WO2020177558A1

WO2020177558A1 - Packaging of mems device having release hole outside packaging space

Info

Publication number: WO2020177558A1
Application number: PCT/CN2020/076211
Authority: WO
Inventors: 张孟伦; 庞慰; 杨清瑞
Original assignee: 天津大学; 诺思(天津)微系统有限责任公司
Priority date: 2019-03-02
Filing date: 2020-02-21
Publication date: 2020-09-10
Also published as: CN111010109A; CN111010109B

Abstract

An MEMS device assembly, comprising: an MEMS device comprising an air gap structure; and a packaging film (20) forming a packaging space (24) enclosing the MEMS device, wherein the MEMS device is provided with a first release hole (11) communicated with the air gap structure; and the first release hole (11) is located outside the packaging space (24).

Description

Packaging of MEMS devices with release holes located outside the packaging space

Technical field

The embodiments of the present invention relate to the field of semiconductors, in particular to a MEMS device assembly, an electronic device having the MEMS device assembly, an electronic device having the MEMS device assembly or the electronic device, and a MEMS device package method.

Background technique

Small, high-performance film bulk acoustic wave (FBAR, film bulk acoustic resonator) bandpass filters are widely used in mobile wireless communication systems. The thin-film bulk acoustic wave bandpass filter is based on a high-Q resonator. The thin-film bulk acoustic wave resonator uses the thickness extension mode of a piezoelectric aluminum nitride (AlN) film.

The thin film bulk acoustic wave resonator mainly has the following three structures:

(1) Silicon reverse etching type. This bulk silicon micro-manufacturing process is used to etch and remove most of the silicon material from the reverse side of the silicon wafer to form an air interface on the lower surface of the piezoelectric oscillatory stack, thereby confining sound waves within the piezoelectric oscillatory stack. Because the large area of silicon substrate is removed, it will inevitably affect the mechanical fastness of the device and greatly reduce the yield.

(2) Air gap type. The surface micro-manufacturing process used forms an air gap on the upper surface of the silicon wafer to limit the sound waves in the piezoelectric oscillator stack. The air gap may be a sinking type formed by removing part of the surface of the silicon wafer, or it may be an upward convex shape formed directly on the silicon surface without removing the silicon. This type of FBAR can not only confine the sound wave within the piezoelectric oscillator stack, and obtain a high Q value. At the same time, because of the surface micro-manufacturing process, it is not necessary to remove most of the silicon substrate, so it is compatible with the silicon wafer. Compared with the reverse side etching type, the mechanical fastness is much better; in addition, there is no need to process the reverse side of the silicon substrate so that this method can be compatible with the traditional silicon integrated circuit process and has the possibility of integration.

(3) Solidly mounted resonator (SMR). Different from the previous two, SMR uses a Bragg reflector to confine the sound wave within the piezoelectric oscillator. The Bragg reflector generally uses W and SiO ₂ as the high and low impedance acoustic layer, because the acoustic impedance between W and SiO ₂ is relatively different. Large, and these two materials are materials in the standard CMOS process. Its biggest advantage is that it has strong mechanical fastness, good integration, and does not need to use technology, which makes it easy for many semiconductor factories that do not have technology to join in. But its disadvantage is that it needs to prepare multi-layer films, the process cost is higher than that of the air gap type, and the acoustic reflection effect of the Bragg reflector is not as good as air. Therefore, the Q value of SMR is generally lower than that of air gap type FBAR.

Figures 1 and 2 are respectively a top view of a typical air gap type FBAR and a cross-sectional view taken along A-A in the top view. Wherein 10 is the air gap structure of the resonator, 11 is the release hole of the air gap, 12 is the bottom electrode of the resonator, 13 is the piezoelectric layer of the resonator, and 14 is the top electrode of the resonator.

Generally, film bulk acoustic resonators have specific packaging requirements under different application environments. For example, certain BAW resonators can work optimally in specific environmental conditions, such as a specific range of humidity or pressure or in an inert gas. In addition, certain bulk acoustic wave resonators may be sensitive to certain pollution.

