Bulk acoustic wave resonator connected in parallel, method of manufacturing the same, and electronic device

Abstract

The application provides a parallelly connected bulk acoustic resonator, comprising a substrate, a laminated structure sequentially comprising an upper electrode, a piezoelectric layer and a lower electrode on the substrate, an acoustic reflection structure below the laminated structure, formed in the substrate or between the laminated structure and the substrate, and an effective working area of the laminated structure formed by the overlapping area of the upper electrode, the piezoelectric layer and the lower electrode above the acoustic reflection structure, which comprises a main area and at least one local area, the thickness of at least one layer of the upper electrode, the piezoelectric layer and the lower electrode in each local area is different from the thickness of the corresponding layer in the main area, and the series resonance frequency of the resonance response generated by each local area is lower than the series resonance frequency of the resonance response generated by the main area or higher than the parallel resonance frequency of the resonance response generated by the main area. The application also provides an electronic device. The bulk acoustic resonator provided by the application is equivalent to the parallel structure of two or more bulk acoustic resonators.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more particularly to a parallel-connected bulk acoustic wave resonator, its manufacturing method, and electronic devices. Background Technology

[0002] Bulk acoustic wave resonators are widely used in the manufacture of electronic devices such as filters, duplexers, and multiplexers due to their advantages such as small size, high operating frequency, high efficiency, low insertion loss, high out-of-band rejection, high Q, high power capacity, low temperature coefficient, good anti-static shock capability, and semiconductor process compatibility.

[0003] like Figure 1 As shown, a conventional bulk acoustic resonator mainly includes a substrate 10, a stacked structure formed on the substrate, and an acoustic reflection structure 11 (here, a cavity) formed below the stacked structure for acoustic wave reflection. The stacked structure, from top to bottom, consists of an upper electrode 14, a piezoelectric layer 13, and a lower electrode 12. The overlapping area of ​​the upper electrode 14, piezoelectric layer 13, and lower electrode 12 above the acoustic reflection structure constitutes the effective working area of ​​the stacked structure. Typically, the edges of the effective working area (e.g., the edge of the upper electrode 12 in the figure) have a raised first frame structure 15 and a recessed second frame structure 16 to suppress transverse acoustic wave leakage. The other areas of the effective working area, excluding the first frame structure 15 and the second frame structure 16 (i.e., the main functional area of ​​the bulk acoustic resonator), have uniform thicknesses for each layer (i.e., the upper electrode has a uniform thickness, the piezoelectric layer has a uniform thickness, and the lower electrode has a uniform thickness). The resonant frequency of a bulk acoustic resonator is related to the thickness of the main functional area in the effective working region. Since the thickness of each layer of the main functional area in the effective working region of the existing bulk acoustic resonator is uniform, only one resonant response is generated in the main functional area in the effective working region.

[0004] In some specific applications of bulk acoustic wave (BAW) resonators, it is necessary to connect two or more BAW resonators with different resonant frequencies in parallel. The following explanation uses a filter as an example. In existing technologies, a BAW resonator 1 is already present in the parallel branch of the filter. One or more BAW resonators 2 are then connected in parallel with this BAW resonator 1. The BAW resonator 1 is mainly used to construct the passband of the filter, while the resonant frequency of the BAW resonator 2 is usually much higher or lower than the resonant frequency of the BAW resonator 1 to form additional transmission zeros, thereby improving the filter's performance. If the filter is a bandpass filter, then when the transmission zero falls on the left or right edge of the bandpass, the edge roll-off of the passband can be effectively improved; when the transmission zero falls on the far stopband of the bandpass, the far stopband rejection can be effectively improved.

[0005] Considering that an excessively large area of ​​the bulk acoustic wave resonator 2 would affect the impedance of the bulk acoustic wave resonator 1 and thus the performance of the filter, the area of ​​the bulk acoustic wave resonator 2 is often designed to be much smaller than the area of ​​the bulk acoustic wave resonator 1. Typically, the area of ​​the bulk acoustic wave resonator 2 is less than 2 × 10⁻⁶. 3 micrometer 2 While this method can effectively address the impedance influence of bulk acoustic wave resonator 2 on bulk acoustic wave resonator 1, the small area of ​​bulk acoustic wave resonator 2 can lead to increased manufacturing errors and enhanced edge parasitic effects, thereby reducing the performance of bulk acoustic wave resonator 2 and consequently the overall performance of the filter.

[0006] To address the aforementioned issues, the current approach involves using a series splitting method, employing multiple series-connected split resonators equivalent to a bulk acoustic wave resonator 2. This method increases the area of ​​each split resonator, thereby improving filter performance to some extent. However, this approach increases both cost and filter area, hindering device miniaturization. Summary of the Invention

[0007] To overcome the above-mentioned deficiencies in the prior art, the present invention provides a bulk acoustic resonator connected in parallel, the bulk acoustic resonator comprising:

[0008] Base;

[0009] A stacked structure located on the substrate and comprising, from top to bottom, an upper electrode, a piezoelectric layer, and a lower electrode;

[0010] A sound-reflecting structure located below the stacked structure, formed within the substrate or between the stacked structure and the substrate;

[0011] The overlapping area of ​​the upper electrode, the piezoelectric layer, and the lower electrode located above the acoustic reflection structure constitutes the effective working area of ​​the stacked structure. The effective working area includes a main area and at least one local area. At least one of the upper electrode, piezoelectric layer, and lower electrode in each local area has a thickness different from the thickness of the corresponding layer in the main area. The series resonant frequency of the first resonant response generated by each local area is lower than the series resonant frequency of the second resonant response generated by the main area, or higher than the parallel resonant frequency of the second resonant response generated by the main area.

[0012] According to one aspect of the invention, in this bulk acoustic resonator, the area of ​​the horizontal cross-section of the main body region is less than or equal to 5 × 10⁻⁶. 4 μm 2 The area of ​​the horizontal cross-section of the local region is less than 2 × 10.3 μm 2 .

