JP5492479B2 - Method for producing transparent conductive film - Google Patents

Description

The present invention relates to a method for producing a transparent conductive film, in particular, low resistivity in the case where the film thickness is thin, and a method for producing a transparent conductive film has high light transmittance.

  In the field of electronic display devices such as mobile phones (PDA, Personal Digital Assistant), game machines, car navigation systems, personal computers, ticket vending machines, bank terminals, etc., display devices and sensor electrodes are A transparent conductive film formed of an oxide obtained by adding other elements to indium (In), zinc (Zn), tin (Sn), or the like, or a metal film formed of copper or an alloy thereof is used. . In particular, since the transparent conductive film is a constituent element of a touch panel installed in a display device of an electronic display device, its demand is increasing.

  Among transparent conductive films, a transparent conductive film made of an oxide of indium (In) -tin (Sn) (ITO, Indium Tin Oxide) has a relatively low resistance, a high light transmittance in the visible region, and Since it is easy to etch, it is used in many electronic display devices.

And in the above-mentioned electronic display device field | area, the improvement of the electrical property of a transparent conductive film is calculated | required especially. In other words, as the liquid crystal panel used in the display device becomes higher in definition, it is necessary to reduce the resistance of the transparent conductive film in response to the reduction in the pixel pitch. Specifically, the resistivity is 1 A transparent conductive film of about × 10 ⁻⁴ to 1 × 10 ⁻⁵ Ωcm is required.

Patent Document 1, by Roman cathode type ion plating, (222) and the peak intensity _{I 1} of the plane, in the range ratio _I 1 / _{I 2} of from 6 to 100 of the peak intensity _{I 2} of the (400) plane, The resistivity is in the range of 0.8 × 10 ^{−4 to} 3.5 × 10 ⁻⁴ Ωcm, the mobility is in the range of 30 to 50 cm ² / Vsec, and the transmittance of light with a wavelength of 550 nm is 80 to 100%. An ITO film that is in the range is disclosed.

Further, in Patent Document 2, the target surface parallel magnetic field strength on the cathode is maintained at 6000 e or more, a direct current electric field and a high frequency electric field are superimposed and applied to the target, and sputtering is performed at a sputtering voltage of 250 V or less. A technique for manufacturing a conductive film has been proposed, and an ITO film having a resistivity of 1.25 × 10 ^{−4 to} 1.9 × 10 ⁻⁴ Ωcm is obtained by this technique.

Japanese Patent No. 3831433 Japanese Patent No. 2936276

  On the other hand, in a transparent conductive film such as an ITO film, it is also an important factor to reduce the film thickness, that is, to reduce the film thickness at the same time as reducing resistance. However, in the thin film field including a transparent conductive film, there is a problem that the thinner the thin film, the higher the resistance value and the lower the durability to heat, humidity, and chemicals. In general, film formation is a process in which molecules of a thin film material are stacked on a substrate, but it is difficult to form a crystal lattice unique to the material from the initial stage of film formation due to mismatching of the lattice spacing with the substrate or the like. Therefore, it can be said that it is a basic problem of thin film deposition in which a certain crystal structure is exhibited and conductivity is increased after a certain amount of molecular layers are stacked, that is, after the film thickness is increased. In particular, the transparent conductive film has a greater dependence of the conductivity on the film thickness than the metal thin film, and the resistance value becomes extremely large when the film thickness is small. Therefore, the transparent conductive film is used in such a film thickness that the film thickness can be increased to at least several tens of nanometers and stable physical properties can be maintained.

  Further, among the transparent conductive films, particularly the ITO thin film has a problem in that the optical properties thereof are large in light absorption in a wavelength region of 400 nm or less, and accordingly, a light brown transmission color is exhibited, so that the transparency is lowered. There is a point. In addition to light absorption, there is also a problem that coloring (interference color) occurs due to light interference. Since these coloration and coloring become more significant as the film thickness increases, the transmittance decreases and the transparency is further impaired.

