A sensor-based inductive computing device and its fabrication method based on a flexible substrate

Abstract

This invention discloses a sensing and in-memory computing device based on a flexible substrate and its fabrication method. The method includes forming two electrodes arranged side-by-side on the flexible substrate and forming a functional layer connecting the two electrodes. The functional layer includes metal oxide nanowires connecting the two electrodes. This invention uses a room-temperature chemical method to fabricate a sensing and in-memory computing device based on a flexible substrate and metal oxide nanowires. This results in a physical morphology more compatible with biological systems while avoiding the problem of deformation of flexible substrates under high-temperature conditions. It is suitable for novel wearable systems and offers advantages such as simple fabrication methods, compatibility with low-temperature CMOS processes, and easy testing of device electrical characteristics. It is expected to find applications in the future manufacturing of wearable sensing and in-memory computing devices.

Description

Technical Field

[0001] This invention relates to the field of semiconductor integrated circuit technology, and in particular to a sensing and memory device based on a flexible substrate and its fabrication method. Background Technology

[0002] With the continuous increase in data volume, traditional sensing systems based on the von Neumann architecture have encountered bottlenecks in information processing capabilities and energy efficiency. Furthermore, rigid devices based on silicon substrates have poor physical compatibility with biological organisms, making them unsuitable for the future development trend of intelligent wearable electronic systems. Human memory is primarily stored in synapses between neurons; the human brain contains as many as 10^6 synapses. 14 One, based on the traditional CMOS transistor and capacitor structure, is difficult to physically realize.

[0003] In recent years, artificial synaptic devices based on flexible substrates have been further developed, making them more compatible with biological systems in terms of physical morphology and suitable for novel wearable systems. Breakthroughs in flexible electronics technology and the development of nanotechnology have made it possible to fabricate high-performance, simple-structured neural synaptic devices on flexible substrates.

[0004] The conductance of a memristor changes continuously with the amount of charge flowing through it, and this change remains even after power is turned off. This characteristic is very similar to the nonlinear transmission characteristics of neural synapses, making memristors a promising candidate for use as neural synapses in neuromorphic circuits. Furthermore, neural synaptic devices based on materials such as copper oxide nanowires can simulate brain synapse connections at the device level. Copper oxide nanowires themselves can be used in gas sensing. Combining memristors constructed from copper oxide nanowires with flexible substrates can realize lightweight, flexible, and integrated sensing-memory-computing neural synaptic devices.

[0005] However, flexible substrates are prone to deformation and shrinkage under high temperatures, making them incompatible with traditional CMOS processes. Furthermore, the fabrication of copper oxide nanowires often requires high temperatures, making it difficult to fabricate copper oxide nanowires on flexible substrates using conventional methods, and further to fabricate integrated sensing, storage, and computing artificial neural synapse devices. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a sensing and memory computing device based on a flexible substrate and its fabrication method.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] This invention provides a sensing and computing device based on a flexible substrate, comprising:

[0009] Flexible substrate;

[0010] Two electrodes are arranged side by side on the substrate;

[0011] A functional layer connecting the two electrodes;

[0012] The functional layer includes metal oxide nanowires connected between the two electrodes.

[0013] Furthermore, the functional layer also includes an oxide layer of the electrode metal formed on the opposing sidewall surfaces of the two electrodes, the oxide layer of the electrode metal being connected to the metal oxide nanowire.

[0014] Furthermore, the electrode metal includes copper, and the metal oxide nanowires include copper oxide nanowires.

[0015] Furthermore, a lower adhesion and barrier layer is provided on the lower surface of the two electrodes respectively, and a trench is formed between the opposite sidewalls of the two electrodes and between the opposite sidewalls of the two lower adhesion and barrier layers. The metal oxide nanowire is located in the trench and is bridged between the opposite sidewalls of the two electrodes.

