CN106941130A - Flexible field-effect transistor and preparation method thereof - Google Patents

Abstract

The invention discloses a flexible field effect transistor and a preparation method thereof. The flexible field effect transistor includes: a source and a drain arranged on the flexible substrate at intervals and located on the same plane, the source and the drain are electrically connected through a semiconductor conductive channel; covering the semiconductor conductive channel a dielectric layer on the track; and a grid stacked on the dielectric layer. Wherein, the semiconductor conductive channel adopts a carbon nanotube layer or a redox graphene layer. In the present invention, a field-effect transistor with good performance is prepared on a flexible substrate by combining micro-electro-mechanical system processing technology, printed electronic technology and nano-carbon materials. It has simple structure, flexible process, low cost, and is suitable for large quantities. Production.

Description

Flexible field effect transistor and its preparation method

technical field

The invention relates to the technical field of semiconductors, in particular to a flexible field effect transistor and a preparation method thereof.

Background technique

At present, conventional electronic devices in the semiconductor and microelectronics industries are usually prepared on silicon substrates combined with micro-nano processing techniques. These silicon-based electronic devices played a major role in the development of human society in the second half of the last century. However, with the needs of future electronic products in terms of convenience, ultra-thinness, and flexibility, it is necessary to find a new generation of electronic devices. Electronic devices and related fabrication techniques. Flexible Electronics (Flexible Electronics) has developed very rapidly in recent years due to its unique advantages in scalability, diversification, and low cost. At present, flexible electronics is a general term for a technology, because it is in the stage of development.

The biggest feature of flexible electronic devices is the flexibility of their structures, which not only has the characteristics of traditional semiconductor functional electronic devices, but also enables the devices to adapt to large deformations in the environment. The key to flexible devices is the flexible design of the structure. Taking plastic straight pipes and corrugated pipes as examples, plastic straight pipes have very little stretchability and bending, but elastic corrugated pipes have great stretching and bending deformation capabilities through the expansion and contraction characteristics of the corrugated structure.

However, due to the physical characteristics of organic semiconductors such as electricity and silicon-based semiconductors, there is still a large distance compared with silicon-based semiconductors. For example, the mobility and device operating frequency of organic semiconductor materials are lower than those of inorganic semiconductors. The conversion efficiency of the device is lower than that of inorganic semiconductor devices.

In recent years, with the continuous improvement of the level of micro-nano processing and the continuous expansion of the field of semiconductors and materials, the preparation of flexible electronic devices can be realized through different high-precision manufacturing processes and methods. Such flexible electronic devices have the ability to maintain good performance under deformations such as tension, compression, bending, and torsion, as well as good portability and adaptability.

Field Effect Transistor (Field Effect Transistor, FET) has the advantages of high input resistance, low noise, low power consumption, large dynamic range, easy integration, no secondary breakdown phenomenon, and wide safe working area. widely used in circuits.

At present, most field effect transistors are based on hard materials such as single crystal silicon, and flexible effect transistors are widely used in flexible, large-area, low-cost electronic paper and radio frequency trademarks due to their advantages of bendability and convenience. Potential applications in storage and memory devices have attracted widespread attention. Among them, Chinese patent application (publication number: CN104051652A) discloses a thin film transistor based on a flexible substrate. This patent application discloses the preparation of indium gallium zinc oxide as a semiconductor layer on a flexible substrate by means of evaporation and etching. Although this patent realizes the preparation of a field effect transistor on a flexible substrate, during the device preparation process, It still needs to go through semiconductor processes such as etching and photolithography. The steps are complicated and the cost is high. It is difficult to realize the advantages of large-volume and low-cost flexible electronic devices.

Contents of the invention

The main purpose of the present invention is to provide a flexible field effect transistor and its preparation method to overcome the deficiencies in the prior art.

