Thin film bulk acoustic resonator and thin film bulk acoustic resonator assembly

Abstract

Various exemplary embodiments relate to a scheme for a thin-film bulk acoustic resonator, the thin-film bulk acoustic resonator comprising: a substrate; at least three electrodes disposed above the substrate; and at least two piezoelectric layers disposed above the substrate, such that each piezoelectric layer is separated from the other piezoelectric layer by an electrode, such that one electrode is disposed below the piezoelectric layer and the other electrode is disposed above the piezoelectric layer. All odd-numbered electrodes are connected together to a first electrical port and have a first potential, and all even-numbered electrodes are connected together to a second electrical port and have a second potential, such that the electric field is oriented in opposite directions within two adjacent piezoelectric layers having the same polarization.

Description

Technical Field

[0001] Various exemplary embodiments generally relate to the field of resonators. Specifically, various exemplary embodiments generally relate to thin-film bulk acoustic resonators and thin-film bulk acoustic resonator assemblies. Background Technology

[0002] Film bulk acoustic wave resonators (FBARs) are a widely used technique for microacoustic filters operating below 2.5 GHz with relatively narrow passbands of 3% to 5%. However, this technique faces some challenges in meeting modern telephone specifications. For example, for high-frequency resonances (for sub-6 GHz bands, 5G Wi-Fi bands, and millimeter-wave bands, >5 GHz), the piezoelectric film needs to be very thin (100 nm to 200 nm). Simultaneously, thinner piezoelectric films are more fragile, resulting in greater acoustic loss and requiring relatively thicker electrodes. Furthermore, thinner electrodes inevitably have higher resistivity, thus generating more heat and reducing heat dissipation capacity.

[0003] Multilayer piezoelectric films with alternating polarities have been used to provide thicker films and higher operating frequencies. However, the fabrication and deposition of piezoelectric films with opposite polarities require high-precision machinery and precise control during the process. Summary of the Invention

[0004] This summary is provided to introduce, in a simplified form, some concepts further described in the following detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. Other implementations will be apparent from the dependent claims, the specification, and the drawings.

[0005] According to a first aspect, a thin-film bulk acoustic wave resonator is provided, comprising: a substrate; at least three electrodes disposed above the substrate; and at least two piezoelectric layers disposed above the substrate, such that each piezoelectric layer is separated from the other piezoelectric layer by an electrode, such that one electrode is disposed below the piezoelectric layer and the other electrode is disposed above the piezoelectric layer. All odd-numbered electrodes are connected together to a first electrical port and have a first potential, and all even-numbered electrodes are connected together to a second electrical port and have a second potential, such that the electric field is oriented in opposite directions within two adjacent piezoelectric layers having the same polarization. For example, this can achieve a scheme that uses piezoelectric layers with the same polarization to simplify device fabrication. Furthermore, the connection of the layers can reduce the resonator area. In addition, the multilayer structure including the metal layer is more robust and has higher heat dissipation capability.

[0006] According to one implementation of the first aspect, electrodes with the same potential are connected to corresponding ports via connection vias in at least two piezoelectric layers. For example, this can achieve a scheme utilizing techniques well-developed in the field of thin-film bulk acoustic resonators.

[0007] According to one implementation of the first aspect, electrodes with the same potential are connected via side electrode connections. For example, this can achieve a scheme that avoids penetrating the etched piezoelectric layer.

[0008] According to one implementation of the first aspect, the electrodes are arranged periodically, but connected in an interdigitated pattern. For example, this can achieve a scheme in which all layers operate efficiently in phase and provide essentially the same piezoelectric coupling as in a single layer. Individual resonators generated by the piezoelectric layers are connected in parallel here.

[0009] According to one implementation of the first aspect, the piezoelectric layer is an aluminum scandium nitride layer, an aluminum nitride layer, a zinc oxide layer, a lithium tantalate layer, or a lithium niobate layer. For example, this can achieve a scheme utilizing materials that provide the required piezoelectric coupling and ultimately provide the resonance-anti-resonance (R-aR) frequency gap necessary for passband filter design. At relatively low frequencies (e.g., 1 GHz), the parallel connection of the resonators can reduce the resonator area.

