CN109721021B

CN109721021B - MEMS device, preparation method and electronic device

Info

Publication number: CN109721021B
Application number: CN201711037349.2A
Authority: CN
Inventors: 王强
Original assignee: Semiconductor Manufacturing International Shanghai Corp; Semiconductor Manufacturing International Beijing Corp
Current assignee: Semiconductor Manufacturing International Shanghai Corp; Semiconductor Manufacturing International Beijing Corp
Priority date: 2017-10-30
Filing date: 2017-10-30
Publication date: 2021-02-02
Anticipated expiration: 2037-10-30
Also published as: CN109721021A

Abstract

The invention provides an MEMS device, a preparation method thereof and an electronic device. The MEMS device includes: a vibrating membrane; a back plate located above the diaphragm; a cavity between the diaphragm and the backplate; a sacrificial layer located between the diaphragm and the backplate and outside the cavity; wherein the sacrificial layer is in a cone shape, and the vertex angle of one end of the cone, which is close to the cavity and is in contact with the back plate, is absent. The structure of the present invention avoids the problem of the backplate being chipped in an Air Pressure Test (APT). The method of the invention does not add a photomask and cost, and improves the performance and yield of the MEMS device.

Description

MEMS device, preparation method and electronic device

Technical Field

The invention relates to the technical field of semiconductors, in particular to an MEMS (micro-electromechanical system) device, a preparation method and an electronic device.

Background

With the continuous development of semiconductor technology, smart phones, integrated CMOS and micro-electro-mechanical systems (MEMS) devices are increasingly becoming the most mainstream and advanced technology in the market of sensor-like products, and with the updating of technology, the development direction of such transmission sensor products is smaller scale, high quality electrical performance and lower loss.

Among them, MEMS sensors are widely used in automotive electronics: such as TPMS, engine oil pressure sensor, automobile brake system air pressure sensor, automobile engine intake manifold pressure sensor (TMAP), diesel engine common rail pressure sensor; consumer electronics: such as a tire pressure meter, a sphygmomanometer, a kitchen scale, a health scale, a pressure sensor for a washing machine, a dish washing machine, a refrigerator, a microwave oven, an oven and a dust collector, an air conditioner pressure sensor, a liquid level control pressure sensor for a washing machine, a water dispenser, a dish washing machine and a solar water heater; industrial electronics: such as digital pressure gauge, digital flow meter, industrial ingredient weighing, etc., the electronic audio-video field: microphones, etc.

The MEMS microphone is a sensing device that converts sound energy into an electrical signal, and the principle of the capacitor MEMS microphone is to change the capacitance by causing sound pressure to vibrate a diaphragm through a sound hole. The main structure is a vibrating membrane (VP), an air cavity (Gap) and a back plate.

Air Pressure Test (APT) is an important reliability parameter for MEMS microphones. A higher APT means that the performance of the MEMS microphone is higher, and the problem of device fracture generally occurs in an Air Pressure Test (APT) at present, which limits the performance and yield of the device.

There is therefore a need for further improvements to the devices and methods of fabrication described so far to eliminate the above problems.

Disclosure of Invention

In this summary, concepts in a simplified form are introduced that are further described in the detailed description. This summary of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

To overcome the problems currently existing, the present invention provides a MEMS device comprising:

a vibrating membrane;

a back plate located above the diaphragm;

a cavity between the diaphragm and the backplate;

a sacrificial layer located between the diaphragm and the backplate and outside the cavity;

wherein the sacrificial layer is in a cone shape, and the vertex angle of one end of the cone, which is close to the cavity and is in contact with the back plate, is absent.

Optionally, the vertex angle missing part is shaped as a groove recessed in a direction away from the cavity.

Optionally, an included angle between a surface of the groove and a surface of the back plate is an obtuse angle.

Optionally, a release hole is arranged in a region of the back plate above the vertex angle missing part, and is used for removing the vertex angle at one end of the cone, which is in contact with the back plate.

