HK1170011B - Method for forming metal oxide film, metal oxide film and apparatus for forming metal oxide film - Google Patents

Description

Method for forming metal oxide film, and apparatus for forming metal oxide film

Technical Field

The present invention relates to a method for forming a metal oxide film, which forms a metal oxide film on a substrate, and an apparatus for forming a metal oxide film, which is capable of performing the method for forming a metal oxide film. Also disclosed is a metal oxide film formed by such a method for forming a metal oxide film.

Background

In the field of solar cells, light-emitting devices, touch panels, and the like, a metal oxide film is formed on a substrate. Patent documents 1, 2, and 3 are related to conventional non-vacuum film formation techniques for forming a metal oxide film on a substrate.

The technique of patent document 1 is to form a metal oxide film on a substrate by bringing a solution in which a metal salt or a metal complex is dissolved into contact with the heated substrate. Here, the solution contains at least one of an oxidizing agent and a reducing agent.

The technique of patent document 2 is to spray a tetrabutyltin or stannic chloride solution to which hydrogen peroxide is added as an oxidizing agent onto a preheated substrate to thermally decompose the substrate. Then, after the substrate temperature lowered by the spraying of the solution is restored, the spraying operation of the solution is repeated. Thus, the tin oxide film grows on the surface of the substrate.

The technique of patent document 3 is to intermittently spray a thin film material dissolved in a volatile solvent from above a substrate kept at a constant heat, thereby forming a transparent conductive film on the surface of the substrate. Here, the intermittent spraying is high-speed pulse intermittent spraying with 1 spraying time of less than one hundred milliseconds.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2006-160600

Patent document 2: japanese patent application laid-open No. 2002-146536

Patent document 3: japanese patent laid-open No. 2007-144297

Disclosure of Invention

Technical problem to be solved by the invention

Under the present circumstances, a film formation method capable of maintaining the low resistance of the formed metal oxide film and further improving the production efficiency has been desired.

Accordingly, an object of the present invention is to provide a metal oxide film forming method capable of maintaining a low resistance of a formed metal oxide film and further improving production efficiency, and a metal oxide film forming apparatus capable of performing the metal oxide film forming method. Also disclosed is a metal oxide film formed by such a method for forming a metal oxide film.

Technical scheme for solving technical problem

In order to achieve the above object, according to the present invention, a method for forming a metal oxide film and an apparatus for forming a metal oxide film atomize a solution containing a metal element and ethylenediamine. On the other hand, the substrate is heated. Then, the atomized solution is supplied onto the first main surface of the heated substrate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the method and the apparatus for forming a metal oxide film supply the solution containing the atomized metal element onto the first main surface of the substrate being heated. This solution also contains ethylenediamine.

Therefore, the metal oxide film formed can be kept low in resistance and the production efficiency of the metal oxide can be further improved.

The objects, features, forms and advantages of the present invention will become more apparent from the detailed description and the accompanying drawings.

Brief description of the drawings

Fig. 1 is a diagram showing a schematic configuration of a film deposition apparatus according to embodiment 1.

Fig. 2 is a diagram illustrating a method for producing a solution containing EDA (ethylenediamine) at a predetermined content.

Fig. 3 is a graph showing the relationship among the EDA content, carrier concentration, and mobility used in determining the EDA content in the solution 4.

Fig. 4 is a graph showing the relationship among the EDA content, carrier concentration, and mobility used in determining the EDA content in the solution 4.

Fig. 5 is a diagram illustrating an effect when the film formation method of embodiment 1 is employed.

Fig. 6 is a diagram illustrating an effect obtained when the film formation method of embodiment 1 is employed.

Fig. 7 is a diagram illustrating an effect obtained when the film formation method of embodiment 1 is employed.

Fig. 8 is a diagram illustrating an effect obtained when the film formation method of embodiment 1 is employed.

Fig. 9 is a diagram showing a schematic configuration of a film deposition apparatus according to embodiment 2.

Fig. 10 is a diagram illustrating an effect obtained when the film formation method of embodiment 2 is employed.

Modes for carrying out the invention

The present invention will be described in detail below with reference to the accompanying drawings showing embodiments thereof.

< embodiment 1>

Fig. 1 is a diagram showing a schematic configuration of a metal oxide film forming apparatus according to the present embodiment.

As shown in fig. 1, a film forming apparatus 100 for a metal oxide film according to embodiment 1 includes a reaction vessel 1, a heater 3, a solution container 5, and an atomizer 6.

