KR20100138078A - Manufacturing method of polymer gate insulating film - Google Patents

Abstract

PURPOSE: A method for manufacturing a polymer gate insulation layer is provided to obtain a high insulation property and a high dielectric constant by reducing the content of OH in an insulation layer. CONSTITUTION: Solutions including polymer and crosslinker to form cross-link by reacting with polymer is spin-coated on a substrate. A coating layer is annealed at 40 to 270 degrees centigrade. The polymer is cyanoethylated polymer selected among pullulan, cellulose, polyvinyl alcohol, and sucrose.

Description

Manufacturing Method of Polymer Gate Insulator {METHOD FOR PREPARING A POLYMER GATE DIELECTRIC}

The present invention relates to a method of manufacturing a gate insulating film for an organic semiconductor device, in particular for an organic thin film transistor, having excellent insulating properties and high dielectric constant.

In order to improve the performance of the organic thin film transistor which is most studied and used as an organic semiconductor device, a gate insulating film having good insulation characteristics and high dielectric constant is essential.

In the polymer insulating layer, there is a large functional group such as a hydroxyl group (OH group), which causes a problem of causing hysteresis when the transistor is operated. Polyvinylphenol (PVP), which is widely used as an insulating film, is a representative example.

In such a case, when the crosslinking agent is used together with the insulating film forming polymer, the crosslinking agent may combine with the hydroxyl group of the molecular chain to reduce the polar group, and the polymer structure may be densified by crosslinking to reduce the hysteresis and improve the insulating property. In addition, the use of an insulator having a high dielectric constant as the gate insulating film forming material has a positive effect of lowering the operating voltage of the transistor.

Accordingly, the present inventors have intensively studied, and as a result, when the insulating film is formed by heat treatment using a solution containing a specific polymer having a high dielectric constant and a specific crosslinking agent that can react with the polymer, excellent insulation properties and a high dielectric constant are obtained. The present invention has been accomplished by discovering that a polymer insulating film can be prepared.

Accordingly, it is an object of the present invention to provide a method for producing a polymer gate insulating film for an organic semiconductor device, in particular for an organic thin film transistor, having excellent insulating properties and high dielectric constant.

The present invention to achieve the above object,

Spin coating a substrate with a solution containing a cyanoethylated polymer selected from pullulan, cellulose, polyvinyl alcohol and sucrose and a crosslinking agent which reacts with the polymer to form crosslinks, wherein a part of the hydroxy group is cyanoethylated After that, including the heat treatment in the range of 40 to 270 ℃,

Provided is a method of manufacturing a polymer insulating film.

According to the polymer insulating film production method according to the present invention, by cross-linking a specific polymer having a high dielectric constant and a crosslinking agent that can react with the polymer through heat treatment, it is possible to reduce the content of hydroxy groups in the formed insulating film and to provide excellent insulation properties and high dielectric constant The polymer insulating film which can have can be manufactured. Such a polymer insulating film of the present invention can be usefully used as a polymer gate insulating film of an organic semiconductor device, particularly an organic thin film transistor due to its excellent physical properties.

The polymer insulating film production method according to the present invention is a cyanoethylated polymer selected from pullulan, cellulose, polyvinyl alcohol and sucrose in which a part of the hydroxy group is cyanoethylated, and a crosslinking agent which reacts with the polymer to form a crosslink. By heat-treating the coating layer consisting of a solution containing from 40 to 270 ℃ range, the alkoxy group and / or hydroxy groups present in the two materials are reacted with each other to form a crosslink between the two materials. That is, when the coating layer of the solution containing the polymer and the crosslinking agent is heat-treated, crosslinking occurs while the solvent and the reaction by-products evaporate. The polymer and the crosslinker form a chain with each other, and the heat treatment causes the water and the alcohol to escape and a dense film is formed.

In the present invention, the crosslinking agent may be used in an amount of 1 to 200 parts by weight based on 100 parts by weight of the cyanoethylated polymer.

The cyanoethylated polymer used in the present invention may have a weight average molecular weight in the range of 10,000 to 10,000,000, and the hydroxy group is substituted with the cyanoethyl group with a degree of substitution of 1 to 100%, preferably 50 to 100%. Can be.

