KR20110092895A - Otft device using bridged silsesquioxane thin film materials - Google Patents

Abstract

PURPOSE: An OTFT device using a bridged silsesquioxane material is provided to form a gate insulator thin film and an organic thin film transistor using the bridged silsesquioxane material as a gate insulator with reduced surface energy, improved crystallinity, and decreased surface roughness. CONSTITUTION: A method for preparing an insulator thin film comprises the steps of: mixing the bridged siloxane material of chemical formula 3, the siloxane material of chemical formula 4, water(H2O), and hydrochloric acid solution; forming a bridged silsesquioxane polymer of chemical formula 1 by polymerizing the mixture at room temperature; applying the polymer composition to a substrate and curing the resultant. In chemical formulas 1, 3 and 4, R1 and R21 are selected from (C2-C6) alkylene, (C6-C12) arylene and (C1-C10) alkyl (C6-C12) arylene; and R2 ~R11 and R22~R32 are independently (C1-C6) alkyl; and m is the interger of 2~1000.

Description

OTFT device using bridged silsesquioxane thin film materials

The present invention relates to an organic thin film transistor using a silsesquioxane connected by a bridge as a thin film material, and more particularly, to an organic thin film transistor including a silsesquioxane connected by a bridge as a gate insulator thin film of an organic thin film transistor.

Organic thin film transistor (OTFT) refers to using an organic material as a channel layer in a thin film transistor (TFT) structure. OTFT has the advantages of easy manufacturing and low cost, impact resistance, bendability and low process temperature. The OTFT study mainly evaluates OTFT properties by depositing pentacene monomolecules on the channel layer by vacuum deposition. However, pentacene has the advantage of having a charge transfer speed of 6 cm ² V ^-1 S ^-1 and a current flashing ratio of 10 ⁶ , but it has the disadvantage of high price of vacuum equipment and difficult to deposit in large area. On the other hand, organic semiconductor polymers such as poly 3-hexythiophene (P3HT) can be applied to a solution process such as printing or spin-coating because the channel layer can be formed using a solution.

Most organic semiconductors crystallize well at room temperature or low temperature, so there is no need to increase the temperature. Therefore, the organic semiconductor polymer can be formed as a channel layer on a flexible substrate having a low maximum temperature but bendable and a strong impact resistance, such as plastic. However, in order to remove the device from the flexible substrate that can bend or bend, it is necessary to manufacture a device at a low temperature. Semiconductors, substrates, electrodes, etc. can be processed at low temperatures, but gate insulators have high leakage current, low thermal and chemical resistance, pinhole formation and low crystallization of organic semiconductors when thin films are fabricated at low temperatures. Due to their properties, their properties are inferior to those of gate insulators fabricated at high temperatures. In addition to improving the characteristics of the gate insulator, when the gate insulator is applied to the OTFT, the transistor performance such as a threshold voltage, an on / off ratio, and mobility is also improved. However, until now, research on OTFT has developed more organic semiconductor materials than the development of gate insulator materials, and research on gate insulators has been neglected, such as improvement using conventional materials such as HMDS and OTS on the surface of conventional thin film insulators. there was. However, as research on organic semiconductors has reached its limit, researches on gate insulators are gradually being conducted as various kinds of thin films such as organic thin film, inorganic thin film, organic / inorganic hybrid thin film, and composite thin film are coming out.

The gate insulator thin films known to date are mainly produced using inorganic materials such as silicon oxide (SiO ₂ ) by vacuum deposition and solution processes. Polyimide, PVP (poly vinylpyrrolidone), PVA (poly vinylalcohol), and PMMA (poly methyl) A method of manufacturing a thin film of a polymer organic material such as methacrylate is known. However, the inorganic material has a high breakdown field such as low electrical conductivity, but the bonding between the inorganic material and the organic semiconductor is a junction of two materials having different characteristics, so the crystallinity of the organic semiconductor is inferior. Organic insulators have the advantages of high toughness and flexibility, but much research is being conducted due to low glass transition temperature, hardness and high threshold voltage.

