Micro-electromechanical structure and manufacturing method thereof, wafer, microphone and terminal

Abstract

The present application discloses a micro-electromechanical structure and a manufacturing method thereof, a wafer, a microphone and a terminal. The manufacturing method comprises: forming a first back plate above a substrate; forming a second sacrificial layer on the first back plate; forming a diaphragm on the second sacrificial layer, the diaphragm extending to the substrate along the side wall of the second sacrificial layer and the side wall of the first back plate; and removing part of the second sacrificial layer, with the remaining second sacrificial layer serving as a second supporting portion. The manufacturing method reduces the risk of the release liquid corroding the side wall of the second sacrificial layer during the release process by allowing the diaphragm to cover the side wall of the second sacrificial layer.

Description

Technical Field

[0001] The present application relates to the field of semiconductor device manufacturing, and more specifically, to a micro-electromechanical structure and a manufacturing method thereof, a wafer, a microphone and a terminal. Background Art

[0002] Microphones based on micro-electromechanical systems (MEMS) are called MEMS microphones, which mainly include a diaphragm and a back plate, with a gap between the diaphragm and the back plate. Changes in air pressure will cause the diaphragm to deform, and the capacitance between the diaphragm and the electrode plate will change, which will be converted into an electrical signal output.

[0003] In common MEMS microphones, it is necessary to use a release process to remove part of the sacrificial layer to form a gap between the back plate and the diaphragm. However, the release solution in the release process will corrode laterally from the scribe line toward the tube core, making the outer wall of the support part formed by each sacrificial layer irregular in shape and difficult to control in size, or even completely corroded, which will cause changes in the stress of the back plate and diaphragm of the tube core, affecting the performance of the product. In addition, due to the irregular shape of the outer wall of each support part, the mechanical strength of the back plate and diaphragm at the connection of the support part is affected, resulting in insufficient strength of the tube core, which will fail with a slight impact or fall.

[0004] Furthermore, since the diaphragm material is mostly made of polycrystalline silicon, the polycrystalline silicon material has an impact on the dicing process, so the diaphragm corresponding to the dicing position needs to be etched away. However, the substrate material is mostly made of single crystal silicon. During the process of etching the diaphragm, the single crystal silicon substrate will also be etched to form defects. In the subsequent release process, the defective substrate causes the mechanical properties of the product to deteriorate, thereby affecting the product yield.

[0005] Therefore, it is desirable to provide an improved micro-electromechanical structure to enhance the performance of products. Summary of the invention

[0006] In view of this, the present invention provides an improved micro-electromechanical structure and its manufacturing method, wafer, microphone and terminal, which reduces the risk of release liquid corroding the outer wall of the second support part during the release process by allowing the diaphragm to cover the outer wall of the second support part.

[0007] According to a first aspect of an embodiment of the present invention, a method for manufacturing a micro-electromechanical structure is provided, comprising: forming a first backplane above a substrate; forming a second sacrificial layer on the first backplane; forming a diaphragm on the second sacrificial layer, the diaphragm extending onto the substrate along side walls of the second sacrificial layer and side walls of the first backplane; forming a cavity in the substrate; and removing a portion of the second sacrificial layer, with the remaining second sacrificial layer serving as a second supporting portion.

[0008] Optionally, before forming the first back plate, the manufacturing method also includes: forming a first sacrificial layer on the substrate, and after forming the diaphragm, the manufacturing method also includes removing a portion of the first sacrificial layer, and the remaining first sacrificial layer serves as a first supporting portion, wherein the first back plate is located between the first sacrificial layer and the second sacrificial layer, and the diaphragm also contacts the side wall of the first sacrificial layer.

[0009] Optionally, the method further includes: forming a third sacrificial layer on the diaphragm; forming a second back plate on the third sacrificial layer; and removing a portion of the third sacrificial layer, with the remaining third sacrificial layer serving as a third supporting portion.

[0010] Optionally, the step of forming the second backplate includes: forming a lower dielectric layer on the third sacrificial layer; forming a first groove extending from the surface of the lower dielectric layer to the surface of the diaphragm; forming a conductive layer on the lower dielectric layer, the conductive layer also filling the first groove and connected to the diaphragm; and forming an upper dielectric layer on the conductive layer, wherein the conductive layer filled in the first groove serves as the sinking portion of the second backplate.

[0011] Optionally, the conductive layer of the second back plate is a polysilicon conductive layer.

[0012] Optionally, before forming an upper dielectric layer on the conductive layer, the step of forming the second backplane also includes: forming a second groove extending from the surface of the conductive layer to the surface of the lower dielectric layer to separate the conductive layer located on the third sacrificial layer into a central portion and an edge portion, wherein the edge portion of the conductive layer surrounds the central portion, and the sunken portion of the second backplane is connected to the edge portion of the conductive layer, and the upper dielectric layer also covers the side and bottom surfaces of the second groove.

[0013] Optionally, before forming the third sacrificial layer, the manufacturing method also includes: forming a third groove extending from the surface of the diaphragm to the surface of the second sacrificial layer to separate the diaphragm located on the second sacrificial layer into a central portion and an edge portion, wherein the edge portion of the diaphragm surrounds the central portion, and the edge portion of the diaphragm extends successively along the side wall of the second sacrificial layer, the side wall of the first back plate, and the side wall of the first sacrificial layer to the substrate, and the third sacrificial layer is also filled in the third groove.

