Non-Faraday junction flexible sensor and preparation method thereof

Abstract

The invention discloses a non-Faraday junction flexible sensor and a preparation method thereof. The non-Faraday junction flexible sensor comprises an ultra-thin silicon functional layer, a positive electrode and a negative electrode which are respectively arranged on two sides of the ultra-thin silicon functional layer, and protective layers arranged on the peripheries of two sides of the ultra-thin silicon functional layer, the ultrathin silicon functional layer comprises a silicon substrate and a silicon nanopillar array arranged on one side of the silicon substrate; and the positive electrode and the negative electrode are inert metal electrodes. According to the invention, the protective layers are carried on the edges of the two sides of the ultrathin silicon nanostructure, so that the problems of low yield, limited service life and poor device flexibility caused by the existence of surface cracks of the ultrathin silicon nanostructure are solved, and the possibility is provided for preparing a silicon electronic device with lower thickness and better flexibility; inert metal electrodes are arranged on the two sides of the ultra-thin silicon nanostructure to form a non-Faraday junction, and lower ground noise and higher sensitivity are achieved when respiration signals and bio-electricity signals are measured.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor preparation, and particularly relates to a non-Faraday junction flexible sensor and a preparation method thereof. Background Art

[0002] Due to its abundance, silicon is an indispensable core material in microelectronic devices. With its excellent electrical properties, silicon dominates the semiconductor market, and silicon-based technologies have promoted the progress of industries such as electronics, communication, and renewable energy in particular. With the emergence of flexible electronic products, the current market's demand for materials that combine flexibility and high performance has become more urgent, which poses challenges to the inherent mechanical properties of silicon. As a rigid and brittle material, silicon is prone to fracture or breakage under stress, especially when there are defects or cracks on the surface. During the manufacturing and long-term use processes, this brittleness will be further exacerbated, resulting in a low yield of flexible silicon devices, greatly limiting the potential of silicon as a substrate material for flexible electronic devices.

[0003] The preparation techniques of ultrathin silicon mainly include bottom-up growth methods and top-down etching methods. Among them, due to the problems of high energy consumption and low efficiency, the bottom-up growth method is mainly applied to silicon substrates with a thickness less than 1 micron. When manufacturing ultrathin silicon flexible electronic devices, the top-down etching method is mainly used. However, this method will form local cracks on the surface and edges of the silicon wafer, and these stress concentration points are considered to be the main reasons for the fracture of the silicon wafer.

[0004] Therefore, how to achieve stress dispersion in ultrathin silicon nanostructures to reduce the probability of wafer breakage, while combining flexibility and excellent electrical properties to break through its application bottleneck has become an urgent problem to be solved today. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the present invention provides a non-Faraday junction flexible sensor and a preparation method thereof, by mounting protective layers on the edges on both sides of the ultrathin silicon functional layer, to overcome the problems of low yield, limited service life, and poor flexibility of the device caused by the existence of surface cracks in the ultrathin silicon nanostructure.

[0006] To solve the above technical problems, on the one hand, the present invention provides a non-Faraday junction flexible sensor, including an ultrathin silicon functional layer, a positive electrode and a negative electrode respectively disposed on both sides of the ultrathin silicon functional layer, and a protective layer disposed on the peripheries on both sides of the ultrathin silicon functional layer;

[0007] The ultrathin silicon functional layer includes a silicon substrate and a silicon nanowire array disposed on one side of the silicon substrate;

[0008] Both the positive electrode and the negative electrode are inert metal electrodes.

[0009] The present invention mounts protective layers on the edges on both sides of the ultra-thin silicon functionality, for centralized stress dispersion and toughness enhancement of the ultra-thin silicon nanostructure, overcoming the problems of low yield, limited service life, and poor device flexibility caused by the presence of surface cracks in the ultra-thin silicon nanostructure, and providing the possibility for preparing silicon electronic devices with lower thickness and better flexibility.

[0010] The present invention sets inert metal electrodes on both sides of the ultra-thin silicon nanostructure of the ultra-thin silicon functional layer to form a non-Faraday junction. Compared with conventional active electrode devices such as copper electrodes and aluminum electrodes, it has lower background noise and higher sensitivity when measuring respiratory signals and bioelectrical signals.

[0011] Further, the thicknesses of the silicon substrate and the silicon nanowire array are independently 5 - 15 μm.

[0012] Further, in the silicon nanowire array, the diameter of the silicon nanowires is 0.5 - 1.5 μm, and the array period length is 1 - 3 μm.

