JP3152249B2 - Method and apparatus for producing transparent conductive film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a transparent conductive film in which a metal oxide film is adhered on a transparent substrate, and to an apparatus for measuring the electric resistance of the film surface of the transparent conductive film.

[0002]

2. Description of the Related Art On a surface of glass or a polymer film,
Transparent conductive films that are transparent and have a metal oxide film with a low electric resistance value attached to the film surface are used for applications utilizing the conductivity, for example, flat displays such as liquid crystal displays and EL displays, and transparent materials such as solar cells. electrode,
It is widely used for electric and electronic applications such as a transparent electrostatic shield plate or a transparent electromagnetic shield plate for a cathode ray tube window, a heating element, and the like. Among such transparent conductive oxide films, those having selective permeability are used for the window material for utilizing solar energy and for reflecting heat rays of buildings, automobiles, etc. by utilizing the infrared light reflection characteristics. Used as a material. As these transparent conductive films, usually, tin oxide, indium oxide,
Generally, indium oxide / tin oxide (ITO) or zinc oxide is formed on a transparent substrate as a coating film, and it is known that it can be formed by a vacuum deposition method, a sputtering method, a CVD method, a spray method, or the like. ing. Among them,
The vacuum vapor deposition method and the sputtering method are methods in which a transparent conductive film having a uniform film thickness and a low film surface electric resistance value (hereinafter referred to as surface resistance value) is obtained. In this case, there are a method using an oxide as a raw material and a method using a metal as a raw material to form a film while reacting with oxygen. For example, in the case of forming a film by sputtering of a thin film of ITO, a method of using a sintered target of ITO as a target and a method of performing reactive sputtering using an indium-tin alloy target while reacting with oxygen. Although both methods are known, it is considered that a method using a metal target is more advantageous in that the target can be easily formed and regenerated, and the film forming speed can be increased. Also for the vacuum deposition method, for the same reason, it is advantageous to perform reactive deposition using a metal as a raw material. The transparent conductive film to be manufactured is preferably a film having high transparency and low surface resistance. The surface resistance is measured by a contact type surface resistance measurement method such as a two-terminal or four-terminal method, and a four-probe method is used to increase the accuracy. In this method, contact probes are pressed at four positions on the surface of the transparent conductive film (coating side),
By applying a constant voltage between the two outer probes and measuring the voltage drop between the two inner probes, the resistance value between the electrodes is obtained, and the influence of the contact resistance can be eliminated.

[0003]

SUMMARY OF THE INVENTION However, ITO
The resistance characteristics of the oxide-based transparent conductive film with respect to the surface electric resistance value greatly depend on the degree of oxidation, and the surface resistance value,
The range satisfying both the light transmittances is very narrow. for that reason,
In particular, in the reactive sputtering or the reactive evaporation method, the oxidizing condition of the material changes depending on the state at the time of manufacturing, which sensitively affects the characteristics of the transparent conductive film, particularly the resistance characteristics. For example, the amount of water remaining in the vacuum chamber or the like has a large effect, and the condition changes for each batch, and a phenomenon that reproducibility is not good occurs. This is the target or
When an oxide is used as the vapor deposition material, it is not as large as in the case of the reactive sputtering method or the reactive vapor deposition method, but it is a problem. For example, when sputtering is performed using an ITO sintered target, a blackening phenomenon occurs in which the target surface becomes black, and the transparency or the film surface resistance value is increased. Similarly, in CVD, variations in characteristics due to fluctuations in the supply amount of the source gas, the temperature of the transparent substrate, and the like have become a problem. Therefore, in the production of a transparent conductive film, the surface resistance value is reduced in the width direction of the film and in the length direction of the film, that is, in a continuous production method, it is possible to reduce the variation over time of the deposition operation of the oxide film. Difficult. The value obtained by the contact-type resistance measurement method is an average between terminals, and a spot in the width direction cannot be determined. In addition, the contact resistance value varies with the pressing pressure and surface shape of the contact terminal, and the measurement accuracy is not good. Further, when the contact measurement method is used in the continuous manufacturing process, the film is often scratched, and the film is discarded and used, which greatly reduces the yield. Therefore, the surface resistance is measured in a non-contact manner, the film forming operation is controlled so that the value is constant, a method of manufacturing a film having high transparency and a low surface resistance, and a method of manufacturing a film having a low surface resistance. The development of a contact measurement device was expected.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, a constant value has been established between the surface electric resistance (R) of the transparent conductive film and the light transmittance of the film. The inventors found a specific relationship in the wavelength range, and came to invent a method of measuring the surface electric resistance of the film by a non-contact method and manufacturing a homogeneous transparent conductive film. That is, the present invention measures the light transmittance of the transparent conductive film, and from the measured value obtained,
A transparent conductive material having a uniform surface resistance value is calculated by calculating the surface resistance value using a relational expression of the surface resistance value and the light transmittance obtained in advance, and controlling the operation in the film forming process based on the calculated value. The present invention relates to a method for manufacturing a film and a device for measuring a surface resistance value.

