Multi-layer SAW device capable of suppressing spurious response

Abstract

The invention provides a multi-layer SAW device capable of suppressing spurious response, and aims to solve the problems that the quality factor and electromechanical coupling coefficient of the device are reduced and in-band ripple and insertion loss are deteriorated due to the fact that a traditional multi-layer SAW device easily generates spurious response when the device works, a mass block layer is deposited above a part of an IDT layer of the traditional multi-layer SAW device, and the quality factor and the electromechanical coupling coefficient of the device are reduced. By changing the length and height parameters of the mass block, observing the suppression degree of the original spurious response in the admittance frequency response, selecting several parameters with better suppression effects, further comparing the electromechanical coupling coefficient with the quality factor, and finally obtaining the optimal length and height parameters of the added mass block after comprehensive comparison. While the stray response suppression effect on the original traditional multilayer SAW device is good, the electromechanical coupling coefficient and the quality factor at the resonant frequency of the SAW device are basically kept unchanged, and the quality factor at the anti-resonant frequency of the SAW device is increased.

Description

Technical Field

[0001] This invention relates to the field of surface acoustic wave (SAW) device technology, and more specifically, to a multilayer SAW device with suppressed stray response. Background Technology

[0002] Against the backdrop of the rapid development of 5G and Sub-6G in the new communication era, radio frequency (RF) front-end filtering devices have encountered new opportunities and challenges: the new communication era demands filtering devices with greater bandwidth and higher frequencies, thus multilayer surface acoustic wave (SAW) devices have emerged as a prominent option. Multilayer SAW devices integrate the advantages of traditional SAW devices and traditional bulk acoustic wave (BAW) devices. Benefiting from advancements in manufacturing processes, they avoid the limitations of traditional SAW devices (limited by high frequencies) and traditional BAW devices (limited by large bandwidth). By rationally selecting materials and designing appropriate structural parameters, they can effectively meet the demands of the new communication era for RF front-end filtering devices.

[0003] However, compared to traditional SAW and BAW devices, multilayer SAW devices are more sensitive to spurious signals, especially near resonant or anti-resonant frequencies, where spurious responses are easily generated during device operation. These spurious responses lead to a decrease in the device's quality factor and electromechanical coupling coefficient, as well as deterioration of insertion loss and in-band ripple. The current common method is to use interdigital transducer (IDT) apodization weighting to suppress spurious responses in multilayer SAW devices. However, the effectiveness of IDT-weighted apodization in suppressing spurious responses is directly related to the apodization trajectory. Different weighted apodization trajectories will produce completely different suppression effects, which is not only time-consuming and laborious to design and verify, but also easily leads to deterioration of insertion loss and quality factor in multilayer SAW devices even when the spurious response suppression effect is good. Summary of the Invention

[0004] This invention aims to solve the above-mentioned existing technical problems and proposes a multilayer SAW device with spurious response suppression: a mass block layer is deposited above part of the IDT layer of a traditional multilayer SAW device. The mass block layer has a symmetrical structure. By changing the length and height parameters of the mass block in the mass block layer, the degree of suppression of the original spurious response in its admittance frequency response is observed. Furthermore, its electromechanical coupling coefficient and quality factor are compared. After comprehensive comparison, the optimal length and height parameters of the added mass block are finally obtained. While the spurious response suppression effect of the original traditional multilayer SAW device is good, its electromechanical coupling coefficient and quality factor at the resonant frequency remain basically unchanged, and the quality factor at the anti-resonant frequency is increased (from 714 to 745).

[0005] To achieve the above objectives, the specific solution of the present invention is as follows: Design a multilayer SAW device, the multilayer SAW device comprising a first substrate layer, a second substrate layer disposed on the first substrate layer, a temperature compensation layer disposed on the second substrate layer, a piezoelectric layer disposed on the temperature compensation layer, an IDT layer disposed on the piezoelectric layer, and a mass block layer covering a portion of the IDT layer; the IDT layer comprises a first busbar, a second busbar, a first electrode, and a second electrode; the mass block layer comprises a first mass block and a second mass block; the multilayer SAW device has a periodic structure with a period length of λ.