Research on gate insulators for organic-inorganic hybrid materials with flexible organic properties and thermal and chemical resistance properties of inorganic materials is incomplete. Most insulators of organic and inorganic materials use OTFT properties using surface treatments such as octadecyltrichlorosilane (OTS), hexamethyldisilazane (HMDS), alkanphosphonic acid, and cinnamic acid. Improved. This surface treatment requires an additional process, thereby increasing the manufacturing cost of the device. However, the organic-inorganic hybrid material has the advantages of organic and inorganic materials as well as lowering the manufacturing cost of the device because the surface treatment effect can be obtained through the operation of the functional group, the organic-inorganic hybrid material is suitable as a gate insulator for OTFT.

According to the present invention, an organic-inorganic hybrid-type gate insulator thin film is manufactured at low temperature, and the characteristics of the transistor should be observed in the organic semiconductor transistor.

The first technical challenge is to form a thin film of gate insulator at a temperature below 150 ℃. Most organic semiconductors crystallize well at room or low temperatures, so there is no need to increase the temperature. Therefore, in order to be used in a flexible yet thin and impact-resistant substrate, the thin film should be formed at a temperature below 150 ℃.

The second challenge is that the surface of the thin film must have low surface energy. The charge mobility of OTFT is greatly influenced by the crystallinity of organic semiconductor. The crystallinity of the organic semiconductor is affected by the surface energy of the surface of the insulator thin film and the type of coating solution. The surface energy can be estimated using the contact angle. Organic semiconductor is coated and the crystallinity is improved when the contact angle is over 60 °. However, since most existing thin films have high surface energy, they are researched into thin surface energy thin films through thin film processing.

In the present invention, the surface energy is changed by using an organic-inorganic hybrid material without additional surface treatment, and organic semiconductor crystals must be prepared in a thin film.

A third challenge is low surface roughness of the thin film. If the surface roughness of the insulator is large, the mobility of the electrons is not smooth, and thus the charge mobility is lowered. The surface roughness of the thin film should be lowered so that the organic semiconductor of the insulator thin film is uniformly coated.

A fourth challenge is to present transistor characteristics in organic semiconductor transistors. This is because the output curve, trans curve, etc. must be displayed in order to be used in the flexible display.

As shown in FIG. 1, the organic thin film transistor belongs to the category of a metal insulating film semiconductor transistor using a field effect, and is composed of a gate insulating layer, a source / drain, and a channel layer. The structure of the organic thin film transistor is largely divided into four as shown in Figure 2 in the order of the three configurations. In general, top contact devices exhibit higher levels of electrical characteristics than bottom contact conditions. This is because the organic semiconductor grows without damage because the source layer and the drain are deposited after the channel layer is first formed.

In the present invention, in the fabrication of an organic thin film transistor, TFT characteristics are obtained by using a bottom gate and a top contact method. In the present invention, Au (gold) is used to reduce the organic semiconductor and resistance as a source and a drain of the organic thin film transistor, and as a gate insulator, a bridged silsecquioxane polymer is used to form a thin film as shown in FIG. To prepare an organic thin film transistor.

The term “bridged silsesquioxane” of the present invention refers to silsesquioxane having a structure in which a bivalent free group, such as alkylene, arylene or alkylarylene, is connected between silsesquioxane molecules as a bridge. "Bridged silsesquioxane polymer" means a polymer having a repeating unit of such bridged silsesquioxane.

The bridged silsesquioxane polymer of the present invention is represented by the following Chemical Formula 1 or the following Chemical Formula 2, and as a monomer for the preparation thereof, homopolymerizes a siloxane compound including a bridge of R ¹ of Chemical Formula 3, or It can be prepared by mixing the siloxane compound of Formula 3 and the siloxane compound of Formula 4. The method for preparing the polymer of the bridged silesquioxane of Formula 1 or Formula 2 may be prepared by hydrolysis and condensation polymerization of Formula 3, or a mixture of Formulas 3 and 4 below.

