CN102906301B - Ito sputtering target - Google Patents

Abstract

The present invention relates to an ITO sputtering target which is configured by arranging a plurality of ITO divided targets on a backing plate and bonding the ITO divided targets to the backing plate, wherein a coating layer of one substance selected from indium, an indium alloy and a tin alloy is provided only on the side surface on the side of a gap between the arranged ITO divided targets. The subject of the invention is to provide: even in the continuous sputtering of the divided ITO target, the ITO sputtering target, especially the sputtering target for FPD, can suppress the generation of nodules and abnormal discharge, and can obtain a film with high uniformity of film characteristics, wherein the characteristics of the film formed on the substrate opposite to the gap part are not different from those of the film at other parts.

Description

ITO sputtering target

technical field

The present invention relates to a sputtering target used when producing a transparent conductive film by a sputtering method, and particularly relates to an ITO sputtering target including a plurality of target materials and having a divided part.

Background technique

ITO thin films for forming transparent conductive films are widely used as transparent electrodes of display devices such as liquid crystal displays, touch panels, and EL displays. Oxide thin films for forming transparent conductive films such as ITO are often formed by sputtering.

ITO (Indium Tin Oxide) thin film has high conductivity and high transmittance, so it is used in display electrodes for flat panels, etc. In recent years, along with the increase in the size of the flat panel display (FPD), the demand for the increase in the size of the ITO target is also increasing.

However, it is very difficult to increase the size of ITO due to investment in new equipment for producing large ITO and reduction in yield due to warpage and the like. Therefore, currently, a large-sized ITO target uses a multi-segmented target formed by bonding a plurality of small-sized ITO members.

When sputtering is performed for a long time using the above-mentioned multi-segmented target, it is known that black deposits called nodules, which are considered to be indium suboxides, are deposited on the surface of the target, especially at the segmented parts, and abnormal discharges are likely to occur. And it becomes the source of particle generation on the surface of the film.

On the other hand, in the prior art, it is described that the generation of nodules and abnormal discharge during sputtering can be suppressed by embedding indium or various alloys in the entire void.

For example, Patent Document 1 discloses a method of filling voids with an indium-tin alloy having an atomic number ratio of indium tin of the target main body. However, for this purpose, it is necessary to measure the indium-tin atomic ratio of the target body, and it is necessary to adjust the composition of the indium-tin alloy to be filled based on the result every time, so there is a problem in the productivity of the target.

In addition, since the indium-tin alloy is injected into the entire gap portion, there is a problem that the electrical characteristics of the film formed from the upper portion thereof are different from those of the film formed from other portions.

Also, Patent Document 2 discloses a method of filling indium in the void, and Patent Document 3 discloses a method of filling the void with an alloy having a melting point higher than that of the joining material.

However, in these methods, since indium is injected into the entire void portion, there is a problem that the electrical characteristics of the film formed above it are different from those of the film formed in other portions.

Patent Document 4 discloses a method of filling voids with a material having the same constituent elements as the metal oxide sintered body but having a different composition. However, when the amount of oxygen is small, since it has substantially the same characteristics as a general alloy, there is a problem that the electrical characteristics of the film formed on its upper part are different from those of the film formed by other parts. In addition, conversely, When there is a large amount of oxygen, since the characteristics are basically the same as those of ITO, there is a problem that it cannot be melted and injected into the void at low temperature.

prior art literature

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 01-230768

Patent Document 2: Japanese Patent Application Laid-Open No. 08-144052

Patent Document 3: Japanese Patent Laid-Open No. 2000-144400

Patent Document 4: Japanese Patent Laid-Open No. 2010-106330

Contents of the invention

The object of the present invention is to provide: even in the continuous sputtering of the divided ITO target, the generation of nodules and abnormal discharge can be suppressed, and the characteristics of the film formed on the substrate opposite to the void portion can be compared with those of other portions. There is no difference in film properties, that is, an ITO sputtering target of a film with high uniformity of film properties, especially a sputtering target for FPD.

In order to solve the above-mentioned problems, the present inventors conducted extensive and intensive studies, and as a result, found that by configuring an ITO sputtering target with a plurality of divided targets and designing the edge portions of the plurality of divided targets, it is possible to provide a sputtering target that can be divided by arranging. On the other hand, by producing a large target, it is possible to reduce defective sputtering targets, especially sputtering targets for FPDs, which are caused by generation of particles at the edges of each divided target.

Based on this finding, the present invention provides:

1) An ITO sputtering target, which is constituted by arranging a plurality of ITO segmented targets on a backing plate and bonding to the backing plate, wherein only the side surface on the side of the gap between the arranged ITO segmented targets has indium , indium alloy or a coating of a substance of tin alloy.

