阅读说明：本技术 Mems麦克风及其制备方法 (MEMS microphone and preparation method thereof ) 是由 王青松 于 2020-03-20 设计创作，主要内容包括：本发明提供一种MEMS麦克风及其制备方法,MEMS麦克风的背板采用依次堆叠设置的背板绝缘层、背板导电层及背板机械层,使得背板绝缘层与振膜相向设置,从而可以避免振膜在过驱动时产生接通漏电现象,避免产品失效,提高产品的使用空间和良品率；采用PECVD法制备背板机械层,降低工艺时间,降低生产成本,降低污染颗粒,且由于PECVD的应力可调性,使得产品具有良好的设计兼容性和多样性,在大规模生产的过程中,也可采用APC系统对背板机械层的应力进行调整,以补偿传感空隙的厚度差异,提高生产的容错率及产品良率。(The invention provides an MEMS microphone and a preparation method thereof.A back plate of the MEMS microphone adopts a back plate insulating layer, a back plate conducting layer and a back plate mechanical layer which are sequentially stacked, so that the back plate insulating layer and a vibrating diaphragm are oppositely arranged, the phenomenon of switching on and leakage of the vibrating diaphragm during overdrive can be avoided, the failure of a product is avoided, and the use space and the yield of the product are improved; the back plate mechanical layer is prepared by adopting a PECVD method, so that the process time is reduced, the production cost is reduced, pollution particles are reduced, and the product has good design compatibility and diversity due to the stress adjustability of the PECVD.)

1. A MEMS microphone, comprising:

a substrate;

the vibrating diaphragm is positioned above the substrate and comprises a first surface and a second surface which are opposite;

the back plate is positioned above the second surface of the vibrating diaphragm and comprises a back plate insulating layer, a back plate conducting layer and a back plate mechanical layer which are sequentially stacked, the thickness of the back plate mechanical layer is respectively greater than that of the back plate insulating layer and that of the back plate conducting layer, and the stress of the back plate mechanical layer is smaller than that of the back plate insulating layer;

a back plate through hole penetrating through the back plate;

the sensing gap is positioned between the back plate insulating layer and the second surface of the vibrating diaphragm and is connected with the back plate through hole so as to expose the second surface of the vibrating diaphragm;

a substrate through-hole penetrating the substrate;

the back cavity is connected with the substrate through hole to expose the first surface of the vibrating diaphragm.

2. The MEMS microphone of claim 1, wherein: the thickness range of the back plate mechanical layer comprises 1-5 mu m; the stress range of the mechanical layer of the back plate comprises-60 MPa to 100 MPa.

3. The MEMS microphone of claim 1, wherein: the thickness range of the back plate insulating layer comprises 0.05-0.3 μm; the stress range of the back plate insulating layer comprises 100 MPa-300 MPa.

4. The MEMS microphone of claim 1, wherein: the thickness range of the backboard conducting layer comprises 0.05-0.8 μm.

5. The MEMS microphone of claim 1, wherein: the back plate insulating layer comprises a silicon nitride insulating layer; the backplane mechanical layer comprises a silicon nitride mechanical layer; the vibrating diaphragm comprises a polycrystalline silicon vibrating diaphragm; the backplane conductive layer comprises a polysilicon conductive layer.

6. The MEMS microphone of claim 1, wherein: comprises one or a combination of a substrate supporting part contacted with the substrate and a diaphragm supporting part contacted with the diaphragm.

7. The MEMS microphone of claim 6, wherein: when the substrate supporting part and the diaphragm supporting part are included, a sacrificial layer which is in contact with the substrate is included between the substrate supporting part and the diaphragm supporting part.

8. A preparation method of an MEMS microphone is characterized by comprising the following steps:

providing a substrate;

forming a first sacrificial layer on the substrate;

forming a vibrating diaphragm on the first sacrificial layer;

forming a second sacrificial layer on the diaphragm;

forming a back plate on the second sacrificial layer, wherein the back plate comprises a back plate insulating layer, a back plate conducting layer and a back plate mechanical layer which are sequentially stacked, the thickness of the back plate mechanical layer is respectively greater than that of the back plate insulating layer and that of the back plate conducting layer, and the stress of the back plate mechanical layer is less than that of the back plate insulating layer;

etching the back plate to form a back plate through hole penetrating through the back plate so as to expose the second sacrificial layer;

etching the substrate to form a substrate through hole penetrating through the substrate so as to expose the first sacrificial layer;

and removing the first sacrificial layer and the second sacrificial layer to expose two opposite surfaces of the vibrating diaphragm to form a sensing gap connected with the backboard through hole and a back cavity connected with the substrate through hole.

9. The method for manufacturing a MEMS microphone according to claim 8, wherein: the method for preparing the back plate mechanical layer comprises a PECVD method; the thickness range of the formed mechanical layer of the back plate comprises 1-5 μm; the stress range of the formed mechanical layer of the back plate comprises-60 MPa to 100 MPa.

