A MEMS device, a preparation method thereof and an electronic device

Abstract

The application provides a MEMS device and a preparation method thereof and an electronic device. The method comprises the following steps: providing a substrate, forming a first sacrificial layer on the substrate, forming a diaphragm on the first sacrificial layer, and forming a second sacrificial layer on the diaphragm; forming an interface layer on the second sacrificial layer; forming a third sacrificial layer on the second sacrificial layer and the interface layer; forming a back plate layer on the third sacrificial layer, and forming a release hole in the back plate layer; removing part of the second sacrificial layer and part of the third sacrificial layer to form a cavity, so that part of the back plate layer is suspended above the diaphragm; and forming a back cavity on the second surface of the substrate. The method of the application sets the interface layer, reduces the etching damage to the material at the interface during etching, thereby improving the interface properties and reducing the cracks at the interface.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, in particular to a MEMS device, a preparation method thereof and an electronic device. BACKGROUND

[0002] With the continuous development of semiconductor technology, in the market of sensor products, smart phones, integrated CMOS and micro-electro-mechanical system (MEMS) devices are increasingly becoming the most mainstream and most advanced technology, and with the update of technology, they are developing towards the direction of small size, high performance and low power consumption.

[0003] Among them, the MEMS microphone prepared based on the micro-electro-mechanical system (MEMS) process is widely used because it has the advantages of small size, low cost and stable performance compared with traditional microphones. The commonly used MEMS microphone includes a diaphragm 101, a back plate 104 and a back cavity 105, etc., and converts sound signals into electrical signals through the diaphragm.

[0004] But some MEMS microphones consider design and performance requirements, such as Figure 1 As shown in the figure, the etching stop layer cannot be formed on the side wall of the second sacrificial layer 102 and the side wall of the third sacrificial layer 103, and after etching to remove the sacrificial layer, damage is easily caused at the interface between the second sacrificial layer 102 and the third sacrificial layer 103, forming a crack, thereby reducing the yield of the product. SUMMARY

[0005] A series of simplified concepts are introduced in the summary part, which will be further described in detail in the specific embodiment part. The summary part of the present application does not mean to try to limit the key features and necessary technical features of the claimed technical solution, nor does it mean to try to determine the protection scope of the claimed technical solution.

[0006] In view of the existing problems, the present application provides a preparation method of a MEMS device, comprising:

[0007] providing a substrate, a first sacrificial layer is formed on the first surface of the substrate, a diaphragm is formed on the first sacrificial layer, and a second sacrificial layer is formed on the diaphragm;

[0008] forming an interface layer on the surface of the second sacrificial layer, the interface layer covering the outer peripheral edge region of the second sacrificial layer;

[0009] forming a third sacrificial layer on the second sacrificial layer and the interface layer;

[0010] forming a back plate layer on the surface of the third sacrificial layer, the back plate layer having a release hole formed therein to expose part of the surface of the third sacrificial layer;

[0011] removing part of the second sacrificial layer and part of the third sacrificial layer to form a cavity between the backplate layer and the diaphragm, so that part of the backplate layer is suspended above the diaphragm;

[0012] forming a back cavity at a second surface of the substrate, wherein the second surface is opposite to the first surface, the back cavity penetrating through the substrate and the first sacrificial layer from the second surface of the substrate and exposing part of the surface of the diaphragm.

[0013] Exemplarily, forming a back cavity at a second surface of the substrate comprises:

[0014] thinning the substrate from the second surface of the substrate before removing part of the second sacrificial layer and part of the third sacrificial layer;

[0015] etching the substrate from the second surface of the substrate to stop at the first sacrificial layer to form a cavity;

[0016] removing part of the first sacrificial layer while removing part of the second sacrificial layer and part of the third sacrificial layer to form the back cavity.

[0017] Exemplarily, removing part of the first sacrificial layer, part of the second sacrificial layer and part of the third sacrificial layer comprises:

[0018] adopting wet etching to remove part of the first sacrificial layer, part of the second sacrificial layer and part of the third sacrificial layer, wherein a first etching rate of the wet etching to the first sacrificial layer, the second sacrificial layer and the third sacrificial layer is higher than a second etching rate of the wet etching to the interface layer.

[0019] Exemplarily, the first etching rate is two times or more than two times of the second etching rate.

