MEMS device components and electronic devices with arc-shaped thin-film encapsulation

Abstract

This invention relates to a MEMS device assembly, comprising: a MEMS device having an encapsulation surface; and an encapsulation film for forming an encapsulation space for encapsulating the MEMS device. The encapsulation film has a top portion, an edge portion, and a connecting portion between the top and the edge portion, wherein the edge portion, the connecting portion, and the top portion define the encapsulation space, and the edge portion is disposed on the encapsulation surface, wherein the connecting portion is arc-shaped. The angle formed between the encapsulation film and the encapsulation surface can be in the range of 2 degrees to 45 degrees. The encapsulation space can be an arc-shaped space. The MEMS device can be a thin-film bulk acoustic resonator. This invention also relates to an electronic device having the above-described MEMS device assembly.

Description

Technical Field

[0001] Embodiments of the present invention relate to the semiconductor field, and more particularly to a MEMS device assembly and an electronic device having the assembly. Background Technology

[0002] MEMS devices based on semiconductor micromachining have advantages such as small size, low power consumption, high integration, good durability, low price, and stable performance. As a type of bulk acoustic wave (BAW) resonator, the film bulk acoustic wave resonator (FBAR) is playing an important role in the field of communication as an important member of MEMS devices. In particular, FBAR filters are gaining an increasingly large market share in the field of radio frequency filters. Due to their excellent characteristics such as small size (um level), high resonant frequency (GHz), high quality factor (1000), large power capacity, and good roll-off effect, FBAR filters have gradually replaced traditional surface acoustic wave (SAW) filters in the 2-10GHz frequency band.

[0003] For BAW resonators, there are currently two main commercially available structures: film bulk acoustic wave (FBAR) and solidly mounted resonator (SMR). These two types of bulk acoustic wave resonators operate on the same principle, the main difference being the way the resonant energy is confined. The FBAR resonator suspends the main body of the piezoelectric film on a silicon substrate through a lower cavity, confining the energy within this part during resonance. The SMR resonator forms "mirrors" beneath the electrodes that reflect sound waves. These "mirrors," called Bragg reflectors, are composed of alternating layers with significantly different acoustic impedances, such as W and SiO2 (approximately a 4:1 impedance ratio) and AlN and SiO2 (approximately a 3:1 impedance ratio). These reflect sound waves back to the core resonant part, effectively limiting energy dissipation.

[0004] Typically, BAW resonators require specific application environments, such as specific humidity or pressure ranges or the presence of inert gases. Furthermore, some bulk acoustic wave (BAW) resonators are sensitive to specific contamination sources. Therefore, BAW resonators require encapsulation.

[0005] Thin-film packaging is a method of packaging MEMS devices, which helps to achieve at least one of the following advantages: reduced package size, simplified packaging process steps, reduced packaging costs, and improved sealing strength.

[0006] Thin-film packaging can also be used for bulk acoustic wave resonators. The following is a brief explanation of the packaging of thin-film bulk acoustic wave resonators.

[0007] Figure 1The thin-film packaging of a thin-film bulk acoustic resonator in the prior art is shown. Figure 1 In the diagram, 10 is the bottom cavity of the resonator, 11 is the bottom electrode of the resonator, 12 is the piezoelectric layer of the resonator, 13 is the top electrode of the resonator; 14 is the thin film encapsulation layer, 15 is the release hole on the thin film encapsulation layer 14, 16 is the sealing layer of the thin film encapsulation layer 14; and 17 is the encapsulation space formed by the thin film encapsulation layer at the top of the resonator.

[0008] from Figure 1 As can be seen, typical thin-film encapsulation methods often involve a right-angled structure 18. At this right-angled structure, stress tends to accumulate. If the stress is too high, it can easily cause cracking at the stress concentration point, i.e., the right-angled structure 18, leading to device sealing failure. Furthermore, excessive stress can worsen the adhesion of multilayer films and reduce mechanical properties. In addition, excessive stress can cause lattice mismatch, resulting in poor film quality. Summary of the Invention

[0009] To alleviate or solve the above-mentioned problems in the prior art and reduce stress concentration in the encapsulation film, this invention is proposed.

[0010] According to one aspect of an embodiment of the present invention, a MEMS device assembly is provided, comprising:

[0011] An encapsulation film is used to form an encapsulation space for encapsulating the MEMS device. The encapsulation film has a top portion, an edge portion, and a connecting portion between the top and the edge portion. The encapsulation space is defined by the edge portion, the connecting portion, and the top, and the edge portion is disposed on the encapsulation surface.

