A TC-SAW resonant structure with a noise suppression unit

Abstract

The present invention provides a TC-SAW resonant structure with a noise suppression unit, wherein the interdigital transducer comprises a first interdigital transducer and a second interdigital transducer; the first interdigital transducer comprises a first bus and first electrode fingers connected to the first bus, and the second interdigital transducer comprises a second bus and second electrode fingers connected to the second bus; a temperature compensation layer covers the surface of each first electrode finger and each second electrode finger; the noise suppression unit is a metal structure arranged in the temperature compensation layer, and the noise suppression unit forms a continuous periodic cosine waveform in the first direction. The present invention provides a surface acoustic wave device with a simple structure, lower cost, and easier processing. By arranging the noise suppression unit above the two ends of the electrode fingers of the interdigital transducer, the noise suppression units at each end are connected to form a continuous periodic cosine waveform structure, thereby suppressing noise and optimizing the performance of the surface acoustic wave device.

Description

Technical Field

[0001] The present invention relates to the field of filters, and in particular to an acoustic filter and a preparation method thereof. Background Art

[0002] At present, filters with resonant structures as basic units are increasingly widely used in the field of communications. Among them, TC-SAW (Temperature compensated-SAW) filters are a type of acoustic filter. Based on ordinary SAW filters, they are improved by covering or bonding temperature compensation layers to reduce the device's temperature coefficient of frequency (TCF). Therefore, they have the characteristics of small size and low insertion loss of SAW filters, and have the advantages of good frequency temperature stability, which can solve the problem of anti-interference in harsh temperature environments.

[0003] However, ordinary TC-SAW resonant structures / filters will generate large clutter signals, which seriously affect the performance of the resonant structure / filter. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a TC-SAW resonant structure with a noise suppression unit to address the deficiencies of the prior art. The noise suppression unit is provided to improve the noise suppression effect of the filter.

[0005] Technical solution: The TC-SAW resonant structure with a clutter suppression unit described in the present invention comprises:

[0006] substrate;

[0007] An IDT, the IDT is disposed on a substrate, the IDT comprises a first IDT and a second IDT; the first IDT comprises a first bus and first electrode fingers connected to the first bus, the second IDT comprises a second bus and second electrode fingers connected to the second bus;

[0008] A temperature compensation layer, wherein the temperature compensation layer covers the surface of each first electrode finger and each second electrode finger;

[0009] The noise suppression unit is a metal structure arranged in the temperature compensation layer. The noise suppression unit forms a cosine waveform with a continuous period in a first direction, and the first direction is parallel to the plane where the substrate is located.

[0010] Further, the clutter suppression unit includes a distributed metal structure or a continuous metal structure;

[0011] The distributed metal structure is constructed as a metal structure correspondingly arranged on the upper side of each first electrode finger and each second electrode finger;

[0012] The continuous metal structure is constructed of a first metal structure correspondingly arranged on the upper side of each first electrode finger and each second electrode finger and a second metal structure connecting each first metal structure.

[0013] Furthermore, the noise suppression unit has a peak / trough flush with the end of one of the first electrode finger and the second electrode finger in a second direction perpendicular to the substrate, and the periodic variation range of the cosine waveform corresponds to four first electrode fingers and four second electrode fingers.

[0014] Furthermore, the cross section of the clutter suppression unit in the second direction is rectangular.

[0015] Furthermore, it also includes contact electrodes, which are arranged on the first bus bar and the second bus bar.

[0016] Furthermore, it also includes a passivation layer, which covers the temperature compensation layer and has an opening on the contact electrode.

[0017] Furthermore, the distance between the outer edge of the noise suppression unit and the end of the first electrode finger / the second electrode finger in the third direction is in the range of (0-0.1)*L, where L is the operating wavelength of the interdigital transducer; the third direction is parallel to the plane where the substrate is located and intersects with the first direction.

[0018] Furthermore, the width of a single said clutter suppression unit along the first direction ranges from (0.3-0.6)*L, which is the same as the width of a single electrode finger in the first direction, and L is the operating wavelength of the interdigital transducer.

[0019] Furthermore, the gap length between the end of the first electrode finger and the second bus is in the range of (0.1-2)*L, and the gap length between the end of the second electrode finger and the first bus is in the range of (0.1-2)*L, where L is the operating wavelength of the interdigital transducer.

[0020] A TC-SAW filter comprises any one of the above-mentioned TC-SAW resonant structures with a noise suppression unit.

[0021] Beneficial effects: The basic structure of the chip of the current surface acoustic wave device is a piezoelectric substrate and a metal electrode structure made on the surface of the piezoelectric substrate: an interdigital transducer, a reflection grid array, a shielding electrode, multiple acoustic wave coupling electrodes, and a sensor sensitive structure. Each surface acoustic wave device has at least one interdigital transducer. The interdigital transducer is arranged in a longitudinal direction, that is, in the direction of acoustic wave propagation, with periodic electrode fingers arranged side by side and perpendicular to the direction of acoustic wave propagation, and the electrode fingers are alternately connected to the first and second buses. The surface acoustic waves excited by the interdigital transducer propagate to both sides. The sound channel of the surface acoustic wave transmission is related to the characteristics of the propagation substrate. In practical devices, the sound channel will generally gradually spread. The expansion of the sound channel leads to the generation of stray acoustic wave modes, and the effective acoustic wave energy is lost, the device Q value is reduced, and the device performance is significantly degraded.

