A MEMS ultrasonic transmitter for ultrasonically modulated optical blood glucose detection

Abstract

The present invention relates to the technical field of micro-electromechanical systems, and specifically to a MEMS ultrasonic emitting device for ultrasonically modulated optical blood glucose detection, comprising a distribution layer, on which a connecting line mechanism and a plurality of transducer mechanisms are provided. The present application can electronically synthesize the emitted ultrasonic beam through a MEMS ultrasonic transducer phased array, focus it on the infrared beam path, and improve the transmittance of near-infrared light in human tissue and reduce the scattering of the light beam in human tissue by ultrasonic modulating optical imaging, thereby improving the resolution and accuracy of the measurement results; and through the structural design and arrangement design of the pMUT unit of the MEMS ultrasonic array device, when a driving signal with a preset phase difference is input, ultrasonic focusing in the shallow skin at different depths can be achieved, and the detection optical path of the near-infrared light can be ultrasonically modulated, while achieving small size, low cost, high performance and high reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-electromechanical systems, and in particular to a MEMS ultrasonic transmitting device for ultrasonically modulated optical blood sugar detection. Background Art

[0002] Ultrasound-modulated Optical Tomography (UOT), also known as Acousto-Optic Imaging (AOI), is a method for improving the spatial resolution of optical imaging in order to penetrate turbid media such as biological tissue. In UOT, focused ultrasound modulates the propagation of transmitted light by periodically exciting the vibration of the medium in the transmission light path and changing the local refractive index. Through UOT, the problems of insufficient measurement depth, poor signal-to-noise ratio and resolution of pure optical methods can be overcome, and a detection distance of several centimeters or even more than ten centimeters can be achieved.

[0003] Currently, blood glucose detection devices that use near-infrared light have limited detection distance and poor measurement accuracy. However, the acousto-optic modulation system in a laboratory environment can achieve higher accuracy. However, the transmitting array composed of traditional ultrasonic probes is large in size and difficult to be applied in current wearable devices, so it needs to be improved. Summary of the Invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a MEMS ultrasonic transmitting device for ultrasonically modulated optical blood glucose detection.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A MEMS ultrasonic transmitting device for ultrasonically modulated optical blood glucose detection includes a distribution layer, wherein a connecting wire structure is provided on the distribution layer. The connecting wire structure includes, from the inside out, an eighth metal layer wiring, a seventh metal layer wiring, a sixth metal layer wiring, a fifth metal layer wiring, a fourth metal layer wiring, a third metal layer wiring, a second metal layer wiring, a first metal layer wiring, and a ninth metal layer wiring, wherein the ninth metal layer wiring and the first metal layer wiring form a group. A plurality of transducer mechanisms are provided on the eighth metal layer wiring, the seventh metal layer wiring, the sixth metal layer wiring, the fifth metal layer wiring, the fourth metal layer wiring, the third metal layer wiring, the second metal layer wiring, the first metal layer wiring, and the ninth metal layer wiring.

[0007] One of the transducer mechanisms is disposed at one end of an eighth metal layer wiring and is located in the middle of a seventh metal layer wiring, a sixth metal layer wiring, a fifth metal layer wiring, a fourth metal layer wiring, a third metal layer wiring, a second metal layer wiring, and a first metal layer wiring, wherein the other transducer mechanisms on the seventh metal layer wiring, the sixth metal layer wiring, the fifth metal layer wiring, the fourth metal layer wiring, the third metal layer wiring, the second metal layer wiring, the first metal layer wiring, and the ninth metal layer wiring are all arranged in a hexagonal shape;

[0008] The distances between two adjacent transducer mechanisms are the same.

[0009] Compared with the existing technology, the present application can perform electronic beam synthesis on the emitted ultrasonic beam through the MEMS ultrasonic transducer phased array, focus on the infrared beam path, and improve the transmittance of near-infrared light in human tissue and reduce the scattering of the light beam in human tissue through ultrasonic modulation optical imaging, which can improve the resolution and accuracy of the measurement results; and through the structural design and layout design of the pMUT unit of the MEMS ultrasonic array device, when a driving signal with a preset phase difference is input, ultrasonic focusing in the shallow skin at different depths can be achieved, and the detection optical path of the near-infrared light can be ultrasonically modulated, while achieving small size, low cost, high performance and high reliability.