[0014] Optionally, before forming the diaphragm, the manufacturing method also includes: forming an isolation groove extending from the surface of the second sacrificial layer to the surface of the substrate, the isolation groove separating the stacked structure consisting of the first sacrificial layer, the first back plate and the second sacrificial layer into a plurality of units arranged in an array, wherein the diaphragm covers the side and bottom surfaces of the isolation groove.

[0015] Optionally, the step of forming the isolation groove includes: before forming the second sacrificial layer, removing a portion of the second back plate to expose a portion of the first sacrificial layer, and then forming the second sacrificial layer connected to the exposed first sacrificial layer; and at the connection between the second sacrificial layer and the first sacrificial layer, removing a portion of the second sacrificial layer and the first sacrificial layer to form the isolation groove.

[0016] Optionally, the step of forming the isolation trench further includes: after removing a portion of the second backplane and before forming the second sacrificial layer, removing a portion of the first sacrificial layer to expose a portion of the substrate, and the second sacrificial layer formed thereafter is also connected to the exposed substrate.

[0017] Optionally, an isotropic wet etching process is used to remove a portion of the second sacrificial layer and the first sacrificial layer, so that the side surface of the isolation groove is inclined, wherein the bottom width of the isolation groove is smaller than the opening width of the isolation groove.

[0018] Optionally, the diaphragm is a polysilicon diaphragm.

[0019] Optionally, the isolation groove exposes the surface of the substrate, and the step of forming the diaphragm includes: depositing amorphous silicon on the surface of the second sacrificial layer, the side of the isolation groove and the exposed surface of the substrate; and through an annealing process, allowing the amorphous silicon in contact with the exposed substrate to grow along the crystal of the substrate.

[0020] Optionally, the polysilicon diaphragm has doped impurities, and the doped impurities include phosphorus.

[0021] Optionally, after removing a portion of the second sacrificial layer, the manufacturing method further comprises cutting the substrate and the diaphragm along a scribe line to separate the plurality of units arranged in an array, wherein the position of the scribe line corresponds to the isolation groove.

[0022] According to a second aspect of an embodiment of the present invention, a wafer is provided, having a scribe line, the wafer comprising: a substrate; a plurality of array units located above the substrate, adjacent array units being separated by the scribe line; and a diaphragm covering the surface of the substrate where the plurality of array units and the scribe line are located, wherein each of the array units comprises a first back plate and a second supporting portion located on the first back plate.

[0023] Optionally, the substrate has cavities corresponding to the multiple array units, each of the cavities has a central axis perpendicular to the corresponding first back plate, each of the second support parts has an outer side wall away from the corresponding central axis, each of the array units also includes a first support part, located between the corresponding first back plate and the substrate, each of the first support parts has an outer side wall away from the corresponding central axis, and the diaphragm extends to the surface of the substrate through the surface of the second support part, the outer side wall of the second support part, the side wall of the first back plate and the outer side wall of the first support part in sequence.

[0024] Optionally, it further includes: a plurality of third supporting parts, which are located on the diaphragm and correspond to the plurality of array units; and a plurality of second back plates, which are respectively located on the corresponding third supporting parts.

[0025] Optionally, each of the third supporting portions has an outer side wall away from the corresponding central axis, and each of the third supporting portions has a sinking portion extending along the outer side wall of the corresponding third supporting portion to the diaphragm.

[0026] According to a third aspect of an embodiment of the present invention, a micro-electromechanical structure is provided, comprising: a substrate having a cavity; a first back plate located above the substrate; a second supporting portion located on the first back plate; a diaphragm located on the second supporting portion; and a second back plate insulated and supported on the diaphragm, wherein the cavity has a central axis perpendicular to the first back plate, the second supporting portion has an outer side wall away from the central axis, and the diaphragm extends to the substrate via a surface of the second supporting portion, an outer side wall of the second supporting portion, and a side wall of the first back plate in sequence, and covers the surface edge of the substrate.

[0027] Optionally, it further includes a first supporting portion, located between the substrate and the first back plate, wherein the first supporting portion has an outer side wall away from the central axis, and the diaphragm also covers the outer side wall of the first supporting portion.

[0028] Optionally, a third supporting portion is further included, located between the diaphragm and the second back plate.

[0029] Optionally, the third supporting portion has an outer side wall away from the central axis of the cavity, and the second back plate includes: a lower dielectric layer, a conductive layer and an upper dielectric layer, wherein a portion of the conductive layer is located between the lower dielectric layer and the upper dielectric layer, and another portion of the conductive layer serves as a sinking portion of the second back plate, penetrating the lower dielectric layer and extending along the outer side wall of the third supporting portion to the diaphragm.

[0030] Optionally, in the second backplane, the upper dielectric layer is connected to the lower dielectric layer through the conductive layer to separate the conductive layer located on the third support portion into a central portion and an edge portion, wherein the edge portion of the conductive layer surrounds the central portion, and the sunken portion of the second backplane is connected to the edge portion of the conductive layer.

[0031] Optionally, a portion of the third supporting portion passes through the diaphragm and is connected to the second supporting portion to separate the diaphragm located on the second supporting portion into a central portion and an edge portion, wherein the edge portion of the diaphragm surrounds the central portion, and the edge portion of the diaphragm extends sequentially along the outer side wall of the second supporting portion, the side wall of the first back plate, and the outer side wall of the first supporting portion to the substrate.

[0032] Optionally, the outer side wall of the second support portion, the side wall of the first back plate and the outer side wall of the first support portion form an inclined surface, and a direction along the outer side wall of the first support portion toward the central axis of the cavity forms an acute angle with the inclined surface.

