MEMS capacitive sensor
Through the double-layer diaphragm structure and insulating layer design, the problem of inaccurate diaphragm fixing position in MEMS microphone is solved, the sensitivity of the microphone is improved and the noise is reduced, and more efficient signal output is achieved.
Patent Information
- Application Number
- CN202421697506.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-17
- Publication Date
- 2025-07-25
- Estimated Expiration
- 2034-07-17
AI Technical Summary
In existing MEMS microphones, the release position of the sacrificial layer between the diaphragm and the substrate is not easy to control, resulting in inaccurate fixing position of the diaphragm, affecting the sensitivity and noise performance of the microphone.
A double-layer diaphragm structure is adopted, with a sealing structure at the end to form a slit and penetrates to the substrate, combining the insulating structure to determine the effective area, and eliminating parasitic capacitance at the backplane through holes, and using polycrystalline silicon and SiN materials to form the electrode and insulating layer.
It increases the effective area of the diaphragm, reduces the noise of the microphone, enhances sensitivity consistency, and eliminates the influence of parasitic capacitance.
Smart Images
Figure CN223157227U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of micro motors, and particularly relates to a MEMS capacitive sensor. Background Art
[0002] With the intelligence of electronic products, the demand for audio interface devices has increased sharply. Currently, the microphones used in electronic products are mainly divided into two categories. One is the ECM (Electret Condenser Microphone) electret microphone, and the other is the MEMS (Micro Electro Mechanical System) microphone. Due to the use of microelectronic technology, MEMS microphones have the advantages of small size, lower cost, better sensitivity consistency, etc., and are used in most electronic products, with a global shipment volume of more than 7 billion pieces. High-performance and high-reliability MEMS microphones are being widely researched and used.
[0003] Generally, there is a sacrificial layer between the diaphragm and the substrate. The diaphragm electrode material is usually Poly Silicon, and the sacrificial layer material is usually SiO2. During the processing of the MEMS chip, the sacrificial layer will be released. The position where the sacrificial layer release stops is the position where the diaphragm is fixed. Usually, the position where the sacrificial layer release stops is not easy to control. The sacrificial layer can be partially etched at the position where the diaphragm needs to be fixed to form a blocking groove, and then filled with a material that has a wet etching selectivity ratio with SiO2 to form a fixed position; the substrate is usually at ground potential, and the diaphragm is the output electrode, so the conductive diaphragm layer cannot be used to fill the blocking groove. Summary of the Utility Model
[0004] To reduce the background noise of the MEMS microphone and increase the effective area of the diaphragm, the utility model provides a MEMS capacitive sensor, including: a plurality of sealing structures are provided at the end of the double-layer diaphragm, and each sealing structure is used to seal the movable part of the double-layer diaphragm and make the movable part form a low-pressure area; the sealing structure and the end of the double-layer diaphragm jointly form a slit, and the slit penetrates through the double-layer diaphragm and extends to the substrate; the double-layer diaphragm includes an insulating structure, and the insulating structure is located between the substrate and the sealing structure and forms a release blocking structure with the substrate to determine the effective area of the double-layer diaphragm.
[0005] In some embodiments of the utility model, at least three sealing structures are provided along the circumferential direction at the end of the double-layer diaphragm.
[0006] In some embodiments of the utility model, the sealing structures are evenly distributed along the circumferential direction.
[0007] In some embodiments of the present utility model, the double-layer diaphragm includes an upper diaphragm structural layer, an upper diaphragm electrode, a lower diaphragm structural layer, and a lower diaphragm electrode.
[0008] Further, the double-layer diaphragm portion corresponding to the through-hole in the backplane is removed to eliminate parasitic capacitance.
[0009] Preferably, the diaphragms at the positions of the upper diaphragm and the lower diaphragm corresponding to the through-hole in the backplane are removed to eliminate parasitic capacitance.
[0010] Preferably, the electrodes at the positions of the upper diaphragm electrode and the lower diaphragm electrode corresponding to the through-hole in the backplane are removed to eliminate parasitic capacitance.
[0011] Further, the material of the upper diaphragm electrode or the lower diaphragm electrode is polysilicon.
[0012] Further, the material of the insulating structure is S i N.
[0013] Further, the width of the slit is not greater than 2 μm.
[0014] Further, the structure of the backplane is a sandwich structure.
[0015] The beneficial effects of the present utility model are:
[0016] The present utility model provides a MEMS capacitive sensor, including: a double-layer diaphragm, a backplane with through-holes, and a substrate. A differential capacitance is formed between the double-layer diaphragm and the backplane. A plurality of sealing structures are provided at the ends of the double-layer diaphragm. Each sealing structure is used to seal the movable part of the double-layer diaphragm and form a low-pressure area for the movable part. The sealing structure and the end of the double-layer diaphragm together form a slit, and the slit penetrates through the double-layer diaphragm and extends to the substrate. The double-layer diaphragm includes an insulating structure, and the insulating structure is located between the substrate and the sealing structure and forms a release blocking structure with the substrate to determine the effective area of the double-layer diaphragm.
