Temperature-compensated surface acoustic wave device structure

Abstract

Provided in the present application is a temperature-compensated surface acoustic wave device structure, comprising a piezoelectric substrate, an IDT electrode layer, a temperature compensation layer, and a passivation layer, which are stacked in sequence from bottom to top, and a loading layer located above the IDT electrode layer or between the piezoelectric substrate and the electrode layer.

Description

Temperature compensation type surface acoustic wave device structure

[0001] Cross-reference to related applications

[0002] The present application is based on the Chinese patent application No. 202410847716.9, filed on June 27, 2024, and claims the priority of the Chinese patent application No. 202410847716.9, the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the technical field of surface acoustic wave devices, in particular to a temperature compensation type surface acoustic wave device structure. BACKGROUND

[0004] The basic structure of a surface acoustic wave (SAW) device is to make an acoustic-electric transducer on a piezoelectric substrate material, which has the advantages of low electric-acoustic conversion loss, flexible design, and easy large-scale production by semiconductor process. The temperature compensation type surface acoustic wave (TC-SAW) device has high temperature stability, low insertion loss, high selectivity, and is widely used in high-frequency and wideband communication systems.

[0005] Currently, there are two routes for the technology of temperature compensation type surface acoustic wave devices. One is a wafer bonding temperature compensation method, which bonds the chip on a wafer substrate with good temperature stability. However, this preparation method has a relatively high cost, which may even be 5-10 times the cost of a standard surface acoustic wave (STD-SAW) device. The other is a widely used method of covering a temperature compensation layer on the surface, that is, covering a layer of material with a positive temperature coefficient such as silicon dioxide and germanium dioxide on the interdigital transducer (IDT), and then plating a passivation layer. By effectively controlling the thickness of each layer, the negative temperature coefficient of the original piezoelectric substrate can be offset, so that the filter can achieve good frequency stability in a wider temperature range. However, the addition of this temperature compensation layer will produce unnecessary transverse stray modes (transverse modes). The stray response caused by these transverse modes causes fluctuations in the passband, increases the insertion loss of the device, and reduces the Q value of the device, thereby causing the overall device performance to deteriorate.

[0006] Therefore, how to provide a temperature compensation type surface acoustic wave device structure that can suppress the influence of transverse modes on device performance has become one of the technical problems that personnel in the field need to solve.

[0007] SUMMARY

[0008] The present application aims to at least partially solve one of the problems in the related art.

[0009] To this end, the first object of the present application is to provide a temperature compensation type surface acoustic wave device structure, which can suppress the influence of the transverse mode on the device performance, reduce the influence of the transverse mode on the Q value of the device, and improve the device performance.

[0010] To achieve the above object, the first aspect of the present application provides a temperature compensation type surface acoustic wave device structure, comprising a piezoelectric substrate, an IDT electrode layer, a temperature compensation layer and a passivation layer stacked in order from bottom to top, and a load layer located above the IDT electrode layer or between the piezoelectric substrate and the electrode layer.

[0011] The load layer comprises a plurality of first load units and a plurality of second load units arranged at intervals along a first direction; in a second direction, the first load units and the second load units correspond to each other one by one and are symmetrical to each other; in a third direction, projections of the first load units and the second load units on the first direction cover both ends of the IDT electrode layer, and the projections are both multi-edge special-shaped structures with grooves; wherein the first direction is orthogonal to the second direction and parallel to the surface of the piezoelectric substrate, and the third direction is perpendicular to the first direction and the second direction.

[0012] Optionally, the IDT electrode layer comprises a plurality of interdigital electrode groups arranged at intervals along the first direction, and each interdigital electrode group comprises at least a pair of first electrode fingers and second electrode fingers extending alternately along the second direction; in the third direction, the projections of the first load units and the second load units on the first direction cover the interdigital electrode groups.

[0013] Optionally, the IDT electrode layer further comprises a first bus bar and a second bus bar parallel to each other and arranged at intervals along the second direction, the first electrode fingers extend from one side of the first bus bar to the side close to the second bus bar, and the second electrode fingers extend from one side of the second bus bar to the side close to the first bus bar; in the third direction, the end projection boundary of the second electrode fingers is located on the projection boundary of the first load unit close to the first bus bar, and the end projection boundary of the first electrode fingers is located on the projection boundary of the second load unit close to the second bus bar.

[0014] Optionally, in the third direction, the extension length of the projection of the first load unit between the first electrode finger and the second electrode finger along the second direction is less than the extension length of the projection of the first load unit on the first electrode finger and the second electrode finger along the second direction, respectively.

[0015] Optionally, the first load unit comprises at least a first load block, a second load block and a third load block connected in sequence along the first direction, a first end of the first load block corresponds to the boundary of the end of the second electrode finger, and a second end of the first load block extends along the second direction by a first preset length; the third load block is symmetrically arranged with the first load block, and the second load block is located between the first load block and the third load block.