[0013] According to another aspect of the invention, in the bulk acoustic resonator, the shape of the horizontal cross-section of the local region is polygonal, annular, circular, or irregular.

[0014] According to another aspect of the invention, in the bulk acoustic resonator, the horizontal cross-section of the local region has the same shape as the horizontal cross-section of the effective working area.

[0015] According to another aspect of the invention, in the bulk acoustic resonator, each side of the horizontal cross section of the local region is arranged parallel to the corresponding side of the horizontal cross section of the effective working area.

[0016] According to another aspect of the invention, in the bulk acoustic resonator, an acoustic leakage suppression structure is formed at the edge of the effective working area, the acoustic leakage suppression structure comprising a raised first frame structure and / or a recessed second frame structure.

[0017] The present invention also includes a method for manufacturing a parallel-connected bulk acoustic resonator, the method comprising:

[0018] The steps of providing a substrate, forming a laminated structure, and forming an acoustic reflection structure are included, wherein the laminated structure is located on the substrate, and the acoustic reflection structure is located below the laminated structure, formed within the substrate, or formed between the laminated structure and the substrate.

[0019] The steps for forming the stacked structure include: sequentially forming a lower electrode, a piezoelectric layer, and an upper electrode on the substrate to form a stacked structure. The overlapping area of ​​the upper electrode, the piezoelectric layer, and the lower electrode above the acoustic reflection structure constitutes the effective working area of ​​the stacked structure. The effective working area includes a main region and at least one local region. At least one of the upper electrode, piezoelectric layer, and lower electrode in each local region has a thickness different from the thickness of the corresponding layer in the main region. The series resonant frequency of the first resonant response generated by each local region is lower than the series resonant frequency of the second resonant response generated by the main region, or higher than the parallel resonant frequency of the second resonant response generated by the main region.

[0020] According to one aspect of the invention, in this manufacturing method, the area of ​​the horizontal cross-section of the main body region is less than or equal to 5 × 10⁻⁶. 4 μm 2 The area of ​​the horizontal cross-section of the local region is less than 2 × 10. 3 μm 2 .

[0021] According to another aspect of the invention, in this manufacturing method, the shape of the horizontal cross-section of the local region is polygonal, annular, circular, or irregular.

[0022] According to another aspect of the invention, in this manufacturing method, the horizontal cross-section of the local region has the same shape as the horizontal cross-section of the effective working area.

[0023] According to another aspect of the invention, in this manufacturing method, each side of the horizontal cross-section of the local region is arranged parallel to the corresponding side of the horizontal cross-section of the effective working area.

[0024] According to another aspect of the invention, the manufacturing method further includes: forming an acoustic leakage suppression structure at the edge of the effective working area, the acoustic leakage suppression structure comprising a raised first frame structure and / or a recessed second frame structure.

[0025] The present invention also includes an electronic device comprising the aforementioned bulk acoustic resonator.

[0026] According to one aspect of the invention, the electronic device is a filter, and the bulk acoustic resonator is disposed in the parallel branch and / or series branch of the filter.

[0027] According to another aspect of the invention, in the electronic device, the filter is a bandpass filter, wherein at least one parallel branch of the bandpass filter is provided with the bulk acoustic wave resonator, wherein the transmission zero generated by the first resonant response of the bulk acoustic wave resonator is located at the passband edge of the bandpass filter, and the absolute value of the difference between the series resonant frequency of the first resonant response and the series resonant frequency of the second resonant response is close to half the bandwidth of the bandpass filter.

[0028] The bulk acoustic wave resonator provided by this invention includes a substrate, a stacked structure, and an acoustic reflection structure. The stacked structure includes an upper electrode, a piezoelectric layer, and a lower electrode. The overlapping region of the upper electrode, piezoelectric layer, and lower electrode above the acoustic reflection structure constitutes the effective working region of the stacked structure. The effective working region includes a main region and at least one local region. In each local region, at least one of the upper electrode, piezoelectric layer, and lower electrode has a thickness different from the thickness of the corresponding layer in the main region. Furthermore, the series resonant frequency of the first resonant response generated by each local region is lower than the series resonant frequency of the second resonant response generated by the main region, or higher than the parallel resonant frequency of the second resonant response generated by the main region. Since the main region and the local region in the effective working region can generate different resonant responses, the bulk acoustic wave resonator provided by this invention can be used to realize a parallel structure of two or more bulk acoustic wave resonators. Compared to the parallel structure of a conventional area bulk acoustic wave resonator and one or more small area bulk acoustic wave resonators in the prior art, the bulk acoustic wave resonator provided by this invention not only achieves the same function as the parallel structure, but also effectively avoids the defects of increased manufacturing errors and increased edge parasitic effects caused by the excessively small area of ​​the bulk acoustic wave resonator. Furthermore, compared to the parallel structure formed by splitting small area bulk acoustic wave resonators in the series in the prior art, the bulk acoustic wave resonator provided by this invention has lower manufacturing cost and smaller size. In other words, compared to the prior art, the bulk acoustic wave resonator provided by this invention has the advantages of superior performance, lower cost, and smaller size. Correspondingly, the parallel-connected bulk acoustic wave resonators formed based on the manufacturing method provided by this invention have the advantages of superior performance, lower cost, and smaller size. And the electronic devices realized based on the bulk acoustic wave resonator provided by this invention also have the advantages of superior performance, lower cost, and miniaturization. Attached Figure Description

[0029] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0030] Figure 1 This is a schematic cross-sectional view of a bulk acoustic resonator in the prior art.

[0031] Figure 2 This is a schematic cross-sectional view of a parallel-connected bulk acoustic resonator according to a specific embodiment of the present invention.

[0032] Figures 3(a) and 3(b) are equivalent circuit diagrams according to two specific embodiments of the present invention;

[0033] Figures 4(a) and 4(b) are respectively Figure 2 A cross-sectional view and a top view of the effective working area in the structure shown.