In general, an oxide-based transparent conductive film is made of a metal film having an opaque and low surface resistance as oxidation proceeds.
In the course of changing to a semiconductor film which is transparent but has a large surface resistance, there is a region where the light transmittance is high and the surface resistance is small. The present inventors have examined this region in detail and found that there is a certain relationship between the surface resistance value and the light transmittance. FIG. 1 shows the relationship between the light transmittance and the surface resistance value accompanying a change in the oxygen supply amount, which is one of the operating factors during the film formation. When this relationship is examined in more detail, as shown in FIG. 2, there is a certain relationship between the surface resistance value, the light transmittance, and the measurement wavelength, and particularly, the measurement wavelength is 300 nm.
It was found that this tendency was strong at 1000 nm. For example, for the wavelengths of 340 nm and 380 nm, the measurement wavelength λ and the light transmittance T (λ) are shown in FIG.
The relationship shown in the following is seen, and when this is converted into a mathematical expression, a relational expression of R = A.EXP (-BT (.lamda.)) Is generally obtained with respect to the surface resistance value R. In the formula, A and B are constants, and do not always take constant values. That is, since the transparent conductive film attaches a metal oxide film on the transparent substrate by a vacuum deposition method, a sputtering method, or the like, the measured light transmittance is obtained by superimposing the light transmittance of the substrate and the light transmittance of the film. This is also because the light transmittance of the film is affected by the degree of oxidation and the thickness of the film. Therefore, in order to determine the above relational expression, it is necessary to determine in advance the relationship between the light transmittance and the surface electrical resistance value for samples having different coating thicknesses and oxidation degrees. The measurement of the surface resistance value for obtaining the relational expression can be obtained by a conventional contact-type measuring method. In this case, the measurement is performed in advance on the sample for obtaining the relational expression, and is not related to the damage of the film in the production process.
The obtained relational expression can be simplified from the above expression and approximated by a broken line or a polynomial curve. The wavelength of the transmitted light is
The range is preferably from 300 nm to 1000 nm, and more preferably from 330 nm to 500 nm.

As the metal oxide forming the transparent conductive film, there are indium oxide, indium oxide / tin oxide (ITO), tin oxide, zinc oxide, zinc oxide / aluminum oxide, cadmium oxide / tin oxide, and the like . Especially I
TO and tin oxide are suitable. As a substrate of the film, quartz glass, borosilicate glass, glass such as low alkali glass , ceramics such as sapphire , polyethylene, polypropylene, polyethylene terephthalate, applied to polymer films such as polyvinyl chloride, especially long A polymer film capable of forming a film is preferable.