[0006] Furthermore, the first and second base layers are made of the same material, optionally Si, wherein the heights of the first and second base layers can be optionally 0.5×λ and 1×λ, respectively, and the first base layer is a perfect matching layer used to absorb excess anchor damage.

[0007] Furthermore, the temperature compensation layer is made of SiO2, and its height can be optionally 0.15×λ.

[0008] Furthermore, the material of the piezoelectric layer can be lithium niobate or lithium tantalate, and its height can be 0.4 × λ.

[0009] Furthermore, the IDT layer is a metal electrode layer, the material of which can be Al, Cu, Au and Pt, and its height can be 0.1×λ.

[0010] Furthermore, the first busbar is connected to the first electrode to form a terminal, which is set to 1V; the second busbar is connected to the second electrode to form a ground terminal.

[0011] Furthermore, the first electrode and the second electrode are symmetrically placed with respect to the centerline position of the multilayer SAW device in the x direction, and the length of the first electrode in the x direction can be selected as 0.175×λ, and the distance of the first electrode relative to the left periodic boundary of the multilayer SAW device can be selected as 0.1625×λ.

[0012] Furthermore, the first busbar and the second busbar are symmetrically placed with respect to the centerline position of the multilayer SAW device in the y-direction, and the length of the first busbar along the y-direction of the multilayer SAW device is Ybus; the first mass block and the second mass block are symmetrically placed with respect to the centerline position of the multilayer SAW device in the y-direction.

[0013] Furthermore, the first mass block and the second mass block respectively cover the first busbar and the second busbar, and the material can be silicon nitride. The height of the first mass block is H, and the value of H is in the range of 0.1×λ<H≤0.5×λ.

[0014] Furthermore, the distance between the first mass block and the second electrode in the y-direction of the multilayer SAW device is the same as the distance between the second mass block and the first electrode in the y-direction of the multilayer SAW device, which is Ygap.

[0015] Furthermore, the length of the first mass block is L, where the value of L is in the range of L≥Ybus.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: Multilayer SAW devices avoid the limitations of traditional SAW devices (limited by high frequency) and traditional BAW devices (limited by large bandwidth). By selecting appropriate materials and designing reasonable structural parameters, they can meet the demands of RF front-end filtering devices in the new communication era. However, multilayer SAW devices are more sensitive to spurious responses, especially near the resonant or anti-resonant frequencies, where spurious responses easily occur during device operation. These spurious responses lead to a decrease in the device's quality factor and electromechanical coupling coefficient, as well as deterioration of insertion loss and in-band ripple. This patent proposes a multilayer SAW device with spurious response suppression: a mass block layer is deposited above part of the IDT layer of a traditional multilayer SAW device. By changing the length and height parameters of the mass block in the mass block layer, the suppression effect on the original spurious response and its impact on the electromechanical coupling coefficient and quality factor are comprehensively compared. Finally, the optimal parameters of the added mass block are selected. While achieving good spurious response suppression of the original traditional multilayer SAW device, its electromechanical coupling coefficient and quality factor at the resonant frequency remain basically unchanged, and the quality factor at the anti-resonant frequency is increased (from 714 to 745). Attached Figure Description

[0017] Figure 1 This is a three-dimensional equivalent model diagram of an improved multilayer SAW device with a single-cycle structure.

[0018] Figure 2 This is a side view of the yz plane under the three-dimensional equivalent model of the improved multilayer SAW device.

[0019] Figure 3 This is a three-dimensional equivalent model diagram of an improved multilayer SAW device after removing the mass block layer in a single-cycle structure.