[0016] Optionally, in the third direction, the projection of the first load block is located in the projection plane of the second electrode finger, the projection of the third load block is located in the projection plane of the first electrode finger, and the projection of the second load block is located in the gap between the first electrode finger and the second electrode finger.

[0017] Optionally, a first end of the second load block corresponds to the boundary of the first end of the first load block in the second direction, and a second end of the second load block extends along the second direction by a second preset length, which is less than the first preset length.

[0018] Optionally, a second end of the second load block corresponds to the boundary of the second end of the first load block in the second direction, and a first end of the second load block extends along the second direction by a second preset length, which is less than the first preset length.

[0019] Optionally, the boundaries of the first end and the second end of the second load block are located between the boundaries of the first end and the second end of the first load block, respectively, and the second preset length by which the second end of the second load block extends along the second direction is less than the first preset length.

[0020] Optionally, the first load unit further comprises a first auxiliary load block and a second auxiliary load block symmetrically arranged along the first direction, and the first auxiliary load block and the second auxiliary load block are arranged between the gaps of two adjacent interdigital electrode groups, respectively.

[0021] A first end of the first auxiliary load block corresponds to the boundary of the first end of the first load block in the second direction, and a second end of the first auxiliary load block extends along the second direction by a third preset length, which is less than the first preset length.

[0022] Optionally, a reflective grating electrode layer is further included, the reflective grating electrode layer is formed on the piezoelectric substrate and is arranged on both sides of the IDT electrode layer at intervals along the first direction, and the projections of the first load unit and the second load unit in the third direction further extend in the first direction to cover the reflective grating electrode layer.

[0023] Optionally, the load layer is located between the piezoelectric substrate and the IDT electrode layer, and the IDT electrode layer is formed on the load layer and extends to cover the exposed part of the surface of the piezoelectric substrate.

[0024] Optionally, the load layer is formed between the piezoelectric substrate and the temperature compensation layer, and the load layer is formed on the IDT electrode layer and covers the part of the surface of the piezoelectric substrate exposed by the IDT electrode layer, and the temperature compensation layer is formed on the load layer and covers the surface exposed by the IDT electrode layer and the piezoelectric substrate.

[0025] Optionally, the temperature compensation layer includes a first surface and a second surface opposite in the third direction, and the load layer is formed in the temperature compensation layer between the first surface and the second surface.

[0026] Optionally, the load layer is formed between the temperature compensation layer and the passivation layer.

[0027] Optionally, the load layer is formed on the passivation layer.

[0028] The TC-SAW device structure provided by the present application has at least the following beneficial effects:

[0029] The present application provides a TC-SAW device structure, which comprises a piezoelectric substrate, an IDT electrode layer, a temperature compensation layer and a passivation layer stacked in order from bottom to top, and a load layer located above the IDT electrode layer or between the piezoelectric substrate and the electrode layer. By setting the projection of the load layer in the direction perpendicular to the thickness of the piezoelectric substrate as a multi-edge irregular shape structure with grooves, and satisfying that the grooves of the projection correspond one-to-one to the finger gaps of the IDT electrode layer, and the projection covers the two ends of the fingers of the IDT electrode layer respectively, the load layer can suppress the transverse mode in the device structure, and block and reflect the propagation path of other stray waves other than the main mode of the surface acoustic wave, thereby improving the performance of the device.

[0030] Further, the TC-SAW device structure provided by the present application sets the load layer 150 on the IDT electrode layer and does not directly contact the IDT electrode layer, which can also avoid direct processing of the finger ends of the IDT electrode layer, reduce the process complexity caused by direct processing of the finger ends of the IDT electrode layer, and will not damage the original finger structure of the IDT electrode layer, optimize the process flow of the TC-SAW device structure, and reduce the production cost.

[0031] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0032] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description, taken in conjunction with the following drawings of which:

[0033] Fig. 1 is a schematic diagram of a cross-sectional structure of a first TC-SAW device structure according to an embodiment of the present application.

[0034] Fig. 2 is a schematic diagram of a longitudinal cross-sectional structure of the first TC-SAW device structure according to an embodiment of the present application.

[0035] Fig. 3 is a schematic diagram of a longitudinal cross-sectional structure of a second TC-SAW device structure according to an embodiment of the present application.

[0036] Fig. 4 is a schematic diagram of a longitudinal cross-sectional structure of a third TC-SAW device structure according to an embodiment of the present application.

[0037] Fig. 5 is a schematic diagram of a longitudinal cross-sectional structure of a fourth TC-SAW device structure according to an embodiment of the present application.

[0038] Fig. 6 is a schematic diagram of a longitudinal cross-sectional structure of a fifth TC-SAW device structure according to an embodiment of the present application.

[0039] Fig. 7 is a schematic diagram of a cross-sectional structure of the second TC-SAW device structure according to an embodiment of the present application.

[0040] Fig. 8 is a schematic diagram of a cross-sectional structure of the third TC-SAW device structure according to an embodiment of the present application.

[0041] Fig. 9 is a schematic diagram of a cross-sectional structure of the fourth TC-SAW device structure according to an embodiment of the present application.

