Acoustic wave filter, acoustic wave die, and radio frequency module having a patterned mass loading layer

Abstract

To provide a bulk elastic wave resonator with a patterned mass loading layer.SOLUTION: Two different bulk elastic wave resonators have respective patterned mass loading layers 25 with different densities. A patterned mass loading layer 25 contributes to a fact that two different bulk elastic wave resonators have different resonance frequencies. The two bulk elastic wave resonators may be included in a common filter and may reside on a common die. The patterned mass loading layer 25 of the bulk elastic wave resonator can be formed during a common processing step.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of priority of U.S. Provisional Application No. 62 / 085,413, entitled "Bulk Acoustic Wave Resonator with Patterned Mass Loading Layer", filed on September 30, 2020; U.S. Provisional Application No. 62 / 085,399, entitled "Bulk Acoustic Wave Resonator with Mass Loading Layer", filed on September 30, 2020; and U.S. Provisional Application No. 62 / 085,398, entitled "Method of Manufacturing a Bulk Acoustic Wave Resonator with Patterned Mass Loading Layer", filed on September 30, 2020, the disclosures of each of which are hereby incorporated by reference in their entireties.

[0002] Embodiments of the present disclosure relate to elastic wave devices, and more particularly to bulk acoustic wave devices.

Background Art

[0003] Elastic wave filters can be implemented in radio frequency electronic systems. For example, the filters in the radio frequency front - end of a mobile phone may include one or more elastic wave filters. Multiple elastic wave filters can be arranged as a multiplexer. For example, two elastic wave filters can be arranged as a duplexer.

[0004] An elastic wave filter may include a plurality of resonators arranged to filter radio frequency signals. Multiple examples of elastic wave filters include surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters. A BAW filter includes BAW resonators. Multiple examples of BAW resonators include thin - film bulk acoustic wave resonators (FBARs) and solidly - mounted resonators (SMRs). In a BAW resonator, the elastic wave propagates through the bulk of the piezoelectric layer.

[0005] Manufacturing BAW resonators with different resonant frequencies may involve several processing steps. As more BAW resonators with different resonant frequencies are manufactured on a single common die, the number of processing steps required to manufacture such BAW resonators will also increase. [Overview of the project]

[0006] Each of the innovations described in the claims has several aspects, and not just one of them is involved in its desired attribute. Some outstanding features of this disclosure are outlined herewithout limiting the scope of the claims.

[0007] One aspect of this disclosure is an elastic wave filter comprising a first bulk elastic wave resonator and a second bulk elastic wave resonator. The first bulk elastic wave resonator includes a first patterned mass loading layer having a first density. The first patterned mass loading layer influences the resonant frequency of the first bulk elastic wave resonator. The second bulk elastic wave resonator includes a second patterned mass loading layer having a second density. The second patterned mass loading layer influences the resonant frequency of the second bulk elastic wave resonator. The second density is different from the first density. The bulk elastic wave filter is arranged to filter radio frequency signals.

[0008] The first patterned mass loading layer and the second patterned mass loading layer can be formed during a common processing step. The first patterned mass loading layer extends from the first piezoelectric layer of the first bulk acoustic wave resonator by the same distance that the second patterned mass loading layer extends from the second piezoelectric layer of the second bulk acoustic wave resonator.

[0009] The first patterned mass loading layer may have a periodic pattern. The first patterned mass loading layer may include a plurality of spaced-apart strips. The first patterned mass loading layer may include a first group of strips and a second group of strips intersecting the first group of strips. The first patterned mass loading layer may have a concentric pattern.

[0010] The first patterned mass loading layer may contain a material different from any other layer of the first bulk acoustic wave resonator that is in physical contact with the first patterned mass loading layer. Alternatively, the first patterned mass loading layer may contain the same material as a layer of the first bulk acoustic wave resonator that is in physical contact with the first patterned mass loading layer. The first patterned mass loading layer may contain a metal. The first patterned mass loading layer may contain a dielectric material.

[0011] The first patterned mass loading layer may be located below the piezoelectric layer of the first bulk acoustic wave resonator. Alternatively, the first patterned mass loading layer may be located above the piezoelectric layer of the first bulk acoustic wave resonator. The first patterned mass loading layer may be located above the electrodes located above the piezoelectric layer of the first bulk acoustic wave resonator.

[0012] The elastic wave filter may include a third bulk elastic wave resonator containing a third patterned mass loading layer having a third density, where the third density is different from both the first and second densities.

[0013] The first bulk acoustic wave resonator may be a thin-film bulk acoustic wave resonator.

[0014] The second density may be higher than the first density, and the resonant frequency of the second bulk elastic wave resonator may be lower than the resonant frequency of the first bulk elastic wave resonator. The resonant frequency of the first bulk elastic wave resonator may be 1% to 10% higher than the resonant frequency of the second bulk elastic wave resonator.

[0015] The first patterned mass loading layer may have a duty factor in the range of 0.05 to 0.95 in the main elastically active region of the first bulk elastic wave resonator. The first patterned mass loading layer may have a duty factor in the range of 0.2 to 0.8 in the main elastically active region of the first bulk elastic wave resonator. The second patterned mass loading layer may have a duty factor in the range of 0.05 to 0.95 in the main elastically active region of the second bulk elastic wave resonator. The second patterned mass loading layer may have a duty factor in the range of 0.2 to 0.8 in the main elastically active region of the second bulk elastic wave resonator.

[0016] Another aspect of this disclosure is an elastic wave filter comprising a first bulk elastic wave resonator and a second bulk elastic wave resonator. The first bulk elastic wave resonator comprises a first patterned mass loading layer and a periodic pattern. The second bulk elastic wave resonator comprises a second patterned mass loading layer. The second mass loading provides a larger mass loading than the first patterned mass loading layer, such that the second bulk elastic wave resonator has a lower resonant frequency than the first bulk elastic wave resonator. The bulk elastic wave filter is arranged to filter radio frequency signals.

[0017] Another aspect of this disclosure is an elastic wave die comprising a first bulk elastic wave resonator on a bulk elastic wave die and a second bulk elastic wave resonator on the bulk elastic wave die. The first bulk elastic wave resonator comprises a first patterned mass loading layer having a first density. The first patterned mass loading layer influences the resonant frequency of the first bulk elastic wave resonator. The second bulk elastic wave resonator comprises a second patterned mass loading layer having a second density, the second density being higher than the first density. The second patterned mass loading layer influences the resonant frequency of the second bulk elastic wave resonator.

[0018] The first bulk acoustic wave resonator and the second bulk acoustic wave resonator may be included in the same filter. Alternatively, the first bulk acoustic wave resonator and the second bulk acoustic wave resonator may be included in different filters. Such different filters are included in the multiplexer.

[0019] The first patterned mass loading layer and the second patterned mass loading layer can be formed during a common processing step. The first patterned mass loading layer extends from the first piezoelectric layer of the first bulk acoustic wave resonator by substantially the same distance as the second patterned mass loading layer extends from the second piezoelectric layer of the second bulk acoustic wave resonator.

[0020] The first patterned mass loading layer may have a periodic pattern. The first patterned mass loading layer may include a plurality of strips spaced apart from each other.

[0021] The first patterned mass loading layer may contain a material different from any other layer of the first bulk acoustic wave resonator that is in physical contact with the first patterned mass loading layer. Alternatively, the first patterned mass loading layer may contain the same material as a layer of the first bulk acoustic wave resonator that is in physical contact with the first patterned mass loading layer. The first patterned mass loading layer may contain a metal. The first patterned mass loading layer may contain a dielectric material.

[0022] The elastic wave die may include a third bulk elastic wave resonator comprising a third patterned mass loading layer having a third density, where the third density is different from both the first and second densities.

[0023] The resonant frequency of the first bulk elastic wave resonator may be 1% to 10% higher than the resonant frequency of the second bulk elastic wave resonator.

[0024] The first patterned mass loading layer may have a duty factor in the range of 0.05 to 0.95 in the central area of ​​the active region of the first bulk elastic wave resonator. The first patterned mass loading layer may have a duty factor in the range of 0.2 to 0.8 in the central area of ​​the active region of the first bulk elastic wave resonator.

[0025] Another aspect of the present disclosure is a radio frequency module including an elastic filter having a patterned mass loading layer and a bulk acoustic wave device, and a radio frequency circuit element coupled to the elastic wave filter. The elastic wave filter and the radio frequency circuit element are encapsulated within a common module package.

[0026] The radio frequency circuit element may be a radio frequency amplifier arranged to amplify a radio frequency signal. The radio frequency circuit element may be a switch configured to selectively couple the elastic wave filter to a port of the radio frequency module.

[0027] Another aspect of the present disclosure is a wireless communication device including an elastic wave filter having a patterned mass loading layer and a bulk acoustic wave device, an antenna operably coupled to the elastic wave filter, a radio frequency amplifier operably coupled to the elastic wave filter and configured to amplify a radio frequency signal, and a transceiver communicating with the radio frequency amplifier.

[0028] The wireless communication device may include a baseband processor communicating with the transceiver. The elastic wave filter may be included in a radio frequency front end. The wireless communication device may be a user device.

[0029] Another aspect of the present disclosure is a bulk acoustic wave resonator, which includes a first electrode on an elastic reflector, a piezoelectric layer on the first electrode, a second electrode on the piezoelectric layer, and a patterned mass loading layer having a duty factor in the range of 0.3 to 0.7 in a main elastic active region of the bulk acoustic wave resonator. The patterned mass loading layer is arranged to affect the resonance frequency of the bulk acoustic wave resonator.

[0030] The patterned mass loading layer may have a periodic pattern. The patterned mass loading layer may include a plurality of strips spaced apart from each other.

[0031] The patterned mass loading layer may contain a material different from any other layer of the bulk acoustic wave resonator that is in physical contact with the patterned mass loading layer. The patterned mass loading layer may contain the same material as one of the layers of the bulk acoustic wave resonator that is in physical contact with the patterned mass loading layer. The patterned mass loading layer may contain a metal. The patterned mass loading layer may contain a dielectric material.

[0032] The patterned mass loading layer may be positioned below the piezoelectric layer. The patterned mass loading layer may be positioned above the piezoelectric layer. The patterned mass loading layer may be positioned above the second electrode.

[0033] The elastic reflector may be an air cavity. Alternatively, the elastic reflector may be a solid acoustic mirror.

[0034] Another aspect of this disclosure is an elastic wave filter comprising a bulk elastic wave resonator and a plurality of additional elastic wave resonators. The bulk elastic wave resonator includes a first electrode on an elastic reflector, a piezoelectric layer on the first electrode, a second electrode on the piezoelectric layer, and a patterned mass loading layer having a duty factor in the range of 0.3 to 0.7 in the main elastically active region of the bulk elastic wave resonator. The patterned mass loading layer is arranged to affect the resonant frequency of the bulk elastic wave resonator. The elastic wave filter is configured to filter radio frequency signals.

[0035] The patterned mass loading layer may have a periodic pattern. The bulk elastic wave resonator may be a series resonator. The bulk elastic wave resonator may be a shunt resonator.

[0036] The filter may be included in the wireless communication device. This wireless communication device also includes an antenna operably coupled to the elastic wave filter, a radio frequency amplifier operably coupled to the elastic wave filter and configured to amplify radio frequency signals, and a transceiver that communicates with the radio frequency amplifier. The wireless communication device may include a baseband processor that communicates with the transceiver. The elastic wave filter may be included in the radio frequency front end. The wireless communication device may be user equipment.

[0037] Another aspect of this disclosure is a method for manufacturing a bulk acoustic wave resonator. The method includes providing a bulk acoustic wave resonator structure including a support substrate, and during a common processing step, (i) forming a first patterned mass loading layer on the bulk acoustic wave resonator structure in a first area for a first bulk acoustic wave resonator, and (ii) forming a second patterned mass loading layer on the bulk acoustic wave resonator structure in a second area for a second bulk acoustic wave resonator. The second patterned mass loading layer has a different density from the first patterned mass loading layer.

[0038] The bulk acoustic wave resonator structure may include a passivation layer and an electrode layer. The bulk acoustic wave resonator structure may also include a piezoelectric layer. The bulk acoustic wave resonator structure may also include a second electrode layer, the piezoelectric layer being positioned between the first electrode layer and the second electrode layer. The bulk acoustic wave resonator structure may also include a second passivation layer on top of the second electrode layer.

[0039] The first patterned mass loading layer may contain a material different from any of the layers of the first bulk acoustic wave resonator that are in physical contact with the first patterned mass loading layer. Alternatively, the first patterned mass loading layer and the layer of the first bulk acoustic wave resonator structure that is in physical contact with the first patterned mass loading layer may be made of the same material. The first patterned mass loading layer may contain a dielectric material. The first patterned mass loading layer may contain a metal.

[0040] The method may also include forming a third patterned mass loading layer on the bulk acoustic wave resonator structure in a third area for the third bulk acoustic wave resonator during the common processing step. The third patterned mass loading layer has a different density from both the first and second patterned mass loading layers.

[0041] The common processing step may include depositing the material for the first patterned layer and the second patterned layer. The common processing step may also include removing material to form the first patterned layer and the second patterned layer.

[0042] The method may further include, during the common processing steps, forming a third patterned mass loading layer on the bulk acoustic wave resonator structure in a third area for the third bulk acoustic wave resonator, and removing material to increase the depth between features of the third patterned mass loading layer. The depth between features of the third patterned mass loading layer may be greater than the depth between features of the first patterned mass loading layer.

[0043] The first patterned mass loading layer may have a periodic pattern. The first patterned mass loading layer may include a plurality of spaced-apart strips. The first patterned mass loading layer may include a first group of strips and a second group of strips intersecting the first group of strips. The first patterned mass loading layer may have a concentric pattern.

[0044] The first bulk acoustic wave resonator may be a thin-film bulk acoustic wave resonator. Alternatively, the first bulk acoustic wave resonator may be a solid-mount resonator.

[0045] The method may include interconnecting multiple bulk acoustic wave resonators such that a first bulk acoustic wave resonator and a second bulk acoustic wave resonator are included in a common filter. Alternatively, the method may include interconnecting multiple bulk acoustic wave resonators such that a first bulk acoustic wave resonator is included in a first filter and a second bulk acoustic wave resonator is included in a second filter. The multiplexer may include a first filter and a second filter. The multiplexer can be a duplexer.

[0046] After manufacturing, the first patterned mass loading layer affects the resonant frequency of the first bulk elastic wave resonator, and the second patterned mass loading layer affects the resonant frequency of the second bulk elastic wave resonator. The resonant frequency of the first bulk elastic wave resonator may be 1% to 10% higher than the resonant frequency of the second bulk elastic wave resonator.

[0047] The first patterned mass loading layer may have a duty factor in the range of 0.05 to 0.95 in the main elastically active region of the first bulk elastic wave resonator. The second patterned mass loading layer may have a duty factor in the range of 0.05 to 0.95 in the main elastically active region of the second bulk elastic wave resonator.

