MEMS element and preparation method therefor

Abstract

Disclosed in the present invention are an MEMS element and a preparation method therefor. The MEMS element comprises: a substrate; a diaphragm, which is connected to the substrate, wherein the diaphragm comprises an upper membrane and a lower membrane, which are arranged opposite each other; a counter electrode; and a plurality of supporting members, which are arranged between the upper membrane and the lower membrane and are spaced apart from the counter electrode, wherein two opposite ends of each supporting member are connected to the upper membrane and the lower membrane respectively. The diaphragm comprises a first area and a second area, the second area being located in the outer circumferential direction of the first area, wherein in the first area, a first electrode covers the surface of the side of the upper membrane away from the lower membrane, and a second electrode covers the surface of the side of the lower membrane away from the upper membrane; and in the second area, reinforcing layers respectively cover the surface of the side of the upper membrane away from the lower diaphragm and the surface of the side of the lower membrane away from the upper membrane. Compared with the prior art, in the present invention, the reinforcing layers are arranged in the second area of the diaphragm, such that the mechanical strength and robustness of the diaphragm can be enhanced by means of the reinforcing layers, thereby improving the preparation process yield.

Description

A MEMS element and its preparation method Technical Field

[0001] The present invention relates to the technical field of micro-electromechanical systems, in particular to a MEMS element and a preparation method thereof. Background Art

[0002] In the prior art, a microphone with a dual-membrane structure has been developed and produced. The microphone has two membranes on opposite sides of the electrode. This creates a sealed accommodation space between the two membranes, which can have different pressures to the external environment. The top and bottom membranes are composed of a double layer of dielectric nitride layer and polysilicon layer, where the nitride layer serves as a diaphragm and the polysilicon serves as a conductive electrode. In order to enhance sensitivity, the diameter of the conductive electrode area is usually smaller than that of the membrane. There is a connecting wall structure between the two membranes as a support member, and an air gap cavity is opened on the support member, which causes the air gap cavity to be unable to withstand the mechanical force acting on the diaphragm, resulting in the membrane breaking. Technical issues

[0003] The purpose of the present invention is to provide a MEMS element and a preparation method thereof to solve the technical problems in the prior art. Technical Solutions

[0004] In a first aspect, the present invention provides a MEMS element, comprising:

[0005] a substrate, a back cavity passing through the substrate;

[0006] a diaphragm connected to the substrate and covering the back cavity, the diaphragm comprising an upper diaphragm and a lower diaphragm arranged opposite to each other, with a receiving space formed between the upper diaphragm and the lower diaphragm;

[0007] a counter electrode, disposed in the accommodation space;

[0008] A plurality of concentric and spaced support members are disposed between the upper diaphragm and the lower diaphragm and spaced from the counter electrode, wherein opposite ends of the support members are connected to the upper diaphragm and the lower diaphragm, respectively, wherein:

[0009] The diaphragm includes a first area and a second area, wherein the second area is located in the outer circumference of the first area, wherein:

[0010] In the first region, a surface of the upper diaphragm facing away from the lower diaphragm is covered with a first electrode, and a surface of the lower diaphragm facing away from the upper diaphragm is covered with a second electrode, and the first electrode and the second electrode are arranged opposite to each other;

[0011] In the second region, a surface of the upper diaphragm facing away from the lower diaphragm and a surface of the lower diaphragm facing away from the upper diaphragm are both covered with a reinforcement layer.

[0012] A MEMS element as described above, wherein preferably, in the second area, a plurality of first chambers are opened in at least one of the support members, the MEMS element has an upper ventilation groove passing through the upper diaphragm corresponding to the first chamber, and a lower ventilation groove passing through the lower diaphragm corresponding to the first chamber, and the upper ventilation groove, the first chamber and the lower ventilation groove are connected.

[0013] In the MEMS element as described above, preferably, the first chamber is only opened in the support member located at the periphery of the diaphragm.

