Bulk acoustic wave device with improved piezoelectric polarization uniformity

Abstract

The present disclosure relates to bulk acoustic wave (BAW) devices, in particular to the manufacturing of BAW devices. The present disclosure accordingly provides a BAW device and a method for manufacturing the BAW device, wherein the BAW device has an improved piezoelectric polarization uniformity. To this end, the BAW device (100) comprises one or more seed elements (105) arranged in a staggered layer (102) of the BAW device and in contact with a piezoelectric layer (103) provided on the staggered layer. The one or more seed elements (105) are arranged below an intermediate region, which is a region of the piezoelectric layer that is immediately adjacent to a resonator core region of the piezoelectric layer (103), the resonator core region being a region of the piezoelectric layer that is sandwiched between a first top electrode (106) and a first bottom electrode (104), the first top electrode and the first bottom electrode sandwiching at least a portion of the piezoelectric layer.

Description

Technical Field

[0001] This disclosure relates to bulk acoustic wave (BAW) devices, and more particularly to the fabrication of BAW devices. Accordingly, this disclosure provides a BAW device and a method for fabricating the BAW device, wherein the BAW device has improved piezoelectric polarization uniformity. The improved piezoelectric polarization uniformity is attributed to the piezoelectric layer of the BAW device, which has enhanced crystal quality, for example, exhibiting lower c-axis orientation disorder, particularly at locations between different BAW resonators of the BAW device. Background Technology

[0002] Acoustic devices are important components of modern electronic circuits. In particular, high-frequency selectivity requires high-quality factor mechanical resonators coupled in the filter topology while maintaining low electron insertion loss.

[0003] BAW resonators are configured to couple electrical time-varying signals to mechanical waves propagating within a piezoelectric bulk material; that is, BAW resonators are configured to couple electrical signals to the BAW. Traditional BAW resonators are manufactured using a thin piezoelectric layer, typically disposed on the reflecting element. In the case of a film bulk acoustic resonator (FBAR), the reflecting element is a cavity, while in the case of a solidly mounted acoustic resonator (SMR), the reflecting element is an acoustic mirror or a Bragg reflector comprising alternating layers of high and low acoustic impedance materials.

[0004] The fundamental vibrational mode that can be electromechanically coupled in a BAW resonator is the thickness-extensional (TE) mode. This mode is based on longitudinal waves propagating along the thickness direction of the thin piezoelectric material. In some cases, other types of piezoelectric materials can be used, in which case the fundamental vibrational mode can also be the thickness-shear (TS) mode. That is, the roles of TE and TS can be interchanged depending on the core vibrational mode of the selected piezoelectric material.

[0005] To obtain high-quality electrical signals, the mechanical resonance generated within a BAW resonator should be as efficient as possible and should produce minimal mechanical losses. Mechanical losses in a BAW resonator are primarily caused by the acoustic radiation of mechanical energy, for example, through reflective elements such as Bragg reflectors, into the substrate. Other pathways contributing to mechanical losses include energy radiation and scattering at the edges of the BAW resonator or at other locations where Bragg reflectors or similar reflective elements are absent.

[0006] Furthermore, poor growth of piezoelectric materials can increase acoustic losses due to wave scattering caused by multiple domains or grain boundaries within the piezoelectric material itself. Thermoelastic damping may also be a significant source of mechanical losses in BAW resonators, which is also caused by poor piezoelectric crystal growth.

[0007] Therefore, high-quality piezoelectric growth is typically required to improve the mechanical quality factor of BAW resonators and the piezoelectric coupling strength between two or more BAW resonators (which ultimately affects the achievable filter bandwidth).

[0008] As the number of filters and devices in the front-end module increases, stricter requirements are placed on the overall implementation size of the filters. Therefore, it is also necessary to reduce the planar area of ​​the BAW resonators and the distance between them. However, as the spacing between different BAW resonators decreases, any small change in the crystal orientation and c-axis orientation of the piezoelectric material will negatively impact the overall performance of the BAW device. In fact, the c-axis of the piezoelectric layer may require a limited horizontal distance to realign it correctly with the vertical axis. Dead zones where the c-axis cannot be correctly oriented can ultimately degrade the performance of the BAW device.

[0009] To date, some of these problems have been solved using the following methods:

[0010] One approach involves selecting the smoothest possible bottom electrode and edge shape for an exemplary BAW resonator, avoiding sharp edges and creating a sloping profile. However, a drawback is the need for a highly optimized bottom electrode etching scheme, which increases the overall device cost. Furthermore, even with large electrode sloping angles, there is always a risk of cracking and strong grain boundaries forming at these edges.

[0011] In another approach, the exemplary BAW resonators are spaced sufficiently large to avoid any effects of misaligned piezoelectricity on the edges. However, a drawback is that this approach is not suitable for ultra-compact filter topologies to avoid the effects of closely adjacent resonators. Another drawback is the lack of a definitive method to simulate the effects of various polarization directions of piezoelectricity at device edges, such as effects on electrostatics, mechanics, etc. Summary of the Invention

[0012] In view of the above-mentioned problems and disadvantages, embodiments of the present invention aim to improve conventional BAW devices, particularly the methods described above and exemplary BAW resonators. One objective is to improve the crystallinity quality of the piezoelectric material in the BAW device to improve polarization quality, i.e., enhance piezoelectric polarization uniformity. Specifically, the quality of the piezoelectric material located between different BAW resonators should be improved. For this purpose, higher quality piezoelectric material growth is required. Therefore, this is geared towards large-scale piezoelectric electromechanical coupling patterns.

[0013] For embodiments of the present invention, a particular problem considered by the inventors is that the deposition of the piezoelectric layer, and the quality of the piezoelectric material produced at the edge of the BAW resonator (region), is highly dependent on the edge termination seed layer or substrate on which the piezoelectric material is deposited, i.e., dependent on the type of material beneath the piezoelectric layer in the BAW device.

[0014] In particular, embodiments of the present invention address the specific problems mentioned above regarding the seed layer beneath the piezoelectric material.

