MEMS ultrasonic transmitting device for ultrasonic modulation optical blood glucose detection

Abstract

The invention relates to the technical field of micro electro mechanical systems, in particular to a micro electro mechanical system (MEMS) ultrasonic transmitting device for ultrasonic modulation optical blood glucose detection, which comprises a distribution layer, and a connecting line mechanism and a plurality of transducer mechanisms are arranged on the distribution layer. Through the MEMS ultrasonic transducer phase control array, the emitted ultrasonic beam can be subjected to electronic beam forming and is focused at an infrared beam path, through an ultrasonic modulation optical imaging mode, the transmittance of near-infrared light in human tissue is improved, scattering of the light beam in the human tissue is reduced, and the imaging quality of the near-infrared light is improved. The effect of improving the resolution and the accuracy of a measurement result can be achieved; through the MEMS ultrasonic array device and the structural design and arrangement design of the pMUT unit, when a driving signal with a preset phase difference is input, ultrasonic focusing in superficial layer skin of different depths can be achieved, ultrasonic modulation is conducted on a near-infrared light detection light path, and meanwhile the MEMS ultrasonic array device has the advantages of being small in size, low in cost, high in performance and high in 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 to improve the spatial resolution of optical imaging through turbid media such as biological tissues. In UOT, the focused ultrasound modulates the propagation of the 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 avoided, and a detection distance of several centimeters or even more than ten centimeters deep can be achieved.

[0003] Currently, blood glucose detection devices that use the principle of near-infrared light have limited detection distance and poor measurement accuracy. The acousto-optic modulation system in a laboratory environment can achieve higher accuracy, but the transmitting array is composed of traditional ultrasonic probes, which are 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 sugar 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 sugar detection, comprising a distribution layer, on which a connecting line mechanism is arranged, wherein the connecting line structure comprises 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 which are sequentially arranged on the distribution layer from the inside to the outside, wherein the ninth metal layer wiring and the first metal layer wiring form a group, and a plurality of transducer mechanisms are commonly arranged 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 arranged at one end of the eighth metal layer wiring and is located in the middle 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, the second metal layer wiring and the first metal layer wiring, and 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 prior art, 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 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.

[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 is a group. To facilitate the wiring of the upper electrode metal layer, the connection PAD below the eighth path is split into two parts, and the two paths can be combined into one through a peripheral circuit board; and a hexagonal structure is adopted to make the distance between each pMUT unit in the array equal, so that the phase difference between the input multi-path drive signals can be kept consistent in beamforming, which is convenient for controlling and realizing unbiased ultrasonic beamforming.

[0012] Preferably, the transducer mechanism includes a Si substrate elastic layer, a diaphragm is arranged 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 reciprocating deformation up and down, 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) to 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 a 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 step of a MEMS ultrasonic transmitting device for ultrasonically modulated optical blood sugar 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 film;

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

[0019] S5, growing a SiO2 insulating layer by ALD, developing it by photolithography, and patterning the insulating layer by ICP etching to cover the subsequent top electrode metal layer wiring part, so as 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, remove the back substrate silicon, ICP etching, remove the middle silicon dioxide layer, and release the device diaphragm.

[0023] Preferably, the specification of the SOI substrate is 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, in 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 mechanisms are 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 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, 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 etching on the piezoelectric film layer, the pMUT device etches the PZT piezoelectric film to release stress, reduce the equivalent stiffness of the film, and increase the sensitivity of transmission and reception;

[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 the PZT material is large, which will cause a large parasitic capacitance, affecting the electromechanical conversion efficiency of the device in actual use. By introducing an insulating layer, the upper electrode metal layer is directly in contact with the PZT only at the center of the pMUT unit, so that the total capacitance of the device is basically the capacitance of the pMUT device, which effectively improves the performance of the device;

[0029] 4. The hexagonal arrangement makes the spacing between each pMUT unit exactly the same, which can achieve the simplification of the driving signal. Due to the symmetry of the hexagon, the best beamforming focusing effect can be achieved, and 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 sugar 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 sugar detection proposed by the present invention;

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

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

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

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

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

[0037] Figure 8 This is a SiO2 insulating layer deposition and graphical diagram in a MEMS ultrasonic transmitting device for ultrasonic modulated optical blood sugar detection proposed by the present invention;

[0038] Fig. 9 This is a top electrode metal layer deposition and graphic diagram in a MEMS ultrasonic transmitting device for ultrasonic modulated optical blood sugar detection proposed by the present invention;

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

[0040] Fig.11 This is the etching diagram of the back handlelayerSi and BoxlayerSiO2 in a MEMS ultrasonic transmitting device for ultrasonic modulated optical blood sugar detection proposed by the present invention;

[0041] In the figure: 1Si substrate elastic layer, 2diaphragm, 3lower electrode layer, 4upper electrode layer, 5piezoelectric film layer, 6connection 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 described clearly and completely 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 ultrasonic modulated optical blood sugar detection includes a distribution layer 18, on which a connecting line mechanism is arranged, the connecting 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 arranged on the distribution layer 18 from inside to outside in sequence, the ninth metal layer wiring 16 and the first metal layer wiring 8 are a group, the eighth metal layer wiring 15, the seventh metal layer wiring 14, the sixth metal layer wiring 13 A plurality of transducer mechanisms are commonly provided on 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; in actual production and 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, the two paths 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, 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 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 in beamforming, which is convenient for controlling and realizing unbiased ultrasonic beamforming.

[0045] Reference Figure 1-3 , 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 at one end, 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 plurality of 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 device is connected through an external circuit, and a driving signal with a preset phase difference is input 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 center point of the device 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 mechanism includes a Si substrate elastic layer 1, a diaphragm 2 is arranged 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 It 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 step of a MEMS ultrasonic transmitting device for ultrasonically modulated optical blood sugar 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 film;

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

[0052] S5, growing a SiO2 insulating layer by ALD, developing it by photolithography, and patterning the insulating layer by ICP etching to cover the subsequent top electrode metal layer wiring part, so as 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, remove the back substrate silicon, ICP etching, remove the middle silicon dioxide layer, and release the device diaphragm.

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

[0057] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A MEMS ultrasonic transmitting device for ultrasonically modulated optical blood sugar 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, and the ninth metal layer wiring (16) and the first metal layer wiring (8) form a group, and 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) are jointly provided with a plurality of transducer mechanisms; 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) and 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. A MEMS ultrasonic transmitting device for ultrasonically modulated optical blood sugar 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), and 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 transmitting device for ultrasonically modulated optical blood sugar detection according to claim 1, characterized in that: The transducer mechanism comprises a Si substrate elastic layer (1), a diaphragm (2) is arranged in the Si substrate elastic layer (1), a lower electrode layer (3), a piezoelectric film layer (5) and an upper electrode layer (4) are arranged in sequence at 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 transmitting device for ultrasonically modulated optical blood sugar 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 film; S4, photolithography, development, and patterning etching of PZT by ICP or wet etching; S5, growing a SiO2 insulating layer by ALD, developing it by photolithography, and patterning the insulating layer by ICP etching to cover the subsequent top electrode metal layer wiring part, so as 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, remove the back substrate silicon, ICP etching, remove the middle silicon dioxide layer, and release the device diaphragm.

5. The MEMS ultrasonic transmitting device for ultrasonically modulated optical blood sugar 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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