Bulk acoustic wave resonator filter

Abstract

A bulk acoustic wave resonator filter is provided. The bulk acoustic wave resonator filter includes: a series bulk acoustic wave resonator electrically connected in series between a first port and a second port through which a radio frequency signal passes; a second shunt bulk acoustic wave resonator electrically connected in shunt between the series bulk acoustic wave resonator and a ground, and having a resonant frequency lower than a resonant frequency of the series bulk acoustic wave resonator; and a first shunt bulk acoustic wave resonator electrically connected in shunt to the second shunt bulk acoustic wave resonator and having a resonant frequency higher than the resonant frequency of the second shunt bulk acoustic wave resonator. One or both of the series bulk acoustic wave resonator and the first shunt bulk acoustic wave resonator includes: a first electrode disposed above a substrate; a piezoelectric layer disposed on an upper surface of the first electrode; a second electrode disposed on an upper surface of the piezoelectric layer; and a trench formed in or above the second electrode and recessed downward.

Description

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2020-0183642, filed December 24, 2020, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety for all purposes. TECHNICAL FIELD

[0002] The following description relates to a bulk acoustic wave resonator filter. BACKGROUND

[0003] With the rapid development of mobile communication devices, chemical testing devices, and biological testing devices, etc., the demand for small and light filters, oscillators, resonant elements, acoustic resonant mass sensors, etc. used in these devices is increasing.

[0004] A bulk acoustic wave resonator such as a bulk acoustic wave (BAW) filter can be configured to implement such small and light filters, oscillators, resonant elements, acoustic resonant mass sensors, etc. Since such a bulk acoustic wave resonator is very small and has good performance compared to dielectric filters, metal cavity filters, waveguide filters, etc., it can be widely used in communication modules of modern mobile devices that require good performance (e.g., wide pass bandwidth). SUMMARY

[0005] This summary is provided to introduce selected concepts in a simplified form, which are further described below in the detailed description. This summary is neither explicitly or implicitly intended to be a key to the identification of key features or essential features of the claimed subject matter, nor is it intended to be used in determining the scope of the claimed subject matter.

[0006] In one general aspect, a bulk acoustic wave resonator filter includes: a series bulk acoustic wave resonator electrically connected in series between a first port and a second port; a second shunt bulk acoustic wave resonator electrically connected in shunt between the series bulk acoustic wave resonator and a ground, and a resonant frequency of the second shunt bulk acoustic wave resonator is lower than a resonant frequency of the series bulk acoustic wave resonator; and a first shunt bulk acoustic wave resonator electrically connected in series to the second shunt bulk acoustic wave resonator, and a resonant frequency of the first shunt bulk acoustic wave resonator is higher than the resonant frequency of the second shunt bulk acoustic wave resonator, wherein one or both of the series bulk acoustic wave resonator and the first shunt bulk acoustic wave resonator includes: a first electrode disposed above a substrate; a piezoelectric layer disposed on an upper surface of the first electrode; a second electrode disposed on an upper surface of the piezoelectric layer; and a trench disposed in an upper surface of the second electrode or above the second electrode and recessed downward.

[0007] The first shunt bulk acoustic wave resonator can include the first electrode, the piezoelectric layer, the second electrode, and the trench.

[0008] The resonant frequency of the first shunt BAW resonator may be equal to or higher than the resonant frequency of the series BAW resonator.

[0009] The trenches may be provided in the first shunt BAW resonator and the series BAW resonator, respectively.

[0010] The width of the trench may be greater than or equal to 0.6 μm and less than or equal to 1.8 μm.

[0011] The depth of the trench may be greater than 0 nm and less than or equal to 100 nm.

[0012] A bandwidth of a passband between the first port and the second port may be 200 MHz or greater.

[0013] When the frequency of the attenuation pole corresponding to the lowest frequency of the passband between the first port and the second port is F and the width of the groove is W, W×F may be greater than or equal to 0.6×3.485 (μm×GHz) and less than or equal to 1.8×3.485 (μm×GHz).

[0014] When the overlapping area of ​​the first electrode, the piezoelectric layer, and the second electrode is A, and the width of the groove is W, W / A may be greater than or equal to 0.6 / 4900 (μm / (μm) 2 ) and less than or equal to 1.8 / 4900(μm / (μm) 2 ).

[0015] The groove may be recessed in the upper surface of the second electrode toward the piezoelectric layer.

[0016] The second electrode may include a frame protruding upward on the upper surface of the second electrode, and a width of the groove may be smaller than a width of the frame.

[0017] The second shunt BAW resonator may include a plurality of second shunt BAW resonators, each of which is disposed in a plurality of shunt connection paths between the series BAW resonator and the ground. The first shunt BAW resonator may be disposed in a portion of the plurality of shunt connection paths, and a shunt connection path in which the first shunt BAW resonator is disposed among the plurality of shunt connection paths may be disposed between a plurality of shunt connection paths in which the first shunt BAW resonator is not disposed.

[0018] The second shunt bulk acoustic wave resonator can include a plurality of second shunt bulk acoustic wave resonators respectively disposed in a plurality of shunt connection paths between the series bulk acoustic wave resonator and ground, the first shunt bulk acoustic wave resonator can include a plurality of first shunt bulk acoustic wave resonators electrically connected in series to respective ones of the plurality of second shunt bulk acoustic wave resonators, and a number of the plurality of second shunt bulk acoustic wave resonators can be greater than a number of the plurality of first shunt bulk acoustic wave resonators.

[0019] An inductance of at least one of the plurality of shunt connection paths in which one of the plurality of first shunt bulk acoustic wave resonators is disposed can be greater than an inductance of each of the remaining ones of the plurality of shunt connection paths.

[0020] The first shunt bulk acoustic wave resonator can include the trench, the second shunt bulk acoustic wave resonator can include a trench, and a width of the trench of the second shunt bulk acoustic wave resonator can be different than a width of the trench of the first shunt bulk acoustic wave resonator.

[0021] The second shunt bulk acoustic wave resonator can not include a trench.

[0022] Other features and aspects will be readily appreciated with reference to the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0023] FIG. 1A 、 FIG. 1B 、 FIG. 1C 、 FIG. 1D 、 FIG. 1E 、 FIG. 1F 、 FIG. 1G and FIG. 1H are graphs showing bulk acoustic wave resonator filters according to various examples.

[0024] FIG. 2 is a graph showing an attenuation pole formed by a series connection of a first shunt bulk acoustic wave resonator and a second shunt bulk acoustic wave resonator of a bulk acoustic wave resonator filter according to an example.

[0025] FIG. 3A and FIG. 3B are graphs showing FIG. 1F S-parameters of the bulk acoustic wave resonator filters shown in

[0026] FIG. 3C is a graph showing a roll-off characteristic of the bulk acoustic wave resonator filter shown in FIG. 1F

[0027] FIG. 4A and FIG. 4B ​is a diagram showing a trench of a bulk acoustic wave resonator filter according to an example.

[0028] FIG. 5A is a plan view showing a detailed structure of a bulk acoustic wave resonator which can be included in a bulk acoustic wave resonator filter according to an example.

[0029] FIG. 5B is a cross-sectional view taken along FIG. 5A line I-I' of

[0030] FIG. 5C is a cross-sectional view taken along FIG. 5A line II-II' of

[0031] FIG. 5D is a cross-sectional view taken along FIG. 5A line III-III' of

[0032] In all of the drawings and detailed description, like reference numerals indicate like elements. The drawings can not be to scale and the relative dimensions, proportions, and depiction of elements in the drawings can be exaggerated for clarity, illustration, and convenience. DETAILED DESCRIPTION

[0033] The following detailed description is provided to help the reader obtain a thorough understanding of the methods, devices, and / or systems described herein. However, various changes, modifications, and equivalents of the methods, devices, and / or systems described herein will be readily apparent to those skilled in the art and are intended to be within the scope of the claims. The order of the operations described herein is merely exemplary and the operations can be done in any order necessary to achieve the results described herein, except where otherwise indicated, such as where a particular order is necessary for the skilled artisan to accomplish an operation described herein or where a particular order is dictated by the specific structures described herein. Furthermore, the description herein of a particular feature can be replaced by any suitable description of an equivalent feature. In addition, descriptions of functions and constructions known in the art can be omitted in order to concisely describe the embodiments.

