Surface acoustic wave device, Electronic device
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HANGZHOU SAPPLAND MICROELECTRONICS TECH CO LTD
- Filing Date
- 2026-04-02
- Publication Date
- 2026-06-23
AI Technical Summary
Existing surface acoustic wave devices have limited effectiveness in suppressing transverse parasitic modes, and bandwidth adjustment is complex and lacks flexibility, affecting device performance and energy loss.
In surface acoustic wave devices, by setting a structure in which the vertical projections of the lower and upper electrodes on the substrate intersect, and by combining the design of the lower electrode being embedded in the functional layer, the electrical boundary conditions and phase randomization are changed, thereby achieving effective suppression of transverse parasitic modes and convenient adjustment of bandwidth.
It effectively suppresses lateral parasitic modes, reduces energy loss, improves device performance, and enables flexible adjustment of device bandwidth through digital logic, thereby enhancing design flexibility and suppressing out-of-band spurious emissions.
Smart Images
Figure CN121966496B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of surface acoustic wave (SAW) devices, and particularly to a SAW device and electronic equipment. Background Technology
[0002] Surface acoustic wave (SAW) devices typically suffer from the problem of suppressing transverse parasitic modes. The presence of transverse parasitic modes causes ripples in the passband, increases the energy loss of the SAW device, and reduces its Q value, thus severely affecting the device's performance. Existing suppression methods mainly involve optimizing piezoelectric substrate materials, interdigital transducer structures, and multilayer film structures. However, these methods are complex to implement and have limited effectiveness.
[0003] Furthermore, with the same electrodes and their thicknesses, it is difficult to adjust the bandwidth of devices on the same wafer. Only by adjusting the thickness or tangential direction of the piezoelectric layer can a wide range of bandwidth adjustments be achieved. The adjustment process is cumbersome and results in poor design flexibility. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a surface acoustic wave device and electronic device that can effectively suppress transverse parasitic modes, high-order parasitic responses, and whose bandwidth is easy to adjust, in order to solve the problems existing in the prior art mentioned above.
[0005] The technical solution adopted by the present invention to solve its technical problem is: a surface acoustic wave device, comprising a substrate, a piezoelectric layer and an upper electrode arranged sequentially from bottom to top, wherein the upper electrode includes a pair of upper busbars spaced apart along a first direction and a plurality of upper electrode fingers spaced apart alternately along a second direction; and further comprising a lower electrode disposed between the substrate and the piezoelectric layer, wherein the lower electrode includes a pair of lower busbars spaced apart along the second direction and a plurality of lower electrode fingers spaced apart alternately along the first direction, wherein the upper electrode fingers and the lower electrode fingers are oriented such that their vertical projections on the substrate intersect to effectively suppress lateral parasitic modes.
[0006] Furthermore, the upper electrode fingers and the lower electrode fingers are oriented perpendicularly to each other on the substrate by their vertical projections.
[0007] Furthermore, all of the lower electrodes are excited.
[0008] Furthermore, a portion of the lower electrode fingers are excited.
[0009] Furthermore, the upper surface of the lower electrode is tangent to the lower surface of the piezoelectric layer, or the top of the lower electrode is embedded in the piezoelectric layer, or the lower surface of the lower electrode is tangent to the lower surface of the piezoelectric layer.
[0010] Furthermore, it also includes a functional layer disposed between the substrate and the lower electrode.
[0011] Furthermore, the lower surface of the lower electrode is tangent to the upper surface of the functional layer, or the bottom of the lower electrode is embedded in the functional layer, or the upper surface of the lower electrode is tangent to the upper surface of the functional layer.
[0012] Furthermore, it also includes a dielectric layer disposed between the substrate and the functional layer.
[0013] Furthermore, the upper electrode also includes an upper dummy finger, which is spaced apart from the upper electrode finger along a first direction.
[0014] An electronic device comprising the aforementioned surface acoustic wave device.