[0012] in:

[0013] The connecting part is arc-shaped.

[0014] Optionally, the angle between the encapsulation film and the encapsulation surface is in the range of 2 degrees to 45 degrees.

[0015] Optionally, the angle between the encapsulation film and the encapsulation surface is in the range of 10 degrees to 20 degrees.

[0016] Optionally, the encapsulation space is an arc-shaped space.

[0017] Optionally, the vertical distance from the highest point of the inner surface of the arcuate space to the packaging surface is between 0.5 micrometers and 10 micrometers. Optionally, the vertical distance H from the highest point of the inner surface of the arcuate space to the MEMS device is between 0.5 micrometers and 10 micrometers.

[0018] Optionally, the top is generally flat.

[0019] Optionally, the edge portion and the connecting portion are integrally formed into an arc shape; or the edge portion has an arc-shaped portion protruding into the encapsulation space.

[0020] Optionally, the boundary shape of the encapsulation space at the junction of the encapsulation film and the encapsulation surface is arc-shaped.

[0021] Optionally, the MEMS device includes an air gap structure.

[0022] Optionally, the MEMS device is provided with a first release hole communicating with the air gap structure, the first release hole being located within the encapsulation space; the encapsulation film is provided with a second release hole communicating with the encapsulation space, the second release hole being filled with sealing material; and in vertical projection, the horizontal distance between at least one second release hole and the corresponding first release hole is less than 20 μm.

[0023] Further optionally, in the vertical projection, the second release hole coincides with or partially coincides with the corresponding first release hole.

[0024] Further optionally, in the vertical projection, the horizontal distance between each of the second release holes and the corresponding first release hole is less than 20 μm.

[0025] Optionally, the MEMS device is provided with a first release hole communicating with the air gap structure, the first release hole being located outside the encapsulation space; the encapsulation film is provided with a second release hole communicating with the encapsulation space, the second release hole being filled with sealing material.

[0026] Alternatively, the encapsulation film may cover and seal the first release hole.

[0027] Optionally, the MEMS device is a bulk acoustic resonator.

[0028] Furthermore, the resonator is a thin-film bulk acoustic resonator including an acoustic mirror cavity.

[0029] According to another aspect of the embodiments of the present invention, an electronic device is provided, including the above-described MEMS device components. Attached Figure Description

[0030] The following description and accompanying drawings will better aid in understanding these and other features and advantages of the various embodiments disclosed herein, wherein the same reference numerals in the drawings always denote the same parts, wherein:

[0031] Figure 1 A cross-sectional schematic diagram illustrating the package of a prior art thin-film bulk acoustic resonator;

[0032] Figure 2A top view schematic diagram of a thin-film bulk acoustic resonator that has been thin-film encapsulated according to an exemplary embodiment of the present invention;

[0033] Figure 3 For along Figure 2 A schematic cross-sectional view taken along line AA in the diagram;

[0034] Figure 4 A cross-sectional view of a thin-film bulk acoustic resonator that has been thin-film encapsulated according to an exemplary embodiment of the present invention;

[0035] Figure 5 A cross-sectional view illustrating a thin-film bulk acoustic resonator that has been thin-film encapsulated according to another exemplary embodiment of the present invention;

[0036] Figure 6 A cross-sectional view of a thin-film bulk acoustic resonator that has been thin-film encapsulated according to another exemplary embodiment of the present invention is shown.

[0037] Figure 7 A cross-sectional view of a thin-film bulk acoustic resonator that has been thin-film encapsulated according to yet another exemplary embodiment of the present invention is shown. Detailed Implementation

[0038] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. In this 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 overall inventive concept of the present invention and should not be construed as a limitation thereof.

[0039] The following is a reference to the appendix. Figure 2-3 Taking the packaging of a thin-film bulk acoustic resonator as an example, the thin-film packaging of a MEMS device according to an embodiment of the present invention is described exemplarily.

[0040] exist Figure 2 In the diagram, 10 is the bottom cavity of the resonator (corresponding to the air gap structure), or any form of acoustic reflector such as a Bragg reflector layer; 20 is the release hole of the bottom cavity of the resonator; 11 is the bottom electrode of the resonator; 12 is the piezoelectric layer of the resonator; 13 is the top electrode of the resonator; 14 is the encapsulation film; and 15 is the release hole on the encapsulation film.