  That is, when the transparent conductive film has a thickness of about several tens of nanometers or more, the resistance value decreases and stabilizes. However, as the film thickness increases, light absorption in the thin film decreases. It becomes larger and the transmittance decreases. On the other hand, the thinner the film thickness, the smaller the light absorption and the better the transmittance, but the resistance value increases, and the resistance value does not become stable and constant. Therefore, when the film thickness of a transparent conductive film is thin, there exists a problem that the use is limited.

In this regard, in Patent Document 1, the resistivity is in the range of 0.8 × 10 ^{−4 to} 3.5 × 10 ⁻⁴ Ωcm, and the transmittance of light having a wavelength of 550 nm is in the range of 80 to 100%. Although a film is disclosed, the film thickness is about 150 nm, and the electrical and optical characteristics of an ITO film with a film thickness smaller than 150 nm (particularly, an ITO film with a film thickness of 20 nm or less) are not shown. . Patent Document 2 discloses an ITO film having a resistivity of 1.25 × 10 ^{−4 to} 1.9 × 10 ⁻⁴ Ωcm, but does not describe its film thickness and optical characteristics. .

An object of the present invention is to provide a method for producing a transparent conductive film that maintains a low resistivity and a high transmittance even when the film thickness is thin, and to provide a production method with high reproducibility.

The subject is a method of forming a transparent conductive film comprising an indium tin oxide (ITO) film provided on a substrate according to the method for producing a transparent conductive film of the present invention, wherein the substrate is formed of indium tin oxide. It is installed in a sputtering apparatus having an (ITO) target, the flow rate of oxygen contained in the carrier gas is in the range of 0.1 to 1.0%, the substrate temperature is in the range of 230 to 250 ° C., the surface of the target The magnetic field is in the range of 600 to 800 G, the RF power with the DC power ratio in the range of 0.5 to 2.0 is superimposed on the DC power source, and sputtering is performed, so that the film thickness is 8 to The problem is solved by forming a transparent conductive film having a range of 20 nm and a resistivity of 1.5 × 10 ⁻⁴ Ωcm or less.

At this time, a transparent conductive film having a low resistivity can be obtained using a normal sputtering apparatus. In addition, by setting the surface magnetic field of the target, the composition ratio of the carrier gas, and the power during sputtering within the above ranges, a transparent conductive film with low reproducibility can be obtained.
Moreover, since the film thickness is thin, there is little influence of interference color, and a highly transparent transparent conductive film can be obtained. Furthermore, since the obtained transparent conductive film has a low resistivity, it is possible to obtain a transparent conductive film having high transparency and low resistivity.
Moreover, when the film thickness of the transparent conductive film is in the range of 8 to 20 nm and the film thickness is thin, there is no influence that the transparency is lowered by the interference color. Further, even when the film thickness is thin, the resistivity of its low, specifically at 1.5 × 10 ^-4 Ωcm or less, has good electrical characteristics. Therefore, it is possible to form a transparent conductive film in which the optical characteristics and electrical characteristics of the transparent conductive film according to the prior art are greatly improved.

In this case, the transparent conductive film ratio _I 1 / _{I 2} of the peak intensity _{I 2} of the X-ray diffraction method (222) plane peak intensity _{I 1} and (400) plane is in a range of 0.1 to 1.0 It is preferable to form a film .
Thus, even when the film thickness is small, the diffraction peak intensity derived from the (400) plane in the X-ray diffraction method is strong, so that the resistivity is low and it has good electrical characteristics. Therefore, it is possible to form a transparent conductive film in which the optical characteristics and electrical characteristics of the transparent conductive film according to the prior art are greatly improved.

Further, transmittance of light with a wavelength in the range of 350~700nm are preferred If you form a transparent conductive film is 85% or more.
Thus, the transparent conductive film formed by the present invention has a high transmittance in a wide wavelength range including the entire visible light region. In particular, the light having a short wavelength range has a high transmittance as compared with the prior art. Thus, since in the prior art can be transmitted sufficiently even light of low wavelength range permeability, without being limited by the wavelength range that Do can be designed having conductivity in an optical member for controlling the wavelength .