[0022] The present invention provides a surface acoustic wave device with a simple structure, lower cost and easier processing. By arranging clutter suppression units above both ends of electrode fingers of an interdigital transducer, the clutter suppression units at each end are connected to form a cosine waveform structure with a continuous period, thereby suppressing clutter and optimizing the performance of the surface acoustic wave device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a cross-sectional view of a TC-SAW resonant structure based on a distributed metal layer (DCM) structure in Example 1;

[0024] Figure 2 A top view of a TC-SAW resonant structure based on a distributed metal layer (DCM) structure in Example 1;

[0025] Figure 3 for Figure 2 A partial enlarged view of the boxed part;

[0026] Figure 4 is a cross-sectional view of a TC-SAW resonant structure based on a continuous metal layer (CCM) structure in Example 2;

[0027] Figure 5 A top view of a TC-SAW resonant structure based on a continuous metal layer (CCM) structure according to Embodiment 2;

[0028] Figure 6 This is the resonator admittance response diagram based on the CCM structure and the ordinary structure of Example 2. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the embodiments.

[0030] Embodiment 1: A TC-SAW resonant structure with a noise suppression unit, such as Figure 1As shown, the device comprises a substrate 1 , an interdigital transducer 2 , a noise suppression unit 3 , a contact electrode 4 , a temperature compensation layer 5 and a passivation layer 6 .

[0031] like Figure 2 As shown, the IDT 2 is arranged on the substrate 1, and the IDT 2 includes a first IDT and a second IDT; the first IDT includes a first bus 211 and each first electrode finger 212 connected to the first bus 211, and the second IDT includes a second bus 221 and each second electrode finger 222 connected to the second bus 221, and the first electrode finger 212 and the second electrode finger 222 extend along the third direction, and the first electrode finger 212 and the second electrode finger 222 are alternately arranged in the first direction. Wherein, the first direction and the third direction are parallel to the plane where the substrate 1 is located, and in this embodiment, the first direction and the third direction are perpendicular to each other.

[0032] The material of the electrode fingers of the IDT 2 can be composed of a single-layer metal film of Ti, Ag or Cu, or a stack of multiple metal films, wherein the first layer is Ti, the second layer is Ag, the third layer is Cu, and the fourth layer is Ti.

[0033] In this embodiment, the temperature compensation layer 5 covers the surface of each first electrode finger 212 and each second electrode finger 222 .

[0034] In this embodiment, the noise suppression unit 3 is constructed as a distributed metal structure and is only arranged on the upper side of each first electrode finger 212 and the second electrode finger 222. Therefore, an intermittent cosine waveform is formed in the first direction, such as Figure 2 This distributed metal structure has a higher degree of freedom and is easier to adjust in size, thereby achieving the effect of suppressing clutter.

[0035] As an extension, the cosine waveform structure of the clutter suppression unit 3 can also be further extended along the first direction to the upper side of the reflection grid, such as Figure 2 shown.

[0036] Specifically, the distributed metal structure has a peak / trough in the second direction perpendicular to the substrate 1 that is flush with the end of one of the first electrode finger 212 and the second electrode finger 222. Figure 2 , the noise suppression unit 3 forms two groups of discontinuous cosine waveforms, one of which has a peak / trough flush with the end of the first electrode finger 212 in the second direction perpendicular to the substrate 1, and the other group has a peak / trough flush with the end of the second electrode finger 222 in the second direction perpendicular to the substrate 1. Exemplarily, the periodic variation range of the cosine waveform corresponds to the four first electrode fingers 212 and the four second electrode fingers 222. Of course, the periodic variation range of the cosine waveform is also adjusted according to the acoustic wave transmission situation.

[0037] Exemplarily, the cross section of the clutter suppression unit 3 in the second direction is a rectangle; of course, the cross section in the second direction is a rectangle or a diamond that conforms to the change of the cosine waveform, which can also meet the requirements.

[0038] Furthermore, the noise suppression unit 3 may be composed of a metal structure, consisting of a single-layer metal film of Ti or Cu, or a stack of metal films of Ti and Cu, wherein the first layer is Ti and the second layer is Cu.

[0039] The temperature compensation layer 5 is generally a SiO2 layer, covering the IDT 2 and the substrate 1, and filling between the distributed metal structure and the IDT 2. Specifically, the clutter suppression unit 3 is wrapped by the temperature compensation layer 5, and the temperature compensation layer 5 fills the gap between the IDT 2.

[0040] The contact electrode 4 is disposed on the first busbar and the second busbar. The material of the contact electrode 4 may be Ti or AlCu.

