A surface acoustic wave transducer with multi-order transverse mode suppression and a manufacturing method thereof

Abstract

The present invention discloses a surface acoustic wave transducer with multi-order transverse mode suppression and a manufacturing method. The surface acoustic wave transducer includes a wafer substrate, a forked metal layer and a temperature compensation layer arranged in sequence from bottom to top; and also includes a load layer, and the load layer adopts one of the following structures or a combination thereof; Structure 1: The load layer is arranged on or in the temperature compensation layer, the load layer does not contact the forked metal layer, and the load layer covers all or part of the finger ends in the forked metal layer; Structure 2: The load layer is in the wafer substrate, the load layer is located at the position corresponding to the finger end position of the forked metal layer, and the load layer is a conductive material; Structure 3: The load layer is located between the forked metal layer and the temperature compensation layer, the load layer covers all or part of the finger ends in the forked metal layer, and the load layer is made of non-metallic material. The finger end area is processed to block the transverse mode, and the electrical performance index and the quality Q value are improved; Structure 1 The load layer is isolated from the forked metal layer by the temperature compensation layer, and is not connected to the forked metal layer for short circuit.

Description

Technical Field

[0001] The invention relates to the field of surface acoustic wave devices and manufacturing processes thereof, and in particular to a surface acoustic wave transducer with multi-order transverse mode suppression and a manufacturing method thereof. Background Art

[0002] Mobile communications have developed from the initial 2G to 3G, and then to today's 4G / 5G. Frequency resources are becoming increasingly crowded, and the protection intervals between frequency bands of different communication systems are becoming smaller and smaller. For example, for the transmitter (Tx) and receiver (Rx) duplexer bands (Band2, 3, 8, 25), the frequency interval between Tx and Rx is very narrow. Under long-term power loading conditions, the frequency may drift due to temperature changes, and Tx and Rx will affect each other, causing serious deterioration of overall performance. Therefore, temperature stability requirements are put forward for surface acoustic wave filters, which are the main filtering devices for RF signals. The technology of maintaining the temperature stability of the surface acoustic wave filter frequency over a wide temperature range has become one of the key issues in the current development of surface acoustic wave filter technology and device applications.

[0003] When ordinary surface acoustic wave filters (STD-SAW) use LiTaO3 as the chip wafer substrate 1, they are very sensitive to temperature changes, and the temperature coefficient is about -40ppm / K. If LiNbO3 material is used as the chip wafer substrate 1, the temperature coefficient of the chip reaches -75ppm / K. In order to meet the temperature stability requirements of the communication system, it is usually necessary to cover the surface of the chip's interdigital transducer (IDT) with a material with a positive temperature coefficient to offset the temperature drift of the wafer substrate 1 material. The filter produced by this process technology can reduce the frequency temperature dependence, while achieving low loss, high suppression and other requirements. However, when a layer of temperature compensation material (such as SiO2, etc.) is plated on the surface of the interdigital transducer of the SAW filter chip, although the temperature characteristics are greatly improved, the chip performance will change. After the temperature compensation layer is added, the propagation and working mode of the sound waves in the entire chip structure will be different from the conventional STD-SAW. If the conventional SAW design method is still used, the resonator and RF filter will have strong transverse mode ripples, and the passband noise will be serious, affecting the main wave mode in the original device, thereby causing a great impact on the performance of the surface acoustic wave device.

[0004] Existing transverse mode suppression methods, such as changing the length of the dummy finger to change the length weighting of the overlapping area of ​​the IDT and ground electrodes, may affect the Q value of the resonator and increase the filter loss. Another example is the method led by foreign manufacturers such as Murata and Qualcomm to increase the duty cycle at the end of the metal finger or add a second layer of metal. This method is good for transverse mode suppression, but it also has requirements for process manufacturing accuracy. If the duty cycle is too large or the second layer is not aligned correctly, short circuit may occur. Summary of the invention

[0005] The present invention aims to at least solve the technical problems existing in the prior art, and in particular innovatively proposes a surface acoustic wave transducer with multi-order transverse mode suppression and a manufacturing method.

[0006] In order to achieve the above-mentioned purpose of the present invention, according to the first aspect of the present invention, the present invention provides a surface acoustic wave transducer with multi-order transverse mode suppression, including a wafer substrate, an interdigitated metal layer and a temperature compensation layer arranged in sequence from bottom to top; and also including a load layer, the load layer adopts one of the following structures or any combination thereof; Structure 1: the load layer is arranged on or in the temperature compensation layer, the load layer is not in contact with the interdigitated metal layer, and the load layer covers all or part of the finger ends in the interdigitated metal layer; Structure 2: the load layer is in the wafer substrate, and the load layer is located at a position corresponding to the position of the finger ends of the interdigitated metal layer; Structure 3: the load layer is located between the interdigitated metal layer and the temperature compensation layer, and the load layer covers all or part of the finger ends in the interdigitated metal layer.

[0007] The above technical solution: the surface acoustic wave transducer can effectively block the superposition of transverse mixed mode signals in the temperature compensation layer and enter the passband and out-of-band suppression of the surface acoustic wave device through the load layer. The load layer can block the generation of transverse modes in the finger end area, improve the electrical performance indicators of the surface acoustic wave transducer, and improve the quality factor Q value; the load layer in structure one is arranged in or on the temperature compensation layer, and the load layer can be isolated from the interdigitated metal layer by the temperature compensation layer, so that the load layer can be made into any shape without being connected to the interdigitated metal layer to cause a short circuit.

[0008] In a preferred embodiment of the present invention, in the structure 1, the load layer is a conductive layer or a non-conductive layer arranged on or in the temperature compensating layer; or the load layer is a hollow layer arranged in the temperature compensating layer.