[0013] Further, the positive electrode and the negative electrode are independently selected from gold electrodes or platinum electrodes;

[0014] And / or, the thicknesses of the positive electrode and the negative electrode are 5 - 15 μm.

[0015] Further, the raw material of the protective layer is silver paste, copper paste or polydimethylsiloxane, which has a high Young's modulus and high flexibility, and realizes high bendability while ensuring edge stress dispersion;

[0016] And / or, the thickness of the protective layer is 10 - 20 μm.

[0017] On the other hand, the present invention provides a preparation method of the non-Faraday junction flexible sensor described in the above aspect, including the following steps:

[0018] S1. Thinning a silicon wafer by wet etching to obtain an ultra-thin silicon wafer;

[0019] S2. Lithographing a silicon nanowire array on the surface of the ultra-thin silicon wafer to obtain an ultra-thin silicon functional layer;

[0020] S3. Providing a mold and etching a frame-shaped groove on the surface of the mold;

[0021] S4. Filling an edge protection material in the frame-shaped groove;

[0022] S5. Covering the ultra-thin silicon functional layer on the mold filled with the edge protection material, performing heat treatment, and demolding the edge protection material and mounting it on the edge on one side of the ultra-thin silicon functional layer to form a protective layer;

[0023] S6. Repeat steps S4 - S5 to load a protective layer on the side of the ultra-thin silicon functional layer without a protective layer.

[0024] It also includes the step of separately loading a positive electrode and a negative electrode on both sides of the ultra-thin silicon functional layer by means of slurry coating or evaporation plating, and this step is set between S2 and S3, or after S6.

[0025] Further, before S1, it also includes the steps of laser marking and cutting, cleaning, and removing the surface oxide layer of the silicon wafer.

[0026] Further, the removal of the surface oxide layer specifically means soaking the silicon wafer in a hydrofluoric acid solution.

[0027] Further, in S1, the wet etching and thinning specifically means etching and thinning the silicon wafer in a mixed solution of NaOH and ethanol.

[0028] Further, in S4, before filling the edge protection material in the frame-shaped groove, a layer of thermal release glue is filled first to facilitate easy demolding during heating and prevent sticky adhesion between the protective layer and the mold.

[0029] Further, in S5, before covering the ultra-thin silicon functional layer on the mold, the ultra-thin silicon functional layer is subjected to plasma cleaning and edge HMDS (hexamethyldisilazane) treatment to ensure a clean surface and increase surface viscosity.

[0030] Further, in S5, when covering the ultra-thin silicon functional layer on the mold, the outer periphery of the ultra-thin silicon functional layer is aligned with the outer periphery of the frame-shaped groove.

[0031] Further, in S5, the temperature of the heat treatment is 110 - 130 °C.

[0032] Advantages of the present invention:

[0033] The present invention loads protective layers on the edges on both sides of the ultra-thin silicon functionality for centralized stress dispersion and toughness enhancement of the ultra-thin silicon nanostructure, overcoming the problems of low yield, limited service life, and poor device flexibility of the ultra-thin silicon nanostructure due to the existence of surface cracks, and providing the possibility for preparing silicon electronic devices with a lower thickness and better flexibility.

[0034] The present invention sets inert metal electrodes on both sides of the ultra-thin silicon nanostructure of the ultra-thin silicon functional layer to form a non-Faraday junction, which has lower background noise and higher sensitivity when measuring respiratory signals and bioelectric signals. Brief Description of the Drawings

[0035] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings required for use in the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0036] Figure 1 It is a schematic structural diagram of the non-Faraday junction flexible sensor based on the ultra-thin silicon nanostructure of the present invention;

[0037] Figure 2 It is the SEM image of the sensor obtained in Example 1 of the present invention;

[0038] Figure 3 It is the SEM image of the silicon - protective layer contact position of the silicon obtained in Example 1 of the present invention after HMDS treatment;

[0039] Figure 4 It is the SEM image of the silicon - protective layer contact position of the silicon obtained in Comparative Example 2 of the present invention without HMDS treatment;

[0040] Figure 5 It is the bending test photo of the sensor obtained in Example 1 of the present invention;

[0041] Figure 6 It is the three - point bending test diagram of the sensors obtained in Example 1 and Comparative Example 1 of the present invention;

[0042] Figure 7 It is the breathing signal test diagram of the device obtained in Example 1 of the present invention;

[0043] Figure 8 It is the weak breathing signal test diagram of the device obtained in Example 1 of the present invention;

