阅读说明：本技术 薄膜体声波谐振器及其制备方法 (Film bulk acoustic resonator and preparation method thereof ) 是由 李国强 于 2020-05-06 设计创作，主要内容包括：本发明提供一种薄膜体声波谐振器及其制备方法,该制备方法包括；S101：刻蚀衬底的一侧形成凹槽,并在凹槽中形成填平凹槽的第一牺牲层；S102：在衬底设置有凹槽开口一侧生长未覆盖第一牺牲层的支撑层,并在第一牺牲层远离衬底的一侧形成第二牺牲层；S103：释放第一牺牲层,在支撑层远离衬底一侧形成覆盖第二牺牲层的底电极,并在底电极远离第二衬底第一形成压电薄膜；S104：在压电薄膜远离底电极一侧形成顶电极,释放第二牺牲层。本发明在凹槽内形成两个牺牲层,从而避免衬底与底电极形成互连,制造工艺对核心结构的损伤小,避免寄生电容的引入,可控性强,同时降低了薄膜体声波谐振器的制造工艺,减少了资源和时间的消耗,降低了生产成本。(The invention provides a film bulk acoustic resonator and a preparation method thereof, wherein the preparation method comprises the following steps of; s101: etching one side of the substrate to form a groove, and forming a first sacrificial layer filling the groove in the groove; s102: growing a supporting layer which is not covered with the first sacrificial layer on one side of the substrate provided with the groove opening, and forming a second sacrificial layer on one side of the first sacrificial layer far away from the substrate; s103: releasing the first sacrificial layer, forming a bottom electrode covering the second sacrificial layer on one side of the supporting layer, which is far away from the substrate, and forming a piezoelectric film on the bottom electrode, which is far away from the second substrate; s104: and forming a top electrode on one side of the piezoelectric film, which is far away from the bottom electrode, and releasing the second sacrificial layer. According to the invention, the two sacrificial layers are formed in the groove, so that the substrate and the bottom electrode are prevented from being interconnected, the core structure is prevented from being damaged by the manufacturing process, the parasitic capacitance is prevented from being introduced, the controllability is strong, meanwhile, the manufacturing process of the film bulk acoustic resonator is reduced, the consumption of resources and time is reduced, and the production cost is reduced.)

1. A method for preparing a film bulk acoustic resonator is characterized by comprising the following steps of;

s101: etching one side of a substrate to form a groove, and forming a first sacrificial layer filling the groove in the groove;

s102: growing a supporting layer which is not covered with the first sacrificial layer on one side of the substrate provided with the groove opening, and forming a second sacrificial layer on one side of the first sacrificial layer far away from the substrate;

s103: releasing the first sacrificial layer, forming a bottom electrode covering the second sacrificial layer on one side, far away from the substrate, of the supporting layer, and forming a piezoelectric film on one side, far away from the second sacrificial layer, of the bottom electrode;

s104: and forming a top electrode on one side of the piezoelectric film, which is far away from the bottom electrode, and releasing the second sacrificial layer.

2. The method for manufacturing a film bulk acoustic resonator according to claim 1, wherein the step of etching one side of the substrate to form the groove specifically comprises:

and after the substrate is subjected to glue coating, exposure and cleaning, etching the substrate by ICP-RIE equipment to form a groove.

3. The method of manufacturing a thin film bulk acoustic resonator according to claim 1, wherein the substrate is high-resistance single crystal silicon, and the depth of the groove is 800nm to 2 μm.

4. The method of manufacturing a thin film bulk acoustic resonator according to claim 1, wherein the step of forming the first sacrificial layer in the groove to fill the groove specifically includes:

and forming a first sacrificial layer made of PSG in the groove, and removing the first sacrificial layer outside the groove through a CMP process.

5. The method for manufacturing the thin film bulk acoustic resonator according to claim 1, wherein the step of growing the support layer not covering the first sacrificial layer on the side of the substrate where the recess opening is provided specifically includes:

and growing a support layer through PEVCD, and removing the support layer covering the first sacrificial layer through a photoetching mode.

6. The method for manufacturing a thin film bulk acoustic resonator according to claim 5, wherein the step of forming the second sacrificial layer on the side of the first sacrificial layer away from the substrate specifically includes:

and depositing a second sacrificial layer through PEVCD, and removing the second sacrificial layer covering the supporting layer through a photoetching mode.

