TWI388013B - Method for making thin film transistor - Google Patents

Description

Method for preparing thin film transistor

The invention relates to a method for preparing a thin film transistor, in particular to a method for preparing a thin film transistor based on a carbon nanotube.

Thin Film Transistor (TFT) is a key electronic component in modern microelectronics technology and has been widely used in flat panel displays and other fields. The thin film transistor mainly includes a gate, an insulating layer, a semiconductor layer, a source, and a drain. The source and the drain are spaced apart from each other and electrically connected to the semiconductor layer, and the gate is insulated from the semiconductor layer and the source and the drain by an insulating layer. The semiconductor layer is located in a region between the source and the drain to form a channel region. The gate, the source and the drain of the thin film transistor are each composed of a conductive material, which is generally a metal or an alloy. When a voltage is applied to the gate, the channel region in the semiconductor layer spaced apart from the gate through the insulating layer accumulates carriers, and when the carrier accumulates to a certain extent, the source drain is electrically connected to the semiconductor layer. Turned on so that current flows from the source to the drain. In practical applications, the requirements for thin film transistors are expected to result in a larger switching current ratio. Factors Affecting the Switching Current Ratio In addition to the preparation process of the thin film transistor, the carrier mobility of the semiconductor material in the thin film transistor layer is one of the most important factors affecting the switching current ratio.

In the prior art, a material for forming a semiconductor layer in a thin film transistor is an amorphous germanium, a polycrystalline germanium or an organic semiconductor polymer (REISchropp, B. Stannowski, JK Rath, New challenges in thin film transistor research, Journal of Non-Crystalline Solids, 299 -302, 1304-1310 (2002)). The manufacturing technique of the amorphous germanium thin film transistor using amorphous germanium as the semiconductor layer is relatively mature, but in the amorphous germanium thin film transistor, since the semiconductor layer usually contains a large number of dangling bonds, the carrier mobility is low ( Generally less than 1 cm ² V ^-1 s ^-1 ), resulting in a slower response of the thin film transistor. A thin film transistor using polycrystalline germanium as a semiconductor layer has a higher carrier mobility (generally about 10 cm ² V ^-1 s ^-1 ) relative to a thin film transistor having amorphous germanium as a semiconductor layer, so the response speed is also higher. fast. However, the low-temperature manufacturing cost of the polycrystalline germanium thin film transistor is relatively complicated, the method is difficult to manufacture in a large area, and the off-state current of the polycrystalline germanium thin film transistor is large. Compared with the above-mentioned conventional inorganic thin film transistor, the organic thin film transistor using the organic semiconductor polymer as the semiconductor layer has the advantages of low cost and low manufacturing temperature, and the organic thin film transistor has high flexibility. However, since the organic semiconductor is mostly skipped at normal temperature, it exhibits high resistivity and low carrier mobility, making the response speed of the organic thin film transistor slow.

Nano carbon tubes have excellent mechanical and electrical properties. Moreover, the nanocarbon tubes may exhibit metallic or semiconducting properties as the carbon nanotubes are spirally changed. Semiconducting carbon nanotubes have a high carrier mobility (generally up to 1000~1500cm ² V ^-1 s ^-1 ) and are ideal materials for transistor fabrication. The prior art uses a semiconducting carbon nanotube to form a carbon nanotube layer as a semiconductor layer of a thin film transistor. The preparation method of the above thin film transistor mainly comprises the following steps: dispersing a carbon nanotube powder in an organic solvent; spraying a mixture of a carbon nanotube and an organic solvent on an insulating substrate by spraying, after the organic solvent is evaporated; Forming a carbon nanotube layer on a predetermined position of the insulating substrate; forming a source and a drain on the carbon nanotube layer by depositing and etching a metal thin film; depositing a layer of tantalum nitride on the carbon nanotube layer Forming an insulating layer; and depositing a metal film on the insulating layer to form a gate. However, in the above method, the carbon nanotubes need to be dispersed by an organic solvent, and the carbon nanotubes are easily agglomerated and cannot be uniformly distributed in the semiconductor layer. Moreover, the organic solvent used for dispersing the carbon nanotubes tends to remain in the carbon nanotube layer, affecting the performance of the thin film transistor. Further, in the above carbon nanotube layer, the carbon nanotubes are randomly distributed. The carrier has a long conduction path in the disordered carbon nanotube layer. Therefore, the arrangement of the carbon nanotubes in the carbon nanotube layer cannot effectively utilize the high carrier mobility of the carbon nanotube. It is not conducive to obtaining a thin film transistor with a high carrier mobility. In addition, the organic solvent-bonded carbon nanotube layer has a loose structure and poor flexibility, which is disadvantageous for preparing a flexible thin film transistor.

In view of this, it is necessary to provide a method for preparing a thin film transistor which is simple in method and suitable for low-cost mass production, and the prepared thin film transistor has high carrier mobility, high response speed, and Good flexibility.

A method for preparing a thin film transistor, comprising the steps of: providing an insulating substrate; growing an array of ribbon-shaped carbon nanotubes on the surface of the insulating substrate, processing the array of ribbon-shaped carbon nanotubes, and making the strip-shaped nano tube The carbon tube array is tilted in a direction perpendicular to the length of the strip of carbon nanotube array, thereby forming a semiconductor layer including a plurality of carbon nanotubes on the surface of the insulating substrate; forming a source and a drain in the space a surface of the semiconductor layer, and electrically connecting the source and the drain to a portion of the carbon nanotubes in the semiconductor layer Connecting; forming an insulating layer on the surface of the semiconductor layer forming the source and the drain; and forming a gate on the surface of the insulating layer to obtain a thin film transistor.