[0009] The above technical solution: the non-void load layer (conductive layer, non-conductive layer) and the void load layer can change the propagation speed of the surface acoustic wave, especially the speed at the edge of the transducer, that is, the end of the finger, destroying the conditions for the generation of transverse mode vibration, and thus blocking the generation of transverse mode in the finger end area; the load layer can be isolated from the interdigitated metal layer by the temperature compensation layer, so that the load layer can be made into any shape without being connected to the interdigitated metal layer to cause a short circuit, thereby effectively blocking the generation of transverse mode, improving the electrical performance indicators of the surface acoustic wave transducer, and improving the quality factor Q value.

[0010] In a preferred embodiment of the present invention, when the load layer is a conductive layer or a non-conductive layer: the load layer includes at least one continuous strip extending along the width direction of the finger, the strip covering a plurality of finger ends and being located above the covered finger ends; or the load layer includes at least one discontinuous strip extending along the width direction of the finger, each segment of the strip covering at least one finger end and being located above the covered finger end; when the load layer is a hollow layer: the load layer includes at least one continuous strip groove extending along the width direction of the finger, the strip groove covering a plurality of finger ends and being located above the covered finger ends; or the load layer includes at least one discontinuous strip groove extending along the width direction of the finger, each segment of the strip groove covering at least one finger end and being located above the covered finger end.

[0011] The above technical solution is easy to manufacture and can effectively block the generation of lateral modes.

[0012] In a preferred embodiment of the present invention, when the load-bearing layer comprises at least one discontinuous strip extending along the width direction of the finger, each segment of the strip covers a finger end and is located directly above the covered finger end.

[0013] The above technical solution achieves overall coverage of the finger ends, can better block the generation of lateral modes, and can also improve the electrical performance indicators of the surface acoustic wave transducer and the quality factor Q value.

[0014] In a preferred embodiment of the present invention, the width of the segment in the fixed strip is taken, and multiple length values ​​are taken in a preset segment length value range. The segments under different length values ​​are subjected to three-dimensional finite element analysis to obtain admittance curves corresponding to the length values ​​one by one, and the length value corresponding to the smoothest and / or peak-free admittance curve among the multiple admittance curves is taken as the optimal length value of the segment.

[0015] The above technical solution can simultaneously satisfy the requirements of best suppressing the lateral mode of the surface acoustic wave transducer and obtaining a higher Q value.

[0016] In a preferred embodiment of the present invention, the second structure is: holes are opened on the wafer substrate at positions corresponding to the finger ends of the interdigitated metal layer, and the holes are filled with conductive material or non-conductive material. When the holes are filled with conductive material, the holes corresponding to the positions of each finger end do not contact the finger ends adjacent to the finger ends; and / or the third structure is: the load layer includes a plurality of non-metallic strips extending along the length directions of the fingers, each of which covers a finger and is located above the covered finger.

[0017] The above technical solution: Structure 2 and Structure 3 can affect the charge distribution at the finger ends, change the electrical and solid mechanical boundary conditions at the finger ends, and ultimately change the wave mode generated in the transducer, thereby effectively blocking the generation of the transverse mode.

[0018] In a preferred embodiment of the present invention, a passivation layer is further included, and the passivation layer is located at the top.

[0019] The above technical solution: when the load layer is a metal layer and is fully or partially exposed on the upper surface of the temperature compensation layer, the passivation layer can make the metal surface less susceptible to oxidation, and the passivation layer can also protect the temperature compensation layer from being easily affected by moisture in the air.

[0020] In order to achieve the above-mentioned purpose of the present invention, according to the second aspect of the present invention, the present invention provides a method for manufacturing a surface acoustic wave transducer, comprising: step S1, generating an interdigitated metal layer on the upper surface of a wafer substrate; step S2, generating a temperature compensation layer with a positive temperature coefficient on the upper surface of the interdigitated metal layer; step S3, performing step one or step two or step three on the temperature compensation layer to obtain a load layer and a passivation layer: the step one is: sequentially performing glue coating, exposure, development, metal deposition and wet stripping on the upper surface of the temperature compensation layer to form a load layer located on the upper surface of the temperature compensation layer; the load layer includes at least one continuous strip extending in the width direction of the finger strip, and the strip The strip covers a plurality of finger ends and is located above the covered finger ends; or the load layer includes at least one discontinuous strip extending in the width direction of the finger, each segment of the strip covers at least one finger end and is located above the covered finger end; a passivation layer is grown above the temperature compensation layer; the step 2 is: sequentially performing glue coating, exposure, development and wet stripping on the upper surface of the temperature compensation layer to form a load layer, the load layer is a hollow layer, and the bottom of the hollow layer does not contact the interdigitated metal layer; the hollow layer includes at least one continuous strip groove extending in the width direction of the finger; or the hollow layer includes at least one continuous strip groove extending in the width direction of the finger An intermittent strip groove, each segment of the strip groove covers at least one finger end and is located above the covered finger end; a passivation layer is grown above the temperature compensation layer avoiding the void position; or the second step is: growing another passivation layer above the temperature compensation layer; sequentially performing glue coating, exposure, development and wet stripping treatment on the upper surface of the passivation layer to form a load layer, the load layer is a void layer passing through the passivation layer and located in the temperature compensation layer, and the bottom of the void layer does not contact the interdigitated metal layer; the void layer includes at least one continuous strip groove extending along the width direction of the finger; or the void layer includes at least one intermittent strip groove extending along the width direction of the finger, the strip Each segment in the strip groove covers at least one finger end and is located above the covered finger end; the step three is: sequentially performing glue coating, exposure, development and wet stripping treatment on the upper surface of the temperature compensation layer to form a load layer, the load layer is a void layer, and the bottom of the void layer does not contact the interdigitated metal layer; the void layer includes at least one continuous strip groove extending along the width direction of the finger; or the void layer includes at least one discontinuous strip groove extending along the width direction of the finger, each segment in the strip groove covers at least one finger end and is located above the covered finger end; filling the strip groove of the void layer with conductive material; and growing another passivation layer above the temperature compensation layer.

