WO2021159677A1

WO2021159677A1 - Cavity structure of thin film bulk acoustic resonator and manufacturing process

Info

Publication number: WO2021159677A1
Application number: PCT/CN2020/108712
Authority: WO
Inventors: 李林萍; 盛荆浩; 江舟
Original assignee: 杭州见闻录科技有限公司
Priority date: 2020-02-15
Filing date: 2020-08-12
Publication date: 2021-08-19
Also published as: CN111294010A; CN111294010B

Abstract

Disclosed are a cavity structure of a thin film bulk acoustic resonator and a manufacturing process. The manufacturing process comprises: providing a supporting layer on a substrate provided with a sacrificial material layer so that the supporting layer at least covers part of an upper surface of the periphery of the sacrificial material layer, the supporting layer having an open region so that the remaining part of the upper surface of the sacrificial material layer is exposed to the exterior; filling the open region of the supporting layer with a sacrificial material; providing a bottom electrode layer on the supporting layer and the sacrificial material, the bottom electrode layer being lapped on the supporting layer; providing a piezoelectric layer and a top electrode layer on the bottom electrode layer; and removing all the sacrificial material to form a cavity structure, such that parasitic capacitance of the thin film bulk acoustic resonator is greatly suppressed, the mechanical stability of a device can be effectively improved, the influence of stress variation of film layers on the resonance performance of device is reduced, and thus the resonance performance of the resonator can be effectively improved.

Description

Cavity structure and manufacturing process of film bulk acoustic wave resonator

Technical field

This application relates to the field of communication devices, and mainly relates to a cavity structure and manufacturing process of a thin-film bulk acoustic resonator.

Background technique

With the increasing congestion of the electromagnetic spectrum and the increase in frequency bands and functions of wireless communication equipment, the electromagnetic spectrum used in wireless communication has grown rapidly from 500MHz to above 5GHz, and there is also a demand for high-performance, low-cost, low-power, and small-sized RF front-end modules. Growing day by day. The filter is one of the radio frequency front-end modules, which can improve the transmission and reception of signals. It is mainly composed of multiple resonators connected through a topological network structure. Fbar (Thin film bulk acoustic resonator) is a thin film bulk acoustic resonator. The filter composed of it has the advantages of small size, strong integration capability, high quality factor Q during high-frequency operation, and strong power tolerance. It is used as a radio frequency The core device of the front end.

The basic structure of Fbar is the upper and lower electrodes and the piezoelectric layer sandwiched between the upper and lower electrodes. The piezoelectric layer can realize the conversion of electrical energy and mechanical energy. When an electric field is applied to the upper and lower electrodes of Fbar, the piezoelectric layer generates mechanical energy, which is in the form of sound waves. However, in practical applications, Fbar will generate parasitic capacitance or parasitic inductance, which will deteriorate the performance of the resonator, especially affecting the band rejection of the filter formed by the interconnection of Fbar.

In the prior art, parasitic capacitance is easily formed between the film layers on the upper edge of the cavity structure of the thin-film bulk acoustic wave resonator, or the performance of the resonator is easily affected by stress. In addition, longitudinal waves are prone to reflection and loss in the edge regions of the bottom electrode layer and the substrate. Therefore, the present invention aims to design a new type of resonator cavity structure and manufacturing process to suppress parasitic capacitance and improve the performance of the resonator.

Summary of the invention

The cavity structure of the above-mentioned thin film bulk acoustic wave resonator is prone to parasitic capacitance or parasitic inductance, the film layer is prone to stress, and longitudinal waves are prone to reflection on the bottom electrode layer and the edge area of the substrate, causing loss. This application proposes a cavity structure and manufacturing process of a thin-film bulk acoustic resonator to solve the above-mentioned problems.

In the first aspect, this application proposes a manufacturing process for the cavity structure of a thin-film bulk acoustic resonator, which includes the following steps:

S1, a support layer is laid on the substrate on which the sacrificial material layer is arranged so that the support layer covers at least part of the upper surface of the periphery of the sacrificial material layer, and the support layer has an open area so that the remaining part of the upper surface of the sacrificial material layer is exposed to the outside ；

S2, using a sacrificial material to fill the opening area of the support layer;

S3, fabricating a bottom electrode layer on the support layer and the sacrificial material, and the bottom electrode layer is erected on the support layer;

S4, fabricating a piezoelectric layer and a top electrode layer on the bottom electrode layer; and

S5, removing all the sacrificial materials to form a cavity structure.

