JPH0853761A - Production of transparent electrically conductive film - Google Patents

Abstract

PURPOSE:To suppress the generation of a lower oxide and joule on the surface of a target by supplying periodically intermittent electric power to the target. CONSTITUTION:A transparent electrically conductive film is formed by using such as the sputtering target consisting essentially of tin or tin oxide. A target consisting essentially of indium or indium oxide and a target consisting essentially of zinc or zinc oxide are exemplified as the other target. The transparent electrically conductive film consisting essentially of the oxide is produced with the tar-get by sputtering method. Then, the intermittent electric power is periodically supplied to the target. A target containing metal antimony or an antimony compound can be used as the target. The voltage waveform in the unit period of the intermittent electric power is controlled to 10mum to 10ms for the time for impressing negative voltage and 10mus to 100ms for the sum of the time for non-impressing and that for impressing positive voltage. In this way, abnormal discharge causing the defect of the transparent electrically conductive film is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a liquid crystal display, a plasma display, an EL (electroluminescence) display, a touch panel, a transparent electrode film for anti-fog glass for vehicles, and an optical element used for a building window having various optical characteristics. The present invention relates to a transparent conductive film manufacturing method for forming a transparent conductive film used as a thin film by a sputtering method.

[0002]

2. Description of the Related Art Conventionally, as a method for forming the above-mentioned transparent conductive film, a sol-gel coating method, a spray method, a vapor phase reaction (CV).
A chemical film forming method such as the D) method and a physical film forming method such as a vacuum vapor deposition method and a sputtering method have been proposed.

However, in the industrial production of these transparent conductive films, it is possible to easily obtain a transparent conductive film excellent in electric characteristics and optical characteristics, and therefore physical film formation such as vacuum deposition method and sputtering method. The method has mainly been used. Particularly in recent years, the sputtering method has been widely used because it is possible to form a film uniformly on a large-area substrate and stably on a substrate at a relatively low temperature.

In the sputtering method, argon gas is ionized by direct current (DC) discharge or high frequency (RF) discharge, collides with a negatively biased metal or oxide target, and the jumped-out target material is deposited on the substrate. It is a film forming method.

For example, when forming a tin oxide film, 0.1-10% by weight of antimony oxide is used as a target material.
0.1-10% by weight of tin oxide and antimony metal
A tin alloy containing it is used.

For example, when forming an ITO film, as a target material, indium oxide containing 5 to 10% by weight of tin oxide (ITO target) and indium-tin alloy containing 5 to 10% by weight of metallic tin ( IT target) or the like is used.

For example, when forming a zinc oxide film, zinc oxide containing 0.1 to 10% by weight of aluminum oxide, zinc oxide containing 0.1 to 15% by weight of gallium oxide, and metallic aluminum are used as target materials. Alloy containing 0.1 to 10% by weight, or 0.1 to 10% gallium metal.
A zinc alloy containing 15% by weight is used.

As the sputtering gas, an inert gas such as argon to which oxygen is added if necessary is used.

[0009]

However, when a transparent conductive film is produced by a conventional sputtering method, no matter whether an oxide target or a metal target is used as a target material, the target material is not changed during continuous sputtering. In comparison, black microscopic protrusions (called nodules), which are considered to be low-grade oxides and have a remarkably small sputtering rate, are generated on the target surface, and the deposition rate of the transparent conductive film is gradually reduced, and at the same time abnormal discharge (arcing) occurs. ) Frequently occurs, and the target material scattered by arcing adheres to the substrate, resulting in a defect of the transparent conductive film.

For example, when continuous sputtering is performed for a long time using a tin oxide target having a thickness of about 6 mm, the tin oxide film formation rate is 60 at the initial stage just before the target is used up.
The frequency of occurrence of abnormal discharge sharply increases at the same time as it decreases to about 70%.

Therefore, in the industrial mass production process, it is the empirical situation that the sputtering power is gradually increased or the film formation time is gradually increased as the film formation rate decreases. is there. In particular, when abnormal discharge occurs or the film formation rate is significantly reduced, the present situation is that the device is once opened to the atmosphere and the nodules are mechanically scraped off.

