CN110672699A - All-solid-state field effect transistor, biosensor using same and detection method - Google Patents

Abstract

An all-solid-state biosensor, comprising an all-solid-state field effect transistor and a specific identifier for a target to be measured, wherein the all-solid-state field effect transistor comprises: a substrate; a gate disposed on the substrate; a first solid-state field effect transistor; a dielectric layer, covering the gate; a sensitive unit, disposed on the first solid dielectric layer and opposite to the gate; a source electrode and a drain electrode, disposed on the first solid dielectric layer , and are respectively connected to both ends of the sensitive unit; a second solid-state dielectric layer, covering the sensitive unit; and a metal floating gate layer, disposed on the second solid-state dielectric layer, and connected to the sensitive unit Relative settings. Wherein, the specific recognition body is fixedly connected to the metal floating gate layer. The present application also provides an all-solid-state field effect transistor and application thereof, and a detection method using the all-solid-state biosensor.

Description

All-solid-state field effect transistor and biosensor and detection method using the same

technical field

The invention relates to a semiconductor electronic device, in particular to an all-solid-state field effect transistor and its application, an all-solid-state biosensor and a detection method using the same.

Background technique

Traditional affinity biosensors form an electric double layer interface capacitance by directly contacting the surface of the sensitive unit connected with the specific recognition body and the aqueous solution containing the target to be detected, so that the charges of the biomolecules apply an electric field to the sensitive unit. effect to achieve affinity detection.

However, the sensitive unit is usually made of materials such as graphene, carbon nanotubes and silicon nanowires. When the aqueous solution containing the target to be tested is in contact with the surface of the sensitive unit, the impurities in the aqueous solution will form non-specific non-specific substances on the surface of the sensitive unit. Heterotropic adsorption, which is irreversible due to the strong hydrophobicity of the surface of the sensitive cell, makes the performance of the biosensor continue to deteriorate over time. In addition, the randomness of this non-specific adsorption is very high, which makes the performance degradation process of biosensors neither controllable nor predictable. Even if the biosensors manufactured in the same batch are subjected to the same test, there are dispersions among biosensors. A high degree of performance difference. For the above reasons, the consistency and substitutability of traditional affinity biosensors are poor.

SUMMARY OF THE INVENTION

Based on this, it is necessary to provide a new type of all-solid-state field effect transistor, an all-solid-state biosensor using the field-effect transistor, and a detection method using the biosensor to solve the problems of inconsistent and unstable performance of traditional affinity biosensors .

An all-solid-state biosensor, comprising an all-solid-state field effect transistor and a specific identifier for a target to be measured, wherein the all-solid-state field effect transistor comprises: a substrate; a gate disposed on the substrate; a first solid-state field effect transistor; a dielectric layer, covering the gate; a sensitive unit, disposed on the first solid dielectric layer and opposite to the gate; a source electrode and a drain electrode, disposed on the first solid dielectric layer , and are respectively connected to both ends of the sensitive unit; a second solid-state dielectric layer, covering the sensitive unit; and a metal floating gate layer, disposed on the second solid-state dielectric layer, and connected to the sensitive unit Relatively arranged; wherein, the specific identification body is fixedly connected to the metal floating gate layer.

In one embodiment, the all-solid-state biosensor further includes a linker molecule, the linker molecule has a first group and a second group, and the linker molecule is connected to the linker molecule through the first group. The metal floating gate layer is fixedly connected and fixedly connected to the specific recognition body through the second group.

In one embodiment, the linker molecule is a conductive compound.

In one embodiment, the conductive compound has an aromatic ring, and the first group and the second group are directly connected to the aromatic ring, respectively.

In one embodiment, the first group is a sulfhydryl group.

In one embodiment, the second group is a group capable of undergoing a condensation reaction with a group of the specific recognizer.

In one embodiment, the linker molecule comprises at least one of nitrogen-hydroxysuccinimide ester p-mercaptobenzoic acid and nitrogen-hydroxysuccinimide ester mercaptobibenzoic acid.

In one of the embodiments, the sensitive cell is completely enclosed by the second solid dielectric layer.

In one of the embodiments, the metal floating gate layer includes an outer layer composed of an inert metal material.