[Formula 1]

[Formula 2]

(3)

[Formula 4]

In Formulas 1 to 4, R ¹ , R ²¹ and R ⁴¹ are selected from (C 2 -C 6) alkylene, (C 6 -C 12) arylene and (C 1 -C 10) acyl (C 6 -C 12) arylene, and R is ² to R ¹¹ , R ²² to R ³² , and R ⁴² to R ⁴⁷ are each independently (C 1 -C 6) alkyl, and m and n are each independently an integer of 2 to 1000.

More specifically, the bridge silsesquioxane polymer of Chemical Formula 2 may be prepared by hydrolysis and condensation polymerization of the compound of Chemical Formula 3 alone. In addition, the compound of formula (3) and the compound of formula (4) by mixing in a molar ratio 1: 0.001 to 1 by hydrolysis and condensation polymerization, it is possible to prepare a bridge silsesquioxane polymer of the formula (1).

R ¹ of Formulas 1 to 3 of the present invention is selected from ethylene, propylene, butylene, ter-butylene, pentylene, hexylene, phenylene and methylphenylene. The “bridge” of the bridged silsesquioxane of the present invention is the same as R ¹ of Chemical Formulas 1 to 3.

The present invention is a specific compound of the formula 3, 1,2-bis (trimethoxysilyl) ethane (BTMSE: 1,2-bis (trimethoxysilyl) ethane), 1,2-bis (trimethoxysilyl) propane, 1,2-bis (trimethoxysilyl) butane, 1,2-bis (trimethoxysilyl) pentane, 1,2-bis (trimethoxysilyl) hexane, 1,2-bis (trimethoxysilyl) One selected from benzene and 1,2-bis (trimethoxysilyl) methylbenzene may be used, and most preferably 1,2-bis (trimethoxysilyl) ethane (BTMSE) is used. Formula 3 of the present invention includes a divalent free group of an alkylene group, an arylene group or an alkylarylene group, and in particular, in the case of BTMSE, the surface energy of the surface of the thin film when the thin film is formed by forming a siloxane polymer. It is very useful for fabricating devices with high mechanical strength despite containing organic materials.

R ⁸ to R ¹¹ of the general formula (4) of the present invention are independently selected from methyl, ethyl, propyl, butyl and ter-butyl, the specific compound of the general formula (4), may be methyltrimethoxysilane (Methyltrimethoxysilane) , Formula 4 is a monomer containing an alkyl group, there is an advantage to reduce the ratio of Si-OH and increase the stability of the thin film in the process of preparing the organic hybrid polymer.

In order to prepare the siloxane polymer of Chemical Formula 1 or Chemical Formula 2 of the present invention, it may be prepared using a sol-gel method, and in detail, the Chemical Formula 3 alone, or the compounds of Chemical Formulas 3 and 4 The siloxane polymer may be prepared by mixing and mixing water (H ₂ O) for hydrolysis and hydrochloric acid solution for condensation polymerization. The mixture is reacted at a temperature of about room temperature for 12 hours to 24 hours, preferably about 16 hours.

According to the present invention, an appropriate mixing ratio of water and hydrochloric acid solution for hydrolysis and condensation polymerization of the siloxane compound (monomer) of Chemical Formula 3 including the bridge, or of Chemical Formulas 3 and 4 is based on the molar ratio: H ₂ O : It is preferable to mix hydrochloric acid (HCl) with 0.001-0.010: 1: 1. In this case, when using a mixture of Formula 3 and Formula 4, it is preferable that the compound of Formula 3: the compound of Formula 4 is mixed in a molar ratio of 1: 0.001 ~ 1 to react.

The siloxane polymer of the bridged silsesquioxane polymer of the present invention is intended to be manufactured to form a gate insulator thin film of an organic thin film transistor. Therefore, the solution containing the bridged silsesquioxane polymer prepared by the above production method can be used by directly applying on the top of the substrate as a coating composition for the preparation of the organic thin film transistor without a separate purification process or cleaning process, Bridged silsesquioxane may be obtained through a separate purification process or a washing process, and then dissolved in an organic solvent. In this case, the organic solvent is not particularly limited. Preferably, the organic solvent may be dissolved in an organic solvent selected from ethanol, tetrahydrofuran, methyl isobutyl ketone, and poly (ethylene glycol) methyl ether acrylate, and used as a coating liquid. The choice of solvent and the choice of concentration can be appropriately adjusted according to the thickness of the desired thin film.