A method for preparing a thin film transistor, comprising the steps of: providing a growth substrate; growing an array of ribbon-shaped carbon nanotubes on the surface of the growth substrate, processing the array of ribbon-shaped carbon nanotubes, and making the strip-shaped nano tube The carbon tube array is poured in a direction perpendicular to the length of the strip of carbon nanotube array, thereby forming a carbon nanotube layer including a plurality of carbon nanotubes on the surface of the growth substrate; providing an insulating substrate; forming a gate Forming an insulating layer covering the gate; transferring the carbon nanotube layer to the surface of the insulating layer to form a semiconductor layer; and spacing to form a source and a drain The source and the drain are electrically connected to both ends of a portion of the carbon nanotubes in the semiconductor layer to form a thin film transistor.

A method for preparing a thin film transistor, comprising the steps of: providing an insulating substrate; uniformly growing a plurality of strip-shaped carbon nanotube arrays on the surface of the insulating substrate, and processing the plurality of strip-shaped carbon nanotube arrays for each a strip of carbon nanotube arrays are all tilted in a direction perpendicular to the length of the strip of carbon nanotube arrays, thereby forming a plurality of semiconductor layers on the surface of the insulating substrate, each semiconductor layer comprising a plurality of carbon nanotubes; Forming a plurality of sources and a plurality of drains, and electrically connecting both ends of a portion of the carbon nanotubes in each of the semiconductor layers to a source and a drain; forming an insulating layer on the surface of each of the semiconductor layers Forming a gate on the surface of each insulating layer to obtain a plurality of thin film transistors.

Compared with the prior art, the method for preparing a thin film transistor provided by the embodiments of the present technical solution has the following advantages: First, since the semiconductor layer can be It is prepared directly on the insulating substrate or by performing an undercut treatment on an array of carbon nanotubes formed on the growth substrate, which is relatively simple. Secondly, the carbon nanotubes in the prepared carbon nanotube layer are arranged in parallel along a certain direction. Therefore, when the carbon nanotube layer is used as the semiconductor layer, the direction of the arrangement of the carbon nanotube layer can be controlled. The arrangement direction of the carbon nanotubes between the source and the drain is controlled, so that the thin film transistor obtains a large carrier mobility, which is advantageous for improving the response speed of the thin film transistor.

Hereinafter, a method for preparing a thin film transistor provided by an embodiment of the present technical solution will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1 and FIG. 2, a first embodiment of the present technical solution provides a method for preparing a top gate type thin film transistor 10, which specifically includes the following steps:

Step 1: An insulating substrate 110 is provided.

The insulating substrate 110 is a high temperature resistant substrate, and the material thereof is not limited as long as the melting point thereof is higher than the growth temperature of the carbon nanotubes. The shape of the insulating substrate 110 is not limited and may be any shape such as a square shape, a circular shape, or the like. The size of the insulating substrate 110 is not limited, and may be determined according to actual conditions. In addition, the insulating substrate 110 can also be selected from a substrate in a large scale integrated circuit.

In the embodiment of the technical solution, the insulating substrate 110 is a square cymbal substrate having a length and a width of 3 cm.

Step 2: forming a carbon nanotube layer on the surface of the insulating substrate 110, the carbon nanotube layer comprising a plurality of carbon nanotubes to form a semiconductor layer 140.

The carbon nanotube layer can be formed by the following two methods: First, forming a carbon nanotube array on the insulating substrate 110, and processing the carbon nanotube array to form a carbon nanotube layer . Second, a carbon nanotube layer is formed directly on the surface of the insulating substrate 110.

Forming a carbon nanotube array on the insulating substrate 110, and processing the carbon nanotube array to form a carbon nanotube layer comprises the steps of: forming a strip catalyst on the surface of the insulating substrate 110 a film, the strip catalyst film has a width of 1 μm to 20 μm; growing a strip of carbon nanotube array by chemical vapor deposition; and processing the strip of carbon nanotube array to make the strip The carbon nanotube array is poured in a direction perpendicular to its length to form a carbon nanotube layer on the surface of the insulating substrate 110.

The strip catalyst film is used to grow a carbon nanotube. The material of the strip catalyst film may be one selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), or any combination thereof. In this embodiment, the material of the strip catalyst film is iron.

The strip catalyst film may be formed on the surface of the insulating substrate 110 by a thermal deposition method, an electron beam deposition method, or a sputtering method. The strip catalyst film has a width of from 1 μm to 20 μm. The strip catalyst film has a thickness of from 0.1 nm to 10 nm.

The method for growing a ribbon carbon nanotube array by chemical vapor deposition comprises the following steps: placing the insulating substrate 110 formed with the strip catalyst film into a reaction chamber; Passing the shielding gas to discharge the air in the reaction chamber; heating the reaction chamber to 600 ° C ~ 900 ° C in a protective gas atmosphere, and maintaining a constant temperature; the carbon source gas and the flow ratio of 1:30 ~ 1:3 Gas, reaction for 5 to 30 minutes, growth of carbon nanotubes; and stop the introduction of carbon source gas, the carbon nanotubes stop growing, while stopping the heating, and cooling, after falling to room temperature, will form a banded nano The insulating substrate 110 of the carbon tube array is taken out of the reaction chamber.