[0020] Exemplarily, the method further comprises:

[0021] forming a via hole outside a region where the cavity is to be formed in the second sacrificial layer and the third sacrificial layer, the via hole exposing part of the surface of the diaphragm;

[0022] forming a rewiring layer, the rewiring layer covering a bottom and a sidewall of the via hole and partially extending onto a surface of the third sacrificial layer;

[0023] forming a first pad on the rewiring layer and a second pad on the backplate layer, wherein the first pad is electrically connected to the diaphragm through the rewiring layer, and the second pad is electrically connected to the backplate layer.

[0024] Exemplarily, the interface layer is annular.

[0025] Another aspect of the present application provides a MEMS device, comprising:

[0026] a substrate, the substrate comprising a first surface and a second surface opposite to the first surface;

[0027] a first sacrificial layer covering a partial area of the first surface of the substrate;

[0028] a diaphragm on the first sacrificial layer, and an outer peripheral edge region of the diaphragm overlapping the first sacrificial layer;

[0029] a second sacrificial layer covering a partial area of the diaphragm;

[0030] an interface layer covering an outer peripheral edge region of the second sacrificial layer;

[0031] a third sacrificial layer covering the second sacrificial layer and the interface layer;

[0032] a backplate layer, a partial area of the backplate layer being suspended above the diaphragm, and an outer peripheral edge of the backplate layer covering the third sacrificial layer;

[0033] a cavity formed between the backplate layer and the diaphragm and penetrating through the second sacrificial layer and the third sacrificial layer;

[0034] a back cavity penetrating through the substrate and the first sacrificial layer from the second surface of the substrate and exposing a partial surface of the diaphragm.

[0035] Illustratively, an outer edge of the interface layer protrudes from edges of the second sacrificial layer and the third sacrificial layer, and / or the interface layer is annular.

[0036] Illustratively, the MEMS device further comprises:

[0037] a plurality of release holes, the plurality of release holes being spaced apart from each other and penetrating through the backplate layer, and the release holes exposing the diaphragm;

[0038] a rewiring layer, a through hole is formed in the second sacrificial layer and the third sacrificial layer outside the cavity, the through hole exposing a partial surface of the diaphragm, and the rewiring layer covering a bottom and a sidewall of the through hole and partially extending onto a surface of the third sacrificial layer;

[0039] a first pad and a second pad, the first pad being disposed on the rewiring layer, and the second pad being disposed on the backplate layer, wherein the first pad is electrically connected to the diaphragm through the rewiring layer, and the second pad is electrically connected to the backplate layer.

[0040] In still another aspect, the present application provides an electronic device comprising the aforementioned MEMS device.

[0041] The MEMS device and the manufacturing method thereof according to the embodiments of the present application can reduce etching damage to the material at the interface during etching by setting the interface layer, thereby improving the interface property, reducing the crack at the interface, and improving the product yield. BRIEF DESCRIPTION OF DRAWINGS

[0042] The following drawings form part of the present specification and are included to further teach the details of the present application. For a better understanding, the detailed description and examples are to be considered together with the accompanying drawings wherein:

[0043] In the drawings:

[0044] Figure 1 A cross-sectional view of a device obtained by sequentially implementing a conventional manufacturing method of a MEMS device is shown;

[0045] Figure 2 A flow chart of a manufacturing method of a MEMS device according to an embodiment of the present application is shown;

[0046] Figures 3A-3H A cross-sectional view of a device obtained by sequentially implementing a manufacturing method of a MEMS device according to an embodiment of the present application is shown;

[0047] Figure 4 A schematic view of an electronic device according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0048] The present application will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the application are shown. This application may, however, 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 application to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions are exaggerated for clarity. Like reference numerals refer to like elements throughout.

[0049] It will be understood that when an element or layer is referred to as being "on" or "connected to" another element or layer, it can be directly on or connected to the other element or layer or intervening elements or layers can be present. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element or layer, there are no intervening elements or layers present. It will also be understood that, although the terms first, second, third, etc. can be used herein 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 application.

[0050] Spatially relative terms, such as "beneath", "below", "lower", "under", "above", "upper" and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) 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 and / or

[0051] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. 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 one or more of the associated listed items.

[0052] Embodiments of the application will be described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the application. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, embodiments of the application should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and / or a gradient of implant concentration at its edges rather than a binary change between implanted and non-implanted regions. Similarly, a buried region formed by implantation can result in some implantation in a region between the buried region and a surface through which the implantation was made. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region of a device and are not intended to limit the scope of the application.

