (d) an SiO layer 6, with a thickness of ts, formed on the ZnO layer 4 so that the SiO layer can cover the IDTs 5. The structure of the SAW device is determined by specific numeric ranges of the parameters kh1 and kh2, which are given in equations kh1&equals;5&middot;2&pgr;&middot;(tz/&lgr;) and kh2&equals;5&middot;2&pgr;(ts/&lgr;), where &lgr; signifies the wavelength of the fundamental wave of the second mode of the SAW. The SAW device uses the fifth harmonic of the second mode of the SAW.

Surface acoustic wave device

The invention offers a hard carbon film and a SAW substrate that are easy to fabricate or low in manufacturing cost while virtually maintaining the quality that affects the important properties of a device that comprises the hard carbon film or the SAW substrate. The hard carbon film comprises a composite film of graphite-like diamond and carbon clusters; the composite film has a continuous crystal structure.

Hard carbon film and surface-acoustic-wave substrate

Hard carbon film and surface acoustic-wave substrate

The present invention directed to a SAW device comprising a diamond layer a ZnO layer and an SiO.sub.2 layer, which can be operated at the frequency of 2 GHz or higher, with superior durability and less energy loss. The SAW device for 2nd mode surface acoustic wave of a wavelength .lambda. (.mu.m) according to the present invention comprises: (i) a diamond layer, (ii) a ZnO layer formed on the diamond layer, the ZnO layer having a thickness t.sub.z, (iii) an interdigital transducer (IDT) formed over the ZnO layer, and (iv) a SiO.sub.2 layer formed over the interdigital transducer onto the ZnO layer, the SiO.sub.2 layer having a thickness of t.sub.s ; wherein parameters kh.sub.z =(2.pi./.lambda.)t.sub.z and kh.sub.s =(2.pi./.lambda.)t.sub.s are given within a region A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-A in a two-dimensional Cartesian coordinate graph having abscissa axis of kh.sub.z and ordinate axis of kh.sub.s, the outer edge of the region A-B-C-D-E-F-G-H-I-J-K-L-M-N-O-P-Q-R-A being given by a closed chain in the Cartesian coordinate, consisting of points A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q and R and lines A-B, B-C, C-D, D-E, E-F, F-G, G-H, H-I, I-J, J-K, K-L, L-M, M-N, N-O, O-P, P-Q, Q-R and R-A, as shown in FIG. 1.

Diamond-ZnO surface acoustic wave device

A pnp transistor is formed having a heterojunction of p-type diamond (or BP.sub.x N.sub.1-x, 6HSiC) and n-type SiC (3CSiC). The transistor is formed such that a p.sup.+ -SiC (3CSiC) layer, a p-SiC (3CSiC) layer, an n.sup.+ -SiC (3CSiC) layer, a p-diamond (or BP.sub.x N.sub.1-x, 6HSiC) layer, and a p.sup.+ -diamond (or BP.sub.x N.sub.1-x, 6HSiC) layer are on a substrate, and a collector electrode, a base electrode. An emitter electrode is formed on and electrically connected to the p.sup.+ -Sic layer, the n.sup.+ -SiC layer, and the layer, respectively. This method produces a semiconductor device having a high resistance to various environmental conditions.

Method for forming heterojunction bipolar transistors

This transistor is a pnp transistor having a heterojunction of p-type diamond (or BP.sub.x N.sub.1-x, 6HSiC) and n-type SiC (3CSiC)and having a structure in which a p.sup.+ -SiC (3CSiC ) layer, a p-SiC (3CSiC) layer, an n.sup.+ -SiC (3CSiC) layer, a p-diamond (or BP.sub.x N.sub.1-x, 6HSiC ) layer, and a p.sup.+ -diamond (or BP.sub.x N.sub.1-x, 6HSiC) layer are formed on a substrate, and a collector electrode, a base electrode, and an emitter electrode are formed on and electrically connected to the p.sup.+ -Sic layer, the n.sup.+ -SiC layer, and the layer, respectively. This semiconductor device has a high resistance to environment.

Heterojunction bipolar transistor

A diamond substrate having a smooth surface, including a polycrystalline diamond film having a surface with a pit, and an insulating material other than diamond, which occupies the pit.

Polycrystalline diamond substrate and process for producing the same

A method of flattening diamond, including: forming a flat coating comprising a material different from diamond, on a surface of diamond having unevenness; and removing the coating and the unevenness of the surface of diamond by dry etching under a condition such that both of the coating and the diamond can be etched, thereby to smooth the surface of the diamond.

Method of polishing/flattening diamond

A surface acoustic wave element has a diamond layer, a piezoelectric thin film formed on the diamond layer, and a pair of electrodes for generating a surface acoustic wave having a specific wavelength and extracting the surface acoustic wave, wherein at least one electrode is a copper electrode epitaxially grown on the surface of the diamond layer. To manufacture this surface acoustic wave element, after the diamond layer is formed on a substrate by epitaxial growth, the copper electrodes each having the predetermined shape are formed on the surface of the diamond layer by epitaxial growth. Since the copper electrodes formed on the diamond layer consist of high-quality single crystal copper, resistances to electromigration and stress migrations can be increased. As a result, there is provided an excellent surface acoustic wave element free from electrical defects caused by degradation and failure of the copper electrodes or free from degradation of the electrical characteristics.

Method of manufacturing a surface acoustic wave element

A layer of boron nitride which is relatively easily workable is positioned in a stacked structure in close contact with a piezoelectric member, to provide a surface acoustic wave device which can be driven in a higher frequency range. Such a surface acoustic device (10) has a substrate (1), a boron nitride film (2) formed on the substrate (1), and a pair of interdigital electrodes (3a, 3b) formed on the boron nitride film (2). The interdigital electrodes (3a, 3b) are covered with a piezoelectric film (4), which is in close contact with the boron nitride film (2).

Stacked piezoelectric surface acoustic wave device with a boron nitride

A surface acoustic wave element includes a hard layer containing a composition component essentially consisting of at least one of diamond and a diamond-like carbon film, a piezoelectric layer formed on the hard layer, a silicon dioxide (SiO.sub.2) layer formed on the piezoelectric layer, and electrodes combined with the piezoelectric layer to perform electro-mechanical conversion. The surface acoustic wave element has a larger electro-mechanical coupling coefficient and a higher surface acoustic wave propagation velocity than does a conventional surface acoustic wave element having no silicon dioxide layer, thereby obtaining a surface acoustic wave element that can operate in a high-frequency range. In particular, the electro-mechanical coupling coefficient is increased. The SiO.sub.2 layer is an electric insulator and rarely reacts with moisture or acids. The SiO.sub.2 layer protects the piezoelectric layer and the electrodes from effects of the external environment, thereby providing a surface acoustic wave element having good high-frequency characteristics and a high resistance to adverse environments.

Growing community of inventors

Itami, Japan

Shinichi Shikata