In one of the embodiments, the sensitive unit is at least one of a graphene layer, a carbon nanotube layer and a silicon nanowire layer.

In one embodiment, the substrate is a doped semiconductor substrate, and the gate is formed by locally complementary doping the doped semiconductor substrate.

A field effect transistor, comprising: a substrate; a gate disposed on the substrate; a first solid-state dielectric layer covering the gate; a sensitive unit disposed on the first solid-state dielectric layer and connected to the first solid-state dielectric layer the gate electrodes are arranged oppositely; the source electrode and the drain electrode are arranged on the first solid-state dielectric layer and are respectively connected to both ends of the sensitive unit; the second solid-state dielectric layer covers the sensitive unit; and a metal floating gate layer disposed on the second solid dielectric layer and opposite to the sensitive unit.

An application of the all-solid-state field effect transistor in bioaffinity detection.

A detection method for the all-solid-state biosensor, comprising:

grounding the source and the substrate, applying a voltage V _ds to the drain, and applying a voltage V _gs to the gate;

contacting the solution containing the target to be detected with the metal floating gate layer, so that the target to be detected has a bioaffinity effect on the specific recognition body;

real-time detection of the current I _ds flowing through the drain;

Calculate the conductivity of the sensitive cell according to the real-time detected current I _ds and the voltage V _ds , and draw a curve of conductivity versus time; and

Obtain the concentration of the target object to be measured according to the curve of the conductivity changing with time;

Wherein, when the conductive doped semiconductor substrate is a p-type doped semiconductor substrate, the voltage V _gs is a positive voltage; when the conductive doped semiconductor substrate is an n-type doped semiconductor substrate, the voltage V gs _gs is the negative voltage.

The all-solid-state field effect transistor and biosensor provided by the present application, since the sensitive unit is covered, will not be in contact with any external pollution source, so that the sensitive unit can maintain its original performance. In addition, due to the hydrophilicity of the metal floating gate layer, there is no specific adsorption with impurities in the solution containing the target to be measured, and the performance (such as conductivity) of the metal floating gate layer is less affected by external impurities Therefore, the biosensor using the field effect transistor has high stability and can improve the consistency of the biosensor produced in the same batch.

Description of drawings

1 is a schematic structural diagram of a field effect transistor provided by the application;

Fig. 2 is the schematic diagram that Pb ²⁺ cuts DNase in the embodiment of the application;

FIG. 3 shows a comparison diagram of the transfer characteristic curves of the FSS-GFET in the embodiment of the present application, the biosensor 1 before the DNase is cleaved, and the biosensor 1 after the DNase is cleaved;

FIG. 4 shows a comparison diagram of the transfer characteristic curves of the FSS-GFET in the embodiment of the present application, the biosensor 2 before the DNase is cleaved, and the biosensor 2 after the DNase is cleaved;

FIG. 5 shows a comparison diagram of the transfer characteristic curves of the SG-GFET in the embodiment of the present application, the biosensor 3 before cleaving the DNase, and the biosensor 3 after cleaving the DNase;

FIG. 6 shows a comparison diagram of kinetic process curves of biosensor 1 using FSS-GFET and biosensor 3 using SG-GFET at different concentrations of Pb ²⁺ in the embodiment of the present application.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Referring to FIG. 1 , the present application provides an all-solid-state field effect transistor 100 , including a substrate 110 , a gate 120 disposed on the substrate 110 , a first solid-state dielectric layer 130 covering the gate 120 , and A sensitive unit 140 disposed on the first solid dielectric layer 130 and opposite to the gate 120 , a source electrode disposed on the first solid dielectric layer 130 and connected to both ends of the sensitive unit 140 respectively 151 and drain electrodes 152 , a second solid dielectric layer 160 covering the sensitive unit 140 , and a metal floating gate layer 170 disposed on the second solid dielectric layer 160 and opposite to the sensitive unit 140 .