Further, it has been conventionally known that the generation of nodules can be suppressed by sputtering with a high power density. However, increasing the power density tends to cause abnormal discharge, and once generated, causes a large amount of damage.

Particularly, in the above-mentioned target capable of forming a transparent conductive film, the target is easily broken due to insufficient cooling of the target. Further, since the sputtering speed tends to be high, there is a defect that the film characteristics of the transparent conductive film are deteriorated.

Further, in order to solve the above problems,
Japanese Patent Laid-Open No. 4-293767 proposes a method for cleaning and removing the nodules by plasma using nitrogen or a gas having a nitrogen component. This method has an advantage that cleaning can be performed without exposing the apparatus to the atmosphere, but it is necessary to stop the film forming process of the transparent conductive film to perform the above cleaning, and when the generation of nodules is remarkable, There was also a drawback that the above-mentioned nodules could not be removed even after long-term cleaning.

The present invention does not require plasma cleaning or a mechanical cleaning process under the atmosphere, and the conventional problems described above such as generation of nodules, abnormal discharge, and reduction of film formation rate are caused. It is an object of the present invention to provide a method for producing a transparent conductive film having excellent productivity that eliminates the above problems.

[0016]

The present invention provides a method for producing a transparent conductive film containing an oxide as a main component by a sputtering method, using a sputtering target capable of forming a transparent conductive film, wherein the target is intermittent. Provided is a method for producing a transparent conductive film, which is characterized in that various electric powers are periodically supplied.

As the sputtering target,
Examples thereof include a sputtering target containing tin or tin oxide as a main component, a sputtering target containing indium or indium oxide as a main component, or a sputtering target containing zinc or zinc oxide as a main component.

When the sputtering target is a sputtering target containing tin or tin oxide as a main component, it is preferable to contain metal antimony or a compound of antimony because the conductivity is increased. The content of the metal antimony or the compound of antimony is preferably 0.1 to 10% by weight.

When the sputtering target is a sputtering target containing indium or indium oxide as a main component, it is preferable to contain metal tin or a compound of tin because the conductivity is increased. The content of metallic tin or a tin compound is preferably 5 to 10% by weight.

When the sputtering target is mainly composed of zinc or zinc oxide, at least one selected from the group consisting of aluminum, gallium, indium, boron and silicon.
It is preferable to contain a simple substance or a compound of a kind of metal because the conductivity is increased. The content of at least one metal element or compound selected from the group consisting of aluminum, gallium, indium, boron and silicon is 0.1 to 10.
15% by weight is preferable, and aluminum oxide is particularly preferable.
1 to 10 wt% or gallium oxide 0.1 to 1
Those containing 5% by weight are preferable.

FIG. 1 is a schematic sectional view of an example of a sputtering apparatus according to the present invention. 1 is a sputtering target, 2 is a substrate on which a thin film is formed, 3 is a sputtering power source, 4 is a magnetron sputtering magnet,
Reference numeral 5 is a heater for heating the substrate, 6 is a sputtering gas inlet, and 7 is a control means for supplying intermittent electric power.

The sputtering power source used in the present invention is not particularly limited as long as it can supply intermittent power. As shown in FIG. 2, the negative application time a ₁ is 1
0 μs to 10 ms, and no application time b ₁
Is capable of supplying a voltage waveform in the range of 10 μs to 100 ms, and the negative application time a ₂ is 1 as shown in FIG.
Positive application time b in the range of 0 μs to 10 ms
₂ can supply a voltage waveform in the range of 10 μs to 100 ms, or, as shown in FIG. 4, the negative application time a ₃ is in the range of 10 μs to 10 ms and the positive application time b ₃ and Total of non-application time b ₄ is 10 μs
Those capable of supplying a voltage waveform in the range of -100 ms are preferred.

Further, the value of negative applied voltage (-V _N) setting is important for the purposes in which generation of nodules suppression of the present invention. As shown in Equation 5, the average value of the electric power during the time when the negative voltage is applied (hereinafter referred to as the average value of the electric power) W _A is the average value of the electric power within the time of one cycle (hereinafter referred to as the electric power of the electric power). by adjusting the negative applied voltage (-V _N) so that 2-10 times the effective value of) W, more favorable results can be obtained.

The effective value W of the electric power is as shown in Equation 1. T represents the time of one cycle. When this is applied to the case of the waveform as shown in FIG.