[0015] The beneficial effects of this invention are:
[0016] (1) The present invention provides a lower electrode on the lower surface of the piezoelectric layer, and the upper electrode finger and the lower electrode finger are oriented with their vertical projections intersecting on the substrate. After the lower electrode is energized, the change of electrical boundary conditions (short circuit effect) causes the surface acoustic wave to generate different sound velocity regions in the Y direction, thereby forming a precise sound velocity difference. This sound velocity difference constitutes an acoustic waveguide, which confines the energy in the central region, thereby effectively suppressing the transverse parasitic mode.
[0017] (2) By changing the excitation log of the lower electrode finger in the lower electrode, the present invention changes the static capacitance or effective coupling coefficient of the surface acoustic wave, so that the bandwidth of the device can be arbitrarily adjusted on the same wafer through digital logic, making the bandwidth adjustment very convenient and increasing the flexibility of the design.
[0018] (3) In this invention, the lower electrode is embedded in the groove of the functional layer in whole or in part, which causes phase randomization and Bragg scattering in the groove, reduces coherent reflection at the interface, thereby weakening out-of-band spurious and further suppressing in-band lateral parasitic modes. Attached Figure Description
[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0020] Figure 1 This is a front cross-sectional view of the first type of surface acoustic wave device shown in an embodiment of the present invention.
[0021] Figure 2 This is a top view of the upper electrode in this invention.
[0022] Figure 3 This is a top view of the first type of lower electrode shown in an embodiment of the present invention.
[0023] Figure 4 This is a top view of the second type of lower electrode shown in an embodiment of the present invention.
[0024] Figure 5 This is a main cross-sectional view of the second type of surface acoustic wave device shown in an embodiment of the present invention.
[0025] Figure 6 This is a main cross-sectional view of the third type of surface acoustic wave device shown in an embodiment of the present invention.
[0026] Figure 7 This is a schematic diagram of phase randomization and Bragg scattering caused by the groove in this invention.
[0027] Figure 8 This is a front cross-sectional view of the fourth surface acoustic wave device shown in an embodiment of the present invention.
[0028] Figure 9 This is a schematic diagram of electrode finger excitation under different logarithms in this invention.
[0029] Figure 10 This is a passband performance diagram of surface acoustic wave devices in the prior art.
[0030] Figure 11 This is a passband performance diagram of a surface acoustic wave device without excitation of the lower electrode, as shown in an embodiment of the present invention.
[0031] Figure 12 This is a diagram showing the performance of the surface acoustic wave device without excitation of the lower electrode in an embodiment of the present invention, compared with the far right end of the passband in the prior art.
[0032] Figure 13 This is a performance diagram of electrode finger excitation under different logarithms in this invention.
[0033] In the figure: 100, substrate; 200, piezoelectric layer; 300, upper electrode; 310, upper busbar; 320, upper electrode finger; 330, upper dummy finger; 400, lower electrode; 410, lower busbar; 420, lower electrode finger; 430, lower dummy finger; 500, functional layer; 600, dielectric layer. Detailed Implementation
[0034] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.
[0035] In this application, the first direction is the length direction of the substrate 100, i.e., the Y direction in the figure; the second direction is the width direction of the substrate 100, i.e., the X direction in the figure; the first direction and the second direction are perpendicular to each other.
[0036] Example 1
[0037] like Figures 1-3As shown, a surface acoustic wave device includes a substrate 100, a lower electrode 400, a piezoelectric layer 200, and an upper electrode 300 arranged sequentially from bottom to top. The upper electrode 300 includes a pair of upper busbars 310 spaced apart along a first direction and a plurality of upper electrode fingers 320 spaced apart alternately along a second direction. The lower electrode 400 includes a pair of lower busbars 410 spaced apart along the second direction and a plurality of lower electrode fingers 420 spaced apart alternately along the first direction. The upper electrode fingers 320 and the lower electrode fingers 420 are oriented so as to intersect the vertical projections of their respective upper and lower electrode fingers on the substrate 100, thereby effectively suppressing lateral parasitic modes.