[0010] According to one implementation of the first aspect, at least three electrodes are alloys of metals such as Al, Mo, Pt, W or Cu, or include sublayers of these metals, and the electrode thickness is less than 20% of the thickness of a piezoelectric layer.

[0011] According to a second aspect, a thin-film bulk acoustic wave (TFT) resonator assembly is provided, comprising two TFT resonators according to the first aspect, wherein each TFT resonator includes two piezoelectric layers, wherein the two TFT resonators are connected in series such that the two TFT resonators share an intermediate electrode disposed between the two piezoelectric layers, wherein a first electrode above a substrate is separated into two electrically disconnected portions corresponding to the two TFT resonators, wherein the top piezoelectric layer has a groove in the middle, the width of the groove being approximately equal to its thickness, and the depth being 10% to 100% of its thickness. For example, this can achieve a scheme in which the impedance level of the resonator can be adjusted, and the power density in the resonator can be reduced to at most one-quarter of its previous value.

[0012] According to a third aspect, a thin-film bulk acoustic wave (TFT) resonator assembly is provided, comprising two TFT resonators according to claim 1, wherein each TFT resonator includes at least three piezoelectric layers, wherein electrodes having the same potential are connected via side electrode connections, and wherein the two TFT resonators are connected in series. For example, this can achieve a scheme in which the impedance level of the resonators can be adjusted and the power density in each resonator can be reduced.

[0013] According to a fourth aspect, an apparatus is provided that includes a thin-film bulk acoustic resonator according to the first aspect.

[0014] According to a fifth aspect, an apparatus is provided that includes a thin-film bulk acoustic resonator assembly according to a second or third aspect. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate exemplary embodiments and form part of this specification. These drawings depict exemplary embodiments and, together with the specification, help to explain them. In the drawings: Figure 1 An example of a multilayer film bulk acoustic resonator according to an exemplary embodiment is shown.

[0016] Figure 2 An example of a multilayer membrane bulk acoustic resonator according to another exemplary embodiment is shown.

[0017] Figure 3 An example of a multilayer film bulk acoustic resonator according to an exemplary embodiment is shown.

[0018] Figure 4A An example of a multilayer film bulk acoustic resonator according to an exemplary embodiment is shown.

[0019] Figure 4B An exemplary embodiment is shown. Figure 4A Simulation results of a multilayer film acoustic resonator.

[0020] Figure 5 An example of a multilayer membrane bulk acoustic resonator connected in series according to an exemplary embodiment is shown.

[0021] Figure 6 An example of the manufacturing process of a multilayer diaphragm bulk acoustic resonator according to an exemplary embodiment is shown.

[0022] Figure 7 Simulation results of two multilayer film bulk acoustic resonators according to an exemplary embodiment are shown.

[0023] Figure 8The results of a 2D finite element simulation of a finite-width multilayer membrane bulk acoustic resonator according to an exemplary embodiment are shown.

[0024] In the accompanying drawings, the same reference numerals are used to denote the same parts. Detailed Implementation

[0025] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below, in conjunction with the accompanying drawings, is intended to illustrate examples of the invention and is not intended to represent the only ways in which the examples of the invention can be constructed or utilized. The detailed description illustrates the functionality of the examples of the invention and the order of steps in constructing and operating the examples of the invention. However, the same or equivalent functionality and order can be implemented through different examples.

[0026] The various embodiments discussed below guide a thin-film bulk acoustic wave resonator, comprising: a substrate; at least three electrodes disposed above the substrate; and at least two piezoelectric layers disposed above the substrate, such that each piezoelectric layer is separated from the other piezoelectric layer by two electrodes, such that one electrode is disposed below the piezoelectric layer and the other electrode is disposed above the piezoelectric layer. All odd-numbered electrodes are connected together to a first electrical port and have a first potential, and all even-numbered electrodes are connected together to a second electrical port and have a second potential, such that the electric field is oriented in opposite directions within two adjacent piezoelectric layers having the same polarization. This achieves a scheme in which resonator fabrication becomes simpler because all piezoelectric layers have the same polarization. The connection of electrodes separating piezoelectric layers with the same orientation / polarity reverses the polarity of the electric field in subsequent layers and makes piezoelectric coupling as efficient as piezoelectric coupling in a single layer. Furthermore, the multilayer structure including electrodes is more robust and has higher heat dissipation capabilities.