[0015] A first aspect of this disclosure provides a BAW device comprising: a substrate; an interleaved layer disposed on the substrate; a piezoelectric layer disposed on the interleaved layer and configured to propagate BAW; a first top electrode and a first bottom electrode sandwiching at least a portion of the piezoelectric layer between them to form a first BAW resonator, wherein the first BAW resonator includes a first resonator core region, the first resonator core region being a region of the piezoelectric layer located between the first top electrode and the first bottom electrode, and wherein the first bottom electrode is disposed in the interleaved layer or in a piezoelectric layer in contact with the interleaved layer; and one or more seed elements disposed in the interleaved layer and in contact with the piezoelectric layer, wherein the one or more seed elements are disposed below an intermediate region, the intermediate region being a region of the piezoelectric layer immediately adjacent to the first resonator core region.

[0016] The one or more seed elements in contact with the piezoelectric layer (i.e., the piezoelectric layer can be deposited on one or more seed elements during the fabrication of the BAW device) help improve the quality of the piezoelectric layer (in particular, they can promote single crystal growth), thereby helping to improve the polarization uniformity of the piezoelectric material, i.e., the polarization uniformity of the piezoelectric layer. Therefore, an improved BAW device is provided because the aforementioned problems are alleviated.

[0017] The selection of an appropriate seed layer beneath the piezoelectric layer (particularly the selection of one or more seed elements) can depend on the crystal structure of the piezoelectric material chosen as the core material for the BAW resonator. During thin film deposition, preferably, there is an appropriate match between the atomic, ionic, and molecular arrangements of the seed layer and the piezoelectric layer to achieve the best possible crystal growth. In particular, the selection of the seed layer can promote single-crystal, near-perfect c-axis growth of the thin-film piezoelectric layer.

[0018] In one embodiment of the first aspect, the BAW device further includes: a second top electrode and a second bottom electrode, sandwiching at least a portion of the piezoelectric layer between them to form a second BAW resonator, wherein the second BAW resonator includes a second resonator core region, which is a region of the piezoelectric layer located between the second top electrode and the second bottom electrode, wherein the second bottom electrode is disposed in or in a piezoelectric layer in contact with the interleaved layer; and wherein at least one of one or more seed elements is arranged below a portion of the intermediate region located between the first resonator core region and the second resonator core region.

[0019] Therefore, in particular, the quality of the piezoelectric material between the first and second BAW resonators is improved by using one or more seed elements. Thus, large-scale piezoelectric coupling patterns can be realized.

[0020] In one embodiment of the first aspect, the first and / or second bottom electrodes are disposed in the interleaved layer and are at the same level as the one or more seed elements.

[0021] The first and / or second bottom electrodes and the one or more seed elements can be formed in the same layer of the BAW device, and / or can be formed in the same process during the fabrication of the BAW device. During the fabrication of the BAW device, the bottom electrodes and seed elements can respectively provide seeds / promote the growth of the piezoelectric layer. This improves the quality of the piezoelectric layer, particularly the uniformity of piezoelectric polarization.

[0022] In one embodiment of the first aspect, the first and / or second bottom electrodes have the same layer structure as the one or more seed elements.

[0023] This allows for improvements in the quality of the piezoelectric layer, particularly in the uniformity of piezoelectric polarization, because the same or at least very similar seeds are provided to the piezoelectric layer by the bottom electrode and the seed element, respectively.

[0024] In one embodiment of the first aspect, the first and / or second bottom electrode and each of the one or more seed elements include one or more metal layers, and include a seed layer disposed on the one or more metal layers and in contact with the piezoelectric layer.

[0025] In one embodiment of the first aspect, the one or more seed elements include two or more seed elements placed one after another in a direction away from the first bottom electrode and / or the second bottom electrode.

[0026] Therefore, larger piezoelectric layers can improve quality, thereby achieving consistent piezoelectric polarization uniformity on BAW devices.

[0027] In one embodiment of the first aspect, the one or more seed elements comprise two or more seed elements placed one after another along one or more side edges of the first BAW resonator and / or the second BAW resonator.

[0028] Therefore, the piezoelectric layer along and / or around one or more or each BAW resonator of the BAW device can be improved.

[0029] In one embodiment of the first aspect, the one or more seed elements comprise a first periodic arrangement of two or more seed elements.

[0030] In one embodiment of the first aspect, the one or more seed elements include a second periodic arrangement of two or more seed elements, and the first periodic arrangement and the second periodic arrangement differ from each other in one or more of the following characteristics: the shape of the seed elements, the size of the seed elements, the spacing between adjacent seed elements, the layer stacking of the seed elements, and the material properties of the seed elements.

[0031] In one embodiment of the first aspect, the one or more seed elements include at least two seed elements of the same shape and / or size; and / or, the one or more seed elements include at least two seed elements of different shapes and / or sizes.

[0032] In one embodiment of the first aspect, in a top view of the BAW device, the intermediate region is arranged adjacent to the first top electrode and / or the second top electrode; and / or the intermediate region surrounds the first top electrode and / or the second top electrode.

[0033] In one embodiment of the first aspect, each of one or more seed elements is at least laterally spaced from the first bottom electrode and / or the second bottom electrode by a minimum distance.

[0034] Therefore, one or more seed elements will not interfere with the bottom electrode, and thus will not interfere with the performance of the corresponding BAW resonator. At the same time, one or more seed elements will improve the quality of the piezoelectric layer adjacent to the BAW resonator and between different BAW resonators.

[0035] In one embodiment of the first aspect, the piezoelectric layer has a free upper surface in the intermediate region.

[0036] In one embodiment of the first aspect, the BAW device further includes an acoustic reflection element located below the first and / or second top electrode, the piezoelectric layer, and the first and / or second bottom electrode.

[0037] This minimizes acoustic losses, especially acoustic losses to the substrate.

[0038] In one embodiment of the first aspect, the acoustic reflecting element includes a plurality of higher and lower acoustic impedance layers forming a Bragg mirror structure; and / or, the acoustic reflecting element includes a plurality of higher and lower dielectric constant layers forming a Bragg mirror structure.

[0039] For example, in the case where the BAW device is an SMR device (i.e., comprising one or more SMRs), the interleaved layer can be a region in which lower and higher refractive index materials are deposited, to form, for example, below the reflective element below the BAW resonator. In that case, the interleaved layer can be formed of a lower refractive index material.

[0040] In one embodiment of the first aspect, the one or more seed elements are disposed on the Bragg reflector structure.

