Ultrasonic transducer and manufacturing method thereof

Abstract

The invention relates to the technical field of ultrasonic transducers, and discloses an ultrasonic transducer and a manufacturing method thereof.The ultrasonic transducer comprises at least one light-emitting unit and at least one transduction unit; each transduction unit comprises at least one top electrode chain, a piezoelectric layer and at least one bottom electrode which are sequentially stacked from top to bottom; the bottom electrode comprises a cavity area; the light-emitting unit comprises a first conductive layer, a light-emitting layer, a second conductive layer, the piezoelectric layer and a substrate layer which are sequentially stacked from top to bottom; the light-emitting unit further comprises a light-emitting part, a first electrode part and a second electrode part; the transduction unit is used for receiving sound waves and generating the sound waves; the light-emitting unit is used for emitting light. According to the ultrasonic transducer, the light-emitting unit and the transduction unit are connected through the same piezoelectric layer, the integration level of the ultrasonic transducer is improved, the light-emitting unit does not use laser, damage to biological tissue can be avoided, and safety is improved.

Description

Technical Field

[0001] This application relates to the technical field of ultrasonic transducers, and particularly to an ultrasonic transducer and a manufacturing method thereof. Background Art

[0002] Laser photoacoustic imaging is one of the most mature and widely used technologies in the field of photoacoustic imaging. It uses pulsed laser to irradiate biological tissue, excite local tissue to generate ultrasonic signals, and then constructs the internal structure or functional image of the tissue by detecting these ultrasonic waves. Laser photoacoustic imaging combines the high contrast of optical imaging and the high resolution of ultrasonic imaging, and is widely used in the fields of medical imaging, biomedical research, etc. However, due to the difficult-to-solve problems such as complex control of the light source energy safety threshold and low integration degree in laser photoacoustic imaging, its convenience is poor and its safety is difficult to guarantee when applied to biological tissue.

[0003] In summary, there is a need to provide an ultrasonic transducer and a manufacturing method thereof that can improve safety and have a high integration degree. Summary of the Invention

[0004] To solve the above problems, this application proposes an ultrasonic transducer and a manufacturing method thereof.

[0005] On the one hand, this application proposes an ultrasonic transducer, including: at least one light-emitting unit and at least one transducer unit;

[0006] The transducer unit includes at least one top electrode chain, a piezoelectric layer, and at least one bottom electrode stacked in sequence from top to bottom;

[0007] The bottom electrode includes a cavity area;

[0008] The light-emitting unit includes a first conductive layer, a light-emitting layer, a second conductive layer, the piezoelectric layer, and a substrate layer stacked in sequence from top to bottom; the light-emitting unit further includes a light-emitting part, a first electrode part, and a second electrode part;

[0009] The transducer unit is used to receive sound waves and generate sound waves;

[0010] The light-emitting unit is used to emit light.

[0011] Preferably, the top electrode chain includes: at least one electrode part and at least one connecting part; at least one end of the connecting part is connected to one of the electrode parts.

[0012] Preferably, the bottom electrode and the cavity area overlap with the electrode part in the vertical direction;

[0013] The number of the bottom electrodes is the same as the number of the electrode parts.

[0014] Preferably, the area of the bottom electrode is larger than the area of the electrode portion.

[0015] Preferably, the shape of the bottom electrode includes: circular and polygonal;

[0016] The shape of the electrode portion includes: circular and polygonal;

[0017] The shape of the light-emitting portion includes: circular and polygonal.

[0018] Preferably, the shape of the top electrode chain includes linear and polygonal.

[0019] In a second aspect, the present application provides a method for manufacturing an ultrasonic transducer, including:

[0020] Stacking a piezoelectric layer, a first conductive layer, and a light-emitting layer on a substrate layer in sequence;

[0021] Patterning the first conductive layer and the light-emitting layer to form a light-emitting portion and expose the piezoelectric layer;

[0022] Depositing a second conductive layer and a third conductive layer on the light-emitting portion and the exposed piezoelectric layer respectively and patterning them to form a top electrode chain, a first electrode portion, and a second electrode portion;

[0023] Performing deep silicon etching on the substrate layer to form a cavity in the substrate layer;

[0024] Depositing a sub-conductive layer in the cavity to form a bottom electrode.

