阅读说明：本技术 具有亥姆霍兹谐振腔的mems超声定位传感器 (MEMS ultrasonic positioning sensor with Helmholtz resonant cavity ) 是由 孙成亮 朱伟 吴志鹏 王磊 胡博豪 林炳辉 周禹 于 2019-09-10 设计创作，主要内容包括：一种MEMS超声定位传感器,包括：上层衬底(3)；亥姆霍兹谐振腔(2),形成于上层衬底(3)内；压电式超声发射单元(9),位于上层衬底(3)上,其上具有至少一个与亥姆霍兹谐振腔(2)连通的通孔(7)；超声接收单元(1),位于亥姆霍兹谐振腔(2)底部；其中,亥姆霍兹谐振腔(2)的谐振频率与压电式超声发射单元(9)的谐振频率相同,超声接收单元(1)的谐振频率大于或等于压电式超声发射单元(9)的谐振频率。本公开的MEMS超声定位传感器,可以提高传感器的能量转换效率和避免传感器的串扰。(A MEMS ultrasonic positioning sensor comprising: an upper substrate (3); a Helmholtz resonant cavity (2) formed in the upper substrate (3); the piezoelectric ultrasonic transmitting unit (9) is positioned on the upper substrate (3) and is provided with at least one through hole (7) communicated with the Helmholtz resonant cavity (2); the ultrasonic receiving unit (1) is positioned at the bottom of the Helmholtz resonant cavity (2); the resonance frequency of the Helmholtz resonant cavity (2) is the same as that of the piezoelectric ultrasonic transmitting unit (9), and the resonance frequency of the ultrasonic receiving unit (1) is greater than or equal to that of the piezoelectric ultrasonic transmitting unit (9). The MEMS ultrasonic positioning sensor can improve the energy conversion efficiency of the sensor and avoid crosstalk of the sensor.)

1. A MEMS ultrasonic positioning sensor, comprising:

an upper substrate (3);

a Helmholtz resonant cavity (2) formed in the upper substrate (3);

the piezoelectric ultrasonic transmitting unit (9) comprises a piezoelectric lamination (8) or a piezoelectric bimorph (16) which is positioned on the upper-layer substrate (3), and the piezoelectric lamination (8) and the piezoelectric bimorph (16) are provided with one or more through holes (7) communicated with the Helmholtz resonant cavity (2);

the ultrasonic receiving unit (1) is positioned at the bottom of the Helmholtz resonant cavity (2);

the resonance frequency of the Helmholtz resonant cavity (2) is the same as that of the piezoelectric ultrasonic transmitting unit (9), and the resonance frequency of the ultrasonic receiving unit (1) is greater than or equal to that of the piezoelectric ultrasonic transmitting unit (9).

2. The MEMS ultrasonic positioning sensor according to claim 1, wherein the piezoelectric stack (8) comprises a first lower electrode (4) arranged on the upper substrate (3), a first piezoelectric layer (5) arranged on the first lower electrode (4), a first upper electrode (6) arranged on the first piezoelectric layer (5).

3. The MEMS ultrasonic positioning sensor according to claim 1, characterized in that the ultrasonic receiving unit (1) is a piezoelectric ultrasonic transducer or a capacitive ultrasonic transducer.

4. The MEMS ultrasonic positioning sensor of claim 3, wherein the ultrasonic receiving unit (1) is a piezoelectric ultrasonic transducer, comprising: a second piezoelectric layer (12) bonded to the bottom of the upper substrate (3); a second upper electrode (13) located within the Helmholtz resonator (2) and disposed on an upper surface of the second piezoelectric layer (12); a second lower electrode (11) bonded to a lower surface of the second piezoelectric layer (12); and a lower substrate (15) bonded to the lower surface of the second lower electrode (11).

5. The MEMS ultrasonic positioning sensor according to claim 3, wherein the ultrasonic receiving unit (1), when being a capacitive ultrasonic transducer, comprises: a lower substrate (15) located below the upper substrate (3); SiO on the lower substrate (15)₂A layer (14); a diaphragm (17) bonded between the upper substrate (3) and the lower substrate (15); and the second upper electrode (13) is positioned in the Helmholtz resonant cavity (2) and is arranged on the vibrating diaphragm (17).

Technical Field

The utility model belongs to the technical field of ultrasonic transducer, a MEMS ultrasonic positioning sensor with Helmholtz resonant cavity is related to.

