Flexible field effect transistor and preparation method thereof

Abstract

The invention provides a flexible field effect transistor and a preparation method thereof. The flexible field effect transistor comprises a flexible insulating substrate, a liquid source electrode, a liquid drain electrode, an ionic liquid dielectric layer, a semiconductor active layer and a gate electrode, the liquid source electrode, the liquid drain electrode, the ionic liquid dielectric layer, the semiconductor active layer and the gate electrode are all located on the upper surface of the flexible insulating substrate. Wherein the two ends of the semiconductor active layer are respectively connected with the liquid source electrode and the liquid drain electrode, the middle part of the semiconductor active layer is connected with the ionic liquid dielectric layer, and the bottom surface of the semiconductor active layer is tightly attached to the assembling surface of the flexible insulating substrate. The liquid material is utilized to manufacture the contact so as to construct the field effect transistor, so that the flexibility is greatly improved, and performance change caused by bending is avoided. And meanwhile, the liquid conductive material greatly improves the healing property of the circuit, and the performance of the device can be quickly recovered after deformation.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor optoelectronic devices, and in particular to a flexible field effect transistor and a preparation method thereof. Background Art

[0002] In the related technology, Flexible Field-Effect Transistor (Flex-FET) technology is a new semiconductor technology based on the principle of field effect transistor (FET). It manufactures transistors on flexible, curved or stretchable substrates, thereby achieving greater flexibility and plasticity in the shape of electronic devices. The basic structure of a typical field effect transistor device includes an active layer, a dielectric layer, a substrate and an electrode. In order to make the device flexible, the components of the field effect transistor are often required to have a certain degree of flexibility, and the performance will not be greatly affected when deformation occurs. Common flexible field effect transistors generally use flexible substrates or paper substrates, use materials such as metal oxides, conductive polymers or carbon nanotubes as active layers, and use inorganic substances, polymers or electrolytes as dielectric layers.

[0003] However, even though traditional solid flexible field effect transistors have good flexibility, their performance will eventually change partially when they are highly deformed, and there is a deformation limit. Active layer dielectric materials that meet the flexibility requirements are also scarce. At the same time, the recovery rate and circuit healing rate of solid field effect transistors when they are deformed and restored to their original shape are also lacking. Summary of the invention

[0004] The present invention provides a flexible field effect tube and a preparation method thereof, which are used to solve the defects existing in the prior art and achieve the following technical effects: the field effect tube is made of liquid material, so that the flexibility is greatly improved and the performance will not change due to bending. At the same time, the liquid conductive material greatly improves the circuit healing property, and the device can quickly restore its performance after deformation.

[0005] The flexible field effect transistor according to the first embodiment of the present invention comprises a flexible insulating substrate, a liquid source electrode, a liquid drain electrode, an ionic liquid dielectric layer, a semiconductor active layer and a gate electrode; The liquid source electrode and the liquid drain electrode are arranged on the assembly surface of the flexible insulating substrate at intervals, and the ionic liquid dielectric layer is also installed on the assembly surface of the flexible insulating substrate and is located between the liquid source electrode and the liquid drain electrode; the gate electrode is installed on the assembly surface of the flexible insulating substrate and is connected to the ionic liquid dielectric layer; The two ends of the semiconductor active layer are respectively connected to the liquid source and the liquid drain, and the middle part thereof is connected to the ionic liquid dielectric layer. The bottom surface of the semiconductor active layer is arranged in close contact with the assembly surface of the flexible insulating substrate.

[0006] According to one embodiment of the present invention, the liquid source and the liquid drain are both made of gallium-indium-tin alloy, the ionic liquid dielectric layer is a liquid with ion conductivity and electronic insulation, and the semiconductor active layer is a semiconductor material suitable for liquid environment.

[0007] According to an embodiment of the present invention, the flexible insulating substrate is made of polydimethylsiloxane (PDMS) material.

[0008] According to an embodiment of the present invention, a layer of metal material is pre-deposited on the assembly surface of the flexible insulating substrate before covering the flow channel to form the gate electrode, and the material of the gate electrode can be gold, silver or copper; Alternatively, the gate electrode material may also be liquid metal. In this case, after the flexible insulating substrate covers the flow channel, a mixture of liquid metal and ionic liquid will be injected into the dielectric layer flow channel together.