[0033] According to a fourth aspect of the embodiments of the present invention, a microphone is provided, comprising the micro-electromechanical structure as described above.

[0034] According to a fifth aspect of the embodiments of the present invention, a terminal is provided, comprising the microphone as described above.

[0035] In the step of forming a diaphragm in the manufacturing method of the micro-electromechanical structure provided by an embodiment of the present invention, the diaphragm is extended onto the substrate along the side walls of the second sacrificial layer and the side walls of the first back plate, thereby reducing the risk of the release liquid corroding the outer wall of the second support part during the release process when the second support part of the second sacrificial layer is utilized.

[0036] Similarly, when the first support portion is formed by using the first sacrificial layer, the diaphragm covers the side wall of the first sacrificial layer, thereby reducing the risk of the release liquid corroding the outer side wall of the first support portion during the release process.

[0037] By setting a sinking portion in the second back plate, the sinking portion of the second back plate extends from the outer wall of the third support portion to the diaphragm. Since the sinking portion of the second back plate is continuous with the main part of the second back plate (the part located on the third support portion), the mechanical strength of the junction between the second back plate and the outer wall of the third support portion is increased, thereby improving the performance of the product. At the same time, the sinking portion of the second back plate also defines the morphology and outer dimensions of the outer wall of the third support portion, preventing the release solution of the release process from corroding the outer wall of the third support portion, thereby improving the consistency of the product and the smoothness of the surface.

[0038] Since the material of the sunken part of the second back plate and the material of the diaphragm are both polycrystalline silicon, the polycrystalline silicon protective wall of a single material composed of the area of ​​the diaphragm covering the first back plate, the first support part, the second support part and the sunken part of the second back plate reduces the defects of the contact interface, thereby further improving the corrosion resistance to the released solution.

[0039] An isotropic wet etching process is used to make the side of the isolation groove into a slope, and the bottom width of the isolation groove is made smaller than the opening width of the isolation groove. When depositing the material used to form the diaphragm, the slope is continuous and no steps are formed, so that the diaphragm material can cover the side of the isolation groove more evenly, thereby enhancing the covering effect of the diaphragm, thereby further improving the corrosion resistance to the release solution, and also enhancing the protection effect of the diaphragm on the first support part, the second support part and the first back plate.

[0040] By separating the conductive layer in the second back plate into a central portion and an edge portion, the sunken portion of the second back plate is connected to the edge portion of the conductive layer and electrically isolated from the central portion, thereby reducing parasitic capacitance in the product. By separating the diaphragm into a central portion and an edge portion, the portion connected to the substrate is the edge portion of the diaphragm and electrically isolated from the central portion, thereby reducing parasitic capacitance in the product.

[0041] By extending the diaphragm into the scribe line, when etching the structure above the diaphragm, the diaphragm in the scribe line acts as an etch stop layer to protect the scribe line. Preferably, phosphorus is doped into the polysilicon diaphragm to further improve the etching selectivity, thereby more effectively protecting the substrate.

[0042] When forming a polysilicon diaphragm, amorphous silicon is deposited in the isolation groove so that the amorphous silicon contacts the substrate at the bottom of the isolation groove. Amorphous silicon (amorphous silicon α-Si), also known as amorphous silicon, is a form of single silicon. During the annealing process, the amorphous silicon at the bottom of the isolation groove will grow along the crystal direction of the substrate, so that the crystal direction of the polysilicon diaphragm in contact with the substrate is consistent with the crystal direction of the substrate. During dicing, the polysilicon diaphragm has little effect on the dicing process. Therefore, the polysilicon diaphragm located in the dicing path does not need to be removed, thereby avoiding damage to the substrate caused by removing the polysilicon diaphragm.

[0043] Therefore, the micro-electromechanical structure and its manufacturing method, wafer, microphone and terminal provided by the present invention can greatly improve the performance of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present application, rather than limiting the present application.

[0045] Figure 1 A schematic diagram of a micro-electromechanical structure according to a first embodiment of the present invention is shown.

[0046] Figure 2a to Figure 2g A schematic diagram showing the manufacturing steps of the micro-electromechanical structure according to the first embodiment of the present invention is shown.

[0047] Figure 3 A schematic diagram of a micro-electromechanical structure according to a second embodiment of the present invention is shown. DETAILED DESCRIPTION

[0048] The present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale. In addition, some well-known parts may not be shown. For the sake of simplicity, the semiconductor structure obtained after several steps can be described in one figure.

[0049] It should be understood that when describing the structure of a device, when a layer or a region is referred to as being "on" or "over" another layer or another region, it may mean that it is directly on the other layer or another region, or that other layers or regions are included between it and the other layer or another region. Furthermore, if the device is turned over, the layer or a region will be "below" or "beneath" another layer or another region.

[0050] If the purpose is to describe the situation of being directly on another layer or another area, this article will use expressions such as "directly on..." or "on... and adjacent to...".

[0051] Many specific details of the present invention are described below, such as device structure, materials, dimensions, processing technology and techniques, so as to more clearly understand the present invention. However, as those skilled in the art will appreciate, the present invention may be implemented without following these specific details.

[0052] The present invention may be embodied in various forms, some examples of which will be described below.

[0053] Figure 1 A schematic diagram of a micro-electromechanical structure according to a first embodiment of the present invention is shown, wherein a dashed line indicates a central axis of the cavity 101 a perpendicular to the first back plate 120 , the diaphragm 130 and the second back plate 140 .

