WO2020258361A1 - Microfilter and acoustic device - Google Patents

Abstract

A microfilter and an acoustic device, comprising a substrate (1) provided with a back cavity (3), and a film layer (2) that is disposed on the substrate (1) and that is suspended on the back cavity (3); the film layer (2) is provided with distributed through holes (4), and the film layer (2) comprises at least one layer of a first diaphragm (2a) having tensile stress and at least one layer of a second diaphragm (2b) having compressive stress, which are composited together; the first diaphragm (2a) and the second diaphragm (2b) are configured to reduce the stress on the entire film layer (2) so as to control the stress on the entire film layer (2) to be within a desired range.

Description

Micro filter and acoustic equipment Technical field

The present invention relates to a micro filter, which can be a micro filter suitable for acoustic equipment to filter dust, particles or/and water and other substances that are not expected to enter the interior of the acoustic equipment.

Background technique

Portable computing devices such as notebook computers and tablet computers are ubiquitous, and portable communication devices such as smart phones are also ubiquitous. However, these devices do not have enough space to accommodate relatively large microphones or speakers. As a result, microphones and speakers have become more compact and reduced in size. In addition, the microphones and speakers in these portable settings usually need to be close to the relevant acoustic input or output ports of the terminal, so that particles and water can easily enter the microphones and speakers and cause the failure of these acoustic devices.

Filter membranes are sometimes deployed in previous equipment to prevent certain types of debris from entering the components. Unfortunately, these filters tend to adversely affect the operation of the microphone. For example, when using these previous methods, the performance of the microphone can sometimes be significantly reduced. Due to performance degradation, microphone customers often choose not to use such microphones in their applications.

When manufacturing filter membranes, ordinary metal thin films have a stress limit. When the stress of the ordinary metal film shows compression to form wrinkles, the optical automatic detection equipment cannot detect the pressure. In order to fabricate the filter chip structure, when a suitable thin metal film is deposited on the substrate, it is necessary to obtain a film with low tensile stress. Films without low tensile stress tend to peel, crack, wrinkle or otherwise detach from their substrates, so PB chips have to be often discarded after being put into operation.

Summary of the invention

An object of the present invention is to provide a new technical solution for the micro filter.

According to the first aspect of the present invention, there is provided a micro filter, including a substrate with a back cavity, and a film layer arranged on the substrate and suspended on the back cavity; the film layer has arranged through holes , And the membrane layer includes at least one layer of first membrane with tensile stress and at least one layer of second membrane with compressive stress that are compounded together; the first membrane and the second membrane are configured as Reduce the stress of the entire film.

Optionally, the stress of the film layer is between -300 MPa and 300 MPa.

Optionally, the stress of the film layer is between 0 and 300 MPa.

Optionally, the first diaphragm is disposed adjacent to the substrate relative to the second diaphragm; or the second diaphragm is disposed adjacent to the substrate relative to the first diaphragm.

Optionally, the first membrane is provided with two layers, the second membrane is provided with a layer, and the second membrane of this layer is clamped between the two layers of the first membrane; or, the first membrane is The membrane is provided with one layer, the second membrane is provided with two layers, and the first membrane of the layer is clamped between the two first membranes.

Optionally, the first membrane and the second membrane in the membrane layer are provided with multiple layers, and the first membrane and the second membrane are spaced apart from each other.

Optionally, the inner diameter of the through hole on the film layer is 1 nm to 100 μm.

Optionally, the inner diameter of the through hole on the film layer is 5 nm to 10 μm.

According to another aspect of the present invention, there is also provided an acoustic device including the above-mentioned micro filter.

Optionally, the acoustic device is a microphone module or a microphone chip.

According to an embodiment of the present disclosure, after the diaphragms with compressive stress and tensile stress are combined together, the stress of the entire film can be reduced, so as to control the stress of the entire film within a desired range.

Through the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, other features and advantages of the present invention will become clear.

Description of the drawings

The drawings incorporated in the specification and constituting a part of the specification illustrate the embodiments of the present invention, and together with the description thereof are used to explain the principle of the present invention.

Fig. 1 is a cross-sectional view of the first embodiment of the microfilter of the present invention.

Fig. 2 is a cross-sectional view from another perspective of the first embodiment of the microfilter of the present invention.

Fig. 3 is a cross-sectional view of a second embodiment of the microfilter of the present invention.

Fig. 4 is a cross-sectional view of a third embodiment of the microfilter of the present invention.

Fig. 5 is a cross-sectional view of a fourth embodiment of the microfilter of the present invention.

Detailed ways

Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless specifically stated otherwise, the relative arrangement, numerical expressions and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present invention.