[0009] A method for preparing a flexible field effect transistor according to an embodiment of the second aspect of the present invention comprises: Step S1, photolithography a mold of a source electrode, a drain electrode and a dielectric layer on a silicon wafer, wherein the source electrode and the drain electrode are respectively located on two sides of the dielectric layer; Step S2, using a flexible insulating material to contact the mold of the source electrode, the drain electrode and the dielectric layer, applying pressure, and then separating to obtain a remolding mold, at which a source electrode flow channel, a drain electrode flow channel and a dielectric layer flow channel are formed on the remolding mold; Step S3, aligning and bonding the mold over the flexible insulating substrate pre-prepared with the semiconductor active layer; Step S4, after evacuating in a closed environment, injecting liquid metal into the source channel and the drain channel to form the liquid source and liquid drain respectively, and injecting an ionic liquid dielectric layer into the dielectric layer channel to form an ionic liquid dielectric layer.

[0010] According to one embodiment of the present invention, in step S2, it further includes: A source injection hole, a drain injection hole and a dielectric layer injection hole are arranged on the mold remodeling die, which are connected to the source flow channel, the drain flow channel and the dielectric layer flow channel respectively, for subsequent injection of liquid materials.

[0011] According to one embodiment of the present invention, a temporary rigid substrate is attached under the flexible insulating substrate, and the temporary rigid substrate is a silicon wafer and is used to protect the bottom surface of the flexible insulating substrate from contamination; wherein the material selected for the flexible insulating substrate is PDMS, and a semiconductor active layer and a gate electrode are arranged on the flexible insulating substrate.

[0012] According to one embodiment of the present invention, before step S3, the method further includes: The semiconductor active layer and the gate electrode are transferred to the flexible insulating substrate respectively by a mechanical peeling method using a flexible insulating material, and the gate electrode is located near the semiconductor active layer.

[0013] According to an embodiment of the present invention, in step S3, it specifically includes: Use a microscope to assist in placing the mold on the flexible insulating substrate so that the semiconductor active layer corresponds to the positions of the source flow channel, the drain flow channel and the dielectric layer flow channel respectively, and the semiconductor active layer is located between the source flow channel and the drain flow channel and in contact with the dielectric layer flow channel; and the gate electrode corresponds to the position of the dielectric layer flow channel, and the gate electrode is in contact with the dielectric layer flow channel.

[0014] According to an embodiment of the present invention, in step S4, it specifically includes: The entire product is placed in a closed environment and evacuated, and the liquid metal and ionic liquid are respectively injected into the injection holes of the corresponding flow channels. The entire product is then transferred to the air, and the liquid metal and ionic liquid are pressed into the flow channel using air pressure to complete the preparation of the flexible field effect tube.

[0015] The present invention provides a flexible field effect tube, which has at least the following advantages compared with the related art.

[0016] (1) Improved flexibility: Even though traditional solid flexible field effect transistors have good flexibility, their performance will decline under high deformation and there is a deformation limit. The present invention uses all-liquid materials to greatly improve the flexibility of the device, allowing it to maintain stable performance under high deformation conditions.

[0017] (2) Enhanced recovery ability: Field effect transistors made of liquid materials can quickly recover their original performance after deformation, solving the problem of slow recovery rate of solid field effect transistors when they return to their original shape after deformation.

[0018] (3) Optimizing material selection: Traditional solid flexible field effect transistors face limitations in selecting active layer and dielectric layer materials. The present invention uses gallium indium tin alloy as liquid metal electrode and ionic liquid as dielectric layer. These materials not only have good conductivity but are also easy to process and integrate.

[0019] (4) Improved electrical properties: The all-liquid design can maintain stable electrical properties under high deformation conditions, solving the problem of decreased performance such as mobility of the active layer and dielectric layer under high deformation.

[0020] (5) Simplified production process: The use of reverse molding technology instead of traditional etching methods simplifies the production process, reduces the manufacturing difficulty, and makes large-scale production possible.

[0021] (6) Enhanced application scenarios: Due to its excellent flexibility and recovery ability, the flexible field effect transistor of the present invention is suitable for a wider range of flexible electronic devices, such as wearable sensors, foldable displays, etc., especially in application scenarios that require high flexibility and fast recovery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 It is a structural schematic diagram of the flexible field effect tube provided by the present invention.

[0024] Figure 2 It is a structural schematic diagram of a mold turning die in the preparation of a flexible field effect tube provided by the present invention.

[0025] Figure 3 It is a structural schematic diagram of a flexible insulating substrate and a temporary rigid substrate in the preparation of a flexible field effect transistor provided by the present invention.

[0026] Figure 4 It is a schematic diagram of the structure of the flexible field effect tube provided by the present invention during the preparation process.

[0027] Figure 5 It is a schematic diagram of the steps of the method for preparing the flexible field effect tube provided by the present invention.