Moreover , it is preferable to use a glass substrate or a resin substrate as the substrate.
At this time, since the substrate temperature can be raised to a range of at least 230 to 250 ° C. during the formation of the transparent conductive film, the crystallinity of the obtained transparent conductive film is improved, and as a result, the transparent having a low resistivity is obtained. A conductive film can be obtained.

According to the manufacturing method of the present onset light of the transparent conductive film, by appropriately controlling the deposition conditions of the permeable transparent conductive film, that good reproducibility to obtain a good transparent conductive film of the electrical and optical properties it can. Further, even when the film thickness is thin, a transparent conductive film with low resistivity and good electrical and optical characteristics can be obtained.
Even when the film thickness of the transparent conductive film is thin, the transparent conductive film having good optical characteristics can be obtained without being affected by the decrease in transparency due to the interference color. Further, even when the film thickness is thin, since the resistivity is low, a transparent conductive film having good electrical characteristics can be obtained.
According to the invention of claim 3, it is possible to obtain a transparent conductive film having a high transmittance for light in a wide wavelength range including the entire visible light region. Therefore, the transparent conductive film obtained by the present invention is useful in designing an optical member having conductivity.
Furthermore, according to the invention of claim 4, the substrate temperature can be maintained at a high temperature when the transparent conductive film is formed. Accordingly, the crystallinity of the obtained transparent conductive film is improved, and a transparent conductive film having good conductivity can be provided.

It is an XRD pattern figure which concerns on Example 1a thru | or 4 of this invention. It is a graph (reference: air) of the optical characteristic which concerns on Example 1a thru | or 4 of this invention. It is a graph (reference: glass) of the optical characteristic which concerns on Example 1a thru | or 4 of this invention. It is a graph which shows the relationship between the film thickness and resistivity which concern on Examples 1a-5 of this invention, and Comparative Examples 1-6. FIG. 6 is an XRD pattern diagram according to Comparative Examples 1 to 5.

The manufacturing method of the transparent conductive film which concerns on embodiment of this invention is demonstrated based on drawing. The materials, configurations, and the like described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.

  FIG. 1 is an XRD pattern diagram according to Examples 1a to 4 of the present invention, FIG. 2 is a graph of optical characteristics (reference: air) according to Examples 1a to 4 of the present invention, and FIG. FIG. 4 is a graph showing optical characteristics according to Examples 1a to 4 of the present invention (reference: glass), and FIG. 4 is a graph showing the relationship between film thickness and resistivity according to Examples 1a to 5 and Comparative Examples 1 to 6 of the present invention. FIG. 5 is an XRD pattern diagram according to Comparative Examples 1 to 5.

  In general, in order to improve the electrical characteristics of the transparent conductive film, it is necessary to reduce the resistivity to increase the electrical conductivity and increase the conductivity. In order to reduce the resistivity of the transparent conductive film, it is necessary to maximize the carrier density (n) and increase the hole mobility (μ).

  Among the transparent conductive films, the ITO film is known to have degenerate n-type semiconductor characteristics. The electrical characteristics of this thin film are mainly dominated by ionized impurity scattering and neutral impurity scattering. In order to increase the carrier density (n), it is necessary to increase the amount of oxygen vacancies and the amount of doping. In the ITO film, the formation of oxygen vacancies by optimizing the oxygen partial pressure during film formation, and more This is achieved by replacing many tin (Sn) atoms with indium (In) sites.

On the other hand, the resistivity of the ITO film depends on the substrate temperature during film formation, and the resistivity value decreases as the substrate temperature increases. Moreover, the resistivity of the thin film obtained by annealing at 200-300 degreeC after forming into a film at low temperature can be made small. Thus, in order to increase the hole mobility (μ), the substrate temperature during film formation is increased as much as possible to reduce the lattice defects of In and the unstable bonding state of Sn and SnO ₂ , It is necessary to improve the performance. At this time, in order to increase ions entering regular lattice points, scattering of conduction electrons decreases and carriers increase. However, if the oxygen concentration is increased more than necessary, oxygen vacancies are reduced and carriers are reduced.