3A-3E show the thin film packaging process of the resonator in the prior art. as the picture shows:

The known thin film packaging process is as follows:

1): As shown in Figure 3A, it is an air gap type film bulk acoustic resonator with good performance;

2): Depositing a sacrificial layer 30 above the resonator, as shown in Figure 3B;

3): A packaging film 31 is formed above the sacrificial layer, as shown in FIG. 3C;

4): forming an opening 32 on the packaging film 31 and releasing the sacrificial layer 30 to form a packaging cavity 33, as shown in FIG. 3D;

5): A sealing layer 35 is formed on the packaging film 31 to seal the openings in the packaging film 31, thereby sealing the packaging cavity 33, as shown in FIG. 3E.

However, for the air gap type film bulk acoustic resonator, during the packaging process, when the sacrificial layer 30 is released to form the packaging cavity 33, the position of the opening 32 is located in the middle of the film 31, so that the liquid medicine enters the packaging. After the cavity 33, the distance into the air gap 10 through the release hole 11 becomes longer, as shown by the arrow in FIG. 3D. Therefore, chemical residues and the like generated during the release of the sacrificial layer 30 are likely to stay in the air gap 10, resulting in deterioration of the performance of the resonator. At the same time, for the air gap type FBAR, there will be a step 34 in the packaging film 34 formed on the release hole 11 of the air gap. Due to the large stress concentration at the step, the stability of the packaging structure will deteriorate. Moreover, when the final sealing is performed, the sealant will easily fall from the opening 32 to the top of the device, which will cause the performance of the resonator to deteriorate.

In the existing packaging methods, such as bonding packaging, a cover substrate is installed above the device. An example cover substrate is a dome or cap-shaped "cap" that can be positioned above each device and then fixed to a supporting substrate. After being unitized, the devices can be packaged one by one at the chip level, for example, packaged in a housing. However, this packaging method increases the overall size of the device, and increases the packaging cost due to a large number of packaging steps. At the same time, it is easy to introduce particle contamination in the chip-scale packaging. Another packaging method, such as thin-film packaging, first deposits a sacrificial layer on the device during processing, then spin-coats a thin film as the packaging layer, and etches the holes to reach the sacrificial layer, and releases the sacrificial layer to form a cavity. Spin on a thin film to seal it. This packaging method has simple process, good sealing, low cost, and is compatible with IC process.

However, when the air gap FBAR is encapsulated by a thin film packaging method, when the packaging cavity is released, chemical residues and the like are easily introduced into the air gap at the bottom of the device, which affects the performance of the device and reduces its Q value.

Summary of the invention

In order to alleviate or solve the above-mentioned problems in the prior art, the present invention is proposed.

According to an aspect of the embodiments of the present invention, a MEMS device assembly is provided, including:

MEMS devices, including air gap structures; and

The packaging film forms a packaging space that closes the MEMS device,

among them:

The MEMS device is provided with a first release hole communicating with the air gap structure; and

The first release hole is located outside the packaging space.

Optionally, the packaging film is provided with a second release hole, and the second release hole is filled with a sealing material.

Optionally, the packaging film covers and seals the first release hole.

Optionally, the packaging film is provided with a plurality of second release holes.

Optionally, the MEMS device includes a bulk acoustic wave resonator. Further, the MEMS device includes a thin film bulk acoustic resonator.

In an optional embodiment, the bulk acoustic wave resonator includes a bottom electrode, a piezoelectric layer and a top electrode, the packaging film covers the bulk acoustic wave resonator, and the component includes a sealing layer at least partially covering the packaging film, The material constituting the sealing layer constitutes the sealing material filling the second release hole; and the material of the sealing layer is the same as the material of the top electrode, and the material of the packaging film is the same as the material of the piezoelectric layer. Further, the material of the sealing layer is selected from one of the following materials: silicon dioxide, polymer, spin-on glass, plastic, resin, dielectric material, metal, silicon nitride, aluminum nitride and other materials; The material of the film is selected from one of the following materials: silicon, silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, metal, photoresist, polymer, graphene, nanotube, TOK DFR material, etc.