[0028] Reference numerals: 1. Flexible insulating substrate; 11. Assembly surface; 2. Liquid source; 3. Liquid drain; 4. Ionic liquid dielectric layer; 5. Semiconductor active layer; 6. Gate electrode; 71. Source channel; 72. Drain channel; 73. Dielectric layer channel; 81. Source injection hole; 82. Drain injection hole; 83. Dielectric layer injection hole; 9. Overmolding mold; 10. Temporary rigid substrate. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0031] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0032] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0033] A flexible field effect transistor and a method for preparing the same provided by the present invention are described below with reference to the accompanying drawings.

[0034] like Figure 1 As shown, the flexible field effect transistor according to the first embodiment of the present invention includes a flexible insulating substrate 1, a liquid source 2, a liquid drain 3, an ionic liquid dielectric layer 4, a semiconductor active layer 5 and a gate electrode 6.

[0035] The liquid source 2 and the liquid drain 3 are arranged at intervals on the assembly surface 11 of the flexible insulating substrate 1, and the ionic liquid dielectric layer 4 is also installed on the assembly surface 11 of the flexible insulating substrate 1 and is located between the liquid source 2 and the liquid drain 3; the gate electrode 6 is installed on the assembly surface 11 of the flexible insulating substrate 1 and is connected to the ionic liquid dielectric layer 4.

[0036] The two ends of the semiconductor active layer 5 are respectively connected to the liquid source 2 and the liquid drain 3 , and the middle part thereof is connected to the ionic liquid dielectric layer 4 . The bottom surface of the semiconductor active layer 5 is arranged closely against the mounting surface 11 of the flexible insulating substrate 1 .

[0037] The following is a detailed explanation of the various components within the flexible field effect tube.

[0038] The flexible insulating substrate 1 provides a basic supporting platform for the entire field effect tube and gives the field effect tube a flexible characteristic. Its purpose and utility are: providing structural support and electrical isolation. The flexible insulating substrate 1 usually uses a material with flexibility and good insulating properties, such as polydimethylsiloxane (PDMS). Among them, the liquid source 2, the liquid drain 3, the ionic liquid dielectric layer 4, the gate electrode 6 and the semiconductor active layer 5 are all installed on the assembly surface 11 of the flexible insulating substrate 1.

[0039] The liquid source 2 and the liquid drain 3 are arranged at intervals on the mounting surface 11 of the flexible insulating substrate 1, and are made of liquid metal material. The commonly used material of the liquid source 2 and the liquid drain 3 is gallium indium tin alloy, which has good electrical conductivity and fluidity. The liquid source 2 and the liquid drain 3 are connected to the two ends of the semiconductor active layer 5, and their use and utility are: as the input and output ports of the current, and also as part of the current transmission path.

[0040] The ionic liquid dielectric layer 4 is mounted on the mounting surface 11 of the flexible insulating substrate 1, and is located between the liquid source 2 and the liquid drain 3. The selected material is usually a conductive liquid, which can be an ionic liquid containing components such as quaternary ammonium salts or imidazole salts. Specifically, the ionic liquid dielectric layer 4 is connected to the middle part of the gate electrode 6 and the semiconductor active layer 5. It serves as a dielectric layer to isolate the source and the drain, and can control the carrier concentration in the semiconductor active layer 5 under the action of the gate electrode 6.

[0041] The two ends of the semiconductor active layer 5 are respectively connected to the liquid source 2 and the liquid drain 3, and the middle part is connected to the ionic liquid dielectric layer 4. The bottom surface of the semiconductor active layer 5 is in close contact with the assembly surface 11 of the flexible insulating substrate 1. The semiconductor active layer 5 can be a semiconductor material suitable for use in a liquid environment, such as silicon, germanium or other suitable semiconductor materials, and its use and utility are: as a carrier transmission channel, its conductivity is controlled by the gate electrode 6.

[0042] The gate electrode 6 is mounted on the mounting surface 11 of the flexible insulating substrate 1 and connected to the ionic liquid dielectric layer 4. The gate electrode 6 is usually made of a metal material with good conductivity, such as gold, silver or copper. The gate electrode 6 controls the carrier concentration in the semiconductor active layer 5 by applying a voltage, thereby controlling the switching state of the field effect tube.

[0043] Furthermore, the working principle and working process of the flexible field effect tube based on the above structure are as follows.

[0044] (1) Initial state: In the absence of an external voltage, the semiconductor active layer 5 is in a high resistance state, no current flows between the source and the drain, and the field effect transistor is turned off.

[0045] (2) Applying voltage: When a voltage is applied to the gate electrode 6 through an external power source, the electric field generated by the gate electrode 6 will affect the ion distribution in the ionic liquid dielectric layer 4. Ions with a polarity opposite to the applied voltage will approach one side of the gate electrode 6, while ions with the same polarity will gather on the other side to form an electric field.

[0046] (3) Change in carrier concentration: Due to the existence of the electric field, the carrier concentration inside the semiconductor active layer 5 will change, causing the semiconductor active layer 5 to change to a low resistance state.

