CN109231150A - A kind of combined film pMUTs and preparation method thereof - Google Patents
A kind of combined film pMUTs and preparation method thereof Download PDFInfo
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- CN109231150A CN109231150A CN201811037084.0A CN201811037084A CN109231150A CN 109231150 A CN109231150 A CN 109231150A CN 201811037084 A CN201811037084 A CN 201811037084A CN 109231150 A CN109231150 A CN 109231150A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B3/00—Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes
- B81B3/0018—Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00349—Creating layers of material on a substrate
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00436—Shaping materials, i.e. techniques for structuring the substrate or the layers on the substrate
Abstract
The present invention provides a kind of combined film pMUTs and preparation method thereof, built up thin membrane structure is by circular membrane and is looped around circular membrane circumferential direction, and concentric annular membrane composition, overall structure successively include top electrode, vibration film Piezoelectric Driving layer, lower electrode, vibration film structure sheaf, film support mechanism and underlying structure from top to bottom；When emitting operating mode for ultrasonic wave, by being motivated to circular membrane and annular membrane with certain phase difference, the coupling between circular membrane-fluid media (medium)-annular membrane is caused, unit ultrasound emission power is greatly improved；When receiving operating mode for ultrasonic wave, circular membrane and annular membrane vibrate, and generate detectable electric signal, while by the resonance frequency deviation of circular membrane and annular membrane structure in fluid media (medium), realizing the wide bandwidth receptivity of ultrasound.Built up thin membrane structure pMUTs proposed by the present invention has high transmitting power and wide bandwidth receptivity.
Description
Technical field
The present invention relates to MEMS (Micro-electromechanical Systems) ultrasonic transducer technologies, specifically relate to
And a kind of high electromechanical coupling factor pMUTs (Piezoelectric Micromachined Ultrasonic Transducers)
And preparation method thereof.
Background technique
Ultrasonic transducer has significant application value for medical diagnosis imaging in non-intervention type body.Conventional ultrasound transducer
It is manufactured by piezoceramic material (such as lead zirconate titanate (PZT) or PZT polymer complex), piezoceramic material is cut
Piece or laser cutting are to form one-dimensional or two-dimensional array multiple individually units.Acoustic lens, matching layer, laying and electrical interconnection
(such as flexible cable, metal pin/conducting wire) etc. is attached to each transducer unit to form transducer assemblies or probe, so
Probe is connected to control circuit with harness or cable afterwards, wherein cable includes to drive each individually unit and receive from it letter
Number individual conductor.The important goal that ultrasonic transducer technology is studied at present be improve transducer performance and with control circuit collection
At, and transducer dimensions, power consumption and the loss of signal as caused by cable connection are reduced simultaneously.These factors are super for three-dimensional
Two-dimensional array needed for acoustic imaging is even more important.
The miniaturization of transducer array is especially important for 2D array energy transducer catheter-based.Its technological challenge is to pass
Complicated, the at high cost and limited capacity of manufacture etc. of system 2D transducer array.It is big that commercial 2D transducer probe is limited to cell spacing
(200 μm to 300 μm) and working frequency are less than the array of 5MHz.The capacitor of unit is greatly lowered the small size of these units
To 10pF is less than, the electrical impedance with system electronics is matched and proposes significant challenge.In addition, production is for being based on conduit
Intravascular imaging probe or heart in the 2D array transducer probe of imaging probe realize commercialization not yet.In order to obtain
Enough resolution ratio should use 10MHz or bigger frequency, and obtain enough imaging performances, and cell spacing should be small
In wavelength, it is desirable that element spacing is 100 μm or smaller.In addition, the piezoelectric layer in higher operating frequency requirements energy converter
It is thinner.So far, traditional transducers array can't meet this with the manufacturing process and enough imaging performances of low cost
It is a little to require.
