Preparation method of suspended array carbon nanotube field effect transistor biosensor

Abstract

The present invention relates to a method for preparing a suspended array carbon nanotube field effect transistor biosensor, belonging to the field of biosensor technology, the method comprising: preparing an array carbon nanotube, providing a substrate, forming a first source electrode and a first drain electrode at two sides above the substrate respectively; making the array carbon nanotube suspended between the first source electrode and the first drain electrode; forming a second source electrode and a second drain electrode; forming a high-K dielectric layer; depositing a gold nanoparticle layer on the surface of the high-K dielectric layer covering the exposed array carbon nanotubes, and forming a DNA probe on the surface of the gold nanoparticle layer. The method provided by the present application greatly reduces the scattering from the background material, thereby significantly reducing the influence of the background noise, improving the signal-to-noise ratio of the biosensor, and after forming the high-K dielectric layer, the array carbon nanotubes are fully coated, significantly improving the gate control capability; it can achieve high-sensitivity detection of targets with a concentration of aM level, and presents excellent linearity.

Description

Technical Field

[0001] The present invention relates to the technical field of biosensors, and in particular to a method for preparing a suspended array carbon nanotube field effect transistor biosensor. Background Art

[0002] As society pays more and more attention to health issues, biosensors are facing increasing demand in the fields of clinical testing, disease treatment and food safety. Currently, technologies such as gene sequencing and editing, tumor cell labeling and tracking, and concentration detection of various disease markers (such as gases, hormones, enzymes and neurotransmitters) have attracted much attention from the research community and have become a hot spot for scientific exploration. Among them, research on photoelectric sensing systems, electrochemical sensors and electrical sensors for the neurotransmitter dopamine has continued to emerge and has made remarkable progress. In the existing technology, the corresponding biological molecules are mainly detected through network carbon nanotube biosensors.

[0003] However, the mobility and transconductance of the network carbon nanotube biosensor are relatively small, which to some extent hinders high-sensitivity testing; in addition, the network carbon nanotube biosensor itself has relatively large noise, which further reduces its detection sensitivity. Summary of the invention

[0004] The present invention is intended to provide a method for preparing a suspended array carbon nanotube field effect transistor biosensor to solve the deficiencies in the prior art. The technical problem to be solved by the present invention is achieved through the following technical solutions.

[0005] The method for preparing the suspended array carbon nanotube field effect transistor biosensor provided by the present invention comprises:

[0006] Transferring the array carbon nanotubes to a first preparation array carbon nanotube, and providing a substrate, and forming a first source electrode and a first drain electrode at two sides of the substrate respectively;

[0007] Above the gap between a source electrode and a first drain electrode, so that the array carbon nanotubes are suspended between the first source electrode and the first drain electrode;

[0008] forming a second source electrode and a second drain electrode on the exposed first source electrode, on the exposed first drain electrode, and on a portion of the area above the arrayed carbon nanotubes;

[0009] forming a high-K dielectric layer covering the exposed second source, the exposed second drain and the exposed array carbon nanotubes;

[0010] A gold nanoparticle layer is deposited on the surface of the high-K dielectric layer covering the exposed array carbon nanotubes, and a DNA probe is formed on the surface of the gold nanoparticle layer.

[0011] In the above scheme, after a gold nanoparticle layer is deposited on the surface of the high-K dielectric layer covering the exposed array carbon nanotubes, a passivation layer covering the exposed high-K dielectric layer is formed to passivate the second source and the second drain.

[0012] In the above solution, the second source electrode is aligned with the first source electrode thereunder in the vertical direction, and the second drain electrode is aligned with the first drain electrode thereunder in the vertical direction.

[0013] In the above scheme, the first source, the first drain and the array carbon nanotubes are exposed by electron beam exposure process, and metal material is deposited on the exposed first source, the exposed first drain and the partial area on the array carbon nanotubes to form two sources and a second drain.

[0014] In the above solution, the material of the first source electrode, the second source electrode, the first drain electrode and the second drain electrode is palladium.

[0015] In the above solution, the array carbon nanotubes are transferred to the gap between the first source electrode and the first drain electrode by a PMMA-assisted transfer method.

[0016] In the above solution, the material used for the high-K dielectric layer is hafnium oxide.

[0017] In the above solution, the high-K dielectric layer is formed by atomic layer deposition.

[0018] In the above scheme, the gold nanoparticle layer is deposited by electron beam evaporation coating process.

[0019] In the above solution, the passivation layer is made of PMMA glue.

