MEMS capacitance differential sensor and microphone

Abstract

The utility model relates to an MEMS capacitance differential sensor and a microphone, the capacitance differential sensor comprises a double-layer diaphragm, a backboard and a substrate, and the double-layer diaphragm and the backboard form a differential capacitor; a plurality of sealing structures are arranged at the end part of the double-layer vibrating diaphragm along the circumferential direction, and the plurality of sealing structures are used for sealing a non-fixed part of the double-layer vibrating diaphragm and enabling the non-fixed part to form a low-pressure area; a slit is formed between the sealing structure and the end part of the double-layer diaphragm, and the slit penetrates through the bottom-layer diaphragm from the top-layer diaphragm of the double-layer diaphragm to the substrate; one side, far away from the double-layer diaphragm, of the slit is provided with an isolation groove, and the isolation groove divides an electrode of the double-layer diaphragm into a plurality of parts. According to the utility model, through the sealing double-diaphragm structure, the microphone noise is reduced, and the effective area of the diaphragm is increased.

Description

Technical Field

[0001] The utility model belongs to the technical field of sensors, and particularly relates to a MEMS capacitive differential sensor and a microphone. 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 exceeding 7 billion. 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 having 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 diaphragm layer cannot be used to fill the blocking groove.

[0004] Since the MEMS diaphragm is fixed around its perimeter, the displacement around the diaphragm is zero, and the deformation displacement of the diaphragm under sound pressure is uneven. Therefore, the diaphragm has a small effective area, and the ratio of the effective area to the actual area of the diaphragm is 48%, which is better than when the diaphragm is completely fixed around its perimeter. The stiffness of the diaphragm is relatively large, resulting in a small sensitivity of the microphone. Summary of the Utility Model

[0005] In order to reduce the background noise of the MEMS microphone and increase the effective area of the diaphragm, in the first aspect of the present utility model, a MEMS capacitive differential sensor is provided, including: a double-layer diaphragm, a back plate, and a substrate. The double-layer diaphragm and the back plate form a differential capacitance. A plurality of sealing structures are provided along the circumferential direction at the end of the double-layer diaphragm. Each sealing structure is used to seal the non-fixed part of the double-layer diaphragm and form a low-pressure area for the non-fixed part. A slit is formed between the sealing structure and the end of the double-layer diaphragm. The slit penetrates from the top diaphragm of the double-layer diaphragm through the bottom diaphragm to the substrate. An isolation groove is provided on the side of the slit away from the double-layer diaphragm. The isolation groove divides the electrodes of the double-layer diaphragm into multiple parts.

[0006] In some embodiments of the present utility model, at least three sealing structures are provided along the circumferential direction at the end of the double-layer diaphragm.

[0007] In some embodiments of the present utility model, the sealing structures are evenly distributed along the circumferential direction.

[0008] In some embodiments of the present utility model, the sealing structure is realized through the following steps: etching a blocking groove on the double-layer diaphragm; etching from the bottom of the etched blocking groove towards the substrate surface until reaching the substrate surface; filling the blocking groove by depositing an insulating material layer.

[0009] In some embodiments of the present utility model, the isolation groove is filled with an insulating material.

[0010] Furthermore, the insulating material has a selectivity ratio with silicon dioxide.

[0011] Preferably, the insulating material is polyimide, polyethylene, polypropylene, aluminum nitride or silicon nitride.

[0012] In some embodiments of the present utility model, the etched blocking groove further includes a lead region.

[0013] Furthermore, the etched blocking groove retains a width region greater than 5 μm free of etching.

[0014] In a second aspect of the present utility model, there is provided a microphone including the MEMS capacitive differential sensor provided in the first aspect of the present utility model.

[0015] The beneficial effects of the present utility model are:

[0016] The present utility model relates to an MEMS capacitive differential sensor and a microphone. The capacitive differential sensor includes: a double-layer diaphragm, a back plate and a substrate. A differential capacitance is formed between the double-layer diaphragm and the back plate. A plurality of sealing structures are provided along the circumferential direction at the end of the double-layer diaphragm. The plurality of sealing structures are used to seal the non-fixed part of the double-layer diaphragm and form a low-pressure region for the non-fixed part. A slit is formed between the sealing structure and the end of the double-layer diaphragm. The slit penetrates from the top diaphragm of the double-layer diaphragm through the bottom diaphragm to the substrate. An isolation groove is provided on one side of the slit away from the double-layer diaphragm. The isolation groove divides the electrodes of the double-layer diaphragm into multiple parts. It can be seen that the microphone provided by the present utility model has a sealed double-membrane structure. The middle of the double membrane is a low-pressure region. The diaphragm as a whole has partially fixed boundaries. The diaphragm forms a fixed anchor point through an insulating material layer at the fixed position. The diaphragm has an isolation groove in the area outside the Slit, forming electrical isolation from the internal area, thereby reducing parasitic capacitance and improving device sensitivity. Description of the Drawings

[0017] Figure 1 A top view schematic diagram of the basic structure of the MEMS capacitive differential sensor in some embodiments of the present invention;

