A MEMS capacitive acceleration sensor with a spiral beam structure and a manufacturing method thereof

Abstract

The present invention discloses a spiral beam structure MEMS capacitive acceleration sensor and a manufacturing method, belonging to the technical field of micro-electromechanical systems. It includes an upper plate layer, an upper plate electrode lead-out point, an upper plate anti-collision frame, an upper plate bonding ring, an upper plate gold ring, an upper plate anti-collision bump group, a mass layer, an electrode lead-out point of the mass layer, a bonding ring on the mass layer, a cantilever circular ring beam group on the mass layer, a mass block, a cantilever circular ring beam group under the mass layer, a bonding ring under the mass layer, a lower plate layer, an electrode lead-out point of the lower plate, an anti-collision frame of the lower plate, a bonding ring of the lower plate, a lower plate gold ring, and an anti-collision bump group of the lower plate. The present invention has an adjustable working frequency, has the advantages of large effective area, high reliability, easy manufacturing, high sensitivity, and low cost, and can be used for acceleration signal pickup in different environments.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-electromechanical systems, and in particular relates to a MEMS capacitive acceleration sensor with a spiral beam structure and a manufacturing method thereof. Technical Background

[0002] MEMS (Micro-Electro-Mechanical System) accelerometer is an important inertial device that can convert the physical signal of external acceleration into an electrical signal that is easy to measure. It is widely used in aviation, aerospace, automobile and other fields. According to the detection principle, MEMS accelerometers can be divided into piezoresistive, piezoelectric and capacitive types.

[0003] A capacitive accelerometer is a sensor that converts the measured acceleration signal into a change in the capacitance of a capacitor. There are usually two ways to achieve this function: variable gap type and variable area type. The movable mass block of the sensor constitutes a movable electrode of the variable capacitor. When the mass block is displaced by acceleration, the gap or relative area of ​​the two differential capacitors formed by the movable electrode and the fixed electrode changes, causing the capacitance of the two differential capacitors to change. This change can be detected by a peripheral circuit to measure the magnitude of the acceleration.

[0004] In 2015, Yi Leiyang and others from the Institute of Geology and Geophysics of the Chinese Academy of Sciences proposed "a new type of MEMS acceleration sensor for seismic geophones" (Reference 1). Among them, one end of the cantilever beam is fixed to the middle of one side of the mass block, and the other end is fixed to the adjacent frame of the fixed side of the mass block. The inclined beam is fixed to the other corner of the fixed side of the mass block. The cantilever beam provides elastic stiffness for the mass block, and the inclined beam disperses the impact stress.

[0005] This structure has improved impact resistance, but it also has the following problems:

[0006] 1) The use of a cable-stayed beam structure is difficult to prepare and has reduced reliability.

[0007] 2) The silicon-silicon bonding temperature is high, causing the cantilever beam to deform and fail.

[0008] In 2011, Qifang Hu of Peking University proposed a high-sensitivity MEMS capacitive accelerometer in his paper “Low cross-axis sensitivity micro-gravity microelectromechanical system sandwich capacitance accelerometer” (Reference 2). In this paper, a layer of gold is sputtered on the lower surface of the upper glass plate as the upper electrode, a layer of gold is sputtered on the upper and lower surfaces of the double-sided SOI silicon wafer as the mass block layer electrode, a layer of gold is sputtered on the upper surface of the lower glass plate as the lower electrode, and 8 cantilever beams provide elastic stiffness for the movement of the mass block.

[0009] This structure can achieve high sensitivity, but there are the following problems:

[0010] 1) The quality layer is made of D-SOI silicon wafer, which is relatively expensive.

[0011] 2)SiO2 material is not conductive, and the method of leading out electrodes of each layer is relatively complicated.

[0012] 3) SiO2 and Au materials are used to make the upper and lower plates, and the parasitic capacitance is relatively large. Summary of the invention

[0013] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and to provide a spiral beam structure MEMS capacitive acceleration sensor and a manufacturing method thereof, wherein the sensor has the advantages of large capacitor facing area, high sensitivity, low manufacturing difficulty and low chip cost.