Compared with traditional piezoelectric ceramic transducer, pMUTs have the advantage that manufacture be easy and can be scaled,
Especially for the bigger 2D array of smaller, density；It integrates and interconnects simpler for 2D array；For broader
The design flexibility of operating frequency range, energy converter is bigger；Cell capacitance is bigger, to have smaller source impedance, with electronics
The matching of device is more preferable.Real-time 3D imaging system needs 2D array, and piezoelectric ceramic transducer cannot achieve smaller conduit and visit
Head (diameter 2-3mm or smaller).Another capacitance type micromachined ultrasonic energy converter (cMUTs), is by between film and substrate
Electrostatic force carry out driving transmitting ultrasound.However, these requirement on devices multiple units in parallel export to provide enough acoustic pressures, institute
To limit the miniaturization of 2D array.
There are the differences in function and structure with pMUTs by cMUTs.Because pMUTs has bigger energy transfer mechanism (i.e.
Piezoelectric layer), so pMUTs usually has the ultrasound emission power bigger than cMUTs.Under the frequency of 8MHz, 75 microns wide
PMUTs2D array can produce the acoustic pressure output of 1MPa to 5MPa.Traditional transducer array can produce the sound greater than 1MPa
Pressure, but much bigger unit size is needed, and work at lower frequencies.The typical acoustic pressure of cMUTs 2D array element
Output is far smaller than 1MPa.Compared with traditional transducers array and cMUTs, the unit in pMUTs array also has bigger
Capacitor (in 100-1000pF magnitude), therefore there is lower source impedance, and the impedance matching with cable and electronic device
More preferably.The capacitor of traditional transducers array element is less than 10pF, and the capacitor of cMUTs unit is less than 1pF.
Compared with traditional transducers and cMUTs, operating voltage needed for pMUTs is lower.Thickness based on ceramic wafer passes
(peak-to-peak value generates sound energy greater than 100V) to the more demanding driving voltage of system energy converter.And for cMUTs, in addition to applying AC letter
Except number, it is also necessary to apply higher DC offset voltage (being greater than 100V) to control intermembrane space, to improve the electromechanics of device
The coefficient of coup.And pMUTs only needs the alternating voltage more much lower than both of the above (typically peak-to-peak value is 30V) to drive piezoresistive material
Material is not necessarily to DC offset voltage to transmit sound energy.Although pMUTs and cMUTs can be directly integrated into control circuit
Miniaturized device, the voltage as needed for pMUTs is low, is more advantageous to the portable device etc. applied to medical ultrasound.But it is existing
PMUTs still needs to further increase in terms of ultrasound emission power, ultrasonic reception, to improve the resolution of ultrasound detection
Rate and performance.
Summary of the invention
In order to overcome the above-mentioned problems of the prior art, the purpose of the present invention is to provide a kind of combined films
PMUTs and preparation method thereof, to improve pMUTs chip while increasing ultrasound emission power, improving ultrasonic reception bandwidth
Feasibility, reliability and the cellular construction of preparation process and the consistency of performance.
The present invention proposes a kind of combined film pMUTs, is made of from top to bottom multi-layer compound film 1 and underlying structure 2；
The multi-layer compound film 1 is composed of Piezoelectric Driving layer structure 1-1 and non-driven layer structure 1-2；It is described
Piezoelectric Driving layer structure 1-1 is in thickness direction from top to bottom by top electrodes 1-1-1, dielectric layer 1-1-2 and bottom electrode 1-
1-3 composition；The dielectric layer 1-1-2 is combined by multi-layer insulation；
Circular cavity 3 and toroidal cavity 4 are etched in the underlying structure 2, and toroidal cavity 4 is in circular cavity 3
Concentric position；Circular cavity 3, toroidal cavity 4 and the multi-layer compound film 1 form the circular membrane 5 that can produce bending vibration
And concentric annular membrane 6；
The top electrodes 1-1-1 is by being covered on the circular membrane driving electrodes 1-1-1-1 of 5 upper surface of circular membrane and covering
Cover the annular membrane driving electrodes 1-1-1-2 composition in 6 upper surface of annular membrane；
Same frequency is taken to circular membrane driving electrodes 1-1-1-1 and annular membrane driving electrodes 1-1-1-2 but with phase
The driving signal of potential difference is motivated, and the range of the phase difference is 0 to 2 π；In circular membrane driving electrodes 1-1-1-1 and ring
The inverse piezoelectric effect effect of piezoelectric material layer in dielectric layer 1-1-2 below the overlay area shape film driving electrodes 1-1-1-2
Lower generation in-plane stress, so that circular membrane 5,6 warpage of annular membrane generate bending vibration.