10. The method for manufacturing a MEMS microphone according to claim 8, wherein: the method for preparing the back plate insulating layer comprises an LPCVD method; the thickness range of the formed backboard insulating layer comprises 0.05-0.3 μm; the stress range of the formed back plate insulating layer comprises 100 MPa-300 MPa.

11. The method for manufacturing a MEMS microphone according to claim 8, wherein: the method for preparing the conductive layer of the back plate comprises an LPCVD method; the thickness range of the formed backboard conducting layer comprises 0.05-0.8 μm.

12. The method for manufacturing a MEMS microphone according to claim 8, wherein: the first sacrificial layer and the second sacrificial layer comprise silicon oxide sacrificial layers; the back plate insulating layer comprises a silicon nitride insulating layer; the backplane mechanical layer comprises a silicon nitride mechanical layer; the vibrating diaphragm comprises a polycrystalline silicon vibrating diaphragm; the backplane conductive layer comprises a polysilicon conductive layer.

13. The method for manufacturing a MEMS microphone according to claim 8, wherein: the method comprises one or a combination of a step of preparing a substrate supporting part in contact with the substrate and a step of preparing a diaphragm supporting part in contact with the diaphragm.

14. The method for manufacturing a MEMS microphone according to claim 13, wherein: and when the first sacrificial layer and the second sacrificial layer are removed, the first sacrificial layer and the second sacrificial layer are reserved between the substrate supporting part and the vibrating diaphragm supporting part.

Technical Field

The invention belongs to the field of semiconductor manufacturing and design, and relates to an MEMS microphone and a preparation method thereof.

Background

Micro-Electro-Mechanical-System (MEMS) technology refers to a Micro-System that integrates Mechanical components, driving components, optical systems, and electrical control systems into a whole, and it uses Micro-electronics and Micro-processing technologies, such as silicon Micro-processing, silicon surface Micro-processing, wafer bonding, etc., to produce various sensors, actuators, drivers, and Micro-systems with excellent performance, low cost, and miniaturization. Common products include MEMS accelerometers, MEMS microphones, micro-motors, micro-pumps, micro-vibrators, MEMS optical sensors, MEMS pressure sensors, MEMS gyroscopes, MEMS humidity sensors, MEMS gas sensors, and the like, as well as integrated products thereof.

The microphone is a miniature acoustic sensor, and mainly comprises a cylindrical polar body microphone (ECM) and a micro electro mechanical system microphone (MEMS microphone). Compared with the traditional cylindrical microphone, the MEMS microphone has the advantages of small size, low cost, low power consumption, high reliability and the like, and is popular. The types of MEMS microphones mainly include a capacitive MEMS microphone, a piezoelectric MEMS microphone, an electro-optical MEMS microphone, and the like according to the operation principle and electrical characteristics.

The main structure of a condenser MEMS microphone, similar to a variable capacitor, has three major parts, two electrodes, namely a Diaphragm (Diaphragm) and a Back Plate (Back Plate), and a Sensing Gap (Sensing Gap) between them. The vibrating diaphragm has good elasticity, can vibrate under the excitation of sound waves, and generates displacement change, so that the distance between the back plate and the vibrating diaphragm is changed, the capacitance of the MEMS microphone is changed, and a circuit at the rear end can obtain acoustic signals by detecting the capacitance change.

Currently, a two-layer structure including a conductive layer and a mechanical layer is mostly adopted for a back plate structure in a capacitive MEMS microphone. In the double-layer structure, because the conducting layer and the vibrating diaphragm are arranged In opposite directions (Face-to-Face), when the vibrating diaphragm is overdriven (Over-Drive), the contact between the vibrating diaphragm and the upper film and the lower film of the conducting layer can generate a connection (Pull-In) phenomenon, generate larger electric leakage and cause product failure; in order to obtain a good quality backplane, the two layers are usually prepared by a Low Pressure Chemical Vapor Deposition (LPCVD) Process, so that it is difficult to reduce the stress of the conductive layer and the mechanical layer, and when a thicker mechanical layer is prepared by LPCVD, the Process time is long, the production cost is high, a large amount of pollution particles are easily generated, the production maintenance and the productivity are challenged, the product design compatibility and the diversity are limited, and the backplane stress cannot be correspondingly compensated by an Automatic Process Compensation (APC) according to a sensing gap, so that the product rejection rate is high.

Therefore, it is necessary to provide a novel MEMS microphone and a method for manufacturing the same.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, the present invention is directed to a MEMS microphone and a method for manufacturing the same, which is used to solve the problems of leakage and the above-mentioned series of production problems of the MEMS microphone in the prior art.

