Micro-nano acoustic transducer and ultrasonic imaging probe based on structural pre-strain

Abstract

The application provides a micro-nano acoustic transducer and an ultrasonic imaging probe based on structural pre-strain, which comprises a first electrode (2), a second electrode (6) and a diaphragm layer (5), the second electrode (6) is attached to the diaphragm layer (5), the first electrode (2) and the diaphragm layer (5) are spaced apart, a cavity (3) is formed between the first electrode (2) and the diaphragm layer (5), and in the state that no voltage is applied to the first electrode (2) and the second electrode (6), the diaphragm layer (5) and part of the second electrode (6) are both curved and recessed to the cavity (3).

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ultrasonic measuring devices, and particularly relates to a micro-nano acoustic transducer and an ultrasonic imaging probe based on structural pre-strain. BACKGROUND

[0002] The micro-nano acoustic transducer is a new type of ultrasonic transducer based on micro-electromechanical system (MEMS) manufacturing, which realizes the emission and measurement of ultrasonic waves through the capacitance change between a layer of suspended vibrating membrane and a fixed electrode. Compared with traditional piezoelectric transducers, the micro-nano acoustic transducer has the advantages of wide frequency band, small size, easy arraying, and strong compatibility with integrated circuits, and is widely used in medical imaging, non-destructive testing, underwater acoustics, and intelligent sensing. The micro-nano acoustic transducer can be mass-produced in micro-nano scale, has excellent consistency and scalability, and is an important technical route to realize high-performance micro ultrasonic systems.

[0003] REFERENCE Figure 1 A possible capacitive micro-mechanical ultrasonic transducer system can include a substrate layer 1, a first electrode 2, a cavity 3, a support layer 4, a diaphragm layer 5, a second electrode 6, electrode leads 7, and a high-voltage DC power supply 8. The first electrode 2 is attached to the substrate layer 1, the support layer 4 is arranged between the diaphragm layer 5 and the first electrode 2, thereby forming a cavity 3 between the diaphragm layer 5 and the first electrode 2, the second electrode 6 is attached to the diaphragm layer 5, and the two electrode leads 7 are respectively connected to the first electrode 2 and the second electrode 6. The high-voltage DC power supply 8 is connected to the electrode leads 7. Among them, the diaphragm layer 5 is a flat plate structure (without deformation caused by pre-strain), and when the capacitive micro-mechanical ultrasonic transducer system is working, a large amplitude DC voltage needs to be applied to the first electrode 2 and the second electrode 6 by the high-voltage DC power supply 8, so as to deform the diaphragm layer 5 and pull it down to the best working position. The emission of ultrasonic waves needs to apply a small amplitude AC to the deformed and pulled down diaphragm layer 5, and the measurement of ultrasonic waves needs to read the capacitance change on the basis of the deformed and pulled down diaphragm layer 5.

[0004] However, the above scheme uses electrostatic force to drive the diaphragm layer 5, which needs to apply a high DC bias voltage (usually tens to hundreds of volts) to realize effective excitation and sensitive reception. This significantly increases the complexity and cost of system design, and causes reliability problems such as electrical breakdown and increased power consumption. Moreover, the large DC bias voltage may cause harm to the human body, which limits its application in human medical devices, such as ultrasonic endoscopes, extracorporeal ultrasonic imaging probes, etc. In addition, the dependence of such micro-nano acoustic transducers on high-voltage and high-power power supplies limits their promotion in portable and low-power applications. In the case of applying a high DC voltage bias, the micro-nano acoustic transducer has a significant nonlinear behavior in the emission and measurement of acoustic pressure, which leads to distortion of the input-output response, and further affects the imaging quality and signal accuracy. SUMMARY

[0005] The present application aims to propose a micro-nano acoustic transducer based on structural pre-strain to solve or improve at least one problem existing in the background art.

[0006] Embodiments of the present application propose a micro-nano acoustic transducer based on structural pre-strain, comprising:

[0007] a first electrode;

[0008] a second electrode; and

[0009] a diaphragm layer, the second electrode being attached to the diaphragm layer, the first electrode and the diaphragm layer being spaced apart, a cavity being formed between the first electrode and the diaphragm layer, in a state where no voltage is applied to the first electrode and the second electrode, a partial area of the diaphragm layer and a partial area of the second electrode are both curved and concave to the cavity.