In the field effect transistor 100 provided in the present application, biological charges can apply an electric field effect to the sensitive unit 140 through the metal floating gate layer 170 and the second solid-state dielectric layer 160 to realize bioaffinity detection. Specifically, when the surface of the metal floating gate layer 170 is connected with a specific recognition body of the target to be measured, if the specific recognition body has a biological affinity with the target to be measured, it will cause the metal floating The charge on the surface of the gate layer 170 changes, thereby causing a potential change on the surface of the sensitive unit 140, and the target object to be detected can be identified and detected by detecting the potential change.

In the field effect transistor 100 provided by the present application, since the sensitive unit 140 is covered, it will not be in contact with any external pollution source, so that the sensitive unit 140 can maintain its original performance. In addition, since the metal floating gate layer 170 is hydrophilic, there is no specific adsorption with impurities in the solution containing the target to be measured, and the performance (eg, conductivity) of the metal floating gate layer 170 is affected by external impurities Therefore, the biosensor using the field effect transistor 100 has higher stability and can improve the consistency of biosensors produced in the same batch.

The substrate 110 may be a silicon substrate or a semiconductor substrate formed of other materials (eg, germanium). The substrate 110 may be a doped semiconductor substrate. The doped semiconductor substrate may be an n-type doped semiconductor substrate or a p-type doped semiconductor substrate. In one embodiment, the substrate 110 is a p-type doped silicon substrate.

The gate 120 may be formed of any suitable material. In one embodiment, the gate 120 may be formed of a metal material. An insulating layer (eg, a SiO ₂ insulating layer) may also be formed between the gate electrode 120 and the substrate 110 . The metal material may be at least one of Ti, Pt, Cr, Au, Al, Ni, Cu, Ag, and the like. In another embodiment, the substrate 110 is a doped semiconductor substrate, and the doped semiconductor substrate can be directly subjected to local complementary doping to form the gate electrode 120 . For example, a p-doped silicon substrate may be heavily doped locally with n-type to form conductive gate 120 .

The first solid dielectric layer 130 serves as a capacitive layer. The material of the first solid dielectric layer 130 may be a high dielectric constant dielectric material. The material of the first solid dielectric layer 130 may include at least one of HfO ₂ , ZrO ₂ , and Al ₂ O ₃ . In one embodiment, the material of the first solid dielectric layer 130 is a hafnium aluminum oxide compound (Hf _x A _y O ₂ , which is formed by compounding HfO ₂ and Al ₂ O ₃ ). The thickness of the first solid dielectric layer 130 may be 1 nm to 100 nm. Preferably, the thickness of the first solid dielectric layer 130 is 10 nm to 15 nm, and the thickness range does not cause the risk of pinhole breakdown. The first solid dielectric layer 130 can be prepared by atomic layer evaporation deposition, preferably by dry oxygen oxidation (using O ₃ precursor) to avoid the risk of pinhole breakdown in water vapor oxidation.

The sensitive unit 140 is the semiconductor channel of the field effect transistor, which can convert the signal expressed by biological activity into an electrical signal. The sensitive unit 140 may be a sensitive unit used in a traditional affinity biosensor, for example, may be at least one of a graphene layer, a carbon nanotube layer, and a silicon nanowire layer. In one embodiment, the sensitive unit 140 is a graphene layer, and the graphene layer may be at least one of single-layer graphene, double-layer graphene, and multi-layer graphene. Preferably, the sensitive unit 140 is a single-layer graphene. The sensitive unit 140 may be disposed vertically above the gate 120 .

The source electrode 151 and the drain electrode 152 may be formed of any suitable material. For example, the material of the source electrode 151 and the drain electrode 152 may include at least one of Ti, Pt, Cr, Au, Al, Ni, Cu, Ag, ITO, and the like. Materials of the source electrode 151 and the drain electrode 152 may be the same. The source electrode 151 and the drain electrode 152 may be formed simultaneously in the same process.

The second solid dielectric layer 160 serves as a capacitive layer. The second solid dielectric layer 160 is basically the same as the first solid dielectric layer 130 , and details are not described herein again. The material of the second solid dielectric layer 160 and the material of the first solid dielectric layer 130 may be the same or different. Preferably, the second solid dielectric layer 160 can completely cover the sensitive unit 140 .