  That is, it is important to find the optimum relationship by examining the hole mobility (μ), the carrier concentration (n), and the film formation conditions.

  In general, when the transparent conductive film is sputtered, a high magnetic field is applied to the target surface, whereby the cathode voltage can be lowered and the resistivity of the obtained thin film can be reduced. Moreover, by superimposing RF power on DC power, the cathode voltage can be further reduced, and the resistivity can be reduced.

In the manufacturing method of the transparent conductive film of this embodiment, it forms into a film so that a target surface magnetic field may become 600-800G using a planar magnetron type | mold sputtering device. More specifically, the target surface magnetic field becomes 600 to 800 G by increasing the magnetic strength of the magnet disposed inside the sputtering apparatus to 600 to 800 G or adjusting the distance to the target surface. To control.

  At this time, if the magnetic field strength is increased, the sputtering efficiency can be improved. However, under strong magnetic field conditions, moisture deterioration of the magnet due to changes in the magnet material increases, and the surrounding magnetic field is shielded and handled due to the strong magnetic field. Since a problem such as an increase in load occurs, it is preferable that the load is set to about 700 G and the magnetic field is not excessively strong.

  As described above, since the resistivity of the transparent conductive film is highly dependent on the film thickness, optimization in each film thickness band is necessary. In order to reduce the resistivity, it is necessary to control at least the ratio of DC power to RF power, the amount of oxygen, and the substrate temperature within an appropriate range. These controls are particularly important in a thin film region. . Hereinafter, film forming conditions such as the ratio of DC power to RF power, the amount of oxygen, and the substrate temperature will be described in detail.

  When RF power is superimposed on DC power, the plasma density in the vicinity of the target surface is improved and the impedance on the target surface is reduced, resulting in a voltage drop across the cathode. Plasma damage entering the substrate is reduced due to the voltage drop, and the reaction between oxygen and ITO is promoted by the high-density plasma with RF power superposition, contributing to crystal growth.

In the manufacturing method of the transparent conductive film of this embodiment, the ratio of the DC power and the RF power is set to the DC power so that the RF power becomes an output of 0.5 to 2.0 when the DC power is 1. It is preferable to superimpose RF power. Thus, by controlling the ratio of DC power and RF power, it is possible to manufacture a transparent conductive film having the same quality with good reproducibility. In addition, a transparent conductive film having high hole mobility (μ) and high carrier concentration (n) can be obtained by forming a film by superimposing RF power on DC power at the above ratio.

  Further, the substrate temperature during film formation is preferably 200 to 300 ° C., more preferably 230 to 250 ° C. At this time, as described above, when the temperature is high, the crystallinity of the transparent conductive film can be improved and the resistance can be lowered. However, the upper limit of the temperature that can be raised depends on the heat resistance of the substrate to be used and is appropriate. The temperature is selected.

  As a material of the substrate used, glass, a resin substrate, or the like can be used. As the resin substrate, a resin having high heat resistance can be used, and a super engineering resin such as a polyallyl heat-resistant resin can be used.

  Further, the substrate material may be a material obtained by combining various glass materials and resin materials. Further, the shape of the substrate is not particularly limited as long as the surface is smooth and can be handled without losing its shape, a thin film that can be bent can be used.

As the target to be used, a metal target such as In, Sn, Zn, Cd—Sn, or Cd—In, or a sintered target of these oxides added with an element serving as a donor as required is used. Therefore, in the manufacturing method of the transparent conductive film of this embodiment , it is possible to add Ga and Ge to ITO in addition to ITO to which 2.5 to 15% by weight of tin is added depending on applications.