According to another aspect of the embodiments of the present invention, an electronic device is provided, which includes a plurality of the aforementioned MEMS device components.

Optionally, at least two MEMS device components have a common first release hole.

Optionally, at least two MEMS devices are packaged in one packaging space formed by a layer of packaging film.

Optionally, the electronic device includes a filter.

According to another aspect of the embodiments of the present invention, an electronic device is provided, which includes the above-mentioned electronic device or the above-mentioned MEMS device assembly.

According to another aspect of the embodiments of the present invention, a method for packaging a MEMS device is provided. The MEMS device includes an air gap structure and is provided with a first release hole communicating with the air gap structure. The method includes step:

Using a packaging film to form a packaging space that closes the MEMS device, and make the first release hole located outside the packaging space;

At least one second release hole communicating with the packaging space is opened on the packaging film; and

Seal the second release hole.

Description of the drawings

The following description and drawings can better help understand these and other features and advantages in the various embodiments disclosed in the present invention. The same reference numerals in the figures always indicate the same components, among which:

Figure 1 is a schematic top view of a thin film bulk acoustic resonator in the prior art;

Fig. 2 is a cross-sectional view taken along the line A-B of the resonator in Fig. 1;

3A-3E are the processes of film packaging of the film bulk acoustic resonator in the prior art;

Fig. 4A is a schematic top view of a film bulk acoustic resonator according to an exemplary embodiment of the present invention;

Fig. 4B is a schematic cross-sectional view along A-A in Fig. 4A;

Fig. 5A is a schematic top view of a filter according to an exemplary embodiment of the present invention;

Figure 5B is a schematic cross-sectional view taken along A-A in Figure 5A;

Figures 6A-6F schematically show a thin-film packaging process of a thin-film bulk acoustic resonator according to an exemplary embodiment of the present invention.

detailed description

In the following, the technical solutions of the present invention will be further described in detail through embodiments and in conjunction with the drawings. In the specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention, and should not be understood as a limitation of the present invention.

Hereinafter, referring to the accompanying drawings, a thin-film bulk acoustic wave resonator is taken as an example to exemplarily describe the MEMS device assembly according to the embodiment of the invention.

4A is a schematic top view of a thin film bulk acoustic resonator according to an exemplary embodiment of the present invention;

Fig. 4B is a schematic cross-sectional view along A-A in Fig. 4A.

In the embodiment shown in FIG. 4A, 10 is the bottom cavity of the FBAR (corresponding to the air gap structure), and 11 is the release hole of the bottom cavity 10 (corresponding to the first release hole, and the typical value of its size can be: 10um); 12 is the bottom electrode of the FBAR, 13 is the piezoelectric layer of the FBAR, and 14 is the top electrode of the FBAR; 20 is the packaging film, and 21 is the opening on the packaging film (corresponding to the second release hole). Obviously, the release hole 11 of the cavity 10 at the bottom of the FBAR is outside the cavity formed by the packaging film 20.

In FIG. 4B, 10 is the cavity at the bottom of the FBAR, 11 is the release hole of the cavity 10 at the bottom of the FBAR, and 12 is the bottom electrode of the FBAR. 23 is a flat layer located on both sides of the bottom electrode 12, the added flat layer is aligned with the oblique end faces at both ends of the bottom electrode 12, thereby forming a flat and smooth surface, which is beneficial to deposit on the connection between the bottom electrode 12 and the flat layer 23 Piezo film with good C-axis orientation. The flat layer can be made of suitable dielectric materials such as silicon dioxide, silicon nitride, silicon carbide, etc. It is not necessary to provide a flat layer. 13 is the piezoelectric layer of FBAR, 14 is the top electrode of FBAR; 20 is the packaging film, 21 is the opening on the packaging film, and 22 is the sealing layer. In the present invention, the release hole 11 of the cavity 10 at the bottom of the FBAR is outside the packaging space 24 formed by the packaging film 20.