[0047] (4) Current flows: At this time, the semiconductor active layer 5 between the liquid source 2 and the liquid drain 3 becomes a conductive path, and the current can flow from the liquid source 2 to the liquid drain 3, and the field effect transistor is turned on.

[0048] (5) Removing voltage: When the voltage on the gate electrode 6 is removed or the voltage direction is reversed, the carrier concentration inside the semiconductor active layer 5 returns to its initial state or drops sharply, and the semiconductor active layer 5 becomes a high resistance state again, preventing current from passing through, and the field effect transistor is turned off.

[0049] In summary, the flexible field effect transistor is made of all-liquid materials, which not only greatly improves the flexibility and deformation recovery ability of the device, but also enables the device to quickly restore normal performance after deformation. It is very suitable for applications that require high flexibility and fast recovery performance.

[0050] In the related technology, Flexible Field-Effect Transistor (Flex-FET) technology is a new semiconductor technology based on the principle of field effect transistor (FET). It manufactures transistors on flexible, curved or stretchable substrates, thereby achieving greater flexibility and plasticity in the shape of electronic devices. The basic structure of a typical field effect transistor device includes an active layer, a dielectric layer, a substrate and an electrode. In order to make the device flexible, the components of the field effect transistor are often required to have a certain degree of flexibility, and the performance will not be greatly affected when deformation occurs. Common flexible field effect transistors generally use flexible substrates or paper substrates, use materials such as metal oxides, conductive polymers or carbon nanotubes as active layers, and use inorganic substances, polymers or electrolytes as dielectric layers.

[0051] However, even though traditional solid flexible field effect transistors have good flexibility, their performance will eventually change partially when they are highly deformed, and there is a deformation limit. Active layer dielectric materials that meet the flexibility requirements are also scarce. At the same time, the recovery rate and circuit healing rate of solid field effect transistors when they are deformed and restored to their original shape are also lacking.

[0052] In summary, in order to solve the technical defects existing in the above-mentioned related technologies, the present invention provides a flexible field effect transistor, which has at least the following advantages compared with the related technologies.

[0053] (1) Improved flexibility: Even though traditional solid flexible field effect transistors have good flexibility, their performance will decline under high deformation and there is a deformation limit. The present invention uses all-liquid materials to greatly improve the flexibility of the device, allowing it to maintain stable performance under high deformation conditions.

[0054] (2) Enhanced recovery ability: Field effect transistors made of liquid materials can quickly recover their original performance after deformation, solving the problem of slow recovery rate of solid field effect transistors when they return to their original shape after deformation.

[0055] (3) Optimizing material selection: Traditional solid flexible field effect transistors face limitations in selecting active layer and dielectric layer materials. The present invention uses gallium indium tin alloy as liquid metal electrode and ionic liquid as dielectric layer. These materials not only have good conductivity but are also easy to process and integrate.

[0056] (4) Improved electrical properties: The all-liquid design can maintain stable electrical properties under high deformation conditions, solving the problem of decreased performance such as mobility of the active layer and dielectric layer under high deformation.

[0057] (5) Simplified production process: The use of reverse molding technology instead of traditional etching methods simplifies the production process, reduces the manufacturing difficulty, and makes large-scale production possible.

[0058] (6) Enhanced application scenarios: Due to its excellent flexibility and recovery ability, the flexible field effect transistor of the present invention is suitable for a wider range of flexible electronic devices, such as wearable sensors, foldable displays, etc., especially in application scenarios that require high flexibility and fast recovery performance.

[0059] like Figure 1 As shown, according to some embodiments of the present invention, the liquid source 2 and the liquid drain 3 are both made of gallium-indium-tin alloy, the ionic liquid dielectric layer 4 is a liquid with ion conductivity and electronic insulation, and the semiconductor active layer 5 is a semiconductor material suitable for liquid environment.

[0060] It can be understood that the liquid source 2 and the liquid drain 3 are made of a gallium-indium-tin alloy, which has good electrical conductivity and fluidity and can serve as an input and output node of current in a flexible field effect transistor.

[0061] Ionic liquid is a conductive liquid used to form an isolation layer between the source and drain electrodes, and also acts as a charge transfer medium to participate in the regulation of carrier concentration. The semiconductor active layer 5 is made of a semiconductor material suitable for use in a liquid environment, and its function is to change its own conductivity under the influence of the gate electric field, thereby controlling the current between the source and drain electrodes.

[0062] In this way, through the selection and design of the above-mentioned materials, the flexible field effect transistor of the present invention not only has excellent flexibility and deformation recovery ability, but also can maintain stable electrical properties in the deformed state. It is suitable for application scenarios with high requirements on flexibility and deformation recovery rate, such as wearable devices, foldable displays, etc.

