JP2010077453A - Target for sputtering, transparent conductive film using the same and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering target for obtaining a low resistance film, a transparent conductive film formed using the same, and a method for producing the same.
A sputtering target containing zinc oxide, aluminum oxide and fluorine, wherein the amount of the fluorine is 0.1 atomic% or more and less than 0.5 atomic% with respect to the total number of atoms. In addition, a transparent conductive material is formed on the substrate by sputtering using a target containing zinc oxide, aluminum oxide and aluminum fluoride, and the amount of fluorine being 0.1 atom or more and less than 0.5 atom% with respect to the total number of atoms. A method for producing a transparent conductive film for forming a film.
[Selection] Figure 2

Description

  The present invention relates to a sputtering target mainly composed of zinc oxide, a transparent conductive film using the target, and a method for producing the same.

Conventionally used transparent conductive films are ITO in which tin oxide is added to indium oxide, TAO in which tin oxide is doped with antimony oxide, fluorine, TFO, and the like. ITO in which tin oxide is added to indium oxide has a problem of high cost because indium is a rare metal and expensive. TAO and TFO have low transparency and insufficient conductivity.
On the other hand, zinc oxide is abundant in resources, has low cost, high transparency, conductivity, and chemical stability, and has attracted attention as a transparent conductive film. The zinc oxide-based transparent conductive film can be formed by various film forming methods such as a vacuum evaporation method, an ion plating method, a CVD method, and a plating method, including a sputtering method. Among them, the sputtering method is a method that has relatively good crystallinity and is suitable for forming a film over a large area.

  Conventionally, it is known that high conductivity can be obtained by adding aluminum, gallium, or the like to a zinc oxide film (see, for example, Patent Document 1). On the other hand, it has also been proposed to form a low-resistance film by sputtering using zinc oxide to which aluminum oxide is added. However, according to the prior art, the zinc oxide-based transparent conductive film has not reached a practical level. In the normal sputtering method, high energy charged particles generated in the discharge space are incident on the substrate surface, thereby generating residual stress in the film and causing various crystal defects. As a result, lowering of the resistance of the film has been hindered by a decrease in doping effect and a decrease in carrier mobility.

JP 2008-16240 A

  The present invention is intended to address such problems, and an object thereof is to provide a sputtering target for obtaining a low-resistance film, a transparent conductive film formed using the sputtering target, and a method for manufacturing the transparent conductive film. To do.

As a result of various studies to solve the above-described problems, the present invention has been completed by using a target containing zinc oxide as a main material and added with aluminum and fluorine.
A first aspect for solving the above problem is characterized in that it contains zinc oxide, aluminum oxide and fluorine, and the amount of the fluorine is 0.1 atomic% or more and less than 0.5 atomic% with respect to the total number of atoms. It is a sputtering target.

The second aspect is a sputtering target characterized in that, in addition to the first aspect, the amount of aluminum oxide is 1 to 4 atomic% with respect to the total number of atoms.
The third aspect is a sputtering target characterized by containing aluminum fluoride in addition to the first or second aspect.
The transparent conductive film of the present invention is obtained using the sputtering target according to the first to third aspects.
The method for producing a transparent conductive film of the present invention contains zinc oxide, aluminum oxide, and aluminum fluoride, and the amount of fluorine is 0.1 atomic% or more and less than 0.5 atomic% with respect to the total number of atoms. A transparent conductive film is formed on a substrate by sputtering using a target.

According to the present invention, a resistance lower than that of a conventional zinc oxide transparent conductive film can be achieved by forming a zinc oxide transparent conductive film using a target obtained by further adding fluorine to aluminum-added zinc oxide.
In patent document 1, although the transparent conductive film is produced using zinc fluoride, the quantity of a fluorine is 0.5-3 atomic%. In the present invention, the low resistance effect of fluorine was able to be exhibited with a very small amount of less than 0.5 atomic%.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a sputtering apparatus applied to the method for producing a transparent conductive film of the present invention. In the sputtering apparatus, a vacuum exhaust system 8 and a sputtering gas introduction pipe 6 are connected to a chamber (sputtering chamber) 100.
A target 4 supported by a cathode 3 incorporating a magnet in a chamber 100 and a glass substrate 2 on which a transparent conductive film is formed are arranged opposite to the anode 1.