In addition, the present invention provides:

2) The ITO sputtering target described in 1) above, characterized in that the indium alloy or tin alloy is selected from In-Sn, In-Bi, In-Bi-Sn, In-Ga, In-Ga-Sn, In Any one of Ga-Bi, Sn-Ga, Sn-Bi and Sn-Ga-Bi.

In addition, the present invention provides:

3) The ITO sputtering target described in 1) or 2) above, characterized in that the gap between the divided ITO targets is 0.2-0.8 mm.

In addition, the present invention provides:

4) The ITO sputtering target according to any one of the above 1) to 3), characterized in that the thickness of the cover layer is 0.04~0.35mm, and the size of the gap obtained by subtracting the thickness of the cover layer from the size of the gap 0.1~0.72mm.

Invention effect

The sputtering target of the present invention prepared in this way has the following advantages: Even when continuous sputtering of the divided ITO target can be provided, the generation of nodules and abnormal discharge can be suppressed, and it can be obtained on the substrate opposite to the void portion. The characteristics of the formed film are no different from those of other parts of the film, that is, the ITO sputtering target of the film with high uniformity of film characteristics, especially the sputtering target for FPD, and can improve the yield of film formation and improve the quality of products. quality.

Description of drawings

FIG. 1 is an explanatory cross-sectional view of a typical ITO sputtering target of the present invention.

FIG. 2 is an explanatory diagram of conventional targets arranged at constant intervals (gap).

Detailed ways

The ITO sputtering target of the present invention is an ITO sputtering target formed by arranging a plurality of ITO segmented targets on a backing plate and bonding to the backing plate, and it is formed only on the gap side between the arranged ITO segmented targets. An ITO sputtering target having a structure whose side is covered with a substance selected from indium, an indium alloy, or a tin alloy is basically used.

That is, the side surfaces of the plurality of divided ITO targets arranged on the backing plate are not in close contact with each other, but have a certain interval (gap). The schematic diagram is shown in FIG. 2 . On the other hand, a cross-sectional view illustrating a representative ITO sputtering target of the present invention is shown in FIG. 1 .

Each member of this divided ITO target can be manufactured by the following method. First, indium oxide powder and tin oxide powder were weighed so that the tin oxide was 10% by weight.

The usual ITO has a tin oxide concentration of 10% by weight, but the tin oxide concentration can be set in the range of 3 to 40% by weight within the allowable range for the properties of a transparent conductor.

Then, the weighed raw material powder is mixed and pulverized by a wet media agitation mill, etc., and granulated for improving fluidity. In the slurry during granulation, PVA for increasing the strength of the molded body can be added. and other adhesives.

Then, after pressure forming, normal-pressure sintering is performed in an oxygen atmosphere or an air atmosphere to obtain an ITO sintered body.

The obtained ITO sintered body was machined to obtain each member of the divided ITO target. In this case, it is more preferable to chamfer the corners to reduce the surface roughness. The number of divided ITO targets can be determined according to the size of a large ITO target, for example, in order to suit FPD.

Such an ITO target generally has a rectangular shape in plan view, and accordingly, a plurality of rectangular segmented ITO targets can be produced by arranging them. However, the segmented ITO target is not limited to a rectangle, and of course may be produced in other shapes such as a square, a triangle, a sector, or an appropriate combination thereof. The invention of the present application includes these aspects.

Indium, an indium alloy, or the like is coated on the side surfaces of each member of the ITO target produced as described above to form a coating layer of the substance. The method for forming the covering layer is not particularly limited, and it can be formed using, for example, a solder containing indium or an indium alloy for soldering on a backing board described below. As other means, a thermal spraying method, a plating method, or the like can be used. In addition, only the side surface can be electrolytically reduced to form an In-based metal.

After the covering layer is formed, soldering is performed on the backing board containing copper or copper alloy as shown in FIG. 1 above using solder containing indium or indium alloy.

The reason why indium or indium alloy is only added to the side is that if no indium is added, abnormal discharges are likely to occur based on the end of the gap between the members of the divided target of the ITO target. In addition, on the contrary, if As in the conventional example, if indium or the like is buried in the entire space, the electrical characteristics of the film formed on the upper part of this part are different from those of the film formed on other parts.

It is necessary to adjust the gap (interval) between each member of the divided target of the ITO target, and the gap is set to 0.2~0.8mm. The gap between the ITO divided targets at this time is the gap before the coating layer is formed. A coating layer of one substance selected from indium, an indium alloy, or a tin alloy is formed only on the side surface of the ITO split target on the side of the void. Then, it is aligned on the backing board and bonded to the backing board.

For each ITO divided target bonded to the backing plate, as mentioned above, a certain gap is required. This is because: when the gap is less than 0.2 mm, after the members of the multi-segmented ITO target are pasted on the backing plate , it is difficult to prevent damage caused by collision between adjacent target members due to thermal contraction when the bonding layer (soldering layer using solder) is cooled.

