Contact configuration processing method of carbon nanotube field effect transistor and field effect transistor

Abstract

The invention provides a contact configuration processing method of a carbon nanotube field effect transistor and the field effect transistor, in the process of manufacturing a source electrode and a drain electrode, after a metal film is deposited and grown, the metal film is heated to an interface reaction temperature in vacuum or inert gas and annealed for a set period of time, and the contact configuration of the carbon nanotube field effect transistor is obtained by utilizing the solubility of carbon in metal. And carbon atoms are diffused into the metal to form chemical bond connection, so that the problem that the resistance is sharply increased when the size is reduced due to the fact that an existing side edge contact structure is used for connecting the source electrode, the drain electrode and the carbon nanotube array is solved.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a contact configuration processing method of a carbon nanotube field effect transistor and a field effect transistor. Background Art

[0002] Silicon-based complementary metal oxide semiconductor (CMOS) technology has reached its physical limit, and it is urgent to find new materials and new devices as a continuation and alternative. Carbon nanotubes (CNT) have become one of the ideal semiconductor channel materials for building new CMOS transistors and integrated circuits due to their excellent electrical properties, quasi-one-dimensional lattice structure, and high carrier mobility. Further developments have shown that arrayed carbon nanotubes (ACNT) with high semiconductor tube purity, high density, and parallel arrangement are considered to be ideal materials for building high-performance, low-power carbon nanotube field effect transistors (CNTFET).

[0003] In ACNT FET, the contact resistance of the source and drain electrodes directly affects the performance and power consumption of the device. With the development of carbon nanotube field effect transistor (CNTFET), the current mainstream contact scheme is side contact, which is to directly evaporate the metal to cover the carbon nanotube array, and the metal and the carbon nanotube array are in van der Waals interaction. Studies have found that the contact resistance (R C ) and contact length (L C )follow (R Q is the quantum resistance; ρ C is the channel resistivity; d CNT is the radius of carbon nanotube), R C It is inversely proportional to the contact length. This results in a decrease in contact length and a rapid increase in contact resistance. Especially when the contact length is below 50nm, the contact between metal and carbon nanotubes fluctuates greatly due to the exposed crystal surface of the metal and the contact ratio between the metal and the carbon nanotube, making it difficult for the side contact solution to meet the contact resistance requirements of ACNT FET advanced nodes. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a contact configuration processing method for a carbon nanotube field effect transistor and a field effect transistor to eliminate or improve one or more defects existing in the prior art, and to solve the problem that the prior art uses a side contact structure to connect the source and drain with the carbon nanotube array based on van der Waals forces, resulting in a sharp increase in resistance when the size is reduced.

[0005] One aspect of the present invention provides a contact configuration processing method for a carbon nanotube field effect transistor, the method comprising:

[0006] cutting and cleaning the carbon nanotube channels of the first preset pattern on the substrate to remove invalid portions;

[0007] Spin-coating photoresist on the carbon nanotube channel, and using an ultraviolet photolithography machine to perform photolithography according to a second preset pattern and removing the exposed area with a developer to define the source and drain positions;

[0008] A coating method based on magnetron sputtering or electron beam evaporation is used to deposit a metal film using a first type of metal, wherein the first type of metal has a mutual solubility with the carbon nanotubes greater than or equal to 0.1% when the temperature is higher than the interface reaction temperature in an inert gas environment;

[0009] Using a photoresist dissolving solution to remove the remaining photoresist and the metal film thereon, leaving the substrate, the carbon nanotube channel based on the first preset pattern, and the metal film based on the second preset pattern;

[0010] The first metal and carbon interface reaction temperature is heated to the interface reaction temperature under vacuum or inert gas environment, and after being maintained for a first set time, the interface is cooled to room temperature to complete annealing, so that the source, the drain and the carbon nanotube are connected by chemical bonds generated by solid phase reaction.

[0011] In some embodiments, the first type of metal is used to deposit a metal film, including: using a DC sputtering mode of a magnetron sputtering apparatus to deposit the metal film at a speed greater than 27 nm / min at a power of 500 W and a gas pressure of 2 mTorr.

[0012] In some embodiments, after heating to the interface reaction temperature of the first type of metal and carbon in a vacuum or inert gas environment, maintaining for a first set time and then cooling to room temperature, the method further includes:

[0013] Using electron microscope scanning to check the macroscopic morphology of the metal film and the carbon nanotube channel, and using X-ray diffraction characterization to check the metal carbide phase of the carbon nanotube;

[0014] If no metal carbide phase is produced, repeat the annealing or extend the high temperature holding time.