The film forming apparatus 100 can perform a spray pyrolysis method, a high temperature sol method, an atomization deposition method, or the like. That is, the film forming apparatus 100 sprays the atomized predetermined solution onto the first main surface of the substrate 2, thereby forming a predetermined metal oxide film on the first main surface of the substrate 2.

In a state where the substrate 2 is placed on the heater 3, a metal oxide film is formed on the first main surface of the substrate 2 by a predetermined reaction in the reaction container 1. In a state where the substrate 2 is placed on the heater 3, the second main surface of the substrate 2 is brought into contact with the heater 3. As is clear from the above description, the first main surface of the substrate 2 described in the present specification means the main surface of the substrate 2 on the side where the metal oxide film is formed. In contrast, the second main surface of the substrate 2 described in the present specification refers to the main surface of the substrate 2 placed on the side of the heater 3.

Here, the metal oxide film may be formed on the substrate 2 under atmospheric pressure by making the inside of the reaction container 1 atmospheric pressure, or the metal oxide film may be formed on the substrate 2 under a reduced pressure atmosphere while reducing the inside of the reaction container 1 to a pressure in the range of 0.0001 to 0.1 MPa.

As the substrate 2, a glass substrate, a plastic substrate, a resin film, or the like used in the field of flat panel displays such as solar cells, light-emitting devices, touch panels, and liquid crystal panels can be used.

The heater 3 is a heater or the like, and can heat the substrate 2 placed on the heater 3. The heating temperature of the heater 3 is adjustable by an external control unit, and the heater 3 is heated to a metal oxide film formation temperature during a film formation process.

The solution container 5 is filled with a material solution (hereinafter referred to as "solution") 4, and a metal salt, a metal complex, or a metal alkoxide compound as a metal source is dissolved in the solution 4. The metal source contained in the solution 4 can be arbitrarily selected depending on the use of the metal oxide film to be formed. As the metal source, for example, titanium (Ti), zinc (Zn), indium (In), and tin (Sn), or at least any one of them can be used.

The solution 4 may not contain a dopant source described below. However, it is preferable that the solution 4 contains at least one metal element selected from boron (B), nitrogen (N), fluorine (F), magnesium (Mg), aluminum (Al), phosphorus (P), chlorine (Cl), gallium (Ga), arsenic (As), niobium (Nb), indium (In), and antimony (Sb) As a dopant source.

As the solvent of the solution 4, water, alcohol such as ethanol or methanol, or a mixed solution of these liquids, or the like can be used.

In the present application, the solution 4 further contains Ethylenediamine (hereinafter referred to as EDA).

As shown in fig. 2, the film forming apparatus 100 is further provided with a container 5a and a container 5 b. The container 5a contains an EDA liquid 4 a. On the other hand, the container 5b contains a solution 4b of the components of the solution 4 other than the EDA solution 4a, i.e., a solution (hereinafter referred to as source solution (ソ - ス solution)) composed of the metal source, the solvent, and/or the dopant source.

The film forming apparatus 100 is operated from the outside to produce the solution 4. This operation is an operation performed in order to adjust or determine the EDA content in the solution 4. When this operation is performed on a predetermined operation portion of the film forming apparatus 100, a predetermined amount of the EDA liquid 4a is output from the container 5a, and another predetermined amount of the source liquid 4b is output from the container 5 b. Thus, the EDA liquid 4a and the source liquid 4b, which are outputted respectively, are supplied to the solution container 5, and the solution 4 containing EDA in a content determined in the above-described manner is prepared in the solution container 5.

The atomizer 6 may employ, for example, an ultrasonic atomizing device. The atomizer 6 as the ultrasonic atomizing device atomizes the solution 4 in the solution container 5 by applying ultrasonic waves to the solution 4 in the solution container 5. The atomized solution 4 is supplied to the first main surface of the substrate 2 in the reaction container 1 through the passage L1.

When the mist-like solution 4 is supplied into the reaction container 1, the solution 4 reacts on the substrate 2 being heated, and a predetermined metal oxide film is formed on the first main surface of the substrate 2. The metal oxide film to be formed is different depending on the kind of the solution 4, and is, for example, a transparent conductive film such as indium oxide, zinc oxide, or tin oxide. Here, the unreacted solution 4 in the reaction vessel 1 is continuously (continuously) discharged to the outside of the reaction vessel 1 through the passage L3.

Next, a method for forming a metal oxide film according to the present embodiment will be described.

First, the EDA solution 4a and the source solution 4b are mixed to prepare a solution 4.