[0048] The first patterned mass loading layer may have a duty factor in the range of 0.2 to 0.8 in the main elastically active region of the first bulk elastic wave resonator. The second patterned mass loading layer may have a duty factor in the range of 0.2 to 0.8 in the main elastically active region of the second bulk elastic wave resonator.

[0049] Another aspect of the present disclosure is a method for manufacturing a bulk acoustic wave resonator. The method comprises providing a bulk acoustic wave resonator structure including a support substrate, and during a common processing step, depositing material to form (i) a first patterned mass loading layer on the bulk acoustic wave resonator structure in a first area for a first bulk acoustic wave resonator, and (ii) a second patterned mass loading layer on the bulk acoustic wave resonator structure in a second area for a second bulk acoustic wave resonator, wherein the second patterned mass loading layer has a different density from the first patterned mass loading layer.

[0050] Another aspect of the present disclosure is a method for manufacturing a bulk acoustic wave resonator. The method comprises providing a bulk acoustic wave resonator structure including a support substrate, and etching a material between common processing steps to form (i) a first patterned mass loading layer on the bulk acoustic wave resonator structure in a first area for a first bulk acoustic wave resonator, and (ii) a second patterned mass loading layer on the bulk acoustic wave resonator structure in a second area for a second bulk acoustic wave resonator, wherein the second patterned mass loading layer has a different density from the first patterned mass loading layer.

[0051] Another aspect of this disclosure is a bulk elastic wave resonator comprising a first electrode on an elastic reflector, a piezoelectric layer on the first electrode, a second electrode on the piezoelectric layer, and a patterned mass loading layer that contributes to the difference in mass loading between at least a major elastically active region and a recessed frame region. The patterned mass loading layer is arranged to influence the resonant frequency of the bulk elastic wave resonator.

[0052] The patterned mass load may be included in both the main elastically active region and the recessed frame region, and the patterned mass load layer may have a higher density in the main elastically active region than in the recessed frame region.

[0053] The patterned mass loading layer may be included in the main elastically active region, and the patterned mass loading layer does not need to be present in the recessed frame region.

[0054] The patterned mass loading layer may have a periodic pattern in the first area. The patterned mass loading layer may include a plurality of spaced-apart strips.

[0055] The patterned mass loading layer may contain a material different from any of the layers of the bulk acoustic wave resonator that are in physical contact with the patterned mass loading layer. The patterned mass loading layer and the layer of the bulk acoustic wave resonator structure that is in physical contact with the patterned mass loading layer may both be made of the same material.

[0056] The patterned mass loading layer may have a duty factor in the second area ranging from 0.05 to 0.3. The patterned mass loading layer may have a duty factor in the first area ranging from 0.3 to 0.8.

[0057] Another aspect of this disclosure is an elastic wave filter comprising a bulk elastic wave resonator and a plurality of additional elastic wave resonators. The bulk elastic wave resonator includes a first electrode on an elastic reflector, a piezoelectric layer on the first electrode, a second electrode on the piezoelectric layer, and a patterned mass loading layer that contributes to the difference in mass loading between at least a primary elastically active region and a recessed frame region. The patterned mass loading layer is arranged to affect the resonant frequency of the bulk elastic wave resonator. The elastic wave filter is configured to filter radio frequency signals.

[0058] Another aspect of this disclosure is a method for manufacturing a bulk acoustic wave resonator. The method includes providing a bulk acoustic wave resonator structure including a support substrate, and during a common processing step, forming a patterned mass loading layer on the bulk acoustic wave resonator structure such that the patterned mass loading layer has a first density in a first area of ​​the bulk acoustic wave resonator structure and a second density in a second area of ​​the bulk acoustic wave resonator structure. The first area corresponds to the main elastically active region of the bulk acoustic wave resonator. The second area corresponds to the recessed frame region of the bulk acoustic wave resonator. The first density is higher than the second density.

[0059] The method may further include forming a passivation layer on the upper electrode of a bulk acoustic wave resonator without etching the material of the passivation layer located on a recessed frame region, the upper electrode being located on the piezoelectric layer of the bulk acoustic wave resonator.

[0060] The patterned mass loading layer may have a duty factor in the second area ranging from 0.05 to 0.3. The patterned mass loading layer may have a duty factor in the first area ranging from 0.3 to 0.8.

[0061] The bulk acoustic wave resonator structure may include a passivation layer on a support substrate, an electrode layer on the passivation layer, and a piezoelectric layer on the electrode layer, with the patterned mass loading layer formed on the piezoelectric layer. The bulk acoustic wave resonator structure may include a passivation layer on a support substrate, a first electrode layer on the passivation layer, a piezoelectric layer on the first electrode layer, and a second electrode on the piezoelectric layer, with the patterned mass loading layer formed on the second electrode.

[0062] The common processing step may include depositing the material for the patterned mass loading layer. The common processing step may also include removing the material for the patterned mass loading layer.

[0063] The patterned mass loading layer may have a periodic pattern in the first area. The patterned mass loading layer may include a plurality of spaced-apart strips. [Brief explanation of the drawing]

[0064] Embodiments of the present disclosure are described here by non-limiting examples with reference to the accompanying drawings.

[0065] [Figure 1A] This is a schematic cross-sectional view of a bulk acoustic wave (BAW) resonator according to one embodiment. [Figure 1B] Figure 1A is an example of a plan view of a BAW resonator. [Figure 1C] This is another example of a plan view of the BAW resonator shown in Figure 1A. [Figure 2] Figure 1A includes a schematic cross-sectional view of the material stack of the BAW resonator. [Figure 3] This includes a schematic cross-sectional view of a material stack of a BAW resonator having a patterned mass loading layer according to one embodiment. [Figure 4] This includes a schematic cross-sectional view of a material stack of a BAW resonator having a patterned mass loading layer according to one embodiment. [Figure 5] This is a schematic cross-sectional view of a material stack of a BAW resonator having a patterned mass loading layer above the lower electrode according to one embodiment. [Figure 6] This is a schematic cross-sectional view of a material stack of a BAW resonator having a patterned mass loading layer located below the lower electrode according to one embodiment. [Figure 7] This is a schematic cross-sectional view of a material stack of a BAW resonator having a patterned mass loading layer located below a lower passivation layer according to one embodiment. [Figure 8] This is a schematic cross-sectional view of a material stack of a BAW resonator having a patterned mass loading layer above the upper electrode according to one embodiment. [Figure 9] This is a schematic cross-sectional view of a material stack of a BAW resonator having a patterned mass loading layer located below the lower passivation layer according to one embodiment of another embodiment. [Figure 10] This is a schematic cross-sectional view of the material stack of a BAW resonator having a patterned mass loading layer located below the lower electrode according to one embodiment of another embodiment. [Figure 11] This is a schematic cross-sectional view of a material stack of a BAW resonator having a patterned mass loading layer embedded in the upper passivation layer according to one embodiment. [Figure 12] This is a schematic cross-sectional view of a material stack of a BAW resonator having a patterned mass loading layer embedded in the lower passivation layer according to one embodiment. [Figure 13]This is a schematic cross-sectional view of a material stack of a BAW resonator having a patterned mass loading layer embedded in the upper electrode layer according to one embodiment. [Figure 14] This is a schematic cross-sectional view of a material stack of a BAW resonator having a patterned mass loading layer embedded in the lower passivation layer according to one embodiment. [Figure 15A-E] Figure 15A includes a cross-sectional view of a BAW material stack according to one embodiment. Figures 15B to 15E show examples of grating shapes for patterned mass loading layers. [Figure 15F-H] Figures 15F to 15H show examples of grating shapes for patterned mass loading layers. [Figure 16A-C] Figures 16A, 16B, and 16C show examples of patterned mass loading layers having a line pattern in a plan view. [Figure 17A-B] Figures 17A and 17B show examples of patterned mass loading layers having a loop pattern in a plan view. [Figure 17C-D] Figures 17C and 17D show examples of patterned mass loading layers having a loop pattern in a plan view. [Figure 18A-B] Figures 18A and 18B show examples of patterned mass loading layers having an intersecting line pattern in a plan view. [Figure 18C-E] Figures 18C, 18D, and 18E show other examples of patterned mass loading layers. [Figure 19A-C] Figures 19A to 19C show examples of patterned mass loading layers with different line patterns in a plan view. [Figure 20A] This shows a plan view of a patterned mass loading layer containing multiple linear features located above the lower layer. [Figure 20B] The side view shows the line features of the patterned mass loading layer and the lower layer. [Figure 20C] Figures 20A and 20B show the simulation results for the patterned mass loading layer. [Figure 21] This is a schematic diagram of a ladder filter containing multiple BAW resonators. [Figure 22] This is an example of a schematic cross-sectional view showing the material stack of an example of a BAW resonator for a ladder filter in Figure 21, which has different patterned mass loading layers. [Figure 23A] This is a flowchart illustrating an example of a method for forming a BAW resonator with a patterned mass loading layer. [Figure 23B] This is a flowchart illustrating an example of a method for forming a BAW resonator with a patterned mass loading layer. [Figure 24A] Figures 24A and 24B show different schematic cross-sections of the BAW resonator material stack corresponding to the process steps in Figure 23A and / or Figure 23B. [Figure 24B] Figures 24A and 24B show different schematic cross-sections of the BAW resonator material stack corresponding to the process steps in Figure 23A and / or Figure 23B. [Figure 25] This is a flowchart of the process for manufacturing a BAW resonator. [Figure 26] This is a schematic upper plan view showing a BAW die including a BAW resonator having different patterned mass loading layers according to one embodiment. [Figure 27] This is a schematic upper plan view showing a BAW die including a BAW resonator having different patterned mass loading layers according to one embodiment. [Figure 28] This is a schematic cross-sectional view of a solid-mount resonator (SMR) having a patterned mass loading layer according to one embodiment. [Figure 29A] This is a schematic cross-sectional view of a portion of the main elastically active region and recessed frame region of a BAW resonator having a patterned mass loading layer. [Figure 29B] This is a schematic cross-sectional view of the main elastically active region and recessed frame region of a portion of another BAW resonator having a patterned mass loading layer. [Figure 30] This is a flowchart illustrating an example of a method for forming a BAW resonator comprising a patterned mass loading layer having high density in the main elastic active region and low density in the raised frame region, according to one embodiment. [Figure 31A]This is a schematic cross-sectional view of a part of a BAW resonator, which has a patterned mass loading layer in the main elastically active region but does not have a patterned mass loading layer in the recessed frame region. [Figure 31B] This is a schematic cross-sectional view of a portion of a BAW resonator, which has a patterned mass loading layer in the main elastically active region where the density is higher than in the recessed frame region. [Figure 31C] This is a schematic cross-sectional view of a portion of a BAW resonator, which has a patterned mass loading layer in the main elastically active region where the density is higher than in the recessed frame region. [Figure 32A-B] Figure 32A is a plan view of a BAW resonator having a patterned mass loading layer. Figure 32B is a plan view of a BAW resonator having a patterned mass loading layer but without a patterned mass loading layer in the recessed frame region. [Figure 33A-C] Figure 33A is a schematic diagram of an elastic wave filter. Figure 33B is a schematic diagram of a duplexer including an elastic wave filter according to one embodiment. Figure 33C is a schematic diagram of a multiplexer including an elastic wave filter according to one embodiment. [Figure 33D-E] This is a schematic diagram of a multiplexer including an elastic wave filter according to one embodiment. [Figure 34] This is a schematic block diagram of the illustrated package-like module according to a predetermined embodiment. [Figure 35] This is a schematic block diagram of the illustrated package-like module according to a predetermined embodiment. [Figure 36] This is a schematic block diagram of the illustrated package-like module according to a predetermined embodiment. [Figure 37] This is a schematic block diagram of the illustrated package-like module according to a predetermined embodiment. [Figure 38] This is a schematic block diagram of the illustrated package-like module according to a predetermined embodiment. [Figure 39] This is a schematic diagram of one embodiment of a mobile device. [Figure 40] This is a schematic diagram of an example of a communication network. [Modes for carrying out the invention]

[0066] The following detailed description of a given embodiment represents various descriptions of a particular embodiment. However, the innovation described herein can be embodied in numerous different forms defined and covered, for example, by the claims. In this description, the same reference numerals refer to drawings in which identical or functionally similar elements may be shown. It should be understood that the elements shown in the drawings are not necessarily to scale. It should also be understood that a given embodiment may include more elements than those shown in the drawings, and / or a subset of the elements shown in the drawings. Furthermore, some embodiments may incorporate any suitable combination of features from two or more drawings. The headings given herein are for convenience only and are not necessarily intended to affect the meaning or scope of the claims.

[0067] Bulk acoustic wave (BAW) filters with BAW resonators have multiple different resonant frequencies that can meet various design specifications, including insertion loss at the passband edge, blocking outside the passband of the BAW filter, power handling, and matching with power amplifiers and / or low-noise amplifiers. It is desirable to manufacture BAW resonators with multiple different resonant frequencies using a low-complexity process.

[0068] Aspects of this disclosure relate to BAW resonators having different patterned mass loading layers and methods for manufacturing such BAW resonators. BAW resonators having different patterned mass loading layers may have different resonant frequencies. Patterned mass loading layers having different densities may achieve different mass loadings resulting in such different resonant frequencies. A BAW resonator having a low-density patterned mass loading layer may have a higher resonant frequency than other identical BAW resonators having a high-density patterned mass loading layer. In a given example, the patterned mass loading layer may include a plurality of mass loading striplines arranged in a periodic pattern. The material of the patterned mass loading layer may be denser than the material of other layers that are in physical contact with the patterned mass loading layer. Although several embodiments are described with reference to BAW resonators, any suitable principles and advantages disclosed herein can be implemented in any suitable BAW device.

[0069] The resonant frequency of a BAW resonator can be tuned by adjusting the density of the patterned mass loading layer. The patterned mass loading layer may have a duty cycle ranging from 0.05 to 0.95 in the central area of ​​the BAW resonator's active region. Increasing the density of the patterned mass loading layer can lower the resonant frequency. Conversely, decreasing the density of the patterned mass loading layer can increase the resonant frequency.

[0070] Any two BAW resonators of a filter can be tuned differently by providing them with patterned mass loading layers of different densities. For example, two series BAW resonators of a filter may have patterned mass loading layers of different densities. Another example is that two shunt BAW resonators of a filter may have patterned mass loading layers of different densities. A further example is that the series BAW resonator and the shunt BAW resonator of a filter may have patterned mass loading layers of different densities.

[0071] In some examples, two or more BAW resonators in a filter may have patterned mass loading layers of the same density, while one or more other BAW resonators in the same filter may have patterned mass loading layers of different densities. Such BAW resonators having patterned mass loading layers of the same density may have resonant frequencies that are tuned by the same amount by each patterned mass loading layer.

