Acoustic wave device and method of manufacturing the same

文档序号：1537787 发布日期：2020-02-14 浏览：17次中文

阅读说明：本技术 声波器件及其制作方法 (Acoustic wave device and method of manufacturing the same ) 是由彭波华李平胡念楚贾斌于 2019-11-25 设计创作，主要内容包括：一种声波器件及其制作方法,声波器件包括：POI结构,包含：高声速层和低声速层交替的材料层,衬底作为最下方的高声速层；以及第一压电层,位于高声速层和低声速层交替的材料层的上方,与所述第一压电层相邻的为表面低声速层；所述高声速层传播的体波声速比所述第一压电层的体波声速高,所述低声速层传播的体波声速比所述第一压电层的体波声速低；POI结构包含至少两个区域,其中两个区域分别为第一区域和第二区域,在第一区域制作有第一振动模式谐振的第一器件；在第二区域制作有第二振动模式谐振的第二器件。能够减少不同区域的器件之间的耦合干扰,提升滤波器或双工器的抑制和隔离度；还能减小器件的尺寸,降低成本,满足通信小型化的要求。(An acoustic wave device and a method of fabricating the same, the acoustic wave device comprising: a POI structure comprising: the high-sound-velocity layers and the low-sound-velocity layers are arranged alternately, and the substrate is used as the lowest high-sound-velocity layer; and a first piezoelectric layer located above the alternating layers of material of high acoustic velocity and low acoustic velocity, adjacent to the first piezoelectric layer being a surface low acoustic velocity layer; the high acoustic velocity layer propagates at a bulk acoustic velocity higher than that of the first piezoelectric layer, and the low acoustic velocity layer propagates at a bulk acoustic velocity lower than that of the first piezoelectric layer; the POI structure comprises at least two areas, wherein the two areas are a first area and a second area respectively, and a first device with first vibration mode resonance is manufactured in the first area; a second device having a second mode resonance is formed in the second region. Coupling interference among devices in different areas can be reduced, and the suppression and isolation of the filter or the duplexer are improved; the size of the device can be reduced, the cost is reduced, and the requirement of communication miniaturization is met.)

1. An acoustic wave device, comprising:

a POI structure comprising: the high-sound-velocity layers and the low-sound-velocity layers are arranged alternately, and the substrate is used as the lowest high-sound-velocity layer; and a first piezoelectric layer located above the alternating layers of material of high acoustic velocity and low acoustic velocity, adjacent to the first piezoelectric layer being a surface low acoustic velocity layer; the high acoustic velocity layer propagates at a bulk acoustic velocity higher than that of the first piezoelectric layer, and the low acoustic velocity layer propagates at a bulk acoustic velocity lower than that of the first piezoelectric layer;

the POI structure comprises at least two areas, wherein the two areas are a first area and a second area respectively, and a first device with first vibration mode resonance is manufactured in the first area; a second device having a second mode resonance is formed in the second region.

2. The acoustic wave device of claim 1, wherein the first and second vibration modes are a combination of any two types of bulk acoustic wave vibration modes (BAW), surface acoustic wave vibration modes (SAW), radial mode modes (CMR);

optionally, the first vibration mode and the second vibration mode are different vibration modes.

3. An acoustic wave device according to claim 1,

the first piezoelectric layer is positioned above the surface low-acoustic-speed layer of the second area;

an interdigitated electrode layer on said first piezoelectric layer;

the piezoelectric structure is positioned above the surface low-acoustic-speed layer of the first region, a space exists between the piezoelectric structure and the first piezoelectric layer, and a first cavity is arranged below the piezoelectric structure;

wherein the piezoelectric structure comprises a lower electrode layer, a second piezoelectric layer and an upper electrode layer which are sequentially stacked.

4. An acoustic wave device according to claim 3, wherein the upper electrode layer is of a thin film structure or of an interdigital electrode structure.

5. An acoustic wave device according to claim 3, wherein the first piezoelectric layer has a second cavity below it, the second cavity being formed by releasing a portion of the surface low acoustic velocity layer below the first piezoelectric layer and the substrate.

6. An acoustic wave device according to claim 3,

the upper surface of the piezoelectric structure and the interdigital electrode layer are covered with dielectric layers;

the second region comprises two sub-regions, namely a first sub-region and a second sub-region, the interdigital electrode layer is located in the first sub-region, the other interdigital electrode layer is located in the second sub-region, and a dielectric layer and a metal connecting layer are sequentially covered on the other interdigital electrode layer.

7. An acoustic wave device according to any of claims 3-6,

the metal layer is arranged on the interdigital electrode layer and is positioned at the edge of an interdigital electrode arm of the interdigital electrode layer; alternatively, the first and second electrodes may be,

a second high-sound-velocity layer is formed in the middle area of the interdigital electrode layer, and the sound velocity of the bulk wave propagated by the second high-sound-velocity layer is higher than that of the bulk wave of the first piezoelectric layer;

optionally, when any one of claims 3-7 is referred to,

the first cavity is formed by releasing part of the surface low-acoustic-speed layer and the substrate below the piezoelectric structure; alternatively, the first and second electrodes may be,

the first cavity is formed by releasing part of the surface low-sound-velocity layer below the piezoelectric structure, and a barrier layer is arranged on the periphery of the first cavity below the piezoelectric structure.

8. An acoustic wave device according to claim 1,

the device of the first area is a bulk acoustic wave device which is an SMR structure, and an acoustic reflection layer which comprises alternately laminated low-acoustic impedance material layers and high-acoustic impedance material layers and is positioned on the first piezoelectric layer of the first area; the piezoelectric structure is positioned on the low acoustic impedance material layer of the acoustic reflection layer; alternatively, the first and second electrodes may be,

the device in the first region is a high-order resonant wave device, and the device in the second region is one or a combination of the following devices: a resonator of bulk acoustic wave vibration modes (BAW), a surface acoustic wave vibration mode (SAW), a resonator of radial mode modes (CMR), wherein the resonator of bulk acoustic wave vibration modes comprises one or a combination of the following resonators: film Bulk Acoustic Resonators (FBAR) and solid state fabricated resonators (SMR).

9. An acoustic wave device according to any of claims 1-8, wherein all or part of the devices in at least two regions of the acoustic wave device act as filters or duplexers;

optionally, the surface low acoustic velocity layer is a temperature compensation layer, and the material of the temperature compensation layer is a dielectric material with a positive frequency temperature coefficient.

10. A method of fabricating an acoustic wave device as claimed in any of claims 1-8, comprising:

fabricating a POI structure, the POI structure comprising: the high-sound-velocity layers and the low-sound-velocity layers are arranged alternately, and the substrate is used as the lowest high-sound-velocity layer; and a first piezoelectric layer, located above the alternating layers of material of high acoustic velocity layers and low acoustic velocity layers, adjacent to said first piezoelectric layer referred to as the surface low acoustic velocity layer; the high acoustic velocity layer propagates at a bulk acoustic velocity higher than that of the first piezoelectric layer, and the low acoustic velocity layer propagates at a bulk acoustic velocity lower than that of the first piezoelectric layer;

the POI structure comprises at least two areas, wherein the two areas are a first area and a second area respectively, and a first device with first vibration mode resonance is manufactured in the first area; a second device is fabricated in the second region having a second mode of vibration resonance.