To achieve the above and other related objects, the present invention provides a MEMS microphone, including:

a substrate;

the vibrating diaphragm is positioned above the substrate and comprises a first surface and a second surface which are opposite;

the back plate is positioned above the second surface of the vibrating diaphragm and comprises a back plate insulating layer, a back plate conducting layer and a back plate mechanical layer which are sequentially stacked, the thickness of the back plate mechanical layer is respectively greater than that of the back plate insulating layer and that of the back plate conducting layer, and the stress of the back plate mechanical layer is smaller than that of the back plate insulating layer;

a back plate through hole penetrating through the back plate;

the sensing gap is positioned between the back plate insulating layer and the second surface of the vibrating diaphragm and is connected with the back plate through hole so as to expose the second surface of the vibrating diaphragm;

a substrate through-hole penetrating the substrate;

the back cavity is connected with the substrate through hole to expose the first surface of the vibrating diaphragm.

Optionally, the thickness of the mechanical layer of the back plate ranges from 1 μm to 5 μm; the stress range of the mechanical layer of the back plate comprises-60 MPa to 100 MPa.

Optionally, the thickness of the back plate insulating layer ranges from 0.05 μm to 0.3 μm; the stress range of the back plate insulating layer comprises 100 MPa-300 MPa.

Optionally, the thickness of the conductive layer of the back plate ranges from 0.05 μm to 0.8 μm.

Optionally, the backplane insulating layer comprises a silicon nitride insulating layer; the backplane mechanical layer comprises a silicon nitride mechanical layer; the vibrating diaphragm comprises a polycrystalline silicon vibrating diaphragm; the backplane conductive layer comprises a polysilicon conductive layer.

Optionally, one or a combination of a substrate support part in contact with the substrate and a diaphragm support part in contact with the diaphragm is included.

Optionally, when the substrate support portion and the diaphragm support portion are included, a sacrificial layer contacting the substrate is included between the substrate support portion and the diaphragm support portion.

The invention also provides a preparation method of the MEMS microphone, which comprises the following steps:

providing a substrate;

forming a first sacrificial layer on the substrate;

forming a vibrating diaphragm on the first sacrificial layer;

forming a second sacrificial layer on the diaphragm;

forming a back plate on the second sacrificial layer, wherein the back plate comprises a back plate insulating layer, a back plate conducting layer and a back plate mechanical layer which are sequentially stacked, the thickness of the back plate mechanical layer is respectively greater than that of the back plate insulating layer and that of the back plate conducting layer, and the stress of the back plate mechanical layer is less than that of the back plate insulating layer;

etching the back plate to form a back plate through hole penetrating through the back plate so as to expose the second sacrificial layer;

etching the substrate to form a substrate through hole penetrating through the substrate so as to expose the first sacrificial layer;

and removing the first sacrificial layer and the second sacrificial layer to expose two opposite surfaces of the vibrating diaphragm to form a sensing gap connected with the backboard through hole and a back cavity connected with the substrate through hole.

Optionally, the method of preparing the mechanical layer of the back plate comprises a PECVD method; the thickness range of the formed mechanical layer of the back plate comprises 1-5 μm; the stress range of the formed mechanical layer of the back plate comprises-60 MPa to 100 MPa.

Optionally, the method of preparing the backplane insulating layer comprises LPCVD; the thickness range of the formed backboard insulating layer comprises 0.05-0.3 μm; the stress range of the formed back plate insulating layer comprises 100 MPa-300 MPa.

Optionally, the method of preparing the conductive layer of the backplate comprises LPCVD; the thickness range of the formed backboard conducting layer comprises 0.05-0.8 μm.

Optionally, the first and second sacrificial layers comprise silicon oxide sacrificial layers; the back plate insulating layer comprises a silicon nitride insulating layer; the backplane mechanical layer comprises a silicon nitride mechanical layer; the vibrating diaphragm comprises a polycrystalline silicon vibrating diaphragm; the backplane conductive layer comprises a polysilicon conductive layer.

Optionally, one or a combination of the steps of preparing a substrate support part in contact with the substrate and preparing a diaphragm support part in contact with the diaphragm is included.

Optionally, when the first sacrificial layer and the second sacrificial layer are removed, the first sacrificial layer and the second sacrificial layer remain between the substrate supporting portion and the diaphragm supporting portion.

As described above, according to the MEMS microphone and the method for manufacturing the same of the present invention, the back plate of the MEMS microphone employs the back plate insulating layer, the back plate conductive layer, and the back plate mechanical layer, which are sequentially stacked, so that the back plate insulating layer and the diaphragm are oppositely disposed, thereby preventing the diaphragm from generating a turn-on leakage phenomenon during overdriving, preventing the product from failing, and improving the usage space and yield of the product; the back plate mechanical layer is prepared by adopting a PECVD method, so that the process time is reduced, the production cost is reduced, pollution particles are reduced, and the product has good design compatibility and diversity due to the stress adjustability of the PECVD.

Drawings

Fig. 1 is a schematic view of a process flow for manufacturing a MEMS microphone according to the present invention.

Fig. 2 to 13 are schematic structural diagrams showing steps of manufacturing a MEMS microphone according to a first embodiment. Fig. 13 is a schematic structural diagram of the MEMS microphone prepared in the first embodiment.

Fig. 14 to 16 are schematic structural diagrams showing steps of manufacturing the MEMS microphone according to the second embodiment. Fig. 16 is a schematic structural diagram of the MEMS microphone prepared in the second embodiment.

