CN102252747A - Micro sound pressure sensor with bionic cricket cilia structure and manufacturing method thereof - Google Patents

Abstract

The invention discloses a sound pressure sensor with a micro-imitation cricket cilium structure and a manufacturing method thereof, belonging to the field of micro-electromechanical systems (MEMS). The cricket cilia structure 1 of the sensor is located above the sensitive diaphragm 2, and the sensitive diaphragm 2 is connected to the ring-shaped fixed structure 4 through the support beam 3; the sensitive diaphragm 2 and the two detection electrodes 5 on the glass substrate 6 form a flat capacitive structure . When there is external sound excitation, the cricket-like cilia structure 1 is bent and deformed, which drives the sensitive diaphragm 2 to move up and down, so that the capacitance between the sensitive diaphragm 2 and the two detection electrodes 5 changes, so as to detect the external sound excitation sound pressure. The ciliary structure 1 proposed by the present invention has the advantages of high strength and large aspect ratio, and overcomes the disadvantages of insufficient rigidity of cilia and insufficient sensitivity of acoustic sensors formed by SU-8 photoresist in the existing method. The sensor can be used in the monitoring fields of ocean, low-altitude and ground moving targets.

Description

A kind of miniature cricket imitation cilia structure sound pressure sensor and its manufacturing method

Field

The invention belongs to the field of micro-electromechanical systems (MEMS), in particular to a sound pressure sensor with a miniature cricket-like cilia structure.

Background technique

Acoustic detection and positioning technology has important applications in the monitoring fields of ocean, low-altitude and ground moving targets. The sound pressure sensor is the key device for underwater acoustic signal reception in the passive acoustic detection device. The sound pressure sensor manufactured by traditional machining is large in size, high in operating frequency and low in sensitivity. In order to improve the detection ability of the target, it is necessary to reduce the operating frequency of the sound pressure sensor, expand the working bandwidth, improve the receiving sensitivity and reduce the volume and weight. The development of MEMS technology provides an important technology for the improvement of the sensitivity and miniaturization of the sound pressure sensor. The method increases the number of sound pressure sensor arrays per unit area, reduces the distance between the sound pressure sensors in the array, and improves the directivity of the sound pressure sensors to low-frequency signals.

The acoustic pressure sensor (MEMS based hairflow-sensors as model systems for acoustic perception studies) developed by Krijnen and others at the University of Twente in the Netherlands, adopts the capacitive detection principle and passes through the sensitive diaphragm twice After spin-coating SU-8 photoresist, exposure and development, a cricket-like cilia structure is formed. Because the cricket-like cilia structure is made of SU-8 photoresist, the stiffness is relatively low, resulting in low sensitivity of the sound pressure sensor.

Contents of the invention

In order to overcome the shortcomings of low rigidity and low sensitivity of the cilia structure in the existing sound pressure sensor imitating the cilium structure of the cricket tail, and also to reduce the volume of the sensor device, the present invention proposes a new miniature cricket-like cilia structure Sound pressure sensor and its manufacturing method.

The technical solution of the present invention is a miniature cricket-imitation cilia structure sound pressure sensor, which includes a cricket-imitation cilia structure 1 , a sensitive diaphragm 2 , a support beam 3 , an annular fixing structure 4 , two detection electrodes 5 and a glass substrate 6 . The cricket-like cilia structure 1 is located above the sensitive diaphragm 2 and is integrated with it. The sensitive diaphragm 2 is connected to the annular fixed structure 4 through two support beams 3, and there is a gap between the sensitive diaphragm 2 and the annular fixed structure 4. Gap 9; the fixed structure 4 is anodically bonded to the glass substrate 6 sputtered with two detection electrodes 5, so that a flat capacitive structure is formed between the sensitive diaphragm 2 and the two detection electrodes 5 to detect the sensitive diaphragm 2 vibration displacement. The metal lead wires of the two detection electrodes 5 are led out from the wire hole 7 on the fixed structure 4, and connected to the external power supply.

When there is external sound excitation, the cricket-like cilia structure 1 on the sensitive diaphragm 2 is bent and deformed, which drives the sensitive diaphragm 2 to move up and down, so that the capacitance between the sensitive diaphragm 2 and the two detection electrodes 5 changes , in order to detect the sound pressure of external sound excitation.

The manufacturing method of the described miniature imitation cricket cilia structure sound pressure sensor comprises the following steps:

Step 1: Select a standard cleaned double-sided polished silicon wafer, apply a photoresist 8 on the back of the silicon wafer, perform photolithography, develop, and transfer the annular fixed structure 4 on the mask plate to the back of the silicon wafer.

