CN115642174A - Carbon-based three-terminal bionic synapse device based on double-layer dielectric medium and preparation method thereof - Google Patents

Abstract

The invention discloses a carbon-based three-terminal bionic synapse device based on a double-layer dielectric medium and a preparation method thereof, wherein the carbon-based three-terminal bionic synapse device comprises a substrate, a gate electrode is arranged on the substrate, the double-layer dielectric medium is arranged on the gate electrode, a source electrode and a drain electrode are arranged on the upper surface of the double-layer dielectric medium, and the source electrode and the drain electrode are connected through a semiconductor channel; the double-layer dielectric comprises a high-k metal oxide dielectric layer and a KH550-GO dielectric layer which are arranged from bottom to top; the semiconductor channel is made of graphene. The invention can reduce the operation voltage of the synapse device and improve the current linearity.

Description

Carbon-based three-terminal bionic synapse device based on double-layer dielectric medium and preparation method thereof

Technical Field

The invention relates to the technical field of bionic synapse devices, in particular to a carbon-based three-terminal bionic synapse device based on a double-layer dielectric medium and a preparation method thereof.

Background

Neuromorphic computations inspired by the brain consist of neurons and synapses, have the ability to perform complex information processing, and provide a new computational paradigm for overcoming the von-neumann bottleneck. Electronic synaptic memory devices that can compete with biological synapses are of great interest for neuromorphic calculations.

Various electronic devices have been tried to implement neuromorphic calculations, such as memristors, phase change memories, conductive bridge memories, and ferroelectric devices. Several synaptic functions have been successfully simulated using these devices, including short-term and long-term memory, double-pulse facilitation, and pulse-time dependent plasticity. Wherein a three-terminal synaptic device can easily control synaptic weights because its structural feature is that there are independent terminals for the training (weight control terminal) and testing (presynaptic and postsynaptic terminals) stages. This structural feature may prevent the trained synaptic weights from being corrupted during the testing phase. However, it is very difficult for such electronic synapse devices to achieve both large conductance variations and small non-linearities to achieve high pattern recognition rates. This is because the nonlinearity of the synapse device typically worsens with increasing amplitude or width of the voltage pulse to achieve greater conductance changes. Therefore, it is very important to search for new innovations in material and structure to reduce the device operating voltage and improve the linearity.

Among various two-dimensional materials, graphene Oxide (GO) is a promising material, has a good frequency-reducing effect due to the atomic thickness between layers and weak van der waals (vdWs) force, and is compatible with conventional silicon-based devices. Furthermore, the band gap engineering of GO can be tuned by controlling the functional groups of the surface, which allows its electrical properties to be better controlled. And the high-k metal oxide with the memristive characteristic is used as a gate dielectric, so that the operating voltage of the device can be effectively reduced. Therefore, the three-terminal bionic synapse device which can reduce the operation voltage of the device and improve the current linearity is prepared by combining the advantages of the two devices and has higher research value in the field of bionic synapses.

Disclosure of Invention

The invention aims to provide a carbon-based three-terminal bionic synapse device based on a double-layer dielectric medium and a preparation method thereof.

The invention is realized by the following technical scheme:

the invention relates to a carbon-based three-terminal bionic synapse device based on a double-layer dielectric medium, which comprises a substrate, wherein a gate electrode is arranged on the substrate, the double-layer dielectric medium is arranged on the gate electrode, a source electrode and a drain electrode are arranged on the upper surface of the double-layer dielectric medium layer, and the source electrode and the drain electrode are connected through a semiconductor channel; the double-layer dielectric medium comprises a high-k metal oxide dielectric medium layer and a gamma-aminopropyl triethoxysilane-graphene oxide (KH 550-GO) dielectric medium layer which are arranged from bottom to top; the semiconductor channel is made of graphene.

Further, the material of the high-k metal oxide dielectric layer includes, but is not limited to, hafnium oxide, aluminum oxide, or tungsten oxide, etc.

Further, the material of the gate electrode, the source electrode, and the drain electrode may be various metals, such as Ti, au, pt, or the like.

Further, the three-terminal bionic synapse device structure is a back gate structure.

Further, the preparation method of the carbon-based three-terminal bionic synapse device based on the double-layer dielectric medium comprises the following steps:

s1, providing a substrate, and carrying out standard cleaning on the substrate;

s2, depositing an electrode metal material on the substrate obtained in the S1 to form a gate electrode;

s3, depositing a high-k metal oxide dielectric layer on the gate electrode obtained in the S2;

s4, forming a KH550-GO dielectric layer on the high-k metal oxide dielectric layer obtained in the S3;

s5, depositing electrode metal materials on the surface of the KH550-GO dielectric layer obtained in the S4 to form a source electrode and a drain electrode;

and S6, forming a semiconductor channel between the source electrode and the drain electrode obtained in the S5 to obtain the carbon-based three-terminal bionic synapse device based on the double-layer dielectric medium.

