A carbon-based three-terminal biomimetic synapse device based on double-layer dielectric and a preparation method thereof

Abstract

This invention discloses a carbon-based three-terminal biomimetic synaptic device based on a double-layer dielectric and its fabrication method. The device includes a substrate, a gate electrode disposed on the substrate, a double-layer dielectric disposed on the gate electrode, and a source electrode and a drain electrode disposed on the upper surface of the double-layer dielectric layer, which are connected by a semiconductor channel. The double-layer dielectric comprises a high-k metal oxide dielectric layer and a KH550-GO dielectric layer disposed from bottom to top. The semiconductor channel is made of graphene. This invention can reduce the operating voltage of the synaptic device and improve current linearity.

Description

Technical Field

[0001] This invention relates to the field of biomimetic synapse device technology, specifically to a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric and its fabrication method. Background Technology

[0002] Brain-inspired neuromorphic computing, composed of neurons and synapses, possesses the ability to perform complex information processing, offering a new computing paradigm for overcoming the von Neumann bottleneck. Electronic synaptic memory devices capable of competing with biological synapses are of great significance for neuromorphic computing.

[0003] Various electronic devices have been attempted to implement neuromorphic computing, such as memristors, phase-change memories, conductive bridge memories, and ferroelectric devices. These devices have successfully simulated several synaptic functions, including short-term and long-term memory, two-pulse facilitation, and pulse-time-dependent plasticity. Three-terminal synaptic devices, in particular, allow for easy control of synaptic weights due to their structural feature of having independent terminals for training (weight control) and testing (presynaptic and postsynaptic phases). This structural feature prevents the destruction of trained synaptic weights during the testing phase. However, achieving both large conductance changes and small nonlinearities to obtain high pattern recognition rates is very difficult for such electronic synaptic devices. This is because the nonlinearity of synaptic devices typically worsens with increasing voltage pulse amplitude or width to achieve larger conductance changes. Therefore, seeking new innovations in materials and structures to reduce device operating voltage and improve linearity is of great significance.

[0004] Among various two-dimensional materials, graphene oxide (GO) is a promising candidate. Due to its atomic thickness and weak van der Waals (vdWs) forces, it exhibits excellent frequency reduction capabilities and is compatible with traditional silicon-based devices. Furthermore, the bandgap of GO can be engineered by controlling surface functional groups, allowing for better control over its electrical properties. Meanwhile, high-k metal oxides with memristor properties can effectively reduce device operating voltage when used as gate dielectrics. Therefore, combining the advantages of both to fabricate a three-terminal biomimetic synapse device that can reduce operating voltage and improve current linearity has significant research value in the field of biomimetic synapses. Summary of the Invention

[0005] The purpose of this invention is to provide a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric and its fabrication method. The device adopts a back-gate field-effect transistor structure and can simulate the learning and memory functions of neural synapses.

[0006] This invention is achieved through the following technical solution:

[0007] The present invention relates to a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric, comprising a substrate, a gate electrode disposed on the substrate, a double-layer dielectric disposed on the gate electrode, a source electrode and a drain electrode disposed on the upper surface of the double-layer dielectric layer, the source electrode and the drain electrode being connected through a semiconductor channel; the double-layer dielectric comprises a high-k metal oxide dielectric layer and a γ-aminopropyltriethoxysilane-graphene oxide (KH550-GO) dielectric layer disposed from bottom to top; the semiconductor channel is made of graphene.

[0008] Furthermore, the material of the high-k metal oxide dielectric layer includes, but is not limited to, hafnium oxide, aluminum oxide, or tungsten oxide.

[0009] Furthermore, the materials of the gate electrode, source electrode, and drain electrode can be various metals, such as Ti, Au, or Pt.

[0010] Furthermore, the three-terminal bionic synaptic device has a back-gate structure.

[0011] Furthermore, the fabrication method of the carbon-based three-terminal biomimetic synaptic device based on a double-layer dielectric includes the following steps:

[0012] S1. Provide a substrate and perform standard cleaning on the substrate;

[0013] S2. Deposit electrode metal material on the substrate obtained in S1 to form a gate electrode;

[0014] S3. Deposit a high-k metal oxide dielectric layer on the gate electrode obtained in S2;

[0015] S4. A KH550-GO dielectric layer is formed on the high-k metal oxide dielectric layer obtained in S3.