[0041] In one embodiment of the first aspect, the Bragg reflector structure consists of staggered layers and multiple Bragg layers, with one Bragg layer arranged on top of another in the staggered layers.

[0042] In one embodiment of the first aspect, the interleaved layer comprises silicon oxide (SiO2) and the Bragg layer comprises a material having a higher acoustic impedance than silicon oxide (SiO2).

[0043] In one embodiment of the first aspect, the piezoelectric layer comprises AlN, or AlN with additional rare earth doping, particularly AlN with additional scandium (Sc) doping.

[0044] In one embodiment of the first aspect, at least one of the one or more seed elements comprises platinum (Pt).

[0045] In one embodiment of the first aspect, the first and / or second bottom electrodes comprise at least one of tungsten (W), molybdenum (Mo), and aluminum (Al).

[0046] A second aspect of the invention provides a method for manufacturing a BAW device, the method comprising: forming a substrate; forming an interleaved layer on the substrate; forming one or more seed elements disposed in the interleaved layer; forming a piezoelectric layer on the interleaved layer and the one or more seed elements, respectively; forming a first bottom electrode in the interleaved layer or in the piezoelectric layer in contact with the interleaved layer; forming a first top electrode on the piezoelectric layer, wherein the first top electrode and the first bottom electrode sandwich at least a portion of the piezoelectric layer to form a first BAW resonator, the first BAW resonator including a first resonator core region, the first resonator core region being a region of the piezoelectric layer located between the first top electrode and the first bottom electrode; wherein the one or more seed elements are in contact with the piezoelectric layer, and wherein the one or more seed elements are disposed below an intermediate region, the intermediate region being a region of the piezoelectric layer immediately adjacent to the first resonator core region.

[0047] In one embodiment of the second aspect, the piezoelectric layer is grown simultaneously on the interleaved layer and the one or more seed elements, for example by sputtering, epitaxy, or vapor deposition.

[0048] In one embodiment of the second aspect, the first bottom electrode and the one or more seed elements are formed in the same one or more process steps of the method.

[0049] In one embodiment of the second aspect, the first bottom electrode and the one or more seed elements comprise the same seed layer that provides seeds for the growth of the piezoelectric layer.

[0050] The second aspect of the method can also have other embodiments that produce the BAW device of the first aspect. Therefore, the second aspect of the method provides at least the same advantages as the BAW device of the first aspect.

[0051] The foregoing aspects and embodiments (of the invention) enable the creation of (more) smooth piezoelectric c-axis growth using one or more seed elements, particularly at the edges of the BAW resonators, which can be embedded with the same layer as the bottom electrodes of one or more BAW resonators in the BAW device. Therefore, a high-quality seed layer (provided by one or more seed elements) can be used adjacent to and / or between the BAW resonators, this high-quality seed layer being the same as the piezoelectric material used to deposit on the bottom electrodes of these BAW resonators in the BAW device. Some advantageous features may include:

[0052] One of the multiple seed elements can be deposited at a given distance from the edge of the BAW resonator.

[0053] • The material of one or more seed elements used to provide seeds for the piezoelectric layer in the intermediate region can be the same as the material used for the bottom electrode used to provide seeds for the piezoelectric layer in the core region of the resonator.

[0054] • The distance between one or more seed elements and the bottom electrode can be optimized to promote the best quality of piezoelectric layer polarization (uniformity).

[0055] • The same (patterned) one or more seed elements can be used between two or more adjacent BAW resonators in a filter configuration.

[0056] • A periodic repeating structure with multiple seed elements, for example, with different sizes and repeating spacing, can be used to further promote polarization uniformity in the piezoelectric layer.

[0057] • The bandgap effect generated by repeating seed elements can be used to further enhance the mechanics at the edges of the BAW resonator.

[0058] It should be noted that all devices, elements, units, and means described in this application can be implemented by software or hardware elements or any combination thereof. All steps performed by the various entities described in this application, and the functions described as being performed by the various entities, are intended to indicate that the various entities are suitable for or configured to perform the various steps and functions. In the following description of specific embodiments, even if a particular function or step performed by an external entity is not reflected in the description of the elements of the specific detailed description of the entity performing that particular step or function, it should be understood by those skilled in the art that these methods and functions can be implemented in their respective software or hardware elements or any combination thereof. Attached Figure Description

[0059] The above aspects and implementation methods will be described in conjunction with the accompanying drawings in the following detailed description of specific embodiments, wherein...

[0060] Figures 1(a) and 1(b) show the piezoelectric c-axis of an exemplary BAW resonator and illustrate possible polarization direction disturbances in this exemplary BAW resonator.

[0061] Figure 2 An exemplary BAW device is shown.

[0062] Figure 3 A BAW device according to an embodiment of the present invention is shown.

[0063] Figure 4 An example of a seed element for a BAW device according to an embodiment of the present invention is shown.

[0064] Figure 5 An example of a seed element for a BAW device according to an embodiment of the present invention is shown.

[0065] Figure 6 An example of a seed element for a BAW device according to an embodiment of the present invention is shown.

[0066] Figure 7 A BAW device according to an embodiment of the present invention is shown.

[0067] Figure 8 A BAW device according to an embodiment of the present invention is shown.

[0068] Figure 9 A BAW device according to an embodiment of the present invention is shown.

[0069] Figure 10 A BAW device according to an embodiment of the present invention is shown.

[0070] Figure 11A BAW device according to an embodiment of the present invention is shown.

[0071] Figure 12 A BAW device according to an embodiment of the present invention is shown.

[0072] Figures 13(a) to 13(d) A comparison between a BAW device according to an embodiment of the present invention and an exemplary BAW device is shown.

[0073] Figures 14(a) to 14(d) A BAW device according to an embodiment of the present invention is shown.

[0074] Figures 15(a) to 15(d) A BAW device according to an embodiment of the present invention is shown.

[0075] Figures 16(a) to 16(d) A BAW device according to an embodiment of the present invention is shown.

