Longitudinal coupling type resonator and preparation method thereof

Abstract

The invention discloses a longitudinal coupling type resonator and a preparation method thereof. The longitudinal coupling type resonator comprises a substrate, a first interdigital transducer and a second interdigital transducer, wherein the first interdigital transducer and the second interdigital transducer are arranged on one side of the substrate and alternately arranged on the surface of the substrate in the first direction; the first interdigital transducer comprises a first bus bar and a second bus bar which are oppositely arranged; the second interdigital transducer comprises a third bus bar and a fourth bus bar which are oppositely arranged; the array substrate further comprises a signal connection layer, a passivation layer and a grounding layer. The grounding layer is arranged on the side, away from the signal connection layer, of the passivation layer and connected with the second bus bar through the first through hole and connected with the third bus bar through the second through hole. According to the technical scheme, a dielectric bridge arranged between the signal connecting layer and the grounding layer in the prior art is omitted, loss deterioration caused by the dielectric bridge and change of interelectrode capacitance of the resonator are avoided, meanwhile, the problem of wafer scrapping caused by falling of the dielectric bridge during etching windowing is avoided, and time and labor cost are saved.

Description

Technical Field

[0001] The present invention relates to the technical field of resonators, and in particular to a longitudinal coupling resonator and a preparation method thereof. Background Art

[0002] As one of the important components in the RF front-end field, the SAW filter has the advantages of low cost, small size, superior performance and reliable quality. It has been widely used in mobile communications, navigation, automotive and other fields.

[0003] The development direction of SAW filters at this stage is miniaturization, multifunctionality and low cost. In recent years, the size of SAW filters has become smaller and smaller. In order to achieve the miniaturization of the filter, a longitudinally coupled resonator SAW filter is proposed, which is different from the traditional ladder structure filter. The structural characteristics of the longitudinally coupled resonator SAW filter determine that during its production and processing, an additional dielectric bridge process will be introduced, which increases the cost of the filter; at the same time, the introduction of the dielectric bridge will increase the capacitive coupling effect in the filter circuit, which is not conducive to the loss of the filter; at the same time, during the production process of the dielectric bridge, it is easy to be stripped along with the photoresist, causing the wafer to be scrapped. Summary of the invention

[0004] The present invention provides a longitudinal coupling type resonator and a preparation method thereof, so as to solve the problems of capacitive coupling effect, cost and reliability introduced by a dielectric bridge in the prior art.

[0005] According to one aspect of the present invention, there is provided a longitudinal coupling type resonator, comprising: a substrate and first interdigital transducers and second interdigital transducers arranged on one side of the substrate and arranged alternately along a first direction on a surface of the substrate;

[0006] The first interdigital transducer includes a first bus bar and a second bus bar that are arranged opposite to each other; the second interdigital transducer includes a third bus bar and a fourth bus bar that are arranged opposite to each other; along the first direction, the first bus bar and the third bus bar are arranged alternately, and the second bus bar and the fourth bus bar are arranged alternately;

[0007] It also includes a signal connection layer, a passivation layer and a ground layer;

[0008] The signal connection layer is arranged on the same layer as the first bus bar; the signal connection layer includes a first signal wiring layer and a second signal wiring layer arranged on the same layer; the first signal wiring layer is connected to the first bus bar; the second signal wiring layer is connected to the fourth bus bar;

[0009] The passivation layer is arranged on the side of the signal connection layer away from the substrate; the passivation layer includes a first through hole and a second through hole; the grounding layer is arranged on the side of the passivation layer away from the signal connection layer and is connected to the second bus bar through the first through hole and to the third bus bar through the second through hole; wherein the grounding layer is grounded.

[0010] Optionally, the longitudinal coupling type resonator further includes a connecting layer;

[0011] The connection layer is arranged between the signal connection layer and the passivation layer;

[0012] The connection layer includes a plurality of sub-connection structures, each of which is respectively connected to the corresponding second bus bar and third bus bar; the grounding layer is connected to the sub-connection structure through the first through hole and the second through hole; wherein the grounding layer is grounded through the connection layer.

[0013] Optionally, along the thickness direction of the longitudinal coupling-type resonator, a projection of the first through hole on the connection layer overlaps with the sub-connection structure; and a projection of the second through hole on the connection layer overlaps with the sub-connection structure.

[0014] Optionally, the first interdigital transducer further includes a first interdigital electrode; the first bus bar and the second bus bar are arranged oppositely on both sides of the first interdigital electrode;

[0015] The second interdigital transducer also includes a second interdigital electrode; the third bus bar and the fourth bus bar are arranged on both sides of the second interdigital electrode opposite to each other.

[0016] Optionally, the longitudinally coupled resonator further includes a suppression structure;

[0017] The suppression structure is arranged at the same layer as the ground layer; along the thickness direction of the longitudinal coupling type resonator, the suppression structure covers the finger gaps of the first interdigital electrode at the plane where the first interdigital electrode is located, and covers the finger gaps of the second interdigital electrode at the plane where the second interdigital electrode is located.

[0018] Optionally, the sum of the number of the first IDTs and the number of the second IDTs is an odd number.