[0034] The features described herein can be implemented in different forms and are not to be construed as limited to the examples described herein. Rather, the examples described herein have been provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0035] Here, it is noted that the use of the term "comprise" with respect to examples or embodiments (e.g., an example or embodiment can include or implement something) means that at least one example or embodiment includes or implements that feature, and is not limited to all examples or embodiments including or implementing that feature.

[0036] Throughout this specification, when an element such as a layer, region or substrate is referred to as being "on" another element, connected to another element or coupled to another element, it can be directly on, connected to or coupled to the other element, or one or more other elements can be interposed therebetween. In contrast, when an element is referred to as being "directly on," "directly connected to" or "directly coupled to" another element, there are no other elements interposed therebetween.

[0037] As used herein, the term "and / or" includes any one of the listed items or any combination of at least two or more of the listed items.

[0038] Although terms such as "first", "second" and "third" can be used herein to describe various components, assemblies, regions, layers or sections, these components, assemblies, regions, layers or sections will not be limited by these terms. Rather, these terms are only used to distinguish one component, assembly, region, layer or section from another component, assembly, region, layer or section. Thus, a component, assembly, region, layer or section referred to as the first component, the first assembly, the first region, the first layer or the first section in an example described herein can also be referred to as the second component, the second assembly, the second region, the second layer or the second section in another example without departing from the teachings of the examples.

[0039] For ease of description, spatial relative terms such as "above", "upper", "below", and "lower" can be used herein to describe the relationship of one element to another element as shown in the figures. Such spatial relative terms can be intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, then the element described as above or upper relative to other elements would then be below or lower relative to the other elements. Accordingly, the term "above" encompasses both the "above" and "below" orientations as the device is oriented in space. The device can also be positioned in other ways (e.g., rotated 90 degrees or at other orientations), and spatial relative terms used herein will be interpreted accordingly.

[0040] The terminology used herein is for the purpose of describing various examples only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises", "comprising", "includes", "including" and "has", "having" recites the presence of the stated features, numbers, operations, components, elements, and / or combinations thereof, but does not preclude the presence or addition of one or more other features, numbers, operations, components, elements, and / or combinations thereof.

[0041] The shapes shown in the drawings can vary due to manufacturing techniques and / or tolerances. Thus, the examples described herein are not limited to the specific shapes illustrated in the drawings, but include changes in shapes that occur during manufacturing.

[0042] Features of the examples described herein can be combined with one another in a variety of ways. Moreover, although examples described herein have a variety of configurations, other configurations are possible in light of the disclosure of the present application.

[0043] FIG. 1A is a diagram illustrating a bulk acoustic wave resonator filter according to an example.

[0044] Referring to FIG. 1A , the bulk acoustic wave resonator filter 50a can include the series part 10a and the first shunt part 20f, and can pass or block a radio frequency (RF) signal between the first port P1 and the second port P2 according to a frequency of the RF signal.

[0045] Referring to FIG. 1A , the bulk acoustic wave resonator filter 50a can include at least one series bulk acoustic wave resonator 16, at least one first shunt bulk acoustic wave resonator 21, and at least one second shunt bulk acoustic wave resonator 22, and can pass or block a radio frequency (RF) signal between the first port P1 and the second port P2 according to a frequency of the RF signal.

[0046] The electrical connection nodes between the at least one series bulk acoustic wave resonator 16, the at least one first shunt bulk acoustic wave resonator 21, and the at least one second shunt bulk acoustic wave resonator 22 can be implemented with a material having a relatively low resistivity. For example, gold (Au), a gold-tin (Au-Sn) alloy, copper (Cu), a copper-tin (Cu-Sn) alloy, aluminum (Al), an aluminum alloy, etc., but are not limited to these materials.

[0047] The at least one series bulk acoustic wave resonator 16, the at least one first shunt bulk acoustic wave resonator 21, and the at least one second shunt bulk acoustic wave resonator 22 can respectively convert electrical energy of an RF signal into mechanical energy through piezoelectric properties, and can convert the mechanical energy into electrical energy. When a frequency of the RF signal is closer to a resonance frequency of the bulk acoustic wave resonator, a rate of energy transfer between the plurality of electrodes can be greatly increased. When the frequency of the RF signal is closer to an anti-resonance frequency of the bulk acoustic wave resonator, the rate of energy transfer between the plurality of electrodes can be greatly decreased. According to the piezoelectric properties, the anti-resonance frequency can be higher than the resonance frequency.

[0048] The at least one series bulk acoustic resonator 16 can be electrically connected in series between the first port P1 and the second port P2. When the frequency of the RF signal is closer to the resonance frequency, the passing rate of the RF signal between the first port P1 and the second port P2 can be increased. When the frequency of the RF signal is closer to the anti-resonance frequency, the passing rate of the RF signal between the first port P1 and the second port P2 can be decreased.

[0049] The at least one second shunt bulk acoustic resonator 22 can be electrically connected in shunt between the at least one series bulk acoustic resonator 16 and the ground, and when the frequency of the RF signal is closer to the resonance frequency, the passing rate of the RF signal toward the ground can be increased, and when the frequency of the RF signal is closer to the anti-resonance frequency, the passing rate of the RF signal toward the ground can be decreased.

[0050] The passing rate of the RF signal between the first port P1 and the second port P2 can be decreased as the passing rate of the RF signal toward the ground is increased, and can be increased as the passing rate of the RF signal toward the ground is decreased.

[0051] That is, the passing rate of the RF signal between the first port P1 and the second port P2 can be lower when closer to the resonance frequency of the at least one second shunt bulk acoustic resonator 22 or closer to the anti-resonance frequency of the at least one series bulk acoustic resonator 16.

[0052] Since the anti-resonance frequency is higher than the resonance frequency, the bulk acoustic resonator filter 50a can have a passband width formed by a lowest frequency and a highest frequency, the lowest frequency corresponding to the resonance frequency of the at least one second shunt bulk acoustic resonator 22, and the highest frequency corresponding to the anti-resonance frequency of the at least one series bulk acoustic resonator 16.

[0053] As the difference between the resonance frequency of the at least one second shunt bulk acoustic resonator 22 and the anti-resonance frequency of the at least one series bulk acoustic resonator 16 increases, the passband width can be widened. However, if the difference is too great, the passband width can be split.

[0054] When the resonance frequency of the at least one series bulk acoustic resonator 16 is appropriately higher than the anti-resonance frequency of the at least one second shunt bulk acoustic resonator 22, the bandwidth of the bulk acoustic resonator filter 50a can be wide and not split.

[0055] The difference between the resonance frequency and the anti-resonance frequency in the bulk acoustic resonator can be determined based on a physical property k t 2 (electromechanical coupling factor) of the bulk acoustic resonator, which can change together when the size or shape of the bulk acoustic resonator changes.

[0056] The series part 10a can include at least one series bulk acoustic resonator 16 electrically connected in series between the first port P1 and the second port P2.

[0057] The first shunt part 20f can be provided in a shunt connection path between the at least one series bulk acoustic resonator 16 and the ground, and can include a first shunt bulk acoustic resonator 21 and a second shunt bulk acoustic resonator 22 connected in series to each other and having different resonance frequencies from each other. The resonance frequency of the first shunt bulk acoustic resonator 21 can be higher than the resonance frequency of the second shunt bulk acoustic resonator 22.