Preferably, the dielectric layer is followed successively by shielded layer 1-1-2-1 and piezoresistive material in 1-1-2 thickness direction from top to bottom
Bed of material 1-1-2-2.
Preferably, the circular membrane driving electrodes 1-1-1-1 is arranged in 5 center of circular membrane, and thin with circle
The concentric circles each other of film 5, the radius of circular membrane driving electrodes 1-1-1-1 be 0.6 to 0.8 times of 5 radius size of circular membrane it
Between；As the preferred embodiment of the present invention, the annular membrane driving electrodes 1-1-1-2 and annular membrane 6 are in concentric ring structure,
The width of annular membrane driving electrodes 1-1-1-2 is between 0.4 to 0.7 times of 6 width dimensions of annular membrane.
Preferably, it loads on respectively on circular membrane driving electrodes 1-1-1-1 and annular membrane driving electrodes 1-1-1-2
Driving signal V1With V2It is sinusoidal model, and the two amplitude is equal, phase by pi.
The preparation method of the combined film pMUTs, comprising the following steps:
Step 1: taking a monocrystalline silicon piece as underlying structure 2, using reactive ion etching (RIE) technology in underlying structure 2
Upper surface etches circular cavity 3 and toroidal cavity 4；
Step 2: a SOI wafer is taken, using its top layer silicon as non-driven layer structure 1-2, using Si V groove technology
It is bonded with the upper surface for the underlying structure 2 for having etched circular cavity 3, toroidal cavity 4；
Step 3: SOI wafer bottom silicon 7 being thinned to by chemically mechanical polishing (CMP) technology and is only left 1 to 50 μm
Thickness；
Step 4: being removed remaining SOI wafer bottom silicon 7 and buried layer 8 by reactive ion etching (RIE) technology；
Step 5: for the film deposition quality for improving piezoelectric material layer 1-1-2-2 in step 7, being existed using magnetron sputtering technique
Between bottom electrode 1-1-3 and non-driven layer structure 1-2, the piezoelectric material of 10-100nm is deposited as piezoelectric material seed layer 9；
Step 6: the metal of 50~200nm is deposited as bottom electrode 1-1-3 using magnetron sputtering technique；
Step 7: the piezoelectric material of 800~1000nm is deposited as piezoelectric material layer 1-1-2-2 using magnetron sputtering technique；
Step 8: using plasma enhances the SiO of chemical vapor deposition (PECVD) technology deposition 60nm2As shielded layer
1-1-2-1；
Step 9: in vibration film and top electrode surface of insulating layer splash-proofing sputtering metal electrode layer, etching forms circular membrane driving
Electrode 1-1-1-1 and annular membrane driving electrodes 1-1-1-2；
Step 10: dry etching fairlead, the electrical connection for bottom electrode and gold thread.
Piezoelectric material described in step 5 is AlN or ZnO.
The material of the top electrodes 1-1-1 and bottom electrode 1-1-3 is Mo.
The present invention be used for ultrasound transmitting transducer when, by circular membrane and annular membrane with certain phase difference
Alternating voltage is motivated, and the coupling between circular membrane-fluid media (medium)-annular membrane is caused, to greatly improve list
First ultrasound emission power；When receiving for ultrasonic wave, pass through circular membrane and resonance of the annular membrane structure in fluid media (medium)
Frequency departure realizes ultrasonic wide bandwidth receptivity；When ultrasonic wave incidence, circular membrane and annular membrane vibrate,
Detectable electric signal is generated, realizes that ultrasonic wave receives.The present invention utilizes built up thin membrane structure, thus realizing pMUTs high
In the case of ultrasonic output power, the performance of wide ultrasonic reception bandwidth is also had both.
