CA1118883A - Surface acoustic wave transducer fabrication to reduce reflections - Google Patents
Surface acoustic wave transducer fabrication to reduce reflectionsInfo
- Publication number
- CA1118883A CA1118883A CA000301799A CA301799A CA1118883A CA 1118883 A CA1118883 A CA 1118883A CA 000301799 A CA000301799 A CA 000301799A CA 301799 A CA301799 A CA 301799A CA 1118883 A CA1118883 A CA 1118883A
- Authority
- CA
- Canada
- Prior art keywords
- substrate
- transducer
- stripes
- combination
- metal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02818—Means for compensation or elimination of undesirable effects
- H03H9/02842—Means for compensation or elimination of undesirable effects of reflections
Landscapes
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
- Diaphragms For Electromechanical Transducers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A surface acoustic wave device having one or more reflectionless interdigital transducers. Each transducer is fabricated as interdigital metal stripes which fill grooves within the surface upon which the surface waves propagate.
The metal of the transducer and the material of the substrate are chosen to have substantially similar elastic properties thereby eliminating reflective mechanisms. Aluminum and quartz are preferred materials for the metal stripes and substrate.
A surface acoustic wave device having one or more reflectionless interdigital transducers. Each transducer is fabricated as interdigital metal stripes which fill grooves within the surface upon which the surface waves propagate.
The metal of the transducer and the material of the substrate are chosen to have substantially similar elastic properties thereby eliminating reflective mechanisms. Aluminum and quartz are preferred materials for the metal stripes and substrate.
Description
11~81383 Background of the Invention _ 1. _ eld of the Invention.
The invention pertains to surface acoustic wave devices and particularly to the construction o-f transducers used for launching and receiving surface waves upon such devices.
The invention pertains to surface acoustic wave devices and particularly to the construction o-f transducers used for launching and receiving surface waves upon such devices.
2. Description of the Prior Art.
-In the constructlon of surface acoustic wave devices,itis almost always desired to provide one or more interdigital transducers for launching and receiving surface waves upon a ;~ piezoelectric substrate or upon a non-piezoelectric substrate with an overlay film of piezoelectric material. Such trans-:
ducers are ordinarily constructed as two sets of interleaved metal stripes or flngers positioned upon the surface of the substrate or pi~ezoelectric film. ~he length of the fingers within each transducer could be constant or varied in accordance with a predetermined frequency characteristic as ~, desired.
Although such transducers functioned well to launch and receiv~ surface waves, the physical presence of the transducer upon the substrate or piezoelectric Eilm also caused unwanted reflection of surface waves propagating to or past the transducer or launched by the transducer itself. Such reElections caused a distortion in the transfer function of the surEace wave derice employing the transducer.
Re-Elections caused by transclucers generally arose from any or all of three cliferent mechanisms. ~lrst, if the metal oE
the ~ransducer had diEferent elastic properties than the substrate, a discontinuity in the acoustic impedance of the device in the region of the transducer resulted producing a mismatch between .
, 1~ iL1~883 the transducer and substrate. Secondly, the low electrical resistance of the metal o.~ the transducer shorted out the piezoel.ectric field of the substrate and causing a change in velocity of surface waves and hence a reflection in the region of the transducer. Thirdly, the physical presence of the metal caused a periodicc topographical variation at the surface of the substrate.
~0 ~ummary of the Invention Accordingly, it is an object of the present invention to provide a surface acoustic wave device having one or more transducers with substantially reduced reflection of sur~ace waves at the transducers.
It is also an object of the present invention to provide a surface acoustic wave device with minimal distortion in the transfer function oE the device.
These as well as other objects of the invention, may be met by providing the combination of a substrate having ~a surface suitable for supporting sur-face wave propagation and transducer means coupled to the surface wave supporting means wherein the topographical surface wave propagation properties are substantially constant in the region of the transducer.
The transducer preferably is a metal which has similar elastic properties to those of the substrate. The preferred materials ~ are aluminum for the metal of the transducer and quartz for the - substrate. l'he surface of the substrate may be substantially planar.