[0021] The above technical solution: The surface acoustic wave transducer manufacturing method can not only be widely applied to TC-SAW structures, but also to other structures with thick film covering layers. In order to prevent the lateral parasitic mode from affecting the main mode in the interdigital transducer (IDT) on the interdigitated metal layer, a strip strip and strip groove structure is adopted. The strip strip and strip groove structure has the characteristics of good lateral mode suppression effect, high Q value of the resonator, and easy process manufacturing.

[0022] In order to achieve the above-mentioned purpose of the present invention, according to the third aspect of the present invention, the present invention provides a method for manufacturing a surface acoustic wave transducer, comprising: A, etching holes on the upper surface of a wafer substrate corresponding to the positions of finger ends of a finger metal layer, and filling the etched holes with conductive material or non-conductive material; B, generating a finger metal layer on the upper surface of the wafer substrate, when the holes are filled with conductive material, the holes corresponding to the positions of each finger end do not contact the finger ends adjacent to the finger ends; C, generating a temperature compensation layer with a positive temperature coefficient on the upper surface of the finger metal layer; D, growing a passivation layer on top of the temperature compensation layer.

[0023] The above technical solution: The surface acoustic wave transducer manufacturing method can not only be widely applied to TC-SAW structures, but also to other structures with thick film covering layers. In order to prevent the lateral parasitic mode from affecting the main mode in the interdigital transducer (IDT) on the interdigitated metal layer, a method of etching holes at the positions corresponding to the finger ends on the wafer substrate and filling the etched holes with conductive materials is adopted. This method has the characteristics of good lateral mode suppression effect, high Q value of the resonator, and easy process manufacturing.

[0024] In order to achieve the above-mentioned purpose of the present invention, according to the fourth aspect of the present invention, the present invention provides a method for manufacturing a surface acoustic wave transducer, comprising: I. generating an interdigitated metal layer on the upper surface of a wafer substrate; II. growing a non-metallic load layer along the end direction of the fingers in the interdigitated metal layer, the load layer comprising a plurality of non-metallic strips extending along the length direction of the fingers, each of the strips covering a finger and being located above the covered finger; III. generating a temperature compensation layer having a positive temperature coefficient on the upper surface of the interdigitated metal layer; IV. growing a passivation layer above the temperature compensation layer.

[0025] The above technical solution: The surface acoustic wave transducer manufacturing method can not only be widely applied to TC-SAW structures, but also to other structures with thick film covering layers. In order to prevent the lateral parasitic mode from affecting the main mode in the interdigital transducer (IDT) on the interdigitated metal layer, a method of growing a non-metallic load layer along the end direction of the fingers in the interdigitated metal layer is adopted. This method has the characteristics of good lateral mode suppression effect, high Q value of the resonator, and easy process manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural diagram of a load layer in a preferred implementation manner of Example 1 of the present invention;

[0027] Figure 2 is a schematic cross-sectional structure diagram of a surface acoustic wave transducer in a preferred implementation manner of Example 1 of the present invention;

[0028] Figure 3 is a schematic diagram of a top view of a surface acoustic wave transducer in a preferred implementation manner of Example 1 of the present invention;

[0029] Figure 4 It is a schematic diagram of the relationship between the simulated admittance amplitude of the surface acoustic wave transducer and the structural parameters of the load layer in a preferred implementation manner of the first embodiment of the present invention;

[0030] Figure 5 It is a schematic diagram of the relationship between the real part of the simulated admittance of the surface acoustic wave transducer and the structural parameters of the load layer in a preferred implementation manner of the first embodiment of the present invention;

[0031] Figure 6 is a schematic structural diagram of a load layer in another preferred implementation manner of Example 1 of the present invention;

[0032] Figure 7 is a schematic cross-sectional structure diagram of a surface acoustic wave transducer in another preferred implementation manner of Example 1 of the present invention;

[0033] Figure 8 is a schematic diagram of a top view of a surface acoustic wave transducer in another preferred implementation manner of Example 1 of the present invention;

[0034] Fig. 9 is a schematic structural diagram of a load layer in Embodiment 2 of the present invention;

[0035] Fig.10 is a schematic cross-sectional structure diagram of a surface acoustic wave transducer in Embodiment 2 of the present invention;

[0036] Fig.11 is a schematic diagram of the structure of the load layer in the third embodiment of the present invention;

[0037] Fig.12 is a schematic cross-sectional structural diagram of a surface acoustic wave transducer in Embodiment 3 of the present invention;

[0038] Fig.13 is a schematic diagram of the wafer substrate structure in Embodiment 7 of the present invention;

[0039] Fig.14 is a schematic diagram of applying photoresist on a wafer substrate in Embodiment 7 of the present invention;

[0040] Fig.15It is a schematic diagram of stripping the photoresist and the metal on the photoresist on the wafer substrate in the seventh embodiment of the present invention;

[0041] Fig.16 is a schematic diagram of the structure after the interdigitated metal layer is formed in Embodiment 7 of the present invention;

[0042] Fig.17 is a schematic diagram of growing a temperature compensation layer on the upper end of the interdigitated metal layer in the seventh embodiment of the present invention;

[0043] Fig.18 yes Fig.17 Schematic diagram of the structure after the temperature compensation layer in the figure is flattened;

[0044] Fig.19 is a performance comparison diagram of the surface acoustic wave transducer of the present invention and the existing common surface acoustic wave transducer, wherein: Fig.19 (a) is a schematic diagram of admittance amplitude comparison. Fig.19 (b) is a schematic diagram of insertion loss.