[0010] In at least one possible embodiment, the diaphragm layer comprises at least two diaphragm layers with different coefficients of thermal expansion, the internal stress generated by temperature change of the diaphragm layers with different coefficients of thermal expansion causes the diaphragm layer to maintain a state of being concave to the cavity.

[0011] In at least one possible embodiment, the diaphragm layer comprises a first diaphragm layer and a second diaphragm layer, the first diaphragm layer being relatively far away from the second electrode, the second diaphragm layer being relatively close to the second electrode, the coefficient of thermal expansion of the first diaphragm layer being greater than the coefficient of thermal expansion of the second diaphragm layer.

[0012] In at least one possible embodiment, the micro-nano acoustic transducer further comprises a support layer, the support layer being arranged between the first electrode and the diaphragm layer, the support layer comprising a support portion, the edge area of the diaphragm layer and the second electrode being supported by the support portion, the middle area of the diaphragm layer and the second electrode being concave to the cavity.

[0013] In at least one possible embodiment, in the working state of the micro-nano acoustic transducer, only alternating voltage is loaded to the first electrode and the second electrode.

[0014] In at least one possible embodiment, the first diaphragm layer comprises one or more of molybdenum, aluminum, gold, copper, nickel, titanium nitride.

[0015] In at least one possible embodiment, the second diaphragm layer comprises one or more of polysilicon, silicon carbide, silicon nitride, aluminum nitride, silicon dioxide, tungsten.

[0016] In at least one possible implementation, the diaphragm layer is disposed between the first electrode and the second electrode.

[0017] In at least one possible implementation, the micro-nano acoustic transducer does not include a direct current power supply for loading direct current.

[0018] Embodiments of the present application also propose an ultrasonic imaging probe comprising the micro-nano acoustic transducer based on structural pre-strain according to any one of the above technical solutions.

[0019] By adopting the above technical solution, by forming the diaphragm layer curvedly recessed to the cavity, without applying a high direct current bias voltage to stimulate the diaphragm layer to deform, the micro-nano acoustic transducer has a simple structure, and the portability and safety are improved. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A structural schematic diagram of a possible capacitive micro-mechanical ultrasonic transducer system is shown.

[0021] Figure 2 A structural schematic diagram of an endoscope probe according to an embodiment of the present application is shown.

[0022] Figure 3 A structural schematic diagram of a micro-nano acoustic transducer according to an embodiment of the present application is shown.

[0023] Figures 4 to 6 A forming process of a diaphragm layer of a micro-nano acoustic transducer according to an embodiment of the present application is shown.

[0024] BRIEF DESCRIPTION OF DRAWINGS

[0025] 100 micro-nano acoustic transducer based on structural pre-strain

[0026] 200 guide tube

[0027] B intestinal tract

[0028] C tissue to be imaged

[0029] 1 substrate layer

[0030] 2 first electrode

[0031] 3 cavity

[0032] 4 support layer

[0033] 5 diaphragm layer 51 first diaphragm layer 52 second diaphragm layer

[0034] 6 second electrode

[0035] 7 electrode lead

[0036] 8 High-voltage DC power supply DETAILED DESCRIPTION

[0037] In order to more clearly illustrate the above-mentioned purposes, features and advantages of the present application, the specific embodiments of the present application are described in detail in this section in conjunction with the drawings. In addition to the various embodiments described in this section, the present application can be implemented in other different ways, and those skilled in the art can make corresponding improvements, modifications and substitutions without departing from the spirit of the present application, so the present application is not limited to the specific embodiments disclosed in this section. The scope of protection of the present application should be subject to the claims.

[0038] As shown in Figures 2 to 6 The embodiments of the present application propose an ultrasonic imaging probe, which can be an endoscope probe as an example. The endoscope probe can include a micro-nano acoustic transducer 100 based on structural pre-strain (hereinafter referred to as micro-nano acoustic transducer 100), a guide tube 200 and a signal transmission line. The guide tube can be a flexible hose, the micro-nano acoustic transducer 100 can be arranged at the front end of the guide tube 200, and the signal transmission line can be arranged inside the guide tube 200. One end of the signal transmission line can be electrically connected to the micro-nano acoustic transducer 100, and the other end of the signal transmission line can be electrically connected to a processing module of an external system. The endoscope probe can emit and receive ultrasonic signals towards the tissue C to be imaged, thereby achieving high-sensitivity imaging of the internal tissue of the body cavity (for example, the internal tissue of the intestinal tract B).