[0014] In order to achieve the above object, the technical solution adopted by the present invention is:

[0015] A spiral beam structure MEMS capacitive acceleration sensor, comprising an upper plate layer 31, an upper plate electrode lead-out point 32, an upper plate anti-collision frame 33, an upper plate bonding ring 34, an upper plate gold ring 35, an upper plate anti-collision bump group 36, a mass layer 41, a mass layer electrode lead-out point 42, a mass layer upper bonding ring 43, a mass layer upper cantilever circular ring beam group 44, a mass block 45, a mass layer lower cantilever circular ring beam group 46, a mass layer lower bonding ring 47, a lower plate layer 51, a lower plate electrode lead-out point 52, and a lower plate anti-collision frame 5 3. Lower plate bonding ring 54, lower plate gold ring 55, lower plate anti-collision bump group 56; the upper plate layer 31, upper plate anti-collision frame 33, mass layer 41, mass block 45, lower plate layer 51, lower plate anti-collision frame 53 are circular structures; the mass layer upper cantilever circular ring beam group 44 and the mass layer lower cantilever circular ring beam group 46 are fan-shaped ring structures; the upper plate bonding ring 34, the upper plate gold ring 35, the mass layer upper bonding ring 43, the mass layer lower bonding ring 47, the lower plate bonding ring 54, and the lower plate gold ring 55 are circular ring structures;

[0016] The upper plate electrode lead-out point 32 is located on the upper surface of the upper plate layer 31, the upper plate anti-collision frame 33 is located on the upper surface of the upper plate layer 31 and its radius is consistent with the inner radius of the upper plate bonding ring 34, the upper plate bonding ring 34 is located on the lower surface of the upper plate layer 31, the upper plate anti-collision convex point group 36 is located on the lower surface of the upper plate layer 31 and is directly opposite to the position of the mass block 45 in the mass layer 41, the upper plate gold ring 35 is located inside the upper plate bonding ring 34, the mass layer electrode lead-out point 42 is located on the upper surface of the mass layer 41, the mass layer upper bonding ring 43 is located on the upper surface of the mass layer 41, the inner ends of the beams of the cantilever circular ring beam group 44 on the mass layer are connected to the upper surface layer of the mass block 45, and the outer ends of the beams of the cantilever circular ring beam group 44 on the mass layer are connected to the mass layer The lower pole plate bonding ring 54 is located on the lower surface of the mass layer 41, and the lower pole plate bonding ring 54 is located on the lower surface of the mass layer 41. The lower pole plate bonding ring 54 is located on the upper surface of the lower pole plate layer 51, and the lower pole plate bonding ring 54 is located on the upper surface of the lower pole plate layer 51. The lower pole plate anti-collision convex point group 56 is located on the upper surface of the lower pole plate layer 51 and is directly opposite to the mass block 45 in the mass layer 41. The lower pole plate gold ring 55 is located inside the lower pole plate bonding ring 54.

[0017] The upper plate layer 31 , the mass layer 41 , and the lower plate layer 51 are bonded from top to bottom by gold-silicon, silicon-silicon, and gold-silicon. The middle mass layer 41 senses acceleration and converts acceleration signals through the differential capacitor formed with the upper plate layer 31 and the lower plate layer 51 .

[0018] Furthermore, the mass layer upper cantilever circular ring beam group 44 and the mass layer lower cantilever circular ring beam group 46 are elastic movable beam structures, and the mass layer upper cantilever circular ring beam group 44 and the mass layer lower cantilever circular ring beam group 46 are parallel and arranged symmetrically relative to the center.

[0019] Furthermore, the mass layer upper cantilever circular ring beam group 44 and the mass layer lower cantilever circular ring beam group 46 are formed by dry etching the bonded mass layer 41 .

[0020] Furthermore, a gold-silicon low-temperature bonding structure is formed between the upper electrode plate gold ring 35 in the upper electrode plate bonding ring 34 and the upper bonding ring 43 of the mass layer, thereby bonding the upper electrode layer 31 and the mass layer 41 together; a gold-silicon low-temperature bonding structure is formed between the lower electrode plate gold ring 55 in the lower electrode plate bonding ring 54 and the lower bonding ring 47 of the mass layer, thereby bonding the mass layer 41 and the lower electrode layer 51 together.

[0021] Furthermore, the mass layer upper cantilever circular ring beam group 44 and the mass layer lower cantilever circular ring beam group 46 each have four beams.