[0044] Figure 9 It is the breathing test diagram of the device obtained in Comparative Example 1 of the present invention;

[0045] Figure 10 It is the myoelectric signal response diagram of the device obtained in Example 1 of the present invention;

[0046] Figure 11 It is the myoelectric signal response diagram of the device obtained in Comparative Example 1 of the present invention;

[0047] Explanation of the reference numerals in the figure: 1. Positive electrode, 2. Protective layer, 3. Silicon substrate, 4. Silicon nanorod array. Detailed implementation manners

[0048] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] Reference Figure 1 , an embodiment of the present invention provides a non-Faraday junction flexible sensor based on an ultra-thin silicon nanostructure, including an ultra-thin silicon functional layer, a positive electrode 1 and a negative electrode (not marked in the figure) respectively disposed on both sides of the ultra-thin silicon functional layer, and a protective layer 2 disposed on the peripheries of both sides of the ultra-thin silicon functional layer; the ultra-thin silicon functional layer includes a silicon substrate 3 and a silicon nanowire array 4 disposed on one side of the silicon substrate; both the positive electrode and the negative electrode are inert metal electrodes, wherein the positive electrode can be disposed on one side of the nanowire array or the silicon substrate side, and the negative electrode is disposed on the other side accordingly.

[0050] This embodiment mounts protective layers on the edges on both sides of the ultra-thin silicon functionality for centralized stress dispersion and toughness enhancement of the ultra-thin silicon nanostructure, overcoming the problems of low yield, limited service life, and poor device flexibility caused by the existence of surface cracks in the ultra-thin silicon nanostructure, and providing the possibility for preparing silicon electronic devices with lower thickness and better flexibility; inert metal electrodes are disposed on both sides of the ultra-thin silicon nanostructure of the ultra-thin silicon functional layer to form a non-Faraday junction, which has lower background noise and higher sensitivity compared with conventional active electrode devices such as copper electrodes and aluminum electrodes when measuring respiratory signals and bioelectric signals.

[0051] As a preferred embodiment, the thicknesses of the silicon substrate and the silicon nanowire array are independently 5 - 15 μm; in the silicon nanowire array, the diameter of the silicon nanowires is 0.5 - 1.5 μm, and the array period length is 1 - 3 μm.

[0052] As a preferred embodiment, the positive electrode and the negative electrode are independently selected from a gold electrode or a platinum electrode; the thicknesses of the positive electrode and the negative electrode are 5 - 15 μm.

[0053] As a preferred embodiment, the raw material of the protective layer is silver paste, copper paste or polydimethylsiloxane, which has a high Young's modulus and high flexibility, and realizes high bendability while ensuring edge stress dispersion; the thickness of the protective layer is 10 - 20 μm.

[0054] Another embodiment provides a preparation method of the non-Faraday junction flexible sensor based on the ultra-thin silicon nanostructure described in the above embodiment, including the following steps:

[0055] S1. Thinning the silicon wafer by wet etching to obtain an ultra-thin silicon wafer;

[0056] S2. Lithographically pattern a silicon nanocolumn array on the surface of the ultra-thin silicon wafer to obtain an ultra-thin silicon functional layer;

[0057] S3. Provide a mold and etch a frame-shaped groove on the surface of the mold;

[0058] S4. Fill the frame-shaped groove with an edge protection material;

[0059] S5. Cover the ultra-thin silicon functional layer on the mold filled with the edge protection material, perform heat treatment, and the edge protection material is demolded and carried on the edge on one side of the ultra-thin silicon functional layer to form a protective layer;

[0060] S6. Repeat steps S4 - S5 to carry a protective layer on the side of the ultra-thin silicon functional layer without a protective layer.

[0061] It further includes the step of respectively loading a positive electrode and a negative electrode on both sides of the ultra-thin silicon functional layer by means of slurry coating or evaporation, and this step is set between S2 and S3, or after S6.

[0062] As a preferred embodiment, before S1, it further includes the steps of laser marking and cutting, cleaning, and removing the surface oxide layer of the silicon wafer; specifically, the removing of the surface oxide layer is to soak the silicon wafer in a hydrofluoric acid solution; in S1, the wet etching and thinning is specifically to etch and thin the silicon wafer in a mixed solution of NaOH and ethanol.

[0063] As a preferred embodiment, in S4, before filling the edge protection material in the frame-shaped groove, first fill a layer of heat-release glue to facilitate easy demolding during heating and prevent the adhesion between the protective layer and the mold.