[0034] Figure 5 This is a cross-sectional structural diagram of the effective working area according to another specific embodiment of the present invention;

[0035] Figure 6 This is a cross-sectional structural schematic diagram of the effective working area according to yet another specific embodiment of the present invention;

[0036] Figure 7 This is a cross-sectional structural schematic diagram of the effective working area according to yet another specific embodiment of the present invention;

[0037] Figure 8 This is a cross-sectional structural schematic diagram of the effective working area according to yet another specific embodiment of the present invention;

[0038] Figure 9 This is a top view of the effective working area according to yet another specific embodiment of the present invention;

[0039] Figure 10 This is a top view of the effective working area according to yet another specific embodiment of the present invention;

[0040] Figure 11 This is a top view of the effective working area according to yet another specific embodiment of the present invention;

[0041] Figure 12 This is a top view of the effective working area according to yet another specific embodiment of the present invention;

[0042] Figure 13 This is a top view of the effective working area according to yet another specific embodiment of the present invention;

[0043] Figure 14 This is a top view of the effective working area according to yet another specific embodiment of the present invention;

[0044] Figure 15 This is a cross-sectional structural schematic diagram of a parallel-connected bulk acoustic resonator according to another specific embodiment of the present invention.

[0045] The same or similar reference numerals in the accompanying drawings represent the same or similar parts. Detailed Implementation

[0046] To better understand and explain the present invention, a further detailed description of the invention will be provided below in conjunction with the accompanying drawings.

[0047] This invention provides a bulk acoustic resonator, which includes:

[0048] Base;

[0049] A stacked structure located on the substrate and comprising, from top to bottom, an upper electrode, a piezoelectric layer, and a lower electrode;

[0050] A sound-reflecting structure located below the stacked structure, formed within the substrate or between the stacked structure and the substrate;

[0051] The overlapping area of ​​the upper electrode, the piezoelectric layer, and the lower electrode above the acoustic reflection structure constitutes the effective working area of ​​the stacked structure. The effective working area includes a main area and at least one local area. At least one of the upper electrode, piezoelectric layer, and lower electrode in each local area has a thickness different from the thickness of the corresponding layer in the main area. The series resonant frequency of the first resonant response generated by each local area is lower than the series resonant frequency of the second resonant response generated by the main area, or higher than the parallel resonant frequency of the second resonant response generated by the main area.

[0052] The following is a detailed description of each component of the aforementioned bulk acoustic resonator.

[0053] Specifically, such as Figure 2 As shown, the bulk acoustic wave resonator provided by this invention includes a substrate 100. In this embodiment, the material of the substrate 100 includes, but is not limited to, semiconductor materials such as silicon, germanium, silicon germanium, and silicon carbide. All existing and future materials suitable for bulk acoustic wave resonator substrates are applicable to this invention; for the sake of simplicity, not all possible materials for the substrate 100 will be listed here. Furthermore, the dimensions of the substrate 100 can be designed according to actual needs.

[0054] like Figure 2 As shown, the bulk acoustic wave resonator provided by this invention also includes a stacked structure. In this embodiment, the stacked structure is located on the substrate 100 and includes, from bottom to top, a lower electrode 120, a piezoelectric layer 130, and an upper electrode 140. The materials of the lower electrode 120 and the upper electrode 140 can be realized using metal layers such as molybdenum, tungsten, and platinum. The material of the piezoelectric layer 130 can be made of wurtzite materials such as aluminum nitride, doped aluminum nitride, and zinc oxide, or perovskite materials such as lead zirconate titanate, barium strontium titanate, lithium niobate, and lithium tantalate. Those skilled in the art will understand that any material suitable for forming electrodes and piezoelectric layers is also suitable for the upper electrode, lower electrode, and piezoelectric layer in this invention. For the sake of simplicity, all possible materials for the upper electrode, piezoelectric layer, and lower electrode will not be listed here. Furthermore, the thickness of the upper electrode, piezoelectric layer, and upper electrode can be determined according to actual design requirements and is not limited here. It should be noted that, in other embodiments, depending on actual design requirements, the stacked structure may also include a passivation layer above the upper electrode 140 and a seed layer forming below the lower electrode 120.

[0055] like Figure 2 As shown, the bulk acoustic resonator provided by the present invention further includes an acoustic reflection structure for acoustic wave reflection, which is located below the stacked structure. In this embodiment, the acoustic reflection structure is a cavity 110 formed on the substrate 100. Those skilled in the art will understand that in other embodiments, the acoustic reflection structure may also be an opening located below the stacked structure and penetrating the substrate, or a Bragg reflection layer located between the stacked structure and the substrate, composed of alternating layers of high acoustic impedance material and low acoustic impedance material. For the sake of simplicity, the present invention will not list all possible acoustic reflection structures.

[0056] In this embodiment, the upper electrode 140, piezoelectric layer 130, and lower electrode 120 in the stacked structure have an overlapping region above the acoustic reflection structure (i.e., Figure 2 The area between the two dashed lines is the effective working area of ​​the stacked structure, which is the region in the stacked structure that vibrates in a predetermined direction due to the piezoelectric effect to generate a resonant response when the bulk acoustic resonator is working.

[0057] In this embodiment, the effective working area includes a main region and at least one local region. In each local region, at least one of the upper electrode, piezoelectric layer, and lower electrode has a thickness different from the thickness of the corresponding layer in the main region. Because the thickness of at least one of the upper electrode, piezoelectric layer, and lower electrode in the local region differs from the thickness of the corresponding layer in the main region, the local region and the main region generate different resonant responses. In this embodiment, the series resonant frequency of the resonant response generated by each local region (hereinafter referred to as the first resonant response) is lower than the series resonant frequency of the resonant response generated by the main region (hereinafter referred to as the second resonant response), or higher than the parallel resonant frequency of the second resonant response generated by the main region.