[0016] S5. Electrode metal material is deposited on the surface of the KH550-GO dielectric layer obtained in S4 to form source and drain electrodes;

[0017] S6. A semiconductor channel is formed between the source electrode and the drain electrode obtained in S5 to obtain a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric.

[0018] Furthermore, the method for preparing the KH550-GO dielectric layer described in S4 is as follows:

[0019] a1. Preparation of KH550-GO solution. GO powder was dispersed in dimethylformamide (DMF) dispersant and sonicated to obtain a stable GO solution. The GO solution was then mixed with a KH-550 solution at a certain ratio (1:15-1:20) and stirred at 100-120 rpm at room temperature for at least 24 hours. The resulting mixed solution was then hydrolyzed with deionized water and ethanol at a certain ratio (1:1-1:1.2).

[0020] a2. The KH550-GO solution is drop-cast onto the target substrate obtained in S3;

[0021] a3. Dry at room temperature to obtain the KH550-GO solid dielectric film.

[0022] Furthermore, in S2 and S5, deposition is performed using methods such as vapor deposition, magnetron sputtering, laser pulse, or atomic layer deposition.

[0023] Furthermore, the method for fabricating the semiconductor channel described in S5 is as follows:

[0024] b1. Prepare graphene and transfer the graphene to a substrate having the source electrode and drain electrode;

[0025] b2. The graphene is subjected to photolithography or plasma etching to obtain the semiconductor channel.

[0026] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0027] This invention provides a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric. The double-layer dielectric is a high-k metal oxide and 3-triethoxysilylpropylamine-modified graphene oxide (KH550-GO), with graphene serving as the channel. The high-k metal oxide, possessing memristor properties, can reduce the operating voltage of the field-effect transistor when used as the gate dielectric layer material. KH550-GO exhibits high proton conductivity, making it an ideal gate dielectric material for double-layer field-effect transistors. The double-layer dielectric, combining the advantages of both, can modulate the channel conductance with a lower operating voltage, improving channel current linearity and simulating the learning and memory functions of a synapse with lower energy consumption. When an external voltage is applied to the gate electrode, the conductive filaments formed in the high-k metal oxide induce free protons in KH550-GO to move, forming a Helmholtz layer at the interface between the dielectric layer and the channel. Furthermore, the protons in KH550-GO electrochemically dope the graphene channel. At the same time, the high specific capacitance of KH550-GO can provide strong capacitive coupling between the gate electrode and the channel, thus making the channel conductivity adjustable.

[0028] This invention also provides a method for fabricating a carbon-based three-terminal biomimetic synaptic device based on a double-layer dielectric. This method utilizes conventional semiconductor processes such as photolithography and magnetron sputtering to fabricate micro / nano-scale thin-film field-effect transistors with a high-k metal oxide and KH550-GO double-layer dielectric and a carbon-based conductive channel. The carbon-based materials, graphene and graphene oxide, are obtained using chemical methods and fabricated on the target substrate using methods such as drop coating, spin coating, or wet transfer. This process plays a crucial role in further reducing device size and improving device integration. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric.

[0030] Figure 2 A flowchart for forming a carbon-based three-terminal biomimetic synaptic device based on a double-layer dielectric;

[0031] Figure 3 A flowchart for the preparation / transfer of KH550-GO;

[0032] Figure 4 A flowchart for the preparation / transfer of graphene;

[0033] Figure 5 A flowchart for forming graphene strips.

[0034] The labels in the diagram represent the following:

[0035] 1. Substrate; 2. Gate electrode; 3. High-k metal oxide dielectric layer; 4. KH550-GO dielectric layer; 5. Source electrode; 6. Drain electrode; 7. Semiconductor channel. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings. These descriptions are for illustrative purposes only and not for limiting the scope of the invention. For clarity, the parts in the drawings are not drawn to scale.

[0037] Hereinafter, an example of the carbon-based three-terminal biomimetic synaptic device based on a double-layer dielectric and its fabrication method, as described in the accompanying drawings, will be explained.

[0038] Reference Figure 1 This invention provides a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric. The biomimetic synapse device includes, from bottom to top, a substrate 1, a gate electrode 2, a double-layer dielectric, a source electrode 5, a drain electrode 6, and a semiconductor channel 7. The double-layer dielectric includes a high-k metal oxide dielectric layer 3 and a KH550-GO dielectric layer 4.

[0039] Specifically, the semiconductor channel 7 is made of graphene.