In order to achieve the above object, the present invention adopts the following technical solutions:

An embodiment of the present invention provides a flexible field effect transistor, comprising: a source and a drain disposed on a flexible substrate at intervals and located on the same plane, and the source and drain are electrically connected through a semiconductor conductive channel; a dielectric layer covering the semiconductor conductive channel; and a grid stacked on the dielectric layer.

Further, the conductive material used to form the source, drain or gate includes nano-carbon material or metal material.

The nanocarbon material includes carbon nanotubes or graphene, but is not limited thereto.

The metal material includes Ag, Au or Al, but is not limited thereto.

More preferably, the thickness of the source, drain or gate is 2-50 μm.

More preferably, the semiconductor conductive channel is mainly composed of carbon nanotubes or redox graphene.

Further, the semiconductor conductive channel adopts a carbon nanotube film or a redox graphene film attached to the flexible substrate.

More preferably, the thickness of the semiconductor conductive channel is 50 nm˜10 μm.

Further, the material used to form the dielectric layer includes polyimide or aluminum oxide, but is not limited thereto.

More preferably, the thickness of the dielectric layer is 1-50 μm.

Further, the material used to form the flexible substrate includes polyimide (PI), polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), but not limited thereto.

More preferably, the thickness of the flexible substrate is 5-50 μm.

An embodiment of the present invention provides a method for preparing the flexible field effect transistor, which includes:

a. Forming a flexible substrate on a hard substrate;

b. preparing and forming source electrodes and drain electrodes arranged at intervals on the flexible substrate;

c, preparing a semiconductor conductive channel between the source and the drain to electrically connect the source and the drain;

d, preparing a dielectric layer on the semiconductor conductive channel;

e, preparing a gate on the dielectric layer.

In some embodiments, the preparation method includes: preparing the source, drain, dielectric layer or gate by using MEMS technology or printed electronics technology. Preferably, the source, drain or gate is fabricated using MEMS technology.

In some embodiments, the preparation method includes: using printed electronics technology to prepare a semiconductor conductive channel.

Further, the printed electronics technology includes air-jet printing process, ink-jet printing process or gravure printing process, but is not limited thereto.

More preferably, the conductive ink adopted in the printed electronic technology is carbon nanotube conductive ink, and the preparation method of the carbon nanotube conductive ink comprises:

(1) Utilize acid solution to carry out impurity removal treatment to carbon nanotube material, remove the metal impurity in carbon nanotube material;

(II) Purify and disperse the carbon nanotube material by using ultrasonic, cleaning and centrifuging process steps;

(III) performing suction filtration on the purified carbon nanotube material to obtain the purified carbon nanotube material;

(IV) Mix the purified carbon nanotube material with a dispersant, perform ultrasonic and centrifugation treatment, and take the centrifuged supernatant, which is the carbon nanotube conductive ink.

Further, the concentration of the carbon nanotube conductive ink is preferably 0.1-5 μg/mL.

More preferably, the conductive ink that described printing electronics technology adopts is redox graphene conductive ink, and the preparation method of described redox graphene conductive ink comprises:

(1) redox graphene is provided;

(II) Disperse and centrifuge the redox graphene with deionized water, and then add an organic solvent to prepare a redox graphene ink suitable for aerosol printing. The organic solvent includes ethanol.

Further, the concentration of the redox graphene conductive ink is preferably 0.1-5 μg/mL.

In some embodiments, the preparation method is characterized in that it also includes:

f. Obtain the flexible field effect transistor by scribing and peeling off.

The invention can ensure the precision of the electrode because the electrode of the field effect transistor is prepared by adopting the micro-electromechanical system technology. At the same time, the present invention uses printed electronics technology to realize the effective construction of carbon nanomaterials, and avoids damage to the substrate caused by high-temperature growth of carbon nanomaterials; in addition, the present invention utilizes micro-electromechanical systems technology or printed electronics technology to achieve the deposition of dielectric layers, The flexibility of device preparation is increased.