[0064] As a preferred embodiment, in S5, before covering the ultra-thin silicon functional layer on the mold, perform plasma cleaning and edge HMDS treatment on the ultra-thin silicon functional layer; when covering the ultra-thin silicon functional layer on the mold, the outer periphery of the ultra-thin silicon functional layer is aligned with the outer periphery of the frame-shaped groove; the temperature of the heat treatment is 110 - 130 °C.

[0065] Example 1

[0066] This example relates to a preparation method of a non-Faraday junction flexible sensor based on an ultra-thin silicon nanostructure, including the following steps:

[0067] (1) Cut a silicon wafer with a thickness of 100 μm into a 1 * 6 * 6 cm square using laser marking method and perform RCA standard cleaning, acetone cleaning, concentrated sulfuric acid cleaning, and oxygen plasma cleaning to obtain a clean silicon wafer;

[0068] (2) Place the silicon wafer on a wash rack, use hydrofluoric acid to remove the surface oxide layer and then perform water washing;

[0069] (3) Put the washed silicon wafer into a mixed solution of NaOH and ethanol for thinning for 4 - 6 h to 20 μm and then dry it.

[0070] (4) Use photolithography to etch a silicon nanocolumn array structure with a height of about 10 μm, a diameter of 1 μm, and a pitch of 1 μm on the surface of the silicon wafer to obtain an ultra-thin silicon functional layer.

[0071] (5) Use 3D printing to produce a mold larger than the size of the ultra-thin silicon functional layer to be protected.

[0072] (6) Use a laser marking machine to engrave a frame-shaped groove with a width of about 1 mm on the edge of the mold, and clean and wash the groove to remove impurities.

[0073] (7) Fill a layer of heat-release glue into the groove and fill polydimethylsiloxane in the remaining positions.

[0074] (8) Perform plasma cleaning and edge HMDS treatment on the ultra-thin silicon functional layer to ensure a clean surface and increase surface viscosity.

[0075] (9) Gently cover one side of the ultra-thin silicon functional layer on the mold, ensure that the outer periphery of the device is aligned with the outer periphery of the frame-shaped groove, and heat to about 120 °C to achieve demolding and the loading of the protective layer.

[0076] (10) Repeat steps (7) - (9) to load the protective layer on the other side edge of the ultra-thin silicon functional layer.

[0077] (11) Load a positive electrode and a negative electrode on both sides of the ultra-thin silicon functional layer respectively to obtain a non-Faraday junction flexible sensor based on the ultra-thin silicon nanostructure.

[0078] Comparative Example 1

[0079] The difference between this comparative example and Example 1 is that steps (5) - (10) are omitted, the protective layer is not loaded on the ultra-thin silicon surface, and the positive electrode and the negative electrode are made of aluminum electrodes to form a Faraday junction, and other steps and parameters remain unchanged.

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is that the edge HMDS treatment in step (8) is omitted, and other steps and parameters remain unchanged.

[0082] Test Example

[0083] Figure 2 The SEM image of the sensor prepared in Example 1 is shown. It can be seen that the ultra-thin silicon nano-functional layer includes a silicon substrate of about 10 μm and a silicon nanocolumn array about 10 μm thick. Place the sensors obtained in Example 1 and Comparative Example 2 in the SEM, as Figure 3As shown, the surface after HMDS treatment in Example 1 is smoother. However, the surface of Comparative Example 2 without HMDS treatment has a large number of protrusions, as Figure 4 shown. Because the silicon wafer after HMDS treatment adheres more closely to the surface of the edge protection layer, further improving the flexibility of the silicon wafer.

[0084] The device obtained in Example 1 was subjected to a bending test, and the results are as Figure 5 shown. The radius of curvature of the bent shape is about 0.3 cm, demonstrating the high flexibility and high toughness of the device reinforcement scheme. The sensors obtained in Example 1 and Comparative Example 1 were placed on a universal material testing machine for a three-point bending test, and the results are as Figure 6 shown. The device in Example 1 with a reinforced protection layer has better flexibility than the non-reinforced device in Comparative Example 1.