Optionally, the edge position of the back plate above the vertex angle missing part is further provided with an extended region extending outwards from the edge position, so as to increase the edge smoothness of the back plate at the vertex angle missing part.

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

forming a vibrating membrane;

forming a sacrificial layer on the diaphragm;

forming a back plate on the sacrificial layer;

forming a plurality of sound holes penetrating through the back plate and a plurality of release holes positioned outside the sound holes on the back plate;

and removing the sacrificial layer below the sound hole to form a cavity between the vibrating membrane and the back plate, and simultaneously removing the top corner of one end, close to the cavity and in contact with the back plate, of the sacrificial layer remaining below the release hole.

Optionally, the shape of the removed vertex angle portion is a groove recessed in a direction away from the cavity, and the release hole is located above the groove.

Optionally, the method of forming the sound holes and the release holes on the back plate comprises:

forming a photoresist layer on the back plate;

providing a photomask, wherein mask patterns corresponding to the sound holes and the release holes are formed on the photomask;

selecting the photomask to expose and develop the photoresist layer so as to form the mask pattern in the photoresist layer;

and etching the back plate by taking the photoresist layer as a mask to form the sound holes and the release holes.

The invention also provides an electronic device which comprises the MEMS device.

The invention provides an MEMS device and a preparation method thereof, wherein a release hole is formed at the outer side of a sound hole in the preparation process of the device, so that when the sacrificial layer below the sound hole is removed, the vertex angle of one end, close to a cavity and in contact with a back plate, of the residual sacrificial layer is removed at the same time, and after the vertex angle is removed, the vertex angle area is not sharp with an acute angle any more, so that the problem that the back plate is cracked in an Air Pressure Test (APT) is avoided. The method of the invention does not add a photomask and cost, and improves the performance and yield of the MEMS device.

Drawings

The following drawings of the invention are included to provide a further understanding of the invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

In the drawings:

FIG. 1A shows a cross-sectional structural view of a MEMS device;

FIG. 1B shows a schematic diagram of an air pressure test of the MEMS device of FIG. 1A;

FIG. 1C is a top view of the backplate and sacrificial layer in a MEMS device;

FIG. 1D is a cross-sectional view of the backplate and sacrificial layer in a MEMS device;

FIG. 2 shows a flow chart of a fabrication process for a MEMS device according to the present invention;

FIG. 3A shows a top view of the backplate and sacrificial layer in the MEMS device of the present invention;

FIG. 3B shows a close-up view of the pattern in the circle of FIG. 3A;

FIG. 3C shows a cross-sectional view of the backplate and sacrificial layer in a MEMS device of the present invention;

FIG. 3D shows a close-up view of the pattern in circle in FIG. 3C;

fig. 4 shows a schematic view of an electronic device according to the invention.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.

It is to be understood that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals refer to like elements throughout.

It will be understood that when an element or layer is referred to as being "on" …, "adjacent to …," "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to the other elements or layers or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on …," "directly adjacent to …," "directly connected to" or "directly coupled to" other elements or layers, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

Spatial relationship terms such as "under …", "under …", "below", "under …", "above …", "above", and the like, may be used herein for ease of description to describe the relationship of one element or feature to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, then elements or features described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "below …" and "below …" can encompass both an orientation of up and down. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

In the following description, for purposes of explanation, specific details are set forth in order to provide a thorough understanding of the present invention. The following detailed description of the preferred embodiments of the invention, however, the invention is capable of other embodiments in addition to those detailed.

The MEMS microphone is a sensing device that converts sound energy into an electrical signal, and the principle of the capacitor MEMS microphone is to change capacitance by vibration of a vibration mode caused by sound pressure. The main structure of the air-cooled piezoelectric ceramic comprises a vibrating membrane (VP), an air cavity (Gap), a back plate and a metal bonding Pad (contact Pad).

In the preparation process of the MEMS device, a substrate 201, an insulating layer 202, a diaphragm 203, a sacrificial layer 204, a backplate 205, and an acoustic hole 206 are sequentially formed, as shown in fig. 1A, wherein most of the gap oxide between the upper and lower plates of the diaphragm and the backplate is used as a sacrificial layer, and is etched away after passing through a BOE acid bath, so as to form a cavity.