The invention may also be practiced by providing the combination of a substrate having a surface suitable -for supporting surface wave propagation and at least one transducer coupled to the substrate which has a plurality of interleaved parallel conductive stripes which are at least partially ~mbedded within the substrate. The upper surface oE each of the s~ripes shoulcl be substantially flush wlth the sur:Eace oE the substrate. The metal stripes of the transducer are constructed within a plurality of substantially parallel grooves extending ;Erom the surface into the substrate for predetermined distance.
As beEore, the substrate and conductive stripes preEerably have , similar elastic pro[)erties. The substrate may be quartz t particularly ST-cut qilartz, while the metal stripes are fabricated of aluminum.
Purther objects of the invention may be met by providing the combination of a substrate of pi.ezoelectric material having at least one surface adapted for surface wave propagation and having first and second sets of substantially parallel grooves extending from the surface into the substrate for predetermined distance and a plurality of stripes of metal filling the first and second sets of grooves in the substrate to form first and second transducers, one surface o~ the metal stripes being : substantially flush with the surface of the substrate. A-t least some of the me~al stripes within each transducer are electrically coupled to other ones of the stripes wi~hin the transducer such as in two groups. In a preferred embodiment as a surface acoustic wave oscillator device, amplifying means are coupled between the first and second transducers. Again, the substrate may comprise quartz, such as ST-cut quartz, while the metal stripes are aluminum.
The invention may also be practiced by a method comprising the steps of providing a substrate of piezoelectric material oovering at least a portion of the substrEIte with a first ~ayer oE metal, removing portions of the first layer of metal in the Eorm o:E parallel stripes in one or more regions of the first layer oE metal, removing portions of the substrate underlying the removed portions of the first layer o:f metal to a predeterm:ined depth to form a plurality oE parallel grooves in the substrate, Eilling the grooves through the removed portions of the first layer of metal with a second layer of metal to substantially the original level o~ the surface o~ the substrate, and removing the remaining portions of the first layer of metal, as well as unwanted portions of the second layer of metal. The substrate is preferably quartz while the second layer of metal is aluminum. The first layer of metal may be vanadium.
In accordance with the invention, there is provided in combi-nation: a pie~oelectric substrate comprising ST-cut quartz having an uncoated surface supporting surface wave propagation; at least one sub-stantially reflectionless transducer coupled to said surface waves on said substrate; and said transducer comprising a plurality of conductors positioned in grooves in said substrate whereby the mechanical energy of surface waves outside saia transducer conductors is substantially entirely within said substrate.
In accordance with another aspect of the invention, there is provided the method of ~anufacturing a surface acoustic wave transducer comprising the steps of: providing a piezoelectric substrate of ST-cut quartz; covering at least a portion of said substrate with a first layer of metal; removing portions of said fi.rst layer oP metal in the form of ; parallel stripes in one or more regions of said first layer of metal;
; re-mo~ing portions o~ said substrate underlying the removed portions of ~0 said first layer of metal to a predetermined depth to form a plurality of parallel grooves in said substrate; filling said grooves through said remoyed portions of said first layer of metal with a second layer of metal to substantially the original leYel of said surface of said s~lbstrate;
and rffmoving the remaining portions of said first layer of m~tal.
38#3 Brief Description of the Drawings FIG. 1 is a perspective view of a surface acoustic wave oscillator device in accordance with the invention having a partially cut away portion; and FIGS. 2A-2E are a series of cross-sectional views showing steps in the constructi.on of one of the transducers of the device shown in FIG. 1.
.
~)escrip-tion of the l~re:ferred ~bodiments Referring flrst to ~rG. 1 ~ there is shown a surface acoustic wave osci.lla-tor device in which the present invention is used to advantage. The oscilla~or device includes two primary operating elementsg surface acoustic wave delay line 5 and feedback amplifier 11.
Delay line 5 includes input a.nd output transducers 14 and 12 respectively, constructed upon piezoelectric substrate 10.
Surface waves produced by input transducer 14 propagate to output transducer 1~ with a delay time determined by the distance between the two transducers and the velocity of propagation of surface waves upon substrate 10. The surface waves received at output transducer 12 are amplified by amplifier 11 and subsequently coupled back to input transducer 1~. Amplifier 11 is connected so that the phase of the sur:face waves produced by input transducer 1~ from the fed-back signal is such as to continually reinforce the surface waves then propagating between input transducer 14 and ou~put transducer 12.