[0017] It can be seen that the present utility model forms a low-pressure area by sealing the double-film structure, reduces the film damping, and thus reduces the microphone noise. Since the diaphragm part is fixed, only the diaphragm displacement is zero at the position where the diaphragm is fixed, and there is a large displacement at other positions. Therefore, the diaphragm has a large effective area, and the ratio of the effective area to the actual area of the diaphragm is 65%. The diaphragm is composed of a double-layer film, an insulating structure layer, and an electrode layer. The introduction of the insulating structure layer enables the free definition of the area of the diaphragm electrode, thereby eliminating unnecessary parasitic capacitance. The insulating structure layer can form a release structure, thereby defining the fixed boundary of the diaphragm, and thus improving the consistency of the device sensitivity. Description of the Drawings
[0018] Figure 1Schematic diagram of the basic structure of the MEMS capacitive sensor in some embodiments of the present invention;
[0019] Figure 2 Top view schematic diagram of the MEMS capacitive sensor in some embodiments of the present invention;
[0020] Figure 3 Schematic diagram of the specific structure of the MEMS capacitive sensor in some embodiments of the present invention;
[0021] Figure 4 Schematic diagram of the signal output of the MEMS capacitive sensor in some embodiments of the present invention;
[0022] Figure 5 Schematic diagram of the diaphragm displacement of the MEMS capacitive sensor in some embodiments of the present invention;
[0023] Figure 6 Schematic diagram of the insulation structure of the MEMS capacitive sensor in some embodiments of the present invention;
[0024] Figure 7 Schematic diagram of the position for eliminating parasitic capacitance of the MEMS capacitive sensor in some embodiments of the present invention.
[0025] Reference numerals
[0026] 1. Double-layer diaphragm; 11. Upper diaphragm; 12. Lower diaphragm; 13. Upper diaphragm electrode; 14. Lower diaphragm electrode;
[0027] 15. Sealing structure; 16. Insulation structure; 18. Slit;
[0028] 2. Backplane; 21. Backplane electrode; 22. Backplane insulation layer; 23. Diaphragm connection structure;
[0029] 24. Sandwich backplane; 25. Backplane through hole;
[0030] 3. Substrate. Detailed implementation manners
[0031] The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.
[0032] Refer to Figure 1 、 Figure 2 and Figure 4, in the first aspect of the present utility model, a MEMS capacitive sensor is provided, comprising: a double-layer diaphragm 1, a backplane 2 with through holes, and a substrate 3, wherein a differential capacitance is formed between the double-layer diaphragm 1 and the backplane 2. A plurality of sealing structures 15 are provided at the end of the double-layer diaphragm 1, and each sealing structure 15 is used to seal the upper diaphragm 11 and the lower diaphragm 12 on the movable part of the double-layer diaphragm 1, and to form a low-pressure area between the upper diaphragm 11 and the lower diaphragm 12 on the movable part. The sealing structure 15 and the end of the double-layer diaphragm 1 together form a slit 18, and the slit 18 penetrates the double-layer diaphragm 1 and extends to the substrate 3. The double-layer diaphragm 1 includes an insulating structure 16, and the insulating structure 16 is located between the substrate 3 and the sealing structure 15, and forms a release blocking structure with the substrate 3, which is used to determine the fixed boundary of the double-layer diaphragm 1 and the area of the double-layer diaphragm 1 electrode.
[0033] Specifically, the MEMS capacitive sensor includes a substrate 3, a backplane 2 with through holes, the backplane 2 has a three-layer structure (sandwich backplane 24), including a backplane electrode 21 in the middle and backplane insulating layers 22 above and below the backplane electrode 21, a double-membrane diaphragm structure 1, a diaphragm connection structure 23 connecting the upper and lower double-layer diaphragms 1, the middle area of the double-layer diaphragm 1 is a low-pressure area, and the double-layer diaphragm 1 forms a differential output. Preferably, the width of the slit 18 does not exceed 2 μm, at this time, while ensuring the effective area of the double-layer diaphragm, the low-frequency performance of the diaphragm is improved.
[0034] In some embodiments of the present utility model, at least three sealing structures 15 are provided along the circumferential direction at the end of the double-layer diaphragm 1. In some embodiments of the present utility model, the sealing structures 15 are evenly distributed along the circumferential direction.
[0035] It can be understood that referring to Figure 5 , the diaphragm is not fixed at the boundary of the sealing structure 15, and the diaphragm in the figure is fixed at the four corners. By sealing the double-membrane structure to form a low-pressure area, the film damping is reduced, thereby reducing the microphone noise. Since the diaphragm is partially fixed at the boundary of the sealing structure 15, the diaphragm displacement is zero only at the position where the diaphragm is fixed, and there is a large displacement at other positions. Therefore, the diaphragm has a large effective area, and the ratio of the effective area to the actual area of the diaphragm is 65%.
[0036] Referring to Figure 3 , Figure 6 and Figure 7 , in some embodiments of the present utility model, the double-layer diaphragm 1 includes an upper diaphragm 11, an upper diaphragm electrode 13, a lower diaphragm 12, and a lower diaphragm electrode 14.