Specifically, the film forming apparatus 100 includes a predetermined operation unit, and the content of EDA in the solution 4 can be input and selected. For the operation portion, the user may perform an operation of inputting or selecting a desired value as the EDA content. Then, a first amount of EDA liquid 4a corresponding to the operation is output from the container 5 a. On the other hand, a second amount of the source liquid 4b corresponding to the operation is output from the container 5 b. Thus, the EDA liquid 4a and the source liquid 4b, which are outputted respectively, are supplied to the solution container 5, and the solution 4 is produced in the solution container 5. Here, the EDA content in the solution 4 is brought to a specific desired value by the operation of the operation portion.

Here, the inventors found that the EDA content in the solution 4, the carrier concentration of the formed metal oxide film, and the mobility of the formed metal oxide film have the relationships shown in fig. 3 and 4. Fig. 3 and 4 do not show data when the EDA content is 0.

The left vertical axis of fig. 3 and 4 shows the carrier concentration (cm) of the formed metal oxide film^-3). The vertical axis on the right side of FIGS. 3 and 4 represents the formed metal oxygenMobility (cm) of chemical film²V.s). In addition, the horizontal axis of fig. 3 represents the ratio (molar ratio) of the number of moles of EDA to the number of moles of zinc (Zn). In addition, the horizontal axis of fig. 4 represents the content (ml) of EDA in the solution 4. In addition, "square marks" in fig. 3 and 4 are data values indicating the relationship between the EDA content and the mobility. In addition, "triangular marks" in fig. 3 and 4 are data values indicating the relationship between the EDA content and the carrier concentration.

Here, as the "source liquid" 4b in FIGS. 3 and 4, a solution in which zinc acetoacetate is added to a mixed solution of 10ml of water and 90ml of methanol was used, and the molar concentration of zinc was 0.02 mol/L (liter).

As is clear from fig. 3, in the solution 4, as the content of EDA increases relative to the content of zinc as a metal source, the mobility of the metal oxide film formed changes as described below. That is, when the content of EDA is small relative to the content of zinc, the mobility sharply increases, and after the mobility passes through a peak, the mobility gradually decreases as the content of EDA increases relative to the content of zinc. As is clear from fig. 3, even if the EDA content in the solution 4 changes with respect to the content of zinc as the metal source, the carrier concentration of the metal oxide film formed hardly changes.

As can be seen from fig. 4, the following changes in mobility of the metal oxide film formed with an increase in the EDA content of the solution 4 occurred. That is, when the amount of EDA is small, the mobility is rapidly increased, and after the mobility passes through a peak, the mobility is gradually decreased as the amount of EDA increases. As is clear from fig. 4, even if the EDA content in the solution 4 changes, the carrier concentration of the metal oxide film formed hardly changes.

It is known that the resistivity of the formed metal oxide film is proportional to the carrier concentration × the reciprocal of the mobility.

Therefore, data on (EDA content-mobility-carrier concentration) as shown in fig. 3 and 4 is prepared in advance before the solution 4 is prepared. Then, the physical properties (e.g., transmittance) of the metal oxide film that change with the user and the changes in the resistivity, mobility, and carrier concentration of the metal oxide film to be formed are considered. Then, when the above-described operation of selecting or inputting the content of EDA is performed, the user determines the content of EDA in the solution 4 in accordance with the use of the metal oxide film to be formed, using the data on (EDA content-mobility-carrier concentration) prepared in advance, taking this into consideration.

Next, if the solution 4 is made in the solution container 5, the solution 4 can be atomized by the atomizer 6 in the solution container 5. The atomized solution 4 was supplied to the reaction vessel 1 through the passage L1.

On the other hand, the substrate 2 placed on the heater 3 is heated by the heater 3 to a metal oxide film forming temperature, and the temperature of the substrate 2 is maintained at the metal oxide film forming temperature. For example, the temperature of the substrate 2 is maintained at about 300 ℃.

The solution 4 is supplied in a mist form to the first main surface of the substrate 2 in the heated state. Thereby, a predetermined metal oxide film is formed on the first main surface of the substrate 2 stored in the reaction chamber 1.

Here, the film forming step may be a step of supplying the solution 4 to the substrate 2 placed at atmospheric pressure to form a metal oxide film on the substrate 2. In contrast, the following steps may be performed: the film forming apparatus 100 further includes a vacuum pump (not shown) capable of reducing the pressure inside the reaction container 1, and supplies the solution 4 to the substrate 2 placed in a reduced pressure (for example, 0.0001 to 0.1MPa) environment to form a metal oxide film on the substrate 2.

As described above, in the method for forming a metal oxide film according to the present embodiment, the solution 4 containing EDA in addition to the metal element is atomized. Then, the mist-like solution 4 is brought into contact with the substrate 2 being heated in the reaction container 1.