[0063] like Figure 1 As shown, according to some embodiments of the present invention, the flexible insulating substrate 1 is made of polydimethylsiloxane (PDMS) material.

[0064] In this way, the flexible insulating substrate 1 of the flexible field effect transistor is made of polydimethylsiloxane (PDMS) material, which gives the substrate excellent flexibility and chemical stability while providing good insulation performance.

[0065] According to some embodiments of the present invention, before covering the flow channel, a layer of metal material is pre-deposited on the assembly surface 11 of the flexible insulating substrate 1 to form a gate electrode 6, and the material of the gate electrode 6 can be gold, silver or copper. Such a design ensures that the gate electrode 6 can effectively control the carrier concentration in the semiconductor active layer 5 when a voltage is applied, thereby achieving effective regulation of the switching state of the flexible field effect tube.

[0066] Alternatively, in some other embodiments, the gate electrode 6 may also be made of liquid metal. In this case, after the flexible insulating substrate 1 covers the flow channel, a mixture of liquid metal and ionic liquid will be injected into the dielectric layer flow channel 73 together.

[0067] like Figures 2 to 5 As shown, the method for preparing a flexible field effect transistor according to the second aspect of the present invention includes: Step S1, photolithography a mold of a source electrode, a drain electrode and a dielectric layer on a silicon wafer, wherein the source electrode and the drain electrode are respectively located on two sides of the dielectric layer; Step S2, using a flexible insulating material to contact the source, drain and dielectric layer molds and apply pressure, and then separate to obtain a mold re-molding mold 9, at which a source channel 71, a drain channel 72 and a dielectric layer channel 73 are formed on the mold re-molding mold 9; Step S3, aligning and bonding the mold 9 to the flexible insulating substrate 1 on which the semiconductor active layer 5 is pre-prepared; Step S4 , after evacuating the vacuum in a closed environment, inject liquid metal into the source channel 71 and the drain channel 72 to form a liquid source 2 and a liquid drain 3 respectively, and inject the ionic liquid dielectric layer 4 into the dielectric layer channel 73 to form an ionic liquid dielectric layer 4 .

[0068] It can be understood that based on the above preparation method, the preparation process of the flexible field effect transistor is as follows: first, a photolithography process is performed on the silicon wafer to produce a source, a drain and a dielectric layer, wherein the source and the drain are located on both sides of the dielectric layer. This step provides a template for the subsequent production of the mold 9. Then, a flexible insulating material (such as PDMS) is used to contact and pressurize the source, drain and dielectric layer on the silicon wafer, and then the mold 9 is separated. At this time, flow channels corresponding to the source, drain and dielectric layer will be formed on the mold 9, namely, the source flow channel 71, the drain flow channel 72 and the dielectric layer flow channel 73. The mold 9 obtained in the above steps is fixed on a flexible insulating substrate 1 (such as a substrate made of PDMS material) pre-prepared with a semiconductor active layer 5, to prepare for the next step of injecting liquid material.

[0069] Finally, vacuum is drawn in a closed environment to remove possible bubbles and other impurities, and then liquid metal (such as gallium indium tin alloy) is injected into the source channel 71 and the drain channel 72 in the mold 9 to form a liquid source 2 and a liquid drain 3. At the same time, a conductive ionic liquid is injected into the dielectric layer channel 73 to form an ionic liquid dielectric layer 4.

[0070] Through the above steps, a fully liquid flexible field effect transistor is finally formed. This method utilizes the fluidity of liquid metal and ionic liquid and the flexibility of PDMS material, so that the produced field effect transistor not only has good flexibility and deformation recovery ability, but also can quickly restore its performance after deformation.

[0071] According to some embodiments of the present invention, step S2 further includes: providing a source injection hole 81, a drain injection hole 82 and a dielectric layer injection hole 83 on the mold remanufacturing mold 9, which are respectively connected to the source flow channel 71, the drain flow channel 72 and the dielectric layer flow channel 73, for subsequent injection of liquid materials.

[0072] In this embodiment, in step S2, in addition to using a flexible insulating material (such as PDMS) to contact and pressurize the source, drain and dielectric layer on the silicon wafer to separate them to obtain the overmolding mold 9, it also includes providing small holes on the overmolding mold 9 that are respectively connected to the source flow channel 71, the drain flow channel 72 and the dielectric layer flow channel 73, namely the source injection hole 81, the drain injection hole 82 and the dielectric layer injection hole 83, for the subsequent injection of liquid materials.