[0010] Preferably, one end of the seventh metal layer wiring, the sixth metal layer wiring, the fifth metal layer wiring, the fourth metal layer wiring, the third metal layer wiring and the second metal layer wiring are all connected to a first connecting piece, the ninth metal layer wiring is connected to a second connecting piece, the first connecting piece and the second connecting piece are both arranged on the distribution layer, and the second connecting piece and multiple first connecting pieces are commonly connected to a PAD component.

[0011] Furthermore, multiple pMUT transducers are divided into eight groups from the inside to the outside; each circle of hexagons constitutes a group. To facilitate wiring of the upper electrode metal layer, the connection PAD below the eighth path is split into two parts, which can be combined into one through an external circuit board. The hexagonal structure is adopted to ensure that the distance between each pMUT unit in the array is equal, so that the phase difference between the input multi-path drive signals can be kept consistent during beamforming, which facilitates the control and realization of deviation-free ultrasonic beamforming.

[0012] Preferably, the transducer mechanism includes a Si substrate elastic layer, a diaphragm is provided in the Si substrate elastic layer, the upper end of the diaphragm is provided with a lower electrode layer, a piezoelectric film layer and an upper electrode layer from bottom to top, and a connecting component is connected to the Si substrate elastic layer, and the connecting component is connected to the connecting line mechanism on the distribution layer.

[0013] Furthermore, the pMUT transducer usually includes a Si substrate elastic layer, a lower electrode layer, a piezoelectric film layer, and an upper electrode layer, which together constitute the diaphragm of the device. The diaphragm is connected to the Si substrate on all sides to constrain the diaphragm, and the bottom is a cavity structure. The working principle of the pMUT device is related to the piezoelectric effect of the piezoelectric film layer. When the piezoelectric effect is positive, that is, the diaphragm receives sound waves, the ultrasonic wave causes the diaphragm to vibrate, and continuously produces up and down reciprocating deformation, periodically stretching / compressing the piezoelectric layer, causing the piezoelectric layer to generate an electric charge, and connected to the outside through the upper and lower electrodes, and the external circuit can receive the changing charge signal; when the piezoelectric effect is reversed, the external circuit passes a high-frequency alternating voltage (such as a sine wave) into the upper and lower electrodes, and the upper and lower electrodes generate an alternating electric field in the piezoelectric layer. The electric field causes the piezoelectric layer to produce stretching / compression deformation, thereby causing the piezoelectric layer to drive the diaphragm to vibrate and generate sound waves.

[0014] The present invention also proposes a preparation process for a MEMS ultrasonic transmitter for ultrasonically modulated optical blood glucose detection, comprising:

[0015] S1, preparing SOI substrate;

[0016] S2, magnetron RF sputtering growth of Pt bottom electrode;

[0017] S3, magnetron RF sputtering growth of PZT piezoelectric thin films;

[0018] S4, photolithography, development, and patterning etching of PZT using ICP or wet etching;

[0019] S5. Grow a SiO2 insulating layer by ALD, perform photolithography development, and pattern the insulating layer by ICP etching to cover the subsequent top electrode metal layer wiring portion to reduce the parasitic capacitance of the device and improve the performance of the device;

[0020] S6, Au top electrode layer is magnetron RF sputtered and patterned by IBE or lift-off;

[0021] S7, thinning the back side of the SOI substrate to improve the accuracy of the subsequent etching process, thereby improving the process consistency of the device;

[0022] S8, Deep-RIE deep silicon etching, removes the back substrate silicon, ICP etching, removes the middle silicon dioxide layer, and releases the device diaphragm.

[0023] Preferably, the specifications of the SOI substrate are 725um-1um-7um; the thickness of the Pt bottom electrode is 200nm; the thickness of the PZT piezoelectric film is 2um; and the thickness of the Au top electrode layer is 200um.