[0058] It should be noted that (1) when the effective working area includes two or more regions, one of which has the largest area compared to the other regions, and at least one of the upper electrode, piezoelectric layer and lower electrode in the other regions has a thickness different from the thickness of the corresponding layer in the region with the largest area, the region with the largest area is defined as the main region of the effective working area, and the other regions are defined as local regions of the effective working area. Of course, those skilled in the art will understand that in other embodiments, any region can be designated as the main region, and the other regions are local regions. (2) When the effective working area includes two or more local regions, the series resonant frequency of the first resonant response generated by all local regions may be lower than the series resonant frequency of the second resonant response generated by the main region, or the series resonant frequency of the first resonant response generated by all local regions may be higher than the parallel resonant frequency of the second resonant response generated by the main region, or the series resonant frequency of the first resonant response generated by some local regions may be lower than the series resonant frequency of the second resonant response generated by the main region, while the series resonant frequency of the first resonant response generated by the remaining local regions may be higher than the parallel resonant frequency of the second resonant response generated by the main region. This document does not impose any limitations on this, and it can be formulated accordingly according to actual design requirements.

[0059] Since the bulk acoustic wave resonator provided by this invention can generate two or more resonant responses, it can be used to realize a parallel structure of two or more bulk acoustic wave resonators. Specifically, the main region in the effective working area of ​​the stacked structure, together with the acoustic reflection structure and the substrate below it, constitutes a bulk acoustic wave resonator (hereinafter referred to as the main resonator). Each local region in the effective working area of ​​the stacked structure, together with the acoustic reflection structure and the substrate below it, constitutes a bulk acoustic wave resonator (hereinafter referred to as a local resonator). Since the upper electrodes of the main resonator and the local resonators are interconnected and their lower electrodes are interconnected, the bulk acoustic wave resonator provided by this invention is equivalent to a parallel structure of the main resonator and at least one local resonator. Therefore, in application scenarios requiring two or more bulk acoustic wave resonators to be connected in parallel, the bulk acoustic wave resonator provided by this invention can be used to realize the parallel structure of the two or more bulk acoustic wave resonators. In one specific embodiment, the effective working area of ​​the stacked structure of the bulk acoustic wave resonator provided by the present invention includes a main region and a local region. Therefore, the bulk acoustic wave resonator can be used to realize a parallel structure of the main resonator and the local resonators. The equivalent circuit diagram of the bulk acoustic wave resonator can be referred to in Figure 3(a), which corresponds to a parallel structure of the main resonator 200 and the local resonator 201. In another specific embodiment, the effective working area of ​​the stacked structure of the bulk acoustic wave resonator provided by the present invention includes a main region and two local regions. Therefore, the bulk acoustic wave resonator can be used to realize a parallel structure of the main resonator and the two local resonators. The equivalent circuit diagram of the bulk acoustic wave resonator can be referred to in Figure 3(b), which corresponds to a parallel structure of the main resonator 200, the local resonator 201, and the local resonator 202.

[0060] Since the bulk acoustic wave resonator provided by this invention can be used to realize the parallel structure of two or more bulk acoustic wave resonators, it can be used in the manufacturing process of electronic devices such as bandpass filters, bandstop filters, and duplexers when encountering a parallel structure of two or more bulk acoustic wave resonators. For example, a filter's parallel branch includes two parallel bulk acoustic wave resonators, one of which (represented by bulk acoustic wave resonator A) is used to construct the passband, and the other (represented by bulk acoustic wave resonator B) is used to form an additional transmission zero. In this case, by rationally designing the main region and local region in the effective working area of ​​the parallel-connected bulk acoustic wave resonator stack structure provided by this invention, the main resonator formed by the main region is equivalent to bulk acoustic wave resonator A, and the local resonator formed by the local region is equivalent to bulk acoustic wave resonator B. Thus, the parallel structure of bulk acoustic wave resonators A and B can be realized using the bulk acoustic wave resonator provided by this invention.

[0061] In existing technologies, when implementing parallel connections of two or more independent bulk acoustic wave (BAW) resonators, to avoid impedance interference between them, the area of ​​one BAW resonator is typically designed to be much larger than the areas of the others. This results in the other BAW resonators having excessively small areas. An excessively small area leads to increased manufacturing errors and edge parasitic effects, ultimately reducing the performance of the BAW resonators. This invention, however, effectively implements the parallel structure of two or more independent BAW resonators using a single BAW resonator. This effectively avoids manufacturing small-area BAW resonators individually, thus preventing the aforementioned defects caused by excessively small BAW resonator areas. In other words, compared to existing parallel structures formed by two or more independent BAW resonators, the BAW resonator provided by this invention can achieve the same functionality as the parallel structure, with superior performance. Furthermore, it should be noted that in the prior art, multiple split resonators are usually connected in series to form an equivalent small-area bulk acoustic wave resonator. Compared with this method, the bulk acoustic wave resonator provided by the present invention has significantly lower manufacturing cost and smaller size.

[0062] The bulk acoustic wave resonator provided by this invention has a stacked structure whose effective working area includes a main region and at least one local region. In each local region, at least one of the upper electrode, piezoelectric layer, and lower electrode has a thickness different from the thickness of the corresponding layer in the main region. In one case, the thickness of one of the upper electrode, piezoelectric layer, and lower electrode in the local region is different from the thickness of the corresponding layer in the main region; in this case, the thickness of the local region in the effective working area of ​​the stacked structure is different from the thickness of the main region. In another case, the thickness of at least two of the upper electrode, piezoelectric layer, and lower electrode in the local region is different from the thickness of the corresponding layer in the main region; in this case, the thickness of the local region in the effective working area of ​​the stacked structure may be different from or the same as the thickness of the main region. Several specific embodiments are described below, wherein the effective working area of ​​the stacked structure includes a main region and a local region.