In some embodiments, S1 includes the following sub-steps:

S11, making a cavity on the substrate, and filling the cavity with a sacrificial material to form a sacrificial material layer;

S12, forming a support layer on the substrate and the sacrificial material layer, and partially remove the support layer to form an open area.

At this time, a cavity is formed on the substrate, and the support layer forms a cantilever structure on the cavity of the substrate to support the bottom electrode layer and make the projection area of the bottom electrode layer in the direction perpendicular to the substrate fall in the cavity , To reduce the generation of parasitics, the thickness of the support layer is very thin, and when the longitudinal wave reaches the boundary of the support layer, it forms total reflection with the air interface, which effectively reduces the loss of the longitudinal wave in the edge area of the bottom electrode.

In some embodiments, the surface of the sacrificial material layer is flush with the surface of the substrate through a polishing step in S11. After polishing, the surface of the sacrificial material layer is flush with the surface of the substrate, so that the surface of the support layer is on a horizontal plane, which is convenient to reduce the stress change of the subsequent film layer and improve the mechanical stability.

In some embodiments, S1 includes the following sub-steps:

S11', fabricating a sacrificial material layer on a substrate with a flat surface to cover part of the surface of the substrate;

S12', making a support layer on the substrate to cover the substrate and the sacrificial material layer;

S13', forming an opening area of the support layer through photolithography and etching processes.

At this time, a cavity is formed in the support layer, and the upper surface of the support layer forms a cantilever structure on the cavity, so that the projection area of the bottom electrode layer in the direction perpendicular to the substrate falls in the cavity, reducing the generation of parasitics, and the cavity The body structure and process do not need to process the substrate, and the process is simple.

In some embodiments, the sub-step S12' further includes a step of smoothing the support layer through a polishing step. After smoothing, the thickness of the support layer is very thin, and when the longitudinal wave reaches the boundary of the support layer, it forms total reflection with the air interface, which effectively reduces the loss of the longitudinal wave in the edge area of the bottom electrode.

In some embodiments, S2 further includes a step of making the surface of the sacrificial material in the opening area flush with the surface of the support layer by polishing. At this time, the surface of the support layer is kept level, which can effectively reduce the stress change of the film layer subsequently produced on the support layer and improve the resonance performance.

In some embodiments, S5 includes forming a release hole on the piezoelectric layer and the support layer, and the release hole extends to the sacrificial material layer. The release hole is formed on the support layer and the piezoelectric layer, outside the resonance region of the film bulk acoustic wave resonator, does not affect the performance of the resonator, and the processing technology is simple.

In some embodiments, the support layer includes an extension part suspended on the cavity, and the bottom electrode layer is erected on the extension part of the cavity. The extended part of the support layer forms a cantilever structure to effectively support the bottom electrode layer, so that the projection area of the bottom electrode layer on the substrate falls within the region of the cavity, which can effectively reduce parasitics.

In some embodiments, the projection area of the bottom electrode layer on the substrate falls within the area of the cavity. The projection area of the bottom electrode layer on the substrate exceeds the cavity and is prone to parasitics, which deteriorates the performance of the resonator.

In some embodiments, the projection area of the top electrode layer on the substrate falls within the projection area of the bottom electrode layer on the substrate. The projection areas of the top electrode layer and the bottom electrode layer on the substrate are both within the region of the cavity, which can effectively reduce the generation of parasitics.

In some embodiments, at least one side of the projection area of the top electrode layer and the bottom electrode layer on the substrate overlaps. Therefore, the horizontal and vertical overlap of the top electrode layer, the bottom electrode layer and the cavity can be increased, and parasitic capacitance can be suppressed.

In some embodiments, the projection area of the top electrode layer on the substrate exceeds the range of the opening area. The range of the top electrode layer beyond the open area can increase the area of the effective resonance area.

In some embodiments, the support layer uses the following materials: Si, SiC, SiN or AlN. The support layer is made of the above materials with high hardness and high etching selection ratio, which is convenient for processing and production.

In some embodiments, the sacrificial material layer uses the following materials: PSG, SiO ₂ or PI. The above materials are selected as sacrificial materials to facilitate the deposition and grinding process.

In the second aspect, this application proposes a thin film bulk acoustic resonator made by the above manufacturing process.