[0015] In some embodiments, heating to the interface reaction temperature of the first type of metal and carbon under vacuum or inert gas environment, maintaining for a first set time and then cooling to room temperature comprises:

[0016] At a vacuum degree of 10 -3 In a Pa environment, nitrogen or argon is introduced as a protective gas, and the temperature is raised to the interface reaction temperature, maintained for at least 1 hour, and then cooled to room temperature to complete annealing.

[0017] In some embodiments, in the method, metallic molybdenum is used as the first type of metal;

[0018] Then, heating to the interface reaction temperature of the first type of metal and carbon in a vacuum or inert gas environment, maintaining for a first set time and then cooling to room temperature, comprises:

[0019] At a vacuum degree of 10 -5 In a Pa environment, the annealing was completed by heating to 850°C at a heating rate of 27.5°C / min, maintaining for 1 hour, and then cooling to room temperature.

[0020] In some embodiments, spin coating a photoresist on the carbon nanotube channel comprises:

[0021] The rotation speed is increased stepwise to spin-coat the photoresist, and the dwell time at each rotation speed increases as the rotation speed increases, until the photoresist reaches a set thickness;

[0022] Bake the glue at the set temperature for the second set time.

[0023] In some embodiments, spin coating a photoresist on the carbon nanotube channel comprises:

[0024] The rotation speed was maintained at 600 rad / min for 10 seconds, and at 4000 rad / min for 30 seconds until the photoresist thickness reached 1.2 μm, and the photoresist was baked at 105° C. for 3 minutes.

[0025] In some embodiments, after heating to the interface reaction temperature of the first type of metal and carbon in a vacuum or inert gas environment, maintaining for a first set time and then cooling to room temperature to complete annealing, the method further includes:

[0026] Polymethyl methacrylate is spin-coated on the substrate, the carbon nanotube channel and the metal film as a support, and the silicon dioxide on the surface of the substrate that has been thermally oxidized is etched using a hydrofluoric acid solution to retain the carbon nanotube channel and the metal film. After washing with deionized water, they are picked up with a microgrid and dried and transferred at 60°C.

[0027] On the other hand, the present invention also provides a field effect transistor based on carbon nanotubes, comprising:

[0028] substrate;

[0029] a first predetermined pattern of carbon nanotube channels, the carbon nanotube channels grown on the substrate;

[0030] A source electrode is arranged at one end of the carbon nanotube and is used for inputting current;

[0031] A drain electrode, arranged at the other end of the carbon nanotube, for outputting current;

[0032] The gate and dielectric layer are arranged in a top gate structure, a bottom gate structure or a surround gate structure to control the on and off of the carbon nanotube channel;

[0033] The source electrode and the drain electrode are manufactured by using the contact configuration processing method for the carbon nanotube field effect transistor, and the source electrode, the drain electrode and the carbon nanotube are connected by chemical bonds generated by solid phase reaction.

[0034] In some embodiments, the carbon nanotube channel is composed of a plurality of carbon nanotubes arranged in an array; the substrate is a silicon wafer and a 50-300 nm silicon dioxide layer is grown; and the gate is made of a heterogeneous bimetallic material.

[0035] The beneficial effects of the present invention are at least:

[0036] The contact configuration processing method of the carbon nanotube field effect transistor and the field effect transistor of the present invention, in the process of making the source and drain, after depositing and growing a metal film, heat it to the interface reaction temperature in a vacuum or inert gas and maintain it for a set time for annealing treatment, and utilize the solubility of carbon in the metal to cause the carbon nanotubes and the metal to undergo a solid phase reaction, and the carbon atoms diffuse into the metal to form a chemical bond connection, thereby solving the problem that the existing side contact structure connecting the source and drain with the carbon nanotube array causes a sharp increase in resistance when the size is reduced.

[0037] Additional advantages, purposes, and features of the present invention will be described in part in the following description, and will become apparent to those skilled in the art after studying the following, or may be learned from the practice of the present invention. The purposes and other advantages of the present invention may be achieved and obtained by the structures specifically indicated in the specification and the accompanying drawings.

[0038] Those skilled in the art will appreciate that the objectives and advantages that can be achieved with the present invention are not limited to the above specific description, and the above and other objectives that can be achieved by the present invention will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute a limitation of the present invention. In the drawings:

[0040] Figure 1 The figure is a schematic flow chart of a contact configuration processing method for a carbon nanotube field effect transistor according to an embodiment of the present invention.