[0063] Please refer to Figures 4(a) and 4(b). Figures 4(a) and 4(b) are respectively... Figure 2 The diagram shows a cross-sectional view and a top view of the effective working area in the structure shown (Figure 4(a) is obtained by cross-sectioning the effective working area shown in Figure 4(b) along line XX'). As shown, the effective working area of ​​the bulk acoustic resonator stack structure includes a main region 300a and a local region 300b. The thickness of the local region 300b (represented by h2 in the figure) is less than the thickness of the main region 300a (represented by h1 in the figure). The thickness of the upper electrode in the local region 300b is less than the thickness of the upper electrode in the main region 300a.

[0064] Please refer to Figure 5 , Figure 5 In the structure shown, the thickness of the piezoelectric layer in the local region 300b is less than the thickness of the piezoelectric layer in the main region 300a. Correspondingly, the thickness of the local region 300b is less than the thickness of the main region 300a.

[0065] Please refer to Figure 6 , Figure 6 In the structure shown, the thickness of the lower electrode in the local region 300b is less than the thickness of the lower electrode in the main region 300a, wherein the thickness of the local region 300b is less than the thickness of the main region 300a.

[0066] Please refer to Figure 7 , Figure 7 In the structure shown, the thickness of the local region 300b is greater than the thickness of the main region 300a, and the thickness of the upper electrode in the local region 300b is greater than the thickness of the upper electrode in the main region 300a.

[0067] Please refer to Figure 8 , Figure 8 In the structure shown, the thickness of the local region 300b is equal to the thickness of the main region 300a. However, the thickness of the lower electrode in the local region 300b is less than the thickness of the lower electrode in the main region 300a, and the thickness of the piezoelectric layer in the local region 300b is greater than the thickness of the piezoelectric layer in the main region 300a.

[0068] Considering Figure 5 , Figure 6 , Figure 7 as well as Figure 8 The top view of the effective working area shown is the same as that shown in Figure 4(a), so it is omitted.

[0069] It should be noted that the above example only illustrates the case where the effective working area includes a main area and a partial area. In other embodiments, the effective working area may include a greater number of partial areas. For example, ... Figure 13 The effective working area shown includes two local regions, namely local region 300b and local region 300c, as follows: Figure 14 The effective working area shown includes four local regions: local region 300b, local region 300c, local region 300d, and local region 300e. Those skilled in the art will understand that the specific number of local regions depends on actual design requirements.

[0070] It should also be noted that, for cases where the thickness of the upper electrode in a localized region differs from that in the main body region, the manufacturing process only requires etching of the upper electrode in the effective working area to achieve this difference. Since the upper electrode processing is simple and easy, it reduces the manufacturing difficulty of the bulk acoustic wave resonator. Similarly, for cases where the thickness of the piezoelectric layer in a localized region differs from that in the main body region, ensuring consistency in the upper / lower electrode thickness between the localized and main regions helps reduce the ohmic loss of the bulk acoustic wave resonator.

[0071] For the bulk acoustic resonator provided by this invention, it is preferable to design each local region in the effective working area of ​​the stacked structure to be relatively small, so as to avoid the local resonator corresponding to the local region affecting the impedance of the main resonator corresponding to the main region. In a specific embodiment, the area of ​​the horizontal cross-section of the main region in the effective working area of ​​the stacked structure is less than or equal to 5 × 10⁻⁶. 4 μm 2 For example, 2×10 4 μm 2 3×10 4 μm 2 In some areas, the area of ​​the horizontal cross-section is less than 2 × 10. 3 μm 2 It should be noted that when there are two or more local regions, the areas of different local regions can be the same or different.

[0072] This invention does not impose any restrictions on the specific shape of the local region within the effective working area of ​​the bulk acoustic resonator stack structure. That is, the shape of the horizontal cross-section of the local region can be arbitrary, such as a polygon, ring, circle, or irregular shape. Furthermore, the shape of the horizontal cross-section of the local region can be the same as or different from the shape of the horizontal cross-section of the effective working area; this invention does not impose any limitations on this. In one specific embodiment, as shown in Figure 4(b), the horizontal cross-section of the effective working area is a regular pentagon, and the horizontal cross-section of the local region 300b is also a regular pentagon. In another specific embodiment, as shown... Figure 9 As shown, the horizontal cross-section of the effective working area is a regular pentagon, while the horizontal cross-section of the local region 300b is a regular hexagon. In another specific embodiment, as... Figure 10 As shown, the horizontal cross-section of the effective working area is a regular pentagon, while the shape of local region 300b is annular and the shape of local region 300c is rectangular. Those skilled in the art will understand that (1) Figure 4(b), Figure 9 as well as Figure 10This is merely an illustrative example. Due to the numerous possibilities for the shape of the effective working area and local regions of the stacked structure, for the sake of simplicity, not all possibilities will be listed here. (2) Figure 10 The irregular ring shape of local region 300b (i.e., the inner and outer edges of local region 300b have different shapes) is only an illustrative example; in other embodiments, Figure 10 The local region 300b can also be a regular ring (i.e., the inner and outer edges of the local region 300b have the same shape), such as a circular ring or a rectangular ring. When the effective working area includes multiple local regions, these multiple local regions can have the same or different shapes. For example... Figure 13 As shown, the effective working area includes local region 300b and local region 300c, both of which have the same shape: regular pentagons. Figure 14 As shown, the effective working area includes local regions 300b to 300e, each with a different shape: a regular pentagon, an irregular quadrilateral, a rectangle, and a regular hexagon, respectively. It should be noted here that... Figure 14 The fact that the four local regions have different shapes is only one possibility. In other embodiments, some local regions may have the same shape, while others may have different shapes. Taking four local regions as an example, two local regions may be regular pentagons, while the other two may be rectangles and regular hexagons, respectively. For the case where the horizontal cross-section of a local region has the same shape as the horizontal cross-section of the effective working area, preferably, each side of the horizontal cross-section of the local region is parallel to the corresponding side of the horizontal cross-section of the effective working area. As shown in Figure 4(b), the horizontal cross-sections of both the effective working area and local region 300b are regular pentagons. The five sides of the horizontal cross-section of the effective working area are AB, BC, CD, DE, and DA, and the five sides of the horizontal cross-section of local region 300b are A1B1, B1C1, C1D1, D1E1, and D1A1. Sides A1B1, B1C1, C1D1, D1E1, and D1A1 are parallel to sides AB, BC, CD, DE, and DA, respectively. Those skilled in the art will understand that, for cases where the horizontal cross-section of a local area has the same shape as the horizontal cross-section of the effective working area, it is also possible to... Figure 11 As shown, each edge of the horizontal section of the local area is set in a non-parallel manner with the corresponding edge of the horizontal section of the effective working area.