[0039] It can be understood that due to the superposition characteristics of wave propagation, the micro-nano acoustic transducer 100 itself can simultaneously emit and measure ultrasonic waves. However, from the actual engineering application, the micro-nano acoustic transducer 100 generally does not simultaneously emit and measure ultrasonic waves. Usually, ultrasonic waves are first emitted, and then the emission is stopped for a period of time to receive ultrasonic echoes. After a “transmit-receive” cycle is completed, the next “transmit-receive” cycle is performed.

[0040] The endoscope probe can include one or more micro-nano acoustic transducers 100, and multiple micro-nano acoustic transducers 100 can form an array, such as a linear array, a planar array, a curved array, etc. The array shape can be circular layout, rectangular layout, irregular shape layout, etc. The specific array shape can be arranged according to actual needs.

[0041] It can be understood that the micro-nano acoustic transducer 100 based on structural pre-strain of the embodiments of the present application is not limited to be applied to the endoscope probe, for example, it can also be applied to an extracorporeal ultrasonic imaging probe, a portable ultrasonic imaging device, etc.

[0042] As shown in Figures 3 to 6As shown, the micro-nano acoustic transducer 100 based on structural pre-strain can include a substrate layer 1, a first electrode 2, a cavity 3, a support layer 4, a diaphragm layer 5, a second electrode 6 and an electrode lead 7.

[0043] The substrate layer 1 can provide support for the micro-nano acoustic transducer 100, and make the micro-nano acoustic transducer 100 connect to other components (for example, the substrate layer 1 connects to the guide tube 200). The first electrode 2 can be attached to the substrate layer 1, and the second electrode 6 can be attached to the diaphragm layer 5. The first electrode 2 and the diaphragm layer 5 can be spaced apart, so as to form the cavity 3 between the first electrode 2 and the diaphragm layer 5, and the cavity 3 can provide a space for the diaphragm layer 5 to vibrate. For example, the first electrode 2 and the diaphragm layer 5 can be spaced apart by arranging the support layer 4 between the first electrode 2 and the diaphragm layer 5. In possible embodiments, the support layer 4 can include columnar or grid-shaped support portions.

[0044] In the present embodiment, the diaphragm layer 5 can be arranged between the first electrode 2 and the second electrode 6.

[0045] A part of the diaphragm layer 5 and the second electrode 6 (for example, an edge region) can be supported by the support portions, and another part of the diaphragm layer 5 and the second electrode 6 (for example, a middle region) can be recessed towards the cavity 3. The sensitivity of the diaphragm layer 5 to receive sound pressure and the intensity of the diaphragm layer 5 to emit sound pressure (acoustic-electric conversion efficiency) are related to the degree of recess of the diaphragm layer 5. The more the diaphragm layer 5 is recessed, the greater the sensitivity and the intensity are. However, if the degree of recess is too large, the first electrode 2 and the second electrode 6 can be in contact failure. Optionally, the degree of recess of the diaphragm layer 5 can be one third of the height of the cavity 3, that is, the minimum distance between the diaphragm layer 5 and the first electrode 2 is two thirds of the maximum distance between the diaphragm layer 5 and the first electrode 2.

[0046] One end of the electrode lead 7 is connected to the first electrode 2 and the second electrode 6 respectively, and the other end of the electrode lead 7 is connected to an external driving or receiving device. The first electrode 2 and the second electrode 6 together form two electrodes of the micro-nano acoustic transducer 100. A voltage can be applied to the two electrodes through the electrode lead 7 to excite the diaphragm layer 5 to vibrate, so as to emit ultrasonic waves outward. The diaphragm layer 5 can be excited by external sound waves to vibrate, and the second electrode 6 attached to the diaphragm layer 5 also vibrates synchronously, so that the capacitance of the capacitor formed by the first electrode 2 and the second electrode 6 changes periodically. An external capacitance measuring device can be connected to the electrode lead 7 to measure the change of the capacitance, so as to detect the sound pressure value.

[0047] The diaphragm layer 5 can include at least two diaphragm layers with different thermal expansion coefficients. For example, the diaphragm layer 5 can include a first diaphragm layer 51 and a second diaphragm layer 52, and the first diaphragm layer 51 and the second diaphragm layer 52 have different thermal expansion coefficients. The thermal expansion coefficient of the first diaphragm layer 51 is greater than that of the second diaphragm layer 52, for example, the first diaphragm layer 51 can be made of molybdenum, aluminum, gold, copper, nickel, titanium nitride, etc., and the second diaphragm layer 52 can be made of polysilicon, silicon carbide, silicon nitride, aluminum nitride, silicon dioxide, tungsten, etc. The first diaphragm layer 51 is close to the second electrode 6 (located in the upper layer in Figures 4 to 6 ), and the second diaphragm layer 52 is close to the cavity 3 (located in the lower layer in Figures 4 to 6 ).