[0045] Reference numerals:

[0046] 1 wafer substrate; 2 interdigitated metal layer; 21 finger strips; 211 finger strip ends; 3 temperature compensation layer; 4 load layer; 5 passivation layer; 6 photoresist. DETAILED DESCRIPTION

[0047] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0048] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0049] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0050] Embodiment 1

[0051] This embodiment discloses a surface acoustic wave transducer, which includes a wafer substrate 1, an interdigitated metal layer 2 and a temperature compensation layer 3 arranged in sequence from bottom to top, and also includes a load layer 4. The load layer 4 adopts structure 1, specifically: Figure 1 As shown, the load layer 4 is disposed on the upper surface of the temperature compensation layer 3, or the load layer 4 is partially embedded in the temperature compensation layer 3 and partially exposed from the temperature compensation layer 3. Through the isolation of the temperature compensation layer 3, the load layer 4 is not in contact with the interdigitated metal layer 2, and is not electrically connected to the interdigitated metal layer 2. The load layer 4 covers all or part of the finger ends 211 in the interdigitated metal layer 2. Preferably, the load layer 4 covers all the finger ends 211 in the interdigitated metal layer 2.

[0052] In this embodiment, the material of the wafer substrate 1 is preferably, but not limited to, LiTaO3 (lithium tantalate), LiNbO3 (lithium niobate), and quartz of various cut types. The interdigitated metal layer 2 is preferably, but not limited to, made of titanium, cadmium, copper, silver, aluminum, or alloys of these metals. The temperature compensation layer 3 has a positive temperature coefficient, and is preferably, but not limited to, silicon dioxide, germanium dioxide, and silicon oxide fluoride. The load layer 4 is a conductive layer or a non-conductive layer. When the load layer 4 is a conductive layer, the load layer 4 is preferably, but not limited to, a metal or a metal alloy or a conductive oxide, such as titanium, chromium, copper, silver, aluminum, platinum, tungsten, etc., or a combination thereof; when the load layer 4 is a non-conductive layer, the load layer 4 is preferably, but not limited to, solid aluminum oxide or Ta2O5 or PI. The load layer 4 is preferably, but not limited to, the same material as the interdigitated metal layer 2. Preferably, the load layer 4 can be of any shape, preferably, but not limited to, a rectangle.

[0053] In a preferred implementation of this embodiment, Figure 2 and Figure 7 As shown, it also includes a passivation layer 5, which is located at the top. The material of the passivation layer 5 is preferably, but not limited to, silicon nitride.

[0054] In another preferred implementation of this embodiment, Figure 3 As shown, the load-bearing layer 4 includes at least one discontinuous strip extending along the width direction of the finger, and each segment in the strip covers at least one finger end 211 and is located above the covered finger end 211. The segments are preferably, but not limited to, rectangular, square, circular, triangular or other irregular shapes.

[0055] In this preferred embodiment, it is further preferred that Figure 3As shown, each segment in the strip covers a finger end 211 and is located directly above the covered finger end 211. Preferably, the width center line of the segment is in the same vertical plane and parallel to the width center line of the covered finger end 211. Further preferably, the segment covers the width of the finger end 211 in the width direction, as shown in FIG. Figure 3 shown.

[0056] In the present preferred embodiment, further preferably, the method for obtaining the optimal length value of the segment is: fix the width of the segment in the strip, take multiple length values ​​in the preset segment length value interval, perform three-dimensional finite element analysis on the segments under different length values ​​to obtain the admittance curves corresponding to the length values ​​one by one, and take the length value corresponding to the smoothest and / or peak-free admittance curve among the multiple admittance curves as the optimal length value of the segment. Further preferably, a three-dimensional finite element model for segment length optimization is established in advance. If the segment width changes, the corresponding optimal length value should also be re-obtained according to the above method. The performance of the surface acoustic wave transducer in this embodiment is simulated, and the simulation results are as follows. Figure 4 and Figure 5 As shown, the width of the segment of the load layer 4 is shown (eg Figure 3 As shown in the figure, when the width direction of the load layer 4 segment is the same as the width direction of the finger end 211, and the length direction of the segment is the same as the length direction of the finger end 211) is fixed at 0.3 wavelengths, the amplitude and real part of the admittance when the length of the load layer 4 changes from 0.2 wavelengths to 1 wavelength. It can be seen that the length and width of the segment in the strip band (which can be used as the structural parameters of the load layer 4) are different, and the transverse mode suppression and performance of the surface acoustic wave transducer are different. Specifically, when the length of the load layer 4 segment is too small, the transverse mode suppression is incomplete, and there are many parasitic peaks in the admittance amplitude and real part curves; when the length of the load layer 4 segment is large, although it has a suppressive effect on the transverse mode parasitics, it also has a serious impact on the main mode in the interdigital transducer IDT, and the Q value at the resonance peak in the admittance curve is significantly reduced. Only when the length of the load layer 4 segment is the optimal value can the best suppression of the transverse mode in the surface acoustic wave transducer be obtained, and a higher Q value can be obtained.

[0057] In another preferred implementation of this embodiment, Figure 6-Figure 8 As shown, the load layer 4 includes at least one continuous strip extending along the width direction of the finger strip, and the strip covers a plurality of finger strip ends 211 and is located above the covered finger strip ends 211. The number of strips is generally two, such as Figure 8 Preferably, the number of strips can be set according to the distribution of the finger ends 211 on the interdigitated metal layer 2. One strip covers a plurality of interdigitated ends.

[0058] In this preferred embodiment, preferably, Figure 8 As shown, the strip is located directly above the finger end 211 , and the strip completely covers the rear edge of the finger end 211 .