[0019] According to another aspect of the present invention, a method for preparing a longitudinally coupled resonator is provided, which is applied to the longitudinally coupled resonator, and the preparation method comprises:

[0020] providing a substrate;

[0021] A first bus bar, a second bus bar, a third bus bar, a fourth bus bar and a signal connection layer are grown on one side of the substrate; wherein, along a first direction, the first bus bar and the third bus bar are arranged alternately, and the second bus bar and the fourth bus bar are arranged alternately; the signal connection layer includes a first signal wiring layer and a second signal wiring layer arranged in the same layer; the first signal wiring layer is connected to the first bus bar; the second signal wiring layer is connected to the fourth bus bar;

[0022] Growing a passivation layer on a side of the signal connection layer away from the substrate and etching the passivation layer to form a first through hole and a second through hole;

[0023] A grounding layer is grown on a side of the passivation layer away from the signal connection layer; wherein the grounding layer is connected to the second bus bar through a first through hole and to the third bus bar through a second through hole; wherein the grounding layer is grounded.

[0024] Optionally, growing a passivation layer on a side of the signal connection layer away from the substrate and etching the passivation layer to form the first through hole and the second through hole comprises:

[0025] A connection layer is grown on a side of the signal connection layer away from the substrate; wherein the connection layer includes a plurality of sub-connection structures, each of which is respectively connected to the corresponding second bus bar and third bus bar; along the thickness direction of the longitudinal coupling resonator, the projection of the first through hole on the connection layer overlaps with the sub-connection structure; and the projection of the second through hole on the connection layer overlaps with the sub-connection structure;

[0026] A passivation layer is grown on a side of the connection layer away from the signal connection layer, and the passivation layer is etched to form a first through hole and a second through hole.

[0027] Optionally, growing a first bus bar, a second bus bar, a third bus bar, a fourth bus bar and a signal connection layer on one side of the substrate includes:

[0028] A first bus bar, a second bus bar, a third bus bar, a fourth bus bar, a signal connection layer, a first interdigitated electrode and a second interdigitated electrode are grown on one side of the substrate; wherein the first bus bar and the second bus bar are relatively arranged on both sides of the first interdigitated electrode; and the third bus bar and the fourth bus bar are relatively arranged on both sides of the second interdigitated electrode.

[0029] Optionally, growing a ground layer on a side of the passivation layer away from the signal connection layer includes:

[0030] A metal layer is grown on a side of the passivation layer away from the signal connection layer and is etched to form a grounding layer and a suppression structure; wherein, along the thickness direction of the longitudinal coupling resonator, the suppression structure covers the finger gaps of the first interdigitated electrode in the plane where the first interdigitated electrode is located, and covers the finger gaps of the second interdigitated electrode in the plane where the second interdigitated electrode is located.

[0031] The technical solution of the present invention eliminates the dielectric bridge provided between the signal connection layer and the ground layer in the prior art, provides a passivation layer after the signal connection layer is prepared, and realizes the connection between the ground layer and the bus bar by etching through holes in the passivation layer, thereby avoiding the loss deterioration introduced by the dielectric bridge and the change of the resonator inter-electrode capacitance, and at the same time avoids the problem of wafer scrapping caused by the falling off of the dielectric bridge when etching the window, saving time and labor costs.

[0032] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 It is a schematic diagram of the arrangement of a longitudinally coupled resonator in the prior art;

[0035] Figure 2 It is a schematic diagram of the structure of a longitudinally coupled resonator in the prior art;

[0036] Figure 3 is a partial structural schematic diagram of a first longitudinally coupled resonator provided according to an embodiment of the present invention;

[0037] Figure 4 is a schematic diagram of the entire structure of a first longitudinally coupled resonator provided according to an embodiment of the present invention;

[0038] Figure 5 yes Figure 4 Schematic diagram of the cross section along A-A';

[0039] Figure 6 is a schematic diagram showing a performance comparison between a longitudinally coupled resonator provided by an embodiment of the present invention and the prior art;

[0040] Figure 7 is a partial structural schematic diagram of a second longitudinally coupled resonator provided according to an embodiment of the present invention;

[0041] Figure 8 is a schematic diagram of the entire structure of a second longitudinally coupled resonator provided according to an embodiment of the present invention;

[0042] Fig. 9 yes Figure 8 Schematic diagram of the cross section along B-B';

[0043] Fig.10 is a schematic diagram of the entire structure of a third longitudinally coupled resonator provided in an embodiment of the present invention;

[0044] Fig.11 is a flow chart of a method for preparing a first longitudinally coupled resonator provided in an embodiment of the present invention;

[0045] Fig.12 is a structural diagram corresponding to a first method for preparing a longitudinally coupled resonator provided in an embodiment of the present invention;

[0046] Fig.13 is a flow chart of a second method for preparing a longitudinally coupled resonator provided in an embodiment of the present invention;

[0047] Fig.14 is a structural diagram corresponding to a second method for preparing a longitudinally coupled resonator provided in an embodiment of the present invention;

[0048] Fig.15 is a flow chart of a third method for preparing a longitudinally coupled resonator provided in an embodiment of the present invention;

[0049] Fig.16 is a flow chart of a fourth method for preparing a longitudinally coupled resonator provided in an embodiment of the present invention;