[0020] Figure 4 It is a front view of the xz plane in the three-dimensional equivalent model of an improved multilayer SAW device with a single-cycle structure after removing the mass block layer.

[0021] Figure 5 It is a top view of the xy plane in the three-dimensional equivalent model of an improved multilayer SAW device with a single-cycle structure after removing the mass block layer.

[0022] Figure 6 This is the admittance frequency response diagram for a traditional multilayer SAW device.

[0023] Figure 7 This is the admittance frequency response diagram for the length L=0.15×λ and height H=0.15×λ, 0.25×λ, and 0.35×λ of the first mass block in the improved multilayer SAW device.

[0024] Figure 8 This is the admittance frequency response diagram for the length L=0.25×λ and height H=0.15×λ, 0.25×λ, and 0.35×λ of the first mass block in the improved multilayer SAW device.

[0025] Figure 9 This is the admittance frequency response diagram for the length L=0.45×λ and height H=0.15×λ, 0.25×λ, and 0.35×λ of the first mass block in the improved multilayer SAW device.

[0026] Figure 10 This is the admittance frequency response diagram for the length L=0.65×λ and height H=0.15×λ, 0.25×λ, and 0.35×λ of the first mass block in the improved multilayer SAW device.

[0027] Figure 11 This is the admittance frequency response diagram for the length L=0.35×λ and height H=0.15×λ of the first mass block in the improved multilayer SAW device.

[0028] Figure 12 This is the admittance frequency response diagram for the length L=0.45×λ and height H=0.15×λ of the first mass block in the improved multilayer SAW device.

[0029] Figure 13 This is the admittance frequency response diagram for the length L=0.55×λ and height H=0.15×λ of the first mass block in the improved multilayer SAW device.

[0030] Figure 14 This is the admittance frequency response diagram for the length L=0.35×λ and height H=0.25×λ of the first mass block in the improved multilayer SAW device.

[0031] Figure 15 This is the admittance frequency response diagram for the length L=0.45×λ and height H=0.25×λ of the first mass block in the improved multilayer SAW device.

[0032] Figure 16 This is the admittance frequency response diagram for the length L=0.35×λ and height H=0.35×λ of the first mass block in the improved multilayer SAW device.

[0033] Figure 17 This is the admittance frequency response diagram for the length L=0.45×λ and height H=0.35×λ of the first mass block in the improved multilayer SAW device.

[0034] Figure 18 This is a graph showing the variation of the electromechanical coupling coefficient for different heights and lengths of the first mass block in traditional and improved multilayer SAW devices.

[0035] Figure 19 This is a graph showing the quality factor variation for different heights and lengths of the first mass block in traditional and improved multilayer SAW devices.

[0036] Figure 20 This is a comparison of the admittance frequency response of the improved multilayer SAW device with the first mass block height H=0.25×λ and length L=0.35×λ, compared with that of the traditional multilayer SAW device.

[0037] Icon labels: 1. First substrate layer; 2. Second substrate layer; 3. Temperature compensation layer; 4. Piezoelectric layer; 5. IDT layer; 6. First busbar; 7. Second busbar; 8. Second electrode; 9. First electrode; 10. First mass block; 11. Second mass block; Ybus, length of the first busbar along the y-direction of the multilayer SAW device; Ygap, distance between the first mass block and the second electrode in the y-direction of the multilayer SAW device; H, height of the first mass block; L, length of the first mass block. Detailed Implementation

[0038] The embodiments of the present invention will be described in further detail and clearly below with reference to the accompanying drawings and specific implementations. The described embodiments are merely some of the embodiments included in the present invention.