Both input transducer 14 and output transducer 12 are fabricated as part of surface acoustic wave delay line 5 in accordance with the teachings of the invention. In the preferred embodiment, the metal forming the fingers of both transducers is aluminum whil.e the substrate 10 is flbricated o ST-cut quartz. These two materials are preferred as they have similar elastic properties so that aluminum is a relatively good acoustic match to quartæ. ~lso, S~ cut quartz has a relatively low piezoelectric coupl:ing coefficient compared to other well-known piezoelectric materials commonly used for surface wave devices. This is advantageous :in that the piezoelectric shorting effect caused by the presence of the metal is minimal.
In accordance with the inventioll, the metal ingers of both input transducer 14 and output transducer 12 are recessed within the surface o~ substrate lO such that the upper sur~ace of the metal of both transducers is substantially flush with the upper surface of substrate lO. In this manner, because o-f the good acoustic match between the metal of the fingers and the substrat~, there is substantially no reflection oE surface waves due to periodic topographical variations as the surface over the transducers is substantially smooth and of constant elastic properties. Hence, with the transducer and surface wave devices as shown in FIG. l, substantially all of the reflection mechanisms at the transducers have been eliminated. Because the transducers are substantially reflectionless, the distortion of the passband characteristics of prior art devices is eliminated.
Referring next to the series oE cross-sectional views of FI~S. 2A-2E, a method of fabricating transducers for a device ~uch as shown in FIG. l ~ill be described. ~irst, as shown in FIG. 2A, a substrate lO of ST-cut quartz is provided having at least one surface suitable for surface wave propagation thereupon.
Substrate lO is next covered with a layer of vanadium 16 using any of a number or well-known metal deposltion technlques. A
thickness o 300 A oE vanadium layer 16 has been Eound adequate.
Atop vanadium layer :l6 is then deposited a layer oE photoresist L8. Next, as shown in FIG. 2B, photoresist layer 18 is masked exposed to developing radiation, and removed chemically in the pattern shown. The portions of vanadium layer 16 exposed through the openings in photoresist layer 18 are then removed using a technlque such as ion-beam etching.
Then, as sho~n in FIG. 2C, grooves 20 are etched into substratc 10 to a predetermined clepth. A depth of 1500 A has been found adequate. A layer of aluminum 22 is next deposited within grooves 20 and atop photoresist la~er 18 until the aluminum in the grooves reaches -the level of the surface of substrate 10. An evaporation deposition technique is preferred.
Finally, the remaining portions of vanadium layer 16 and photoresist layer 18, as well as that portion of the aluminum layer 22 lying atop photoresist layer 18, are chemically stripped away leaving the completed transducer as shown in the view of FIG. 2E.
This completes the description of the preferred embodiments of the invention. Although preferred embodiments have been described, it is believed that numerous modifications and alterations thereto would be apparent to one having ordinary skill in the art without departing from the spirit and scope of the invention.
ZO
-In the constructlon of surface acoustic wave devices,itis almost always desired to provide one or more interdigital transducers for launching and receiving surface waves upon a ;~ piezoelectric substrate or upon a non-piezoelectric substrate with an overlay film of piezoelectric material. Such trans-:
ducers are ordinarily constructed as two sets of interleaved metal stripes or flngers positioned upon the surface of the substrate or pi~ezoelectric film. ~he length of the fingers within each transducer could be constant or varied in accordance with a predetermined frequency characteristic as ~, desired.
Although such transducers functioned well to launch and receiv~ surface waves, the physical presence of the transducer upon the substrate or piezoelectric Eilm also caused unwanted reflection of surface waves propagating to or past the transducer or launched by the transducer itself. Such reElections caused a distortion in the transfer function of the surEace wave derice employing the transducer.
Re-Elections caused by transclucers generally arose from any or all of three cliferent mechanisms. ~lrst, if the metal oE
the ~ransducer had diEferent elastic properties than the substrate, a discontinuity in the acoustic impedance of the device in the region of the transducer resulted producing a mismatch between .