Further, the preparation method of the KH550-GO dielectric layer S4 comprises the following steps:

a1, preparing KH550-GO solution. Dispersing GO powder in a Dimethylformamide (DMF) dispersing agent, and performing ultrasonic treatment to obtain a stable GO solution; mixing the GO solution with the KH-550 solution in a ratio (1; the prepared mixed solution is hydrolyzed by deionized water and ethanol according to a certain ratio (1;

a2, dripping the KH550-GO solution onto a target substrate obtained in the step 3;

and a3, drying at normal temperature to obtain the KH550-GO solid dielectric film.

Further, in S2 and S5, deposition is performed by evaporation, magnetron sputtering, laser pulse or atomic layer deposition.

Further, the preparation method of the semiconductor channel in S5 is as follows:

b1, preparing graphene, and transferring the graphene to a substrate with a source electrode and a drain electrode;

and b2, carrying out photoetching or plasma etching on the graphene to obtain the semiconductor channel.

Compared with the prior art, the invention has at least the following beneficial technical effects:

the invention provides a carbon-based three-terminal bionic synapse device based on a double-layer dielectric medium, wherein high-k metal oxide and 3-triethoxysilylpropylamine modified graphene oxide (KH 550-GO) are used as the double-layer dielectric medium, and graphene is used as a channel. The high-k metal oxide with the memristive characteristic is used as a gate dielectric layer material of the field effect transistor, so that the operating voltage of the device can be reduced; KH550-GO has higher proton conductivity and is an ideal gate dielectric material of the double electric layer field effect transistor. The double-layer dielectric prepared by combining the advantages of the two can realize the modulation of the channel conductance with smaller operating voltage, improve the channel current linearity and simulate the learning and memory functions of synapse with lower energy consumption. When voltage is applied to the gate electrode, the conductive filaments formed in the high-k metal oxide can induce free protons in the KH550-GO to move, a Helmholtz layer is formed on the interface between the dielectric layer and the channel, the protons in the KH550-GO can generate electrochemical doping on the graphene channel, meanwhile, the high specific capacitance of the KH550-GO can provide strong capacitive coupling between the gate electrode and the channel, and the channel conductance is adjustable.

The invention also provides a preparation method of the carbon-based three-terminal bionic synapse device based on the double-layer dielectric medium, and the preparation method is used for preparing the micro-nano-scale thin film field effect transistor with the high-k metal oxide, the KH550-GO double-layer dielectric medium and the carbon-based conductive channel through conventional semiconductor processes such as photoetching, magnetron sputtering and the like. The carbon-based material graphene and the graphene oxide are obtained by a chemical method and prepared on a target substrate by adopting modes of dropping coating, spin coating or wet transfer and the like. The process flow can play a key role in further reducing the size of the device and improving the integration level of the device.

Drawings

FIG. 1 is a schematic structural diagram of a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric medium;

FIG. 2 is a flow diagram of forming a double-layer dielectric-based carbon-based three-terminal biomimetic synapse device;

FIG. 3 is a flow chart for the preparation/transfer of KH 550-GO;

fig. 4 is a flow chart of preparation/transfer of graphene;

fig. 5 is a flow chart of forming a graphene strip.

The reference numerals in the figures represent the following:

1. a substrate; 2. a gate electrode, 3, a high-k metal oxide dielectric layer; 4. a KH550-GO dielectric layer; 5. a source electrode; 6. a drain electrode; 7. a semiconductor channel.

Detailed Description

The present invention will now be described in further detail with reference to the attached drawings, which are illustrative, but not limiting, of the present invention. For purposes of clarity, the various features in the drawings are not necessarily to scale.

Hereinafter, an example of a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric and a method for fabricating the same according to the present invention will be described with reference to the accompanying drawings.

Referring to fig. 1, the invention provides a carbon-based three-terminal bionic synapse device based on a double-layer dielectric medium, which comprises a substrate 1, a gate electrode 2, the double-layer dielectric medium, a source electrode 5, a drain electrode 6 and a semiconductor channel 7 which are arranged from bottom to top in sequence. Wherein the double-layer dielectric comprises a high-k metal oxide dielectric layer 3 and a KH550-GO dielectric layer 4.