[0041] Figure 2 A schematic diagram of a method for transferring carbon nanotubes and metal films in a contact configuration processing method for a carbon nanotube field effect transistor according to an embodiment of the present invention.

[0042] Figure 3 This is a schematic diagram of the detection results of molybdenum carbide under different annealing methods using XRD combined with transfer-low-pressure spherical aberration corrected transmission electron microscopy in one embodiment of the present invention.

[0043] FIG. 4( a ) is a characterization diagram of the contact configuration between molybdenum carbide and array carbon tubes using an 80 kV spherical aberration corrected transmission electron microscope according to an embodiment of the present invention.

[0044] FIG4( b ) is the nanodiffraction pattern of FIG4( a ).

[0045] Figure 4(c) is an enlarged view of the yellow frame portion in Figure 4(a). DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0047] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0048] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, elements, steps or components, but does not exclude the presence or addition of one or more other features, elements, steps or components.

[0049] It should also be noted that, unless otherwise specified, the term “connection” herein may refer not only to a direct connection but also to an indirect connection with an intermediate.

[0050] In the current mainstream carbon nanotube field effect transistor source and drain structures, the metal and the channel material carbon nanotube adopt a side contact structure. This structure increases the channel resistance sharply when the transistor size is reduced, making it difficult to meet the technical requirements of future nodes.

[0051] The present invention proposes to use an end contact scheme. The principle of the end contact scheme comes from the solubility of carbon in metals. At high temperatures, carbon nanotubes and metals undergo solid-phase reactions, and carbon atoms diffuse into metals. Metals with good solubility in carbon, such as molybdenum and nickel, have been proven to be chemically bonded to carbon nanotubes after high-temperature solid-phase reactions, replacing the side contacts of van der Waals action. Metal electrical tests show that the carbon nanotube field effect transistor (given a single carbon tube) using molybdenum as the end contact metal has a contact resistance as low as 11kΩ at a contact length of 10nm, and has good uniformity. At present, this end contact has only been reported in single carbon nanotube transistors, and there is a lack of characterization of the end contact, the microstructure is still unclear, and it has not been applied to carbon nanotube field effect transistors ACNT FETs.

[0052] Specifically, the present invention provides a contact configuration processing method for a carbon nanotube field effect transistor, such as Figure 1 As shown, the method includes steps S101 to S105:

[0053] Step S101: cutting and cleaning the carbon nanotube channels of a first preset pattern on a substrate to remove invalid parts.

[0054] Step S102: Spin-coat photoresist on the carbon nanotube channel, and use an ultraviolet photolithography machine to perform photolithography according to a second preset pattern and use a developer to remove the exposed area to define the source and drain positions.

[0055] Step S103: depositing a metal film using a first type of metal in a magnetron sputtering or electron beam evaporation coating method, wherein the first type of metal has a mutual solubility with the carbon nanotubes greater than or equal to 0.1% in an inert gas environment at a temperature higher than the interface reaction temperature.

[0056] Step S104: using a photoresist dissolving solution to remove the remaining photoresist and the metal film thereon, leaving behind the substrate, the carbon nanotube channel based on the first preset pattern, and the metal film based on the second preset pattern.

[0057] Step S105: heating to the interface reaction temperature of the first type of metal and carbon in a vacuum or inert gas environment, maintaining for a first set time, and then cooling to room temperature to complete annealing, so that the source, the drain and the carbon nanotubes are connected by chemical bonds generated by a solid phase reaction.

[0058] Steps S101 to S105 are mainly for processing the contact configuration of the source and drain of the carbon nanotube field effect transistor.

[0059] In step S101, the substrate is a silicon wafer that has been subjected to thermal oxidation treatment. The silicon wafer is cleaned using an RCA cleaning method to remove organic pollutants, metal ions and dust on the surface of the wafer. RCA cleaning is a standardized wet cleaning process for cleaning the surface of silicon wafers. It was first developed by technicians of RCA Corporation of America in 1965. This method is still widely used today, especially in the semiconductor manufacturing process, and is the main means of removing various pollutants on the surface of silicon wafers.