The shielding gas is nitrogen or an inert gas. The carbon source gas may be selected from the chemically active hydrocarbons such as ethanol, acetylene and ethylene. The carrier gas is hydrogen. The flow rate of the carbon source gas is 20 to 200 sccm, and the flow rate of the carrier gas is 50 to 600 sccm. After the carbon source gas is stopped, the protective gas is continuously supplied until the temperature of the reaction chamber is lowered to room temperature to prevent the grown carbon nanotube from being oxidized.

In this embodiment, the shielding gas is argon, the carbon source gas is acetylene, the reaction temperature is 800 ° C, and the growth time of the carbon nanotubes is 60 minutes.

In addition, the properties of the grown carbon nanotubes, such as pipe diameter, transparency, electrical resistance, etc., can be controlled by adjusting the flow ratio of the carbon source gas to the carrier gas. In the embodiment of the technical solution, when the flow ratio of the carbon source gas and the carrier gas is 1:100 to 10:100, a single-walled carbon nanotube can be grown. When the flow ratio of the carbon source gas is continuously increased, a double-walled carbon nanotube can be grown. Therefore, the carbon nanotubes in the array of ribbon-shaped carbon nanotubes formed may be single-walled carbon nanotubes or double-walled carbon nanotubes. The single-walled carbon nanotube has a diameter of 0.5 nm to 50 nm, and the double-walled carbon nanotube has a diameter of 1.0 nm to 50 nm. Preferably, The diameter of the carbon nanotubes is less than 10 nm.

Under certain conditions, the growth height of the ribbon-shaped carbon nanotube array increases with the growth time. The strip-shaped carbon nanotube array has a growth height of up to 1 mm to 10 mm. In the embodiment of the technical solution, after the carbon source gas and the carrier gas are introduced for 60 minutes, the height of the strip-shaped carbon nanotube array grown is 1 mm to 2 mm.

The ribbon-shaped carbon nanotube array is a pure carbon nanotube array formed of a plurality of long-length carbon nanotubes. By controlling the growth conditions, such as the growth temperature, the flow ratio of the carbon source gas and the carrier gas, etc., the carbon nanotubes in the ribbon-shaped carbon nanotube array are substantially free of impurities such as amorphous carbon or residual catalyst metal particles. Wait.

The step of processing the ribbon-shaped carbon nanotube array to form the carbon nanotube layer can be achieved in the following three ways: First, the strip-shaped carbon nanotube array is processed by an organic solvent treatment method to form a nano carbon Pipe layer. Second, the strip-shaped carbon nanotube array is treated by a mechanical external force treatment to form a carbon nanotube layer. Third, the strip-shaped carbon nanotube array is treated by a gas flow treatment to form a carbon nanotube layer.

The method for treating the carbon nanotube array by an organic solvent treatment method to form a carbon nanotube layer comprises the following steps: providing a container containing an organic solvent; forming a ribbon-shaped carbon nanotube array The insulating substrate 110 is immersed in a container containing an organic solvent; and the insulating substrate 110 is taken out from the organic solvent in a length direction perpendicular to the array of the ribbon-shaped carbon nanotubes, the array of the carbon nanotubes being in an organic solvent Dipping under the action of surface tension, adhering to the surface of the insulating substrate 110; volatilizing the organic solvent Forming a carbon nanotube layer. The organic solvent may be selected from a volatile organic solvent such as ethanol, methanol, acetone, dichloroethane or chloroform, and ethanol is used in this embodiment. The formed carbon nanotube layer can be attached to the surface of the substrate under the action of the surface tension of the volatile organic solvent, and the surface volume ratio is reduced, the viscosity is lowered, and the mechanical strength and toughness are good.

The method for processing the ribbon carbon nanotube array by using a mechanical external force treatment method to form a carbon nanotube layer specifically includes the steps of: providing a pressure head; and directing the pressure head perpendicular to the ribbon The ribbon carbon nanotube array is milled in the longitudinal direction of the carbon nanotube array, and the carbon nanotubes are poured perpendicularly to the length of the ribbon-shaped carbon nanotube array to form a carbon nanotube layer. The indenter is a roller-shaped indenter. The mechanical external force applying device is not limited to the above-mentioned indenter, and may be another device having a certain flat surface as long as the carbon nanotubes in the strip-shaped carbon nanotube array can be perpendicular to the strip shape. The length of the carbon nanotube array can be dumped. Under the action of pressure, the array of ribbon-shaped carbon nanotubes can be separated from the grown substrate to form a carbon nanotube layer having a self-supporting structure composed of a plurality of carbon nanotubes.

The method for treating the ribbon carbon nanotube array by using a gas flow treatment method to form a carbon nanotube layer comprises the following steps: providing a fan, the fan generating an air flow; and the fan being perpendicular to the Applying a gas flow to the array of the ribbon-shaped carbon nanotubes in the longitudinal direction of the ribbon-shaped carbon nanotube array, the carbon nanotubes are poured perpendicularly to the length of the array of the ribbon-shaped carbon nanotubes to form a nanometer Carbon tube layer. The application means of the air flow is not limited to the above-described fan, and may be any device that can generate an air flow.

In this embodiment, the density of the carbon nanotube layer and the above strip catalyst The width of the film is related. The greater the width of the strip catalyst film, the greater the density of the prepared carbon nanotube layer; conversely, the smaller the width of the strip catalyst film, the higher the density of the prepared carbon nanotube layer. small. It will be appreciated that by controlling the width of the strip catalyst film, the density of the prepared carbon nanotube layer can be controlled.