The metal floating gate layer 170 may be formed of a metal material. The material of the metal floating gate layer 170 may include at least one of Ti, Pt, Cr, Au, Al, Ni, Cu, Ag, and the like. Preferably, the outer layer of the metal floating gate layer 170 is composed of an inert metal material (eg, at least one of Pt and Au). The metal floating gate layer 170 may be disposed vertically above the sensitive cell 140 . In one embodiment, the orthographic projections of the metal floating gate layer 170 and the sensitive cells 140 on the substrate 110 fall into the region of the substrate 110 for arranging the gate electrode 120 .

The present application further provides an all-solid-state biosensor, including the all-solid-state field effect transistor 100 and a specific recognizer for the target to be measured. The specific identifier can be fixedly connected to the metal floating gate layer 170 .

The biosensor may further include linker molecules, and the specific recognition body may be fixedly connected to the metal floating gate layer 170 through the linker molecules. The linker molecule may have a first group and a second group. The linker molecule can be fixedly connected to the metal floating gate layer 170 through the first group, and fixedly connected to the specific recognition body through the second group, so that the specific recognition body It is fixedly connected with the metal floating gate layer 170 .

In traditional affinity biosensors, the surface of the sensitive unit is connected with the specific recognizer of the target to be detected through a non-conductive linker molecule, so that the target to be tested and its specific recognizer have an affinity interaction During the process, the induced charge change can apply an electric field effect to the sensitive unit through the interface capacitance; if the linker molecule conducts electricity, the voltage will be conducted to the surface of the sensitive unit through the linker molecule, thereby generating an interface current and destroying the electric field effect. principle.

In the present application, the linker molecule may also be a non-conductive molecule. For example, the linker molecule may have an alkane chain, one end of the alkane chain is fixedly connected to the metal floating gate layer 170 through the first group, and the other end is connected to the specificity through the second group Recognize body connection. When the linker molecule is non-conductive, similar to traditional affinity biosensors, the solution containing the target to be detected and the metal floating gate layer 170 can form an interface capacitance, and biological charges can pass through the interface capacitance and the The capacitance layer formed by the second solid dielectric layer 160 applies an electric field effect to the sensitive unit 140 .

In a preferred embodiment, the linker molecule is a conductive molecule. The biological charges can be conducted to the surface of the metal floating gate layer 170 through the linker molecules, and then an electric field effect can be applied to the sensitive unit 140 through the capacitance layer formed by the second solid dielectric layer 160 . As compared with non-conductive linker molecules, the use of conductive linker molecules only needs to apply electric field effects through a capacitive layer, thereby increasing the sensitivity of the biosensor.

The linker molecule may be a conductive compound, eg, the linker molecule may be an organic conductive compound. The organic conductive compound is generally an organic molecule with a large conjugated π bond. One end of the organic molecule is fixedly connected to the metal floating gate layer 170 through the first group, and the other end is connected to the to-be-tested through the second group. Target-specific recognizers are immobilized. The organic conductive compound may have an aromatic ring, and the aromatic ring may be directly connected to the first group and the second group, respectively. The aromatic ring may include at least one of a benzene ring, a naphthalene ring, a fluorene ring, a thiophene ring, a pyrrole ring, and a piperazine ring. The first group may be a group capable of irreversibly adsorbing with a metal material, such as a thiol group. The second group can be a group that can undergo condensation reaction with the group of the specific recognizer, for example, when the specific recognizer has a hydroxyl group or a carboxyl group, the second group can be an amino group . In one embodiment, the linker molecule may include a nitrogen-hydroxysuccinimide ester p-mercaptobenzoic acid (4-mercaptobenzoic acid N-hydroxysuccinimide ester, MBA-NHS) and a nitrogen-hydroxysuccinimide ester thiol linker. At least one of benzoic acid (4-mercaptodiphenic acid N-hydroxysuccinimide ester, MDPA-NHS).