[0073] Specifically, the small holes formed on the mold 9 are to facilitate the injection of liquid metal and ionic liquid dielectric layer 4 in the subsequent steps. The design of these small holes ensures that the liquid material can be accurately injected into the specified flow channel, thereby forming the required liquid source 2, liquid drain 3 and ionic liquid dielectric layer 4. In this way, material dislocation or other adverse conditions during the injection process can be effectively avoided, ensuring the quality and performance of the flexible field effect tube.

[0074] like Figure 3 As shown, according to some embodiments of the present invention, a temporary rigid substrate 10 is attached below the flexible insulating substrate 1, and the temporary rigid substrate 10 is a silicon wafer and is used to protect the bottom surface of the flexible insulating substrate 1 from contamination; wherein the flexible insulating substrate 1 is made of PDMS, and a semiconductor active layer 5 and a gate electrode 6 are arranged on the flexible insulating substrate 1. The flexible insulating substrate 1 can also be replaced by other flexible materials.

[0075] It can be understood that the temporary rigid substrate 10 plays a supporting role in the manufacturing process and can protect the bottom surface of the flexible insulating substrate 1 from contamination. This not only ensures sufficient support and flatness during the manufacturing process, but also allows the final flexible field effect transistor to have better flexibility and applicability to adapt to different application scenarios. In this way, the convenience of the production process is guaranteed, while taking into account the final flexibility and portability of the product.

[0076] like Figure 3 As shown, according to some embodiments of the present invention, before step S3, it also includes: using a flexible insulating material to transfer the semiconductor active layer 5 and the gate electrode 6 to the flexible insulating substrate 1 according to a mechanical stripping method, and making the gate electrode 6 located in addition to the semiconductor active layer 5.

[0077] In this embodiment, a flexible insulating material (such as PDMS) is used to transfer the semiconductor active layer 5 to the flexible insulating substrate 1 according to the mechanical peeling method. Here, the semiconductor active layer 5 refers to a semiconductor material that works in a liquid environment, which is located between the source and the drain, and is in contact with the ionic liquid dielectric layer 4. In addition, the gate electrode 6 is also fixed to the flexible insulating substrate 1 using a flexible insulating material, but this time the gate electrode 6 is located near the semiconductor active layer 5. The gate electrode 6 is used to control the carrier concentration in the semiconductor active layer 5, thereby determining the switching state of the field effect tube.

[0078] These two steps ensure the correct position of the semiconductor active layer 5 and the gate electrode 6 in the final structure, thereby ensuring the normal operation of the flexible field effect transistor. In this way, the performance of the device can be effectively controlled and it can be ensured that in the subsequent preparation process, the various components can be assembled according to the predetermined design.

[0079] According to some embodiments of the present invention, in step S3, it specifically includes: using a microscope to assist in placing the mold 9 on the flexible insulating substrate 1, so that the semiconductor active layer 5 corresponds to the positions of the source flow channel 71, the drain flow channel 72 and the dielectric layer flow channel 73 respectively, and the semiconductor active layer 5 is located between the source flow channel 71 and the drain flow channel 72 and in contact with the dielectric layer flow channel 73; and making the gate electrode 6 correspond to the position of the dielectric layer flow channel 73, and the gate electrode 6 is in contact with the dielectric layer flow channel 73.

[0080] In this embodiment, in step S3, the following steps are specifically included: (1) Placement of the mold 9: Use a microscope to assist in placing the mold 9 on the flexible insulating substrate 1. The mold 9 mentioned here is made on a silicon wafer through photolithography and other processes, and a source channel 71, a drain channel 72 and a dielectric layer channel 73 are formed on the mold 9. With the help of a microscope, the mold 9 can be placed in the correct position very accurately to ensure that the semiconductor active layer 5 is aligned with the channel position on the mold 9. (2) Position correspondence: When placing the mold 9, ensure that the semiconductor active layer 5 corresponds to the position of the source channel 71, the drain channel 72 and the dielectric layer channel 73 on the mold 9 respectively. This means that the semiconductor active layer 5 should be located between the source channel 71 and the drain channel 72 on the mold 9 and in contact with the dielectric layer channel 73. (3) Alignment of the gate electrode 6: At the same time, it is also necessary to ensure that the position of the gate electrode 6 corresponds to the dielectric layer flow channel 73 on the mold turning mold 9, that is, the gate electrode 6 is in contact with the dielectric layer flow channel 73.

[0081] In this way, with the help of a microscope, the placement accuracy of the mold 9 can be ensured, so that the semiconductor active layer 5 and the gate electrode 6 can be accurately aligned with the flow channel on the mold 9, ensuring that the flexible field effect tube finally manufactured has the correct structure and function. This series of operation steps ensures that the device can form the correct liquid source 2, liquid drain 3 and ionic liquid dielectric layer 4 when the liquid material is subsequently injected, and ensures that the gate electrode 6 can effectively control the carrier concentration in the semiconductor active layer 5, thereby realizing the switch control of the field effect tube.