Since the release hole 11 is outside the packaging space 24, the release hole is sealed during the process of forming the packaging film 20, so in the process of releasing the packaging space 24, there will be no liquid medicine residues, particles, etc. entering the FBAR In the bottom cavity 10, the performance of the resonator will not be affected. Moreover, the position and number of the openings 21 on the packaging film 20 can be flexibly selected. At the position of the opening, the process steps for aligning with the bottom cavity release hole 11 can be omitted, and the packaging cost can be reduced; at the same time, the number of openings can be increased, and the formation of the cavity 24 can be accelerated. In addition, for the FBAR of the same area, encapsulating the release hole 11 outside the cavity 24 can reduce the area of the cavity 24 on the top of the resonator, thereby reducing the package size of the resonator.

Fig. 5A is a schematic top view of a filter according to an exemplary embodiment of the present invention; Fig. 5B is a schematic cross-sectional view along line A-A in Fig. 5A.

In the embodiment shown in FIG. 5A, the filter is composed of an air gap type FBAR according to a ladder structure, that is, each stage is composed of a series resonator and a parallel resonator. Among them, 30, 31, 32 are series resonators, 33 and 34 are parallel resonators; 11 is the release hole of the cavity at the bottom of the resonator, 20 is the packaging film, and 21 is the opening on the packaging film 20.

In Figure 5B, 10 is the bottom cavity of FBAR, 11 is the release hole of the bottom cavity of FBAR; 12 is the bottom electrode of FBAR, 23 is the flat layer, 13 is the piezoelectric layer of FBAR, and 14 is the top electrode of FBAR; In the packaging film, 21 is the opening of the packaging film, 24 is the cavity on the top of the FBAR, and 22 is the sealing layer. In FIG. 5B, the release hole 11 of the cavity at the bottom of the resonator is outside the cavity 24 at the top of the resonator.

Since the release hole 11 of the cavity at the bottom of the resonator is outside the packaging space formed by the packaging film 20, the release hole 11 is sealed by the packaging film during the process of forming the packaging film 20, so in the process of releasing the packaging space 24 No chemical residues, particles, etc. enter the bottom cavity 10 of the FBAR, so the performance of the resonator will not be affected, and a high-performance filter can be obtained after packaging.

Figures 6A-6F schematically illustrate the thin-film packaging process of a thin-film bulk acoustic resonator according to an exemplary embodiment of the present invention, specifically:

1): As shown in Figure 6A, it is a cavity-type thin-film bulk acoustic resonator with good performance. It includes: 10 bottom cavity structure, 11 bottom cavity release hole; 12 bottom electrode, 23 is the flat layer on both sides of the bottom electrode, 13 piezoelectric layer, 14 top electrode;

2): Deposit a sacrificial layer 41 on the top of the resonator by plasma enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), chemical vapor deposition (CVD), spin coating and other similar film deposition processes, Its thickness can be 0.1-10um, as shown in Figure 6B. The material of the sacrificial layer can be organic materials, polymers, silicon, amorphous silicon, silicon dioxide, PSG, metals (such as germanium, titanium, copper), metal oxides (magnesium oxide, zinc oxide), photoresist and other materials .

3): Through a photolithography process, an etching barrier layer is formed on the surface of the sacrificial layer, and then the excess material on the sacrificial layer is etched away by dry etching or wet etching, and finally the photoresist is removed After that, a desired pattern is formed on the sacrificial layer, as shown in FIG. 6C.