[0016] Furthermore, an upper adhesion and a barrier layer are respectively provided on the upper surface of the two electrodes, and a window is formed between the two upper adhesion and barrier layers to communicate with the outside of the functional layer.

[0017] This invention also provides a method for fabricating a sensor-memory computing device based on a flexible substrate, comprising:

[0018] Provide flexible substrates;

[0019] Two parallel-arranged under-adhesion and barrier layers are formed on the substrate;

[0020] An electrode is formed on each of the two lower adhesion and barrier layers, such that a trench is formed between the opposite sidewalls of the two electrodes and between the opposite sidewalls of the two lower adhesion and barrier layers.

[0021] An upper adhesion and barrier layer is formed on each of the two electrodes, thereby forming a window communicating with the trench on the electrode between the two upper adhesion and barrier layers;

[0022] A functional layer is formed in the trench connecting the two electrodes; wherein the functional layer includes an oxide layer of electrode metal formed on the opposing sidewall surfaces of the two electrodes, and metal oxide nanowires connecting the oxide layers.

[0023] Furthermore, the electrode metal is copper, the oxide layer is a copper oxide layer, and the metal oxide nanowires are copper oxide nanowires.

[0024] Furthermore, the formation of a functional layer connecting the two electrodes in the trench specifically includes:

[0025] At room temperature, thioglycerol is added to an aqueous solution of copper acetate and stirred to form a mixed solution;

[0026] An aqueous solution of sodium hydroxide was poured into the mixed solution, and stirring was continued after adding water to obtain a suspension containing copper oxide nanowires;

[0027] The suspension is dropped into the trench and dried to form a copper oxide layer on the opposite sidewall surfaces of the two electrodes. The dried copper oxide nanowires are then fused with the copper oxide layer to form a functional layer connecting the two electrodes.

[0028] Furthermore, the drying temperature is less than or equal to 100°C.

[0029] Furthermore, ultraviolet lithography and physical vapor deposition techniques are used to form the lower adhesion and barrier layer, the electrode, and the upper adhesion and barrier layer.

[0030] The present invention has the following advantages:

[0031] (1) Artificial neural synapse devices (sensing and computing devices) based on flexible substrates are more compatible with biological systems in terms of physical form and can be applied to novel wearable systems.

[0032] (2) CuO nanowires were prepared by a room temperature chemical method. After preparation, the suspension was dropped onto the device to complete the preparation, thus avoiding the problem that the flexible substrate is prone to deformation under high temperature conditions.

[0033] (3) The device fabrication method is simple and the process is compatible with low-temperature CMOS process.

[0034] (4) Copper oxide nanowires can be used for gas sensing. By combining CuO nanowires with memristors, a device-based in-memory computing device can be realized, and it is expected to be used in the manufacturing of wearable in-memory computing devices in the future.

[0035] (5) Devices can be fabricated based on photolithography, and device dimensions can be precisely controlled.

[0036] (6) The electrical characteristics of the device are easy to test. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a preferred embodiment of the present invention, showing the structure of a sensing and computing device based on a flexible substrate.

[0038] Figure 2This is a flowchart of a preferred embodiment of the present invention for fabricating a sensor-memory computing device based on a flexible substrate;

[0039] Figures 3-8 According to a preferred embodiment of the present invention Figure 2 A schematic diagram of the process steps for fabricating a sensing and memory device based on a flexible substrate. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0041] Rigid devices based on silicon substrates have poor physical compatibility with biological organisms, making them unsuitable for the future development trend of intelligent wearable electronic systems. Artificial synaptic devices based on flexible substrates represent a new direction for developing next-generation low-power and highly biocompatible biomimetic sensing systems. Common flexible substrates include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), both of which are semi-crystalline thermoplastic polymers. PET and PEN exhibit inherent good transparency, good mechanical properties, and high oxygen and water vapor permeability barrier properties as flexible substrates. However, they are not heat-resistant; as the temperature rises, polymer substrates such as PET and PEN shrink, causing defects in the thin-film devices on the substrate. Common methods for synthesizing metal oxide nanowires as functional layers, such as the synthesis of CuO nanowires (e.g., copper thermal oxidation and hydrothermal methods), require high reaction temperatures. Therefore, conventional thermal oxidation methods cannot be used to prepare CuO nanowires on flexible substrates.