Compared with prior art, a kind of combined film pMUTs of the present invention and preparation method thereof, it is a technical advantage that:
1) circular membrane and annular membrane form built up thin membrane structure, and use and have to circular membrane and annular membrane
The driving signal of certain phase difference, which carries out excitation, makes its vibration, enhances the phase between circular membrane-fluid media (medium)-annular membrane
Mutual coupling, to greatly improve the ultrasound emission power of pMUTs unit.
2) when motivating the phase difference between circular membrane and the driving voltage of annular membrane is π, in each vibration period
Middle circular membrane and annular membrane can mutually absorb flow of the other side by vibrating fluid media (medium) be discharged；When pMUTs unit
When composition array is worked, it can prevent the changes in flow rate of the fluid media (medium) near unit caused by each pMUTs unit from pressing down
The ultrasound emission power of pMUTs unit adjacent thereto is made, thus on the basis of enhancing itself ultrasound emission power, further
Inhibit interfering with each other between each pMUTs unit in array, promotes the pMUTs array being made of pMUTs unit
Whole ultrasound emission power.
3) reasonably combined by the size progress to circular membrane and annular membrane, so that the resonance frequency of the two generates partially
Difference, to widen the ultrasonic reception bandwidth of pMUTs.
4) combined film pMUTs preparation process of the present invention is simple, reliability of technology is high, it is caused by chip unit structure and
Consistency of performance is good.
Detailed description of the invention:
Fig. 1 is combined film pMUTs axonometric schematic diagram of the present invention.
Fig. 2 is combined film pMUTs top view of the present invention and cross-sectional view.
Fig. 3 is combined film pMUTs driving signal of the present invention load and the vibration shape schematic diagram that works.
Fig. 4 is combined film pMUTs preparation method step schematic diagram of the present invention.
Fig. 5 is the optimization of combined film pMUTs of the present invention and identical working frequency typical round film pMUTs
The ultrasound emission remolding sensitivity of structure in water compared with.
In the operating condition for combined film pMUTs of the present invention, the film vibration shape and fluid Jie flow shape to Fig. 6 (a)
The correlation schematic diagram of state.
In the operating condition for combined film pMUTs of the present invention, the film vibration shape and fluid Jie flow shape to Fig. 6 (b)
The correlation schematic diagram of state.
Fig. 7 is element number schematic diagram in unit deployment scenarios in one-dimensional linear array and array, and minimum between unit
Spacing is 10 μm.
Fig. 8 is that combined film pMUTs shown in the present invention is arranged with array shown in Fig. 7, and is carried out with phase ultrasound emission；It is right
Output power frequency when each pMUTs unit works independently with combined film pMUTs unit of the present invention should be numbered to ring
Curve is answered to compare.
Fig. 9 is that typical round film pMUTs is arranged with array shown in Fig. 7, and is carried out with phase ultrasound emission；Reference numeral is each
A pMUTs unit is compared with output power frequency response curve when typical round film pMUTs unit works independently.
Figure 10 (a) is the two-dimensional rectangle array as composed by typical round film pMUTs unit by same-phase pumping signal
Motivate operating condition schematic diagram.
Figure 10 (b) is that the two-dimensional rectangle array as composed by combined film pMUTs unit of the present invention is motivated by same-phase
Signal motivates operating condition schematic diagram.
Figure 11 is that the array as composed by traditional pMUTs unit and combined film pMUTs unit of the present invention exists
The ultrasonic acoustic pressure of same position point becomes with exciting signal frequency on axis in an array under operating mode shown in Figure 10 (a) (b)
The comparison of change.