In order to form the siloxane polymer thin film, the siloxane thin film may be formed by spin coating a coating composition prepared above or a coating composition washed and dissolved in an organic solvent on a substrate, followed by heat treatment to cure it. The spin coating is not particularly limited because it can be used according to the desired thin film thickness, preferably can be coated by rotating at 10 to 10000 rpm. The curing may form a thin film in a low temperature process of room temperature to 150 ℃.

When the siloxane polymer thin film of the present invention is used as a gate insulator thin film of an organic thin film transistor, the siloxane polymer thin film of the present invention is a silsesquioxane polymer having a divalent organic group as a bridge, thereby reducing the surface energy of the thin film surface and increasing the crystallinity. By improving the charge mobility can be improved.

In the present invention, in order to apply to the gate insulator thin film of the organic thin film transistor, a siloxane polymer thin film was prepared using BTMSE, MTMS and water solvent. There are three major effects of the invention on such thin films.

First, when the thin film is manufactured using a water solvent, the surface of the thin film is improved. When the siloxane polymer is synthesized using the THF solvent, there is a problem of generating a pinhole on the surface of the siloxane polymer thin film. In order to solve this problem, the pinhole was removed by checking the thin film surface of the siloxane polymer by changing the solvent into water. In addition, it is an environmentally friendly method because it is synthesized using water rather than an organic solvent.

Second, it has the advantage of lowering the manufacturing cost of the OTFT device. In case of fabricating gate insulator thin film using organic and inorganic materials, deposition and crystallinity of organic semiconductors are improved through surface treatment such as Octadecyltrichlorosilane (OTS), Hexamethyldisilazane (HMDS), alkanphosphonic acid and cinnarnic. However, such surface treatment requires an additional step in the device fabrication process. However, when fabricating a device using the siloxane polymer thin film of BTMSE and MTMS, organic semiconductor can be deposited on the siloxane polymer thin film without surface treatment, thereby reducing the manufacturing cost of the device related to the surface treatment.

Third is the improvement of charge mobility, one of the characteristics of the device. The charge mobility of the conventional SiO ² has a property of 0.0003 cm ² V ^-1 S ^-1 . However, when the device was fabricated using siloxane polymer thin films of BTMSE and MTMS, the charge mobility was measured to be about 130 times higher than 0.039 cm ² V ^-1 S ^-1 . Based on these results, further research is expected that siloxane polymer thin films of BTMSE and MTMS can be applied to large area OTFT fabrication.

1 is a schematic diagram for evaluating the organic thin film transistor and its OTFT characteristics,
2 is a schematic diagram of four types of organic thin film transistors,
3 is a change of the thin film according to the ratio of MTMS and BTMSE through FT-IR measurement,
Figure 4 is a schematic diagram of the leakage current (leakage current) measuring method,
5 is a change in leakage current according to the ratio of MTMS and BTMSE,
6 is a change in refractive index according to the ratio of MTMS and BTMSE,
7 is a schematic diagram of a capacitance-voltage measurement method;
8 is a dielectric constant according to the ratio of BTMSE and MTMS,
9 is an output curve characteristic evaluation result according to the ratio MTMS: BTMSE = 10: 0,
10 is a trans curve characteristic evaluation result according to the ratio MTMS: BTMSE = 10: 0,
11 is an output curve characteristic evaluation results according to the ratio MTMS: BTMSE = 8: 2,
12 is a trans curve characteristic evaluation result according to the ratio MTMS: BTMSE = 8: 2,
13 is an output curve characteristic evaluation results according to the ratio MTMS: BTMSE = 6: 4,
14 is a trans curve characteristic evaluation result according to MTMS: BTMSE = 6: 4 ratio,
15 is an AFM measurement result according to the ratio of MTMS and BTMSE,
16 is a contact angle measurement results according to the ratio of MTMS and BTMSE.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are not intended to limit the invention only.