4): After plasma enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), chemical vapor deposition (CVD), spin coating and other similar film deposition processes, the packaging film 20 is formed on the sacrificial layer and passed through light The process of etching and etching forms a sacrificial layer with openings 21 reaching the bottom on the packaging film 20, as shown in FIG. 6D. The thickness of the packaging film can be 1-10um, typically 3um. The packaging film material can be silicon, silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, metal, photoresist (such as SU-8), polymer, graphene, nanotube, TOK and DFR materials, etc.

5): Introduce an etchant from the opening 21 on the packaging film 20, remove the sacrificial layer under the packaging film 20, and form a cavity structure 24 on the top of the resonator, as shown in FIG. 6E.

6): Finally, the opening 21 on the packaging film 20 is sealed with a sealant, thereby forming a closed packaging space on the top of the resonator, as shown in FIG. 6F. The sealing layer material can be dense materials such as silicon dioxide, polymers, spin-on glass, plastics, resins, dielectric materials, metals, silicon nitride, aluminum nitride, and other materials.

As can be understood by those skilled in the art, although the above embodiments use a thin-film bulk acoustic resonator as an example to illustrate thin-film packaging, thin-film packaging can also be applied to other MEMS devices containing air gap structures.

Based on the above, the present invention provides a MEMS device assembly, including:

MEMS device, including an air gap structure (corresponding to cavity 10); and

The packaging film 20 forms a packaging space 24 enclosing the MEMS device,

among them:

The MEMS device is provided with a first release hole (corresponding to the release hole 11) communicating with the air gap structure; and

The first release hole is located outside the packaging space.

Further, the packaging film is provided with a second release hole (corresponding to the opening 21), and the second release hole is filled with a sealing material.

Further, the packaging film covers and seals the first release hole.

Based on the above, the embodiment of the present invention also proposes an electronic device including a plurality of the above-mentioned MEMS device components. Optionally, at least two MEMS device components have a common first release hole. Further, at least two MEMS devices are packaged in one package space formed by a layer of package film.

Based on the above, the present invention also provides a packaging method for a MEMS device. The resonator includes an air gap structure and is provided with a first release hole communicating with the air gap structure. The method includes the steps:

Seal the second release hole.

In the present invention, the electrode constituent materials can be gold (Au), tungsten (W), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), titanium tungsten (TiW), aluminum (Al) , Titanium (Ti) and other similar metals.

The piezoelectric layer material can be aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO ₃ ), quartz (Quartz), potassium niobate (KNbO ₃ ) or tantalic acid Materials such as lithium (LiTaO ₃ ).

The material of the sacrificial layer can be organic material, polymer, silicon, amorphous silicon, silicon dioxide, PSG, metal (such as Ge, Ti, Cu), metal oxide (such as MgO, ZnO), photoresist (such as SU- 8) and other easily soluble materials.

The packaging film material can be silicon, silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, metal, photoresist, polymer, graphene, nanotubes and other materials;

The sealing layer material can be dense materials such as silicon dioxide, polymers, spin-on glass, plastics, resins, dielectric materials, metals, silicon nitride, aluminum nitride, and other materials.

In an alternative embodiment, the material of the sealing layer is the same as the material of the top electrode, and the material of the packaging film is the same as the material of the piezoelectric layer. More specifically, the material of the sealing layer is selected from one of the following materials: silicon dioxide, polymer, spin-on glass, plastic, resin, dielectric material, metal, silicon nitride, aluminum nitride and other materials; The material of the packaging film is selected from one of the following materials: silicon, silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, metal, photoresist, polymer, graphene, nanotubes, TOK DFR materials, etc. In addition, the sacrificial layer forming the air gap structure and the sacrificial layer forming the packaging space can use the same material, which is selected from one of the following materials: organic materials, polymers, silicon, amorphous silicon, silicon dioxide, PSG, metal ( Such as Ge, Ti, Cu), metal oxides (such as MgO, ZnO), photoresist (such as SU-8) and other easily soluble materials.