Therefore, the metal oxide film formed can be kept low in resistance and the production efficiency of the metal oxide can be further improved. Fig. 5 and 6 are graphs showing experimental data for explaining the effect.

Fig. 5 shows the results of measuring the film thickness of the metal oxide film formed by changing the ratio of the number of moles of EDA contained in the solution 4 to the number of moles of zinc. The vertical axis of fig. 5 represents the film thickness (nm) of the formed metal oxide, and the horizontal axis of fig. 5 represents the molar ratio of EDA/zinc (Zn).

Fig. 6 shows the results of measuring the thickness of the formed metal oxide film when the amount of the EDA solution 4a in the solution 4 was changed. In addition, the vertical axis of fig. 6 represents the film thickness (nm) of the formed metal oxide, and the horizontal axis of fig. 6 represents the content (ml) of the EDA solution 4a in the solution 4.

Here, in fig. 5 and 6, only the content of EDA in the solution 4 was changed, and the contents of other components in the solution 4 were the same. The conditions for forming the metal oxide film (such as the heating temperature (300 ℃) of the substrate 2, the atmospheric pressure (atmospheric pressure) in the reaction vessel 1, and the film formation reaction time (30 minutes)) in each data of fig. 5 and 6 are the same among the data.

As the source liquid 4b in fig. 5 and 6, a solution in which zinc acetoacetate is added to a mixed solution of water and methanol 9 times the amount of water was used, and the molar concentration of zinc solution was 0.02 mol/L (liter).

As is clear from the results of fig. 5 and 6, when EDA is contained in the solution 4, the film formation rate of the metal oxide film is increased. For example, in the examples of fig. 5 and 6, the film formation rate was increased by about 3 times at the highest by including EDA as compared with the case of not including EDA. This effect of increasing the film formation rate was also confirmed when the film formation conditions and the components other than EDA in the solution 4 were changed.

By increasing the film formation rate, a metal oxide film having a predetermined film thickness can be formed in a short time. Therefore, the increase in the film formation rate means that the production efficiency of the metal oxide film is improved by containing EDA in the solution 4.

In the case of fig. 5, when the molar ratio of EDA to zinc is "1" or more, the film formation rate of the metal oxide film is significantly improved. In the case of fig. 6, when the content of the EDA liquid 4a in the solution 4 is "0.13 (ml)" or more, the film formation rate of the metal oxide film is significantly improved.

As is clear from the experimental data shown in fig. 7 and 8, even when an appropriate amount of EDA is contained in the solution 4, the sheet resistance of the metal oxide film formed can be maintained at a low resistance value.

Here, fig. 7 shows the measurement results of the resistivity and sheet resistance of the metal oxide film formed when the ratio of the number of moles of EDA to the number of moles of zinc contained in the solution 4 was changed. The left vertical axis of fig. 7 represents the resistivity (Ω · cm) of the formed metal oxide, and the right vertical axis of fig. 7 represents the sheet resistance (Ω/sq.) of the formed metal oxide film. In addition, the horizontal axis of fig. 7 represents the mole ratio represented by the mole of EDA/the mole of zinc (Zn).

Fig. 8 shows the results of measuring the resistivity and sheet resistance of the metal oxide film formed when the amount of the EDA solution 4a in the solution 4 was changed. The left vertical axis of fig. 8 represents the resistivity (Ω · cm) of the formed metal oxide, and the right vertical axis of fig. 8 represents the sheet resistance (Ω/sq.) of the formed metal oxide film. In addition, the horizontal axis of fig. 8 represents the content (ml) of the EDA solution 4a in the solution 4.

Here, in fig. 7 and 8, the content of EDA in the solution 4 is changed only, and the contents of other components in the solution 4 are the same. The conditions for forming the metal oxide film (such as the heating temperature (300 ℃) of the substrate 2, the atmospheric pressure (atmospheric pressure) in the reaction vessel 1, and the film formation reaction time (30 minutes)) in each data of fig. 7 and 8 are the same among the data.

As the source liquid 4b in fig. 7 and 8, a solution in which zinc acetoacetate is added to a mixed solution of water and methanol 9 times the amount of water was used, and the molar concentration of zinc was 0.02 mol/L (liter).