[0054] like Figure 1As shown, the micro-electromechanical structure of the first embodiment of the present invention includes: a substrate 101, a first support portion 111, a second support portion 112, a third support portion 113, a first back plate 120, a diaphragm 130 and a second back plate 140. The substrate 101 has a cavity 101a. The first support portion 111 is located at the edge of the substrate 101, and has an inner side wall close to the central axis of the cavity 101a and an outer side wall away from the central axis of the cavity 101a. The first back plate 120 is located on the first support portion 111 and covers the cavity 101a. The second support portion 112 is located on the first back plate 120, and the position corresponds to the first support portion 111. The second support portion 112 has an inner side wall close to the central axis of the cavity 101a and an outer side wall away from the central axis of the cavity 101a. The diaphragm 130 is located on the second support portion 112, and there is a gap 102 between it and the first back plate 120. The third support portion 113 is located on the diaphragm 130 and corresponds to the second support portion 112. The third support portion 113 has an inner wall close to the center axis of the cavity 101a and an outer wall away from the center axis of the cavity 101a. The second back plate 140 is located on the third support portion 113 and has a gap 103 between it and the diaphragm 130.

[0055] In this embodiment, the diaphragm 130 sequentially extends along the surface of the second support portion 112, the outer side wall of the second support portion 112, the side wall of the first back plate 120, and the outer side wall of the first support portion 111 to the substrate 101, and covers the surface edge of the substrate 101. In some specific embodiments, the outer side wall of the second support portion 112, the side wall of the first back plate 120, and the outer side wall of the first support portion 111 constitute an inclined surface. Among them, those skilled in the art can set the inclination angle of the inclined surface as needed.

[0056] In this embodiment, the second back plate 140 has a sinking portion 140a, the sinking portion 140a of the second back plate has an inner wall close to the central axis of the cavity 101a and an outer wall away from the central axis of the cavity 101a, and the sinking portion 140a of the second back plate extends along the outer wall of the third support portion 113 to the diaphragm 130.

[0057] In some specific embodiments, the first back plate 120 includes a lower dielectric layer 121, a conductive layer 122, and an upper dielectric layer 123, wherein the conductive layer 122 is sandwiched between the upper dielectric layer 123 and the lower dielectric layer 121. The second back plate 140 includes a lower dielectric layer 141, a conductive layer 142, and an upper dielectric layer 143, wherein a portion of the conductive layer 142 is sandwiched between the upper dielectric layer 143 and the lower dielectric layer 141, and another portion of the conductive layer 142 as a sinking portion 140a of the second back plate penetrates the lower dielectric layer 141 and extends along the outer side wall of the third support portion 113 to the diaphragm 130.

[0058] More specifically, the conductive layer 122 and the conductive layer 142 are made of the same material as the diaphragm 130, for example, both are polysilicon, the upper dielectric layer 123, the lower dielectric layer 121, the upper dielectric layer 143 and the lower dielectric layer 141 are made of, for example, silicon nitride, the first support portion 111, the second support portion 112 and the third support portion 113 are made of, for example, silicon oxide, and the substrate 101 is, for example, a silicon substrate or other substrates. Of course, those skilled in the art can make other arrangements for the materials of the substrate 101, the first support portion 111, the second support portion 112, the third support portion 113, the first back plate 120, the diaphragm 130 and the second back plate 140 as needed.

[0059] In this embodiment, the portions of the first back plate 120, the diaphragm 130, and the second back plate 140 corresponding to the gaps 102 and 103 are effective portions, and those skilled in the art can electrically isolate the effective portions of the substrate 101, the first back plate 120, the diaphragm 130, and the second back plate 140 from each other as needed. Taking the second back plate 140 as an example, in some specific embodiments, the upper dielectric layer 143 in the second back plate 140 is connected to the lower dielectric layer 141 through the conductive layer 142 to separate the conductive layer 142 located on the third support portion 113 into a central portion and an edge portion, so that the central portion and the edge portion of the conductive layer 142 are electrically isolated, the edge portion of the conductive layer 142 surrounds the central portion, and the sinking portion 140a of the second back plate is connected to the edge portion of the conductive layer 142. The connection between the upper dielectric layer 143 and the lower dielectric layer 141 corresponds to the third support portion 113, so that the central portion of the conductive layer 142 includes the effective portion of the second backplane 140, and the effective portion of the second backplane 140 is electrically isolated from the sinking portion 140a of the second backplane.

[0060] In this embodiment, the orthographic projection of the diaphragm 130 covering the outer wall of the second support portion 112, the side wall of the first back plate 120, and the outer wall of the first support portion 111 on the surface of the substrate 101 is in a circular shape surrounding the cavity 101a, and the orthographic projection of the sinking portion 140a of the second back plate on the surface of the substrate 101 is in a circular shape surrounding the cavity 101a. The first support portion 111 is the portion left on the substrate 101 after the sacrificial layer is released. The first support portion 111 is located on the peripheral edge of the substrate 101, and the first back plate 120 located above the first support portion 111 is supported on the substrate 101 by a fully fixed support method at the peripheral edge. The second support portion 112 is the portion left on the first back plate 120 after the sacrificial layer is released. The second support portion 112 is located on the peripheral edge of the first back plate 120, and the diaphragm 130 located above the second support portion 112 is supported and fixed by a fully fixed support method at the peripheral edge. The third support portion 113 is the portion remaining on the diaphragm 130 after the sacrificial layer is released. The third support portion 113 is located on the peripheral edge of the diaphragm 130, and the second back plate 140 located above the third support portion 113 is supported and fixed by a peripheral edge full fixation method.