[0072] Patterned mass loading layers affect the resonant frequency of a BAW resonator. Other layers of the BAW resonator also affect the resonant frequency. Patterned mass loading layers with different densities may account for some or all of the difference in resonant frequencies between two BAW resonators. Differences in mass loading provided by one or more other layers (e.g., one or more electrode layers and / or one or more passivation layers) along with patterned mass loading layers of different densities can cause BAW resonators to have different resonant frequencies in a given application. Alternatively, differences in the densities of multiple patterned mass loading layers may account for the overall difference in resonant frequencies between BAW resonators in various applications.

[0073] Several methods for manufacturing BAW resonators involve numerous process steps to ensure that the BAW resonators have different resonant frequencies. A single lithography and etching process can be performed for each of the different resonant frequencies. The lithography and etching processes can be designed to form high resonant frequencies. A single lithography and deposition process can be performed for each of the different resonant frequencies. The lithography and deposition processes can be designed to form low resonant frequencies. The number of process steps may increase as a single die contains many BAW resonators with different resonant frequencies. As the number of processing steps increases, the manufacturing of BAW resonators can become complex and expensive.

[0074] Patterned mass loading layers having different densities can be formed in a single common processing step. Therefore, the method for manufacturing BAW resonators disclosed herein can reduce the number of processing steps required to form BAW resonators having multiple different resonant frequencies.

[0075] This common processing step reduces the complexity and cost of the process for manufacturing BAW resonators. By modifying the resonant frequencies of multiple different BAW resonators using a single common processing step, the resonant frequencies can be tuned using a single common processing step and a single parameter. By adjusting the density of the mass loading layer from no fill to 100% fill, the resonant frequencies of the BAW resonators can be tuned within a certain tuning range. This provides flexibility in tuning the resonant frequencies within that tuning range using a single photolithography process step. The common processing step may be used to form BAW resonators having different frequencies contained in the same filter. The common processing step may be used to form BAW resonators having different frequencies contained in two or more filters on a single shared die.

[0076] Patterned mass loading layers can be precisely manufactured. Photolithography techniques used to manufacture surface acoustic wave (SAW) devices may be applied to form patterned mass loading layers in a given application. In some applications, the patterned mass loading layer can be formed during the manufacturing process of SAW and BAW devices on the same die. The methods disclosed herein enable precise control of the resonant frequency of each BAW resonator.

[0077] The patterned mass loading layer may include a pattern of a stripline. The strip pattern may have a pitch P < 3h. Here, h is the total thickness of the resonator stack from the lower passivation above the elastic reflector (e.g., air cavity or solid acoustic mirror) to the upper passivation. In a given application, P < 2.4h is preferred. The patterned mass loading layer may have a thickness d such that h < 1.5h. The patterned mass loading layer may have a thickness d such that 0.001h < d < 1.5h. In a given application, d < 0.3h is preferred.

[0078] The patterned mass loading layer may have any suitable pattern such as a periodic pattern, an inclined pattern, a pitch modulation pattern or a random pattern. The patterned mass loading layer may be equivalent to a uniform mass loading distribution. In a plan view, the shape of the pattern may include a strip, a grating, an inclination, etc., or any suitable combination thereof. In a cross-sectional view, the shape of the pattern may include a rectangle, a trapezoid, a lens, etc., or any suitable combination thereof.

[0079] The patterned mass loading layer may be disposed above the elastic reflector (e.g., air cavity or solid acoustic mirror) of the BAW device. Here, the elastic reflector is disposed between the support substrate and the lower electrode of the BAW device. The patterned mass loading layer may be positioned at the top of the BAW device, between the top electrode and the passivation, or at any other suitable position above the elastic reflector. Here, the elastic reflector is disposed between the support substrate and the lower electrode of the BAW device. The mass loading pattern is positioned in at least the main elastic active region of the BAW device. In a given application, the mass loading pattern may be present in the recessed frame region. In such an application, the mass loading pattern may have a lower density in the recessed frame region than in the main elastic active region.

[0080] The patterned mass loading layer may contain any suitable material, such as a dielectric, a metal, a metallic alloy, or any suitable combination thereof. A patterned mass loading layer made of high-density material may produce a greater change in resonant frequency for the same change in duty factor than a patterned mass loading layer made of low-density material. A patterned mass loading layer made of high-density material can tune the resonant frequency with a smaller change in duty factor compared to a patterned mass loading layer made of low-density material. The patterned mass loading layer may contain a dielectric layer such as silicon dioxide (SiO2), silicon nitride (SiN), aluminum oxide (Al2O3), silicon carbide (SiC), aluminum nitride (AlN), titanium nitride (TiN), silicon oxynitride (SiON), or diamond-like carbon (DLC). The patterned mass-loaded layer may contain layers of metals such as titanium (Ti), ruthenium (Ru), molybdenum (Mo), tungsten (W), platinum (Pt), aluminum (Al), iridium (Ir), chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), gold (Au), or any suitable alloy thereof.

[0081] Examples of BAW resonators having patterned mass loading layers are described below. Any suitable principles and advantages of these BAW resonators can be implemented together. Although several embodiments disclosed herein include a single patterned mass loading layer, any suitable principles and advantages disclosed herein may be applied to BAW resonators having two or more patterned mass loading layers. In applications having two or more patterned mass loading layers, the mass loading layers may have different patterns or the same pattern.

[0082] Figure 1A is a schematic cross-sectional view of a BAW resonator 10 according to one embodiment. The BAW resonator 10 includes a patterned mass loading layer. The patterned mass loading layer influences the resonant frequency of the BAW resonator 10. The BAW resonator 10 is a thin-film bulk acoustic wave resonator (FBAR). As shown, the BAW resonator 10 includes a support substrate, an air cavity 12, a recessed frame structure 13, a raised frame structure 14, a material stack 15 in the active region, and an electrical interconnection layer 16. The material stack 15 includes the patterned mass loading layer. Details of the material stack 15 are described below with reference to Figure 2.

[0083] The active region or active domain of the BAW resonator 10 is defined by a portion of the piezoelectric layer of a material stack 15 that overlaps with an elastic reflector such as an air cavity 12 or a solid acoustic mirror, in contact with both the lower and upper electrodes. In applications where multiple piezoelectric layers exist in the BAW device, the active region may be defined by the piezoelectric material of the piezoelectric layer contacting both the lower and upper electrodes above the elastic reflector. The active region corresponds to the location where a voltage is applied to opposite sides of the piezoelectric layer above the elastic reflector. The active region may be the elastically active region of the BAW resonator 10. The BAW resonator 10 also includes a recessed frame region having a recessed frame structure 13 in the active region, and a raised frame region having a raised frame structure 14 in the active region. Elastic activity is significantly reduced in the recessed frame region and the raised frame region. The primary elastically active region may be located in the central part of the active region where the frame structures 13 and 14 are not present. The primary resonant frequency of the BAW resonator 10 may be set by the primary elastically active region.

[0084] Figure 1A includes a recessed frame structure 13 and a raised frame structure 14, but other frame structures may be implemented as alternatives or additionally. For example, a raised frame structure having multiple layers, including a layer between the electrodes of the BAW resonator and the piezoelectric layer, may be implemented. As another example, the raised frame structure may include a layer embedded in the piezoelectric material. As yet another example, a floating raised frame structure may be implemented. As yet another example, a raised frame structure without recessed frame structures in the frame zone may be implemented.

[0085] The air cavity 12 is an example of an elastic reflector. As shown in the figure, the air cavity 12 is positioned above the support substrate 11. The air cavity 12 is placed between the support substrate 11 and the material stack 15. In some other embodiments, the air cavity can be etched into the support substrate. The support substrate 11 may be a silicon substrate. The support substrate 11 may be any other suitable support substrate. The electrical interconnection layer 16 can electrically connect the electrodes of the BAW resonator 10 to one or more other BAW resonators, one or more other circuit elements, one or more signal ports, etc., or any suitable combination thereof.

[0086] Figure 1B is an example of a plan view of the BAW resonator 10 in Figure 1A. The cross-sectional view in Figure 1A follows the line A to A' in Figure 1B. As shown in Figure 1B, the BAW resonator 10 includes a frame zone 17 around the periphery of the main elastically active region 18 of the BAW resonator 10. The frame zone 17 may include the recessed frame structure 13 and the raised frame structure 14 in Figure 1A. In a given example, the frame zone 17 may be referred to as a boundary ring. The material stack 15 may extend further above the piezoelectric layer 19 in the raised frame region than the main elastically active area 18, and the material stack 15 may extend further above the piezoelectric layer 19 in the main elastically active area 18 than the recessed frame region. Figure 1B shows a BAW resonator 10 having a semi-elliptical shape in plan view.

[0087] Figure 1C is another example of a plan view of the BAW resonator 10 shown in Figure 1A. The cross-sectional view of Figure 1A follows the line from A to A' in Figure 1C. Figure 1C shows the BAW resonator 10 having a pentagonal shape with curved sides in its plan view.

[0088] In some other embodiments, BAW resonators relating to any suitable principles and advantages disclosed herein may have any other suitable shape in plan view, such as a quadrilateral, a quadrilateral with curved sides, a pentagon, a semicircle, a circle, an ellipse, etc.

[0089] Figure 2 includes a schematic cross-sectional view of the material stack 15 of the BAW resonator 10 in Figure 1A. Figure 2 also shows a plan view of the patterned mass loading layer 25. The material stack 15 is positioned in the main elastically active region of the BAW resonator 10. In Figure 1A, the material stack 15 is placed on top of the air cavity 12. In other BAW resonators, the material stack 15 may be placed on top of any other suitable elastic reflector, such as a solid acoustic mirror. As shown, the material stack 15 includes a first passivation layer 21, a first electrode layer 22, a piezoelectric layer 19, a second electrode layer 23, a second passivation layer 24, and a patterned mass loading layer 25.

[0090] In the material stack 15, the piezoelectric layer 19 is positioned between the first electrode layer and the second electrode layer 23. As shown in the figure, the piezoelectric layer 19 is in physical contact with the respective flat surfaces of the first electrode layer 22 and the second electrode layer 24. The piezoelectric layer 19 may be an aluminum nitride layer. The piezoelectric layer 19 may be a zinc oxide layer. The piezoelectric layer 19 may contain any suitable piezoelectric material. The piezoelectric layer 19 may be doped with any suitable dopant such as scandium (Sc), chromium (Cr), magnesium (Mg), etc. By doping the piezoelectric layer 19, the resonant frequency can be adjusted. By doping the piezoelectric layer 19, the coupling coefficient k of the BAW device 10 can be adjusted. 2 It is possible to increase the bond coefficient k2. Doping that increases the bond coefficient k 2 This can be advantageous at high frequencies where degradation can occur.

[0091] The first passivation layer 21 is placed between the elastic reflector and the first electrode layer 22. The first passivation layer 21 may be referred to as the lower passivation layer. The first passivation layer 21 may be a silicon dioxide layer or any other suitable passivation layer, such as a layer of aluminum oxide, silicon carbide, aluminum nitride, silicon nitride, or silicon oxynitride. As shown in Figure 1A (but not in Figure 2), an adhesive layer such as a titanium layer may be placed between the first passivation layer 21 and the first electrode layer 22.

[0092] The first electrode layer 22 may be referred to as the lower electrode. The first electrode layer 22 may have a relatively high acoustic impedance. The first electrode layer 22 may contain molybdenum (Mo), tungsten (W), ruthenium (Ru), chromium (Cr), iridium (Ir), platinum (Pt), Ir / Pt, or any suitable alloy and / or combination thereof. Similarly, the second electrode layer 23 may have a relatively high acoustic impedance. The second electrode layer 23 may contain Mo, W, Ru, Cr, Ir, Pt, Ir / Pt, or any suitable alloy and / or combination thereof. In a given example, the second electrode layer 23 may be formed from the same material as the first electrode layer 22. The second electrode layer 23 may be referred to as the upper electrode. The piezoelectric layer 19 is placed between the first electrode layer 22 and the second electrode layer 23.

[0093] The second passivation layer 24 may be referred to as the upper passivation layer. The second passivation layer 24 may be a silicon dioxide layer or any other suitable passivation layer, such as a layer of aluminum oxide, silicon carbide, aluminum nitride, silicon nitride, or silicon oxynitride. In a given example, the second passivation layer 24 may be made of the same material as the first passivation layer 21.

[0094] In the material stack 15, the patterned mass loading layer 25 is formed on the second passivation layer 24 and is in physical contact with the second passivation layer 24. The patterned mass loading layer 25 and the second passivation layer 24 are formed from the same material in the material stack 15. The patterned mass loading layer 25 may be a silicon dioxide layer or any other suitable passivation layer, such as a layer of aluminum oxide, silicon carbide, aluminum nitride, silicon nitride, or silicon oxynitride.

[0095] The patterned mass loading layer 25 may include multiple strips spaced apart from each other in a periodic pattern. The patterned mass loading layer 25 has a height d and a pitch P. The pitch P and height d affect the mass loading of the BAW resonator 10 in the central area of ​​the active region, and consequently affect the resonant frequency of the BAW resonator 10. By adjusting the pitch P, the density of the through-load layer 25 is adjusted. A smaller pitch P results in a higher density and a lower resonant frequency. Similarly, a larger pitch P results in a lower density and a higher resonant frequency. By adjusting the height d, the mass loading of the patterned mass loading layer 25 can be adjusted alternatively or additionally.

[0096] As shown in the figure, the patterned mass loading layer may have a periodic pattern. The periodic pattern may have a constant duty factor, where the duty factor is defined as the strip width divided by the pitch. The duty factor can range from 0 (no mass loading layer) to 1 (filled with a mass loading layer). Different BAW resonators may have different duty factors to tune their resonant frequencies. More generally, the duty factor may correspond to the fill percentage or pattern density of the mass loading layer on a given area of ​​the BAW device. For example, a patterned mass loading layer in the main elastically active region of a BAW device has a duty factor of 0.2 relative to the main elastically active region when 20% of the main elastically active region is filled with the patterned mass loading material. For example, a patterned mass loading layer in the main elastically active region of a BAW device has a duty factor of 0.7 relative to the main elastically active region when 20% of the main elastically active region is filled with the patterned mass loading material. Different regions of the BAW device may have different duty factors. For example, in some embodiments, the patterned mass loading layer may have a lower duty cycle in the recessed frame region of the BAW device than in the main elastically active region of the BAW device.

[0097] The patterned mass loading layer 25 may be formed in the same processing steps as one or more other patterned mass loading layers for each of the different BAW resonators having different correspondence densities. The different BAW resonators may be included in the same filter as the BAW resonator 10, and / or in one or more filters different from the BAW resonator 10. The patterned mass loading layer 25 may be formed by lithography and deposition. The patterned mass loading layer 25 may be formed by lithography and etching. Lithography techniques used to manufacture surface acoustic wave devices may be used to form the patterned mass loading layer.