As is clear from the results of fig. 7 and 8, the sheet resistance and the resistivity of the metal oxide film formed when the solution 4 contains an appropriate amount of EDA are lower than those of the metal oxide film containing no EDA. As shown in fig. 7 and 8, when a metal oxide film is formed using the solution 4 containing a large amount of EDA, the sheet resistance and the resistivity of the formed metal oxide film increase. Therefore, from the viewpoint of reducing the sheet resistance and resistivity of the formed metal oxide film, it should be noted that the content of EDA in the solution 4 cannot be large. The effects of the decrease in sheet resistance and resistivity caused by the incorporation of EDA in the solution 4 were also confirmed when the film formation conditions and the components other than EDA in the solution 4 were changed.

Here, in general, when the amount of the metal source as a solute in the solution containing no EDA is increased, the film formation rate of the metal oxide film can be increased. However, when the method of increasing the content of the metal source is adopted, the resistivity and sheet resistance of the formed metal oxide film become worse.

In contrast, in the present embodiment, by including EDA in the solution 4, as described with reference to fig. 5 to 8, the film formation rate of the metal oxide film can be increased while maintaining the low resistance of the metal oxide film to be formed.

In the case of fig. 7, when the molar ratio of EDA to zinc is in the range of "0.5 to 5", the sheet resistance and the resistivity of the metal oxide film are lowered. In the case of fig. 8, when the content of the EDA solution 4a in the solution 4 is in the range of "0.067 to 0.67 (ml)", the sheet resistance and the resistivity of the metal oxide film are lowered.

In the present embodiment, the data on (EDA content-mobility-carrier concentration) shown in fig. 3 and 4 are prepared in advance, and the EDA content in the solution 4 is determined using the data.

Therefore, depending on the use of the metal oxide film to be formed, a metal oxide film having appropriate physical property values can be provided.

For example, if the carrier concentration and mobility are increased, the resistivity of the formed metal oxide film is increased (or decreased). On the other hand, if the carrier concentration is increased, the transmittance of the formed metal oxide film is lowered, particularly in the infrared region. On the other hand, in the case of a transparent conductive film used as a solar cell for generating electricity by absorbing visible light and infrared light, for example, a CIGS (Copper Indium Gallium DiSelenide) type solar cell, low resistance and high transmittance including an infrared region are required. In forming the transparent conductive film of the solar cell, data (EDA content-mobility-carrier concentration) on the transparent conductive film is prepared in advance, and the content of EDA in the solution 4 may be determined by using the data so as to reduce the carrier concentration and the resistance value.

As described in the present embodiment, the carrier concentration and the mobility of the metal oxide film to be formed can be adjusted by adjusting the content of EDA in the solution 4, and as a result, a metal oxide film having physical property values according to the use application can be provided.

Further, at least any one of titanium, zinc, indium, and tin may be used as the metal source contained in the solution 4. When these metal sources are used, a transparent conductive film can be formed on the substrate 2.

In a state where the solution 4 contains titanium, zinc, indium, and tin, the solution 4 may contain at least one of boron, nitrogen, fluorine, magnesium, aluminum, phosphorus, chlorine, gallium, arsenic, niobium, indium, and antimony as a dopant.

Depending on the kind of the dopant, the metal oxide film (transparent conductive film) which is an N-type semiconductor can be made to have a more electron-excess state. In this case, the resistance of the formed metal oxide film (transparent conductive film) can be further reduced. Further, depending on the kind of the dopant, the metal oxide film can be made to be a P-type semiconductor. In the metal oxide film of the P-type semiconductor, holes are carriers, and the metal oxide film can be made conductive, and its utility value as a light-emitting device is higher than that as a transparent conductive film.

As described above, the inside of the reaction container 1 may be brought to atmospheric pressure, and the metal oxide film may be formed on the substrate 2 under the atmospheric pressure. This makes it possible to omit a vacuum apparatus or the like, thereby reducing the cost of the film deposition apparatus 100.

On the other hand, as described above, a vacuum pump or the like capable of reducing the pressure inside the reaction vessel 1 may be included. Further, the inside of the reaction container 1 may be depressurized to a range of 0.0001 to 0.1MPa, and a metal oxide film may be formed on the substrate 2 in the depressurized atmosphere. Thus, although the cost of the film forming apparatus 100 increases, a metal oxide film having a higher quality can be formed on the substrate 2 than a metal oxide film formed under atmospheric pressure.

In addition, when ammonia is contained in the solution 4, the effect of maintaining the low resistance of the metal oxide film and increasing the film rate can be achieved. However, in order to achieve this effect, the solution 4 must contain a large amount of ammonia. In contrast, in the present invention, the solution 4 only needs to contain a small amount of EDA (1/10 or less of the ammonia content), and the above-described effect "of maintaining the low resistance of the metal oxide film and increasing the film formation rate" (the effect is comparable to that in the case of containing ammonia) "can be obtained.