Step 2: Etching the back of the silicon wafer to a certain depth by high-density plasma (ICP) to form a ring-shaped fixed structure 4 , the spacing between plates of the flat capacitor, and wire holes 7 , and remove the photoresist 8 .

Step 3: Coating photoresist 8 on the back of the silicon wafer again, photolithography, developing, and transferring the sensitive film 2 on the mask plate to the back of the silicon wafer.

Step 4: ICP etching the back of the silicon wafer to form the lower surface of the sensitive membrane 2 and the gap 9 between the sensitive membrane 2 and the fixed structure 4, and remove the photoresist 8.

Step 5: Sputter metal on the front surface of the glass substrate 6, apply photoresist 8, photolithography and develop, and etch the metal to form two detection electrodes 5.

Step 6: Perform anodic bonding of the back side of the silicon wafer in step 4 and the front side of the glass substrate 6 in step 5.

Step 7: Coating photoresist 8 on the front side of the silicon wafer, photolithography, developing, and transferring the imitation cricket cilia structure 1 pattern on the mask plate to the front side of the silicon wafer.

Step 8: ICP etching the front side of the silicon wafer to form the cricket-imitation cilia structure 1 and the upper surface of the sensitive diaphragm 2, remove the photoresist 8, and complete the production of the micro-cricket-imitation cilia structure sound pressure sensor.

Description of drawings

Fig. 1 is the three-dimensional structure schematic diagram of the sound pressure sensor of the miniature imitation cricket cilia structure that the present invention proposes

Fig. 2 is the technological process schematic diagram of the miniature imitation cricket cilia structure acoustic pressure sensor that the present invention proposes

In the figure: 1-imitation cricket cilia structure, 2-sensitive diaphragm, 3-support beam, 4-annular fixed structure, 5-two detection electrodes, 6-glass substrate, 7-wire hole, 8-photoresist, 9-gap

Specific implementation method

Referring to Fig. 1, the miniature cricket imitation cricket cilia structure sound pressure sensor in the present embodiment comprises imitation cricket cilia structure 1, sensitive diaphragm 2, support beam 3, fixed structure 4, two detection electrodes 5 and glass substrate 6; imitation cricket The ciliary structure 1 is located above the sensitive diaphragm 2 and is integrated with it. The cricket-like cilia structure 1 has a diameter of 500 nm and a length of 10 μm; the sensitive diaphragm 2 is connected to the ring-shaped fixed structure 4 through two supporting beams 3, and There is a 20 μm gap 9 between the sensitive diaphragm 2 and the annular fixed structure 4; the annular fixed structure 4 is anodically bonded to the glass substrate 6 with two detection electrodes 5 sputtered, so that the gap between the sensitive diaphragm 2 and the two detection electrodes 5 A flat capacitive structure is formed through a certain gap to detect the vibration displacement of the sensitive diaphragm 2 . The metal lead wires of the two detection electrodes 5 are led out from the wire hole 7 on the fixed structure 4, and connected to the external power supply.

When there is external sound excitation, the cricket-like cilia structure on the sensitive diaphragm will bend and deform, driving the sensitive diaphragm to move up and down, causing the capacitance between the sensitive diaphragm and the glass electrode to change, so as to detect the external sound. The sound pressure of the sound excitation.

The manufacturing method of the described miniature imitation cricket cilia structure sound pressure sensor comprises the following steps:

Step 1: Choose <100> crystal orientation, double-sided polished silicon wafer with a thickness of 200 μm. At a temperature of 120°C, boil in 98% concentrated sulfuric acid and 30% hydrogen peroxide solution with a volume ratio of 4:1 for 30 minutes, and then place them in alkaline hydrogen peroxide solution (with a volume ratio of 1:1:5) Soak in 28% ammonia water, 30% hydrogen peroxide and water, 75°C) and acidic hydrogen peroxide solution (36% hydrochloric acid, 30% hydrogen peroxide and water, 75°C with a volume ratio of 1:1:5, 75°C) for 10 minutes , and finally rinse the silicon wafer with deionized water and dry it to complete the standard cleaning of the silicon wafer. Coating photoresist 8, photolithography, developing, transferring the annular fixed structure 4 on the mask plate to the lower surface of the silicon wafer, as shown in FIG. 2(a).