[0098] Other embodiments of material stacks for BAW resonators having patterned mass loading layers are described with reference to the cross-sectional examples shown in Figures 3 to 14. These material stacks may be implemented instead of the material stack 15 in Figure 1A and / or Figure 2. Any suitable combination of the features of the material stacks in Figures 2 to 14 may be combined with each other. The examples of material stacks in Figures 3 to 14 include patterned mass loading layers in different locations and / or made of different materials than the patterned mass loading layer 25 in Figure 2. Any suitable manufacturing techniques and / or advantages for the material stacks in Figures 3 to 14 may be implemented with respect to the material stack 15 in Figure 2. Although the examples of embodiments show a single patterned mass loading layer, two or more patterned mass loading layers may be implemented in a single BAW resonator in some applications. The patterned mass loading layers in Figures 2 to 14 may be located in the main elastically active region of the BAW resonator.

[0099] Figure 3 includes a schematic cross-sectional view of the material stack 30 of the BAW resonator. Figure 3 also shows a plan view of the patterned mass loading layer 35 having passivation material contained between the feature materials of the patterned mass loading layer 35. The material stack 30 may be mounted in the central area of ​​the active region of the BAW resonator. The material stack 30 is similar to the material stack 15 in Figure 2, except that (1) the material stack 30 includes a patterned mass loading layer 35 of a different material at a different location than the patterned mass loading layer 25 in Figure 2, and (2) the material stack 30 also includes a second passivation layer 34 with a different geometric shape than the second passivation layer 24 in Figure 2.

[0100] In Figure 3, the patterned mass loading layer 35 is placed on the second electrode layer 23. The second passivation layer 34 is located on top of the patterned mass loading layer. The patterned mass loading layer 35 is formed from a different material than the second electrode layer 23. The patterned mass loading layer 35 is also formed from a different material than the second passivation layer 34. The patterned mass loading layer 35 may be formed from any suitable mass loading material. The patterned mass loading layer 35 may contain dielectric materials and / or metals. The patterned mass loading layer 35 contains one or more of SiO2, SiN, Al2O3, SiC, Ti, Ru, Mo, or Al, and both the second electrode layer 23 and the second passivation layer 34 are formed from materials different from the patterned mass loading layer 35. The density of the material of the patterned mass loading layer 35 may be higher than the density of the material of the second passivation layer 34. In a given application, the density of the material in the patterned mass loading layer 35 may be higher than the density of the material in the second electrode layer 23. The patterned mass loading layer 35 can result in a different geometric shape for the second passivation layer 34 than that of the passivation layer 24 shown in Figure 2.

[0101] Figure 4 includes a schematic cross-sectional view of the material stack 40 of the BAW resonator. Figure 4 also shows a plan view of the patterned mass loading layer 45. The material stack 40 may be mounted in the central area of ​​the active region of the BAW resonator. The material stack 40 is similar to the material stack 30 in Figure 3, except that the patterned mass loading layer 45 contains the same material as the second electrode layer 23 in the material stack 40. The patterned mass loading layer 45 may function as part of the upper electrode in the material stack 40.

[0102] Figure 5 includes a schematic cross-sectional view of the material stack 50 of the BAW resonator. The material stack 50 may be mounted in the central area of ​​the active region of the BAW resonator. The material stack 50 is similar to the material stack 40 in Figure 4, except that the patterned mass loading layer 55 is positioned differently. The patterned mass loading layer 55 is placed between the piezoelectric layer 18 and the first electrode layer 22. The patterned mass loading layer 55 contains the same material as the first electrode layer 22. The patterned mass loading layer 55 may function as part of the lower electrode in the material stack 50.

[0103] Figure 6 includes a schematic cross-sectional view of the material stack 60 of the BAW resonator. The material stack 60 may be mounted in the central area of ​​the active region of the BAW resonator. The material stack 60 is similar to the material stack 50 in Figure 5, except that the patterned mass loading layer 65 is positioned on the opposite side of the first electrode layer 22 compared to the patterned mass loading layer 55. The patterned mass loading layer 65 is placed between the first passivation layer 21 and the first electrode layer 22. The patterned mass loading layer 65 contains the same material as the first electrode layer 22. The patterned mass loading layer 65 may function as part of the lower electrode in the material stack 60.

[0104] Figure 7 includes a schematic cross-sectional view of the material stack 70 of the BAW resonator. The material stack 70 may be mounted in the central area of ​​the active region of the BAW resonator. In the material stack 70, the patterned mass loading layer 75 is positioned below the first passivation layer 21 and contains the same material as the first passivation layer 21. The patterned mass loading layer 75 is positioned between the elastic reflector and the first passivation layer 21. The patterned mass loading layer 75 is patterned on a sacrificial layer, which is subsequently removed in a given application to form an air cavity beneath the patterned mass loading layer 75.

[0105] In a given embodiment, the patterned mass loading layer may be made of a different material from any other layer of the BAW material stack that is in physical contact with the patterned mass loading layer. Such a patterned mass loading layer may contain any suitable dielectric and / or metal. For example, such a patterned mass loading may contain one or more of SiO, SiN, Al2O3, SiC, Ti, Ru, Mo, or Al, and any other layer in contact with the patterned mass loading layer may be made of a different material. Figures 8 to 10 show embodiments similar to the given embodiments described above, but differ in that instead of a patterned mass loading layer made of the same material as the other layer in physical contact with the patterned mass loading layer, a patterned mass loading layer made of a different material is included. Figures 11 to 14 show embodiments in which the patterned mass loading layer is embedded in other layers of the BAW material stack made of different materials.

[0106] Figure 8 includes a schematic cross-sectional view of the material stack 80 of the BAW resonator. The material stack 80 is similar to the material stack 15 in Figure 2, but differs in that it includes a patterned mass loading layer 85 made of a different material than the second passivation layer 24, instead of the patterned mass loading layer 25.

[0107] Figure 9 includes a schematic cross-sectional view of the material stack 90 of the BAW resonator. The material stack 90 is similar to the material stack 70 in Figure 7, but differs in that it includes a patterned mass loading layer 95 made of a different material than the first passivation layer 21, instead of the patterned mass loading layer 75.

[0108] Figure 10 includes a schematic cross-sectional view of the material stack 100 of the BAW resonator. The material stack 100 is similar to the material stack 60 in Figure 6, but differs in that it includes a patterned mass loading layer 105 made of a different material than the first electrode layer 22, instead of the patterned mass loading layer 65. The patterned mass loading layer 105 is also made of a different material than the first passivation layer 21.

[0109] Figure 11 includes a schematic cross-sectional view of the material stack 110 of the BAW resonator. In the material stack 110, a patterned mass loading layer 115 is embedded in the second passivation layer 24. The patterned mass loading layer 115 is made of a different material from the second passivation layer 24. The patterned mass loading layer 115 may have a higher density than the second passivation layer 24.

[0110] Figure 12 includes a schematic cross-sectional view of the material stack 120 of the BAW resonator. In the material stack 120, a patterned mass loading layer 125 is embedded in the first passivation layer 21. The patterned mass loading layer 125 is made of a different material from the first passivation layer 21. The patterned mass loading layer 125 may have a higher density than the first passivation layer 21.

[0111] Figure 13 includes a schematic cross-sectional view of the material stack 130 of the BAW resonator. In the material stack 130, a patterned mass loading layer 135 is embedded in the second electrode layer 23. The patterned mass loading layer 135 is made of a different material from the second electrode layer 23. The patterned mass loading layer 135 may have a higher density than the second electrode layer 23.

[0112] Figure 14 includes a schematic cross-sectional view of the material stack 140 of the BAW resonator. In the material stack 140, a patterned mass loading layer 145 is embedded in the first electrode layer 22. The patterned mass loading layer 145 is made of a different material from the first electrode layer 22. The patterned mass loading layer 145 may have a higher density than the first electrode layer 22.

[0113] The patterned mass loading layer may include features having various different cross-sectional shapes. The patterned mass loading layer may include gratings spaced apart from each other. These gratings may have any suitable cross-sectional shape, such as any of the cross-sectional shapes shown in Figures 15B to 15H. Figure 15A includes, for illustrative purposes, a cross-sectional view of the BAW material stack 30 of Figure 3 and a plan view of the patterned mass loading layer 35. The cross-sectional shapes shown in Figures 15B to 15H are examples of shapes for the gratings of the patterned mass loading layer 35. The cross-sectional shapes shown in Figures 15B to 15H may be included in the patterned mass loading layer relating to any suitable principles and advantages disclosed herein. In a given embodiment, all gratings of the patterned mass loading layer may have the same shape in the cross-sectional view. In some other embodiments, the gratings of the patterned mass loading layer may have two or more different shapes.

[0114] Figure 15B shows a schematic cross-sectional view of a rectangular grating 155B. A certain illustrated embodiment here has a rectangular grating. Figure 15C shows a schematic cross-sectional view of a trapezoidal grating 155C. Figure 15D shows a schematic cross-sectional view of a triangular grating 155D. The triangular grating 155 is symmetrical in cross-section. Figure 15E shows a schematic cross-sectional view of a semi-elliptical grating 155E. The grating 155E may be called a lens-shaped grating. A semi-circular grating may be implemented. Figure 15F shows a schematic cross-sectional view of a grating 155F having one tapered side and one flat side. Figure 15G shows a schematic cross-sectional view of an asymmetrical triangular grating 155G. The sides of the triangular grating 155 have different slopes. Figure 15H shows a schematic cross-sectional view of an asymmetrical lens-shaped grating 155H.

[0115] The patterned mass loading layer may include any suitable pattern in the plan view. Examples of patterns include line patterns, loop patterns, intersecting line patterns, random patterns, etc. The mass loading of the patterned mass loading layer can be adjusted by adjusting the density of the feature parts of the pattern in the patterned mass loading layer. Examples of patterns shown in the plan view are shown in Figures 16A to 19C. The patterns shown in these drawings can be implemented with different spacings between feature parts in order to adjust the mass loading. The patterns shown in any of Figures 16A to 19C can be implemented in a patterned mass loading layer relating to any suitable principle and advantages disclosed herein.

[0116] Figures 16A to 16C show examples of patterned mass loading layers having line patterns in a plan view. Figure 16A shows a plan view of a patterned mass loading layer 160 containing multiple spaced-apart line-shaped features 161. Figure 16B shows a plan view of a patterned mass loading layer 162 containing multiple spaced-apart angled line-shaped features 163. Figure 16C shows a plan view of a patterned mass loading layer 164 containing multiple spaced-apart angled line-shaped features 165. Here, the angles are different from those in the patterned mass loading layer 162. These drawings show features of a patterned mass loading layer that can be given any appropriate angle α, where 0 ≤ α ≤ 180 degrees.

[0117] Figures 17A to 17D show examples of patterned mass loading layers having loop patterns in a plan view. These loop patterns include concentric features of the patterned mass loading layer. Figure 17A shows a plan view of a patterned mass loading layer 170 that includes multiple concentric rectangular features 171 spaced apart from each other. As shown, the rectangular features 171 are square in shape. Figure 17B shows a plan view of a patterned mass loading layer 172 that includes multiple concentric pentagonal features 173 spaced apart from each other. Figure 17C shows a plan view of a patterned mass loading layer 174 that includes multiple concentric circular features 175 spaced apart from each other. Figure 17D shows a plan view of a patterned mass loading layer 176 that includes multiple concentric elliptical features 177 spaced apart from each other.

[0118] Figures 18A and 18B show examples of patterned mass loading layers having intersecting line patterns in a plan view. Figure 18A shows a plan view of a patterned mass loading layer 180 that includes multiple first lines 181 intersecting with multiple second lines 182. Figure 18B shows a plan view of a patterned mass loading layer 184 that includes multiple first lines 185 intersecting with multiple second lines 186. In patterned mass loading layers 180 and 184, the lines are at different angles. The lines in the intersecting line patterned mass loading layers may be at any appropriate angle.

[0119] Figures 18C, 18D, and 18E show other examples of patterned mass loading layers. Figure 18C shows a patterned mass loading layer 187 with rectangular island features. The rectangular island features may be square island features as shown. Any other suitable island features, such as polygon island features, ellipsoidal features, or dot features, may be implemented on the patterned mass loading layer. Figure 18D shows a patterned mass loading layer 188 with dot features. Figure 18E shows a patterned mass loading layer 189 with holes.

[0120] A patterned mass loading layer may have multiple different feature types in its plan view. These include continuous features, dashed line features, angled features, zigzag features, etc. Figures 19A to 19C show examples of patterned mass loading layers with different line pattern feature types in their plan views. These feature types can be applied to any other suitable pattern. Figure 19A shows a plan view of a patterned mass loading layer 190 containing multiple continuous line features 191. Figure 19B shows a plan view of a patterned mass loading layer 192 containing multiple dashed line features 193. Figure 19C shows a plan view of a patterned mass loading layer 194 containing multiple zigzag line features 195.

[0121] FIG. 20A shows a plan view of a patterned mass loading layer 190 including a plurality of line features 191 on a lower layer 192. FIG. 20B shows a side view of the line features 191 of the patterned mass loading layer and the lower layer. All of the line features 191 have a height d. The i-th line feature has a width ai. In a given embodiment, each line feature may have the same width. The line features 191 have a period P. The period P may be constant for the line features. In some examples, the pitch can be modulated by changing the spacing between adjacent features. For example, there may be a slope in the spacing between the line features 191 of the patterned mass loading layer.

[0122] The mass loading may depend on the material of the line features 191, the height of the line features 191, and the pattern density / duty factor of the line features 191.

[0123] The line features 191 may include any suitable mass loading material. The mass loading material may be a dielectric and / or passivation material such as SiO2, SiN, Al2O3, SiC, AlN or TiN. The mass loading material may be a metal layer such as Ti, Ru, Mo, W, Pt, Al, Ir, Cr, or any suitable alloy thereof.

[0124] The line features may have a height less than 250 nanometers (nm) and greater than the minimum height for manufacturing. The height d may be in the range of about 10 nm to about 220 nm in a given application. The height d may be in the range of about 20 nm to about 100 nm in a given application. The height d may be in the range of about 20 nm to about 50 nm in a given application. The line features have a height d in the range of 0.001h < d < 1.5h. Here, h is the total thickness of the resonator stack from the lower passivation to the upper passivation on an elastic reflector (e.g., an air cavity or a solid acoustic mirror). In a given application, d < 0.3h is preferred.

[0125] The pitch P may be less than 3h, where h is the total thickness of the resonator stack. In a given application, P < 2.4h is preferred. In some applications, the pitch P may be in the range of 0.2 micrometers to 2 micrometers. In various applications, the pitch P may be in the range of 0.2 micrometers to 1 micrometer. In a given application, the pitch P may be less than 1 micrometer.

[0126] Line features may have a pattern density ranging from 0 to 100%. In a given application, multiple BAW resonators of a single filter may have a duty factor in the central region of the active area ranging from 0.05 to 0.95, where the duty factor is defined as the width of the line features divided by the pitch P. In some such examples, multiple BAW resonators of a single filter may have a duty factor in the central region of the active area ranging from 0.2 to 0.8. In some applications, multiple BAW resonators of a single filter may have a duty factor in the central region of the active area ranging from 0.3 to 0.7. A duty factor of 0.3 to 0.7 for the patterned mass loading layer in the main elastically active region of the BAW resonator is desirable for various applications. The duty factor may represent the ratio of the area covered by the patterned mass loading layer. In a given application, BAW devices with high duty factors and high Qp values ​​may be insensitive to variations in thickness and pitch length.