Description of the element reference numerals

100. 1001 substrate

210. 2101 first sacrificial layer

220. 2201 second sacrificial layer

221. 2211 first groove

222. 2221 second groove

223. 2231 third groove

300. 3001 diaphragm

400. 4001 Back plate

410. 4101 back plate insulating layer

420. 4201 conductive layer of back plate

430. 4301 mechanical layer of back plate

401. 4011 backboard lug

402. 4021 diaphragm support part

403. 4031 substrate support

500. 5001 backboard through hole

600. 6001 Metal pad

700. 7001 through substrate via

800. 8001 sensing gap

900. 9001 Back Cavity

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

Please refer to fig. 1 to 16. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated. Fig. 2 to 16 only show schematic diagrams of a part of the structure of the MEMS microphone, and the structure of the part of the MEMS microphone not shown may be the same as or different from that shown in the drawings, and is not limited herein.

Example one

Referring to fig. 1, the present embodiment provides a method for manufacturing an MEMS microphone, which includes the following steps:

referring to fig. 2, a substrate 100 is provided.

Specifically, the material of the substrate 100 may be a silicon substrate, or may also be a germanium substrate, a silicon germanium substrate, a gallium arsenide substrate, or a silicon-on-insulator (SOI) substrate, and the material may be selected according to the requirement.

Next, a first sacrificial layer 210 is formed on the substrate 100.

Specifically, since the first sacrificial layer 210 needs to be removed in a subsequent process, in this embodiment, it is preferable that the first sacrificial layer 210 is made of silicon oxide so as to form insulation with the diaphragm 300 formed subsequently, and form a high selective etching ratio, so as to avoid damage to the diaphragm 300. However, the material of the first sacrificial layer 210 is not limited thereto, and may also include, for example, silicon nitride or a stack of silicon oxide and silicon nitride, and the material may be selected according to the requirement, and is not limited herein.

Next, referring to fig. 3, the diaphragm 300 is formed on the first sacrificial layer 210.

Specifically, the diaphragm 300 is used as a diaphragm of the MEMS microphone, and the material of the diaphragm 300 may be, for example, polysilicon, germanium-silicon, germanium, or other metal or semiconductor material with elasticity, so as to ensure that the diaphragm 300 can generate vibration deformation when receiving an acting force such as sound or inertia force, and can recover to its original shape after the vibration deformation, and ensure that the diaphragm 300 has good electrical conductivity. In this embodiment, the diaphragm 300 is made of polysilicon, but is not limited thereto.

As an example, the method further includes a step of patterning the diaphragm 300 to expose the first sacrificial layer 210.

Specifically, a photoresist layer (not shown) is formed on the diaphragm 300, the photoresist layer is exposed and developed to form an imaged photoresist layer, the pre-etched position on the diaphragm 300 is exposed, the diaphragm 300 is etched by using the imaged photoresist layer as a mask until the first sacrificial layer 210 is exposed, and then the imaged photoresist layer is removed by an ashing process.

Next, referring to fig. 4, a second sacrificial layer 220 is formed on the diaphragm 300.

Specifically, the material of the second sacrificial layer 220 may refer to the first sacrificial layer 210, in this embodiment, for convenience of process control, the second sacrificial layer 220 is made of the same material as the first sacrificial layer 210, that is, a silicon oxide material, but not limited thereto, and the second sacrificial layer 220 may also be made of a material different from the first sacrificial layer 210, such as silicon nitride or a stack of silicon oxide and silicon nitride, which may be specifically selected according to needs and is not limited herein. However, it is preferable that the material of the second sacrificial layer 220 and the diaphragm 300 and the backplate insulating layer 410 formed later have a high selective etching ratio, so that the diaphragm 300 and the backplate insulating layer 410 can also be used as an etching stop layer, thereby avoiding damage to the diaphragm 300 and the backplate 400.

As an example, the method further includes the step of etching the second sacrificial layer 220 to form the first groove 221, so as to form the backplate bump 401 subsequently, so as to reduce the contact area between the backplate 400 and the diaphragm 300 and prevent adhesion between the backplate 400 and the diaphragm 300.

Specifically, a photoresist layer (not shown) is formed on the second sacrificial layer 220, the photoresist layer is exposed and developed to form an imaged photoresist layer, the pre-etched position of the first trench 221 is exposed, the second sacrificial layer 220 is etched by using the patterned photoresist layer as a mask to form the first trench 221, and then the patterned photoresist layer is removed by an ashing process. In the formation of the first trench 221, a second trench 222 and a third trench 223 may be formed at the same time, which is described in reference to the second embodiment and will not be described here.

Next, referring to fig. 5 to 8, the backplate 400 is formed on the second sacrificial layer 220, the backplate 400 includes the backplate insulating layer 410, the backplate conductive layer 420 and the backplate mechanical layer 430 stacked in sequence, the thickness of the backplate mechanical layer 430 is greater than the thickness of the backplate insulating layer 410 and the thickness of the backplate conductive layer 420, respectively, and the stress of the backplate mechanical layer 430 is less than the stress of the backplate insulating layer 410. The preparation steps for the backsheet 400 are as follows:

referring to fig. 5, the backplate insulating layer 410 is formed on the second sacrificial layer 220.