The following description of at least one exemplary embodiment is actually only illustrative, and in no way serves as any limitation to the present invention and its application or use.

The technologies, methods, and equipment known to those of ordinary skill in the relevant fields may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be regarded as part of the specification.

In all the examples shown and discussed herein, any specific value should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiment may have different values.

It should be noted that similar reference numerals and letters indicate similar items in the following drawings, so once a certain item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

The invention provides a micro filter and an acoustic device using the micro filter. The acoustic device can be, for example, a microphone chip or a microphone module. For example, when the acoustic device is a microphone chip, the micro-filter is provided on the microphone chip; when the acoustic device is a microphone module, the micro-filter can be provided at the sound hole of the housing in the module. Of course, for those skilled in the art, the acoustic device may also be other types of acoustic transducers, and the types are not described in detail here.

The micro filter provided by the present invention includes a substrate and a film layer arranged on the substrate. The substrate has a hollow back cavity structure, the edge of the film layer is connected to the substrate, and the middle area of the film layer is suspended above the back cavity, so that the film layer forms a cantilever bridge structure.

Figures 1 and 2 show schematic structural diagrams of one embodiment of the microfilter of the present invention. Referring to FIGS. 1 and 2, the film layer 2 is connected above the substrate 1 and suspended on the hollow back cavity 3 of the substrate 1. The membrane layer 2 has through holes 4 arranged for air flow. The substrate 1 can be made of metal, silicon or SiO ₂ , and a hollow back cavity 3 can be formed in a manner well known to those skilled in the art. For example, it is formed by etching and other processes, which will not be described in detail here.

The film layer 2 can be a non-metallic film, such as polyimide material, SiO ₂ , SiN, etc. The film layer 2 can also be a metal thin film, such as a crystalline thin film containing Cr, Al, Ti, or Cu as an example.

In the present invention, it is preferable to use an amorphous metal film, such as metallic glass. Amorphous metal thin films can be formed by extreme cooling, physical vapor deposition, electroplating, pulsed laser deposition, solid-state reaction, ion radiation or mechanical alloying. These forming methods belong to the common knowledge of those skilled in the art and will not be described here. Specific instructions.

Since metallic glass has irregular atomic arrangement and no specific slip surface, it has higher strength than crystalline metal and has excellent fatigue properties and elastic deformation to resist deformation. The modulus of elasticity of metallic glass is about one-third that of crystalline metal, but its tensile strength is three times that of it. For example, the strength of Mg alloy is 300MPa, the strength of Mg-based metallic glass is 800MPa, the strength of FeCoBSiNb metallic glass is 4400MPa, and the strength of SUS304 stainless steel is 1400MPa.

Therefore, the use of metallic glass as the membrane layer of the micro filter can increase the open porosity of the membrane layer on the basis of ensuring the strength of the membrane layer, and can make the thickness of the membrane layer thinner, making the permeation treatment easier and more effective. A smaller through hole is formed to avoid the acoustic resistance caused by the larger hole depth after the traditional thick film is opened.

In an optional embodiment of the present invention, the inner diameter of the through hole 4 on the film layer 2 may be 1 nm to 100 μm.

In an optional embodiment of the present invention, the inner diameter of the through hole 4 on the film layer 2 may be 5 nm to 10 μm.

In an optional embodiment of the present invention, the thickness of the film layer 2 is 5 nm to 5 μm.

In an optional embodiment of the present invention, the thickness of the film layer 2 is 20 nm to 1000 nm.

Since metallic glass is an amorphous material, it is isotropic and uniform. In addition, there are substantially no defects caused by polycrystalline structures such as grain boundaries and segregation, and the size effect is small. Therefore, when designing the micro filter, it is not necessary to consider the changes in physical properties due to anisotropy and size, which is beneficial to the design of the structure of the micro filter. In addition, since metallic glass is an alloy composed of multiple elements, the range of material selection in the design of microfilters is widened, and higher performance PB chips can be designed and manufactured.

For example, the metallic glass may contain multiple transition metal elements, and may optionally contain one or more non-metal elements. The metallic glass containing transition metal elements can have Sc, Y, La, Al, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh At least one of, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd and Hg. Depending on the application, any suitable transition metal element or their combination can be used. Any suitable non-metallic elements or their combination can be used. For example, non-metal elements can be F, Cl, Br, I, At, O, S, Se, Te, Po, N, P, As, Sb, Bi, C, Si, Ge, Sn, Pb and B. any type.

In an optional embodiment of the present invention, the glass transition temperature Tg of the metallic glass is 150°C or higher.

In an optional embodiment of the present invention, the glass transition temperature Tg of the metallic glass is 250° C. or higher.