After the MEME device is prepared, an Air Pressure Test (APT) is usually performed, and is an important reliability parameter for the MEMS microphone. A higher APT means that the performance of the MEMS microphone is higher, and the problem of device chipping generally occurs in the Air Pressure Test (APT) at present, as shown in fig. 1B and 1D, which limits the performance and yield of the device.

The inventor finds out through analysis that the part where the device is cracked is the back plate and the boundary of the back plate and the sacrificial layer, and the remaining contact area of the sacrificial layer and the back plate is a very sharp acute angle in the process of forming the cavity, as shown in fig. 1C and 1D, the back plate is damaged by the sharp angle in the Air Pressure Test (APT), and a fine crack is caused in the back plate.

In order to solve the above-mentioned problems, the present application provides a MEMS device, as shown in fig. 3A to 3D, including:

a vibrating membrane 303;

a back plate 305 located above the diaphragm;

a cavity between the diaphragm and the backplate;

a sacrificial layer 304 located between the diaphragm and the backplate and outside the cavity;

wherein the sacrificial layer is in the form of a cone, wherein the apex angle of the end of the cone near the cavity and in contact with the backplate is missing, as shown by the circled portion in fig. 3C, and fig. 3D shows a close-up view of the pattern in the circle in fig. 3C.

Optionally, the part with the missing vertex angle is shaped as a groove which is concave towards the direction away from the edge of the cavity.

Optionally, the included angle between the surface of the groove and the surface of the back plate is an obtuse angle, as shown in fig. 3C.

Optionally, a release hole 307 is disposed in a region of the back plate above the missing part of the vertex angle, for removing the vertex angle at the end contacted by the back plate.

Optionally, the edge position of the back plate above the vertex angle missing part is further provided with an extended region extending towards the outer edge, so as to increase the smoothness of the edge position of the back plate above the vertex angle missing part, as shown in fig. 3A, the shape of the back plate changes from an inner shape to an outer shape.

In addition, the invention also provides a preparation method of the MEMS device, which comprises the following steps:

forming a vibrating membrane;

forming a sacrificial layer on the diaphragm;

forming a back plate on the sacrificial layer;

forming a plurality of sound holes penetrating through the back plate and release holes positioned outside the sound holes on the back plate;

and removing the sacrificial layer below the sound holes and the release holes to form a cavity between the vibrating membrane and the back plate, wherein the residual sacrificial layer outside the cavity is in a cone shape, and the vertex angle of one end, close to the cavity and in contact with the back plate, in the cone is absent.

A method for fabricating the MEMS device of the present invention is described in detail below with reference to fig. 2 and 3A-3D, and fig. 2 shows a flow chart of a process for fabricating the MEMS device of the present invention; FIG. 3A is a top view of the backplate and sacrificial layer in the MEMS device of the present invention; FIG. 3B shows a close-up view of the pattern in the circle of FIG. 3A; FIG. 3C shows a cross-sectional view of the backplate and sacrificial layer in a MEMS device of the present invention; FIG. 3D shows a close-up view of the pattern in circle in FIG. 3C;

as shown in fig. 3C, the MEMS device in the present invention includes:

a vibrating membrane 303;

a back plate 305 located above the diaphragm;

a cavity between the diaphragm and the backplate;

Specifically, as shown in fig. 3C, the MEMS element may include a MEMS microphone, a MEMS pressure sensor, an acceleration sensor, and the like, but is not limited to a certain type, and the following describes a method for manufacturing the MEMS device in detail by taking the MEMS microphone as an example.

In particular, the MEMS substrate (not shown in the figures) may be at least one of the materials mentioned below: silicon, silicon-on-insulator (SOI), silicon-on-insulator (SSOI), silicon-on-insulator-silicon-germanium (S-SiGeOI), silicon-on-insulator-silicon-germanium (SiGeOI), and germanium-on-insulator (GeOI), among others.