Compared with the prior art, the present invention has at least the following beneficial effects: by combining micro-electro-mechanical system processing technology, printed electronics technology and nano-carbon materials, a field-effect transistor with good performance is prepared on a flexible substrate, and its structure Simple, flexible process, low cost, suitable for mass production.

Description of drawings

Fig. 1 is a schematic structural diagram of a flexible field effect transistor in a typical embodiment of the present invention.

detailed description

One aspect of the present invention provides a flexible field effect transistor, comprising a substrate, a source, a drain, a conductive channel, a dielectric layer and a gate stacked in sequence.

Wherein, the materials of the substrate, the source, the drain, the conductive channel, the dielectric layer, the gate, etc. may be as described above, and will not be repeated here.

Another aspect of the present invention provides a method for preparing the flexible field effect transistor as described above, comprising steps:

(1) on hard substrate (as glass, silicon etc.) spin-coat one deck organic matter and solidify as flexible substrate;

(II) The source and drain of field effect transistors are prepared on flexible substrates using MEMS technology or printed electronics technology;

(III) Using printed electronics technology to prepare conductive channels of carbon nanomaterials;

(IV) The dielectric layer is prepared by MEMS technology or printed electronic technology;

(V) The gate is prepared by using micro-electro-mechanical system technology or printed electronic technology;

(VI) peel off the flexible material spin-coated in the first step from the hard substrate to obtain the flexible field effect transistor.

Preferably, the micro-electro-mechanical system processing technology includes photolithography, sputtering, evaporation, etching and other steps.

Preferably, the printed electronics process is selected from airjet printing process, inkjet printing process or gravure printing process.

More preferably, the air-jet printing process adopts the ultrasonic fogging mode, uses micro-nozzles with a diameter of about 100 μm, and controls the ratio of the surrounding airflow and the jetting airflow at the same time, so that the line width of the sprayed solution is 20-100 μm.

Preferably, the method further includes the step of: treating the flexible substrate with an oxygen plasma process or a solution activation method, so as to increase the contact between the flexible substrate and the material layer (such as source, Drain and conductive channel) binding force.

Preferably, the preparation method also includes the step of preparing carbon nanomaterial printing ink, firstly, using a chemical solution to remove impurities from the carbon nanomaterials, and then using ultrasonic, cleaning, and centrifugation steps to purify the carbon nanomaterials; and then using The dispersant disperses the purified carbon nanomaterials to form conductive ink.

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described below with examples in conjunction with the accompanying drawings.

Embodiment 1 Please refer to FIG. 1. The flexible flexible field effect transistor provided in this embodiment includes a flexible substrate 1, a source electrode 2, a drain electrode 3, a semiconductor conductive channel 4, a dielectric layer 5 and Grid 6.

Wherein, the material of the flexible substrate 1 is polyimide (Polyimide, PI).

Wherein, the material of the source electrode and the drain electrode is Ag.

Wherein, the semiconductor conductive channel is a single-walled carbon nanotube.

Wherein, the material of the dielectric layer is polyimide.

Wherein, the gate material is Ag.

The following describes the preparation method of the above-mentioned flexible field effect transistor, the method includes steps:

(1) Prepare the base material of the flexible field effect transistor on the hard substrate. Specifically, the glass substrate is first cleaned to remove particles and pollutants on the surface; then a layer of polyimide is spin-coated on the surface of the silicon substrate using the spin-coating process diagram, and cured in a programmed oven to obtain a thickness of Flexible polyimide film 1 on the scale of 5-50 microns;

(2) On the prepared polyimide film substrate, use inkjet printing technology combined with nano-Ag conductive ink to print out the source electrode 2 and drain electrode 3 of the flexible field effect transistor, with a thickness of 2-20 μm and an area of 100×100 μm ² to 500×500 μm ² .