[0025] Preferably, the materials of the first conductive layer, the second conductive layer, the third conductive layer, and the sub-conductive layer include: conductive silicon, conductive oxide, and metal.

[0026] Preferably, the material of the light-emitting layer includes: gallium nitride, indium gallium nitride, and indium gallium arsenide.

[0027] Preferably, the material of the piezoelectric layer includes: lead zirconate titanate, aluminum nitride, and scandium-doped aluminum nitride.

[0028] The advantages of the present application are as follows: By connecting the light-emitting unit and the transducer unit through the same piezoelectric layer, the integration degree of the ultrasonic transducer is improved. Moreover, since the light-emitting unit does not use a laser, damage to biological tissues can be avoided, and the safety is improved. Description of the Drawings

[0029] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0030] Figure 1 It is a schematic diagram of an ultrasonic transducer provided by this application;

[0031] Figure 2 It is a top view schematic diagram of an ultrasonic transducer provided by this application;

[0032] Figure 3 It is a front view schematic diagram of an ultrasonic transducer provided by this application;

[0033] Figure 4 It is a top view schematic diagram of another ultrasonic transducer provided by this application;

[0034] Figure 5 It is a schematic diagram of a manufacturing method of an ultrasonic transducer provided by this application;

[0035] Figure 6 It is a stacked schematic diagram of a manufacturing method of an ultrasonic transducer provided by this application;

[0036] Figure 7 It is a schematic diagram of forming a light-emitting part in a manufacturing method of an ultrasonic transducer provided by this application;

[0037] Figure 8 It is a schematic diagram of forming a top electrode chain, a first electrode part, and a second electrode part in a manufacturing method of an ultrasonic transducer provided by this application;

[0038] Figure 9 It is a schematic diagram of forming a cavity in a substrate layer in a manufacturing method of an ultrasonic transducer provided by this application;

[0039] Figure 10 It is a schematic diagram of forming a bottom electrode in a manufacturing method of an ultrasonic transducer provided by this application;

[0040] Figure 11 It is a schematic diagram of forming a top electrode chain in a manufacturing method of an ultrasonic transducer provided by this application. Detailed implementation manners

[0041] Hereinafter, the exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0042] LED photoacoustic imaging is an emerging branch of photoacoustic imaging technology. It uses light-emitting diodes as light sources to replace traditional laser light sources to generate photoacoustic signals. Compared with traditional laser photoacoustic imaging, the light source of LED photoacoustic imaging is cheaper. At the same time, since the output power of the LED is weaker than that of the laser, it is safer in human biological tissue imaging and can avoid the risk of tissue damage that may be brought by high-power lasers. However, there are currently relevant commercial products, which are mainly assembled based on bulk materials, with a single frequency and low integration and resolution.

[0043] In a first aspect, to solve the above problems, an embodiment of the present application proposes an ultrasonic transducer, as Figure 1 and Figure 2 shown, including: at least one light-emitting unit 100 and at least one transducer unit 200; the transducer unit 200 includes at least one top electrode chain 201, a piezoelectric layer 202, and at least one bottom electrode 203 stacked in sequence from top to bottom; the bottom electrode 203 includes a cavity region 231; the light-emitting unit 100 includes a first conductive layer 101, a light-emitting layer 102, a second conductive layer 103, a piezoelectric layer, and a substrate layer 10 stacked in sequence from top to bottom; the light-emitting unit 100 further includes a light-emitting portion 121, a first electrode portion 141, and a second electrode portion 142; the transducer unit 200 is configured to receive sound waves and generate sound waves; the light-emitting unit 100 is configured to emit light.

[0044] In the transducer unit, the piezoelectric layer is controlled to vibrate by the top electrode chain and the bottom electrode to generate sound waves, and the vibration generated by the piezoelectric layer due to receiving sound waves causes an electrical signal to be output through the top electrode chain and the bottom electrode, realizing the reception and generation of sound waves.

