JP2009224737A - Insulating film formed of metal oxide mainly containing gallium oxide, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an insulating film formed of metal oxide mainly containing oxide gallium of good quality at low temperatures on a substrate with low heat resistance. <P>SOLUTION: A solution containing a gallium alkoxide compound is applied to the substrate 2 to form a film of the gallium alkoxide compound. Energy 3 necessary to dissolve an organic substance contained in the film is provided to the film, and the film is changed into a metal oxide film 4 mainly containing the gallium oxide. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an insulating film made of a metal oxide containing gallium oxide as a main component and a method for manufacturing the same, and more particularly to a method for forming an insulating film suitable for a flexible device.

  In recent years, various flexible devices have attracted a great deal of attention. Flexible devices have a wide range of applications, including the development of electronic paper and flexible circuit boards. The manufacturing method of these devices has been mainly vacuum deposition and photolithography, which are the same as those used on a glass substrate, but recently, a circuit is directly drawn on a substrate using a semiconductor material or a metal material. Studies using direct drawing (inkjet printing, screen printing, etc.) by a coating method are also actively conducted. When the coating method is used, it is not necessary to go through complicated processes such as photolithography and vacuum film formation, which are used in the conventional device process, so that the production cost can be greatly reduced. In the case of a flexible device, a plastic substrate having a lower heat resistance than that of an inorganic substrate such as a glass substrate is used, and all processes must be performed at a temperature lower than the heat resistant temperature of the substrate. The heat-resistant temperature of the plastic substrate is usually about 150 to 200 ° C. although it depends on the material. Even a relatively heat-resistant material such as polyimide has a heat-resistant temperature of about 300 ° C. at most.

  Currently, research on coating-type semiconductor materials has been actively conducted including organic semiconductor materials, but not much research has been conducted on insulating films. Therefore, development of a technique for producing a high-quality insulating film by a low temperature process is expected.

In addition, the most commonly used insulating film is a thermal oxide film of Si. Recently, a high-k material has been used to reduce the film thickness with the miniaturization of a large scale integrated circuit (LSI). In other words, research on materials having a high dielectric constant is being actively conducted. Examples include hafnium oxide (HfO ₂ ), zirconium oxide (ZrO ₂ ), yttrium oxide (Y ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), and the like. It is done. There are also reports on research on coating-type insulating films using high-k materials, but no examples of producing high-quality insulating films with coating-type Ga ₂ O ₃ have been reported so far.

Patent Document 1 discloses a transistor characterized in that a film including an organic or inorganic amorphous insulating film and high dielectric constant inorganic compound particles dispersed in the amorphous insulating film is used as the insulating film. Further, it is described that heat treatment at high temperature is not required by dispersing high dielectric constant inorganic compound particles.
JP 2002-110999 A

  Patent Document 1 describes that heat treatment at a high temperature is not required by dispersing high dielectric constant inorganic compound particles. Although it is possible to produce high-k materials with this method, it is usually difficult to make the particle size distribution uniform when high dielectric constant inorganic compound particles are dispersed. When used, there is a problem that variations in insulation characteristics occur between elements. For this reason, from the viewpoint of practicality, it is desired to produce a uniform insulating film having excellent insulating characteristics. Further, Patent Document 1 has no description about not using an insulating film or fine particles of gallium oxide.

  The present invention has been made in view of the above circumstances, and provides a method for manufacturing an insulating film that has a superior insulating property and is formed of a metal oxide containing gallium oxide as a main component on a substrate. It is intended to provide.

Another object of the present invention is to provide an insulating film obtained by using the above manufacturing method and a semiconductor device such as a TFT using the insulating film.

  The present invention is a method for producing an insulating film made of a metal oxide containing gallium oxide as a main component, the step of forming a film of the compound by applying a solution containing a gallium alkoxide compound to a substrate, The method includes a step of applying energy necessary for decomposing an organic substance contained in the film to the film to change the film into a metal oxide film containing gallium oxide as a main component.

  The insulating film containing gallium oxide as a main component of the present invention is manufactured by the manufacturing method of the present invention.