[0127] The resonant frequency of a BAW resonator can be adjusted by adjusting the pattern density for a specific mass loading material having a specific material height. By adjusting the duty factor from 0 to 1, the resonant frequency of the BAW resonator can be changed by an amount ranging from approximately 0.5% to approximately 10% of the BAW resonator's resonant frequency. Two BAW resonators having patterned mass loading layers of different densities formed in the same processing step may have resonant frequencies that differ by an amount ranging from approximately 1% to approximately 10% of the lower resonant frequency. In some applications, two BAW resonators having patterned mass loading layers of different densities formed in the same processing step may have resonant frequencies that differ by an amount ranging from approximately 1% to approximately 5%.

[0128] Variations in resonant frequencies between BAW devices on a common die can be fully achieved in a given application by adjusting the density of the patterned mass loading layer. Variations in resonant frequencies between BAW devices on a common die can also be achieved in several other applications by adjusting the density of the patterned mass loading layer in combination with other techniques.

[0129] Figure 20C is a graph of the simulation results for the patterned mass loading layer in Figures 20A and 20B. In these simulations, SiO2 was used for the patterned mass loading layer, and Ru was used for both electrodes. The simulation results in Figure 20C show that the resonant frequency can be adjusted by 40 MHz by changing the duty factor (DF) from 0.3 to 0.7 for a specific thickness of the patterned mass loading layer. In the given example, a patterned mass loading layer with a thickness less than 200 nm is desirable. The thicker the patterned mass loading layer, the greater the effect on the change in resonant frequency for the same duty factor difference.

[0130] A BAW resonator having a patterned mass loading layer can be included in any suitable filter. This filter can be used to filter radio frequency signals. The filter may include multiple BAW resonators, one or more BAW resonators and one or more other types of elastic resonators, one or more BAW resonators and inductor-capacitor (LC) circuits, or any suitable combination thereof. The filter may be any suitable type of filter, such as a band-pass filter or a band-stop filter. A band-pass filter can be implemented in applications to pass a specific frequency band and block frequencies outside that specific frequency band. The filter may have any suitable topology, such as a ladder topology, a grid topology, or a hybrid ladder-grid topology. Examples of ladder filters with BAW resonators having different patterned mass loading layers are shown with reference to Figure 21.

[0131] Figure 21 is a schematic diagram of a ladder filter 210 that includes multiple BAW resonators 211-219. As shown in the figure, the ladder filter 210 includes series BAW resonators 211-215 and shunt BAW resonators 216-219. The BAW resonators 211-219 of the ladder filter 210 have seven different resonant frequencies. The series resonators have four resonant frequencies. That is, BAW resonators 211 and 217 have a resonant frequency F1, BAW resonator 213 has a resonant frequency F2, BAW resonator 214 has a resonant frequency F3, and BAW resonator 215 has a resonant frequency F4. Here, F1>F2>F3>F4. The shunt resonators have three resonant frequencies. That is, BAW resonators 216 and 217 have a resonant frequency F5, BAW resonator 218 has a resonant frequency F6, and BAW resonator 219 has a resonant frequency F7. Here, F5 > F6 > F7. F4 may be greater than F5. These examples of resonant frequency relationships may be used for band-pass filters. For band-pass filters, the series resonator provides the upper band edge of the frequency response, and the shunt resonator provides the lower band edge of the frequency response. In contrast, for band-stop filters, the series resonator provides the lower band edge of the frequency response, and the shunt resonator provides the upper band edge of the frequency response. The relative frequency relationships of F1 to F7 described above may be modified as appropriate when applied to band-stop filters.

[0132] In some existing methods, forming a resonator with seven different resonant frequencies involves six different processing iterations. For example, to give a BAW resonator where seven different mass loads result in seven different resonant frequencies, there may be six iterations of depositing material into the BAW resonator structure. As another example, to give a BAW resonator where seven different mass loads result in seven different resonant frequencies, there may be six iterations of etching the material into the BAW resonator structure.

[0133] The method disclosed herein can yield seven resonant frequencies F1 to F7 through a single common processing step. The patterned mass loading layers of different BAW resonators of the ladder filter 210 can be formed at different pattern densities during the common processing step. This allows the mass loading of the BAW resonators with different densities to be adjusted, resulting in different respective resonant frequencies. Such a method can be used to provide a BAW resonator of the ladder filter 210 having seven different resonant frequencies F1 to F7.

[0134] For example, the patterned mass loading layer of the BAW resonator of the ladder filter 210 may have a stripline pattern. The stripline pattern can be formed at different densities (e.g., different pitches) in a common processing step to produce different resonant frequencies. Different densities can be formed by depositing material to form the patterned mass loading layer. Different densities can be formed by etching material to form the patterned mass loading layer. In some examples, both deposition and etching can be performed to impart mass loading to the BAW resonator of the ladder filter 210. For example, a common processing step may be performed to form a patterned mass loading layer for BAW resonators 211-219. Subsequently, the etching process can remove material between strips of the patterned mass loading layer for series BAW resonators 211-215 to reduce the mass loading of the series BAW resonators 211-215 without affecting the mass loading of the shunt BAW resonators 216-219.

[0135] Figure 22 is an example of a schematic cross-sectional view showing the material stack of an example BAW resonator of the ladder filter 210 of Figure 21 having different patterned mass loading layers. These different patterned mass loading layers can be formed in a single common processing step. The BAW resonator shown in Figure 22 has an example of a patterned mass loading layer. However, the principles and advantages of these resonators may be implemented with any suitable patterned mass loading layer disclosed herein.

[0136] BAW resonator 221 has a resonant frequency F1. Since BAW resonator 221 does not include a patterned mass loading layer, it can give the highest resonant frequency of the illustrated BAW resonators. BAW resonator 221 may correspond to examples of BAW resonators 211 and 212 in Figure 21. BAW resonator 222 has a resonant frequency F2. BAW resonator 222 has a patterned mass loading layer 35 that is less dense than the corresponding patterned mass loading layers 35' and 35'' of BAW resonators 226 and 227, respectively. BAW resonator 222 may correspond to an example of BAW resonator 213 in Figure 21. BAW resonator 226 has a resonant frequency F6 and a patterned mass loading layer 35'. BAW resonator 226 may correspond to an example of BAW resonator 218 in Figure 21. BAW resonator 227 has a resonant frequency F7 and a patterned mass loading layer 35'. The BAW resonator 226 may correspond to an example of the BAW resonator 219 in Figure 21. The BAW resonator 227 has the maximum density at which the patterned mass loading layer 35'' is 100% fill. The BAW resonator 227 may have the lowest resonant frequency of the illustrated BAW resonator due to having the maximum mass loading. A similar patterned mass loading layer having densities between the densities of the patterned mass loading layer 35 and 35' can be mounted on a BAW resonator having resonant frequencies between F2 and F6.

[0137] Figures 23A and 23B are flow diagrams of an example of a method for forming a BAW resonator with a patterned mass loading layer. Figure 23A relates to a process including lift-off, in which material is deposited on the BAW structure to form the patterned mass loading layer. Figure 23B relates to a process including etching, in which material is removed to form the patterned mass loading layer. Any suitable combination of the features of the methods in Figures 23A and 23B may be combined with each other.

[0138] Figure 23A is a flow diagram of process 230 for manufacturing a BAW resonator. The BAW resonator may be an FBAR and / or a BAW SMR. Process 230 includes giving a BAW resonator structure in block 232. The BAW resonator structure includes at least a support substrate. The BAW resonator structure may include one or more other layers on the support substrate. For example, the BAW resonator structure may include a layer of material stacks below any of the patterned mass loading layers shown in any of Figures 2 to 14.

[0139] In block 234, material is deposited on the BAW resonator structure to form patterned mass loading layers during a common processing step. The common processing step may include forming multiple patterned mass loading layers simultaneously. The common processing step may include using a common mask. During the common processing step, material is deposited such that a first patterned mass loading layer i is formed on the bulk acoustic wave resonator structure in a first area for a first bulk acoustic wave resonator, and a second patterned mass loading layer is formed on the bulk acoustic wave resonator structure in a second area for a second bulk acoustic wave resonator. The second patterned mass loading layer has a different density than the first patterned mass loading layer. Any appropriate number of patterned mass loading layers may be formed for each of the different BAW resonators during the common processing step. These patterned mass loading layers may have any appropriate number of different densities. For example, in the examples in Figures 21 and 22, six patterned mass loading layers of densities can be formed to result in BAW resonators with seven different resonant frequencies.

[0140] During the common processing step in block 234, a patterned mass loading layer may be formed for multiple BAW resonators of the same filter. Alternatively or additionally, the common processing step may include forming patterned mass loading layers for BAW resonators of different filters on the same die.

[0141] The patterned mass loading layer may be any of the patterned mass loading layers shown in Figures 2 to 14. The patterned mass loading layer may contain a different material from the layer on which it is deposited. In addition, the patterned mass loading layer may contain a different material from the layer subsequently formed on top of it. In some other embodiments, the patterned mass loading layer may be made of the same material as the lower or upper layer.

[0142] Figure 23B is a flow diagram of process 235 for manufacturing a BAW resonator. The resonator may be an FBAR and / or SMR. Process 235 includes giving a BAW resonator structure in block 236. The BAW resonator structure includes at least a support substrate. The BAW resonator structure may include one or more other layers on the support substrate. For example, the BAW resonator structure may include a material stack below it that includes a patterned mass loading layer (before 100% fill pattern formation) as shown in any of Figures 2 to 14.

[0143] The patterned mass loading layer may be any of the patterned mass loading layers shown in Figures 2 to 14. The patterned mass loading layer may contain a different material from the layer on which it is deposited. In addition, the patterned mass loading layer may contain a different material from the layer subsequently formed on top of it. In some other embodiments, the patterned mass loading layer may be made of the same material as the lower or upper layer.

[0144] In block 238, material is removed from the BAW resonator structure to form patterned mass loading layers during the common processing step. By etching the material, a first patterned mass loading layer is formed on the bulk acoustic wave resonator structure in a first area for the first bulk acoustic wave resonator, and a second patterned mass loading layer is formed on the bulk acoustic wave resonator structure in a second area for the second bulk acoustic wave resonator. The second patterned mass loading layer has a different density than the first patterned mass loading layer. Any appropriate number of patterned mass loading layers may be formed for each of the different BAW resonators during the common processing step in block 238. These patterned mass loading layers may have any appropriate number of different densities. For example, in the examples in Figures 21 and 22, six patterned mass loading layers of densities can be formed to result in BAW resonators with seven different resonant frequencies.

[0145] During the common processing step in block 238, a patterned mass loading layer may be formed for multiple BAW resonators of the same filter. Alternatively or additionally, the common processing step may include forming patterned mass loading layers for BAW resonators of different filters on the same die.

[0146] The patterned mass loading layer may be any suitable patterned mass loading layer shown in Figures 2 to 14. The patterned mass loading layer may contain a different material from the layer on which it is deposited. In addition, the patterned mass loading layer may contain a different material from the layer subsequently formed on top of it. In some other embodiments, the patterned mass loading layer may be made of the same material as the lower and / or upper layers.

[0147] Figures 24A and 24B show different schematic cross-sections of the BAW resonator material stack corresponding to the process steps in Figure 23A and / or Figure 23B. The illustrated BAW resonators may be contained in the same filter. The illustrated BAW resonators may be contained in two or more filters on the same die.

[0148] Figure 24A shows three BAW structures 242, 244, and 246 having the same material stack. These BAW structures may correspond to the BAW structure given in block 232 of process 230 and / or the BAW structure given in block 236 of process 235.

[0149] Figure 24B shows three BAW structures 242', 244', and 246' having different material stacks after the formation of patterned mass-loading layers. BAW structures 242', 244', and 246' include corresponding mass-loading layers 25, 25', and 25'' to influence the resonant frequencies by providing different mass loads. These BAW structures may correspond to BAW structures formed by material deposition in block 234 of process 230. Alternatively, these BAW structures may correspond to BAW structures formed by material removal (e.g., etching) in block 238 of process 235.

[0150] Figure 25 is a flow chart of process 250 for manufacturing a BAW resonator. The BAW resonator may be an FBAR and / or a BAW SMR. Process 250 includes giving the BAW resonator structure in block 252. In block 254, multiple patterned mass loading layers are formed for multiple BAW resonators. This may include material deposition and / or material removal. In block 256, the multiple BAW resonators are interconnected. This interconnection may include connecting multiple BAW resonators together as a single filter. In some examples, the interconnection may include connecting multiple BAW resonators together as two or more filters. In some such examples, the interconnection may include connecting the BAW resonators of two or more filters together at a common node to form a single multiplexer, such as a duplexer.

[0151] Figure 26 is a schematic top plan view of a BAW die 260 containing BAW resonators having different patterned mass loading layers. The BAW resonators of the BAW die 260 can be manufactured according to any suitable principles and advantages disclosed herein. Figure 26 shows a diagram of the material stacks of the BAW resonators 266 and 268 of the BAW die 260. The BAW resonators 266 and 268 have different patterned mass loading layers. These patterned mass loading layers have different densities that affect their corresponding resonant frequencies. The patterned mass loading layers of the BAW resonators 266 and 268 have periodic patterns. The periodic patterns have different due factors. Each of the patterned mass loading layers of the BAW resonators 266 and 268 extends the same amount above the lower layer. The BAW resonators 266 and 268 may be contained in a single filter. The BAW resonators 266 and 268 may be contained in different filters. These different filters may be contained within a single multiplexer, such as a duplexer. In a given embodiment, the BAW resonators 266 and 268 may have the shape shown in Figure 1B or the shape shown in Figure 1C in a plan view.

[0152] Figure 27 is a schematic top plan view of a BAW die 270 containing BAW resonators having different patterned mass loading layers. The BAW resonators of the BAW die 270 can be manufactured according to any suitable principles and advantages disclosed herein. Figure 27 shows a diagram of the material stacks of the BAW resonators 272, 274, and 276 of the BAW die 270. The BAW resonators 272, 274, and 276 have different patterned mass loading layers. These patterned mass loading layers have different densities that affect their corresponding resonant frequencies. The patterned mass loading layers of the BAW resonators 272, 274, and 276 have periodic patterns. The periodic patterns have different fill factors. Each of the patterned mass loading layers of the BAW resonators 272, 274, and 276 extends the same amount above the lower layer. The BAW resonators 272, 274, and 276 may be contained in a single filter. Any suitable number of BAW resonators having patterned mass loading layers may be included in a single filter. BAW resonators 272, 274, and 276 may be included in two different filters. These two different filters may be included in a single multiplexer, such as a duplexer. BAW resonators 272, 274, and 276 may be included in three different filters. These three different filters may be included in a single multiplexer, such as a triplexer. The principles and advantages disclosed herein can be applied to the manufacture of multiple BAW resonators on a single BAW die, where the multiple BAW resonators are included in a single multiplexer and / or any suitable number of independent filters, in any suitable number of different filters. In a given embodiment, BAW resonators 272, 274, and 276 may have the shape shown in Figure 1B or Figure 1C in a plan view.