Figure 12 (a) is that the phased array operating condition of the two-dimensional rectangle array as composed by typical round film pMUTs unit is illustrated
Figure.
Figure 12 (b) is that the phased array operating condition of the two-dimensional rectangle array as composed by shown combined film pMUTs unit is shown
It is intended to.
Figure 13 (a) is the array as composed by typical round film pMUTs under operating condition shown in Figure 12 (a), in different works
Acoustic pressure distribution situation on array central axes under working frequency.
Figure 13 (b) is the array as composed by the combined film pMUTs unit under operating condition shown in Figure 12 (b),
Acoustic pressure distribution situation on array central axes under different operating frequency.
Figure 14 is combined film pMUTs unit of the present invention, by circular membrane and annular membrane in fluid media (medium)
The deviation of center resonant frequency causes ultrasonic wide reception bandwidth characteristic schematic illustration.
Specific embodiment
Below in conjunction with attached drawing, the present invention is described in detail:
The present invention proposes a kind of combined film pMUTs and preparation method thereof, to increase pMUTs transmission power, mentioning
While high ultrasonic reception bandwidth improve pMUTs chip preparing process feasibility, reliability and cellular construction and performance one
Cause property.
As shown in Figure 1, Figure 2 and Figure 3, a kind of combined film pMUTs of the present invention, from top to bottom by multi-layer compound film 1
It is formed with underlying structure 2.
The multi-layer compound film 1 is composed of Piezoelectric Driving layer structure 1-1 and non-driven layer structure 1-2.It is described
Piezoelectric Driving layer structure 1-1 is in thickness direction from top to bottom by top electrodes 1-1-1, dielectric layer 1-1-2, bottom electrode 1-1-
3 compositions.
The dielectric layer 1-1-2 is combined by multi-layer insulation, and as the preferred embodiment of the present invention, electricity is situated between
Matter layer is followed successively by shielded layer 1-1-2-1, piezoelectric material layer 1-1-2-2 in thickness direction from top to bottom.
Circular cavity 3 and toroidal cavity 4 are etched in the underlying structure 2, and toroidal cavity 4 is in circular cavity 3
Concentric position.Circular cavity 3, toroidal cavity 4 and the multi-layer compound film 1 form the circular membrane 5 that can produce bending vibration
And concentric annular membrane 6.
The top electrodes 1-1-1 is by being covered on the circular membrane driving electrodes 1-1-1-1 of 5 upper surface of circular membrane and covering
Cover the annular membrane driving electrodes 1-1-1-2 composition in 6 upper surface of annular membrane；It is described as the preferred embodiment of the present invention
Circular membrane driving electrodes 1-1-1-1 is arranged in 5 center of circular membrane, and concentric circles, circle are thin each other with circular membrane 5
The radius of film driving electrodes 1-1-1-1 is between 0.5 to 0.8 times of 5 radius size of circular membrane；As preferred reality of the invention
Example is applied, the annular membrane driving electrodes 1-1-1-2 and annular membrane 6 are in concentric ring structure, annular membrane driving electrodes 1-1-
The width of 1-2 is between 0.4 to 0.7 times of 6 width dimensions of annular membrane.