[0061] In this embodiment, the micro-electromechanical structure further includes a plurality of pads (not shown) located on the second back plate 140 , which are used to electrically connect to the second back plate 140 , the diaphragm 130 , and the first back plate 120 .

[0062] Furthermore, the first back plate 120 also has a plurality of sound holes 11, and the second back plate 140 also has a plurality of sound holes 12 to use the micro-electromechanical structure for a microphone. The diaphragm 130 may also be provided with an air leak hole (not shown), wherein the number, shape, and size of the sound holes 11 and the air leak hole may be set by a person skilled in the art as required. The micro-electromechanical structure of this embodiment also includes a plurality of anti-adhesion structures 150, which are located on the surface of the second back plate 140 close to the diaphragm 130 to prevent the second back plate 140 from adhering to the diaphragm 130, and the plurality of anti-adhesion structures 150 are also located on the surface of the diaphragm 130 close to the first back plate 120 to prevent the first back plate 120 from adhering to the diaphragm 130.

[0063] Figure 1 The MEMS structure shown in FIG. 1 is a double back plate and single diaphragm structure. In some other embodiments, the third support portion 113 and the second back plate 140 may not be provided, so as to form a single back plate and single diaphragm structure. In some other embodiments, the first support portion 111 may not be provided.

[0064] Figure 2a to Figure 2g A schematic diagram showing the manufacturing steps of the micro-electromechanical structure according to the first embodiment of the present invention is shown.

[0065] like Figure 2a As shown, a first sacrificial layer 211 is formed on the substrate 101 , and a first back plate 120 is formed on the first sacrificial layer 211 .

[0066] In some specific embodiments, the step of forming the first back plate 120 includes: forming a lower dielectric layer 121 on the first sacrificial layer 211 , forming a conductive layer 122 on the lower dielectric layer 121 , and forming an upper dielectric layer 123 on the conductive layer 122 .

[0067] Furthermore, a portion of the first back plate 120 is removed at the scribe line 20 to expose the first sacrificial layer 211, as shown in FIG. Figure 2b In some preferred embodiments, the first sacrificial layer 211 at the scribe line 20 is removed to expose a portion of the substrate 101 .

[0068] Furthermore, a second sacrificial layer 212 is formed on the first back plate 120, such as Figure 2c As shown, the second sacrificial layer 212 is connected to the exposed first sacrificial layer 211 and the exposed substrate 101 .

[0069] Furthermore, near the scribe line 20, a portion of the second sacrificial layer 212 and the first sacrificial layer 211 are removed to form an isolation trench 104, such as Figure 2d shown.

[0070] In this step, the second sacrificial layer 212 and the first sacrificial layer 211 are made of the same material, for example, both are silicon oxide, and an isotropic wet etching process is used to remove part of the second sacrificial layer 212 and the first sacrificial layer 211 so that the side of the isolation groove 104 is inclined, wherein the bottom width of the isolation groove 104 is smaller than the opening width of the isolation groove 104.

[0071] In this embodiment, the isolation groove 104 extends from the surface of the second sacrificial layer 212 to the surface of the substrate 101, and the surface of the substrate 101 at the dicing line 20 is exposed. The isolation groove 104 separates the stacked structure composed of the first sacrificial layer 211, the first backplane 120 and the second sacrificial layer 212 into a plurality of units arranged in an array.

[0072] Further, a diaphragm 130 is formed on the second sacrificial layer 212. In each unit, the diaphragm 130 sequentially extends along the surface of the second sacrificial layer 212, the side wall of the second sacrificial layer 212, the side wall of the first back plate 120 and the side wall of the first sacrificial layer 211 to the substrate 101. Figure 2e shown.

[0073] In this embodiment, the diaphragm 130 covers the side and bottom surfaces of the isolation groove 104 (the surface of the substrate 101 exposed at the diaphragm 20 ) near the scribe line 20 . Since the side surfaces of the isolation groove 104 are inclined, the diaphragm 130 has better coverage in the isolation groove 104 .

[0074] In the step of forming the diaphragm 130, for example, amorphous silicon is first deposited on the surface of the second sacrificial layer 212, the side of the isolation groove 104, and the exposed surface of the substrate 101 by a deposition process, and then the amorphous silicon is grown by an annealing process to form the diaphragm 130, wherein the amorphous silicon in contact with the exposed substrate 101 grows along the crystal direction of the substrate 101 to complete the transformation of the amorphous silicon material to the polycrystalline silicon material. Optionally, the polycrystalline silicon diaphragm has doped impurities, and the doped impurities include but are not limited to phosphorus atoms.

[0075] Furthermore, a third sacrificial layer 213 is formed on the diaphragm 130, such as Figure 2f shown.

[0076] In this embodiment, the material of the third sacrificial layer 213 is the same as that of the second sacrificial layer 212. The third sacrificial layer 213 covers the diaphragm 130 and fills the isolation groove 104. In some preferred embodiments, the surface of the third sacrificial layer 213 is planarized by chemical mechanical polishing.

[0077] Furthermore, corresponding to each unit, a second back plate 140 is formed on the third sacrificial layer 213, such as Figure 2f shown.