[0053] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and / or the

[0054] For a thorough understanding of the application, reference should be made to the following detailed description together with the accompanying drawings, in which:

[0055] Therefore, in view of the foregoing technical problems, the present application provides a method for manufacturing a MEMS device, as shown in the accompanying drawings, which mainly comprises the following steps: Figure 2 The method comprises the following steps:

[0056] Step S1, providing a substrate, a first sacrificial layer is formed on a first surface of the substrate, a diaphragm is formed on the first sacrificial layer, and a second sacrificial layer is formed on the diaphragm;

[0057] Step S2, forming an interface layer on a surface of the second sacrificial layer, the interface layer covers an outer peripheral edge region of the second sacrificial layer;

[0058] Step S3, forming a third sacrificial layer on the second sacrificial layer and the interface layer;

[0059] Step S4, forming a back plate layer on a surface of the third sacrificial layer, the back plate layer is formed with a release hole exposing a part of a surface of the third sacrificial layer;

[0060] Step S5: Remove a portion of the second sacrificial layer and a portion of the third sacrificial layer to form a cavity between the backplate layer and the diaphragm, so that a portion of the backplate layer is suspended above the diaphragm;

[0061] Step S6: A back cavity is formed on the second surface of the substrate, wherein the second surface is opposite to the first surface, and the back cavity extends from the second surface of the substrate through the substrate and the first sacrificial layer and exposes a portion of the surface of the diaphragm.

[0062] The method for fabricating MEMS devices of the present invention improves interface properties by setting an interface layer, thereby reducing etching damage to the interface material during etching, and thus reducing interface cracks and improving product yield.

[0063] Example 1

[0064] Below, for reference Figures 2-3H The fabrication method of the MEMS device of the present invention is described in detail, wherein, Figure 2 A flowchart illustrating a method for fabricating a MEMS device according to a specific embodiment of the present invention is shown. Figures 3A-3H The diagram shows a cross-sectional view of the device obtained by sequentially implementing a method for fabricating a MEMS device according to a specific embodiment of the present invention.

[0065] Exemplarily, the method for fabricating the MEMS device of the present invention includes the following steps:

[0066] First, step S1 is performed, a substrate is provided, a first sacrificial layer is formed on a first surface of the substrate, a diaphragm is formed on the first sacrificial layer, and a second sacrificial layer is formed on the diaphragm.

[0067] The MEMS device can be any suitable device known to those skilled in the art. In this embodiment, the technical solution of the present invention is explained and illustrated mainly by taking the case of the MEMS device being a MEMS microphone.

[0068] Specifically, such as Figure 3A As shown, the substrate 300 is a bulk silicon substrate, which can be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs or other III / V compound semiconductors, including multilayer structures composed of these semiconductors, or silicon on insulator (SOI), silicon on insulator (SSOI), silicon on insulator (S-SiGeOI), silicon on insulator (SiGeOI), and germanium on insulator (GeOI), etc.

[0069] In one example, such as Figure 3AAs shown, a patterned first sacrificial layer 301 is formed on the first surface of the substrate 300, wherein the first sacrificial layer 301 is selected from an oxide layer, such as silicon oxide and silicon oxide doped with carbon (SiOC), and the like, but is not limited to the above examples.

[0070] In addition, the first sacrificial layer 301 can be formed by various deposition methods commonly used in the art, such as by chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD), and the like.

[0071] The first sacrificial layer 301 is then patterned, and optionally includes the following steps:

[0072] A mask layer, such as a photoresist layer, is formed on the first sacrificial layer 301;

[0073] The first sacrificial layer 301 is etched using the mask layer as a mask, and then the mask layer is removed.

[0074] Dry etching, reactive ion etching (RIE), ion beam etching, and plasma etching can be selected in this step.

[0075] In one example, as shown, a diaphragm 302 is formed on the first sacrificial layer 301 to cover the first sacrificial layer 301. The diaphragm 302 can be selected from polysilicon, SiGe, and the like, and is not limited to a certain material. Figure 3B

[0076] The deposition method of the diaphragm 302 can 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).