[0039] The specific implementation scheme of the present invention to solve the above-mentioned technical problems is as follows: A multilayer SAW device with spurious response suppression, such as Figures 1-5 As shown, a multilayer SAW device is designed, comprising a first substrate layer 1, a second substrate layer 2 placed on the first substrate layer 1, a temperature compensation layer 3 placed on the second substrate layer 2, a piezoelectric layer 4 placed on the temperature compensation layer 3, an IDT layer 5 placed on the piezoelectric layer 4, and a mass block layer covering a portion of the IDT layer 5; the IDT layer 5 comprises a first busbar 6, a second busbar 7, a first electrode 9, and a second electrode 8; the mass block layer comprises a first mass block 10 and a second mass block 11; the multilayer SAW device has a periodic structure with a period length of λ, which in this embodiment is λ=2µm.

[0040] Furthermore, the first base layer 1 and the second base layer 2 are made of the same material, which is Si in this embodiment. The heights of the first base layer 1 and the second base layer 2 are 0.5×λ and 1×λ, respectively, and the first base layer 1 is a perfect matching layer used to absorb excess anchor damage.

[0041] Furthermore, the temperature compensation layer 3 is made of SiO2, and in this embodiment, its height is 0.15×λ.

[0042] Furthermore, the material of the piezoelectric layer 4 can be lithium niobate or lithium tantalate. In this embodiment, the material of the piezoelectric layer 4 is 42°YX-cut lithium tantalate, and its height is 0.4×λ.

[0043] Furthermore, the IDT layer 5 is a metal electrode layer, and its material can be selected from Al, Cu, Au and Pt. In this embodiment, the material of the IDT layer 5 is Al, and its height is 0.1×λ.

[0044] Furthermore, the first busbar 6 is connected to the first electrode 9 to form a terminal, which is set to 1V; the second busbar 7 is connected to the second electrode 8 to form a ground terminal.

[0045] Furthermore, in this embodiment, the length of the multilayer SAW device stretched along the Y direction is 50×λ.

[0046] Furthermore, the first electrode 9 and the second electrode 8 are symmetrically placed with respect to the centerline position of the multilayer SAW device in the x direction, and the length of the first electrode 9 in the x direction can be selected as 0.175×λ, and the distance of the first electrode 9 relative to the left periodic boundary of the multilayer SAW device can be selected as 0.1625×λ.

[0047] Furthermore, the first busbar 6 and the second busbar 7 are symmetrically placed with respect to the centerline position of the multilayer SAW device in the y-direction, and the length of the first busbar 6 along the y-direction of the multilayer SAW device is Ybus. In this embodiment, the length of Ybus is set to 1.5×λ; the first mass block 10 and the second mass block 11 are symmetrically placed with respect to the centerline position of the multilayer SAW device in the y-direction.

[0048] Furthermore, the first mass block 10 and the second mass block 11 respectively cover the first busbar 6 and the second busbar 7, and their material can be silicon nitride. The height of the first mass block 10 is H, and the value of H is in the range of 0.1×λ<H≤0.5×λ. In this embodiment, the specific value of H is {0.15×λ, 0.25×λ, 0.35×λ}.

[0049] Furthermore, the distance between the first mass block 10 and the second electrode 8 in the y-direction of the multilayer SAW device is the same as the distance between the second mass block 11 and the first electrode 9 in the y-direction of the multilayer SAW device, which is Ygap. In this embodiment, the length of Ygap is set to 1.5×λ.

[0050] Furthermore, the length of the first mass block 10 is L, where the value of L is in the range of L≥Ybus. In this embodiment, the specific value of L is {0.15×λ, 0.2×λ, 0.25×λ, 0.3×λ, 0.35×λ, 0.4×λ, 0.45×λ, 0.5×λ, 0.55×λ, 0.6×λ, 0.65×λ}.

[0051] Furthermore, in this embodiment, compared with the improved multilayer SAW device, the traditional multilayer SAW device is completely identical to the improved multilayer SAW device except for the absence of a mass block layer. Its three-dimensional equivalent model diagram is the same as... Figure 3 Totally consistent.