[0050] Fig.17 It is a structural diagram corresponding to the fourth method for preparing a longitudinally coupled resonator provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0052] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0053] Before describing the technical solution of the embodiment of the present invention in detail, the longitudinal coupling resonator in the prior art is described first. Figure 1 It is a schematic diagram of the arrangement of a longitudinally coupled resonator in the prior art. Figure 2 is a schematic diagram of the structure of a longitudinally coupled resonator in the prior art, such as Figure 1 and Figure 2 As shown, Figure 1 This is the commonly used structure of the 5th-order longitudinal coupling resonator, which is a three-input and two-output structure. Figure 1S is the signal end, and G is the ground end. One side of the interdigital transducer is connected to the signal line, which is the same as the input signal, and the other side is connected to the ground line. Along the arrangement direction of the interdigital transducer, the signal end S and the ground end G are arranged alternately. In the preparation process, the interdigital transducer and the signal end S are first prepared, and on this basis, a dielectric bridge 5 is prepared so that the dielectric bridge 5 isolates the ground end G and the signal end S, and then the grounded metal layer and the passivation layer are sequentially arranged on the basis of the dielectric bridge 5. In the working process, the input signal is connected to the interdigital transducer through a signal line on one side, and the interdigital transducer converts the electric energy into sound, and then converts it into electric energy, which is output from the signal line on the other side, so the signal line and the ground line on the same side of the longitudinal coupling resonator are cross-distributed. In order to prevent the wiring short circuit between the signal line and the ground line, the process sets up a dielectric bridge 5, and the material is an insulating medium, which falls between the signal line and the ground line. However, it is also due to the establishment of the dielectric bridge 5 that the process complexity and cost will be increased. At the same time, when connecting the subsequent process, the dielectric bridge 5 has the risk of being stripped together with the photoresist, causing the scrapping of the wafer, increasing the time and manpower and material costs. Therefore, the embodiment of the present invention provides a new longitudinal coupling resonator. Figure 3 is a partial structural schematic diagram of a first longitudinally coupled resonator provided according to an embodiment of the present invention, Figure 4 is a schematic diagram of the entire structure of a first longitudinally coupled resonator provided according to an embodiment of the present invention, Figure 5 yes Figure 4 Schematic diagram of the cross section along A-A', combined with Figure 3 , Figure 4 and Figure 5 As shown, the longitudinal coupling type resonator comprises: a substrate 1 and first interdigital transducers 2 and second interdigital transducers 3 arranged on one side of the substrate 1 and arranged alternately along a first direction x on the surface of the substrate 1;

[0054] The first IDT 2 includes a first bus bar 21 and a second bus bar 22 that are arranged opposite to each other; the second IDT 3 includes a third bus bar 31 and a fourth bus bar 32 that are arranged opposite to each other; along the first direction x, the first bus bar 21 and the third bus bar 31 are arranged alternately, and the second bus bar 22 and the fourth bus bar 32 are arranged alternately;

[0055] It also includes a signal connection layer 4, a passivation layer 6 and a ground layer 7;

[0056] The signal connection layer 4 is arranged on the same layer as the first bus bar 21; the signal connection layer 4 includes a first signal wiring layer 41 and a second signal wiring layer 42 arranged on the same layer; the first signal wiring layer 41 is connected to the first bus bar 21; the second signal wiring layer 42 is connected to the fourth bus bar 32;

[0057] The passivation layer 6 is arranged on the side of the signal connection layer 4 away from the substrate 1; the passivation layer 6 includes a first through hole 61 and a second through hole 62; the grounding layer 7 is arranged on the side of the passivation layer 6 away from the signal connection layer 4 and is connected to the second bus bar 22 through the first through hole 61, and is connected to the third bus bar 31 through the second through hole 62; wherein the grounding layer 7 is grounded.

[0058] The longitudinal coupling resonator includes a substrate 1 and an interdigital transducer arranged on the surface of the substrate 1. The substrate 1 may include a piezoelectric layer and other structures to ensure the normal operation of the longitudinal coupling resonator.

[0059] Wherein, a first IDT 2 and a second IDT 3 arranged along a first direction x are arranged on a substrate 1, and the first IDT 2 and the second IDT 3 may have the same structure or different structures. The first IDT 2 includes a first bus bar 21 and a second bus bar 22 arranged oppositely, and the second IDT 3 includes a third bus bar 31 and a fourth bus bar 32 arranged oppositely. In some embodiments, the first IDT 2 also includes a first interdigital electrode 23; the first bus bar 21 and the second bus bar 22 are arranged oppositely on both sides of the first interdigital electrode 23; the second IDT 3 also includes a second interdigital electrode 33; the third bus bar 31 and the fourth bus bar 32 are arranged oppositely on both sides of the second interdigital electrode 33. The first bus bar 21 and the second bus bar 22 are respectively arranged at both ends of the first interdigital electrode 23, playing a busing role, and the third bus bar 31 and the fourth bus bar 32 are respectively arranged at both ends of the second interdigital electrode 33, playing a busing role. Based on the coupling characteristics of the longitudinal coupling resonator, the first bus bar 21 on the first IDT 2 can be used to connect the signal line, and the second bus bar 22 can be used for grounding; the fourth bus bar 32 on the second IDT 3 can be used to connect the signal line, and the third bus bar 31 can be used for grounding. When the first IDT 2 and the second IDT 3 are alternately arranged on the substrate 1 along the first direction x, the corresponding first bus bar 21 and the third bus bar 31 are also alternately arranged along the first direction x, and the second bus bar 22 and the fourth bus bar 32 are alternately arranged along the first direction x.

[0060] Among them, the signal connection layer 4 can be used to provide a signal input or output channel for the interdigital transducer. Therefore, the signal connection layer 4 needs to connect the first bus bar 21 of the first interdigital transducer 2 and the fourth bus bar 32 of the second interdigital transducer 3. The signal connection layer 4 includes a first signal wiring layer 41 and a second signal wiring layer 42 that are independent of each other. The first signal wiring layer 41 is used to connect the first bus bar 21 of the first interdigital transducer 2, and the second signal wiring layer 42 is used to connect the fourth bus bar 32 of the second interdigital transducer 3. During operation, a signal can be input into the first signal wiring layer 41, and a signal can be output along the second signal wiring layer 42 after passing through the interdigital transducer; or, a signal can be input into the second signal wiring layer 42, and a signal can be output along the first signal wiring layer 41 after passing through the interdigital transducer. The signal connection layer 4 can be etched and set in the same layer as the first bus bar 21, the second bus bar 22, the third bus bar 31 and the fourth bus bar 32. The specific structure of the signal connection layer 4 can be determined according to demand, and the embodiment of the present invention does not limit this.