[0076] Figure 17 A method according to an embodiment of the present invention is shown. Specific Implementation

[0077] Figures 1(a) and 1(b) illustrate the piezoelectric c-axis of an exemplary BAW resonator and demonstrate polarization orientation disorder in an example of a BAW resonator. Specifically, Figure 1(a) shows how the polarization vector direction (indicated by the arrows) would ideally align with an external electric field, such as the one established between the top and bottom electrodes of the exemplary BAW resonator. However, Figure 1(b) illustrates a c-axis orientation disorder that frequently occurs in exemplary BAW resonators, where the polarization vector direction is not well aligned with the external electric field. This typically occurs next to a BAW resonator or between two BAW resonators in a conventional BAW device, particularly when there is no bottom electrode. This is because the bottom electrode typically includes a seed layer that promotes high-quality piezoelectric layers deposited thereon.

[0078] The electromechanical efficiency of any BAW device is related to the collinearity of piezoelectric polarization and electric field. Variations in the polarization vector direction (i.e., polarization direction disorder) can be caused by multidomains or grain boundaries and reduce the achievable electromechanical coupling (kt2).

[0079] Figure 2 A cross-sectional view of an example BAW device including a BAW resonator is shown, which is formed by a top electrode and a bottom electrode sandwiching at least a portion of a piezoelectric layer between them. The BAW resonator includes a resonator core region, which is the area of ​​the piezoelectric layer located between the top and bottom electrodes of the BAW resonator. Figure 2The BAW device is further shown to include a Bragg reflector formed by Bragg layer 1 and Bragg layer 2 embedded with interlaced layers, which serves as a reflective element arranged between the resonator core region and the substrate (body).

[0080] Figure 2 The diagram also illustrates that the bottom electrode may include a seed layer on which a piezoelectric layer is formed. In this example, the bottom electrode includes two metal layers, metal layer 1 and metal layer 2, and a seed layer disposed on the metal layers. The seed layer typically results in the deposition of a piezoelectric layer of acceptable or good quality, thus causing the polarization vector direction to be acceptablely or well aligned with the external electric field established between the top and bottom electrodes.

[0081] However, Figure 2 A region of disordered polarization orientation (dashed box) is also shown, in which a piezoelectric layer is deposited directly on an interleaved layer, and where the piezoelectric layer has a free upper surface. In this region of disordered orientation, the deposition of the piezoelectric layer typically results in poor quality of the piezoelectric material, leading to disordered polarization vector orientation. In particular, piezoelectric layers that can be grown on interleaved layers can have a non-uniform polarization vector distribution.

[0082] Figure 3 A BAW device 100 according to an embodiment of the present invention is shown, which solves the problem regarding Figure 2 The example BAW device describes the defects.

[0083] BAW device 100 includes a body or substrate 101 (e.g., including silicon or silicon-based materials) and an interleaved layer 102 (e.g., including a silicon oxide layer) disposed on the substrate 101. Furthermore, a piezoelectric layer 103 is disposed on the interleaved layer 102. The piezoelectric layer 103 is configured to propagate BAW. A first top electrode 106 and a first bottom electrode 104 are provided, and at least a portion of the piezoelectric layer 103 is sandwiched therebetween; that is, the first top electrode 106 and the first bottom electrode 104 sandwich the piezoelectric layer 103 in a region of the BAW device 100 to form a first BAW resonator. The first BAW resonator includes a first resonator core region, which is the region of the piezoelectric layer 103 located between the first top electrode 106 and the first bottom electrode 104.

[0084] In BAW device 100, the first bottom electrode 104 may be disposed in the interleaved layer 102 (as shown in Figures 1(a) and 1(b)) or may be disposed in the piezoelectric layer 103 in contact with the interleaved layer 102 (alternatively, not shown in Figures 1(a) and 1(b)). Furthermore, BAW device 200 includes one or more seed elements 105 (one shown in Figures 1(a) and 1(b)) disposed in the interleaved layer 102 and in contact with the piezoelectric layer 103. This means that the piezoelectric layer 103 is disposed on one or more seed elements 105. For example, during the fabrication of BAW device 100, the piezoelectric layer 102 may be deposited on / above one or more seed elements 105. It is noteworthy that if the first bottom electrode 104 is located in the interleaved layer 102 (as shown in Figures 1(a) and 1(b)), the piezoelectric layer 103 may also, for example, be deposited simultaneously on or above the first bottom electrode 104. One or more seed elements 105 are disposed below an intermediate region, which is the region of the piezoelectric layer 103 located next to the core region of the first resonator. The one or more seed elements 105 improve the quality of the piezoelectric layer 103 in the intermediate region, thereby enhancing polarization uniformity. That is, the piezoelectric layer 103 deposited (e.g., grown) on the one or more seed elements 105 can have, for example... Figure 2 The piezoelectric layer shown has a more uniform polarization vector distribution grown on the staggered layer of the exemplary BAW device.

[0085] The BAW device 100 may also include an acoustic reflection element located below the first top electrode 106, the piezoelectric layer 103, and the first bottom electrode 104.

[0086] Figure 4 A cross-sectional view of an example seed element 105 that can be used in a BAW device 100 according to an embodiment of the present invention is shown. This example illustrates a simple seed element 105, which can be formed from material elements (e.g., including a single material), wherein the seed element 105 is embedded in an interleaved layer 102. During the fabrication of the BAW device 100, the material of the seed element 105 can be specifically selected to promote single-crystal growth of the piezoelectric material deposited thereon. Figure 4 A portion of the BAW device 100 shown can be considered a "unit cell" that can be repeated once or multiple times along one or more directions of the BAW device 100 to form one or more arrangements of, for example, a plurality of seed elements 105, such as a periodic arrangement. Thus, each seed element 105 can be identical, or it can differ from another seed element in one or more of the following aspects: size, shape, material composition, number of material layers, width, thickness (i.e., height), or, in general, differ in one or more structural parameters.

[0087] Figure 5 With Figure 4 A similar manner is illustrated in the cross-sectional view of another example seed element 105 that can be used in a BAW device 100 according to an embodiment of the present invention. Again, the seed element 105 can be considered a "unit cell" and can be repeated once or multiple times as described above to form an arrangement or structure comprising a plurality of seed elements 105. Figure 5 In this embodiment, the seed element 105 includes two metal layers 105b and 105c, and includes a seed layer 105a as the top layer, i.e., the seed layer 105a is a layer on which the piezoelectric layer 103 is disposed. Typically, the seed element 105 may include one or more metal layers 105b and 105c, and the seed layer 105a may be disposed on one or more metal layers 105b and 105c, wherein the seed layer 105a is in contact with the piezoelectric layer 103.