[0073] Furthermore, this invention does not impose any restrictions on the specific location of the local region in the bulk acoustic resonator stack structure; that is, the local region can be located anywhere within the effective working area. In one specific embodiment, the local region is located in a non-edge region of the effective working area, meaning there is a certain distance between the local region and the edge of the effective working area. Further, for the case where the local region is located in a non-edge region of the effective working area, the local region can be located at the center of the effective working area as shown in Figure 4(b), or as shown in... Figure 9 The area shown is located off-center from the center of the effective working area. In another specific embodiment, the local area may also be located at the edge of the effective working area, coinciding with a portion of the edge of the effective working area. For example... Figure 12 As shown, local region 300b is located at the edge of the effective working area and coincides with one side edge of the effective working area.

[0074] It should be noted that, since this invention does not impose any limitations on the specific shape and location of local areas within the effective working region of the bulk acoustic resonator stack structure, it greatly improves the flexibility of bulk acoustic resonator design.

[0075] In another specific embodiment, such as Figure 15 As shown, the effective working area of ​​the stacked structure of the parallel-connected bulk acoustic wave resonator provided by the present invention also has an acoustic leakage suppression structure formed at its edge. This acoustic leakage suppression structure includes a raised first frame structure 150 and a recessed second frame structure 160. In this embodiment, the first frame structure 150 and the second frame structure 160 are formed at the edge of the upper electrode 140, which is used to suppress the leakage of transverse acoustic waves from the device to the outside. Based on the function of the first frame structure 150 and the second frame structure 160, it is known that they can only be formed at the edge of the effective resonant area. The local region in the effective working area of ​​the stacked structure of the bulk acoustic wave resonator provided by the present invention is used to generate a resonant response different from the main region, so as to realize the parallel structure of two or more bulk acoustic wave resonators. Therefore, the formation position of the local region can be any position in the effective working area. Furthermore, those skilled in the art will understand that in other embodiments, the edge of the effective working area may only include the first frame structure 150 or only the second frame structure 160. The present invention does not impose any limitations on this and can be formulated accordingly according to actual design requirements.

[0076] The present invention also provides a method for manufacturing a parallel-connected bulk acoustic resonator, the method comprising:

[0077] The steps of providing a substrate, forming a laminated structure, and forming an acoustic reflection structure are included, wherein the laminated structure is located on the substrate, and the acoustic reflection structure is located below the laminated structure, formed within the substrate, or formed between the laminated structure and the substrate.

[0078] The steps for forming the stacked structure include: sequentially forming a lower electrode, a piezoelectric layer, and an upper electrode on the substrate to form a stacked structure. The overlapping area of ​​the upper electrode, the piezoelectric layer, and the lower electrode above the acoustic reflection structure constitutes the effective working area of ​​the stacked structure. The effective working area includes a main region and at least one local region. At least one of the upper electrode, piezoelectric layer, and lower electrode in each local region has a thickness different from the thickness of the corresponding layer in the main region. The series resonant frequency of the first resonant response generated by each local region is lower than the series resonant frequency of the second resonant response generated by the main region, or higher than the parallel resonant frequency of the second resonant response generated by the main region.

[0079] The following is a detailed explanation of each step of the above manufacturing method.

[0080] Specifically, the manufacturing method provided by this invention includes a substrate provision step, a laminated structure formation step, and an acoustic reflection structure formation step. The laminated structure is located on the substrate, and the acoustic reflection structure is located below the laminated structure, formed within the substrate, or formed between the laminated structure and the substrate. The material dimensions of the substrate can be referred to the relevant sections above. The acoustic reflection structure can be a cavity formed between the laminated structure and the substrate, an opening penetrating the substrate, or a Bragg reflector layer. The method for forming the acoustic reflection structure is prior art and will not be described in detail here for the sake of simplicity.

[0081] The formation of the laminated structure involves two stages. The first stage involves pre-designing the effective working area of ​​the laminated structure. The overlapping area of ​​the upper electrode, piezoelectric layer, and lower electrode above the acoustic reflection structure is defined as the effective working area. Specifically, the location of at least one local region within the effective working area needs to be determined first. The remaining areas of the effective working area, excluding the local regions, constitute the main region of the effective working area. In each local region, at least one of the upper electrode, piezoelectric layer, and lower electrode has a thickness different from the thickness of the corresponding layer in the main region. The second stage involves sequentially forming the lower electrode, piezoelectric layer, and upper electrode on the substrate according to the pre-design to construct the laminated structure, ensuring that the main region and at least one local region within the effective working area of ​​the laminated structure meet the aforementioned pre-design requirements. In this embodiment, the series resonant frequency of the first resonant response generated by each local region is lower than the series resonant frequency of the second resonant response generated by the main region, or higher than the parallel resonant frequency of the second resonant response generated by the main region.

[0082] The implementation process is illustrated using the example of the thickness of the upper electrode in a local region differing from that in the main region. Specifically, a lower electrode is first formed on the substrate; then, a piezoelectric layer covering the entire substrate surface (including the lower electrode) is formed; next, a metal material is deposited on the piezoelectric layer and etched. If the thickness of the upper electrode in the local region is greater than that in the main region, the metal material in the main region is etched until the thickness of the metal material in the main region meets the thickness requirement. If the thickness of the upper electrode in the local region is less than that in the main region, the metal material in the local region is etched until the thickness of the metal material in the local region meets the thickness requirement. For cases where the thickness of the piezoelectric layer and the lower electrode in the local region differs from the corresponding layer thickness in the main region, the same method as for the upper electrode can be used, and for simplicity, it will not be described again here.

