KR101056599B1 - Method for forming organic-inorganic composite typed gate insulator of organic thin film transistor and organic-inorganic composite typed gate insulator of organic thin film transistor formed therefrom - Google Patents

Abstract

PURPOSE: A method for forming the organic-inorganic composite gate insulating film of an organic thin film transistor and the organic-inorganic composite typed gate insulating film of an organic thin film transistor using the same are provided to simply form the gate insulation layer of a organic thin film transistor with a low cost, easily coat the surface, and efficiently apply to a substrate with a high molecule which is flexible and hard to be processed at a high temperature. CONSTITUTION: The carbon number of an alkyl group dissolves the alkyl alkoxide of 1 to 20 metallic oxides and an insulating organic polymer in an organic solvent and prepares organic-inorganic composite solutions for forming a gate dielectric layer. Organic-inorganic composite solutions are spread in the substrate of an organic thin film transistor and form a coating layer. An organic solvent is dried in the coating layer and an organic-inorganic composite gate insulating layer is formed.

Description

Method for forming organic-inorganic composite gate insulating film of organic thin film transistor and organic-inorganic composite gate insulating film formed from organic thin film transistor and organic-inorganic composite typed gate insulator gate insulator of organic thin film transistor formed therefrom}

The present invention relates to a method for forming a gate insulating film of an organic thin film transistor and an organic-inorganic hybrid gate insulating film of an organic thin film transistor formed therefrom.

 The biggest technical obstacle in the manufacture of flexible displays, which is being discussed as next generation displays, is the TFT array. Silicon semiconductor materials typically used in manufacturing TFT arrays are not satisfactory for making flexible displays that can be bent or folded. Accordingly, there has been a need to develop organic semiconductors suitable for flexible displays. In other words, the organic thin film transistor (OTFT), which can be bent or folded without breaking due to impact, is easy to use because of its simple manufacturing process, and is inexpensive. Field.

By the way, in order for the organic thin film transistor to work properly, it is necessary to develop an excellent organic semiconductor, but at the same time, it is necessary to develop a gate insulating film that can effectively express the characteristics of the organic semiconductor while being well bonded with the organic semiconductor.

The gate insulating film of the organic thin film transistor can be roughly classified into a gate insulating film made of an inorganic insulating film and a gate insulating film made of an organic insulating polymer.

Inorganic gate insulating film has the advantage of having a large dielectric constant, but has a disadvantage of generating a relatively large leakage current, and also requires a high temperature post-treatment process and poor adhesion to organic semiconductors. There is.

On the contrary, in the case of a gate insulating film made of an insulating organic polymer, the gate insulating film is excellent in bonding property with the organic semiconductor and has a small leakage current and can be easily formed. However, the insulating polymer, which is organic, has a lower dielectric constant than the inorganic material, resulting in an increase in driving voltage of the organic thin film transistor.

Nevertheless, the reason why many organic thin film transistors use an insulating organic polymer as a gate insulating film is because the junction voltage of the organic semiconductor and the organic semiconductor used is relatively low, thus making it possible to construct a stable device. In addition, since the inorganic insulating film is generally an inorganic oxide made by high temperature treatment on a substrate such as Si, the substrate cannot be used for a flexible polymer material or the like.

In order to solve the above-mentioned problems of the organic gate insulating film, an organic-inorganic hybrid type is prepared by mixing an insulating organic polymer used as an insulating film with a small metal oxide having a nanoparticle size such as Ti0 ₂ or SiO ₂ having a higher dielectric constant than the organic polymer. A method of forming a gate insulating film has been proposed. However, the organic-inorganic composite gate insulating film thus formed may act as a defect due to partial accumulation of metal oxide, and mechanical defects may occur at the interface between the metal oxide and the organic polymer.

Therefore, there is a need for a method of forming a gate insulating film of an organic thin film transistor which can effectively improve the characteristics of the organic thin film transistor while having the advantages of the organic insulating film and the inorganic insulating film.

