JP4599595B2 - Method and apparatus for producing transparent conductive film - Google Patents

Description

  The present invention relates to a method for producing a transparent conductive film, and more particularly to a method and apparatus for producing a transparent conductive film using a magnetron sputtering apparatus.

  In recent years, with the increase in size and performance of flat panel displays (hereinafter referred to as FPDs) such as liquid crystal displays and plasma displays, there has been an increasing demand for performance improvement and cost reduction required for transparent conductive films used therefor. Yes.

  Conventionally, a magnetron sputtering apparatus is known as a thin film forming technique for producing a transparent conductive film (see Patent Document 1). The magnetron sputtering apparatus can form a film by generating plasma near the target by discharge or the like, sputtering particles by colliding ions in the plasma with the target, and attaching the particles to a substrate.

Moreover, as a transparent conductive film used for FPD, tin-doped indium oxide (In ₂ O ₃ : Sn, hereinafter referred to as ITO) is widely used, but indium contained as a raw material is a rare metal and expensive. Therefore, there are concerns from the viewpoint of stable supply and cost.

Therefore, aluminum-doped zinc oxide (ZnO: Al, hereinafter referred to as AZO) that can be supplied in abundant manner has attracted attention as an alternative material for the ITO transparent conductive film.
JP-A-6-172959

  However, when a ZnO-based transparent conductive film or the like is produced on a substrate of about 300 ° C. or lower using a magnetron sputtering (hereinafter referred to as MSP) method, the resistivity distribution on the substrate arranged to face the target surface. Therefore, it is a major factor that hinders the reduction of the resistivity of the conductive film.

The present invention has been made in view of the above-described problems, and its object is to manufacture a transparent conductive film that improves the uniformity of resistivity distribution when forming a conductive film using an oxide by the MSP method. It is to provide a method and a manufacturing apparatus.

  In order to solve the above-described problems, a method for producing a transparent conductive film according to an aspect of the present invention is a method for producing high-frequency direct-current power in an atmosphere using an oxide as a target and introducing hydrogen and / or organic gas into an inert gas. A transparent conductive film is formed on the substrate by a magnetron sputtering method using a sputtering voltage with superimposed power.

  Examples of the oxide include zinc oxide doped with at least one element selected from the group consisting of Al, Ga, B, In, Y, Sc, F, V, Si, Ge, Ti, Zr, and Hf. It may be. More preferably, Al and Ga, which are low in cost and relatively easy to obtain and have low resistivity, are preferable.

  According to this aspect, by using a sputtering voltage in which high-frequency power is superimposed on DC power in an atmosphere in which hydrogen and / or organic gas is introduced into an inert gas, it is possible to suppress oxidation at the erosion facing portion, and excessive oxidation. Therefore, it is possible to improve the uniformity of the resistivity distribution of the transparent conductive film containing zinc oxide as a main component. Note that discharge plasma generated by a voltage in which high-frequency power is superimposed on DC power may be used. In addition, hydrogen or organic gas introduced into the atmosphere may be introduced into a vacuum vessel or the like in a state where it is mixed with an inert gas, or after being introduced into a vacuum vessel or the like from a separate gas supply source, It may be mixed.

  As the inert gas, for example, argon gas can be used. Moreover, as organic gas, organic gas which expresses reducibility, such as methane, alcohol, a ketone, etc. which do not have CC bond, for example can be used. Further, the amount of hydrogen introduced into the atmosphere may be in the range of 0.1% to 2.0%. More preferably, the amount of hydrogen introduced is in the range of 0.2% to 1.0%. Even more preferably, it may be in the range of 0.3% to 0.6%. According to this aspect, the resistivity itself of the transparent electrode can be lowered. Further, the resistivity distribution is also improved by reducing the resistivity of the erosion facing portion.

  Further, the frequency of the high-frequency power superimposed on the DC power may be in the range of 2 MHz to 700 MHz. Further, the high frequency power may be in a range of 30% to 300% of the direct current power. More preferably, it may be in the range of 60% to 200% of the DC power.

  A combination of the above-described elements as appropriate can also be included in the scope of the invention for which patent protection is sought by this patent application.

  According to the present invention, a transparent conductive film with improved uniformity of resistivity distribution can be produced.

(Basic principle)
Conventionally, the increase in resistivity of the target erosion facing portion is due to the impact of oxygen accelerated to high energy (oxygen (negative ions) accelerated toward the substrate by a DC electric field (sputtering voltage) on the erosion portion). It was thought to be caused by film damage.

  However, the inventors' research has found that this research result (interpretation) is not accurate, and the present invention has been devised based on this finding.

  According to the inventors' interpretation, on the substrate at the erosion facing portion, the amount of oxygen reaching the substrate is larger than that at other portions and the oxygen activity is high, which is the main cause of the increase in resistivity at the erosion facing portion. I believe.