Various methods for forming the transparent conductive film are known, and a physical vapor deposition method (PVD) such as a vacuum vapor deposition method, a sputtering method, an ion plating method, or a chemical vapor deposition method (CVD) is appropriately used. Can be In the vacuum deposition method, a thin film material is heated and evaporated under a high vacuum of 10 ⁻³ Torr or less, and deposited on a substrate. The vacuum vapor deposition method has the advantages that the apparatus is simple and a high film-forming rate can be easily obtained, but it also has disadvantages such as low adhesion speed between the substrate and the film, and difficulty in controlling the composition and film thickness. The sputter method uses a phenomenon in which high kinetic energy particles, such as ions and atoms, of several + eV or more collide with a solid (target) in a low-pressure gas discharge, and solid constituent atoms or molecules are repelled from the target surface. To form a coating. Compared to vacuum deposition, the adhesion between the film and the substrate is large, and it is possible to form a film of a high melting point material, and it is easy to control the composition and thickness of the film. Chemical vapor deposition is a method in which one or two or more compounds composed of elements constituting a thin film material to be formed, or a single gas is supplied to a base of a reaction region, and in a gas phase or on a surface of the base. Is a method of forming a desired thin film by the chemical reaction in the above. As described above, various methods for forming the transparent conductive film are known, but the present invention can be applied to these methods. For example, in the case of the sputtering method, there are various methods such as using a direct current as a power supply, a high frequency or using an oxide or a metal as a target,
Applicable in any case. The control parameters in the sputter method include vacuum pressure during sputtering, oxygen partial pressure, oxygen flow rate, sputtering current, voltage and the like. For example, the sputtering pressure is 5 × 10 ^-4 to 8 × 10 ^-2 To
rr, the oxygen partial pressure is preferably in the range of 5 × 10 ⁻⁶ to 10 ⁻² Torr. Further, sputtering current, 0.2 to 100 Å, preferably in the range of sputter power 0.1～100Kw.

[0008] In the vacuum deposition method, metals such as indium and tin, alloys and compounds such as indium oxide and tin oxide are used as a vapor deposition source material. As a heating method, resistance heating, high-frequency induction heating, electron beam heating, or the like can be used. Further, oxygen, nitrogen, water vapor, or the like may be introduced as a reactive gas, or reactive vapor deposition using means such as ozone addition or ion assist may be used.
In addition, a bias is applied to the base, the base temperature rises,
Alternatively, as long as the object of the present invention is not impaired, such as cooling, the operating conditions at the time of film formation can be changed.
The same applies to other forming methods such as a sputter method and a vacuum evaporation method. The control parameters in the vacuum deposition method, a vacuum pressure during deposition outside the above there is an oxygen partial pressure has heating power and the like, for example, the vacuum pressure during the deposition, 1 × 10 ^-5 ~
5 × 10 ⁻¹ Torr, heating power, and a range of 0.1 to 100 Kw are preferable. In addition, control parameters common to various film forming methods include a feed speed of a substrate, a substrate temperature, and the like. table
The method of controlling the sheet resistance is divided into two methods , control of the degree of oxidation of the film and control of the film thickness. As a method for controlling the degree of oxidation,
There are an oxygen partial pressure for adjusting an oxidizing atmosphere, an oxygen flow rate, an argon gas flow rate, and the like, and a substrate temperature for controlling reactivity, ozone addition, bias addition, and the like. In order to control the film thickness, it is effective to adjust the substrate feeding speed, the film forming speed, the film thickness limiting plate, and the like. For example, if you want to lower the surface resistance, increase the degree of oxidation, there are of two ways increasing the film thickness, the increase of oxidation, the O ₂ flow rate, for example 100
Increase from cc / min to 105 cc / min. The flow rate is preferably controlled at a sensitivity of about 0.5 cc / min, although it may vary somewhat depending on the size of the vacuum chamber and the film forming conditions. On the other hand, in order to increase the film thickness, there are methods of decreasing the film feeding speed or increasing the film forming speed. For this purpose, for example, the sputtering power is increased. As the sputter power, for example, 2 Kw is increased to 2.2 Kw, and
Control with a sensitivity of about 0.05 Kw is preferred.