[0058] When the first shunt bulk acoustic resonator 21 and the second shunt bulk acoustic resonator 22 are electrically connected in series to each other, since the first shunt bulk acoustic resonator 21 and the second shunt bulk acoustic resonator 22 can function as capacitors to each other, the resonance frequency of each shunt bulk acoustic resonator can be increased. Accordingly, the resonance frequency of the first shunt bulk acoustic resonator 21 can be closer to the anti-resonance frequency of the first shunt bulk acoustic resonator 21, and the resonance frequency of the second shunt bulk acoustic resonator 22 can be closer to the anti-resonance frequency of the second shunt bulk acoustic resonator 22.

[0059] Accordingly, a transmission zero pole can be formed near the resonance frequency of the first shunt bulk acoustic resonator 21 and the resonance frequency of the second shunt bulk acoustic resonator 22, a transmission zero pole can be formed near the bandwidth of the bulk acoustic resonator filter 50a, and an attenuation characteristic of the bandwidth can be improved. That is, the transmission zero pole can increase a rate of change of admittance according to a frequency change of a lowest frequency of the bandwidth and / or a frequency change at a highest frequency, and sharpen a roll-off characteristic of the bulk acoustic resonator filter 50a.

[0060] For example, the resonance frequency of the first shunt bulk acoustic resonator 21 can be greater than or equal to the resonance frequency of the at least one series bulk acoustic resonator 16. Accordingly, a roll-off characteristic near a lowest frequency of a passband of the bulk acoustic resonator filter 50a and a roll-off characteristic near a highest frequency can be sharpened together.

[0061] FIG. 1B to FIG. 1H FIG. 1 is a diagram illustrating a bulk acoustic resonator filter according to various examples. Hereinafter, in order to avoid redundancy, a description that is repeated with the above description can be omitted.

[0062] Referring to FIG. 1B The number of the at least one series bulk acoustic resonator 12 and 16 of the series part 10b of the bulk acoustic resonator filter 50b can be plural, and the first shunt part 20b can be electrically connected between a node between the plural series bulk acoustic resonators 12 and 16 in series and the ground. The number of the at least one series bulk acoustic resonator 12 and 16 can be appropriately set according to a specification required for the series bulk acoustic resonator filter 50b.

[0063] Referring to FIG. 1B , the connection positions of the first shunt bulk acoustic resonator 21 and the second shunt bulk acoustic resonator 22 of the first shunt part 20b can be different from the connection positions of the first shunt bulk acoustic resonator 21 and the second shunt bulk acoustic resonator 22 of the first shunt part shown in FIG. 1. FIG. 1A

[0064] Referring to FIG. 1C , the bulk acoustic resonator filter 50c can further include a second shunt part 40-1.

[0065] The second shunt part 40-1 can be provided in a shunt connection path between a connection node between at least one of the series bulk acoustic resonators 12, 13, and 16 and the ground, and can include a second shunt bulk acoustic resonator 42-1 having a resonance frequency lower than the higher resonance frequency among the plurality of resonance frequencies of the first shunt bulk acoustic resonator 21 and the second shunt bulk acoustic resonator 22 of the first shunt part 20f.

[0066] Accordingly, the second shunt bulk acoustic resonator 42-1 of the second shunt part 40-1 can form a pole near the lowest frequency of the bandwidth of the bulk acoustic resonator filter 50c, and a roll-off characteristic near the lowest frequency of the bandwidth of the bulk acoustic resonator filter 50c can be sharper. For example, at least one resonance frequency of the second shunt bulk acoustic resonator 42-1 of the second shunt part 40-1 can be the same as the lower resonance frequency among the plurality of resonance frequencies of the first shunt bulk acoustic resonator 21 and the second shunt bulk acoustic resonator 22 of the first shunt part 20f.

[0067] As the number of the plurality of series bulk acoustic resonators 12, 13, and 16 of the series part 10c increases, a roll-off characteristic near the highest frequency of the bandwidth of the bulk acoustic resonator filter 50c can become sharper.

[0068] Referring to FIG. 1D , the second shunt part 40d of the bulk acoustic resonator filter 50d can include a plurality of second shunt parts 40-1 and 40-5 provided on a plurality of shunt connection paths between connection nodes between the series bulk acoustic resonators 11, 12, 13, and 16 and the ground, respectively.

[0069] The plurality of second shunt parts 40-1 and 40-5 can include second shunt bulk acoustic resonators 42-1 and 42-5, respectively, having a resonance frequency lower than the higher resonance frequency among the plurality of resonance frequencies of the first shunt bulk acoustic resonator 21 and the second shunt bulk acoustic resonator 22 of the first shunt part 20f.

[0070] ​The series part 10d can include series bulk acoustic resonators 11 and 12 electrically connected between the plurality of second shunt parts 40-1 and 40-5, and the first shunt part 20f can be electrically connected between a connection node between the series bulk acoustic resonators 11 and 12 and the ground.

[0071] Accordingly, the first shunt part 20f can be disposed farther from the first port P1 and the second port P2 than the plurality of second shunt parts 40-1 and 40-5, and can be relatively less affected by heat generated according to power of an external noise or an RF signal. Accordingly, a transmission zero point formed by the first shunt part 20f can be more stably formed (e.g., more stable to temperature variation), and the bulk acoustic resonator filter 50d can have a more stable roll-off characteristic.

[0072] Referring to FIG. 1E , the bulk acoustic resonator filter 50e can include a second shunt part 40e and a series part 10e, the second shunt part 40e can include a plurality of second shunt parts 40-2, 40-3, 40-4, and 40-5, the plurality of second shunt parts 40-2, 40-3, 40-4, and 40-5 can respectively include second shunt bulk acoustic resonators 42-2, 42-3, and 42-4, and 42-5, and the series part 10e can include a plurality of series bulk acoustic resonators 11, 12, 14, 15, and 16.

[0073] The number of the plurality of second shunt bulk acoustic resonators 22, 42-2, 42-3, 42-4, and 42-5 can be greater than the number of the first shunt bulk acoustic resonator 21.

[0074] Accordingly, the plurality of second shunt bulk acoustic resonators 22, 42-2, 42-3, 42-4, and 42-5 can form a main bandwidth of the bulk acoustic resonator filter 50e, and the plurality of first shunt bulk acoustic resonators 21 can sharpen a roll-off characteristic of the main bandwidth of the bulk acoustic resonator filter 50e.

[0075] Referring to FIG. 1F , the bulk acoustic resonator filter 50f can include a second shunt part 40g and a series part 10f, the second shunt part 40g can include a plurality of second shunt parts 40-1, 40-2, 40-3, 40-4, and 40-5, the plurality of second shunt parts 40-1, 40-2, 40-3, 40-4, and 40-5 can respectively include second shunt bulk acoustic resonators 42-1, 42-2, 42-3, 42-4, and 42-5, and the series part 10f can include a plurality of series bulk acoustic resonators 11, 12, 13, 14, 15, and 16.

[0076] Referring to FIG. 1GThe first shunt part 20g of the bulk acoustic resonator filter 50g can include a plurality of first shunt parts 20g-1 and 20g-2 disposed in a plurality of shunt connection paths between connection nodes between the plurality of series-connected bulk acoustic resonators 11, 12, 13, 14, 15, and 16 and the ground.

[0077] The first shunt part 20g-1 can include a first shunt bulk acoustic resonator 21-1 and a second shunt bulk acoustic resonator 22-1, and the first shunt part 20g-2 can include a first shunt bulk acoustic resonator 21-2 and a second shunt bulk acoustic resonator 22-2.

[0078] At least one of the plurality of series-connected bulk acoustic resonators 11, 12, 13, 14, 15, and 16 of the series part 10g can be electrically connected between the first shunt parts 20g-1 and 20g-2.

[0079] As the number of the plurality of first shunt bulk acoustic resonators 21-1 and 21-2 increases, the roll-off characteristic of the bulk acoustic resonator filter 50g can become sharp.

[0080] Referring to FIG. 1H The plurality of first shunt parts 20h-1 and 20h-2 of the first shunt part 20h of the bulk acoustic resonator filter 50h can each include an inductor 26-1 and 26-2 electrically connected in series to the second shunt bulk acoustic resonator 22-1 and 22-2, respectively.