In the third aspect, the present application proposes a cavity structure of a thin film bulk acoustic resonator, which includes a substrate, a support layer, and a bottom electrode layer stacked in sequence, wherein the substrate, the support layer and the bottom electrode layer are surrounded by a cavity and support The layer has an extension part suspended on the cavity, and the bottom electrode layer is erected on the extension part of the support layer.

In some embodiments, the sidewalls of the cavity are formed by the substrate. At this time, the cavity is formed on the substrate, and the support layer is fabricated after the substrate is processed, and the process is mature.

In some embodiments, the sidewall of the cavity is formed by a support layer. At this time, the cavity is formed on the support layer, the process is simple and convenient, and it is easy to process.

In some embodiments, the projection area of the bottom electrode layer on the substrate is completely within the range of the cavity. Therefore, the parasitic capacitance between the bottom electrode layer and the substrate can be effectively reduced.

In some embodiments, it further includes a piezoelectric layer and a top electrode layer sequentially stacked on the bottom electrode layer, and the projection area of the top electrode layer on the substrate is located in the range of the extension of the support layer. At this time, the projection area of the top electrode layer on the substrate is within the cavity, so the generation of parasitic capacitance can be effectively reduced.

In some embodiments, a release hole is provided in the extension part of the support layer, and the release hole penetrates the piezoelectric layer and the support layer. The position of the release hole does not affect the effective resonance area, and will not affect the resonance performance of the film bulk acoustic wave resonator.

The present invention provides a cavity structure and manufacturing process of a thin-film bulk acoustic wave resonator. The cavity is surrounded by a substrate, a support layer and a bottom electrode layer, the support layer is suspended on the cavity and an extension is provided. The bottom electrode The layer is erected on the extension of the supporting layer. And the part of the projection area of the top electrode layer on the substrate is located in the range of the extension part of the support layer. Therefore, the parasitic capacitance of the thin film bulk acoustic wave resonator is greatly suppressed, the mechanical stability of the device can be effectively improved, the influence of the stress change of the film layer on the resonance performance of the device can be reduced, and the resonance performance of the resonator can be effectively improved.

Description of the drawings

The drawings are included to provide a further understanding of the embodiments and the drawings are incorporated into this specification and constitute a part of this specification. The drawings illustrate the embodiments and together with the description serve to explain the principles of the present invention. It will be easy to recognize the other embodiments and the many expected advantages of the embodiments because they become better understood by quoting the following detailed description. The elements of the drawings are not necessarily in proportion to each other. The same reference numerals refer to corresponding similar components.

FIG. 1 shows a flowchart of a manufacturing process of a cavity structure of a thin-film bulk acoustic resonator according to an embodiment of the present invention;

2 shows a flowchart of step S1 of the manufacturing process of the cavity structure of the film bulk acoustic resonator according to the first embodiment of the present invention;

3a-3k show a schematic diagram of the structure of a thin-film bulk acoustic resonator manufactured according to the manufacturing process of the cavity structure of the thin-film bulk acoustic resonator according to the first embodiment of the present invention;

4 shows a flowchart of step S1 of the manufacturing process of the cavity structure of the film bulk acoustic resonator according to the second embodiment of the present invention;

5a-5k show a schematic diagram of the structure of a thin-film bulk acoustic resonator manufactured according to the manufacturing process of the cavity structure of the thin-film bulk acoustic resonator according to the second embodiment of the present invention;

FIG. 6 shows a simulation test result diagram of a thin-film bulk acoustic resonator manufactured by the manufacturing process of the cavity structure of the thin-film bulk acoustic resonator according to an embodiment of the present invention;

Figure 7 shows a simulation test result graph of a control group with obvious parasitic effects.

Detailed ways

The application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described here are only used to explain the related invention, but not to limit the invention. In addition, it should be noted that, for ease of description, only the parts related to the relevant invention are shown in the drawings. It should be noted that the dimensions and sizes of the components in the drawings are not to scale, and the size of some components may be highlighted for obvious reasons.

It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other if there is no conflict. Hereinafter, the present application will be described in detail with reference to the drawings and in conjunction with the embodiments.

The present invention provides a manufacturing process for the cavity structure of a thin-film bulk acoustic wave resonator, as shown in FIG. 1, including the following steps:

S2, using a sacrificial material to fill the opening area of the support layer;

S5, removing all the sacrificial materials to form a cavity structure.