Background

Position sensors can be broadly classified into three categories. (1) Fine position sensing types operating over short distances, such as eddy current, magnetoresistive and hall effect sensors. The sensor has the advantages of high sensitivity and strong anti-interference capability, but is not suitable for long-distance measurement. (2) Optical time-of-flight and optical coherence position sensors, such as laser interferometry, ergonomic triangulation, etc. The advantage is high precision, and the disadvantage is that this kind of equipment is usually complicated in structure, and needs to be equipped with a plurality of optical elements. (3) An acoustic or ultrasonic position sensor. Among such sensors is a piezoelectric acoustic resonator (PSRC) position sensor, which is characterized by having a helmholtz resonator, and emitting sound waves by using a piezoelectric stack layer above the helmholtz resonator, and then receiving the sound waves by an acoustic sensor below the helmholtz resonator. This has the advantage of high resolution, but the measurement distance is short, and in addition, the resonance frequency of the helmholtz resonator is difficult to match with the resonance frequency of the piezoelectric stack layer when the device size is small, so that such sensors are usually large in size and have a low resonance frequency when in operation, resulting in poor resolution at close distances. Meanwhile, in order to achieve the best receiving effect, the resonant frequencies of the receiving sensor, the transmitting transducer and the helmholtz resonant cavity are generally set to be the same, but crosstalk occurs when sound waves are transmitted and received.

Disclosure of Invention

The MEMS ultrasonic positioning sensor with the Helmholtz resonant cavity aims to improve the energy conversion efficiency of the sensor and avoid signal crosstalk of the sensor.

According to an aspect of the embodiments of the present disclosure, there is provided a MEMS ultrasonic positioning sensor, including:

an upper substrate;

a Helmholtz resonant cavity formed in the upper substrate;

the piezoelectric ultrasonic transmitting unit comprises a piezoelectric lamination or a piezoelectric bimorph which is positioned on the upper-layer substrate, and one or more through holes communicated with the Helmholtz resonant cavity are formed in the piezoelectric lamination or the piezoelectric bimorph;

the ultrasonic receiving unit is positioned at the bottom of the Helmholtz resonant cavity;

the resonance frequency of the Helmholtz resonant cavity is the same as the resonance frequency of the piezoelectric ultrasonic transmitting unit, and the resonance frequency of the ultrasonic receiving unit is greater than or equal to the resonance frequency of the piezoelectric ultrasonic transmitting unit.

In the above MEMS ultrasonic positioning sensor, the piezoelectric stack includes a first lower electrode disposed on the upper substrate, a first piezoelectric layer disposed on the first lower electrode, and a first upper electrode disposed on the first piezoelectric layer.

In the above MEMS ultrasonic positioning sensor, the ultrasonic receiving unit is a piezoelectric ultrasonic transducer or a capacitive ultrasonic transducer.

In the above MEMS ultrasonic positioning sensor, the piezoelectric ultrasonic receiving unit includes: a second piezoelectric layer bonded to the bottom of the upper substrate; a second upper electrode positioned in the Helmholtz resonant cavity and disposed on an upper surface of the second piezoelectric layer; a second lower electrode bonded to a lower surface of the second piezoelectric layer; and the lower layer substrate is bonded on the lower surface of the second lower electrode.

In the above MEMS ultrasonic positioning sensor, the capacitive ultrasonic receiving unit includes: the lower layer substrate is positioned below the upper layer substrate; SiO on the lower substrate₂A layer; the vibrating diaphragm is bonded between the upper substrate and the lower substrate; and the second upper electrode is positioned in the Helmholtz resonant cavity and arranged on the vibrating diaphragm.

The present disclosure combines a MEMS piezoelectric ultrasonic transducer (pMUT), a helmholtz resonator, and an acoustic sensor. The MEMS piezoelectric ultrasonic transducer is used for driving the Helmholtz resonant cavity to produce sound. The resonance frequency of the MEMS piezoelectric ultrasonic transducer is consistent with the resonance frequency of the Helmholtz resonant cavity, and the amplitude of sound waves emitted by the ultrasonic transducer is greatly increased through the Helmholtz resonant cavity, so that the electroacoustic energy conversion efficiency of the ultrasonic transducer is improved. The acoustic sensor is used for receiving ultrasonic waves, and the ultrasonic waves reflected back by obstacles can increase the sound pressure acting on the acoustic sensor through the amplification of the Helmholtz resonant cavity, so that the output electric signals are improved. Meanwhile, when the resonant frequency of the acoustic sensor is different from that of the pMUT and is higher than that of the pMUT, the crosstalk phenomenon can be effectively avoided when ultrasonic waves are transmitted and received.

Drawings

The present disclosure is described in further detail below with reference to the attached drawings and the detailed description.

FIG. 1 shows a cross-sectional view of a MEMS ultrasonic positioning sensor having a Helmholtz resonator.

Fig. 2 shows a top view of the MEMS ultrasonic positioning sensor shown in fig. 1.