The technical problem of the present invention was devised to solve the above problems. The organic-inorganic hybrid gate insulating film having a high dielectric constant and low leakage current with a high dielectric constant and an organic thin film in a simple manner has been developed. A method that can be formed in a transistor and an organic-inorganic hybrid gate insulating film of an organic thin film transistor formed therefrom are provided.

In order to achieve the above object, the organic-inorganic hybrid gate insulating film forming method of the organic thin film transistor according to the present invention,

(S1) dissolving an alkyl alkoxide and an insulating organic polymer of a metal oxide having 1 to 20 carbon atoms of an alkyl group in an organic solvent to prepare an organic-inorganic composite solution for forming a gate insulating film;

(S2) coating the organic-inorganic composite solution on an organic thin film transistor substrate to form a coating layer; And

(S3) drying the organic solvent from the coating layer to form an organic-inorganic hybrid gate insulating film.

In the gate insulating film forming method of the present invention, the alkyl alkoxide of the metal oxide is aluminum ethoxide, Aluminum isopropoxide, Aluminum tributoxide, Aluminum sec-butoxide, Aluminum tert-butoxide, Aluminum tri-sec-butoxide, Tin (IV) tert-butoxide, Tributyltin ethoxide, Tin (IV) tert-butoxide, Hafnium (IV) n-butoxide, Hafnium (IV) tert-butoxide, Hafnium isopropoxide isopropanol adduct, Antimony (III) methoxide, Antimony (III) ethoxide, Antimony (III) propoxide, Antimony (III) butoxide, Tantalum (V) methoxide, Tantalum (V) ethoxide, Tantalum (V) butoxide, Titanium (IV) methoxide, Titanium (IV) ethoxide, Titanium (IV) propoxide, Titanium (IV) isopropoxide, Titanium ( IV) butoxide, Titanium (IV) tert-butoxide, Zinc methoxide, Zirconium (IV) ethoxide, Zirconium (IV) propoxide, Zirconium (IV) butoxide, Zirconium (IV) tert-butoxide, Zirconium (IV) isopropoxide isopropanol complex, Thallium (I) ethoxide, Zirconium (IV) ethoxide, Vanadium (V) oxytriethoxide, Vanadium (V) oxytriisopropoxide, Indium (III ) tert-butoxide, Yttrium (III) butoxide, Barium tert-butoxide, Lanthanum (III) isopropoxide, Scandium (III) isopropoxide, Niobium (V) ethoxide, etc. can be used alone or in combination of two or more of them. .

In the gate insulating film forming method of the present invention, the metal component of the alkyl alkoxide of the metal oxide is preferably titanium, tantalum, zirconium or the like. In addition, the alkyl alkoxide (a) and the insulating organic polymer (b) of the metal oxide may be added to the organic-inorganic composite solution in a weight ratio (a: b) of 1: 100 to 100: 1.

The organic-inorganic hybrid gate insulating film of the organic thin film transistor formed in this manner can effectively improve the characteristics of the organic thin film transistor while having the advantages of the organic insulating film and the inorganic insulating film.

According to the forming method of the present invention, the gate insulating film of the organic thin film transistor can be formed by a simple method, and a large area coating is also easy. In addition, it is possible to form a gate insulating film at low cost since no vacuum equipment is required, and can be effectively applied to a polymer substrate which is not capable of high temperature processing and is flexible.

On the other hand, the organic-inorganic composite gate insulating film of the organic thin film transistor formed according to the present invention is excellent in bonding with the organic semiconductor. In addition, since the dielectric constant is large and there is little leakage current, the organic thin film transistor can effectively express the characteristics.

1 to 3 are graphs illustrating the measurement of the dielectric constant according to the frequency change of the gate insulating film formed according to the embodiments of the present invention and the comparative examples.
4 is a graph illustrating a dielectric constant measured according to a frequency change of the gate insulating film according to the tenth embodiment of the present invention.
5 to 7 are graphs illustrating leakage currents according to electric field changes of gate insulating layers formed according to embodiments and comparative examples of the present invention.