[0061] Figure 3 This is a schematic diagram without a ground plane. Figure 3 As shown, the passivation layer 6 plays an insulating role. Since the second bus bar 22 and the third bus bar 31 need to be grounded, a grounding layer 7 is required. Figure 4 As shown. In order to prevent the grounding layer 7 and the signal connection layer 4 from being short-circuited, a passivation layer 6 is provided before the grounding layer 7 is provided. The passivation layer 6 is made of insulating material. After the passivation layer 6 is deposited, the first through hole 61 and the second through hole 62 are formed by etching. The purpose of etching the first through hole 61 and the second through hole 62 is to connect the second bus bar 22 and the third bus bar 31 after the grounding layer 7 is filled, and the second bus bar 22 and the third bus bar 31 are all connected in series and then grounded.

[0062] It can be understood that the first bus bar 21, the second bus bar 22, the third bus bar 31, the fourth bus bar 32, and the signal connection layer 4 in the embodiment of the present invention are all made of metal materials, such as Al, Au, aluminum-copper alloy, etc., and the material of the grounding layer 7 can be Ti, Cr, Cu, etc. The first bus bar 21, the second bus bar 22, the third bus bar 31, the fourth bus bar 32 and the signal connection layer 4 can be arranged in the same layer to simplify the process flow.

[0063] Specifically, a metal layer is first grown on the substrate 1, and the metal layer is etched to form the first bus bar 21, the second bus bar 22, the third bus bar 31, the fourth bus bar 32 and the signal connection layer 4. The etched signal connection layer 4 is connected to the first bus bar 21 and the fourth bus bar 32 respectively. As shown in the figure, the first signal wiring layer 41 is connected to the first bus bar 21 and led out in series, the second signal wiring layer 42 is connected to the fourth bus bar 32 and led out in series, and there is no signal connection layer 4 at the corresponding positions of the second bus bar 22 and the third bus bar 31. Then, a passivation layer 6 is grown on one side of the signal connection layer 4, and a first through hole 61 and a second through hole 62 are etched at the corresponding positions of the second bus bar 22 and the third bus bar 31. The first through hole 61 and the second through hole 62 penetrate the passivation layer 6 to expose the second bus bar 22 and the third bus bar 31 or the lead-out ends of the second bus bar 22 and the third bus bar 31. A grounding layer 7 is prepared on one side of the passivation layer 6, and the grounding layer 7 covers the passivation layer 6 and fills the first through hole 61 and the second through hole 62 to achieve connection with the second bus bar 22 and the third bus bar 31. The grounding layer 7 is grounded to achieve grounding of the second bus bar 22 and the third bus bar 31.

[0064] It is understandable that the longitudinal coupling resonator in the embodiment of the present invention omits the preparation of the dielectric bridge in the prior art, simplifying the process flow. The preparation order of the passivation layer 6 is changed, and the passivation layer 6 is set and etched after the signal connection layer 4 is prepared, so that when the grounding layer 7 is subsequently prepared, the grounding layer 7 can be connected to the second bus bar 22 and the third bus bar 31 through the first through hole 61, avoiding the loss deterioration introduced by the dielectric bridge and the change of the resonator inter-electrode capacitance, while avoiding the problem of wafer scrapping caused by the dielectric bridge falling off when etching the window, saving time and labor costs. Figure 6 FIG. 4 is a schematic diagram showing a performance comparison between a longitudinally coupled resonator provided in an embodiment of the present invention and the prior art. Figure 6 As shown, the dotted line represents the prior art, and the solid line represents the longitudinal coupling resonator of an embodiment of the present invention. Without the influence of the dielectric bridge on the inter-electrode capacitance, the suppression at the right end of the longitudinal coupling resonator is improved, and the passband performance is close. After simplifying the process, the performance of the longitudinal coupling resonator has not deteriorated.

[0065] In some embodiments, the sum of the numbers of the first IDTs 2 and the second IDTs 3 is an odd number, so as to ensure the normal operation of the longitudinal coupling resonator.

[0066] The technical solution of the embodiment of the present invention eliminates the dielectric bridge set between the signal connection layer and the ground layer in the prior art, sets a passivation layer after the signal connection layer is prepared, and realizes the connection between the ground layer and the bus bar by etching through holes in the passivation layer, thereby avoiding the loss deterioration introduced by the dielectric bridge and the change of the resonator inter-electrode capacitance, and at the same time avoids the problem of wafer scrapping caused by the falling off of the dielectric bridge when etching the window, saving time and labor costs.

[0067] Optional, Figure 7 is a partial structural schematic diagram of a second longitudinally coupled resonator provided according to an embodiment of the present invention, Figure 8 is a schematic diagram of the entire structure of a second longitudinally coupled resonator provided according to an embodiment of the present invention, Fig. 9 yes Figure 8 Schematic diagram of the cross section along B-B', combined with Figure 7 , Figure 8 and Fig. 9 As shown, the longitudinal coupling type resonator further includes a connecting layer 8;

[0068] The connection layer 8 is arranged between the signal connection layer 4 and the passivation layer 6;

[0069] The connection layer 8 includes a plurality of sub-connection structures 80, each of which is connected to the corresponding second bus bar 22 and third bus bar 31 respectively; the grounding layer 7 is connected to the sub-connection structure 80 through the first through hole 61 and the second through hole 62; wherein the grounding layer 7 is grounded by connecting the connection layer 8.