[0041] exist Figure 3 The diagram shows a piezoelectric layer 12, an encapsulation film 14, a release hole 15 on the encapsulation film, a sealing layer 16 sealing the release hole 15, and an encapsulation space 17 formed by the encapsulation film on top of the resonator.

[0042] like Figure 3As shown, the portion of the encapsulation film 14 forming the encapsulation space 17 is arc-shaped, and it overlaps with the encapsulation plane of the resonator (in...). Figure 3 The upper surface of the piezoelectric layer 12 is shown in the middle. It should be noted that, based on different MEMS devices and different requirements, the packaging plane can be different. An angle α is formed between the two surfaces. The arc-shaped packaging film can effectively reduce the stress concentration phenomenon in the film, thereby avoiding the phenomenon of cracking of the resonator packaging film due to excessive stress. This can improve the adhesion and mechanical properties of the multilayer film in the packaging structure, making the packaged resonator more stable, reliable, and with better sealing performance.

[0043] Based on the above, in order to solve or alleviate Figure 1 Regarding the stress concentration problem at reference numeral 18 in the attached figure, the present invention proposes the following encapsulation film for encapsulating MEMS devices: the encapsulation film has a top, an edge, and a connecting portion between the top and the edge, the encapsulation space is defined by the edge, the connecting portion, and the top, and the edge is disposed on the encapsulation surface, wherein the connecting portion is arc-shaped.

[0044] For example, see Figure 3 The edge, connecting part and top are formed together into an arc shape, and the arc shape of the connecting part is part of the whole arc shape.

[0045] For example, see Figure 6 The boundary portion indicated by reference numeral 61 in the attached drawing is shown to have an arc-shaped connection between the top and the edge. Because the boundary 61 is arc-shaped, stress concentration is reduced, making the packaging structure more stable and reliable.

[0046] For example, see also Figure 7 In addition to the fact that the boundaries or connections are curved, the edges of the encapsulation film have curved portions that protrude into the encapsulation space, for example, in Figure 7 On the left side, you can see that the edge and the connection form an S-shape. The arc shape reduces stress concentration, making the packaging structure more stable and reliable.

[0047] In exemplary embodiments of the present invention, for example Figure 3 , Figure 4 and Figure 5 The angle α formed between the encapsulation film and the encapsulation surface is in the range of 2 degrees to 45 degrees, and further, in the range of 10 degrees to 20 degrees. For example, in addition to the above-mentioned endpoint values, the angle can also be 15 degrees, 30 degrees, etc.

[0048] As those skilled in the art will understand, although the present invention describes thin-film packaging using a thin-film bulk acoustic resonator as an example, the technical solutions of the present invention can also be used for other MEMS devices suitable for thin-film packaging.

[0049] like Figure 3 As shown, in an optional embodiment, the MEMS device includes an air gap structure, such as a bottom cavity 10, which can be a cavity structure etched into the substrate or an upwardly convex cavity structure, or a Bragg reflection structure or other acoustic wave reflection form formed by alternating high acoustic impedance materials and low acoustic impedance materials. Figure 3 The middle section shows the cavity structure etched into the substrate. Figure 3-4 The following description uses a thin-film bulk acoustic resonator as an example of a MEMS device. As those skilled in the art will understand, the following description is also applicable to other MEMS devices with air gap structures.

[0050] Although not shown, in an optional embodiment, the vertical distance from the highest point of the inner surface of the arcuate space to the encapsulation surface is between 0.5 micrometers and 10 micrometers, for example, 0.5 micrometers, 1 micrometer, and 5 micrometers, etc.

[0051] In an optional embodiment, the MEMS device is provided with a first release hole (e.g., corresponding to release hole 20) communicating with the air gap structure, the first release hole being located within the encapsulation space 17; the encapsulation film 14 is provided with a second release hole (e.g., corresponding to release hole 15) communicating with the encapsulation space 17, the second release hole being filled with sealing material; and in vertical projection, the horizontal distance between at least one second release hole and the corresponding first release hole is less than 20 μm. For example, in Figure 3 In the figure, the horizontal distance between the rightmost release hole 15 and the release hole 20 is less than 20 μm.

[0052] Although not shown, in an optional embodiment, in vertical projection, the second release hole coincides with or partially coincides with the corresponding first release hole; for example, it could be... Figure 3 The rightmost release hole 15 shown in the figure coincides or partially coincides with the vertical projection of the release hole 20.

[0053] Although not shown, in an optional embodiment, in vertical projection, the horizontal distance between each second release hole and its corresponding first release hole is less than 20 μm. For example, in Figure 3 There is no setting in Figure 3 The horizontal distance between the release hole 15 on the left and in the middle, or other existing release holes 15, and the corresponding release hole 20 is less than 20 μm.