[0014] A MEMS element as described above, wherein preferably, the upper diaphragm includes a plurality of first protrusions protruding toward the accommodating space and spaced apart from each other, the lower diaphragm includes a plurality of second protrusions protruding toward the accommodating space and spaced apart from each other, the plurality of support members, the plurality of first protrusions and the plurality of second protrusions are in one-to-one correspondence, the two ends of the support member are respectively connected to the first protrusion and the second protrusion, the upper ventilation groove is opened on the first protrusion, and the lower ventilation groove is opened on the second protrusion.

[0015] In the MEMS element as described above, preferably, the surface of the upper diaphragm, the surface of the lower diaphragm, the inner wall surface of the first protrusion, and the inner wall surface of the second protrusion are all covered with a reinforcement layer.

[0016] In the MEMS element as described above, preferably, the reinforcement layer only covers the surfaces of the upper diaphragm and the lower diaphragm.

[0017] In the MEMS element as described above, preferably, the reinforcement layer is made of a conductive material, the reinforcement layer is electrically connected to the counter electrode, and the reinforcement layer and the counter electrode have the same electric potential.

[0018] In the MEMS element as described above, preferably, the reinforcement layer is made of insulating material.

[0019] In a second aspect, the present invention provides a method for preparing a MEMS element, which is used for the aforementioned MEMS element, comprising the following steps:

[0020] Step S1: forming an upper membrane or a lower membrane, wherein the upper membrane or the lower membrane is preset with a first area and a second area;

[0021] Step S2: depositing a deposited layer on the upper membrane or the lower membrane;

[0022] Step S3: Plasma implantation on the deposition layer corresponding to the first region and the second region;

[0023] Step S4: annealing;

[0024] Step S5: etching the deposition layer to form an isolation trench, wherein the isolation trench is located at the junction of the first region and the second region.

[0025] In a third aspect, the present invention provides a method for preparing a MEMS element, which is used for the aforementioned MEMS element, comprising the following steps:

[0026] Step S1: forming an upper membrane or a lower membrane, wherein the upper membrane or the lower membrane is preset with a first area and a second area;

[0027] Step S2: depositing a deposited layer on the upper membrane or the lower membrane;

[0028] Step S3: Plasma is injected into the deposited layer corresponding to the first region;

[0029] Step S4: annealing;

[0030] Step S5: etching the deposition layer to form an isolation trench, wherein the isolation trench is located at the junction of the first region and the second region. Beneficial effects

[0031] Compared with the prior art, the present invention provides a reinforcement layer in the second region of the diaphragm. The reinforcement layer can enhance the mechanical strength and robustness of the diaphragm and improve the yield rate of the manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a schematic structural diagram of a MEMS element of a first structure according to an embodiment of the present invention;

[0033] FIG2 is a schematic structural diagram of a MEMS element of a second structure according to an embodiment of the present invention;

[0034] FIG3 is a first method for preparing a reinforcement layer according to an embodiment of the present invention;

[0035] FIG4 is a second method for preparing the reinforcement layer of the embodiment provided by the present invention.

[0036] Description of reference numerals:

[0037] 10-base, 11-dorsal cavity;

[0038] 20 - diaphragm, 21 - upper diaphragm, 211 - upper ventilation slot, 22 - lower diaphragm, 221 - lower ventilation slot, 23 - accommodation space, 24 - first protrusion, 25 - second protrusion;

[0039] 30-support member, 31-first chamber;

[0040] 40-counter electrode;

[0041] 50-first electrode;

[0042] 60- second electrode;

[0043] 70-reinforcement layer;

[0044] 80-sedimentary layer;

[0045] Z1-first zone;

[0046] Z2 - Second zone. Best Mode for Carrying Out the Invention

[0047] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limiting the present invention.

[0048] 1 and 2 , an embodiment of the present invention provides a MEMS element, including a substrate 10 , a diaphragm 20 , a counter electrode 40 , and a support member 30 , wherein:

[0049] A back cavity 11 passes through the base 10 . Preferably, the inner contour surface of the back cavity 11 is a circular groove structure.