[0088] Figure 6 A cross-sectional view of another example seed element 105 forming a "unit cell" is shown, which is built on Figure 5 Based on the example shown, and applicable to BAW device 100 according to embodiments of the present invention. In this example, the "unit cell" also includes a Bragg layer 600 embedded in the interlaced layer 102. The "unit cell" of BAW device 100 is as follows: Figure 5 As shown, or as Figure 6 The location of one or more seed elements 105 within the BAW device 100 may vary depending on their arrangement. Typically, the Bragg reflector structure (as an acoustic reflector) may be formed from an interlaced layer 102 and multiple Bragg layers 600 (e.g., two Bragg layers 600), wherein the Bragg layers 600 may be arranged one on top of the other within the interlaced layer 102.

[0089] Figure 7 A cross-sectional view of a BAW device 100 according to an embodiment of the present invention is shown, which is based on Figure 3 Based on the illustrated embodiment. In particular, Figure 7 The BAW device 100 shown includes one or more according to, as Figure 5 Seed element 105 of the “unit cell” shown. One of one or more seed elements 105 is shown next to the first bottom electrode 104, that is, below the middle region of the piezoelectric layer 103 (immediately adjacent to the resonator core region of the BAW resonator shown).

[0090] exist Figure 7In the BAW device 100 shown, at least one of the first bottom electrode 104 and one or more seed elements 105 includes one or more metal layers 104b, 104c, 105b, 105c, and each includes a seed layer 104a, 105a disposed on the one or more metal layers 104b, 104c, 105b, 105c and in contact with the piezoelectric layer 103. The first bottom electrode 104 and at least one seed element 105 have the same layer structure 104a, 104b, 104c, 105a, 105b, 105c. The same layer structure may also have other structures; for example, at least one seed element 105 and the bottom electrode 104 may both comprise the same single material, such as, for example... Figure 3 As shown in Figure 4. The bottom electrode 104 and one or more seed elements 105 can be formed in the same one or more process steps during the fabrication of the BAW device 100.

[0091] Figure 7 Furthermore, the BAW device 100 may include a Bragg mirror structure formed by an interlaced layer 102 and a plurality of Bragg layers 600, wherein the Bragg layers 600 are arranged one on top of the other in the interlaced layer 102. Additionally, Figure 7 The BAW device 100 is shown to include a via 601 extending from the first bottom electrode 104 to the top surface of the BAW device 100, particularly to the top surface adjacent to the first top electrode 106.

[0092] Figure 8 A BAW device 100 according to an embodiment of the present invention is shown, which is built on Figure 3 Based on the illustrated embodiment, and with Figure 7 The illustrated embodiment is similar. (And...) Figure 7 Compared to the previous embodiment, one or more seed elements 105 include at least one seed element 105 (as shown), which has a different structure from the bottom electrode 104. Here, as an example, one or more seed elements 105 are designed as follows: Figure 4 As shown, the bottom electrode 104 is designed as follows: Figure 7 As shown.

[0093] Figure 9 A BAW device 100 according to an embodiment of the present invention is shown, which is built on Figure 3 Based on the illustrated embodiment. In particular, Figure 8 The BAW device 100 includes two adjacent BAW resonators. The first BAW resonator (BAW 1) is as follows: Figure 3 As described, in particular, such as Figure 7As shown in the figure. Furthermore, the BAW device 100 includes a second top electrode 906 and a second bottom electrode 904 sandwiching at least a portion of the piezoelectric layer 103 between them to form a second BAW resonator (BAW 2). The second BAW resonator includes a second resonator core region, which is the region of the piezoelectric layer 103 located between the second top electrode 906 and the second bottom electrode 904. The second bottom electrode 904 is disposed in the interleaved layer 102 (as shown), or disposed in the piezoelectric layer 103 in contact with the interleaved layer 102 (alternatively, not shown).

[0094] In the case of two adjacent BAW resonators, at least one of one or more seed elements 105 (here, by example, multiple seed elements 105) is arranged below a portion of the intermediate region located between the core regions of the first and second resonators. Therefore, the piezoelectric layer 103 between the two BAW resonators has improved quality and a more uniform polarization vector distribution compared to the case without one or more seed elements 105. Specifically, the polarization in this region is expected to be uniform compared to the case without seed elements 105, which improves the coupling pattern between the BAW resonators. It is worth noting that in Figure 9 In the example, both the first BAW resonator and the second BAW resonator have multiple separate Bragg layers 600.

[0095] Figure 10 A cross-sectional view of a BAW device 100 according to an embodiment of the present invention is shown, which is based on Figure 3 Based on the illustrated embodiment, and with Figure 9 The illustrated embodiment is similar. Two adjacent BAW resonators (BAW 1 and BAW 2) are formed, and one or more seed elements 105 are included in the intermediate region between the resonator core regions of these adjacent BAW resonators. These one or more seed elements 105 may include two or more seed elements 105 placed one after another in a direction away from the first bottom electrode 104 and the second bottom electrode 904, respectively. These two or more seed elements 105 can thus be arranged regularly, particularly with a fixed spacing 1000. However, the spacing 1000 may also be variable.

[0096] and Figure 9 Compared to the previous embodiment, Figure 10 The BAW device 100 shown includes Bragg layers 600, which are shared by two adjacent BAW resonators. Therefore, the Bragg layer 600 can be referred to as a Bragg line.

[0097] Furthermore, the BAW device 100 may include one or more top materials disposed on the first top electrode 106 and / or the second top electrode 906, for example, including a passivation layer and / or a protective layer and / or a load layer. Figure 10 In this process, a first top material 1002 is disposed on both the first top electrode 106 and the second top electrode 906, and a second top material 1001 is disposed on the first top material 1002.