Examples of crosslinking agents used in the present invention include diisocyanate compounds, acyl halide compounds, trialkoxysilyl or trichlorosilyl compounds, two or more epoxy group-containing epoxides, melamine derivatives or melamine derivative-containing polymers, and mixtures thereof. Can be.

Specific examples of the diisocyanate compound include compounds represented by the following Chemical Formulas 1a to 1i:

Where

R ¹ to R ⁷ are each independently hydrogen or C _1-10 alkyl,

이고,R ⁸ to R ¹⁰ are each independently hydrogen or

ego,

X is halogen.

Specific examples of the acyl halide compound include compounds represented by the following Chemical Formulas 2a to 2d:

Where

X ¹ to X ⁸ are each independently halogen,

n is each independently an integer of 1 to 10.

Specific examples of the trialkoxysilyl or trichlorosilyl compound include compounds represented by the following formulas 3a to 3d:

Specific examples of the two or more epoxy group-containing epoxides include compounds represented by the following general formula (4):

Specific examples of the melamine derivatives or melamine derivative-containing polymers include compounds represented by the following formulas 5a to 5c:

Where

Y ¹ to Y ⁶ are each independently hydrogen or C _1-10 alkyl,

m is each independently 1-10.

As the solvent of the solution containing the polymer and the crosslinking agent, a polar solvent may be used, and preferably, a solvent selected from the group consisting of dimethylformamide, CH ₃ CN, dimethyl sulfoxide and mixtures thereof may be used. The polymer concentration in the solution may be 0.5 to 50% by weight, and the crosslinking agent concentration may be 0.1 to 25% by weight.

When spin coating a solution containing a polymer and a crosslinking agent onto a substrate, it is preferable to perform spin coating within a range not exceeding 10,000 rpm, and more preferably, spin coating may be performed at a speed of 500 to 10,000 rpm.

In the present invention, the spin-coated coating layer may be heat-treated for a suitable time in the range of 40 to 270 ℃, preferably 150 to 200 ℃. If heat treated at a temperature higher than 270 ° C, thermal decomposition of the polymer may occur.

As described above, according to the polymer insulating film production method according to the present invention, by cross-linking a specific polymer having a high dielectric constant and a crosslinking agent that can react with the polymer through heat treatment, the content of the hydroxyl group in the insulating film to be formed to reduce the excellent insulating properties and high A polymer insulating film having a dielectric constant can be prepared. The thickness of the polymer insulating film may range from 0.02 to 5 μm.

Such a polymer insulating film of the present invention can be usefully used as a polymer gate insulating film of an organic semiconductor device, particularly an organic thin film transistor due to its excellent physical properties.

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: Preparation of Polymer Insulating Film

Cyanoethylated pullulan (degree of substitution: 89%, weight average molecular weight: 489,000) and poly (methylated melamine-co-formaldehyde) (compound of formula 5b, Y ¹ to Y ⁴ : methyl, m: 1) Was dissolved in a 1: 1 (v / v) mixture of dimethylformamide and CH ₃ CN to give 5% by weight of cyanoethylated pullulan and 1.5% of poly (methylated melamine-co-formaldehyde). A solution by weight was prepared.

The solution was spin-coated on an n-type silicon wafer at a rate of 3,000 rpm, and then the coating layer was heat-treated at temperatures of 50, 100, 150 and 200 ° C. to obtain polymer insulating films of 0.260, 0.234, 0.232 and 0.217 μm in thickness. Prepared.

Example 2 Fabrication of Organic Thin Film Transistor-(1)

Pentacene was deposited at a rate of 0.2 to 0.3 μs ⁻¹ at 50 ° C. using an organic molecular beam deposition system on a polymer insulating film coated on an n-type silicon wafer prepared in Example 1 To form a pentacene film having a thickness of 60 nm. After depositing an Au electrode on the formed pentacene film, a top-contact structure as shown in FIG. 4 was patterned to form a channel having a width of 1500 μm and a length of 150 μm using a shadow mask. An organic thin film transistor having a was prepared.

Absorption intensity graph showing a change in the hydroxyl group content according to the heat treatment temperature (50, 100, 150 and 200 ℃) of the thin film obtained in Example 1 is shown in Figure 1, and a graph showing the change in hysteresis and dielectric constant in Figure 2 Respectively.