[0081] The additional inductance due to the addition of the inductors 26-1 and 26-2 of the plurality of first shunt parts 20h-1 and 20h-2 can contribute to the resonance frequency of the plurality of first shunt parts 20h-1 and 20h-2 and substantially not contribute to the anti-resonance frequency of the plurality of first shunt parts 20h-1 and 20h-2. That is, the characteristic of the plurality of first shunt parts 20h-1 and 20h-2 having increased inductance can be similar to the characteristic due to the increase in k t 2 of the bulk acoustic resonator.

[0082] As k t 2 increases, the difference between the resonance frequency and the anti-resonance frequency of the plurality of first shunt parts 20h-1 and 20h-2 can be greater than the difference between the resonance frequency and the anti-resonance frequency of the plurality of second shunt parts 40-1, 40-2, 40-3, and 40-4 due to the increase in the difference between the resonance frequency and the anti-resonance frequency of the bulk acoustic resonator.

[0083] Since the difference between the resonance frequency and the anti-resonance frequency of the plurality of first shunt portions 20h-1 and 20h-2 is larger than the difference between the resonance frequency and the anti-resonance frequency of the plurality of second shunt portions 40-1, 40-2, 40-3, and 40-4, the division of the passband width can be compensated for when the difference between the resonance frequency and the anti-resonance frequency of the plurality of series bulk acoustic wave resonators 11, 12, 13, 14, 15, and 16 of the series portion 10h becomes too large. Thus, the passband width of the bulk acoustic wave resonator filter 50h can also be widened.

[0084] FIG. 2 is a diagram illustrating an attenuation pole formed by a first shunt bulk acoustic wave resonator and a second shunt bulk acoustic wave resonator connected in series through a bulk acoustic wave resonator filter according to an example.

[0085] Referring to FIG. 2 In the S parameter FS between the first port and the second port of the bulk acoustic wave resonator filter, a frequency range higher than the reference value REF can be a bandwidth of the bulk acoustic wave resonator filter, and a slope of a line starting from the lowest frequency BL and the highest frequency BH where the attenuation of the S parameter FS starts can be a roll-off characteristic of the bulk acoustic wave resonator filter.

[0086] The transmission zero pole formed by the first shunt bulk acoustic wave resonator and the second shunt bulk acoustic wave resonator of the first shunt portion can correspond to the attenuation poles FL and FH of the S parameter FS.

[0087] The attenuation poles FL and FH can make the slope of the line of the S parameter FS starting from the lowest frequency BL and the highest frequency BH steeper.

[0088] FIG. 3A and FIG. 3B is a diagram illustrating FIG. 1F is a graph illustrating the S parameter of the bulk acoustic wave resonator filter shown in

[0089] Referring to FIG. 3A The S parameter FSf between the first port and the second port of the bulk acoustic wave resonator filter can include the attenuation poles FLf and FHf, and a bandwidth of the bulk acoustic wave resonator filter can be formed to be about 0.14 GHz in width, with a center frequency at about 3.55 GHz. The lowest frequency of the bandwidth of the bulk acoustic wave resonator filter can be formed within 3.4 GHz to 3.6 GHz. In addition, the bandwidth of the passband between the first port and the second port can be 200 MHz or more, as an example.

[0090] FIG. 4A and FIG. 4B is a diagram illustrating a trench of a bulk acoustic wave resonator filter according to an example.

[0091] Referring to FIG. 4AThe bulk acoustic resonator included in the bulk acoustic resonator filter according to the example can be a film bulk acoustic resonator (FBAR) in which the cavity 112 is located between the substrate 110 and the resonator 135.

[0092] Referring to FIG. 4B The bulk acoustic resonator included in the bulk acoustic resonator filter according to the example can be a solidly mounted resonator (SMR) in which the support portion 123 is located between the substrate 110 and the resonator 135, in which the at least one insulating layer 121 and the at least one metal layer 122 are alternately stacked in the support portion 123.

[0093] Referring to FIG. 4A and FIG. 4B The bulk acoustic resonator can include the resonator 135, and further include the protective layer 170 and / or the metal layers 181 and 182, and the resonator 135 can be disposed above the substrate 110, the insulating layer 120, and the sacrificial layers 130a and 130b.

[0094] The resonator 135 can include the first electrode 140, the piezoelectric layer 150, and the second electrode 160. The first electrode 140 can be disposed above the substrate 110, the piezoelectric layer 150 can be disposed on an upper surface of the first electrode 140, and the second electrode 160 can be disposed on an upper surface of the piezoelectric layer 150.

[0095] The protective layer 170 can be disposed above the resonator 135, and the metal layers 181 and 182 can be disposed on an upper surface of the first electrode 140 or the second electrode 160, and can correspond to the connection nodes between the bulk acoustic resonators of the bulk acoustic resonator filter shown in FIG. 1A to FIG. 1H

[0096] Referring to FIG. 4A and FIG. 4B The series bulk acoustic resonator and / or the first shunt bulk acoustic resonator of the bulk acoustic resonator filter according to various examples can include a trench 164 formed on or above an upper surface of the second electrode 160 to be concave downward. For example, the trench 164 can have a form concave toward the piezoelectric layer 150 on the upper surface of the second electrode 160, and when viewed in the Z direction, the trench 164 can have a structure surrounding the center of the resonator 135.

[0097] Accordingly, since the attenuation pole shown in FIG. 3A can be formed more sharply, the S parameter in the attenuation pole can be greatly reduced, and the roll-off characteristic of the bulk acoustic resonator filter can be sharper.

[0098] FIG. 3B ​The plurality of curves of FIG. 10 represent S parameters in the vicinity of the lowest frequency of the bandwidth of the bulk acoustic wave resonator filter according to the presence or absence of a trench or the width of the trench in the first shunt bulk acoustic wave resonator of the first shunt section.

[0099] Referring to FIG. 3B When the first shunt bulk acoustic wave resonator of the first shunt section does not include a trench, the attenuation pole FSf-5 can be formed relatively blunt, but when the first shunt bulk acoustic wave resonator of the first shunt section includes a trench, the attenuation poles FSf-1, FSf-2, FSf-3, and FSf-4 can be formed relatively sharp.

[0100] The sharper the attenuation poles FSf-1, FSf-2, FSf-3, and FSf-4, the steeper the slope of the S parameters in the vicinity of the lowest frequency of the bandwidth of the bulk acoustic wave resonator filter.

[0101] Referring to FIG. 4A and FIG. 4B The width W1 of the trench 164 and the width and length of the resonator 135 can be appropriately designed. Referring to FIG. 3B , the sharpness of the attenuation poles FSf-1, FSf-2, FSf-3, and FSf-4 can vary according to the width of the trench.

[0102] The trench 164 can have a greater influence on admittance in a lower frequency range than in a frequency range higher than the resonance frequency of the bulk acoustic wave resonator (including the trench 164), and can reduce spurious noise in a frequency range lower than the resonance frequency of the acoustic wave resonator.

[0103] Since the lowest frequency of the bandwidth of the bulk acoustic wave resonator filter is lower than the relatively high resonance frequency of the series bulk acoustic wave resonator and / or the first shunt bulk acoustic wave resonator, the series bulk acoustic wave resonator and / or the first shunt bulk acoustic wave resonator can include the trench 164, so that spurious noise in the vicinity of the lowest frequency of the bandwidth can be reduced, and the attenuation poles can be made sharper. That is, the roll-off characteristics of the bulk acoustic wave resonator filter according to various examples of the disclosure can be sharper.

[0104] In addition, since the resonance frequency of the series bulk acoustic wave resonator and / or the resonance frequency of the first shunt bulk acoustic wave resonator can be lower than the highest frequency of the bandwidth, a frequency range lower than the resonance frequency of the series bulk acoustic wave resonator and / or the resonance frequency of the first shunt bulk acoustic wave resonator can belong to the bandwidth. Accordingly, spurious noise of the bandwidth can be reduced, and insertion loss and / or passband ripple characteristics of the bulk acoustic wave resonator filter according to various examples of the disclosure can also be reduced.

