CN104218152A - A kind of preparation method of organic thin film transistor - Google Patents

Abstract

A preparation method of an organic thin film transistor comprises the following steps: selecting a substrate; preparing a gate electrode layer on the substrate layer; preparing a gate dielectric layer on the gate electrode layer; preparing a semiconductor active layer on the gate dielectric layer; preparing a source-drain microchannel layer with a microchannel groove on the semiconductor active layer; and preparing a source electrode and a drain electrode on the source-drain micro-channel layer. The invention utilizes the microfluidic technology, uses the conductive material in a liquid form to replace the original solid source and drain electrodes through the prepared microchannel, thereby completing the organic thin film transistor with the top contact structure, not only simplifying the preparation method and reducing the cost for preparing the device, but also well solving the defects commonly existing in the organic thin film transistor with the top contact structure on the premise of ensuring the original advantages of the organic thin film transistor with the top contact structure, namely the defect of influence on semiconductor materials when the electrodes are deposited, and further improving the performance of the device.

Description

A kind of preparation method of organic thin film transistor

technical field

The invention relates to the field of transistors, in particular to a preparation method of an organic thin film transistor.

Background technique

With the deepening of information technology, electronic products have entered every part of people's life and work. Traditional devices based on inorganic semiconductor materials are difficult to meet people's needs for portability, low cost, and flexibility. Devices made of organic semiconductor materials have the characteristics of wide material sources, relatively simple manufacturing process, low manufacturing cost, and good compatibility with flexible substrates. This has led to increasing interest in organic microelectronics based on organic polymer semiconductor materials.

An organic thin film transistor usually includes a gate electrode, an insulating layer between the gate electrode and the semiconductor, a semiconductor layer made of organic semiconductor material between the source and drain electrodes, and the source electrode and the drain electrode. According to the characteristics and positions of the gate electrodes, organic thin film transistors can be divided into bottom-gate thin film transistors (bottom-gate), top-gate thin film transistors (top-gate), side-gate thin film transistors (side-gate) and liquid gate thin film transistors ( liquid-gate). At present, the most common organic thin-film transistor is a bottom-gate thin-film transistor, mainly because the chemical and physical properties of the semiconductor layer are generally unstable, and the preparation of the device dielectric layer will have a negative impact on the shape and quality of the semiconductor layer, thereby reducing the device performance. Therefore, the semiconductor layer is usually prepared after the dielectric layer is prepared, that is, a bottom-gate device configuration is adopted.

According to the different deposition sequences of source and drain electrodes and semiconductors, thin film transistors can be divided into top contact structure and bottom contact structure. The top contact structure is to deposit a semiconductor layer on the substrate surface first, and then deposit the source and drain electrodes on the semiconductor surface, while the bottom contact structure is to build the source and drain electrodes on the dielectric layer, and then deposit the semiconductor layer on the source and drain electrodes. The transistors of these two structures have their own advantages and disadvantages. The contact between the source and drain electrodes of the transistor with the top contact structure and the semiconductor layer is better than that of the bottom contact structure, and the area of the semiconductor layer affected by the electric field of the gate electrode is larger than that of the source and drain electrodes at the bottom layer. , resulting in a higher carrier mobility during the period. In addition, the active layer in the top contact structure is not affected by the source and drain electrodes, and can be deposited on the surface of the dielectric layer in a large area, and the surface of the dielectric layer can also be functionally modified by physical or chemical methods to improve the semiconductor layer. Thin film structure and morphology to enhance carrier mobility in thin film transistor devices. However, during the electrode deposition process of this structure, the electrode material will diffuse into the active layer, resulting in an increase in the off-state current of the transistor device and a decrease in the switching ratio, especially for narrow channel devices, this phenomenon is more obvious.

The working principle of the organic thin film transistor is to use the field effect to realize the work of the device. The field effect is a phenomenon in which the electrical conductivity of a semiconductor material or the current flow in a semiconductor material is modulated by an electric field perpendicular to the semiconductor surface. When the gate voltage (Vg) applied to the gate electrode is zero, due to the low intrinsic conductivity of the semiconductor, even if the source-drain voltage (Vds) is applied to the gate electrode, there is almost no leakage current (Ids) passing through, at this time The transistor is in the off state, and the leakage current of the transistor in this state is the off-state current (Ioff). When a negative voltage is applied to the gate electrode, according to the capacitor effect, the holes at the source terminal will be injected into the semiconductor layer from the source electrode under the action of the gate voltage, and accumulate at the interface between the semiconductor layer and the dielectric layer. At this time, a negative voltage is applied between the source electrode and the drain electrode, and the holes accumulated in the channel region will migrate and move under the drive of the source-drain voltage to form a current, and the device is in an on state at this time. As the source-drain voltage increases and reaches a certain value, the channel region is pinched off. Since the channel resistance of the pinch-off region is very large, the increased source-drain voltage is almost all applied to the pinch-off region, and the two sides of the conductive channel The voltage at the terminal basically does not change, and the channel current no longer increases with the increase of the source-drain voltage, and the channel current reaches saturation.