, 1~ iL1~883 the transducer and substrate. Secondly, the low electrical resistance of the metal o.~ the transducer shorted out the piezoel.ectric field of the substrate and causing a change in velocity of surface waves and hence a reflection in the region of the transducer. Thirdly, the physical presence of the metal caused a periodicc topographical variation at the surface of the substrate.
~0 ~ummary of the Invention Accordingly, it is an object of the present invention to provide a surface acoustic wave device having one or more transducers with substantially reduced reflection of sur~ace waves at the transducers.
It is also an object of the present invention to provide a surface acoustic wave device with minimal distortion in the transfer function oE the device.
These as well as other objects of the invention, may be met by providing the combination of a substrate having ~a surface suitable for supporting sur-face wave propagation and transducer means coupled to the surface wave supporting means wherein the topographical surface wave propagation properties are substantially constant in the region of the transducer.
The transducer preferably is a metal which has similar elastic properties to those of the substrate. The preferred materials ~ are aluminum for the metal of the transducer and quartz for the - substrate. l'he surface of the substrate may be substantially planar.
The invention may also be practiced by providing the combination of a substrate having a surface suitable -for supporting surface wave propagation and at least one transducer coupled to the substrate which has a plurality of interleaved parallel conductive stripes which are at least partially ~mbedded within the substrate. The upper surface oE each of the s~ripes shoulcl be substantially flush wlth the sur:Eace oE the substrate. The metal stripes of the transducer are constructed within a plurality of substantially parallel grooves extending ;Erom the surface into the substrate for predetermined distance.
As beEore, the substrate and conductive stripes preEerably have , similar elastic pro[)erties. The substrate may be quartz t particularly ST-cut qilartz, while the metal stripes are fabricated of aluminum.
Purther objects of the invention may be met by providing the combination of a substrate of pi.ezoelectric material having at least one surface adapted for surface wave propagation and having first and second sets of substantially parallel grooves extending from the surface into the substrate for predetermined distance and a plurality of stripes of metal filling the first and second sets of grooves in the substrate to form first and second transducers, one surface o~ the metal stripes being : substantially flush with the surface of the substrate. A-t least some of the me~al stripes within each transducer are electrically coupled to other ones of the stripes wi~hin the transducer such as in two groups. In a preferred embodiment as a surface acoustic wave oscillator device, amplifying means are coupled between the first and second transducers. Again, the substrate may comprise quartz, such as ST-cut quartz, while the metal stripes are aluminum.
The invention may also be practiced by a method comprising the steps of providing a substrate of piezoelectric material oovering at least a portion of the substrEIte with a first ~ayer oE metal, removing portions of the first layer of metal in the Eorm o:E parallel stripes in one or more regions of the first layer oE metal, removing portions of the substrate underlying the removed portions of the first layer o:f metal to a predeterm:ined depth to form a plurality oE parallel grooves in the substrate, Eilling the grooves through the removed portions of the first layer of metal with a second layer of metal to substantially the original level o~ the surface o~ the substrate, and removing the remaining portions of the first layer of metal, as well as unwanted portions of the second layer of metal. The substrate is preferably quartz while the second layer of metal is aluminum. The first layer of metal may be vanadium.
In accordance with the invention, there is provided in combi-nation: a pie~oelectric substrate comprising ST-cut quartz having an uncoated surface supporting surface wave propagation; at least one sub-stantially reflectionless transducer coupled to said surface waves on said substrate; and said transducer comprising a plurality of conductors positioned in grooves in said substrate whereby the mechanical energy of surface waves outside saia transducer conductors is substantially entirely within said substrate.
In accordance with another aspect of the invention, there is provided the method of ~anufacturing a surface acoustic wave transducer comprising the steps of: providing a piezoelectric substrate of ST-cut quartz; covering at least a portion of said substrate with a first layer of metal; removing portions of said fi.rst layer oP metal in the form of ; parallel stripes in one or more regions of said first layer of metal;
; re-mo~ing portions o~ said substrate underlying the removed portions of ~0 said first layer of metal to a predetermined depth to form a plurality of parallel grooves in said substrate; filling said grooves through said remoyed portions of said first layer of metal with a second layer of metal to substantially the original leYel of said surface of said s~lbstrate;
and rffmoving the remaining portions of said first layer of m~tal.