Optionally, in an embodiment, the manufacturing method includes:

the POI structure comprises at least two areas, wherein the two areas are a first area and a second area respectively, and the first piezoelectric layer of the first area is etched away, so that the surface low acoustic velocity layer is exposed;

manufacturing a piezoelectric structure on the exposed surface low-acoustic-velocity layer, wherein a space exists between the piezoelectric structure and the first piezoelectric layer; wherein the piezoelectric structure comprises a lower electrode layer, a second piezoelectric layer and an upper electrode layer which are sequentially stacked;

manufacturing an interdigital electrode layer on the first piezoelectric layer of the second area;

and releasing part of the temperature compensation layer and the substrate below the piezoelectric structure to form a first cavity, and obtaining a first device with first vibration mode resonance in a first area and a second device with second vibration mode resonance in a second area.

Optionally, in another embodiment, the manufacturing method includes:

etching part of the surface low-acoustic-velocity layer to obtain an annular hollow area, and growing a barrier layer in the annular hollow area, wherein the material of the barrier layer and the material of the surface low-acoustic-velocity layer have different etching rates;

manufacturing a piezoelectric structure on a surface low-acoustic-speed layer of a first region, wherein a space exists between the piezoelectric structure and the first piezoelectric layer; wherein the piezoelectric structure comprises a lower electrode layer, a second piezoelectric layer and an upper electrode layer which are sequentially stacked;

manufacturing an interdigital electrode layer on the first piezoelectric layer of the second area;

etching the surface low-acoustic-velocity layer on the inner side of the barrier layer as a sacrificial layer based on the etching rate difference to form a first cavity;

a first device for obtaining a first vibration mode resonance in a first region, and a second device for obtaining a second vibration mode resonance in a second region;

optionally, the interdigital electrode layer is manufactured by multiplexing the material and the thickness of the lower electrode layer; or, a layer of electrode material is separately grown to manufacture the interdigital electrode layer.

Technical Field

The disclosure belongs to the technical field of communication devices, and relates to an acoustic wave device and a manufacturing method thereof.

Background

The acoustic wave filter may be used in a high frequency circuit, for example, as a band pass filter. The acoustic wave filter is formed by combining a plurality of acoustic wave resonators.

In recent years, filters, duplexers, and the like, which have acoustic wave resonators as basic units, have been increasingly downsized, high-frequency, and wide-band. Acoustic Wave resonators are generally classified into Surface Acoustic Wave (SAW) devices and Bulk Acoustic Wave (BAW) devices according to vibration modes. However, the SAW device is not suitable for high frequency applications of 2.5GHz or more because the line width of the interdigital electrode (IDT) is too small to be easily manufactured and the electrode loss is large. The BAW device generally uses a ladder structure, and has a larger area and a limited miniaturization compared with a Dual Mode Saw (DMS). In addition, the resonators are too close to each other, so that coupling is easily generated due to leakage of acoustic waves, and there is a problem that suppression and isolation are deteriorated.

With the development of mobile communication to 5G, the frequency bands of communication are increasing, and the requirements of different frequency bands on insertion loss and bandwidth are different, which also puts diversified demands on the filter technology.

Disclosure of Invention

The present disclosure provides an acoustic wave device and a method for manufacturing the same to reduce coupling interference between devices, improve suppression and isolation of a filter or a duplexer, and further reduce the size of the device to meet the requirement of miniaturization.

According to an aspect of the present disclosure, there is provided an acoustic wave device including: a POI structure comprising: the high-sound-velocity layers and the low-sound-velocity layers are arranged alternately, and the substrate is used as the lowest high-sound-velocity layer; and a first piezoelectric layer, located above the alternating layers of material of high acoustic velocity layers and low acoustic velocity layers, adjacent to said first piezoelectric layer referred to as the surface low acoustic velocity layer; the high acoustic velocity layer propagates at a bulk acoustic velocity higher than that of the first piezoelectric layer, and the low acoustic velocity layer propagates at a bulk acoustic velocity lower than that of the first piezoelectric layer; the POI structure comprises at least two areas, wherein the two areas are a first area and a second area respectively, and a first device with first vibration mode resonance is manufactured in the first area; a second device having a second mode resonance is formed in the second region.

In an embodiment of the present disclosure, the first vibration mode and the second vibration mode are a combination of any two types of bulk acoustic wave vibration mode (BAW), surface acoustic wave vibration mode (SAW), radial mode (CMR).

In an embodiment of the present disclosure, the first vibration mode and the second vibration mode are different vibration modes.

In an embodiment of the present disclosure, the first piezoelectric layer is located above the surface low acoustic velocity layer of the second region; an interdigitated electrode layer on said first piezoelectric layer; the piezoelectric structure is positioned above the surface low-acoustic-speed layer of the first region, a space exists between the piezoelectric structure and the first piezoelectric layer, and a first cavity is arranged below the piezoelectric structure; wherein the piezoelectric structure comprises a lower electrode layer, a second piezoelectric layer and an upper electrode layer which are sequentially stacked.

In an embodiment of the present disclosure, the upper electrode layer is of a thin film structure or an interdigital electrode structure.

In an embodiment of the disclosure, a second cavity is provided below the first piezoelectric layer, the second cavity being formed by releasing a portion of the surface low acoustic speed layer below the first piezoelectric layer and the substrate.

In an embodiment of the present disclosure, a dielectric layer covers both the upper surface of the piezoelectric structure and the interdigital electrode layer; the second region comprises two sub-regions, namely a first sub-region and a second sub-region, the interdigital electrode layer is located in the first sub-region, the other interdigital electrode layer is located in the second sub-region, and a dielectric layer and a metal connecting layer are sequentially covered on the other interdigital electrode layer.

In an embodiment of the present disclosure, there is a metal layer on the interdigital electrode layer, and the metal layer is located at an edge of an interdigital electrode arm of the interdigital electrode layer; alternatively, the first and second electrodes may be,

and a second high-sound-velocity layer is formed in the middle area of the interdigital electrode layer, and the sound velocity of the bulk wave propagated by the second high-sound-velocity layer is higher than that of the bulk wave of the first piezoelectric layer.

In an embodiment of the present disclosure, in the above scheme, the first cavity is formed by releasing a portion of the temperature compensation layer and the substrate under the piezoelectric structure; alternatively, the first and second electrodes may be,

the first cavity is formed by releasing part of the temperature compensation layer below the piezoelectric structure, and a barrier layer is arranged on the periphery of the first cavity below the piezoelectric structure.

In one embodiment of the present disclosure, the device of the first region is a bulk acoustic wave device, the bulk acoustic wave device is an SMR structure, an acoustic reflection layer comprising alternately stacked layers of low acoustic impedance material and high acoustic impedance material is disposed on the first piezoelectric layer of the first region; the piezoelectric structure is positioned on the low acoustic impedance material layer of the acoustic reflection layer; alternatively, the first and second electrodes may be,

In one embodiment of the present disclosure, all or part of the devices in at least two regions of the acoustic wave device act as filters or duplexers.

In an embodiment of the present disclosure, the POI structure includes: the temperature compensation device comprises a substrate, a temperature compensation layer and a first piezoelectric layer. Optionally, a plurality of alternating layers of high acoustic velocity and low acoustic velocity may be disposed between the temperature compensation layer and the first piezoelectric layer, and a surface low acoustic velocity layer is disposed adjacent to the first piezoelectric layer.