On the other hand, the time during which sputtering actually occurs (negative voltage is applied) (a in FIG. 2)
The average value W _A of the electric power in ₁ ) is as shown in Formula 3. In addition 2, the voltage of the time a in ₁ V (t) = (-
Since it is V _N ), when this is substituted, it becomes as shown in Formula 4.

In order to effectively remove the nodules, it is preferable that the average value W _A of the electric power is 2 to 10 times the effective value W of the electric power, as shown in the equation (5). When it is applied to the case of the waveform as shown in FIG. 2, it becomes as shown in the formula 6, so that the formula 6 is satisfied (−V _N ), a ₁
(10 μs ≦ a ₁ ≦ 10 ms), b ₁ (10 μs ≦ b ₁
≦ 100 ms) may be adjusted.

Particularly, the average value ω of the power density of the intermittent power
_A (7) is, good results can be obtained in the range of ^{2.5W / cm 2 ~30W / cm 2} .

In this case, it is not necessary to have an accurate rectangular wave as shown in FIG. 2, and ( _-VN ), a ₁ and b ₁ are optimized depending on the target size, state, or individual device. do it.

When a positive voltage is applied as shown in FIGS. 3 and 4, the application of the positive voltage does not work effectively for sputtering. Consider _P = 0.

The deposition rate of the transparent conductive film can be easily controlled by the effective value W of the intermittently supplied sputtering power. For example, when the desired film formation rate obtained by the conventional DC sputtering method is to be obtained by the method of the present invention, if the effective value W of the intermittently supplied power is set to the same as the DC power value, A desired film formation rate can be obtained.

That is, the following equation is substantially established: film formation rate according to the conventional DC sputtering method / DC power = film formation rate according to the present invention / effective power value W.

The power source used in the present invention is not particularly limited as long as it can supply intermittent power, and other configurations such as a sputtering cathode and a sputtering magnet are not particularly limited. Usual sputtering equipment can be used.

[0033]

[Equation 1]

[0034]

[Equation 2]

[0035]

(Equation 3)

[0036]

[Equation 4]

[0037]

(Equation 5)

[0038]

(Equation 6)

[0039]

(Equation 7)

[0040]

The present invention has an excellent feature that the generation of nodules on the target surface can be suppressed without stopping the film forming process by intermittently supplying the sputtering power. That is, by stopping the supply of sputtering power for 10 μs or more or by applying a positive voltage, it has an excellent effect of extinguishing the charges accumulated on the target surface, which cause abnormal discharge.

However, stopping the supply of sputtering power for more than 100 ms or applying a positive voltage not only causes a decrease in sputtering speed, but also in the case of an in-line type apparatus in which the substrate passes in front of the target at a predetermined transport speed. In particular, it is not preferable because unevenness of film thickness or unevenness of film quality is likely to occur in the traveling direction of the substrate.

Therefore, in order to fully exert the effects of the present invention, the voltage waveform of the sputtering power is such that the sum of the non-application time and the positive voltage application time is 10 μs to 100 ms.
It is preferably in the range of.

Further, by intermittently supplying the sputtering power as in the present invention, the average value W _{A of the} power supplied to the target can be made several times the DC sputtering power value.

For example, if the ratio between the sputtering power supply time and the stop time is 1: 1, the average power W _A is DC.
It becomes about twice the sputtering power value, and if it is 1: 4, the average value W _A of the power becomes about 5 times. This is an important effect of suppressing the generation of nodules.

That is, there is an excellent effect that the sputtering is instantaneously performed with a high power density, and the nuclei of the nodules or the nodules themselves are removed by the sputtering. In order to effectively bring about this effect, it is necessary to instantaneously supply a large power density necessary for suppressing the generation of nodules, and therefore, the voltage waveform applied to the target has a negative application time of 10 μs to 10 μs.
It is preferably in the range of ms.

Furthermore, the value of the negative applied voltage is preferably set so that the average value of the supplied power is 2 to 10 times the effective power value. If it is less than 2 times, the sputtering power density is small and it is insufficient to eliminate nodules by sputtering.
This is because if it is more than double, abnormal discharge occurs frequently.