[0054] based on Figure 2 and Figure 3In the illustrated embodiment, since the horizontal distance between at least one second release hole and the corresponding first release hole is less than 20 μm in vertical projection, the following technical effects can be achieved: during the formation of the encapsulation space 17, after the liquid medicine enters the air gap at the bottom of the resonator through the release hole 15, it can quickly circulate out, carrying away the liquid medicine residue, etc., thus reducing the possibility of liquid medicine residue remaining in the air gap, which is beneficial to improving the performance of the resonator or MEMS device.

[0055] Furthermore, when the release holes 15 of the encapsulation film 14 are located on both sides of the effective area of ​​the resonator or MEMS device, even if sealing agent falls down when the release holes 15 of the encapsulation film are sealed at the end, it will not affect the performance of the resonator or MEMS device.

[0056] Furthermore, when the release hole 15 of the encapsulation film 14 is located above the release hole 20 of the air gap 10 (the two coincide or substantially coincide in vertical projection), no step will be generated at the position of the encapsulation film corresponding to the release hole 10 during the formation of the encapsulation film, and there is no stress accumulation phenomenon, thereby making the encapsulation structure of the resonator or MEMS device more stable.

[0057] Figure 4 A cross-sectional view illustrating a thin-film bulk acoustic resonator already encapsulated according to an exemplary embodiment of the present invention. (See attached image.) Figure 4 As shown, this MEMS device is a thin-film bulk acoustic resonator, comprising: a bottom cavity 10 (corresponding to an air gap structure), a first release hole 11 communicating with the cavity 10, a bottom electrode 12, a piezoelectric layer 13, a top electrode 14, a planarization layer 23, an encapsulation film 20, a release hole 21, a sealing layer 22, and a sealing space 24. Figure 4 As shown, the first release hole is located outside the encapsulation space 17; the encapsulation film is provided with a second release hole 15 communicating with the encapsulation space, and the second release hole is filled with sealing material. Figure 4 As shown, the encapsulation film covers and seals the first release hole 11.

[0058] based on Figure 4In this embodiment, since the release hole 11 is outside the encapsulation space 24, it is sealed during the formation of the encapsulation film 20. Therefore, no liquid residue, particles, etc., will enter the bottom cavity 10 of the FBAR during the process of releasing the encapsulation space 24, and the performance of the resonator will not be affected. Moreover, the position and number of openings 21 on the encapsulation film 20 can be flexibly selected. In terms of opening position, the alignment process with the bottom cavity release hole 11 can be eliminated, reducing the encapsulation cost; at the same time, the number of openings can be increased, which can speed up the formation of the cavity 24. In addition, for FBARs or MEMS devices of the same area, encapsulating the release hole 11 outside the cavity 24 can reduce the area of ​​the encapsulation space 24, thereby reducing the package size of the resonator or MEMS device.

[0059] Figure 5 The diagram shown is a schematic representation of a thin-film bulk acoustic resonator according to another embodiment. It is similar to... Figure 3 The basic structure is the same, the difference lies in the shape of the boundary 51 of the encapsulation cavity formed by the encapsulation film on the encapsulation surface. In this embodiment, the boundary is formed by an inwardly curved arc. In this embodiment, since the boundary 51 is an inwardly curved arc, it can avoid excessive film stress caused by the encapsulation film being too sharp at the boundary when the angle of the encapsulation cavity formed by the encapsulation film is small, which could lead to the breakage of the encapsulation film and make the encapsulation structure unstable.

[0060] Figure 6 The diagram shown is a cross-sectional schematic of another embodiment of a thin-film bulk acoustic resonator, which is similar to... Figure 3 The structures are basically the same, the difference lies in the shape of the encapsulation film. In this embodiment, the connecting part of the encapsulation film is arc-shaped, and the top is flat. More specifically, the connecting part and the edge part are integrally arc-shaped, and the top is flat. Because the top of the encapsulation film is flat, a planar structure is formed on the top of the resonator, which facilitates further encapsulation or integration applications.