[0038] A lower electrode 400 is disposed on the lower surface of the piezoelectric layer 200, and the upper electrode finger 320 and the lower electrode finger 420 are oriented so that their vertical projections on the substrate 100 intersect. After the lower electrode 400 is energized, the change in electrical boundary conditions (short-circuit effect) causes the surface acoustic wave to generate different sound velocity regions in the Y direction, thereby forming a precise sound velocity difference. This sound velocity difference constitutes an acoustic waveguide, which confines the energy to the central region, thereby effectively suppressing transverse parasitic modes.
[0039] Specifically, the connection ends of adjacent upper electrode fingers 320 are respectively connected to a pair of upper busbars 310, and the connection ends of adjacent lower electrode fingers 420 are respectively connected to a pair of lower busbars 410. This is existing technology and will not be described in detail here.
[0040] It should be noted that in this application, the orientation of the upper electrode finger 320 and the lower electrode finger 420 on the substrate 100 where their vertical projections intersect means that the upper electrode finger 320 and the lower electrode finger 420 are not arranged in parallel.
[0041] In this embodiment, the upper electrode finger 320 and the lower electrode finger 420 are oriented perpendicularly to each other on the substrate 100, as shown below. Figure 2 and Figure 3 As shown, the upper electrode finger 320 is arranged parallel to the first direction, and the lower electrode finger 420 is arranged parallel to the second direction.
[0042] In some embodiments, the lower electrode finger 420 is not parallel along the second direction, but is at an angle od, preferably 0° to 90°. Figure 4 As shown, the vertical projections of the upper electrode finger 320 and the lower electrode finger 420 on the substrate 100 are not vertically oriented at this time.
[0043] In this embodiment, the upper surface of the lower electrode 400 is tangent to the lower surface of the piezoelectric layer 200, but it is not limited to this. Alternatively, the top of the lower electrode 400 may be embedded in the piezoelectric layer 200, that is, the lower electrode 400 may be partially embedded in the piezoelectric layer 200.
[0044] In some embodiments, the lower electrode 400 is entirely embedded within the piezoelectric layer 200, and the lower surface of the lower electrode 400 is tangent to the lower surface of the piezoelectric layer 200, such as... Figure 5 As shown, this is to further suppress the lateral parasitic mode.
[0045] In this embodiment, the upper electrode 300 further includes an upper dummy finger 330 connected to the upper busbar 310. The upper dummy finger 330 and the upper electrode finger 320 are spaced apart along a first direction, such as... Figure 2 As shown.
[0046] In some embodiments, the lower electrode 400 further includes a lower dummy finger 430 connected to the lower busbar 410, the lower dummy finger 430 and the lower electrode finger 420 being spaced apart along a second direction, such as... Figure 3 As shown.
[0047] In some embodiments, a functional layer 500 is disposed between the substrate 100 and the lower electrode 400, and the upper surface of the lower electrode 400 is tangent to the upper surface of the functional layer 500, that is, the lower electrode 400 is entirely embedded in the groove of the functional layer 500, such as... Figure 6 As shown. Alternatively, the bottom of the lower electrode 400 is embedded in the groove of the functional layer 500, that is, the lower electrode 400 is partially embedded in the groove of the functional layer 500.
[0048] The lower electrode 400 is wholly or partially embedded in the groove of the functional layer 500, causing phase randomization and Bragg scattering (such as...) within the groove. Figure 7 As shown in the figure, it reduces coherent reflections at the interface, thereby weakening out-of-band spurious signals and further suppressing in-band lateral parasitic modes. The variable resonance characteristics of this structure provide the filter with applications in dynamic frequency band switching scenarios.
[0049] Specifically, the functional layer 500 can serve as a low-sound-velocity layer, and the preferred material for the functional layer 500 is silicon dioxide (SiO2).
[0050] Of course, the positional relationship between the lower electrode 400 and the functional layer 500 is not limited to that shown above. Alternatively, the lower surface of the lower electrode 400 may be tangent to the upper surface of the functional layer 500.
[0051] In some embodiments, a dielectric layer 600 is disposed between the substrate 100 and the functional layer 500, such as... Figure 8 As shown, this is to increase the stability of the structure and the stability of the processing.
[0052] Specifically, the preferred material for the dielectric layer 600 is polycrystalline silicon (pSi).