Fig. 3 shows a cross-sectional view of a MEMS ultrasonic positioning sensor with a sandwich structure pMUT as the transmitting and receiving unit, according to one embodiment of the present disclosure.

Fig. 4 shows a top view of the MEMS ultrasonic positioning sensor shown in fig. 3.

Fig. 5 illustrates a cross-sectional view of a MEMS ultrasonic positioning sensor with a dual-wafer pMUT as the transmitting unit and a sandwich pMUT as the receiving unit, according to one embodiment of the disclosure.

FIG. 6 shows a top view of the MEMS ultrasonic positioning sensor shown in FIG. 5.

Fig. 7 shows a cross-sectional view of a MEMS ultrasonic positioning sensor with a sandwich structure pMUT as the transmitting unit and cMUT as the receiving unit, according to one embodiment of the present disclosure.

FIG. 8 illustrates a top view of the MEMS ultrasonic positioning sensor shown in FIG. 7.

FIG. 9 illustrates a cross-sectional view of a MEMS ultrasonic positioning sensor having a plurality of through-hole Helmholtz resonators, according to one embodiment of the present disclosure.

FIG. 10 illustrates a top view of the MEMS ultrasonic positioning sensor shown in FIG. 9.

Description of reference numerals:

1-ultrasonic receiving unit, 2-Helmholtz resonant cavity, 3-upper substrate, 4-first lower electrode, 5-first piezoelectric layer, 6-first upper electrode, 7-through hole, 8-piezoelectric lamination, 9-piezoelectric ultrasonic transmitting unit and 10-piezoelectric ultrasonic transmitting unitSound receiving unit, 11-second lower electrode, 12-second piezoelectric layer, 13-second upper electrode, 14-SiO₂Layer, 15-lower substrate, 16-piezoelectric bimorph, 17-diaphragm, 18-capacitive ultrasound receiving unit.

In addition, the MEMS piezoelectric ultrasonic transducer is generally called a piezoelectric micro-machined ultrasonic transducer, which is abbreviated as: pMUT. The MEMS capacitive ultrasonic transducer is called a capacitive piezoelectric ultrasonic transducer for short: cMUT.

Detailed Description

FIG. 1 illustrates a cross-sectional view of a MEMS ultrasonic positioning sensor having a Helmholtz cavity, according to one embodiment of the present disclosure. Fig. 2 shows a top view of the MEMS ultrasonic positioning sensor shown in fig. 1. As shown in fig. 1 and 2, the MEMS ultrasonic transducer having a helmholtz resonator includes an ultrasonic receiving unit 1, a helmholtz resonator 2, and a piezoelectric ultrasonic transmitting unit 9. The helmholtz resonator 2 is formed in an upper substrate 3 of Si material. The shape of the helmholtz resonator 2 may be circular, square, rectangular or other geometric shapes. The piezoelectric type ultrasonic transmission unit 9 is located on the upper substrate 3, and has at least one through hole 7 communicating with the helmholtz resonant cavity 2. The ultrasonic receiving unit 1 is located at the bottom of the helmholtz resonator 2. The resonance frequency of the helmholtz resonant cavity 2 is the same as the resonance frequency of the piezoelectric ultrasonic transmitting unit 9, and the resonance frequency of the ultrasonic receiving unit 1 is greater than or equal to the resonance frequency of the piezoelectric ultrasonic transmitting unit 9.

As shown in fig. 3 and 4, the ultrasonic transmission unit 9 employs a piezoelectric ultrasonic transducer (pMUT) including a first lower electrode 4 bonded to the upper substrate 3, a first piezoelectric layer 5 bonded to the first lower electrode 4, and a first upper electrode 6 bonded to the first piezoelectric layer 5. That is, the upper substrate 3, the first lower electrode 4, and the first piezoelectric layer 5 constitute one piezoelectric stack 8. The through hole 7 penetrates through the piezoelectric lamination 8 and is communicated with the Helmholtz resonant cavity 2. The first lower electrode 4 is a bulk electrode, and a metal such as Mo or Al may be used as an electrode material. As the first piezoelectric layer 5, a piezoelectric material such as AlN or PZT can be used. The first upper electrode 6 may be made of a metal such as Mo or Al. The first upper electrode 6 is formed by an etching process, and the etched pattern may be ring-shaped.

As shown in fig. 5 and 6, alternatively, the piezoelectric type ultrasonic transmission unit 9 may be a piezoelectric bimorph structure in which a piezoelectric bimorph 16 is bonded to the upper substrate 3. The through hole 7 penetrates through the piezoelectric bimorph 16 and is communicated with the Helmholtz resonant cavity 2.

The ultrasound receiving unit 1 may employ a piezoelectric ultrasound transducer (pMUT), or a capacitive ultrasound transducer (cMUT), or other types of acoustic sensors.