FIG. 4 is an example of a schematic view of an apparatus for producing a transparent conductive film for performing the method of the present invention and a measuring apparatus for measuring the surface resistance of the film of the present invention. In the drawing, a transparent base film 8 sent out from an unwinding roll 5 is guided to a chill roll 4, a metal oxide film is formed on the surface of the transparent base film by a sputter target 7 below the chill roll 4, and is wound by a winding roll 6. Taken. On the other hand, light from the light source of the light source unit 1 is guided to the vacuum chamber 11 by an optical fiber, and light transmitted through the film is again guided to the outside of the chamber by the optical fiber, separated by the filter of the light splitting unit 9, and separated by the filter of the light splitting unit 9.
The signal is converted into an electric signal by a photometer of 0, and converted into a value indicating the surface resistance value by the above-described relational expression by the arithmetic processing unit 12 having a computer, and output. The output is input to the output control device 22, and a film forming operation such as a target heating current, a film supply speed, and an oxygen gas supply speed, which are operation factors of the film formation process, is performed so that the surface resistance value of the film becomes constant. Controlled. The control can be performed by PID control. Light emission and light reception on the film surface are preferably performed near the film surface, and it is convenient to use an optical fiber at an arbitrary position near the film surface. In the film forming process, the light emitting end and the light receiving end are not fixed to one point, but are traversed without damaging the film in the width direction of the film, and the average value and distribution of the surface resistance values in the width direction can be known. If the distribution of the surface resistance in the width direction of the film is out of the allowable range, reduce the width of the film, use multiple targets in the width direction of the film, or use a shielding plate between the sputter target and the film surface. Can be used.

The light source unit 1 needs to have a function of irradiating the transparent conductive film in the vacuum chamber with light having a wavelength of 300 nm to 1000 nm corresponding to the measurement range, and it may be continuous light emission or intermittent light emission. The light may be narrowed, or the light may be projected as parallel light. The light splitting unit 9 only needs to have a function of splitting light into at least a wavelength indicating the absorption characteristics of the transparent conductive film. The light to be spectrally separated by the filter may have a predetermined wavelength.However, in order to eliminate influences such as fluctuations in the light source light amount, the reference wavelength is also measured, and the surface resistance value is calculated based on the ratio. Accuracy can also be improved. The light receiving unit 10 includes a photomultiplier tube, a silicon photodiode, and the like having good light receiving sensitivity characteristics in a light absorption wavelength band of the transparent conductive film.
The arithmetic processing unit 12 converts the light transmitted through the transparent conductive film into
A light-receiving element that converts the electric signal into an electric signal corresponding to the intensity, an amplifier circuit that amplifies the obtained electric signal to a level that can be calculated, a filter circuit that removes background noise,
It is composed of an operation circuit for obtaining the surface resistance value by operation and a display circuit for monitoring the result. The operation may be analog operation or digital operation.

[0011]

Example 1 In the apparatus shown in FIG . 4, a xenon lamp was used as a light source, light was guided into the tank with an ultraviolet transmitting quartz optical fiber, and the fiber tip was fixed at a position 5 mm away from the surface of the transparent conductive film. A continuous light is projected perpendicularly to the surface of the transparent conductive film from the portion, and the transmitted light is received by an optical fiber of the same type as the optical fiber fixed at a position separated from the back surface of the film by 5 mm, and guided out of the vacuum chamber. The transmitted light of 380 nm is passed through the optical band pass filter from the optical fiber, the light is converted into an electric signal by a silicon photodiode, the signal is amplified by a lock-in amplifier, and then the signal is digitalized by a 12-bit analog / digital converter. The values were converted into values, calculated by a microcomputer circuit, and the surface resistance was continuously measured. Measurement wavelength λ and surface resistance R
Is a previously measured relational expression R = 1.45 ×
10 ⁵ EXP (-10.4T (λ)) was used. A transparent film (thickness of 300 Å) was formed on a 75 μm-thick polyester film by reactive sputtering using indium tin (containing 5% by weight of tin ) as an alloy material for forming the film. The film forming condition is a vacuum pressure of 3 × 10 ⁻³ Torr.
r, a sputter current of 5 A, and a sputter voltage of 300 V, and the film was formed at a feed speed of 10 m / min. The supply rate of the oxygen gas was controlled between 10 cc / min and 100 cc / min by controlling the input voltage of the mass flow meter with the output value obtained from the surface resistance detector. Table 1 shows the results. Since the non-contact type surface resistance measuring device according to the present invention was used, no damage was observed on the obtained film, and the production yield was greatly improved. Further, the variation in the surface resistance was within ± 3%, which was remarkably improved as compared with the level of a conventional commercially available product of ± 20%.