[0060] RCA cleaning usually includes three main steps, each of which uses a different chemical solution, namely: SC-1 cleaning, using a solution of ammonia, hydrogen peroxide and water in a ratio of 1:1:5, reacting at 75-80°C for 10-15 minutes to remove organic pollutants and particles. HF immersion, the solution is hydrofluoric acid and water in a ratio of 1:50 to 1:100, removing the natural oxide layer for 1-2 minutes. SC-2 cleaning, using a solution of ammonia, hydrogen peroxide and water in a ratio of 1:1:6, reacting at 75-80°C for 10-15 minutes to remove metal ion contamination. After cleaning, the silicon wafer can be thermally oxidized to grow 50-300nm thick silicon dioxide at a reaction temperature of 1000 to 1200°C to isolate the silicon base from the electric field.

[0061] Carbon nanotubes can be grown in situ or transferred externally onto a substrate.

[0062] The in-situ growth method uses chemical vapor deposition (CVD) to grow carbon nanotubes directly on a substrate. The CVD process generally includes: coating a catalyst (such as nanoparticles of iron, cobalt, and nickel) on the substrate, heating to 700-900°C, introducing a carbon source gas (such as methane, acetylene, and ethylene) in an inert gas (such as argon and hydrogen) environment, decomposing the carbon source, and depositing carbon atoms to form single-walled or multi-walled carbon nanotubes (SWCNTs or MWCNTs).

[0063] The external transfer method is to transfer from the prepared carbon nanotube powder or film. The carbon nanotubes are dispersed in a solvent (such as SDS solution) using a solution method, and then the carbon nanotubes are transferred to the substrate by solution coating, drip coating or spraying. Using dry transfer, the carbon nanotube film is transferred to the target substrate through a PDMS (polydimethylsiloxane) support layer.

[0064] Further, the carbon nanotube channel is patterned, and the carbon nanotube is patterned using photolithography or electron beam lithography to define the channel area. Photoresist is applied, and the photoresist is exposed and developed through a mask to leave the channel area. Plasma etching is used to remove the carbon nanotubes in the non-channel area.

[0065] In step S102, first ensure that the surface of the carbon nanotube channel is clean and dust-free. If necessary, plasma cleaning or solvent cleaning can be used to remove organic residues and other contaminants on the surface. Spin the photoresist evenly on the carbon nanotube channel. Commonly used photoresists are SU-8 2021 negative photoresists. The rotation speed and time need to be controlled during the spin coating process to ensure that the thickness of the photoresist layer is uniform and appropriate. Place the spin-coated sample on a hot plate and bake to remove the solvent in the photoresist. This step is usually performed at a temperature of 110°C to 130°C for about 1 minute. Use a UV lithography machine to expose the sample. During exposure, a pre-designed mask needs to be used, which contains a second preset pattern for defining the position of the source and drain. The exposure time and the intensity of the ultraviolet light need to be adjusted according to the type and thickness of the photoresist. After exposure, the sample is placed on the hot plate again for baking to complete the cross-linking reaction of the photoresist. This step is usually carried out at a slightly higher temperature. For example, for SU-8 2021 photoresist, it is recommended to bake at 95°C for about 1 minute. Use an appropriate developer to remove the photoresist in the exposed area. For positive photoresists, the exposed parts will dissolve in the developer; for negative photoresists such as SU-82021, the unexposed parts will be dissolved, while the exposed parts will remain to form the desired pattern. The development process needs to be carried out under well-controlled temperature conditions to avoid over-development or under-development. After development, rinse the sample thoroughly with deionized water or other appropriate solvent to remove residual developer. Finally, blow dry the sample using a nitrogen gun or other drying method.

[0066] In some embodiments, spin coating photoresist on the carbon nanotube channel includes steps S1021 to S1022:

[0067] Step S1021: The rotation speed is increased stepwise to spin-coat the photoresist, and the dwell time at each rotation speed increases as the rotation speed increases until the photoresist reaches a set thickness.

[0068] Step S1022: baking the glue at the set temperature for a second set time.

[0069] In some embodiments, spin coating photoresist on the carbon nanotube channel includes: selecting AZ5214 photoresist, maintaining a rotation speed of 600 rad / min for 10 seconds, maintaining a rotation speed of 4000 rad / min for 30 seconds until the photoresist thickness is 1.2 μm, and baking the photoresist at 105° C. for 3 minutes.

[0070] The exposed photoresist will selectively dissolve in the developer, developer ZX-238, with a development time of 35s. After development, it is placed in deionized water for fixing for 1min and finally blown dry with a nitrogen gun.

[0071] In step S103, the present invention uses metal molybdenum or metal nickel as the first type of metal. Of course, depending on the application scenario, titanium, palladium, gold, platinum, etc. can also be selected as the first type of metal. According to the specific metal type and film requirements, select a suitable magnetron sputtering or electron beam evaporation equipment. For magnetron sputtering, it is necessary to set parameters such as sputtering power, gas pressure, target type, etc.; for electron beam evaporation, it is necessary to set parameters such as electron beam energy, evaporation rate, vacuum degree, etc.