[0077] The diaphragm 302 is then patterned, and optionally includes the following steps:

[0078] A mask layer, such as a photoresist layer, is formed on the diaphragm 302;

[0079] The photoresist layer is exposed and developed to remove the outer portion of the photoresist layer, exposing the diaphragm 302;

[0080] The diaphragm is then etched using the mask layer as a mask, and optionally, the outer edge of the etched diaphragm and the outer edge of the first sacrificial layer 301 are substantially flush, and then the mask layer is removed.

[0081] In one example, as shown, a diaphragm 302 is formed on the first sacrificial layer 301 to cover the first sacrificial layer 301. The diaphragm 302 can be selected from polysilicon, SiGe, and the like, and is not limited to a certain material. Figure 3C ​As shown, a patterned second sacrificial layer 303 is formed on the diaphragm 302. The second sacrificial layer 303 is selected from oxide layers, such as silicon oxide and silicon carbide oxide (SiOC), but is not limited to the above examples.

[0082] Furthermore, the second sacrificial layer 303 can be formed by various deposition methods commonly used in the art, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).

[0083] The second sacrificial layer 303 is then patterned, optionally including the following steps:

[0084] A mask layer, such as a photoresist layer, is formed on the second sacrificial layer 303;

[0085] The second sacrificial layer 303 is etched using the mask layer as a mask to form a via and expose a portion of the surface of the diaphragm 302, after which the mask layer is removed. The via formation step can be performed selectively. In some embodiments, the mask layer can be made to expose the edge region of the second sacrificial layer 303, and then the edge region of the second sacrificial layer 303 is etched using the mask layer as a mask. Optionally, the etched second sacrificial layer 303 also surrounds the edges of the diaphragm and the first sacrificial layer.

[0086] In this step, dry etching, reactive ion etching (RIE), ion beam etching, and plasma etching can be selected.

[0087] Subsequently, step S2 is performed to form an interface layer on the surface of the second sacrificial layer, the interface layer covering the outer peripheral edge region of the second sacrificial layer.

[0088] Specifically, such as Figure 3D As shown, an interface material layer is deposited on the surface of the second sacrificial layer 303, and the interface material layer is patterned to form an interface layer 304. Optionally, the interface layer 304 covers the outer peripheral edge region of the second sacrificial layer 303, and the interface layer 304 has a ring-shaped structure, such as a circular ring, or other suitable shape.

[0089] In this invention, to further simplify the process steps, optionally, the step of patterning the interface material layer includes:

[0090] A mask layer, such as a photoresist layer, is formed on the interface material layer;

[0091] Then, the interface material layer is etched using the mask layer as a mask to form the interface layer 304.

[0092] In this step, dry etching, reactive ion etching (RIE), ion beam etching, and plasma etching can be selected.

[0093] In this embodiment, the material of the interface layer 304 can be silicon nitride or other materials that can improve the interface, such as polysilicon.

[0094] The thickness of the interface layer 304 can be reasonably set according to actual needs. For example, the thickness range of the interface layer 304 is 5-100 angstroms, or other suitable ranges.

[0095] Optionally, the interface layer 304 may use a different material than the first sacrificial layer, the second sacrificial layer, and the subsequent third sacrificial layer.

[0096] Subsequently, step S3 is performed to form a third sacrificial layer on the second sacrificial layer and the interface layer.

[0097] Specifically, such as Figure 3E As shown, a patterned third sacrificial layer 305 is formed on the second sacrificial layer 303 and the interface layer 304. The third sacrificial layer 305 is selected from oxide layers, such as silicon oxide and silicon carbide oxide (SiOC), but is not limited to the above examples.

[0098] Furthermore, the third sacrificial layer 305 can be formed by various deposition methods commonly used in the art, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).

[0099] The third sacrificial layer 305 is then patterned, optionally including the following steps:

[0100] A mask layer, such as a photoresist layer, is formed on the third sacrificial layer 305;

[0101] The third sacrificial layer 305 is etched using the mask layer as a mask to form a through-hole located outside the region where the cavity is to be formed, exposing a portion of the surface of the diaphragm 302. The mask layer is then removed. In some embodiments, the mask layer may be made to expose the edge region of the third sacrificial layer 305, and then the edge region of the third sacrificial layer 305 is etched using the mask layer as a mask. Optionally, the edge of the etched third sacrificial layer 305 is substantially flush with the edge of the second sacrificial layer 303.

[0102] In this step, dry etching, reactive ion etching (RIE), ion beam etching, and plasma etching can be selected.