7. The method for manufacturing a thin film bulk acoustic resonator according to claim 1, wherein the step of forming the piezoelectric thin film on the side of the bottom electrode away from the second sacrificial layer specifically includes:

and forming the piezoelectric film on the side of the bottom electrode far away from the second sacrificial layer by one or more of PVD, MOCVD and PLD.

8. The method of claim 1, wherein the first sacrificial layer is one or more of polysilicon, PSG, and porous silicon, and the second sacrificial layer is SiO₂The piezoelectric film is one or more of AlN, ZnO and PZT, the bottom electrode and the top electrode are both metal electrode layers, and the supporting layer is Si₃N₄。

9. The method of manufacturing a thin film bulk acoustic resonator according to claim 1, wherein the thickness of the first sacrificial layer is 800nm to 2 μm, the thickness of the support layer is 100nm to 2 μm, the thickness of the second sacrificial layer is 100nm to 2 μm, the thickness of the piezoelectric thin film is 100nm to 2 μm, and the thicknesses of the top electrode and the bottom electrode are each 40nm to 450 nm.

10. A thin film bulk acoustic resonator, comprising:

the device comprises a substrate, a first substrate and a second substrate, wherein one side of the substrate is provided with a groove;

the supporting layer is arranged on one side of the opening of the groove and covers the area of the substrate where the groove is not arranged;

the bottom electrode is arranged on one side of the opening of the groove, one side of the bottom electrode, facing the groove, is connected with the supporting layers on the two sides of the groove, and the piezoelectric film and the top electrode are sequentially stacked on one side of the bottom electrode, far away from the groove;

the thin film bulk acoustic resonator is formed by the method of manufacturing a thin film bulk acoustic resonator according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of film bulk acoustic resonators, in particular to a film bulk acoustic resonator and a preparation method thereof.

Background

The Film Bulk Acoustic Resonator (FBAR) is a new type of filter, and compared with the surface Acoustic wave filter, it not only has small volume, large power capacity, integratable performance and high working frequency, but also has better out-of-band rejection and insertion loss, and has a wide application in the current 5G communication.

When the film bulk acoustic resonator is manufactured, a sacrificial layer needs to be formed in a groove, and the conventional sacrificial layer is of a one-step release type. However, if the metal grows directly on the sacrificial layer, when the sacrificial layer is released, the metal is easily absorbed on the groove due to the internal and external pressure difference, so that the substrate and the bottom electrode are interconnected, the core structure of the product is damaged, and the product preparation fails. In order to avoid this, it is often necessary to increase the thickness of the thin film and to provide a complicated structure or process, consuming a lot of resources and time.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides the film bulk acoustic resonator and the preparation method thereof, two sacrificial layers are formed in the groove, so that the interconnection between the substrate and the bottom electrode is avoided, the formed film bulk acoustic resonator has a simple and stable structure, the damage of a manufacturing process to a core structure is small, the introduction of parasitic capacitance is avoided, the controllability is strong, meanwhile, the manufacturing process of the film bulk acoustic resonator is reduced, the consumption of resources and time is reduced, the production cost is reduced, a very thin film can be processed, the film bulk acoustic resonator is suitable for the high-frequency field, and the manufacturing range is expanded.

In order to solve the above problems, the present invention adopts a technical solution as follows: a method for preparing a film bulk acoustic resonator comprises the following steps: s101: etching one side of a substrate to form a groove, and forming a first sacrificial layer filling the groove in the groove; s102: growing a supporting layer which is not covered with the first sacrificial layer on one side of the substrate provided with the groove opening, and forming a second sacrificial layer on one side of the first sacrificial layer far away from the substrate; s103: releasing the first sacrificial layer, forming a bottom electrode covering the second sacrificial layer on one side, far away from the substrate, of the supporting layer, and forming a piezoelectric film on one side, far away from the first sacrificial layer, of the bottom electrode; s104: and forming a top electrode on one side of the piezoelectric film, which is far away from the bottom electrode, and releasing the second sacrificial layer.

Further, the step of etching one side of the substrate to form the groove specifically includes: and after the substrate is subjected to glue coating, exposure and cleaning, etching the substrate by ICP-RIE equipment to form a groove.

Furthermore, the substrate is high-resistance monocrystalline silicon, and the depth of the groove is 800 nm-2 μm.

Further, the step of forming the first sacrificial layer in the groove to fill and level the groove specifically includes: and forming a first sacrificial layer made of PSG in the groove, and removing the first sacrificial layer outside the groove through a CMP process.