[0072] In some embodiments, the first type of metal is used to deposit a metal film, including: using a magnetron sputtering apparatus in a DC sputtering mode, at a power of 500 watts and a pressure of 2 millitorr, at a rate greater than 27 nm / min to deposit the metal film. A relatively large coating rate is selected here to destroy the intrinsic carbon tube structure under the metal through the kinetic energy of the metal atoms, which is conducive to the formation of chemical bonds in the subsequent solid phase reaction.

[0073] In step S104, the photoresist dissolving solution may be NMP solution, ie N-methylpyrrolidone solution, to dissolve the photoresist and the metal film attached thereto, and then wash with deionized water and dry.

[0074] In step S105, the first type of metal and the carbon nanotubes undergo a solid phase reaction through annealing. Different metals have different reactivity with carbon, which determines the starting temperature of the solid phase reaction.

[0075] Highly reactive metals (such as titanium Ti, vanadium V, palladium Pd): These metals easily form metal carbides with carbon, and the reaction temperature is relatively low, usually in the range of 400-600°C.

[0076] Moderately reactive metals (such as nickel (Ni), tungsten (W), and molybdenum (Mo): These metals may chemically react with carbon nanotubes at temperatures between 600 and 800°C.

[0077] Low-reactivity metals (such as gold Au, silver Ag, platinum Pt): These metals may react with carbon nanotubes only at higher temperatures and are relatively stable even above 1000°C.

[0078] The different chemical stabilities of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) also affect the starting temperature of the solid-state reaction.

[0079] Exemplarily, the interface reaction temperature of titanium and carbon is 400-600°C, the interface reaction temperature of nickel and carbon is 600-800°C, and the interface reaction temperature of palladium and carbon is 300-500°C.

[0080] In the present invention, heating to the interface reaction temperature of the first type of metal and carbon in a vacuum or inert gas environment, maintaining for a first set time and then cooling to room temperature comprises: -3 In a Pa environment, nitrogen or argon is introduced as a protective gas, and the temperature is raised to the interface reaction temperature, maintained for at least 1 hour, and then cooled to room temperature to complete annealing.

[0081] In some embodiments, the method uses metal molybdenum as the first type of metal, and heats to the interface reaction temperature of the first type of metal and carbon in a vacuum or inert gas environment, maintains for a first set time, and then cools to room temperature, including: -5 In a Pa environment, the annealing was completed by heating to 850°C at a heating rate of 27.5°C / min, maintaining for 1 hour, and then cooling to room temperature.

[0082] In some embodiments, after heating to the interface reaction temperature of the first type of metal and carbon in a vacuum or inert gas environment, maintaining for a first set time and then cooling to room temperature, the method further includes steps S201 to S202:

[0083] Step S201: using electron microscope scanning to check the macroscopic morphology of the metal film and the carbon nanotube channel, and using X-ray diffraction characterization to check the metal carbide phase of the carbon nanotube.

[0084] Step S202: If no metal carbide phase is generated, repeat the annealing or extend the high temperature maintenance time.

[0085] In some embodiments, the annealing is completed by heating to the interface reaction temperature of the first type of metal and carbon in a vacuum or inert gas environment, maintaining the temperature for a first set time, and then cooling to room temperature. Figure 2 As shown, it also includes: spin coating polymethyl methacrylate as a support on the substrate, carbon nanotube channel and metal film, using hydrofluoric acid solution to etch the silicon dioxide on the surface of the substrate that has been thermally oxidized, retaining the carbon nanotube channel and the metal film, washing with deionized water, and then picking up with a micro-gate, and drying and transferring at 60°C.

[0086] On the other hand, the present invention also provides a field effect transistor based on carbon nanotubes, comprising:

[0087] substrate;

[0088] a first predetermined pattern of carbon nanotube channels, the carbon nanotube channels grown on the substrate;

[0089] A source electrode is arranged at one end of the carbon nanotube and is used for inputting current;

[0090] A drain electrode, arranged at the other end of the carbon nanotube, for outputting current;

[0091] The gate and dielectric layer are arranged in a top gate structure, a bottom gate structure or a surround gate structure to control the on and off of the carbon nanotube channel;

[0092] The source electrode and the drain electrode are manufactured by using the contact configuration processing method for carbon nanotube field effect transistors described in steps S101 to S105, and the source electrode, the drain electrode and the carbon nanotube are connected by chemical bonds generated by solid phase reaction.