Hereinafter, the present invention will be described in detail. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

The present inventors apply an organic-inorganic composite solution obtained by dissolving an alkyl alkoxide of a metal oxide having a high dielectric constant in an organic solvent together with an insulating organic polymer to an organic thin film transistor substrate to form a gate insulating film. The objective was achieved.

According to the method for forming an organic-inorganic hybrid gate insulating film of the organic thin film transistor of the present invention, first, the alkyl alkoxide and insulating organic polymer of a metal oxide having 1 to 20 carbon atoms of an alkyl group are dissolved in an organic solvent to form a gate insulating film. Prepare an organic-inorganic complex solution (step S1).

The alkyl alkoxide of the metal oxide may be represented by M (-O-Alkyl) n, where M is a metal element, and examples thereof include titanium, tantalum, zirconium, and the like. n is an integer of 1 or more, as is well known depending on the oxidation state of the metal element. Moreover, it is preferable that carbon number of an alkyl group is 1-20, More preferably, it is 1-10.

Alkyl alkoxides of these metal oxides include Aluminum ethoxide, Aluminum isopropoxide, Aluminum tributoxide, Aluminum sec-butoxide, Aluminum tert-butoxide, Aluminum tri-sec-butoxide, Tin (IV) tert-butoxide, Tributyltin ethoxide, Tin (IV) tert- butoxide, Hafnium (IV) n-butoxide, Hafnium (IV) tert-butoxide, Hafnium isopropoxide isopropanol adduct, Antimony (III) methoxide, Antimony (III) ethoxide, Antimony (III) propoxide, Antimony (III) butoxide, Tantalum (V ) methoxide, Tantalum (V) ethoxide, Tantalum (V) butoxide, Titanium (IV) methoxide, Titanium (IV) ethoxide, Titanium (IV) propoxide, Titanium (IV) isopropoxide, Titanium (IV) butoxide, Titanium (IV) tert -butoxide, Zinc methoxide, Zirconium (IV) ethoxide, Zirconium (IV) propoxide, Zirconium (IV) butoxide, Zirconium (IV) tert-butoxide, Zirconium (IV) isopropoxide isopropanol complex, Thallium (I) ethoxide, Zirconium (IV) ethoxide, Vanadium (V) oxytriethoxide, Vanadium (V) oxytriisopropoxide, Indium (III) tert-butoxide, Yttrium (III) butoxide, Barium ter t-butoxide, Lanthanum (III) isopropoxide, Scandium (III) isopropoxide, Niobium (V) ethoxide, etc. can be exemplified, and these may be used alone or in combination of two or more thereof.

As the insulating organic polymer, any organic polymer that can be used or used to form the organic gate insulating film of the organic thin film transistor can be used. Therefore, in the present invention, the insulating organic polymer is not only a homopolymer but also a copolymer in which at least two monomers are polymerized. , Graft polymer, as well as cross-linked polymer formed by cross-linking reaction by heat or light irradiation should be interpreted to include all.

Known insulating organic polymers include, for example, polyester, polycarbonate, polyvinylalcohol, polyvinylbutyral, polyacetal, polyarylate, poly Amide (polyamide), polyamidimide, polyetherimide, polyphenylenether, polyphenylenesulfide, polyethersulfone, polyetherketone, polyetherketone, polyetherketone Phthalamide, polyethernitrile, polyethersulofone, polybenzimidazole, polycarbodiimide, polysiloxane, polymethylmethacrylate, Polymethacrylamide, nitrile rubber, acrylic rubber, poly Ethylenetetrafluoride, epoxy resin, phenol resin, melamine resin, urea resin, polybutene, polypentene, polypentene, ethylene- Ethylene-co-propylene, ethylene-co-butene diene, polybutadiene, polyisoprene, ethylene-propylene-diene copolymer -propylene diene, butyl rubber, polymethylpentene, polystyrene, styrene-butadiene copolymer, hydrogenated styrene-butadiene copolymer (hydrogenated styrene-co-butadiene ), Hydrogenated polyisoprene, hydrogenated polybutadiene, and the like, but are not limited thereto.