It can be understood that, due to the high growth temperature of the above-mentioned carbon nanotubes, the material of the above-mentioned insulating substrate 110 must use a hard material resistant to high temperature, thereby limiting the selection of the substrate material. In order to enable the thin film transistor 10 to adopt a wider substrate material, especially a flexible substrate material, a flexible thin film transistor 10 is formed, which can be further passed through a transfer step after growing the carbon nanotube layer. The carbon nanotube layer is transferred onto other substrates. Specifically, the transferring step includes the steps of: firstly, providing a transfer substrate; secondly, inverting the insulating substrate 110 formed with the carbon nanotube layer on the transfer substrate to make the surface of the carbon nanotube layer Contacting the surface of the transfer substrate to form a three-layer structure including an insulating substrate 110, a carbon nanotube layer and a transfer substrate in order from top to bottom; again, hot pressing the three-layer structure; finally, removing the insulating substrate 110 Thereby, the above-mentioned carbon nanotube layer is adhered to the surface of the transfer substrate.

The material of the transfer substrate is a flexible material such as a plastic or resin material. In this embodiment, the transfer substrate is a PET film. The temperature and time of hot pressing depend on the kind of material of the transfer substrate. When the material of the transfer substrate is a plastic or a resin, the hot pressing temperature is 50 to 200 ° C, and the hot pressing time is 5 to 30 minutes. By the hot pressing step, the carbon nanotubes are more closely bonded to the surface of the transfer substrate, so that they can be easily separated from the insulating substrate 110.

Referring to FIG. 3, the prepared carbon nanotube layer comprises a plurality of carbon nanotubes arranged in a preferred orientation. The plurality of carbon nanotubes in the carbon nanotube layer have substantially equal lengths. Preferably, the plurality of carbon nanotubes in the carbon nanotube layer are parallel to each other.

The step of forming a carbon nanotube layer directly on the surface of the insulating substrate 110 specifically includes the steps of: providing a growth substrate having a monodisperse catalyst layer formed on the surface thereof; placing the growth substrate and the insulating substrate 110 a reaction chamber, and the growth substrate and the insulating substrate 110 are spaced apart, heated to a growth temperature of the carbon nanotubes under a protective gas atmosphere, and a carbon source gas is introduced to grow the carbon nanotubes along the direction of the gas flow. A carbon nanotube film is formed on the surface of the insulating substrate 110 to form a carbon nanotube layer.

The material of the catalyst may be an alloy material of iron, cobalt, nickel or any combination thereof, or a monodisperse solution of a metal salt or a monodisperse solution of a metal. When a monodisperse catalyst layer is prepared using an alloy material of iron, cobalt, nickel or any combination thereof, a deposition method may be used to deposit the catalyst material onto the surface of the growth substrate; when a monodisperse solution of the metal salt or monodispersity of the metal is selected The solution prepares a monodisperse catalyst layer, and a monodispersity solution of a metal salt or a metal can be applied to the growth substrate, and the catalyst layer is formed after drying.

The growth substrate is a high temperature resistant substrate, and the material thereof is not limited as long as the melting point thereof is higher than the growth temperature of the carbon nanotubes. The shape of the substrate is not limited and may be any shape such as a square shape, a circular shape, or the like. The growth substrate described in the embodiment of the present technical solution adopts the same material and the same size substrate as the insulating substrate 110.

The carbon nanotube has a growth temperature of 800 ° C to 1000 ° C. After the carbon source gas is introduced, the growth of the carbon nanotubes is started under the action of the catalyst particles on the surface of the growth substrate. The carbon nanotube is fixed at one end to the growth substrate and the other end is continuously grown. Since the catalyst layer includes a plurality of monodisperse catalyst particles, the grown carbon nanotubes are not dense, so that a part of the carbon nanotubes can grow into a longer length of carbon nanotubes. The carbon source gas is introduced from near the growth substrate, so as the carbon source gas is continuously introduced, the grown carbon nanotubes float over the insulating substrate 110 with the carbon source gas. This growth mechanism is called the “flying kite mechanism”. The growth time of the carbon nanotubes is related to the length of the carbon nanotubes to be prepared. In this embodiment, when the growth time is 30 minutes, the length of the carbon nanotubes grown can be up to 8 cm. When the carbon source gas is stopped, the carbon nanotubes stop growing, and are formed in parallel and spaced on the insulating substrate 110 to form a carbon nanotube film. The distance between two adjacent carbon nanotubes in the carbon nanotube film is greater than 20 microns.

Further, in order to increase the density of the carbon nanotubes in the grown carbon nanotube film, the carbon nanotubes can be realized by replacing the new growth substrate or removing the original growth substrate and depositing a new catalyst film after cleaning. The plurality of carbon nanotube films are formed by a plurality of growths, thereby increasing the density of the grown carbon nanotube film, and the plurality of carbon nanotube films form a carbon nanotube layer. In addition, in the multiple growth of the above carbon nanotubes, the insulating substrate 110 may also be rotated by a certain angle so that the carbon nanotubes in the adjacent two layers of carbon nanotube film have a crossing angle α. , α is greater than or equal to 0 degrees and less than or equal to 90 degrees. The carbon nanotube layer comprises a plurality of carbon nanotubes, and the carbon nanotubes are tightly combined by a van der Waals force to form a self-supporting structure.