[0085] The sensors obtained in Example 1 and Comparative Example 1 were connected to a mid-end microcontroller signal processing device and a backend signal monitoring platform for a breathing test. The results are as Figure 7 shown. It can be seen that about 400 ms after the release of the breathing gas, the backend can clearly detect the relevant current signal. At the same time, when there is no breathing behavior, the current signal is very stable, without large fluctuations, and the signal-to-noise ratio is very high. This reflects the high response speed and lower background noise of this non-Faraday junction sensor to humidity signals. In addition, even a slight breathing behavior can be monitored by this sensor, as Figure 8 shown. This also indicates that this non-Faraday junction sensor has high sensitivity. Correspondingly, for the Faraday junction sensor in Comparative Example 1, due to relevant chemical reactions occurring on the active electrode, it will cause a large background electrical signal and background noise in the device, and the Faraday junction will also slow down the response recovery rate of the device, as Figure 9 shown.

[0086] The sensor device prepared in Example 1 was connected to an electromyograph to measure the human electromyogram signal and measure bioelectricity. The results are as Figure 10 shown. It can be seen that this sensor has excellent noise reduction performance, very low background noise, a very high signal-to-noise ratio, and is highly sensitive to electromyogram signals, accurately detecting relevant signals. Correspondingly, for the Faraday junction device in Comparative Example 1, as Figure 11 shown, although the electromyogram signal is stronger, it has a high background noise and a very low signal-to-noise ratio, making it difficult to capture tiny electromyogram signals. At the same time, the fluctuation of the background noise will also affect the waveform of the electromyogram signal, making it difficult to accurately judge the electromyogram signal.

[0087] The present invention has been described in detail above in connection with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention. The protection scope of the present invention shall be subject to the appended claims.

Claims

1. An illegal Faraday knot flexible sensor, characterized in that, It includes an ultra-thin silicon functional layer, a positive electrode and a negative electrode respectively disposed on both sides of the ultra-thin silicon functional layer, and a protective layer disposed on the peripheries on both sides of the ultra-thin silicon functional layer; The ultra-thin silicon functional layer includes a silicon substrate and a silicon nanowire array disposed on one side of the silicon substrate; Both the positive electrode and the negative electrode are inert metal electrodes.

2. The non-Faraday junction flexible sensor according to claim 1, wherein The thicknesses of the silicon substrate and the silicon nanowire array are independently 5 - 15 μm.

3. The non-Faraday junction flexible sensor according to claim 1, wherein, In the silicon nanowire array, the diameter of the silicon nanowires is 0.5 - 1.5 μm, and the array period length is 1 - 3 μm.

4. The non-Faraday knot flexible sensor according to claim 1, wherein, The positive electrode and the negative electrode are independently selected from a gold electrode or a platinum electrode; And / or, the thickness of the positive electrode and the negative electrode is 5 - 15 μm.

5. The non-Faraday knot flexible sensor according to claim 1, wherein The raw material of the protective layer is silver paste, copper paste or polydimethylsiloxane; And / or, the thickness of the protective layer is 10 - 20 μm.

6. A method for preparing the non-Faraday knot flexible sensor according to any one of claims 1-5, characterized in that, It includes the following steps: S1. Thinning the silicon wafer by wet etching to obtain an ultra-thin silicon wafer; S2. Lithographing a silicon nanowire array on the surface of the ultra-thin silicon wafer to obtain an ultra-thin silicon functional layer; S3. Providing a mold and etching a frame-shaped groove on the surface of the mold; S4. Filling an edge protection material in the frame-shaped groove; S5. Covering the ultra-thin silicon functional layer on the mold filled with the edge protection material, performing heat treatment, the edge protection material is demolded and carried on the edge on one side of the ultra-thin silicon functional layer to form a protective layer; S6. Repeating steps S4 - S5 to carry a protective layer on the side of the ultra-thin silicon functional layer without a protective layer. It further includes the step of respectively loading a positive electrode and a negative electrode on both sides of the ultra-thin silicon functional layer, and this step is disposed between S2 and S3, or after S6.

7. The preparation method of the non-Faraday junction flexible sensor according to claim 6, characterized in that, In S4, before filling the edge protection material in the frame-shaped groove, a layer of heat-release glue is filled first.

8. The preparation method of the non-Faraday knot flexible sensor according to claim 6, characterized in that, In S5, before covering the ultra-thin silicon functional layer on the mold, the ultra-thin silicon functional layer is subjected to plasma cleaning and edge HMDS treatment.

9. The preparation method of the non-Faraday knot flexible sensor according to claim 6, wherein, In S5, when covering the ultra-thin silicon functional layer on the mold, the outer periphery of the ultra-thin silicon functional layer is aligned with the outer periphery of the frame-shaped groove.

10. The preparation method of the non-Faraday knot flexible sensor according to claim 6, wherein, In S5, the temperature of the heat treatment is 110 - 130 °C.

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