In the micro filter of the present invention, the membrane layer 2 can be provided with one layer, or two, three or more layers.

Referring to FIG. 2, the film layer includes a first film 2a and a second film 2b that are compounded together. Among them, the first diaphragm 2a has tensile stress, and the second diaphragm 2b has compressive stress. After the first membrane and the second membrane are compounded together, the stress of the entire membrane layer 2 is reduced under the interaction of tensile stress and compressive stress, so that the entire membrane layer 2 can be placed on the substrate 1 evenly.

The first diaphragm 2a and the second diaphragm 2b can be made of the same material or different materials. For example, the first diaphragm 2a and the second diaphragm 2b can be selected from a crystalline metal film, an amorphous metal film or a non-metal film. In order to improve the elasticity and impact resistance of the film layer 2, at least one film in the film layer 2 is selected from an amorphous metal film.

The membrane can show various internal stresses, from stretching to compression, depending on the film deposition conditions and deposition thickness. The internal stress of the diaphragm can greatly change the properties of the diaphragm, such as mechanical properties. Therefore, the tensile stress membrane and the compressive stress membrane are combined together to eliminate the internal stress of the membrane and adjust it to the desired stress range.

For example, in an alternative embodiment, the stress of the film layer 2 is controlled between -300 MPa (compressive stress) and 300 MPa (tensile stress).

For example, in an alternative embodiment, the stress of the film layer 2 is controlled between 0 and 300 MPa (tensile stress). Controlling the film layer 2 at a lower tensile stress allows the film layer 2 to be in a tensioned state and maintain its own shape, which is beneficial to the flatness of the film 2 on the substrate 1 for optical automatic monitoring.

In an alternative embodiment, the second diaphragm 2b is disposed adjacent to the substrate 1 relative to the first diaphragm 2a. The second diaphragm 2b with compressive stress is arranged on the side adjacent to the substrate 1, and the compressive stress of the second diaphragm 2b is offset by the first diaphragm 2a with tensile stress.

In an alternative embodiment, the first diaphragm 2a is disposed adjacent to the substrate 1 relative to the second diaphragm 2b. The first diaphragm 2a with tensile stress is arranged on the side adjacent to the substrate 1, and the second diaphragm 2b with compressive stress offsets the tensile stress of the first diaphragm 2a; and because the first diaphragm 2a itself has tensile stress Therefore, problems such as separation of the first diaphragm 2a from the substrate 1 can be further avoided.

Fig. 3 shows a schematic structural diagram of another embodiment of the microfilter of the present invention. Different from the embodiment shown in FIG. 2, the film layer on the substrate 10 includes a three-layer film, which is suspended on the hollow back cavity 30 of the substrate 10. The three-layer diaphragm includes a first diaphragm 20a with tensile stress and two second diaphragms 20b with compressive stress. The first diaphragm 20a is located between the two second diaphragms 20b, and the three diaphragms are combined together. The second diaphragm with compressive stress on both sides offsets the tensile stress of the first diaphragm in the middle; conversely, the first diaphragm with tensile stress in the middle also offsets the compressive stress of the second diaphragms on both sides , I will not elaborate here.

The three-layer diaphragm structure of the film layer may also include two first diaphragms 20a with tensile stress and one second diaphragm 20b with compressive stress. The second diaphragm 20b is located between the two layers of first diaphragm 20a.

Based on a similar principle, the first film and the second film in the film layer may be provided with multiple layers, for example, four layers, five layers or more. The first diaphragm and the second diaphragm are arranged to be spaced apart from each other.

In an optional embodiment of the present invention, the substrate is made of a photosensitive polymer material, and the shape of the substrate is formed through exposure and polymerization processes. For example, in a specific embodiment of the present invention, the substrate may be epoxy resin or polyimide resin. Optionally, epoxy resin and polyimide resin are selected as dry film or liquid type.

The substrate is made of photosensitive polymer, for example, epoxy-based negative photoresist or photosensitive polyimide can be used, which makes the manufacturing process easy.

For example, SU-8 is a commonly used epoxy-based negative photoresist. Negative refers to the photoresist in which the part exposed to UV becomes cross-linked, while the remaining part remains soluble and can be washed off during development.

Polyimide is a polymer of imide monomers. Polyimide has high heat resistance and has many applications in processes requiring strong and durable organic materials. Polyimide can be used like photoresist, for example, "positive" and "negative" types of photoresist polyimide.

The micro filter can be manufactured on the wafer at the same time. For example, when manufacturing a micro filter, you can first form a film layer on the substrate by deposition, etching and other processes, and then bond the photopolymer as the base by laminating, and then form the film by exposure and polymerization. The base of the back cavity finally separates the film from the substrate.