Since the first report of organic thin film transistors in 1986, more and more researchers have paid attention to this field, and significant breakthroughs have been made. The performance of organic semiconductor materials is improving year by year. Due to the rapid development of research on the synthesis of high-mobility organic semiconductor materials, thin-film physics, and device construction technology in recent years, the performance of organic thin-film transistors, such as mobility and on-off current ratio, especially the mobility has been greatly improved, making organic thin-film transistors Transistors become possible in practical applications.

Contents of the invention

Technical problem to be solved: Aiming at the deficiencies in the prior art, the purpose of the present invention is to provide a method for preparing an organic thin film transistor. The thin film transistor adopting a top contact structure can be combined with microfluidic technology to ensure that the top contact structure On the premise of the advantages of thin film transistors, the shortcomings of the impact on the surface of semiconductor materials during electrode deposition can be effectively avoided, so as to prepare high-performance devices.

Technical solution: In order to solve the problems of the prior art, the technical solution adopted by the present invention is:

A method for preparing an organic thin film transistor, comprising the steps of:

Choose the substrate;

preparing a gate electrode layer on the substrate;

preparing a gate dielectric layer on the gate electrode layer;

preparing a semiconductor active layer on the gate dielectric layer;

Prepare a source-drain microchannel layer with microchannel grooves on the semiconductor active layer;

The source electrode and the drain electrode are prepared on the source-drain microchannel layer, the distance between the source electrode and the drain electrode is less than or equal to 200 μm, which is to drill a hole above the microchannel groove of the source-drain microchannel layer, and then use a ring Oxygen resin glues the hole and the hollow conduit of equal diameter into one body, and finally injects the material at one end of the conduit, and extracts it under pressure at the other end, and finally forms the source electrode and the drain electrode on the source-drain microchannel layer.

As an improvement, an interface modification layer is prepared on the semiconductor active layer.

The material of the gate electrode layer is one of silver, gold, aluminum, copper, poly-3,4-ethylenedioxythiophene or polystyrene sulfonate; the preparation method is vacuum thermal physical deposition, inkjet printing, One of spin coating, electron beam deposition or sputtering.

The material of the gate dielectric layer is one of silicon oxide, silicon nitride, aluminum oxide, tantalum oxide, polyimide, polyvinylpyrrolidone or polymethyl methacrylate; the preparation method is One of low pressure chemical vapor deposition, inkjet printing, sputtering, atomic layer deposition, electron beam evaporation, ion assisted deposition or spin coating techniques.

The material of the semiconductor active layer is one of poly-3-hexylthiophene P3HT, pentacene or titanium bronze; the preparation method is one of vacuum thermal evaporation, spin coating, inkjet printing or drop coating.

The material of the interface modification layer is molybdenum oxide MoO ₃ ; the preparation method is one of vacuum thermal evaporation, spin coating or inkjet printing.

The material of the source-drain microchannel layer is one of polyamide, polymethyl methacrylate, polycarbonate, polyethylene terephthalate or polydimethylsiloxane; the preparation method is plastic One of the following methods, hot pressing, LIGA technology, laser lithography or soft lithography.

After the source-drain microchannel layer and the interface modification layer are pasted together, a source electrode and a drain electrode are prepared in the source-drain microchannel.

The material of the source electrode and the drain electrode is one of conductive silver ink, conductive gold ink, copper ink, graphene solution or poly-3,4-ethylenedioxythiophene.

Beneficial effect

The method for preparing an organic thin film transistor provided by the present invention uses a traditional organic thin film transistor with a top contact structure, and can ensure that the contact resistance of a top contact structure thin film transistor is lower than that of a transistor with a bottom contact structure and a semiconductor layer with a top contact structure. The area affected by the electric field of the electrode is large, and it has a higher mobility than the thin film transistor with the bottom contact structure, and the semiconductor layer in the top contact structure is not affected by the source and drain electrodes, and can be deposited on a large area of the dielectric layer surface by physical or chemical methods Functional modification of the surface of the dielectric layer to improve the structure and morphology of the semiconductor layer film, thereby improving the carrier mobility of the thin film transistor, effectively avoiding the disadvantages of the impact on the surface of the semiconductor material during electrode deposition , so as to prepare high-performance devices.