  In the present invention, the term “main component” of gallium oxide means that the content of gallium elements in all metal elements in the metal oxide film is 50 mol% or more. The content of the gallium element among all the metal elements is preferably 50 mol% or more, and preferably 57 mol% or more.

  The solution containing the gallium alkoxide compound may contain an organometallic compound other than the gallium alkoxide compound, and the organometallic compound is preferably a metal alkoxide compound.

  The substrate is not particularly limited as long as a coating method can be applied, and the shape is not limited to a sheet. The production method of the present invention can also be suitably applied when the substrate is a substrate having low heat resistance such as a resin substrate, and the substrate is more preferably a flexible substrate. It does not specifically limit as an application | coating method, What is necessary is just what forms a coating film using a solution.

  The energy is preferably thermal energy such as heating, light energy, or energy that promotes oxidation by radical oxygen generated by UV ozone treatment or oxygen plasma treatment. More preferably, it is ultraviolet light, and still more preferably, the ultraviolet light is a pulse laser.

  The insulating film of the present invention is manufactured by the manufacturing method of the present invention described above. In addition, the gate insulating film, the interlayer insulating film, and the protective film of the transistor of the present invention are provided with the insulating film of the present invention.

  The method for producing an insulating film containing gallium oxide as a main component of the present invention decomposes an organic substance in a film of the compound with respect to the coating film of the compound formed by coating a solution containing a gallium alkoxide compound on a substrate. By applying energy necessary for the sagging, it is changed into a metal oxide film containing gallium oxide as a main component. Therefore, an insulating film having good insulating characteristics can be obtained by a low temperature process. By using a solution containing a gallium alkoxide compound, it is not necessary to produce high dielectric constant inorganic compound particles as in Patent Document 1, so the number of steps can be reduced compared to Patent Document 1. In addition, it is possible to produce an insulating film having a more uniform insulating property than that in which high dielectric constant inorganic compound particles are dispersed in the film. Therefore, according to the method for manufacturing an insulating film of the present invention, a metal oxide film can be directly formed on a flexible resin substrate having low heat resistance by using a simple and low-cost coating method.

  In addition, a semiconductor device such as a thin film transistor (TFT) including an insulating film obtained by using the above manufacturing method can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the manufacturing method of this invention is demonstrated using FIG. 1A and FIG. 1B.

  In the method for producing an insulating film made of a metal oxide containing gallium oxide as a main component of the present invention, a film 1 of the compound is formed by applying a solution containing a gallium alkoxide compound to the substrate 2 (FIG. 1A). And applying energy 3 necessary for decomposing organic substances contained in the film 1 to the film 1 to change the film 1 into a metal oxide film 4 containing gallium oxide as a main component (FIG. 1B). It is characterized by including. The insulating film containing gallium oxide as a main component of the present invention is manufactured by the manufacturing method of the present invention.

  Components other than gallium oxide contained in the metal oxide film 4 are preferably metal compounds having an ion radius close to that of gallium ions, more preferably Zn, Al, Mg, and In compounds, and further Zn compounds, particularly zinc oxide (ZnO). Is preferred. When the metal oxide film 4 contains an oxide of a metal other than gallium, the gallium element content of all metal elements in the metal oxide film 4 is preferably 50 mol% or more, preferably 57 mol%. The above is good. The content of the gallium element in all the metal elements in the metal oxide film 4 can be measured by ICP (inductively coupled plasma) or XRF (fluorescence X-ray analysis). From this, since the said gallium alkoxide compound turns into gallium oxide by giving the said energy 3, content of a gallium oxide can be known by measuring content of the said gallium element.

  However, if the content of components other than gallium oxide is increased, a function as a semiconductor may appear even if the specific resistance value is high. Therefore, more preferably, the gallium oxide in the metal oxide film The higher the content, the better. Therefore, it is preferable that the metal oxide film contains gallium as a main component, that is, the gallium content in the metal oxide film is 50% or more.

By evaluating the insulating characteristics of the insulating film obtained by the manufacturing method of the present invention based on the specific resistance value, it is possible to evaluate the material-specific insulating properties that are not influenced by the film thickness. In general, when the resistivity is less than 10 ¹² Ω · cm, it does not function as a high-quality insulating film.