[0024] Furthermore, during actual production and preparation, the dimensional data in the process is only used as an example and is not limited to the dimensions in this process. The dimensions are set according to actual needs to ensure that the transducer mechanism is distributed in a hexagon and the distance between two adjacent transducer mechanisms is the same, and to ensure that the transducers located in the same hexagon can be connected. At the same time, the outermost circle connection line is divided into two parts to ensure that other lines can be arranged stably.

[0025] The beneficial effects of the present invention are:

[0026] 1. Compared with traditional ceramic ultrasonic transducer probes, it can ensure small device size, large quality factor (Q-factor), high energy conversion efficiency when working at the resonant frequency, and high emission sensitivity, and can be actually applied to portable and wearable infrared blood glucose detection equipment;

[0027] 2. Compared with the current pMUT device that does not perform piezoelectric film etching, the pMUT device etches the PZT piezoelectric film, releasing stress, reducing the equivalent stiffness of the film, and increasing the transmit and receive sensitivity;

[0028] 3. An additional insulating layer is used on the PZT film. Although PZT itself is a dielectric material that can achieve insulation of the upper electrode metal layer routing, the relative dielectric constant of PZT material is relatively large, which will cause a large parasitic capacitance, affecting the electromechanical conversion efficiency of the device in actual use. By introducing the insulating layer, the upper electrode metal layer is only in direct contact with the PZT at the center of the pMUT unit, so that the total capacitance of the device is basically the capacitance of the pMUT device, effectively improving the performance of the device;

[0029] 4. The hexagonal arrangement ensures that the spacing between each pMUT unit is exactly the same, which can achieve the simplification of the driving signal. Due to the symmetry of the hexagon, it can achieve the best beamforming and focusing effect. The focusing position can be adjusted by changing the phase difference of the driving signal. It is an electronic beamforming method, which is convenient for adjustment in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a structural diagram of a transducer in a MEMS ultrasonic transmitting device for ultrasonically modulated optical blood glucose detection proposed by the present invention;

[0031] Figure 2 This is a structural diagram of a MEMS ultrasonic transmitting device for ultrasonically modulated optical blood glucose detection proposed by the present invention;

[0032] Figure 3 This is an example diagram of two-way hexagonal array drive signal input and beamforming in a MEMS ultrasonic transmitter device for ultrasonically modulated optical blood glucose detection proposed by the present invention;

[0033] Figure 4 This is a SOI structure diagram of a MEMS ultrasonic transmitter device for ultrasonically modulated optical blood glucose detection proposed by the present invention;

[0034] Figure 5 This is a bottom electrode structure diagram of a MEMS ultrasonic transmitter device for ultrasonically modulated optical blood glucose detection proposed by the present invention;

[0035] Figure 6 This is a diagram of the piezoelectric film growth structure in a MEMS ultrasonic transmitter device for ultrasonically modulated optical blood glucose detection proposed by the present invention;

[0036] Figure 7 This is a diagram of the etching structure of the piezoelectric thin film layer in a MEMS ultrasonic transmitting device for ultrasonically modulated optical blood glucose detection proposed by the present invention;

[0037] Figure 8 This is a diagram of the deposition and patterning of the SiO2 insulating layer in a MEMS ultrasonic transmitter device for ultrasonically modulated optical blood glucose detection proposed by the present invention;

[0038] Figure 9 This is a diagram of the deposition and patterning of the top electrode metal layer in a MEMS ultrasonic transmitter device for ultrasonically modulated optical blood glucose detection proposed by the present invention;

[0039] Figure 10 This is a diagram of the back handle layer Si thinning structure in a MEMS ultrasonic transmitting device for ultrasonically modulated optical blood glucose detection proposed by the present invention;

[0040] Figure 11 This is the etching pattern of the back handle layer Si and Box layer SiO2 in a MEMS ultrasonic transmitting device for ultrasonic modulated optical blood glucose detection proposed by the present invention;