[0082] According to some embodiments of the present invention, in step S4, specifically including: placing the entire product in a closed environment and evacuating the environment, and injecting liquid metal and ionic liquid into the injection holes of the corresponding flow channels respectively, and then transferring the entire product into the air, and using air pressure to press the liquid metal and ionic liquid into the flow channel to complete the preparation of the flexible field effect transistor.

[0083] In this embodiment, specifically, the entire product is placed in a closed environment and subjected to a vacuum treatment. The purpose of vacuuming is to remove impurities in the air, ensure the purity of the liquid metal and ionic liquid during injection, and avoid the introduction of unnecessary pollutants.

[0084] Liquid metal and ionic liquid are respectively injected into the source channel 71, drain channel 72 and dielectric layer channel 73 on the mold overmolding mold 9 through the pre-set injection holes. This step ensures that the liquid metal can be accurately filled into the source and drain positions, while the ionic liquid is filled into the dielectric layer position.

[0085] Then, after the liquid material is injected, the entire product is transferred from the closed vacuum environment to the air. At this time, the liquid metal and ionic liquid are pressed into the corresponding flow channels using air pressure. The role of air pressure is to help the liquid material fill the flow channel evenly and ensure that there are no gaps, thereby ensuring the performance and quality of the final product.

[0086] Finally, through the above steps, the preparation of the flexible field effect transistor is completed. At this point, the liquid source 2, the liquid drain 3 and the ionic liquid dielectric layer 4 have been accurately fixed in the flow channel of the mold 9 and have formed a correct connection relationship with the semiconductor active layer 5.

[0087] In this way, through the above steps, it is ensured that the liquid material can be accurately injected into the predetermined position, and with the help of air pressure, the liquid material can be evenly filled into the flow channel, thereby ensuring the good performance and reliability of the flexible field effect tube.

[0088] A specific embodiment of a flexible field effect transistor and a method for preparing the same is provided below with reference to the accompanying drawings.

[0089] like Figures 1 to 5 As shown, the present invention designs a fully liquid flexible field effect tube, and uses the method of reverse molding to make a fully liquid flexible field effect tube using gallium indium tin alloy and MoS2 semiconductor materials. Conventional field effect tubes, whether rigid or flexible, are made of solid materials, while the present invention uses fully liquid materials to make field effect tubes. Because liquid has fluidity, the usual etching method cannot be used during production. Instead, the flow channel for storing liquid metal and ionic liquid electrodes is first molded out with insulating flexible materials to complete the production.

[0090] First, electrodes are photolithographically formed on a silicon wafer. Figure 1 The two sides are liquid metal areas, and the middle is an ionic liquid area. Then, the flexible PDMS material is used to contact the electrodes and pressurize them to obtain a mold 9. Figure 2 As shown, small holes are punched at the corresponding positions of the grooves on the mold 9 for subsequent injection of liquid materials. The subsequent production is completed on the substrate. Figure 3 A flexible insulating substrate 1 is placed on the silicon wafer. First, MoS2 is glued to the flexible insulating substrate 1 using PDMS as the semiconductor part of the field effect transistor, and the gate electrode 6 is glued to some position below the MoS2 using PDMS for powering the ionic liquid later.

[0091] After completing the production of each part, the field effect transistor can be produced. First, place the PDMS with the electrode flow channel molded out on the flexible insulating substrate 1 under a microscope. It is necessary to ensure that MoS2 is exactly between the liquid metal electrodes on both sides, and the ionic liquid flow channel in the middle is in contact with the metal electrode. Then put the entire product in a closed environment and evacuate it. Drop the liquid metal and ionic liquid on the corresponding through holes of the flow channel respectively. Then transfer the entire device to the air, and use air pressure to press the two liquid materials into the flow channel to complete the process. Figure 4 Fabrication of all-liquid field effect transistors.

[0092] This field effect transistor relies on the electric field of the gate metal electrode to control the movement of ions in the semiconductor material to achieve switching. Figure 5 As shown, the main principle is that when a voltage is applied to the gate electrode 6 through an external power supply, the ions in the ionic liquid dielectric layer 4 in the field effect tube with the opposite polarity to the applied voltage will approach one side of the gate electrode 6, so that more ions with the same polarity as the applied voltage accumulate on the other side and form an electric field. Under the influence of the electric field, the concentration of carriers in the semiconductor active layer 5 will increase, and the semiconductor active layer 5 will be converted to a low resistance state. The source and drain on both sides are connected together through the semiconductor active layer 5, and the field effect tube is turned on and is in a working state. When the voltage on the gate electrode 6 is removed, the electric field affecting the semiconductor active layer 5 disappears, and the semiconductor active layer 5 is in a high resistance state, and the field effect tube is turned off.