[0098] Figure 11 A cross-sectional view of a BAW device 100 according to an embodiment of the present invention is shown, which is based on Figure 3 Based on the illustrated embodiment, and with Figure 10 The embodiments shown are similar. Figure 11 The BAW device 100 includes one or more cavities 1100 (two cavities 1100 are shown as an example) as one or more acoustic reflecting elements, and these cavities 1100 are disposed in place of one or more Bragg structures formed by the Bragg layer 600. Specifically, the cavities 1100 may be disposed below the resonator core region of each BAW resonator (BAW1 and BAW2), i.e., below the respective top electrodes 106, 906, piezoelectric layer 103, and respective bottom electrodes 104, 904. The BAW resonators of the BAW device 100 are now FBARs. That is, the BAW device 100 is an FBAR device.

[0099] One or more seed elements 105 are now included in a central support region 1101 arranged between adjacent BAW resonators, and in particular in a central support region 1101 arranged between two cavities 1100.

[0100] Figure 12 A cross-sectional view of a BAW device 100 according to an embodiment of the present invention is shown, which is based on Figure 3 Based on the illustrated embodiment, and with Figure 11 The illustrated embodiment is similar. (And...) Figure 11 Compared to the previous embodiment, the BAW device 100 includes only one cavity 1100, which is applied to two adjacent BAW resonators. Figure 12 The BAW device 100 may include a fully suspended film resonator. Therefore, there is no [specific application / design]. Figure 11 The space of the central support region 1101 shown. Therefore, one or more seed elements 105 can be embedded in the bottom metal layer, which forms the first bottom electrode 104 and the second bottom electrode 904, respectively.

[0101] Figures 13(a) to 13(d)A comparison is shown between the BAW device 100 according to the embodiments of the present invention in Figures 13(b) and 13(d) and the exemplary BAW devices in Figures 13(a) and 13(c). Figure 13 specifically shows top views of these BAW devices (Figures 13(a) and 13(b)) and corresponding cross-sectional views of these BAW devices (Figures 13(c) and 13(d)). The exemplary BAW device does not include any seed element 105 (see Figure 13(a)) and therefore has a disordered c-axis polarity direction (see Figure 13(c)). The BAW device 100 includes one or more seed elements 105 (see Figure 13(b)) and therefore exhibits improved piezoelectric polarization uniformity outside the resonator core region (see Figure 13(d)).

[0102] Specifically, the BAW device 100 includes two or more seed elements 105 arranged one after another along one or more side edges of the BAW resonator, particularly along each side edge of the BAW resonator (i.e., in top view, the seed elements 105 are arranged adjacent to the first top electrode 106 and / or the first bottom electrode 104). That is, the intermediate region can be arranged adjacent to the first top electrode 106 and / or the first bottom electrode 104; or the intermediate region can be arranged surrounding the first top electrode 106 and / or the first bottom electrode 104.

[0103] One or more seed elements 105 may thus include one or more periodic arrangements of two or more seed elements 105. For example, a periodic arrangement may be provided along each edge of the BAW resonator. In the case of more than one periodic arrangement (as shown), the first periodic arrangement and the second periodic arrangement may differ from each other in one or more of the following characteristics: the shape of the seed element 105, the size of the seed element 105, the spacing between adjacent seed elements 105, the layer stacking of the seed elements 105, and the material properties of the seed elements 105.

[0104] Figures 14(a) to 14(d) The BAW device 100 according to an embodiment of the present invention is shown in both top view and cross-sectional view, which is based on Figure 3 Based on the embodiments shown.

[0105] Figures 14(a) and 14(c) illustrate a BAW device 100 with different seed elements 105 according to an embodiment. In particular, elongated seed elements 105 are arranged along one edge of the BAW resonator of the BAW device 100. Furthermore, along the other edge of the BAW resonator of the BAW device 100, a periodic arrangement of seed elements 105 of different shapes (specifically, not elongated) is provided.

[0106] Figures 14(b) and 14(d) illustrate a BAW device 100 with two BAW resonators according to an embodiment, the two BAW resonators sharing a bottom electrode layer forming a first bottom electrode and a second bottom electrode. Different seed elements 105 are arranged along the edges of the two BAW resonators, particularly along the top and bottom edges of the common bottom electrode layer, as shown in the top view of (Figure 14(b)). The plurality of seed elements 105 includes elongated seed elements 105 (in region C), a first periodic arrangement of identical seed elements 105 (in region A), a second periodic arrangement of identical seed elements 105 (in region B), and a third periodic arrangement of different seed elements 105 (in region D).

[0107] Figures 15(a) to 15(d) A BAW device 100 according to an embodiment of the present invention is shown. Figures 15(a) and 15(c) show a BAW device 100 similar to that shown in Figures 14(b) and 14(d). However, the BAW device 100 includes another periodic arrangement of seed elements 105 located between two adjacent BAW resonators, in which the two BAW resonators do not have a common bottom electrode layer, but instead each include a first bottom electrode and a second bottom electrode layer. This other periodic arrangement includes seed elements 105 arranged one after another in a direction perpendicular to the direction from the first BAW resonator to the second BAW resonator.

[0108] Figures 15(b) and 15(d) show the BAW device 100, with the common top electrode 106 of the two BAW resonators having a more complex shape. In the top view, seed elements 105 of different shapes and / or sizes are arranged along the edges of the more complex shape of the top electrode 106.

[0109] Figures 16(a) to 16(d) A BAW device 100 according to an embodiment of the present invention is shown. In particular, Figures 16(b), 16(c) and 16(d) show BAW resonators with different top electrode shapes and different seed elements 105 arranged along the edge of the BAW resonator. Figures 16(a) to 16(d) It should be noted that, in particular, this disclosure and embodiments of the invention should not be limited to any particular type, shape, size or arrangement of one or more seed elements 105, nor should they be limited to any type or shape of BAW resonators.

[0110] In the above embodiments of the present invention, that is, for the BAW device 100 described with respect to the various figures, the following materials may be selected.

[0111] The substrate 101 may include silicon, glass, ceramic, etc. (e.g., thin film) The piezoelectric layer 103 may include lithium niobate, lithium tantalate, aluminum nitride, etc. The top electrodes 106, 906 and / or the bottom electrodes 104, 904 may include metal and / or metal alloy layers, such as copper, titanium, etc., or may be highly doped silicon layers.