According to another aspect of the present disclosure, there is provided a method of manufacturing an acoustic wave device, including:

the POI structure comprises at least two areas, wherein the two areas are a first area and a second area respectively, and a first device with first vibration mode resonance is manufactured in the first area; a second device is fabricated in the second region having a second mode of vibration resonance.

According to the technical scheme, the acoustic wave device and the manufacturing method thereof have the following beneficial effects:

(1) by using the POI structure based on which acoustic waves formed by device vibration propagate only in the piezoelectric layer and the low acoustic velocity layer without leaking into a deeper substrate layer than in a conventional SAW device piezoelectric substrate such as lithium niobate or lithium tantalate, etc., energy leakage in the longitudinal direction is suppressed. But in the transverse direction, partial energy still spreads outwards, at least two modes of devices are integrated on the same device based on at least two regions, the implementation mode is simple and convenient, and the vibration modes or the spreading directions are different by controlling the difference of the two modes, so that the coupling interference between the devices in different regions can be reduced, and the suppression and the isolation of the filter or the duplexer formed by combining the devices in different regions are improved; therefore, the size of the device can be reduced, the cost is reduced, and the requirement of communication miniaturization is met;

(2) as the devices in various vibration modes do not need to use piezoelectric materials with the same material and thickness, the design freedom degree is improved, and the device is beneficial to manufacturing products meeting different bandwidths, different insertion losses, isolation degrees, different power capacities and the like.

Drawings

Fig. 1 is a schematic cross-sectional structure view of an acoustic wave device according to a first embodiment of the present disclosure.

Fig. 2 is a schematic top view of an acoustic wave device according to a first embodiment of the present disclosure.

Fig. 3 is a schematic cross-sectional structure view of an acoustic wave device according to a second embodiment of the present disclosure.

Fig. 4 is a schematic cross-sectional structure view of an acoustic wave device according to a third embodiment of the present disclosure.

Fig. 5 is a schematic cross-sectional structure view of an acoustic wave device according to a fourth embodiment of the present disclosure.

Fig. 6 is a schematic cross-sectional structure view of an acoustic wave device according to a fifth embodiment of the present disclosure.

Fig. 7 is a schematic cross-sectional structure view of an acoustic wave device according to a sixth embodiment of the present disclosure.

Fig. 8 is a schematic sectional structure view of an acoustic wave device according to a seventh embodiment of the present disclosure.

Fig. 9 is a schematic top view of an acoustic wave device according to an eighth embodiment of the present disclosure.

Fig. 10 is a method of fabricating an acoustic wave device according to a ninth embodiment of the present disclosure.

[ notation ] to show

11-a substrate; 12-a temperature compensation layer;

13-a first piezoelectric layer; 14-an interdigitated electrode layer;

15-a metal layer; 16-a reflective grating;

21-a lower electrode layer; 22-upper electrode layer;

23-a second piezoelectric layer;

d1 — first region; d2 — second region;

3-a first cavity; 4-a barrier layer;

5-an acoustically reflective layer;

51-a layer of low acoustic impedance material; 52-a layer of high acoustic impedance material;

22' -an upper electrode layer of an interdigitated electrode structure;

6-a second cavity;

14' -the interdigital electrode layer of the third resonance section;

7-a dielectric layer; 8-a metal connection layer;

9-high sound velocity layer.

Detailed Description

For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.

SAW devices use interdigitated electrodes to convert electrical energy to acoustic energy, or conversely acoustic energy to electrical energy. The interdigital electrode uses a piezoelectric substrate and two opposing bus bars (buss bars) at two different potentials and two sets of electrodes connected to the two bus bars. Due to the inverse piezoelectric effect, an electric field between two successive electrodes at different potentials provides a source of acoustic waves. Conversely, if the transducer receives an incident wave, an electric charge is generated in the electrodes due to the piezoelectric effect, the resonator being obtained by placing the transducer between two reflecting gratings.

BAW devices, like SAW devices, rely on the piezoelectric effect of piezoelectric materials to create resonance. BAW devices typically have higher Q values and better power handling capabilities, but the equivalent coupling coefficient (which determines the filter bandwidth) is slightly less than SAW. BAW resonators generally consist of a sandwich of an upper electrode layer, a piezoelectric layer, and a lower electrode layer, which creates resonance. Below the lower electrode is an air cavity (FBAR) or acoustically reflective layer (SMR), with the resonance region occurring within the piezoelectric layer rather than at the surface.

In addition, a resonator such as a radial mode resonator (CMR) can be manufactured by using a lamb wave (mode) mode of the piezoelectric layer, but the resonator has the disadvantages of small equivalent coupling coefficient (k2eff) and low Q value.

The performance of acoustic wave filtering technologies such as BAW, SAW and CMR are good and bad, so how to integrate these technologies in the same chip becomes a technical problem to be overcome in the industry. The method for solving the technical problems has important value for manufacturing products meeting different bandwidths, different insertion losses, different isolation degrees, different power capacities and the like.

Some researches produce the acoustic wave device by growing different material layers on the silicon substrate or bonding different substrates, so that the process steps are more, meanwhile, different resonators are limited to use the same piezoelectric material, the industrial popularization of the device is not facilitated, and the application range is limited. Some researches mention that two filters of the duplexer use different vibration modes respectively, but are manufactured based on different chips, and the vibration modes of resonators in the filters are the same; some filters are formed by using resonators with different vibration modes based on the same substrate, but only a combination form of the resonators with different vibration modes of CMR + BAW is provided, and the application range is limited.

According to the acoustic wave device and the manufacturing method thereof, the POI structure is adopted, the two devices are integrated on the same substrate, the piezoelectric film layer of the POI structure is used as the piezoelectric layer of one device, and the temperature compensation layer of the POI structure is used as the sacrificial layer of the other device, so that the requirements of different devices on the thickness, the roughness, the crystal direction and the like of the film are effectively controlled, the number of materials and layers for integrating the two devices is reduced, and the manufacturing cost is effectively reduced.

An acoustic wave device of the present disclosure includes: a POI structure comprising: the high-sound-velocity layers and the low-sound-velocity layers are arranged alternately, and the substrate is used as the lowest high-sound-velocity layer; and a first piezoelectric layer, located above the alternating layers of material of high acoustic velocity layers and low acoustic velocity layers, adjacent to said first piezoelectric layer referred to as the surface low acoustic velocity layer; the high acoustic velocity layer propagates at a bulk acoustic velocity higher than that of the first piezoelectric layer, and the low acoustic velocity layer propagates at a bulk acoustic velocity lower than that of the first piezoelectric layer;

In an embodiment of the present disclosure, the first region is a resonator having a first vibration mode, such as a bulk acoustic wave vibration mode resonator (BAW), and the second region is a resonator having a second vibration mode, such as a surface acoustic wave vibration mode (SAW) or a radial mode (CMR). Specifically, the resonator of the bulk acoustic wave vibration mode may be a Film Bulk Acoustic Resonator (FBAR), such as the structures exemplified in the first and second embodiments, in such a manner that the devices of the first region and the second region are combined: FBAR (a kind of BAW) + SAW; the resonator of the bulk acoustic wave vibration mode may also be a solid state fabricated resonator (SMR), such as the structure illustrated in the third embodiment, in which the devices of the first and second regions are combined in such a manner that: SMR (one belonging to BAW) + SAW.