(3) A semiconductor conductive channel 4 made of carbon nanotubes is prepared between the source electrode 2 and the drain electrode 3 by using a printed electronic process. First prepare carbon nanotube conductive ink, including:

1. Utilize the mixed solution of hydrochloric acid and hydrogen peroxide (volume ratio about 3:1) to carry out reflux treatment at 70°C for 6h, carry out impurity removal treatment, and remove metal impurities in carbon nanotubes;

II. The purified carbon nanotubes are suction-filtered and rinsed repeatedly with a suction filter bottle to clean the hydrogen peroxide, hydrochloric acid and metal ions in the carbon nanotubes. The cleaned carbon nanotubes were dried at 50°C.

III. Purify and disperse nano-scale carbon nanotube materials by using ultrasonic, cleaning and centrifuging process steps;

IV. Carry out suction filtration again to the purified carbon nanotubes, and extract semiconducting single-walled carbon nanotubes with high purity;

V. Disperse the purified carbon nanotubes in an aqueous solution of sodium dodecyl sulfate (SDS) (mass ratio H ₂ O:SDS=99:1). The carbon nanotube solution was ultrasonically dispersed with a cell pulverizer, and after ultrasonication for 5 hours at a power of 200W, the carbon nanotubes were uniformly dispersed in the SDS aqueous solution;

VI. Centrifuge the dispersed carbon nanotube SDS solution (8000-12000rpm), and let it stand for 24 hours;

VII. Take the centrifuged supernatant, which is the carbon nanotube conductive ink. Then, the prepared carbon nanotube conductive ink is used to form a single-walled carbon nanotube conductive channel 4 between the source electrode 2 and the drain electrode 3 by using an inkjet printing process.

(4) Preparing a dielectric layer 5 on the carbon nanotube conductive channel by using a printed electronics process. First, take an appropriate amount of polyimide solution and dilute it with ethanol to obtain a printable polyimide solution; then use air jet printing technology to print the diluted polyimide solution on the carbon nanotube conductive channel to obtain The dielectric layer 5 made of polyimide has a thickness of about 5-20 μm.

(5) On the prepared polyimide dielectric layer, the gate 6 of the flexible field effect transistor is printed by using inkjet printing technology combined with nano-Ag conductive ink.

(6) Then, the flexible field effect transistor is released from the glass substrate by scribing and stripping techniques to obtain a polyimide-based flexible field effect transistor.

Embodiment 2 Please refer to FIG. 1. The flexible field effect transistor provided in this embodiment includes a flexible substrate 1, a source electrode 2, a drain electrode 3, a semiconductor conductive channel 4, a dielectric layer 5 and a gate electrode that are sequentially stacked. Pole 6.

Wherein, the material of the flexible substrate 1 is polydimethylsiloxane (PDMS).

Wherein, the source and drain materials are Au.

Wherein, the semiconductor conductive channel is redox graphene.

Wherein, the material of the dielectric layer is aluminum oxide.

Wherein, the gate material is Au.

The following describes the preparation method of the above-mentioned flexible field effect transistor, the method includes steps:

(1) Prepare the base material of the flexible field effect transistor on the hard substrate. Specifically, the glass substrate is first cleaned to remove particles and pollutants on the surface; then a layer of PDMS is spin-coated on the surface of the silicon substrate using the spin-coating process diagram, and cured in a programmed oven to obtain a thickness of 5-50 Micron-scale flexible PDMS film 1;

(2) On the prepared PDMS thin film substrate, the source electrode 2 and the drain electrode 3 of the flexible field effect transistor made of Au material are formed on the PDMS thin film by using processes such as photolithography and sputtering in the MEMS processing technology;

(3) A semiconductor conductive channel 4 made of graphene is prepared between the source electrode 2 and the drain electrode 3 by using a printed electronic process. First prepare graphene conductive ink, including step (1) after oxidation reaction with concentrated sulfuric acid, potassium permanganate and graphite powder, obtain brown graphite flakes, graphite flakes can be peeled off by ultrasonic or high-shear vigorous stirring to be oxidized Graphene; (II) Use deionized water to disperse and centrifuge graphene oxide to control a certain viscosity, and combine organic solvents such as ethanol to prepare a high-quality graphene oxide aqueous solution suitable for aerosol printing. Then, aerosol printing is used to print a well-dispersed graphene oxide solution between the source electrode 2 and the drain electrode 3 with a concentration of about 0.5-20 mg/mL. Finally, the graphene oxide is reduced by gas phase HI to obtain a conductive channel 4 made of redox graphene.