[0112] In the example, the acoustic resonator frame disposed around one or more BAW resonators (passivation layers) may include a dielectric material. For example, the dielectric material may include SiCOH, phosphosilicate glass, or oxides or nitrides of aluminum, silicon, germanium, gallium, indium, tin, antimony, tellurium, bismuth, titanium, vanadium, chromium, manganese, cobalt, nickel, copper, zinc, zirconium, niobium, molybdenum, palladium, cadmium, hafnium, tantalum, or tungsten, or any combination thereof.

[0113] Metallization layers, such as those forming the bottom electrodes 104 and 904, may include materials such as copper, aluminum, tungsten, and titanium. For example, the back-end of line (BEOL) dielectric layer forming the interlaced layer 102 may include, for instance, a copper capping layer (CCL), an etch stop layer (ESL), a diffusion barrier (DB), an antireflection coating (ARC), and low-k dielectrics such as SiCOH, SiOCN, SiCN, SiOC, and SiN.

[0114] Materials that can be used in the CMOS BEOL layer (e.g., forming the top electrodes 106, 906) include, for example, copper metallization, tungsten, low-k dielectric, silicon dioxide, copper overlay, etch stop layer, anti-reflective coating, etc.

[0115] In the example, substrate 101 may include silicon, SOI technology substrate, gallium arsenide, gallium phosphide, gallium nitride and / or indium phosphide or other example substrates, alloy semiconductors including GaAsP, AlInAs, GaInAs, GaInP or GaInAsP, or combinations thereof.

[0116] In a particular embodiment, the BAW device 100 may include an interlaced layer 102 comprising silicon dioxide and may include a Bragg layer 600 comprising a material having a higher acoustic impedance than silicon dioxide. In another particular embodiment, the BAW device 100 may include a piezoelectric layer 103 comprising AlN or AlN comprising additional rare earth elements (particularly Sc). In another particular embodiment, the BAW device 100 may include at least one of one or more seed elements 105 comprising Pt. In yet another particular embodiment, the BAW device 100 may include a first bottom electrode 104 and / or a second bottom electrode 904 comprising at least one of W, Mo, and Al. Two or more of these particular embodiments may be combined.

[0117] Figure 17 A method 1700 according to an embodiment of the present invention is shown. According to the above embodiment, method 1700 is used to manufacture a BAW device 100. Method 1700 may include the following steps: forming a substrate 101 (1701); forming an interlaced layer 102 (1702) on the substrate 101; forming one or more seed elements 105 (1703) disposed in the interlaced layer 102; forming a piezoelectric layer 103 (1704) on the interlaced layer 102 and the one or more seed elements 105, respectively; forming a first bottom electrode 104 (1705) in the interlaced layer 102 or in the piezoelectric layer 103 in contact with the interlaced layer 102; and forming a first top electrode 106 (1706) on the piezoelectric layer 103. A first top electrode 106 and a first bottom electrode 104 sandwich at least a portion of the piezoelectric layer 103 to form a first BAW resonator. The first BAW resonator includes a first resonator core region, which is the region of the piezoelectric layer 103 located between the first top electrode 106 and the first bottom electrode 104. Furthermore, one or more seed elements 105 are in contact with the piezoelectric layer 103. Additionally, one or more seed elements 105 are disposed below an intermediate region, which is the region of the piezoelectric layer 103 immediately adjacent to the first resonator core region.

[0118] Embodiments of the present invention use one or more seed elements 105 to maintain proper piezoelectric polarization growth of the piezoelectric layer 103 at the edges of the BAW resonator. Furthermore, to aid in uniformity, these seed elements 105 can use the same fabrication deposition mask as the bottom electrodes 104, 904 of the BAW resonator.

[0119] Some advantages of the various embodiments of the present invention are:

[0120] • Even when the piezoelectric layer 103 grows away from the bottom electrodes 104 and 904, C-axis orientation disorder can be avoided.

[0121] Since the seed element 105 is provided, there is no need to pattern the large bottom electrodes 104, 904.

[0122] • It can avoid parasitic capacitance.

[0123] One or more seed elements 105 can be formed using the same mask as used for the patterning steps of bottom electrodes 104, 904.

[0124] • By minimizing the generation of grain boundaries in the piezoelectric layer 103 crystal, stress distribution at the edge of the BAW resonator can be avoided.

[0125] • It enables better polarization control, for example, in the doped AlN piezoelectric layer 103, which is highly dependent on seed layer optimization.

[0126] • Due to better control over the piezoelectric effect in the immediate region, the interaction between adjacent BAW resonators may be closer.

[0127] The invention has been described with reference to various embodiments as examples and implementation methods. However, other variations can be understood and implemented by those skilled in the art who practice the claimed invention through study of the drawings, this disclosure, and the independent claims. In the claims and the description, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. A single element or other unit can perform the function of several entities or items listed in the claims. The listing of certain measures in mutually different dependent claims does not indicate that a combination of these measures cannot be used in advantageous implementations.

Claims

1. A bulk acoustic wave (BAW) device (100), characterized in that, include: Substrate (101); An interleaved layer (102) is disposed on the substrate (101), the interleaved layer comprising silicon oxide; A piezoelectric layer (103) is disposed on the interleaved layer (102) and configured to propagate BAW; A first top electrode (106) and a first bottom electrode (104) sandwich at least a portion of the piezoelectric layer (103) to form a first BAW resonator. The first BAW resonator includes a first resonator core region, which is the region of the piezoelectric layer (103) located between the first top electrode (106) and the first bottom electrode (104). The first bottom electrode (104) is disposed in the interlaced layer (102) or in the piezoelectric layer (103) in contact with the interlaced layer (102); and One or more seed elements (105) are arranged in the interlaced layer (102) and in contact with the piezoelectric layer (103). The one or more seed elements (105) are arranged below the intermediate region, which is the region of the piezoelectric layer (103) adjacent to the core region of the first resonator.

2. The BAW device (100) according to claim 1, characterized in that, Also includes: A second top electrode (906) and a second bottom electrode (904) sandwich at least a portion of the piezoelectric layer (103) to form a second BAW resonator. The second BAW resonator includes a second resonator core region, which is the region of the piezoelectric layer (103) located between the second top electrode (906) and the second bottom electrode (904). The second bottom electrode (904) is disposed in the interlaced layer (102) or in the piezoelectric layer (103) in contact with the interlaced layer (102); and At least one of the one or more seed elements (105) is arranged below a portion of the intermediate region located between the first resonator core region and the second resonator core region.