[0042] This invention provides a sensing-memory computing device based on a flexible substrate and its fabrication method. To adapt to the characteristics of the flexible substrate, a room-temperature chemical method is used to prepare, for example, CuO nanowires. Furthermore, by combining the CuO nanowire gas sensor system with a memristor, a neural synapse is physically simulated based on the flexible substrate, realizing an integrated sensing-memory computing artificial neural synapse device. This sensing-memory computing device based on a flexible substrate is suitable for the research of novel low-power devices and is expected to be applied in the future manufacturing of wearable sensing-memory computing devices.

[0043] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0044] Please see Figure 1 , Figure 1 This is a schematic diagram of a preferred embodiment of the present invention, showing the structure of a sensing and memory device based on a flexible substrate. Figure 1 As shown, a sensing and computing device based on a flexible substrate according to the present invention includes: a flexible substrate 10; two electrodes 12 arranged in parallel on the flexible substrate 10; a functional layer 17 connected between the two electrodes 12, and other main structural components.

[0045] The functional layer 17 may include metal oxide nanowires 16 connected between the two electrodes 12.

[0046] Furthermore, the functional layer 17 may also include an oxide layer 15 of the electrode metal formed on the opposing sidewall surfaces of the two electrodes 12. The oxide layer 15 of the electrode metal is connected to the metal oxide nanowire 16.

[0047] Please see Figure 1 In a preferred embodiment, the flexible substrate 10 may include a polymer flexible substrate 10. For example, the flexible substrate 10 may include a polymer flexible substrate 10 such as a PET substrate 10 or a PEN substrate 10.

[0048] In a preferred embodiment, the electrode metal may include metallic copper, i.e., electrode 12 is a copper electrode 12. Thus, the oxide layer 15 of the electrode metal formed on the opposing sidewall surfaces of the two electrodes 12 is a copper oxide layer 15' (see reference). Figure 8 ).

[0049] In a preferred embodiment, the metal oxide nanowire 16 may include copper oxide nanowire 16' (see reference). Figure 8 The copper oxide nanowires 16' and the copper oxide layer 15' form a fused connection and together to form the functional layer 17.

[0050] By utilizing the novel morphology of the functional layer 17 coupled with copper oxide nanowires 16' and copper oxide layer 15', a novel memristor structure based on copper oxide nanowires 16' is formed.

[0051] Please see Figure 1 In a preferred embodiment, a lower adhesion and barrier layer 11 may be provided on the lower surface of each of the two electrodes 12. That is, the two lower adhesion and barrier layers 11 are located side by side between a corresponding electrode 12 and the flexible substrate 10. This forms a trench 18 structure between the opposite sidewalls of the two electrodes 12 and between the opposite sidewalls of the two lower adhesion and barrier layers 11.

[0052] In a preferred embodiment, each lower adhesion and barrier layer 11 is the same size as a corresponding electrode 12, that is, the sidewall of each lower adhesion and barrier layer 11 is flush with the corresponding sidewall of the corresponding electrode 12, so that the formed trench 18 has a sidewall structure with the upper and lower sides flush.

[0053] The copper oxide nanowire 16' is located in the trench 18 and is bridged between the opposite sidewalls of the two copper electrodes 12.

[0054] In a preferred embodiment, the lower adhesion and barrier layer 11 material may be made of a stack of Ti and Pt materials.

[0055] In another preferred embodiment, the material of the lower adhesion and barrier layer 11 may be made of a stack of Ta and TaN.