As the organic solvent used to prepare the organic-inorganic composite solution, any solvent capable of dissolving both the alkyl alkoxide and the insulating organic polymer of the metal oxide can be used. Such an organic solvent may be appropriately selected by those skilled in the art according to the type of the alkyl alkoxide and the insulating organic polymer of the metal oxide used. As such, the organic-inorganic composite solution in which both the alkyl alkoxide and the insulating organic polymer of the metal oxide are dissolved is present in a state in which the inorganic component and the organic component are well mixed.

Representative examples of the organic solvent may include toluene, tetrahydrofuran, butyl acetate, isopropanol, ethanol, PGMEA and the like, but is not limited thereto. An organic solvent can be used individually or in mixture of 2 or more types, respectively.

In the organic-inorganic hybrid gate insulating film formation method of the organic thin film transistor according to the present invention, the alkyl alkoxide (a) and the insulating organic polymer (b) of the metal oxide is 1: 100 to 100: 1 by weight ratio (a: b) It may be added to the organic-inorganic composite solution. The concentration of the solid component dissolved in the organic-inorganic composite solution, that is, the alkyl alkoxide of the metal oxide and the insulating organic polymer can be appropriately adjusted to form a uniform coating layer, for example, 0.1 based on the total weight of the organic-inorganic composite solution. To 40% by weight.

Subsequently, the prepared organic-inorganic composite solution is applied to the organic thin film transistor substrate to form a coating layer (step S2).

As a method of coating the organic-inorganic composite solution, all known solution coating methods such as spin coating and dip coating may be applied.

Then, the organic solvent is dried from the coating layer, that is, the organic-inorganic composite solution coating layer, to form an organic-inorganic hybrid gate insulating film (step S3).

If a polymer containing a functional group capable of crosslinking reaction is used as the insulating organic polymer, a step of applying a heat or irradiating light to the crosslinking reaction may be added if necessary.

As described above, according to the present invention, the organic-inorganic hybrid gate insulating film can be formed by a simple method without a high temperature post-treatment process. In addition, the formed organic-inorganic hybrid gate insulating film is excellent in adhesion with the organic semiconductor due to the insulating organic polymer included and less leakage current. In addition, due to the alkyl alkoxide component of the metal oxide, the dielectric constant is large so that the characteristics of the organic semiconductor can be effectively expressed.

Hereinafter, examples will be described in detail to help understand the present invention. However, embodiments according to the present invention can be modified in many different forms, the scope of the invention should not be construed as limited to the following examples. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Synthesis of Dielectric Organic Polymer

Synthesis Example 1

To 100 ml of tetrahydrofuran, 1.2 ml of MMA (Methyl methacrylate), 3.88 g of N-phenylmaleimide, and 0.055 g of AIBN, an initiator, were reacted at 75 ° C. for 24 hours in a nitrogen atmosphere, and then precipitated in hexane to obtain a copolymer (MMA: N- The molar ratio of phenylmaleimide = 1: 2) was synthesized.

Synthesis Example 2

Synthesis was carried out in the same manner as in Synthesis Example 1, except that the molar ratio of the copolymer (MMA: N-phenylmaleimide) was changed to 2: 1.

Synthesis Example 3

Synthesis was carried out in the same manner as in Synthesis Example 1, except that the molar ratio of the copolymer (MMA: N-phenylmaleimide) was changed to 3: 1.

Example

Example 1

0.54 g of the copolymer synthesized in Synthesis Example 1 was added to 5 ml of PGMEA (Propylene Glycol Methyl Ether Acetate), and 0.041 ml of Titanium (IV) isopropoxide (97%) was added thereto to prepare an organic-inorganic composite solution. Before applying the prepared composite solution to the substrate through a 0.2um filter to remove fine dust and the like.

The composite solution was dropped on acetone and ultrasonically cleaned, and the composite solution was spin coated by maintaining the solution at 3000 rpm for 30 seconds. Thereafter, the resultant was dried in a vacuum oven at 150 ° C. for at least 10 hours to form a gate insulating film. The thickness of the formed gate insulating film was about 130 nm.