[0045] Among them, for the first electrode portion and the second electrode portion, one of them serves as the positive electrode of the light-emitting portion, and the other serves as the negative electrode of the light-emitting portion. The first conductive layer is used to form one of the first electrode portion and the second electrode portion, serving as the top electrode of the light-emitting unit; the second conductive layer is used to form the other of the first electrode portion and the second electrode portion, serving as the bottom electrode of the light-emitting unit. For the first conductive layer and the second conductive layer, one layer serves as the positive electrode of the light-emitting portion, and the other layer serves as the negative electrode of the light-emitting portion. The light-emitting layer includes an LED. The transducer unit can be designed in a variety of different sizes to achieve multi-frequency compatibility or bandwidth expansion to improve performance. The first conductive layer and the second conductive layer of the light-emitting unit do not overlap with the top electrode chain and the bottom electrode of the transducer unit in the vertical direction, that is, there cannot be overlapping regions.

[0046] Embodiments of the present application integrate the light-emitting unit and the transducer unit through a stacked compatibility design, thereby realizing an integrated LED light source and acoustic transducer, improving the integration degree of the ultrasonic transducer device and the effect of its application. Compared with the traditional LED photoacoustic imaging probe, the volume of the ultrasonic transducer (probe) in the embodiments of the present application is reduced to one-tenth of that of the traditional LED photoacoustic imaging probe. Moreover, the ultrasonic transducers in the embodiments of the present application are fabricated using the standardized processes of Micro-Electro-Mechanical System (MEMS) technology, which can significantly reduce costs while improving process consistency and performance consistency.

[0047] As Figure 2 shown, the top electrode chain 201 includes: at least one electrode portion 211 and at least one connecting portion 212; at least one end of the connecting portion 212 is connected to an electrode portion 211.

[0048] As Figure 3 shown, the bottom electrode 203 and the cavity region 231 overlap with the electrode portion 211 in the vertical direction; the number of bottom electrodes 203 is the same as the number of electrode portions 211.

[0049] Among them, the bottom electrode 203 and the cavity region 231 overlapping with the electrode portion 211 in the vertical direction may be partially overlapping.

[0050] The area of the bottom electrode is larger than the area of the electrode portion.

[0051] The shape of the bottom electrode includes: circular and polygonal.

[0052] The shape of the electrode portion includes: circular and polygonal.

[0053] The shape of the light-emitting portion includes: circular and polygonal.

[0054] The shape of the top electrode chain includes straight and folded lines.

[0055] Among them, multiple top electrode chains can be straight and folded top electrode chains with different sizes and shapes respectively. The multiple top electrode chains are spaced apart from each other, that is, the multiple top electrode chains do not contact each other.

[0056] As Figure 4 shown, the light-emitting unit 100 can form an ultrasonic transducer with one or more transducer units 200 on either side thereof. The transducer unit 200 can be not only on the left and right sides of the light-emitting unit 100, but also in front of it, behind it, at the left diagonal and right diagonal, etc.

[0057] The transducer unit in the embodiments of the present application is a piezoelectric micromachined ultrasonic transducer (PMUT). The vibration elements (transducer units) in its receiving area can be designed with different shapes for frequency and bandwidth. The shapes of the hollow cavity areas of the bottom electrodes include circles and combinations of circles with different sizes, as well as polygons and combinations of polygons with different sizes. The light-emitting part of the light-emitting unit can be freely defined as regular or irregular figures of various sizes according to specific needs.

[0058] In the embodiments of the present application, through finite element analysis, drive models of transducer units (piezoelectric) with the same area but different stack thicknesses and shapes are established. By applying the same AC voltage or quasi-static voltage, the frequency, bandwidth, amplitude, transmission, and reception sensitivity of the transducer unit devices are observed. Since under equal voltage drive, the amplitude of the transducer unit with a larger radius is larger, the frequency of the transducer unit with a thicker stack is higher and the sensitivity is lower. In the transducer unit, if the aperture of the cavity area of the bottom electrode corresponding to the top electrode chain is larger, the bandwidth of the transducer unit is larger. Therefore, by adjusting these parameters, transducer arrays that meet different applications can be obtained.