In the method for forming a transparent conductive film according to this embodiment , the sputtering apparatus is evacuated and depressurized before forming the transparent conductive film, and the pressure in the apparatus is preferably about 1 × 10 ⁻⁴ Pa. . The oxygen amount in the carrier gas introduced after exhausting the apparatus is preferably 0.1% or more and 1% or less with respect to the inert gas used at the same time. In particular, the flow rate ratio between the inert gas and oxygen is preferably about 300: 1 (oxygen amount: 0.33%). At this time, argon (Ar), krypton (Kr), xenon (Xe) or the like can be used as the inert gas, and among these, Ar is preferable.

Respect manufacturing method of the transparent conductive film of the present invention, hereinafter, the embodiment will be described with reference to Figures 1-5.

(Example 1a: film thickness 8.4 nm, Example 1b: film thickness 10.0 nm)
A sufficiently cleaned glass substrate (Corning, No. 1737) is held on a substrate holder of a planar magnetron type sputtering apparatus, and the inside of the apparatus is evacuated to 1 × 10 ⁻⁴ Pa. Oxygen was introduced as a reaction gas so as to have a flow rate ratio of 300: 1 (oxygen amount: 0.33%). As a target, a sintered body (density: 99%) in which SnO ₂ was added to In ₂ O ₃ by 10% by weight was used. Thereafter, the total pressure in the apparatus was maintained at about 0.1 to 0.9 Pa, and the substrate temperature was heated to 230 ° C.

  At this time, sputtering was performed so that the ratio of DC power to RF power was 1: 1, and an ITO film was formed with the vicinity of each film thickness as a target value. At this time, the magnet is replaced with a strong magnetic field strength, the target surface magnetic field is about 700G, the DC power and the RF power are connected to the cathode, and the input power ratio is arranged to be freely controllable. ing.

  After the film formation, the substrate on which the ITO film was formed was taken out from the sputtering apparatus, and various measurements described below were performed on the obtained ITO film.

(Example 2: film thickness 20.8 nm, Example 3: film thickness 14.7 nm, Example 4: film thickness 48.5 nm, Example 5: film thickness 100 nm)
A sufficiently cleaned glass substrate (Corning, No. 1737) is held on a substrate holder of a planar magnetron type sputtering apparatus, and the inside of the apparatus is evacuated to 1 × 10 ⁻⁴ Pa. Oxygen was introduced as a reaction gas so as to have a flow rate ratio of 300: 1 (oxygen amount: 0.33%). As a target, a sintered body (density: 99%) in which SnO ₂ was added to In ₂ O ₃ by 10% by weight was used. Thereafter, the total pressure in the apparatus was maintained at about 0.1 to 0.9 Pa, and the substrate temperature was heated to 250 ° C.

  At this time, sputtering was performed so that the ratio of DC power to RF power was 1: 1, and an ITO film was formed with the vicinity of each film thickness as a target value. At this time, the target surface magnetic field is about 700 G, DC power and RF power are connected to the cathode, and the input power ratio is arranged to be freely controllable.

  After the film formation, the substrate on which the ITO film was formed was taken out from the sputtering apparatus, and various measurements described below were performed on the obtained ITO film. The analysis conditions are the same as those in Examples 1a and 1b.

(Comparative example 1: film thickness 9.9 nm, comparative example 2: 14.5 nm, comparative example 3: 22.5 nm, comparative example 4: 48.2 nm, comparative example 5: 95.5 nm, comparative example 6: film thickness 205 nm )
A sufficiently cleaned glass substrate (Corning, No. 1737) is held on a substrate holder of a planar magnetron type sputtering apparatus, and the inside of the apparatus is evacuated to 1 × 10 ⁻⁴ Pa. Oxygen was introduced as a reaction gas so as to have a flow rate ratio of 300: 1. As a target, a sintered body (density: 99%) in which SnO ₂ was added to In ₂ O ₃ by 10% by weight was used. Thereafter, the total pressure was maintained at about 0.1 to 0.9 Pa, and the substrate temperature was heated to 250 ° C.