[0070] A connection layer 8 may also be provided in the longitudinal coupling resonator. The connection layer 8 may also be a metal layer. The connection layer 8 may play a role of grounding and may also play a role of leading out the second bus bar 22 and the third bus bar 31 .

[0071] Specifically, after the signal connection layer 4 is prepared, a connection layer 8 is prepared. The connection layer 8 does not overlap with the signal connection layer 4. Since the first bus bar 21 and the fourth bus bar 32 are arranged at intervals, when setting the signal connection layer 4, it is necessary to bypass the lead-out areas of the second bus bar 22 and the third bus bar 31 and then merge and connect them. Therefore, the connection layer 8 includes a plurality of sub-connection structures 80. The sub-connection structures 80 can be used to lead out the second bus bar 22 and the third bus bar 31, so that when etching the first through hole 61 and the second through hole 62 on the passivation layer 6, only the sub-connection structure 80 or the bus bar needs to be exposed, which helps to improve the accuracy and precision of etching.

[0072] It is understandable that the connection layer 8 can be grounded, so that when the grounding layer 7 is connected to the connection layer 8 , the second bus bar 22 and the third bus bar 31 can be connected in series and grounded at the same time.

[0073] The technical solution of the embodiment of the present invention is to set a connecting layer before setting the passivation layer, and the connecting layer leads out the second bus bar and the third bus bar and performs grounding treatment, so that the fault tolerance rate is higher when etching the first through hole and the second through hole on the passivation layer, and at the same time, the connection and grounding between the grounding layer and the second bus bar and the third bus bar are guaranteed.

[0074] Optional, continue to refer to Fig. 9 As shown, along the thickness direction y of the longitudinal coupling resonator, the projection of the first through hole 61 on the connection layer 8 overlaps with the sub-connection structure 80 ; the projection of the second through hole 62 on the connection layer 8 overlaps with the sub-connection structure 80 .

[0075] Among them, along the thickness direction y of the longitudinal coupling resonator, the projection of the first through hole 61 on the connecting layer 8 overlaps with the sub-connection structure 80; the projection of the second through hole 62 on the connecting layer 8 overlaps with the sub-connection structure 80, in order to ensure that the first through hole 61 and the second through hole 62 can expose the sub-connection structure 80, so as to ensure that the ground layer 7 can be connected to the sub-connection structure 80.

[0076] Optional, Fig.10 is a schematic diagram of the entire structure of a third longitudinal coupling resonator provided according to an embodiment of the present invention, such as Fig.10 As shown, the longitudinal coupling type resonator further includes a suppression structure 9;

[0077] The suppression structure 9 is arranged in the same layer as the ground layer 7; along the thickness direction y of the longitudinal coupling resonator, the suppression structure 9 covers the finger gaps of the first interdigitated electrode 23 in the plane where the first interdigitated electrode 23 is located, and covers the finger gaps of the second interdigitated electrode 33 in the plane where the second interdigitated electrode 33 is located.

[0078] The suppression structure 9 may be made of metal material, and may overlap with the first interdigital electrode 23 and the second interdigital electrode 33 to adjust the charge distribution on the first interdigital electrode 23 and the second interdigital electrode 33, thereby suppressing the lateral mode.

[0079] Specifically, the suppression structure 9 can be two strip structures arranged along the second direction and extending in the first direction x. The strip structure covers the finger gaps of the first interdigitated electrode 23 in the plane where the first interdigitated electrode 23 is located, and covers the finger gaps of the second interdigitated electrode 33 in the plane where the second interdigitated electrode 33 is located. Therefore, during operation, the charge distribution on the first interdigitated electrode 23 and the second interdigitated electrode 33 can be changed, thereby playing a role in suppressing the lateral mode.

[0080] It can be understood that, since the suppression structure 9 is also made of metal, it can be prepared on the same layer as the grounding layer 7, which simplifies the process flow.

[0081] The technical solution of the embodiment of the present invention ensures the normal operation of the longitudinal coupling resonator by preparing a suppression structure on the first interdigital electrode and the second interdigital electrode, while achieving the purpose of suppressing the lateral mode of the resonator without adding additional process steps.

[0082] Based on the same inventive concept, Fig.11 is a flow chart of a method for preparing a first longitudinally coupled resonator provided according to an embodiment of the present invention, Fig.12 is a structural diagram corresponding to a first method for preparing a longitudinally coupled resonator provided in an embodiment of the present invention, combined with Fig.11 and Fig.12 As shown, an embodiment of the present invention provides a method for preparing a longitudinal coupling type resonator, which is applied to a longitudinal coupling type resonator, and the preparation method includes:

[0083] S10, providing a substrate. Fig.12 As shown in step (a).

[0084] The longitudinal coupling resonator includes a substrate 1, and the substrate 1 may include a piezoelectric layer and other structures to ensure the normal operation of the longitudinal coupling resonator.

[0085] S11, growing a first bus bar, a second bus bar, a third bus bar, a fourth bus bar and a signal connection layer on one side of the substrate. Fig.12 As shown in step (b), along the first direction x, the first bus bar 21 and the third bus bar 31 are arranged alternately, and the second bus bar 22 and the fourth bus bar 32 are arranged alternately; the signal connection layer 4 includes a first signal wiring layer 41 and a second signal wiring layer 42 arranged in the same layer; the first signal wiring layer 41 is connected to the first bus bar 21; the second signal wiring layer 42 is connected to the fourth bus bar 32.