Particularly, the average value ω of the power density of the intermittent power
_A is, good results are obtained in the range of ^{2.5W / cm 2 ~30W / cm 2} .

Further, the effect of suppressing the abnormal discharge by stopping the supply of the sputtering power or applying the positive voltage of the present invention can suppress the abnormal discharge up to a high sputtering effective power value as compared with the normal DC sputtering.
It has an effect of realizing higher-speed sputtering.

The sputtering rate of the present invention also has the effect that it can be easily controlled by the effective value W of the electric power supplied intermittently. For example, in order to obtain a speed equivalent to the sputtering speed of the conventional DC sputtering, the effective value W of the intermittently supplied power in the present invention may be adjusted to the DC power value.

[0050]

【Example】

[Example 1] by using a conventional magnetron sputtering apparatus as shown in FIG. 1, the target 1 of tin oxide containing antimony oxide 5 wt%, as shown in FIG. 2, a ₁
Was 100 μs and b ₁ was 400 μs, and intermittent power having a voltage waveform was supplied. As the substrate 2, non-alkali glass preheated to 300 ° C. was used.

First, after the film formation chamber was evacuated to 1 × 10 ^-5 Torr or less, argon gas containing 1% by volume of oxygen gas was introduced so that the gas pressure became 3 × 10 ^-3 Torr, and the sputtering power was increased. Was set to an effective value of 1.1 kW, and the nodule generation state after 23 hours of continuous sputtering, the frequency of abnormal discharge, and the characteristics of the tin oxide film were investigated. The results are shown in Table 1.

Example 2 A target 1 of tin oxide containing 5% by weight of antimony oxide was used, and a ₃ as shown in FIG.
Is 100 μs, a time b ₃ for applying a positive applied voltage V _P of about 10% of the negative applied voltage V _N is 10 μs, and further b ₄
Was set in the same manner as in Example 1 except that an intermittent electric power having a voltage waveform of 390 μs was supplied, and the generation state of nodules after 23 hours of continuous sputtering was investigated in the same manner as in Example. The results are shown in Table 1.

[Comparative Example 1] The same conditions as in Example 1 were applied except that a direct current voltage was applied to the tin oxide target 1 containing 5% by weight of antimony oxide, and the nodules were generated after 23 hours of continuous sputtering. Was investigated in the same manner as in the example. The results are shown in Table 1.

[Examples 3 to 4 and Comparative Example 2] Examples 1 to 4 except that an indium oxide target containing 10% by weight of tin oxide was used in place of the tin oxide target containing 5% by weight of antimony oxide. Examples 3 to 4 and Comparative Example 2 were carried out under the same conditions as those of No. 2 and Comparative Example 1, and the same investigation was conducted. The results are shown in Table 2.

[Examples 5 to 6 and Comparative Example 3] Examples 1 to 6 except that a target of zinc oxide containing 5% by weight of gallium oxide was used in place of the target of tin oxide containing 5% by weight of antimony oxide. Examples 5 to 6 and Comparative Example 3 were carried out under the same conditions as those of No. 2 and Comparative Example 1, and the same investigation was conducted. Table 3 shows the results.

Examples 1, 3 and 5 in which intermittent electric power having a voltage waveform as shown in FIG. 2 was supplied.
Then, even after continuous sputtering for 23 hours (drilling a target having a thickness of 6 mm), nodules were generated very little, and the sputtering rate was hardly reduced. Further, the frequency of occurrence of abnormal discharge is also reduced to about 1/5 of that of the normal sputtering method shown in each of Comparative Examples 1, 2 and 3.

Further, Example 1, Example 3 and Example 5
The specific resistance of each transparent conductive film obtained in 1. was about the same as that of a normal sputtering sample.

Embodiments 2, 4, and 6 in which intermittent electric power having a voltage waveform as shown in FIG. 4 is supplied.
Then, even after continuous sputtering for 23 hours (drilling a target having a thickness of 6 mm), nodules were generated very little, and the sputtering rate was hardly reduced. The frequency of occurrence of abnormal discharge is reduced to one-third as compared with each of the embodiments in which intermittent electric power having a voltage waveform as shown in FIG. 2 is supplied.

Further, Example 2, Example 4 and Example 6
The specific resistance of each transparent conductive film obtained in 1. was about the same as that of a normal sputtering sample.