[0083] The parallel-connected bulk acoustic wave resonators formed by the manufacturing method provided by this invention can generate two or more resonant responses, and can be used to realize the parallel structure of two or more bulk acoustic wave resonators, and have the advantages of high performance, low cost and small size.

[0084] Preferably, the area of ​​the horizontal cross-section of the main body region in the effective working area of ​​the bulk acoustic resonator provided by the present invention is less than or equal to 5 × 10⁻⁶. 4 μm 2 The area of ​​the horizontal cross-section in the local region is less than 2×10 3 μm 2 It should be noted that when there are two or more local regions, the areas of different local regions can be the same or different.

[0085] This invention does not impose any restrictions on the specific shape of local regions within the effective working area of ​​the bulk acoustic resonator stack structure. That is, the shape of the horizontal cross-section of the local region can be arbitrary, such as a polygon, ring, circle, or irregular shape. Furthermore, the shape of the horizontal cross-section of the local region can be the same as or different from the shape of the horizontal cross-section of the effective working area; this invention does not impose any limitations in this regard. It should also be noted that when the effective working area includes multiple local regions, the shapes of these multiple local regions can be the same or different. For the case where the shape of the horizontal cross-section of the local region is the same as that of the horizontal cross-section of the effective working area, preferably, each side of the horizontal cross-section of the local region is parallel to the corresponding side of the horizontal cross-section of the effective working area. Those skilled in the art will understand that, for the case where the shape of the horizontal cross-section of the local region is the same as that of the horizontal cross-section of the effective working area, each side of the horizontal cross-section of the local region can also be arranged in a non-parallel manner to the corresponding side of the horizontal cross-section of the effective working area.

[0086] This invention does not impose any restrictions on the specific location of the local region in the bulk acoustic resonator stack structure; that is, the local region can be located anywhere within the effective working area. In one specific embodiment, the local region is located in a non-edge region of the effective working area, meaning there is a certain distance between the local region and the edge of the effective working area. In another specific embodiment, the local region can also be located in the edge region of the effective working area, partially coinciding with the edge of the effective working area.

[0087] Furthermore, the manufacturing method provided by the present invention may further include: forming an acoustic leakage suppression structure at the edge of the effective working area (e.g., the edge of the upper electrode), wherein the acoustic leakage suppression structure is a raised first frame structure and / or a recessed second frame structure. Forming the first frame structure and / or the second frame structure at the edge of the effective working area is a conventional technique, and for the sake of simplicity, it will not be described in detail here.

[0088] Accordingly, the present invention also provides an electronic device comprising a bulk acoustic wave resonator, wherein the bulk acoustic wave resonator is implemented using the aforementioned parallel-connected bulk acoustic wave resonators. Considering that the specific structure of the parallel-connected bulk acoustic wave resonators can be referred to the corresponding sections above, it will not be repeated here for the sake of brevity. Since the aforementioned parallel-connected bulk acoustic wave resonators have the advantages of high performance, low cost, and miniaturization, the electronic device provided by the present invention also correspondingly possesses the advantages of high performance, low cost, and miniaturization.

[0089] In a preferred embodiment, the electronic device is a filter, such as a bandpass filter, and the bulk acoustic resonator provided by this invention is disposed in the parallel branch of the filter. The second resonant response generated in the main region of the effective working area of ​​the bulk acoustic resonator stack structure provided by this invention is used to construct the passband, while the first resonant response generated in the local region is used to form additional transmission zeros. In the prior art, based on the existing bulk acoustic resonator in the parallel branch of the filter, one or more small-area bulk acoustic resonators are connected in parallel to that resonator to form transmission zeros, thereby improving filter performance. Specifically, if the transmission zero is generated at the edge of the passband of the bandpass filter, the edge roll-off can be significantly improved; if the transmission zero falls into the far stopband of the bandpass filter, the far stopband suppression can be effectively improved. For this invention, since the bulk acoustic resonator provided by this invention is equivalent to two or more bulk acoustic resonators connected in parallel, setting the bulk acoustic resonator provided by this invention in the parallel branch of the filter can also achieve the same function as the prior art. However, existing technologies suffer from drawbacks such as the small area of ​​the bulk acoustic wave resonator leading to increased manufacturing errors and enhanced edge parasitic effects, thus affecting filter performance. The bulk acoustic wave resonator provided by this invention, however, does not suffer from the aforementioned drawbacks because it does not have an excessively small area. Therefore, compared to existing filters, the filter formed based on the bulk acoustic wave resonator provided by this invention exhibits superior performance. Furthermore, compared to filters formed by series splitting in existing technologies, the filter formed based on the bulk acoustic wave resonator provided by this invention clearly has lower manufacturing costs and a smaller size.

[0090] It should be noted that the bulk acoustic resonator provided by the present invention can not only be set in the parallel branch of the filter, but also in the series branch of the filter in other embodiments, depending on the actual design requirements, or simultaneously set in the parallel and series branches of the filter. The present invention does not impose any limitations on this.

[0091] For the case where the filter is a bandpass filter, preferably, at least one parallel branch of the bandpass filter is provided with a bulk acoustic wave resonator provided by the present invention. For each bulk acoustic wave resonator, a local region in the effective working area of ​​its stacked structure generates a first resonant response, and the main region generates a second resonant response. The transmission zero generated by the first resonant response is located at the passband edge of the bandpass filter, and the absolute value of the difference between the series resonant frequency of the first resonant response and the series resonant frequency of the second resonant response is close to half the bandwidth of the bandpass filter. In this way, the transmission zero generated by the first resonant response falls precisely at the passband edge of the bandpass filter, thereby significantly improving the edge roll-off. It should be noted that, theoretically, the absolute value of the difference between the series resonant frequency of the first resonant response and the series resonant frequency of the second resonant response should be equal to half the bandwidth of the bandpass filter. However, due to manufacturing limitations, in actual filter products, the absolute value of the difference between the series resonant frequency of the first resonant response and the series resonant frequency of the second resonant response is close to half the bandwidth of the bandpass filter (with a deviation of approximately ±10MHz), and not strictly equal.