[0040] Specifically, graphene oxide (GO) has advantages such as low cost, mass production, simple dissolution process, and ease of functionalization. Due to the condensation reaction between the -NH2 group in KH550 and the -COOH group in GO, GO is easily modified by KH550. The reaction product, KH550-GO, contains a large amount of -SiOC2H5 on its surface, which can be decomposed into -SiOH. KH550-GO exhibits a high proton conductivity of approximately 1.2 × 10⁻⁶. -4S / cm is an ideal gate dielectric material for double-layer field-effect transistors.

[0041] High-k metal oxides with memristor properties generate oxygen vacancies under electrical pulse stimulation, forming conductive filaments. The accumulation of these filaments is analogous to signal transmission in biological neurons. Similarly, high-k metal oxide KH550-GO generates mobile protons under electrical pulse stimulation, forming double-layer capacitive coupling between the channel and the dielectric layer—a process also analogous to signal transmission in biological neurons. By considering the gate electrode as a presynaptic neuron, the channel between the source and drain electrodes as a postsynaptic neuron, and the channel conductance as the synaptic weight, the channel conductance can be adjusted by applying an electrical pulse to the gate, thereby achieving synaptic plasticity and simulating learning and memory functions.

[0042] This invention also provides a method for fabricating the aforementioned carbon-based three-terminal biomimetic synaptic device based on a double-layer dielectric, such as... Figure 2 As shown, it includes the following steps:

[0043] S1.1 Provide a substrate and perform standard cleaning on the substrate;

[0044] S1.2 Deposit a gate electrode on the substrate;

[0045] S1.3 Deposit a high-k metal oxide dielectric layer on the gate electrode;

[0046] S1.4. Prepare KH550-GO solution, drop-cast it onto a high-k metal oxide dielectric layer and dry it at room temperature to form a KH550-GO dielectric layer;

[0047] S1.5 Deposit source and drain electrodes on the surface of the KH550-GO dielectric layer;

[0048] S1.6. Prepare a graphene film and transfer it between the source and drain electrodes on the target substrate to pattern a graphene channel, thereby obtaining a carbon-based three-terminal biomimetic synaptic transistor based on a bilayer dielectric.

[0049] The preparation method further includes annealing the high-k metal oxide dielectric layer, gate electrode, source electrode, drain electrode, and channel after forming them. The annealing conditions are annealing at 20-300℃ for 1-2 hours, with the specific annealing conditions selected according to actual needs.

[0050] In this embodiment, the substrate can be a silicon substrate, but it is not limited to this. Other substrates can also be used, such as flexible substrates, polyethylene terephthalate (PET), etc., which will not be listed here. Before use, the substrate needs to be ultrasonically cleaned with acetone, isopropanol, and ethanol, and then dried under a nitrogen gas flow.

[0051] In this embodiment, the gate electrode, source electrode, and drain electrode can be made of metals such as aluminum, silver, and platinum. No specific material is specified here; the choice can be made according to actual needs. The deposition method can be any one of electron beam evaporation, magnetron sputtering, or laser pulse deposition. No specific material is specified here; the choice can be made according to actual needs.

[0052] In this embodiment, the dielectric layer material is selected from high-k metal oxides, and the deposition method can be electron beam evaporation or atomic layer deposition (ALD), depending on the material.

[0053] This embodiment uses a solution method to prepare the transfer KH550-GO dielectric layer. Specific process steps are as follows: Figure 3 ,include:

[0054] S2.1 Disperse the GO powder in the DMF dispersant;

[0055] S2.2. A stable GO solution was obtained by sonication;

[0056] S2.3. Mix the GO solution and KH-550 solution in a certain proportion and stir at a constant speed at room temperature for at least 24 hours.

[0057] S2.4 Hydrolyze the prepared mixed solution with deionized water and ethanol in a certain proportion;

[0058] S2.5. Drop casting the KH550-GO solution onto the target substrate;

[0059] S2.6. Dry at room temperature to obtain KH550-GO solid dielectric film.

[0060] The GO used in this embodiment can be purchased directly or prepared using the Hummer's method.

[0061] Graphene can be prepared using methods such as micromechanical exfoliation, graphene oxide reduction, silicon carbide (SiC) epitaxial growth, and chemical vapor deposition (CVD). Graphene transfer methods include basic etching, roll-to-roll transfer, mechanical exfoliation, and dry transfer. This example uses CVD, a method that can prepare large-area graphene films, is low-cost, and has good self-limiting properties. This example uses basic etching to transfer the graphene film onto the target substrate. Specific process steps are as follows... Figure 4 ,include:

[0062] S3.1. A uniform and complete graphene film is grown on copper foil using the CVD method.