[0059] Embodiment 2

[0060] This embodiment discloses a surface acoustic wave transducer. The structural principle of the surface acoustic wave transducer in this embodiment is basically the same as that of the first embodiment. The difference is that the load layer 4 is arranged in the temperature compensation layer 3. Fig. 9 and Fig.10 As shown, the load layer 4 does not contact the interdigitated metal layer 2, so there is no risk of short circuit between the load layer 4 and the interdigitated metal layer 2. As in the first embodiment, the load layer 4 can be a continuous strip covering a plurality of finger ends 211 or a discontinuous strip covering at least one finger end 211. Fig. 9 and Fig.10 As shown, the upper surface of the load layer 4 can be flush with the upper surface of the temperature compensation layer 3 ; the upper surface of the load layer 4 can also be lower than the upper surface of the temperature compensation layer 3 .

[0061] In a preferred implementation of this embodiment, Fig.10 As shown, it also includes a passivation layer 5, which is located at the top. The material of the passivation layer 5 is preferably, but not limited to, silicon nitride.

[0062] Embodiment 3

[0063] The present embodiment discloses a surface acoustic wave transducer, including a wafer substrate 1, an interdigitated metal layer 2 and a temperature compensation layer 3 arranged in sequence from bottom to top, and also including a load layer 4, the load layer 4 adopts structure 1, the load layer 4 is a hollow layer arranged in the temperature compensation layer 3, the bottom of the hollow layer does not contact the interdigitated metal layer 2, and the hollow layer covers all or part of the finger ends 211 in the interdigitated metal layer 2, such as Fig.11 and Fig.12 As shown, the upper surface of the cavity layer can be flush with the upper surface of the temperature compensation layer 3 ; the upper surface of the load layer 4 can also be lower than the upper surface of the temperature compensation layer 3 .

[0064] In a preferred implementation of this embodiment, Fig.12 As shown, it also includes a passivation layer 5, which is located at the top. The material of the passivation layer 5 is preferably, but not limited to, silicon nitride.

[0065] In another preferred implementation of the present embodiment, the load layer 4 includes at least one continuous strip groove extending along the width direction of the finger, the strip groove covers multiple finger ends 211 and is located above the covered finger ends 211; the number of strip grooves is generally two, and preferably, the number of strip grooves can be set according to the distribution of the finger ends 211 on the forked metal layer 2, and one strip groove covers multiple forked finger ends.

[0066] In another preferred implementation of this embodiment, the load-bearing layer 4 includes at least one discontinuous strip groove extending along the width direction of the finger bar, and each segment of the strip groove covers at least one finger bar end 211 and is located above the covered finger bar end 211 .

[0067] In this preferred embodiment, it is further preferred that each segmented groove in the strip groove covers a finger end 211 and is located directly above the covered finger end 211. Preferably, the width direction center line of the segmented groove and the width direction center line of the covered finger end 211 are in the same vertical plane and are parallel to each other. It is further preferred that the segmented groove should cover the width of the finger end 211 in the width direction, and the optimal length of the segmented groove can be obtained by referring to the segment optimal length acquisition method of the first embodiment.

[0068] Embodiment 4

[0069] This embodiment discloses a surface acoustic wave transducer, not shown in the figure, including a wafer substrate 1, a forked metal layer 2 and a temperature compensation layer 3 arranged in sequence from bottom to top; and also including a load layer 4, the load layer 4 adopts the second mechanism, the load layer 4 is in the wafer substrate 1, the load layer 4 is located at the position corresponding to the finger end 211 of the forked metal layer 2, the load layer 4 can be a conductive layer or a non-conductive layer, when the load layer 4 is a conductive layer, it is preferably but not limited to selecting a metal or a metal alloy or a conductive oxide, such as titanium, chromium, copper, silver, aluminum, platinum, tungsten, etc. or a combination thereof, and can also be the same as the finger material; when the load layer 4 is a non-conductive layer, it is preferably but not limited to selecting solid alumina or Ta2O5 or PI. Preferably, the load layer 4 is a metal material, and the load layer 4 is pre-buried in the wafer substrate 1. Preferably, the load layer 4 includes multiple parts, the multiple parts are intermittent or dispersed, and a load layer 4 part is arranged at the position corresponding to each finger end 211.

[0070] In a preferred implementation of this embodiment, not shown in the figure, holes are provided on the wafer substrate 1 at positions corresponding to the finger ends 211 of the interdigitated metal layer 2, and the holes are filled with conductive material or non-conductive material. When the holes are filled with conductive material, the holes corresponding to the positions of each finger end do not contact the finger ends 211 adjacent to the finger end, and the adjacent holes do not contact each other, ensuring that after the holes are provided and the conductive material is filled in the holes, the adjacent finger ends 211 are not short-circuited (contact short-circuited or connected short-circuited), and the conductive material is preferably, but not limited to, a metal material. The holes are preferably, but not limited to, located directly below or beside the finger ends 211.

[0071] Embodiment 5

[0072] The present embodiment discloses a surface acoustic wave transducer, not shown in the figure, comprising a wafer substrate 1, a forked metal layer 2 and a temperature compensation layer 3 arranged in sequence from bottom to top; and also comprising a load layer 4, wherein the load layer 4 adopts mechanism three, the load layer 4 is located between the forked metal layer 2 and the temperature compensation layer 3, and the load layer 4 covers all or part of the finger ends 211 in the forked metal layer 2, and the load layer 4 is made of a conductive or non-conductive material. When the load layer 4 is made of a conductive material, it is preferably but not limited to selecting a metal or a metal alloy or a conductive oxide, such as titanium, chromium, copper, silver, aluminum, platinum, tungsten, etc. or a combination thereof, and can also be the same as the finger material; when the load layer 4 is made of a non-conductive layer material, it is preferably but not limited to selecting solid alumina or Ta2O5 or PI.