Thus, the gate insulating film formed according to Example 1 was named MP1-Ti according to the type of insulating polymer used and the type of metal component of the alkoxide of the metal oxide.

Example 2

The same procedure as in Example 1 was carried out except that the copolymer synthesized in Synthesis Example 2 was used instead of the copolymer synthesized in Synthesis Example 1.

Thus, the gate insulating film formed in accordance with Example 2 was named MP2-Ti.

Example 3

The same procedure as in Example 1 was carried out except that the copolymer synthesized in Synthesis Example 3 was used instead of the copolymer synthesized in Synthesis Example 1.

Thus, the gate insulating film formed in accordance with Example 3 was named MP3-Ti.

Example 4

The same procedure as in Example 1 was conducted except that 0.038 ml of Zirconium (IV) propoxide (70 wt% under Solvent 1-propanol) was added instead of the Titanium (IV) isopropoxide of Example 1.

Thus, the gate insulating film formed in accordance with Example 4 was named MP1-Zr.

Example 5

The same procedure as in Example 2 was carried out except that 0.038 ml of Zirconium (IV) propoxide (70 wt% under Solvent 1-propanol) was added instead of the Titanium (IV) isopropoxide of Example 2.

Thus, the gate insulating film formed in accordance with Example 5 was named MP2-Zr.

Example 6

The same procedure as in Example 3 was conducted except that 0.038 ml of Zirconium (IV) propoxide (70 wt% under Solvent 1-propanol) was added instead of Titanium (IV) isopropoxide of Example 3.

Thus, the gate insulating film formed in accordance with Example 6 was named MP3-Zr.

Example 7

The same procedure as in Example 1 was conducted except that 0.025 ml of tantalum (V) ethoxide (99.98%) was added instead of the titanium (IV) isopropoxide of Example 1.

Thus, the gate insulating film formed in accordance with Example 7 was named MP1-Ta.

Example 8

The same procedure as in Example 2 was conducted except that 0.025 ml of tantalum (V) ethoxide (99.98%) was added instead of the titanium (IV) isopropoxide of Example 2.

Thus, the gate insulating film formed in accordance with Example 8 was named MP2-Ta.

Example 9

The same procedure as in Example 3 was conducted except that 0.025 ml of Tantalum (V) ethoxide (99.98%) was added instead of the Titanium (IV) isopropoxide of Example 3.

Thus, the gate insulating film formed in accordance with Example 9 was named MP3-Ta.

Example 10

As an organic-inorganic composite solution of Example 1, except that 0.2 g of poly (melamine-co-formaldehyde) was added to 45 ml of 2-propanol, and 3.07 ml of Titanium (IV) isopropoxide (97%) was added. Was carried out in the same manner as in Example 1.

Comparative example

Comparative Example 1

The same procedure as in Example 1 was conducted except that no alkyl alkoxide of metal oxide was added.

Thus, the gate insulating film formed according to Comparative Example 1 was named MP1.

Comparative Example 2

The same process as in Example 2 was conducted except that no alkyl alkoxide of the metal oxide was added.

The gate insulating film formed according to Comparative Example 2 was named MP2.

Comparative Example 3

The same process as in Example 3 was conducted except that no alkyl alkoxide of metal oxide was added.

Thus, the gate insulating film formed according to Comparative Example 3 was named MP3.

Dielectric constant and leakage current measurement

A gold electrode was placed on the gate insulating film prepared according to Examples and Comparative Examples to measure the dielectric constant using an LCR meter, and the results are shown in FIGS. 1 to 4. In addition, the leakage current was measured and the results are shown in FIGS. 5 to 7.

1 to 3, the gate insulating films of the comparative examples in which the gate insulating films of the embodiments formed of the organic-inorganic composite solution in which the alkoxide of the inorganic oxide and the insulating organic polymer were dissolved simultaneously were formed of a solution in which only the insulating polymer was dissolved. The dielectric constant was higher in all frequency ranges than In addition, the gate insulating film of the embodiments exhibits good characteristics because there is little change in the dielectric constant value according to the frequency change.