[0103] Subsequently, step S4 is performed to form a backplate layer on the surface of the third sacrificial layer, wherein a release hole is formed in the backplate layer that exposes a portion of the surface of the third sacrificial layer.

[0104] Specifically, in some embodiments, the method of forming the backsheet layer may include the following steps: such as Figure 3FAs shown, a backplate material layer is deposited to cover the surface of the third sacrificial layer 305, wherein the backplate material layer also covers the bottom and sidewall of the through hole when the through hole exposing part of the surface of the diaphragm is formed in the second and third sacrificial layers.

[0105] In one example, as shown, Figure 3F The backplate material layer is etched to form the backplate layer 307 and the re-wiring layer 306 separated from the backplate layer 307. The backplate layer 307 can be made of polycrystalline silicon, SiGe, etc., and is not limited to a certain material. In the embodiment of the present application, the backplate layer 307 and the re-wiring layer 306 can be formed synchronously by the backplate material layer, and in other embodiments, the backplate layer and the re-wiring layer 306 can be formed by independent steps in sequence. Thus, the backplate layer 307 and the re-wiring layer 306 can also be made of different materials.

[0106] The deposition method of the backplate material layer can be one of chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD), such as low pressure chemical vapor deposition (LPCVD), laser ablation deposition (LAD), and selective epitaxial growth (SEG).

[0107] In one example, as shown, Figure 3F A release hole penetrating the backplate layer 307 is formed in the backplate layer 307, and the release hole exposes part of the surface of the third sacrificial layer 305. The release hole can be formed by different photolithography combined with etching process. Alternatively, the release hole can also be used as an acoustic hole.

[0108] In one example, as shown, Figure 3F The re-wiring layer 306 covers the bottom and sidewall of the through hole and partially extends onto the surface of the third sacrificial layer 305.

[0109] Alternatively, in other embodiments, the method of forming the re-wiring layer 306 includes:

[0110] A through hole is formed outside the region where the cavity is to be formed in the second and third sacrificial layers, and the through hole exposes part of the surface of the diaphragm. The through hole can be formed when the second and third sacrificial layers are etched as described above, or can be formed after the backplate layer is formed. The re-wiring layer 306 is formed, and the re-wiring layer covers the bottom and sidewall of the through hole and partially extends onto the surface of the third sacrificial layer. Alternatively, a seed layer can be deposited on the bottom and sidewall of the through hole and part of the surface of the third sacrificial layer 305 before the re-wiring layer 306 is formed.

[0111] Optionally, the seed layer can be formed by electroplating or electroless plating. In some embodiments, the seed layer can be formed by physical vapor deposition or other suitable techniques. It is to be noted that the seed layer is a metal layer, which can include one or more metal layers. For example, the seed layer can include a first metal layer and a second metal layer on the first metal layer, the first metal layer can be a titanium layer, and the second metal layer can be a copper layer. In some embodiments, the seed layer can also be made of other suitable metals. In this embodiment, the re-distribution layer 306 can be multi-layered, and the multi-layered re-distribution layer 306 can be formed by repeating the electroplating process.

[0112] After forming the re-distribution layer 306 and the back plate layer 307, the following steps are further included:

[0113] A first pad 308 is formed on the re-distribution layer 306, and a second pad 309 is formed on the back plate layer 307, wherein the first pad 308 is electrically connected to the diaphragm 302 through the re-distribution layer 306, and the second pad 309 is electrically connected to the back plate layer 307.

[0114] Subsequently, step S5 is performed to remove part of the second sacrificial layer and part of the third sacrificial layer to form a cavity between the back plate layer and the diaphragm, so that part of the back plate layer is suspended above the diaphragm.

[0115] Specifically, as shown in FIG. 5, part of the second sacrificial layer 303 and part of the third sacrificial layer 305 are removed through the release hole to form a cavity between the back plate layer 307 and the diaphragm 302, so that part of the back plate layer 307 is suspended above the diaphragm 302. Figure 3H

[0116] Finally, step S6 is performed to form a back cavity on the second surface of the substrate, wherein the second surface is opposite to the first surface, the back cavity penetrates through the substrate and the first sacrificial layer from the second surface of the substrate and exposes part of the surface of the diaphragm.