Same frequency is taken to circular membrane driving electrodes 1-1-1-1 and annular membrane driving electrodes 1-1-1-2 but with phase
The driving signal of potential difference is motivated, and the range of the phase difference is 0 to 2 π；As the preferred embodiment of the present invention, respectively plus
The driving signal V being loaded on circular membrane driving electrodes 1-1-1-1 and annular membrane driving electrodes 1-1-1-21With V2It is sine
Signal, and the two amplitude is equal, phase by pi；In circular membrane driving electrodes 1-1-1-1 and annular membrane driving electrodes 1-1-
The inverse piezoelectric effect effect of piezoelectric material layer 1-1-2-2 is lower below the overlay area 1-2 generates in-plane stress, so that circular membrane 5,
6 warpage of annular membrane generates bending vibration；
A kind of combination is the preparation method of membrane structure pMUTs, comprising the following steps:
Step 1: taking a monocrystalline silicon piece as underlying structure 2, using reactive ion etching (RIE) technology in underlying structure 2
Upper surface etches circular cavity 3 and toroidal cavity 4；
Step 2: a SOI wafer is taken, using its top layer silicon as non-driven layer structure 1-2, using Si V groove technology
It is bonded with the upper surface for the underlying structure 2 for having etched circular cavity 3, toroidal cavity 4；
Step 3: SOI wafer bottom silicon 7 being thinned to by chemically mechanical polishing (CMP) technology and is only left 1 to 50 μm
Thickness；
Step 4: being removed remaining SOI wafer bottom silicon 7 and buried layer 8 by reactive ion etching (RIE) technology；
Step 5: for the film deposition quality for improving piezoelectric material layer 1-1-2-2 in step 7, being existed using magnetron sputtering technique
Between bottom electrode 1-1-3 and non-driven layer structure 1-2, the piezoelectric material of 10-100nm is deposited as piezoelectric material seed layer 9；
Step 6: the metal of 50~200nm is deposited as bottom electrode 1-1-3 using magnetron sputtering technique；
Step 7: the piezoelectric material of 800~1000nm is deposited as piezoelectric material layer 1-1-2-2 using magnetron sputtering technique；
Step 8: using plasma enhances the SiO of chemical vapor deposition (PECVD) technology deposition 60nm2As shielded layer
1-1-2-1；
Step 9: in vibration film and top electrode surface of insulating layer splash-proofing sputtering metal electrode layer, etching forms circular membrane driving
Electrode 1-1-1-1 and annular membrane driving electrodes 1-1-1-2；
Step 10: dry etching fairlead, the electrical connection for bottom electrode and gold thread.
Piezoelectric material described in the present embodiment step 5 is AlN.
The material of the present embodiment top electrodes 1-1-1 and bottom electrode 1-1-3 is Mo.
The present embodiment is not precluded using AlN as the preferred embodiments of piezoelectric material and selects numerous piezoelectricity such as PZT, ZnO
Feasibility of the material as piezoelectric material layer 1-1-2-2 material；Herein using Mo as top electrodes 1-1-1 and bottom electrode 1-1-
The preferred embodiments of 3 materials, but numerous metal materials such as Au, Al is not precluded are as top electrodes 1-1-1 and bottom electrode 1-
The feasibility of 1-3 material.
By Comsol Multiphysics simulation software in water with the biography of same unit resonance frequency 9.7MHz
Unite the circular membrane structure pMUTs and builtup film formula pMUTs, in the driving voltage amplitude situation identical with working frequency
Under, the emulation for carrying out ultrasound emission sensitivity in water is compared；As shown in figure 5, the ultrasound emission of builtup film formula pMUTs is sensitive
The optimization structure spent compared to traditional pMUTs unit of only circular membrane improves 1500%.
When motivating the phase difference between circular membrane and the driving voltage of annular membrane is π, in each vibration period
Circular membrane and annular membrane can mutually absorb flow of the other side by vibrating fluid media (medium) be discharged；When pMUTs unit group
When being worked at array, the changes in flow rate that can be avoided the fluid media (medium) near unit caused by each pMUTs unit inhibits
The ultrasound emission power of pMUTs unit adjacent thereto, to further press down on the basis of enhancing itself ultrasound emission power
System interfering with each other between each pMUTs unit in array；Promote the whole of the pMUTs array being made of pMUTs unit
Body ultrasound emission power.In the operating condition for combined film pMUTs of the present invention, the film vibration shape and fluid are situated between Fig. 6 (a)
The correlation schematic diagram of nowed forming, as can be seen from the figure reclinate circular membrane is absorbed by being bent upwards annular
The flow rate that film excludes；It can be seen that reclinate annular membrane is absorbed by being bent upwards circle from Fig. 6 (b)
The flow rate of shape film discharge.