  The solution containing the gallium alkoxide compound of the present invention is a raw material containing at least a gallium alkoxide compound, such as metal alkoxide or composite metal alkoxide, metal acetate, and other carboxylates, nitrates, acetylacetonates, and chlorides. Is dissolved in a solvent such as glycols such as polyethylene glycol, β-diketones such as acetylacetone, alkanolamines such as ethanolamine, and the like.

  The solution containing the gallium alkoxide compound may contain an organometallic compound other than the gallium alkoxide compound, and preferably contains an organometallic compound such as zinc, aluminum, and magnesium. The solution containing the gallium alkoxide compound is preferably a solution obtained by dissolving a metal alkoxide compound in an organic solvent. This is because the metal alkoxide compound can be sublimated and purified, so that a highly pure compound can be obtained.

  When the metal alkoxide compound is gallium alkoxide, examples thereof include gallium trimethoxide, gallium triisopropoxide, and gallium triisobutoxide.

  The solution in which the metal alkoxide compound is dissolved in an organic solvent contains a suitable solvent for dissolving the metal alkoxide compound. Examples of the solvent include alcohols, amino alcohols, glycols and the like, and may contain a small amount of water.

  The metal oxide film 4 need not be crystalline and may be amorphous. Since the obtained metal insulator film may be in an amorphous state, a semiconductor device can be formed at a relatively low temperature. Therefore, not only an inorganic material but also an organic material can be used as a substrate when forming a semiconductor device. However, when changing from an organometallic compound to a metal oxide, the organic component must be decomposed. This is because if the organic substance remains, the organic substance becomes an impurity and adversely affects and it is difficult to obtain desired electrical characteristics.

  Whether or not the organic component is decomposed is determined by observing the FT-IR spectrum to confirm that the peaks such as C—H and C═O derived from the organic matter disappear, and other organic component detection methods. be able to.

  The energy 3 is preferably ultraviolet light of 400 nm or less from the viewpoint of effectively decomposing organic matter. In addition, when using a substrate with low heat resistance, it is necessary to absorb the film itself in order to suppress damage to the substrate and heat the film of the organometallic compound, so the band gap of the organometallic compound containing gallium oxide is required. More energy is required.

  Examples of the energy 3 include energy by laser irradiation. The laser can be used to focus on the coating film by irradiating the beam, so only the coating film can be heated with high energy, and the metal oxide film can be adjusted by adjusting the laser pulse width. This is because the densification and crystallization of can be caused only at a desired site. As a result, it can be applied even to a substrate that is generally not high in heat resistance, such as a plastic substrate.

 Since annealing by laser is a scanning heat treatment using heat rays with high energy, the crystallization efficiency is good, and the energy that reaches the substrate can be changed by changing the laser irradiation conditions such as scanning speed and laser power. Can be adjusted. Therefore, by determining the laser irradiation conditions according to the heat resistance of the substrate, the substrate temperature can be set to a temperature lower than the substrate heat resistance temperature, which is suitable for a substrate having low heat resistance such as a resin substrate. is there.

The intensity of the irradiation light of this laser irradiation is not particularly limited as long as the organometallic compound forms a metal oxide and the metal oxide thin film is dense enough to crystallize if necessary. It is preferably 150 to 400 mJ / cm ² (for example, when KrF is 248 nm, the pulse width is about 20 to 30 ns). Laser irradiation may be continuous or pulsed multiple times.

  Typical lasers include excimer lasers (XeCl, KrF, ArF, etc.), dye lasers, third harmonics of YAG lasers, and the like. Short-wavelength pulsed laser light such as excimer laser light absorbs a large amount of energy on the surface layer of the film, making it easy to control the energy that reaches the substrate. The pulsed laser is preferably used because it can be applied to a flexible substrate having low heat resistance. In addition to lasers, means for irradiating ultraviolet light include a low-pressure mercury lamp, a xenon flash lamp, and the like.