First, the chamber 100 is depressurized to 2.0 × 10 ⁻³ Torr or less and stabilized, and then the ceramic heater 5 is turned on to heat the glass substrate 2 to about 100 ° C., and argon gas is introduced into the sputtering gas. Supply from the tube 6 into the chamber 100 so as to be about 2.0 × 10 ⁻³ Torr.
The pressure in the chamber 100 is preferably adjusted in the range of 1 × 10 ⁻³ to 10 × 10 ⁻³ Torr. When the pressure is less than 1 × 10 ⁻³ Torr, the discharge is not stable and abnormal discharge is likely to occur. When the pressure is higher than 10 × 10 ⁻³ Torr, the plasma density is lowered, the sputtering efficiency is deteriorated, and a dense film tends to be formed.
The temperature of the glass substrate 2 is preferably adjusted in the range of 100 ° C to 200 ° C. When the temperature is higher than 200 ° C., the electron concentration is likely to decrease due to the resistivity. When the temperature is lower than 100 ° C., the zinc oxide is not sufficiently crystallized due to the resistivity, and the resistivity is likely to increase. Because.

Next, after the pressure in the chamber 100 is stabilized, a high frequency power of 13.56 MHz is applied to the cathode 3 from the high frequency power source 7, and the target 4 is sputtered with an output of 100W to perform a deposition reaction for 2 hours. The output is preferably adjusted in the range of 80W to 120W. If the output is less than 80 W, sufficient crystal growth cannot be achieved, and the resistivity tends to increase. If it is higher than 120 W, the surface of the thin film is damaged, and a film with a disordered crystal structure is formed, which tends to increase the resistivity.
The thickness of the transparent conductive film deposited by sputtering is about 50 to 4000 mm.

The target 4 contains zinc oxide, aluminum, and fluorine, and the amount of the fluorine is required to be 0.1 atomic% or more and less than 0.5 atomic% with respect to the total number of atoms. 1 atomic% or more and 0.4 atomic% or less are preferable. When the amount of fluorine is less than 0.1 atomic% with respect to the total number of atoms, the effect of fluorine addition does not appear and the resistivity does not decrease. On the other hand, when it is 0.5 atomic% or more, the electron concentration is lowered and the resistivity is increased. Moreover, as the target 4, it is preferable that the amount of aluminum oxide is 1 to 4 atomic% with respect to the total number of atoms in order to increase the electron concentration and decrease the resistivity.
In order to adjust the amount of fluorine and aluminum in the target 4 as described above, zinc oxide (hereinafter referred to as ZnO), aluminum oxide (hereinafter referred to as Al ₂ O ₃ ), and aluminum fluoride (hereinafter referred to as AlF ₃ ). ) Must be used. The target 4 is placed on the cathode 3 by mixing these ZnO, Al ₂ O ₃ and AlF ₃ powders. In particular, it is preferable to change the amount of AlF ₃ in order to adjust the amount of fluorine and the amount of aluminum in the target 4 because it can be easily controlled.

Examples of the target 4 of the present invention include gallium oxide (Ga ₂ O ₃ ), indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), antimony oxide (Sb ₂ O ₅ ), and tellurium oxide (TeO ₂ ). An oxide may be contained.

  There is no restriction | limiting in particular as a board | substrate in this invention, All the board | substrates used when forming into a film normally by vacuum film forming, such as a metal, a metal oxide, glass, ceramics, a plastics, can be used. The heating temperature of the substrate can also be selected in the range of about 20 ° C to 500 ° C, preferably about 20 ° C to 200 ° C.

  EXAMPLES Next, the present invention will be described with reference to examples, but the following specific examples are not intended to limit the present invention.

A glass substrate 2 is installed on the anode 1 using the high frequency magnetron sputtering apparatus shown in FIG. 1, and a ZnO powder and an Al ₂ O ₃ powder (the amount of aluminum oxide is based on the total number of atoms) as a target 4 on the cathode 3. 2.5 atomic%) and AlF ₃ powder (the amount of fluorine is 0.1 atomic% with respect to the total number of atoms) are mixed well.
After reducing the pressure in the chamber 100 to 2.0 × 10 ⁻³ Torr or less and stabilizing it, the ceramic heater 5 is turned on to heat the glass substrate 2 to 100 ° C., and argon gas is supplied from the sputter gas introduction pipe 6. It supplied so that it might become 2.0 * 10 < ^-3 > Torr in the chamber 100. FIG.

