A surface acoustic wave device including a LiTaO3 substrate, and an interdigital transducer is provided on the LiTaO3 substrate. The interdigital transducer includes as a major component at least one of Au, Ag, Ta, Mo, Cu, Ni, Cr, Zn, and W, and the interdigital transducer has a normalized film thickness h/λ of approximately 0.05 or less so as to excite a shear horizontal wave.
|
21. A surface acoustic wave device comprising:
a LiTaO3 substrate; and
an interdigital transducer provided on the LiTaO3 substrate, said interdigital transducer containing as a major component at least one of Au, Ag, Ta, Mo, Cu, Ni, Cr, Zn, and W; wherein
said interdigital transducer has a normalized film thickness h/λ within a range of approximately 0.001 to approximately 0.05;
the substrate has Euler angles of approximately (0°, 136° to 147°, 0°±5°).
0. 1. A surface acoustic wave device comprising:
a LiTaO3 substrate; and
an interdigital transducer provided on the LiTaO3 substrate, said interdigital transducer containing as a major component at least one of Au, Ag, Ta, Mo, Cu, Ni, Cr, Zn, and W; wherein
said interdigital transducer has a normalized film thickness h/λ within a range of approximately 0.001 to approximately 0.05 so as to excite a shear horizontal wave.
2. A surface acoustic wave device according to
a LiTaO3 substrate; and
an interdigital transducer provided on the LiTaO3 substrate, said interdigital transducer containing Au as a major component; wherein
said interdigital transducer has a normalized film thickness h/λ within a range of approximately 0.001 to approximately 0.05 so as to excite a shear horizontal wave; and
said substrate has Euler angles of approximately (0°, 125°-146°, 0°±5°).
3. A surface acoustic wave device according to
a LiTaO3 substrate; and
an interdigital transducer provided on the LiTaO3 substrate; wherein
said interdigital transducer has a normalized film thickness h/λ within a range of approximately 0.002 to approximately 0.05 so as to excite a shear horizontal wave;
said interdigital transducer includes Ag as a major component, ; and
said substrate has Euler angles of approximately (0°, 125°-140°, 0°±5°), and said normalized film thickness h/λ is within the range of approximately 0.002 to 0.05 .
4. A surface acoustic wave device according to
a LiTaO3 substrate; and
an interdigital transducer provided on the LiTaO3 substrate; wherein
said interdigital transducer has a normalized film thickness h/λ within a range of approximately 0.002 to approximately 0.05 so as to excite a shear horizontal wave;
said interdigital transducer includes Ta as a major component, ; and
said substrate has Euler angles of approximately (0°, 125°-140°, 0°±5°), and said normalized film thickness h/λ is within the range of approximately 0.002 to 0.05 .
5. A surface acoustic wave device according to
a LiTaO3 substrate; and
an interdigital transducer provided on the LiTaO3 substrate; wherein
said interdigital transducer has a normalized film thickness h/λ within a range of approximately 0.005 to approximately 0.05 so as to excite a shear horizontal wave;
said interdigital transducer includes Mo as a major component, ; and
said substrate has Euler angles of approximately (0°, 125°-134°, 0°±5°), and said normalized film thickness h/λ is within the range of approximately 0.005 to 0.05 .
6. A surface acoustic wave device according to
a LiTaO3 substrate; and
an interdigital transducer provided on the LiTaO3 substrate; wherein
said interdigital transducer has a normalized film thickness h/λ within a range of approximately 0.003 to approximately 0.05 so as to excite a shear horizontal wave;
said interdigital transducer includes Cu as a major component, ; and
said substrate has Euler angles of approximately (0°, 125°-137°, 0°±5°), and said normalized film thickness h/λ is within the range of approximately 0.003 to 0.05 .
7. A surface acoustic wave device according to
a LiTaO3 substrate; and
an interdigital transducer provided on the LiTaO3 substrate; wherein
said interdigital transducer has a normalized film thickness h/λ within a range of approximately 0.006 to approximately 0.05 so as to excite a shear horizontal wave;
said interdigital transducer includes Ni as a major component, ; and
said substrate has Euler angles of approximately (0°, 125°-133°, 0°±5°), and said normalized film thickness h/λ is within the range of approximately 0.006 to 0.05 .