[0042] Fig. 10 is a schematic diagram of a cross-sectional structure of the fifth TC-SAW device structure according to an embodiment of the present application.

[0043] Fig. 11 is a schematic diagram of a cross-sectional structure of a sixth TC-SAW device structure according to an embodiment of the present application.

[0044] Fig. 12 is a performance diagram of a TC-SAW device structure according to a related art.

[0045] Fig. 13 is a performance diagram of a TC-SAW device structure according to an embodiment of the present application.

[0046] Fig. 14 is a performance comparison diagram of a TC-SAW device structure according to an embodiment of the present application and a TC-SAW device structure according to another related art.

[0047] 110 piezoelectric substrate; 120 IDT electrode layer; 121 first electrode finger; 122 second electrode finger; 123 first bus bar; 124 second bus bar; 130 temperature compensation layer; 140 passivation layer; 150 load layer; 151 first load unit; 1511 first load block; 1512 second load block; 1513 third load block; 1514 first auxiliary load block; 1515 second auxiliary load block; 152 second load unit; 160 reflector electrode layer. DETAILED DESCRIPTION

[0048] Embodiments of the present application are described below in detail, examples of which are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application.

[0049] A surface acoustic wave (SAW) device is an acoustic device widely used in the field of radio frequency, including a surface acoustic wave resonator or a surface acoustic wave filter, which has low insertion loss and good suppression performance, and is also small in size, mainly utilizing the piezoelectric effect to convert electrical energy and mechanical energy. In order to enable the surface acoustic wave device to maintain performance stability in a larger temperature range, the prior art usually covers a material layer having a positive temperature coefficient on the interdigital electrode layer of the surface acoustic wave device to offset the influence of the negative temperature coefficient of the piezoelectric substrate material on the frequency stability of the device, i.e., a SAW device with temperature compensation function (TC-SAW)

[0050] For a TC-SAW device, the acoustic wave propagating transversely along the length direction of the finger will cause the device to have a transverse resonant mode, i.e., a spurious wave appearing in the passband and near the passband, which will increase the device loss, cause a large fluctuation in Q value, and reduce the performance of the TC-SAW device (resonator, filter). Therefore, the prior art suppresses the transverse mode by increasing the mass load at the end of the finger, i.e., setting a thickened and / or widened metal end (Piston structure) at the end of the finger to reduce the acoustic velocity in this area. This method can achieve a certain transverse mode suppression effect, but since the suppression effect of the transverse mode is sensitive to the size and weight of the mass load, the processing technology requirements are relatively high, the process cost is increased, and the processing of the end of the finger will also affect the propagation of the main mode to some extent, resulting in a decrease in the Q value of the device.

[0051] Therefore, how to suppress the transverse spurious mode in a surface acoustic wave device with temperature compensation function, improve the Q value of the device, and at the same time reduce the manufacturing process requirements and manufacturing cost of the device, is the key problem to be solved by the present technical solution.

[0052] Based on the above problems, the embodiment of the present application provides a TC-SAW device structure, as shown in FIG. 1 and FIG. 2, which comprises a piezoelectric substrate 110, an IDT electrode layer 120, a temperature compensation layer 130 and a passivation layer 140 stacked in sequence from bottom to top, and further comprises a load layer 150 located above the IDT electrode layer 120 or between the piezoelectric substrate 110 and the electrode layer.

[0053] The load layer 150 comprises a plurality of first load units 151 and a plurality of second load units 152 arranged in a first direction; in a second direction, the first load units 151 and the second load units 152 correspond to each other and are symmetrical to each other; in a third direction, projections of the first load units 151 and the second load units 152 in the first direction respectively cover both ends of the finger of the IDT electrode layer 120, and the projections are all polygonal special-shaped structures with grooves.

[0054] For the convenience of description, the propagation direction of the surface acoustic wave is set as the first direction, i.e. the X direction in the drawing, the direction of the finger extension of the IDT electrode layer 120 is set as the second direction, i.e. the Y direction in the drawing, and the direction of the thickness of the stacked layers of the device structure is set as the third direction, i.e. the Z direction in the drawing. Among them, the first direction and the second direction are orthogonal to each other and parallel to the surface of the piezoelectric substrate 110, and the third direction is perpendicular to the first direction and the second direction.

[0055] It can be understood that the acoustic wave is a typical elastic wave, and by applying an alternating voltage on the IDT electrode layer 120, the device structure can be excited to generate an elastic wave. When the elastic wave propagates in a material, it will be reflected to the wave not parallel to the interface direction when encountering the interface of different media (having different sound propagation speeds), avoiding the formation of spurious waves to form resonance, thereby reducing energy loss.