Description of drawings

Figure 1 is a top view of the design schematic diagram of the source-drain microchannel layer model;

Figure 2 is a side view of the design schematic diagram of the source-drain microchannel layer model;

Fig. 3 is a structural schematic diagram of an organic thin film transistor, wherein, 1, substrate, 2, gate electrode layer, 3, gate dielectric layer, 4, semiconductor active layer, 5, interface modification layer, 6, microchannel groove, 7 , Source-drain microchannel layer.

Detailed ways

The following examples can enable those skilled in the art to understand the present invention more fully, but do not limit the present invention in any way.

The present invention utilizes microfluidic technology to replace the original solid-state source-drain electrodes with liquid-form conductive materials through prepared micro-channels, thereby completing an organic thin-film transistor with a top-contact structure, which not only simplifies the preparation method, but also reduces the cost of preparing devices. cost, and on the premise of ensuring the original advantages of top-contact organic thin-film transistors, it solves the common defects of top-contact organic thin-film transistors, that is, the shortcomings of the impact on semiconductor materials when depositing electrodes. The performance of the device is further improved.

As shown in Figure 1, the required microchannel model is designed through SolidWorks software. This figure shows a three-channel design model. Since conductive liquid needs to be added to the head and tail of the channel, the width of the head and tail of the designed channel needs to be at least Greater than 1mm, to facilitate the drop of conductive liquid. The distance between the three channel parallel regions shown in the middle part of the model is 60um, the width of the channels on the left and right sides is 1mm, and the width of the middle channel is 60um. According to different needs, multiple channels can be designed to realize the preparation of organic thin film transistors in the form of arrays. After completing the design of the channel model, the curable polymer polydimethylsiloxane (PDMS) is selected to fabricate a flexible source-drain microchannel layer with channels through soft lithography technology, as shown in Figure 2.

Example 1

A method for preparing an organic thin film transistor, comprising the steps of:

An insulating glass sheet is selected as the substrate 1; a gate electrode layer 2 is prepared on it by inkjet printing technology, and the silver nano-ink is prepared on the insulating glass sheet through a piezoelectric inkjet printer to complete the patterning preparation. After the grid electrode is printed, the The insulating glass sheet is placed on a hot stage at 200°C and annealed for 1 hour to prepare a 100nm-thick gate electrode layer 2; through piezoelectric inkjet printing technology, the PVP solution is printed on the prepared gate electrode layer 2. After the printing is completed, Place the insulating glass sheet on a hot stage and heat and anneal at 200°C for 1 hour to prepare a gate dielectric layer 3 with a thickness of 600nm; evaporate titanium bronze CuPc on the PVP gate dielectric layer 3 by vacuum thermal evaporation to form 60nm thick semiconductor active layer 4; molybdenum trioxide is evaporated on the titanium bronze CuPc semiconductor active layer 4 by vacuum thermal evaporation to form a 40nm thick interface modification layer 5; the microchannel model designed according to the software is subjected to soft light Engraving technology, prepared a flexible PDMS source-drain microchannel layer 7 with microchannel grooves 6, and then treated the side of PDMS with microchannel grooves 6 for 10 minutes with ultraviolet and ozone, and then covered it on the interface modification layer 5; The silver ink prepared by conductive silver nanoparticles is passed into the channel groove 6 to complete the preparation of the source electrode and the drain electrode. the

Example 2

A method for preparing an organic thin film transistor, comprising the steps of:

Select an insulating glass sheet as the substrate 1; after 10 minutes of UVO ₃ treatment, the aluminum is patterned on the insulating glass sheet by vacuum thermal evaporation to form a 100nm thick aluminum gate electrode layer 2; by spin coating , Spin-coat the PVP solution on the prepared gate electrode layer 2 at a speed of 4000 RPM for 30 seconds, then place the insulating glass sheet on a hot stage and heat and anneal at 200°C for 1 hour to prepare a 600nm-thick gate dielectric. Electrical layer 3; titanium bronze CuPc is evaporated on the PVP gate dielectric layer 3 by vacuum thermal evaporation to form a 60nm thick semiconductor active layer 4; molybdenum trioxide is evaporated on the titanium bronze CuPc semiconductor active layer by vacuum thermal evaporation On the layer, a 40nm-thick interface modification layer 5 is formed; the microchannel model designed according to the software is processed by soft photolithography to prepare a flexible PDMS source-drain microchannel layer 7 with microchannel grooves 6, and then the PDMS with microchannel One side of the channel groove 6 was treated with ultraviolet and ozone for 10 minutes, and then covered on the interface modification layer; the silver ink prepared by conductive silver nanoparticles was passed into the microchannel groove 6 to complete the preparation of the source electrode and the drain electrode.