Example one

The schematic diagram of the manufacturing process of Embodiment 1 of the present application is shown in FIGS. 3a-3k. A cavity 7 is formed on the substrate 2 by processing the substrate 2, the supporting layer 3, the bottom electrode layer 4 and the cavity 7 to form a cavity structure. The supporting layer 3 covers at least the upper surface of the outer periphery of the sacrificial material layer 1 A cantilever support structure is formed on the cavity 7. As shown in Figure 2, S1 includes the following sub-steps:

S11, forming a cavity 7 on the substrate 2, and filling the cavity 7 with a sacrificial material to form a sacrificial material layer 1;

S12, forming a supporting layer 3 on the substrate 2 and the sacrificial material layer 1, and partially removing the supporting layer 3 to form an open area 31.

In a specific embodiment, as shown in FIG. 3a, a cavity 7 is etched on the substrate 2. In a preferred embodiment, the material of the substrate 2 is Si/Glass/Sapphire/spinel, etc. , The height of the cavity 7 is 3-4μm. The height of the specific cavity 7 can be adjusted according to the requirements of the device, and its shape is regarded as any shape. As shown in FIG. 3b, a sacrificial material is deposited in the cavity 7 to form the sacrificial material layer 1. After the cavity 7 is filled with the sacrificial material, chemical mechanical polishing (CMP) is performed on the surface of the substrate 2 filled with the sacrificial material layer 1. As shown in FIG. 3b, in S11, the surface of the sacrificial material layer 1 is flush with the surface of the substrate 2 through a polishing step. In a preferred embodiment, the sacrificial material on the surface of the substrate 2 can be removed after chemical mechanical polishing, so that the surfaces of the substrate 2 and the sacrificial material layer 1 are flattened. In a preferred embodiment, the cavity after chemical mechanical polishing The height of 7 is 2 μm. After polishing, the surface of the sacrificial material layer 1 is flush with the surface of the substrate 2, so that the surface of the support layer 3 produced subsequently remains level, which can effectively reduce the stress change of the subsequent film layer and improve the mechanical stability.

In a specific embodiment, the support layer 3 is made by PECVD, photolithography, and etching processes in S12. As shown in FIG. 3c, the support layer 3 is provided with an extension portion 32 on the surface of the sacrificial material layer 1, and the edge of the extension portion 32 of the support layer 3 forms an opening area 31. Among them, in order to be compatible with subsequent processes, Si with a high etching selection ratio to the sacrificial material layer 1 is selected as the material of the support layer 3. The material of the support layer 3 can also be selected from other high-hardness materials, including but not limited to SiC/SiN/AlN/ and other materials that are easy to prepare and have relatively high etching options.

In a specific embodiment, as shown in FIG. 3d, the sacrificial material is deposited on the opening area 31 of the support layer 3 by PECVD in S2, and then the surface of the sacrificial material in the opening area 31 is made flat with the surface of the support layer 3 by polishing. together. In a preferred embodiment, the surfaces of the sacrificial material and the support layer 3 are planarized by chemical mechanical polishing. In addition, the sacrificial material and the material of the sacrificial material layer 1 include any other types of sacrificial layer materials such as _{PSG (P-doped SiO 2} ) or SiO _{2, such as the resin material PI.}

In a specific embodiment, as shown in FIG. 3e, the bottom electrode layer 4 is fabricated on the surface of the flat sacrificial material and the support layer 3 through sputtering, photolithography and etching processes, and the bottom electrode layer 4 covers the support layer 3. And erected on the extension portion 32 of the supporting layer 3. The extension portion 32 of the support layer 3 effectively supports the bottom electrode layer 4 so that the projection area of the bottom electrode layer 4 on the substrate 2 falls within the region of the cavity 7 and does not exceed the region of the cavity 7. The projection area of the bottom electrode layer 4 on the substrate 2 is beyond the area of the cavity 7 to easily generate parasitic capacitance and deteriorate the performance of the resonator. On the premise that the support layer 3 guarantees mechanical stability, the bottom electrode layer 4 projected inside the cavity 7 can effectively reduce parasitics relative to the bottom electrode layer 4 straddling the cavity 7.