[0153] Patterned mass loading layers relating to any suitable advantages disclosed herein may be incorporated into a variety of different elastic wave devices. Although several embodiments are disclosed in relation to FBARs, any suitable features of such embodiments disclosed herein can be applied to solid-mount resonators (SMRs), Lamb wave resonators, plate wave resonators, oscillators having one or more elastic resonators, and the like. An example of a BAW SMR having a patterned mass loading layer is described with reference to Figure 28. In a Lamb wave resonator, one patterned mass loading layer may be included above and / or below the lower electrode positioned between the piezoelectric layer and the elastic reflector.

[0154] Figure 28 is a schematic cross-sectional view of a BAW SMR280 having a patterned mass loading layer according to one embodiment. The BAW SMR280 is similar to the BAW resonator 10 in Figure 1A, but differs in that it includes a solid acoustic mirror 285 instead of an air cavity 12. The solid acoustic mirror 285 is an acoustic Bragg reflector. The solid acoustic mirror 285 includes alternating low acoustic impedance layers and high acoustic impedance layers. As an example, the solid acoustic mirror 285 may include alternating silicon dioxide layers as low impedance layers and tungsten layers as high impedance layers. As shown, the BAW SMR280 includes a material stack 15 having a patterned mass loading layer. Any other material stacks and / or principles and advantages of the patterned mass loading layer disclosed herein may be applied to the BAW SMR.

[0155] Multiple patterned mass loading layers may have different densities in the primary elastically active regions of different corresponding BAW resonators to adjust the resonant frequency. One patterned mass loading layer may influence the mass loading in a BAW device, where the mass loading is lower in the recessed frame region than in the primary elastically active region. Such patterned mass loading layers can be implemented with any suitable principles and advantages disclosed herein. One patterned mass loading layer may contribute at least to the difference in mass loading between the primary elastically active region and the recessed frame region of a BAW resonator. One patterned mass loading layer may be part or all of the factor in the difference in mass loading between the primary elastically active region and the recessed frame region. For example, one patterned mass loading layer may be the factor in all of the difference in mass loading between the primary elastically active region and the recessed frame region of a BAW resonator in a given application. Alternatively, one patterned mass loading layer and one or more other layers may together be factors in the difference in mass loading between the primary elastically active region and the recessed frame region of a BAW resonator in various applications. In both examples, the patterned mass loading layer contributes at least to the difference in mass loading.

[0156] In a given embodiment, a patterned mass loading layer may be included in both the main elastically active region and the recessed frame region. In such an embodiment, the patterned mass loading layer may be denser in the main elastically active region than in the recessed frame region. According to some embodiments, a patterned mass loading layer may be included in the main elastically active region, and the patterned mass loading layer may not be present in the recessed frame region.

[0157] In a BAW resonator, the mass loading boundary between the primary elastically active region and the recessed frame region can be provided in various different ways. In some examples, this mass loading boundary can be provided by making the upper passivation layer in the recessed frame region thinner compared to the primary elastically active region. Schematic cross-sectional examples of a BAW resonator with a thin upper passivation layer in the recessed frame region are shown in Figures 29A and 29B. In a given application, a single patterned mass loading layer can provide the mass loading boundary between the primary elastically active region and the recessed frame region. Schematic cross-sectional examples of a BAW resonator in which the patterned mass loading layer provides more mass loading in the primary elastically active region compared to the recessed frame region are shown in Figures 31A, 31B, and 31C. In these examples, the patterned mass loading layer contains the same material as the upper electrode of the BAW resonator. In some other examples, a patterned mass loading layer may contain the same material as the upper passivation layer (e.g., silicon dioxide), the recessed frame region may have less mass loading than the upper passivation layer (e.g., a thinner upper passivation layer), and / or the recessed frame region may have less mass loading than the patterned mass loading layer (e.g., the recessed frame region may not have a patterned mass loading layer, or the patterned mass loading layer in the recessed frame region may be less dense than in the main elastically active region). Any suitable principles and advantages of the embodiments in Figures 29A to 32B may be implemented together with each other. Any suitable principles and advantages of the embodiments in Figures 29A to 32B may be implemented together with one or more other features of any other embodiments disclosed herein.

[0158] Figure 29A is a schematic cross-sectional view of a portion of the main elastic active region (MAIN) and recessed frame region (ReF) of a BAW resonator 290 having a patterned mass loading layer 294. In Figure 29A, the upper passivation layer 292, the patterned mass loading layer 294, and the upper electrode layer 296 are shown. Not shown in Figure 29A, the BAW device 290 may include a piezoelectric layer, a lower electrode layer, a lower passivation, an elastic reflector, and a support substrate below the illustrated layers. The patterned mass loading layer 294 contains the same material as the upper electrode layer 296 in Figure 29A. The patterned mass loading layer 294 is present in both the recessed frame region (ReF) and the main elastic active region (MAIN) of the BAW resonator 290. The upper passivation layer 292 is thinner in the recessed frame region (ReF) than in the main elastic active region (MAIN) of the BAW resonator 290. This results in a difference in mass loading between the recessed frame region ReF and the main elastic active region MAIN.

[0159] Figure 29B is a schematic cross-sectional view of a portion of the main elastically active region and recessed frame region of another BAW resonator 298 having a patterned mass loading layer 294. The BAW resonator 298 is similar to the BAW resonator 290 in Figure 29A, except that the upper passivation layer 292' in the BAW resonator 298 has a different geometry from the upper passivation layer 292 of the BAW resonator 290. The upper passivation layer 292' has a geometry influenced by the patterned mass loading layer 294. In contrast, the upper passivation layer 292 in Figure 29A has a flat upper surface.

[0160] Figure 30 is a flowchart of an example of a method 300 for forming a BAW resonator comprising a patterned mass loading layer having high density in the main elastically active region and low density in the raised frame region according to one embodiment. The lower density of the patterned mass loading layer can provide a difference in mass loading to the main elastically active region, such that the upper passivation has substantially the same thickness over both the main elastically active region and the recessed frame region. In such an example, the recessed frame region can be realized without etching the upper passivation layer. This eliminates the step of etching the upper passivation to create the recessed frame region from a predetermined method for manufacturing a BAW resonator. Method 300 can create the recessed frame region by including a patterned mass loading layer with a lower duty factor in the recessed frame region compared to the main elastically active region, instead of a separate processing step to create the recessed frame region.

[0161] In block 302 of Method 300, a bulk acoustic wave resonator structure including a support substrate is provided. The bulk acoustic wave resonator structure may also include a passivation layer on the support substrate, an electrode layer on the passivation layer, and a piezoelectric layer on the electrode layer. In some applications, the bulk acoustic wave resonator structure may further include a second electrode on the piezoelectric layer.

[0162] In block 304 of Method 300, a common processing step is performed to form a patterned mass loading layer on a bulk acoustic wave resonator structure, which has a low density in an area corresponding to the recessed frame region of the bulk acoustic wave resonator and a high density in an area corresponding to the main elastically active region of the bulk acoustic wave resonator. The common processing step may include depositing the material for the patterned mass loading layer. The common processing step may optionally or additionally include removing material from the patterned mass loading layer. In a given application, the patterned mass loading layer may have a duty factor in the range of 0.05 to 0.3 in the area corresponding to the recessed frame region. In such an application, the patterned mass loading layer may have a duty factor in the range of 0.3 to 0.8 in the area corresponding to the main elastically active region.

[0163] The patterned mass loading layer can be implemented according to any suitable principles and advantages disclosed herein. For example, the patterned mass loading layer may include a periodic pattern. As another example, the patterned mass loading layer may include a plurality of spaced-apart strips.

[0164] After forming the patterned mass loading layer, a passivation layer may be formed on the upper electrode of the bulk elastic wave resonator without etching the material of the upper passivation layer above the recessed frame region. This advantageously eliminates processing steps compared to some other methods for manufacturing BAW resonators. In such embodiments, the upper passivation layer may have substantially the same thickness in both the primary elastically active region and the recessed frame region.

[0165] Figure 31A is a schematic cross-sectional view of a portion of a BAW resonator 310 having a patterned mass loading layer 294'' in the main elastic active region (MAIN) but not in the recessed frame region (ReF). The upper passivation layer 292'' may have a geometric shape that is influenced by the lower patterned mass loading layer 294''. By forming the patterned mass loading layer 294'' in the main elastic active region (MAIN) but not in the recessed frame region (ReF), the recessed frame region (ReF) can be formed without etching the upper passivation layer 292'' or removing other materials. This eliminates the step of etching the upper passivation in the recessed frame region, compared to other predetermined methods for manufacturing BAW resonators.

[0166] Figure 31B is a schematic cross-sectional view of a portion of a BAW resonator 312 having a patterned mass loading layer 294''' which is denser in the main elastic active region MAIN than in the recessed frame region ReF. The BAW resonator 312 can be manufactured by method 300. The upper passivation layer 292''' has a geometric shape influenced by the lower patterned mass loading layer 294'''. The upper passivation layer 292''' extends far from the lower piezoelectric layer above the features of the patterned mass loading layer 294''' in both the main elastic active region MAIN and the recessed frame region ReF.

[0167] Figure 31C is a schematic cross-sectional view of a portion of a BAW resonator 314 having a patterned mass loading layer 294'''' which is denser in the main elastic active region (MAIN) than in the recessed frame region (ReF). The upper passivation layer 292'''' extends far from the underlying piezoelectric layer above the features of the patterned mass loading layer 294'''' in the main elastic active region (MAIN), but not in the recessed frame region (ReF). The upper passivation layer 292'''' may be flattened in the recessed frame region (ReF). Alternatively, a flat upper passivation layer may be formed, and a second patterned mass loading layer of the same material as the upper passivation layer may be formed only above the main elastic active region. This is an example of another layer in the recessed frame region that provides a smaller mass loading in the recessed frame region compared to the main elastic active region, and is combined with the patterned mass loading layer that provides a smaller mass loading in the recessed frame region compared to the main elastic active region.

[0168] Figure 32A is a plan view of a BAW resonator 320 having a patterned mass loading layer 322. In the BAW resonator 320, the patterned mass loading layer can provide the same or identical mass loading in the main elastically active region as in the recessed frame region. The recessed frame region can be provided by one or more other layers in the material stack, such as an upper passivation layer that is thinner in the recessed frame region compared to the main elastically active region.

[0169] Figure 32B is a plan view of a BAW resonator 325 having a patterned mass loading layer 328 and a recessed frame region 329 where the patterned mass loading layer 328 is absent. The recessed frame region 329 surrounds the area in the BAW resonator 325 associated with the patterned mass loading layer 328. The recessed frame region 329 has a reduced mass loading compared to the main elastically active region of the BAW resonator 325 due to the absence of the patterned mass loading layer 328. The absence of the patterned mass loading layer 328 can be part or all of the reason for the difference in mass loading compared to the main elastically active region.

[0170] The principles and advantages disclosed herein can be implemented in standalone filters and / or in one or more filters in any suitable multiplexer. Such filters may have any suitable topology described herein, such as any filter topology relating to any suitable principles and advantages disclosed with reference to any of Figure 21. The filters may be band-pass filters arranged to filter fourth-generation (4G) long-term evolution (LTE) bands and / or fifth-generation (5G) nu-radio (NR) bands. Examples of standalone filters and multiplexers are described with reference to Figures 33A to 33E. Any suitable principles and advantages of these filters and / or multiplexers can be implemented together. Furthermore, the inverse-series bulk elastic bulk acoustic wave resonators disclosed herein may be included in filters that also include one or more inductors and one or more capacitors.

[0171] Figure 33A is a schematic diagram of the elastic wave filter 330. The elastic wave filter 330 is a band-pass filter. The elastic wave filter 330 is arranged to filter radio frequency signals. The elastic wave filter 330 includes a plurality of elastic wave resonators coupled between a first input / output port RF_IN and a second input / output port RF_OUT. The elastic wave filter 330 includes one or more BAW resonators on which patterned mass loading layers relating to any suitable principles and advantages disclosed herein are implemented.

[0172] Figure 33B is a schematic diagram of a duplexer 332 including an elastic wave filter according to one embodiment. The duplexer 332 includes a first filter 330A and a second filter 330B which are coupled together at a common node COM. One filter of the duplexer 332 may be a transmit filter and the other filter of the duplexer 332 may be a receive filter. In some other examples, such as in diversity receive applications, the duplexer 332 may include two receive filters. Alternatively, the duplexer 332 may include two transmit filters. The common node COM may be an antenna node.

[0173] The first filter 330A is an elastic wave filter arranged to filter radio frequency signals. The first filter 330A includes an elastic wave resonator coupled between a first radio frequency node RF1 and a common node COM. The first radio frequency node RF1 may be a transmitting node or a receiving node. The first filter 330A includes one or more BAW resonators on which patterned mass loading layers relating to any suitable principles and advantages disclosed herein are implemented.

[0174] The second filter 330B may be any suitable filter arranged to filter the second radio frequency signal. The second filter 330B may be, for example, an elastic wave filter, an elastic wave filter including one or more BAW resonators on which patterned mass loading layers relating to any suitable principle and advantages disclosed herein are implemented, an LC filter, a hybrid elastic wave LC filter, and the like. The second filter 330B is coupled between the second radio frequency node RF2 and a common node. The second radio frequency node RF2 may be a transmitting node or a receiving node.

[0175] Notwithstanding that examples of embodiments having filters or duplexers are described for illustrative purposes, any suitable principles and advantages disclosed herein can be implemented in a multiplexer having multiple filters coupled together at a common node. Examples of multiplexers include, but are not limited to, a duplexer having two filters coupled together at a common node, a triplexer having three filters coupled together at a common node, a quadplexer having four filters coupled together at a common node, a hexaplexer having six filters coupled together at a common node, an octaplexer having eight filters coupled together at a common node, and so on. A multiplexer may include multiple filters having different passbands. A multiplexer may include any suitable number of transmit filters and any suitable number of receive filters. For example, a single multiplexer may include all of multiple receive filters, all of multiple transmit filters, or one or more transmit filters and one or more receive filters. One or more filters in a multiplexer may include any suitable number of BAW resonators having a patterned mass loading layer.

[0176] Figure 33C is a schematic diagram of a multiplexer 334 including an elastic wave filter according to one embodiment. The multiplexer 334 includes a plurality of filters 330A to 330N coupled together at a common node COM. These plurality of filters may include any appropriate number of filters. For example, it may include three filters, four filters, five filters, six filters, seven filters, eight filters, or more filters. Some or all of the plurality of elastic wave filters may be elastic wave filters. As shown in the figure, each of the filters 330A to 330N has a fixed electrical connection to the common node COM. This may be called hard multiplexing or fixed multiplexing. In a hard multiplexing application, the filters have a fixed electrical connection to the common node. Each of the filters 330A to 330N has a corresponding input / output node RF1 to RFN.

