CN206670783U - Based on the MEMS of piezo-electric effect with the spherical oscillator vector hydrophone of the vibration shape - Google Patents

Abstract

The utility model discloses a MEMS co-vibration spherical vibrator vector hydrophone based on the piezoelectric effect, which comprises a frame-shaped base, a beam, an annular connector, a spherical polyethylene vibration pickup unit, and a PZT piezoelectric film; the spherical The polyethylene vibration pickup unit is fixed on the annular connector, and the annular connector is connected to the center of the frame-shaped base through a beam. A PZT piezoelectric film is grown on the outside of each beam, and the lower electrode is under the PZT piezoelectric film, and each The lower electrode of the root beam is independent from the electrodes on other beams and the frame-shaped base; the upper surface of each PZT piezoelectric film is sputtered with mutually independent upper electrodes. The utility model is a co-vibration type spherical vibrator vector hydrophone with high sensitivity of common mode output and differential mode suppression and wide working frequency band; micro-nano processing technology is adopted to realize miniaturization of the spherical vibrator vector hydrophone. And the signal acquisition module is arranged on the four beams connected with the spherical vibrator, and the acoustic signal component perpendicular to the direction of the beams can be detected.

Description

MEMS co-vibration spherical vibrator vector hydrophone based on piezoelectric effect

technical field

The utility model relates to a vector hydrophone in the field of MEMS sensors, in particular to a piezoelectric effect-based MEMS co-vibration spherical vibrator vector hydrophone.

Background technique

At present, the vector hydrophones developed at home and abroad are generally divided into two categories: co-vibration type and differential pressure type. For the differential pressure vector hydrophone, because the depth of the "8" cosine directivity pit is too shallow, the pointing accuracy is not high, which limits its application in the field of underwater acoustics. For the co-vibration vector hydrophone, according to the different sound wave receiving theories of the particle velocity hydrophone, the co-vibration vector hydrophone can be divided into the co-vibration cylindrical oscillator vector hydrophone and the co-vibration spherical oscillator vector hydrophone device. Conventional co-vibration vector hydrophones must be fixed on a rigid frame with elastic suspension elements (such as rubber ropes or metal springs, etc.), and the mechanical characteristics of the suspension elements directly affect the electroacoustic performance of the hydrophone. This type of vector hydrophone is uniformly arranged with one or more acceleration sensors in the center or inside of the vibration pickup unit to measure the vibration velocity and acceleration of the vibration pickup unit, so as to obtain relevant information about the particle velocity in the sound field. Due to the conventional design and processing technology, there are problems such as poor low-frequency characteristics, low sensitivity, high quality, mismatch between acoustic impedance and water, and difficulty in using on small-volume platforms.

Utility model content

In order to solve the problem of poor anti-flow noise, low sensitivity, poor impact resistance, high quality, mismatch between acoustic impedance and water, and complex processing of the spherical vibrator vector underwater acoustic sensor brought about by the existing technical solutions such as conventional design and processing technology, etc. Problem, the utility model provides a MEMS co-vibration spherical vibrator vector hydrophone based on the piezoelectric effect.

In order to achieve the above object, the technical scheme that the utility model takes is:

The MEMS co-vibration spherical vibrator vector hydrophone based on the piezoelectric effect includes a frame base, a beam, a ring connector, a spherical polyethylene vibration pickup unit, and a PZT piezoelectric film; the spherical polyethylene vibration pickup unit is fixed on On the annular connecting body, the annular connecting body is connected to the center of the frame-shaped base through a beam, and a PZT piezoelectric film is grown on the outside of each beam, and the lower electrode is below the PZT piezoelectric film, and the lower electrode of each beam It is independent from other beams and electrodes on the frame-shaped base; each PZT piezoelectric film is sputtered with mutually independent upper electrodes on the upper surface.

Preferably, the beam and the annular connector are processed by ICP front etching and DRIE back cavity etching; the PZT piezoelectric film is a piezoelectric layer with a thickness of 1 μm made by a sol-gel method .

Preferably, the outer side of the frame-shaped base is 5000 μm long, and the inner side is 3500 μm long; the beam is 900 μm long, 120 μm wide, and 30 μm thick.

Preferably, the outer diameter of the annular connector is 1700 μm, the inner diameter is 1500 μm, and the thickness is 30 μm; the diameter of the spherical vibrator is 1500 μm.

Preferably, the lower electrode is a Pt/Ti layer, and the upper electrode is an Au layer.

Preferably, the length of the lower electrode, the PZT piezoelectric thin film, and the upper electrode Au are all 600 μm, the width is 120 μm, and the thicknesses are 150 nm, 1 μm, and 150 nm, respectively.