[0093] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flexible field effect transistor, characterized in that: It includes a flexible insulating substrate, a liquid source electrode, a liquid drain electrode, an ionic liquid dielectric layer, a semiconductor active layer and a gate electrode; The liquid source electrode and the liquid drain electrode are arranged on the assembly surface of the flexible insulating substrate at intervals, and the ionic liquid dielectric layer is also installed on the assembly surface of the flexible insulating substrate and is located between the liquid source electrode and the liquid drain electrode; the gate electrode is installed on the assembly surface of the flexible insulating substrate and is connected to the ionic liquid dielectric layer; The two ends of the semiconductor active layer are respectively connected to the liquid source and the liquid drain, and the middle part thereof is connected to the ionic liquid dielectric layer. The bottom surface of the semiconductor active layer is arranged in close contact with the assembly surface of the flexible insulating substrate.

2. The flexible field effect transistor according to claim 1, characterized in that: The liquid source and the liquid drain are both made of gallium-indium-tin alloy, the ionic liquid dielectric layer is a liquid with ion conductivity and electronic insulation, and the semiconductor active layer is a semiconductor material suitable for liquid environment.

3. The flexible field effect transistor according to claim 1, characterized in that: The flexible insulating substrate is made of polydimethylsiloxane (PDMS) material.

4. The flexible field effect transistor according to claim 3, characterized in that: Before covering the flow channel, a layer of metal material is pre-deposited on the assembly surface of the flexible insulating substrate to form the gate electrode, and the material of the gate electrode can be gold, silver or copper; Alternatively, the gate electrode material may also be liquid metal. In this case, after the flexible insulating substrate covers the flow channel, a mixture of liquid metal and ionic liquid will be injected into the dielectric layer flow channel together.

5. A method for preparing a flexible field effect transistor, characterized in that: include: Step S1, photolithography a mold of a source electrode, a drain electrode and a dielectric layer on a silicon wafer, wherein the source electrode and the drain electrode are respectively located on two sides of the dielectric layer; Step S2, using a flexible insulating material to contact the mold of the source electrode, the drain electrode and the dielectric layer, and separating them after applying pressure to obtain a remolding mold, at which point the remolding mold has a source electrode flow channel, a drain electrode flow channel and a dielectric layer flow channel formed thereon; Step S3, aligning and bonding the mold over the flexible insulating substrate pre-prepared with the semiconductor active layer; Step S4, after evacuating in a closed environment, injecting liquid metal into the source channel and the drain channel to form a liquid source and a liquid drain respectively, and injecting an ionic liquid dielectric layer into the dielectric layer channel to form an ionic liquid dielectric layer.

6. The method for preparing a flexible field effect transistor according to claim 5, characterized in that: In the step S2, it also includes: A source injection hole, a drain injection hole and a dielectric layer injection hole are arranged on the mold remodeling die, which are connected to the source channel, the drain channel and the dielectric layer channel respectively, for subsequent injection of liquid materials.

7. The method for preparing a flexible field effect transistor according to claim 5, characterized in that: A temporary rigid substrate is attached under the flexible insulating substrate, and the temporary rigid substrate is a silicon wafer and is used to protect the bottom surface of the flexible insulating substrate from contamination; wherein the flexible insulating substrate is made of PDMS, and a semiconductor active layer and a gate electrode are arranged on the flexible insulating substrate.

8. The method for preparing a flexible field effect transistor according to claim 7, characterized in that: Before step S3, the method further includes: The semiconductor active layer and the gate electrode are transferred to the flexible insulating substrate respectively by a mechanical peeling method using a flexible insulating material, and the gate electrode is located near the semiconductor active layer.

9. The method for preparing a flexible field effect transistor according to claim 7, characterized in that: In the step S3, it specifically includes: Use a microscope to assist in placing the mold on the flexible insulating substrate so that the semiconductor active layer corresponds to the positions of the source flow channel, the drain flow channel and the dielectric layer flow channel respectively, and the semiconductor active layer is located between the source flow channel and the drain flow channel and in contact with the dielectric layer flow channel; and the gate electrode corresponds to the position of the dielectric layer flow channel, and the gate electrode is in contact with the dielectric layer flow channel.

10. The method for preparing a flexible field effect transistor according to any one of claims 5 to 9, characterized in that: In the step S4, it specifically includes: The entire product is placed in a closed environment and evacuated, and the liquid metal and ionic liquid are respectively injected into the injection holes of the corresponding flow channels. The entire product is then transferred to the air, and the liquid metal and ionic liquid are pressed into the flow channel using air pressure to complete the preparation of the flexible field effect tube.

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