[0022] Furthermore, the upper plate layer 31, the upper plate electrode lead-out point 32, the mass layer 41, the mass layer electrode lead-out point 42, the mass layer upper bonding ring 43, the mass layer upper cantilever circular ring beam group 44, the mass block 45, the mass layer lower cantilever circular ring beam group 46, the mass layer lower bonding ring 47, the lower plate layer 51, and the lower plate electrode lead-out point 52 are all made of low-resistance silicon material; the upper plate gold ring 35 and the lower plate gold ring 55 are made of gold material; the upper plate anti-collision frame 33, the upper plate bonding ring 34, the upper plate anti-collision bump group 36, the lower plate anti-collision frame 53, the lower plate bonding ring 54, and the lower plate anti-collision bump group 56 are all made of low-resistance silicon material, and there is an oxide layer on the surface.

[0023] The method for manufacturing the mass layer in the above-mentioned spiral beam structure MEMS capacitive acceleration sensor comprises the following steps:

[0024] 1) Two double-sided polished low-resistance silicon wafers are subjected to deep wet etching on the front side to obtain the cavities under the beams of the cantilever circular ring beam group 44 on the quality layer and the cantilever circular ring beam group 46 under the quality layer;

[0025] 2) performing silicon-silicon bonding on the two low-resistance silicon wafers processed in step 1) with their front faces facing each other;

[0026] 3) Etching the upper bonding ring 43 of the quality layer, the lower bonding ring 47 of the quality layer, the upper cantilever circular ring beam group 44 of the quality layer, and the lower cantilever circular ring beam group 46 of the quality layer on the upper and lower surfaces of the bonded silicon wafers.

[0027] The method for manufacturing the upper electrode plate layer and the lower electrode plate layer in the above-mentioned spiral beam structure MEMS capacitive acceleration sensor comprises the following steps:

[0028] 1) Performing the first oxidation on the double-sided polished low-resistance silicon wafer;

[0029] 2) etching the upper electrode layer 31 and the lower electrode layer 51 facing the mass block 45 on the front side of the low-resistance silicon wafer processed in step 1), and etching a circular pattern with the same inner radius as the upper bonding ring 43 and the lower bonding ring 47 of the mass layer on the back side;

[0030] 3) Perform a second oxidation on the low-resistance silicon wafer;

[0031] 4) etching the upper electrode layer 31 and the lower electrode layer 51 on the front side of the low-resistance silicon wafer after the treatment in step 3) to face the mass block 45, retaining the upper electrode anti-collision bump group 36 and the lower electrode anti-collision bump group 56, and obtaining the upper electrode bonding ring 34 and the lower electrode bonding ring 54;

[0032] 5) Etching the upper plate electrode lead-out point 32 and the lower plate electrode lead-out point 52 on the reverse side of the upper plate layer 31 and the lower plate layer 51 on the low-resistance silicon wafer processed in step 4).

[0033] Furthermore, the upper electrode layer 31 and the lower electrode layer 51 are oxidized twice to form a step spacing, thereby providing a capacitance gap for the acceleration sensor.

[0034] The present invention has the following beneficial effects:

[0035] 1) The present invention adopts a circular mass block structure, which effectively increases the area facing the capacitor plates and improves the capacitance value generated by the mass block per unit movement distance.

[0036] 2) The present invention adopts a circular mass block structure, which effectively reduces the negative impact of the capacitor edge effect on the acceleration sensor and improves the reliability of the acceleration sensor.

[0037] 3) The present invention adopts a circular or annular structure, and there is no need to perform convex corner protection during the etching process, which effectively reduces the device inconsistency caused by setting the convex corners during the manufacturing process.

[0038] 4) The bonding of each layer of the electrode plate of the present invention adopts gold-silicon low-temperature bonding, which effectively reduces the bonding difficulty and reduces the negative impact of cantilever beam bending caused by high temperature.

[0039] 5) Each layer of the present invention adopts low-resistance silicon material, which effectively reduces the production cost and reduces the difficulty of producing each layer of electrodes.

[0040] 6) The present invention provides an anti-collision frame to prevent damage or failure of the sensor during bonding, slicing and use.

[0041] 7) The present invention adopts a method in which the number of cantilever circular ring beams can be adjusted to obtain sensors with different working frequency bands, which are adjustable and highly adaptable. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a structural schematic diagram of the MEMS acceleration sensor in the background technology document 1.

[0043] Figure 2 It is a schematic diagram of the structure of the MEMS capacitive acceleration sensor in background technology document 2.

[0044] Figure 3 FIG. 4 is a schematic diagram of the overall structure of an acceleration sensor in an embodiment of the present invention.