  When the substrate is heat resistant such as glass or quartz, it can be heated using an electric furnace or the like as an energy application means other than laser. When the decomposition temperature of the organic substance is higher than the heat resistance temperature of the substrate, it is also preferable to decompose the organic substance by performing an oxidation treatment using oxygen radicals or the like. Examples of the oxidation treatment using oxygen radicals include treatment of irradiating ultraviolet rays having a wavelength of 300 nm or less in the presence of oxygen or ozone, or treatment of irradiating oxygen plasma. Examples of ultraviolet rays having a wavelength of 300 nm or less include ultraviolet rays generated from a light source such as a mercury lamp or an excimer lamp.

  The substrate 2 is not particularly limited as long as a coating method can be applied, and the shape is not limited to a sheet shape, but a plate shape such as a film is preferable. More preferably, it is a resin substrate. More preferably, it is a flexible substrate.

  The present invention is particularly effective when a flexible resin substrate having low heat resistance is used. This is because the Si thermal oxide film, which is most commonly used as an insulating film, cannot be formed below the heat resistant temperature of the substrate. According to the method for manufacturing an insulating film of the present invention, a metal oxide film can be directly formed on a flexible resin substrate having low heat resistance at a temperature lower than the heat resistant temperature of the substrate using a simple and low-cost coating method. it can. As the resin substrate, a resin substrate such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI) is preferably used.

  The coating method is not particularly limited, and various coating methods such as spin coating, dip coating, extrusion coating, bar coating, screen printing method, and ink jet method can be mentioned. There is no.

  Although the film thickness of the insulating film of the present invention varies depending on the intended use, it cannot be said unconditionally. For example, when applied to a semiconductor device, it is preferably 50 to 1000 nm, more preferably 50 to 500 nm, and further 50 to 300 nm. Is preferred.

  Moreover, the insulating film manufactured with the manufacturing method of this invention can be used for semiconductor devices, such as TFT. Preferably, it is used as a gate insulating film, an interlayer insulating film, or a protective film of a transistor. Regarding a method for manufacturing a semiconductor device such as a TFT, it can be appropriately manufactured by a known method.

  As an example, a semiconductor device (TFT) using the metal oxide film 4 as a gate insulating film of a transistor and a manufacturing method thereof will be described with reference to FIG. In the present embodiment, a bottom gate type will be described as an example. FIG. 2 is a manufacturing process diagram of a TFT (cross-sectional view in the thickness direction of the substrate). In order to facilitate visual recognition, the scale of the constituent elements is appropriately changed from the actual one.

  The TFT 10 according to this embodiment includes an active layer 14 made of a semiconductor film, electrodes 12, 15, 16 and an insulating film 13 obtained by using a metal oxide film on a substrate 11.

First, as shown in FIG. 2A, a substrate 11 is prepared, and a gate electrode 12 made of n ⁺ Si, ITO or the like is formed. As the substrate 11, the same substrate as described in the method for manufacturing an insulating film of the present invention can be used.

  The film thickness as the gate insulating film varies depending on the desired electrical characteristics, but is generally preferably 50 to 1000 nm.

Next, as shown in FIG. 2B, a gate insulating film 13 made of a metal oxide film obtained by the manufacturing method of the present invention is formed. The metal oxide film can be manufactured by a coating method.
Next, as shown in FIG. 2B, the semiconductor film 14 is formed by the same coating method or the like. As the semiconductor film 14, a metal oxide semiconductor film having a semiconductor property including at least one metal element selected from the group consisting of In, Ga, Zn, Sn, and Ti, or a semiconductor composed of Si and / or Ge. A membrane is preferred.

  Next, as shown in FIG. 2C, the source region and the drain region of the semiconductor film 14 are formed to form an active layer of the TFT. For example, in the case of a silicon semiconductor film or the like, an active layer can be formed by doping a dopant such as P or B. A region between the source region and the drain region becomes a channel region.

  Finally, as shown in FIG. 2D, the source electrode 15 and the drain electrode 16 are formed on the active layer, and various wirings are similarly applied to obtain the semiconductor device (TFT) 10 of the present embodiment.

  The semiconductor device (TFT) 10 of this embodiment is manufactured through the above steps.