[0059] Moreover, in order to further demonstrate the modulation effect of the stack and device design on optics, theoretical analysis is also carried out on the LED light intensity of the light-emitting unit. For the light-emitting unit, near the turn-on voltage of the LED, the light intensity has an exponential relationship with the voltage; as the voltage increases, the current roll-off effect continuously strengthens, and the light intensity and voltage have a linear or sub-linear relationship; when the voltage exceeds the breakdown voltage, the light intensity will rapidly decay to 0. Therefore, the turn-on voltage of the LED in the light-emitting unit is about 3V, and the breakdown voltage is about 8V. Within this range, signal reception or pure electrical DC modulation of the light-emitting unit can be realized for regulation.

[0060] The embodiments of the present application address the problems of low integration, poor resolution, and single frequency in traditional LED photoacoustic imaging systems. A design that makes the light-emitting layer of the LED and the stacks required for ultrasonic transducers compatible is proposed, so as to integrate the light-emitting unit and the transducer unit. Moreover, an integrated ultrasonic transducer manufactured based on the MEMS process flow is provided, which improves the system integration and the performance of the ultrasonic transducer probe, reduces the probe volume and production cost, expands the application scenarios, and reduces the pain of patients in potential invasive medical applications.

[0061] In a second aspect, according to the embodiments of the present application, a manufacturing method of an ultrasonic transducer is also proposed, as Figure 5 shown, including:

[0062] S101, as Figure 6 shown, stack a piezoelectric layer 202, a first conductive layer 103, and a light-emitting layer 102 on the substrate layer 10 in sequence;

[0063] S102, as Figure 7 shown, pattern the first conductive layer 103 and the light-emitting layer 102 to form a light-emitting portion 121, and expose the piezoelectric layer 202;

[0064] S103, as Figure 8 shown, deposit a second conductive layer and a third conductive layer on the light-emitting portion 121 and the exposed piezoelectric layer 202 respectively and pattern them to form a top electrode chain 201, a first electrode portion, and a second electrode portion;

[0065] S104, as Figure 9 shown, perform deep silicon etching on the substrate layer 10 to form a cavity (back cavity) 231 in the substrate layer;

[0066] S105, as Figure 10 shown, deposit a sub-conductive layer in the cavity 11 to form a bottom electrode 203.

[0067] Depositing a second conductive layer and a third conductive layer on the light-emitting portion and the exposed piezoelectric layer respectively and patterning them to form a top electrode chain, a first electrode portion, and a second electrode portion includes: depositing a second conductive layer on the light-emitting portion; as Figure 11 shown, pattern the second conductive layer to form a top electrode chain; deposit a third conductive layer on the exposed piezoelectric layer and pattern the third conductive layer to form a first electrode portion and a second electrode portion.

[0068] Before performing deep silicon etching on the substrate layer to form a cavity in the substrate layer, it further includes: the light-emitting layer

[0069] The materials of the first conductive layer, the second conductive layer, the third conductive layer, and the sub-conductive layer include: conductive silicon, conductive oxide, and metal.

[0070] The material of the light-emitting layer includes: gallium nitride (GaN), indium gallium nitride (InGaN), and indium gallium arsenide (InGaAs).

[0071] The material of the piezoelectric layer includes: lead zirconate titanate (PZT), aluminum nitride (ALN), and scandium-doped aluminum nitride (ScALN).

[0072] The material of the substrate layer includes: silicon, silicon-on-insulator (SOI), sapphire, and diamond.