The present application also provides a method for preparing an all-solid-state field effect transistor, comprising:

S10, providing a substrate 110;

S20, performing photolithography patterning on the substrate 110 to expose the region where the gate electrode 120 is to be arranged, and then disposing the gate electrode 120 in the exposed region;

S30, disposing a first solid dielectric layer 130 covering the gate electrode 120 on the substrate 110;

S40, disposing a sensitive unit 140 on the first solid dielectric layer 130 at a position opposite to the gate 120;

S50, photoresist patterning is performed on the substrate 110 provided with the sensitive unit 140 to expose the region where the source electrode 151 and the drain electrode 152 are to be provided, and then the source electrode 151 and all the source electrode 151 and the drain electrode 152 are provided in the exposed region. the drain electrode 152, so that the source electrode 151 and the drain electrode 152 are respectively connected to both ends of the sensitive unit 140;

S60, disposing a second solid dielectric layer 160 covering the sensitive unit 140 on the base 110; and

S70 , providing a metal floating gate layer 170 on the second solid dielectric layer 160 at a position opposite to the sensitive unit 140 .

The method for manufacturing field effect transistors provided by the present application can manufacture field effect transistors with good consistency and stable performance in large quantities, wherein the substrate 110, the gate 120, the first solid dielectric layer 130, The sensitive cell 140 , the source electrode 151 , the drain electrode 152 and the second solid dielectric layer 160 may be provided, prepared or formed by a process known in the art, respectively. The metal floating gate layer 170 may be formed by a conventional metal layer forming process (eg, evaporation, sputtering, etc.).

The present application also provides a preparation method of the all-solid-state biosensor, comprising:

S1, providing the all-solid-state field effect transistor 100;

S2, the linker molecules are fixedly connected to the surface of the metal floating gate layer 170;

S3, the specific recognition body of the target to be detected is fixedly connected to the linker molecule.

In one embodiment, the metal floating gate layer 170 may be soaked in a solution containing the linker molecule, so that the first group and the metal floating gate layer 170 are irreversibly adsorbed, so as to obtain a fixed connection with the metal floating gate layer 170 . The metal floating gate layer 170 of the linker molecule.

In one embodiment, the metal floating gate layer 170 to which the linker molecules are fixedly connected can be soaked with a solution containing the specific recognition body, so that the linker molecules can interact with all the linker molecules through the second group. The specific recognition body undergoes a condensation reaction, so that the specific recognition body is fixedly connected to the metal floating gate layer 170 .

In one embodiment, after the biosensor is obtained, the metal floating gate layer 170 to which the specific recognition body is fixedly connected can also be soaked in a solution containing a blocking agent, so as to block the unconnected specific recognition body. linker molecule. The blocking agent may be a molecule containing a short chain capable of undergoing a condensation reaction with the second group. For example, the linker molecule can be ethanolamine.

The present application also provides a method for detecting the biosensor, comprising:

S01, grounding the source electrode 151 and the substrate 110, applying a voltage V _ds to the drain electrode 152, and applying a voltage V _gs to the gate electrode 120;

S02, contacting the solution containing the target to be measured with the metal floating gate layer 170, so that the target to be measured and the specific recognition body have a biological affinity;

S03, real-time detection of the current I _ds flowing through the drain 152;

S04, calculating the conductivity of the sensitive unit according to the current I _ds and the voltage V _ds detected in real time, and drawing a curve of the conductivity changing with time; and

S05, obtaining the concentration of the target to be measured according to the curve of the conductivity changing with time.

Under the condition that the drain voltage V _ds and the gate voltage V _gs remain unchanged, the change of the bio-charge on the metal floating gate layer 170 will cause the potential change of the sensitive cell, and the solutions containing different concentrations of the target to be tested will cause Different conductivity change rates, so the concentration of the target object to be measured can be obtained according to the curve of the conductivity changing with time.

When the gate electrode 120 is formed by locally complementary doping the p-type doped semiconductor substrate 110 , a positive voltage V _gs can be applied to the gate electrode 120 , so that the gate electrode 120 and the silicon substrate 110 are formed between the gate electrode 120 and the silicon substrate 110 . The reverse biased pn junction is isolated to avoid the risk of leakage of the silicon substrate 110 . When the gate 120 is formed by locally complementary doping the n-type doped semiconductor substrate 110 , a negative voltage V _gs can be applied to the gate 120 , so that the gate 120 and the silicon substrate 110 are formed between the gate 120 and the silicon substrate 110 . The reverse biased pn junction is isolated to avoid the risk of leakage of the silicon substrate 110 . Conductivity of the sensitive cell = V _ds /I _ds .