In addition, when the area of the prepared carbon nanotube layer is large, or when it is required to prepare a plurality of thin film transistors 10, the formed carbon nanotube layer can be etched into a plurality of shapes and sizes having a desired shape. The carbon nanotube layer is used as the semiconductor layer 140. The etching method is not limited and may be any etching method in the prior art.

Step 3: A source 151 and a drain 152 are formed at intervals, and the source 151 and the drain 152 are electrically connected to both ends of a portion of the carbon nanotubes in the semiconductor layer 140.

The material of the source 151 and the drain 152 should have good electrical conductivity. Specifically, the material of the source 151 and the drain 152 may be conductive, such as metal, alloy, indium tin oxide (ITO), antimony tin oxide (ATO), conductive silver paste, conductive polymer, and carbon nanotube film. material. The source 151 and the drain 152 can be formed by different methods depending on the type of material forming the source 151 and the drain 152. Specifically, when the material of the source 151 and the drain 152 is metal, alloy, ITO or ATO, the source 151 and the drain 152 may be formed by sputtering, sputtering, deposition, masking, etching, or the like. . When the material of the source 151 and the drain 152 is a conductive silver paste, a conductive polymer or a carbon nanotube film, the conductive silver paste or the carbon nanotube film can be coated by direct adhesion or printing. The source 151 and the drain 152 are formed by being applied or adhered to the surface of the insulating substrate 110 or the semiconductor layer 140. Generally, the source 151 and the drain 152 have a thickness of 0.5 nm to 100 μm, and the distance between the source 151 and the drain 152 is 1 to 100 μm.

In this embodiment, the material of the source 151 and the drain 152 is metal. The above step 3 can be specifically carried out in the following two ways. The first method specifically includes the following steps: First, uniformly coating the surface of the above semiconductor layer 140 Coating a layer of photoresist; secondly, forming a source 151 and a drain 152 region on the photoresist by a lithography method such as exposure and development, exposing the semiconductor layer 140 in the source 151 and the drain 152; again, by vacuum sputtering A deposition method such as plating, magnetron sputtering or electron beam evaporation deposition deposits a metal layer on the surface of the photoresist, source 151 and drain 152 regions, preferably a palladium, titanium or nickel metal layer; finally, an organic solvent such as acetone The photoresist and the metal layer thereon are removed, that is, the source 151 and the drain 152 formed on the semiconductor layer 140 are obtained. The second method specifically includes the following steps: first, depositing a metal layer on the surface of the semiconductor layer 140; secondly, applying a layer of photoresist on the surface of the metal layer; again, removing the source 151 region by a lithography method such as exposure and development; The photoresist outside the drain 152 region; finally, the metal layer outside the source 151 region and the drain 152 region is removed by plasma etching or the like, and the source 151 region and the drain 152 region are removed by an organic solvent such as acetone. The photoresist, that is, the source 151 and the drain 152 formed on the semiconductor layer 140 are obtained. In this embodiment, the source 151 and the drain 152 have a thickness of 1 micron, and the distance between the source 151 and the drain 152 is 50 micrometers.

It can be understood that, in order to obtain the semiconductor layer 140 having better semiconductor properties, after the source electrode 151 and the drain electrode 152 are formed, a step of removing the conductive carbon nanotubes in the semiconductor layer 140 may be further included. Specifically, the method includes the following steps: first, providing an external power supply, and secondly, connecting the positive and negative poles of the external power source to the source 151 and the drain 152; finally, applying a large voltage across the source 151 and the drain 152 through the external power source. The conductive carbon nanotube is heated and ablated to obtain a semiconducting semiconductor layer 140. This voltage is in the range of 1 to 1000 volts.

In addition, the above method of removing the conductive carbon nanotubes in the semiconductor layer 140 is also The semiconductor layer 140 may be irradiated with hydrogen plasma, microwave, terahertz (THz), infrared (IR), ultraviolet (UV) or visible light (Vis) to heat and ablate the conductive carbon nanotube to obtain a semiconducting property. Semiconductor layer 140.

Step 4: Form an insulating layer 130 on the semiconductor layer 140.

The material of the insulating layer 130 may be a hard material such as tantalum nitride or tantalum oxide or a flexible material such as benzocyclobutene (BCB), polyester or acrylic resin. The insulating layer 130 may be formed by different methods depending on the kind of the material of the insulating layer 130. Specifically, when the material of the insulating layer 130 is tantalum nitride or tantalum oxide, the insulating layer 130 may be formed by a deposition method. When the material of the insulating layer 130 is benzocyclobutene (BCB), polyester or acrylic resin, the insulating layer 130 can be formed by a printing coating method. Generally, the insulating layer 130 has a thickness of 0.5 nm to 100 μm.

In the present embodiment, a tantalum nitride insulating layer 130 is formed on the surface of the semiconductor layer 140 and the source electrode 151 and the drain 152 formed on the semiconductor layer 140 by a deposition method such as plasma chemical vapor deposition. The insulating layer 130 has a thickness of about 1 micron.

It can be understood that, depending on the different applications of the thin film transistor 10, a portion of the source 151 and the drain 152 may be exposed outside the insulating layer 130 by lithography or etching similar to the formation of the source 151 and the drain 152.

Step 5: forming a gate 120 on the surface of the insulating layer 130 to obtain a thin film transistor 10.