[0020] The embodiments of the present invention include the following advantages:

[0021] The preparation method of the suspended array carbon nanotube field effect transistor biosensor provided in the embodiment of the present invention accurately transfers the array carbon nanotubes to the pre-prepared first source and first drain to form a suspended array carbon nanotube structure, deposits the second source and the second drain after alignment by electron beam exposure, and constructs a suspended gate carbon-based sensor by atomic layer deposition. Compared with the network carbon nanotubes, the suspended array carbon nanotube structure greatly reduces the scattering from the background material, thereby significantly reducing the influence of the background noise and improving the signal-to-noise ratio of the biosensor. After forming the high-K dielectric layer, the array carbon nanotubes are fully coated, which significantly improves the gate control capability. The biosensor obtained by the preparation method provided in the embodiment of the present invention shows excellent performance in the field of DNA detection, can achieve high-sensitivity detection of targets with aM concentration, and exhibits excellent linearity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flowchart of the steps of a method for preparing a suspended array carbon nanotube field effect transistor biosensor according to an embodiment of the present invention;

[0023] Figure 2 is a schematic diagram of a process for preparing array carbon nanotubes in an embodiment of the present invention;

[0024] Figure 3 is a schematic diagram of a process for forming a substrate, a first source electrode and a first drain electrode in an embodiment of the present invention;

[0025] Figure 4 is a schematic diagram of a process of transferring an array of carbon nanotubes to a space above a first source electrode and a first drain electrode in an embodiment of the present invention;

[0026] Figure 5 is a schematic diagram of a process for forming a second source electrode and a second drain electrode in an embodiment of the present invention;

[0027] Figure 6 is a schematic diagram of a process for forming a high-K dielectric layer in an embodiment of the present invention;

[0028] Figure 7 is a schematic diagram of a process for depositing a gold nanoparticle layer in an embodiment of the present invention;

[0029] Figure 8 is a schematic diagram of a process for forming a passivation layer in an embodiment of the present invention;

[0030] Fig. 9 is an Ids-Vgs curve corresponding to a suspended array carbon nanotube field effect transistor biosensor according to an embodiment of the present invention;

[0031] Fig.10 is an Ids-time curve corresponding to a suspended array carbon nanotube field effect transistor biosensor according to an embodiment of the present invention;

[0032] Fig.11 It is a graph of the responsivity-ORF1ab corresponding to the suspended array carbon nanotube field effect transistor biosensor in one embodiment of the present invention. DETAILED DESCRIPTION

[0033] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] like Figure 1 As shown, the present invention provides a method for preparing a suspended array carbon nanotube field effect transistor biosensor, the method comprising the following steps:

[0035] Step S1: Prepare the array carbon nanotube 1 by using the dimensionally restricted self-assembly (DLSA) process. Figure 2 ;

[0036] Step S2: Provide a substrate 2, and deposit metal materials on both sides of the substrate 2 to form a first source 31 and a first drain 41, respectively. Figure 3 ;

[0037] Specifically, the substrate 2 is a Si substrate, a SiC substrate, a SO 2 substrate, etc., and the metal material used by the first source electrode 31 and the first drain electrode 41 is palladium (Pd).

[0038] Step S3: Transferring the array carbon nanotubes 1 to the gap between the first source electrode 31 and the first drain electrode 41 by PMMA-assisted transfer method, so that the array carbon nanotubes 1 are suspended between the first source electrode 31 and the first drain electrode 41. For details, please refer to Figure 4 ;

[0039] Specifically, due to the interaction between individual carbon nanotubes in the array carbon nanotube 1 and the mechanical properties of the carbon nanotubes themselves, they can be suspended when the gap is less than 300nm, thereby transferring the array carbon nanotube 1 to above the gap between the first source 31 and the first drain 41. In addition, the process of suspending the array carbon nanotube 1 between the first source 31 and the first drain 41 is simple and easy to operate, and can be expanded to the wafer level, with the potential for mass production.

[0040] Step S4: Expose the first source electrode 31, the first drain electrode 41 and the array carbon nanotube 1 by electron beam exposure process, and deposit metal material again on the exposed first source electrode 31, the exposed first drain electrode 41 and the partial area on the array carbon nanotube 1 to form a second source electrode 32 and a second drain electrode 42, wherein the second source electrode 32 is vertically aligned with the first source electrode 31 thereunder, and the second drain electrode 42 is vertically aligned with the first drain electrode 41 thereunder. For details, please refer to Figure 5 ;

[0041] Specifically, the metal material used by the second source electrode 32 and the second drain electrode 42 is palladium (Pd);

[0042] Specifically, when the metal material is deposited again on the exposed first source 31, the exposed first drain 41 and the partial area above the array carbon nanotube 1, a certain stress is applied to the array carbon nanotube, making the suspended structure more secure. In addition, by depositing the metal material again on the exposed first source 31, the exposed first drain 41 and the partial area above the array carbon nanotube 1, the contact resistance of the obtained carbon nanotube field effect transistor is reduced, which is beneficial to the preparation of a suspended array carbon nanotube field effect transistor biosensor.