On the other hand, in the case of the solution 4 containing ammonia without EDA or 1, 3-propanediamine (TMDA) which is the same amine compound as EDA, the above-mentioned effects could not be obtained. That is, even if TMDA was contained in solution 4, the film formation rate was not improved. Further, when TMDA is contained in the solution 4, the resistivity of the metal oxide film to be formed increases, and the sheet resistance of the metal oxide film also increases significantly.

< embodiment 2>

Fig. 9 is a diagram showing a schematic configuration of a metal oxide film forming apparatus according to the present embodiment.

As is clear from a comparison between fig. 1 and 9, the metal oxide film forming apparatus 200 according to the present embodiment is configured by adding the ozone generator 7 to the metal oxide film forming apparatus 100 according to embodiment 1. In the film formation apparatus 200, a passage L2 is provided for supplying ozone from the ozone generator 7 to the reaction container 1.

The film formation apparatus 100 and the film formation apparatus 200 are the same as each other for other configurations except that the ozone generator 7 and the passage L2 are added. Therefore, embodiment 1 can be referred to for matters other than the matters related to the ozone generator and the passage L2.

The ozone generator 7 can generate ozone. The ozone generated by the ozone generator 7 is supplied to the first main surface of the substrate 2 in the reaction container 1 through a passage L2 different from the passage L1. In the ozone generator 7, ozone can be generated by applying a high voltage between parallel electrodes arranged in parallel, for example, and introducing oxygen between the electrodes to decompose oxygen molecules and bind to other oxygen molecules.

When ozone and the mist-like solution 4 are supplied into the reaction container 1, the ozone and the solution 4 react with each other on the substrate 2 being heated, and a predetermined metal oxide film is formed on the first main surface of the substrate 2. The metal oxide film to be formed is different depending on the kind of the solution 4, and is, for example, a transparent conductive film such as indium oxide, zinc oxide, or tin oxide. Here, the unreacted ozone and the solution 4 in the reaction vessel 1 are continuously (continuously) discharged to the outside of the reaction vessel 1 through the passage L3.

Next, a method for forming a metal oxide film according to the present embodiment will be described.

First, the EDA content in the solution 4 was determined as described in embodiment 1 (see fig. 2, 3, and 4). Then, a solution 4 containing the EDA at the determined content was prepared in a solution container 5.

Next, if the solution 4 is made in the solution container 5, the solution 4 can be atomized by the atomizer 6 in the solution container 5. The atomized solution 4 was supplied to the reaction vessel 1 through the passage L1. Further, ozone is generated by the ozone generator 7. The generated ozone is supplied to the reaction container 1 through the passage L2.

On the other hand, the substrate 2 placed on the heater 3 is heated by the heater 3 to a metal oxide film forming temperature, and the temperature of the substrate 2 is maintained at the metal oxide film forming temperature. For example, the temperature of the substrate 2 is maintained below 220 ℃.

Ozone and the mist-like solution 4 are supplied to the first main surface of the substrate 2 in the heated state. When the substrate 2 in a heated state is brought into contact with ozone and the mist-like solution 4, the ozone is thermally decomposed to generate oxygen radicals, and the decomposition of the solution 4 is promoted by the oxygen radicals, thereby forming a predetermined metal oxide film on the first main surface of the substrate 2.

Here, the film forming step may be a step of supplying the solution 4 and ozone to the substrate 2 disposed at atmospheric pressure to form a metal oxide film on the substrate 2. In contrast, the following steps may be performed: the film forming apparatus 200 further includes a vacuum pump (not shown) capable of reducing the pressure inside the reaction container 1, and supplies the solution 4 and ozone to the substrate 2 placed in a reduced pressure (for example, 0.0001 to 0.1MPa) environment to form a metal oxide film on the substrate 2.

As described above, in the method for forming a metal oxide film according to the present embodiment, the solution 4 containing the metal source and EDA is atomized. Then, the mist-like solution 4 is brought into contact with the substrate 2 being heated in the reaction container 1 in the atmosphere containing ozone.

Therefore, ozone and active oxygen generated by decomposition of ozone by heat or the like have high reactivity, and thus decomposition and oxidation of the material compound in the solution 4 are promoted. Thereby, a metal oxide film can be formed on the substrate 2 even in a low-temperature heating state. Ozone is decomposed from about room temperature, and the decomposition rate increases as the heating temperature of the substrate 2 increases, and when the heating temperature of the substrate 2 reaches about 200 ℃, the self-decomposition rate is several seconds. Therefore, even when the substrate 2 is heated at a low temperature of about room temperature to 200 ℃, the metal oxide film can be formed on the substrate 2.