Of course, the two vibration modes may be: any two combinations of bulk acoustic wave vibration modes (BAW), surface acoustic wave vibration modes (SAW), and radial mode modes (CMR), and preferably the first vibration mode and the second vibration mode are different, as described in the embodiments.

In an embodiment of the present disclosure, the first vibration mode and the second vibration mode are different vibration modes.

In an embodiment of the present disclosure, the upper electrode layer is of a thin film structure or an interdigital electrode structure.

In one embodiment of the present disclosure, all or part of the devices in at least two regions of the acoustic wave device act as filters or duplexers.

First embodiment

In a first exemplary embodiment of the present disclosure, an acoustic wave device is provided.

Fig. 1 is a schematic cross-sectional structure view of an acoustic wave device according to a first embodiment of the present disclosure. Fig. 2 is a schematic top view of an acoustic wave device according to a first embodiment of the present disclosure.

Referring to fig. 1 and 2, an acoustic wave device of the present disclosure includes: a POI structure comprising: the high-sound-velocity layers and the low-sound-velocity layers are arranged alternately, and the substrate is used as the lowest high-sound-velocity layer; and a piezoelectric layer located above the alternating layers of material of high acoustic velocity and low acoustic velocity, adjacent to which is a low acoustic velocity layer; the high acoustic velocity layer propagates at a bulk acoustic velocity higher than that of the first piezoelectric layer, and the low acoustic velocity layer propagates at a bulk acoustic velocity lower than that of the first piezoelectric layer;

dividing into at least two regions on the POI structure, including: a first region in which a first device having a first vibration mode resonance is formed; a second device having a second mode resonance is formed in the second region.

Here, poi (piezoelectric on insulator) is an acronym of a piezoelectric material on an insulating substrate.

In an embodiment of the present disclosure, the acoustic wave device includes a first region D1 and a second region D2, the first region D1 being a resonator having a first vibration mode, for example, a bulk acoustic wave vibration mode, and the second region being a resonator having a second vibration mode, for example, a surface acoustic wave vibration mode or a radial mode.

The thickness of the first piezoelectric layer 13 is set to be in the range of 0.05 to 1 λ; the thickness of the temperature compensation layer 12 is set to a range of 2 λ or less; where λ represents the period of the interdigital electrode, that is, the acoustic wave wavelength corresponding to the resonance frequency.

In the present embodiment, referring to fig. 1, the acoustic wave device includes: a substrate 11; a temperature compensation layer 12 located over the substrate 11; a first piezoelectric layer 13 located on the temperature compensation layer 12 of the second area D2; an interdigitated electrode layer 14 on top of said first piezoelectric layer 13;

in the first region D1, a bulk acoustic wave resonator (BAW) is formed, and in the second region D2, a surface acoustic wave resonator (SAW) is formed.

In this embodiment, the first cavity 3 is formed by releasing a portion of the temperature compensation layer 12 and the substrate 11 under the piezoelectric structure.

In one embodiment, referring to fig. 1, the piezoelectric structure includes a lower electrode layer 21, a second piezoelectric layer 23, and an upper electrode layer 22, which are sequentially stacked.

The respective parts of the acoustic wave device will be described in detail below.

The substrate 11, the temperature compensation layer 12 and the first piezoelectric layer 13 are comprised in both the first region D1 and the second region D2. The substrate 11, the temperature compensation layer 12 and the first piezoelectric layer 13 serve as an example of a POI structure, and structures having different vibration modes are further grown on the common POI structure, thereby realizing integration of acoustic wave structures of two or more operation modes on the same substrate. In this embodiment, referring to fig. 1, a part of the substrate 11 and a part of the temperature compensation layer 12 in the first region D1 are etched away to release the space under the piezoelectric structure, and a first cavity 3 is formed under the piezoelectric structure, so as to obtain a bulk acoustic wave device, which is a structure of a Film Bulk Acoustic Resonator (FBAR); in addition, the first piezoelectric layer 13 overlying the temperature compensation layer 12 of the first area D1 is also partially etched, leaving only the first piezoelectric layer 13 of the second area. In terms of the forming process, after the first piezoelectric layer 13 of the first region D1 is etched away, a piezoelectric structure may be grown on the temperature compensation layer 12 of the first region, that is, the lower electrode layer 21, the second piezoelectric layer 23 and the upper electrode layer 22 are grown in sequence from bottom to top to form a sandwich structure of the BAW device, and then the above-mentioned etching of the temperature compensation layer 12 of the first region D1 and the substrate 11 is performed to release the first cavity 3.

Of course, in other embodiments, the structure of the bulk acoustic wave device may be changed, for example, the bulk acoustic wave structure in the third embodiment is a solid-State Mounted Resonator (SMR) structure, which will be described in detail later.

In addition, in the present embodiment, the first cavity 3 is formed by etching away (releasing) the substrate 11 and the temperature compensation layer 12 under the piezoelectric structure. The release process of the first cavity may also be varied in other embodiments, for example in the second embodiment the first cavity 3 is formed by releasing the temperature compensation layer 12 under the piezoelectric structure, as will be described in more detail later.

The interdigital electrode layer 14 and the metal layer 15 are grown on the surface of the first piezoelectric layer 13 of the second region D2. In the forming process, the interdigital electrode layer 14 can multiplex the material and thickness of the lower electrode layer 21, or can grow a layer of electrode material alone to manufacture the interdigital electrode layer 14; the metal layer 15 may be formed by multiplexing the material and thickness of the upper electrode 22, or by growing a single layer of metal material to form the metal layer 15. In other embodiments, the metal layer may not be grown, for example, as shown in the sixth embodiment, the structure of the grown metal layer has a sound velocity transition region compared to the structure without the grown metal layer, which is helpful to reduce energy leakage of the acoustic wave in the extending direction of the interdigital electrode arm, effectively suppress a noise mode near the resonant frequency, and improve the Q value of the device.

The materials of the lower electrode layer 21, the upper electrode layer 22, the interdigital electrode layer 14, and the metal layer 15 included in the acoustic wave device of the present embodiment may be, but are not limited to, metals, alloys, or other conductive materials having good electrical conductivity. Such as aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, tungsten, etc., which are compatible with semiconductor processing. Of course, the lower electrode layer, the upper electrode layer, the interdigital electrode layer and the metal layer may be an alloy of these metals.

The material of the temperature compensation layer 12 is a dielectric material, such as silicon dioxide, phosphosilicate glass, etc., or other materials with positive temperature coefficient of frequency. In addition, the dielectric material of the temperature compensation layer is preferably small in dielectric coefficient, which contributes to an increase in the equivalent coupling coefficient of the device.

The material of the first piezoelectric layer 13 and the second piezoelectric layer 23 can be, but is not limited to, aluminum nitride, zinc oxide, lithium niobate or lithium tantalate, or the like or a mixture thereof.

The substrate 11 may be a semiconductor substrate such as silicon, quartz, or alumina.

As shown in fig. 1 and fig. 2, a metal layer 15 is further provided on the interdigital electrode layer 14, and the metal layer 15 is located at an edge of an interdigital electrode arm of the interdigital electrode layer 14 and is in a bump structure with respect to the interdigital electrode layer 14.