  The insulating film of the present invention can also be used as an interlayer insulating film. As an example of an interlayer insulating film using the insulating film of the present invention, as shown in FIG. 3, by forming a metal oxide film 30 on a wiring substrate on which a wiring pattern 32 is formed on a substrate 31, An interlayer insulating film for preventing leakage can be obtained.

  The insulating film of the present invention can also be used as a protective film. As an example of a protective film using the insulating film of the present invention, as shown in FIG. 4, a metal oxide film 20 is formed on a semiconductor device (TFT) 10 to form a protective film from moisture, the atmosphere, and the like. It can also be used. As another example, when used as a protective film for a wiring board as shown in FIG. 3, the metal oxide film 30 is formed of oxygen, moisture, etc. present in the outside air in the thin film element through a gas-permeable substrate. By being taken in, the device characteristics are prevented from being adversely affected.

  Examples of the method for manufacturing an insulating film according to the present invention and comparative examples will be described below.

Example 1
A solution (solution A) obtained by dissolving 10 mmol of gallium isopropoxide (Ga (OC ₃ H ₇ ) ₃ ) in 100 ml of diethylaminoethanol was spin-coated on a Si substrate twice at 1000 rpm, and then at room temperature. A film having a thickness of 100 nm was formed by drying for 1 hour. The obtained film was fired at 600 ° C. in an electric furnace.

(Evaluation)
The insulation characteristic specific to the substance was evaluated by evaluating the insulation characteristic based on the specific resistance value not affected by the film thickness. As a result of measuring the resistivity of the fired film (film A) by applying 1000 V by the double ring probe method, 2.18 × 10 ¹² Ω · cm was obtained.

(Example 2)
When adjusting the liquid A, instead of 10 mmol of gallium isopropoxide in Example 1, as shown in Table 1, gallium isopropoxide and zinc acetate dihydrate (Zn (CH ₃ COO) ₂ .2H ₂ Each solution having a different blending ratio of O) was dissolved in 100 ml of diethylaminoethanol to obtain each solution (solution B) according to the contents of zinc and gallium elements in the solution shown in Table 1. About each obtained solution, the 600 degreeC baking film (B film | membrane) was each produced similarly to Example 1 after that, and the specific resistance value was measured about each baking film | membrane (Table 1). The results are plotted in FIG.

(Evaluation)
FIG. 5 shows specific resistance values corresponding to the content of gallium elements among all the metal elements contained in the B film. When the content of gallium element among all metal elements in the B film is 57 mol% or more, the specific resistance value of the B film is generally 10 ¹² Ω · cm, which is a specific resistance value that functions as a high-quality insulating film. That was all.

(Example 3)
The same process as in Example 2 was performed until the thin film was formed by spin coating, and each film obtained was subjected to KrF excimer laser (248 nm, pulse width 20 to 30 ns, beam shape 100 mm × 0.4 mm) at 50 Hz, 150 to 400 mJ / cm ² was irradiated for 200 shots, and the specific resistance of the obtained film (C film) was measured (Table 2). The measurement results are shown in FIG.

(Evaluation)
FIG. 6 shows the specific resistance value corresponding to the content of gallium element among all the metal elements contained in the C film. When the content of gallium element in the total metal elements in the C film is 57 mol% or more, the specific resistance value of the C film is 10 ¹² Ω · cm, which is a specific resistance value that generally functions as a high-quality insulating film. That was all. In the case where the C film is formed with a laser in this manner, since heat treatment at a high temperature is not required, it can be applied to a substrate such as a resin substrate having low heat resistance.

Example 4
The process up to the production of the thin film by spin coating was performed in the same manner as in Example 1. The obtained film was cut into two, and one was fired at 600 ° C. and the other at 1000 ° C. in an electric furnace. For each fired film, RINT ULTIMA III (manufactured by RIGAKU) is used to measure the diffraction X-ray by changing the detection angle only by fixing the incident angle to around the critical angle (0.4 °). X-ray diffraction measurement was performed by (grazing inicidence techinique). The measurement results are shown in FIG. From this measurement result, it was found that the 600 ° C. fired film was amorphous, and the 1000 ° C. fired film was crystalline.