[0056] Please see Figure 1 In a preferred embodiment, an upper adhesion and barrier layer 13 may be provided on the upper surface of each of the two electrodes 12.

[0057] Furthermore, the upper surfaces of the two upper adhesion and barrier layers 13 can be flush.

[0058] In a preferred embodiment, two upper adhesion and barrier layers 13 are disposed opposite to each other on corresponding electrodes 12, and the opening width between the two upper adhesion and barrier layers 13 is greater than the distance between the two electrodes 12 (i.e., the width of the trench 18). This forms a window 14 structure between the two upper adhesion and barrier layers 13, allowing the functional layer 17 in the trench 18 to communicate with the outside, thus realizing the sensing function between the copper oxide nanowire 16' and the external gas.

[0059] In a preferred embodiment, the material of the upper adhesion and barrier layer 13 may be made of a laminate of Ta and TaN.

[0060] The following detailed description of a method for fabricating a flexible substrate-based inductive computing device according to the present invention, with reference to the accompanying drawings and specific embodiments, is provided in detail.

[0061] Please see Figure 2 The present invention provides a method for fabricating a flexible substrate-based inductive computing device, which can be used to fabricate the aforementioned flexible substrate-based inductive computing device, and may include the following steps:

[0062] Step S1: Provide a flexible substrate.

[0063] Please see Figure 3 In a preferred embodiment, the flexible substrate 10 may be a polymer flexible substrate 10, such as a PEN substrate 10. Furthermore, the PEN substrate 10 may be cleaned and dried to provide a clean PEN substrate 10 suitable for the subsequent preparation steps described below.

[0064] Step S2: Form two parallel under-adhesion and barrier layers on the substrate.

[0065] Please see Figure 4 In a preferred embodiment, ultraviolet lithography and physical vapor deposition techniques can be used to form two patterned, side-by-side under-adhesion and barrier layers 11 on the PEN substrate 10. The distance between the two under-adhesion and barrier layers 11 defines the width of the trench 18, which in turn defines the size of the subsequently formed functional layer 17.

[0066] In a preferred embodiment, the lower adhesion and barrier layer 11 can be fabricated using a stacked material of Ta and TaN. Specifically, a Ta adhesion layer is first deposited on the PEN substrate 10, followed by the deposition of a TaN barrier layer on the Ta adhesion layer, and then a patterning process is performed to form a lower adhesion and barrier layer 11 with a stacked structure composed of the Ta adhesion layer and the TaN barrier layer.

[0067] In a preferred embodiment, the thickness of the Ta adhesion layer can be 10-20 nm, and the thickness of the TaN barrier layer can be 30-100 nm.

[0068] Step S3: Form an electrode on each of the two under-adhesion and barrier layers, such that a trench is formed between the opposite sidewalls of the two electrodes and between the opposite sidewalls of the two under-adhesion and barrier layers.

[0069] Please see Figure 5 In a preferred embodiment, ultraviolet lithography and physical vapor deposition techniques can be used to form a copper electrode 12 on each of the two under-adhesion and barrier layers 11 by depositing, for example, copper metal layers on the two under-adhesion and barrier layers 11 and patterning them.

[0070] Specifically, the copper electrode 12 and the corresponding lower adhesion and barrier layer 11 can have the same or substantially the same dimensions, and the sidewalls of the copper electrode 12 are flush with the sidewalls of the corresponding lower adhesion and barrier layer 11. This forms a trench 18 structure between the opposite sidewalls of the two copper electrodes 12 and between the opposite sidewalls of the two lower adhesion and barrier layers 11.

[0071] In a preferred embodiment, the thickness of the copper electrode 12 can be 300–1000 nm.

[0072] Step S4: Form an upper adhesion and barrier layer on each of the two electrodes, thereby forming a window communicating with the trench on the electrode between the two upper adhesion and barrier layers.