[0027] Figure 1 An example of a multilayer film bulk acoustic resonator 100 according to an exemplary embodiment is shown. The resonator 100 includes three piezoelectric layers 106 disposed above a substrate 108 and separated from a first electrode 102 and a second electrode 104. The piezoelectric layers 106 are disposed above the substrate 108 such that each piezoelectric layer is separated from the other by an electrode, such that one electrode is disposed below the piezoelectric layer and the other electrode is disposed above the piezoelectric layer. For example, the piezoelectric layer 106 may be an aluminum scandium nitride layer, an aluminum nitride layer, a zinc oxide layer, a lithium tantalate layer, or a lithium niobate layer. The first electrode 102 is connected to each other through a first connection via 112. Similarly, the second electrode is connected to each other through a second connection via 114. The electrodes 102 and 104 may be alloys of metals such as Al, Mo, Pt, W, or Cu, or sublayers comprising these metals, with an electrode thickness less than 20% of the thickness of a single piezoelectric layer. For example, the substrate 108 may be a Si substrate or a SiC substrate.

[0028] Thickness of piezoelectric layer t It can be determined by the desired resonant frequency. F R It is determined, and is usually close to half the wavelength of the sound waves that bounce up and down in the layer: V is the velocity of bulk acoustic waves. Roughly estimated, for AlN, V = 7 km / s. For a 2 GHz device, there is a 1.75 μm thick piezoelectric layer. In reality, the presence of metal electrodes will reduce the frequency, and the interlayer interactions must be considered. Therefore, careful device design using software such as FEM is necessary to achieve the desired results. F R Piezoelectric coupling, static capacitance, impedance at resonance, and other parameters.

[0029] The first electrode 102 is connected together to the first electrical port 116 and has a first potential, and the second electrode 104 is connected together to the second electrical port 118 and has a second potential, such that the electric fields are oriented in opposite directions inside the two adjacent piezoelectric layers with the same polarization. Alternatively, the electrical port 118 can be connected to the top of the top piezoelectric layer 106 (…). Figure 1 The connection via 114 is shown in the figure. The opening 110 in the substrate 108 provides a resonator region for the resonator to avoid bulk wave radiation inside the substrate 108. Obviously, the number of layers can be increased, correspondingly increasing the top piezoelectric layer and electrodes, and alternatively, the electrodes can be connected to the terminals 110 and 118 (not shown in the figure) via correspondingly extended vias 112 and 114. Figure 1 (Not shown in the image). The piezoelectric layer 106 is shown as a planar film or plate, but in practice it is a deposited AlN (or AlScN) layer, and there will be no gaps between the layers, as shown in the image. Figure 2 As shown.

[0030] Figure 2 An example of a multilayer film bulk acoustic resonator 200 according to another exemplary embodiment is shown. The resonator 200 includes two piezoelectric layers 206 disposed above a substrate 208 and separated from a first electrode 202 and a second electrode 204. In other words, the piezoelectric layers 206 are disposed above the substrate 208 such that each piezoelectric layer is separated from the other by an electrode, such that one electrode is disposed below the piezoelectric layer and the other electrode is disposed above the piezoelectric layer. For example, the piezoelectric layer 206 may be an aluminum scandium nitride layer, an aluminum nitride layer, a zinc oxide layer, a lithium tantalate layer, or a lithium niobate layer. The first electrodes 202 are connected to each other via a connection via 216. Electrodes 202, 204 may be alloys of metals such as Al, Mo, Pt, W, or Cu, or sublayers comprising these metals, with an electrode thickness less than 20% of the thickness of one piezoelectric layer. For example, the substrate 208 may be a Si substrate or a SiC substrate.