[0056] By setting the projection of the load layer 150 in the third direction to cover both ends of the finger of the IDT electrode layer 120, the present application can change the propagation speed of the acoustic wave in the corresponding area of the load layer 150, avoiding the excitation of transverse mode resonance. By setting the projection of the load layer 150 in the third direction to be a polygonal special-shaped structure with grooves, and setting the groove position of the projection to correspond to the gap of the finger of the IDT electrode layer 120, different sound speed regions can be generated in the corresponding area of the load layer 150, thereby reflecting various spurious waves and not easily being excited to form resonance, while not affecting the main acoustic mode, so that most of the acoustic wave energy can be concentrated on the main acoustic mode, avoiding additional energy dissipation, thereby improving the performance of the device.

[0057] In some embodiments, the piezoelectric substrate 110 is composed of a material capable of providing piezoelectric effect, including but not limited to one of LiTaO3 (lithium tantalate), LiNbO3 (lithium niobate), quartz, zinc oxide (ZnO), aluminum nitride (AIN), and the like in various cut types. For example, the piezoelectric substrate 110 can be made of lithium niobate or lithium tantalate material, which has excellent piezoelectric effect and electromechanical coupling effect, and is widely used in the structure of surface acoustic wave devices.

[0058] The IDT electrode layer 120 is deposited on the upper surface of the piezoelectric substrate 110. As the most basic unit constituting a surface acoustic wave device, the IDT electrode layer 120 includes but is not limited to one of titanium, chromium, copper, silver, aluminum, platinum, tungsten, molybdenum, and the like, or a metal alloy thereof, and can be a single-layer metal film or a laminated metal film stacked with multiple metal layers.

[0059] As an example, the IDT electrode layer 120 includes first and second bus bars 123 and 124 arranged in parallel with each other in the second direction, and a plurality of interdigital electrode groups arranged in the first direction, each of which includes at least a pair of first and second electrode fingers 121 and 122 extending alternately in the second direction. Each first electrode finger 121 extends from one side of the first bus bar 123 to the side close to the second bus bar 124, and the end of the first electrode finger 121 does not contact the second bus bar 124, and each second electrode finger 122 extends from one side of the second bus bar 124 to the side close to the first bus bar 123, and does not contact the first bus bar 123, and the plurality of first electrode fingers and the plurality of second electrode fingers 122 are alternately arranged in the first direction.

[0060] The temperature compensation layer 130 is also formed on the upper surface of the piezoelectric substrate 110 and covers the IDT electrode layer 120 deposited on the upper surface of the piezoelectric substrate 110. The temperature compensation layer 130 is composed of a material capable of providing a positive temperature coefficient, including but not limited to a combination of one or more of silicon dioxide, germanium dioxide, and silicon oxyfluoride. Since the SAW device is susceptible to temperature changes, a SAW device with temperature compensation function (TC-SAW) can be constructed by coating a layer of temperature compensation material with a positive frequency temperature coefficient to improve the temperature drift phenomenon.

[0061] The passivation layer 140 is formed on the upper surface of the temperature compensation layer 130 and is composed of a material with stable properties, including but not limited to silicon nitride, for protecting and isolating the surface of the temperature compensation layer.

[0062] The load layer 150 can be composed of a conductive material or an insulating material. When the load layer 150 is a conductive layer, the material constituting the load layer 150 includes, but is not limited to, a metal or a metal alloy or a conductive oxide, such as titanium, chromium, copper, silver, aluminum, platinum, tungsten, molybdenum, and the like. The material constituting the load layer 150 can be a single layer of a metal film or a laminated metal film having multiple layers of metal.

[0063] When the load layer 150 is an insulating layer, the material constituting the load layer 150 includes, but is not limited to, solid silicon dioxide (SiO2), aluminum trioxide (Al2O3), titanium dioxide (TiO2), tantalum pentoxide (Ta2O5), aluminum nitride (AlN), or PI, and the like.

[0064] The thickness of the load layer 150 in the third direction can be the same as or different from the thickness and material of the IDT electrode layer 120. As an example, the thickness of the load layer 150 can be the same as the thickness of the IDT electrode layer 120.

[0065] In some embodiments, the third direction of the load layer 150 in the TC-SAW device can not be specifically defined, as shown in FIGS. 2 and 5. That is, the load layer 150 can be disposed above the IDT electrode layer 120 or between the piezoelectric substrate 110 and the IDT electrode layer 120.

[0066] As an example, as shown in FIG. 3, the load layer 150 can be formed between the piezoelectric substrate 110 and the temperature compensation layer 130, and the IDT electrode layer 120 can be directly formed on the load layer 150, covering part of the surface of the load layer 150 and extending to cover part of the surface of the piezoelectric substrate 110 exposed.

[0067] As an example, as shown in FIG. 4, the load layer 150 can be formed between the piezoelectric substrate 110 and the temperature compensation layer 130, and the load layer 150 can be formed on the IDT electrode layer 120, covering part of the surface of the piezoelectric substrate 110 exposed by the IDT electrode layer 120, including the end of the first electrode finger 121 and part of the area adjacent to the second electrode finger 122, and the end of the second electrode finger 122 and part of the area adjacent to the first electrode finger 121, and the temperature compensation layer 130 can be formed on the load layer 150 and cover the surfaces of the IDT electrode layer 120 and the piezoelectric substrate 110 exposed.