Example 1

Material preparation for gate insulators adds 0.002 mol of BTMSE to the vial. Then, 0.1 mol of DI water solvent is added, and then 0.216 g of 0.1 mol HCl solution is added per 0.002 mol of BTMSE. The vial was sealed with a stopper and reacted at 600 rpm at room temperature for about 16 hours.

[Example 2]

In Example 1, it carried out under the same conditions except using the mixture which mixed BTMSE and MTMS in 8: 2 molar ratio instead of BTMSE.

Example 3

Example 2 was carried out under the same conditions except that a mixture of BTMSE and MTMS was mixed at a molar ratio of 6: 4.

Example 4

Except for using a mixture of BTMSE and MTMS in a molar ratio of 5: 5 in Example 2, it was carried out under the same conditions.

Example 5

Thin film fabrication was performed using a 0.2 μm syringe filter (PTFE) to filter the precursors, spincoating at 500 rpm for 5 seconds on a silicon wafer with a resistivity value <0.005 Ωcm (low resistance), and hotplate at 80 ° C. It was cured for 30 minutes in a hot plate and cured at 150 ° C. for 1 hour under normal atmospheric conditions.

Example 6

In Example 5, it carried out under the same conditions except having used the silicon wafer whose 1--30 ohm-cm (high resistance) instead of the silicon wafer whose specific resistance value is <0.005 ohm-cm (low resistance).

Example 7

In Example 5, the spin coating was performed under the same conditions except that spin coating was performed at 2000 rpm for 25 seconds instead of spin coating at 500 rpm for 5 seconds.

Example 8

In Example 6, the spin coating was performed under the same conditions except that the spin coating was performed at 2000 rpm for 25 seconds instead of 500 rpm for 5 seconds.

[evaluation]

Analysis of thin films includes FT-IR, Capacitance-Voltage (CV), Current-Voltage (IV), Spectroscopic Ellipsometry (SE), Atomic force microscope (AFM), and contact angle measurements Was carried out.

(1) FT-IR analysis

FT-IR analysis used model IFS66v to identify functional groups of organic-inorganic hybrid materials in thin films. FT-IR analysis used thin films cured on the high resistance silicon wafers of Examples 6 and 8. All samples were measured in transmission mode in the range of 4000 cm ⁻¹ to 400 cm ⁻¹ with 7 cm ⁻¹ resolution.

(2) C-V measurement

CV measurements were taken to calculate the dielectric constant of the thin film. The sample was the same as the FT-IR measurement sample, was prepared in the size of about 4 cm ² and deposited 0.229 mm ² Al electrode using the thermal evaporation (Thermal evaporation). The CV measurement converts the DC bias from -40 V to 40 V and 40 V to -40 V at 1 MHz of measurement frequency and 1 V of AC voltage. Information was obtained.

(3) I-V measurement

IV measurement was performed to measure the leakage current of the thin film. The sample used the thin film apply | coated to the low resistance silicon wafer of Examples 5 and 7. The sample was cut to a size of about 225 cm ^{2 and} the top electrode was deposited as in the CV measurement. The IV was measured using a HP4145B with a resolution of 0.5 V in the AC voltage range of 0-40 V.

(4) SE analysis

SE (spectral ellipsometry) analysis was performed to measure the thickness and refractive index (n) of the thin film. The sample is the same as the IV measurement sample and is 4 cm ² in size. Wollan Co.'s M2000D (RCT) model instrument was measured using a reflection angle of 75 ° with a wavelength ranging from 191 to 1000 nm.

(5) AFM measurement

AFM measurements provide information on the roughness of the films and were measured using a non-contact method with AFM (XE-100).

(6) TFT characteristic evaluation

TFT characteristic evaluation was made by evaluating the OTFT device as shown in FIG. In the device fabrication as shown in FIG. 7, P3HT organic semiconductor was used for the same sample as the IV measurement. P3HT was dissolved in chlorobenzene and spin-coated at 1000 rpm for 15 seconds. Chlorobenzene contained in the organic semiconductor was removed in a vacuum at 120 ° C. for about 4 hours. Thereafter, a shadow mask was placed on the thin film to prepare a source and a drain, and then Au was deposited by thermal deposition. Output curves and trans curve measurements were evaluated using the HP4145B.