An insulating layer 302 is also formed over the MEMS substrate, wherein the insulating layer can be formed by using an inorganic insulating layer such as a silicon oxide layer, a silicon nitride layer, or a silicon oxynitride layer, an insulating layer such as a layer containing polyvinyl phenol, polyimide, siloxane, or the like. Further, polyvinyl phenol, polyimide, or siloxane can be effectively formed by a droplet discharge method, printing, or spin coating method. Siloxanes can be classified according to their structure into silica glass, alkyl siloxane polymers, alkyl silsesquioxane polymers, silsesquioxane hydride polymers, alkyl silsesquioxane hydride polymers, and the like.

In addition, the insulating layer 302 may be formed by various deposition methods commonly used in the art.

Wherein a first recess is formed in the MEMS substrate.

The first grooves are a plurality of square grooves spaced from each other, and for example, the first grooves may be uniformly distributed on the edge of the MEMS substrate.

The method for forming the first groove comprises the following steps: forming a photoresist layer on the MEMS substrate, exposing and developing to form a mask, and etching the MEMS substrate with the photoresist layer as the mask to form the groove on the surface of the MEMS substrate, as shown in fig. 3A.

The depth of the groove is not limited to a certain range of values and can be set as required.

Dry etching, Reactive Ion Etching (RIE), ion beam etching, plasma etching may be selected for this step.

The diaphragm 303 may be made of polysilicon, SiGe, or the like, but is not limited to this. In this example, the diaphragm 303 is made of polysilicon.

The deposition method of the diaphragm 303 may be one of Low Pressure Chemical Vapor Deposition (LPCVD), Laser Ablation Deposition (LAD) and Selective Epitaxial Growth (SEG) formed by Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD) or Atomic Layer Deposition (ALD), and the Physical Vapor Deposition (PVD) method is selected in the present invention.

A sacrificial layer is formed on the diaphragm 303, and specifically includes:

a backplate 305 is formed on the MEMS substrate and on the sacrificial layer inside it to cover the sacrificial layer.

The back plate 305 may be made of polysilicon, SiGe, or the like, but is not limited to one. In this example, the back plate 305 is selected from polysilicon.

The deposition method of the back plate 305 may be one of Low Pressure Chemical Vapor Deposition (LPCVD), Laser Ablation Deposition (LAD) and Selective Epitaxial Growth (SEG) formed by Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), Atomic Layer Deposition (ALD), etc., and the Physical Vapor Deposition (PVD) method is used in the present invention.

A cavity is formed between the diaphragm and the backplate.

And the remaining sacrificial layer is arranged on the outer side of the hollow space and used for supporting and fixing the back plate, wherein the back plate is in a shape of a cone with a wide top and a narrow bottom, such as a trapezoid cone and the like, but not limited to a certain shape.

The cone is formed in the process of forming the cavity by etching with the etching solution, wherein the part of the cone where the vertex angle is missing is shaped as a groove which is concave towards the direction away from the edge of the cavity, so that the vertex angle of an acute angle is removed.

Optionally, the edge position of the back plate above the vertex angle missing part is further provided with an expanded region extending towards the outer edge for increasing the smoothness degree of the edge position of the back plate above the vertex angle missing part, as shown in fig. 3A, where fig. 3B shows a partial enlarged view of the pattern in the circle of fig. 3A, and the release hole may be provided by modifying the back plate, so as to remove the sharp corner of the acute angle.

After the top angle is removed, the top angle area of the MEMS device is not a sharp angle of an acute angle any more, so that the problem of fragmentation of the back plate in an Air Pressure Test (APT) is avoided. The method of the invention does not add a photomask and cost, and improves the performance and yield of the MEMS device.

The invention also provides a preparation method of the MEMS device, as shown in FIG. 2, the preparation method mainly comprises the following steps:

step S1: forming a vibrating membrane;

step S2: forming a sacrificial layer on the diaphragm;

step S3: forming a back plate on the sacrificial layer;

step S4: forming a plurality of sound holes penetrating through the back plate and a plurality of release holes positioned outside the sound holes on the back plate;

step S5: and removing the sacrificial layer below the sound hole to form a cavity between the vibrating membrane and the back plate, and simultaneously removing the top corner of one end, close to the cavity and in contact with the back plate, of the sacrificial layer remaining below the release hole.