[0177] The first filter 330A is an elastic wave filter arranged to filter radio frequency signals. The first filter 330A may include one or more elastic wave devices coupled between a first radio frequency node RF1 and a common node COM. The first radio frequency node RF1 may be a transmitting node or a receiving node. The first filter 330A includes one or more BAW resonators having a patterned mass loading layer relating to any suitable principles and advantages disclosed herein. Other filters of the multiplexer 334 may include one or more elastic wave filters, one or more elastic wave filters including one or more BAW resonators having a patterned mass loading layer, one or more LC filters, one or more hybrid elastic wave LC filters, or any suitable combination thereof.

[0178] Figure 33D is a schematic diagram of a multiplexer 336 including an elastic wave filter according to one embodiment. Multiplexer 336 is similar to multiplexer 334 in Figure 33C, except that multiplexer 336 implements switched multiplexing. In switched multiplexing, filters are coupled to a common node via switches. In multiplexer 336, switches 337A to 337N can selectively and electrically connect the corresponding filters 330A to 330N to the common node COM. For example, switch 337A can selectively and electrically connect the first filter 330A to the common node COM via switch 337A. Any appropriate number of switches 337A to 337N can electrically connect the corresponding filters 330A to 330N to the common node COM in a given state. Similarly, any appropriate number of switches 337A-337N can electrically isolate the corresponding filters 330A-330N from the common node COM under given conditions. The functionality of switches 337A-337N can support various carrier aggregations.

[0179] Figure 33E is a schematic diagram of a multiplexer 338 including an elastic wave filter according to one embodiment. The multiplexer 338 shows that a single multiplexer may include any suitable combination of hard-multiplexed filters and switched-multiplexed filters. One or more BAW resonators having a patterned mass loading layer may be included in a single filter that is hard-multiplexed to a common node of a single multiplexer. Alternatively or additionally, one or more BAW resonators having a patterned mass loading layer may be included in a single filter that is switched-multiplexed to a common node of a single multiplexer.

[0180] The acoustic wave device having a patterned mass loading layer disclosed herein may be implemented in various package modules. Several examples of package modules in which any suitable principles and advantages of the acoustic wave device disclosed herein can be implemented are described below. These examples of package modules may include a package enclosing the illustrated circuit elements. The illustrated circuit elements may be arranged on a common package substrate. The package substrate may be, for example, a multilayer substrate. Figures 34 to 38 are schematic block diagrams of exemplary package modules according to a given embodiment. Any suitable combination of the features of these package modules can be implemented together. A duplexer is shown in the example package modules of Figures 35 to 38, but any other suitable multiplexer including multiple filters coupled to a common node can be implemented instead of one or more duplexers. For example, a quadplexer may be implemented in a given application. Alternatively or additionally, one or more filters of the package module can be arranged as transmit filters or receive filters not included in the multiplexer.

[0181] Figure 34 is a schematic diagram of a radio frequency module 340 including an elastic wave component 342 according to one embodiment. The illustrated radio frequency module 340 includes the elastic wave component 342 and other circuits 343. The elastic wave component 342 may include one or more BAW resonators having patterned mass loading layers relating to any suitable combination of the features disclosed herein. The elastic wave component 342 may include a BAW die containing the BAW resonators.

[0182] The elastic wave component 342 shown in Figure 34 includes a filter 344 and terminals 345A and 345B. The filter 344 includes one or more BAW resonators implemented according to any suitable principles and advantages disclosed herein. Terminals 345A and 345B may serve, for example, as input and output contacts. The elastic wave component 342 and other circuits 343 reside on a common package substrate 346 in Figure 34. The package substrate 346 may be a laminate. Terminals 345A and 345B may be electrically connected to contacts 347A and 347B on the package substrate 346 via electrical connectors 348A and 348B, respectively. Electrical connectors 348A and 348B may be, for example, bumps or wire bonds.

[0183] Other circuits 343 may include any suitable additional circuits. For example, other circuits may include one or more radio frequency amplifiers (e.g., one or more power amplifiers and / or one or more low-noise amplifiers), one or more power amplifiers, one or more radio frequency switches, one or more additional filters, one or more low-noise amplifiers, one or more RF couplers, one or more delay lines, one or more phase shifters, etc., or any suitable combination thereof. Other circuits 343 may be electrically connected to filter 344. The radio frequency module 340 may include one or more package structures, for example, to protect the radio frequency module 340 and / or to facilitate its handling. Such package structures may include overmolded structures formed on the package substrate 340. The overmolded structures may enclose some or all of the components of the radio frequency module 340.

[0184] Figure 35 is a schematic block diagram of module 350 including duplexers 351A-351N and an antenna switch 352. One or more filters of duplexers 351A-351N may include one or more BAW resonators having patterned mass loading layers relating to any suitable principles and advantages described herein. Any suitable number of duplexers 351A-351N can be implemented. The antenna switch 352 may have a certain number of projections corresponding to the number of duplexers 351A-351N. The antenna switch 352 may include one or more additional projections coupled to one or more filters outside module 350 and / or coupled to other circuits. The antenna switch 352 can electrically couple selected duplexers to the antenna ports of module 350.

[0185] Figure 36 is a schematic block diagram of module 354, which includes a power amplifier 355, a radio frequency switch 356, and duplexers 351A to 351N according to one or more embodiments. The power amplifier 355 can amplify radio frequency signals. The radio frequency switch 356 may be a multi-throw radio frequency switch. The radio frequency switch 356 can electrically couple the output of the power amplifier 355 to a selected transmit filter of the duplexers 351A to 351N. One or more filters of the multiplexers 351A to 351N may include any suitable number of BAW resonators having patterned mass loading layers relating to any suitable principles and advantages described herein. Any suitable number of multiplexers 351A to 351N can be implemented.

[0186] Figure 37 is a schematic block diagram of module 357, which includes filters 351A'~351N', a radio frequency switch 358', and a low-noise amplifier 359 according to one embodiment. One or more filters of the multiplexers 351A'~351N' may include any suitable number of BAW resonators having patterned mass loading layers relating to any suitable principles and advantages described herein. Any suitable number of multiplexers 351A'~351N' can be implemented. The radio frequency switch 358 may be a multi-throw radio frequency switch. The radio frequency switch 358 can electrically couple the output of a selected filter of filters 351A'~351N' to the low-noise amplifier 359. In some embodiments (not illustrated), multiple low-noise amplifiers can be implemented. Module 357 may include a diversity receiving feature in a given application.

[0187] Figure 38 is a schematic diagram of a radio frequency module 380 including an elastic wave filter according to one embodiment. As shown, the radio frequency module 380 includes duplexers 382A to 382N, including corresponding transmit filters 383A1 to 383N1 and corresponding receive filters 383A2 to 383N2, a power amplifier 384, a selector switch 385, and an antenna switch 386. The radio frequency module 380 may include a package enclosing the illustrated elements. The illustrated elements can be arranged on a common package substrate 387. The package substrate 387 may be, for example, a multilayer substrate. A radio frequency module including a power amplifier may be referred to as a power amplifier module. The radio frequency module may include a subset of the elements and / or additional elements illustrated in Figure 38. The radio frequency module 380 may include one or more BAW resonators having patterned mass loading layers relating to any suitable principles and advantages disclosed herein.

[0188] Each of the duplexers 382A to 382N may include two elastic wave filters coupled to a common node. For example, the two elastic wave filters may be a transmit filter and a receive filter. As shown in the figure, each of the transmit filter and the receive filter may include a band-pass filter arranged to filter radio frequency signals. One or more of the transmit filters 383A1 to 383N1 may include one or more BAW resonators having a patterned mass loading layer relating to any suitable principle and advantages disclosed herein. Similarly, one or more of the receive filters 383A2 to 383N2 may include one or more BAW resonators having a patterned mass loading layer relating to any suitable principle and advantages disclosed herein. Although Figure 38 illustrates a duplexer, any suitable principle and advantages disclosed herein can be implemented in other multiplexers (e.g., quadplexers, hexaplexers, octaplexers, etc.) and / or switched multiplexers.

[0189] The power amplifier 384 can amplify radio frequency signals. The illustrated switch 385 is a multi-throw radio frequency switch. Switch 385 can electrically couple the output of the power amplifier 384 to a selected transmit filter of the transmit filters 383A1 to 383N1. In some examples, switch 385 can electrically connect the output of the power amplifier 384 to two or more of the transmit filters 383A1 to 383N1. The antenna switch 386 can selectively couple signals from one or more of the duplexers 212A to 212N to the antenna port ANT. The duplexers 382A to 382N can be associated with different frequency bands and / or different operating modes (e.g., different power modes, different signal modes, etc.).

[0190] The BAW resonator having a patterned mass loading layer disclosed herein may be implemented in various wireless communication devices such as portable devices. Figure 39 is a schematic diagram of one embodiment of a portable device 390. The portable device 390 includes a baseband system 391, a transceiver 392, a front-end system 393, an antenna 394, a power management system 395, a memory 396, a user interface 397, and a battery 398.

[0191] The mobile device 390 can be used to communicate using a wide variety of communication technologies, including but not limited to second-generation (2G), third-generation (3G), fourth-generation (4G) (including LTE®, LTE Advanced, and LTE Advanced Pro), fifth-generation (5G) New Radio (NR), wireless local area network (WLAN) (e.g., Wi-Fi), wireless personal area network (WPAN) (e.g., Bluetooth® and ZigBee®), WMAN (wireless metropolitan area network) (e.g., WiMAX®), global positioning system (GPS) technology, or any appropriate combination thereof.

[0192] The transceiver 392 generates RF signals for transmission and processes incoming RF signals received from the antenna 394. It is understood that various functions associated with transmitting and receiving RF signals can be achieved by one or more components, collectively represented in Figure 39 as the transceiver 392. In one example, a separate component (e.g., a separate circuit or die) may be provided to handle a given type of RF signal.

[0193] The front-end system 393 assists in conditioning the signals transmitted to and / or received from the antenna 394. In the illustrated embodiment, the front-end system 393 includes a charge pump 400, a power amplifier (PA) 811, a low-noise amplifier (LNA) 812, a filter 403, a switch 404, and a signal splitting / coupling circuit 405. However, other implementations are possible. One or more of the filters 403 may be implemented according to any suitable principles and advantages disclosed herein. For example, one or more of the filters 403 may include at least one BAW resonator having a patterned mass loading layer according to any suitable principles and advantages disclosed herein.

[0194] For example, the front-end system 393 can provide a certain number of functions, including, but not limited to, signal amplification for transmission, signal amplification, signal filtering, switching between different bandwidths, switching between different power modes, switching between transmit and receive modes, signal duplexing, signal multiplexing (e.g., diplexing or triplexing), or any combination thereof.

[0195] In a given implementation example, the mobile device 390 supports carrier aggregation, providing flexibility to increase the peak data rate. Carrier aggregation can be used with both frequency-division duplexing (FDD) and time-division duplexing (TDD) and can be used to aggregate multiple carriers or channels. Carrier aggregation includes adjacent aggregation, where adjacent carriers within the same operating frequency band are aggregated. Carrier aggregation may also be discontinuous and may include carriers with separated frequencies within a common band or in different bands.

[0196] Antenna 394 may include antennas used for a wide variety of types of communication. For example, antenna array 394 may include antennas that transmit and / or receive signals associated with a wide variety of frequencies and communication standards.

[0197] In a given implementation example, antenna 394 supports MIMO communication and / or switched diversity communication. For example, MIMO communication uses multiple antennas to communicate multiple data streams over a single radio frequency channel. MIMO communication benefits from a high signal-to-noise ratio, improved coding, and / or reduced signal interference due to spatial multiplexing differences in the radio environment. Switched diversity refers to communication in which a particular antenna is selected to operate at a particular time. For example, a switch can be used to select a particular antenna from a group of antennas based on various factors such as the observed bit error rate and / or signal strength indicator.

[0198] The portable device 390 may operate with beamforming in a given implementation. For example, the front-end system 393 includes an amplifier with controllable gain and a phase shifter with controllable phase to give beam formation and directivity for transmitting and / or receiving signals using the antenna 394. For example, in the context of signal transmission, the amplitude and phase of the transmitted signal supplied to the antenna 394 are controlled so that the signal radiated from the antenna 394 is combined using constructive and destructive interference to produce an aggregated transmitted signal exhibiting beam-like quality of signal intensity propagating in a given direction. In the context of signal reception, the amplitude and phase are controlled so that more signal energy is received when the signal arrives at the antenna 394 from a particular direction. In a given implementation, the antenna 394 includes one or more arrays of multiple antenna elements to improve beamforming.

[0199] The baseband system 391 is coupled to the user interface 397 to facilitate the processing of various user inputs and outputs (I / O), such as voice and data. The baseband system 391 provides the transceiver 392 with a digital representation of the transmit signal, which the transceiver 392 generates an RF signal for transmission. The baseband system 391 also processes the digital representation of the receive signal provided by the transceiver 392. As shown in Figure 39, the baseband system 391 is coupled to the memory 396 to facilitate the operation of the portable device 390.

[0200] Memory 396 can be used for a wide variety of purposes, such as storing data and / or instructions, to facilitate the operation of the portable device 390 and / or to provide storage for user information.

[0201] The power management system 395 provides a certain number of power management functions for the portable device 390. In a given implementation example, the power management system 395 includes a PA supply control circuit that controls the supply voltage of the power amplifier 401. For example, the power management system 395 can be configured to vary the supply voltage supplied to one or more of the power amplifier 401 in order to improve an efficiency such as power added efficiency (PAE).

[0202] As shown in Figure 39, the power management system 395 receives the battery voltage from the battery 398. The battery 398 may be any suitable battery used in the portable device 390, including, for example, a lithium-ion battery.

[0203] The technology disclosed herein can be implemented in elastic wave filters for fifth-generation (5G) applications. 5G technology is also referred to herein as 5G New Radio (NR). 5G NR supports and / or is planned to support a variety of features, including millimeter-wave spectrum communication, beamforming capability, high spectral efficiency waveforms, low latency communication, multiplex radio numerology, and / or non-orthogonal multiplex access (NOMA). While such RF capabilities provide network flexibility and increase user data rates, supporting these features may present a number of technical challenges.

[0204] The teachings herein are applicable to a wide variety of communication systems, including but not limited to those using advanced cellular technologies such as LTE Advanced, LTE Advanced Pro, and / or 5G NR. Acoustic wave devices incorporating any suitable combination of the features disclosed herein may be included in filters arranged to filter radio frequency signals in the fifth-generation (5G) New Radio (NR) operating band within frequency range 1 (FR1). Filters arranged to filter radio frequency signals in the 5G NR operating band may include one or more SAW devices disclosed herein. FR1 can be, for example, 410 MHz to 7.125 GHz according to the current 5G NR specification. One or more acoustic wave devices relating to any suitable principles and advantages disclosed herein may be included in filters arranged to filter fourth-generation (4G) Long-Term Evolution (LTE) radio frequency signals. One or more acoustic wave devices relating to any suitable principles and advantages disclosed herein may be included in filters having passbands including the 4G LTE operating band and the 5G NR operating band. Such filters can be implemented in dual connectivity applications, such as E-UTRAN New Radio Dual Connectivity (ENDC) applications.