[0086] Among them, since the first bus bar 21, the second bus bar 22, the third bus bar 31, the fourth bus bar 32, and the signal connection layer 4 are all made of metal materials, such as Al, Au, aluminum-copper alloy, etc., the first bus bar 21, the second bus bar 22, the third bus bar 31, the fourth bus bar 32 and the signal connection layer 4 can be arranged on the same layer to simplify the process flow.

[0087] Among them, based on the coupling characteristics of the longitudinal coupling resonator, the first bus bar 21 on the first IDT 2 can be used to connect the signal line, and the second bus bar 22 can be used for grounding; the fourth bus bar 32 on the second IDT 3 can be used to connect the signal line, and the third bus bar 31 can be used for grounding. When the first IDT 2 and the second IDT 3 are alternately arranged on the substrate 1 along the first direction x, the corresponding first bus bar 21 and the third bus bar 31 are also alternately arranged along the first direction x, and the second bus bar 22 and the fourth bus bar 32 are alternately arranged along the first direction x.

[0088] The signal connection layer 4 can be used to provide a signal input or output channel for the IDT, so the signal connection layer 4 needs to connect the first bus bar 21 of the first IDT 2 and the fourth bus bar 32 of the second IDT 3 .

[0089] S12, growing a passivation layer on the side of the signal connection layer away from the substrate and etching the passivation layer to form a first through hole and a second through hole. Fig.12 As shown in step (c).

[0090] Among them, the passivation layer 6 plays an insulating and isolating role. Since the second bus bar 22 and the third bus bar 31 need to be grounded, a grounding layer 7 needs to be set. In order to prevent the grounding layer 7 and the signal connection layer 4 from being short-circuited, a passivation layer 6 is set before the grounding layer 7 is set. The passivation layer 6 is an insulating material. After the passivation layer 6 is deposited, the first through hole 61 and the second through hole 62 are etched. The purpose of etching the first through hole 61 and the second through hole 62 is to be connected to the second bus bar 22 and the third bus bar 31 after the grounding layer 7 is filled, and the second bus bar 22 and the third bus bar 31 are all connected in series and then grounded.

[0091] S13. Grow a ground layer on the side of the passivation layer away from the signal connection layer. Fig.12 As shown in step (d), the grounding layer 7 is connected to the second bus bar 22 through the first through hole 61 and is connected to the third bus bar 31 through the second through hole 62; the grounding layer 7 is grounded.

[0092] Specifically, a metal layer is first grown on the substrate 1, and the metal layer is etched to form the first bus bar 21, the second bus bar 22, the third bus bar 31, the fourth bus bar 32 and the signal connection layer 4. The etched signal connection layer 4 is connected to the first bus bar 21 and the fourth bus bar 32 respectively. As shown in the figure, the first signal wiring layer 41 is connected to the first bus bar 21 and led out in series, the second signal wiring layer 42 is connected to the fourth bus bar 32 and led out in series, and there is no signal connection layer 4 at the corresponding positions of the second bus bar 22 and the third bus bar 31. Then, a passivation layer 6 is grown on one side of the signal connection layer 4, and a first through hole 61 and a second through hole 62 are etched at the corresponding positions of the second bus bar 22 and the third bus bar 31. The first through hole 61 and the second through hole 62 penetrate the passivation layer 6 to expose the second bus bar 22 and the third bus bar 31 or the lead-out ends of the second bus bar 22 and the third bus bar 31. A grounding layer 7 is prepared on one side of the passivation layer 6, and the grounding layer 7 covers the passivation layer 6 and fills the first through hole 61 and the second through hole 62 to achieve connection with the second bus bar 22 and the third bus bar 31. The grounding layer 7 is grounded to achieve grounding of the second bus bar 22 and the third bus bar 31.

[0093] The technical solution of the embodiment of the present invention, in the process flow of preparing a longitudinally coupled resonator, eliminates the dielectric bridge set between the signal connection layer and the ground layer in the prior art, sets a passivation layer after the signal connection layer is prepared, and realizes the connection between the ground layer and the bus bar by etching through holes in the passivation layer, thereby avoiding the loss deterioration introduced by the dielectric bridge and the change of the inter-electrode capacitance of the resonator, and at the same time avoids the problem of wafer scrapping caused by the falling off of the dielectric bridge when etching the window, saving time and labor costs.

[0094] Based on the above embodiments, Fig.13 is a flow chart of a second method for preparing a longitudinally coupled resonator provided in an embodiment of the present invention, Fig.14 is a structural diagram corresponding to a second method for preparing a longitudinally coupled resonator provided in an embodiment of the present invention, combined with Fig.13 and Fig.14 As shown, the preparation method comprises:

[0095] S20, providing a substrate. Fig.14 As shown in step (e).

[0096] S21, growing a first bus bar, a second bus bar, a third bus bar, a fourth bus bar and a signal connection layer on one side of the substrate. Fig.14 As shown in step (f), along the first direction x, the first bus bar 21 and the third bus bar 31 are arranged alternately, and the second bus bar 22 and the fourth bus bar 32 are arranged alternately; the signal connection layer 4 includes a first signal wiring layer 41 and a second signal wiring layer 42 arranged in the same layer; the first signal wiring layer 41 is connected to the first bus bar 21; and the second signal wiring layer 42 is connected to the fourth bus bar 32.

[0097] S22, growing a connection layer on the side of the signal connection layer away from the substrate. Fig.14 As shown in step (g), the connection layer 8 includes a plurality of sub-connection structures 80, each of which is connected to the corresponding second bus bar 22 and third bus bar 31; along the thickness direction y of the longitudinal coupling resonator, the projection of the first through hole 61 on the connection layer 8 overlaps with the sub-connection structure 80; and the projection of the second through hole 62 on the connection layer 8 overlaps with the sub-connection structure 80.