[0093] In some embodiments, the carbon nanotube channel is composed of a plurality of carbon nanotubes arranged in an array; the substrate is a silicon wafer and a 50-300nm silicon dioxide layer is grown; the gate is made of a heterogeneous bimetallic material. The dielectric layer usually uses a high dielectric constant material, such as hafnium oxide HfO2, aluminum oxide Al2O3, and barium aluminum titanate BST, to improve the electric field effect.

[0094] Specifically, the gate may adopt a top-gate structure, a bottom-gate structure or a gate-all-around structure.

[0095] In the top-gate structure, the gate is made after the source and drain electrodes. Commonly used in carbon nanotube field-effect transistors (CNT-FETs), organic thin-film transistors (OTFTs), etc.

[0096] In a bottom-gate structure, the gate and dielectric layers are usually fabricated first. Common in traditional silicon-based FETs and some thin-film transistors (TFTs).

[0097] In a gate-all-around structure, the gate electrode wraps around the channel material, providing greater electric field control capabilities. Commonly used in advanced nanowire FETs and next-generation high-performance transistors.

[0098] The present invention is described below in conjunction with a specific embodiment:

[0099] This embodiment provides a contact configuration processing method for a carbon nanotube field effect transistor, comprising the following steps:

[0100] (1) Cutting and cleaning the carbon nanotube array substrate: Cutting the carbon nanotube wafer substrate is convenient for subsequent cleaning, coating and other operations. Use organic solvents (such as acetone, isopropyl alcohol, etc., preferably organic solvents that leave less residue on the wafer after drying) and deionized water to clean the carbon nanotube array substrate. After cleaning, use an optical microscope and a scanning electron microscope to observe to ensure the cleanliness of the wafer.

[0101] Specifically, the carbon nanotube wafer substrate was cut, and the cut substrate was immersed in an acetone solution, heated and immersed at 65° C. for 3 minutes, and then immersed in deionized water for 3 minutes. After cleaning, the substrate was observed using an optical microscope and a scanning electron microscope to ensure the cleanliness of the wafer.

[0102] (2) Spin coating photoresist: AZ5214 photoresist was selected, and the rotation speed was 600 rad / min, and the rotation was maintained for 10 s. The rotation speed was 4000 rad / min, and the rotation was maintained for 30 s. The photoresist thickness was 1.2 μm, and the photoresist was baked at 105°C for 3 min.

[0103] (3) Photolithography and development: Use a UV lithography machine to transfer the customized pattern to the carbon nanotube substrate. The exposed photoresist will selectively dissolve in the developer, and a specific developer is used to remove the photoresist in the exposed area.

[0104] Specifically, AZ5214 photoresist is selected to transfer the customized pattern to the carbon nanotube substrate. The exposed photoresist will selectively dissolve in the developer, developer ZX-238, the development time is 35s, and after development, it is placed in deionized water for fixing for 1min, and finally blown dry with a nitrogen gun.

[0105] (4) Coating: Use magnetron sputtering or electron beam evaporation equipment to deposit metal film on the substrate surface. The thickness / shape of the metal film can be designed according to the requirements (carbon tube array density / device structure). The type of metal film should be selected from metals with high solubility with carbon and low solid phase reaction temperature with carbon. Select a larger coating rate to destroy the intrinsic carbon tube structure under the metal through the kinetic energy of metal atoms, which is conducive to the formation of chemical bonds in the subsequent solid phase reaction.

[0106] Specifically, in a magnetron sputtering apparatus DE-500, DC mode, 500W power, gas pressure 2mtorr, it takes 1.5 minutes to plate 40nm of metallic molybdenum.

[0107] (5) Stripping: Soak the coated sample in a solution that can dissolve the photoresist to remove the remaining photoresist and the metal film on it, leaving only the exposed and patterned part.

[0108] Specifically, the sample after film coating is immersed in NMP solution to remove the remaining photoresist and the metal film thereon, leaving the exposed patterned portion.

[0109] (6) Inspection: Check the effects of photolithography, coating and stripping under a scanning electron microscope. Compare the coating results with the layout to confirm that the graphics are correct.