[0205] The elastic wave filter disclosed herein can suppress second harmonics. This feature may be advantageous in 5G NR applications. By suppressing second harmonics, filter linearity can be increased. Higher filter linearity can accommodate the high peak-to-average power ratio present in a given 5G NR application. Harmonic suppression and / or improved filter linearity may be advantageous in meeting one or more other specifications in 5G technology.

[0206] Figure 40 is a schematic diagram of an example of a communication network 410. The communication network 410 includes a macrocell base station 411, a small cell base station 413, and various examples of user equipment (UEs), including a first portable device 412a, a radio-connected vehicle 412b, a laptop 412c, a stationary radio device 412d, a radio-connected train 412e, a second portable device 412f, and a third portable device 412g. The UEs are radio communication devices. One or more of the macrocell base station 141, small cell base station 413, or UEs shown in Figure 40 may implement one or more elastic wave filters relating to any suitable principles and advantages disclosed herein. For example, one or more of the UEs shown in Figure 40 may include one or more elastic wave filters including any suitable number of BAW resonators having patterned mass loading layers.

[0207] Although specific examples of base stations and user equipment are shown in Figure 40, a communication network may include a wide variety of types and / or numbers of base stations and user equipment. For example, in the illustrated example, the communication network 410 includes a macrocell base station 411 and a smallcell base station 413. The smallcell base station 413 can operate with relatively lower power, a shorter range, and / or fewer simultaneous users compared to the macrocell base station 411. The smallcell base station 413 may also be referred to as a femtocell, picocell, or microcell. Although the communication network 410 is shown to include two base stations, the communication network 410 may be implemented to include more or fewer base stations and / or other types of base stations.

[0208] Although various examples of user equipment are presented, the teachings herein are applicable to a wide variety of user equipment, including, for example, mobile phones, tablets, laptops, Internet of Things (IoT) devices, wearable electronic devices, customer premises equipment (CPE), wirelessly connected vehicles, wireless relays, and / or a wide variety of other communication devices. Furthermore, user equipment includes not only currently available communication devices operating in cellular networks, but also subsequently developed communication devices that can be easily implemented with the systems, processes, methods and devices of the present invention described herein and claimed herein.

[0209] The communication network 410 illustrated in Figure 40 supports communication using various cellular technologies, including, for example, 4G LTE and 5G NR. In a given implementation example, the communication network 410 is further adapted to provide a wireless local area network (WLAN) such as Wi-Fi. Despite the various examples of communication technologies provided, the communication network 410 can be adapted to support a wide variety of communication technologies.

[0210] Various communication links of the communication network 410 are depicted in Figure 40. Communication links can be duplicated in a wide variety of ways, including, for example, frequency division duplexing (FDD) and / or time division duplexing (TDD). FDD is a type of radio frequency communication that uses different frequencies for signal transmission and signal reception. FDD can offer a number of advantages, such as high data rates and low latency. In contrast, TDD is a type of radio frequency communication that uses nearly the same frequency for signal transmission and signal reception, with transmission and reception switching over time. TDD can offer a number of advantages, such as efficient use of the spectrum and variable allocation of throughput between the transmission and reception directions.

[0211] In a given implementation example, user equipment can communicate with a base station using one or more of the following technologies: 4G LTE, 5G NR, and WiFi. In a given implementation example, Extended License Assisted Access (eLAA) is used to aggregate one or more licensed frequency carriers (e.g., licensed 4G LTE frequencies and / or 5G NR frequencies) together with one or more unlicensed carriers (e.g., unlicensed WiFi frequencies).

[0212] As shown in Figure 40, the communication link includes not only the communication link between user equipment (UE) and base stations, but also UE-to-UE communication and base station-to-base station communication. For example, the communication network 410 can be implemented to support self-fronthaul and / or self-backhaul (e.g., between mobile device 412g and mobile device 412f).

[0213] Communication links can operate across a wide variety of frequencies. In a given implementation, communication is supported using 5G NR technology over one or more frequency bands below 6 gigahertz (GHz) and / or over one or more frequency bands above 6 GHz. According to a given implementation, the communication link can correspond to frequency range 1 (FR1), frequency range 2 (FR2), or a combination thereof. Elastic wave filters relating to any suitable principles and advantages disclosed herein can filter radio frequency signals within FR1. In one embodiment, one or more portable devices support the HPUE power class specification.

[0214] In a given implementation example, a base station and / or user equipment communicate using beamforming. For example, beamforming can be used to concentrate signal strength to overcome path losses, such as high losses associated with communication over high signal frequencies. In a given embodiment, one or more user devices, such as mobile phones, communicate using beamforming in the millimeter-wave frequency band ranging from 30 GHz to 300 GHz, and / or in the upper centimeter-wave frequency range of 6 GHz to 30 GHz, and more specifically from 24 GHz to 30 GHz.

[0215] Different users of the communication network 410 can share available network resources, such as the available frequency spectrum, in a wide variety of ways. For example, Frequency Division Multiple Access (FDMA) is used to divide a frequency band into multiple frequency carriers. Additionally, one or more carriers are allocated to specific users. Examples of FDMA include, but are not limited to, single-carrier FDMA (SC-FDMA) and quadrature FDMA (OFDMA). OFDMA is a multi-carrier technique that subdivides the available bandwidth into numerous mutually orthogonal narrowband subcarriers, which can be allocated individually to different users.

[0216] Other examples of shared access include, but are not limited to, time-division multiple access (TDMA), where users are assigned to specific time slots that use frequency resources; code-division multiple access (CDMA), where frequency resources are shared among different users by assigning a unique code to each user; spatial-division multiple access (SDMA), where beamforming is used to provide shared access through spatial division; and non-orthogonal multiple access (NOMA), where power domains are used for multiple access. For example, NOMA can be used to accommodate a large number of users who are on the same frequency, time, and / or code, but at different power levels.

[0217] Enhanced Mobile Broadband (eMBB) refers to technologies for the increasing system capacity of LTE networks. For example, eMBB can refer to communication at a peak data rate of at least 10 Gbps, with each user receiving a minimum of 100 Mbps. Ultra-High Reliability Low Latency Communication (uRLLC) refers to technologies for communication with extremely low latency, for example, less than 3 milliseconds. uRLLC can be used for mission-critical communications such as autonomous driving applications and / or remote surgery applications. Massive Machine Communication (mMTC) refers to low-cost, low-data-rate communications associated with wireless connectivity to everyday objects, such as those associated with Internet of Things (IoT) applications.

[0218] The communication network 410 in Figure 40 can be used to support a wide variety of advanced communication functions, including but not limited to eMBB, uRLLC, and / or mMTC. Applications, terminology, and conclusions

[0219] Any of the embodiments described above can be implemented in connection with a portable device such as a cellular handset. The principles and advantages of the embodiments can be used in any system or device, such as any uplink wireless communication device, which may benefit from any of the embodiments described herein. The teachings herein are applicable to a variety of systems. Although this disclosure includes examples of embodiments, the teachings described herein are applicable to a variety of structures. Any of the principles and advantages described herein can be implemented in connection with an RF circuit configured to process signals having frequencies in the range of about 30 kHz to 300 GHz, such as in the range of about 450 MHz to 8.5 GHz.

[0220] Multiple aspects of this disclosure can be implemented in various electronic devices. Examples of electronic devices include, but are not limited to, consumer electronic products, components of consumer electronic products such as packaged radio frequency modules, radio frequency filter dies, uplink wireless communication devices, wireless communication infrastructure, and electronic test equipment. Examples of electronic devices include, but are not limited to, portable telephones such as smartphones, wearable computing devices such as smartwatches or earpieces, telephones, televisions, computer monitors, computers, modems, handheld computers, laptop computers, tablet computers, microwave ovens, refrigerators, automotive electronic systems such as automotive electronic systems, robots such as industrial robots, Internet of Things devices, stereo systems, digital music players, radios, cameras such as digital cameras, portable memory chips, household appliances such as washing machines or dryers, peripheral devices, wristwatches, and clocks. Furthermore, electronic devices may also include unfinished products.

[0221] Throughout this specification and the claims, unless the context indicates otherwise, terms such as “equip,” “include,” and “incorporate” should be interpreted in a comprehensive sense, as opposed to an exclusive or exhaustive sense, i.e., “include, but not limited to.” Conditional language as used herein, in particular, such as “can,” “may,” “may,” “might,” “for example,” and “like,” is generally intended to convey that a given embodiment includes a given feature, element, and / or state, while other embodiments do not, unless it is specifically stated that they do not, or understood in the context of use that they do not. The word “combined” as used herein refers to two or more elements that may be directly connected or connected via one or more intermediate elements. Similarly, the word “connected” as used herein refers to two or more elements that may be directly connected or connected via one or more intermediate elements. In addition, the words “here,” “above,” “below,” and words of a similar nature, when used in this application, refer to the entire application and not to any particular part thereof. Where the context allows, each term used in the above detailed explanation, whether singular or plural, may also be plural or singular.

[0222] While certain embodiments have been described, these embodiments are presented only as examples and are not intended to limit the scope of this disclosure. In fact, the novel filters, wireless communication devices, apparatus, methods, and systems described herein can be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and modifications in the forms of filters, wireless communication devices, apparatus, methods, and systems described herein can be made without departing from the essence of this disclosure. For example, while several blocks are presented in a given arrangement, alternative embodiments may perform similar functions with different components and / or circuit topologies, and some blocks may be deleted, moved, added, subdivided, combined, and / or modified. Each of these blocks can be implemented in a variety of different forms. Any suitable combination of elements and processes of the various embodiments described above can be combined to give further embodiments. The appended claims and their equivalents are intended to cover such forms or modifications that fall within the scope and essence of this disclosure.

Claims

1. It is an elastic wave filter, A first bulk acoustic wave resonator including a first patterned mass loading layer, A second bulk acoustic wave resonator including a second patterned mass loading layer and Includes, The first patterned mass loading layer influences the resonant frequency of the first bulk elastic wave resonator. The second patterned mass loading layer affects the resonant frequency of the second bulk elastic wave resonator. The aforementioned elastic wave filter is arranged to filter radio frequency signals, The first patterned mass loading layer has a first density in the main elastically active region of the first bulk elastic wave resonator and a second density in the recessed frame region of the first bulk elastic wave resonator. The recessed frame region is formed around the periphery of the main elastically active region, An elastic wave filter wherein the second density is different from the first density.

2. The elastic wave filter according to claim 1, wherein the first patterned mass loading layer has a periodic pattern.

3. The elastic wave filter according to claim 1, wherein the first patterned mass loading layer includes a plurality of strips spaced apart from each other.

4. The elastic wave filter according to claim 1, wherein the first patterned mass loading layer is made of metal.

5. The elastic wave filter according to claim 1, wherein the first patterned mass loading layer is made of a dielectric material.

6. The elastic wave filter according to claim 1, wherein the first patterned mass loading layer is disposed below the piezoelectric layer of the first bulk elastic wave resonator.

7. The elastic wave filter according to claim 1, wherein the first patterned mass loading layer is disposed above the piezoelectric layer of the first bulk elastic wave resonator.

8. The elastic wave filter according to claim 1, wherein the first patterned mass loading layer extends from the first piezoelectric layer of the first bulk elastic wave resonator by the same distance as the second patterned mass loading layer extends from the second piezoelectric layer of the second bulk elastic wave resonator.

9. The elastic wave filter according to claim 1, further comprising a third bulk elastic wave resonator including a third patterned mass loading layer having a third density.

10. The elastic wave filter according to claim 1, wherein the resonant frequency of the first bulk elastic wave resonator is in a range of 1% to 10% greater than the resonant frequency of the second bulk elastic wave resonator.

11. The elastic wave filter according to claim 1, wherein the second patterned mass loading layer has a duty factor in the range of 0.05 to 0.95 in the central area of ​​the active region of the second bulk elastic wave resonator.

12. The elastic wave filter according to claim 1, wherein the first patterned mass loading layer has a duty factor in the range of 0.2 to 0.8 in the central area of ​​the active region of the first bulk elastic wave resonator.

13. It is an elastic wave die, A first bulk elastic wave resonator located on the elastic wave die, A second bulk elastic wave resonator located above the elastic wave die and Includes, The first bulk acoustic wave resonator includes a first patterned mass loading layer, The first patterned mass loading layer influences the resonant frequency of the first bulk elastic wave resonator. The second bulk acoustic wave resonator includes a second patterned mass loading layer, The second patterned mass loading layer affects the resonant frequency of the second bulk elastic wave resonator. The first patterned mass loading layer has a first density in the main elastically active region of the first bulk elastic wave resonator and a second density in the recessed frame region of the first bulk elastic wave resonator. The recessed frame region is formed around the periphery of the main elastically active region, The elastic wave die wherein the second density is different from the first density.

14. The elastic wave die of claim 13, wherein the first bulk elastic wave resonator and the second bulk elastic wave resonator are included in the same filter.

15. The elastic wave die of claim 13, wherein the first bulk elastic wave resonator and the second bulk elastic wave resonator are included in different filters.

16. The elastic wave die according to claim 13, wherein the first patterned mass loading layer includes a plurality of strips spaced apart from each other.

17. The elastic wave die of claim 13 further comprises a third bulk elastic wave resonator including a third patterned mass loading layer having a third density.

18. The elastic wave die according to claim 13, wherein the resonant frequency of the first bulk elastic wave resonator is in a range of 1% to 10% greater than the resonant frequency of the second bulk elastic wave resonator.

19. The elastic wave die of claim 13, wherein the first patterned mass loading layer has a duty factor in the range of 0.2 to 0.8 in the central area of ​​the active region of the first bulk elastic wave resonator.

20. A radio frequency module, An elastic wave filter including a first bulk elastic wave resonator and a second bulk elastic wave resonator, At least a radio frequency circuit element coupled to the elastic wave filter and Includes, The first bulk acoustic wave resonator includes a first patterned mass loading layer, The first patterned mass loading layer influences the resonant frequency of the first bulk elastic wave resonator. The second bulk acoustic wave resonator includes a second patterned mass loading layer, The second patterned mass loading layer affects the resonant frequency of the second bulk elastic wave resonator. The elastic wave filter and the radio frequency circuit element are enclosed in a common module package. The first patterned mass loading layer has a first density in the main elastically active region of the first bulk elastic wave resonator and a second density in the recessed frame region of the first bulk elastic wave resonator. The recessed frame region is formed around the periphery of the main elastically active region, A radio frequency module in which the second density is different from the first density.

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