[0048] It can be understood that the diaphragm layer 5 can include more diaphragm layers with different thermal expansion coefficients, such as three layers, four layers, etc.

[0049] Referring to Figures 3 to 5 , the forming process of the diaphragm layer 5 is introduced. Figures 3 to 5 The diaphragm layer 5 is shown in stages from a flat shape after deposition is completed, to stress gradually accumulated in cooling, and finally to a stable shape, which helps to intuitively understand the forming process of the diaphragm layer 5.

[0050] In the manufacturing process of the diaphragm layer 5, the first diaphragm layer 51 and the second diaphragm layer 52 are sequentially deposited and combined at a high temperature (for example, 500 to 700 degrees Celsius, preferably 600 degrees Celsius) to form a composite film structure. The second diaphragm layer 52 is deposited first and is located in the lower layer, and the first diaphragm layer 51 is deposited later and is located in the upper layer. Here, the deposition can be dry deposition (such as chemical vapor deposition, physical vapor deposition, electron beam evaporation, etc.). The deposited composite film structure is connected to the support layer 4, and during the cooling process to room temperature (for example, 25 degrees Celsius), residual stress is generated due to the difference in thermal expansion coefficients of the first diaphragm layer 51 and the second diaphragm layer 52, thereby causing the diaphragm layer 5 to bend and deform downward. After cooling is completed, the diaphragm layer 5 can form a stable structure in a pre-strained state.

[0051] In this way, by pre-introducing internal stress in the diaphragm layer 5, the diaphragm layer 5 is bent and recessed by itself. In the state that no (direct current) voltage is applied to the first electrode 2 and the second electrode 6, part of the diaphragm layer 5 bends and recesses towards the cavity 3. Before the diaphragm is used, no additional direct current voltage needs to be applied to make the diaphragm recessed. The diaphragm layer 5 will remain in a recessed state whether the micro-nano acoustic transducer 100 is working or not.

[0052] It can be understood that the diaphragm layer 5 can be brought to the concave state by other means, for example, during the process of processing the diaphragm layer 5, the diaphragm layer 5 is subjected to pressure to induce the diaphragm layer 5 to be concave downward, and after cooling, the diaphragm layer 5 can remain in a concave state. The diaphragm layer 5 formed in this way can be single-layered or multi-layered.

[0053] The micro-nano acoustic transducer 100 of the present application can not include a direct current power supply for loading direct current, and the diaphragm layer 5 can be concave to the cavity 3 without applying a direct current voltage, thereby having better sensitivity for receiving sound pressure and intensity for emitting sound pressure (acoustic-electric conversion efficiency). During the process of ultrasonic waves emitted and received by the diaphragm layer 5, only a small amplitude alternating voltage is involved, and no large amplitude direct current voltage is involved, thereby making the micro-nano acoustic transducer 100 portable and suitable for application in wearable acoustic devices; safety is improved, and is suitable for application in medical instruments.

[0054] It can be understood that the micro-nano acoustic transducer 100 of the present application does not need to apply a direct current bias voltage, thereby avoiding the serious influence of the direct current voltage on the dielectric properties of the electrode layer (the first electrode 2 and the second electrode 6) and the diaphragm layer 5. The non-linear behavior of emitting and receiving sound waves is improved, the input-output response is faithful, and the imaging quality and signal accuracy are improved. And significantly improve the biological safety and circuit integration, suitable for, for example, minimally invasive endoscopic imaging scenarios such as the digestive tract (for example, the intestinal tract B), the urinary tract, blood vessels, etc.

[0055] The present application is not limited to the above-mentioned embodiments, and those skilled in the art can make various modifications to the above-mentioned embodiments of the present application under the teaching of the present application without departing from the scope of the present application. In addition, the following is described.

[0056] In the above-mentioned embodiments, the diaphragm layer 5 is arranged between the first electrode 2 and the second electrode 6 (i.e. Figure 3 In the above-mentioned embodiments, the diaphragm layer 5 is arranged between the first electrode 2 and the second electrode 6 (i.e.