The material of the gate 120 should have good electrical conductivity. Specifically, the material of the gate 120 may be metal, alloy, ITO, ATO, conductive silver paste, A conductive material such as a conductive polymer or a carbon nanotube film. The metal or alloy material may be aluminum, copper, tungsten, molybdenum, gold or alloys thereof. Specifically, when the material of the gate 120 is metal, alloy, ITO or ATO, the gate 120 may be formed by sputtering, sputtering, deposition, masking, etching, or the like. When the material of the gate 120 is a conductive silver paste, a conductive polymer or a carbon nanotube film, the gate 120 can be formed by direct adhesion or printing. Generally, the gate 120 has a thickness of 0.5 nm to 100 μm.

In the embodiment of the present technical solution, a conductive film is formed as the gate 120 at a position on the surface of the insulating layer 130 and opposite to the semiconductor layer 140 by a method similar to the formation of the source electrode 151 and the drain electrode 152. The gate 120 is electrically insulated from the semiconductor layer 140 by an insulating layer 130. In the embodiment of the technical solution, the material of the gate 120 is palladium, and the thickness of the gate 120 is about 1 micrometer.

Referring to FIG. 4 and FIG. 5, the second embodiment of the present invention provides a method for preparing the bottom gate type thin film transistor 20, which is basically the same as the method for preparing the thin film transistor 10 in the first embodiment. The main difference is that the thin film transistor 20 formed in this embodiment is a bottom gate type structure. The method for preparing the thin film transistor 20 of the second embodiment of the present technical solution includes the following steps:

Step 1: Provide a growth substrate.

Step 2: forming a carbon nanotube layer on the surface of the growth substrate, the carbon nanotube layer comprising a plurality of carbon nanotubes.

Step 3: Provide an insulating substrate 210.

Step 4: Form a gate 220 on the surface of the insulating substrate 210.

Step 5: Form an insulating layer 230 to cover the gate 220.

Step 6: Transfer the carbon nanotube layer to the surface of the insulating layer 230 to form a semiconductor layer 240.

The transferring step specifically includes the following steps: first, the growth substrate formed with the carbon nanotube layer is inverted on the insulating substrate 210 to bring the surface of the carbon nanotube layer into contact with the surface of the insulating layer 230, thereby forming a top to bottom The lower layer comprises a three-layer structure of a growth substrate, a carbon nanotube layer and an insulating substrate 210; again, the three-layer structure is hot-pressed; finally, the growth substrate is removed, thereby adhering the carbon nanotube layer to the insulating layer. At the surface of 230, a semiconductor layer 240 is formed.

When the growth substrate on which the carbon nanotube layer is formed is inverted on the insulating substrate 210, it is ensured that the surface of the carbon nanotube layer is adhered to the surface of the insulating layer 230, thereby adhering the carbon nanotube layer to the insulation. On layer 230.

Step 7: forming a source 251 and a drain 252 at intervals, and electrically connecting the source 251 and the drain 252 to both ends of a portion of the carbon nanotubes in the semiconductor layer 240.

The source 251, the drain 252, the gate 220, and the insulating layer 230 may be formed in the same manner as in the first embodiment.

Referring to FIG. 6, a third embodiment of the present technical solution provides a method for preparing a thin film transistor, which is basically the same as the method for preparing the thin film transistor 10 of the first embodiment. The main difference is that this embodiment forms a plurality of thin film transistors on the same insulating substrate to form a thin film transistor array. The method for preparing the thin film transistor of the embodiment specifically includes the following steps:

Step 1: Provide an insulating substrate.

Step 2: uniformly forming a plurality of carbon nanotube layers on the surface of the insulating substrate, the carbon nanotube layer comprising a plurality of carbon nanotubes to form a plurality of semiconductor layers.

Step 2 above can be performed in two ways. The first method specifically includes the steps of: forming a large area of the carbon nanotube layer on the surface of the insulating substrate; and patterning the carbon nanotube layer by a mask and etching, thereby different in forming a thin film transistor The location forms a plurality of carbon nanotube layers. The second method specifically includes the steps of: forming a plurality of strip-shaped catalyst films at positions where the thin film transistors are pre-formed; growing a plurality of strip-shaped carbon nanotube arrays by chemical vapor deposition; and applying a plurality of strip-shaped nanotubes The carbon tube array is processed to form a plurality of carbon nanotube layers.

The plurality of strip catalyst films may be formed by multiple deposition by a thermal deposition method, an electron beam deposition method, or a sputtering method, or may be realized by a lithography method or a mask mold method. The spacing between the strip catalyst films is preferably from 10 micrometers to 15 millimeters. The strip catalyst film has a width of from 1 μm to 20 μm. The strip catalyst film has a thickness of from 0.1 nm to 10 nm.

Step 4: forming a plurality of sources and a plurality of drains at intervals, and electrically connecting both ends of each of the carbon nanotubes in each of the semiconductor layers to a source and a drain.

Similar to the method of forming the source electrode 151 and the drain electrode 152 in the first embodiment of the present technical solution, a metal film may be deposited on the surface of the entire insulating substrate on which the plurality of semiconductor layers are formed, and then patterned by etching or the like. The film is such that a plurality of sources and a plurality of drains are formed at a predetermined position. The above source and drain materials can also be ITO, ATO, conductive polymerization Material, conductive silver glue or carbon nanotubes.

Step 5: forming an insulating layer on the surface of each of the semiconductor layers.