[0052] Furthermore, Figure 6 This is the admittance frequency response diagram of a traditional multilayer SAW device, such as... Figure 6 As shown: A large resonance peak appears to the left of the anti-resonance frequency, along with some small resonance peaks nearby. These resonance peaks are parasitic modes, or stray responses. These stray responses are mainly caused by energy leakage to the bus.

[0053] Furthermore, this embodiment illustrates the variation of the admittance frequency response of the improved multilayer SAW device with the height H of the first mass block 10 when the length L of the first mass block 10 is 0.15×λ, 0.25×λ, 0.45×λ, and 0.65×λ, respectively. Figures 7-10As shown: when the length L of the first mass block 10 is fixed, the admittance frequency response of the multilayer SAW device remains basically unchanged as the height H of the first mass block 10 changes. It can be seen that the change of the height H parameter of the first mass block 10 has little impact on the original spurious response of the traditional multilayer SAW device. The length L parameter in the first mass block 10 is the key to suppressing the spurious response of the traditional multilayer SAW device.

[0054] Furthermore, this embodiment does not display the admittance frequency response diagrams of all improved multilayer SAW devices. Instead, it selects several admittance frequency responses with good spurious response suppression effects of traditional multilayer SAW devices under different lengths L and heights H of the first mass block 10 for analysis, such as... Figures 11-17 As shown, the admittance frequency response of the selected first mass block 10 with different lengths L and heights H all showed good suppression of the large spurious resonance peak to the left of the anti-resonance frequency of the original traditional multilayer SAW device. When the length L of the first mass block 10 is 0.45×λ and the height H is 0.15×λ, 0.25×λ, and 0.35×λ, the suppression effect on the small spurious resonance peak near the anti-resonance frequency of the original traditional multilayer SAW device is the best, but a small spurious resonance peak also appears to the left of the resonant frequency. When the length L of the first mass block 10 is 0.35×λ and the height H is 0.15×λ, 0.25×λ, and 0.35×λ, the suppression effect on the small spurious resonance peak near the anti-resonance frequency of the original traditional multilayer SAW device is second only to the suppression effect when the length L of the first mass block 10 is 0.45×λ.

[0055] Furthermore, Figure 18 The graph shows the variation of the electromechanical coupling coefficient for different heights H and lengths L of the first mass block 10 in traditional and improved multilayer SAW devices, as shown in the figure. Figure 18 As shown: The electromechanical coupling coefficient of the improved multilayer SAW device is slightly lower than that of the traditional multilayer SAW device, but remains basically unchanged. Under the improved multilayer SAW device, the change of the length L and height H of the first mass block 10 will not cause a change in the electromechanical coupling coefficient.

[0056] Furthermore, Figure 19 The graph shows the variation of the quality factor for different heights H and lengths L of the first mass block 10 in traditional and improved multilayer SAW devices, as shown in the figure. Figure 19As shown: The quality factor at the resonant frequency remains basically unchanged in the improved multilayer SAW device compared to the traditional multilayer SAW device, and changes in the length L and height H of the first mass block 10 in the improved multilayer SAW device do not cause a significant change in the quality factor at the resonant frequency; however, the quality factor at the anti-resonant frequency is significantly different in the improved multilayer SAW device compared to the traditional multilayer SAW device. In the improved multilayer SAW device, when the length L = 0.25 × λ and the height H = 0.35 × λ of the first mass block 10, the quality factor at the anti-resonant frequency is significantly improved compared to the traditional multilayer SAW device.

[0057] Furthermore, considering the spurious emission suppression effect under different length L and height H parameters of the first mass block 10, as well as the improvements in electromechanical coupling coefficient and quality factor compared to traditional multilayer SAW devices, the length L = 0.25 × λ and height H = 0.25 × λ of the improved multilayer SAW first mass block 10 were ultimately selected as the optimal parameters in this embodiment. Its admittance frequency response was then compared with that of traditional multilayer SAW devices. Figure 20 As shown: After adding a first mass block 10 with a length L=0.25×λ and a height H=0.25×λ, the admittance frequency response of the improved multilayer SAW device is smoother and more even than that of the traditional multilayer SAW device. It has a good suppression effect on the stray response near the anti-resonance frequency caused by energy leakage to the bus, while maintaining the original electromechanical coupling coefficient basically unchanged and increasing the quality factor at the anti-resonance frequency.