[0073] Please see Figure 6In a preferred embodiment, ultraviolet lithography and physical vapor deposition techniques can be used to form two patterned, side-by-side top adhesion and barrier layers 13 on the two copper electrodes 12. That is, one patterned top adhesion and barrier layer 13 is formed on each copper electrode 12.

[0074] Two upper adhesion and barrier layers 13 are disposed opposite to each other on the corresponding copper electrodes 12, and the opening width between the two upper adhesion and barrier layers 13 is greater than the distance between the two copper electrodes 12 (i.e., the width of the trench 18). This forms a window 14 on the copper electrode 12 between the two upper adhesion and barrier layers 13, communicating with the trench 18. Using this window 14, the functional layer 17 subsequently formed in the trench 18 can communicate with the outside, realizing the sensing function between the copper oxide nanowire 16' and the external gas.

[0075] In a preferred embodiment, the upper adhesion and barrier layer 13 can be manufactured using a stacked material of Ta and TaN. Specifically, a Ta adhesion layer is first deposited on the copper electrode 12, followed by the deposition of a TaN barrier layer on the Ta adhesion layer, and then a patterning process is performed to form an upper adhesion and barrier layer 13 with a stacked structure composed of the Ta adhesion layer and the TaN barrier layer.

[0076] In a preferred embodiment, the thickness of the Ta adhesion layer can be 10-20 nm, and the thickness of the TaN barrier layer can be 30-100 nm.

[0077] Step S5: Form a functional layer in the trench connecting the two electrodes; wherein the functional layer includes an oxide layer of electrode metal formed on the opposite sidewall surfaces of the two electrodes, and metal oxide nanowires connecting the oxide layers.

[0078] In a preferred embodiment, the metal oxide nanowire 16 may be a copper oxide nanowire 16'.

[0079] In a preferred embodiment, a functional layer 17 connecting the two electrodes 12 is formed in the trench 18, which may specifically include the following steps:

[0080] Step S51: At room temperature, add thioglycerol to an aqueous solution of copper acetate and stir to form a mixed solution.

[0081] In a preferred embodiment, two solutions, copper acetate aqueous solution and sodium hydroxide aqueous solution, can be prepared separately.

[0082] For example, a 0.5M aqueous solution of copper acetate and a 5M aqueous solution of sodium hydroxide can be prepared separately.

[0083] Then, for example, 1 μL of thioglycerol can be added to an aqueous solution of copper acetate and stirred at room temperature for, for example, 5 min to form a mixed solution.

[0084] Step S52: Pour the sodium hydroxide aqueous solution into the mixed solution, and continue stirring after adding water to obtain a suspension containing copper oxide nanowires 16'.

[0085] Subsequently, an aqueous solution of sodium hydroxide was poured into the above mixed solution, and an appropriate amount of water was immediately added. Stirring was continued for, for example, 5 minutes, to prepare a suspension containing copper oxide nanowires 16'.

[0086] Step S53: Drop the suspension into the trench 18 and dry it to form a copper oxide layer 15' on the opposite sidewall surface of the two electrodes 12. Then, fuse the dried copper oxide nanowires 16' with the copper oxide layer 15' to form a functional layer 17 connecting the two electrodes 12.

[0087] Please see Figure 7 In a preferred embodiment, a dropper 19 can be used to drop the obtained suspension into the trench 18 of the device structure obtained in step S4, and the suspension can be heated below 100°C for example for 12 hours to completely dry the suspension, resulting in dried CuO nanowires 16'. Furthermore, the drying process oxidizes the Cu on the opposing sidewall surfaces of the two copper electrodes 12, forming a CuO layer 15' on the opposing sidewall surfaces of the two copper electrodes 12. This allows the CuO layer 15' to fuse with the CuO nanowires 16' during formation, resulting in better bonding between the CuO nanowires 16' and the two copper electrodes 12. Thus, a novel functional layer 17, composed of CuO nanowires 16' and the CuO layer 15', and connected to the two copper electrodes 12, is formed between the two copper electrodes 12, such as... Figure 8 As shown.