[0050] The diaphragm 20 is connected to the base 10 and covers the back cavity 11. The diaphragm 20 includes an upper diaphragm 21 and a lower diaphragm 22 that are relatively arranged. In this embodiment, the upper diaphragm 21 and the lower diaphragm 22 are both concentrically arranged circular structures. A preset gap is maintained between the upper diaphragm 21 and the lower diaphragm 22 to form an accommodating space 23, and the lower diaphragm 22 is located below the upper diaphragm 21.

[0051] Preferably, the accommodation space 23 is hermetically sealed, and the internal pressure of the accommodation space 23 is less than the external atmospheric pressure. The internal pressure of the accommodation space 23 is less than 0.2 atm, and preferably, the pressure in the accommodation space 23 is equal to 0.1 atm. In some embodiments, the accommodation space 23 is vacuum.

[0052] The counter electrode 40 is disposed in a suspended state within the accommodation space 23 . Under normal conditions, the counter electrode 40 has no contact with the upper diaphragm 21 and the lower diaphragm 22 , and has no mechanical coupling with the support member 30 .

[0053] In the embodiment provided by the present invention, the diaphragm 20 includes a first area Z1 and a second area Z2. The second area Z2 is located on the outer circumference of the first area Z1. The first area Z1 and the second area Z2 are artificially defined areas, and the shapes and coverage of the first area Z1 and the second area Z2 can be modified according to actual product requirements. The first area Z1 is located in the middle of the diaphragm 20, and the second area Z2 is located at the edge of the diaphragm 20. The first area Z1 is preferably a circular structure, and the second area Z2 is preferably an annular structure. The inner annular surface of the annular structure is continuous with the outer annular surface of the circular structure, wherein:

[0054] 1 and 2 , in the first region Z1 , the surface of the upper membrane 21 facing away from the lower membrane 22 is covered with a first electrode 50 , and the surface of the lower membrane 22 facing away from the upper membrane 21 is covered with a second electrode 60 . The first electrode 50 and the second electrode 60 are arranged opposite to each other.

[0055] In the first region Z1, a first capacitor is formed between the first electrode 50 and the counter electrode 40, and a second capacitor is formed between the second electrode 60 and the counter electrode 40. In response to pressure applied to the upper diaphragm 21 and the lower diaphragm 22, the upper diaphragm 21 and the lower diaphragm 22 are movable relative to the corresponding counter electrode 40, thereby changing the distance between the first electrode 50 and the second electrode 60 and the corresponding counter electrode 40, which causes the capacitance to change and outputs an electrical signal accordingly.

[0056] Furthermore, in the second region Z2 , a surface of the upper diaphragm 21 facing away from the lower diaphragm 22 and a surface of the lower diaphragm 22 facing away from the upper diaphragm 21 are both covered with the reinforcement layer 70 .

[0057] In the embodiment provided in the present application, since the second area Z2 is located at the edge of the diaphragm 20, the stress concentration and deflection of the diaphragm 20 are the highest here. By covering the second area Z2 with a reinforcing layer 70, the mechanical strength of the diaphragm 20 in the second area Z2 can be enhanced, and the diaphragm 20 can withstand greater mechanical forces to prevent the diaphragm 20 from breaking.

[0058] Multiple support members 30 are concentrically and spaced apart in the accommodating space 23 and spaced apart from the counter electrode 40. Multiple support members 30 are spaced apart along the radial direction of the diaphragm 20 with the center of the circle of the diaphragm 20 as the center. At least in one of the support members 30, a plurality of first chambers 31 are opened. Preferably, the first chambers 31 are only opened in the support member 30 located at the periphery of the diaphragm 20. In the local area of ​​this support member 30, the opposite ends of the support member 30 are respectively connected to the upper diaphragm 21 and the lower diaphragm 22.