[0073] In a preferred implementation of this embodiment, not shown, the load layer 4 includes a plurality of non-metallic strips extending along the length direction of the finger strips, each strip covering a finger strip and being located above the covered finger strip. Preferably, the strip completely covers the underlying finger strip, and its width is greater than the width of the finger strip.

[0074] Embodiment 6

[0075] The present embodiment discloses a surface acoustic wave transducer, not shown in the figure, comprising a wafer substrate 1, an interdigitated metal layer 2 and a temperature compensation layer 3 arranged in sequence from bottom to top; and also comprising a load layer 4, the load layer 4 adopts any combination of structure one, structure two and structure three, such as when the load layer includes two parts, one part of the load layer adopts structure one, and the other part of the load layer adopts structure two; or one part of the load layer adopts structure one, and the other part of the load layer adopts structure three; or one part of the load layer adopts structure two, and the other part of the load layer adopts structure three; for example, when the load layer includes three parts, the first part of the load layer adopts structure one, the second part of the load layer adopts structure two, and the third part of the load layer adopts structure three. The combination can more effectively and comprehensively suppress the transverse mode.

[0076] Embodiment 7

[0077] This embodiment discloses a method for manufacturing a surface acoustic wave transducer, comprising:

[0078] Step S1, forming an interdigitated metal layer 2 on the upper surface of a wafer substrate 1. Preferably, step S1 specifically includes: selecting a suitable piezoelectric material wafer substrate 1 according to design requirements, which can be various cut types of LiTaO3 (lithium tantalate), LiNbO3 (lithium niobate), quartz, etc. Fig.13 Afterwards, the photoresist 6 is evenly coated on the surface of the wafer substrate 1. Preferably, multiple layers of photoresist 6 are evenly coated to protect the surface from contamination, such as Fig.14 Then, exposure, development, baking and other processes are performed to make the side of the photoresist 6 in an inverted trapezoidal shape, and then a metal film is deposited on its surface by electron beam evaporation, magnetron sputtering and the like. The metal film material can be titanium, cadmium, copper, silver, aluminum or their alloys, such as Fig.15 The photoresist 6 and the metal on the photoresist 6 are removed by a wet stripping process, and the interdigitated metal electrodes in close contact with the substrate are retained to form an interdigitated metal layer 2, as shown in FIG. Fig.16 shown.

[0079] Step S2, forming a temperature compensation layer 3 with a positive temperature coefficient on the upper surface of the interdigitated metal layer 2. Preferably, step S2 specifically includes: first, using PVD (Physical Vapor Deposition) magnetron sputtering or electron beam evaporation to grow a layer of temperature compensation material with a positive temperature coefficient on the upper end surface of the metal, such as silicon dioxide, germanium dioxide, silicon oxyfluoride, etc. The thickness is controlled between 500 and 2000nm, such as Fig.17 As shown. Finally, CMP (Chemical Mechanical Planarization) treatment is used to achieve the flatness of the temperature compensation layer and achieve the target thickness of the temperature compensation layer. The target thickness is determined by the electromechanical coupling coefficient required by the design and the material parameters itself. Too thick will reduce the coupling coefficient, and too thin will not achieve the temperature compensation effect. The specific target thickness can be calculated and simulated by 3D finite element software in advance. Fig.18 Step S3, in order to effectively block the lateral heterogeneous mode signals in the temperature compensation layer from being superimposed and entering the passband and out-of-band suppression of the surface acoustic wave device, which will seriously affect the performance, step one, step two or step three is performed on the temperature compensation layer 3 to obtain the load layer 4:

[0080] Step one is: sequentially performing glue coating, exposure, development, metal deposition and wet stripping treatments on the upper surface of the temperature compensation layer 3 to form a load layer 4 located on the upper surface of the temperature compensation layer 3. The structure of the load layer 4 can refer to Example 1; the load layer 4 includes at least one continuous strip extending along the width direction of the finger, the strip covers multiple finger ends 211 and is located above the covered finger ends 211, or the load layer 4 includes at least one discontinuous strip extending along the width direction of the finger, each segment in the strip covers at least one finger end 211 and is located above the covered finger end.

[0081] Step 2 is: sequentially performing glue coating, exposure, development and wet stripping treatment on the upper surface of the temperature compensation layer 3 to form a load layer 4, wherein the load layer 4 is a hollow layer, and the bottom of the hollow layer is not in contact with the interdigitated metal layer 2. The structure of the load layer 4 can refer to Example 3; the hollow layer includes at least one continuous strip groove extending along the width direction of the finger; or the hollow layer includes at least one discontinuous strip groove extending along the width direction of the finger, and each segment in the strip groove covers at least one finger end 211 and is located above the covered finger end 211.

[0082] Step three is: execute step two, fill the hollow layer of step two with conductive material, and the structure of the load layer 4 can refer to embodiment two;

[0083] Step S4, after executing step 1 and step 3, grow another passivation layer 5 on the temperature compensating layer 3, and after executing step 2, grow another passivation layer 5 on the temperature compensating layer 3 to avoid the hole position. Preferably, specifically, PECVD (Plasma Enhanced Chemical Vapor Deposition) is used to grow another passivation layer 5 on the temperature compensating layer 3, specifically, the temperature compensating layer 3 can be coated with glue, exposed, developed, and then a passivation layer is grown, and then peeled off, and the passivation layer 5 avoids the hole position.