38#3 Brief Description of the Drawings FIG. 1 is a perspective view of a surface acoustic wave oscillator device in accordance with the invention having a partially cut away portion; and FIGS. 2A-2E are a series of cross-sectional views showing steps in the constructi.on of one of the transducers of the device shown in FIG. 1.
.
~)escrip-tion of the l~re:ferred ~bodiments Referring flrst to ~rG. 1 ~ there is shown a surface acoustic wave osci.lla-tor device in which the present invention is used to advantage. The oscilla~or device includes two primary operating elementsg surface acoustic wave delay line 5 and feedback amplifier 11.
Delay line 5 includes input a.nd output transducers 14 and 12 respectively, constructed upon piezoelectric substrate 10.
Surface waves produced by input transducer 14 propagate to output transducer 1~ with a delay time determined by the distance between the two transducers and the velocity of propagation of surface waves upon substrate 10. The surface waves received at output transducer 12 are amplified by amplifier 11 and subsequently coupled back to input transducer 1~. Amplifier 11 is connected so that the phase of the sur:face waves produced by input transducer 1~ from the fed-back signal is such as to continually reinforce the surface waves then propagating between input transducer 14 and ou~put transducer 12.
Both input transducer 14 and output transducer 12 are fabricated as part of surface acoustic wave delay line 5 in accordance with the teachings of the invention. In the preferred embodiment, the metal forming the fingers of both transducers is aluminum whil.e the substrate 10 is flbricated o ST-cut quartz. These two materials are preferred as they have similar elastic properties so that aluminum is a relatively good acoustic match to quartæ. ~lso, S~ cut quartz has a relatively low piezoelectric coupl:ing coefficient compared to other well-known piezoelectric materials commonly used for surface wave devices. This is advantageous :in that the piezoelectric shorting effect caused by the presence of the metal is minimal.
In accordance with the inventioll, the metal ingers of both input transducer 14 and output transducer 12 are recessed within the surface o~ substrate lO such that the upper sur~ace of the metal of both transducers is substantially flush with the upper surface of substrate lO. In this manner, because o-f the good acoustic match between the metal of the fingers and the substrat~, there is substantially no reflection oE surface waves due to periodic topographical variations as the surface over the transducers is substantially smooth and of constant elastic properties. Hence, with the transducer and surface wave devices as shown in FIG. l, substantially all of the reflection mechanisms at the transducers have been eliminated. Because the transducers are substantially reflectionless, the distortion of the passband characteristics of prior art devices is eliminated.
Referring next to the series oE cross-sectional views of FI~S. 2A-2E, a method of fabricating transducers for a device ~uch as shown in FIG. l ~ill be described. ~irst, as shown in FIG. 2A, a substrate lO of ST-cut quartz is provided having at least one surface suitable for surface wave propagation thereupon.
Substrate lO is next covered with a layer of vanadium 16 using any of a number or well-known metal deposltion technlques. A
thickness o 300 A oE vanadium layer 16 has been Eound adequate.
Atop vanadium layer :l6 is then deposited a layer oE photoresist L8. Next, as shown in FIG. 2B, photoresist layer 18 is masked exposed to developing radiation, and removed chemically in the pattern shown. The portions of vanadium layer 16 exposed through the openings in photoresist layer 18 are then removed using a technlque such as ion-beam etching.
Then, as sho~n in FIG. 2C, grooves 20 are etched into substratc 10 to a predetermined clepth. A depth of 1500 A has been found adequate. A layer of aluminum 22 is next deposited within grooves 20 and atop photoresist la~er 18 until the aluminum in the grooves reaches -the level of the surface of substrate 10. An evaporation deposition technique is preferred.
Finally, the remaining portions of vanadium layer 16 and photoresist layer 18, as well as that portion of the aluminum layer 22 lying atop photoresist layer 18, are chemically stripped away leaving the completed transducer as shown in the view of FIG. 2E.