[0031] The first electrode 202 is connected to the first electrical port 212 and has a first potential, and the second electrode 204 is connected to the second electrical port 214 and has a second potential, such that the electric field is oriented in opposite directions inside the two adjacent piezoelectric layers with the same polarization. The opening 210 in the substrate 208 provides the resonator region for the resonator.

[0032] Figure 3 An example of a multilayer film bulk acoustic resonator 300 according to an exemplary embodiment is shown. The resonator 300 includes three piezoelectric layers 306 disposed (i.e., provided) above a substrate 308 and separated from a first electrode 302 and a second electrode 304. In other words, the piezoelectric layers 306 are disposed above the substrate 308 such that an inner piezoelectric layer is separated from another piezoelectric layer by electrodes, such that one electrode is disposed below the piezoelectric layer and the other electrode is disposed above the piezoelectric layer. For example, the piezoelectric layer 306 may be an aluminum scandium nitride layer, an aluminum nitride layer, a zinc oxide layer, a lithium tantalate layer, or a lithium niobate layer. The first electrodes 302 are connected to each other on a first side by electrode connections. Similarly, the first electrodes 304 are connected to each other on a second side by electrode connections. Electrodes 302 and 304 may be alloys of metals such as Al, Mo, Pt, W, or Cu, or sublayers comprising these metals, with an electrode thickness less than 20% of the thickness of a piezoelectric layer. For example, the substrate 308 may be a Si substrate, a SiC substrate, or other high resistivity material.

[0033] The first electrode 302 is connected together to the first electrical port 312 and has a first potential, and the second electrode 304 is connected together to the second electrical port 314 and has a second potential, such that the electric field is oriented in opposite directions inside the two adjacent piezoelectric layers with the same polarization. The opening 310 in the substrate 308 provides the resonator region for the resonator.

[0034] Figure 4A An example of a multilayer film bulk acoustic resonator 400 according to another exemplary embodiment is shown. Figure 4A The resonator 400 shown is connected in series via an intermediate electrode 416. Figure 2 The combination of the two resonators 200 shown.

[0035] The resonator 400 includes two piezoelectric layers 406 disposed above a substrate 408 and separated from the first electrodes 402A, 402B and the intermediate electrode 416. In other words, the piezoelectric layers 406 are disposed above the substrate 408 such that each piezoelectric layer is separated from the other by an electrode, such that one electrode is disposed below the piezoelectric layer and the other electrode is disposed above the piezoelectric layer. In this example, the first electrodes 402A, 402B above the substrate 408 are separated into two electrically disconnected portions corresponding to the two resonators. For example, the piezoelectric layer 406 can be an aluminum scandium nitride layer, an aluminum nitride layer, a zinc oxide layer, a lithium tantalate layer, or a lithium niobate layer. The electrodes 402A, 402B, 416 can be alloys of metals such as Al, Mo, Pt, W, or Cu, or sublayers comprising these metals, with an electrode thickness less than 20% of the thickness of one piezoelectric layer. For example, the substrate 408 can be a Si substrate or a SiC substrate.

[0036] The first electrode 402A of the first resonator is connected to the first electrical port 412 via the side electrode 418 of the first resonator and has a first potential. The first electrode 402B of the second resonator is connected to the second electrical port 414 via the side electrode 420 of the second resonator and has a second potential, such that the electric field is oriented in opposite directions within the two adjacent piezoelectric layers with the same polarization. An opening 410 in the substrate 408 provides the resonator region for the resonator. The first electrodes 402A, 402B and the intermediate electrode 416 can be a first metal, and the first side electrode 418 and the second side electrode 420 can be a second metal. The second metal does not participate in the resonator oscillation; it only serves to reduce resistivity and can be quite thick, comparable to the thickness of the piezoelectric layer. The upper piezoelectric layer 406 can have a groove 404 in the middle, the width of which is comparable to its thickness, and the depth which is 10% to 100% of its thickness. Such a groove prevents the propagation of operating modes (e.g., A0, S0, SH0) along the structure, thereby reducing the number and amplitude of stray responses / resonances. In addition, the groove "liberates" the top of the piezoelectric layer to vibrate more freely, resulting in a certain increase in the piezoelectric coupling of the resonator (increase in R-aR).