In addition, by adopting the film formation method of the present embodiment, the sheet resistance of the metal oxide film to be formed can be made lower in a low temperature range (for example, 220 ℃ or lower) of the heating temperature of the substrate 2, as compared with embodiment 1. Fig. 10 is experimental data showing the effect of the invention of the present embodiment.

The vertical axis of fig. 10 represents the sheet resistance (Ω/sq.) of the formed metal oxide film, and the horizontal axis of fig. 10 represents the heating temperature (c) of the substrate 2. In fig. 10, the data of the "∘" mark represents the relationship between the heating temperature of the substrate 2 and the sheet resistance of the metal oxide film formed when the EDA-containing solution 4 (no ozone) was supplied to the substrate 2 in the reaction vessel 1, i.e. in the case of embodiment 1. The data of "Δ mark" indicates the relationship between the heating temperature of the substrate 2 and the sheet resistance of the metal oxide film formed when the EDA-containing solution 4 and ozone are supplied to the substrate 2 in the reaction chamber 1, that is, in the case of embodiment 2. The data of "□ mark" indicates the relationship between the heating temperature of the substrate 2 and the sheet resistance of the metal oxide film formed when the EDA-free solution 4 and ozone are supplied to the substrate 2 in the reaction chamber 1.

As shown in fig. 10, when the substrate 2 is heated at a low temperature of at least 220 to 200 ℃ and the metal oxide film is formed on the substrate 2, the sheet resistance of the metal oxide film formed in embodiment 2 is lower than that of the metal oxide film formed in embodiment 1. In addition, although not shown in fig. 10, when the heating temperature of the substrate 2 is 200 ℃.

That is, when the solution 4 is supplied to the substrate 2 and ozone is also supplied, the sheet resistance of the metal oxide film formed can be increased even when a lower temperature is adopted for heating the substrate 2 than in the case where ozone is not supplied to the substrate 2. In particular, when the heating temperature of the substrate 2 is 220 ℃ or lower, the sheet resistance of the metal oxide film produced by the method of embodiment 2 is improved by about two orders of magnitude as compared with the sheet resistance of the metal oxide film produced by the method of embodiment 1.

As is clear from the structure of fig. 9, the solution 4 and the ozone are supplied to the substrate 2 through different passages L1 and L2. In the configuration of fig. 9, the solution 4 is supplied to the substrate 2 in the reaction container 1 through the passage L1. On the other hand, ozone is supplied to the substrate 2 in the reaction container 1 through the passage L2.

Thus, by supplying the solution 4 and the ozone to the substrate 2 through the different passages L1 and L2, the position where the ozone and the solution 4 are mixed with each other can be limited to the reaction container 1 (the arrangement region of the substrate 2). That is, the solution 4 and ozone can be prevented from being mixed with each other in the passage of the supply process. Therefore, the reaction between the solution 4 and ozone can be performed only in the arrangement region of the substrate 2, and the reaction efficiency on the substrate 2 can be improved.

Further, since the solution 4 and ozone are mixed with each other in the process of supplying the solution, the solution 4 and ozone may react before reaching the substrate to generate an unnecessary reaction product in the gas phase. The generation of the unnecessary reaction product may inhibit film growth on the surface of the substrate 2 (a decrease in film quality and a decrease in film formation rate due to deposition of the unnecessary reaction product). Therefore, by supplying the solution 4 and ozone to the substrate 2 through the different passages L1 and L2, the generation of the unnecessary reaction product can be suppressed.

The film deposition apparatus 200 may further include a control unit (not shown) for performing the following control. The control unit performs the following control: the atomized solution 4 and ozone are supplied to the substrate 2 in the reaction container 1 at the same time or at a predetermined timing.

By supplying the atomized solution 4 and ozone to the substrate 2 in the reaction container 1 at the same time, the reactivity (oxidizing ability) of ozone in the reaction container 1 can be sufficiently utilized. On the other hand, by supplying the atomized solution 4 and ozone to the substrate 2 in the reaction container 1 at different timings, respectively, the reaction of ozone and the solution 4 at a position other than the surface of the substrate 2 can be suppressed.

Further, by supplying the atomized solution 4 and ozone to the substrate 2 in the reaction container 1 at different timings, the reactivity (oxidizing ability) of ozone in the reaction container 1 cannot be fully utilized. However, by supplying ozone while heating the substrate 2, the characteristics of the metal oxide film to be formed (for example, improvement in crystallinity, improvement in resistance according to the mobility and the carrier concentration, and the like) can be improved.