  In other words, in magnetron sputtering, in principle, there is a portion (DC electric field) that can generate sputtering by accelerating argon gas (positive ions), so that oxygen ions (negative ions) are accelerated. Is also present (distributed).

  As a result, there is a distribution in the activity and amount of oxygen that reaches the substrate. Although depending on the film production conditions, in the case of zinc oxide or the like, normally, the substrate is already in an excessively oxidized state (excessive supply of oxygen) only with oxygen sputtered from the target. Therefore, it is considered that the erosion facing portion is further oxidized excessively (oxygen supply excessively), and the resistivity is increased.

  Therefore, the inventors have found that the resistivity and the resistivity distribution are improved by introducing reducing hydrogen or organic gas in order to suppress the excessive oxidation state.

  On the other hand, the inventors have insufficient reduction of hydrogen and organic gas with only high-frequency power or direct-current power, but this reduces the reduction of hydrogen and organic gas by superimposing high-frequency power on DC power. We found that the resistivity and resistivity distribution were improved.

  FIG. 1 is a graph comparing resistivity distributions of AZO films fabricated on a glass substrate in an Ar atmosphere with constant DC power and different high frequency power.

  As shown in FIG. 1, when high frequency power is superimposed on DC power even in an Ar atmosphere, the resistivity itself is lowered and the uniformity of the resistivity distribution is improved as compared with the case of only DC power. . In addition, there is an effect that the film forming speed is improved by superposition of the high frequency power.

  Based on the above knowledge, further improvement of resistivity and resistivity distribution is achieved by performing magnetron sputtering method using sputtering voltage in which high frequency power is superimposed on DC power in an atmosphere introduced with hydrogen or organic gas. It became possible.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

(Embodiment)
FIG. 2 is a main part sectional view schematically showing an example of the magnetron sputtering apparatus 10 according to the present embodiment. FIG. 2 shows a configuration housed in the vacuum chamber 70 among the configurations of the magnetron sputtering apparatus 10.

  In the magnetron sputtering apparatus 10, a target 20 and a base body 30 that is a base on which a thin film is formed are arranged to face each other. An anode 60 is provided in contact with the surface of the substrate 30 opposite to the target 20. The anode 60 functions as a substrate holder that holds the substrate 30 on which the components of the sputtered target 20 are formed as a thin film. On the other hand, the target 20 is held by a magnetron cathode portion 22 having a target holder.

  The magnetron cathode portion 22 is made of a metal such as stainless steel. Further, the magnetron cathode unit 22 is supplied with DC power on which AC power (high frequency power) is superimposed by a power supply source 40 having a high frequency power source and a DC power source, and also functions as a cathode. A magnet 50 and a yoke 52 are provided on the back surface of the magnetron cathode portion 22 as magnetic field generating means. In the gap between the magnet 50 and the yoke 52, a pipe 54 for circulating a coolant such as cooling water is provided as means for cooling the magnetron cathode portion 22. As the magnet 50, a permanent magnet or an electromagnet may be used.

  The means for cooling the magnetron cathode portion 22 is not limited to heat radiation by circulating cooling water, and may be heat radiation by a metal such as an aluminum block. The magnet 50 and the yoke 52 are surrounded by a shield plate 43 formed of a metal such as stainless steel. The shield plate 43 prevents discharge and sputtering other than above the erosion portion of the target 20.

  The vacuum chamber 70 can maintain the space including the target 20 and the substrate 30 at a desired degree of vacuum. The gas supply source 72 that supplies the sputtering gas and the inside of the vacuum chamber are evacuated to obtain the desired degree of vacuum. A vacuum pump 74 for obtaining is attached. Further, a heating means (not shown) for changing the temperature of the substrate 30 during film formation is provided.

  Hereinafter, the manufacturing method of the transparent conductive film using the magnetron sputtering apparatus 10 which concerns on the above-mentioned embodiment is demonstrated with reference to an Example.

(Example)
First, the target 20 and the substrate 30 according to the present embodiment used in the magnetron sputtering apparatus 10 will be described.

  The target 20 is made of ZnO, which is a high-density sintered body having a diameter of about 150 mm, doped with Al. Note that the shape of the target is not limited to a circle but may be any shape such as a square, and may be appropriately selected according to the apparatus, material, and film forming conditions. Further, a glass substrate is used for the base 30. Then, the target 20 and the substrate 30 are disposed at predetermined positions of the magnetron sputtering apparatus 10, and the vacuum chamber 70 is evacuated by the vacuum pump 74 so as to achieve a desired degree of vacuum. In that case, the glass substrate which is the base | substrate 30 is heated to 200 degreeC with a heating means (not shown).

In a state where the vacuum chamber 70 has a desired degree of vacuum, a sputtering gas in which X ₂ % of H ₂ is introduced into Ar is supplied from the gas supply source 72 into the vacuum chamber 70. Note that the H ₂ or organic gas introduced into the atmosphere may be introduced into the vacuum chamber 70 after being mixed with an inert gas, or may be introduced into the vacuum chamber 70 from a separate gas supply source. Here, the sputtering gas pressure is 0.4 Pa. And the direct-current power which superimposed the high frequency electric power is applied to the magnetron cathode part 22 from the power supply source 40, and a transparent conductive film is created. In this embodiment, the high frequency power is 100 W and the direct current power is 80 W.