8. A surface acoustic wave device according to
a LiTaO3 substrate; and
an interdigital transducer provided on the LiTaO3 substrate; wherein
said interdigital transducer has a normalized film thickness h/λ within a range of approximately 0.003 to approximately 0.05 so as to excite a shear horizontal wave;
said interdigital transducer includes Cr as a major component, ; and
said substrate has Euler angles of approximately (0°, 125°-147°, 0°±5°), and said normalized film thickness h/λ is within the range of approximately 0.003 to 0.05 .
9. A surface acoustic wave device according to
a LiTaO3 substrate; and
an interdigital transducer provided on the LiTaO3 substrate; wherein
said interdigital transducer has a normalized film thickness h/λ within a range of approximately 0.003 to approximately 0.05 so as to excite a shear horizontal wave;
said interdigital transducer includes Zn as a major component, ; and
said substrate has Euler angles of approximately (0°, 125°-138°, 0°±5°), and said normalized film thickness h/λ is within the range of approximately 0.003 to 0.05 .
10. A surface acoustic wave device according to
a LiTaO3 substrate; and
an interdigital transducer provided on the LiTaO3 substrate; wherein
said interdigital transducer has a normalized film thickness h/λ within a range of approximately 0.002 to approximately 0.05 so as to excite a shear horizontal wave;
said interdigital transducer includes W as a major component, ; and
said substrate has Euler angles of approximately (0°, 125°-138°, 0°±5°), and said normalized film thickness h/λ is within the range of approximately 0.002 to 0.05 .
0. 11. A communication device including the surface acoustic wave device according to
0. 22. A surface acoustic wave device according to
0. 23. A surface acoustic wave device according to
0. 24. A surface acoustic wave device according to
0. 25. A surface acoustic wave device according to
0. 26. A surface acoustic wave device according to
the normalized thickness h/λ is within a range of approximately 0.03 to approximately 0.05; and
the substrate has Euler angles of approximately (0°, 136° to 137°, 0°±5°).
0. 27. A surface acoustic wave device according to
the normalized thickness h/λ is approximately 0.04; and
the substrate has Euler angles of approximately (0°, 136° to 137°, 0°±5°).
0. 28. A surface acoustic wave device according to
the normalized thickness h/λ is within a range of approximately 0.03 to approximately 0.05; and
the substrate has Euler angles of approximately (0°, 136.5°, 0°±5°).
0. 29. A surface acoustic wave device according to
the normalized thickness h/λ is approximately 0.04; and
the substrate has Euler angles of approximately (0°, 136.5°, 0°±5°).
0. 30. A surface acoustic wave device according to
the substrate has Euler angles of approximately (0°, 136° to 137°, 0°±5°).
0. 31. A surface acoustic wave device according to
the substrate has Euler angles of approximately (0°, 136.5°, 0°±5°).
|
The present application is the parent application of U.S. patent application Ser. No. 10/831,108, filed Apr. 26, 2004, which is currently pending and is also a Reissue Application of U.S. Pat. No 6,366,002, issued Aug. 31, 2000.
1. Field of the Invention
The present invention relates to a surface acoustic wave device such as a surface acoustic wave resonator, a surface acoustic wave filter, a sharing device, or other suitable device, and more particularly, to a surface acoustic wave device which uses a Shear Horizontal wave (“SH wave”).
2. Description of the Related Art
Conventionally, surface acoustic wave devices have been widely used as band-pass filters for use in mobile communication equipment. One such conventional surface acoustic wave devices include a surface acoustic wave resonator having an IDT (interdigital transducer) composed of interdigital electrodes having electrode fingers interdigitated with each other, the IDT being disposed on a piezoelectric substrate, and a surface acoustic wave filter using the surface acoustic wave resonator.