[0098] A connection layer 8 may also be provided in the longitudinal coupling resonator. The connection layer 8 may also be a metal layer. The connection layer 8 may play a role of grounding and may also play a role of leading out the second bus bar 22 and the third bus bar 31 .

[0099] Specifically, after the signal connection layer 4 is prepared, a connection layer 8 is prepared. The connection layer 8 does not overlap with the signal connection layer 4. Since the first bus bar 21 and the fourth bus bar 32 are arranged at intervals, when setting the signal connection layer 4, it is necessary to bypass the lead-out areas of the second bus bar 22 and the third bus bar 31 and then merge and connect them. Therefore, the connection layer 8 includes a plurality of sub-connection structures 80. The sub-connection structures 80 can be used to lead out the second bus bar 22 and the third bus bar 31, so that when etching the first through hole 61 and the second through hole 62 on the passivation layer 6, only the sub-connection structure 80 or the bus bar needs to be exposed, which helps to improve the accuracy and precision of etching.

[0100] S23, growing a passivation layer on the side of the connection layer away from the signal connection layer and etching the passivation layer to form a first through hole and a second through hole. Fig.14 As shown in step (h).

[0101] S24, grow a ground layer on the side of the passivation layer away from the signal connection layer. Fig.14 As shown in step (i), the grounding layer 7 is connected to the second bus bar 22 through the first through hole 61 and connected to the third bus bar 31 through the second through hole 62; the grounding layer 7 is grounded.

[0102] The technical solution of the embodiment of the present invention is to set a connecting layer before setting the passivation layer, and the connecting layer leads out the second bus bar and the third bus bar and performs grounding treatment, so that the fault tolerance rate is higher when etching the first through hole and the second through hole on the passivation layer, and at the same time, the connection and grounding between the grounding layer and the second bus bar and the third bus bar are guaranteed.

[0103] Based on the above embodiments, Fig.15 is a flow chart of a third method for preparing a longitudinally coupled resonator according to an embodiment of the present invention, Fig.15 and Fig.12 As shown, the preparation method comprises:

[0104] S30, providing a substrate. Fig.12 As shown in step (a).

[0105] S31, growing a first bus bar, a second bus bar, a third bus bar, a fourth bus bar, a signal connection layer, a first interdigital electrode, and a second interdigital electrode on one side of the substrate. Fig.12 The first bus bar 21 and the second bus bar 22 are arranged on both sides of the first interdigital electrode 23 ; the third bus bar 31 and the fourth bus bar 32 are arranged on both sides of the second interdigital electrode 33 .

[0106] Among them, the first bus bar 21 and the second bus bar 22 are respectively arranged at both ends of the first interdigital electrode 23, playing a busing role, and the third bus bar 31 and the fourth bus bar 32 are respectively arranged at both ends of the second interdigital electrode 33, playing a busing role, ensuring the normal operation of the longitudinal coupling resonator.

[0107] S32, growing a passivation layer on the side of the signal connection layer away from the substrate and etching the passivation layer to form a first through hole and a second through hole. Fig.12 As shown in step (c).

[0108] S33, growing a ground layer on the side of the passivation layer away from the signal connection layer. Fig.12 As shown in step (d), the grounding layer 7 is connected to the second bus bar 22 through the first through hole 61 and is connected to the third bus bar 31 through the second through hole 62; the grounding layer 7 is grounded.

[0109] Based on the above embodiments, Fig.16 is a flow chart of a fourth method for preparing a longitudinally coupled resonator provided according to an embodiment of the present invention, Fig.17 is a structural diagram corresponding to a fourth method for preparing a longitudinally coupled resonator provided in an embodiment of the present invention, combined with Fig.16 and Fig.17 As shown, the preparation method comprises:

[0110] S40, providing a substrate. Fig.17 As shown in step (j).

[0111] S41, growing a first bus bar, a second bus bar, a third bus bar, a fourth bus bar, a signal connection layer, a first interdigital electrode, and a second interdigital electrode on one side of the substrate. Fig.17 The first bus bar 21 and the second bus bar 22 are arranged on both sides of the first interdigital electrode 23 ; the third bus bar 31 and the fourth bus bar 32 are arranged on both sides of the second interdigital electrode 33 .

[0112] S42, growing a passivation layer on the side of the signal connection layer away from the substrate and etching the passivation layer to form a first through hole and a second through hole. Fig.17 As shown in step (l).

[0113] S43, growing a metal layer on the side of the passivation layer away from the signal connection layer and etching the metal layer to form a grounding layer and a suppression structure. Fig.17 In the thickness direction y of the longitudinal coupling type resonator, the suppression structure 9 covers the interdigital gaps of the first interdigital electrodes 23 in the plane where the first interdigital electrodes 23 are located, and covers the interdigital gaps of the second interdigital electrodes 33 in the plane where the second interdigital electrodes 33 are located.

[0114] The suppression structure 9 may be made of metal material, and may overlap with the first interdigital electrode 23 and the second interdigital electrode 33 to adjust the charge distribution on the first interdigital electrode 23 and the second interdigital electrode 33, thereby suppressing the lateral mode.

[0115] Among them, the suppression structure 9 is prepared on the same layer as the ground layer 7, a metal layer is grown on the side of the passivation layer 6 away from the signal connection layer 4, and the metal layer is etched to form the ground layer 7 and the suppression structure 9, so that the charge distribution on the first interdigitated electrode 23 and the second interdigitated electrode 33 can be changed during operation, thereby playing a role in suppressing the lateral mode.