  At this time, sputtering was performed so that the DC power was 1 kW, and an ITO film was formed with the vicinity of each film thickness described above as a target value. The target surface magnetic field at this time is about 700G.

  After the film formation, the substrate on which the ITO film was formed was taken out from the sputtering apparatus, and various measurements described below were performed on the obtained ITO film. The analysis conditions are the same as those in Examples 1a to 4.

(XRD measurement)
The ITO films obtained in Examples 1a to 4 and Comparative Examples 1 to 5 were subjected to X-ray diffraction measurement to evaluate crystallinity. X-ray diffraction measurement was performed under the following conditions. Regarding Examples 1a to 4, the obtained XRD pattern diagrams are shown in FIG. FIG. 5 also shows XRD pattern diagrams of Comparative Examples 1 to 5.
Measurement device: Smart. Lab. Made by RIGAKU ・ Target: Cu
・ Optical system: Concentration method ・ Tube voltage ・ Tube current: 40 kV, 30 mA
・ Measurement mode: Step ・ θ-2θ interlock ・ Normal ・ Atnotator: Open
・ Measurement angle: 15-70 °
-Incident slit: 1.5 mm
・ Step angle: 0.04 °
・ Reception slit: 1.5mm
・ Counting time: 4 ° / min
・ Measurement temperature: Room temperature

  As a result, in FIG. 1, in the XRD pattern diagrams of Examples 1a to 4, diffraction peaks attributed to the (222) plane near 2θ = 30 °, and to the (400) plane near 2θ = 35 °. A diffraction peak was observed. FIG. 1 shows XRD patterns related to ITO films of various film thicknesses at intervals.

In general, it is known that the higher the diffraction peak intensity on the (400) plane, the lower the resistance of the ITO film. Compared to the XRD pattern diagrams of Comparative Examples 1 to 5 (FIG. 5) in which the ITO film according to the prior art was measured, the XRD pattern diagrams (FIG. 1) of the ITO films according to Examples 1a to 4 of the present invention (400) Even when the diffraction peak intensity of the surface is strong and the film thickness is as thin as 8 nm (more specifically, 8.4 nm), the peak is observed.
Therefore, it is clear that the ITO films according to Examples 1a to 4 of the present invention have a low resistivity.

  On the other hand, in FIG. 5, in the XRD pattern diagrams of Comparative Examples 1 to 5 according to the prior art, the diffraction peak attributed to the (400) plane near 2θ = 35 ° is small, and the film thickness is about 50 nm (more specifically, It has become clear that it is observed at 48.2 nm) or more. Therefore, it is clear from the XRD pattern diagram that the ITO film according to the prior art has a high resistivity unless it has a film thickness of at least about 50 nm (more specifically, 48.2 nm) or more. It is.

In contrast to Comparative Examples 1 to 5, as in Examples 1a to 4 , the ITO films of Examples 1a to 4 of the present invention retain a low resistivity even when the film thickness is sufficiently thin. It was shown by X-ray diffraction.

  Table 1 shows the details of each peak of Examples 1a to 4 and the ratio between the peak intensity of the (222) plane and the peak intensity of the (400) plane. Table 2 shows the details of each peak of Comparative Examples 1 to 5, and the ratio between the peak intensity of the (222) plane and the peak intensity of the (400) plane.

As a result, the ratio of the peak intensity _{I 2} of Example 1A～4 (222) plane peak intensity _{I 1} and (400) plane, i.e. _I 1 / _{I 2} is in the range of 0.1 to 1.0 It has been shown. On the other hand, in Comparative Examples 1 to 5 formed by the conventional technique, it was shown that I ₁ / I ₂ was at least larger than 1 and the peak intensity of the (400) plane was weak. As described above, it is known that when the peak of the (400) plane is large, the resistance tends to decrease. More specifically, the peak intensity of the (400) plane is more specifically I ₁ / I _2. Can be defined as a range of 0.1 to 1.0.