[0037] In each resonator, the admittance is approximately doubled compared to a single-layer device with the same piezoelectric layer area, but due to the series connection of the resonators, the admittance is divided by 2. Therefore, Figure 4A The admittance of the resonator shown is roughly the same as that of a similar single-layer resonator. However, this series connection reduces the power density in the piezoelectric layer, decreasing heat generation to about one-quarter of its previous level, thereby correspondingly increasing the resonator's power handling capability.

[0038] Figure 4B An exemplary embodiment is shown. Figure 4ASimulation results for a multilayer film bulk acoustic resonator. The resonator consists of a double-layer stack with opposite polarities in an AlScN piezoelectric layer, t=500 nm, and a 100 nm thick Mo electrode. It is assumed that the groove etching depth in the top piezoelectric layer is 100% of the piezoelectric layer thickness. Figure 4B It shows Figure 4A Simulation results of the admittance and displacement distribution of a multilayer diaphragm bulk acoustic resonator at resonance 4.56 GHz. This resonator exhibits strong compressive coupling, with R-aR approximately 10%, making it suitable for the design of many RF filters in 5G mobile phones.

[0039] Figure 5 Examples of multilayer membrane acoustic resonators 500, 502, and 504 connected in series according to an exemplary embodiment are shown.

[0040] Figure 5 The exemplary embodiments shown include Figure 3 The three resonators shown are connected in series above the substrate 506.

[0041] As Figure 5 In summary of the exemplary embodiments shown, M multilayer resonators with N layers can be connected in series, which will cause the impedance of a single-layer resonator Y0 to change in the following proportion: Y = Y0 N / M. The power absorbed and the heat generated will be reduced to 1 / (N) of the previous value. M) (if the final admittance is equivalent to Y0).

[0042] Figure 6 An example of the manufacturing process of a multilayer film bulk acoustic resonator according to an exemplary embodiment is shown. In this example, the multilayer film bulk acoustic resonator corresponds to... Figure 3 The resonator shown in the figure.

[0043] At (a), the first Al electrode can be deposited on top of the SiC substrate.

[0044] At (b), the first piezoelectric layer of AlScN can be deposited and etched.

[0045] At (c), a second Al electrode can be deposited and etched.

[0046] At (d), a second piezoelectric layer of AlScN can be deposited and etched.

[0047] At (e), a third Al electrode can be deposited and etched.

[0048] At (f), a third piezoelectric layer of AlScN can be deposited and etched.

[0049] At (g), a fourth Al electrode can be deposited and etched.

[0050] An opening can be made in the substrate at (h).

[0051] The second metal deposition of the busbar (contact) Figure 6 It is not shown in the document.

[0052] Figure 7 The finite element (FEM) simulation results of two multilayer membrane bulk acoustic resonators according to an exemplary embodiment are shown. Figure 7 The piezoelectric coupling k of a resonator suitable for use in a mobile phone RF filter is shown. t 2 = Simulated excitation of resonance in bilayer and trilayer stacks of 20.3%. A 500 nm thick AlScN (Sc 30%) was used with a 100 nm Mo electrode of the same polarity. Due to the alternating direction of the electric field, the individual piezoelectric layers operate in phase, resulting in minimal stress on the interlayer Mo electrode. Figure 7 In the image, the short vertical arrow near the piezoelectric layer shown in the top section indicates the polarity of the piezoelectric layer.

[0053] Figure 8 2D simulation results of a finite-width multilayer film bulk acoustic resonator according to an exemplary embodiment are shown. In the simulation, k t 2 Approximately 20%. Despite the presence of Mo electrodes, the piezoelectric coupling is essentially the same as that in a monolayer resonator.

[0054] Any ranges or device values ​​given herein can be extended or changed without loss of the desired effect. Furthermore, unless expressly prohibited, any embodiment can be combined with other embodiments.

[0055] Although the subject matter has been described in specific language of structural features and / or actions, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are disclosed as examples of implementing the claims, and other equivalent features and actions are intended to be included within the scope of the claims.