The invention provides an MEMS device and a preparation method thereof, wherein a release hole is formed at the outer side of a sound hole opening in the preparation process of the device, so that when the sacrificial layer below the sound hole is removed, the vertex angle of one end, close to a cavity and in contact with a back plate, of the residual sacrificial layer is removed at the same time, and after the vertex angle is removed, the vertex angle area is not a sharp angle of an acute angle any more, so that the problem that the back plate is cracked in an Air Pressure Test (APT) is avoided. The method of the invention does not add a photomask and cost, and improves the performance and yield of the MEMS device.

Next, a detailed description will be given of a specific embodiment of the method for manufacturing a MEMS device of the present invention.

Firstly, executing a first step, providing a MEMS substrate 301; a diaphragm 303 and a sacrifice layer 304 are formed in this order on the MEMS substrate.

Specifically, as shown in fig. 3, the MEMS element may include a MEMS microphone, a MEMS pressure sensor, an acceleration sensor, and the like, but is not limited to any one, and the following describes the method for manufacturing the MEMS device in detail by taking the MEMS microphone as an example.

Sequentially forming a vibrating membrane 303 and a sacrificial layer 304 on the MEMS substrate to serve as the vibrating membrane and the sacrificial layer, wherein the forming method specifically comprises the following steps:

specifically, an insulating layer 302 is first formed over the MEMS substrate, wherein the insulating layer can be formed by using an inorganic insulating layer such as a silicon oxide layer, a silicon nitride layer, or a silicon oxynitride layer, an insulating layer such as a layer containing polyvinyl phenol, polyimide, siloxane, or the like. Further, polyvinyl phenol, polyimide, or siloxane can be effectively formed by a droplet discharge method, printing, or spin coating method. Siloxanes can be classified according to their structure into silica glass, alkyl siloxane polymers, alkyl silsesquioxane polymers, silsesquioxane hydride polymers, alkyl silsesquioxane hydride polymers, and the like.

The method further comprises the step of patterning the MEMS substrate before the insulating layer is formed so as to form a first groove in the MEMS substrate.

Wherein, the method for forming the first groove comprises the following steps: forming a photoresist layer on the MEMS substrate, exposing and developing to form a mask, and etching the MEMS substrate with the photoresist layer as the mask to form the groove on the surface of the MEMS substrate, as shown in fig. 3A.

The MEMS substrate is etched in this step with an O-based etchant, in one example of the invention O is used₂May also be added simultaneously with other small amounts of gases such as CF₄、CO₂、N₂The etching pressure can be 50-200mTorr, such as 100-150mTorr, with a power of 200-600W, while a larger gas flow is selected in the present invention, optionally O in the present invention₂The flow rate of (2) is 30-300 sccm.

The diaphragm is then formed on the MEMS substrate and patterned, for example, by forming a diaphragm 303 in the first recess so as to cover the first recess.

The deposition method of the diaphragm 303 may be one of Low Pressure Chemical Vapor Deposition (LPCVD), Laser Ablation Deposition (LAD) and Selective Epitaxial Growth (SEG) formed by Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), Atomic Layer Deposition (ALD), or the like, and the Physical Vapor Deposition (PVD) method is used in the present invention.

Forming a sacrificial layer on the diaphragm 303, specifically including:

step 1: forming a first sacrificial layer on the diaphragm and on the insulating layer;

step 2: patterning the first sacrificial layer to form a plurality of second grooves on the surface of the first sacrificial layer;

and step 3: a second sacrificial layer is conformally deposited to cover the first sacrificial layer.

Wherein, in the step 1, the first sacrificial layer is selected from an oxide, for example, an oxide having a larger etching selectivity with respect to the diaphragm.