[0059] The function of the support member 30 is to keep the upper diaphragm 21 and the lower diaphragm 22 flat, or at least limit / control the bending / deformation of the upper diaphragm 21 and the lower diaphragm 22 between the support member 30, so as to avoid the upper diaphragm 21 and the lower diaphragm 22 folding against each other when the sealed volume of the accommodating space 23 is at a reduced atmospheric pressure and the outside is at ambient atmospheric pressure.

[0060] 1 and 2 , the MEMS element has an upper ventilation groove 211 passing through the upper diaphragm 21 corresponding to the first chamber 31, and a lower ventilation groove 221 passing through the lower diaphragm 22 corresponding to the first chamber 31. The upper ventilation groove 211 and the lower ventilation groove 221 are connected via the first chamber 31 to form a ventilation channel. Compared with placing the ventilation channel at the center of the diaphragm 20, this embodiment will not reduce the local stiffness of the diaphragm 20, and at the same time can improve the flexibility of the diaphragm 20.

[0061] Controlling the acoustic impedance through openings in the upper or lower diaphragm 21, 22 allows for shallower, more controlled etching to be used, allowing etching and photolithography to be performed on a more uniform topology, simplifying the process and reducing variability.

[0062] Positioning the first chamber 31 within the support member 30 ensures that the local rigidity of the placement area is not altered, while also providing mechanical support to the edges of the upper ventilation slot 211, the first chamber 31, and the lower ventilation slot 221. This prevents inherent stress within the diaphragm 20 from causing the upper ventilation slot 211, the first chamber 31, and the lower ventilation slot 221 to expand, thereby causing the acoustic impedance to deviate from the designed value.

[0063] Furthermore, the upper ventilation groove 211 and the lower ventilation groove 221 are close to the edge of the diaphragm 20, and the upper ventilation groove 211 and the lower ventilation groove 221 are preferably slit-shaped groove bodies. Their length is much greater than their width, which prevents the problem of slit opening due to inherent stress in the film, thereby causing the acoustic impedance to deviate from the design value.

[0064] 1 and 2 , the upper diaphragm 21 and the lower diaphragm 22 are both corrugated structures and are made of conductive materials or insulating films including conductive materials or insulating films including conductive regions formed by material doping or injection. The upper diaphragm 21 includes a plurality of first protrusions 24 protruding toward the accommodating space 23 and spaced apart from each other. The lower diaphragm 22 includes a plurality of second protrusions 25 protruding toward the accommodating space 23 and spaced apart from each other. The plurality of first protrusions 24 and the plurality of second protrusions 25 are all spaced apart along the radial direction of the diaphragm 20. The plurality of support members 30, the plurality of first protrusions 24 and the plurality of second protrusions 25 correspond one to one. The two ends of the support member 30 are respectively connected to the first protrusion 24 and the second protrusion 25. The upper ventilation groove 211 is opened on the first protrusion 24, and the lower ventilation groove 221 is opened on the second protrusion 25.

[0065] Preferably, the first protrusion 24 and the second protrusion 25 have the same shape and size to form regular corrugations, thereby evenly distributing the stress on the entire diaphragm 20 and facilitating molding processing. Furthermore, the cross-sectional shape of the first protrusion 24 and the second protrusion 25 in the direction perpendicular to the diaphragm 20 can be rectangular, trapezoidal, or triangular, etc., and the angle of the inclined surface of the first protrusion 24 and the second protrusion 25 is greater than 0° and less than or equal to 90°. Those skilled in the art will appreciate that the cross-sectional shape of the first protrusion 24 and the second protrusion 25 in the direction perpendicular to the diaphragm 20 can be regular or irregular, and this is not limited here.

[0066] The first protrusion 24 and the second protrusion 25 together constitute the corrugation of the diaphragm 20, so that the diaphragm 20 has greater tension and can withstand greater sound pressure. At the same time, the diaphragm 20 has smaller internal stress, the stiffness of the diaphragm 20 is reduced, and the mechanical sensitivity of the MEMS element is effectively improved.