[0078] In this step, for example, a lower dielectric layer 141 is first formed on the third sacrificial layer 213; then, for example, an etching process is used to form a first groove extending from the surface of the lower dielectric layer 141 to the surface of the diaphragm 130; then a conductive layer 142 is formed on the lower dielectric layer 141, and the conductive layer 142 is also filled in the first groove and connected to the diaphragm 130; finally, an upper dielectric layer 143 is formed on the conductive layer 142, wherein the conductive layer 142 filled in the first groove serves as the sinking portion of the second back plate 140.

[0079] In some preferred embodiments, before forming the upper dielectric layer 143 on the conductive layer 142, the step of forming the second backplane 140 also includes: forming a second groove extending from the surface of the conductive layer 142 to the surface of the lower dielectric layer 141 to separate the conductive layer 142 located on the third sacrificial layer 213 into a central portion and an edge portion, wherein the edge portion of the conductive layer 142 surrounds the central portion, and the sinking portion 140a of the second backplane 140 is connected to the edge portion of the conductive layer 142, and the upper dielectric layer 143 also covers the side and bottom of the second groove.

[0080] Furthermore, corresponding to each unit, a cavity 101a is formed in the substrate 101, such as Figure 2f shown.

[0081] Further, part of the first sacrificial layer, part of the second sacrificial layer and part of the third sacrificial layer are removed, and the remaining first sacrificial layer is used as the first supporting portion 111, the remaining second sacrificial layer is used as the second supporting portion 112, and the remaining third sacrificial layer is used as the third supporting portion 113, as shown in FIG. Figure 2g shown.

[0082] In this step, at the scribe line 20 of the wafer, the third sacrificial layer 213 covers the diaphragm 130 and the substrate 101. In order to facilitate the subsequent scribe process, the third sacrificial layer 213 at the scribe line 20 needs to be removed. In the release process, the release solution removes part of the sacrificial layer through the acoustic holes of the second back plate, the acoustic holes of the first back plate, and the back cavity of the substrate to form the first support part 111, the second support part 112, and the third support part 113. At the same time, the release solution also removes the third sacrificial layer at the scribe line 20 to re-expose the diaphragm 130 near the scribe line 20. In this process, the diaphragm 130 and the sinking part 140a of the second back plate act as an etching stop layer to protect the substrate 101, the first support part 111, the second support part 112, and the third support part 113.

[0083] Furthermore, the substrate 101 and the diaphragm 130 are cut at the scribe line 20 to separate the plurality of array-arranged units, forming a Figure 1 In the micro-electromechanical structure shown, the method of cutting the substrate 101 and the diaphragm 130 includes but is not limited to laser cutting.

[0084] Figure 3 A schematic diagram of a micro-electromechanical structure according to a second embodiment of the present invention is shown.

[0085] like Figure 3 As shown, the difference between the second embodiment of the present invention and the first embodiment lies in that a portion of the third support portion 113 passes through the diaphragm 130 and is connected to the second support portion 112 to separate the diaphragm 130 into a central portion and an edge portion, wherein the edge portion of the diaphragm 130 surrounds the central portion, and the edge portion of the diaphragm 130 extends successively along the outer wall of the second support portion 112, the side wall of the first back plate 120, and the outer wall of the first support portion 111 to the substrate 101.

[0086] Accordingly, the manufacturing method of the micro-electromechanical structure of the second embodiment of the present invention can refer to Figure 2a to Figure 2gThe description of the second sacrificial layer 212 is not repeated here. The difference is that before forming the third sacrificial layer 213, it is also necessary to form a third groove extending from the surface of the diaphragm 130 to the surface of the second sacrificial layer 212 to separate the diaphragm 130 into a central portion and an edge portion, wherein the edge portion of the diaphragm 130 surrounds the central portion and extends along the side wall of the second sacrificial layer 212, the side wall of the first back plate 120, and the side wall of the first sacrificial layer 211 to the substrate 101. After forming the third sacrificial layer 213, the third sacrificial layer 213 is also filled in the third groove.

[0087] The present invention also provides a microphone, comprising the micro-electromechanical structure as described above.

[0088] The present invention also provides a terminal, comprising the microphone as described above.

[0089] In the step of forming a diaphragm in the manufacturing method of the micro-electromechanical structure provided by an embodiment of the present invention, the diaphragm is sequentially extended along the side walls of the second sacrificial layer, the side walls of the first back plate and the side walls of the first sacrificial layer to the substrate, thereby reducing the risk of the release liquid corroding the outer walls of the first support part and the second support part during the release process when the first sacrificial layer and the second sacrificial layer are used to form the first support part and the second support part.

[0090] By setting a sinking portion in the second back plate, the sinking portion of the second back plate extends from the outer wall of the third support portion to the diaphragm. Since the sinking portion of the second back plate is continuous with the main part of the second back plate (the part located on the third support portion), the mechanical strength of the junction between the second back plate and the outer wall of the third support portion is increased, thereby improving the performance of the product. At the same time, the sinking portion of the second back plate also defines the morphology and outer dimensions of the outer wall of the third support portion, preventing the release solution of the release process from corroding the outer wall of the third support portion, thereby improving the consistency of the product and the smoothness of the surface.

[0091] Since the material of the sunken part of the second back plate and the material of the diaphragm are both polycrystalline silicon, the polycrystalline silicon protective wall of a single material composed of the area of ​​the diaphragm covering the first back plate, the first support part, the second support part and the sunken part of the second back plate reduces the defects of the contact interface, thereby further improving the corrosion resistance to the released solution.