Further, the step of growing the support layer not covering the first sacrificial layer on the side of the substrate provided with the groove opening specifically includes: and growing a support layer through PEVCD, and removing the support layer covering the first sacrificial layer through a photoetching mode.

Further, the step of forming the second sacrificial layer on the side of the first sacrificial layer away from the substrate specifically includes: and depositing a second sacrificial layer through PEVCD, and removing the second sacrificial layer covering the supporting layer through a photoetching mode.

Further, the step of forming the piezoelectric film on the side of the bottom electrode away from the second sacrificial layer specifically includes: and forming the piezoelectric film on the side of the bottom electrode far away from the second sacrificial layer by one or more of PVD, MOCVD and PLD.

Further, the first sacrificial layer is one or more of polysilicon, PSG and porous silicon, and the second sacrificial layer is SiO₂The piezoelectric film is one or more of AlN, ZnO and PZT, the bottom electrode and the top electrode are both metal electrode layers, and the supporting layer is Si₃N₄。

Further, the thickness of the first sacrificial layer is 800 nm-2 μm, the thickness of the supporting layer is 100 nm-2 μm, the thickness of the second sacrificial layer is 100 nm-2 μm, the thickness of the piezoelectric film is 100 nm-2 μm, and the thicknesses of the top electrode and the bottom electrode are both 40 nm-450 nm.

Based on the same inventive concept, the present invention further provides a thin film bulk acoustic resonator, including: the device comprises a substrate, a first substrate and a second substrate, wherein one side of the substrate is provided with a groove; the supporting layer is arranged on one side of the opening of the groove and covers the area of the substrate where the groove is not arranged; the bottom electrode is arranged on one side of the opening of the groove, one side of the bottom electrode, facing the groove, is connected with the supporting layers on the two sides of the groove, and the piezoelectric film and the top electrode are sequentially stacked on one side of the bottom electrode, far away from the groove; the film bulk acoustic resonator is formed by the preparation method of the film bulk acoustic resonator.

Compared with the prior art, the invention has the beneficial effects that: two sacrificial layers are formed in the groove, so that the substrate and the bottom electrode are prevented from being interconnected, the formed film bulk acoustic resonator is simple and stable in structure, the damage of a manufacturing process to a core structure is small, the introduction of parasitic capacitance is avoided, the controllability is high, meanwhile, the manufacturing process of the film bulk acoustic resonator is reduced, the consumption of resources and time is reduced, the production cost is reduced, a very thin film can be processed, the method is suitable for the high-frequency field, and the manufacturing range is enlarged.

Drawings

FIG. 1 is a flow chart of an embodiment of a method for fabricating a film bulk acoustic resonator according to the present invention;

FIG. 2 is a cross-sectional view of one embodiment of a supporting layer formed on a substrate in the method for fabricating a film bulk acoustic resonator according to the present invention;

FIG. 3 is a cross-sectional view of one embodiment of FIG. 2 after the first sacrificial layer is released;

FIG. 4 is a cross-sectional view of the embodiment of FIG. 3 after forming the bottom electrode, piezoelectric film, and top electrode;

FIG. 5 is a cross-sectional view of one embodiment of FIG. 4 after the second sacrificial layer is released;

fig. 6 is a cross-sectional view of an embodiment of the film bulk acoustic resonator of the present invention.

In the figure: 101. a substrate; 102. a first sacrificial layer; 103. a support layer; 104. a second sacrificial layer; 105. a bottom electrode; 106. a piezoelectric film; 107. a top electrode.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and the detailed description, and it should be noted that any combination of the embodiments or technical features described below can be used to form a new embodiment without conflict.

Referring to fig. 1-5, fig. 1 is a flow chart of a method for manufacturing a film bulk acoustic resonator according to an embodiment of the present invention; FIG. 2 is a cross-sectional view of one embodiment of a supporting layer formed on a substrate in the method for fabricating a film bulk acoustic resonator according to the present invention; FIG. 3 is a cross-sectional view of one embodiment of FIG. 2 after the first sacrificial layer is released; FIG. 4 is a cross-sectional view of the embodiment of FIG. 3 after forming the bottom electrode, piezoelectric film, and top electrode; FIG. 5 is a cross-sectional view of the embodiment of FIG. 4 after the second sacrificial layer is released. The method for manufacturing the film bulk acoustic resonator of the present invention is described in detail with reference to fig. 1 to 5.