[0045] Figure 4 for Figure 3 Schematic diagram of the structure of the middle and upper plates.

[0046] Figure 5 for Figure 3 Schematic diagram of the structure of the middle mass layer.

[0047] Figure 6for Figure 3 Schematic diagram of the structure of the middle and lower plates.

[0048] Figure 7 and 8 Schematic diagram of the structure of acceleration sensors with different numbers of beams in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0050] Figure 1 In the MEMS acceleration sensor shown, one end of the cantilever beam 12 is fixed to the middle of one side of the mass block 11, and the other end is fixed to the adjacent side frame of the fixed side of the mass block 11. The diagonal beam 13 is fixed to the other corner of the fixed side of the mass block 11. The cantilever beam 12 provides elastic stiffness for the mass block, and the diagonal beam 13 disperses impact stress.

[0051] Figure 2 In the MEMS capacitive acceleration sensor shown, a gold layer 22 is sputtered on the lower surface of the upper glass plate 21 as an upper electrode plate, a gold layer 24 and 25 are sputtered on the upper and lower surfaces of the double-sided SOI silicon wafer 23 as mass block layer electrodes, a gold layer is sputtered on the upper surface of the lower glass plate 26 as a lower electrode plate, and 8 cantilever beams 27 provide elastic stiffness for the movement of the mass block.

[0052] The disadvantages of the above two existing acceleration sensors have been pointed out in the background technology section and will not be repeated here.

[0053] In order to solve the defects of the above acceleration sensors, this embodiment provides a circular MEMS capacitive acceleration sensor based on a spiral beam structure.

[0054] like Figures 3 to 6 As shown, the acceleration sensor includes an upper pole plate layer 31, an upper pole plate electrode lead-out point 32, an upper pole plate anti-collision frame 33, an upper pole plate bonding ring 34, an upper pole plate gold ring 35, an upper pole plate anti-collision bump group 36, a mass layer 41, a mass layer electrode lead-out point 42, an upper bonding ring 43 of the mass layer, an upper cantilever circular ring beam group 44 of the mass layer, a mass block 45, a lower cantilever circular ring beam group 46 of the mass layer, a lower bonding ring 47 of the mass layer, a lower pole plate layer 51, a lower pole plate electrode lead-out point 52, a lower pole plate anti-collision frame 53, a lower pole plate bonding ring 54, a lower pole plate gold ring 55, and a lower pole plate anti-collision bump group 56.

[0055] Among them, the upper electrode plate electrode lead-out point 32 is located on the upper surface of the upper electrode layer 31, the upper electrode plate anti-collision frame 33 is located on the upper surface of the upper electrode layer 31 and its radius is consistent with the inner radius of the upper electrode plate bonding ring 34, the upper electrode plate bonding ring 34 is located on the lower surface of the upper electrode layer 31, the upper electrode plate anti-collision convex point group 36 is located on the lower surface of the upper electrode layer 31 and is directly opposite to the position of the mass block 45 in the mass layer 41, the upper electrode plate gold ring 35 is located inside the upper electrode plate bonding ring 34, the mass layer electrode lead-out point 42 is located on the upper surface of the mass layer 41, the mass layer upper bonding ring 43 is located on the upper surface of the mass layer 41, the inner ends of each beam of the cantilever circular ring beam group 44 on the mass layer are connected to the upper surface layer of the mass block 45, and the outer ends of each beam of the cantilever circular ring beam group 44 on the mass layer are connected to the mass The mass layer 41 is connected to the upper surface layer of the frame, the inner ends of the cantilever circular ring beam group 46 under the mass layer are connected to the lower surface layer of the mass block 45, the outer ends of the cantilever circular ring beam group 46 under the mass layer are connected to the lower surface layer of the frame of the mass layer 41, the bonding ring 47 under the mass layer is located on the lower surface of the mass layer 41, the lower electrode lead-out point 52 is located on the lower surface of the lower electrode layer 51, the lower electrode anti-collision frame 53 is located on the lower surface of the lower electrode layer 51 and the radius is consistent with the inner circle radius of the lower electrode bonding ring 54, the lower electrode bonding ring 54 is located on the upper surface of the lower electrode layer 51, the lower electrode anti-collision bump group 56 is located on the upper surface of the lower electrode layer 51 and is opposite to the position of the mass block 45 in the mass layer 41, and the lower electrode gold ring 55 is located inside the lower electrode bonding ring 54.