Referring to fig. 3 to 6, the piezoelectric type ultrasonic receiving unit 10 includes a second lower electrode 11, a second piezoelectric layer 12, a second upper electrode 13, SiO₂Layer 14, underlying substrate 15. The lower substrate 15 is located below the upper substrate 3, and the second lower electrode 11 and the second piezoelectric layer 12 are disposed between the substrates 3 and 15. The lower substrate 15 is composed of two parts so as to form a cavity in the lower substrate 15, which is closed after bonding, wherein SiO₂The layer 14 is disposed on the bonding face. The second piezoelectric layer 12 is bonded to the bottom of the upper substrate 3. A second upper electrode 13 is located within the helmholtz resonator 2 and is arranged on top of the second piezoelectric layer 12. The second lower electrode 11 is bonded on the lower surface to the lower substrate 15, and the upper surface is bonded to the lower surface of the second piezoelectric layer 12.

As shown in fig. 7 and 8, if the capacitive ultrasonic receiving unit 18 is employed, a diaphragm 17 is provided between the upper substrate 3 and the lower substrate 15. The second upper electrode 13 located in the helmholtz resonator 2 is disposed on the diaphragm 17, and the lower surface of the diaphragm 17 serves as the top of the cavity of the lower substrate 15. SiO 2₂ Layer 14 is disposed at the bottom of the cavity of the underlying substrate 15.

The second lower electrode 11 is a block electrode, and metal such as Mo, Al, etc. may be used as an electrode material. Piezoelectric materials such as AlN and PZT can be used for the second piezoelectric layer 12. The second upper electrode 13 is a block-shaped electrode, and may be formed by using a metal such as Mo or Al as an electrode material or by an etching process.

This MEMS supersound positioning sensor with helmholtz resonant cavity disclosed is when being used for the location, at first add an electric signal on piezoelectric type supersound emission unit 9, piezoelectric type supersound emission unit 9 flexural vibration under the drive of electric signal, then drive helmholtz resonant cavity 2 vibration sound production, when piezoelectric type supersound emission unit 9 is unanimous with helmholtz resonant cavity 2's resonant frequency, the acoustic pressure of the sound wave of piezoelectric type supersound emission unit 9 transmission will strengthen by a wide margin through the enlargement of helmholtz resonant cavity 2, thereby improve the energy conversion efficiency of sensor. The ultrasonic wave that sends can reflect when meetting the barrier, and the frequency of reflection sound wave is unanimous with 2 resonant frequency of helmholtz resonator, thereby the sound wave propagation arouses the sound pressure increase in the cavity to through-hole 7 arouses medium resonance consumption resonant frequency's in the cavity sound wave energy, and then improves the sound pressure that is used in ultrasonic receiving unit 1 surface, produces great signal. The position of the obstacle can be measured by measuring the time difference between the transmission and the reception of the ultrasonic wave. In addition, the resonant frequency of the ultrasonic receiving unit 1 is different from the resonant frequency of the piezoelectric ultrasonic transmitting unit 9, and is usually higher than the resonant frequency of the piezoelectric ultrasonic transmitting unit 9, so that the crosstalk phenomenon can be effectively avoided when the ultrasonic wave is transmitted and received. In addition, as shown in fig. 9 and 10 in the present disclosure, a plurality of through holes 7 may be opened in the piezoelectric type ultrasonic emission unit 9 to increase the resonance frequency of the helmholtz resonator 2.

The resonance frequency of the helmholtz resonator 2 is:

in the formula, c is the sound velocity in the medium, S is the opening area of the through hole 7, t is the height of the through hole 7, d is the opening diameter of the through hole 7, and V is the volume of the helmholtz resonant cavity.

The above formula is the case where there is one through hole 7 above the helmholtz resonator 2, and if there are a plurality of through holes 7 above, the resonance frequency of the helmholtz resonator 2 is

Where n is the number of vias 7. The resonance frequency of the Helmholtz resonant cavity can be further improved through the through hole structure, and the number of the holes can be selected according to actual conditions.

The utility model discloses a MEMS ultrasonic positioning sensor with Helmholtz resonant cavity belongs to ultrasonic position sensor, compares in PSRC position sensor, and the ultrasonic positioning sensor of this disclosure belongs to the MEMS field, and the size is micron order or submicron order usually. The resonance frequency of the Helmholtz resonant cavity can be made to coincide with the resonance frequency of the MEMS piezoelectric ultrasonic transducer (pMUT) above it by adjusting the size and structure, so as to obtain higher device operating frequency. In addition, by staggering the resonance frequencies of the pMUT for transmitting the ultrasonic wave and the ultrasonic receiving unit, the problem of crosstalk of the sensor can be effectively avoided.