(4) The dielectric layer 5 is prepared on the redox graphene conductive channel by using a MEMS process. Using the photolithography and development technology in MEMS technology, the patterning of the dielectric layer structure is first formed, and then the vapor deposition technology is used to deposit the Al2O3 material on the conductive channel, and finally the excess Al2O3 material is removed to obtain The thickness of the dielectric layer 5 is about 5-20 μm.

(5) On the prepared Al2O3 dielectric layer, a flexible field-effect transistor gate 6 made of Au is prepared by using processes such as photolithography, development, and sputtering in MEMS technology;

(6) Then, the flexible field effect transistor is released from the glass substrate by scribing and stripping techniques to obtain a flexible field effect transistor on the PDMS substrate.

Embodiment 3 Please refer to FIG. 1. The flexible field effect transistor provided in this embodiment includes a flexible substrate 1, a source electrode 2, a drain electrode 3 and a semiconductor conductive channel 4, a dielectric layer 5 and a gate electrode that are sequentially stacked. Pole 6.

Wherein, the material of the flexible substrate 1 is polyethylene terephthalate (PET).

Wherein, the source and drain materials are multi-walled carbon nanotubes.

Wherein, the semiconductor conductive channel is a single-walled carbon nanotube.

Wherein, the material of the dielectric layer is polyimide.

Wherein, the gate material is multi-walled carbon nanotubes.

The following describes the preparation method of the above-mentioned flexible field effect transistor, the method includes steps:

(1) Prepare a conductive solution of multi-walled carbon nanotubes with good conductivity, including:

1. Use chemical solutions such as sulfuric acid to carry out impurity removal treatment to remove metal impurities in carbon nanotubes;

II. Purify and disperse nano-scale carbon nanotube materials by using ultrasonic, cleaning and centrifuging process steps;

III. Carry out suction filtration to the purified carbon nanotubes to extract high-purity multi-walled carbon nanotubes;

IV, then take an appropriate amount of purified single-walled carbon nanotubes in conjunction with SDS dispersant, carry out noise and centrifugation, and prepare a multi-walled carbon nanotubes conductive solution;

(2) On the prepared PET film substrate 1, the source electrode 2 and the drain electrode 3 of the flexible field effect transistor made of multi-wall carbon nanotube material are formed on the PET film by using the air jet printing equipment in the printed electronics technology;

(3) A semiconductor conductive channel 4 made of carbon nanotubes is prepared between the source electrode 2 and the drain electrode 3 by using a printed electronic process. First prepare carbon nanotube conductive ink, including steps (I) using chemical solutions such as sulfuric acid to remove impurities to remove metal impurities in carbon nanotubes; Purify and disperse the tube material; (III) filter the purified carbon nanotubes to extract high-purity semiconducting single-walled carbon nanotubes; (IV) take an appropriate amount of purified single-walled carbon nanotubes The tube is combined with SDS dispersant for noise and centrifugation; (V) take the supernatant after centrifugation, which is the carbon nanotube conductive ink. Then, the prepared carbon nanotube conductive ink is used to form a single-walled carbon nanotube conductive channel 4 between the source electrode 2 and the drain electrode 3 by using an air jet printing process.

(4) Preparing a dielectric layer 5 on the carbon nanotube conductive channel by using a printed electronics process. First, take an appropriate amount of polyimide solution and dilute it with ethanol to obtain a printable polyimide solution; then use air jet printing technology to print the diluted polyimide solution on the carbon nanotube conductive channel to obtain The dielectric layer 5 made of polyimide.