[0041] In the figure: 1Si substrate elastic layer, 2diaphragm, 3lower electrode layer, 4upper electrode layer, 5piezoelectric film layer, 6connecting component, 7first connecting piece, 8first metal layer wiring, 9second metal layer wiring, 10third metal layer wiring, 11fourth metal layer wiring, 12fth metal layer wiring, 13sixth metal layer wiring, 14seventh metal layer wiring, 15eighth metal layer wiring, 16ninth metal layer wiring, 17second connecting piece, 18distribution layer, 19PAD component. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0043] Reference Figure 1-11 A MEMS ultrasonic transmitting device for ultrasonically modulated optical blood glucose detection includes a distribution layer 18, on which a connecting wire mechanism is provided. The connecting wire structure includes, from the inside to the outside, an eighth metal layer wiring 15, a seventh metal layer wiring 14, a sixth metal layer wiring 13, a fifth metal layer wiring 12, a fourth metal layer wiring 11, a third metal layer wiring 10, a second metal layer wiring 9, a first metal layer wiring 8, and a ninth metal layer wiring 16, which are sequentially arranged on the distribution layer 18 from the inside out. The ninth metal layer wiring 16 and the first metal layer wiring 8 form a group. The eighth metal layer wiring 15, the seventh metal layer wiring 14, the sixth metal layer wiring 13, the fifth metal layer wiring 12, the fourth metal layer wiring 11, the third metal layer wiring 10, the second metal layer wiring 9, the first metal layer wiring 8, and the ninth metal layer wiring 16. , the fifth metal layer wiring 12, the fourth metal layer wiring 11, the third metal layer wiring 10, the second metal layer wiring 9, the first metal layer wiring 8 and the ninth metal layer wiring 16 are commonly provided with a plurality of transducer mechanisms; in actual production preparation, each single-point pMUT transducer mechanism is divided into eight groups from the inside to the outside; that is, each circle of hexagons is a group, and in order to facilitate the wiring of the upper electrode metal layer, the connection PAD below the eighth path is split into two parts; that is, the first metal layer wiring 8 and the ninth metal layer wiring 16, which can be combined into one through an external circuit board; and a hexagonal structure is adopted to make the distance between each pMUT unit in the array equal.

[0044] Reference Figure 1-3 One of the transducer mechanisms is arranged at one end of the eighth metal layer wiring 15 and is located in the middle of the seventh metal layer wiring 14, the sixth metal layer wiring 13, the fifth metal layer wiring 12, the fourth metal layer wiring 11, the third metal layer wiring 10, the second metal layer wiring 9 and the first metal layer wiring 8. The other transducer mechanisms on the seventh metal layer wiring 14, the sixth metal layer wiring 13, the fifth metal layer wiring 12, the fourth metal layer wiring 11, the third metal layer wiring 10, the second metal layer wiring 9 and the first metal layer wiring 8 and the ninth metal layer wiring 16 are all arranged in a hexagonal shape; the spacing between two adjacent transducer mechanisms is the same. Due to the use of the hexagonal structure, the distance between each pMUT unit in the array is equal, so that the phase difference between the input multi-channel driving signals can be kept consistent during beamforming, which is convenient for controlling and realizing deviation-free ultrasonic beamforming.

[0045] Reference Figure 1-3 , one end of the seventh metal layer wiring 14, the sixth metal layer wiring 13, the fifth metal layer wiring 12, the fourth metal layer wiring 11, the third metal layer wiring 10 and the second metal layer wiring 9 are all connected to the first connecting piece 7, the ninth metal layer wiring 16 is connected to the second connecting piece 17, the first connecting piece 7 and the second connecting piece 17 are both arranged on the distribution layer 18, and the second connecting piece 17 and the multiple first connecting pieces 7 are commonly connected to the PAD component 19; for a simpler explanation, please refer to the attached Figure 2, so that the corresponding connecting components can operate. In actual application, the six-layer transducer mechanism and the connection between the corresponding lines are summarized through the situation of two pMUT arrays. The PAD on the external circuit connection device is used to input a driving signal with a preset phase difference to each pMUT array, so that each pMUT unit emits an ultrasonic wave with a phase difference, so that a focused ultrasonic wave can be obtained at a preset position. The intensity of the ultrasonic wave is maximum and the beam width is minimum, so that the optical path can be accurately modulated; by changing the phase difference, ultrasonic focusing at different depths along the central axis of the device center point can be achieved, and the focusing position can be adjusted at any time according to actual conditions during use.