The method for forming the insulating layer is similar to the method for preparing the insulating layer 130 in the thin film transistor 10 in the first embodiment of the present invention. A tantalum nitride film may be deposited on the surface of the entire insulating substrate, and then etched or the like. The tantalum nitride film is patterned to form a plurality of insulating layers at a predetermined position. The material of the insulating layer may be a hard material such as cerium oxide or a flexible material such as benzocyclobutene (BCB), polyester or acrylic resin.

Step 6: forming a gate on the surface of each insulating layer to obtain a plurality of thin film transistors.

It can be understood that a plurality of thin film transistors can be formed by a method similar to that of the second embodiment, thereby forming a thin film transistor array, which specifically includes the following steps:

Step 1: Provide a growth substrate.

Step 2: forming a carbon nanotube layer on the surface of the growth substrate, the carbon nanotube layer comprising a plurality of carbon nanotubes.

Step 3: Provide an insulating substrate.

Step 4: forming a plurality of gates on the surface of the insulating substrate.

Step 5: forming at least one insulating layer to cover the plurality of gates.

Step 6: laying the at least one carbon nanotube layer on the surface of the insulating layer, patterning the carbon nanotube layer to form a plurality of semiconductor layers, and the plurality of semiconductor layers and the plurality of gates are opposite to each other through the insulating layer Insulation setting.

Step 7: forming a plurality of source electrodes and a plurality of drain electrodes at intervals, and electrically connecting the source and the drain electrodes to both ends of a portion of the carbon nanotubes in the semiconductor layer to form a plurality of thin film transistors.

The method for preparing a thin film transistor of the embodiment of the present invention has the following advantages: first, since the semiconductor layer can be directly formed on the insulating substrate, or by performing an array of carbon nanotubes formed on the growth substrate The method of forming a semiconductor layer is simpler than the method of forming a thin film transistor semiconductor layer by a spray method in the prior art, and does not require a step of dispersing a carbon nanotube in an organic solvent. Second, since the carbon nanotubes in the prepared carbon nanotube layer are arranged in parallel in a certain direction, when the carbon nanotube layer is used as a semiconductor layer, it can be controlled by controlling the direction in which the carbon nanotube layer is disposed. The orientation of the source-to-deuterium carbon nanotubes allows the thin film transistor to achieve a large carrier mobility. Thirdly, due to the excellent mechanical properties of the carbon nanotubes, the semiconductor layer composed of a plurality of preferentially oriented or carbon nanotubes having a certain angle of intersection has good toughness and mechanical strength, thereby facilitating the preparation of the flexible film. Transistor. Fourth, a plurality of thin film transistors can be prepared by etching the prepared large-area carbon nanotube layer or preparing a plurality of carbon nanotube layers, thereby realizing mass production of the thin film transistor, and the method is prepared by the method. Thin film transistors are less expensive. Fifthly, since the carbon nanotube layer provided in the embodiment can transfer the carbon nanotube layer to other substrates by a transfer step, the material of the substrate can be selected from a flexible material that is not resistant to high temperature, which is advantageous for preparation. Flexible film transistor.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above is only a preferred embodiment of the present invention. It is not possible to limit the scope of patent application in this case. Equivalent modifications or variations made by those skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

10,20‧‧‧film transistor

110,210‧‧‧Insulation base

120,220‧‧‧ gate

130,230‧‧‧Insulation

140,240‧‧‧ semiconductor layer

151,251‧‧‧ source

152,252‧‧‧汲polar

1 is a flow chart of a method for preparing a thin film transistor according to a first embodiment of the present technical solution.

2 is a flow chart showing a process for preparing a thin film transistor of the first embodiment of the present technical solution.

Fig. 3 is a scanning electron micrograph of a carbon nanotube layer of the first embodiment of the present technical solution.

4 is a flow chart of a method for preparing a thin film transistor according to a second embodiment of the present technical solution.

FIG. 5 is a flow chart showing the preparation process of the thin film transistor of the second embodiment of the present technical solution.

6 is a flow chart of a method for preparing a thin film transistor according to a third embodiment of the present technical solution.

Claims (13)