In a specific embodiment, as shown in FIGS. 3f and 3g, in S4, the piezoelectric layer 5 and the top electrode layer 6 are formed on the bottom electrode layer 4 and the support layer 3 through sputtering, photolithography, and etching processes, respectively. In a preferred embodiment, the material of the bottom electrode layer 4 and the top electrode layer 6 includes Mo, and the material of the piezoelectric layer 5 includes AlN. The projection area of the top electrode layer 6 on the substrate 2 falls within the projection area of the bottom electrode layer 4 on the substrate 2. In a preferred embodiment, the projection area of the top electrode layer 6 on the substrate 2 exceeds the opening The extent of area 31. The top electrode layer 6 beyond the range of the opening area 31 can increase the area of the effective resonance area, and the projection areas of the top electrode layer 6 and the bottom electrode layer 4 on the substrate 2 are both within the area of the cavity 7, which can effectively reduce parasitics. The production. In another embodiment, as shown in FIG. 3h, the projection areas of the top electrode layer 6 and the bottom electrode layer 4 on the substrate 2 in the effective resonant region I1 of the device completely overlap.

In a specific embodiment, as shown in FIG. 3i, S5 uses a dry etching process to form a release hole 8 on the piezoelectric layer 5 and the support layer 3 next to the effective resonance area of the device, and the release hole 8 extends to the sacrificial material layer 1. . The sacrificial material in the cavity 7 is completely removed through the release hole 8. The removal method includes wet etching or a gaseous release process. In a preferred embodiment, the etchant includes HF. The release hole 8 is formed on the support layer 3 and the piezoelectric layer 5, outside the resonance region of the film bulk acoustic wave resonator, does not affect the performance of the resonator, and the processing technology is simple, and the film body as shown in Figs. 3j and 3k is finally formed Acoustic wave resonator, where Fig. 3j is a cross-sectional view of Fig. 3k in the AA direction. The resonator can improve the horizontal and vertical overlap of the bottom electrode layer 4, the top electrode layer 6 and the cavity 7 under the premise of ensuring the mechanical stability of the device. The projections on the bottom 2 are completely overlapped to suppress parasitic capacitance, and the thickness of the support layer 3 is relatively thin. When the longitudinal wave reaches the boundary of the support layer 3, it forms total reflection with the air interface, effectively reducing the loss of the longitudinal wave in the edge area of the bottom electrode layer 4.

Example two

The cavity 7 can also be formed by etching the support layer 3'without etching the substrate 2'. The support layer 3'and the upper and lower bottom electrode layers 4 and the substrate 2'constitute a cavity structure. As shown in Figure 4, S1 includes the following sub-steps:

S11', fabricating a sacrificial material layer 1 on a substrate 2'with a flat surface to cover part of the surface of the substrate 2';

S12', forming a support layer 3'on the substrate 2'to cover the substrate 2'and the sacrificial material layer 1;

S13', forming the opening area 31' of the support layer 3'by photolithography and etching processes.

The schematic diagram of the manufacturing process of the second embodiment of the present application is shown in FIGS. 5a-5k. In a specific embodiment, as shown in FIG. 5a, the sacrificial material layer 1 is formed on the flat substrate 2'by PECVD, photolithography and etching processes. In a preferred embodiment, the material of the sacrificial material layer 1 includes any other types of sacrificial layer materials such as _{PSG (P-doped SiO 2} ) or SiO _{2, such as the resin material PI.} The height of the sacrificial material layer 1 is about 2 μm. As shown in Figure 5b, a support layer 3'is deposited on the substrate 2'and the sacrificial material layer 1 by PECVD. For compatibility with subsequent processes, Si with a higher etching selection ratio than the sacrificial material layer 1 is selected as the support layer 3' Material. The material of the support layer 3'can also be selected from other high-hardness materials, including but not limited to SiC/SiN/AlN/ and other materials that are easy to prepare and have relatively high etching options.

In a specific embodiment, as shown in Fig. 5c, the sub-step S12' further includes a step of smoothing the support layer 3'through a polishing step. In a preferred embodiment, the support layer 3'is ground flat by chemical mechanical polishing. After the support layer 3'is flattened, it is easy to process to form an open area, which reduces the processing difficulty.

In a specific embodiment, as shown in FIG. 5d, the open area 31' of the support layer 3'is formed on the flattened support layer 3'through photolithography and etching processes. The opening area 31' of the supporting layer 3'is formed inside the sacrificial material layer 1, so that the supporting layer 3'forms an extension 32' on the sacrificial material layer 1.