[0018] Figure 2 A half-sectional view schematic diagram of the basic structure of the MEMS capacitive differential sensor in some embodiments of the present invention;

[0019] Figure 3 A partially enlarged cross-sectional view schematic diagram of the basic structure of the MEMS capacitive differential sensor in some embodiments of the present invention;

[0020] Figure 4 A signal output schematic diagram of the MEMS capacitive differential sensor in some embodiments of the present invention;

[0021] Figure 5 A diaphragm displacement nephogram of the MEMS capacitive differential sensor in some embodiments of the present invention;

[0022] Figure 6 One of the etching structure schematic diagrams of the MEMS capacitive differential sensor in some embodiments of the present invention;

[0023] Figure 7 Another etching structure schematic diagram of the MEMS capacitive differential sensor in some embodiments of the present invention;

[0024] Figure 8 A third etching structure schematic diagram of the MEMS capacitive differential sensor in some embodiments of the present invention;

[0025] Figure 9 A fourth etching structure schematic diagram of the MEMS capacitive differential sensor in some embodiments of the present invention;

[0026] Figure 10 A fifth etching structure schematic diagram of the MEMS capacitive differential sensor in some embodiments of the present invention.

[0027] Reference numerals

[0028] 1. Double-layer diaphragm; 11. Upper diaphragm; 12. Lower diaphragm;

[0029] 13. Sealing structure; 14. Slit; 15. Diaphragm sealing boundary; 151. Electrical connection area; 152. External welding area;

[0030] 16. Sacrificial layer; 17. Etching barrier layer;

[0031] 18. Diaphragm fixing filling layer; 19. Diaphragm isolation groove;

[0032] 2. Backplate; 21. Backplate electrode; 22. Backplate insulating layer; 23. Diaphragm connection structure;

[0033] 24 Sandwich backplate;

[0034] 3. Substrate. Detailed implementation manners

[0035] The principles and features of the present utility model will be described below in conjunction with the accompanying drawings. The examples given are only used to explain the present utility model and are not intended to limit the scope of the present utility model.

[0036] Reference Figure 1 、 Figure 2 And Figure 4 In the first aspect of the present utility model, a MEMS capacitive differential sensor is provided, which includes a double-layer diaphragm (1), a backplate (2) and a substrate (3). The double-layer diaphragm (1) and the backplate (2) form a differential capacitance. A plurality of sealing structures (13) are provided along the circumferential direction at the end of the double-layer diaphragm (1). Each sealing structure (13) is used to seal the non-fixed part of the double-layer diaphragm (1) and form a low-pressure area for the non-fixed part. A slit (14) is provided between the sealing structure (13) and the end of the double-layer diaphragm (1). The slit (14) penetrates through the upper diaphragm (11) and the lower diaphragm (12) to the substrate (3). An isolation groove (19) is provided on one side of the slit (14) far from the double-layer diaphragm (1). The isolation groove (19) divides the electrodes of the double-layer diaphragm (1) into multiple parts.

[0037] Specifically, referring to Figure 2 And Figure 3 In this embodiment, the microphone has a substrate (3) and a backplate (2) with through holes. The backplate (2) has a three-layer structure, including a middle backplate electrode (21) and backplate insulating layers (22) above and below the backplate electrode (21). It has a double-membrane diaphragm structure and 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. The double-layer diaphragm (1) forms a differential output. The overall diaphragm has no less than three fixed parts. In the non-fixed part of the diaphragm (1), the upper and lower diaphragms (11, 12) are sealed by a boundary sealing structure (13).

[0038] It can be understood that in some embodiments of the present utility model, at least three sealing structures (13) are provided along the circumferential direction at the end of the double-layer diaphragm (1).

[0039] In some embodiments of the present utility model, without loss of generality, the sealing structures (13) are evenly distributed along the circumferential direction, so that the displacement of the diaphragm forms a symmetric structure at the boundary, and displacement cancellation is formed to a certain extent to reduce the noise of the diaphragm and improve the sensitivity.

[0040] As Figure 5 shown, a low-pressure region is formed through a sealed double-membrane structure to reduce the film damping pressure, thereby reducing the microphone noise. Since part of the diaphragm (1) is fixed, the diaphragm displacement is zero only at the fixed position of the diaphragm (1), and there is a large displacement at other positions. Therefore, the diaphragm (1) has a large effective area, and the ratio of the effective area to the actual area of the diaphragm is 65%.

[0041] Referring Figures 6 to 9 , in some embodiments of the present invention, the sealing structure (13) is achieved through the following steps: etching a blocking groove on the double-layer diaphragm (1); etching the sacrificial layer (16) along the direction of the substrate (3) from the etched blocking groove until reaching the surface of the substrate (3); filling the blocking groove by depositing an etching blocking layer (17).

[0042] Specifically, first, the etching of the blocking groove profile is performed on the diaphragm (1); then, the etching of the sacrificial layer material (16) is performed at the corresponding position, and the etching stops at the surface of the substrate (3); then, the diaphragm fixing filling layer (18) is deposited to fill the blocking groove.