[0053] In this embodiment, an excitation is applied to all or part of the lower electrode fingers 420 in the lower electrode 400. For example, an excitation can be applied to one, five, or nine pairs of lower electrode fingers 420 in the lower electrode 400. Figure 9 As shown.
[0054] By changing the excitation logarithm of the lower electrode finger 420 in the lower electrode 400, the static capacitance (C0) or effective coupling coefficient (k) of the surface acoustic wave is changed. 2 eff This allows for arbitrary adjustment of device bandwidth via digital logic on the same wafer, making bandwidth adjustment very convenient and increasing design flexibility.
[0055] In some embodiments, both the upper electrode 300 and the lower electrode 400 further include a reflective grid electrode, which is prior art and will not be described in detail here.
[0056] from Figures 10-12 It can be seen that, compared with the prior art, the admittance curve of the surface acoustic wave device provided in this application is smoother, and the high-frequency parasitic intensity on the right side of the admittance curve at the anti-resonance point is significantly reduced, thus playing a more effective role in suppressing parasitic modes. From Figure 13 It can be seen that the bandwidth decreases as the number of 420 pairs of excitation lower electrode fingers increases.
[0057] This application applies to surface acoustic wave devices on piezoelectric material insulators (POI-SAW), temperature compensated surface acoustic wave devices (TC-SAW), transverse exciter acoustic wave devices (XBAR), and conventional surface acoustic wave devices.
[0058] Example 2
[0059] An electronic device includes the surface acoustic wave device described in Embodiment 1.
[0060] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.
Claims
1. A surface acoustic wave device, comprising a substrate (100), a piezoelectric layer (200), and an upper electrode (300) arranged sequentially from bottom to top, wherein the upper electrode (300) includes a pair of upper busbars (310) spaced apart along a first direction and a plurality of upper electrode fingers (320) spaced apart alternately along a second direction; characterized in that: It also includes a lower electrode (400) disposed between the substrate (100) and the piezoelectric layer (200). The lower electrode (400) includes a pair of lower busbars (410) spaced apart along a second direction and a plurality of lower electrode fingers (420) spaced apart alternately along a first direction. The upper electrode fingers (320) and the lower electrode fingers (420) are oriented to intersect the vertical projections of the upper electrode fingers (320) and the lower electrode fingers (420) on the substrate (100) to effectively suppress lateral parasitic modes.
2. The surface acoustic wave device according to claim 1, characterized in that: The upper electrode finger (320) and the lower electrode finger (420) are oriented perpendicularly to the vertical projections on the substrate (100).
3. The surface acoustic wave device according to claim 1, characterized in that: Excitation is applied to all lower electrode fingers (420) in the lower electrode (400).
4. The surface acoustic wave device according to claim 1, characterized in that: The lower electrode (400) is partially excited by the lower electrode finger (420).
5. The surface acoustic wave device according to claim 1, characterized in that: The upper surface of the lower electrode (400) is tangent to the lower surface of the piezoelectric layer (200), or the top of the lower electrode (400) is embedded in the piezoelectric layer (200), or the lower surface of the lower electrode (400) is tangent to the lower surface of the piezoelectric layer (200).
6. The surface acoustic wave device according to claim 1, characterized in that: It also includes a functional layer (500) disposed between the substrate (100) and the lower electrode (400).
7. The surface acoustic wave device according to claim 6, characterized in that: The lower surface of the lower electrode (400) is tangent to the upper surface of the functional layer (500), or the bottom of the lower electrode (400) is embedded in the functional layer (500), or the upper surface of the lower electrode (400) is tangent to the upper surface of the functional layer (500).
8. The surface acoustic wave device according to claim 5, characterized in that: It also includes a dielectric layer (600) disposed between the substrate (100) and the functional layer (500).
9. The surface acoustic wave device according to claim 1, characterized in that: The upper electrode (300) also includes an upper dummy finger (330), which is spaced apart from the upper electrode finger (320) along a first direction.
10. An electronic device, characterized in that: Includes the surface acoustic wave device as described in any one of claims 1-9.