[0110] (7) Annealing: The inspected metal / carbon nanotube substrate is placed in an annealing device and the vacuum degree is ensured to be 10 -3 After the temperature drops below Pa, a protective gas (nitrogen or argon) is introduced, heated to the required temperature, maintained for a period of time, and then cooled to room temperature. Heating only provides enough energy for the reaction, and there is no restriction on the heating method itself. Tube furnace annealing, RTP annealing and even laser annealing can meet the requirements under appropriate parameters.

[0111] Specifically, for a 40nm thick metal molybdenum, vacuum annealing requires a vacuum degree of 10 -5 Pa, the vacuum requirement can be appropriately reduced by passing the atmosphere. Raise the temperature to 850℃ at a rate of 27.5℃ / min, maintain at high temperature for 1h, and then cool to room temperature.

[0112] (8) Phase characterization: Preliminary characterization is performed under a scanning electron microscope to characterize the macroscopic morphology of the metal film and array carbon tubes. Subsequently, the carbon nanotube substrate is characterized by X-ray diffraction to determine the formation of molybdenum carbide phase. If no carbide phase is produced or carbon nanotubes still remain under the metal, the annealing experiment should be repeated, or the annealing experiment should be extended to maintain the temperature at a high temperature.

[0113] (9) Transfer: Spin-coat PMMA on the metal / array carbon tube as a support, use a certain concentration of HF solution to etch SiO2, retain the array carbon nanotubes and metal film, wash with deionized water three times, then pick up with a microgrid and completely dry at 60°C.

[0114] (10) Microscopic characterization: The specific contact structure between MoC and CNTs was observed under an 80 kV transmission electron microscope.

[0115] In this embodiment, Figure 3 As shown, the characterization method of XRD combined with transfer-low-pressure spherical aberration corrected transmission electron microscopy was adopted. Under annealing conditions, obvious Mo2C peaks appeared at 36.4° and 39.5°, confirming the formation of molybdenum carbide phase at the macro level; as shown in Figure 4 (a) to (c), the contact structure of array carbon tube-molybdenum carbide was clarified at the micro level. Compared with the traditional side contact structure, the end contact structure constructed on the array carbon tube in this embodiment is formed at a high temperature, and the metal forms carbides with the contacting carbon nanotubes, which can maintain a relatively uniform morphological structure at a small size, thereby obtaining a relatively stable transistor performance. The end contact structure can be directly patterned according to the shape of the transistor without introducing additional processing procedures.

[0116] In summary, the contact configuration processing method of the carbon nanotube field effect transistor and the field effect transistor described in the present invention, in the process of making the source and drain, after depositing and growing a metal film, heat it to the interface reaction temperature in a vacuum or inert gas and maintain it for a set time for annealing treatment, and utilize the solubility of carbon in the metal to cause a solid phase reaction between the carbon nanotubes and the metal, and the carbon atoms diffuse into the metal to form a chemical bond connection, thereby solving the problem of the existing side contact structure connecting the source and drain with the carbon nanotube array, which causes a sharp increase in resistance when the size is reduced.

[0117] It should be understood by those skilled in the art that the exemplary components, systems and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software or a combination of the two. Whether it is performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention. When implemented in hardware, it can be, for example, an electronic circuit, an application specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, etc. When implemented in software, the elements of the present invention are programs or code segments used to perform the required tasks. The program or code segment can be stored in a machine-readable medium, or transmitted on a transmission medium or a communication link via a data signal carried in a carrier.

[0118] It should be clear that the present invention is not limited to the specific configuration and processing described above and shown in the figures. For the sake of simplicity, a detailed description of the known method is omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the order between the steps after understanding the spirit of the present invention.

[0119] In the present invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with features of other embodiments or replace features of other embodiments.

[0120] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A contact configuration processing method for a carbon nanotube field effect transistor, characterized in that: The method comprises: cutting and cleaning the carbon nanotube channels of the first preset pattern on the substrate to remove invalid portions; Spin-coating photoresist on the carbon nanotube channel, and using an ultraviolet photolithography machine to perform photolithography according to a second preset pattern and removing the exposed area with a developer to define the source and drain positions; A coating method based on magnetron sputtering or electron beam evaporation is used to deposit a metal film using a first type of metal, wherein the first type of metal has a mutual solubility with the carbon nanotubes greater than or equal to 0.1% in an inert gas environment at a temperature higher than an interface reaction temperature; Using a photoresist dissolving solution to remove the remaining photoresist and the metal film thereon, leaving the substrate, the carbon nanotube channel based on the first preset pattern, and the metal film based on the second preset pattern; The first metal and carbon interface reaction temperature is heated to the interface reaction temperature under vacuum or inert gas environment, and after being maintained for a first set time, the interface is cooled to room temperature to complete annealing, so that the source, the drain and the carbon nanotube are connected by chemical bonds generated by solid phase reaction.