[0116] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0117] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A longitudinally coupled resonator, characterized in that: It comprises: a substrate and a first interdigital transducer and a second interdigital transducer arranged on one side of the substrate and arranged alternately along a first direction on the surface of the substrate; The first interdigital transducer comprises a first bus bar and a second bus bar which are arranged opposite to each other; the second interdigital transducer comprises a third bus bar and a fourth bus bar which are arranged opposite to each other; along the first direction, the first bus bar and the third bus bar are arranged alternately, and the second bus bar and the fourth bus bar are arranged alternately; It also includes a signal connection layer, a passivation layer and a ground layer; The signal connection layer is arranged on the same layer as the first bus bar; the signal connection layer includes a first signal wiring layer and a second signal wiring layer arranged on the same layer; the first signal wiring layer is connected to the first bus bar; the second signal wiring layer is connected to the fourth bus bar; The passivation layer is arranged on the side of the signal connection layer away from the substrate; the passivation layer includes a first through hole and a second through hole; the grounding layer is arranged on the side of the passivation layer away from the signal connection layer and is connected to the second bus bar through the first through hole, and is connected to the third bus bar through the second through hole; wherein the grounding layer is grounded.

2. The longitudinally coupled resonator according to claim 1, characterized in that: The longitudinal coupling type resonator further includes a connection layer; The connection layer is arranged between the signal connection layer and the passivation layer; The connection layer includes a plurality of sub-connection structures, each of which is respectively connected to the corresponding second bus bar and the third bus bar; the grounding layer is connected to the sub-connection structure through the first through hole and the second through hole; wherein the grounding layer is grounded by connecting the connection layer.

3. The longitudinally coupled resonator according to claim 2, characterized in that: Along the thickness direction of the longitudinal coupling resonator, a projection of the first through hole on the connection layer overlaps with the sub-connection structure; a projection of the second through hole on the connection layer overlaps with the sub-connection structure.

4. The longitudinally coupled resonator according to claim 1, characterized in that: The first interdigital transducer further comprises a first interdigital electrode; the first bus bar and the second bus bar are arranged oppositely on both sides of the first interdigital electrode; The second interdigital transducer further includes a second interdigital electrode; the third bus bar and the fourth bus bar are arranged oppositely on two sides of the second interdigital electrode.

5. The longitudinally coupled resonator according to claim 4, characterized in that: The longitudinal coupling type resonator further includes a suppression structure; The suppression structure is arranged in the same layer as the ground layer; along the thickness direction of the longitudinal coupling resonator, the suppression structure covers the finger gaps of the first interdigital electrodes in the plane where the first interdigital electrodes are located, and covers the finger gaps of the second interdigital electrodes in the plane where the second interdigital electrodes are located.

6. The longitudinally coupled resonator according to claim 1, characterized in that: The sum of the numbers of the first IDTs and the second IDTs is an odd number.

7. A method for preparing a longitudinally coupled resonator, characterized in that: The longitudinally coupled resonator applied to any one of claims 1 to 6, wherein the preparation method comprises: providing a substrate; A first bus bar, a second bus bar, a third bus bar, a fourth bus bar and a signal connection layer are grown on one side of the substrate; wherein, along a first direction, the first bus bar and the third bus bar are arranged alternately, and the second bus bar and the fourth bus bar are arranged alternately; the signal connection layer includes a first signal wiring layer and a second signal wiring layer arranged in the same layer; the first signal wiring layer is connected to the first bus bar; the second signal wiring layer is connected to the fourth bus bar; Growing a passivation layer on a side of the signal connection layer away from the substrate and etching the passivation layer to form a first through hole and a second through hole; A ground layer is grown on the side of the passivation layer away from the signal connection layer; wherein the ground layer is connected to the second bus bar through the first through hole and connected to the third bus bar through the second through hole; wherein the ground layer is grounded.

8. The method for preparing a longitudinally coupled resonator according to claim 7, characterized in that: Growing a passivation layer on a side of the signal connection layer away from the substrate and etching the passivation layer to form a first through hole and a second through hole, comprising: A connection layer is grown on the side of the signal connection layer away from the substrate; wherein the connection layer includes a plurality of sub-connection structures, each of which is respectively connected to the corresponding second bus bar and the third bus bar; along the thickness direction of the longitudinal coupling resonator, the projection of the first through hole on the connection layer overlaps with the sub-connection structure; and the projection of the second through hole on the connection layer overlaps with the sub-connection structure; A passivation layer is grown on a side of the connection layer away from the signal connection layer, and the passivation layer is etched to form a first through hole and a second through hole.

9. The method for preparing a longitudinally coupled resonator according to claim 7, characterized in that: A first bus bar, a second bus bar, a third bus bar, a fourth bus bar and a signal connection layer are grown on one side of the substrate, comprising: A first bus bar, a second bus bar, a third bus bar, a fourth bus bar, a signal connection layer, a first interdigitated electrode and a second interdigitated electrode are grown on one side of the substrate; wherein the first bus bar and the second bus bar are relatively arranged on both sides of the first interdigitated electrode; and the third bus bar and the fourth bus bar are relatively arranged on both sides of the second interdigitated electrode.

10. The method for preparing a longitudinally coupled resonator according to claim 9, characterized in that: Growing a ground layer on a side of the passivation layer away from the signal connection layer comprises: A metal layer is grown on a side of the passivation layer away from the signal connection layer and the metal layer is etched to form a ground layer and a suppression structure; wherein, along the thickness direction of the longitudinal coupling resonator, the suppression structure covers the finger gaps of the first interdigitated electrodes in the plane where the first interdigitated electrodes are located, and covers the finger gaps of the second interdigitated electrodes in the plane where the second interdigitated electrodes are located.

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