[0117] Optionally, as shown in FIG. 6 and FIG. 7, the step of forming the back cavity 311 includes: Figure 3G Figure 3H

[0118] The substrate 300 is thinned from the second surface of the substrate 300, for example, by a chemical mechanical polishing process and / or an etching process, etc. The thickness of the thinned substrate 300 can be reasonably set according to actual needs, which is not specifically limited here.

[0119] The substrate 300 is etched from the second surface of the substrate 300 and stopped at the first sacrificial layer 301 to form a cavity. In this step, dry etching or wet etching can be used to remove part of the substrate 300.

[0120] ​​​In some embodiments, the first sacrificial layer 301 can be removed at the same time as the second sacrificial layer 303 and the third sacrificial layer 305 are removed, or the first sacrificial layer 301 can be removed before the second sacrificial layer 303 and the third sacrificial layer 305 are removed.

[0121] In this embodiment, the step of forming the back cavity 311 and the step of forming the cavity can be performed at the same time, or can be performed in sequence, or can be performed by using different etching methods. In some embodiments, the cavity and the back cavity 311 at least partially correspond.

[0122] In this embodiment, the first sacrificial layer 301, the second sacrificial layer 303 and the third sacrificial layer 305 are removed by using a wet etching method, wherein the first etching rate of the wet etching method on the first sacrificial layer 301, the second sacrificial layer 303 and the third sacrificial layer 305 is higher than the second etching rate of the wet etching method on the interface layer 304. In this embodiment, the first etching rate is twice or more than twice the second etching rate. Thus, when the etching of the first sacrificial layer 301, the second sacrificial layer 303 and the third sacrificial layer 305 meets the requirements, the interface layer 304 is still arranged at the junction of the second sacrificial layer and the third sacrificial layer 305. Optionally, the wet etching method can use a hydrofluoric acid solution, such as a buffer oxide etchant (BOE) or a buffer solution of hydrofluoric acid (BHF) or a hydrofluoric acid vapor.

[0123] It is worth mentioning that the above steps are only examples, and the order of the above steps can also be adjusted without conflict.

[0124] The key steps of the method for manufacturing the MEMS device of the present application have been described so far. Other steps can also be included in the complete manufacturing of the MEMS device, which will not be described here.

[0125] In summary, the method for manufacturing the MEMS device of the present application sets the interface layer to reduce the etching damage to the material at the interface during etching, thereby improving the interface properties and reducing the cracks at the interface, and improving the product yield.

[0126] Embodiment two

[0127] The present application also provides a MEMS device manufactured by the method of the aforementioned embodiment one, as shown in Figure 3H The MEMS device of the present application comprises:

[0128] a substrate 300, the substrate 300 comprising a first surface and a second surface opposite to the first surface;

[0129] The first sacrificial layer 301 covers a portion of the first surface of the substrate 300;

[0130] A diaphragm 302 is located on the first sacrificial layer 301, and the outer peripheral edge region of the diaphragm 302 overlaps with the first sacrificial layer 301;

[0131] The second sacrificial layer 303 covers a portion of the diaphragm 302;

[0132] Interface layer 304 covers the outer peripheral edge region of the second sacrificial layer 303;

[0133] The third sacrificial layer 305 covers the second sacrificial layer 303 and the interface layer 304;

[0134] Backing plate layer 307, a portion of which is suspended above the diaphragm 302, with the outer peripheral edge of the backing plate layer 307 covering the third sacrificial layer 305;

[0135] A cavity 310 is formed between the backplate layer 307 and the diaphragm 302, and extends through the second sacrificial layer 303 and the third sacrificial layer 305;

[0136] The back cavity 311 extends from the second surface of the substrate 300 through the substrate 300 and the first sacrificial layer 301 and exposes a portion of the surface of the diaphragm 302.

[0137] Specifically, such as Figure 3H As shown, the substrate 300 is a bulk silicon substrate, which can be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs or other III / V compound semiconductors, including multilayer structures composed of these semiconductors, or silicon on insulator (SOI), silicon on insulator (SSOI), silicon on insulator (S-SiGeOI), silicon on insulator (SiGeOI), and germanium on insulator (GeOI), etc.

[0138] In this embodiment, the first sacrificial layer 301, the second sacrificial layer 303, and the third sacrificial layer 305 may be oxide layers, such as silicon oxide and silicon oxide with carbon doped carbon (SiOC), but are not limited to the examples described above.