Preferably, the spherical polyethylene vibration pickup unit adopts spherical polyethylene with the same density as water or close to it.

The utility model has the following beneficial effects:

The utility model designs and optimizes a high-sensitivity common-mode output, differential-mode suppression, and a wide operating frequency band co-vibration spherical vibrator vector hydrophone; adopts micro-nano processing technology to realize the miniature size of the spherical vibrator vector hydrophone change. And the signal acquisition module is arranged on the four beams connected to the spherical vibrator, which can detect the acoustic signal component in the direction perpendicular to the beam. The output signals on each beam are exactly the same, and the signals in this direction are superimposed in series, so that get bigger output. The symmetrical distribution in the XOY plane of the utility model, when receiving the acoustic signal from the horizontal direction, the two beams in the same direction are respectively subjected to tensile stress and compressive stress of equal size, and the symmetrically distributed piezoelectric modules on each beam Charges of equal magnitude and different sign are generated, and since the piezoelectric outputs in the same direction are connected in series, the charges generated on the same beam can be completely canceled out. Therefore, this structure can effectively improve the output of the acoustic signal component from the Z direction, and suppress the output of the acoustic signal component from the X or Y direction.

Description of drawings

Figure 1 is a schematic structural diagram of a MEMS co-vibration spherical vibrator vector hydrophone based on the piezoelectric effect.

2 is a schematic diagram of charge distribution and circuit connection when two piezoelectric modules in the X or Y direction are subjected to acceleration in the Z direction.

Figure 3 is the first-order mode diagram of the vector hydrophone simulation model.

Fig. 4 is the stress nephogram of the structure obtained by applying 1g acceleration in the Z direction to the vector hydrophone simulation model.

Fig. 5 is the piezoelectric response obtained by applying 1g acceleration in the Z direction of the vector hydrophone simulation model.

Fig. 6 is the piezoelectric response obtained by applying 1g acceleration in the X direction of the vector hydrophone simulation model.

In the figure: 1-frame base, 2-beam, 3-ring connector, 4-spherical polyethylene vibration pickup unit, 5-PZT piezoelectric film, 6-lower electrode, 7-upper electrode.

detailed description

In order to make the purpose and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

As shown in Figure 1, the embodiment of the utility model provides a MEMS co-vibration spherical vibrator vector hydrophone based on the piezoelectric effect, including a frame-shaped base 1, a beam 2, an annular connector 3, and a spherical polyethylene vibration pickup unit 4. PZT piezoelectric film 5; the spherical polyethylene vibration pickup unit 4 is fixed on the annular connector 3, and the annular connector 3 is connected to the center of the frame base 1 through the beam 2, and each beam 2 A PZT piezoelectric film 5 is grown on the outside, and the lower electrode 6 is below the PZT piezoelectric film 5, and the lower electrode 6 of each beam is independent from the electrodes on other beams and the frame-shaped base; each PZT piezoelectric film 5 The surfaces are all sputtered with mutually independent upper electrodes 7 . The beam and the annular connector are processed by ICP front etching and DRIE back cavity etching; the PZT piezoelectric film is a piezoelectric layer with a thickness of 1 μm made by a sol-gel method; the The spherical polyethylene vibration pickup unit adopts spherical polyethylene with the same density as water or close to it.

The outer side of the frame-shaped base 1 is 5000 μm long, and the inner side is 3500 μm long; the beam 2 is 900 μm long, 120 μm wide, and 30 μm thick; the annular connector 3 has an outer diameter of 1700 μm, an inner diameter of 1500 μm, and a thickness of 30 μm; the base is 5000 μm; The vibration unit 4 has a diameter of 1500 μm;

The lower electrode Pt/Ti6, PZT piezoelectric thin film 5, and upper electrode Au 7 are 600 μm long, 120 μm wide, and 150 nm, 1 μm, and 150 nm thick, respectively.

When processing in this specific implementation, the <100> crystalline silicon sputtered with the lower electrode Pt/Ti is grown by the sol-gel method to a thickness of 1um PZT, and the PZT is first etched, and then the lower electrode is etched by IBE, and then The upper electrode is made by stripping technology, and then the beam 2 and the ring connector 3 are released by ICP front etching and DRIE back etching; finally, the spherical polyethylene vibration pickup unit 4 is bonded to the ring connector 3 by secondary integration. superior.