[0061] Figure 7 The diagram shown is a cross-sectional schematic of another embodiment of a thin-film bulk acoustic resonator, which is similar to... Figure 3 The structures are basically the same, the difference lies in the shape of the encapsulation film. In this embodiment, the shape of the connecting part in the encapsulation film is a transitional arc shape, that is, the arc connecting to the edge is concave inward, and the arc connecting to the top is concave outward. Because the connecting part is arc-shaped, it can avoid excessive film stress at the boundary of the encapsulation film due to excessive sharpness when the angle of the encapsulation cavity formed by the encapsulation film is small, which could lead to the breakage of the encapsulation film and make the encapsulation structure unstable.

[0062] In this invention, the electrode composition material can be formed from similar metals such as gold (Au), tungsten (W), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), titanium-tungsten (TiW), aluminum (Al), and titanium (Ti).

[0063] The piezoelectric layer material can be aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO3), quartz, potassium niobate (KNbO3), or lithium tantalate (LiTaO3), etc.

[0064] The sacrificial layer material can be an organic material, polymer, silicon, amorphous silicon, silicon dioxide, PSG, metals (such as Ge, Ti, Cu), metal oxides (such as MgO, ZnO), photoresist (such as SU-8), and other easily soluble materials.

[0065] The encapsulation film materials can be silicon, silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, metal, photoresist, polymer, graphene, nanotubes, TOK DFR materials, etc.

[0066] The sealing layer material can be a dense material such as silicon dioxide, a polymer, spin-coated glass, a plastic, a resin, a dielectric material, a metal, silicon nitride, aluminum nitride, or other similar materials. According to another aspect of an embodiment of the present invention, an electronic device is provided, comprising the aforementioned MEMS device assembly.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that variations may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A MEMS device assembly, comprising: a MEMS device having a packaging surface; a packaging film for forming a packaging space for packaging the MEMS device, the packaging film having a top portion, an edge portion, and a connecting portion between the top portion and the edge portion, the packaging space being defined by the edge portion, the connecting portion, and the top portion, and the edge portion being disposed on the packaging surface, wherein: the connecting portion is arc-shaped, a circular arc where the connecting portion connects with the edge portion is concave inward, and a circular arc where the connecting portion connects with the top portion is concave outward, so as to reduce the film stress of the packaging film at the boundary. 2.The assembly of claim 1, wherein: an angle formed by the packaging film and the packaging surface is in a range of 2 degrees to 45 degrees. 3.The assembly of claim 2, wherein: an angle formed by the packaging film and the packaging surface is in a range of 10 degrees to 20 degrees. 4.The assembly of claim 1, wherein: the packaging space is an arc-shaped space. 5.The assembly of claim 4, wherein: a vertical distance from a highest point of an inner side surface of the arc-shaped space to the packaging surface is between 0.5 microns and 10 microns. 6.The assembly of claim 4, wherein: a vertical distance from a highest point of an inner side surface of the arc-shaped space to the MEMS device is between 0.5 microns and 10 microns. 7.The assembly of claim 1, wherein: the top portion is substantially flat. 8.The assembly of claim 1 or 7, wherein: the edge portion is arc-shaped integrally with the connecting portion; or the edge portion has an arc-shaped portion protruding toward the packaging space. 9.The assembly of any one of claims 1-8, wherein: a boundary shape of the packaging space at a joint of the packaging film and the packaging surface is arc-shaped. 10.The assembly of any one of claims 1-9, wherein: the MEMS device comprises an air gap structure. 11.The assembly of claim 10, wherein: the MEMS device is provided with a first release hole communicating with the air gap structure, the first release hole being located inside the packaging space; the packaging film is provided with a second release hole communicating with the packaging space, the second release hole being filled with a sealing material; and in a vertical projection, a horizontal distance between at least one of the second release holes and a corresponding first release hole is less than 20 um. 12.The assembly of claim 11, wherein: in a vertical projection, the second release hole and the corresponding first release hole are coincident or partially coincident. 13.The assembly of claim 11, wherein: in a vertical projection, a horizontal distance between each of the second release holes and a corresponding first release hole is less than 20 um. 14.The assembly of claim 10, wherein: the MEMS device is provided with a first release hole communicating with the air gap structure, the first release hole being located outside the packaging space; the packaging film is provided with a second release hole communicating with the packaging space, the second release hole being filled with a sealing material.

15. The assembly of claim 14, wherein: the encapsulation film covers and seals the first release hole.

16. The assembly of any of claims 1-15, wherein: the MEMS device is a bulk acoustic resonator.

17. The assembly of claim 16, wherein: the resonator is a film bulk acoustic resonator including an air gap structure.

18. An electronic device comprising the MEMS device assembly of any of claims 1-17.

19. The electronic device of claim 18, the electronic device comprising a filter.

Images