Specifically, the material of the semiconductor channel 7 is graphene.

In particular, graphene Oxide (GO) has the advantages of low cost, batch production, simple dissolving process, easy functionalization and the like. Due to-NH in KH550 ₂ The group and-COOH group in GO have condensation reaction, and GO is easily modified by KH 550. The reaction product KH550-GO contains a large amount of-SiOC on the surface ₂ H ₅ Can be decomposed into-SiOH. KH550-GO has high proton conductivity, about 1.2X 10 ^-4 S/cm, is an ideal gate dielectric material of the double-layer field effect transistor.

The high-k metal oxide with the memristive characteristic can generate oxygen vacancies under the stimulation of electric pulses to form conductive filaments, and the accumulation process of the conductive filaments is similar to signal transmission in biological neurons; the high-k metal oxide KH550-GO generates movable protons under the stimulation of electric pulses, and forms electric double layer capacitive coupling between the channel and the dielectric layer, which is also similar to the signal transmission in biological neurons. The gate electrode is regarded as a presynaptic neuron, a channel between the source electrode and the drain electrode is regarded as a postsynaptic neuron, channel conductance is regarded as synaptic weight, and electric pulse is applied through the gate electrode to regulate the channel conductance, so that synaptic plasticity is realized, and further the simulation of learning and memory functions is realized.

The invention also provides a preparation method of the carbon-based three-terminal bionic synapse device based on the double-layer dielectric medium, as shown in FIG. 2, comprising the following steps:

s1.1, providing a substrate, and carrying out standard cleaning on the substrate;

s1.2, depositing a gate electrode on a substrate;

s1.3, depositing a high-k metal oxide dielectric layer on a gate electrode;

s1.4, preparing a KH550-GO solution, drop-casting the solution on a high-k metal oxide dielectric layer and drying the solution at normal temperature to form a KH550-GO dielectric layer;

s1.5, depositing a source electrode and a drain electrode on the surface of the KH550-GO dielectric layer;

s1.6, preparing a graphene film, transferring the graphene film between a source electrode and a drain electrode on a target substrate, and patterning a graphene channel to obtain the carbon-based three-terminal bionic synapse transistor based on the double-layer dielectric medium.

The preparation method further comprises the step of annealing after the high-k metal oxide dielectric layer, the gate electrode, the source electrode, the drain electrode and the channel are formed respectively. Wherein the annealing condition is annealing at 20-300 ℃ for 1-2h, and the specific annealing condition is selected according to actual needs.

In this embodiment, the substrate may be a silicon substrate, but is not limited thereto, and other substrates such as a flexible substrate, polyethylene terephthalate (PET), and the like may also be used, which are not listed here. Before use, the substrate needs to be cleaned by ultrasonic cleaning with acetone, isopropanol and ethanol in sequence and dried under nitrogen gas flow.

In this embodiment, the gate electrode, the source electrode, and the drain electrode may be made of metal materials such as aluminum, silver, and platinum, which are not specifically set herein and may be selected according to actual needs. The deposition method can be any one of electron beam evaporation, magnetron sputtering and laser pulse deposition methods, and is not specifically set herein and can be selected according to actual needs.

In this embodiment, the dielectric layer material is selected from a high-k metal oxide, and the deposition method may be an electron beam evaporation or Atomic Layer Deposition (ALD) method, which may be selected according to the material.

This example uses a solution process to prepare a transfer KH550-GO dielectric layer. The specific process steps are shown in figure 3 and comprise:

s2.1, dispersing GO powder in a DMF dispersing agent;

s2.2, obtaining a stable GO solution by ultrasonic;

s2.3, mixing the GO solution with the KH-550 solution in a certain ratio, and stirring at a constant speed for at least 24 hours at room temperature;

s2.4, hydrolyzing the prepared mixed solution by using deionized water and ethanol according to a certain proportion;

s2.5, dripping and casting the KH550-GO solution on a target substrate;

s2.6, drying at normal temperature to obtain the KH550-GO solid dielectric film.

The GO used in this example was either purchased directly or prepared using the Hummer's method.

The graphene can be prepared by a micro-mechanical lift-off method, a graphite oxide reduction method, a silicon carbide (SiC) epitaxial growth method, a Chemical Vapor Deposition (CVD) method, or the like. The graphene transfer method includes a basic etching method, a roll-to-roll transfer technology, a mechanical peeling technology, a dry transfer technology, and the like. In the example, a CVD method is used, and the method can be used for preparing a large-area graphene film and is low in cost and good in self-limitation. This example employs a basic etch process to transfer a graphene thin film onto a target substrate. The specific process steps are shown in figure 4 and comprise:

and S3.1, growing a uniform and complete graphene film on the copper foil by adopting a CVD method.