A method for preparing a thin film transistor, comprising the steps of: providing an insulating substrate; growing an array of ribbon-shaped carbon nanotubes on the surface of the insulating substrate, processing the array of ribbon-shaped carbon nanotubes, and making the strip-shaped nano tube The carbon tube array is tilted in a direction perpendicular to the length of the strip of carbon nanotube array, thereby forming a semiconductor layer including a plurality of carbon nanotubes on the surface of the insulating substrate; forming a source and a drain in the space a surface of the semiconductor layer, and electrically connecting the source and the drain to both ends of the portion of the carbon nanotube; forming an insulating layer on the surface of the semiconductor layer forming the source and the drain; and forming A gate is formed on the surface of the insulating layer to obtain a thin film transistor. The method for preparing a thin film transistor according to the first aspect of the invention, wherein the method for growing a strip of carbon nanotube array on the surface of the insulating substrate comprises the following steps: forming a strip on the surface of the insulating substrate The catalyst film has a width of 1 micrometer to 20 micrometers, and a strip of carbon nanotube array is grown by chemical vapor deposition. The method for preparing a thin film transistor according to the second aspect of the invention, wherein the method for growing a ribbon carbon nanotube array by chemical vapor deposition comprises the following steps: forming a strip catalyst film as described above The substrate is placed in a reaction chamber; the shielding gas is introduced to discharge the air in the reaction chamber; and the reaction chamber is heated to 600 ° C to 900 ° C in a protective gas atmosphere, and maintained Constant temperature; carbon source gas and carrier gas with a flow ratio of 1:30~1:3, reacting for 5~30 minutes, growing carbon nanotubes; and stopping the introduction of carbon source gas, the carbon nanotubes stop growing, and at the same time The heating was stopped and the temperature was lowered. After the temperature was lowered to room temperature, the substrate on which the ribbon-shaped carbon nanotube array was formed was taken out from the reaction chamber. The method for preparing a thin film transistor according to claim 1, wherein the strip-shaped carbon nanotube array is processed such that the strip-shaped carbon nanotube array is perpendicular to a length of the strip-shaped carbon nanotube array The method of pouring in the direction is an organic solvent treatment method, which specifically comprises the steps of: providing a container containing an organic solvent; immersing the insulating substrate formed with the array of ribbon-shaped carbon nanotubes in a container containing an organic solvent; The substrate is taken out from the organic solvent in a direction perpendicular to the length of the strip of carbon nanotube array, the carbon nanotube array is poured under the surface tension of the organic solvent, adhered to the surface of the insulating substrate; The solvent evaporates. The method for preparing a thin film transistor according to the above aspect of the invention, wherein the processing the strip-shaped carbon nanotube array, the strip-shaped carbon nanotube array is perpendicular to the strip-shaped carbon nanotube array The method of tilting the direction of the length is a mechanical external force treatment method, which specifically includes the steps of: providing an indenter; and rolling the indenter along the length direction perpendicular to the array of the strip of carbon nanotubes In the tube array, the carbon nanotubes are poured along a length perpendicular to the array of the ribbon-shaped carbon nanotube tubes. a method for preparing a thin film transistor according to claim 1, wherein The method for processing the ribbon-shaped carbon nanotube array to cause the ribbon-shaped carbon nanotube array to be tilted in a direction perpendicular to the length of the strip-shaped carbon nanotube array is an airflow treatment method, which specifically includes the following steps: Providing a fan that generates a gas flow; and applying a gas flow to the array of the ribbon carbon nanotubes along a length perpendicular to the array of the ribbon carbon nanotubes, the carbon nanotubes being vertical It is poured in the longitudinal direction of the ribbon-shaped carbon nanotube array. The method for producing a thin film transistor according to claim 1, wherein after the source and the drain are formed, a step of removing the conductive carbon nanotube in the semiconductor layer is further included. The method for preparing a thin film transistor according to claim 7, wherein the method for removing the conductive carbon nanotube in the semiconductor layer comprises the steps of: providing an external power source; connecting the positive and negative poles of the external power source To the source and the drain; and applying a voltage of 1 to 1000 volts across the source and the drain by an external power source, the conductive carbon nanotube is heated and ablated to obtain a semiconducting semiconductor layer. The method for producing a thin film transistor according to claim 7, wherein the step of removing the conductive carbon nanotube in the semiconductor layer is by hydrogen plasma, microwave, terahertz, infrared, ultraviolet or visible light. The semiconductor layer is irradiated to ablate the conductive carbon nanotube. A method for preparing a thin film transistor, comprising the steps of: providing a growth substrate; growing an array of ribbon-shaped carbon nanotubes on the surface of the growth substrate, processing the array of ribbon-shaped carbon nanotubes, and making the strip-shaped nano tube The carbon tube array is perpendicular to the strip The direction of the length of the carbon nanotube array is poured, thereby forming a carbon nanotube layer including a plurality of carbon nanotubes on the surface of the growth substrate; providing an insulating substrate; forming a gate on the surface of the insulating substrate; forming An insulating layer covers the gate; transferring the carbon nanotube layer to a surface of the insulating layer to form a semiconductor layer; and spacing to form a source and a drain, and the source and the drain are A plurality of carbon nanotubes in the semiconductor layer are electrically connected to each other to form a thin film transistor. The method for preparing a thin film transistor according to claim 10, wherein the method of transferring the carbon nanotube layer to the surface of the insulating layer to form a semiconductor layer comprises the following steps: The growth substrate of the carbon nanotube layer is inverted on the insulating substrate to form a three-layer structure including a growth substrate, a carbon nanotube layer and an insulating substrate from top to bottom; the three-layer structure is hot pressed; and the growth is removed. The substrate is such that the above-mentioned carbon nanotube layer is adhered to the surface of the insulating substrate. A method for preparing a thin film transistor, comprising the steps of: providing an insulating substrate; uniformly growing a plurality of strip-shaped carbon nanotube arrays on the surface of the insulating substrate, and processing the plurality of strip-shaped carbon nanotube arrays for each a strip of carbon nanotube arrays are all tilted in a direction perpendicular to the length of the strip of carbon nanotube array, thereby forming a plurality of semiconductor layers on the surface of the insulating substrate, each semiconductor layer comprising a plurality of carbon nanotubes; Forming a plurality of sources and a plurality of drains at intervals, and electrically connecting both ends of a portion of the carbon nanotubes in each of the semiconductor layers to a source and a drain; forming an insulating layer on each of the semiconductor layers a surface; and forming a gate on the surface of each insulating layer to obtain a plurality of thin film transistors. The method for producing a thin film transistor according to claim 12, wherein the method of uniformly growing a plurality of strip-shaped carbon nanotube arrays on the surface of the insulating substrate comprises the step of: pre-forming a position of the thin film transistor A plurality of strip-shaped catalyst films are formed; and a plurality of strip-shaped carbon nanotube arrays are grown by chemical vapor deposition.