[0084] Embodiment 8

[0085] This embodiment discloses a method for manufacturing a surface acoustic wave transducer, comprising:

[0086] Step S1, forming an interdigitated metal layer 2 on the upper surface of a wafer substrate 1. Preferably, step S1 specifically includes: selecting a suitable piezoelectric material wafer substrate 1 according to design requirements, which can be various cut types of LiTaO3 (lithium tantalate), LiNbO3 (lithium niobate), quartz, etc. Fig.13 Afterwards, the photoresist 6 is evenly coated on the surface of the wafer substrate 1. Preferably, multiple layers of photoresist 6 are evenly coated to protect the surface from contamination, such as Fig.14Then, exposure, development, baking and other processes are performed to make the side of the photoresist 6 in an inverted trapezoidal shape, and then a metal film is deposited on its surface by electron beam evaporation, magnetron sputtering and the like. The metal film material can be titanium, cadmium, copper, silver, aluminum or their alloys, such as Fig.15 The photoresist 6 and the metal on the photoresist 6 are removed by a wet stripping process, and the interdigitated metal electrodes in close contact with the substrate are retained to form an interdigitated metal layer 2, as shown in FIG. Fig.16 shown.

[0087] Step S2, forming a temperature compensation layer 3 with a positive temperature coefficient on the upper surface of the interdigitated metal layer 2. Preferably, step S2 specifically includes: first, using PVD (Physical Vapor Deposition) magnetron sputtering or electron beam evaporation to grow a layer of temperature compensation material with a positive temperature coefficient on the upper end surface of the metal, such as silicon dioxide, germanium dioxide, silicon oxyfluoride, etc. The thickness is controlled between 500 and 2000nm, such as Fig.17 As shown. Finally, CMP (Chemical Mechanical Planarization) treatment is used to achieve the flatness of the temperature compensation layer and achieve the target thickness of the temperature compensation layer. The target thickness is determined by the electromechanical coupling coefficient required by the design and the material parameters itself. Too thick will reduce the coupling coefficient, and too thin will not achieve the temperature compensation effect. The specific target thickness can be calculated and simulated by 3D finite element software in advance. Fig.18 shown.

[0088] Step S3, in order to effectively block the lateral heterogeneous mode signals in the temperature compensation layer from being superimposed and entering the passband and out-of-band suppression of the surface acoustic wave device, which would seriously affect the performance, a load layer 4 and a passivation layer 5 are obtained on the temperature compensation layer 3:

[0089] A passivation layer 5 is grown on the top of the temperature compensation layer 3. Specifically, PECVD (Plasma Enhanced Chemical Vapor Deposition) is used to grow another passivation layer on the temperature compensation layer 3. The upper surface of the passivation layer 5 is subjected to sequential processing such as coating, exposure, development, metal deposition and wet stripping to form a load layer 4. The load layer 4 is a hollow layer passing through the passivation layer 5 and located in the temperature compensation layer 3. The structure of the load layer 4 can refer to the third embodiment; the hollow layer includes at least one continuous strip groove extending along the width direction of the finger strip; or the hollow layer includes at least one discontinuous strip groove extending along the width direction of the finger strip, and each segment in the strip groove covers at least one finger strip end 211 and is located above the covered finger strip end 211.

[0090] Embodiment 9

[0091] This embodiment discloses a method for manufacturing a surface acoustic wave transducer, comprising:

[0092] A, etching holes at positions corresponding to the positions of the finger ends 211 of the interdigitated metal layer on the upper surface of the wafer substrate 1, and filling the etched holes with conductive material or non-conductive material;

[0093] B, generating an interdigitated metal layer 2 on the upper surface of the wafer substrate 1, when the holes are filled with conductive material, the holes corresponding to the positions of each finger end 211 do not contact the finger end 211 adjacent to the finger end 211;

[0094] C, a temperature compensation layer 3 with a positive temperature coefficient is generated on the upper surface of the interdigitated metal layer 2;

[0095] D. A passivation layer 5 is grown on top of the temperature compensation layer 3.

[0096] In this embodiment, steps B, C, and D can all be performed with reference to the process in embodiment 7. The structure of the surface acoustic wave transducer manufactured in this embodiment can refer to embodiment 5. Structure 3

[0097] Embodiment 10

[0098] This embodiment discloses a method for manufacturing a surface acoustic wave transducer, comprising:

[0099] Ⅰ, forming an interdigitated metal layer 2 on the upper surface of the wafer substrate 1;

[0100] II, growing a non-metallic load layer 4 along the direction of the finger ends 211 in the interdigitated metal layer 2, the load layer 4 comprising a plurality of non-metallic strips extending along the length direction of the fingers, each strip covering a finger and being located above the covered finger;

[0101] III, a temperature compensation layer 3 with a positive temperature coefficient is generated on the upper surface of the interdigitated metal layer 2;

[0102] IV, a passivation layer 5 is grown on top of the temperature compensation layer 3. Structure 2

[0103] In this embodiment, steps I, III, and IV can all be performed with reference to the process in embodiment 7. The structure of the surface acoustic wave transducer manufactured in this embodiment can refer to embodiment 6.

[0104] In one application scenario of the present invention, after adding the temperature compensation layer to the surface acoustic wave transducer, resonator and RF filter in the existing products, strong transverse mode ripples will appear, and the passband clutter will be serious, which will lead to the deterioration of the overall device performance. Fig.19 As shown by the dotted line in FIG, more parasitic resonance peaks appear. The performance comparison test is conducted between the surface acoustic wave transducer after adding the temperature compensation layer in the existing product and the surface acoustic wave transducer of the present invention. The test results are shown in FIG. Fig.19As shown, Fig.19 (a) is a schematic diagram of admittance amplitude comparison. Fig.19 (b) is a schematic diagram of insertion loss. Fig.19 In the figure, the solid line is the effect of the surface acoustic wave transducer of the present invention, and the dotted line is the effect of the existing surface acoustic wave transducer without transverse mode suppression. It can be seen that the surface acoustic wave transducer of the present invention can effectively suppress the transverse mode structure in the resonator and RF filter, and further improve the Q value of the resonator or RF filter, and the performance improvement effect is very obvious.