[0058] The embodiments described above should be understood only as specific illustrations of this invention and are not intended to limit the specific scope of protection of this invention. After reading the description of this invention, those skilled in the art will understand that this invention can have various changes and modifications. Any changes, modifications, substitutions, combinations, simplifications, improvements, etc., made within the spirit and principles of this application should be considered equivalent substitutions and are included within the scope of protection of this invention.

Claims

1. A multilayer SAW device with spurious response suppression, characterized in that, Design a multilayer SAW device, the multilayer SAW device comprising a first substrate layer, a second substrate layer disposed on the first substrate layer, a temperature compensation layer disposed on the second substrate layer, a piezoelectric layer disposed on the temperature compensation layer, an IDT layer disposed on the piezoelectric layer, and a mass block layer covering a portion of the IDT layer; the IDT layer comprises a first busbar, a second busbar, a first electrode, and a second electrode; the mass block layer comprises a first mass block and a second mass block; the multilayer SAW device has a periodic structure with a period length of λ.

2. The multilayer SAW device with spurious response suppression according to claim 1, characterized in that, The first and second base layers are made of the same material, optionally Si. The heights of the first and second base layers can be 0.5×λ and 1×λ, respectively. The first base layer is a perfect matching layer used to absorb excess anchor damage.

3. A multilayer SAW device with spurious response suppression according to claim 1, characterized in that, The temperature compensation layer is made of SiO2, and its height can be selected as 0.15×λ.

4. A multilayer SAW device with spurious response suppression according to claim 1, characterized in that, The piezoelectric layer can be made of lithium niobate or lithium tantalate, and its height can be 0.4 × λ.

5. A multilayer SAW device with spurious response suppression according to claim 1, characterized in that, The IDT layer is a metal electrode layer, and its material can be selected from Al, Cu, Au and Pt, and its height can be selected from 0.1×λ.

6. A multilayer SAW device with spurious response suppression according to claim 1, characterized in that, The first busbar is connected to the first electrode to form a terminal, which is set to 1V; the second busbar is connected to the second electrode to form a ground terminal.

7. A multilayer SAW device with spurious response suppression according to claim 1, characterized in that, The first electrode and the second electrode are symmetrically placed with respect to the centerline position of the multilayer SAW device in the x direction, and the length of the first electrode in the x direction can be selected as 0.175×λ, and the distance of the first electrode relative to the left periodic boundary of the multilayer SAW device can be selected as 0.1625×λ.

8. A multilayer SAW device with spurious response suppression according to claim 1, characterized in that, The first busbar and the second busbar are symmetrically placed with respect to the centerline position of the multilayer SAW device in the y-direction, and the length of the first busbar along the y-direction of the multilayer SAW device is Ybus; the first mass block and the second mass block are symmetrically placed with respect to the centerline position of the multilayer SAW device in the y-direction.

9. A multilayer SAW device with spurious response suppression according to claim 1, characterized in that, The first mass block and the second mass block respectively cover the first busbar and the second busbar. The material can be silicon nitride. The height of the first mass block is H, and the value of H is in the range of 0.1×λ<H≤0.5×λ.

10. A multilayer SAW device with spurious response suppression according to claim 1, characterized in that, The distance between the first mass block and the second electrode in the y-direction of the multilayer SAW device is the same as the distance between the second mass block and the first electrode in the y-direction of the multilayer SAW device, which is Ygap.

11. A multilayer SAW device with spurious response suppression according to claim 8, characterized in that, The length of the first mass block is L, where the value of L is in the range of L≥Ybus.

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