(7) measurement result

Examples 1 to 4 of the present invention prepared an ethylene bridged silsesquioxane polymer by hydrolysis and condensation reaction of MTMS and BTMSE. As a result, Si-OH generated during the hydrolysis process remains in the process of forming a thin film. These Si-OH is to absorb the large amount of H ₂ O to a thin film while in combination with H ₂ O. H ₂ O and Si-OH increase the leakage current of the thin film, the change of H ₂ O according to the amount of Si-OH can be seen through the FT-IR measurement. The functional group of Si-OH can be confirmed at 910 cm ^-1 , and the H ₂ O absorption band by Si-OH can be observed at 3400-3500 cm ^-1 . Figure 3 is the ratio of Si-OH and H ₂ O according to the ratio of BTMSE and MTMS was measured by FT-IR. As the ratio of MTMS increases, the content of Si-OH contained in the polymer decreases, and the amount of H ₂ O decreases. It can be seen from FIG. 16 that the contact angle of the surface of the thin film increases as the amount of MTMS increases due to the amount of Si-OH. Mainly ethylene, methyl and Si-OH are present on the thin film surface. When the ratio of MTMS is increased under the manufacturing conditions, the Si-OH decreases and the surface of the polymer increases Si-Me and Si-OH decreases due to the presence of methyl groups. The influence of the contact angle affects the growth of crystals by organic semiconductors. 6 is a result of refractive index according to the ratio of MTMS and BTMSE. MTMS is widely known as a material for reducing the refractive index of thin films. As a result, as the ratio of MTMS increases, the refractive index decreases from 1.50 to 1.48.

The dielectric constant of the ethylene bridged silsesquioxane thin film has a dielectric constant of about 9.68 when using only BTMSE without MTMS as shown in FIG. 8, and when the ratio of MTMS is increased, dielectric constant decreases to 8.15 and 6.5. . The reason why the dielectric constant decreases is that as the ratio of MTMS increases in the ethylene bridged silsesquioxane thin film, the content of Si-OH decreases and the amount of H ₂ O decreases. This phenomenon occurs because H ₂ O acts to change orientation polarization.

It can be seen from FIG. 5 that the Si-OH ratio does not coincide with the leakage current value. 1.21 × 10 ^-5 , 4.31 × 10 ^-5 , 6.93 × 10 ^-5 A / with BTMSE and MTMS at 0.5 MV / cm for 10: 0 (BTMSE only), 8: 2, and 5: 5 samples, respectively has a current of cm ² . All thin films have a high leakage current, because Si-OH, H ₂ O has a large influence on the leakage current. Coating of 1.5% P3HT on a thin film of ethylene bridged silsesquioxane resulted in coating without other surface treatments. After the Au was deposited on the organic semiconductor, the TFT characteristics were evaluated. As shown in FIGS.

The charge mobility was calculated by the following theory.

Organic thin film transistors operate on the same principle as field effect transistors, so they are divided into linear and saturation regions. When a voltage is applied to the gate, a channel is formed in the organic semiconductor without a current flowing from the gate electrode to the drain due to the insulating film. Applying a voltage between the source and the drain blurs the current in the device and grounds the source to serve as a carrier. If no voltage is applied to the source-drain and gate, the charges in the semiconductor will spread evenly within the organic semiconductor. When a potential difference is generated between the source and the drain by applying a voltage between the source and the drain, a current proportional to the voltage flows under a low voltage, and Ids having a conductivity of the thin film as shown in Equation 1 flows.