Simulating, verifying is carried out to above-mentioned working mechanism by Comsol Multiphysics:
First: as shown in fig. 7, by unit resonance frequency in water be 9.7MHz builtup film formula pMUTs with only
Traditional pMUTs of circular membrane separately constitutes one-dimensional linear array, and make each unit with mutually carry out ultrasound emission, to unit it
Between mutual crosstalk effect verified.As shown in figure 8, discovery is in each of one-dimensional linear array builtup film formula
The frequency response curve when frequency response curve of pMUTs unit works independently with it always is consistent, and resonant frequency point
It does not shift；As shown in figure 9, and typical round pMUTs unit in one-dimensional linear array, it is mutual dry between each unit
Disturb serious, frequency response when leading to it frequency response curve of each unit working independently relative to it in one-dimensional array is bent
Line is severely deformed, and can not accurately obtain its resonance frequency in one-dimensional linear array.
Secondly: being the builtup film of 9.7MHz by unit resonance frequency in water as shown in Figure 10 (a) and Figure 10 (b)
Formula pMUTs and traditional pMUTs of only circular membrane separately constitute the identical two-dimensional rectangle array of area, and keep each unit same
Mutually carry out ultrasound emission；As shown in figure 11, finite element has been carried out to the sound pressure level of the position distance arrays 0.8mm on array central axes
Emulation finds that the array being made of builtup film formula pMUTs unit generated acoustic pressure in array axis is much higher than traditional round
The acoustic pressure of the homalographic array of shape pMUTs unit composition, and generate resonance when maximum sound pressure working frequency works independently with it
Frequency is no different；
It is final: to be the builtup film of 6.3MHz by unit resonance frequency in water as shown in Figure 12 (a) and Figure 12 (b)
Formula pMUTs and traditional pMUTs of only circular membrane separately constitute the identical two-dimensional rectangle array of area, and in two-dimensional array
Each column unit between ultrasound emission phase difference controlled, using phased array line focus ultrasound transmission modes；Such as Figure 13
(a) and shown in Figure 13 (b), finite element simulation has been carried out to the acoustic pressure distribution on array central axes.It was found that by builtup film formula
The array of pMUTs unit composition generated acoustic pressure in array axis is formed much higher than typical round film pMUTs unit
Homalographic array, and the resonance frequency generated when maximum sound pressure Frequency point is worked normally with individual unit is no different.By typical round
Array composed by film pMUTs unit can not recognize its center operating frequency when working, and increase the complexity of Array Design.
As shown in figure 14, the present invention is carried out reasonably combined by the size to circular membrane and annular membrane, so that the two
Resonance frequency generate deviation, to widen the ultrasonic reception bandwidth of pMUTs.
The foregoing is merely one embodiment of the present invention, it is not all of or unique embodiment, this field is common
Any equivalent transformation that technical staff takes technical solution of the present invention by reading description of the invention, is the present invention
Claim covered.
Claims (7)
1. a kind of combined film pMUTs, it is characterised in that: from top to bottom by multi-layer compound film (1) and underlying structure (2) group
At；
The multi-layer compound film (1) is composed of Piezoelectric Driving layer structure (1-1) and non-driven layer structure (1-2)；Institute
Piezoelectric Driving layer structure (1-1) is stated in thickness direction from top to bottom by top electrodes (1-1-1), dielectric layer (1-1-2) and bottom
Portion's electrode (1-1-3) composition；The dielectric layer (1-1-2) is combined by multilayer material；
Circular cavity (3) and toroidal cavity (4), and toroidal cavity (4) and circular cavity are etched on the underlying structure (2)
(3) it is in concentric position；Circular cavity (3), toroidal cavity (4) and the multi-layer compound film (1) form and can produce bending vibration
Dynamic circular membrane (5) and concentric annular membrane (6)；
The top electrodes (1-1-1) by be covered on circular membrane (5) upper surface circular membrane driving electrodes (1-1-1-1) and
It is covered on annular membrane driving electrodes (1-1-1-2) composition of annular membrane (6) upper surface；
Same frequency is used with annular membrane driving electrodes (1-1-1-2) to circular membrane driving electrodes (1-1-1-1) but there are phases
The driving signal of potential difference is motivated, and the range of the phase difference is 0 to 2 π；Circular membrane driving electrodes (1-1-1-1) with
The piezoelectric material layer in dielectric layer (1-1-2) below the overlay area annular membrane driving electrodes (1-1-1-2) is in inverse piezoelectricity
Effect effect is lower to generate in-plane stress, and circular membrane (5), annular membrane (6) warpage is caused to generate bending vibration.