Step 2: Using the photoresist 8 as a mask, high-density plasma (ICP) etches the back of the silicon wafer to a depth of 5 μm to form a ring-shaped fixed structure 4 and wire holes 7. At this time, the gap between the upper and lower plates of the flat capacitor is The pitch is 5 μm, and finally the photoresist 8 is removed, as shown in FIG. 2( b ).

Step 3: Apply photoresist 8 again on the back of the silicon wafer, perform photolithography, develop, and transfer the sensitive film 2 on the mask plate to the back of the silicon wafer, as shown in Figure 2(c).

Step 4: Using the photoresist 8 as a mask, ICP etches the back of the silicon wafer with an etching depth of 3 μm to form a gap 9 between the sensitive diaphragm 2 and the fixed structure 4, and the lower surface of the sensitive diaphragm 2. At this time The thickness of the sensitive membrane 2 is 3 μm, and finally the photoresist 8 is removed, as shown in FIG. 2( d ).

Step 5: Sputter 300nm metal aluminum on the upper surface of the glass substrate 6, apply photoresist 8, photolithography, develop, use photoresist 8 as a mask, etch metal aluminum to form two detection electrodes 5, as shown in Figure 2 ( e).

Step 6: Perform anodic bonding of the back side of the silicon wafer in step 4 and the front side of the glass substrate 6 in step 5, as shown in FIG. 2(f).

Step 7: Coating photoresist 8 on the front side of the silicon wafer, photolithography, developing, and transferring the cricket-like cilia structure 1 pattern on the mask plate to the front side of the silicon wafer, as shown in Figure 2(g).

Step 8: Using the photoresist 8 as a mask, ICP etches the front side of the silicon wafer with an etching depth of 195 μm to form the cricket-like cilia structure 1 and the upper surface of the sensitive diaphragm 2, the length of the cilia structure 1 is 195 μm, and the sensitive diaphragm 2 The thickness is 5 μm, and finally the photoresist 8 is removed to complete the fabrication of the microscopic cricket-like cilia structure sound pressure sensor, as shown in Figure 2(h).

Claims (2)

1. A miniature imitation cricket cilia structure sound pressure sensor is characterized in that: comprise imitation cricket cilia structure (1), sensitive diaphragm (2), support beam (3), annular fixed structure (4), two detection electrodes (5) and glass substrate (6). The cricket-like cilia structure (1) is located above the sensitive membrane (2) and is integrated with it. The sensitive membrane (2) is connected to the ring-shaped fixed structure (4) through two support beams (3), and the sensitive membrane There is a gap (9) between the sheet (2) and the annular fixed structure (4); the fixed structure (4) is anodically bonded to the glass substrate (6) sputtered with two detection electrodes (5), so that the sensitive diaphragm ( 2) and the two detection electrodes (5) pass through a certain gap to form a flat capacitive structure to detect the vibration displacement of the sensitive diaphragm (2). The metal lead wires of the two detection electrodes (5) are led out from the wire hole (7) on the fixed structure (4) and connected with the external power supply. 2. a kind of manufacture method of miniature imitation cricket cilia structure sound pressure transducer as claimed in claim 1, is characterized in that, comprises the steps: Step 1: Select a standard cleaning double-sided polished silicon wafer, apply a photoresist (8) on the back of the silicon wafer, perform photolithography, develop, and transfer the annular fixed structure (4) on the mask plate to the back of the silicon wafer. Step 2: high-density plasma (ICP) etching the back of the silicon wafer to a certain depth to form a ring-shaped fixed structure (4), the spacing between plates of the flat capacitor, and wire holes (7), and remove the photoresist (8). Step 3: Coating photoresist (8) on the back of the silicon wafer again, photolithography, developing, and transferring the sensitive film (2) on the mask to the back of the silicon wafer. Step 4: ICP etching the back of the silicon wafer to form the lower surface of the sensitive membrane (2) and the gap (9) between the sensitive membrane (2) and the fixed structure (4), and remove the photoresist (8). Step 5: sputtering metal on the front surface of the glass substrate (6), coating photoresist (8), photolithography and developing, and etching the metal to form two detection electrodes (5). Step 6: performing anodic bonding on the back side of the silicon wafer in step 4 and the front side of the glass substrate (6) in step (5). Step 7: Coating photoresist (8) on the front side of the silicon wafer, photolithography, developing, and transferring the imitation cricket cilia structure 1) pattern on the mask plate to the front side of the silicon wafer. Step 8: ICP etching the front side of the silicon wafer to form the cricket-like cilia structure (1) and the upper surface of the sensitive diaphragm (2), remove the photoresist 8, and complete the production of the micro-cricket-like cilia-structure sound pressure sensor.

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