As an example, the backplate insulating layer 410 includes a silicon nitride insulating layer; the method of preparing the back plate insulating layer 410 includes LPCVD method; the thickness range of the back plate insulating layer 410 is formed to include 0.05 μm to 0.3 μm; the stress range of the back plate insulating layer 410 is 100MPa to 300 MPa.

Specifically, the material of the backplate insulating layer 410 is selected to be an insulating material relative to the diaphragm 300, so as to avoid the contact between the diaphragm 300 and the backplate conductive layer 420 when the diaphragm 300 is overdriven (Over-Drive), thereby avoiding the occurrence of a Pull-In phenomenon and avoiding the problems of electric leakage and product failure. Preferably, the backplate insulating layer 410 and the second sacrificial layer 220 have a good selective etching ratio, so that the backplate insulating layer 410 can be used as an etching stop layer for removing the second sacrificial layer 220 subsequently, thereby avoiding removing the second sacrificial layer 220Avoiding damage to the backplate conductive layer 420. In this embodiment, the back plate insulating layer 410 is preferably a silicon nitride insulating layer, but is not limited thereto, and for example, a silicon oxide or a stacked structure of a silicon oxide and a silicon nitride may be used. The LPCVD method is preferably used to prepare the high-quality back plate insulating layer 410 having good insulating properties, but since the LPCVD method has a long process time for growing a thin film and a high production cost, when preparing the back plate insulating layer 410, the silicon content of the SiH, which is a high proportion of the silicon content, is required to prepare the back plate insulating layer 410 having low stress, high quality and good insulating properties, such as a silicon nitride insulating layer₄The process gas has a high proportion, which can generate a large amount of contaminant particles (particles) in the production process, and can pose a great challenge to the maintenance and productivity of the production. Accordingly, the backplane insulating layer 410 is preferably formed to have a thickness in a range including 0.05 μm to 0.3 μm, and any limits and ranges within the range, such as 0.10 μm, 0.12 μm, or 0.15 μm. The stress range of the backplane insulating layer 410 preferably formed therein may include 100MPa to 300MPa, and any limits and ranges within this range, such as 150MPa, 200MPa, or 250MPa, and the like.

Next, the backplate conductive layer 420 is formed on the backplate insulating layer 410.

As an example, the backplane conductive layer 420 comprises a polysilicon conductive layer; the method of preparing the backplane conductive layer 420 includes LPCVD; the thickness of the back plate conductive layer 420 is formed to be in a range of 0.05 μm to 0.8 μm.

Specifically, the material of the back plate conductive layer 420 can be selected according to the diaphragm 300, and can be selected from semiconductor materials such as polysilicon, silicon germanium, or germanium, and can also be other metal materials such as aluminum, as required. In this embodiment, the back plate conductive layer 420 is preferably made of the same material as the diaphragm 300, i.e., a polysilicon material, but is not limited thereto, and may be made of a different material. In order to prepare the diaphragm 300 with high quality and low stress, the LPCVD method is preferably used, and the thickness of the conductive layer 420 of the back plate can be formed to be in a range from 0.05 μm to 0.8 μm, and any limit value and range value in the range, such as 0.10 μm, 0.3 μm, 0.5 μm, or 0.6 μm, and the like, which is not limited herein.

Next, referring to fig. 6, the backplane conductive layer 420 is patterned to facilitate subsequent formation of backplane vias 500.

Specifically, a photoresist layer (not shown) is formed, the photoresist layer is exposed and developed to form an imaged photoresist layer, the pre-etched position of the back plate conductive layer 420 is exposed, the patterned photoresist layer is used as a mask to etch the back plate conductive layer 420, and then the patterned photoresist layer is removed through an ashing process.

As an example, the method further includes a step of etching the backplate insulating layer 410 and the second sacrificial layer 220 to form a second groove 222 exposing the diaphragm 300, so as to prepare a diaphragm supporting portion 402 in contact with the diaphragm 300; and etching the back plate insulating layer 410, the second sacrificial layer 220 and the first sacrificial layer 210 to form a third trench 223 exposing the substrate 100, for one or a combination of the steps of preparing the substrate supporting portion 403 in contact with the substrate 100, so as to improve the firmness of the back plate 400.

Specifically, referring to fig. 7 and 8, the embodiment includes the steps of forming the second trench 222 and the third trench 223, but the invention is not limited thereto, and the steps of preparing the second trench 222 or the third trench 223 may be included, and are not limited thereto. The preparation method comprises the steps of forming a photoresist layer (not shown), exposing and developing the photoresist layer to form an imaged photoresist layer, exposing the pre-etched positions of the second trench 222 or/and the third trench 223, etching by using the imaged photoresist layer as a mask, and removing the imaged photoresist layer through an ashing process.