2. The contact configuration processing method for a carbon nanotube field effect transistor according to claim 1, characterized in that: The first type of metal is used to deposit a metal film, including: using a direct current sputtering mode of a magnetron sputtering apparatus to deposit the metal film at a speed greater than 27 nm / min at a power of 500 watts and a gas pressure of 2 mTorr.

3. The contact configuration processing method for a carbon nanotube field effect transistor according to claim 2, characterized in that: After heating to the interface reaction temperature of the first type of metal and carbon in a vacuum or inert gas environment, maintaining for a first set time and then cooling to room temperature, the method further includes: Using electron microscope scanning to check the macroscopic morphology of the metal film and the carbon nanotube channel, and using X-ray diffraction characterization to check the metal carbide phase of the carbon nanotube; If no metal carbide phase is produced, repeat the annealing or extend the high temperature holding time.

4. The contact configuration processing method for a carbon nanotube field effect transistor according to claim 3, characterized in that: The method comprises heating the first metal to the interface reaction temperature of the first metal and carbon in a vacuum or inert gas environment, maintaining the temperature for a first set time, and then cooling the temperature to room temperature, including: At a vacuum degree of 10 -3 In a Pa environment, nitrogen or argon is introduced as a protective gas, and the temperature is raised to the interface reaction temperature, maintained for at least 1 hour, and then cooled to room temperature to complete annealing.

5. The contact configuration processing method for a carbon nanotube field effect transistor according to claim 4, characterized in that: In the method, metallic molybdenum is used as the first type of metal; Then, heating to the interface reaction temperature of the first type of metal and carbon in a vacuum or inert gas environment, maintaining for a first set time and then cooling to room temperature, comprises: At a vacuum degree of 10 -5 In a Pa environment, the annealing was completed by heating to 850°C at a heating rate of 27.5°C / min, maintaining for 1 hour, and then cooling to room temperature.

6. The contact configuration processing method for a carbon nanotube field effect transistor according to claim 5, characterized in that: Spin coating photoresist on the carbon nanotube channel, comprising: The rotation speed is increased stepwise to spin-coat the photoresist, and the dwell time at each rotation speed increases as the rotation speed increases, until the photoresist reaches a set thickness; Bake the glue at the set temperature for the second set time.

7. The contact configuration processing method for a carbon nanotube field effect transistor according to claim 4, characterized in that: Spin coating photoresist on the carbon nanotube channel, comprising: The rotation speed was maintained at 600 rad / min for 10 seconds, and at 4000 rad / min for 30 seconds until the photoresist thickness reached 1.2 μm, and the photoresist was baked at 105° C. for 3 minutes.

8. The contact configuration processing method for a carbon nanotube field effect transistor according to claim 7, characterized in that: After heating to the interface reaction temperature of the first type of metal and carbon in a vacuum or inert gas environment, maintaining for a first set time and then cooling to room temperature to complete annealing, the method further includes: Polymethyl methacrylate is spin-coated on the substrate, the carbon nanotube channel and the metal film as a support, and the silicon dioxide on the surface of the substrate that has been thermally oxidized is etched using a hydrofluoric acid solution to retain the carbon nanotube channel and the metal film. After washing with deionized water, they are picked up with a microgrid and dried and transferred at 60°C.

9. A field effect transistor based on carbon nanotubes, characterized in that: include: substrate; a first predetermined pattern of carbon nanotube channels, the carbon nanotube channels grown on the substrate; A source electrode is arranged at one end of the carbon nanotube and is used for inputting current; A drain electrode, arranged at the other end of the carbon nanotube, for outputting current; The gate and dielectric layer are arranged in a top gate structure, a bottom gate structure or a surround gate structure to control the on and off of the carbon nanotube channel; The source electrode and the drain electrode are manufactured by using the contact configuration processing method for a carbon nanotube field effect transistor as claimed in any one of claims 1 to 7, and the source electrode, the drain electrode and the carbon nanotube are connected by chemical bonds generated by a solid phase reaction.

10. The carbon nanotube-based field effect transistor according to claim 9, characterized in that: The carbon nanotube channel is composed of a plurality of carbon nanotubes arranged in an array; the substrate is a silicon wafer and a 50-300nm silicon dioxide layer is grown; and the gate is made of a heterogeneous bimetallic material.

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