In such a surface acoustic wave device, a technique is known in which a leaky surface acoustic wave having a large attenuation which propagates in a Y-X LiTaO3 substrate with Euler angles (0°, −90°, 0°) as a piezoelectric substrate is converted to a Love wave type surface acoustic wave having no propagation loss by providing an IDT having a predetermined thickness and made of a metal having a large mass load such as Au, Ta, W, or other suitable metal.
As shown in
However, as the thickness of IDT increases, the production accuracy decreases. Accordingly, a sufficiently large thickness cannot be achieved. Unless the film thickness is adequately large, for example, the thickness H/λ is at least 0.033 for the Au electrodes, a propagation loss of zero cannot be achieved.
On the other hand, the film thickness H/λ (electrode thickness/excited SH wavelength) at which the electrode fingers of an IDT can be made with general accuracy is up to 0.05.When the propagation loss is desired to be zero, the film thickness H/λ is required to be at least 0.033. Thus, the range of the film thickness where the electrode fingers of IDT can be formed with high accuracy is very narrow.
Further, if an IDT is formed of an electrode material having a slightly lower density than Au, such as Ta or W, the thickness of the electrodes must be further increased as compared with that of the Au electrodes. Thus, the propagation loss cannot be reduced to zero in the range of film thickness in which the film can be accurately formed.
Regarding materials such as Au having a considerably higher density as compared with electrodes materials generally used in the IDTs of surface acoustic wave devices such as Al, the frequencies differ with even slight variations in film thickness, electrode finger width, and electrode finger pitch of the IDTs. Thus, after the IDTs are formed, the frequencies are conditioned by trimming the IDTs. However, when an IDT is formed from Au so as to have H/λ of about 0.034, as an example, but the frequency is less than a desired value, such a frequency conditioning is carried out, causing the film thickness H/λ to be less than 0.033. That is, the propagation loss cannot be set at zero.
To overcome the above-described problems, preferred embodiments of the present invention provide a surface acoustic wave device in which the IDT are produced with high accuracy, the propagation losses in the IDT and the piezoelectric substrate are approximately zero, and the conditioning range for frequency trimming is substantially wider than the surface acoustic wave devices of the prior art.
According to one preferred embodiment of the present invention, a surface acoustic wave device includes a LiTaO3 substrate and an interdigital transducer provided on the LiTaO3 substrate. The interdigital transducer includes at least one of Au, Ag, Ta, Mo, Cu, Ni, Cr, Zn, and W, and the interdigital transducer has a normalized film thickness H/λ of about 0.05 or less so as to excite a shear horizontal wave.
If the interdigital transducer includes Au as a major component, the substrate preferably has Euler angles of approximately (0°, 125°-146°, 0°±5°), and the standardized film thickness H/λ is preferably within the range of about 0.001 to about 0.05.
If the interdigital transducer includes Ag as a major component, the substrate preferably has Euler angles of approximately (0°, 125°-146°, 0°±5°), and the standardized film thickness H/λ is preferably within the range of about 0.002 to about 0.05.
If the interdigital transducer includes Ta as a major component, the substrate preferably has Euler angles of approximately (0°, 125°-140°, 0°±5°), and the standardized film thickness H/λ is preferably within the range of about 0.002 to about 0.05.
If the interdigital transducer includes Mo as a major component, the substrate preferably has Euler angles of approximately (0°, 125°-134°, 0°±5°), and the standardized film thickness H/λ is preferably within the range of about 0.005 to about 0.05.
If the interdigital transducer includes Cu as a major component, the substrate preferably has Euler angles of approximately (0°, 125°-137°, 0°±5°), and the standardized film thickness H/λ is preferably within the range of about 0.003 to about 0.05.
If the interdigital transducer includes Ni as a major component, the substrate preferably has Euler angles of approximately (0°, 125°-133°, 0°±5°), and the standardized film thickness H/λ is preferably within the range of about 0.006 to about 0.05.
If the interdigital transducer includes Cr as a major component, the substrate preferably has Euler angles of approximately (0°, 125°-147°, 0°±5°), and the standardized film thickness H/λ is preferably within the range of about 0.003 to about 0.05.