[0067] As shown in Figure 1, the surface of the upper diaphragm 21, the surface of the lower diaphragm 22, the inner wall surface of the first protrusion 24 and the inner wall surface of the second protrusion 25 are all covered with a reinforcement layer 70. The reinforcement layer 70 is a diaphragm structure, which can effectively improve the structural robustness of the second area Z2 and further reduce the risk of mechanical damage.

[0068] As shown in Figure 2, the reinforcement layer 70 only covers the surfaces of the upper diaphragm 21 and the lower diaphragm 22, and the inner wall surfaces of the first protrusion 24 and the second protrusion 25 are not covered with the reinforcement layer 70. This can improve the mechanical strength of the diaphragm 20 while maintaining the flexibility and sensitivity of the diaphragm 20.

[0069] In a feasible embodiment, the reinforcing layer 70 is made of a conductive material, and the same material as the first electrode 50 or the second electrode 60 can be selected. The reinforcing layer 70 is electrically connected to the counter electrode 40. The reinforcing layer 70 and the counter electrode 40 have the same electric potential. The reinforcing layer 70 will not act as an electrode that may change the capacitance sensing area. Although the distance between the reinforcing layer 70 and the counter electrode 40 will change according to the external pressure, it will not cause the capacitance to change, and no electrical signal will be output.

[0070] 3 , the method for preparing the reinforcing layer 70 of conductive material includes the following steps:

[0071] Step S1 : forming an upper membrane 21 or a lower membrane 22 , wherein a first area Z1 and a second area Z2 are preset on the upper membrane 21 or the lower membrane 22 .

[0072] Step S2 : completing deposition on the upper membrane 21 or the lower membrane 22 to form a deposition layer 80 .

[0073] Step S3 : Plasma implantation is performed on the deposition layer 80 corresponding to the first area Z1 and the second area Z2 .

[0074] Step S4: Annealing.

[0075] Step S5: Etching an isolation groove on the deposition layer 80, the isolation groove is located at the junction of the first area Z1 and the second area Z2. In this embodiment, the isolation groove is an annular groove. The portion of the deposition layer 80 located on the inner side of the annular groove forms the first electrode 50 or the second electrode 60, and the portion of the deposition layer 80 located on the outer side of the annular groove forms the reinforcement layer 70, and the reinforcement layer 70 is electrically connected to the counter electrode 40. The reinforcement layer 70 and the counter electrode 40 have the same electric potential, and the reinforcement layer 70 will not act as an electrode that may change the capacitance sensing area.

[0076] In another possible embodiment, the reinforcement layer 70 is made of an insulating material and is non-conductive, so it does not need to be electrically connected to the counter electrode 40 and does not act as an electrode that may change the capacitance sensing area.

[0077] 4 , the method for preparing the reinforcing layer 70 of insulating material includes the following steps:

[0078] Step S1 : forming an upper membrane 21 or a lower membrane 22 , wherein a first area Z1 and a second area Z2 are preset on the upper membrane 21 or the lower membrane 22 .

[0079] Step S2 : depositing a deposition layer 80 on the upper membrane 21 or the lower membrane 22 .

[0080] Step S3: Plasma implantation is performed in the first region Z1 to form the first electrode 50 or the second electrode 60 , while no plasma implantation is performed in the second region Z2 .

[0081] Step S4: Annealing.

[0082] Step S5: Etching on the deposition layer 80 to form an isolation groove, the isolation groove is located at the junction of the first area Z1 and the second area Z2. In this embodiment, the isolation groove is an annular groove, and the portion of the deposition layer 80 located on the inner side of the annular groove forms the first electrode 50 or the second electrode 60, and the portion of the deposition layer 80 located on the outer side of the annular groove forms the reinforcement layer 70. Since the deposition layer 80 in the second area Z2 is not plasma-implanted, it is non-conductive and will not change the capacitance sensing area. The reinforcement layer 70 does not need to be connected to the counter electrode 40, which provides greater flexibility for structural design.