[Calculation 1]

Here, W represents the width of the channel, L represents the length of the channel, t represents the thickness of the channel, V _d represents the voltage of the drain. When a positive voltage is applied to the gate, the holes are pushed away by the electric field, creating a depletion layer without conduction charge near the insulator. All of the charge goes out towards the source. Under these conditions, applying a voltage to the source and drain reduces the charge carriers, allowing a lower amount of current to flow than when no voltage is applied to the gate. When a negative voltage is applied to the gate, holes are injected from the electrode between the organic material and the heating element by an electric field, and an alluvial layer is formed between the insulator and the semiconductor. When voltage is applied to the source and drain, current flows due to the potential difference. ΔV _G Increasing the gate voltage by, the electric charge of the channel is changed by C _i ΔV _G and WLC _i ΔV _G in the entire channel region. If the changing charge has a mobility of μ, a small positive drain voltage V _d Current is increased by ΔI _d Is given by Equation 2 below.

[Equation 2]

Here, C _i represents the storage capacitance of the gate insulating film, and V _G refers to the voltage applied to the gate insulating film. The field effect mobility in the accumulation layer is calculated as a function of V _G as shown in Equation 3 below, which is a formula for calculating mobility in a linear region.

[Calculation 3]

If a larger negative voltage is applied to the drain, the depletion region extends to the drain electrode and completely depletes the organic active layer. At this point, the current begins to saturate and the current-voltage graph begins to appear as a saturation region current-voltage characteristic of the transistor. In each area, the current is first linear, gate voltage V _G is the threshold voltage V _T If higher, the relationship between Q and V _G flowing into the channel may be expressed as in Equation 5 below.

[Calculation 4]

This equation ignores the diffusion component in the equation of current density.

[Calculation 5]

Ey = dV / dy and the equation substituted in Equation 4 above are integrated in the range of y = 0 to L _ch and V = 0 to V _d to obtain the basic equation 6 for Id.

[Calculation 6]

In the linear region where V _d is very low, it is represented by Equation 7 below.

[Calculation 7]

In addition, in the saturation region, by setting Q to 0, a drive current in the saturation region can be induced. Eventually, it can be said that V = V _G -V _T = V _d . Substituting Equation 7 above, Equation 8 can be obtained.

[Calculation 8]

For thin films with a 10: 0 molar ratio of BTMSE and MTMS, a charge mobility of 0.039 cm ² / VS and a threshold voltage of -1 V were measured, and a thin film of 0.069 cm ² / VS and a threshold of 0.4 V for 6: 4 thin films. The voltage was measured. Through this, it can be seen that the TFT device operates in the ethylene bridged silsesquioxane thin film. However, all thin films have a problem of having a low current flicker ratio of 10 to 40, and it can be seen that the maximum current value changes according to the direction of the voltage. The main reason for the change of the current blink rate and the maximum current value is the influence of Si-OH and H ₂ O in the thin film. When the current flicker ratio is generally measured in a thin film having a high leakage current value, the change of the maximum current value is a change generated by changing the capacitance of the thin film.

It can be seen that the value of charge mobility varies with the ratio of MTMS. This increase in charge mobility is closely related to the contact angle of the surface. In general, all thin films are generally hydrophobic. However, a thin film having a molar ratio of BTMSE: MTMS of 10: 0 has a lower contact angle than a thin film having a molar ratio of 6: 4 of BTMSE: MTMS. As mentioned above, the contact angle of the surface is different because the amount of Si-OH and methyl groups on the surface of the thin film is different. Thin films having a molar ratio of 10: 0 BTMSE: MTMS contain more Si-OH than thin films having a molar ratio of 6: 4, making it difficult for hydrophobic organic semiconductors to grow crystalline at low temperatures. As a result, when the amount of MTMS is increased, the surface of the thin film becomes more hydrophobic and the organic semiconductor has an advantage in forming crystals. The charge mobility is the roughness of the insulator after the formation of organic semiconductor crystals. When the roughness value of the thin film is high, the charge is difficult to move, which causes the charge mobility to decrease. The ethylene bridged silsesquioxane thin film can investigate the surface roughness through AFM analysis, and the ethylene bridged silsesquioxane thin film of the present invention has the roughness of the thin film as shown in FIG. 15. It can be seen that the ethylene bridged silsesquioxane thin film has a low overall roughness and the roughness decreases with the ratio of MTMS.