[0088] In summary, this invention utilizes a room-temperature chemical method to fabricate a sensing and memory computing device based on a flexible substrate 10 and CuO nanowires 16'. This device is more compatible with biological systems in terms of physical morphology and avoids the problem of deformation of the flexible substrate 10 under high-temperature conditions. It is suitable for novel wearable systems and research on novel low-power devices, and is expected to be applied in the manufacturing of wearable sensing and memory computing devices in the future. It has advantages such as simple fabrication method, compatibility with low-temperature CMOS processes, and easy testing of device electrical characteristics.

[0089] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A sensing and computing device based on a flexible substrate, characterized in that, include: Flexible substrate; Two electrodes are arranged side by side on the substrate, and a lower adhesion and barrier layer is respectively provided on the lower surface of the two electrodes. A trench is formed between the opposite sidewalls of the two electrodes and between the opposite sidewalls of the two lower adhesion and barrier layers. A functional layer connecting the two electrodes; The functional layer includes metal oxide nanowires connected between the two electrodes. The metal oxide nanowires are located in the trench and bridge the opposite sidewalls of the two electrodes.

2. The inductive computing device based on a flexible substrate according to claim 1, characterized in that, The functional layer further includes an oxide layer of the electrode metal formed on the opposing sidewall surfaces of the two electrodes, the oxide layer of the electrode metal being connected to the metal oxide nanowire.

3. The inductive computing device based on a flexible substrate according to claim 2, characterized in that, The electrode metal includes copper, and the metal oxide nanowires include copper oxide nanowires.

4. The inductive computing device based on a flexible substrate according to claim 1, characterized in that, An upper adhesion and a barrier layer are respectively provided on the upper surface of the two electrodes, and a window is formed between the two upper adhesion and barrier layers to connect the functional layer with the outside.

5. A method for fabricating a sensing and memory computing device based on a flexible substrate, characterized in that, include: Provide flexible substrates; Two parallel-arranged under-adhesion and barrier layers are formed on the substrate; An electrode is formed on each of the two lower adhesion and barrier layers, such that a trench is formed between the opposite sidewalls of the two electrodes and between the opposite sidewalls of the two lower adhesion and barrier layers. An upper adhesion and barrier layer is formed on each of the two electrodes, thereby forming a window communicating with the trench on the electrode between the two upper adhesion and barrier layers; A functional layer is formed in the trench connecting the two electrodes; wherein the functional layer includes an oxide layer of electrode metal formed on the opposing sidewall surfaces of the two electrodes, and metal oxide nanowires connecting the oxide layers.

6. The method for fabricating a sensing and memory computing device based on a flexible substrate according to claim 5, characterized in that, The electrode metal is copper, the oxide layer is a copper oxide layer, and the metal oxide nanowires are copper oxide nanowires.

7. The method for fabricating a sensing and memory computing device based on a flexible substrate according to claim 6, characterized in that, The formation of a functional layer connecting the two electrodes in the trench specifically includes: At room temperature, thioglycerol is added to an aqueous solution of copper acetate and stirred to form a mixed solution; An aqueous solution of sodium hydroxide was poured into the mixed solution, and stirring was continued after adding water to obtain a suspension containing copper oxide nanowires; The suspension is dropped into the trench and dried to form a copper oxide layer on the opposite sidewall surfaces of the two electrodes. The dried copper oxide nanowires are then fused with the copper oxide layer to form a functional layer connecting the two electrodes.

8. The method for fabricating a sensing and memory computing device based on a flexible substrate according to claim 7, characterized in that, The drying temperature is less than or equal to 100°C.

9. The method for fabricating a sensing and memory computing device based on a flexible substrate according to claim 5, characterized in that, The lower adhesion and barrier layer, the electrode, and the upper adhesion and barrier layer are formed using ultraviolet lithography and physical vapor deposition techniques.

Images