In this embodiment, the method for manufacturing the film bulk acoustic resonator includes:

s101: a groove is formed by etching one side of the substrate 101, and a first sacrificial layer 102 filling the groove is formed in the groove.

In this embodiment, the step of etching one side of the substrate 101 to form the groove specifically includes: after the substrate 101 is subjected to resist, exposure, and cleaning, the substrate 101 is etched by an ICP-RIE (plasma etching) apparatus to form a groove.

In this embodiment, the substrate 101 is high-resistance single crystal silicon, and the depth of the groove formed by etching the high-resistance single crystal silicon is 800nm to 2 μm.

In this embodiment, the step of forming the first sacrificial layer 102 in the groove to fill the groove specifically includes: a first sacrificial layer 102 of PSG (phosphosilicate glass) is formed in the groove, and the first sacrificial layer 102 outside the groove is removed by a CMP (Chemical mechanical polishing) process.

In a preferred embodiment, the first sacrificial layer is one or more of polysilicon, PSG and porous silicon, and has a thickness of 800 nm-2 μm.

S102: a support layer 103 which is not covered with the first sacrificial layer 102 is grown on the side of the substrate 101 provided with the recess opening, and a second sacrificial layer 104 is formed on the side of the first sacrificial layer 102 away from the substrate 101.

In this embodiment, the step of growing the support layer 103 on the side of the substrate 101 where the groove opening is provided, where the first sacrificial layer 102 is not covered, specifically includes: the support layer 103 is grown by PEVCD (Plasma Enhanced Chemical Vapor Deposition), and the support layer 103 covering the first sacrificial layer 102 is removed by means of photolithographic etching.

In the present embodiment, the support layer 103 is Si₃N₄The thickness is 100 nm-2 μm.

In this embodiment, the step of forming the second sacrificial layer 104 on the side of the first sacrificial layer 102 away from the substrate 101 specifically includes: a second sacrificial layer 104 is deposited by PEVCD and the second sacrificial layer 104 covering the support layer 103 is removed by means of photolithographic etching.

In the present embodiment, the second sacrificial layer 104 is SiO₂The thickness is 100 nm-2 μm.

S103: the first sacrificial layer 102 is released, a bottom electrode 105 covering the second sacrificial layer 104 is formed on the side of the support layer 103 away from the substrate 101, and a piezoelectric film 106 is first formed on the bottom electrode 105 away from the second substrate 101.

In this example, the first sacrificial layer 102 is released using a 1-20% strength KOH solution, and the bottom electrode 105 is deposited using magnetron sputtering PVD (Physical Vapor Deposition).

In this embodiment, the step of forming the piezoelectric film 106 on the side of the bottom electrode 105 away from the second sacrificial layer 104 specifically includes: the piezoelectric thin film 106 is formed on the side of the bottom electrode 105 away from the second sacrificial layer 104 by one or more of PVD, MOCVD (Metal-organic chemical vapor deposition), PLD (Pulsed laser deposition).

In this embodiment, the piezoelectric thin film 106 is one or more of AlN, ZnO and PZT, and has a thickness of 100nm to 2 μm.

In a preferred embodiment, the piezoelectric film 106 is AlN and has a thickness of 1.2 μm.

In this embodiment, the bottom electrode 105 is a metal electrode and is made of one or more of Pt, Mo, W, Ti, and Au.

In a preferred embodiment, the bottom electrode 105 is Mo and has a thickness of 300 nm.

S104: a top electrode 107 is formed on the piezoelectric film 106 on the side away from the bottom electrode 105, releasing the second sacrificial layer 104.

In the present embodiment, hydrofluoric acid solution is selected for releasing the second sacrificial layer 104.

In this embodiment, the top electrode 107 is formed by means of magnetron sputtering PVD deposition.

In this embodiment, the top electrode 107 is a metal electrode with a thickness of 40nm to 450 nm.

In a preferred embodiment, the top electrode 107 is Mo and has a thickness of 300 nm.

In the present embodiment, the thin film bulk resonator is formed to include a top electrode 107, a piezoelectric thin film 106, a bottom electrode 105 and a support layer 103 distributed in sequence from top to bottom, the support layer 103 is grown on the substrate 101, and the support layer 103, the substrate 101 and the bottom electrode 105 enclose an air gap. The upper surface and the lower surface of the piezoelectric film 106 are respectively and oppositely connected with a top electrode 107 and a bottom electrode 105, the bottom electrode 105 is directly contacted with an air gap, and the top electrode 107, the piezoelectric film 106 and the bottom electrode 105 form a sandwich structure.