This completes the description of the preferred embodiments of the invention. Although preferred embodiments have been described, it is believed that numerous modifications and alterations thereto would be apparent to one having ordinary skill in the art without departing from the spirit and scope of the invention.
ZO
Claims (15)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A surface acoustic wave transducer comprising in combination:
a piezoelectric substrate comprising ST-cut quartz, having an uncoated surface supporting surface wave propagation;
at least one substantially reflectionless aluminum transducer coupled to said surface waves on said substrate; and said transducer comprising a plurality of conductors positioned in grooves in said substrate whereby the mechanical energy of surface waves outside said transducer conductors is substantially entirely within said substrate.
a piezoelectric substrate comprising ST-cut quartz, having an uncoated surface supporting surface wave propagation;
at least one substantially reflectionless aluminum transducer coupled to said surface waves on said substrate; and said transducer comprising a plurality of conductors positioned in grooves in said substrate whereby the mechanical energy of surface waves outside said transducer conductors is substantially entirely within said substrate.
2. A surface acoustic wave transducer comprising in combination:
a piezoelectric substrate comprising ST-cut quartz, having an uncoated surface supporting surface wave propagation;
aluminum transducer means coupled to said surface waves propa-gation, the topographical surface waves propagation properties being substantially constant in the region of said transducer; and said transducer means comprising a plurality of conductors positioned in grooves in said substrate whereby the mechanical energy of surface waves outside said transducer means is substantially entirely within said substrate.
a piezoelectric substrate comprising ST-cut quartz, having an uncoated surface supporting surface wave propagation;
aluminum transducer means coupled to said surface waves propa-gation, the topographical surface waves propagation properties being substantially constant in the region of said transducer; and said transducer means comprising a plurality of conductors positioned in grooves in said substrate whereby the mechanical energy of surface waves outside said transducer means is substantially entirely within said substrate.
3. The combination of claim 2 wherein:
said aluminum and said ST-cut quartz have similar elastic properties.
said aluminum and said ST-cut quartz have similar elastic properties.
4. The combination of claim 3 wherein:
said surface of said substrate is substantially planar.
said surface of said substrate is substantially planar.
5. A surface acoustic wave transducer comprising in combination:
a piezoelectric substrate comprising ST-cut quartz, having an uncoated surface supporting surface wave propagation;
at least one aluminum transducer coupled to surface waves propa-gating in said substrate surface; and said transducer comprising a plurality of interleaved parallel conductive stripes at least partially embedded ingrooves in said substrate whereby the mechanical energy of surface waves outside said transducer is substantially entirely within said substrate.
a piezoelectric substrate comprising ST-cut quartz, having an uncoated surface supporting surface wave propagation;
at least one aluminum transducer coupled to surface waves propa-gating in said substrate surface; and said transducer comprising a plurality of interleaved parallel conductive stripes at least partially embedded ingrooves in said substrate whereby the mechanical energy of surface waves outside said transducer is substantially entirely within said substrate.
6. The combination of claim 5 wherein:
at least one surface of each of said stripes is substantially flush with said surface of said substrate.
at least one surface of each of said stripes is substantially flush with said surface of said substrate.
7. The combination of claim 5 wherein:
said substrate has a plurality of substantially parallel grooves extending from said surface into said substrate for a predetermined dis-tance.
said substrate has a plurality of substantially parallel grooves extending from said surface into said substrate for a predetermined dis-tance.
8. The combination of claim 7 wherein:
said conductive stripes substantially fill said grooves; and one surface of each of said conductive stripes is substantially flush with said surface of said substrate.
said conductive stripes substantially fill said grooves; and one surface of each of said conductive stripes is substantially flush with said surface of said substrate.
9. The combination of claim 8 wherein:
said substrate and said conductive stripes have similar elastic properties.
said substrate and said conductive stripes have similar elastic properties.