Referring to fig. 2, the first region D1 is a bulk acoustic wave device BAW, the dashed line box indicates the shape formed by etching the substrate 11 from the back side, and the region where the upper electrode 22, the second piezoelectric layer 23, and the lower electrode 21 overlap in the piezoelectric structure defines the effective vibration region of the device. The second region D2 is a surface acoustic wave device SAW, the upper and lower ends of the interdigital electrode layer 14 are bus bars (busbars), the middle is an interdigital electrode arm, the two sides of the interdigital electrode 14 are reflective grids 16, in order to highlight the interdigital electrode layer 14, the reflective grids 16 on the left and right sides of the interdigital electrode 14 are not shown in fig. 1, and in addition, the number of the interdigital electrode arms is only shown in fig. 1 and fig. 2, and the numbers of the interdigital electrode arms may not completely correspond to each other. With continued reference to fig. 2, the interdigitated electrode arms are divided into a middle region, an edge region and a gap region, each region being represented in fig. 2 by the area bounded between the dashed lines in the second region. In the two sets of opposite interdigital electrode arms, a metal layer 15 is grown at the edge of each set of interdigital electrode arms, a metal layer 15 is also grown at the corresponding parallel position of the other set of interdigital electrode arms, the metal layer 15 is in a bump structure relative to the interdigital electrode layer, which is illustrated by a frame in fig. 2, so that the range between two parallel arranged metal layers 15 is defined as a middle area, the metal layer 15 is located at the edge area, and the area between the metal layer 15 and the bus-bar is defined as a gap area. Therefore, along the extending direction of the interdigital electrode arm, a sound velocity transition region from a medium sound velocity to a low sound velocity and from the low sound velocity to a high sound velocity is formed from the middle region to the edge region and from the edge region to the gap region, so that the energy leakage of sound waves in the extending direction of the interdigital electrode arm is reduced, a clutter mode near a resonant frequency is effectively inhibited, and the Q value of the device is improved.

As shown in fig. 2, the electrode arm of the reflective gate 16 also has a bump structure formed by a metal layer at a position on the same straight line corresponding to the metal layer in the interdigital electrode layer 14.

Thus, the first region D1 and the second region D2 together constitute an acoustic wave device having hybrid integration of different vibration modes. The acoustic wave device may be a filter including resonators of the two regions, or a duplexer or a multiplexer configured based on a filter including resonators of the same or different vibration modes.

The advantages of the acoustic wave device described above will be described here by taking as an example a duplexer formed of filters having different vibration modes, for example, a first region is a bulk acoustic wave filter, a second region is a surface acoustic wave filter, and the first and second regions together form the duplexer. If the filters in the first region and the second region both use the same vibration mode, if the regions are too close to each other, vibration leakage is likely to occur, and due to coupling between the filters, the attenuation characteristics of both and the isolation of the duplexer become worse, and it is also not advantageous to make the device size small.

Here, resonators of both BAW and SAW modes are integrated on the same POI structure, so that the first region D1 is a bulk acoustic wave type resonator, with the vibration mode in a direction perpendicular to the device, e.g. in an up-down direction as seen with reference to fig. 1; the second region D2 is a surface acoustic wave resonator, and the vibration mode propagates in a direction parallel to the device surface, for example, in the left-right direction as viewed with reference to fig. 1; on one hand, the difference between the vibration and the propagation direction of the device in the two regions can effectively reduce the coupling between the first region filter and the second region filter, improve the attenuation and the isolation of the whole device, reduce the distance between the two filters and reduce the size of the device.

On the other hand, SAW has a larger equivalent coupling coefficient (k2eff), a larger dielectric coefficient, a worse Temperature Coefficient of Frequency (TCF) and power capacity than BAW, and is complementary to BAW; the resonance devices with different vibration modes are integrated on the same device, the design freedom degree can be improved, filters with different sizes, different bandwidths, different insertion loss, isolation degrees, different power capacities and a plurality of regions can be manufactured respectively, and in addition, the design freedom degree is improved, and meanwhile the advantages of different working modes can be complemented in strength and in weakness and combined in strength. Therefore, the duplexer can better meet the requirements of different performances.

Second embodiment

In a second exemplary embodiment of the present disclosure, an acoustic wave device is provided. The release pattern of the first cavity in the acoustic wave device in the second embodiment is optimized as compared with the first embodiment.

Fig. 3 is a schematic cross-sectional structure view of an acoustic wave device according to a second embodiment of the present disclosure.

Referring to fig. 3, in the present embodiment, the acoustic wave device includes: a substrate 11; a temperature compensation layer 12 located over the substrate 11; a first piezoelectric layer 13 located on the temperature compensation layer 12 of the second area D2; an interdigitated electrode layer 14 on top of said first piezoelectric layer 13; a metal layer 15 is further arranged on the interdigital electrode layer 14, and the metal layer 15 is positioned at the edge of an interdigital electrode arm of the interdigital electrode layer 14;

in the first region D1, a bulk acoustic wave resonator (BAW) is formed, and in the second region D2, a surface acoustic wave resonator (SAW) is formed.

In this embodiment, the first cavity 3 is formed by releasing a portion of the temperature compensation layer 12 under the piezoelectric structure, and a barrier layer 14 is disposed around the first cavity 3 under the piezoelectric structure. Referring to fig. 3, the barrier layer 14 is adjacent to the inside of the temperature compensation layer 12 of the first region D1.

In one embodiment, referring to fig. 3, the piezoelectric structure includes a lower electrode layer 21, a second piezoelectric layer 23, and an upper electrode layer 22, which are sequentially stacked.

In this embodiment, a portion of the temperature compensation layer 12 under the piezoelectric structure in the first region D1 is etched away, for example, a ring portion, and the etched portion is filled with the barrier layer 14, the material of the barrier layer 14 and the material of the temperature compensation layer 12 have different etching rates, and the material of the barrier layer 14 has a larger difference in etching rate than the material of the temperature compensation layer 12. The temperature compensation layer 12 on the inner side of the barrier layer 14 is etched away as a sacrificial layer, thereby releasing the first cavity 3 in the area corresponding to the sacrificial layer. Of course, the above formation process also includes a conventional planarization step after the deposition of the barrier layer.

In the acoustic wave device of the present embodiment, the first region D1 is a bulk acoustic wave device BAW, and the bulk acoustic wave device is also a thin Film Bulk Acoustic Resonator (FBAR) structure, as in the first embodiment.

It should be noted that the same parts as those in the first embodiment can be referred to the description of the first embodiment, and are not described again here.

In a second embodiment, the first cavity is formed by releasing the temperature compensation layer under the piezoelectric structure without releasing the substrate. The bulk acoustic wave device of the second embodiment has advantages of being more robust and better in reliability than the first embodiment.

Third embodiment

In a third exemplary embodiment of the present disclosure, an acoustic wave device is provided. In the acoustic wave device in the third embodiment, the structure of the bulk acoustic wave of the first region is changed as compared with the first embodiment.

Fig. 4 is a schematic cross-sectional structure view of an acoustic wave device according to a third embodiment of the present disclosure.