The following describes the method for manufacturing a film bulk acoustic resonator according to the present invention with a specific process for manufacturing a film bulk acoustic resonator.

(1) Selecting a monocrystalline silicon wafer as a substrate 101, and etching a groove by using ICP-RIE equipment after gluing, exposing and cleaning;

(2) filling the groove using the PSG as the first sacrificial layer 102, and then removing all the PSG outside the groove using a CMP process;

(3) placing the processed wafer into PECVD to grow a supporting layer 103, wherein the supporting layer 103 is Si₃N₄And performing photolithography etching to remove the support layer 103 on the first sacrificial layer 102;

(4) second sacrificial layer 104 is deposited using PECVD, second sacrificial layer 104 being SiO₂And the second sacrificial layer 104 on the support layer 103 is removed by photolithography etching;

(5) releasing the first sacrificial layer 102 using a 1-20% strength KOH solution;

(6) depositing a bottom electrode 105 by using a magnetron sputtering PVD method;

(7) depositing a piezoelectric film 106;

(8) the top electrode 107 is deposited using magnetron sputtering PVD followed by release of the second sacrificial layer 104 and release of an optional hydrofluoric acid solution.

If metal is directly grown on the sacrificial layer in the traditional one-step release mode, when the sacrificial layer is released, the metal can be easily adsorbed on the cavity due to the difference of internal pressure and external pressure, so that the substrate 101 and the bottom electrode 105 are interconnected, and great loss is caused.

Has the advantages that: the preparation method of the film bulk acoustic resonator of the invention forms two sacrificial layers in the groove, thereby avoiding the interconnection between the substrate and the bottom electrode, the formed film bulk acoustic resonator has simple and stable structure, small damage to the core structure caused by the manufacturing process, strong controllability, reduced manufacturing process of the film bulk acoustic resonator, reduced consumption of resources and time, reduced production cost, capability of processing very thin films, suitability for the high-frequency field and enlarged manufacturing range.

Based on the same inventive concept, the present invention further provides a film bulk acoustic resonator, please refer to fig. 6, fig. 6 is a cross-sectional view of an embodiment of the film bulk acoustic resonator of the present invention, and the film bulk acoustic resonator of the present invention is specifically described with reference to fig. 6.

In the present embodiment, the thin film bulk acoustic resonator includes:

a substrate 101, wherein one side of the substrate 101 is provided with a groove;

the supporting layer 103 is arranged on one side of the opening of the groove and covers the area of the substrate 101 without the groove;

the bottom electrode 105 is arranged on one side of the opening of the groove, one side, facing the groove, of the bottom electrode 105 is connected with the supporting layers 103 on two sides of the groove, and the piezoelectric film 106 and the top electrode 107 are sequentially stacked on one side, far away from the groove, of the bottom electrode 105;

the thin film bulk acoustic resonator is formed by the method of manufacturing a thin film bulk acoustic resonator as described in the above embodiment.

Has the advantages that: the two sacrificial layers are formed in the groove when the film bulk acoustic resonator is manufactured, so that the substrate and the bottom electrode are prevented from being interconnected, the formed film bulk acoustic resonator is simple and stable in structure, the damage of a manufacturing process to a core structure is small, the introduction of parasitic capacitance is avoided, the controllability is strong, meanwhile, the manufacturing process of the film bulk acoustic resonator is reduced, the consumption of resources and time is reduced, the production cost is reduced, a very thin film can be processed, the film bulk acoustic resonator is suitable for the high-frequency field, and the manufacturing range is expanded.

In the embodiments provided in the present invention, it should be understood that the disclosed devices, modules and circuits may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the structural components of the modules may be divided into only one logical function, and other divisions may be made in practice, for example, a plurality of modules or modules may be combined or integrated into another system, or some features may be omitted, or not implemented. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be through some interfaces, devices or indirect coupling or communication connection, and may be in an electrical, mechanical or other form.

The components described as separate parts may or may not be physically separate, and the components shown may or may not be physically separate, may be located in one place, or may be distributed in a plurality of places. Some or all of them can be selected according to actual needs to achieve the purpose of the embodiment.

The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.