[0063] S3.2 Select a relatively smooth side of the copper foil and spin-coat it with polymethyl methacrylate (PMMA) adhesive. Dry it at 120-150℃ for 5 minutes to establish a support layer.

[0064] S3.3. Place the copper foil coated with PMMA prepared in step S3.2 into an ammonium persulfate solution to etch away the copper foil beneath the graphene.

[0065] S3.4 Transfer the PMMA / graphene obtained in step S3.3 to the target position on the target substrate, air dry naturally, and then dry at high temperature for at least 30 minutes.

[0066] S3.5. Place the substrate prepared in step S3.4 into acetone to dissolve the PMMA, then wash it in sequence with isopropanol, anhydrous ethanol and deionized water, and dry it. At this point, the graphene film has been successfully transferred onto the prepared substrate.

[0067] The present invention is not limited to the method described above for forming graphene films on the target substrate; graphene films can be obtained using methods known in the art for graphene preparation and transfer.

[0068] This embodiment uses a combination of photolithography and plasma etching to form graphene strips. Specific process steps are as follows: Figure 5 ,include:

[0069] S4.1 Spin-coat negative photoresist onto the device structure of the transferred graphene film prepared in step S3.5.

[0070] S4.2, Exposure.

[0071] S4.3. Use plasma etching to etch away the graphene outside the channel region.

[0072] S4.4. Soak and clean the sample after photolithography in step S4.3 in sequence with acetone, isopropanol and anhydrous ethanol to remove the photoresist.

[0073] The width of the graphene strips can be 10–30 micrometers, and the length can be 10–100 micrometers. The graphene strips can be formed using other etching processes known in the art, and the process parameters can be adjusted according to the actual situation.

[0074] The fabrication method of carbon-based three-terminal biomimetic synaptic devices based on a double-layer dielectric is described in detail below with specific examples:

[0075] Example 1

[0076] Step 1: Use a Si / SiO2 substrate with a Si thickness of 500 μm and a SiO2 thickness of 300 nm. Clean the substrate sequentially with acetone, isopropanol, and anhydrous ethanol, rinse with deionized water, and then dry the substrate with nitrogen gas.

[0077] Step 2: Use magnetron sputtering to sputter 10nm Ti as an adhesion layer on the substrate, then sputter 100nm Al. After lift-off, the gate electrode is formed in the gate electrode pattern area.

[0078] Step 3: A 20 nm thick HfO2 dielectric layer is deposited on the substrate obtained in Step 2 using the ALD method. Hf(NMe2)4 and H2O are used as precursors, and N2 is used as the carrier gas.

[0079] Step 4: Preparation of KH550-GO solution. Dissolve GO powder in DMF dispersant to prepare GO solution (2 mg / ml); mix GO solution with KH-550 solution at a ratio of 1:20 and stir at a constant stirring speed of 120 rpm at room temperature for 24 h; then mix KH550-GO solution, deionized water and ethanol at a ratio of 1:1:1 and hydrolyze for 30 min.

[0080] Step 5: Drop casting the KH550-GO solution prepared in Step 4 onto the substrate obtained in Step 3, and drying it in room temperature air overnight to obtain a KH550-GO solid dielectric film, forming a bilayer dielectric.

[0081] Step 6: Sputter 10nm Ti as an adhesion layer using magnetron sputtering, and then sputter 100nm Al on the substrate obtained in step 5. After lift-off, source and drain electrodes are formed in the source and drain electrode pattern regions.

[0082] Step 7: Prepare graphene film on Cu foil using CVD method. Select a smoother side of the copper foil and spin-coat polymethyl methacrylate (PMMA) adhesive. Dry at 120-150℃ for 5 min to establish a support layer. Immerse in ammonium persulfate solution to etch away the copper foil beneath the graphene. After cleaning the obtained PMMA / graphene film, transfer it to the target position on the substrate obtained in Step 7. Air dry naturally and then dry at high temperature for at least 30 min. Then dissolve the PMMA in acetone, and wash successively with isopropanol, anhydrous ethanol and deionized water. Dry to obtain graphene film.