3. The BAW device (100) according to claim 1 or 2, characterized in that: The first bottom electrode (104) and / or the second bottom electrode (904) are arranged in the staggered layer (102) and are at the same level as the one or more seed elements (105).

4. The BAW device (100) according to claim 1 or 2, characterized in that: The first bottom electrode (104) and / or the second bottom electrode (904) have the same layer structure as the one or more seed elements (105).

5. The BAW device (100) according to claim 1 or 2, characterized in that: The first bottom electrode (104) and / or the second bottom electrode (904) and the one or more seed elements (105) each include one or more metal layers (104b, 104c, 904b, 904c, 105b, 105c) and a seed layer (104a, 904a, 105a) disposed on the one or more metal layers (104b, 104c, 904b, 904c, 105b, 105c) and in contact with the piezoelectric layer (103).

6. The BAW device (100) according to claim 1 or 2, characterized in that: The one or more seed elements (105) comprise two or more seed elements (105) placed one after another in a direction away from the first bottom electrode (104) and / or the second bottom electrode (904).

7. The BAW device (100) according to claim 1 or 2, characterized in that: The one or more seed elements (105) include two or more seed elements (105) placed one after another along one or more side edges of the first BAW resonator and / or the second BAW resonator.

8. The BAW device (100) according to claim 1 or 2, characterized in that: The one or more seed elements (105) comprise a first periodic arrangement of two or more seed elements (105).

9. The BAW device (100) according to claim 8, characterized in that: The one or more seed elements (105) comprise a second periodic arrangement of two or more seed elements (105), and The first periodic arrangement and the second periodic arrangement differ from each other in one or more of the following characteristics: the shape of the seed element (105), the size of the seed element (105), the spacing between adjacent seed elements (105), the layer stacking of the seed elements (105), and the material properties of the seed elements (105).

10. The BAW device (100) according to claim 1 or 2, characterized in that: The one or more seed elements (105) include at least two seed elements (105) that are identical in shape and / or size; and / or The one or more seed elements (105) include at least two seed elements (105) that are different from each other in shape and / or size.

11. The BAW device (100) according to claim 1 or 2, characterized in that, In the top view of the BAW device (100): The intermediate region is arranged adjacent to the first top electrode (106) and / or the second top electrode (906); and / or The intermediate region is surrounding the first top electrode (106) and / or the second top electrode (906).

12. The BAW device (100) according to claim 1 or 2, characterized in that: Each of the one or more seed elements (105) is at least laterally spaced from the second bottom electrode (904) by a minimum distance.

13. The BAW device (100) according to claim 1 or 2, characterized in that: The piezoelectric layer (103) has a free upper surface in the intermediate region.

14. The BAW device (100) according to claim 1 or 2, characterized in that, Also includes: Acoustic reflective elements (600, 1100) are located below the first top electrode (106) and / or the second top electrode (906), the piezoelectric layer (103), and the first bottom electrode (104) and / or the second bottom electrode.

15. The BAW device (100) according to claim 14, characterized in that: The acoustic reflection element (600, 1100) includes a plurality of higher and lower acoustic impedance layers (600), which form a Bragg reflector structure; and / or The acoustic reflection element (600, 1100) includes a plurality of higher and lower dielectric constant layers (600) that form a Bragg reflector structure.

16. The BAW device (100) according to claim 15, characterized in that: The one or more seed elements (105) are disposed on the Bragg reflector structure.

17. The BAW device (100) according to claim 15 or 16, characterized in that: The Bragg reflector structure consists of the staggered layer (102) and a plurality of Bragg layers (600), wherein the Bragg layers (600) are arranged one on top of the other in the staggered layer (102).

18. The BAW device (100) according to claim 17, characterized in that: The interlaced layer (102) comprises SiO2, and the Bragg layer (600) comprises a material having a higher acoustic impedance than the SiO2.

19. The BAW device (100) according to claim 1 or 2, characterized in that: The piezoelectric layer (101) comprises AlN, or AlN with additional rare earth elements doped.

20. The BAW device (100) according to claim 19, characterized in that, The AlN with additional rare earth elements includes AlN with additional Sc doping.

21. The BAW device (100) according to claim 1 or 2, characterized in that: At least one of the one or more seed elements (105) includes Pt.

22. The BAW device (100) according to claim 1 or 2, characterized in that: The first bottom electrode (104) and / or the second bottom electrode (904) include at least one of W, Mo and Al.

23. A method (1700) for manufacturing a bulk acoustic wave (BAW) device (100), characterized in that, The method (1700) includes: Forming substrates (101) and (1701); An interleaved layer (102) (1702) is formed on the substrate (101), the interleaved layer comprising silicon oxide; One or more seed elements (105) (1703) are formed in the interleaved layer (102); Piezoelectric layers (103) (1705) are formed on the interlaced layer (102) and the one or more seed elements (105), respectively. A first bottom electrode (104) is formed in the interlaced layer (102) or in the piezoelectric layer (103) in contact with the interlaced layer (102). A first top electrode (106) is formed on the piezoelectric layer (103). Wherein, the first top electrode (106) and the first bottom electrode (104) sandwich at least a portion of the piezoelectric layer (103) in the middle to form a first BAW resonator, the first BAW resonator including a first resonator core region, the first resonator core region being the region of the piezoelectric layer (103) located between the first top electrode (106) and the first bottom electrode (104). The one or more seed elements (105) are in contact with the piezoelectric layer (103), and The one or more seed elements (105) are arranged below the intermediate region, which is the region of the piezoelectric layer (103) adjacent to the core region of the first resonator.

24. The method (1700) according to claim 23, characterized in that: The piezoelectric layer (103) is grown simultaneously on the interleaved layer (102) and the one or more seed elements (105) by sputtering, epitaxy or vapor deposition.

25. The method (1700) according to claim 23 or 24, characterized in that: The first bottom electrode (104) and the one or more seed elements (105) are formed in the same one or more process steps of the method (1700).

26. The method (1700) according to claim 25, characterized in that: The first bottom electrode (104) and the one or more seed elements (105) include the same seed layer (104a, 105a) that provides seeds for the growth of the piezoelectric layer (103).

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