[0073] The processes of sequentially stacking a piezoelectric layer, a first conductive layer, and a light-emitting layer on a substrate layer include processes such as evaporation coating, physical vapor deposition (PVD), and chemical vapor deposition (CVD). The processes of patterning the first conductive layer, the second conductive layer, the third conductive layer, and the sub-conductive layer include processes such as wet etching or dry etching. The processes of depositing the second conductive layer and the third conductive layer on the light-emitting part and the exposed piezoelectric layer respectively include processes such as evaporation coating, PVD, and CVD. The processes of deep silicon etching of the substrate layer include processes such as deep reactive ion etching (DRIE) and lithography, electroforming, and injection molding (Lithographie GaVanoformung Abformung, LIGA). The process of depositing a sub-conductive layer in a cavity to form a bottom electrode includes processes such as evaporation coating, PVD, and CVD. The requirement for patterning the light-emitting part is not to cover the top electrode chain, that is, the light-emitting part does not contact the top electrode chain.

[0074] In the method of the present application, the light-emitting unit and the transducer unit are connected through the same piezoelectric layer, improving the integration of the ultrasonic transducer. Moreover, the light-emitting unit does not use a laser, which can avoid damage to biological tissues and improve safety. The system integration and the performance consistency of the ultrasonic transducer probe are improved through the MEMS process; and it can also reduce the probe volume and production cost; expand the application scenarios, and reduce the pain of patients in potential invasive medical applications.

[0075] As mentioned above, only the specific preferred embodiments of the present application are described, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An ultrasonic transducer, characterized in that, Comprising: At least one light-emitting unit and at least one transducer unit; The transducer unit includes at least one top electrode chain, a piezoelectric layer, and at least one bottom electrode stacked in sequence from top to bottom; The bottom electrode includes a cavity region; The light-emitting unit includes a first conductive layer, a light-emitting layer, a second conductive layer, the piezoelectric layer, and a substrate layer stacked in sequence from top to bottom; the light-emitting unit further includes a light-emitting portion, a first electrode portion, and a second electrode portion; The transducer unit is configured to receive and generate acoustic waves; The light-emitting unit is configured to emit light.

2. The ultrasonic transducer according to claim 1, wherein The top electrode chain includes: at least one electrode portion and at least one connecting portion; at least one end of the connecting portion is connected to one of the electrode portions.

3. The ultrasonic transducer according to claim 2, wherein The bottom electrode and the cavity region overlap with the electrode portion in the vertical direction; The number of the bottom electrodes is the same as the number of the electrode portions.

4. The ultrasonic transducer according to claim 2, characterized in that, The area of the bottom electrode is larger than the area of the electrode portion.

5. The ultrasonic transducer according to claim 1, characterized in that, The shape of the bottom electrode includes: circular and polygonal; The shape of the electrode portion includes: circular and polygonal; The shape of the light-emitting portion includes: circular and polygonal.

6. The ultrasonic transducer according to claim 1, characterized in that, The shape of the top electrode chain includes linear and zigzag.

7. A manufacturing method of an ultrasonic transducer, characterized in that, Comprising: Stacking a piezoelectric layer, a first conductive layer, and a light-emitting layer on the substrate layer in sequence; Patterning the first conductive layer and the light-emitting layer to form a light-emitting portion and expose the piezoelectric layer; Depositing and patterning a second conductive layer and a third conductive layer on the light-emitting portion and the exposed piezoelectric layer respectively to form a top electrode chain, a first electrode portion, and a second electrode portion; Performing deep silicon etching on the substrate layer to form a cavity in the substrate layer; Depositing a sub-conductive layer in the cavity to form a bottom electrode.

8. The manufacturing method of the ultrasonic transducer according to claim 7, characterized in that, The materials of the first conductive layer, the second conductive layer, the third conductive layer, and the sub-conductive layer include: conductive silicon, conductive oxide, and metal.

9. The manufacturing method of the ultrasonic transducer according to claim 7, characterized in that, The material of the light-emitting layer includes: gallium nitride, indium gallium nitride, and indium gallium arsenide.

10. The manufacturing method of the ultrasonic transducer according to claim 7, characterized in that, The material of the piezoelectric layer includes: lead zirconate titanate, aluminum nitride, and scandium-doped aluminum nitride.

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