The detection method of the biosensor may also include the step of obtaining a standard curve of electrical conductivity changing with time, which is basically the same as the steps S01 to S04, the difference is only that in step S02, different known concentrations are used. The solution of the target object to be tested is in contact with the metal floating gate layer 170 . The concentration of the target object to be measured can be obtained according to the curve of the change of conductivity with time obtained by the detection and the curve of the change of the standard of conductivity with time.

Example 1

Fabrication of Field Effect Transistors

The field effect transistor is prepared by the following steps:

S10, providing a boron-doped p-type silicon wafer with an impurity concentration of n=2×10 ¹⁶ cm ⁻³ , the surface of the silicon wafer having a silicon dioxide layer of about 100 nm to form ion jet scattering.

S20, performing photolithography patterning on the silicon wafer substrate, exposing the region where the gate is to be formed, injecting phosphorus element into the exposed region and annealing and activating to form a thickness of about 500 nm and an impurity concentration of about 2×10 ¹⁸ cm ^-3 n-type heavily doped gate, and oxide etchant hydrofluoric acid solution (buffered oxide etchant, BOE) silicon dioxide layer on the surface of the silicon wafer. Among them, when the phosphorus element is implanted, the ion implantation energy is about 150keV, and the phosphorus element beam current density is about 10 ¹⁵ cm ^-2 . Annealing activation conditions were annealing at 1050°C for 30 seconds.

S30 , using a dry oxygen oxidation atomic layer evaporation deposition process to grow a HfO ₂ dielectric layer with a thickness of 15 nm on the wafer surface after step S30 .

S40, prepare a graphene layer, transfer the graphene layer to the HfO ₂ dielectric layer formed in step S30, perform photoresist patterning and plasma etching on the graphene layer to form a plurality of graphene sensitive units, and make The position of each graphene-sensitive cell is exactly above the corresponding gate so as to be controlled by the electric field from the gate below, and the size of each graphene-sensitive cell is about 20 μm×20 μm.

S50, the source and drain electrodes are fabricated by photoresist patterning and metal deposition at both ends of the graphene sensitive cell. The source and drain electrodes are both double-layer metal structures. The inner layer is a 5nm thick chromium or titanium adhesion layer. The layers are 45nm thick gold or platinum.

S60 , using a dry oxygen oxidation atomic layer evaporation deposition process to grow a HfO ₂ dielectric layer with a thickness of 10 nm on the wafer surface after step S50 .

S70, performing photoresist patterning and evaporation deposition on the HfO ₂ dielectric layer formed in step 60, thereby forming a plurality of metal floating gate layers, each metal floating gate layer is located vertically above the corresponding graphene sensitive cell. The metal floating gate layer is a double-layer metal structure, the inner layer is a 5nm thick chromium or titanium adhesion layer, and the outer layer is a 45nm thick gold or platinum layer.

In Example 1, both step S50 and step S70 form field effect transistors, wherein the field effect transistor formed in step S50 is a traditional affinity field effect transistor that makes the solution containing the target object to be tested contact the sensitive unit for detection. The transistor, which is named SG-GFET herein; and the field effect transistor formed in step S70 is the novel affinity field effect transistor described above, which is named FSS-GFET herein.

Example 2

Preparation of Biosensors

Preparation of biosensor 1: For FSS-GFET, first, the metal floating gate layer was soaked with a solution containing MBA-NHS, so that the thiol group of MBA-NHS was irreversibly adsorbed with gold or platinum in the outer layer of the metal floating gate layer; secondly, Soak the metal floating gate layer connected with MBA-NHS with a solution containing DNase sensitive to Pb ²⁺ , so that the DNase and MBA-NHS undergo condensation reaction, so as to be fixedly connected to the metal floating gate layer; finally, use Ethanolamine soaks the metal floating gate layer to block linker molecules that have not yet attached DNase.

Preparation of biosensor 2: basically the same as that of biosensor 1, except that 3-mercaptopropionic acid N-hydroxysuccinimide ester (MPA-NHS) was used instead of MBA -NHS.