[0037] Further, a part of the double-layer diaphragm 1 corresponding to the backplane through hole 25 is removed to eliminate parasitic capacitance. Preferably, the diaphragm 1 at the position of the upper diaphragm 11 and the lower diaphragm 12 corresponding to the backplane through hole 25 is removed to eliminate parasitic capacitance. Preferably, the electrodes at the positions of the upper diaphragm electrode 13 and the lower diaphragm electrode 14 corresponding to the backplane through hole 25 are removed to eliminate parasitic capacitance.
[0038] It should be noted that the diaphragm moves under the action of sound pressure, resulting in a change in the capacitance between the diaphragm and the backplane electrode. Parasitic capacitance will also be formed between the upper and lower diaphragms. Parasitic capacitance C is formed between the immovable part of the diaphragm and the backplane electrode. p , and the parasitic capacitance will reduce the sensitivity of the microphone. Therefore, at least one of the upper diaphragm and the lower diaphragm corresponding to the backplane through hole, and at least one of the upper diaphragm electrode or the lower diaphragm electrode is removed at the corresponding position to eliminate the parasitic capacitance between the upper and lower backplanes, which is expressed as:
[0039]
[0040] Where V is the bias voltage, ΔC is the capacitance change under the action of sound pressure, and C0 is the initial capacitance.
[0041] It can be understood that the introduction of the insulating structure 16, the upper diaphragm 11, and the lower diaphragm 12 enables the free definition of the areas of the diaphragm electrodes 13 and 14, thereby eliminating unnecessary parasitic capacitance. The insulating structure 16 can form a release blocking structure, thereby defining the fixed boundary 15 of the diaphragm and improving the consistency of the device sensitivity.
[0042] There is usually a sacrificial layer between the diaphragm 1 and the substrate 3. The diaphragm electrode material is usually PolySilicon, and the sacrificial layer material is usually SiO2. The sacrificial layer will be released during the processing of the MEMS chip, and the position where the sacrificial layer release stops is the position where the diaphragm is fixed. Usually, the position where the sacrificial layer release stops is not easy to control. The sacrificial layer can be partially etched at the position where the diaphragm needs to be fixed to form a blocking groove, and then filled with a material having a wet etching selectivity ratio with SiO2 to form a fixed position.
[0043] Further, the material of the upper diaphragm electrode 13 or the lower diaphragm electrode 14 is polysilicon. Further, the material of the insulating structure 16 is SiN.
[0044] Embodiment 2
[0045] In a second aspect of the present utility model, there is provided a microphone including the MEMS capacitive sensor provided in the first aspect of the present utility model. Specifically, the MEMS microphone consists of three parts: MEMS Sensor, ASIC chip, and packaging. Generally, the MEMS chip mainly includes a diaphragm, a backplate, and a substrate. The diaphragm and the backplate form a parallel-plate capacitor. A bias voltage is applied to the diaphragm or the backplate. The sound pressure acts on the diaphragm, causing the distance between the diaphragm and the backplate to change, thereby resulting in a change in capacitance and generating an output of a voltage signal. The MEMS Sensor adopts the MEMS capacitive sensor provided in the first aspect of the present utility model.
[0046] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code that contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than that marked in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or operations, or can be implemented by a combination of dedicated hardware and computer instructions.
[0047] The above are only the preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.
Claims
1. A MEMS capacitive sensor, comprising: A double-layer diaphragm, a back plate with through holes, and a substrate, wherein the double-layer diaphragm and the back plate form a differential capacitance, characterized in that a plurality of sealing structures are provided at the end of the double-layer diaphragm, and each sealing structure is used to seal the movable part of the double-layer diaphragm and form a low-pressure area for the movable part; the sealing structure and the end of the double-layer diaphragm together form a slit, and the slit penetrates the double-layer diaphragm and extends to the substrate; the double-layer diaphragm includes an insulating structure, and the insulating structure is located between the substrate and the sealing structure and forms a release blocking structure with the substrate for determining the effective area of the double-layer diaphragm.
2. The MEMS capacitive sensor according to claim 1, characterized in that, At least three sealing structures are provided along the circumferential direction at the end of the double-layer diaphragm.
3. The MEMS capacitive sensor according to claim 1, wherein The sealing structures are uniformly distributed along the circumferential direction.
4. The MEMS capacitive sensor according to claim 1, wherein The double-layer diaphragm includes an upper diaphragm structure layer, an upper diaphragm electrode, a lower diaphragm structure layer, and a lower diaphragm electrode.
5. The MEMS capacitive sensor according to claim 4, wherein The material of the upper diaphragm electrode or the lower diaphragm electrode is polysilicon.
6. The MEMS capacitive sensor according to claim 4, wherein, The material of the insulation structure is S i N.
7. The MEMS capacitive sensor according to claim 1, wherein The width of the slit is not greater than 2 μm.
8. The MEMS capacitive sensor according to claim 1, characterized in that, The structure of the back plate is a sandwich structure.