In a specific embodiment, as shown in FIG. 5e, the sacrificial material is deposited on the opening area 31' of the support layer 3'by PECVD in S2, and then the surface of the sacrificial material in the opening area 31' is polished to the support layer 3 'The surface is flush. In a preferred embodiment, the surfaces of the sacrificial material and the support layer 3'are planarized by chemical mechanical polishing. In addition, the sacrificial material and the material of the sacrificial material layer 1 include any other types of sacrificial layer materials such as _{PSG (P-doped SiO 2} ) or SiO _{2, such as the resin material PI.}

In a specific embodiment, as shown in FIG. 5f, the bottom electrode layer 4 is fabricated on the surface of the flat sacrificial material and the support layer 3'through sputtering, photolithography and etching processes, and the bottom electrode layer 4 covers the support layer. 3', and erected on the extension 32' of the support layer 3'. The extension 32' of the support layer 3'effectively supports the bottom electrode layer 4, so that the projection area of the bottom electrode layer 4 on the substrate 2'falls within the region of the cavity 7 and does not exceed the region of the cavity 7. The projection area of the bottom electrode layer 4 on the substrate 2'extends beyond the area of the cavity 7 to easily generate parasitic capacitance and deteriorate the performance of the resonator. On the premise of ensuring the mechanical stability of the support layer 3', the bottom electrode layer 4 projected inside the cavity 7 can effectively reduce parasitics relative to the bottom electrode layer 4 spanning above the cavity 7.

In a specific embodiment, as shown in FIGS. 5g and 5h, in S4, the piezoelectric layer 5 and the top electrode layer 6 are formed on the bottom electrode layer 4 and the support layer 3'by sputtering, photolithography, and etching processes, respectively. In a preferred embodiment, the material of the bottom electrode layer 4 and the top electrode layer 6 includes Mo, and the material of the piezoelectric layer 5 includes AlN. The projection area of the top electrode layer 6 on the substrate 2'falls within the range of the projection area of the bottom electrode layer 4 on the substrate 2'. In a preferred embodiment, the projection of the top electrode layer 6 on the substrate 2' The area exceeds the range of the opening area 31'. The area of the top electrode layer 6 beyond the opening area 31' can increase the effective resonance area, and the projection area of the top electrode layer 6 and the bottom electrode layer 4 on the substrate 2'can be effectively reduced within the area of the cavity 7 The generation of small parasites. In another embodiment, the projection areas of the top electrode layer 6 and the bottom electrode layer 4 on the substrate 2'are completely overlapped in the effective resonance area of the device.

In a specific embodiment, as shown in FIG. 5i, S5 uses a dry etching process to form a release hole 8 on the piezoelectric layer 5 and the support layer 3'next to the effective resonance region of the device, and the release hole 8 extends to the sacrificial material layer. 1. The sacrificial material in the cavity 7 is completely removed through the release hole 8. The removal method includes wet etching or a gaseous release process. In a preferred embodiment, the etchant includes HF. The release hole 8 is formed on the support layer 3'and the piezoelectric layer 5, outside the resonant region of the film bulk acoustic wave resonator, does not affect the performance of the resonator, and the processing technology is simple, and the film as shown in Figs. 5j and 5k is finally formed The bulk acoustic wave resonator, wherein Fig. 5j is a cross-sectional view of Fig. 5k in the BB direction. The resonator can improve the horizontal and vertical overlap of the bottom electrode layer 4, the top electrode layer 6 and the cavity 7 under the premise of ensuring the mechanical stability of the device. The projections on the bottom 2'completely overlap to suppress parasitic capacitance.

In the embodiments of the present application, a thin film bulk acoustic resonator made by more than one manufacturing process is proposed.

In the embodiment of the present application, a cavity structure of a thin film bulk acoustic resonator is proposed, which includes a substrate 2, a support layer 3, a bottom electrode layer 4, a piezoelectric layer 5, and a top electrode layer 6, which are sequentially stacked. 2. The support layer 3 and the bottom electrode layer 4 surround the cavity 7, the support layer 3 has an extension portion 32 suspended on the cavity 7, and the bottom electrode layer 4 is erected on the extension portion 32 of the support layer 3.

In a specific embodiment, as shown in FIGS. 3j and 3k, the sidewall of the cavity 7 is formed by the substrate 2. Figure 3j is a cross-sectional view of Figure 3k in the A-A direction. The substrate 2 is etched to form a cavity 7, the cavity 7 is formed on the substrate 2, and the support layer 3 is fabricated after the substrate 2 is processed. In this case, the support layer 3 is disposed on the substrate and extends toward the inside of the cavity 7 to form an extension portion 32 to facilitate the subsequent bottom electrode layer 4 to be erected on the extension portion 32 of the support layer 3. Because the thickness of the support layer 3 is relatively small, the longitudinal wave forms total reflection with the air interface when it reaches the boundary of the support layer 3, which effectively reduces the loss of the longitudinal wave in the edge area of the bottom electrode layer 4.