[0105] FIG. 3C is a graph showing the roll-off characteristics of the bulk acoustic wave resonator filter shown in FIG. 1F ​

[0106] Referring to FIG. 3C , in FIG. 3B , the slope (roll-off value) of the frequency range of 3.48 GHz to 3.50 GHz in the S parameter can vary depending on the trench width.

[0107] When the trench width is greater than or equal to 0.6 µm and less than or equal to 1.8 µm, the slope (roll-off value) can be the largest. That is, the series bulk acoustic wave resonator and / or the first shunt bulk acoustic wave resonator of the bulk acoustic wave resonator filter according to the example can include a trench having a width greater than or equal to 0.6 µm and less than or equal to 1.8 µm. Accordingly, the roll-off characteristic of the bulk acoustic wave resonator filter can be sharper.

[0108] Since FIG. 3B and FIG. 3C , the graph shows the S parameter in a state where A (the overlapping area of the first electrode, the piezoelectric layer, and the second electrode) is set to (70 µm) 2 , W / A can be greater than or equal to 0.6 / 4900 (µm / (µm 2 ) and less than or equal to 1.8 / 4900 (µm / (µm 2 ), where W FIG. 4A and FIG. 4B in W1) is the width of the trench. That is, the larger A is, the larger W can be.

[0109] In FIG. 3B , since the attenuation poles FSf-1, FSf-2, FSf-3, and FSf-4 are formed at 3.485 GHz, WxF can be greater than or equal to 0.6x3.485 (µm x GHz) and less than or equal to 1.8x3.485 (µm x GHz).

[0110] Here, F is the frequency of the attenuation pole, for example, F is the frequency of the attenuation pole corresponding to the lowest frequency of the passband between the first port P1 and the second port P2. That is, the higher F is, the smaller W can be. Accordingly, the roll-off characteristic of the bulk acoustic wave resonator filter can be sharper.

[0111] According to the design, referring to FIG. 4A and FIG. 4B , the second electrode 160 can include a frame 166 protruding upward on the upper surface of the second electrode 160. The width W1 of the trench 164 can be smaller than the width W2 of the frame 166. The width W1 of the trench 164 can be longer than the depth of the trench. The depth of the trench can be greater than 0 nm and less than or equal to 100 nm.

[0112] According to design, the shape of the cross section of the trench 164 can not be rectangular, and the width of the upper portion and the width of the lower portion of the trench 164 can be different from each other. Here, the width W1 of the trench 164 can be defined as an average of the width of the upper portion and the width of the lower portion of the trench 164, and can be defined as a value obtained by dividing the integral value of the width from the upper portion to the lower portion of the trench 164 by the height.

[0113] According to design, the second shunt bulk acoustic wave resonator of the bulk acoustic wave resonator filter can include a trench substantially the same as the trench 164 of the series bulk acoustic wave resonator and / or the first shunt bulk acoustic wave resonator, and can include a trench having a width different from the width W1 of the trench 164, or can not include a trench.

[0114] For example, the width W1 and the depth of the trench can be measured by analyzing the cross section of the bulk acoustic wave resonator using at least one of a transmission electron microscope (TEM), an atomic force microscope (AFM), and a surface profiler.

[0115] FIG. 5A is a plan view showing a detailed structure of a bulk acoustic wave resonator which can be included in a bulk acoustic wave resonator filter according to an example, FIG. 5B is a cross-sectional view taken along FIG. 5A line I-I' of FIG. 5C is a cross-sectional view taken along FIG. 5A line II-II' of FIG. 5D is a cross-sectional view taken along FIG. 5A line III-III' of

[0116] Referring to FIG. 5A to FIG. 5D , the bulk acoustic wave resonator 100 can include a support substrate 1110, an insulating layer 1115, a resonator 1120, and a hydrophobic layer 1130.

[0117] The support substrate 1110 can be a silicon substrate. For example, a silicon wafer can be used as the support substrate 1110, or a silicon-on-insulator (SOI) type substrate can be used.

[0118] The insulating layer 1115 can be disposed on the upper surface of the support substrate 1110 to electrically isolate the support substrate 1110 and the resonator 1120. In addition, when the cavity C is formed in the manufacturing process of the bulk acoustic wave resonator, the insulating layer 1115 prevents the support substrate 1110 from being etched by etching gas.

[0119] In this case, the insulating layer 1115 can be formed with at least one of silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3), and aluminum nitride (AlN), and can be formed by any one process of chemical vapor deposition, RF magnetron sputtering, and evaporation.

[0120] The support layer 1140 can be formed on the insulating layer 1115, and can be disposed around the cavity C and the etching stop portion 1145 in a form of surrounding the cavity C and the etching stop portion 1145 inside the support layer 1140.

[0121] The cavity C can be formed as an empty space, and can be formed by removing a portion of a sacrificial layer formed in a process of manufacturing the support layer 1140, and the support layer 1140 can be formed with a remaining portion of the sacrificial layer.

[0122] The support layer 1140 can be formed with a material that is easily etched, such as polysilicon or a polymer. However, the support layer 1140 is not limited to these materials.

[0123] The etching stop portion 1145 is disposed along a boundary of the cavity C. The etching stop portion 1145 is provided to prevent etching from being performed beyond a cavity region in a process of forming the cavity C.

[0124] The film layer 1150 is formed on the support layer 1140, and forms an upper surface of the cavity C. Accordingly, the film layer 1150 is also formed with a material that is not easily removed in a process of forming the cavity C.

[0125] For example, when a portion (e.g., a cavity region) of the support layer 1140 is removed using a halide-based etching gas such as fluorine (F), chlorine (Cl), or the like, the film layer 1150 can be made of a material that has a low reactivity with the etching gas. In this case, the film layer 1150 can include at least one of silicon dioxide (SiO2) and silicon nitride (Si3N4).

[0126] In addition, the film layer 1150 can be made of a dielectric layer including at least one material of magnesium oxide (MgO), zirconium dioxide (ZrO2), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium dioxide (HfO2), aluminum oxide (Al2O3), titanium dioxide (TiO2), and zinc oxide (ZnO), or a metal layer including at least one material of aluminum (Al), nickel (Ni), chromium (Cr), platinum (Pt), gallium (Ga), and hafnium (Hf). However, the configuration is not limited thereto.

[0127] The resonator 1120 includes a first electrode 1121, a piezoelectric layer 1123, and a second electrode 1125. The resonator 1120 is configured such that the first electrode 1121, the piezoelectric layer 1123, and the second electrode 1125 are sequentially stacked from the bottom. Accordingly, the piezoelectric layer 1123 in the resonator 1120 is disposed between the first electrode 1121 and the second electrode 1125.

[0128] Since the resonator 1120 is formed on the film layer 1150, the film layer 1150, the first electrode 1121, the piezoelectric layer 1123, and the second electrode 1125 are sequentially stacked on the support substrate 1110 to form the resonator 1120.

[0129] The resonator 1120 can resonate the piezoelectric layer 1123 according to a signal applied to the first electrode 1121 and the second electrode 1125 to generate a resonance frequency and an anti-resonance frequency.

[0130] The resonator 1120 can be divided into a central portion S in which the first electrode 1121, the piezoelectric layer 1123, and the second electrode 1125 are stacked to be substantially flat, and an extension portion E in which the interposition layer 1170 is interposed between the first electrode 1121 and the piezoelectric layer 1123.

[0131] The central portion S is a region disposed in the center of the resonator 1120, and the extension portion E is a region disposed along the periphery of the central portion S. Therefore, the extension portion E is a region extending outward from the central portion S, and refers to a region formed to have a continuous annular shape along the periphery of the central portion S. However, if necessary, the extension portion E can be configured to have a discontinuous annular shape in which some regions are disconnected.