Preparation of biosensor 3: For SG-GFET, the graphene-sensitive cell was soaked with a solution containing 1-pyrenebutyric acid N-hydroxysuccinimide ester (PBA-NHS) to make PBA-NHS The pyrene group is connected with the graphene-sensitive unit; secondly, soak the graphene-sensitive unit connected with PBA-NHS with a solution containing DNase, so that a condensation reaction between DNase and PBA-NHS occurs, so as to be fixedly connected to the graphene-sensitive unit on the cell; finally, the graphene-sensitive cell was soaked with ethanolamine to block the linker molecules that had not yet been attached to DNase.

Example 3

The detection of the transfer characteristic curve was carried out for the SG-GFET and FSS-GFET of Example 1, the biosensor 1-3 of Example 2, and the biosensor 1-3 that completed the bioaffinity effect.

Wherein, the bioaffinity is accomplished by contacting the metal floating gate layers of the biosensors 1 and 2 and the graphene sensitive unit of the biosensor 3 with a solution containing Pb ²⁺ . During bioaffinity, Pb ²⁺ cleaves the DNase, so that a part of the DNase is detached from the surface of the metal floating gate layer or the graphene-sensitive cell, as shown in Figure 2.

The detection steps of the transfer characteristic curve include:

a) The source is grounded together with the substrate (0V), and a small constant DC voltage Vds is applied to the drain.

b) A continuous scanning voltage Vgs is applied to the gate, and Vgs is always kept positive to ensure the isolation of the reverse-biased pn junction between the gate and the substrate.

c) Measure the current Ids flowing through the drain corresponding to each Vgs value, and then the device conductivity σ can be calculated, and the curve of the conductivity σ versus Vgs is the transfer characteristic curve.

Please refer to Fig. 3 to Fig. 5, Fig. 3 shows the comparison graph of the transfer characteristic curves of FSS-GFET, biosensor 1 and biosensor 1 that completes bioaffinity; Fig. 4 shows FSS-GFET, biosensor 2 Fig. 5 shows a comparison diagram of the transfer characteristic curves of SG-GFET, biosensor 3 and biosensor 3 with bioaffinity. It can be seen from Fig. 3 to Fig. 5 that compared with the conventional biosensor 1, the transfer characteristic curves of the new biosensors 1 and 2 have larger slopes, indicating that the new biosensors 1 and 2 have larger transconductance , the gate voltage has a stronger control effect on the drain voltage. In addition, it can be seen that the conductivity of the sensitive cells of the novel biosensors 1 and 2 compared with the conventional biosensor 1 before and after the bioaffinity effect when the gate voltage and the drain voltage are the same The change is larger, indicating that the new biosensors 1 and 2 have higher test sensitivity.

Example 4

For the biosensor 1 (using FSS-GFET) and biosensor 3 (using SG-GFET) of Example 2, the kinetic process test is performed, and the specific steps include:

a) The source is grounded together with the substrate (0V), and a small constant DC voltage Vds is applied to the drain.

b) A constant positive voltage Vgs is applied to the gate to ensure reverse-biased pn junction isolation between the gate and the substrate.

c) Continuously measure the current Ids flowing through the drain at a certain time interval, and then the change of the conductivity σ of the sensitive unit with time can be calculated, and the curve of the change of the conductivity σ with time is the kinetic process curve.

The specific steps of the bioaffinity in the above kinetic process are: first, use the HEPES buffer solution without Pb ²⁺ to rinse the metal floating gate layer for 15 minutes (buffer rinsing), and then wash the HEPES buffer solutions containing different concentrations of Pb ²⁺ . The surface of the metal floating gate layer was introduced for 30 minutes (sample detection), and then HEPES buffer solution containing a high concentration (1 μM) of Pb ²⁺ was introduced into the surface of the metal floating gate layer to terminate the reaction (end of 1 μM sample).

Please refer to Fig. 6. Fig. 6 shows the comparison of the kinetic process curves of biosensor 1 and biosensor 3 at different concentrations. It can be seen from the figure that compared with the biosensor using traditional field effect transistors, the The applied biosensor using the novel field effect transistor can generate a larger response signal to the same bio-affinity, thereby being more conducive to the detection of a low-concentration target to be detected.