[0068] As an example, as shown in FIG. 5, the load layer 150 can be formed inside the temperature compensation layer 130. The temperature compensation layer 130 includes a first surface and a second surface opposite in the third direction, the first surface being the surface close to the piezoelectric substrate 110, and the second surface being the surface away from the piezoelectric substrate 110, and the load layer 150 is formed between the first surface and the second surface of the temperature compensation layer 130, so that the load layer 150 can be located on the IDT electrode layer 120 without directly contacting the IDT electrode layer 120.

[0069] As an example, as shown in FIG. 2 and FIG. 6, the load layer 150 can be formed between the temperature compensation layer 130 and the passivation layer 140, or directly on the passivation layer 140.

[0070] In the above examples, the formation position of the load layer 150 in the third direction can be above the IDT electrode layer 120 without directly contacting the IDT electrode layer 120.

[0071] For the specific selection of the load layer 150 by conductive material or non-conductive material, it can be flexibly set according to the setting position of the load layer 150 in the device. For example, when the load layer 150 directly contacts the IDT electrode layer 120, the load layer 150 can be composed of non-conductive material to avoid the problem of short circuit between the fingers of the IDT electrode layer 120. Conversely, when the load layer 150 does not directly contact the IDT electrode layer 120, the load layer 150 can be composed of conductive material.

[0072] In some embodiments, as shown in FIG. 1, the load layer 150 includes a first load unit 151 and a second load unit 152, and in the third direction, the projections of the first load unit 151 and the second load unit 152 cover the ends of the fingers of the interdigital electrode group in the first direction, that is, the end of the first electrode finger 121 and part of the region adjacent to the second electrode finger 122, and the end of the second electrode finger 122 and part of the region adjacent to the first electrode finger 121, thereby limiting the formation position of the load layer 150 in the first direction and the second direction.

[0073] Further, by limiting the projection boundary position of the first load unit 151 and the second load unit 152, and locating the end projection boundary of the second electrode finger 122 on the projection boundary of the first load unit 151 close to the first bus bar 123, and locating the end projection boundary of the first electrode finger 121 on the projection boundary of the second load unit 152 close to the second bus bar 124, the end projection boundary of each first electrode finger 121 can be located on the projection boundary of each corresponding second load unit 152, and the end projection boundary of each second electrode finger 122 can be located on the projection boundary of each corresponding first load unit 151.

[0074] Meanwhile, in the third direction, the first load unit 151 is configured such that the extension length of the projection of the first load unit 151 along the second direction between the first electrode finger 121 and the second electrode finger 122 is less than the extension length of the projection of the first load unit 151 respectively on the first electrode finger 121 and the second electrode finger 122 along the second direction, so that the projection of the first load unit 151 in the third direction presents a multi-edge irregular structure with a groove, and the difference in the extension length of the projection of the different local structures of the first load unit 151 in the second direction corresponds to the extension length of the groove in the projection.

[0075] Since the structure of the second load unit 152 in the second direction is completely symmetrical with the first load unit 151, the specific structure and the setting position of the second load unit 152 can refer to the first load unit 151, and the specific structure of the second load unit 152 will not be described in detail here and in the subsequent content.

[0076] Therefore, the different local structures of the first load unit 151 (the second load unit 152) have different extension lengths in the second direction, which will also produce different sound speed zones in the area corresponding to the first load unit 151. Different sound speed zones not only inhibit transverse mode resonance, but also further reflect various stray waves, thereby improving the performance of the device.

[0077] Further, as shown in FIG. 7, the TC-SAW device structure further includes a reflector electrode layer 160 formed on the piezoelectric substrate 110 and arranged on both sides of the IDT electrode layer 120 in the first direction, and the projection of the first load unit 151 and the second load unit 152 in the third direction further extends to cover the reflector electrode layer 160 in the first direction.

[0078] It should be noted that in the third direction, the end projection boundary of each first electrode finger 121 can be located on the projection boundary of each corresponding second load unit 152, and the end projection boundary of each second electrode finger 122 can be located on the projection boundary of each corresponding first load unit 151. However, considering the precision limitation of actual process or equipment, the end projection boundary of the first electrode finger 121 can also be located inside the projection of each corresponding second load unit 152, so that the projection of the second load unit 152 is located between the end boundary of the corresponding first electrode finger 121 and the boundary of the second bus bar 124; and the end projection boundary of the second electrode finger 122 can also be located inside the projection of each corresponding first load unit 151, so that the projection of the first load unit 151 is located between the end boundary of the corresponding second electrode finger 122 and the boundary of the second bus bar 124.

[0079] In some embodiments, as shown in FIG. 7, the first load unit 151 at least includes a first load block 1511, a second load block 1512 and a third load block 1513 connected in sequence along a first direction, a first end of the first load block 1511 corresponds to the boundary of the end of the second electrode finger 122, a second end of the first load block 1511 extends along a second direction by a first preset length D1, the third load block 1513 is symmetrically arranged with the first load block 1511, and the second load block 1512 is located between the first load block 1511 and the third load block 1513.