[0139] In this embodiment, the diaphragm 302 can be made of materials such as polycrystalline silicon or SiGe, and is not limited to any one of them.

[0140] The deposition method of the diaphragm 302 can be one of low pressure chemical vapor deposition (LPCVD), laser ablation deposition (LAD) and selective epitaxial growth (SEG) formed by chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method or atomic layer deposition (ALD) method.

[0141] As shown in the figure, the outer edge of the interface layer 304 protrudes from the edges of the second sacrificial layer 303 and the third sacrificial layer 305. Figure 3H

[0142] In this embodiment, the material of the interface layer 304 can be silicon nitride, or other materials that can improve the interface, such as polysilicon.

[0143] In this embodiment, the thickness of the interface layer 304 can be reasonably set according to actual needs, for example, the thickness of the interface layer 304 ranges from 5 to 100 angstroms, or other suitable ranges.

[0144] In this embodiment, the backplate layer 307 can be made of polysilicon, SiGe or other materials, and is not limited to a certain type.

[0145] The deposition method of the backplate layer 307 can be one of low pressure chemical vapor deposition (LPCVD), laser ablation deposition (LAD) and selective epitaxial growth (SEG) formed by chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method or atomic layer deposition (ALD) method.

[0146] Further, as shown in the figure, the MEMS device of the present application further comprises: Figure 3H

[0147] A plurality of release holes are arranged at intervals and penetrate the backplate layer 307, and the release holes expose the diaphragm 302, which can be used as the sound hole of a microphone;

[0148] A rewiring layer 306 is formed in the second sacrificial layer 303 and the third sacrificial layer 305 outside the cavity 310, and the through hole exposes part of the surface of the diaphragm 302, and the rewiring layer 306 covers the bottom and sidewall of the through hole and partially extends to the surface of the third sacrificial layer 305;

[0149] A first pad 308 and a second pad 309, the first pad 308 is arranged on the rewiring layer 306, and the second pad 309 is arranged on the backplate layer 307, wherein the first pad 308 is electrically connected to the diaphragm 302 through the rewiring layer 306, and the second pad 309 is electrically connected to the backplate layer 307.

[0150] ​​The MEMS device can be a MEMS microphone device. During operation of the MEMS microphone, gas enters the cavity through the release hole in the back plate layer 307, so that the sound pressure of the gas acts on the diaphragm 302 to cause the diaphragm 302 to vibrate, and the gas is further discharged through the release hole in the back plate layer 307. The diaphragm 302 and the back plate layer 307 can form a parallel-plate capacitor. When external sound pressure acts on the diaphragm 302, the diaphragm 302 vibrates, the distance between the diaphragm 302 and the back plate layer 307 changes, and the capacitance changes. The capacitance change is used for calculation and operation to complete the conversion between the sound signal and the electric signal.

[0151] The structure of the MEMS device of the present application has been described above. The complete device can also include other structures, which are not described herein.

[0152] The interface layer is formed in the MEMS device of the present application, which reduces the etching damage to the material at the interface during etching, improves the interface properties, reduces the cracks at the interface, and improves the product yield.

[0153] Example Three

[0154] The present application also provides an electronic device comprising the MEMS device of example two or the MEMS device prepared by the method of example one.

[0155] The electronic device can be a mobile phone, a tablet computer, a notebook computer, a netbook, a game console, a television, a VCD, a DVD, a navigation device, a camera, a video camera, a voice recorder, an MP3, an MP4, a PSP, or any other electronic product or device. The electronic device can also be an intermediate product having the MEMS device, such as a mobile phone mainboard having the integrated circuit.

[0156] The electronic device also has the advantages of the MEMS device.

[0157] In the electronic device, Figure 4 An example of a mobile phone is shown. The mobile phone 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 included in a housing 401.

[0158] The electronic device uses the MEMS device of the present application, and thus has all the advantages of the MEMS device.

[0159] While several embodiments have been described, it should be apparent that many modifications can be made by those skilled in the art without departing from the spirit and scope of the disclosed concept. More specifically, it is intended that modifications and variations of the subject matter described herein will occur to those skilled in the art upon reading this disclosure, and such modifications and variations are intended to be included within the scope of the disclosure. Although specific arrangements were described herein, it will be appreciated that other arrangements can be utilized and the generic or specific components described herein can be arranged and combined in a wide variety of other ways. Other substitutions and modifications will occur to those skilled in the art, and are also intended to be within the scope of the application.