  In order to evaluate the characteristics of the insulating film, the dielectric strength characteristics of the 600 ° C. fired film and the 1000 ° C. fired film were measured. Specifically, a voltage was applied in the film thickness direction of the insulating film, and the voltage at which dielectric breakdown occurred was measured. As a result, it was found that the 600 ° C. fired film was 5 MV / cm, and the 1000 ° C. fired film was 7.5 MV / cm.

(Comparative Example 1)
A solution obtained by dissolving 10 mmol of TEOS (tetraethoxysilane) in 100 ml of diethylaminoethanol was spin-coated on a Si substrate twice at 1000 rpm, and then dried at room temperature to form a silicon oxide film (film) A thickness of 100 nm) was obtained. Thereafter, a fired film was produced under the same conditions as in Example 4, and the dielectric strength characteristics of the 600 ° C. fired film and the 1000 ° C. fired film were measured. The 600 ° C. fired film was 2.5 MV / cm and fired at 1000 ° C. The membrane was found to be 4 MV / cm.

(Evaluation)
From the comparison between Example 4 and Comparative Example 1, the gallium oxide insulating film obtained by the method in Example 4 is a silicon thermal oxide film that is generally used as an insulating film under the same conditions. Compared with, it was excellent in withstand voltage and high practicality.

The schematic diagram which shows the process of forming the film | membrane of a compound by apply | coating the solution containing a compound to a board | substrate in the manufacturing method of the insulating film of this invention In the manufacturing method of the insulating film of this invention, the schematic diagram which shows the process of giving energy required for decomposing | disassembling the organic substance contained in a film | membrane, and changing a film | membrane into the metal oxide film which has gallium oxide as a main component. 2A to 2D are schematic views showing steps of a method of manufacturing a semiconductor device (TFT) according to an embodiment of the present invention, and FIG. 2A is formed by forming a gate electrode on a substrate and forming a metal oxide film. The process of forming a gate insulating film is shown. Schematic diagram showing the process of forming a semiconductor film by a coating method, etc. Schematic diagram showing the process of forming the active layer of the TFT by forming the source and drain regions of the semiconductor film Schematic diagram showing a process of forming the source electrode and the drain electrode on the active layer and similarly providing various wirings to obtain the semiconductor device (TFT) of this embodiment. Sectional drawing of the interlayer insulation film of one Embodiment which concerns on this invention Sectional drawing of the protective film of one Embodiment which concerns on this invention The graph which shows the Ga content dependence of the specific resistance of the insulating film obtained by Example 2 of the manufacturing method of this invention The graph which shows the Ga content dependence of the specific resistance of the insulating film similarly obtained by Example 3 XRD pattern of gallium oxide 600 ° C fired film and 1000 ° C fired film

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gallium alkoxide compound film 2 Substrate 3 Energy 4 Metal oxide film mainly composed of gallium
10 Semiconductor device (TFT)
11 Board
12 Gate insulation film
13 Gate electrode
14 Semiconductor film
15 Source electrode
16 Drain electrode
20 Protective film
30 Interlayer insulation film
31 Board
32 Wiring pattern

Claims (7)

A method of manufacturing an insulating film made of a metal oxide containing gallium oxide as a main component,
Applying a solution containing a gallium alkoxide compound to a substrate to form a film of the compound;
Applying energy necessary for decomposing an organic substance contained in the compound film to the compound film, and changing the compound film to a metal oxide film containing gallium oxide as a main component. Insulating film manufacturing method   2. The method of manufacturing an insulating film according to claim 1, wherein the content of gallium element in all metal elements in the metal oxide film is 50 mol% or more.   3. The method of manufacturing an insulating film according to claim 1, wherein the energy is thermal energy.   3. The method of manufacturing an insulating film according to claim 1, wherein the energy is ultraviolet light.   5. The method of manufacturing an insulating film according to claim 4, wherein the ultraviolet light is a pulse laser.   6. The method of manufacturing an insulating film according to claim 1, wherein the substrate is a resin substrate.   An insulating film manufactured by the manufacturing method according to claim 1.

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