Referring to fig. 4, in the present embodiment, an acoustic wave device includes:

a substrate 11; a temperature compensation layer 12 located over the substrate 11; a first piezoelectric layer 13 located on the temperature compensation layer 12;

an interdigitated electrode layer 14 on the first piezoelectric layer 13 of the second area D2;

an acoustic reflection layer 5 comprising alternately laminated layers of low acoustic impedance material 51 and high acoustic impedance material 52 on the first piezoelectric layer 13 of the first region D1; a distance exists between the acoustic reflection layer 5 and the interdigital electrode layer 14;

a piezoelectric structure located on the low acoustic impedance material layer 51 of the acoustic reflection layer 5;

here, a solid-State Mounted Resonator (SMR) is formed in the first region D1, and a surface acoustic wave resonator (SAW) is formed in the second region D2. The acoustic mode for an SMR is a bulk acoustic wave.

In one embodiment, referring to fig. 4, the piezoelectric structure includes a lower electrode layer 21, a second piezoelectric layer 23, and an upper electrode layer 22, which are sequentially stacked.

In this embodiment, compared to the first embodiment, the acoustic reflection layer 5 is provided between the piezoelectric structure and the temperature compensation layer without releasing the temperature compensation layer 12 and the substrate 11 under the piezoelectric structure, so that the POI structure formed by the temperature compensation layer 12 and the first piezoelectric layer 13 on the substrate 11 and the acoustic reflection layer 5 constitute bragg reflection, and the propagation of acoustic wave energy to the substrate can be suppressed.

In this embodiment, the thicknesses of the low acoustic impedance material layer 51 and the high acoustic impedance material layer 52 are about 1/4 of the equivalent wavelength of each layer material at the resonance frequency; in addition, the thickness of the low acoustic impedance material layer close to the lower electrode layer can be properly adjusted according to the requirements of temperature compensation and device bandwidth.

In one example, the material of the low acoustic impedance material layer 51 is a material with low acoustic impedance, and may be, but is not limited to, the same material as the temperature compensation layer 12, such as silicon dioxide, phosphosilicate glass, etc., or may be other materials, such as SiO₂Porous silicon, etc. The material of the high acoustic impedance material layer 52 is a material having high acoustic impedance, including but not limited to W, Mo, AlN, etc.

As described above, in the acoustic wave device in the third embodiment, the bulk acoustic wave device in the first region is the SMR structure, and the acoustic reflection layer 5 and the piezoelectric structure are formed in this order above the temperature compensation layer 12 in the first region, thereby forming bragg reflection and suppressing the acoustic wave energy in the bulk acoustic wave device from propagating to the substrate 11. It should be noted that the same parts as those in the first embodiment can be referred to the description of the first embodiment, and are not described again here.

Fourth embodiment

In a fourth exemplary embodiment of the present disclosure, an acoustic wave device is provided. In the acoustic wave device in the fourth embodiment, the form of the upper electrode layer 22 is changed as compared with the first embodiment. In this embodiment, the upper electrode layer 22 is not a planar electrode layer as in the first embodiment, but an upper electrode layer 22' of an interdigitated electrode structure.

Fig. 5 is a schematic cross-sectional structure view of an acoustic wave device according to a fourth embodiment of the present disclosure.

Referring to fig. 5, the acoustic wave device of the present embodiment includes:

a substrate 11; a temperature compensation layer 12 located over the substrate 11; a first piezoelectric layer 13 located on the temperature compensation layer 12 of the second area D2; an interdigitated electrode layer 14 on top of said first piezoelectric layer 13;

a piezoelectric structure located above the temperature compensation layer 12 of the first area D1, there being a spacing between the piezoelectric structure and the first piezoelectric layer 13, the piezoelectric structure having a first cavity 3 below it; the piezoelectric structure comprises a lower electrode layer 21, a second piezoelectric layer 23 and an upper electrode layer 22' of an interdigital electrode structure which are sequentially laminated;

here, a resonator (CMR) of a radial mode is formed in the first region D1, and a resonator (SAW) of a surface acoustic wave vibration mode is formed in the second region D2.

In this embodiment, the upper electrode 22 'corresponding to the piezoelectric structure in the first region D1 is an interdigital electrode structure, and for example, the upper electrode 22 in the first embodiment can be patterned to form the upper electrode 22' of the interdigital electrode structure. The acoustic wave mode corresponding to the excitation at the first region D1 is a Lamb (Lamb) wave, and a CMR structure is formed corresponding to the first region D1.

Wherein, Lamb wave means: when the plate is thin, two boundary surfaces of the plate can influence the sound wave, the sound wave can be reflected on two free boundaries, and Lamb waves are formed after superposition.

By forming the CMR device in the first region D1 and forming the SAW in the second region D2, since the devices in the two regions have different vibration modes, the difference of the vibration modes can effectively reduce the coupling between the filters in the first and second regions, improve the attenuation and isolation of the whole device, and reduce the distance between the two filters, and the size of the device.

In other embodiments, the lower electrode 21 may not be grown in the piezoelectric structure, and the upper electrode layer 22' of the interdigital electrode structure is only used to excite the second piezoelectric layer 23 to vibrate, but the equivalent coupling coefficient is relatively small in this case.

In other embodiments, CMR is formed in the first region D1, and the excited acoustic wave mode is a Lamb wave; a solid-State Mounted Resonator (SMR) is formed in the second region D2, wherein the SMR has an interdigital structure rather than a thin-film plate structure, and the corresponding acoustic wave mode is also Lamb wave because the upper electrode is an interdigital structure. Thus, the devices formed in the first and second regions D1 and D2 may have the same vibration mode. However, compared to an acoustic wave device in which devices having different vibration modes are integrated in two regions, such a method is likely to cause mutual vibration coupling due to the same device vibration modes in the two regions, and the isolation is relatively poor, resulting in reduced performance.

In summary, in the acoustic wave device of the fourth embodiment, the device of the first area may be a CMR, the device of the second area may be a SAW, or the vibration modes of the device of the first area and the device of the second area may be the same, for example, the device of the first area is a CMR, and the device of the second area is an SMR.

Fifth embodiment

In a fifth exemplary embodiment of the present disclosure, an acoustic wave device is provided. In the acoustic wave device in the fifth embodiment, compared with the first embodiment, the second cavity 6 is further included in the second region D2.

Fig. 6 is a schematic cross-sectional structure view of an acoustic wave device according to a fifth embodiment of the present disclosure.

Referring to fig. 6, in the present embodiment, an acoustic wave device includes:

here, a bulk acoustic wave resonator (BAW) is formed in the first region D1, and either a surface acoustic wave resonator (SAW) or a radial mode resonator (CMR) is formed in the second region D2.

In this embodiment, referring to fig. 6, the first cavity 3 is formed by releasing a portion of the temperature compensation layer 12 and the substrate 11 under the piezoelectric structure. The second cavity 6 is formed by releasing a portion of the temperature compensation layer 12 and the substrate 11 under the first piezoelectric layer 13. The first cavity and the second cavity can be finished in the same step of process, and manufacturing cost is saved.

The piezoelectric structure includes a lower electrode layer 21, a second piezoelectric layer 23, and an upper electrode layer 22, which are sequentially stacked.

In this embodiment, the vibration mode of the second region D2 may be a surface acoustic wave mode, such as an SH wave, or a LOVE wave, or a radial mode, such as a Lamb wave.

