Patent EP0200304A2 successfully refreshed from Google Patents.
EP0200304A2
Expired / Lapsed
EP
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Saw devices including resistive films
Assignee: Nortel Networks Ltd
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Filing: 1986-02-24
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Granted: —
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Expires: 2006-02-24
Abstract
Abstract Each IDT (inter-digital transducer) (22, 24) of a SAW (surface acoustic wave) device (20) is formed on a thin resistive doped silicon film having the same pattern as the IDT, which improves adhesion of the IDT to the substrate. The silicon film also constitutes electro-acoustic absorbers (26, 28) between the IDTs and edges (40, 42) of the substrate, and can have a linearly tapered edge adjacent to each IDT to suppress reflections at the absorber boundary. The SAW device is formed by sputtering silicon onto the substrate, subsequently forming the IDTs, and then etching the silicon from areas where it is not wanted.
Inventors
- 👤 Grantley Oliver Este
- 👤 Mark Spencer Suthers
- 👤 Richard William Streater
- 👤 Blair Kenneth Maclaurin
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 08:29
CPC Classifications
H; H03; H03H; H03H3/00; H03H3/007; H03H3/08
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
43 words
A method of producing a SAW (surface acoustic wave) device comprising the steps of: forming a resistive film on a surface of a substrate of piezo-electric material; and forming at least one IDT (inter-digital transducer) for the SAW device on the resistive film.
Claim 2
Independent Claim
43 words
A method of producing a SAW (surface acoustic wave) device comprising the steps of: forming a resistive film on a surface of a substrate of piezo-electric material; and forming at least one IDT (inter-digital transducer) for the SAW device on the resistive film.
Claim 3
Dependent Claim
36 words
A method as claimed in claim 1 wherein the resistive film is formed on substantially all of said surface, the method further including the step of removing part of the resistive film after forming the IDT.
Claim 4
Dependent Claim
45 words
A method as claimed in claim 2 wherein the step of removing part of the resistive film comprises the step of leaving the resistive film in at least one area on the substrate surface to define a surface acoustic wave absorber region in this area.
Claim 5
Dependent Claim
34 words
A method as claimed in claim 3 wherein the resistive film is left in at least one area defining a surface acoustic wave absorber region adjacent to an IDT formed on the resistive film.
Claim 6
Dependent Claim
38 words
A method as claimed in claim 4 wherein the resistive film is left, in each area defining a surface acoustic wave absorber region region adjacent to an IDT, with a substantially linear tapered edge adjacent to the IDT.
Claim 7
Dependent Claim
27 words
A method as claimed in claim 1 wherein the resistive film is formed on the substrate surface in the pattern of each IDT to be formed thereon.
Claim 8
Dependent Claim
56 words
A method as claimed in claim 1 wherein the resistive film is formed on the substrate surface in the pattern of each IDT to be formed thereon and with at least one area defining a surface acoustic wave absorber region adjacent to this pattern, the resistive film constituting a surface acoustic wave absorber in this region.
Claim 9
Independent Claim
34 words
A method as claimed in claim, 7 wherein the resistive film is formed with a substantially linear tapered edge of each area defining a surface acoustic wave absorber region adjacent to an IDT pattern.
Claim 10
Independent Claim
29 words
A method as claimed in any of claims 1 to 8 wherein the the resistive film comprises a silicon film having a sheet resistivity of at least about 0.5Mohm/sq.
Claim 11
Independent Claim
28 words
A method as claimed in claims 2 and 9 wherein the step of removing part of the silicon film after forming the IDT comprises etching the silicon film.
Claim 12
Dependent Claim
27 words
A method as claimed in claim 10 wherein the step of forming the IDT comprises evaporating aluminum onto the silicon film in the pattern of the IDT.
Claim 13
Independent Claim
23 words
A method as claimed in any of claims 9 to 11 wherein the silicon film is formed on the substrate surface by sputtering.
Claim 14
Independent Claim
18 words
A method as claimed in any of claims 1 to 12 wherein the substrate material is lithium niobate.
Claim 15
Dependent Claim
39 words
A SAW (surface acoustic wave) device comprising at least one IDT (inter-digital transducer) - (22, 24) on a resistive film (46), having substantially the same pattern as the IDT, on a surface of a substrate (20) of piezo-electric material.
Claim 16
Dependent Claim
39 words
A SAW (surface acoustic wave) device comprising at least one IDT (inter-digital transducer) - (22, 24) on a resistive film (46), having substantially the same pattern as the IDT, on a surface of a substrate (20) of piezo-electric material.
Claim 17
Dependent Claim
33 words
A SAW device as claimed in claim 14 and including on the substrate surface a resistive film - (26, 28) constituting a surface acoustic wave absorber in a region adjacent to the IDT.
Claim 18
Dependent Claim
40 words
A SAW device as claimed in claim 15 wherein the resistive film (26, 28) constituting the surface acoustic wave absorber and the resistive film (46) having the IDT (22, 24) thereon are films of substantially the same material and thickness.
Claim 19
Dependent Claim
33 words
A SAW device as claimed in claim 15 or 16 wherein the resistive film (26, 28) constituting the surface acoustic wave absorber has a substantially linear tapered edge adjacent to the IDT pattern.
Claim 20
Dependent Claim
41 words
A SAW device as claimed in any of claims 15 to 17 wherein the resistive film (26, 28) constituting the surface acoustic wave absorber extends from adjacent to the IDT (22, 24) pattern to an edge (40, 42) of the substrate.
Claim 21
Dependent Claim
22 words
A SAW device as claimed in any of claims 15 to 19 wherein each of said films comprises an amorphous silicon film.
Claim 22
Dependent Claim
26 words
A SAW device as claimed in any of claims 15 to 19 wherein each of said films has a sheet resistivity of at least about 0.5Mohm/sq.
Claim 23
Dependent Claim
19 words
A SAW device as claimed in any of claims 14 to 20 wherein the substrate material is lithium niobate.
Claim 24
Dependent Claim
77 words
A SAW (surface acoustic wave) device comprising a substrate (20) having an IDT (inter-digital transducer) (22, 24) on a surface thereof, and a resistive film (26, 28) on the surface between a back edge of the IDT and an edge (40,42) of the substrate, the resistive film constituting a surface acoustic wave absorber and having a tapered front edge adjacent to the back edge of the IDT across at least part of the aperture of the IDT.
Claim 25
Dependent Claim
77 words
A SAW (surface acoustic wave) device comprising a substrate (20) having an IDT (inter-digital transducer) (22, 24) on a surface thereof, and a resistive film (26, 28) on the surface between a back edge of the IDT and an edge (40,42) of the substrate, the resistive film constituting a surface acoustic wave absorber and having a tapered front edge adjacent to the back edge of the IDT across at least part of the aperture of the IDT.
Claim 26
Dependent Claim
27 words
A SAW device as claimed in claim 22 wherein the tapered front edge of the resistive film extends across substantially all of the aperture of the IDT.
Claim 27
Dependent Claim
23 words
A SAW device as claimed in claim 22 or 23 wherein the resistive film has a sheet resistivity of at least about 0.5Mohm/sq.
Claim 28
Dependent Claim
20 words
A SAW device as claimed in any of claims 22 to 24 wherein the resistive film comprises amorphous doped silicon.
References Cited (Backward Citations)
No citation records indexed.
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