[0080] In the third direction, the projection of the first load block 1511 is located in the projection plane of the second electrode finger 122, the projection of the third load block 1513 is located in the projection plane of the first electrode finger 121, and the projection of the second load block 1512 is located in the gap between the first electrode finger 121 and the second electrode finger 122. Thus, the load layer can reflect other stray waves other than the elastic waves excited by the first electrode finger 121 and the second electrode finger 122 in its projection coverage range, and make their energy exhausted, thereby avoiding the excitation of transverse mode resonance.

[0081] Since the projection of the second load block 1512 is located between the first electrode finger 121 and the second electrode finger 122, and the extension length of the second load block 1512 along the second direction is less than that of the first load block 1511 and the third load block 1513, the extension length of the projection of the first load unit between the first electrode finger and the second electrode finger along the second direction is less than the extension length of the projections of the first load unit on the first electrode finger and the second electrode finger along the second direction, and further the projection of the first load unit 151 in the third direction is a multi-edge heterogeneous structure with a groove,

[0082] When the second load block 1512 is arranged between the two ends (the first end and the second end) of the first load block 1511 and the second load block 1512 along the second direction, the projection of the first load unit 151 in the third direction is a multi-edge heterogeneous structure with a groove. For the specific arrangement position of the second load block 1512 along the second direction, the present application does not make specific limitation here.

[0083] As an example, the first end of the second load block 1512 corresponds to the boundary of the first end of the first load block 1511 along the second direction, and the second end of the second load block extends along the second direction by a second preset length D2, and the second preset length D2 is less than the first preset length D1.

[0084] Thus, the first load unit 151 in the third direction of the projection is a multi-edge-shaped structure with a groove, and the groove is located in the center of the projection boundary near the second bus bar 124 side to the first bus bar 123 side, and the groove width corresponds to the gap distance between the first electrode finger 121 and the second electrode finger 122.

[0085] As an example, as shown in FIG. 8, the boundary of the second end of the second load block 1512 and the second end of the first load block 1511 corresponds in the second direction, the first end of the second load block 1512 extends in the second direction by a second preset length D2, and the second preset length D2 is less than the first preset length D1.

[0086] Thus, the first load unit 151 in the third direction of the projection is a multi-edge-shaped structure with a groove, and the groove is located in the center of the projection boundary near the second bus bar 124 side to the first bus bar 123 side, and the groove width corresponds to the gap distance between the first electrode finger 121 and the second electrode finger 122.

[0087] Further, as shown in FIG. 9, the first load unit 151 further includes a first auxiliary load block 1514 and a second auxiliary load block 1515 symmetrically arranged along the first direction, and the first auxiliary load block 1514 and the second auxiliary load block 1515 are respectively arranged between the gaps of two adjacent interdigital electrode groups, so that the projections of the first auxiliary load block 1514 and the second auxiliary load block 1515 between adjacent interdigital electrode groups in the third direction can be connected, and cover the gap between adjacent interdigital electrode groups in the first direction. Wherein, the boundary of the first end of the first auxiliary load block 1514 and the first end of the first load block 1511 corresponds in the second direction, the second end of the first auxiliary load block 1514 extends in the second direction by a third preset length, and the third preset length is less than the first preset length D1.

[0088] By arranging the first auxiliary load block 1514 and the second auxiliary load block 1515 between adjacent interdigital electrode groups, the projections of adjacent first load units 151 in the third direction can be connected in sequence in the first direction, thereby forming a continuous multi-edge structure with multiple grooves, and the position of each groove corresponds to the gap between the first electrode finger 121 and the second electrode finger 122, to further suppress the transverse mode resonance and improve the device performance.

[0089] As an example, as shown in FIG. 10, the boundaries of the first end and the second end of the second load block 1512 are respectively located between the boundaries of the first end and the second end of the first load block 1511, and the second preset length D2 of the second end of the second load block 1512 extending in the second direction is less than the first preset length D1.

[0090] Therefore, the projection of the first load unit 151 in the third direction is a multi-edge special-shaped structure with two grooves, and the two grooves are oppositely arranged, and the groove width corresponds to the gap distance between the first electrode finger 121 and the second electrode finger 122.

[0091] It should be noted that the present application does not make specific limitations on the specific parameter values of the first preset length D1 of the first load block 1511 extending in the second direction and the second preset length D2 of the second load block 1512 extending in the second direction in the first load unit 151; the parameter values of the first preset length D1 and the second preset length D2 of different first load units 151 can be the same or different, and the present application does not make specific limitations on this.