In embodiments 1 and 2, only one solution container 5 is provided, but a plurality of solution containers may be provided to fill different types of solutions. In this configuration, an atomizer is disposed for each solution container, and a passage serving as a solution passage is disposed between each solution container and the reaction container 1. In this case, the solutions may be supplied simultaneously or may be supplied separately at different times in a predetermined order.

In embodiment 2 including the plurality of solution containers, different solutions may be supplied in a predetermined order while continuously supplying ozone. Further, the solutions and ozone may be supplied separately at different times. In either supply method, it is preferable that the solutions and ozone are supplied to the substrates 2 in the reaction container 1 through different passages.

In embodiment 2, an ultraviolet generator for irradiating ozone supplied to the substrate 2 with ultraviolet rays (having a wavelength of about 10nm to 400 nm) may be additionally provided. In the case of this structure, ozone is decomposed into oxygen radicals by the ultraviolet light irradiation, and the reaction for forming the metal oxide film in the reaction container 1 (more specifically, on the first main surface of the substrate 2) is promoted. Further, since ozone supplied to the reaction container 1 is decomposed into oxygen radicals by the irradiation of ultraviolet rays, the heater 3 for heating the substrate 2 may be omitted. In addition, from the viewpoint of promoting the reaction, it is preferable that the substrate 2 is also heated in the case of a structure in which ultraviolet rays are irradiated. In the case of the ultraviolet irradiation structure, oxygen may be used instead of ozone.

In embodiment 2, a plasma generator for plasmatizing ozone supplied to the substrate 2 may be additionally provided. In the case of this structure, ozone is decomposed into oxygen radicals by plasma, and a reaction for forming a metal oxide film in the reaction container 1 (more specifically, on the first main surface of the substrate 2) can be promoted. Further, since ozone supplied to the reaction container 1 is decomposed into oxygen radicals by plasma, the heater 3 for heating the substrate 2 may be omitted. In addition, from the viewpoint of promoting the reaction, it is preferable that the substrate 2 is also heated when the plasma generator is provided. In the case of the structure in which the plasma generator is provided, oxygen may be used instead of ozone.

When comparing the metal oxide film produced by the film formation method according to embodiments 1 and 2 (referred to as the "former film") with the metal oxide film produced by the film formation method not containing EDA in the solution 4 (referred to as the "latter film"), the amount of nitrogen atoms contained in the former film is increased as compared with the amount of nitrogen atoms contained in the latter film. The increase in the amount of nitrogen atoms is caused by the use of the solution 4 containing EDA having nitrogen as a constituent in the film forming method of the present invention.

Although the present invention has been described in detail, all of the forms described above are exemplary, and the present invention is not limited thereto. Innumerable modifications that are not illustrated can be interpreted as examples that can be conceived without departing from the scope of the invention.

Description of the symbols

1 reaction vessel

2 base plate

3 heating device

4 solution

4a EDA solution

4b Source liquid

5 solution container

5a, 5b container

6 atomizer

7 ozone generator

L1, L2, L3 pathway

100. 200 film forming apparatus

Claims (9)

1. A method for forming a metal oxide film, comprising:

(A) atomizing a solution (4) containing a metal element and ethylenediamine (4 a);

(B) a step of heating the substrate (2);

(C) supplying the solution atomized in the step (a) onto the first main surface of the substrate in the step (B);

(D) preparing data indicating a relationship among a content of the ethylenediamine in the solution, a carrier concentration of the metal oxide film to be formed, and a mobility of the metal oxide film to be formed, in advance before the step (a); and

(E) and (D) determining the content of ethylenediamine in the solution using the data in the step (D), and producing the solution containing the determined content of ethylenediamine.

2. The method of forming a metal oxide film according to claim 1, wherein the metal element is at least one of titanium, zinc, indium, and tin.

3. The method of forming a metal oxide film according to claim 1, wherein the step (C) is a step of supplying the solution atomized in the step (A) and ozone onto the first main surface of the substrate in the step (B).

4. A metal oxide film produced by the method for forming a metal oxide film according to claim 1.

5. A metal oxide film produced by the method for forming a metal oxide film according to claim 2.

6. A metal oxide film produced by the method for forming a metal oxide film according to claim 3.

7. A metal oxide film forming apparatus capable of performing the method of claim 1.

8. A metal oxide film forming apparatus capable of performing the method of claim 2.

9. A metal oxide film forming apparatus capable of performing the method of claim 3.