Next, referring to fig. 8, the backplane mechanical layer 430 is formed.

By way of example, the backplate mechanical layer 430 comprises a silicon nitride mechanical layer; the method of preparing the back plate mechanical layer 430 includes a PECVD method; the thickness range of the formed back plate mechanical layer 430 comprises 1-5 μm; the stress range of the mechanical layer 430 of the back plate is-60 MPa to 100 MPa.

Specifically, in the embodiment, the backplate mechanical layer 430 is made of a silicon nitride material having an insulating property with respect to the diaphragm 300 and the backplate conductive layer 420, and preferably having a good selective etching ratio with respect to the first sacrificial layer 210 and the second sacrificial layer 220, but the backplate mechanical layer is not limited thereto, and may also be a silicon oxide or a stacked structure of a silicon oxide and a silicon nitride, which is not limited herein and can be selected as needed. Wherein, since the back plate mechanical layer 430 plays a role of mechanically supporting the back plate 400, the thickness of the back plate mechanical layer 430 is preferably in a range of 1 μm to 5 μm, and any limit value and range value within the range, such as 2 μm, 3 μm or 4 μm, etc., which are not limited herein; moreover, since the back plate mechanical layer 430 is relatively thick, the back plate mechanical layer 430 with the largest thickness in the back plate 400 is preferably prepared by a PECVD method, so that the process time is reduced, the production cost is reduced, and pollution particles are reduced, for example, when the silicon nitride mechanical layer is prepared by PECVD method, the growth speed of the silicon nitride mechanical layer is relatively high, and the silicon nitride mechanical layer with the thickness of 3 microns can be completed in about 20 minutes; the PECVD method is very easy to adjust the stress, the stress can be adjusted generally by radio frequency power (RF power), the adjustment space is very large, the stress can be easily adjusted to be below 100MPa, even from tensile stress to compressive stress, and once the process condition is determined, the stress control drift range is small and is about +/-10MPa, so that the method has very good space for the design compatibility and diversity of products and a very sufficient design window; moreover, since the stress adjustment of the PECVD method is very convenient, an APC system can be completely adopted in the process of mass production, and the thickness difference of the sensing gap 800 between the backplate insulating layer 410 and the diaphragm 300 is compensated by adjusting the stress of the backplate mechanical layer 430 process, so that the production fault tolerance is higher, and the on-line yield (line yield) of the product is well guaranteed, thereby improving the production fault tolerance and the product yield.

Next, referring to fig. 9, the backplane 400 is etched to form a backplane via 500 penetrating the backplane 400 to expose the second sacrificial layer 220.

Specifically, a photoresist layer (not shown) is formed on the backplane 400, the photoresist layer is exposed and developed to form an imaged photoresist layer, the pre-etched position of the backplane through hole 500 is exposed, the backplane through hole 500 is etched by using the imaged photoresist layer as a mask, and then the imaged photoresist layer is removed by an ashing process.

Next, referring to fig. 10, a metal pad 600 is formed on the backplate 400 to be electrically led out through the metal pad 600 for subsequent testing of capacitance variation of the MEMS microphone. The material and the manufacturing method of the metal pad 600 are not limited herein.

Next, referring to fig. 11 and 12, the substrate 100 is thinned, and the substrate 100 is etched to form a substrate through hole 700 penetrating through the substrate 100, so as to expose the first sacrificial layer 210.

Specifically, before thinning the base 100, a support base (not shown), such as a silicon oxide substrate, may be formed on the side of the backplate 400, and then the support substrate may be removed in a subsequent process to be supported by the support substrate for facilitating the process operation, but the invention is not limited thereto.

Finally, the first sacrificial layer 210 and the second sacrificial layer 220 are removed to expose two opposite sides of the diaphragm 300, thereby forming the sensing gap 800 connected to the backplate through hole 500 and the back cavity 900 connected to the substrate through hole 700.

Specifically, the method for removing the first sacrificial layer 210 and the second sacrificial layer 220 may use a Buffered Oxide Etch (BOE), but is not limited thereto, and in this embodiment, the method for removing the first sacrificial layer 210 and the second sacrificial layer 220 uses a BOE method, which specifically includes: etching the second sacrificial layer 220 through the backplate through-hole 500 by using an etching solution until the second surface of the diaphragm 300 is exposed, so as to form a sensing gap 800 connected with the backplate through-hole 500; meanwhile, the etching solution is used to etch the first sacrificial layer 210 through the substrate through hole 700 until the first surface of the diaphragm 300 is exposed, so as to form the back cavity 900 connected to the substrate through hole 700. In the wet etching process, the etching solution may simultaneously etch the supporting substrate to reduce the process steps, but is not limited thereto, and in the wet etching process, the wet etching process may be controlled to retain the first sacrificial layer 210 and the second sacrificial layer 220 between the base supporting portion 403 and the diaphragm supporting portion 402, so as to further improve the structural stability of the MEMS microphone.