  Here, the high frequency power may be set in the range of 30% to 300%, more preferably 60% to 200% of the DC power. This is because if the ratio of the high-frequency power is too small or too large, one of the characteristics of the DC component and the high-frequency component is too strong.

  Further, the frequency of the high frequency power superimposed on the DC power is preferably in the range of 2 MHz to 700 MHz. This is because, when the frequency is less than 2 MHz, it is difficult to generate plasma, whereas when the frequency is greater than 700 MHz, the power loss increases and the sputtering efficiency deteriorates. More preferably, it may be in the range of 10 MHz to 100 MHz, and for example, a frequency of 13.56 MHz is suitably used.

FIG. 3 is a graph comparing the resistivity distributions of AZO films fabricated on a glass substrate with different amounts of H ₂ introduced into Ar gas. As shown in FIG. 3, the AZO film produced under the conditions of the H ₂ introduction amount X = 0.4%, 0.6%, 0.8% compared to the condition of Ar only (X = 0%) The resistivity is lowered and the uniformity of the resistivity distribution is also improved. This is considered to be because the oxidation at the erosion facing portion can be suppressed.

On the other hand, in the AZO film produced under the condition of the H ₂ introduction amount X = 1.0%, the resistivity slightly increases and the uniformity of the resistivity distribution also slightly decreases. This is considered to be caused by deterioration of crystallinity due to an increase in the amount of H ₂ introduced. Considering the above results, the upper limit of the preferable range of the H ₂ introduction amount is 2.0% or less, more preferably 1.0% or less. The lower limit of the preferable range of the H ₂ introduction amount is 0.1% or more, more preferably 0.2% or more. This is because if it is less than that, the suppression of oxidation by the introduction of H ₂ becomes insufficient. Above that, hydrogen is taken into the film and oxygen is excessively reduced.

  FIG. 4 is a graph showing the relationship between the average resistivity of the AZO film produced by the production method of this example and the amount of hydrogen introduced. As shown in FIG. 4, the average resistivity with respect to the location and film thickness of the entire substrate surface is about 0.2% to about 0.7% in hydrogen introduction amount compared to 0% hydrogen introduction amount. The effect is recognized. More preferably, Ar having a hydrogen introduction amount of 0.3% to 0.6% is used as the sputtering gas.

It is the graph which compared the resistivity distribution of the AZO film produced on the glass substrate by making DC power constant and making high frequency power different. It is principal part sectional drawing which showed typically an example of the magnetron sputtering apparatus which concerns on this embodiment. By varying the introduction of H ₂ to be introduced into Ar gas is a graph comparing the resistivity distribution of the AZO film formed on a glass substrate. It is a graph which shows the relationship between the average resistivity of the AZO film produced by the production method of a present Example, and the amount of hydrogen introduction.

Explanation of symbols

  10 magnetron sputtering apparatus, 20 target, 22 magnetron cathode section, 30 substrate, 40 power supply source, 43 shield plate, 50 magnet, 52 yoke, 54 pipe, 60 anode, 70 vacuum chamber, 72 gas supply source, 74 vacuum pump.

Claims (9)

Magnetron using sputtering voltage in which high frequency power is superimposed on DC power in an atmosphere in which at least one gas selected from the group consisting of hydrogen, methane, alcohol and ketone is introduced as an inert gas using zinc oxide as a target A method for producing a transparent conductive film, comprising forming a transparent conductive film on a substrate by a sputtering method.   The zinc oxide is doped with at least one element selected from the group consisting of Al, Ga, B, In, Y, Sc, F, V, Si, Ge, Ti, Zr, and Hf. The manufacturing method of the transparent conductive film of description.   The method for producing a transparent conductive film according to claim 1, wherein the inert gas is Ar.   The method for producing a transparent conductive film according to claim 1, wherein the amount of hydrogen introduced into the atmosphere is in the range of 0.1% to 2.0%.   The method for producing a transparent conductive film according to claim 1, wherein the amount of hydrogen introduced into the atmosphere is in the range of 0.2% to 1.0%.   The method for producing a transparent conductive film according to claim 1, wherein the amount of hydrogen introduced into the inert gas is in the range of 0.3% to 0.6%.   The method for producing a transparent conductive film according to claim 1, wherein the frequency of the high-frequency power superimposed on the direct-current power is in the range of 2 MHz to 700 MHz.   The method for producing a transparent conductive film according to claim 1, wherein the high-frequency power is in a range of 30% to 300% of the direct-current power.   The method for manufacturing a transparent conductive film according to claim 1, wherein the high-frequency power is in a range of 60% to 200% of the direct-current power.

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