S3.2, selecting a smooth surface of the copper foil, spin-coating polymethyl methacrylate (PMMA) glue, drying at 120-150 ℃ for 5min, and establishing the supporting layer.

S3.3, placing the copper foil coated with PMMA prepared in the step S3.2 into ammonium persulfate solution, and etching away the copper foil below the graphene.

And S3.4, transferring the PMMA/graphene obtained in the step S3.3 to a target position of a target substrate, naturally drying the PMMA/graphene in the air, and drying the PMMA/graphene at high temperature for at least 30min.

And S3.5, putting the substrate prepared in the step S3.4 into acetone to dissolve PMMA, sequentially washing the substrate with isopropanol, absolute ethyl alcohol and deionized water, and drying until the graphene film is successfully transferred to the prepared substrate.

The present invention is not limited to the above method for forming a graphene thin film on a target substrate, and a graphene thin film may be obtained using a method for preparing and transferring graphene, which is well known in the art.

In this embodiment, a graphene strip is formed by a method combining photolithography and plasma etching. The specific process steps are shown in fig. 5, and comprise:

s4.1, spin-coating a negative photoresist on the device structure of the transferred graphene film prepared in the step S3.5.

S4.2, exposure.

And S4.3, etching away the graphene outside the channel region by adopting a plasma etching method.

And S4.4, sequentially soaking and cleaning the sample wafer subjected to photoetching in the step S4.3 by using acetone, isopropanol and absolute ethyl alcohol, and removing the photoresist.

The graphene strips may have a width of 10-30 microns and a length of 10-100 microns. The graphene strips may be etched using other etching processes known in the art, and the process parameters may be adjusted according to the actual situation.

The following description is made in detail with specific embodiments regarding a method for manufacturing a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric medium:

example one

Step one, using Si/SiO ₂ Substrate, si thickness 500um, siO ₂ The thickness is 300nm. The substrate is washed by acetone, isopropanol and absolute ethyl alcohol in sequence, washed by deionized water and dried by nitrogen.

And step two, sputtering 10nm Ti on the substrate by adopting magnetron sputtering as an adhesion layer, then sputtering 100nm Al, and forming a gate electrode in a gate electrode pattern area after Lift-off.

Step three, depositing HfO with the thickness of 20nm on the substrate obtained in the step two by adopting an ALD method ₂ As a dielectric layer. With Hf (NMe) ₂ ) ₄ And H ₂ O is a precursor, N ₂ Is a carrier gas.

Step four, preparing KH550-GO solution. Dissolving GO powder in a DMF dispersing agent to prepare GO solution (2 mg/ml); mixing GO solution with KH-550 solution in a ratio of 1:20, stirring at a constant stirring speed of 120rpm for 24 hours at room temperature; then mixing the KH550-GO solution, deionized water and ethanol according to the weight ratio of 1:1:1, and hydrolyzing for 30min.

And step five, dripping the KH550-GO solution prepared in the step four onto the substrate obtained in the step three, and drying in the air at normal temperature overnight to obtain a KH550-GO solid dielectric film and form a double-layer dielectric medium.

And sixthly, sputtering 10nm Ti serving as an adhesion layer by adopting a magnetron sputtering method, then sputtering 100nm Al on the substrate obtained in the fifth step, and forming a source electrode and a drain electrode in the pattern areas of the source electrode and the drain electrode after Lift-off.

Preparing a graphene film on a Cu foil by using a CVD method, selecting a smooth surface of a copper foil to spin-coat polymethyl methacrylate (PMMA) glue, drying at 120-150 ℃ for 5min, and establishing a supporting layer; placing the graphene film into an ammonium persulfate solution to etch away copper foil below the graphene; cleaning the obtained PMMA/graphene film, transferring the cleaned PMMA/graphene film to the target position of the substrate obtained in the step seven, naturally drying the PMMA/graphene film in the air, and drying the PMMA/graphene film at high temperature for at least 30min; and then, putting the graphene film into acetone to dissolve PMMA, sequentially washing the graphene film with isopropanol, absolute ethyl alcohol and deionized water, and drying to obtain the graphene film.

And step eight, spin-coating negative photoresist on the substrate obtained in the step seven, exposing, etching away graphene outside the channel region by adopting a plasma etching method, sequentially soaking and cleaning the graphene with acetone, isopropanol and absolute ethyl alcohol, removing the photoresist, and obtaining a channel to finally obtain the carbon-based three-terminal bionic synapse device based on the double-layer dielectric medium.