[0092] In addition, the above structure of the first load unit 151 is based on each interdigital electrode group having a pair of first electrode fingers 121 and second electrode fingers 122 extending in the second direction. Each interdigital electrode group can also have two or more pairs of first electrode fingers 121 and second electrode fingers 122 extending in the second direction, as shown in FIG. 11. Therefore, the projection of the first load unit 151 in the third direction also needs to cover each pair of first electrode fingers 121 and second electrode fingers 122 and the gap between each pair of first electrode fingers 121 and second electrode fingers 122 in the first direction. Correspondingly, the projection of the first load unit 151 in the third direction has a continuous multi-edge structure with multiple grooves, and the position of each groove corresponds to the gap between the first electrode finger 121 and the second electrode finger 122, so as to further suppress the transverse mode and improve the device performance.

[0093] In order to further illustrate the transverse mode suppression effect of the TC-SAW device structure in the present application, the TC-SAW device structure in the present application can be applied to specific scenarios, for example, the TC-SAW device structure is applied to a resonator or a filter and the like acoustic surface wave device, and the performance graph of the resonator or the filter is viewed. If there are many parasitic resonance peaks in the graph, it indicates that the resonator or the filter has a strong transverse mode ripple, the passband noise is serious, and the use of the TC-SAW device structure will cause the deterioration of the overall device performance.

[0094] As an example, the existing TC-SAW device structure and the TC-SAW device structure of the present application can be applied to resonators for performance comparison, and the comparison results are shown in FIG. 12 and FIG. 13, where FIG. 12 is a performance diagram of a resonator applying a common TC-SAW device structure without transverse mode suppression effect, and FIG. 13 is a performance diagram of a resonator applying the TC-SAW device structure of the present application. According to the comparison of FIG. 12 and FIG. 13, it can be seen that the admittance curves in FIG. 13 are smoother, and compared with the admittance curves in FIG. 12, the number of spurious resonance peaks in the admittance curves in FIG. 13 is almost invisible, which indicates that the TC-SAW device structure provided by the present application can effectively suppress the transverse mode in the resonator, and can further improve the Q value of the resonator or filter, so that the performance of the resonator or filter can be significantly improved.

[0095] Further, the TC-SAW device structure with Piston structure and the TC-SAW device structure of the present application can be applied to resonators for performance comparison, and the comparison results are shown in FIG. 14. As can be seen from the admittance curves in the figure, the TC-SAW resonator with the structure of the opposite load layer 150 of the present application can not only effectively suppress the transverse mode in the resonator, but also has a good suppression effect on other unwanted spurious modes (such as SH Spurious). Among them, the piezoelectric substrate 110 adopts Y-cut-X 127.85° LiNbO3.

[0096] In addition, the TC-SAW device structure with transverse mode suppression effect in any of the embodiments disclosed herein can also be provided in or integrated into any processor-based device. Examples include, but are not limited to, set-top boxes, entertainment units, navigation devices, communication devices, fixed location data units, mobile location data units, Global Positioning System (GPS) devices, mobile phones, cell phones, smart phones, Session Initiation Protocol (SIP) phones, tablets, phablets, servers, computers, portable computers, mobile computing devices, wearable computing devices (e.g., smart watches, health or fitness trackers, glasses, etc.), desktop computers, Personal Digital Assistants (PDAs), monitors, computer monitors, televisions, tuners, radios, satellite radios, music players, digital music players, portable music players, digital video players, video players, Digital Video Disc (DVD) players, portable digital video players, automobiles, vehicle components, avionics systems, drones, and multicopter aircraft.

[0097] In summary, the application provides a TC-SAW device structure, which comprises, from bottom to top, a piezoelectric substrate 110, an IDT electrode layer 120, a temperature compensation layer 130, and a passivation layer 140, and a load layer 150 located above the IDT electrode layer 120 or between the piezoelectric substrate 110 and the electrode layer. By setting the projection of the load layer 150 in the direction perpendicular to the thickness of the piezoelectric substrate 110 as a multi-edge irregular shape with grooves, and satisfying that the grooves of the projection correspond one-to-one to the finger gaps of the IDT electrode layer 120, and the projection covers both ends of the fingers of the IDT electrode layer 120 respectively, the load layer 150 can effectively suppress the transverse mode in the device structure, and block and reflect other stray waves other than the main mode of the surface acoustic wave, thereby improving the performance of the device.

[0098] Further, the application provides that by setting the load layer 150 on the IDT electrode layer 120 without direct contact with the IDT electrode layer, the processing of the finger ends of the IDT electrode layer 120 can be avoided, the process complexity caused by the processing of the finger ends of the IDT electrode layer 120 is reduced, the original finger structure of the IDT electrode layer 120 is not damaged, the process flow of the TC-SAW device structure is optimized, and the production cost is reduced.

[0099] In the foregoing embodiment descriptions, the description of the terms “one embodiment”, “some embodiments”, “an example”, “a specific example”, or “some examples” means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the application. In the description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, the different embodiments or examples described in the specification and the features of the different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0100] In addition, the terms “first”, “second” are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with “first”, “second” can explicitly or implicitly include at least one of the features. In the description of the application, the meaning of “a plurality of” is at least two, for example, two, three, etc., unless otherwise specifically limited.