After the pressure in the chamber 100 was stabilized, a high frequency power of 13.56 MHz was applied to the cathode by the high frequency power source 7, the target 4 was sputtered with an output of 100 W, and a deposition reaction was performed for 2 hours.
The resistivity and electron concentration of the obtained film were measured by the van der Pol method, and the resistivity was 6.3 × 10 ⁻⁴ Ω · cm and the electron concentration was 4.1 × 10 ²⁰ cm ⁻³ .

A transparent conductive film was formed by the sputtering method, except that the AlF ₃ powder added to the target 4 was the same as Example 1 except that the amount of fluorine was 0.2 atomic% with respect to the total number of atoms. The resistivity of the obtained film was 4.7 × 10 ⁻⁴ Ω · cm, and the electron concentration was 4.5 × 10 ²⁰ cm ⁻³ .

A transparent conductive film was formed in the same manner as in Example 1 except that the AlF ₃ powder added to the target 4 was 0.4% by atom with respect to the total number of atoms. The obtained film had a resistivity of 6.8 × 10 ⁻⁴ Ω · cm and an electron concentration of 5.0 × 10 ²⁰ cm ⁻³ .

[Comparative Example 1]
A transparent conductive film was formed in the same manner as in Example 1 except that the target 4 did not contain AlF ₃ powder (the amount of fluorine was 0 atomic% based on the total number of atoms). The obtained film had a resistivity of 7.5 × 10 ⁻⁴ Ω · cm and an electron concentration of 3.9 × 10 ²⁰ cm ⁻³ .

[Comparative Example 2]
A transparent conductive film was formed in the same manner as in Example 1 except that the AlF ₃ powder added to the target 4 had an amount of fluorine of 0.6 atomic% with respect to the total number of atoms. The obtained film had a resistivity of 1.1 × 10 ⁻³ Ω · cm and an electron concentration of 3.7 × 10 ²⁰ cm ⁻³ .

About the obtained aluminum and fluorine dope zinc oxide transparent conductive film, the result of having measured the relationship between the resistivity of a film | membrane and the fluorine amount in a target was shown in FIG.
As shown in FIG. 2, in Examples 1 to 3 in which the amount of fluorine is 0.1 atomic% or more and less than 0.5 atomic% with respect to the total number of atoms, it is confirmed that the resistivity of the film is extremely low. It was. In particular, when the amount of fluorine is 0.1 atomic% or more and 0.4 atomic% or less with respect to the total number of atoms, the resistivity is lower than 7.0 × 10 ⁻⁴ Ω · cm, and the effect of extremely reducing the resistance is obtained. It was confirmed that there was.

Moreover, about the obtained aluminum and fluorine dope zinc oxide transparent conductive film, the result of having measured the relationship between the electron concentration of a film | membrane and the fluorine amount in a target was shown in FIG.
The amount of fluorine as seen in FIG. 3 in the case of Examples 1 to 3 of less than 0.5 atomic% 0.1 atomic% or more with respect to the total number of atoms, 4.0 × ¹⁰ 20 ^{cm -3} or more It was confirmed to have a high electron concentration. When the electron concentration is high, the resistivity can be reduced because the number of electrons due to conductivity is large.

It is sectional drawing which shows an example of the sputtering device used for this invention. It is the figure which showed the relationship between the resistivity of the film | membrane obtained from the result of the Example of this invention, and the fluorine amount in a target. It is the figure which showed the relationship between the electron concentration of the film | membrane obtained from the result of the Example of this invention, and the fluorine amount in a target.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode 2 Glass substrate 3 Cathode 4 Target 5 Ceramic heater 6 Sputtering gas introduction tube 7 High frequency power supply 8 Vacuum exhaust system

Claims (5)

  A sputtering target comprising zinc oxide, aluminum oxide, and fluorine, wherein the amount of fluorine is 0.1 atomic% or more and less than 0.5 atomic% with respect to the total number of atoms.   The amount of aluminum oxide is 1-4 atom% with respect to the total number of atoms, The sputtering target of Claim 1 characterized by the above-mentioned.   The sputtering target according to claim 1, comprising aluminum fluoride.   A transparent conductive film obtained by using the sputtering target according to claim 1.   A transparent conductive film is formed on a substrate by sputtering using a target containing zinc oxide, aluminum oxide and aluminum fluoride, and the amount of fluorine being 0.1 atomic% or more and less than 0.5 atomic% with respect to the total number of atoms. Forming a transparent conductive film.

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