In Comparative Examples 1, 2 and 3, after continuous sputtering for 23 hours (drilling of a 6 mm thick target).
In the above, a large amount of black nodules are generated on the entire surface of the erosion region excluding the erosion center of the target where the sputtering power is concentrated, and the frequency of abnormal discharge is extremely high at 15 times or more per minute. The sputtering rate is reduced by about 40%.

At this time, the initial specific resistance of each transparent conductive film obtained in Comparative Examples 1, 2 and 3 deteriorates after 23 hours due to the decrease in the sputtering rate. Further, the nodules produced at this time were extremely strong and required mechanical polishing cleaning.

[0062]

[Table 1]

[0063]

[Table 2]

[0064]

[Table 3]

[0065]

EFFECTS OF THE INVENTION The present invention forms a transparent conductive film at the same time as a means for stopping the film-forming process that causes a decrease in productivity, and at the same time, lowers the sputtering rate on the surface of the target. Generation of oxide nodules can be suppressed. At the same time, abnormal discharge that causes defects in the transparent conductive film can be suppressed.

Due to the above-mentioned effect of suppressing abnormal discharge, the conventional D
Compared to the C sputtering method, a large amount of power can be input,
A high deposition rate can be obtained. Furthermore, according to the invention, D
The abnormal discharge can be easily suppressed without adding the abnormal discharge prevention circuit used for the C sputtering power source.

By a simple method of controlling the effective value of the intermittently applied power, the film forming conditions can be controlled as in the conventional DC sputtering method, and a transparent conductive film having the same characteristics as the conventional one can be obtained. .

[Brief description of drawings]

FIG. 1 is a conceptual sectional view of an example of a sputtering apparatus of the present invention.

FIG. 2 is a voltage waveform diagram of a sputtering power source used in the present invention.

FIG. 3 is a voltage waveform diagram of a sputtering power source used in the present invention.

FIG. 4 is a voltage waveform diagram of a sputtering power source used in the present invention.

[Explanation of symbols]

 1: Sputtering target 2: Substrate 3: Sputtering power supply 4: Sputtering magnet 5: Substrate heating heater 6: Sputtering gas inlet 7: Control means for supplying intermittent electric power

 ─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 6-124052 (32) Priority date Hei 6 (1994) June 6 (33) Country of priority claim Japan (JP) (72) Inventor Satoru Takagi 1160 Matsubara, Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Pref.A.G.Technology Co., Ltd.

Claims (11)

[Claims] 1. A method for producing a transparent conductive film containing an oxide as a main component by a sputtering method using a sputtering target capable of forming a transparent conductive film, wherein intermittent power is periodically supplied to the target. A method for producing a transparent conductive film, comprising: 2. The manufacturing method according to claim 1, wherein the sputtering target is a sputtering target containing tin or tin oxide as a main component. 3. The method according to claim 2, wherein the sputtering target contains metallic antimony or a compound of antimony. 4. The manufacturing method according to claim 1, wherein the sputtering target is a sputtering target containing indium or indium oxide as a main component. 5. The sputtering target contains metallic tin or a compound of tin.
Manufacturing method. 6. The manufacturing method according to claim 1, wherein the sputtering target is a sputtering target containing zinc or zinc oxide as a main component. 7. The method according to claim 6, wherein the sputtering target contains a simple substance or a compound of at least one metal selected from the group consisting of aluminum, gallium, indium, boron and silicon. 8. The voltage waveform in a unit cycle of the intermittent electric power has a negative voltage application time in a range of 10 μs to 10 ms, and a sum of no application time and a positive voltage application time is 10 μs. The manufacturing method according to claim 1, wherein the manufacturing method is in the range of ˜100 ms. 9. The average value of the electric power within the time when the negative voltage is applied is 2 to 10 times the average value of the electric power within the time of one cycle. The manufacturing method according to any one of items. 10. The average value of the power density of the power within the time when the negative voltage is applied is 2.5 W / cm ^{2 to} 30 W.
The method according to claim 9, characterized in that a / cm ^2. 11. The sputtering rate is controlled by the effective value of the intermittent electric power.
7. The manufacturing method according to any one of 7 to 7.