[0132] Therefore, as FIG. 5B shown, in a cross section in which the resonator 1120 is cut, the extension portions E are respectively disposed at both ends of the central portion S. The interposition layer 1170 is disposed on both sides of the extension portions E disposed at both ends of the central portion S.

[0133] The interposition layer 1170 has an inclined surface L, and the thickness of a portion corresponding to the inclined surface L becomes large as the distance from the central portion S increases.

[0134] In the extension portion E, the piezoelectric layer 1123 and the second electrode 1125 are disposed on the interposition layer 1170. Therefore, the piezoelectric layer 1123 and the second electrode 1125 located in the extension portion E have an inclined surface corresponding to the shape of the interposition layer 1170.

[0135] The extension portion E included in the resonator 1120 is described, and thus resonance can also occur in the extension portion E. However, various examples are not limited thereto, and depending on the structure of the extension portion E, resonance can not occur in the extension portion E, but resonance can occur only in the central portion S.

[0136] The first electrode 1121 and the second electrode 1125 can be formed of a conductor, for example, can be formed of gold, molybdenum, ruthenium, iridium, aluminum, platinum, titanium, tungsten, palladium, tantalum, chromium, nickel, or a metal including at least one of them, but are not limited to these materials.

[0137] In the resonator 1120, the first electrode 1121 is formed to have an area larger than that of the second electrode 1125, and the first metal layer 1180 is provided on the first electrode 1121 along the outer circumference of the first electrode 1121. Therefore, the first metal layer 1180 may be provided to be spaced apart from the second electrode 1125 by a predetermined distance and may be provided in a form surrounding the resonator 1120.

[0138] Since the first electrode 1121 is provided on the membrane layer 1150 , the first electrode 1121 is formed to be completely flat. On the other hand, since the second electrode 1125 is provided on the piezoelectric layer 1123 , it can be formed to be curved corresponding to the shape of the piezoelectric layer 1123 .

[0139] The first electrode 1121 may function as any one of an input electrode for inputting an electrical signal such as a radio frequency (RF) signal and an output electrode for outputting an electrical signal such as a radio frequency (RF) signal.

[0140] The second electrode 1125 is provided in the entire central portion S and in a portion of the extension portion E. Therefore, the second electrode 1125 can be divided into a portion provided on the piezoelectric portion 1123 a of the piezoelectric layer 1123 (described later) and a portion provided on the bent portion 1123 b of the piezoelectric layer 1123 .

[0141] For example, the second electrode 1125 may be provided to cover the entire piezoelectric portion 1123a and a portion of the inclined portion 11231 of the piezoelectric layer 1123. FIG. 5D 1125a) in the resonator 1120 is formed to have an area smaller than the inclined surface of the inclined portion 11231, and the second electrode 1125 in the resonator 1120 is formed to have an area smaller than the area of ​​the piezoelectric layer 1123.

[0142] Therefore, if FIG. 5B As shown, in the cut cross section of the resonator 1120, the end portion of the second electrode 1125 is disposed in the extension E. In addition, at least a portion of the end portion of the second electrode 1125 disposed in the extension E is disposed so as to overlap with the insertion layer 1170. Here, "overlap" means that when the second electrode 1125 is projected onto a plane on which the insertion layer 1170 is disposed, the shape of the second electrode 1125 projected onto the plane overlaps with the insertion layer 1170.

[0143] The second electrode 1125 can function as any one of an input electrode for inputting an electrical signal such as a radio frequency (RF) signal and an output electrode for outputting an electrical signal such as a radio frequency (RF) signal. That is, when the first electrode 1121 functions as an input electrode, the second electrode 1125 can function as an output electrode, and when the first electrode 1121 functions as an output electrode, the second electrode 1125 can function as an input electrode.

[0144] As shown in FIG. 11B, when the end portion of the second electrode 1125 is located on the inclined portion 11231 of the piezoelectric layer 1123, since the local structure of the acoustic impedance of the resonator 1120 is formed in a sparse / dense / sparse / dense structure from the central portion S, a reflection interface that reflects a transverse wave to the inside of the resonator 1120 is increased. Thus, since most of the transverse waves cannot flow out from the resonator 1120 and are reflected and then propagated to the inside of the resonator 1120, the performance of the acoustic wave resonator can be improved. FIG. 5D

[0145] The piezoelectric layer 1123 is a portion that converts electrical energy into mechanical energy in the form of an elastic wave through a piezoelectric effect, and is formed on the first electrode 1121 and the interposer layer 1170.

[0146] Zinc oxide (ZnO), aluminum nitride (AlN), doped aluminum nitride, lead zirconate titanate, quartz, or the like can be selectively used as a material of the piezoelectric layer 1123. In the case of the doped aluminum nitride, a rare earth metal, a transition metal, or an alkaline earth metal can also be included. The rare earth metal can include at least one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). The transition metal can include at least one of hafnium (Hf), titanium (Ti), zirconium (Zr), tantalum (Ta), and niobium (Nb). Further, the alkaline earth metal can include magnesium (Mg).

[0147] In order to improve piezoelectric properties, when the content of the element doped into the aluminum nitride (AlN) is less than 0.1 at%, piezoelectric properties higher than those of the aluminum nitride (AlN) cannot be achieved. When the content of the element doped into the aluminum nitride (AlN) exceeds 30 at%, it is difficult to manufacture and to control the composition for deposition, and thus a non-uniform crystalline phase can be formed.

[0148] Thus, the content of the element doped into the aluminum nitride (AlN) can be in the range of 0.1 at% to 30 at%.

[0149] The piezoelectric layer 1123 can be formed with aluminum nitride (AlN) doped with scandium (Sc). In this case, the piezoelectric constant can be increased to increase the K t 2 .

[0150] ​The piezoelectric layer 1123 can include a piezoelectric portion 1123a disposed in the central portion S and a curved portion 1123b disposed in the extended portion E.

[0151] The piezoelectric portion 1123a is a portion directly stacked on the upper surface of the first electrode 1121. Thus, the piezoelectric portion 1123a is interposed between the first electrode 1121 and the second electrode 1125 to be formed together with the first electrode 1121 and the second electrode 1125 to have a flat shape.

[0152] The curved portion 1123b can be defined as a region extending outward from the piezoelectric portion 1123a and located in the extended portion E.

[0153] The curved portion 1123b is disposed on the insertion layer 1170 and is formed in a shape in which an upper surface of the curved portion 1123b is convex along the shape of the insertion layer 1170. Thus, the piezoelectric layer 1123 is curved at a boundary between the piezoelectric portion 1123a and the curved portion 1123b, and the curved portion 1123b is convex corresponding to the thickness and shape of the insertion layer 1170.

[0154] The curved portion 1123b can be divided into an inclined portion 11231 and an extended portion 11232. The inclined portion 11231 refers to a portion formed to be inclined along the inclined surface L of the insertion layer 1170. The extended portion 11232 refers to a portion extending outward from the inclined portion 11231. The inclined portion 11231 is formed to be parallel to the inclined surface L of the insertion layer 1170, and an inclined angle of the inclined portion 11231 can be formed to be the same as an inclined angle of the inclined surface L of the insertion layer 1170.

[0155] The insertion layer 1170 is disposed along a surface formed by the film layer 1150, the first electrode 1121, and the etching stop portion 1145. Thus, the insertion layer 1170 is partially disposed in the resonator 1120 and disposed between the first electrode 1121 and the piezoelectric layer 1123.

[0156] The insertion layer 1170 is disposed around the central portion S to support the curved portion 1123b of the piezoelectric layer 1123. Thus, the curved portion 1123b of the piezoelectric layer 1123 can be divided into the inclined portion 11231 and the extended portion 11232 according to the shape of the insertion layer 1170.

[0157] The insertion layer 1170 can be disposed in a region other than the central portion S. For example, the insertion layer 1170 can be disposed in the entire region other than the central portion S or in some regions on the support substrate 1110.