[0092] An isotropic wet etching process is used to make the side of the isolation groove into a slope, and the bottom width of the isolation groove is made smaller than the opening width of the isolation groove. When depositing the material used to form the diaphragm, the slope is continuous and no steps are formed, so that the diaphragm material can cover the side of the isolation groove more evenly, thereby enhancing the covering effect of the diaphragm, thereby further improving the corrosion resistance to the release solution, and also enhancing the protection effect of the diaphragm on the first support part, the second support part and the first back plate.

[0093] By separating the conductive layer in the second back plate into a central portion and an edge portion, the sunken portion of the second back plate is connected to the edge portion of the conductive layer and electrically isolated from the central portion, thereby reducing parasitic capacitance in the product. By separating the diaphragm into a central portion and an edge portion, the portion connected to the substrate is the edge portion of the diaphragm and electrically isolated from the central portion, thereby reducing parasitic capacitance in the product.

[0094] By extending the diaphragm into the scribe line, when etching the structure above the diaphragm, the diaphragm in the scribe line acts as an etch stop layer to protect the scribe line. Preferably, phosphorus is doped into the polysilicon diaphragm to further improve the etching selectivity, thereby more effectively protecting the substrate.

[0095] When forming a polysilicon diaphragm, amorphous silicon is deposited in an isolation groove so that the amorphous silicon contacts the substrate at the bottom of the isolation groove. During the annealing process, the amorphous silicon at the bottom of the isolation groove will grow along the crystal direction of the substrate, thereby making the crystal direction of the polysilicon diaphragm in contact with the substrate consistent with the crystal direction of the substrate. During dicing, the polysilicon diaphragm has little effect on the dicing process. Therefore, the polysilicon diaphragm located in the dicing path does not need to be removed, thereby avoiding damage to the substrate caused by removing the polysilicon diaphragm.

[0096] Therefore, the micro-electromechanical structure and its manufacturing method, wafer, microphone and terminal provided by the present invention can greatly improve the performance of the product.

[0097] In the above description, the technical details of the patterning and etching of each layer are not described in detail. However, it should be understood by those skilled in the art that various technical means can be used to form layers, regions, etc. of the desired shape. In addition, in order to form the same structure, those skilled in the art can also design methods that are not completely the same as the methods described above. In addition, although the various embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage.

[0098] The embodiments of the present invention are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A method for manufacturing a micro-electromechanical structure, comprising: forming a first backplane over the substrate; forming a second sacrificial layer on the first backplane; forming a diaphragm on the second sacrificial layer, wherein the diaphragm extends along a side wall of the second sacrificial layer and a side wall of the first back plate to the substrate; forming a third sacrificial layer on the diaphragm; forming a second back plate on the third sacrificial layer, wherein the second back plate comprises a conductive layer, the conductive layer of the second back plate has a sinking portion penetrating the third sacrificial layer, and the sinking portion contacts the upper surface of the diaphragm; forming a cavity in the substrate; and Parts of the second sacrificial layer and the third sacrificial layer are removed, and the remaining second sacrificial layer serves as a second supporting portion, and the remaining third sacrificial layer serves as a third supporting portion.

2. The manufacturing method according to claim 1, before forming the first backplane, the manufacturing method further comprises forming a first sacrificial layer on the substrate, After forming the diaphragm, the manufacturing method further includes removing a portion of the first sacrificial layer, and using the remaining first sacrificial layer as a first supporting portion. in, The first back plate is located between the first sacrificial layer and the second sacrificial layer, and the diaphragm is also in contact with a side wall of the first sacrificial layer.

3. The manufacturing method according to claim 1, wherein: The step of forming the second backplane includes: forming a lower dielectric layer on the third sacrificial layer; forming a first groove extending from the surface of the lower dielectric layer to the surface of the diaphragm; forming a conductive layer on the lower dielectric layer, wherein the conductive layer is also filled in the first groove and connected to the diaphragm; and forming an upper dielectric layer on the conductive layer, The conductive layer filled in the first groove serves as a sinking portion of the second backplane.

4. The manufacturing method according to claim 3, wherein: The conductive layer of the second back plate is a polysilicon conductive layer.

5. The manufacturing method according to claim 3, wherein: Before forming the upper dielectric layer on the conductive layer, the step of forming the second backplane further includes: forming a second groove extending from the surface of the conductive layer to the surface of the lower dielectric layer to separate the conductive layer located on the third sacrificial layer into a central portion and an edge portion, The edge of the conductive layer surrounds the central portion, and the sinking portion of the second back plate is connected to the edge of the conductive layer, and the upper dielectric layer also covers the side surface and bottom surface of the second groove.

6. The manufacturing method according to claim 2, before forming the third sacrificial layer, the manufacturing method further comprises: forming a third groove extending from the surface of the diaphragm to the surface of the second sacrificial layer to separate the diaphragm into a central portion and an edge portion, The edge of the diaphragm surrounds the central portion and extends along the sidewall of the second sacrificial layer, the sidewall of the first back plate and the sidewall of the first sacrificial layer to the substrate. The third sacrificial layer is also filled in the third groove.

7. The manufacturing method according to any one of claims 2 to 6, before forming the diaphragm, the manufacturing method further comprises: An isolation groove is formed extending from the surface of the second sacrificial layer to the surface of the substrate, wherein the isolation groove separates the stacked structure consisting of the first sacrificial layer, the first back plate and the second sacrificial layer into a plurality of units arranged in an array. Wherein, the diaphragm covers the side surface and the bottom surface of the isolation groove.