[0056] The three-layer structure of the upper electrode layer 31, the mass layer 41, and the lower electrode layer 51 of the acceleration sensor is made of four pieces of low-resistance silicon; the upper electrode layer 31, the upper electrode anti-collision frame 33, the mass layer 41, the mass block 45, the lower electrode layer 51, and the lower electrode anti-collision frame 53 are circular structures; the upper cantilever circular ring beam group 44 of the mass layer and the lower cantilever circular ring beam group 46 of the mass layer are fan-shaped ring structures; the upper electrode plate bonding ring 34, the upper electrode plate gold ring 35, the upper bonding ring 43 of the mass layer, the lower bonding ring 47 of the mass layer, the lower electrode plate bonding ring 54, and the lower electrode plate gold ring 55 are circular ring structures.

[0057] The bonding between the upper electrode layer 31 and the mass layer 41 is achieved by using the upper electrode gold ring 35 in the upper electrode bonding ring 34 and the mass layer upper bonding ring 43 using gold-silicon low-temperature bonding. The bonding between the mass layer 41 and the lower electrode layer 51 is achieved by using the lower electrode gold ring 55 in the lower electrode bonding ring 54 and the mass layer lower bonding ring 47 using gold-silicon low-temperature bonding.

[0058] The setting of the upper electrode plate anti-collision frame 33 and the lower electrode plate anti-collision frame 53 can provide a warning for bonding, scribing, and use, prevent scratching from damaging the sensor, and prevent the quality layer 41 from being attracted to the upper electrode layer 31 and the lower electrode layer 51 due to external forces during bonding and use, resulting in failure of the sensor.

[0059] The arrangement of the upper plate anti-collision convex point group 36 and the lower plate anti-collision convex point group 56 can prevent the mass block 45 from being attracted to the upper plate layer 41 and the lower plate layer 51 when moving up and down, thereby causing failure of the sensor.

[0060] The cantilever circular ring beam group 44 on the mass layer and the cantilever circular ring beam group 46 under the mass layer are formed by dry etching the bonded mass layer 41, are respectively located on the upper and lower sides of the mass block 45, and are elastic movable beam structures. The cantilever circular ring beam group 44 on the mass layer is parallel to the cantilever circular ring beam group 46 under the mass layer and are arranged in a centrally symmetrical manner.

[0061] The upper electrode layer 31 and the lower electrode layer 51 are oxidized twice to form a step distance, thereby providing a capacitance gap for the acceleration sensor.

[0062] The circular MEMS capacitive acceleration sensor uses 4 pairs of 8 cantilever beams, namely, the mass layer upper cantilever ring beam group 44 and the mass layer lower cantilever ring beam group 46. The fan-shaped ring cantilever beams can be extended or shortened, and the number can be increased or decreased according to different application environments and sensitivity requirements. For example, Figure 7 There are 6 beams in the middle. Figure 8 There are 4 beams in the middle.

[0063] The working principle of the present invention is as follows:

[0064] The circular MEMS capacitive acceleration sensor based on the spiral beam structure consists of an upper plate layer, a lower plate layer and a mass layer, which are the upper plate layer, the mass layer and the lower plate layer from top to bottom. The middle mass layer senses acceleration and transmits the acceleration signal through the differential capacitance formed with the upper and lower plate layers. The displacement change caused by acceleration causes the capacitance between the middle mass block and the upper and lower fixed plates to change. Ideally, the mass block is located in the middle of the two fixed plates. In the absence of acceleration, the mass layer does not move, and the expression of the upper and lower capacitance values ​​is:

[0065]

[0066] Where C1 and C2 are the capacitance values ​​of the upper and lower parts, ε is the relative dielectric constant, ε0 is the vacuum dielectric constant, S is the area facing the two electrodes, and d0 is the initial distance between the electrodes. Since the mass layer does not move, the capacitances C1 and C2 are equal, and ΔC = 0, which means that no capacitance change occurs.

[0067] When the circular MEMS capacitive acceleration sensor based on the spiral beam structure senses external acceleration, due to the existence of inertial force, the mass layer will shift in the opposite direction of the acceleration, resulting in a displacement of x. At this time, the expression of the upper and lower capacitance values ​​is:

[0068]

[0069]

[0070] At this time, the difference between the upper and lower capacitances is:

[0071]

[0072] Through the conversion output of the differential capacitor, the acceleration value can be calculated as:

[0073]

[0074] Where m is the mass of the mass layer mass block, and k is the total elastic stiffness of the system.