[0083] Step 8: Spin-coat negative photoresist onto the substrate obtained in Step 7, expose it, and then use plasma etching to etch away the graphene outside the channel region. Afterwards, immerse and clean it in acetone, isopropanol, and anhydrous ethanol in sequence to remove the photoresist and obtain the channel. Finally, a carbon-based three-terminal biomimetic synapse device based on a double-layer dielectric is obtained.

[0084] The above embodiments are merely several ways of implementing the present invention, and the present invention is not limited thereto.

[0085] The carbon-based three-terminal biomimetic synaptic device fabricated in this invention, based on a bilayer dielectric, can simulate the learning and memory functions of a synapse. Electrical stimulation received at the gate electrode can be considered a presynaptic signal, electrical stimulation received at the drain electrode a postsynaptic signal, and channel conductivity a synaptic weight. When the gate electrode is stimulated by prolonged continuous positive / negative pulses, the channel conductivity exhibits a stepwise increase / decrease, stabilizing after multiple pulse cycles. This phenomenon is similar to the long-term duration enhancement (LTP) / long-term duration inhibition (LTD) plasticity of a synapse. When both the gate and drain electrodes are stimulated by pulses, pulse frequency-dependent plasticity (SRDP) can be achieved by adjusting the frequency of the pulse sequence applied to both ports. These results can be applied to pattern recognition, sequence learning, and consistency detection.

[0086] Furthermore, this invention employs a double-layer dielectric structure, which can significantly reduce the operating voltage, increase the capacitance of the dielectric layer, and improve current linearity, thereby simulating synaptic learning and memory functions. Moreover, this structure is simple to manufacture, has low production costs, and a wider range of applications.

[0087] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A carbon-based three-terminal biomimetic synapse device based on double-layer dielectric, characterized in that, The biomimetic synaptic device comprises, from bottom to top, a substrate (1), a gate electrode (2) on the substrate (1), a double-layer dielectric on the gate electrode (2), the upper surface of the double-layer dielectric layer is respectively provided with a source electrode (5) and a drain electrode (6), and the source electrode (5) and the drain electrode (6) are connected through a semiconductor channel (7); the double-layer dielectric comprises, from bottom to top, a high-k metal oxide dielectric layer (3) with a memristive property and a KH550-GO dielectric layer (4), and the material of the semiconductor channel (7) is graphene.

2. The carbon-based three-terminal biomimetic synapse device based on double-layer dielectric according to claim 1, characterized in that, The material of the high-k metal oxide dielectric layer (3) is hafnium oxide, aluminum oxide or tungsten oxide. 3.The carbon-based three-terminal biomimetic synapse device based on double-layer dielectric according to claim 1, wherein, The materials of the gate electrode (2), the source electrode (5) and the drain electrode (6) are independently Ti, Au or Pt.

4. The method of claim 1, wherein the method of fabricating a carbon-based three-terminal biomimetic synapse device based on double-layer dielectric is characterized in that, Comprise: 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 an electrode metal material on the surface of the KH550-GO dielectric layer to form a source electrode and a drain electrode; S5, forming a semiconductor channel between the source electrode and the drain electrode to obtain a carbon-based three-terminal biomimetic synaptic device based on a double-layer dielectric.

5. The method of claim 4, wherein the method further comprises: S2 adopts electron beam evaporation or atomic layer deposition (ALD) method for deposition.

6. The method of claim 4, wherein the method further comprises: S3 specifically comprises: a1, preparing a KH550-GO solution; dispersing GO powder in a dimethylformamide (DMF) dispersant, and ultrasonicating to obtain a stable GO solution; mixing the GO solution with a KH-550 solution at a ratio of 1:15-1:20, stirring at a stirring speed of 100-120 rpm at room temperature for 24-30 h; and hydrolyzing the prepared mixed solution with deionized water and ethanol at a ratio of 1:1-1:1.2; a2, drop-casting the KH550-GO solution on the target substrate obtained in S2; a3, drying at room temperature to obtain a KH550-GO solid dielectric thin film.

7. The method of claim 4, wherein the method further comprises: In S1 and S4, the deposition is performed by evaporation, magnetron sputtering, laser pulse or atomic layer deposition.

8. The method of claim 4, wherein the method further comprises: The preparation method of the semiconductor channel in S5 is as follows: b1, preparing graphene and transferring the graphene to a substrate with the source electrode and the drain electrode; b2, performing photolithography or plasma etching on the graphene to obtain the semiconductor channel.

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