[0158] A portion of the insertion layer 1170 is formed to have a thickness that increases as the distance from the center portion S increases. Thus, the insertion layer 1170 has a side surface (inclined surface L) disposed adjacent to the center portion S, and the side surface of the insertion layer 1170 has a constant inclination angle θ.

[0159] When the inclination angle θ of the side surface of the insertion layer 1170 is formed to be less than 5°, in order to manufacture it, the thickness of the insertion layer 1170 is formed to be very thin, or the area of the inclined surface L is formed to be very large.

[0160] In addition, when the inclination angle θ of the side surface of the insertion layer 1170 is formed to be greater than 70°, the inclination angle of the piezoelectric layer 1123 or the second electrode 1125 stacked on the insertion layer 1170 is also formed to be greater than 70°. In this case, since the piezoelectric layer 1123 or the second electrode 1125 stacked on the inclined surface L is excessively bent, a crack can be generated in the bent portion.

[0161] Thus, the inclination angle θ of the inclined surface L can be formed in a range of equal to or greater than 5° and equal to or less than 70°.

[0162] In addition, the inclined portion 11231 of the piezoelectric layer 1123 is formed along the inclined surface L of the insertion layer 1170, and thus is formed to have the same inclination angle as the inclination angle of the inclined surface L of the insertion layer 1170. Thus, like the inclined surface L of the insertion layer 1170, the inclination angle of the inclined portion 11231 is also formed in a range of equal to or greater than 5° and equal to or less than 70°. This configuration can also be equally applied to the second electrode 1125 stacked on the inclined surface L of the insertion layer 1170.

[0163] The insertion layer 1170 can be formed using a dielectric material such as silicon dioxide (SiO2), aluminum nitride (AlN), aluminum oxide (Al2O3), silicon nitride (Si3N4), magnesium oxide (MgO), zirconium dioxide (ZrO2), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium dioxide (HfO2), titanium dioxide (TiO2), and zinc oxide (ZnO), but can be formed using a material different from that of the piezoelectric layer 1123.

[0164] In addition, the insertion layer 1170 can be implemented with a metallic material. When a bulk acoustic wave resonator is used for 5G communication, since a large amount of heat is generated from the resonator, it is necessary to smoothly release the heat generated from the resonator 1120. To this end, the insertion layer 1170 can be made of an aluminum alloy material containing scandium (Sc).

[0165] The resonator 1120 is disposed to be spaced apart from the support substrate 1110 by a cavity C formed as an empty space.

[0166] In the process of manufacturing the bulk acoustic wave resonator, the cavity C can be formed by supplying an etching gas (or etching solution) to the inlet hole (H) in the support layer 1140 to remove a portion of the support layer 1140. FIG. 5A

[0167] Accordingly, the cavity C consists of a top surface (upper surface) and a side surface (wall surface) formed by the film layer 1150 and a bottom surface of the cavity C formed by the support substrate 1110 or the insulating layer 1115. In addition, the film layer 1150 can be formed only on the top surface (upper surface) of the cavity C according to the order of the manufacturing method.

[0168] The protective layer 1160 is disposed along the surface of the bulk acoustic wave resonator 100 to protect the bulk acoustic wave resonator 100 from external influences. The protective layer 1160 can be disposed along the surface formed by the second electrode 1125 and the bent portion 1123b of the piezoelectric layer 1123.

[0169] The protective layer 1160 can be partially removed for frequency control in the final process during the manufacturing process. For example, the thickness of the protective layer 1160 can be controlled by frequency trimming during the manufacturing process.

[0170] To this end, the protective layer 1160 can include one of silicon dioxide (SiO2), silicon nitride (Si3N4), magnesium oxide (MgO), zirconium dioxide (ZrO2), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium dioxide (HfO2), aluminum oxide (Al2O3), titanium dioxide (TiO2), zinc oxide (ZnO), amorphous silicon (a-Si), and polycrystalline silicon (p-Si) suitable for frequency trimming, but is not limited thereto.

[0171] The first electrode 1121 and the second electrode 1125 can extend outward from the resonator 1120. In addition, the first metal layer 1180 and the second metal layer 1190 can be disposed on the upper surfaces of the extension portions E, respectively.

[0172] The first metal layer 1180 and the second metal layer 1190 can be made of any one material of gold (Au), a gold-tin (Au-Sn) alloy, copper (Cu), a copper-tin (Cu-Sn) alloy, aluminum (Al), or an aluminum alloy. Here, the aluminum alloy can be an aluminum-germanium (Al-Ge) alloy or an aluminum-scandium (Al-Sc) alloy.

[0173] The first metal layer 1180 and the second metal layer 1190 can serve as connection wiring that electrically connects the electrodes 1121 and 1125 of the bulk acoustic wave resonator to the electrodes of other bulk acoustic wave resonators disposed adjacent to each other.

[0174] ​At least a portion of the first metal layer 1180 can contact the protective layer 1160 and can be bonded to the first electrode 1121.

[0175] In addition, in the resonator 1120, the first electrode 1121 is formed to have a larger area than that of the second electrode 1125, and the first metal layer 1180 is formed on a peripheral portion of the first electrode 1121.

[0176] Accordingly, the first metal layer 1180 is disposed along the periphery of the resonator 1120, and thus is disposed in the form of surrounding the second electrode 1125. However, the configuration is not limited thereto.

[0177] In the bulk acoustic wave resonator, the hydrophobic layer 1130 can be disposed on a surface of the protective layer 1160 and on an inner wall of the cavity C.

[0178] When the bulk acoustic wave resonator is used in a humid environment or is left for a long time at room temperature, hydroxyl groups (OH groups) are adsorbed to the protective layer 1160 of the bulk acoustic wave resonator, and thus a problem in which frequency fluctuation increases due to mass loading or resonance performance deteriorates can occur.

[0179] For example, when the hydrophobic layer 1130 is not formed on the surface of the bulk acoustic wave resonator, hydroxyl groups (OH groups) can be more easily adsorbed to the protective layer 1160 to form hydroxylates. Since the hydroxylates have high surface energy and are unstable, it attempts to reduce the surface energy by adsorbing water or the like, resulting in mass loading.

[0180] On the other hand, when the hydrophobic layer 1130 is formed on the surface of the bulk acoustic wave resonator, since the surface energy is low and stable, there is no need to reduce the surface energy by adsorbing water, hydroxyl groups (OH groups), or the like. Accordingly, the hydrophobic layer 1130 can be used to suppress adsorption of water, hydroxyl groups (OH groups), or the like, thereby significantly reducing frequency fluctuation, and thus maintaining uniform resonator performance.

[0181] The hydrophobic layer 1130 can be formed using a self-assembled monolayer (SAM) rather than a polymer. When the hydrophobic layer 1130 is formed using a polymer, mass due to the polymer can affect the resonator 1120. However, in the bulk acoustic wave resonator, since the hydrophobic layer 1130 is formed using a self-assembled monolayer, frequency fluctuation of the bulk acoustic wave resonator can be significantly reduced. In addition, the thickness of the hydrophobic layer 1130 can be uniformly formed according to a position in the cavity C.

[0182] The hydrophobic layer 1130 can be formed by depositing a precursor having hydrophobicity by vapor deposition. In this case, the hydrophobic layer 1130 can be deposited to have a thickness of 1 nm or less (for example, several or less (for example, several to tens of The hydrophobic layer 1130 can be formed of a single layer having a thickness of 1 nm to 10 nm. As a precursor material having hydrophobicity, a material having a contact angle of 90° or more with water after deposition can be used. For example, the hydrophobic layer 1130 can include a fluorine (F) component, and can include fluorine (F) and silicon (Si). For example, a fluorocarbon having a silica head can be used, but the configuration is not limited thereto.

[0183] Further, in order to improve adhesion between the self-assembled monolayer constituting the hydrophobic layer 1130 and the protective layer 1160, a bonding layer (not shown) can be first formed on the surface of the protective layer 1160 before forming the hydrophobic layer 1130.