[0043] It should be noted that generally, there is a sacrificial layer between the diaphragm and the substrate. The diaphragm electrode material is usually PolySilicon, and the sacrificial layer material is usually SiO2. In the processing of the MEMS chip, the sacrificial layer will be released, and the position where the sacrificial layer release stops is the fixed position of the diaphragm; however, the position where the sacrificial layer release stops is not easy to control. By partially etching the sacrificial layer at the position where the diaphragm needs to be fixed to form a blocking groove, and then filling it with a material having a wet etching selectivity ratio with SiO2, the fixed position can be formed; the substrate is usually at the ground potential, and the diaphragm is the output electrode, so the diaphragm layer cannot be used to fill the blocking groove. A closed area for the sacrificial layer (16) can be formed within the circle, which can form a fixing effect on the diaphragm (1).

[0044] It can be understood that in wet etching, having a selectivity ratio with SiO2 (silicon dioxide) means that the etching rate of these materials is relatively slow compared to SiO2 during the etching process, so they can be retained while etching SiO2. In this embodiment, the insulating materials having a selectivity ratio with SiO2 include, but are not limited to: one or more of Polyimide (PI), Silicon Nitride (SiN or Si3N4), Aluminum Nitride (AlN), Polyethylene (PE), or Polypropylene (PP).

[0045] In some embodiments of the present utility model, the isolation groove (19) is filled with an insulating material.

[0046] Specifically, by setting the isolation groove (19) around the diaphragm (1), the electrodes of the diaphragm (1) are divided into two parts, thereby reducing the parasitic capacitance and improving the sensitivity of the microphone. The isolation groove (19) is outside the Slit of the diaphragm (1). At the position of the isolation groove (19) of the diaphragm (1), it is filled with an insulating material, and this insulating material has a selectivity ratio with SiO2 in wet etching, usually SiN.

[0047] Preferably, the insulating material is polyimide, polyethylene, polypropylene, aluminum nitride or silicon nitride.

[0048] Reference Figure 10 In some embodiments of the present utility model, the sealing structure of the double-layer diaphragm further includes an electrode lead-out area, and the width of the pin area is greater than 5 μm.

[0049] Specifically, the diaphragm fixing position in this embodiment is usually also the electrode lead-out position. Therefore, the diaphragm etching blocking groove at the diaphragm fixing position usually does not completely cover the pin area of the diaphragm, that is, the electrical connection area 151; at least a width greater than 5 μm of the diaphragm pin area remains unetched for electrical connection with an external pad, that is, the external welding area 152.

[0050] Embodiment 2

[0051] In a second aspect of the present utility model, there is provided a microphone including the MEMS capacitive differential sensor provided in the first aspect of the present utility model.

[0052] It can be understood that based on the microphone of the present utility model, it has a sealed double-membrane structure. The middle part of the double membrane is a low-pressure area. The diaphragm as a whole has partially fixed boundaries. The diaphragm forms a fixed anchor point through a layer of insulating material at the fixed position; the area of the diaphragm outside the Slit has an isolation groove to form electrical isolation from the internal area, thereby reducing the parasitic capacitance and improving the sensitivity of the device.

[0053] Embodiment 3

[0054] 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 segment of a program, or a part of code that contains one or more executable instructions for implementing a 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 that performs the specified functions or operations, or can be implemented by a combination of dedicated hardware and computer instructions.

[0055] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A MEMS capacitive differential sensor, comprising: A double-layer diaphragm, a back plate and a substrate, wherein a differential capacitor is formed between the double-layer diaphragm and the back plate, characterized in that a plurality of sealing structures are provided along the circumferential direction at the end of the double-layer diaphragm, and each sealing structure is used to seal the non-fixed part of the double-layer diaphragm and form a low-pressure area for the non-fixed part; a slit is formed between the sealing structure and the end of the double-layer diaphragm, and the slit penetrates from the top diaphragm of the double-layer diaphragm through the bottom diaphragm to the substrate; an isolation groove is provided on one side of the slit away from the double-layer diaphragm, and the isolation groove divides the electrodes of the double-layer diaphragm into multiple parts.

2. The MEMS capacitive differential 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 differential sensor according to claim 1, characterized in that, The sealing structures are evenly distributed along the circumference.

4. The MEMS capacitive differential sensor according to claim 1, characterized in that The isolation groove is filled with an insulating material.

5. The MEMS capacitive differential sensor according to claim 4, wherein The insulating material has a selectivity ratio with silicon dioxide.

6. The MEMS capacitive differential sensor according to claim 5, wherein, The insulating material is polyimide, polyethylene, polypropylene, aluminum nitride or silicon nitride.

7. The MEMS capacitive differential sensor according to claim 1, characterized in that, The double-layer diaphragm further includes a pin area.

8. The MEMS capacitive differential sensor according to claim 1, wherein An etching groove at the fixed position of the double-layer diaphragm retains a width area greater than 5 μm without etching.

9. A MEMS microphone, characterized in that, An MEMS capacitive differential sensor according to any one of claims 1 to 8.

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