In the step 2, the first sacrificial layer is patterned to form a plurality of second grooves which are uniformly distributed on the surface of the first sacrificial layer.

Wherein the second groove is a tapered groove.

The forming method of the second groove may refer to the forming method of the first groove, and is not described herein again.

Then, a second sacrificial layer is deposited, and in the step, the second sacrificial layer is formed by adopting a conformal deposition method, and the second groove is formed in the second sacrificial layer.

The second groove is formed to form a pattern protruding downward in the back plate, i.e., the back plate, in a subsequent step, thereby forming the blocking member 3072.

The first sacrificial layer and the second sacrificial layer are made of the same material and are formed by the same forming method.

And step two, patterning the vibrating membrane and the sacrificial layer to remove part of the vibrating membrane and the sacrificial layer and expose the MEMS substrate.

In order to simplify the process steps, the step of patterning the diaphragm and the sacrificial layer includes:

forming a mask layer, such as a photoresist layer, on the vibrating membrane and the sacrificial layer;

exposing and developing the photoresist layer to remove the outer part of the photoresist layer and expose the sacrificial layer;

and etching the vibration film and the sacrificial layer by taking the mask layer as a mask so as to remove part of the vibration film and the sacrificial layer and expose the MEMS substrate.

And step three, forming a back plate 305 on the exposed MEMS substrate and the sacrificial layer on the inner side of the MEMS substrate so as to cover the sacrificial layer.

And step four is executed, a plurality of sound holes penetrating through the back plate and release holes positioned at the outer sides of the sound holes are formed on the back plate.

Specifically, the method comprises the following steps:

step 1: patterning the backplate to form sound holes 306 and release holes 307 in the backplate outside the sound holes, exposing the sacrificial layer;

step 2: and removing the sacrificial layer by a buffer etching method to form the cavity.

In step 1, the back plate is first patterned to form openings in the back plate as a plurality of sound holes for conducting sound waves into the cavity.

Specifically, a patterned mask layer, such as a photoresist layer, is first formed on the back plate, and then the back plate is etched using the mask layer as a mask, so that a number of the sound holes and release holes are formed in the back plate.

Wherein the sound holes and the release holes are used for removing the sacrificial layer between the back plate and the vibrating membrane in the subsequent step to form a cavity, and simultaneously removing the top sharp corners of the residual sacrificial layer through the release holes.

Wherein the critical dimension of the release hole is much smaller than the critical dimension of the sound hole.

The method of forming the sound holes and the release holes on the back plate includes:

forming a photoresist layer on the sacrificial layer;

providing a photomask, and forming a mask pattern with the sound holes and the release holes on the photomask;

Specifically, in this step, no additional mask is needed, and only corresponding modifications need to be made to the mask, for example, a pattern corresponding to the release holes and the sound hole openings is formed on the mask, as shown in fig. 3C.

The opening is formed by dry etching or wet etching in this step, which is not described in detail herein.

The sacrificial layer is removed by a buffer etching method to form a cavity between the backplate and the diaphragm.

In particular, the sacrificial layer is etched away through the acoustic holes in the backplate to form the cavity between the diaphragm and the backplate.

For example, a Buffered Oxide Etch (Buffered Oxide Etch) process is used to Etch away the sacrificial layer.

Immersing the MEMS device into the buffered etching solution, wherein the BOE is HF and NH₄F is mixed in different proportions.

For example, a 6:1BOE etch means 49% aqueous HF: 40% NH₄F aqueous solution 1: 6 (volume ratio) are mixed. Wherein HF is the main etching liquid, NH₄F is used as a buffer. Wherein NH is utilized₄F fixed H⁺So as to maintain a constant etching rate.

The cavity is obtained after the sacrificial layer is removed.

In this step, a part of the sacrificial layer remains outside the cavity as a support.

The step of cleaning the MEMS device may be further included after the cavity is formed.

This completes the description of the steps associated with the method of fabricating the MEMS device of the present example. The method may further include the step of forming a transistor and other related steps, which are not described in detail herein. Besides the above steps, the preparation method of the present example may further include other steps among the above steps or between different steps, and these steps may be implemented by various processes in the current process, and are not described herein again.