Although not shown, the embodiment of the present invention also relates to an electronic device, including the above-mentioned MEMS device assembly or the above-mentioned electronic device.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that changes can be made to these embodiments without departing from the principle and spirit of the present invention, and the scope of the present invention is determined by The appended claims and their equivalents are defined.

Claims

A MEMS device assembly, including:

MEMS devices, including air gap structures; and

The packaging film forms a packaging space that closes the MEMS device,

among them:

The MEMS device is provided with a first release hole communicating with the air gap structure; and

The first release hole is located outside the packaging space.
The assembly of claim 1, wherein:

The packaging film is provided with a second release hole, and the second release hole is filled with a sealing material.
The assembly according to claim 1 or 2, wherein:

The packaging film covers and seals the first release hole.
The assembly of claim 2, wherein:

The packaging film is provided with a plurality of second release holes.
The assembly according to any one of claims 1-4, wherein:

The MEMS device includes a bulk acoustic wave resonator.
The assembly of claim 5, wherein:

The MEMS device includes a thin film bulk acoustic wave resonator.
The assembly according to claim 5 or 6, wherein:

The bulk acoustic wave resonator includes a bottom electrode, a piezoelectric layer, and a top electrode, the packaging film covers the bulk acoustic wave resonator, and the component includes a sealing layer at least partially covering the packaging film, and the sealing layer is composed of materials A sealing material filling the second release hole; and

The material of the sealing layer is the same as that of the top electrode, and the material of the packaging film is the same as that of the piezoelectric layer.
The assembly of claim 7, wherein:

The material of the sealing layer is selected from one of the following materials: silicon dioxide, polymer, spin-on glass, plastic, resin, dielectric material, metal, silicon nitride, aluminum nitride;

The material of the packaging film is selected from one of the following materials: silicon, silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, metal, photoresist, high molecular polymer, graphene, nanotube, TOK DFR material .
An electronic device comprising a plurality of MEMS device components according to any one of claims 1-8.
The electronic device according to claim 9, wherein:

At least two MEMS device components have a common first release hole.
The electronic device according to claim 9, wherein:

At least two MEMS devices are packaged in one package space formed by a layer of package film.
The electronic device according to any one of claims 9-11, wherein:

The electronic device includes a filter.
An electronic device comprising the electronic device according to any one of claims 9-12 or the MEMS device assembly according to any one of claims 1-8.
A method for packaging a MEMS device. The MEMS device includes an air gap structure and is provided with a first release hole communicating with the air gap structure. The method includes the steps:

Using a packaging film to form a packaging space that closes the MEMS device, and make the first release hole located outside the packaging space;

At least one second release hole communicating with the packaging space is opened on the packaging film; and

Seal the second release hole.
The method according to claim 14, further comprising the steps:

The first release hole is covered and sealed with the packaging film.
The method of claim 14, wherein:

The air gap structure is formed by releasing a first sacrificial layer, and the packaging space is formed by releasing a second sacrificial layer; and

The first sacrificial layer and the second sacrificial layer are made of the same material, and are selected from one of the following materials: organic material, polymer, silicon, amorphous silicon, silicon dioxide, PSG, metal, metal oxide, photoresist.
The method of claim 16, wherein:

The MEMS device is a bulk acoustic wave resonator, the bulk acoustic wave resonator includes a bottom electrode, a piezoelectric layer, and a top electrode, the packaging film covers the bulk acoustic wave resonator, and the component includes a seal at least partially covering the packaging film Layer, the material constituting the sealing layer constitutes the sealing material filling the second release hole; and

The material of the sealing layer is the same as that of the top electrode, and is selected from one of the following materials: silicon dioxide, polymer, spin-on glass, plastic, resin, dielectric material, metal, silicon nitride, aluminum nitride and other materials; And

The material of the packaging film is the same as that of the piezoelectric layer, and is selected from one of the following materials: organic material, polymer, silicon, amorphous silicon, silicon dioxide, PSG, metal, metal oxide, and photoresist.