[0012]

Example 2 In Example 1, a 200 Å-thick polyester film having a thickness of 75 μm was applied to a polyester film having a thickness of 75 μm by magnetron sputtering using a sintered target of ITO ( containing SnO ₂ : 10 wt%). Molded. Film formation conditions are vacuum pressure 3
The film was formed at a feed rate of 3 m / min, with × 10 ⁻³ Torr, a sputter current of 3 A, and a sputter voltage of 250 V.
In the control of the film formation, the film formation was performed five times while feeding back the sputtering current value between 3.5 A and 5.0 A based on the output value obtained from the film resistance measuring device. Table 2 shows the measurement results of the surface resistance values. The variation in the length direction of one film and the variation between the films were very small as compared with the conventional method, and the maximum deviation was 3% compared with the target value of 200Ω / port.

[0013]

Comparative Example 1 In the same manner as in Example 1 , the reactive sputtering
A TO film was formed. At this time, a copper electrode was brought into contact with the formed transparent conductive film, and the film formation was performed while changing the film forming conditions while monitoring the resistance value. The sample was taken out and its surface resistance was measured. The film was found to have scratches caused by the contact of the electrodes, and the yield of the transparent conductive film thus produced was 60%. The surface resistance value is the target value of 20
It was ± 20% with respect to 0Ω / mouth.

[0014]

Comparative Example 2 In the same manner as in Example 1 , the reactive sputtering
An O film was formed, but no particular monitoring was performed.
The surface resistance of this film was measured. As a result, the surface resistance was good at the beginning of the film formation, but the degree of oxidation gradually increased, the surface resistance increased, and finally the conductivity was lost.

[0015]

[Table 1]

[Table 2]

[0016]

According to the present invention, the relationship between the light transmittance of the transparent conductive film and the surface resistance value of the film is measured in advance, and a surface resistance measuring device having an arithmetic processing unit into which the obtained relational expression is input is used online in the film forming process. By controlling the production conditions in the film forming process, a transparent conductive film having a uniform surface resistance can be manufactured without damaging the film.

[Brief description of the drawings]

FIG. 1 shows a general relationship between light transmittance and surface resistance of a transparent conductive film.

FIG. 2 shows light wavelength, light transmittance, and surface resistance of a transparent conductive film.

FIG. 3 shows a specific relationship in FIG.

FIG. 4 illustrates a schematic view of a film forming apparatus for carrying out the method of the present invention, together with a schematic view of a measuring apparatus of the present invention.

[Description of Signs] 1 light source unit 2 evacuation system 3 optical fiber 4 chill roll 5 unwind roll 6 take-up roll 7 target 8 transparent substrate film 9 spectral unit 10 light receiving unit 11 vacuum chamber 12 arithmetic processing unit 13 converter 14 mass spectrometer 15 Vacuum gauge 16 Temperature sensor 17 Speed sensor 18 Sputter power supply 19 Ionization power supply 20 Flow meter 21 Motor 22 Output control device 23 Signal input device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C23C 14/00-14/58

Claims (2)

(57) [Claims] In a manufacturing process of a transparent conductive film, a light transmittance of the transparent conductive film is measured, and a film forming operation in the manufacturing process is controlled by a film surface electric resistance value obtained by processing the measured value. A method for producing a transparent conductive film. 2. A transparent conductive material having a light source unit, a spectral unit, a light receiving unit, and an arithmetic processing unit, which is input to the arithmetic processing unit in advance.
An apparatus for calculating and outputting a film surface electric resistance value based on a relational expression between a film light transmittance and a film surface electric resistance value and a light transmittance of a transparent conductive film obtained from a spectroscopic unit.