[0105] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0106] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A surface acoustic wave transducer with multi-order transverse mode suppression, characterized in that: It includes a wafer substrate, an interdigitated metal layer and a temperature compensation layer which are arranged in sequence from bottom to top; Also included is a load layer, wherein the load layer adopts structure 2, or any combination of structure 2 and the other two structures; Structure 1: The load layer is arranged on or in the temperature compensating layer, the load layer does not contact the interdigitated metal layer, the load layer covers all or part of the finger ends in the interdigitated metal layer, the load layer is a conductive layer or a non-conductive layer arranged on or in the temperature compensating layer; or the load layer is a hollow layer arranged in the temperature compensating layer; Structure 2: The load layer is within the wafer substrate, the load layer is located at a position corresponding to the finger end of the interdigitated metal layer, holes are opened on the wafer substrate at positions corresponding to the finger ends of the interdigitated metal layer, and the holes are filled with conductive material or non-conductive material. When the holes are filled with conductive material, the holes at each finger end position do not contact the finger ends adjacent to the finger ends, and the temperature compensation layer has a positive temperature coefficient; Structure three: the load layer is located between the interdigitated metal layer and the temperature compensation layer, the load layer closely covers all or part of the finger ends of the interdigitated metal layer, and the load layer is made of non-metallic material.

2. The multi-order transverse mode suppressed surface acoustic wave transducer according to claim 1, characterized in that: In the structure 1, when the load layer is a conductive layer or a non-conductive layer: The load-bearing layer includes at least one continuous strip extending along the width direction of the finger strip, and the strip covers a plurality of finger strip ends and is located above the covered finger strip ends; Or the load-bearing layer comprises at least one discontinuous strip extending in the width direction of the finger, each segment of the strip covering at least one finger end and being located above the covered finger end; When the load layer is a hollow layer: The load-bearing layer comprises at least one continuous strip-shaped groove extending along the width direction of the finger strip, wherein the strip-shaped groove covers a plurality of finger strip ends and is located above the covered finger strip ends; Alternatively, the load-bearing layer comprises at least one discontinuous strip-shaped groove extending along the width direction of the finger strip, and each segment of the strip-shaped groove covers at least one finger strip end and is located above the covered finger strip end.

3. The multi-order transverse mode suppressed surface acoustic wave transducer according to claim 2, characterized in that: When the load layer includes at least one discontinuous strip extending along the width direction of the finger, each segment in the strip covers a finger end and is located directly above the covered finger end, and the width center line of the segment is in the same vertical plane and parallel to the width center line of the covered finger end.

4. The multi-order transverse mode suppressed surface acoustic wave transducer according to claim 3, characterized in that: The width of the segment in the fixed strip is selected, multiple length values ​​are selected in a preset segment length value range, and three-dimensional finite element analysis is performed on the segments under different length values ​​to obtain admittance curves corresponding to the length values ​​one by one. The length value corresponding to the smoothest and / or peak-free admittance curve among the multiple admittance curves is taken as the optimal length value of the segment.

5. The surface acoustic wave transducer with multi-order transverse mode suppression as claimed in claim 1, characterized in that: The third structure is as follows: the load-bearing layer comprises a plurality of non-metallic strips extending along the length direction of the finger strips, each of which covers a finger strip and is located above the covered finger strip.

6. The surface acoustic wave transducer with multi-order transverse mode suppression according to any one of claims 1 to 5, characterized in that: Also included is a passivation layer, which is located on the uppermost layer.

7. A method for manufacturing a surface acoustic wave transducer, characterized in that: include: Step S1, generating an interdigitated metal layer on the upper surface of a wafer substrate; Step S2, generating a temperature compensation layer having a positive temperature coefficient on the upper surface of the interdigitated metal layer; Step S3, performing the following steps on the temperature compensation layer to obtain a load layer and a passivation layer: The steps are: sequentially performing glue coating, exposure, development and wet stripping on the upper surface of the temperature compensation layer to form a load layer, wherein the load layer is a hollow layer and is located in the temperature compensation layer, and the bottom of the hollow layer does not contact the interdigitated metal layer; The cavity layer includes at least one continuous strip groove extending along the width direction of the finger strip; or the cavity layer includes at least one discontinuous strip groove extending along the width direction of the finger strip, and each segment of the strip groove covers at least one finger strip end and is located above the covered finger strip end; Growing another passivation layer above the temperature compensation layer avoiding the void position; Or the step is: growing another passivation layer on the temperature compensation layer; Sequentially performing glue coating, exposure, development and wet stripping on the upper surface of the passivation layer to form a load layer, wherein the load layer is a hollow layer passing through the passivation layer and located in the temperature compensation layer, and the bottom of the hollow layer does not contact the interdigitated metal layer; The cavity layer includes at least one continuous strip groove extending along the width direction of the finger strip; or the cavity layer includes at least one discontinuous strip groove extending along the width direction of the finger strip, each segment of the strip groove covers at least one finger strip end and is located above the covered finger strip end.

8. A method for manufacturing a surface acoustic wave transducer, characterized in that: include: Step 1, etching holes on the upper surface of the wafer substrate at positions corresponding to the ends of the fingers of the interdigitated metal layer, and filling the etched holes with conductive material or non-conductive material; Step 2, generating an interdigitated metal layer on the upper surface of the wafer substrate, when the holes are filled with conductive material, the holes corresponding to the positions of each finger end do not contact the finger ends adjacent to the finger ends; Step 3, generating a temperature compensation layer with a positive temperature coefficient on the upper surface of the interdigitated metal layer; Step 4: growing another passivation layer on the temperature compensation layer.

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