The SH wave is a transverse wave in which all particles vibrate horizontally during wave propagation. The LOVE wave is also called a Q wave or ground roll wave, and refers to a wave that vibrates in a horizontal plane perpendicular to a propagation direction in a case where a low-speed layer occurs over a semi-wireless medium.

In summary, in the acoustic wave device of the present embodiment, the device in the first area corresponds to BAW, and the second cavity is obtained by etching away part of the temperature compensation layer and the substrate under the first piezoelectric layer in the second area, so as to form, for example, SH wave, SAW in the low wave mode, or CMR based on Lamb wave vibration in the second area, thereby providing more ways for combining different modes.

Sixth embodiment

In a sixth exemplary embodiment of the present disclosure, an acoustic wave device is provided. In the acoustic wave device of the sixth embodiment, compared with the first embodiment, the first cavity 3 is not formed; in the acoustic wave device of the sixth embodiment, compared with the third embodiment, the acoustic reflection layer 5 is not required to be provided, and the bragg reflection layer is not formed. The device of the first region D1 in this embodiment is not the FBAR in the first embodiment nor the SMR in the third embodiment, but a higher order resonant wave device (HBAR).

Fig. 7 is a schematic cross-sectional structure view of an acoustic wave device according to a sixth embodiment of the present disclosure.

Referring to fig. 7, in the present embodiment, an acoustic wave device includes:

a substrate 11; a temperature compensation layer 12 located on the substrate 11 of the second region D2; a first piezoelectric layer 13 located on the temperature compensation layer 12; an interdigitated electrode layer 14 on top of said first piezoelectric layer 13;

a piezoelectric structure located over the substrate 11 of the first region D1;

a high-order resonant wave device (HBAR) is formed in the first region D1, and a surface acoustic wave resonator (SAW) is formed in the second region D2.

In this embodiment, the piezoelectric structure is located on the substrate 11 in the first region, and no other physical layer or cavity exists between the piezoelectric structure and the substrate 11, so that in the formed HBAR device, acoustic energy can propagate to the substrate and be reflected back, and the HBAR device has a high Q value and a small equivalent coupling coefficient (k2eff), and can be applied to the fields of oscillators, clocks and the like. Thus, the first region D1 is an oscillator. In addition, the second region may be further subdivided into a plurality of (≧ 2) sub-regions to form different resonator devices, so as to form a filter, a duplexer, a multiplexer, or the like in the second region, and the scheme of dividing the second region into sub-regions will be exemplarily described in the seventh embodiment. The integration of multiple devices is realized on the same POI structure, and the devices have better isolation.

In summary, in the acoustic wave device of the present embodiment, the device in the first area corresponds to the HBAR, and can be used as an oscillator, and the device in the second area corresponds to the SAW. As can be seen from the above embodiments, the device in the first area may be one of SAW (e.g., FBAR or SMR) or HBAR, the device in the second area may be SAW, or CMR, and the cases of the first area and the second area may be freely combined. In addition, the second region may be divided into a combination of a plurality of sub-regions in a manner described in any of the above embodiments, and different sub-regions may have the same or different vibration modes, preferably have different vibration modes or have a combination of different vibration directions, so as to effectively reduce coupling between filters of the respective sub-regions, improve attenuation and isolation of the entire device, reduce distances between filters of the respective sub-regions, and reduce the size of the device.

Similarly, in the above-described embodiments, the first region may be divided into a plurality of sub-regions, the concept is the same as that described above, and detailed description is omitted here.

Seventh embodiment

In a seventh exemplary embodiment of the present disclosure, an acoustic wave device is provided. Compared with the first embodiment, the acoustic wave device of the present embodiment further includes a dielectric layer.

Fig. 8 is a schematic sectional structure view of an acoustic wave device according to a seventh embodiment of the present disclosure.

Referring to fig. 8, in the present embodiment, an acoustic wave device includes:

the upper surface of the piezoelectric structure and the interdigital electrode layer 14 are covered with a dielectric layer 7;

another interdigital electrode layer 14 'is further arranged beside the interdigital electrode layer 14 in the second region D2, the interdigital electrode layer 14' serves as a third resonance part, the interdigital electrode layer 14 serves as a second resonator, the first region forms a first resonator, and the second resonator and the third resonance part form a temperature compensation surface acoustic wave device (TC-SAW).

Referring to fig. 8, a metal layer 15 is further provided on the interdigital electrode layer 14, the metal layer 15 is located at an edge of an interdigital electrode arm of the interdigital electrode layer 14, and is of a bump structure relative to the interdigital electrode layer 14, and the dielectric layer 7 covers the interdigital electrode layer 14 and the metal layer 15.

The material of the dielectric layer 7 includes but is not limited to SiO₂SiN, AlN, etc. With SiO₂For example, a thicker dielectric layer 7 is grown on the interdigital electrode 14' of the third resonance portion to constitute a temperature compensated surface acoustic wave device (TC-SAW) having a higher Q value and a better Temperature Coefficient of Frequency (TCF) than the conventional surface acoustic wave device. The dielectric layer 7 can also be used as a frequency adjusting layer to further adjust the frequency of the first or second resonator, and can also protect the upper electrode 22 of the first resonator and the metal layer 15/interdigital electrode layer 14 (when no metal layer is provided, the interdigital electrode layer; when both are present, the metal layer) of the second resonator and the interdigital electrode layer 14' of the third resonance part from external contamination. There is also a metal connection layer 8 at the periphery of the dielectric layer 7 of the third resonance section.

The TC-SAW includes a resonator and a dual mode surface acoustic wave (DMS), which generally requires a dielectric bridge layer to isolate the interdigital electrode layer 14 of the second resonator from the metal connection layer 8 of the third resonance portion. The dielectric bridge layer generally has a smaller dielectric coefficient to reduce the parasitic capacitance between signals. As shown in fig. 8, the dielectric bridge layer in the second region may also be reused as the dielectric layer 7, so as to reduce the number of material layers and reduce the cost.

In summary, the present embodiment exemplarily describes a structure that the second region is divided into two sub-regions, where the two sub-regions in the second region form two associated portions in an integral device, and in other embodiments, the two associated portions may also be two independent device portions. Similarly, the division into the first area may be similar, and will not be described here.

Eighth embodiment

In an eighth exemplary embodiment of the present disclosure, an acoustic wave device is provided. Compared with the first embodiment, the sound speed transition region of the present embodiment is formed in a different manner from that in the first embodiment.

Fig. 9 is a schematic top view of an acoustic wave device according to an eighth embodiment of the present disclosure.

In the first embodiment, a metal layer is grown on the edges of the interdigital electrode arms of the interdigital electrode layer 14 to form a sound velocity transition region, while in the present embodiment, as shown in fig. 9, by growing a high sound velocity layer 9 on the middle region, the sound velocity propagated by the material of the high sound velocity layer 9 is higher than the sound velocity propagated by the interdigital electrode layer, and a low sound velocity region is formed at the edge of the interdigital electrode arm exposed at the edge region, so that along the extending direction of the interdigital electrode arm, from the middle region to the edge region, and then from the edge region to the gap region, a sound velocity transition region from the medium sound velocity to the low sound velocity, and then from the low sound velocity to the high sound velocity is formed, which helps to reduce the energy leakage of the sound wave in the extending direction of the interdigital electrode arms, and effectively suppress the noise wave mode near the resonant frequency, and improve the Q value of the device.