If the interdigital transducer includes Zn as a major component, the substrate preferably has Euler angles of approximately (0°, 125°-137°, 0°±5°), and the standardized film thickness H/λ is preferably within the range of about 0.003 to about 0.05.
If the interdigital transducer includes W as a major component, the substrate preferably has Euler angles of approximately (0°, 125°-138°, 0°±5°), and the standardized film thickness H/λ is preferably within the range of about 0.002 to about 0.05.
The above-explained surface acoustic wave device is suitable for use in a communication device.
According to preferred embodiments of the present invention, on a LiTaO3 substrate having adequate Euler angles, an IDT is formed from an electrode material having a large specific gravity such as Au, Ag, Ta, Mo, Cu, Ni, Cr, Zn, Pt, W, or other suitable material, at an adequate film thickness, whereby an SH wave having a low propagation loss is excited. Thus, the leaky surface acoustic wave component is significantly reduced. A surface acoustic wave device having a very low propagation loss is produced.
Further, the propagation loss becomes substantially zero even where the film thickness is extremely small. Accordingly, even where the film thickness is altered by trimming IDT to control the frequency, the propagation loss is prevented from deteriorating, in contrast to the conventional surface acoustic wave devices. Thus, the conditioning range of the frequency trimming is much wider than the conventional surface acoustic wave devices.
Other features, characteristics, elements and advantages of the present invention will become apparent from the following description of preferred embodiments thereof with reference to the attached drawings.
Hereinafter, preferred embodiments of the present invention are explained in detail with reference to the drawings.
As seen in
The IDT 3 is configured such that one set of interdigital electrodes including as a major component at least one of Au, Ag, Ta, Mo, Cu, Ni, Cr, Zn, and W are arranged such that the interdigital tooth portions of the respective interdigital electrodes are opposed to each other.
The electrode fingers constituting the interdigital tooth portions of the IDT 3 preferably have a normalized film thickness H/λ of about 5% or less, and particularly, have a normalized film thickness H/λ (electrode thickness/excited SH wavelength)≦0.05. In this range, the electrode fingers are arranged with high accuracy.
As seen in
The IDTs 13a and 13b are preferably made of an electrode material including as a major component, at least one of Au, Ag, Ta, Mo, Cu, Ni, Cr, Zn, and W, and are configured such that a set of interdigital electrodes are arranged such that the interdigital tooth portions of the respective interdigital electrodes are opposed to each other. Further, the IDTs 13a, 13b are arranged substantially parallel to each other at a desired distance in the surface acoustic wave propagation direction. Also in this preferred embodiment, the electrode fingers constituting the interdigital tooth portion of each of the IDTs 13a and 13b preferably have a normalized film thickness H/λ of approximately 5% or less, and particularly, preferably have a normalized film thickness H/λ (electrode thickness/excited SH wavelength)≦0.05. In this range, the electrode fingers are formed with high accuracy.
As seen in
The IDTs 23a, 23b are preferably made of an electrode material including as a major component at least one of Au, Ag, Ta, Mo, Cu, Ni, Cr, Zn, and W, and are configured with a set of interdigital electrodes which are provided such that the interdigital tooth portions of the respective interdigital electrodes 23a, 23b are opposed to each other. The IDTs 23a and 23b are arranged in a substantially perpendicular direction relative to the surface acoustic wave propagation direction. In this preferred embodiment, as in the first and second preferred embodiments, the electrode fingers constituting the interdigital tooth portions of each of the IDTs 23a, 23b preferably have a normalized film thickness H/λ of approximately 5% or less, and particularly, preferably have a normalized film thickness H/λ (electrode thickness/excited SH wavelength)≦0.05. In this range, the electrode fingers are formed with high accuracy.