3A to 3C show graphs of voltage-current change according to the thin film heat treatment temperature of the organic thin film transistor obtained in Example 2 (FIG. 3A: 50 ° C. heat treatment, FIG. 3B: no heat treatment, and FIG. 3C: 200 ° C.). Heat treatment).

From Figure 1, increasing the heat treatment temperature reduces the amount of the hydroxy group (-OH) appearing near 3000 cm ^-1 it can be seen that decreasing the relative transfer of the methyl group (-CH ₃₎ appears to 2800cm ^-1. Accordingly, it can be seen from FIG. 2 that the hysteresis of the formed film is reduced and the dielectric constant is increased.

Further, as shown in FIGS. 3A to 3C, it can be seen that the transistor made of the insulating film heat-treated at 200 ° C. has a high flow rate of current and the current rapidly increases with the change of the voltage, thereby improving the characteristics of the device.

Example 3 Fabrication of Organic Thin Film Transistor-(2)

A polymer insulating film was prepared in the same manner as in Example 1, except that the compound shown in Table 1 below was used instead of the poly (methylated melamine-co-formaldehyde) as a crosslinking agent, and the heat treatment was performed at 200 ° C. Using this, an organic thin film transistor was manufactured in the same manner as in Example 2.

Voltage-current change graphs of various organic thin film transistors obtained in Example 3 are shown together in Tables 1A to 1E.

1 is a graph of absorbance intensity showing the change of the hydroxyl group content according to the heat treatment temperature (50, 100, 150 and 200 ℃) of the thin film obtained in Example 1,

2 is a graph showing changes in hysteresis and dielectric constant according to the heat treatment temperatures (50, 100, 150, and 200 ° C.) of the thin film obtained in Example 1,

3A to 3C are graphs of voltage-current change according to the thin film heat treatment temperature of the organic thin film transistor obtained in Example 2, and FIG. 3A is a thin film prepared by heat treatment at 50 ° C., and FIG. 3B is a thin film prepared without heat treatment. 3c illustrates a case where a thin film prepared by heat treatment at 200 ° C. is used.

4 is a schematic cross-sectional view of a top-side organic thin film transistor manufactured in Example 2. FIG.

Claims (10)

Spin coating a substrate with a solution containing a cyanoethylated polymer selected from pullulan, cellulose, polyvinyl alcohol and sucrose and a crosslinking agent which reacts with the polymer to form crosslinks, wherein a part of the hydroxy group is cyanoethylated After that, including the heat treatment in the range of 40 to 270 ℃, Method for producing a polymer insulating film. The method of claim 1, The crosslinking agent is used in an amount of 1 to 200 parts by weight based on 100 parts by weight of the cyanoethylated polymer. The method of claim 1, The cyanoethylated polymer has a weight average molecular weight of 10,000 to 10,000,000, characterized in that the manufacturing method of the polymer insulating film. The method of claim 1, The cyanoethylated polymer is a method of producing a polymer insulating film, characterized in that 1 to 100% of the hydroxy group is substituted with a cyanoethyl group. The method of claim 1, Wherein the crosslinking agent is a diisocyanate compound, an acyl halide compound, a trialkoxysilyl compound, a trichlorosilyl compound, two or more epoxy group-containing epoxides, melamine derivatives, melamine derivative-containing polymers, or mixtures thereof Method for producing an insulating film. The method of claim 1, The solution containing the polymer and the crosslinking agent is formed using a solvent selected from the group consisting of dimethylformamide, CH ₃ CN, dimethyl sulfoxide and mixtures thereof. The method of claim 1, The solution containing the polymer and the crosslinking agent contains the polymer and the crosslinking agent at concentrations of 0.5 to 50% by weight and 0.1 to 25% by weight, respectively. The method of claim 1, Method for producing a polymer insulating film, characterized in that to perform the heat treatment of the coating layer at 150 to 200 ℃. The polymer insulating film manufactured by the method of any one of Claims 1-8. The method of claim 9, The insulating film is a polymer insulating film, characterized in that used as a gate insulating film for an organic thin film transistor.

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