Referring to fig. 13, the present embodiment further provides a MEMS microphone, which can be prepared by the above method, but is not limited thereto.

Specifically, the MEMS microphone includes a substrate 100, a diaphragm 300, a backplate 400, a backplate through hole 500, a sensing gap 800, a substrate through hole 700, and a back cavity 900. The diaphragm 300 is located above the substrate 100, and includes a first surface and a second surface opposite to each other; the backplate 400 is located above the second surface of the diaphragm 300, and includes a backplate insulating layer 410, a backplate conducting layer 420 and a backplate mechanical layer 430 stacked in sequence, the thickness of the backplate mechanical layer 430 is greater than the thickness of the backplate insulating layer 410 and the thickness of the backplate conducting layer 420, respectively, and the stress of the backplate mechanical layer 430 is less than the stress of the backplate insulating layer 410; the backplate through-hole 500 penetrates the backplate 400; the sensing gap 800 is located between the backplate insulating layer 410 and the second side of the diaphragm 300, and is connected to the backplate through hole 500 to expose the second side of the diaphragm 300; the substrate via 700 penetrates the substrate 100; the back cavity 900 is connected to the substrate through hole 700 to expose the first side of the diaphragm 300.

By way of example, the thickness of the backplate mechanical layer 430 ranges from 1 μm to 5 μm; the stress range of the back plate mechanical layer 430 comprises-60 MPa to 100 MPa.

By way of example, the thickness range of the backplane insulating layer 410 includes 0.05 μm to 0.3 μm; the stress range of the back plate insulating layer comprises 100 MPa-300 MPa.

By way of example, the thickness of the backplane conductive layer 420 ranges from 0.05 μm to 0.8 μm.

As an example, the backplate insulating layer 410 includes a silicon nitride insulating layer; the backplate mechanical layer 430 comprises a silicon nitride mechanical layer; the diaphragm 300 comprises a polysilicon diaphragm; the backplane conductive layer 420 comprises a polysilicon conductive layer.

As an example, one or a combination of a substrate support part 403 contacting the substrate 100 and a diaphragm support part 402 contacting the diaphragm 300 is included.

As an example, when the substrate supporting portion 403 and the diaphragm supporting portion 402 are included, a sacrificial layer, namely, the first sacrificial layer 210 and the second sacrificial layer 220, contacting the substrate 100 is included between the substrate supporting portion 403 and the diaphragm supporting portion 402.

In the MEMS microphone in this embodiment, in the product ft (final test), the failure rate caused by leakage is lower than 0.3%, and the failure rate in the use of good products is also lower than 200PPM, so that the MEMS microphone can effectively prevent the diaphragm 300 from generating a turn-on leakage phenomenon when overdriven, thereby preventing the product from failing.

Example two

Referring to fig. 14 to 16, the present embodiment provides a method for manufacturing an MEMS microphone, which is different from the first embodiment in that: the steps of forming the first trench 2211, the second trench 2221 and the third trench 2231 are performed before the step of forming the backplate insulating layer 4101, so that the backplate bump 4011, the diaphragm support portion 4021 and the substrate support portion 4031 are formed finally to have the backplate insulating layer 4101. The back plate insulating layer 4101 is prepared by an LPCVD method, so that the back plate insulating layer 4101 with high quality and high insulation can be prepared, the insulating properties of the back plate bump 4011, the diaphragm supporting part 4021 and the substrate supporting part 4031 are further improved, the probability of electric leakage of the MEMS microphone is further reduced, and the product yield is improved. Regarding the selection of the preparation process, the structure and the material of the MEMS microphone, reference may be made to the first embodiment, which is not repeated herein, but not limited thereto, and those skilled in the art may also make corresponding changes according to specific requirements, and only the differences between the first embodiment and the second embodiment are described below, which specifically includes:

referring to fig. 14, a schematic structural diagram of the device after forming the first trench 2211, the second trench 2221 and the third trench 2231 is shown; referring to fig. 15, a schematic structural diagram of the device after forming a backplane insulating layer 4101 and a backplane conductive layer 4201 is shown, wherein the backplane insulating layer 4101 covers sidewalls and bottoms of the first trench 2211, the second trench 2221, and the third trench 2231; referring to fig. 16, a schematic structural diagram of the MEMS microphone is shown, in which the backplate bump 4011, the diaphragm support portion 4021 and the substrate support portion 4031 are formed to have the backplate insulating layer 4101, and preferably, the backplate insulating layer 4101 is prepared by an LPCVD method, so that the backplate insulating layer 4101 with high insulation can be prepared, and the insulating properties of the backplate bump 4011, the diaphragm support portion 4021 and the substrate support portion 4031 can be further improved, so that the probability of leakage of the MEMS microphone can be further reduced, and the yield of products can be improved. The forming method of the back plate mechanical layer 4301 is preferably a PECVD method to reduce process time, reduce production cost and reduce contamination particles, and due to the stress adjustability of the PECVD, the product has good design compatibility and diversity, and in the process of large-scale production, the APC system may also be used to adjust the stress of the back plate mechanical layer 4301 to compensate the thickness difference of the sensing gap 8001, and improve the fault tolerance rate and the product yield rate of production.