As seen in
The IDTs 33a, 33b each are preferably made of an electrode material including as a major component at least one of Au, Ag, Ta, Mo, Cu, Ni, Cr, Zn, and W, and have the configuration in which a set of interdigital electrodes are provided such that the interdigital tooth portions of the respective interdigital electrodes are opposed to each other. The IDTs 33a are arranged in the series arm, and the IDTs 33b are arranged in the parallel arm so as to provide a ladder configuration. In this preferred embodiment, as well as in the first, second, and third preferred embodiments, the electrode fingers constituting the interdigital tooth portions of each of the IDTs 33a and 33b preferably have a normalized film thickness H/λ of approximately 5% or less, and preferably have a normalized film thickness H/λ (electrode thickness/excited SH wavelength)≦0.05. In this range, the electrode fingers are formed with high accuracy.
Next, fifth and sixth preferred embodiments of the present invention will be described.
As seen in
Next, the normalized film thickness H/λ (electrode thickness/excited SH wavelength) will be described with reference to an example.
As seen in
As seen in
This is because in the conventional LiTaO3 substrate having Euler angles of (0°, −90°, 0°), the Love wave is excited, while in the surface acoustic wave device of preferred embodiments of the present invention, an SH wave having a very low propagation loss is used. Here, Au has been described. The present invention is not restricted to Au. In the case of other materials such as Ag, Ta, Mo, Cu, Ni, Cr, Zn, Pt, W, or other suitable materials, an SH wave is similarly used. Thus, the propagation loss is substantially improved similarly to when Au is used.
The film thickness at which an SH wave can be sufficiently used in the surface acoustic wave device of various preferred embodiments of the present invention varies depending on electrode materials. For example, the H/λ values are at least about 0.001 for Au, at least about 0.002 for Ag, at least about 0.002 for Ta, at least about 0.005 for Mo, at least about 0.003 for Cu, at least about 0.006 for Ni, at least about 0.003 for Cr, at least about 0.003 for Zn, and at least about 0.002 for W. Considering the propagation loss and the electromechanical coupling coefficient, it is suitable that the H/λ values are higher than these values.
In
Further, it is seen that in the case of Ag used as the electrodes of IDT, the cut angle at which the propagation loss of 0 is attained is approximately (0°, 125°-140°, 0°±5°) according to the Euler angle indication system of (φ, θ, ψ).
It is seen that in the case of Ta used as the electrodes of IDT, the cut angle at which the propagation loss of 0 is attained is approximately (0, 125°-140°, 0°±5°) according to the Euler angle indication system of (φ, θ, ψ).
It is seen that in the case of Mo used as the electrodes of IDT, the cut angle at which the propagation loss of 0 is attained is approximately (0°, 125°-134°, 0°±5°) according to the Euler angle indication system of (φ, θ, ψ).
It is seen that in the case of Cu used as the electrodes of IDT, the cut angle at which the propagation loss of 0 is attained is approximately (0°, 125°-137°, 0°±5°) according to the Euler angle indication system of (φ, θ, ψ).
It is seen that in the case of Ni used as the electrodes of IDT, the cut angle at which the propagation loss of 0 is attained is approximately (0°, 125°-133°, 0°±5°) according to the Euler angle indication system of (φ, θ, ψ).
It is seen that in the case of Cr used as the electrodes of IDT, the cut angle at which the propagation loss of 0 is attained is approximately (0°, 125°-147°, 0°±5°) according to the Euler angle indication system of (φ, θ, ψ).
It is seen that in the case of Zn used as the electrodes of IDT, the cut angle at which the propagation loss of 0 is attained is approximately (0°, 125°-137°, 0°±5°) according to the Euler angle indication system of (φ, θ, ψ).
It is seen that in the case of W used as the electrodes of IDT, the cut angle at which the propagation loss of 0 is attained is approximately (0°, 125°-138°, 0°±5°) according to the Euler angle indication system of (φ, θ, ψ).
Accordingly, by using a LiTaO3 substrate having a cut angle shown in
Furthermore, electromechanical coupling factors greater than that of Al are obtained, which can realize surface acoustic wave filters having a smaller insertion loss.