(Transmittance measurement)
With respect to the ITO films obtained in Examples 1a to 4, the light transmittance was measured. The transmittance was measured with a Hitachi Electronic Recording Spectrometer (U-4100). FIG. 2 shows the air as the reference, and FIG. 3 shows the glass as the reference. In addition, although the film thickness was shown in FIG.2 and FIG.3, each film thickness is a film thickness of Example 1a-4, and is 8.4, 10.0, 14.7, 20.8, respectively. The light transmittance of the 48.5 nm ITO film is shown.

  As a result, in Examples 1a to 4, when the reference was air, the light transmittance was 70% or more in the entire visible light region, that is, in the wavelength range of 350 nm to 700 nm. Moreover, it was shown that the transmittance | permeability is 75% or more in the ITO film | membrane (Example 1a-2) whose film thickness is 8.4-14.7 nm. Further, when the reference is glass (FIG. 3), the ITO film (Examples 1a to 2) having a film thickness of 8.4 to 14.7 nm has a transmittance of 85% or more in the wavelength range of 350 to 700 nm. It was shown to have.

Further, in the ultraviolet light region, that is, in the short wavelength region having a wavelength of about 300 nm, the ITO film (Examples 1a to 2) having a film thickness of 8.4 to 14.7 nm has a transmittance of 65% or more. It was done. Therefore, the ITO films of Examples 1a to 4 of the present invention are also useful in fields that require transmission in the ultraviolet region, for example, fields that require ultraviolet light for sterilization, catalyst, drawing, and the like.

From the above measurement results, in the ITO films of Examples 1a to 4 of the present invention , it is possible to improve the light transmittance in the entire wavelength region including the ultraviolet region by sufficiently reducing the film thickness. It was shown that. This is because the interference color generated due to the thick film thickness and the coloration due to the absorption of the thin film are reduced by reducing the film thickness.

(Resistivity calculation)
The resistance value was measured with a Mitsubishi Yuka 4-end needle tester (Loresta AP), and the film thickness was measured with an ULVAC stylus-type film thickness meter (DEKTAK). Based on the obtained resistance value R (Ω) and film thickness d (nm), the resistivity ρ (Ωcm) was calculated using the following formula 1.
ρ = d × 10 ⁻⁷ × R (1)
4 and Table 3 show the resistivity of the ITO films of Examples 1a to 5 and Comparative Examples 1 to 6 according to the prior art.

As a result, it was shown that when the film thickness was comparable, Examples 1a to 5 had a lower resistivity than Comparative Examples 1 to 6 according to the prior art. In the examples of the present invention, even when the film thickness was as thin as 8.4 nm, the resistivity was small, 1.2 × 10 ⁻⁴ Ωcm. At other film thicknesses, the ITO film according to the example of the present invention has a smaller resistivity than that of the comparative examples 1 to 6 according to the prior art having the same film thickness, and is 1.5 × 10 ⁻⁴ Ωcm. It is as follows. Thus, the ITO film of the present onset Ming embodiment (more specifically, 8.4～20.8Nm) especially thickness 8~20nm in the range of, the ITO film formed by the prior art comparative It was shown that the resistivity is small.

(Hole mobility, carrier concentration, Hall coefficient measurement)
Moreover, regarding Examples 1a to 4, the hole mobility (μ), the carrier concentration (n), and the Hall coefficient were measured by RESITEST 8200 manufactured by Toyo Technica. The results are shown in Table 4.

As a result, the hole mobility (μ) is in the range of 36.4 to 43.7 cm ² / Vs, the carrier concentration (n) is in the range of 1.20 × 10 ^{21 to} 1.54 × 10 ²¹ cm ⁻³ , and the Hall coefficient. It was shown that an ITO film in the range of 4.0-5.2 cm ³ / C was obtained.

Therefore, from the various measurements described above, the ITO film of the embodiment of the present invention has a sufficient light transmittance in a wide wavelength range including the entire visible light region, that is, a wavelength range of 350 to 700 nm, and a thin film thickness. Even so, the resistivity was shown to have a sufficiently small value.