The metal film or polyimide film is carried on the base of the photosensitive material, and the film is supported by the base. On the basis of ensuring the structure, the micro filter can be made small.

Fig. 4 shows a schematic structural diagram of another embodiment of the microfilter of the present invention. In the embodiment shown in FIG. 4, unlike the embodiments shown in FIGS. 1, 2, and 3, the metal film 6 a is disposed on the substrate 5 and suspended above the hollow back cavity 7 of the substrate 5. The metal film 6a may be an amorphous metal film, such as metallic glass. The substrate 5 can be made of polymer material, metal, silicon or SiO ₂ .

The outer surface of the metal film 6a is coated with a non-stick layer 6b. The adhesion between the non-stick layer 6b and the particles is lower than the adhesion between the metal film 6a and the particles; the metal film 6a and the non-stick layer 6b have arranged through holes (not shown in the view).

In an optional embodiment of the present invention, the non-stick layer 6b is a silicone compound coating or a fluoropolymer coating.

In an optional embodiment of the present invention, the non-stick layer 6b is a Teflon coating. Teflon has high temperature characteristics and low friction coefficient.

By providing a non-stick layer on the metal film, the problem of particles sticking to the metal film with through holes after long-term use can be avoided, thereby ensuring the sensitivity of the sensor.

In an optional embodiment of the present invention, the metal film 6a is configured to have compressive stress; the non-stick layer 6b is configured to have tensile stress; the metal film 6a and the non-stick layer 6b are composited together to reduce the overall film stress. Of course, it is also possible that the metal thin film 6a is configured to have tensile stress, and the non-stick layer 6b is configured to have compressive stress. The specific principle is the same as the embodiment shown in FIG. 2 and FIG.

For example, in an alternative embodiment, the stress of the film layers combined together is controlled between -300 MPa (compressive stress) and 300 MPa (tensile stress).

For example, in an alternative embodiment, the stress of the composite film layers is controlled between 0 and 300 MPa (tensile stress).

Figure 5 shows a schematic structural view of another embodiment of the microfilter of the present invention. The difference from the embodiment shown in FIG. 4 is that the film layer on the substrate 50 includes a three-layer film, which is suspended on the hollow back cavity 70 of the substrate 50. The three-layer film includes a metal film 60a with compressive stress and two non-stick layers 60b with tensile stress. The metal film 60a is located between the two non-stick layers 60b, and the three layers are compounded together. The non-stick layer 60b with tensile stress on both sides is used to offset the compressive stress of the metal film in the middle; conversely, the metal film 60a with compressive stress in the middle will also offset the compressive stress of the non-stick layer 60b on both sides. No more details.

In addition, the non-stick layers 60b are provided on both sides of the metal film 60a, which can avoid or reduce particle adsorption of the metal film 60a and ensure the performance of the micro filter.

Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of the present invention. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present invention. The scope of the invention is defined by the appended claims.

Claims (10)

1. A micro filter is characterized by comprising a substrate with a back cavity, and a film layer arranged on the substrate and suspended on the back cavity; the film layer has arranged through holes, and the film layer It includes at least one layer of first diaphragm with tensile stress and at least one layer of second diaphragm with compressive stress that are compounded together; the first and second diaphragms are configured to reduce the stress of the entire film .
2. The micro filter according to claim 1, wherein the stress of the membrane layer is between -300 MPa and 300 MPa.
3. The micro filter according to claim 2, wherein the stress of the membrane layer is between 0 and 300 MPa.
4. The micro filter according to claim 1, wherein the first diaphragm is disposed adjacent to the substrate relative to the second diaphragm; or the second diaphragm is disposed adjacent to the substrate relative to the first diaphragm.
5. The micro filter according to claim 1, wherein the first membrane is provided with two layers, the second membrane is provided with one layer, and the second membrane is sandwiched between the two layers of the first membrane. Between the membranes; or, the first membrane is provided with one layer, the second membrane is provided with two layers, and the first membrane of this layer is clamped between the two layers of first membranes.
6. The micro filter according to claim 1, wherein the first membrane and the second membrane in the membrane layer are provided with multiple layers, and the first membrane and the second membrane are spaced apart from each other. .
7. The micro filter according to claim 1, wherein the inner diameter of the through hole on the membrane layer is 1 nm to 100 μm.
8. The micro filter according to claim 7, wherein the inner diameter of the through hole on the membrane layer is 5 nm to 10 μm.
9. An acoustic device, characterized by comprising the micro filter according to any one of claims 1 to 8.
10. The acoustic device according to claim 9, wherein the acoustic device is a microphone module or a microphone chip.

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