10. A surface acoustic wave transducer comprising in combination:
a piezoelectric substrate of ST-cut quartz, having at least one uncoated surface, said surface having first and second sets of sub-stantially parallel grooves extending from said surface into said sub-strate for a predetermined distance;
a plurality of stripes of aluminum filling said first and second sets of grooves in said substrate to form first and second trans-ducers coupled to said substrate, one surface of said aluminum stripes being substantially flush with said surface of said substrate; and each of said transducers comprising said plurality of stripes positioned in grooves in said substrate whereby the mechanical energy of surface waves outside said stripes of aluminum is substantially entirely within said substrate.
a piezoelectric substrate of ST-cut quartz, having at least one uncoated surface, said surface having first and second sets of sub-stantially parallel grooves extending from said surface into said sub-strate for a predetermined distance;
a plurality of stripes of aluminum filling said first and second sets of grooves in said substrate to form first and second trans-ducers coupled to said substrate, one surface of said aluminum stripes being substantially flush with said surface of said substrate; and each of said transducers comprising said plurality of stripes positioned in grooves in said substrate whereby the mechanical energy of surface waves outside said stripes of aluminum is substantially entirely within said substrate.
11. The combination of claim 10 wherein:
at least some of said aluminum stripes within each transducer are electrically coupled to other ones of said stripes within each transducer.
at least some of said aluminum stripes within each transducer are electrically coupled to other ones of said stripes within each transducer.
12. The combination of claim 11 wherein:
said stripes within each of said transducers are coupled in two groups.
said stripes within each of said transducers are coupled in two groups.
13. The combination of claim 10 further comprising:
amplifying means coupled between first and second transducers.
amplifying means coupled between first and second transducers.
14. The method of manufacturing a surface acoustic wave transducer comprising the steps of:
providing a piezoelectric substrate of ST-cut quartz;
covering at least a portion of said substrate with a first layer of metal;
removing portions of said first layer of metal in the form of parallel stripes in one or more regions of said first layer of metal;
removing portions of said substrate underlying the removed portions of said first layer of metal to a predetermined depth to form a plurality of parallel grooves in said substrate;
filling said grooves through said removed portions of said first layer of metal with a layer of aluminum to substantially the original level of said surface of said substrate; and removing the remaining portions of said first layer of metal.
providing a piezoelectric substrate of ST-cut quartz;
covering at least a portion of said substrate with a first layer of metal;
removing portions of said first layer of metal in the form of parallel stripes in one or more regions of said first layer of metal;
removing portions of said substrate underlying the removed portions of said first layer of metal to a predetermined depth to form a plurality of parallel grooves in said substrate;
filling said grooves through said removed portions of said first layer of metal with a layer of aluminum to substantially the original level of said surface of said substrate; and removing the remaining portions of said first layer of metal.
15. The method of claim 14 wherein:
said first layer of metal comprises vanadium.
said first layer of metal comprises vanadium.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US80259377A | 1977-06-02 | 1977-06-02 | |
| US802,593 | 1977-06-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1118883A true CA1118883A (en) | 1982-02-23 |
Family
ID=25184157
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000301799A Expired CA1118883A (en) | 1977-06-02 | 1978-04-24 | Surface acoustic wave transducer fabrication to reduce reflections |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1118883A (en) |
| DE (1) | DE2821748A1 (en) |
| FR (1) | FR2393465A1 (en) |
| GB (1) | GB1596077A (en) |
| IT (1) | IT7849468A0 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4237433A (en) * | 1979-03-13 | 1980-12-02 | Sperry Corporation | Surface acoustic wave resonators with integrated internal coupler reflectors |
| US4577169A (en) * | 1984-08-01 | 1986-03-18 | At&T Bell Laboratories | Small ripple surface acoustic wave filter with low insertion loss |
-
1978
- 1978-04-24 CA CA000301799A patent/CA1118883A/en not_active Expired
- 1978-05-18 DE DE19782821748 patent/DE2821748A1/en not_active Withdrawn
- 1978-05-19 IT IT7849468A patent/IT7849468A0/en unknown
- 1978-05-22 GB GB21024/78A patent/GB1596077A/en not_active Expired
- 1978-05-29 FR FR7815927A patent/FR2393465A1/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| GB1596077A (en) | 1981-08-19 |
| FR2393465A1 (en) | 1978-12-29 |
| DE2821748A1 (en) | 1978-12-14 |
| IT7849468A0 (en) | 1978-05-19 |
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