[0083] The above describes in detail the structure, features and effects of the present invention based on the embodiments shown in the drawings. The above is only a preferred embodiment of the present invention, but the scope of implementation of the present invention is not limited to what is shown in the drawings. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which do not exceed the spirit covered by the description and drawings, should be within the scope of protection of the present invention.

Claims

1. A MEMS element, comprising: a substrate, a back cavity passing through the substrate; a diaphragm connected to the substrate and covering the back cavity, the diaphragm comprising an upper diaphragm and a lower diaphragm arranged opposite to each other, with a receiving space formed between the upper diaphragm and the lower diaphragm; a counter electrode, disposed in the accommodation space; a plurality of concentric and spaced support members, disposed between the upper diaphragm and the lower diaphragm and spaced from the counter electrode, wherein opposite ends of the support members are connected to the upper diaphragm and the lower diaphragm respectively; Its characteristics are: The diaphragm includes a first area and a second area, wherein the second area is located in the outer circumference of the first area, wherein: In the first region, a surface of the upper diaphragm facing away from the lower diaphragm is covered with a first electrode, and a surface of the lower diaphragm facing away from the upper diaphragm is covered with a second electrode, and the first electrode and the second electrode are arranged opposite to each other; In the second region, a surface of the upper diaphragm facing away from the lower diaphragm and a surface of the lower diaphragm facing away from the upper diaphragm are both covered with a reinforcement layer.

2. The MEMS element according to claim 1, wherein: In the second area, a plurality of first chambers are opened in at least one of the supporting members, and the MEMS element has an upper ventilation groove passing through the upper diaphragm corresponding to the first chamber, and a lower ventilation groove passing through the lower diaphragm corresponding to the first chamber, and the upper ventilation groove, the first chamber and the lower ventilation groove are connected.

3. The MEMS element according to claim 2, wherein: The first chamber is only opened in the supporting member located at the periphery of the diaphragm.

4. The MEMS element according to claim 3, wherein: The upper diaphragm includes several first protrusions protruding toward the accommodating space and spaced apart from each other, and the lower diaphragm includes several second protrusions protruding toward the accommodating space and spaced apart from each other. The several support members, the several first protrusions and the several second protrusions are all in one-to-one correspondence, and the two ends of the support member are respectively connected to the first protrusion and the second protrusion, the upper ventilation groove is opened on the first protrusion, and the lower ventilation groove is opened on the second protrusion.

5. The MEMS element according to claim 4, characterized in that The surface of the upper diaphragm, the surface of the lower diaphragm, the inner wall surface of the first protrusion, and the inner wall surface of the second protrusion are all covered with a reinforcement layer.

6. The MEMS element according to claim 4, wherein: The reinforcement layer only covers the surfaces of the upper diaphragm and the lower diaphragm.

7. The MEMS element according to claim 1, wherein: The reinforcement layer is made of a conductive material, is electrically connected to the counter electrode, and has the same electric potential as the counter electrode.

8. The MEMS element according to claim 1, wherein: The reinforcement layer is made of insulating material.

9. A method for preparing a MEMS element, for preparing the MEMS element according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step S1: forming an upper membrane or a lower membrane, wherein the upper membrane or the lower membrane is preset with a first area and a second area; Step S2: depositing a deposited layer on the upper membrane or the lower membrane; Step S3: Plasma implantation on the deposition layer corresponding to the first region and the second region; Step S4: annealing; Step S5: etching the deposition layer to form an isolation trench, wherein the isolation trench is located at the junction of the first region and the second region.

10. A method for preparing a MEMS element, for preparing the MEMS element according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step S1: forming an upper membrane or a lower membrane, wherein the upper membrane or the lower membrane is preset with a first area and a second area; Step S2: depositing a deposited layer on the upper membrane or the lower membrane; Step S3: Plasma is injected into the deposited layer corresponding to the first region; Step S4: annealing; Step S5: etching the deposition layer to form an isolation trench, wherein the isolation trench is located at the junction of the first region and the second region.

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