[0057] It should be understood that at least part of the aspects or features of the above-mentioned embodiments, examples or examples can be appropriately combined.

[0058] It can be understood that, in the present application, the number of components or members is one or more when the number of components or members is not particularly limited, and the plurality herein refers to two or more. For the case where the number of components or members is specifically described as, for example, two, three, four, etc. in the drawings and / or the description, the specific number is generally exemplary and not restrictive, and it can be understood as a plurality, i.e., two or more, but this does not mean that the present application excludes the case of one.

[0059] In the present application, unless otherwise explicitly stated or limited, the terms "mounting", "assembly", "assembly", "connection", "connection", "coupling", "connection", "abutment", "communication", "communication", "conduction", "fixing", "fastening", etc. should be understood broadly, for example, it can be direct or indirect. For example, in terms of connection, it can be a fixed connection, or a detachable connection, or integrated; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication or interaction relationship between two elements, unless otherwise explicitly stated or limited. For example, in terms of communication / conduction, etc., it can be direct communication / conduction, or indirect communication / conduction via an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0060] In the present application, unless otherwise explicitly stated or limited, one member is disposed in / installed in / located in / contained in / placed in another member, etc. can be any of the following two cases: a part or most of the one member is located in the other member; and the one member is completely contained in the other member.

[0061] Although the present application has been described in detail using the above embodiments, it is clear to those skilled in the art that the present application is not limited to the embodiments described in the present specification. The present application can be modified and implemented as a modified embodiment without departing from the spirit and scope of the present application defined by the claims. Therefore, the description in the present specification is for the purpose of illustration, and has no any limiting meaning on the present application.

Claims

1. A micro- or nano-acoustic transducer based on structural pre-strain, characterized in that, Comprise: a first electrode (2); a second electrode (6); and a diaphragm layer (5), the second electrode (6) being attached to the diaphragm layer (5), the first electrode (2) and the diaphragm layer (5) being spaced apart to form a cavity (3) between the first electrode (2) and the diaphragm layer (5), in a state where no voltage is applied to the first electrode (2) and the second electrode (6), both a partial region of the diaphragm layer (5) and a partial region of the second electrode (6) are concave to the cavity (3), the diaphragm layer (5) comprises at least two diaphragm layers with different coefficients of thermal expansion, the diaphragm layer (5) is kept in a state of being concave to the cavity (3) by internal stress generated by temperature change of the diaphragm layers with different coefficients of thermal expansion, the micro-nano acoustic transducer further comprises a support layer (4), the support layer (4) is arranged between the first electrode (2) and the diaphragm layer (5), the support layer (4) comprises a support part, an edge region of the diaphragm layer (5) and the second electrode (6) is supported by the support part, and a middle region of the diaphragm layer (5) and the second electrode (6) is concave to the cavity (3). The diaphragm layer (5) comprises a first diaphragm layer (51) and a second diaphragm layer (52), the first diaphragm layer (51) is relatively far away from the second electrode (6), the second diaphragm layer (52) is relatively close to the second electrode (6), and the coefficient of thermal expansion of the first diaphragm layer (51) is greater than the coefficient of thermal expansion of the second diaphragm layer (52).

2. The micro / nano-acoustic transducer based on structural pre-strain according to claim 1, characterized in that, In the working state of the micro-nano acoustic transducer (100), only an alternating voltage is loaded on the first electrode (2) and the second electrode (6).

3. The micro / nano-acoustic transducer based on structural pre-strain according to claim 1, characterized in that, The first diaphragm layer (51) comprises one or more of molybdenum, aluminum, gold, copper, nickel, and titanium nitride.

4. The micro / nano-acoustic transducer based on structural pre-strain according to claim 2, characterized in that, The second diaphragm layer (52) comprises one or more of polysilicon, silicon carbide, silicon nitride, aluminum nitride, silicon dioxide, and tungsten.

5. The micro / nano-acoustic transducer based on structural pre-strain according to claim 2, characterized in that, The diaphragm layer (5) is arranged between the first electrode (2) and the second electrode (6).

6. The micro / nano-acoustic transducer based on structural pre-strain according to claim 1, characterized in that, The micro-nano acoustic transducer (100) does not comprise a direct current power supply for loading a direct current.

7. The micro / nano-acoustic transducer based on structural pre-strain according to claim 1, characterized in that, The micro-nano acoustic transducer based on structural pre-strain according to any one of claims 1 to 7.

8. An ultrasound imaging probe, characterized by, ​

Images