[0043] Step S5: forming a high-K dielectric layer 5 covering the exposed second source 32, the exposed second drain 42 and the exposed array carbon nanotubes 1. For details, please refer to Figure 6 ;

[0044] Specifically, the material used for the high-K dielectric layer 5 is hafnium oxide.

[0045] Specifically, the high-K dielectric layer 5 is formed by atomic layer deposition (ALD) to obtain a floating gate field effect transistor biosensor with better performance.

[0046] Specifically, hafnium oxide has excellent chemical stability and has a more diverse selection of test systems in biological tests. In addition, hafnium oxide has a very high dielectric constant and good gate control. Moreover, due to the effect of atomic layer deposition and the formation of the second source 32 and the second drain 42, the array carbon nanotube 1 is completely coated, forming a gate control effect similar to a gate all around (GAA), that is, a larger sensor response signal can be obtained at the same concentration.

[0047] Step S6: depositing a gold nanoparticle layer 6 on the surface of the high-K dielectric layer 5 covering the exposed array carbon nanotubes 1. For details, please refer to Figure 7 ;

[0048] Specifically, an electron beam evaporation coating process with an ultra-low evaporation speed is used to deposit a gold nanoparticle layer 6, and the deposited gold nanoparticle layer 6 is used as a connecting layer for a subsequently formed DNA probe. This step has wafer-level scalability. In addition, the electron beam evaporation coating process with an ultra-low evaporation speed can obtain excellent sheet-level particle size and uniformly distributed gold nanoparticles.

[0049] Step S7: forming a passivation layer 7 covering the exposed high-K dielectric layer 5 to passivate the second source 32 and the second drain 42. For details, please refer to Figure 8 ;

[0050] Specifically, the passivation layer 7 is made of PMMA glue, and the second source electrode 32 and the second drain electrode 42 are passivated by the passivation layer 7, which can effectively prevent the source and the drain from short-circuiting and effectively improve the stability of the biosensor.

[0051] Step S8: forming a DNA probe on the surface of the gold nanoparticle layer 6;

[0052] Specifically, the DNA probe is any probe with a thiol group, including nucleic acids, proteins, aptamers, small biological molecules, etc. The DNA probe makes the suspended array carbon nanotube field effect transistor biosensor an excellent platform for detecting various biological targets.

[0053] Specifically, the DNA sequence corresponding to the DNA probe is shown in the following table:

[0054] Table 1 DNA sequence corresponding to DNA probe

[0055]

[0056] In one embodiment of the present invention, a suspended array carbon nanotube field effect transistor biosensor obtained by the above-mentioned preparation method of a suspended array carbon nanotube field effect transistor biosensor is used to test a DNA molecule to be tested, wherein the DNA molecule to be tested is negatively charged in a test environment, and the subthreshold voltage of the suspended array carbon nanotube field effect transistor biosensor ranges from -0.2 to 0.3 V;

[0057] like Fig. 9 As shown, Vds=-0.1V, and different concentrations of DNA molecules to be tested are tested in turn, and the Ids-Vgs curve A corresponding to the suspended array carbon nanotube field effect transistor biosensor is obtained. Compared with the Ids-Vgs curve B corresponding to the suspended array carbon nanotube field effect transistor biosensor when the DNA molecules to be tested are not tested, the Ids-Vgs curve A is shifted to the right. This is because the DNA molecules are negatively charged in the test environment. When the added DNA molecules to be tested combine with the DNA probe, the potential change caused is equivalent to applying a positive voltage to the gate of the carbon nanotube field effect transistor, which is manifested in the rightward shift on the transfer characteristic curve;

[0058] Specifically, the concentrations of the DNA molecules to be tested include: ≤0.1aM, 1aM, 10aM, 100aM, 1fM, 10fM and 100fM;

[0059] like Fig.10As shown, when Vgs=0.12V, Vds=-0.1V and SS(Vgs=0.12) = 88.7mv / dec, the above-mentioned different concentrations of the DNA molecules to be tested are tested in turn to obtain Ids-time curves. It can be seen from the obtained Ids-time curves that when the concentration of the DNA molecules to be tested is greater than or equal to 1aM, Ids increases with the concentration of the DNA molecules to be tested, but when the concentration is less than 1aM, the change of Ids is relatively small. Therefore, the minimum concentration of DNA molecules that can be detected by the suspended array carbon nanotube field effect transistor biosensor obtained by the present invention is 1aM, wherein SS=ΔVds / Δ(log10(Ids)), Fig.10 PBS is the blank control group reflecting the stability of the system, mismatch1 is the non-completely complementary paired DNA fragment 1, mismatch2 is the non-completely complementary paired DNA fragment 2, and PBS, mismatch1 and mismatch2 are mainly used to detect the specificity of the suspended array carbon nanotube field effect transistor biosensor.