[0041] The passivation layer 6 covers the temperature compensation layer 5 and has an opening on the contact electrode 4. The passivation layer 6 can protect the metal structure from oxidation. The material of the passivation layer 6 can be silicon oxide or SiN x .

[0042] The relevant parameters of the clutter suppression unit 3 include, for example, Figure 3 As shown:

[0043] The width dimension b of a single distributed metal structure in the first direction is 0.3-0.6 times the central wavelength of the filter operating frequency, which is the same as the width of a single electrode finger in the first direction, and the height is 10-100 nm.

[0044] The distance a between the outer edge of the noise suppression unit 3 and the end of the first electrode finger 212 / the second electrode finger 222 in the third direction is in the range of 0-0.1 times the central wavelength of the filter operating frequency.

[0045] The gap length c between the end of the first electrode finger 212 and the second bus 221 ranges from 0.1 to 2 times the center wavelength of the filter operating frequency, and the gap length c between the end of the second electrode finger 222 and the first bus 211 ranges from 0.1 to 2 times the center wavelength of the filter operating frequency.

[0046] This embodiment further provides a TC-SAW filter, including the TC-SAW resonant structure having the clutter suppression unit 3 .

[0047] Embodiment 2: It is substantially the same as Embodiment 1, except that the noise suppression unit 3 is a continuous metal structure, such as Figure 4 , 5As shown, the continuous metal structure is constructed as a first metal structure 301 correspondingly arranged on the upper side of each first electrode finger 212 and each second electrode finger 222 and a second metal structure 302 connecting each adjacent first metal structure 301, so as to form a continuous cosine waveform in the second direction. The continuous metal structure is easier to process than the distributed metal structure.

[0048] Figure 6 This is a comparison diagram of the frequency characteristics of a common filter structure and a filter using the continuous metal structure of this embodiment at the same frequency. It can be seen that compared with curve A and curve B, the burrs are much smoother and the stray signals are significantly eliminated.

[0049] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A TC-SAW resonant structure with a noise suppression unit, characterized in that: include: substrate; An IDT, the IDT is disposed on a substrate, the IDT comprises a first IDT and a second IDT; the first IDT comprises a first bus and first electrode fingers connected to the first bus, the second IDT comprises a second bus and second electrode fingers connected to the second bus; A temperature compensation layer, wherein the temperature compensation layer covers the surface of each first electrode finger and each second electrode finger; A noise suppression unit, wherein the noise suppression unit is a metal structure arranged in the temperature compensation layer, and the noise suppression unit forms a cosine waveform with a continuous period in a first direction, and the first direction is parallel to the plane where the substrate is located; the noise suppression unit has a peak / trough flush with the end of one of the first electrode finger and the second electrode finger in a second direction, and the second direction is perpendicular to the plane where the substrate is located; the periodic variation range of the cosine waveform corresponds to the four first electrode fingers and the four second electrode fingers.

2. The TC-SAW resonant structure with a noise suppression unit according to claim 1, characterized in that: The clutter suppression unit includes a distributed metal structure or a continuous metal structure; The distributed metal structure is constructed as a metal structure correspondingly arranged on the upper side of each first electrode finger and each second electrode finger; The continuous metal structure is constructed of a first metal structure correspondingly arranged on the upper side of each first electrode finger and each second electrode finger and a second metal structure connecting each first metal structure.

3. The TC-SAW resonant structure with a noise suppression unit according to claim 1, characterized in that: The cross section of the clutter suppression unit in the second direction is rectangular.

4. The TC-SAW resonant structure with a noise suppression unit according to claim 1, characterized in that: Also included is a contact electrode, which is disposed on the first bus bar and the second bus bar.

5. The TC-SAW resonant structure with a noise suppression unit according to claim 4, characterized in that: The invention also comprises a passivation layer, wherein the passivation layer covers the temperature compensation layer and is provided with an opening on the contact electrode.

6. The TC-SAW resonant structure with a noise suppression unit according to claim 1, characterized in that: The distance between the outer edge of the noise suppression unit and the end of the first electrode finger / the second electrode finger in the third direction ranges from (0-0.1)*L, where L is the working wavelength of the interdigital transducer; the third direction is parallel to the plane where the substrate is located and intersects with the first direction.

7. The TC-SAW resonant structure with a noise suppression unit according to claim 1, characterized in that: The width of a single said clutter suppression unit along the first direction ranges from (0.3 to 0.6)*L, which is the same as the width of a single electrode finger in the first direction, and L is the working wavelength of the interdigital transducer.

8. The TC-SAW resonant structure with a noise suppression unit according to claim 1, characterized in that: The gap length between the end of the first electrode finger and the second bus is in the range of (0.1-2)*L, and the gap length between the end of the second electrode finger and the first bus is in the range of (0.1-2)*L, where L is the operating wavelength of the interdigital transducer.

9. A TC-SAW filter, comprising the TC-SAW resonant structure with a clutter suppression unit as claimed in any one of claims 1 to 8.

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