[0092] It should be noted that the above-mentioned electronic device is a filter, which is only a preferred embodiment. In other embodiments, any electronic device involving two or more bulk acoustic resonators connected in parallel, such as duplexers and multiplexers, falls within the scope of protection of this invention. For the sake of brevity, not all possible electronic devices will be listed one by one.

[0093] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be embraced within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims. Furthermore, it is clear that the word "comprising" does not exclude other components, units, or steps, and the singular does not exclude the plural. Multiple components, units, or devices recited in the system claims may also be implemented by a single component, unit, or device in software or hardware.

[0094] The above-disclosed embodiments are merely some preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A parallel-connected bulk acoustic resonator, characterized in that, The bulk acoustic resonator includes: Base; A stacked structure located on the substrate and comprising, from top to bottom, an upper electrode, a piezoelectric layer, and a lower electrode; A sound-reflecting structure located below the stacked structure, formed within the substrate or between the stacked structure and the substrate; The overlapping area of ​​the upper electrode, the piezoelectric layer, and the lower electrode above the acoustic reflection structure constitutes the effective working area of ​​the stacked structure. The effective working area includes a main area and at least one local area. The main area is the area with the largest horizontal cross-sectional area in the effective working area, and the local area is the area in the effective working area excluding the main area. The main area and the at least one local area together constitute the entire area of ​​the effective working area. At least one of the upper electrode, piezoelectric layer, and lower electrode in each local area has a thickness different from the thickness of the corresponding layer in the main area. The series resonant frequency of the first resonant response generated by each local area is lower than the series resonant frequency of the second resonant response generated by the main area, or higher than the parallel resonant frequency of the second resonant response generated by the main area.

2. The bulk acoustic resonator according to claim 1, characterized in that, in: The area of ​​the horizontal cross-section of the main region is less than or equal to 5 × 10 4 μm 2 ; The area of ​​the horizontal cross-section of the local region is less than 2×10. 3 μm 2 .

3. The bulk acoustic resonator according to claim 1 or 2, characterized in that, in, The shape of the horizontal cross-section of the local area is polygonal, annular, circular, or irregular.

4. The bulk acoustic resonator according to claim 1 or 2, characterized in that, in, The horizontal cross-section of the local area has the same shape as the horizontal cross-section of the effective working area.

5. The bulk acoustic resonator according to claim 4, characterized in that, in, Each side of the horizontal section of the local area is set parallel to the corresponding side of the horizontal section of the effective working area.

6. The bulk acoustic resonator according to claim 1, characterized in that, in: The edge of the effective working area is formed with an acoustic leakage suppression structure, which includes a raised first frame structure and / or a recessed second frame structure.

7. A method for manufacturing a parallel-connected bulk acoustic resonator, characterized in that, The manufacturing method includes: The steps of providing a substrate, forming a laminated structure, and forming an acoustic reflection structure are included, wherein the laminated structure is located on the substrate, and the acoustic reflection structure is located below the laminated structure, formed within the substrate, or formed between the laminated structure and the substrate. The steps for forming the stacked structure include: sequentially forming a lower electrode, a piezoelectric layer, and an upper electrode on the substrate to form a stacked structure. The overlapping area of ​​the upper electrode, the piezoelectric layer, and the lower electrode above the acoustic reflection structure constitutes the effective working area of ​​the stacked structure. The effective working area includes a main area and at least one local area. The main area is the area with the largest horizontal cross-sectional area in the effective working area. The local area is the area in the effective working area excluding the main area. The main area and the at least one local area together constitute the entire area of ​​the effective working area. At least one of the upper electrode, piezoelectric layer, and lower electrode in each local area has a thickness different from the thickness of the corresponding layer in the main area. The series resonant frequency of the first resonant response generated by each local area is lower than the series resonant frequency of the second resonant response generated by the main area, or higher than the parallel resonant frequency of the second resonant response generated by the main area.

8. The manufacturing method according to claim 7, characterized in that, in: The area of ​​the horizontal cross-section of the main region is less than or equal to 5 × 10 4 μm 2 ; The area of ​​the horizontal cross-section of the local region is less than 2×10. 3 μm 2 .

9. The manufacturing method according to claim 7 or 8, characterized in that, in, The shape of the horizontal cross-section of the local area is polygonal, annular, circular, or irregular.

10. The manufacturing method according to claim 7 or 8, characterized in that, in, The horizontal cross-section of the local area has the same shape as the horizontal cross-section of the effective working area.

11. The manufacturing method according to claim 10, characterized in that, in, Each side of the horizontal section of the local area is set parallel to the corresponding side of the horizontal section of the effective working area.

12. The manufacturing method according to claim 7, characterized in that, The manufacturing method also includes: An acoustic leakage suppression structure is formed at the edge of the effective working area, the acoustic leakage suppression structure comprising a raised first frame structure and / or a recessed second frame structure.

13. An electronic device, characterized in that, The electronic device includes: The bulk acoustic resonator as described in any one of claims 1 to 6.

14. The electronic device according to claim 13, characterized in that, in: The electronic device is a filter, and the bulk acoustic resonator is disposed in the parallel branch and / or series branch of the filter.

15. The electronic device according to claim 14, characterized in that, in: The filter is a bandpass filter, and at least one parallel branch of the bandpass filter is provided with the bulk acoustic wave resonator, wherein the transmission zero generated by the first resonant response of the bulk acoustic wave resonator is located at the passband edge of the bandpass filter, and the absolute value of the difference between the series resonant frequency of the first resonant response and the series resonant frequency of the second resonant response is close to half of the bandwidth of the bandpass filter.

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