[0060] like Fig.11 As shown, in another embodiment of the present invention, a suspended array carbon nanotube field effect transistor biosensor obtained by the above-mentioned preparation method of the suspended array carbon nanotube field effect transistor biosensor is used to test the ORF1ab to be tested. When the concentration of the ORF1ab to be tested changes, the response of the suspended array carbon nanotube field effect transistor biosensor is obtained to obtain a response-ORF1ab curve. According to the response-ORF1ab curve, when the concentration of ORF1ab is less than 1aM, the response of the suspended array carbon nanotube field effect transistor biosensor is small. When the concentration of ORF1ab is greater than or equal to 1aM, as the concentration of ORF1ab increases, the response of the suspended array carbon nanotube field effect transistor biosensor rises linearly. Therefore, the suspended array carbon nanotube field effect transistor biosensor obtained by the invention can realize the detection of ORF1ab with a concentration greater than or equal to 1aM.

[0061] Specifically, in various embodiments of the present invention, the suspended array carbon nanotube field effect transistor biosensor can detect molecules to be detected in detection environments such as sweat, saliva, tears and blood.

[0062] It should be noted that the above detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present application belongs.

[0063] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0064] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0065] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0066] For ease of description, spatially relative terms, such as "above", "above", "on the upper surface of", "above", etc., may be used herein to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" may include both "above" and "below". The device may also be positioned in other different ways, such as rotated 90 degrees or in other orientations, and the spatially relative descriptions used herein are interpreted accordingly.

[0067] In the above detailed description, reference is made to the accompanying drawings, which form a part of this document. In the accompanying drawings, similar symbols typically identify similar components unless the context indicates otherwise. The illustrated embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be used, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a suspended array carbon nanotube field effect transistor biosensor, characterized in that: The method comprises: An array of carbon nanotubes (1) is prepared, and a substrate (2) is provided, and a first source electrode (31) and a first drain electrode (41) are respectively formed at two sides above the substrate (2); Transferring the array carbon nanotubes (1) to the top of the gap between the first source electrode (31) and the first drain electrode (41), so that the array carbon nanotubes (1) are suspended between the first source electrode (31) and the first drain electrode (41); forming a second source electrode (32) and a second drain electrode (42) above the exposed first source electrode (31), above the exposed first drain electrode (41), and on a partial area above the array carbon nanotubes (1); forming a high-K dielectric layer (5) covering the exposed second source (32), the exposed second drain (42) and the exposed array carbon nanotube (1); A gold nanoparticle layer (6) is deposited on the surface of a high-K dielectric layer (5) covering the exposed array carbon nanotubes (1), and then a passivation layer (7) covering the exposed high-K dielectric layer (5) is formed to passivate the second source electrode (32) and the second drain electrode (42), and a DNA probe is formed on the surface of the gold nanoparticle layer (6), wherein the DNA probe is a probe with a thiol group.

2. The method for preparing the suspended array carbon nanotube field effect transistor biosensor according to claim 1, characterized in that: The second source electrode (32) is aligned with the first source electrode (31) thereunder in the vertical direction, and the second drain electrode (42) is aligned with the first drain electrode (41) thereunder in the vertical direction.

3. The method for preparing the suspended array carbon nanotube field effect transistor biosensor according to claim 1, characterized in that: The first source electrode (31), the first drain electrode (41) and the array carbon nanotube (1) are exposed by an electron beam exposure process, and a metal material is deposited on a portion of the exposed first source electrode (31), the exposed first drain electrode (41) and the array carbon nanotube (1) to form a second source electrode (32) and a second drain electrode (42).

4. The method for preparing the suspended array carbon nanotube field effect transistor biosensor according to claim 1, characterized in that: The material of the first source electrode (31), the second source electrode (32), the first drain electrode (41) and the second drain electrode (42) is palladium.

5. The method for preparing the suspended array carbon nanotube field effect transistor biosensor according to claim 1, characterized in that: The arrayed carbon nanotubes (1) are transferred to the gap between the first source electrode (31) and the first drain electrode (41) by a PMMA-assisted transfer method.

6. The method for preparing the suspended array carbon nanotube field effect transistor biosensor according to claim 1, characterized in that: The material used for the high-K dielectric layer (5) is hafnium oxide.

7. The method for preparing the suspended array carbon nanotube field effect transistor biosensor according to claim 1, characterized in that: The high-K dielectric layer (5) is formed by atomic layer deposition.

8. The method for preparing the suspended array carbon nanotube field effect transistor biosensor according to claim 1, characterized in that: The gold nanoparticle layer was deposited using an electron beam evaporation process (6).

9. The method for preparing the suspended array carbon nanotube field effect transistor biosensor according to claim 1, characterized in that: The passivation layer (7) is made of PMMA glue.

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