2. a kind of combined film pMUTs according to claim 1, it is characterised in that: the dielectric layer is at (1-1-2)
Thickness direction is followed successively by shielded layer (1-1-2-1) and piezoelectric material layer (1-1-2-2) from top to bottom.
3. a kind of combined film pMUTs according to claim 1, it is characterised in that: the circular membrane driving electrodes
(1-1-1-1) is arranged in circular membrane (5) center, and with circular membrane (5) concentric circles each other, circular membrane driving electrodes
The radius of (1-1-1-1) is between 0.5 to 0.8 times of circular membrane (5) radius size；As the preferred embodiment of the present invention,
The annular membrane driving electrodes (1-1-1-2) and annular membrane (6) are in concentric ring structure, annular membrane driving electrodes (1-1-
Width 1-2) is between 0.4 to 0.7 times of annular membrane (6) width dimensions.
4. a kind of combined film pMUTs according to claim 1, it is characterised in that: load on circular membrane driving electricity
Driving signal V on pole (1-1-1-1) and annular membrane driving electrodes (1-1-1-2)1With V2It is sinusoidal signal, and the two width
It is worth equal, phase by pi.
5. the preparation method of the described in any item combined film pMUTs of Claims 1-4, it is characterised in that: including following step
It is rapid:
Step 1: taking a monocrystalline silicon piece as underlying structure (2), using reactive ion etching RIE technology on underlying structure (2)
Surface etch goes out circular cavity (3) and toroidal cavity (4)；
Step 2: a SOI wafer is taken, it, will using Si V groove technology using its top layer silicon as non-driven layer structure (1-2)
Be bonded with the upper surface for the underlying structure (2) for having etched circular cavity (3), toroidal cavity (4)；
Step 3: SOI wafer bottom silicon (7) is thinned to by only remaining 1 to 50 μm of thickness by chemical Mechanical Polishing Technique；
Step 4: being removed remaining SOI wafer bottom silicon (7) and buried layer (8) by reactive ion etching technology；
Step 5: for improve step 7 in piezoelectric material layer (1-1-2-2) film deposition quality, using magnetron sputtering technique the bottom of at
Between portion's electrode (1-1-3) and non-driven layer structure (1-2), the piezoelectric material of 10-100nm is deposited as piezoelectric material seed layer
(9)；
Step 6: the metal of 50~200nm is deposited as bottom electrode (1-1-3) using magnetron sputtering technique；
Step 7: the piezoelectric material of 800~1000nm is deposited as piezoelectric material layer (1-1-2-2) using magnetron sputtering technique；
Step 8: using plasma enhances the SiO of chemical gaseous phase technology deposition method deposition 60nm2As shielded layer (1-1-2-
1)；
Step 9: in vibration film and top electrode surface of insulating layer splash-proofing sputtering metal electrode layer, etching forms circular membrane driving electrodes
(1-1-1-1) and annular membrane driving electrodes (1-1-1-2)；
Step 10: dry etching fairlead, the electrical connection for bottom electrode and gold thread.
6. preparation method according to claim 5, it is characterised in that: piezoelectric material described in step 5 is AlN or ZnO.
7. preparation method according to claim 5, it is characterised in that: the top electrodes (1-1-1) and bottom electrode (1-
Material 1-3) is Mo.
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