In a specific embodiment, as shown in FIGS. 5j and 5k, the sidewall of the cavity 7 is formed by the support layer 3'. Figure 5j is a cross-sectional view of Figure 5k in the BB direction. In this case, the cavity 7 is formed on the support layer 3', the process is simple and convenient, and it is easy to process. And the upper surface of the support layer 3'is processed to form an extension portion 32', and the side walls of the cavity 7 and the extension portion 32' are formed on the left and right sides, respectively.

and

type. In a specific embodiment, the projection area of the bottom electrode layer 4 on the substrate 2, 2 ′ is completely within the range of the cavity 7. Therefore, the parasitic capacitance between the bottom electrode layer 4 and the substrates 2, 2'can be effectively reduced.

In a specific embodiment, the part of the projection area of the top electrode layer 6 on the substrate 2, 2'is located in the range of the extension portion 32, 32' of the support layer 3, 3'. In a preferred embodiment, the projection areas of the top electrode layer 6 and the bottom electrode layer 4 on the substrate 2, 2'completely overlap. Therefore, the horizontal and vertical overlap of the bottom electrode layer 4, the top electrode layer 6 and the cavity 7 can be improved, and the projections of the bottom electrode layer 4 and the top electrode layer 6 on the substrates 2, 2'can be completely overlapped, thereby suppressing parasitics. capacitance.

In a specific embodiment, a release hole 8 is provided in the extension portion 32, 32' of the support layer 3, 3', and the release hole 8 penetrates the piezoelectric layer 5 and the support layer 3, 3'. The position of the release hole 8 does not affect the effective resonance area, and will not negatively affect the resonance performance of the film bulk acoustic wave resonator.

In order to be compatible with subsequent processes, Si, which has a high etching selection ratio with respect to the sacrificial material layer 1, is selected as the material of the support layers 3, 3'. The material of the support layer 3, 3'can also be selected from other high-hardness materials, including but not limited to SiC/SiN/AlN/ and other materials that are easy to prepare and have relatively high etching options.

The embodiment of the present invention discloses a novel cavity structure. Under the premise of ensuring the mechanical stability of the resonator, the fabricated bottom electrode layer is projected inside the cavity. When at least one side of the top electrode layer extends out of the cavity and is interconnected with other resonators to form a filter, the parasitic capacitance can be effectively reduced.

Fig. 6 is a simulated Smith circle diagram of a thin film bulk acoustic resonator according to an embodiment of the present invention. The lower half of the circle shows that the impedance of the resonator is capacitive. The smooth curve in the lower half of the figure shows that the parasitic capacitance is effectively suppressed. As shown in the control group with obvious parasitic effect in Fig. 7, if the lower half of the area is in a zigzag or curled shape, it indicates that the parasitic effect is obvious.

The present invention provides a cavity structure and manufacturing process of a thin-film bulk acoustic wave resonator. The cavity is surrounded by a substrate, a support layer and a bottom electrode layer, the support layer is suspended on the cavity and an extension is provided. The bottom electrode The layer is erected on the extension of the supporting layer. And the part of the projection area of the top electrode layer on the substrate is located in the range of the extension part of the support layer. Therefore, the parasitic capacitance of the thin film bulk acoustic wave resonator is greatly suppressed, the mechanical stability of the device can be effectively improved, the influence of the stress change of the film layer on the resonance performance of the device can be reduced, and the resonance performance of the resonator can be effectively improved. It can also cause the longitudinal wave to form total reflection with the air interface when it reaches the boundary of the support layer, effectively reducing the loss of the longitudinal wave in the edge area of the bottom electrode layer.

The specific implementation manners of this application are described above, but the protection scope of this application is not limited to this. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in this application, and they should all be covered Within the scope of protection of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

In the description of this application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", etc. It is convenient to describe the application and simplify the description, instead of indicating or implying that the device or element referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore cannot be understood as a limitation of the application. The word'comprising' does not exclude the presence of elements or steps not listed in the claims. The wording'a' or'one' in front of an element does not exclude the existence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used for improvement. Any reference signs in the claims should not be construed as limiting the scope.