8. The manufacturing method according to claim 7, wherein: The steps of forming the isolation trench include: Before forming the second sacrificial layer, removing a portion of the second back plate to expose a portion of the first sacrificial layer, and then the second sacrificial layer formed is connected to the exposed first sacrificial layer; and At the connection point between the second sacrificial layer and the first sacrificial layer, a portion of the second sacrificial layer and the first sacrificial layer is removed to form the isolation groove.

9. The manufacturing method according to claim 8, wherein: The step of forming the isolation trench further includes: After removing a portion of the second back plate and before forming the second sacrificial layer, a portion of the first sacrificial layer is removed to expose a portion of the substrate, and the second sacrificial layer formed thereafter is also connected to the exposed substrate.

10. The manufacturing method according to claim 8, wherein: An isotropic wet etching process is used to remove a portion of the second sacrificial layer and the first sacrificial layer, so that the side surface of the isolation groove is inclined. Wherein, the bottom width of the isolation groove is smaller than the opening width of the isolation groove.

11. The manufacturing method according to claim 7, wherein: The diaphragm is a polysilicon diaphragm.

12. The manufacturing method according to claim 11, wherein: The isolation groove exposes the surface of the substrate, and the step of forming the diaphragm includes: Depositing amorphous silicon on the surface of the second sacrificial layer, the side of the isolation trench and the exposed surface of the substrate; and The amorphous silicon in contact with the exposed substrate is grown along the crystal direction of the substrate through an annealing process.

13. The manufacturing method according to claim 11, wherein: The polysilicon diaphragm has doping impurities, and the doping impurities include phosphorus.

14. The manufacturing method according to claim 12, after removing part of the second sacrificial layer, the manufacturing method further comprises cutting the substrate and the diaphragm along a scribe line to separate the plurality of cells arranged in an array, in, The position of the scribe line corresponds to the isolation groove.

15. A wafer formed by the manufacturing method according to any one of claims 1 to 14, the wafer having a scribe line, the wafer comprising: substrate; A plurality of array units are located above the substrate, and adjacent array units are separated by the scribe lines; as well as A diaphragm covers the plurality of array units and the substrate surface where the scribe line is located, Each of the array units includes a first back plate and a second supporting portion located on the first back plate.

16. The wafer according to claim 15, wherein: The substrate has cavities corresponding to the plurality of array units, each of the cavities has a central axis perpendicular to the corresponding first backplane, and each of the second support portions has an outer side wall away from the corresponding central axis. Each of the array units further comprises a first support portion, which is located between the corresponding first back plate and the substrate, and each of the first support portions has an outer side wall away from the corresponding central axis. The diaphragm extends to the surface of the substrate via the surface of the second supporting portion, the outer side wall of the second supporting portion, the side wall of the first back plate and the outer side wall of the first supporting portion in sequence.

17. The wafer according to claim 16, further comprising: A plurality of third supporting parts, located on the diaphragm and corresponding to the plurality of array units; as well as A plurality of second back plates are respectively located on the corresponding third supporting parts.

18. The wafer according to claim 17, wherein each of the third supporting portions has an outer side wall away from the corresponding central axis. Each of the third supporting parts has a sinking part extending along the outer side wall of the corresponding third supporting part to the diaphragm.

19. A micro-electromechanical structure comprising: a substrate having a cavity; A first back plate, located above the substrate; A second supporting portion, located on the first back plate; a diaphragm, located on the second supporting portion; A third supporting portion, located on the diaphragm; as well as a second back plate, located on the third supporting portion, The cavity has a central axis perpendicular to the first back plate, and the second support portion and the third support portion have outer side walls away from the central axis. The diaphragm sequentially extends to the substrate through the surface of the second supporting portion, the outer side wall of the second supporting portion, and the side wall of the first back plate, and covers the surface edge of the substrate. The second back plate includes a conductive layer, the conductive layer of the second back plate has a sinking portion, and the sinking portion extends along the outer side wall of the third supporting portion to the upper surface of the diaphragm.

20. The micro-electromechanical structure according to claim 19, further comprising a first support portion located between the substrate and the first back plate, in, The first supporting portion has an outer side wall away from the central axis, and the diaphragm also covers the outer side wall of the first supporting portion.

21. The micro-electromechanical structure according to claim 20, wherein: The second backplane further comprises: a lower dielectric layer and an upper dielectric layer, Wherein, a portion of the conductive layer is located between the lower dielectric layer and the upper dielectric layer, Another part of the conductive layer serves as the sinking portion of the second back plate and penetrates the lower dielectric layer.

22. The micro-electromechanical structure according to claim 21, wherein: In the second backplane, the upper dielectric layer is connected to the lower dielectric layer through the conductive layer, so as to separate the conductive layer on the third supporting portion into a central portion and an edge portion. The edge portion of the conductive layer surrounds the central portion, and the sinking portion of the second back plate is connected to the edge portion of the conductive layer.

23. The micro-electromechanical structure according to claim 22, wherein: A portion of the third supporting portion passes through the diaphragm and is connected to the second supporting portion to separate the diaphragm into a central portion and an edge portion. The edge portion of the diaphragm surrounds the central portion, and the edge portion of the diaphragm extends to the substrate along the outer side wall of the second supporting portion, the side wall of the first back plate, and the outer side wall of the first supporting portion.

24. The micro-electromechanical structure according to any one of claims 20 to 23, wherein: The outer side wall of the second supporting portion, the side wall of the first back plate and the outer side wall of the first supporting portion form an inclined surface.

25. A microphone comprising the micro-electromechanical structure according to any one of claims 19 to 24.

26. A terminal comprising the microphone according to claim 25.

Images