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

The present invention is supported by the following research projects: National Natural Science Foundation of China (61901300), Natural Science Foundation of Jiangsu Province (SBK2018041725), Natural Science Foundation of Tianjin (18JCYBJC86000), Scientific Research Program of Tianjin Municipal Education Commission (2018KJ153). Tianjin Normal University Talent Introduction Fund (011/5RL153).

Claims (14)

1. An all-solid-state biosensor, comprising an all-solid-state field effect transistor and a specific identifier for a target to be measured, wherein the all-solid-state field effect transistor comprises: base; a gate, disposed on the substrate; a first solid dielectric layer covering the gate; a sensitive unit, disposed on the first solid dielectric layer and opposite to the gate; a source electrode and a drain electrode, disposed on the first solid dielectric layer, and connected to two ends of the sensitive unit respectively; a second solid dielectric layer overlying the sensitive cell; and a metal floating gate layer, disposed on the second solid dielectric layer, and disposed opposite to the sensitive unit; Wherein, the specific recognition body is fixedly connected to the metal floating gate layer. 2 . The all-solid-state biosensor according to claim 1 , further comprising a linker molecule, the linker molecule has a first group and a second group, and the linker molecule passes through the first group. 3 . The group is fixedly connected to the metal floating gate layer and is fixedly connected to the specific recognition body through the second group. 3 . The all-solid-state biosensor according to claim 2 , wherein the linker molecule is a conductive compound. 4 . 4 . The all-solid-state biosensor according to claim 3 , wherein the conductive compound has an aromatic ring, and the first group and the second group are respectively directly connected to the aromatic ring. 5 . 5. The all-solid-state biosensor of claim 2, wherein the first group is a thiol group. 6 . The all-solid-state biosensor according to claim 2 , wherein the second group is a group capable of undergoing a condensation reaction with a group of the specific recognizer. 7 . 7. The all-solid-state biosensor of claim 2, wherein the linker molecule comprises nitrogen-hydroxysuccinimide ester p-mercaptobenzoic acid and nitrogen-hydroxysuccinimide ester mercaptobibenzoic acid at least one of. 8. The all-solid-state biosensor of claim 1, wherein the sensitive unit is completely enclosed by the second solid-state dielectric layer. 9 . The all-solid-state biosensor according to claim 1 , wherein the metal floating gate layer comprises an outer layer composed of an inert metal material. 10 . 10 . The all-solid-state biosensor according to claim 1 , wherein the sensitive unit is at least one of a graphene layer, a carbon nanotube layer and a silicon nanowire layer. 11 . 11. The all-solid-state biosensor according to any one of claims 1 to 8, wherein the substrate is a doped semiconductor substrate, and the gate is subjected to local complementary doping on the doped semiconductor substrate form. 12. An all-solid-state field effect transistor, comprising: base; a gate, disposed on the substrate; a first solid dielectric layer covering the gate; a sensitive unit, disposed on the first solid dielectric layer and opposite to the gate; a source electrode and a drain electrode, disposed on the first solid dielectric layer, and connected to two ends of the sensitive unit respectively; a second solid dielectric layer overlying the sensitive cell; and The metal floating gate layer is disposed on the second solid dielectric layer and is disposed opposite to the sensitive unit. 13. An application of the all-solid-state field effect transistor according to claim 12 in bioaffinity detection. 14. A detection method using the all-solid-state biosensor of claim 11, comprising: grounding the source and the substrate, applying a voltage V _ds to the drain, and applying a voltage V _gs to the gate; contacting the solution containing the target to be detected with the metal floating gate layer, so that the target to be detected has a bioaffinity effect on the specific recognition body; real-time detection of the current I _ds flowing through the drain; Calculate the conductivity of the sensitive cell according to the real-time detected current I _ds and the voltage V _ds , and draw a curve of conductivity versus time; and Obtain the concentration of the target object to be measured according to the curve of the conductivity changing with time; Wherein, when the conductive doped semiconductor substrate is a p-type doped semiconductor substrate, the voltage V _gs is a positive voltage; when the conductive doped semiconductor substrate is an n-type doped semiconductor substrate, the voltage V gs _gs is the negative voltage.

Images