[0075] The preparation process of the upper electrode layer 31 mainly includes the following steps:

[0076] 1) The double-sided polished low-resistance silicon wafer is oxidized for the first time, and an oxide layer is formed on the upper and lower surfaces of the silicon wafer;

[0077] 2) using dry etching to remove the oxide layer on the surface of the silicon wafer to form a circular pattern on the front side, the circular pattern is consistent with the shape of the mass block 45, and the position is the projection position of the mass block 45;

[0078] 3) Dry etching is used to remove the oxide layer on the surface of the silicon wafer to form a reverse circular pattern, the radius of which is consistent with the inner radius of the upper plate anti-collision frame 33, the upper bonding ring 43 of the mass layer, the lower bonding ring 47 of the mass layer, and the lower plate anti-collision frame 53, and the position is the projection position of the upper bonding ring 43 of the mass layer and the lower bonding ring 47 of the mass layer

[0079] 4) performing a second oxidation on the silicon wafer after photolithography, at which time the thickness of the oxide layer at the circular pattern on the front side and the circular pattern on the back side is lower than the thickness of the oxide layer at the peripheral position;

[0080] 5) Dry etching is used to remove the oxide layer on the surface of the silicon wafer to form a front circular pattern, and the upper plate anti-collision bump group 36 is retained. The circular pattern is consistent with the shape of the mass block 45, and the position is the projection position of the mass block 45. At the same time, a front circular ring pattern is formed, and the inner circle radius of the circular ring pattern is greater than the radius of the above circular pattern, so as to obtain the upper plate bonding ring 34;

[0081] 6) using dry etching to remove the oxide layer on the surface of the silicon wafer to form a reverse electrode lead-out pattern, which is the upper plate electrode lead-out point 32;

[0082] 7) Using the gold sputtering method, a gold ring 35 for the upper electrode is formed on the circular pattern on the front side of the silicon wafer.

[0083] The preparation process of the quality layer 41 mainly includes the following steps:

[0084] 1) Deeply etch the double-sided polished low-resistance silicon wafer on the front side using wet etching, and obtain the cavity under the cantilever circular ring beam using a self-stop etching process;

[0085] 2) Select two deep-etched low-resistance silicon wafers and perform silicon-silicon bonding on the front side to complete the cavity structure under the double-sided cantilever circular ring beam of the quality layer 41;

[0086] 3) Using dry etching to remove the excess part of the silicon wafer, forming an upper bonding ring 43 and a lower bonding ring 47 of the quality layer on the upper and lower sides of the silicon wafer after bonding;

[0087] 4) using dry etching to remove the excess portion of the silicon wafer, forming an upper cantilever ring beam group 44 and a lower cantilever ring beam group 46 of the quality layer on the upper and lower sides of the silicon wafer after bonding;

[0088] The preparation process of the lower electrode layer 51 mainly includes the following steps:

[0089] 1) The double-sided polished low-resistance silicon wafer is oxidized for the first time, and an oxide layer is formed on the upper and lower surfaces of the silicon wafer;

[0090] 2) using dry etching to remove the oxide layer on the surface of the silicon wafer to form a circular pattern on the front side, the circular pattern is consistent with the shape of the mass block 45, and the position is the projection position of the mass block 45;

[0091] 3) Dry etching is used to remove the oxide layer on the surface of the silicon wafer to form a reverse circular pattern, the radius of which is consistent with the inner radius of the upper plate anti-collision frame 33, the upper bonding ring 43 of the mass layer, the lower bonding ring 47 of the mass layer, and the lower plate anti-collision frame 53, and the position is the projection position of the upper bonding ring 43 of the mass layer and the lower bonding ring 47 of the mass layer

[0092] 4) performing a second oxidation on the silicon wafer after photolithography, at which time the thickness of the oxide layer at the circular pattern on the front side and the circular pattern on the back side is lower than the thickness of the oxide layer at the peripheral position;

[0093] 5) Dry etching is used to remove the oxide layer on the surface of the silicon wafer to form a front circular pattern, and the upper plate anti-collision bump group 55 is retained. The circular pattern is consistent with the shape of the mass block 45, and the position is the projection position of the mass block 45. At the same time, a front circular ring pattern is formed, and the inner circle radius of the circular ring pattern is greater than the radius of the above circular pattern, so as to obtain an upper plate bonding ring 53;

[0094] 6) Using dry etching to remove the oxide layer on the surface of the silicon wafer to form a reverse electrode lead-out pattern, which is the upper plate electrode lead-out point 52;

[0095] 7) Using the gold sputtering method, a gold ring 54 for the upper electrode is formed on the circular pattern on the front side of the silicon wafer.