The above-described embodiments are merely illustrative of several ways to carry out the invention, and the invention is not limited thereto.

The carbon-based three-terminal bionic synapse device based on the double-layer dielectric medium can simulate learning and memorizing functions of synapses. The electrical stimulus experienced by the gate electrode of the device can be considered a presynaptic signal, the electrical stimulus experienced by the drain electrode of the device can be considered a postsynaptic signal, and the device channel conductance can be considered a synaptic weight. When the gate electrode is stimulated by a long continuous positive/negative pulse, the channel conductivity will undergo a stepwise increase/decrease and stabilize after multiple pulse cycles, similar to the synaptic long-term increase (LTP)/long-term inhibition (LTD) plasticity. When both the gate and drain electrodes are pulsed, pulse frequency dependent plasticity (SRDP) can be achieved by adjusting the frequency at which the pulse sequences are applied at both ports. These results can be applied in the direction of pattern recognition, sequence learning, consistency detection, etc.

In addition, the invention adopts a double-layer dielectric medium structure, can obviously reduce the operating voltage, improve the capacitance of the dielectric layer, improve the current linearity and realize the simulation of the synapse learning and memory functions. The structure has simple process, low manufacturing cost and wider application range.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims (9)

1. A carbon-based three-terminal bionic synapse device based on a double-layer dielectric medium is characterized by sequentially comprising a substrate (1), a gate electrode (2) positioned on the substrate (1) and the double-layer dielectric medium positioned on the gate electrode (2) from bottom to top, wherein a source electrode (5) and a drain electrode (6) are respectively arranged on the upper surface of the double-layer dielectric medium, and the source electrode (5) is connected with the drain electrode (6) through a semiconductor channel (7); the double-layer dielectric comprises a high-k metal oxide dielectric layer (3) and a KH550-GO dielectric layer (4) which are arranged from bottom to top.

2. The double-layer dielectric-based carbon-based three-terminal biomimetic synapse device according to claim 1, wherein the material of the high-k metal oxide dielectric layer (3) is hafnium oxide, aluminum oxide or tungsten oxide.

3. The double-layer dielectric-based carbon-based three-terminal biomimetic synapse device of claim 1, wherein the gate electrode (2), the source electrode (5), and the drain electrode (6) are each independently Ti, au, or Pt.

4. The double-layer dielectric-based carbon-based three-terminal biomimetic synapse device of claim 1, wherein the semiconductor channel (7) material is graphene.

5. The method for preparing the double-layer dielectric-based carbon-based three-terminal biomimetic synapse device according to claim 1, comprising:

s1, depositing an electrode metal material on a substrate to form a gate electrode;

s2, depositing a high-k metal oxide dielectric layer on the gate electrode;

s3, forming a KH550-GO dielectric layer on the high-k metal oxide dielectric layer;

s4, depositing electrode metal materials on the surface of the KH550-GO dielectric layer to form a source electrode and a drain electrode;

and S5, forming a semiconductor channel between the source electrode and the drain electrode to obtain the double-layer dielectric-based carbon-based three-terminal bionic synapse device.

6. The method for preparing a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric medium as claimed in claim 5, wherein S2 is deposited by using an Atomic Layer Deposition (ALD) method or an electron beam evaporation method.

7. The method for preparing a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric medium of claim 5, wherein S3 specifically comprises:

a1, preparing a KH550-GO solution; dispersing GO powder in a dimethyl formamide DMF dispersing agent, and performing ultrasonic treatment to obtain a stable GO solution; mixing the GO solution with the KH-550 solution in a ratio of 1; hydrolyzing the prepared mixed solution by using deionized water and ethanol according to the proportion of 1;

a2, dripping KH550-GO solution onto a target substrate obtained in the S2;

and a3, drying at normal temperature to obtain the KH550-GO solid dielectric film.

8. The method for preparing the double-layer dielectric-based carbon-based three-terminal biomimetic synapse device according to claim 5, wherein S1 and S4 are deposited by evaporation, magnetron sputtering, laser pulse or atomic layer deposition.

9. The method for preparing the double-layer dielectric-based carbon-based three-terminal biomimetic synapse device according to claim 5, wherein the semiconductor channel of S5 is prepared as follows:

b1, preparing graphene, and transferring the graphene to a substrate with a source electrode and a drain electrode;

and b2, carrying out photoetching or plasma etching on the graphene to obtain the semiconductor channel.

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