Example 3

A method for preparing an organic thin film transistor, comprising the steps of:

Select an insulating glass sheet as the substrate 1; after 10 minutes of UVO ₃ treatment, spin-coat the poly-3,4-ethylenedioxythiophene solution on the substrate 1 at a speed of 2000rpm for 30s to form a 200nm Thick poly-3,4-ethylenedioxythiophene gate electrode layer 2; spin-coat the PVP solution on the prepared gate electrode layer 2 by spin-coating method, the rotation speed is 4000RPM, the time is 30S, and then the insulating glass The sheet is placed on a hot stage and heated and annealed at 200°C for 1 hour to prepare a gate dielectric layer 3 with a thickness of 600nm; P3HT is prepared as a semiconductor active material on the PVP gate dielectric layer 3 by piezoelectric inkjet printing technology; Select a single nozzle, print a single layer of P3HT layer under the conditions of 35V voltage and 40μm dot spacing, and print according to the vertical arrangement to form a 60nm thick semiconductor active layer 4. Annealing at a temperature of 70°C for 1 hour; molybdenum trioxide was vapor-deposited on the P3HT semiconductor active layer 4 by vacuum thermal evaporation to form a 40nm thick interface modification layer 5; the microchannel model designed according to the software was subjected to soft light Engraving technology, prepared a flexible PDMS source-drain microchannel layer 7 with microchannel grooves 6, and then treated the side of PDMS with microchannel grooves 6 for 10 minutes with ultraviolet and ozone, and then covered it on the interface modification layer 5; The gold ink prepared by conducting gold and silver nanoparticles is passed into the channel groove 6 to complete the preparation of the source electrode and the drain electrode.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. A method for preparing an organic thin film transistor, comprising the following steps: Choose the substrate; preparing a gate electrode layer on the substrate; preparing a gate dielectric layer on the gate electrode layer; preparing a semiconductor active layer on the gate dielectric layer; Prepare a source-drain microchannel layer with microchannel grooves on the semiconductor active layer; preparing a source electrode and a drain electrode on the source-drain microchannel layer, It is characterized in that: the distance between the source electrode and the drain electrode is less than or equal to 200 μm, and the hole is drilled above the microchannel groove of the source-drain microchannel layer, and then the hole is adhered to a hollow conduit of equal diameter with epoxy resin glue Integrate, and finally inject material at one end of the conduit, pressurize and extract at the other end, and finally form a source electrode and a drain electrode on the source-drain microchannel layer. 2 . The method for preparing an organic thin film transistor according to claim 1 , wherein an interface modification layer is prepared on the semiconductor active layer. 3 . 3. The preparation method of the organic thin film transistor according to claim 1, characterized in that: the material of the gate electrode layer is silver, gold, aluminum, copper, poly 3,4-ethylenedioxythiophene or polystyrene sulfonate One of acid salts; the preparation method is one of vacuum thermal physical deposition, inkjet printing, spin coating, electron beam deposition or sputtering. 4. according to the preparation method of the described organic thin film transistor of claim 1, it is characterized in that: the material of described gate dielectric layer is silicon oxide, silicon nitride, aluminum oxide, tantalum oxide, polyimide, polyethylene pyroxene One of alkanone or polymethyl methacrylate; the preparation method is one of low-pressure chemical vapor deposition, inkjet printing, sputtering, atomic layer deposition, electron beam evaporation, ion-assisted deposition or spin coating technology . 5. according to the preparation method of the described organic thin film transistor of claim 1, it is characterized in that: the material of described semiconductor active layer is the one in poly-3-hexylthiophene P3HT, pentacene or titanium bronze; Preparation method is vacuum One of thermal evaporation, spin coating, inkjet printing or drop coating. 6 . The preparation method of the organic thin film transistor according to claim 2 , characterized in that: the material of the interface modification layer is molybdenum oxide MoO ₃ ; and the preparation method is one of vacuum thermal evaporation, spin coating or inkjet printing. 7. according to the preparation method of the described organic thin film transistor of claim 1, it is characterized in that: the material of described source-drain microchannel layer is polyamide, polymethyl methacrylate, polycarbonate, polyethylene terephthalate One of alcohol ester or polydimethylsiloxane; the preparation method is one of plastic method, hot pressing method, LIGA technology, laser etching method or soft lithography. 8 . The method for preparing an organic thin film transistor according to claim 1 , characterized in that: after the source-drain microchannel layer and the semiconductor active layer are bonded together, a source electrode and a drain electrode are prepared in the source-drain microchannel. 9. according to the preparation method of the described organic thin film transistor of claim 1, it is characterized in that: the material of described source electrode and drain electrode is conductive silver ink, conductive gold ink, copper ink, graphene solution or poly-3,4-ethylene One of dioxythiophene.