[0056] It will be understood that the benefits and advantages described above may relate to one embodiment or several embodiments. The embodiments are not limited to embodiments that solve any or all of the described problems, nor are they limited to embodiments that have any or all of the described benefits and advantages. It will also be understood that a reference to "one" item may refer to a reference to one or more of these items.

[0057] The steps or operations of the methods described herein can be performed in any suitable order, or simultaneously where appropriate. Additionally, individual blocks can be removed from any of these methods without departing from the scope of the subject matter described herein. Aspects of any of the exemplary embodiments described above can be combined with aspects of any other exemplary embodiments described to form other exemplary embodiments without losing the desired effect.

[0058] The term “comprising” is used herein to mean including identified methods, blocks or elements, but such blocks or elements do not include an exclusive list, and methods or devices may include additional blocks or elements.

[0059] While an object may be referred to as the "first" object or the "second" object, this does not necessarily indicate any order or importance of the objects. Rather, such properties can simply be used to distinguish objects.

[0060] It will be understood that the above description is given by way of example only, and various modifications can be made by those skilled in the art. The foregoing specification, examples, and data provide a complete description of the structure and application of exemplary embodiments. Although various embodiments have been described above by way of a degree of specificity or in combination with one or more individual embodiments, those skilled in the art can make various modifications to the disclosed embodiments without departing from the scope of this specification.

Claims

1. A film bulk acoustic resonator, characterized by, include: Substrate; At least three electrodes are disposed above the substrate; At least two piezoelectric layers are disposed above the substrate, such that each piezoelectric layer is separated from the other piezoelectric layer by an electrode, such that one electrode is disposed below the piezoelectric layer and the other electrode is disposed above the piezoelectric layer; In this configuration, all odd-numbered electrodes are connected together to a first electrical port and have a first potential, while all even-numbered electrodes are connected together to a second electrical port and have a second potential, such that the electric field is oriented in opposite directions inside two adjacent piezoelectric layers with the same polarization.

2. The film bulk acoustic resonator of claim 1, wherein, Electrodes with the same potential are connected to the corresponding ports through connection vias in at least two piezoelectric layers.

3. The film bulk acoustic resonator of claim 1, wherein, Electrodes with the same potential are connected via side electrode connection.

4. The film bulk acoustic resonator of claim 3, wherein, The electrodes are arranged periodically, but connected in an interdigital pattern.

5. The thin-film bulk acoustic resonator according to any one of claims 1 to 4, characterized in that, The piezoelectric layer is an aluminum nitride scandium layer, an aluminum nitride layer, a zinc oxide layer, a lithium tantalate layer, or a lithium niobate layer.

6. The thin-film bulk acoustic resonator according to any one of claims 1 to 5, characterized in that, The at least three electrodes are alloys of metals such as Al, Mo, Pt, W or Cu, or include sublayers of these metals, and the electrode thickness is less than 20% of the thickness of a piezoelectric layer.

7. A thin-film bulk acoustic resonator assembly, characterized in that, include: According to claim 1, each of the two thin-film bulk acoustic resonators comprises two piezoelectric layers. The two thin-film bulk acoustic wave resonators are connected in series, so that the two thin-film bulk acoustic wave resonators share an intermediate electrode arranged between the two piezoelectric layers. The first electrode above the substrate is divided into two electrically disconnected portions corresponding to the two thin-film bulk acoustic resonators. The top piezoelectric layer has a groove in the middle, the width of which is equal to its thickness, and the depth is 10% to 100% of its thickness.

8. A thin-film bulk acoustic resonator assembly, characterized in that, include: According to claim 1, each of the two thin-film bulk acoustic resonators includes at least three piezoelectric layers, wherein electrodes having the same potential are connected by side electrode connections. The two thin-film bulk acoustic resonators are connected in series.

9. A device, characterized in that, Includes a thin-film bulk acoustic resonator according to any one of claims 1 to 6.

10. A device, characterized in that, Includes the thin-film bulk acoustic resonator assembly according to claim 7 or 8.

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