The application provides a preparation method of an MEMS device, wherein a release hole is formed at the outer side of a sound hole in the preparation process of the MEMS device, so that when the sacrificial layer below the sound hole is removed, the vertex angle of one end, close to the cavity and in contact with the back plate, of the residual sacrificial layer is removed at the same time, and after the vertex angle is removed, the vertex angle area is not a sharp angle of an acute angle any more, so that the problem that the back plate is cracked in an Air Pressure Test (APT) is avoided. The method of the invention does not add a photomask and cost, and improves the performance and yield of the MEMS device.

The electronic device may be any electronic product or device such as a mobile phone, a tablet computer, a notebook computer, a netbook, a game machine, a television, a VCD, a DVD, a navigator, a camera, a video camera, a recording pen, an MP3, an MP4, a PSP, or an intermediate product having the MEMS device, for example: a mobile phone mainboard with the integrated circuit, and the like.

The electronic device also has the advantages described above, since the MEMS device comprised has a higher performance.

Wherein figure 4 shows an example of a mobile telephone handset. The mobile phone handset 400 is provided with a display portion 402, operation buttons 403, an external connection port 404, a speaker 405, a microphone 406, and the like, which are included in a housing 401.

Wherein the mobile telephone handset comprises the aforementioned MEMS device, the MEMS device comprising a diaphragm; a back plate located above the diaphragm; a cavity between the diaphragm and the backplate; a sacrificial layer located between the diaphragm and the backplate and outside the cavity; wherein the sacrificial layer is in a cone shape, and the vertex angle of one end of the cone, which is close to the cavity and is in contact with the back plate, is absent. After the top corners of the MEMS device are removed, the top corner areas are not sharp corners with acute angles, so that the problem that the backboard is cracked in an Air Pressure Test (APT) is solved. The method of the invention does not add a photomask and cost, and improves the performance and yield of the MEMS device.

The present invention has been illustrated by the above examples, but it should be understood that the above examples are for illustrative and descriptive purposes only and are not intended to limit the invention to the scope of the described examples. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the examples described above, and that many variations and modifications may be made in accordance with the teachings of the present invention, all of which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A MEMS device, comprising:

a vibrating membrane;

a back plate located above the diaphragm;

a cavity between the diaphragm and the backplate;

wherein the sacrificial layer is in a cone shape, and the vertex angle of one end, which is close to the cavity and is in contact with the back plate, of the cone is absent;

the edge position of the back plate above the vertex angle missing part is further provided with an extension area extending outwards from the edge position, and the extension area is used for increasing the edge smoothness degree of the back plate at the vertex angle missing part.

2. The MEMS device, as recited in claim 1, wherein the apex angle absence is shaped as a recess recessed away from the cavity.

3. The MEMS device, as recited in claim 2, wherein an angle between a surface of the recess and a surface of the backplate is an obtuse angle.

4. The MEMS device, as recited in claim 2, wherein release holes are provided in the area of the back plate above the missing apex corners for removing apex corners of the cone at the end in contact with the back plate.

5. A method of fabricating a MEMS device, the method comprising:

forming a vibrating membrane;

forming a sacrificial layer on the diaphragm;

forming a back plate on the sacrificial layer;

removing the sacrificial layer below the sound hole to form a cavity between the diaphragm and the backplate, and simultaneously removing a top corner of one end, which is close to the cavity and is in contact with the backplate, of the sacrificial layer remaining below the release hole;

6. The method of claim 5, wherein the removing the apex portion is in the form of a recess that is recessed away from the cavity, the relief hole being located above the recess.

7. The method of claim 6, wherein the included angle between the surface of the groove and the surface of the back plate is an obtuse angle.

8. The method of claim 5, wherein forming the sound holes and the release holes on the back plate comprises:

forming a photoresist layer on the back plate;

9. An electronic device, characterized in that it comprises a MEMS device according to one of claims 1 to 4.