Patent EP0353073A2 successfully refreshed from Google Patents.
EP0353073A2
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EP
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Acoustic surface wave devices
Assignee: Fujitsu Ltd
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Filing: 1989-07-27
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Granted: —
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Expires: 2009-07-27
Abstract
Abstract An acoustic surface wave device (1) having an oscillation frequency stable against temperature changes, and a wide range of oscillation frequency adjustment, is provided by an acoustic surface wave element comprising: a substrate (2) of a 36° rotated Y-cut single crystal lithium tantalate having X, Y and Z crystal axes and a top surface and side walls; electrodes (3, 4) formed on the top surface of the substrate such that an acoustic surface wave is propagated in a direction of the X-axis of the substrate and an oscillation of the acoustic surface wave occurs at a predetermined frequency, the electrodes having a thickness equal to 1 to 4% of a wavelength of the acoustic surface wave at the oscillation; and a plasma CVD-deposited layer of silicon dioxide covering the electrodes and the substrate, the silicon dioxide layer having a refractive index of 1.445 to 1.486 and a thickness equal to 16 to 26% of the wavelength of the acoustic surface wave at the oscillation.
Inventors
- 👤 Kiyoshi Satoh
- 👤 Yoshiro Fujiwara
- 👤 Kazushi Hashimoto
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 02:18
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/02; H03H9/02535; H03H9/02818; H03H9/02834; H03H9/02543; H03H9/02559
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
112 words
An acoustic surface wave device of the kind having operating electrodes (3, 4) formed on a main surface of a monocrystalline piezoelectric substrate (2), such that when it is in operation an acoustic surface wave of a predetermined frequency is propagated in a preset direction over the said main surface, there being a layer of silicon dioxide (5) deposited over the said main surface so as to cover the said operating electrodes thereon, which layer was produced by an energy-enhanced chemical vapour deposition method; characterised in that the thickness of the said layer (5) is in the range from 16 percent to 26 percent of the wavelength of the said acoustic wave.
Claim 2
Dependent Claim
112 words
An acoustic surface wave device of the kind having operating electrodes (3, 4) formed on a main surface of a monocrystalline piezoelectric substrate (2), such that when it is in operation an acoustic surface wave of a predetermined frequency is propagated in a preset direction over the said main surface, there being a layer of silicon dioxide (5) deposited over the said main surface so as to cover the said operating electrodes thereon, which layer was produced by an energy-enhanced chemical vapour deposition method; characterised in that the thickness of the said layer (5) is in the range from 16 percent to 26 percent of the wavelength of the said acoustic wave.
Claim 3
Dependent Claim
24 words
A device as claimed in claim 1, wherein the silicon dioxide layer (5) has a refractive index in the range from 1.445 to 1.486.
Claim 4
Dependent Claim
38 words
A device as claimed in claim 1 or 2, wherein the operating electrodes (3, 4) have a thickness, measured perpendicularly to the said main surface, in the range from 1 percent to 4 percent of the said wavelength.
Claim 5
Dependent Claim
20 words
A device as claimed in claim 1, 2 or 3, wherein the monocrystalline substrate (2) is made of lithium tantalate.
Claim 6
Dependent Claim
63 words
A device as claimed in claim 4, wherein in relation to x, y and z crystal axes of the monocrystalline substrate the said main surface is a plane containing the x axis and perpendicular to a line obtained by rotating the y axis, about the x axis, through 36 o towards the z axis; the said preset direction being along the x axis.
Claim 7
Independent Claim
39 words
A device as claimed in any preceding claim, wherein the operating electrodes include drive electrodes (3) spaced from adjacent reflective electrodes (4), in the said preset direction, by a distance substantially equal to one half of the said wavelength.
Claim 8
Dependent Claim
136 words
An acoustic surface wave element, comprising: a substrate of a 36° rotated Y-cut single crystal lithium tantalate having X, Y and Z crystal axes and a top surface and side walls; electrodes formed on the top surface of the substrate such that an acoustic surface wave is propagated in a direction of the X-axis of the substrate and an oscillation of the acoustic surface wave occurs at a predetermined frequency, the electrodes having a thickness equal to 1 to 4% of a wavelength of the acoustic surface wave at the oscillation; and a plasma CVD-deposited layer of silicon dioxide covering the electrodes and the substrate, the silicon dioxide layer having a refractive index of 1.445 to 1.486 and a thickness equal to 16 to 26% of the wavelength of the acoustic surface wave at the oscillation.
Claim 9
Dependent Claim
136 words
An acoustic surface wave element, comprising: a substrate of a 36° rotated Y-cut single crystal lithium tantalate having X, Y and Z crystal axes and a top surface and side walls; electrodes formed on the top surface of the substrate such that an acoustic surface wave is propagated in a direction of the X-axis of the substrate and an oscillation of the acoustic surface wave occurs at a predetermined frequency, the electrodes having a thickness equal to 1 to 4% of a wavelength of the acoustic surface wave at the oscillation; and a plasma CVD-deposited layer of silicon dioxide covering the electrodes and the substrate, the silicon dioxide layer having a refractive index of 1.445 to 1.486 and a thickness equal to 16 to 26% of the wavelength of the acoustic surface wave at the oscillation.
Claim 10
Dependent Claim
22 words
An acoustic surface wave element according to claim 7, wherein the silicon dioxide layer has a refractive index of 1.450 to 1.486.
Claim 11
Dependent Claim
33 words
An acoustic surface wave element according to claim 7 or 8, wherein the electrodes have a thickness equal to 2 to 3% of a wavelength of the acoustic surface wave at the oscillation.
Claim 12
Dependent Claim
36 words
An acoustic surface wave element according to claim 7, 8 or 9, wherein the silicon dioxide layer has a thickness equal to 18 to 22% of the wavelength of the acoustic surface wave at the oscillation.
Claim 13
Dependent Claim
28 words
An acoustic surface wave element according to any one of claims 7 to 10, having a temperature coefficient of the oscillation frequency of not more than 5 ppm/°C.
Claim 14
Dependent Claim
30 words
An acoustic surface wave element according to any one of claims 7 to 11, further having an insulator film deposited over the silicon dioxide layer for adjusting the oscillation frequency.
Claim 15
Dependent Claim
31 words
An acoustic surface wave element according to any one of claims 7 to 12, further having a dielectric layer at least on the side walls of the substrate, for preventing pyroelectricity.
Claim 16
Dependent Claim
38 words
An acoustic surface wave element according to any one of claims 7 to 13, further having an electric conductor layer at least on the side walls but not on the top surface of the substrate, for preventing pyroelectricity.
Claim 17
Dependent Claim
42 words
An acoustic surface wave element according to any one of claims 7 to 14, further having an etching stopper of a metal on the electrodes and outer wires connected thereto through windows of the silicon dioxide layer formed on the etching stopper.
References Cited (Backward Citations)
No citation records indexed.
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