Claims

1. A temperature-compensated surface acoustic wave device structure, comprising a piezoelectric substrate, an IDT electrode layer, a temperature compensation layer and a passivation layer stacked sequentially from bottom to top, and a load layer located above the IDT electrode layer or between the piezoelectric substrate and the electrode layer; The load layer includes a plurality of first load units and a plurality of second load units spaced apart along a first direction; in a second direction, the first load units and the second load units correspond one-to-one and are symmetrical to each other; in a third direction, the projections of the first load units and the second load units respectively cover both ends of the fingers of the IDT electrode layer in the first direction, and the projections are all polygonal irregular structures with grooves; wherein... The first direction is orthogonal to the second direction and parallel to the surface of the piezoelectric substrate, and the third direction is perpendicular to the first direction and the second direction, respectively.

2. The device structure according to claim 1, wherein, The IDT electrode layer includes a plurality of interdigitated electrode groups spaced apart along a first direction, each interdigitated electrode group including at least a pair of first electrode fingers and second electrode fingers extending alternately along a second direction; in the third direction, the projections of the first load unit and the second load unit cover the interdigitated electrode groups in the first direction.

3. The device structure according to claim 2, wherein, The IDT electrode layer further includes a first bus bar and a second bus bar that are parallel to each other and spaced apart from each other in a second direction. The first electrode finger extends from one side of the first bus bar toward the side closer to the second bus bar, and the second electrode finger extends from one side of the second bus bar toward the side closer to the first bus bar. In the third direction, the projection boundary of the end of the second electrode finger is located on the projection boundary of the first load unit on the side closer to the first bus bar, and the projection boundary of the end of the first electrode finger is located on the projection boundary of the second load unit on the side closer to the second bus bar.

4. The device structure according to claim 2, wherein, In the third direction, the projection of the first load unit between the first electrode finger and the second electrode finger along the second direction is less than the projection of the first load unit on the first electrode finger and the second electrode finger along the second direction.

5. The device structure according to claim 4, wherein, The first load unit includes at least a first load block, a second load block, and a third load block connected sequentially along a first direction. The first end of the first load block corresponds to the end boundary of the second electrode finger, and the second end of the first load block extends a first preset length along the second direction. The third load block is symmetrically arranged with the first load block, and the second load block is located between the first load block and the third load block.

6. The device structure according to claim 5, wherein, In the third direction, the projection of the first load block is located within the projection plane of the second electrode finger, the projection of the third load block is located within the projection plane of the first electrode finger, and the projection of the second load block is located within the gap between the first electrode finger and the second electrode finger.

7. The device structure according to claim 5, wherein, The first end of the second load block corresponds to the boundary of the first end of the first load block in the second direction, and the second end of the second load block extends along the second direction for a second preset length, and the second preset length is less than the first preset length.

8. The device structure according to claim 5, wherein, The second end of the second load block corresponds to the boundary of the second end of the first load block in the second direction, and the first end of the second load block extends along the second direction for a second preset length, and the second preset length is less than the first preset length.

9. The device structure according to claim 5, wherein, The boundaries of the first end and the second end of the second load block are located between the boundaries of the first end and the second end of the first load block, respectively; and the second preset length of the second end of the second load block extending along the second direction is less than the first preset length.

10. The device structure according to claim 8, wherein, The first load unit further includes a first auxiliary load block and a second auxiliary load block symmetrically arranged along a first direction, and the first auxiliary load block and the second auxiliary load block are respectively disposed between the gaps of two adjacent interdigital electrode groups; The first end of the first auxiliary load block and the boundary of the first end of the first load block correspond to each other in the second direction. The second end of the first auxiliary load block extends along the second direction by a third preset length, and the third preset length is less than the first preset length.

11. The device structure according to claim 2, wherein, It also includes a reflective gate electrode layer, which is formed on the piezoelectric substrate and spaced apart on both sides of the IDT electrode layer along the first direction. The first load unit and the second load unit also extend over the reflective gate electrode layer in the third direction.

12. The device structure according to any one of claims 1 to 11, wherein, The load layer is located between the piezoelectric substrate and the IDT electrode layer, and the IDT electrode layer is formed on the load layer and extends to cover the exposed surface of the piezoelectric substrate.

13. The device structure according to any one of claims 1 to 11, wherein, The load layer is formed between the piezoelectric substrate and the temperature compensation layer, and the load layer is formed on the IDT electrode layer and covers a portion of the surface of the piezoelectric substrate exposed by the IDT electrode layer. The temperature compensation layer is formed on the load layer and covers the exposed surfaces of the IDT electrode layer and the piezoelectric substrate.

14. The device structure according to any one of claims 1 to 11, wherein, The temperature compensation layer includes a first surface and a second surface facing each other in a third direction, and the load layer is formed in the temperature compensation layer between the first surface and the second surface.

15. The device structure according to any one of claims 1 to 11, wherein, The load layer is formed between the temperature compensation layer and the passivation layer.

16. The device structure according to any one of claims 1 to 11, wherein, The load layer is formed on the passivation layer.

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