In particular, when the film thickness is about 15 nm or less (more specifically, 14.7 nm), the light transmittance is 85% or more in the wavelength range of 350 to 700 nm. For example, the display is formed through the obtained ITO film. When visually observing, high visibility can be secured. Moreover, by the measurement of the resistance value and the film thickness, the ITO film of the example of the present invention has a resistivity of 1.5 × 10 ⁻⁴ Ωcm or less even when the film thickness is thin, An ITO film having a small resistivity can be obtained.

In general, it is known that when the diffraction peak intensity on the (400) plane is strong, the ITO film tends to have a low resistance. However, in the prior art, the film thickness is about 50 nm (more specifically, 48 nm). .2 nm) or more, the diffraction peak of the (400) plane becomes prominent, whereas the ITO film of the example of the present invention has a film thickness of about 8 nm (more specifically, 8.4 nm). Even so, a diffraction peak of (400) plane was observed. Therefore, it was revealed not only from the resistivity measurement but also from the X-ray diffraction that the ITO film of the embodiment of the present invention has a low resistivity even when the film thickness is sufficiently thin. . When addition this, (222) ratio of the peak intensity _{I 2} of the peak intensity _{I 1} and (400) plane of the surface was shown to be 0.1 to 1.0.

  As a method for forming these ITO films, the film can be formed by sputtering, and the thickness of the film can be reduced by adjusting the substrate temperature, reaction gas, and film formation rate, including the power supply and magnetic field, and combining appropriate conditions. However, a good ITO film can be obtained. In particular, when the DC power is set to 1, the power supply may superimpose the RF power on the DC power so that the RF power has an output of 0.5 to 2.0. The reactive gas has an oxygen content of about 0.1% to 1.0% with respect to the inert gas. Further, regarding the magnetic field, when the surface magnetic field of the target is 600 to 800 G, the above ITO film is placed on a substrate such as glass. A film can be formed.

The transparent conductive film according to the present invention has good electrical characteristics such that the resistivity is 1.5 × 10 ⁻⁴ Ωcm or less even when the film thickness is small. Therefore, the transparent conductive film of the present invention is particularly useful in the field of electronic devices such as mobile terminals (PDA, Personal Digital Assistant) such as mobile phones and electronic notebooks, game machines, car navigation systems, personal computers, ticket vending machines, and bank terminals. It is expected to be useful for various sensors and displays that require a thin transparent conductive film.
In addition, since the transparent conductive film of the present invention maintains high transmittance over a wide range including the visible light region, the ultraviolet light region, and the near infrared light region, various optical filters, electromagnetic wave prevention, antistatic and photoelectric conversion Applications and applications in the field of optoelectronics such as devices are possible.

Claims (4)

A method of forming a transparent conductive film made of an indium tin oxide (ITO) film provided on a substrate ,
The substrate is placed in a sputtering apparatus having a target of indium tin oxide (ITO),
The flow rate of oxygen contained in the carrier gas is in the range of 0.1 to 1.0%,
The substrate temperature is in the range of 230 to 250 ° C .;
The surface magnetic field of the target is in the range of 600 to 800 G,
By applying a RF power with a DC power ratio in a range of 0.5 to 2.0 superimposed on the DC power source and performing sputtering ,
A method for producing a transparent conductive film, comprising forming a transparent conductive film having a thickness of 8 to 20 nm and a resistivity of 1.5 × 10 ⁻⁴ Ωcm or less . In the X-ray diffraction method (222) the ratio _I 1 / _{I 2} is a transparent conductive film area by der of 0.1 to 1.0 between the peak intensity _{I 2} of the peak intensity _{I 1} and (400) plane of the plane formed The method for producing a transparent conductive film according to claim 1, wherein the film is formed . Transmittance of light with a wavelength in the range of 350~700nm The method for producing a transparent conductive film according to claim 2, characterized in that a transparent conductive film is 85% or more. The method for producing a transparent conductive film according to claim 3 , wherein a glass substrate or a resin substrate is used as the substrate.

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