When the present invention is put together, the ethylene bridged silsesquioxane thin film is a very suitable material as an insulator for OTFT. The present invention can produce a thin film at a low temperature of 150 ℃, it is possible to coat the organic semiconductor without additional surface treatment. In addition, the use of MTMS to reduce the Si-OH ratio of the surface has the effect of increasing the charge mobility.

Claims (16)

(a) mixing a bridged siloxane compound of Formula 3 and a siloxane compound of Formula 4, water (H ₂ O) and a hydrochloric acid solution;
(b) polymerizing the mixture of step (a) at room temperature to form a bridged silsesquioxane polymer of Formula 1; And
(c) applying and curing the polymer composition of step (b) on a substrate;
Method for producing an insulator thin film comprising a.
[Formula 1]

(3)

[Chemical Formula 4]

[In Formula 1, 3 and 4, R ¹ And R ²¹ is selected from (C2-C6) alkylene, (C6-C12) arylene and (C1-C10) acyl (C6-C12) arylene, and R ² to R ¹¹ and R ²² to R ³² Are independently from each other (C1-C6) alkyl, m is an integer from 2 to 1000.
(a) mixing a bridged siloxane compound of Formula 3, water (H ₂ O) and a hydrochloric acid solution;
(b) polymerizing the mixture of step (a) at room temperature to form a bridged silsesquioxane polymer of formula (2); And
(c) applying and curing the polymer composition of step (b) on a substrate;
Method for producing an insulator thin film comprising a.
(2)

(3)

[In Formulas 2 and 3, R ¹ And R ⁴¹ is selected from (C2-C6) alkylene, (C6-C12) arylene and (C1-C10) acyl (C6-C12) arylene, and R ² to R ⁷ and R ⁴² to R ⁴⁷ are each other Independently (C1-C6) alkyl, n is an integer from 2 to 1000.
The method of claim 1,
R ¹ and R ²¹ are each independently selected from ethylene, propylene, butylene, ter-butylene, pentylene, hexylene, phenylene and methylphenylene; R ² to R ¹¹ and R ²² to R ³² are each independently selected from methyl, ethyl, propyl, butyl and ter-butyl.
The method of claim 2,
R ¹ and R ⁴¹ are each independently selected from ethylene, propylene, butylene, ter-butylene, pentylene, hexylene, phenylene and methylphenylene; R ² to R ⁷ And R ⁴² to R ⁴⁷ are each independently selected from methyl, ethyl, propyl, butyl and ter-butyl.
The method of claim 1,
The compound of Formula 3 and Formula 4: H ₂ O: hydrochloric acid is mixed in a molar ratio of 0.001 ~ 0.010: 1: 1 method for producing an insulator thin film.
The method of claim 2,
The compound of Formula 3: H ₂ O: hydrochloric acid is mixed in a molar ratio of 0.001 ~ 0.010: 1: 1 method for producing an insulator thin film.
The method of claim 5,
Formula 3: Formula 4 is a method for producing an insulator thin film, characterized in that mixing in a molar ratio of 10: 0.01 ~ 10.
The method according to claim 1 or 2,
The coating of step (c) is a method of manufacturing an insulator thin film, characterized in that the spin coating.
The method according to claim 1 or 2,
The polymer composition of step (c) is a method for producing an insulator thin film, characterized in that diluted in an organic solvent.
10. The method of claim 9,
The organic solvent is selected from ethanol, tetrahydrofuran, methyl isobutyl ketone and poly (ethylene glycol) methyl ether acrylate.
The method according to claim 1 or 2,
The curing of the step (c) is a method for producing an insulator thin film, characterized in that carried out at room temperature to 150 ℃.
The insulator thin film formed by the manufacturing method of the insulator thin film of any one of Claims 1 or 2.
The method of claim 12,
The insulator thin film has an insulator thin film, characterized in that it has a charge mobility of 0.039 to 0.070 cm ² / VS.
The method of claim 12,
The insulator thin film has a dielectric constant of 6.5 to 9.7.
The method of claim 12,
Insulator thin film, characterized in that the contact angle of the insulator thin film is 41 ° to 63 °.
An organic thin film transistor comprising the insulator thin film according to claim 12 as a gate insulator.

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