The high-speed layer is, for example, a dielectric material, the material of the second piezoelectric layer 23 can be multiplexed, or a layer of dielectric material with high speed can be grown separately.

Referring to fig. 9, the high sound velocity layer 9 covers not only the interdigital electrode layer 14 but also the reflective grid 16, and the middle area is covered by the high sound velocity layer.

In summary, in the acoustic wave device of the present embodiment, another way of providing the acoustic velocity transition region is proposed to suppress the noise mode near the resonant frequency, and improve the Q value of the device, and the high acoustic velocity layer 9 is grown in the middle region, so that the interdigital electrode arms in the edge region are exposed, and the acoustic velocity transition region is formed.

Ninth embodiment

In a ninth exemplary embodiment of the present disclosure, a method of fabricating an acoustic wave device is provided. In the present embodiment, the method of manufacturing the acoustic wave device shown in the first embodiment is taken as an example.

Fig. 10 is a method of fabricating an acoustic wave device according to a ninth embodiment of the present disclosure.

Referring to fig. 10 (a) to (f), in the present embodiment, a method of manufacturing an acoustic wave device includes:

step S21: manufacturing a POI structure, and sequentially forming a temperature compensation layer and a first piezoelectric layer on a substrate;

a temperature compensation layer 12 and a first piezoelectric layer 13 are formed in this order on a substrate 11, and the resulting structure is shown in fig. 10 (a).

Step S22: removing the first piezoelectric layer of the first area so that part of the temperature compensation layer is exposed;

by etching the first piezoelectric layer 13 of the first region so that the temperature compensation layer 12 under the etched first piezoelectric layer 13 is exposed, the structure shown in (b) in fig. 10 is obtained.

Step S23: manufacturing a piezoelectric structure above the exposed temperature compensation layer; manufacturing an interdigital electrode layer above the first piezoelectric layer of the second area;

in this embodiment, the process of fabricating the piezoelectric structure over the exposed temperature compensation layer may include: sequentially manufacturing a lower electrode layer 21, a second piezoelectric layer 23 and an upper electrode layer 22 above the exposed temperature compensation layer; the process of fabricating the interdigital electrode layer 14 on the first piezoelectric layer 13 in the second area may be performed simultaneously with the step of fabricating the lower electrode layer 21 or the upper electrode layer 22, for example, by depositing a metal material on the structure obtained in step S22, and performing a patterning process on the metal material, so that the metal material in the second area presents a pattern of the interdigital electrode, a remaining portion of the metal material in the first area is used as the lower electrode layer 21, and the rest portions are etched away, so as to obtain the structure shown in fig. 10 (c), and the corresponding lower electrode layer is reused as the process of preparing the interdigital electrode layer; or a layer of metal material can be deposited to manufacture the interdigital electrode layer after the preparation of the lower electrode layer is completed. After the lower electrode layer 21 is manufactured, the structure of forming the second piezoelectric layer 23 is shown in fig. 10 (d); the structure of further forming the upper electrode layer 22 is shown with reference to (e) in fig. 10.

Step S24: releasing the area below the piezoelectric structure to obtain a first cavity;

in the present embodiment, the first cavity 3 is formed by etching away (releasing) the substrate 11 and the temperature compensation layer 12 under the piezoelectric structure. For example, a portion of the substrate 11 and the temperature compensation layer 12 under the piezoelectric structure may be etched away from the back surface of the device by dry etching, so as to obtain a device structure including the first cavity 3, as shown in fig. 10 (f).

Of course, the manufacturing method of the structure corresponding to the other embodiments has been described when the structure is introduced, and is not described in detail here, and the manufacturing of the structure in the other embodiments can be realized by referring to the process of this embodiment.

It should be noted that, instead of etching the first piezoelectric layer in the first area, the lower electrode layer may be directly grown on the surface of the first piezoelectric layer, and finally the substrate, the temperature compensation layer, and the first piezoelectric layer in the first area are back-etched, or a bulk acoustic wave device in the first area may also be formed; however, at this time, the second piezoelectric layer is easily coupled to the first piezoelectric layer below the lower electrode through the lower electrode layer, which affects the device performance, so it is preferable to partially etch the first piezoelectric layer and then perform the subsequent processes. In addition, if the device lateral mode of the second region is not severe, the metal layer 15 may not be grown.

In addition, it should be noted that the manufacturing process is within the scope of the present disclosure as long as the above-mentioned respective structures and positional relationships can be formed.

The acoustic wave devices in the above embodiments may be used as a filter or a duplexer, and the filter or duplexer may be designed, for example, by connecting several acoustic wave resonators to form a ladder-type or lattice-type topology, or by forming a DMS with one or more IDTs that generate acoustic energy.

In view of the above, the present disclosure provides an acoustic wave device in which energy leakage in the longitudinal direction is suppressed by using a POI structure based on which an acoustic wave formed by vibration of the device propagates only in a piezoelectric layer and a low sound velocity layer without leaking into a deeper substrate layer as compared with a conventional SAW device piezoelectric substrate such as lithium niobate or lithium tantalate or the like. But in the transverse direction, partial energy still spreads outwards, at least two modes of devices are integrated on the same device based on at least two regions, the implementation mode is simple and convenient, and the vibration modes or the spreading directions are different by controlling the difference of the two modes, so that the coupling interference between the devices in different regions can be reduced, and the suppression and the isolation of the filter or the duplexer formed by combining the devices in different regions are improved; therefore, the size of the device can be reduced, the cost is reduced, and the requirement of communication miniaturization is met; as the devices in various vibration modes do not need to use piezoelectric materials with the same material and thickness, the design freedom degree is improved, and the device is beneficial to manufacturing products meeting different bandwidths, different insertion losses, isolation degrees, different power capacities and the like.

It should also be noted that while the present disclosure has been described in connection with the accompanying drawings, the embodiments disclosed in the drawings are intended to be illustrative of the preferred embodiments of the present disclosure and should not be construed as limiting the present disclosure. The dimensional proportions in the drawings are merely schematic and are not to be understood as limiting the disclosure. Directional phrases used in the embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., refer only to the direction of the attached drawings and are not intended to limit the scope of the present disclosure. Throughout the drawings, like elements are represented by like or similar reference numerals. Conventional structures or constructions will be omitted when they may obscure the understanding of the present disclosure.

And the shapes and sizes of the respective components in the drawings do not reflect actual sizes and proportions, but merely illustrate the contents of the embodiments of the present disclosure. Furthermore, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

The use of ordinal numbers such as "first," "second," "third," etc., in the specification and claims to modify a corresponding element does not by itself connote any ordinal number of the element or any ordering of one element from another or the order of manufacture, and the use of the ordinal numbers is only used to distinguish one element having a certain name from another element having a same name.

Furthermore, the word "comprising" or "comprises" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

Unless a technical obstacle or contradiction exists, the above-described various embodiments of the present disclosure may be freely combined to form further embodiments, which are all within the scope of protection of the present disclosure.

The above-mentioned embodiments are intended to illustrate the objects, aspects and advantages of the present disclosure in further detail, and it should be understood that the above-mentioned embodiments are only illustrative of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.

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Acoustic wave device and method of manufacturing the same

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