Claims

A manufacturing process of the cavity structure of a thin film bulk acoustic wave resonator is characterized in that it comprises the following steps:

S1, a support layer is laid on a substrate on which a sacrificial material layer is arranged so that the support layer covers at least a part of the upper surface of the periphery of the sacrificial material layer, and the support layer has an open area so that the sacrificial material The remaining part of the upper surface of the layer is exposed;

S2, using a sacrificial material to fill up the opening area of the support layer;

S3, fabricating a bottom electrode layer on the support layer and the sacrificial material, and the bottom electrode layer is erected on the support layer;

S4, fabricating a piezoelectric layer and a top electrode layer on the bottom electrode layer; and

S5, removing all the sacrificial materials to form the cavity structure.
The manufacturing process according to claim 1, wherein the S1 includes the following sub-steps:

S11, making a cavity on a substrate, and filling the cavity with a sacrificial material to form the sacrificial material layer;

S12, fabricating the supporting layer on the substrate and the sacrificial material layer, and partially removing the supporting layer to form the opening area.
The manufacturing process according to claim 2, wherein the surface of the sacrificial material layer is flush with the surface of the substrate through a polishing step in the S11.
The manufacturing process according to claim 1, wherein the S1 includes the following sub-steps:

S11', fabricating the sacrificial material layer on a substrate with a flat surface to cover part of the surface of the substrate;

S12', fabricating the support layer on the substrate to cover the substrate and the sacrificial material layer;

S13', forming the opening area of the support layer by photolithography and etching processes.
The manufacturing process according to claim 4, wherein the sub-step S12' further comprises a step of smoothing the support layer through a polishing step.
The manufacturing process according to claim 1, wherein the S2 further comprises a step of making the surface of the sacrificial material in the opening area flush with the surface of the support layer by polishing.
The manufacturing process according to claim 1, wherein the S5 comprises forming a release hole on the piezoelectric layer and the support layer, and the release hole extends to the sacrificial material layer.
The manufacturing process according to claim 1, wherein the support layer comprises an extension part suspended on the cavity of the cavity structure, and the bottom electrode layer is erected on the extension part of the cavity .
8. The manufacturing process according to claim 8, wherein the projection area of the bottom electrode layer on the substrate falls within the area of the cavity.
The manufacturing process according to claim 9, wherein the projection area of the top electrode layer on the substrate falls within the projection area of the bottom electrode layer on the substrate.
The manufacturing process according to claim 9, wherein at least one side of the projection area of the top electrode layer and the bottom electrode layer on the substrate overlaps.
The manufacturing process according to claim 10 or 11, wherein the projection area of the top electrode layer on the substrate exceeds the range of the opening area.
The manufacturing process according to any one of claims 1-11, wherein the supporting layer is made of the following materials: Si, SiC, SiN or AlN.
The manufacturing process according to any one of claims 1-11, wherein the sacrificial material layer is made of the following materials: PSG, SiO 2 or PI.
A thin film bulk acoustic resonator made by the manufacturing process of any one of claims 1-14.
A cavity structure of a film bulk acoustic wave resonator, comprising a substrate, a supporting layer and a bottom electrode layer stacked in sequence, wherein the substrate, the supporting layer and the bottom electrode layer are surrounded by a cavity, The support layer has an extension part suspended on the cavity, and the bottom electrode layer is erected on the extension part of the support layer.
The cavity structure of the thin film bulk acoustic resonator according to claim 16, wherein the sidewall of the cavity is formed by the substrate.
The cavity structure of the film bulk acoustic resonator according to claim 16, wherein the side wall of the cavity is formed by the support layer.
The cavity structure of the film bulk acoustic resonator according to any one of claims 16-18, wherein the projection area of the bottom electrode layer on the substrate is completely located within the range of the cavity .
The cavity structure of the film bulk acoustic resonator according to any one of claims 16-18, further comprising a piezoelectric layer and a top electrode layer stacked on the bottom electrode layer in sequence, and the top electrode layer The part of the projection area of the electrode layer on the substrate is located in the range of the extension part of the support layer.
22. The cavity structure of the thin film bulk acoustic resonator according to claim 20, wherein at least one side of the projection area of the top electrode layer and the bottom electrode layer on the substrate overlaps.
The cavity structure of the film bulk acoustic resonator according to claim 20, wherein a release hole is provided in the extension portion of the support layer, and the release hole penetrates the piezoelectric layer and the Support layer.
The cavity structure of the film bulk acoustic resonator according to any one of claims 16-18, wherein the supporting layer is made of the following materials: Si, SiC, SiN or AlN.