[0096] After the upper electrode layer 31, the quality layer 41, and the lower electrode layer 51 are prepared respectively, the upper electrode layer 31 faces the quality layer 41, and the lower electrode layer 51 faces the quality layer. The order of the upper electrode layer 31, the quality layer 41, and the lower electrode layer 51 is adopted from top to bottom. The low-temperature gold-silicon bonding method is used to utilize the low melting point of the gold material to complete the bonding of the three-layer structure of the sensor.

[0097] The present invention has an adjustable operating frequency and has the advantages of large effective area, high reliability, easy manufacture, high sensitivity and low cost. In addition, the present invention adopts a spiral beam structure, which is easy to adjust the number of cantilever circular ring beams, so as to obtain different system elastic coefficients and system characteristic frequencies. By adjusting the number of cantilever circular ring beams, it can adapt to different use environments. For example, when the number of cantilever circular ring beams is adjusted to 2 to 4 or 3 to 6, the system elastic coefficient of the acceleration sensor increases and the system characteristic frequency decreases, which can increase the range of the system's perception of acceleration, thereby obtaining a large-range, high-precision circular MEMS capacitive acceleration sensor.

[0098] It should be noted that the above description is only a specific example of the present invention and does not constitute any limitation to the present invention. Obviously, for professionals in this field, after understanding the content and principles of the present invention, it is possible to make various modifications and changes in form and details without departing from the principles and structures of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A spiral beam structure MEMS capacitive acceleration sensor, characterized in that: It includes an upper plate layer, an upper plate electrode lead-out point, an upper plate anti-collision frame, an upper plate bonding ring, an upper plate gold ring, an upper plate anti-collision convex point group, a mass layer, a mass layer electrode lead-out point, an upper bonding ring of the mass layer, an upper cantilever circular ring beam group of the mass layer, a mass block, a lower cantilever circular ring beam group of the mass layer, a lower bonding ring of the mass layer, a lower plate layer, a lower plate electrode lead-out point, a lower plate anti-collision frame, a lower plate bonding ring, a lower plate gold ring, and a lower plate anti-collision convex point group; the upper plate layer, the upper plate anti-collision frame, the mass layer, the mass block, the lower plate layer, and the lower plate anti-collision frame are circular structures; the upper cantilever circular ring beam group of the mass layer and the lower cantilever circular ring beam group of the mass layer are fan-shaped ring structures; the upper plate bonding ring, the upper plate gold ring, the upper bonding ring of the mass layer, the lower bonding ring of the mass layer, the lower plate bonding ring, and the lower plate gold ring are circular ring structures; The upper electrode lead-out point is located on the upper surface of the upper electrode layer, the upper electrode anti-collision frame is located on the upper surface of the upper electrode layer and its radius is consistent with the inner radius of the upper electrode bonding ring, the upper electrode bonding ring is located on the lower surface of the upper electrode layer, the upper electrode anti-collision convex point group is located on the lower surface of the upper electrode layer and is directly opposite to the mass block position in the mass layer, the upper electrode gold ring is located inside the upper electrode bonding ring, the mass layer electrode lead-out point is located on the upper surface of the mass layer, the mass layer upper bonding ring is located on the upper surface of the mass layer, the inner ends of each beam of the cantilever circular ring beam group on the mass layer are connected to the upper surface layer of the mass block, and the outer ends of each beam of the cantilever circular ring beam group on the mass layer are connected to the mass layer The frame is connected to the upper surface layer, the inner ends of each beam of the cantilever circular ring beam group under the mass layer are connected to the lower surface layer of the mass block, the outer ends of each beam of the cantilever circular ring beam group under the mass layer are connected to the lower surface layer of the mass layer frame, the lower bonding ring of the mass layer is located on the lower surface of the mass layer, the lower electrode plate electrode lead-out point is located on the lower surface of the lower electrode plate layer, the lower electrode plate anti-collision frame is located on the lower surface of the lower electrode plate layer and the radius is consistent with the inner radius of the lower electrode plate bonding ring, the lower electrode plate bonding ring is located on the upper surface of the lower electrode plate layer, the lower electrode plate anti-collision convex point group is located on the upper surface of the lower electrode plate layer and is directly opposite to the mass block position in the mass layer, and the lower electrode plate gold ring is located inside the lower electrode plate bonding ring; The upper plate layer, the mass layer, and the lower plate layer are bonded from top to bottom by gold-silicon, silicon-silicon, and gold-silicon. The middle mass layer senses acceleration and converts acceleration signals through the differential capacitor formed with the upper plate layer and the lower plate layer. The cantilever circular ring beam group on the mass layer and the cantilever circular ring beam group under the mass layer are elastic movable beam structures, and the cantilever circular ring beam group on the mass layer is parallel to the cantilever circular ring beam group under the mass layer and is arranged symmetrically relative to the center; A gold-silicon low-temperature bonding structure is formed between the upper electrode plate gold ring in the upper electrode plate bonding ring and the upper bonding ring of the mass layer, thereby bonding the upper electrode layer and the mass layer together; a gold-silicon low-temperature bonding structure is formed between the lower electrode plate gold ring in the lower electrode plate bonding ring and the lower bonding ring of the mass layer, thereby bonding the mass layer and the lower electrode layer together.