The practical implementation of the utility model adopts the micro-nano processing technology, and realizes the miniaturization of the spherical vibrator vector hydrophone. And the signal acquisition module is arranged on the four beams connected to the spherical vibrator, which can detect the acoustic signal component in the direction perpendicular to the beam. The output signals on each beam are exactly the same, and the signals in this direction are superimposed in series, so that Get a bigger output (Figure 2). According to the sound wave receiving theory of the particle velocity hydrophone, when ka << 1 (k is the wave number of the sound wave, a is the diameter of the vibration pickup unit), the sound field near the vibration pickup unit will not be significantly distorted. When the upper limit operating frequency of the vector hydrophone is 2000 Hz, since a=1500 μm, the detection target sound wave number k<8.4 (k=2πf/u, where v is the speed of sound in water, which is 1500 m/s). The vector hydrophone designed by the utility model satisfies the condition of ka<<1 (ka<0.0125), and the sound field near the spherical vibrator will not be distorted; through theoretical analysis, the structure is reasonable.

Using COMSOL to carry out modal analysis on the vector hydrophone (Fig. 3), it is obtained that the natural frequency of the vector hydrophone is 3.3KHz; an acceleration load of 1g is applied in the Z direction, and the maximum stress on the beam is about 0.4MPa (Fig. 4 ); the single-beam piezoelectric output is 0.88mV/g (Figure 5), and the system sensitivity is 3.5mV/g without using any external amplifier circuit. Applying an acceleration of 1g in the horizontal direction (X or Y direction), the maximum normal stress on the beam is 0.03MPa, and the piezoelectric output on the four beams is 3.4×10 ^-5 mV (Figure 6). The simulation results also show that the utility model superimposes four common-mode signals in the vertical direction, and the differential-mode signals in the horizontal direction are mutually suppressed, which fully reflects that the hydrophone has common-mode output and differential-mode suppression. The sensitivity in the vertical direction is well improved, and the signal component in the horizontal direction is suppressed; thus the utility model can well improve the resolution and sensitivity of the vector hydrophone.

The above is only a preferred embodiment of the utility model, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the utility model, some improvements and modifications can also be made. These improvements and modifications It should also be regarded as the protection scope of the present utility model.

Claims (7)

1. based on the MEMS of piezo-electric effect with the spherical oscillator vector hydrophone of the vibration shape, it is characterised in that including frame-type pedestal, horizontal stroke Beam, circular connector, spherical polyethylene pick-up unit, PZT piezoelectric membranes；The spherical polyethylene pick-up unit is fixed on annular On connector, the circular connector is connected to by crossbeam at the center of frame-type pedestal, and the outside growth of every crossbeam has PZT Piezoelectric membrane, is bottom electrode below PZT piezoelectric membranes, and the bottom electrode of every crossbeam with other crossbeams and frame-type pedestal Electrode is separate；Each PZT piezoelectric membranes upper surface sputters separate Top electrode.

2. as claimed in claim 1 based on the MEMS of piezo-electric effect with the spherical oscillator vector hydrophone of the vibration shape, it is characterised in that Crossbeam and circular connector form through ICP fronts etching and DRIE back of the body chamber lithographies；Described PZT piezoelectric membranes are to pass through The piezoelectric layer of the μ m-thick of thickness 1 is made in the method for sol-gel.

3. as claimed in claim 1 based on the MEMS of piezo-electric effect with the spherical oscillator vector hydrophone of the vibration shape, it is characterised in that Outer 5000 μm of the length of side of described frame-type pedestal, interior 3500 μm of the length of side；Crossbeam grows 900 μm, wide 120 μm, 30 μm of thickness.

4. as claimed in claim 1 based on the MEMS of piezo-electric effect with the spherical oscillator vector hydrophone of the vibration shape, it is characterised in that 1700 μm of the circular connector external diameter, 1500 μm of internal diameter, 30 μm of thickness；Spherical vibrator diameter is 1500 μm.

5. as claimed in claim 1 based on the MEMS of piezo-electric effect with the spherical oscillator vector hydrophone of the vibration shape, it is characterised in that The bottom electrode is Pt/Ti layers, and the Top electrode is Au layers.

6. as claimed in claim 1 based on the MEMS of piezo-electric effect with the spherical oscillator vector hydrophone of the vibration shape, it is characterised in that The bottom electrode, PZT piezoelectric membranes, Top electrode Au length be 600 μm, wide is 120 μm, thickness be respectively 150nm, 1 μm, 150nm。

7. as claimed in claim 1 based on the MEMS of piezo-electric effect with the spherical oscillator vector hydrophone of the vibration shape, it is characterised in that The spherical polyethylene pick-up unit uses density and aqueous phase together or subglobular polyethylene.