[0046] Reference Figure 1 The transducer structure includes a Si substrate elastic layer 1, a diaphragm 2 is provided in the Si substrate elastic layer 1, and the upper end of the diaphragm 2 is provided with a lower electrode layer 3, a piezoelectric film layer 5 and an upper electrode layer 4 in order from bottom to top. The Si substrate elastic layer 1 is connected with a connecting component 6, and the connecting component 6 is connected to the connecting line mechanism on the distribution layer 18; the transducer usually includes a Si substrate elastic layer, a lower electrode layer, a piezoelectric film layer, and an upper electrode layer, which together constitute the diaphragm of the device. The diaphragm is connected to the Si substrate on all sides to constrain the diaphragm, and the bottom is a cavity structure; the working principle of the pMUT device is similar to that of the pressure The piezoelectric effect of the piezoelectric film layer is related to the piezoelectric effect of the piezoelectric film layer. When the piezoelectric effect is positive, that is, the diaphragm receives sound waves, the ultrasonic wave causes the diaphragm to vibrate, and continuously produces up and down reciprocating deformation, periodically stretching / compressing the piezoelectric layer, causing the piezoelectric layer to generate electric charge, and connected to the outside through the upper and lower electrodes, and the external circuit can receive the changing charge signal; when the piezoelectric effect is reversed, the external circuit passes a high-frequency alternating voltage (such as a sine wave) through the upper and lower electrodes, and the upper and lower electrodes generate an alternating electric field in the piezoelectric layer. The electric field causes the piezoelectric layer to produce stretching / compression deformation, thereby causing the piezoelectric layer to drive the diaphragm to vibrate and generate sound waves.

[0047] Reference Figure 1-11 The present invention also proposes a preparation process of a MEMS ultrasonic emitting device for ultrasonically modulated optical blood glucose detection, comprising:

[0048] S1, preparing SOI substrate;

[0049] S2, magnetron RF sputtering growth of Pt bottom electrode;

[0050] S3, magnetron RF sputtering growth of PZT piezoelectric thin films;

[0051] S4, photolithography, development, and patterning etching of PZT using ICP or wet etching;

[0052] S5. Grow a SiO2 insulating layer by ALD, perform photolithography development, and pattern the insulating layer by ICP etching to cover the subsequent top electrode metal layer wiring portion to reduce the parasitic capacitance of the device and improve the performance of the device;

[0053] S6, Au top electrode layer is magnetron RF sputtered and patterned by IBE or lift-off;

[0054] S7, thinning the back side of the SOI substrate to improve the accuracy of the subsequent etching process, thereby improving the process consistency of the device;

[0055] S8, Deep-RIE deep silicon etching, removes the back substrate silicon, ICP etching, removes the middle silicon dioxide layer, and releases the device diaphragm.

[0056] In the present invention, when preparing this product, an SOI substrate is first prepared with a thickness of 725um-1um-7um; then a Pt bottom electrode is grown by magnetron RF sputtering with a thickness of 200nm; a PZT piezoelectric film is grown by magnetron RF sputtering with a thickness of 2um; the PZT is patterned and etched by photolithography, development, and ICP or wet etching; a SiO2 insulating layer is grown by ALD, photolithography developed, and patterned by ICP etching to cover the subsequent top electrode metal layer routing portion to reduce the parasitic capacitance of the device and improve the performance of the device; the Au top electrode layer is magnetron RF sputtering with a thickness of 200um, and patterned by IBE or Lift-off; the back side of the SOI substrate is thinned to improve the accuracy of the subsequent etching process, thereby improving the process consistency of the device; Deep-RIE deep silicon etching is performed to remove the back substrate silicon, and ICP etching is performed to remove the intermediate silicon dioxide layer to release the device diaphragm.