Claims

1. A method of fabricating a MEMS device, characterized by, The method comprises: providing a substrate, a first sacrificial layer is formed on a first surface of the substrate, a diaphragm is formed on the first sacrificial layer, and a second sacrificial layer is formed on the diaphragm; forming an interface layer on a surface of the second sacrificial layer, the interface layer covering a peripheral edge region of the second sacrificial layer; forming a third sacrificial layer on the second sacrificial layer and the interface layer; forming a backplate layer on a surface of the third sacrificial layer, the backplate layer having a release hole formed therein to expose a part of a surface of the third sacrificial layer; removing part of the second sacrificial layer and part of the third sacrificial layer to form a cavity between the backplate layer and the diaphragm, and to suspend part of the backplate layer above the diaphragm; forming a back cavity on a second surface of the substrate, wherein the second surface is opposite to the first surface, the back cavity penetrating through the substrate and the first sacrificial layer from the second surface of the substrate and exposing a part of a surface of the diaphragm.

2. The method of claim 1, wherein, Forming a back cavity on a second surface of the substrate comprises: thinning the substrate from the second surface of the substrate before removing part of the second sacrificial layer and part of the third sacrificial layer; stopping etching the substrate from the second surface of the substrate at the first sacrificial layer to form a cavity; removing part of the first sacrificial layer while removing part of the second sacrificial layer and part of the third sacrificial layer to form the back cavity.

3. The method of claim 2, wherein, Removing part of the first sacrificial layer, part of the second sacrificial layer, and part of the third sacrificial layer comprises: removing part of the first sacrificial layer, part of the second sacrificial layer, and part of the third sacrificial layer by wet etching, wherein a first etching rate of the wet etching on the first sacrificial layer, the second sacrificial layer, and the third sacrificial layer is higher than a second etching rate of the wet etching on the interface layer.

4. The method of claim 3, wherein, The first etching rate is at least twice the second etching rate.

5. The method of claim 1, wherein, The method further comprises: forming a through hole outside a region where the cavity is to be formed in the second sacrificial layer and the third sacrificial layer, the through hole exposing a part of a surface of the diaphragm; forming a rewiring layer, the rewiring layer covering a bottom and a sidewall of the through hole and partially extending onto a surface of the third sacrificial layer; forming a first pad on the rewiring layer and a second pad on the backplate layer, wherein the first pad is electrically connected to the diaphragm through the rewiring layer, and the second pad is electrically connected to the backplate layer.

6. The method of claim 1, wherein, The interface layer is annular.

7. A MEMS device, characterized by The MEMS device comprises: a substrate comprising a first surface and a second surface opposite to the first surface; a first sacrificial layer covering part of the first surface of the substrate; a diaphragm on the first sacrificial layer, and a peripheral edge region of the diaphragm overlapping the first sacrificial layer; a second sacrificial layer covering part of the diaphragm; an interface layer covering a peripheral edge region of the second sacrificial layer; a third sacrificial layer covering the second sacrificial layer and the interface layer; a backplate layer, part of the backplate layer being suspended above the diaphragm, and a peripheral edge of the backplate layer covering the third sacrificial layer; a cavity formed between the back plate layer and the diaphragm and penetrating through the second and third sacrificial layers; a back cavity penetrating through the substrate and the first sacrificial layer from the second surface of the substrate and exposing part of the surface of the diaphragm.

8. The MEMS device of claim 7, wherein, the outer edge of the interface layer protrudes from the edge of the second sacrificial layer and the edge of the third sacrificial layer; and / or, the interface layer is annular.

9. The MEMS device of claim 7, wherein, The MEMS device further comprises: a plurality of release holes spaced apart from each other and penetrating through the back plate layer, the release holes exposing the diaphragm; a rewiring layer formed in the second and third sacrificial layers outside the cavity, the rewiring layer having a through hole exposing part of the surface of the diaphragm, the rewiring layer covering the bottom and sidewall of the through hole and partially extending onto the surface of the third sacrificial layer; a first pad and a second pad, the first pad being disposed on the rewiring layer, the second pad being disposed on the back plate layer, wherein the first pad is electrically connected to the diaphragm through the rewiring layer, and the second pad is electrically connected to the back plate layer.

10. An electronic device, comprising: The electronic device comprises the MEMS device of any one of claims 7 to 9.

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