As an example, forming a metal pad 6001 on the backplate 4001 is further included, so as to be electrically led out through the metal pad 6001 for subsequent testing of capacitance variation of the MEMS microphone. The material and the manufacturing method of the metal pad 6001 are not limited here.

Referring to fig. 16, the present embodiment further provides an MEMS microphone, which is different from the first embodiment in that: the backplate bump 4011, the diaphragm support 4021, and the substrate support 4031 each have a backplate insulating layer 4101; the back plate insulating layer 4101 is prepared by an LPCVD method, so that the back plate insulating layer 4101 with high insulation can be prepared, the insulating properties of the back plate bump 4011, the diaphragm supporting part 4021 and the substrate supporting part 4031 are further improved, the probability of electric leakage of the MEMS microphone is further reduced, and the product yield is improved. The manufacturing process of the MEMS microphone can refer to the above-mentioned manufacturing method of the MEMS microphone, but is not limited thereto, and those skilled in the art can make corresponding changes according to specific requirements.

Specifically, the MEMS microphone includes a substrate 1001, a diaphragm 3001, a backplate 4001, a backplate through hole 5001, a sensing gap 8001, a substrate through hole 7001, and a back cavity 9001. The diaphragm 3001 is located above the substrate 1001 and includes a first surface and a second surface opposite to each other; the backplate 4001 is located above the second surface of the diaphragm 3001, and includes a backplate insulating layer 4101, a backplate conductive layer 4201, and a backplate mechanical layer 4301, which are stacked in sequence, the thickness of the backplate mechanical layer 4301 is greater than the thickness of the backplate insulating layer 4101 and the thickness of the backplate conductive layer 4201, respectively, and the stress of the backplate mechanical layer 4301 is less than the stress of the backplate insulating layer 4101; the backboard through hole 5001 penetrates through the backboard 4001; the sensing gap 8001 is located between the back plate insulating layer 4101 and the second surface of the diaphragm 3001, and is connected to the back plate through hole 5001 to expose the second surface of the diaphragm 3001; the substrate via 7001 extends through the substrate 1001; the back cavity 9001 is connected to the substrate via 7001 to expose a first side of the diaphragm 3001.

As an example, the MEMS microphone includes one or a combination of the substrate support 4031 in contact with the substrate 1001 and the diaphragm support 4021 in contact with the diaphragm 3001; and when the substrate support 4031 and the diaphragm support 4021 are included, it is preferable that a sacrificial layer in contact with the substrate 1001, that is, the first sacrificial layer 2101 and the second sacrificial layer 2201, is included between the substrate support 4031 and the diaphragm support 4021.

Specifically, in this embodiment, the MEMS microphone includes a backplate bump 4011, a diaphragm support portion 4021, and a substrate support portion 4031, so that the backplate bump 4011 reduces the contact area between the backplate 4001 and the diaphragm 3001, and prevents the backplate 4001 and the diaphragm 3001 from being adhered to each other; and the firmness of the back plate 4001 is improved by the diaphragm supporting part 4021 and the substrate supporting part 4031. The backplate bump 4011, the diaphragm support portion 4021 and the substrate support portion 4031 are preferably provided with the backplate insulating layer 4101, so that the backplate insulating layer 4101 with high quality and high insulation is prepared by the backplate insulating layer 4101 prepared by an LPCVD method, the insulation properties of the backplate bump 4011, the diaphragm support portion 4021 and the substrate support portion 4031 are further improved, the probability of electric leakage of the MEMS microphone is further reduced, and the product yield is improved. The structure of the MEMS microphone is not limited thereto, and for example, the MEMS microphone may include only one or a combination of two of the backplate bump 4011, the diaphragm support 4021 and the substrate support 4031, which is not limited herein. For the selection of the preparation process, structure and material of the MEMS microphone, reference may be made to the first embodiment, and details are not described here.

In the MEMS microphone in this embodiment, in the product ft (final test), the failure rate caused by leakage is lower than 0.3%, and the failure rate in the use of good products is also lower than 200PPM, so that the MEMS microphone can effectively prevent the diaphragm 3001 from generating a turn-on leakage phenomenon during overdriving, thereby preventing the product from failing.

In summary, according to the MEMS microphone and the method for manufacturing the same of the present invention, the back plate of the MEMS microphone employs the back plate insulating layer, the back plate conductive layer, and the back plate mechanical layer, which are stacked in sequence, so that the back plate insulating layer and the diaphragm are oppositely disposed, thereby avoiding the occurrence of a turn-on leakage phenomenon when the diaphragm is overdriven, avoiding the failure of the product, and improving the usage space and yield of the product; the back plate mechanical layer is prepared by adopting a PECVD method, so that the process time is reduced, the production cost is reduced, pollution particles are reduced, and the product has good design compatibility and diversity due to the stress adjustability of the PECVD.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.