[0184] The bonding layer can be formed by vapor depositing a precursor having a hydrophobic functional group on the surface of the protective layer 1160. As a precursor material for depositing the bonding layer, a hydrocarbon having a silicon head or a siloxane having a silicon head can be used, but the configuration is not limited thereto.

[0185] Since the hydrophobic layer 1130 is formed after the first metal layer 1180 and the second metal layer 1190 are formed, the hydrophobic layer 1130 can be formed along the surface of the protective layer 1160, the surface of the first metal layer 1180, and the surface of the second metal layer 1190. In the drawing, an example in which the hydrophobic layer 1130 is not disposed on the surface of the first metal layer 1180 and the surface of the second metal layer 1190 is shown, but the configuration is not limited thereto. The hydrophobic layer 1130 can also be disposed on the surface of the first metal layer 1180 and the surface of the second metal layer 1190 as needed.

[0186] In addition, the hydrophobic layer 1130 can be disposed not only on the upper surface of the protective layer 1160 but also on the inner surface of the cavity C.

[0187] The hydrophobic layer 1130 formed in the cavity C can be formed on the entire inner wall forming the cavity C. Accordingly, the hydrophobic layer 1130 can also be formed on the lower surface of the film layer 1150 forming the lower surface of the resonator 1120.

[0188] In this case, adsorption of hydroxyl groups to the lower portion of the resonator 1120 can be suppressed.

[0189] Adsorption of hydroxyl groups can occur not only in the cavity C but also in the protective layer 1160. Accordingly, in order to minimize mass loading and a corresponding frequency drop due to adsorption of hydroxyl groups, it can be preferable to not only prevent adsorption of hydroxyl groups on the protective layer 1160 but also prevent adsorption of hydroxyl groups on the upper surface of the cavity C (the lower surface of the film layer), the lower surface of the resonator.

[0190] In addition, when the hydrophobic layer 1130 is formed on the upper surface / lower surface or side surface of the cavity C, the hydrophobic layer 1130 can also provide an effect of suppressing the occurrence of a sticking phenomenon in which the resonator 1120 adheres to the insulating layer 1115 due to surface tension in a wet process or a cleaning process after the cavity C is formed.

[0191] Further, a case in which the hydrophobic layer 1130 is formed on the entire inner wall of the cavity C is shown by way of example, but the configuration is not limited thereto, and various modifications can be made, such as forming the hydrophobic layer only on the upper surface of the cavity C, or forming the hydrophobic layer on at least a portion of the lower surface and side surface of the cavity C.

[0192] As described above, according to various examples of the present disclosure, in a bulk acoustic wave resonator, a sharper roll-off characteristic can be obtained.

[0193] However, various advantageous properties and effects of various examples are not limited to the above description, and will be more readily understood in the course of describing specific examples of the present disclosure.

[0194] While the present disclosure includes specific examples, it will be readily apparent to one of ordinary skill in the art that various modifications can be made in the form and details of these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects in each example are to be considered as being applicable to similar features or aspects in other examples. Suitable results can be achieved if the described techniques are performed in a different order, and / or if the described systems, architectures, devices, or circuits are combined in a different manner, and / or if the described components are replaced by other components or their equivalents. Thus, the scope of the present disclosure is not to be interpreted, in limiting, but rather in a generic sense. The scope of the disclosure, therefore, is to be interpreted only in accordance with the claims and their equivalents. All modifications available from the disclosure will be interpreted as being included in the present disclosure.

Claims

1. A bulk acoustic wave resonator filter, comprising: a series bulk acoustic wave resonator electrically connected in series between the first port and the second port; a second shunt BAW resonator, electrically connected between the series BAW resonator and ground, wherein the resonant frequency of the second shunt BAW resonator is lower than the resonant frequency of the series BAW resonator; as well as a first shunt BAW resonator electrically connected in series to the second shunt BAW resonator, and a resonant frequency of the first shunt BAW resonator being higher than the resonant frequency of the second shunt BAW resonator, Wherein, one or both of the series BAW resonator and the first shunt BAW resonator include: a first electrode disposed above the substrate; a piezoelectric layer, disposed on an upper surface of the first electrode; a second electrode disposed on an upper surface of the piezoelectric layer; and a groove provided in the upper surface of the second electrode or above the second electrode and recessed downward, The frequency of the attenuation pole corresponding to the lowest frequency of the passband between the first port and the second port is F, the width of the groove is W, and W×F is greater than or equal to 0.6×3.485 (μm×GHz) and less than or equal to 1.8×3.485 (μm×GHz).

2. The bulk acoustic wave resonator filter according to claim 1, wherein The first shunt bulk acoustic wave resonator includes the first electrode, the piezoelectric layer, the second electrode, and the groove.

3. The BAW resonator filter according to claim 2, wherein: The resonant frequency of the first shunt BAW resonator is equal to or higher than the resonant frequency of the series BAW resonator.

4. The BAW resonator filter according to claim 3, wherein: The trenches are respectively provided in the first shunt BAW resonator and the series BAW resonator.

5. The BAW resonator filter according to claim 2, wherein: The width of the groove is greater than or equal to 0.6 μm and less than or equal to 1.8 μm.

6. The BAW resonator filter according to claim 5, wherein: The depth of the trench is greater than 0 nm and less than or equal to 100 nm.

7. The BAW resonator filter according to claim 5, wherein: A bandwidth of a passband between the first port and the second port is 200 MHz or greater.

8. The BAW resonator filter according to claim 1, wherein The one or both of the series BAW resonator and the first shunt BAW resonator further include a hydrophobic layer formed over the second electrode.

9. The BAW resonator filter according to claim 2, wherein: The overlapping area of ​​the first electrode, the piezoelectric layer and the second electrode is A, the width of the groove is W, and W / A is greater than or equal to 0.6 / 4900 (μm / (μm) 2 ) and less than or equal to 1.8 / 4900(μm / (μm) 2 ).

10. The BAW resonator filter according to claim 1, wherein The groove is recessed in the upper surface of the second electrode toward the piezoelectric layer.

11. The BAW resonator filter according to claim 10, wherein: The second electrode includes a frame protruding upward on the upper surface of the second electrode, and Wherein, the width of the groove is smaller than the width of the frame.

12. The bulk acoustic wave resonator filter according to any one of claims 1 to 11, wherein: The second shunt BAW resonator includes a plurality of second shunt BAW resonators, each of which is disposed in a plurality of shunt connection paths between the series BAW resonator and the ground. wherein the first shunt bulk acoustic wave resonator is provided in a portion of the plurality of shunt connection paths, and A shunt connection path in which the first shunt bulk acoustic wave resonator is provided among the plurality of shunt connection paths is provided between a plurality of shunt connection paths in which the first shunt bulk acoustic wave resonator is not provided among the plurality of shunt connection paths.

13. The bulk acoustic wave resonator filter according to any one of claims 1 to 11, wherein: The second shunt BAW resonator includes a plurality of second shunt BAW resonators, each of which is disposed in a plurality of shunt connection paths between the series BAW resonator and the ground. wherein the first shunt BAW resonator comprises a plurality of first shunt BAW resonators, the plurality of first shunt BAW resonators being electrically connected in series to corresponding second shunt BAW resonators among the plurality of second shunt BAW resonators, and The number of the second plurality of split BAW resonators is greater than the number of the first plurality of split BAW resonators.

14. The BAW resonator filter according to claim 13, wherein: An inductance of at least one of the plurality of shunt connection paths, in which one of the plurality of first shunt bulk acoustic wave resonators is disposed, is greater than an inductance of each of the remaining shunt connection paths of the plurality of shunt connection paths.

15. The bulk acoustic wave resonator filter according to any one of claims 1 to 11, wherein: The first shunt BAW resonator includes the trench, the second shunt BAW resonator includes a trench, and a width of the trench of the second shunt BAW resonator is different from a width of the trench of the first shunt BAW resonator.

16. The bulk acoustic wave resonator filter according to any one of claims 1 to 11, wherein: The second shunt BAW resonator does not include a trench.

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