(5) On the prepared polyimide dielectric layer, the grid 6 of the flexible field effect transistor is printed out by using air jet printing technology combined with multi-walled carbon nanotube conductive ink;

Wherein, the aforementioned printed electronics process may be an air jet printing process, an inkjet printing process or a gravure printing process.

The foregoing is only a specific embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A flexible field-effect transistor, characterized in that it comprises: a source electrode and a drain electrode arranged at intervals on a flexible substrate and positioned on the same plane, electrically connected between the source electrode and the drain electrode through a semiconductor conductive channel; covering a dielectric layer on the semiconductor conductive channel; and a grid stacked on the dielectric layer. 2. The flexible field effect transistor according to claim 1, characterized in that: the conductive material used to form the source, drain or gate includes nano-carbon material or metal material, and the nano-carbon material includes carbon nano tube or graphene, the metal material includes Ag, Au or Al, and the thickness of the source, drain or gate is 2-50 μm. 3. The flexible field effect transistor according to claim 1, characterized in that: the semiconductor conductive channel adopts a carbon nanotube layer or a redox graphene layer, and the thickness of the semiconductor conductive channel is 50nm-10μm. 4. The flexible field effect transistor according to claim 1, characterized in that: the material used to form the dielectric layer includes polyimide or aluminum oxide, and the thickness of the dielectric layer is 1- 50 μm. 5. The flexible field effect transistor according to claim 1, characterized in that: the thickness of the flexible substrate is 5-50 μm, and the material used to form the flexible substrate includes polyimide, polyparaphenylene Ethylene Dicarboxylate or Dimethicone. 6. The method for preparing a flexible field effect transistor according to any one of claims 1-5, characterized in that it comprises: a. Forming a flexible substrate on a hard substrate; b. preparing and forming source electrodes and drain electrodes arranged at intervals on the flexible substrate; c, preparing a semiconductor conductive channel between the source and the drain to electrically connect the source and the drain; d, preparing a dielectric layer on the semiconductor conductive channel; e, preparing a gate on the dielectric layer. 7. The preparation method according to claim 6, characterized in that it comprises: preparing the source, drain, dielectric layer or gate by using MEMS technology or printed electronics technology, and preparing the semiconductor by using printed electronics technology Conductive channels; the printed electronics technology includes air jet printing process, inkjet printing process or gravure printing process. 8. The preparation method according to claim 6, characterized in that: the conductive ink used in the printed electronics technology is a carbon nanotube conductive ink with a concentration of 0.1 to 5 μg/mL, and the preparation method of the carbon nanotube conductive ink include: (1) Utilize acid solution to carry out impurity removal treatment to carbon nanotube material, remove the metal impurity in carbon nanotube material; (II) Purify and disperse the carbon nanotube material by using ultrasonic, cleaning and centrifuging process steps; (III) performing suction filtration on the purified carbon nanotube material to obtain the purified carbon nanotube material; (IV) Mix the purified carbon nanotube material with a dispersant, perform ultrasonic and centrifugation treatment, and take the centrifuged supernatant, which is the carbon nanotube conductive ink. 9. The preparation method according to claim 6, characterized in that: the conductive ink used in the printed electronics technology is a redox graphene conductive ink with a concentration of 0.1 to 5 μg/mL, and the redox graphene conductive ink is Preparation methods include: (1) redox graphene is provided; (II) Disperse and centrifuge the redox graphene with deionized water, and then add an organic solvent to prepare a redox graphene ink suitable for aerosol printing. The organic solvent includes ethanol. 10. The preparation method according to claim 7, further comprising: adopting an air jet printing process, using a micro-nozzle with a diameter of 100 μm through an ultrasonic fogging mode, and simultaneously controlling the ratio of the surrounding air flow and the ejected air flow, so that The line width of the sprayed solution is 20-100 μm.