4 is a diagram showing a dielectric constant of a gate insulating film according to the tenth embodiment. As shown in the figure, the dielectric constant of Example 10 was very high, since the alkoxide of the metal oxide was added relatively more than the insulating organic polymer when preparing the organic-inorganic composite solution.

On the other hand, as shown in Figures 5 to 7, it can be seen that the gate insulating films of the embodiments formed of an organic-inorganic composite solution in which the alkoxide of the inorganic oxide and the insulating organic polymer are dissolved simultaneously have good leakage current characteristics. Referring to the drawings, except for the MP3-Ti of FIG. 7, the gate insulating films of the embodiments formed of the organic-inorganic composite solution are compared to the gate insulating films of the comparative examples formed of a solution in which only an insulating polymer is dissolved in most electric field regions. On the contrary, the amount of leakage current generated was low, which is presumed to be due to the good mixing of the organic polymer and the alkoxide of the inorganic oxide in the gate insulating film.

Claims (6)

(S1) dissolving an alkyl alkoxide and an insulating organic polymer of a metal oxide having 1 to 20 carbon atoms of an alkyl group in an organic solvent to prepare an organic-inorganic composite solution for forming a gate insulating film;
(S2) coating the organic-inorganic composite solution on an organic thin film transistor substrate to form a coating layer; And
(S3) drying the organic solvent from the coating layer to form an organic-inorganic hybrid gate insulating film,
A method of forming an organic-inorganic hybrid gate insulating film of an organic thin film transistor. 2. The method of forming an organic-inorganic hybrid gate insulating film of an organic thin film transistor according to claim 1, wherein the alkyl group has 1 to 10 carbon atoms. The method of claim 1, wherein the alkyl alkoxide of the metal oxide is Aluminum ethoxide, Aluminum isopropoxide, Aluminum tributoxide, Aluminum sec-butoxide, Aluminum tert-butoxide, Aluminum tri-sec-butoxide, Tin (IV) tert-butoxide, Tributyltin ethoxide, Tin (IV) tert-butoxide, Hafnium (IV) n-butoxide, Hafnium (IV) tert-butoxide, Hafnium isopropoxide isopropanol adduct, Antimony (III) methoxide, Antimony (III) ethoxide, Antimony (III) propoxide, Antimony (III) ) butoxide, Tantalum (V) methoxide, Tantalum (V) ethoxide, Tantalum (V) butoxide, Titanium (IV) methoxide, Titanium (IV) ethoxide, Titanium (IV) propoxide, Titanium (IV) isopropoxide, Titanium (IV) butoxide , Titanium (IV) tert-butoxide, Zinc methoxide, Zirconium (IV) ethoxide, Zirconium (IV) propoxide, Zirconium (IV) butoxide, Zirconium (IV) tert-butoxide, Zirconium (IV) isopropoxide isopropanol complex, Thallium (I) ethoxide, Zirconium (IV) ethoxide, Vanadium (V) oxytriethoxide, Vanadium (V) oxytriisopropoxide, Indium (III) tert-butoxide, Yttrium (III) b Forming an organic-inorganic hybrid gate insulating film of an organic thin film transistor, characterized in that at least one selected from the group consisting of utoxide, Barium tert-butoxide, Lanthanum (III) isopropoxide, Scandium (III) isopropoxide and Niobium (V) ethoxide Way. The method of claim 1, wherein the metal component of the alkyl alkoxide of the metal oxide is at least one selected from the group consisting of titanium, tantalum and zirconium. The organic-inorganic hybrid type of organic thin film transistor according to claim 1, wherein the alkyl alkoxide and the insulating organic polymer of the metal oxide are added to the organic-inorganic composite solution in a weight ratio of 1: 100 to 100: 1. Method for forming a gate insulating film. An organic-inorganic hybrid gate insulating film of an organic thin film transistor formed according to any one of claims 1 to 5.

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