In the first to sixth preferred embodiments of the present invention, the surface acoustic wave device having reflectors is described. The present invention is not restricted to such a device, and is applicable to a surface acoustic wave device having no reflectors.
While preferred embodiments of the invention have been disclosed, various modes of carrying out the principles disclosed herein are contemplated as being within the scope of the following claims. Therefore, it is understood that the scope of the invention is not to be limited except as otherwise set forth in the claims.
Patent | Priority | Assignee | Title |
10355668, | Jan 20 2015 | Taiyo Yuden Co., Ltd. | Acoustic wave device |
Patent | Priority | Assignee | Title |
4001767, | Nov 18 1975 | The United States of America as represented by the Secretary of the Air | Low diffraction loss-low spurious response LiTaO3 substrate for surface acoustic wave devices |
5081389, | Nov 30 1990 | Tekelec Temex | Crystal cut angles for lithium tantalate crystal for novel surface acoustic wave devices |
5283037, | Sep 29 1988 | Hewlett-Packard Company | Chemical sensor utilizing a surface transverse wave device |
5302788, | Aug 06 1992 | CONNECTICUT ELECTRIC, INC | Molded case circuit breaker having trapezoidally shaped shaft |
5302877, | Mar 16 1992 | Kinseki, Limited | Surface acoustic wave device |
5760522, | Apr 10 1995 | SANYO ELECTRIC CO , LTD ; SHIMIZU, YASUTAKA | Surface acoustic wave device |
5854527, | Mar 08 1996 | SANYO ELECTRIC CO , LTD | Surface acoustic wave device and portable telephone using same |
5874869, | Nov 28 1996 | TAIYO YUDEN CO , LTD | Surface acoustic wave filter device on 40° to 42° rotated Y-X LITAO3 |
5914645, | Jun 05 1996 | HANGER SOLUTIONS, LLC | Surface acoustic wave device with optimized ratio of film thickness to electrode period |
6037699, | Apr 10 1995 | Sanyo Electric Co., Ltd.; Yasutaka Shimizu | Surface acoustic wave device |
6037847, | Oct 13 1995 | TAIYO YUDEN CO , LTD | Surface acoustic wave device using a leaky surface acoustic wave with an optimized cut angle of a piezoelectric substrate |
6556104, | Aug 31 2000 | TRIQUINT, INC | Surface acoustic wave devices using optimized cuts of a piezoelectric substrate |
EP353073, | |||
EP734120, | |||
GB2244880, | |||
GB2288503, | |||
JP10247835, | |||
JP10335965, | |||
JP2001355692, | |||
JP200177662, | |||
JP6164306, | |||
JP8316781, | |||
JP8340234, | |||
JP90018272, | |||
JP9018272, | |||
JP9153757, | |||
JP9167936, | |||
JP9331229, |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Mar 31 2004 | Murata Manufacturing Co., Ltd. | (assignment on the face of the patent) | / |
Date | Maintenance Fee Events |
Sep 02 2009 | M1552: Payment of Maintenance Fee, 8th Year, Large Entity. |
Jun 24 2010 | ASPN: Payor Number Assigned. |
Sep 04 2013 | M1553: Payment of Maintenance Fee, 12th Year, Large Entity. |
Date | Maintenance Schedule |
Jan 01 2011 | 4 years fee payment window open |
Jul 01 2011 | 6 months grace period start (w surcharge) |
Jan 01 2012 | patent expiry (for year 4) |
Jan 01 2014 | 2 years to revive unintentionally abandoned end. (for year 4) |
Jan 01 2015 | 8 years fee payment window open |
Jul 01 2015 | 6 months grace period start (w surcharge) |
Jan 01 2016 | patent expiry (for year 8) |
Jan 01 2018 | 2 years to revive unintentionally abandoned end. (for year 8) |
Jan 01 2019 | 12 years fee payment window open |
Jul 01 2019 | 6 months grace period start (w surcharge) |
Jan 01 2020 | patent expiry (for year 12) |
Jan 01 2022 | 2 years to revive unintentionally abandoned end. (for year 12) |