[0057] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A MEMS ultrasonic emitting device for ultrasonically modulated optical blood glucose detection, comprising a distribution layer (18), characterized in that: The distribution layer (18) is provided with a connection line mechanism, and the connection line structure includes an eighth metal layer wiring (15), a seventh metal layer wiring (14), a sixth metal layer wiring (13), a fifth metal layer wiring (12), a fourth metal layer wiring (11), a third metal layer wiring (10), a second metal layer wiring (9), a first metal layer wiring (8), and a ninth metal layer wiring (16) which are sequentially arranged on the distribution layer (18) from the inside to the outside, wherein the ninth metal layer wiring (16) and the first metal layer wiring (8) form a group, and a plurality of transducer mechanisms are commonly provided on the eighth metal layer wiring (15), the seventh metal layer wiring (14), the sixth metal layer wiring (13), the fifth metal layer wiring (12), the fourth metal layer wiring (11), the third metal layer wiring (10), the second metal layer wiring (9), the first metal layer wiring (8), and the ninth metal layer wiring (16); One of the transducer mechanisms is arranged at one end of the eighth metal layer wiring (15) and is located in the middle of the seventh metal layer wiring (14), the sixth metal layer wiring (13), the fifth metal layer wiring (12), the fourth metal layer wiring (11), the third metal layer wiring (10), the second metal layer wiring (9) and the first metal layer wiring (8); and the other transducer mechanisms on the seventh metal layer wiring (14), the sixth metal layer wiring (13), the fifth metal layer wiring (12), the fourth metal layer wiring (11), the third metal layer wiring (10), the second metal layer wiring (9), the first metal layer wiring (8) and the ninth metal layer wiring (16) are all arranged in a hexagonal shape; The distances between two adjacent transducer mechanisms are the same.

2. The MEMS ultrasonic transmitter for ultrasonically modulated optical blood glucose detection according to claim 1, characterized in that: One end of the seventh metal layer wiring (14), the sixth metal layer wiring (13), the fifth metal layer wiring (12), the fourth metal layer wiring (11), the third metal layer wiring (10) and the second metal layer wiring (9) are all connected to a first connecting piece (7); the ninth metal layer wiring (16) is connected to a second connecting piece (17); the first connecting piece (7) and the second connecting piece (17) are both arranged on a distribution layer (18); the second connecting piece (17) and a plurality of first connecting pieces (7) are commonly connected to a PAD component (19).

3. The MEMS ultrasonic transmitter for ultrasonically modulated optical blood glucose detection according to claim 1, characterized in that: The transducer mechanism comprises a Si substrate elastic layer (1), a diaphragm (2) is provided in the Si substrate elastic layer (1), a lower electrode layer (3), a piezoelectric film layer (5) and an upper electrode layer (4) are sequentially provided on the upper end of the diaphragm (2) from bottom to top, a connecting component (6) is connected to the Si substrate elastic layer (1), and the connecting component (6) is connected to a connecting line mechanism on a distribution layer (18).

4. The MEMS ultrasonic transmitter for ultrasonically modulated optical blood glucose detection according to claim 1, characterized in that: The preparation method comprises the following steps: S1, preparing SOI substrate; S2, magnetron RF sputtering growth of Pt bottom electrode; S3, magnetron RF sputtering growth of PZT piezoelectric thin films; S4, photolithography, development, and patterning etching of PZT using ICP or wet etching; S5. Grow a SiO2 insulating layer by ALD, perform photolithography development, and pattern the insulating layer by ICP etching to cover the subsequent top electrode metal layer wiring portion to reduce the parasitic capacitance of the device and improve the performance of the device; S6, Au top electrode layer is magnetron RF sputtered and patterned by IBE or lift-off; S7, thinning the back side of the SOI substrate to improve the accuracy of the subsequent etching process, thereby improving the process consistency of the device; S8, Deep-RIE deep silicon etching, removes the back substrate silicon, ICP etching, removes the middle silicon dioxide layer, and releases the device diaphragm.

5. The MEMS ultrasonic transmitting device for ultrasonically modulated optical blood glucose detection according to claim 4, characterized in that: The specifications of the SOI substrate are 725um-1um-7um; the thickness of the Pt bottom electrode is 200nm; the thickness of the PZT piezoelectric film is 2um; and the thickness of the Au top electrode layer is 200um.

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