2. The spiral beam structure MEMS capacitive acceleration sensor according to claim 1, characterized in that: The mass layer upper cantilever circular ring beam group and the mass layer lower cantilever circular ring beam group are formed by dry etching the bonded mass layers.

3. The spiral beam structure MEMS capacitive acceleration sensor according to claim 1, characterized in that: The mass layer upper cantilever circular ring beam group and the mass layer lower cantilever circular ring beam group each have 4 beams.

4. The spiral beam structure MEMS capacitive acceleration sensor according to claim 1, characterized in that: The upper plate layer, the upper plate electrode lead-out point, the mass layer, the mass layer electrode lead-out point, the bonding ring on the mass layer, the cantilever circular ring beam group on the mass layer, the mass block, the cantilever circular ring beam group below the mass layer, the bonding ring below the mass layer, the lower plate layer, and the lower plate electrode lead-out point are all made of low-resistance silicon material; the upper plate gold ring and the lower plate gold ring are made of gold material; the upper plate anti-collision frame, the upper plate bonding ring, the upper plate anti-collision bump group, the lower plate anti-collision frame, the lower plate bonding ring, and the lower plate anti-collision bump group are all made of low-resistance silicon material, and there is an oxide layer on their surface.

5. The method for manufacturing the mass layer in the spiral beam structure MEMS capacitive acceleration sensor according to claim 1, characterized in that: The steps include: 1) Two double-sided polished low-resistance silicon wafers are subjected to deep front wet etching to obtain cavities under the beams of the cantilever circular ring beam group on the quality layer and the cantilever circular ring beam group under the quality layer; 2) performing silicon-silicon bonding on the two low-resistance silicon wafers processed in step 1) with their front faces facing each other; 3) Etching an upper bonding ring for the quality layer, a lower bonding ring for the quality layer, an upper cantilever circular ring beam group for the quality layer, and a lower cantilever circular ring beam group for the quality layer on the upper and lower sides of the bonded silicon wafers.

6. The method for manufacturing the upper electrode layer and the lower electrode layer in the spiral beam structure MEMS capacitive acceleration sensor according to claim 1, characterized in that: The steps include: 1) Performing the first oxidation on the double-sided polished low-resistance silicon wafer; 2) etching the upper electrode layer and the lower electrode layer facing the mass block on the front side of the low-resistance silicon wafer processed in step 1), and etching a circular pattern with the same radius as the inner circle of the upper bonding ring of the mass layer and the lower bonding ring of the mass layer on the back side; 3) Perform a second oxidation on the low-resistance silicon wafer; 4) etching the upper electrode layer and the lower electrode layer on the front side of the low-resistance silicon wafer processed in step 3) to face the mass block, retaining the upper electrode anti-collision bump group and the lower electrode anti-collision bump group, and obtaining the upper electrode bonding ring and the lower electrode bonding ring; 5) Etching the upper plate electrode lead-out points and the lower plate electrode lead-out points on the reverse sides of the upper plate layer and the lower plate layer on the low-resistance silicon wafer processed in step 4).

7. The manufacturing method according to claim 6, characterized in that: The upper electrode layer and the lower electrode layer are oxidized twice to form a step spacing, thereby providing a capacitance gap for the acceleration sensor.

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