In addition, on the contrary, when it is larger than 0.8mm, even if indium or the like is formed on the side surface of each target member, the electrical characteristics of the film formed on the side surface are slightly different from the target member, so the gap (interval) is too large to cause film damage during sputtering. The in-plane uniformity becomes worse.

In addition, during the sputtering and cooling of the ITO target, thermal expansion and contraction are more or less repeated, and the gap between the divided targets has the function of moderately adjusting the thermal expansion and contraction, so it also has the function of preventing cracking and cracking of the target. Effect.

The thickness of the coating layer formed on the side surface of each divided ITO target was set to 0.04 to 0.35 mm. The covering layer has the thickness of one side facing the voids. The purpose of this covering layer is to suppress the generation of nodules and abnormal discharge, and to make the characteristics of the film formed on the substrate opposite to the void portion not different from those of other portions.

When the thickness of the covering layer is less than 0.04 mm, this effect is lost, and when it exceeds 0.35 mm, the gap itself for dividing the target must be enlarged, causing problems with the uniformity of the film. Therefore, it is preferable to set the thickness of the covering layer to 0.04 to 0.35 mm. Of course, the thickness of the covering layer should be adjusted within the above range according to the gap of the divided target. From the above results, it is appropriate to set the gap (size) obtained by subtracting the thickness of the coating layer from the size of the gap to 0.1 to 0.72 mm.

As the material added to the side surface of the split target, indium, an indium alloy, and a tin alloy are preferable. These metals or alloys have relatively low melting points and are therefore easy to attach to the sides. In addition, preferred examples of indium alloys and tin alloys include: In-Sn, In-Bi, In-Bi-Sn, In-Ga, In-Ga-Sn, In-Ga-Bi, Sn-Ga, Sn- Bi and Sn-Ga-Bi. These alloys, especially when alloyed with indium, have a relatively low melting point and are more preferable materials.

Example

Hereinafter, it demonstrates based on an Example and a comparative example. In addition, this Example is just an example, and this invention is not limited to this example by any means. That is, the present invention is limited only by the scope of claims, and includes various modifications other than the examples included in the present invention.

(Example 1)

The mixed powder obtained by mixing indium oxide powder and tin oxide powder with a specific surface area of 5 m ² /g as a raw material at a weight ratio of 9:1 is mixed and pulverized by a wet media agitation mill based on a ball mill, and then injected into a die. Forming with a pressure of 700kg/cm ² produces an ITO molded body.

Then, the ITO molded body was heated from room temperature to 1500° C. at a rate of 5° C./min in an oxygen atmosphere, then kept at 1500° C. for 20 hours, and then furnace-cooled and sintered.

The surface of the sintered body thus obtained was ground to a thickness of 6.5 mm using No. 400 diamond abrasive grains on a surface grinder, and the side was cut into a size of 127 mm×508 mm with a diamond cutter to obtain an ITO target member. Make two such processed bodies.

These sintered bodies were placed on a hot plate set at 200° C., and after the temperature was raised, indium was attached to only the sides with a thickness of 0.05 mm.

Then, a backing plate made of oxygen-free copper was placed on a hot plate set at 200° C., and indium was used as solder to coat the solder so that the thickness thereof was about 0.2 mm. The two ITO sintered bodies to which indium was added on the sides as described above were placed on the backing plate with a gap of 0.4 mm so that the bonding surfaces faced each other, and were naturally cooled to room temperature. From the above, it can be seen that the distance (interval) between the covering layers of adjacent divided targets is 0.3 mm.

The target was installed in a magnetron sputtering device (BSC-7011) manufactured by Synkron, with an input power of 2.3 W/cm ² from a DC power supply, a gas pressure of 0.6 Pa, argon (Ar) as a sputtering gas and a gas flow rate of 300 sccm, and the sputtering cumulative electric quantity is 120 WHr/cm ² .

The number (times) of micro-arc generation is measured during sputtering. The criterion for judging the micro-arc is that the detection voltage is 100V or more, and the released energy (sputtering voltage at the time of arc discharge x sputtering current x generation time) is 10mJ or less.

After the sputtering cumulative electric quantity is 160WHr/cm ² , set Corning 1737 as the substrate, set the film thickness to 200nm, and measure the substrate surface opposite to the void portion and a total of 5 samples at a distance of 2cm and 4cm from it in the opposite direction. The sheet resistance of the point, calculate the average value and the deviation of the sheet resistance (=100×2 (maximum sheet resistance value-minimum sheet resistance value)/(maximum sheet resistance value+minimum sheet resistance value)%) to evaluate the membrane resistance Uniformity (R1).

Table 1 shows the results of R1 (sheet resistance at 5 points, average value, and variation of sheet resistance) in Example 1.

In addition, results such as voids, the state of adhesion of indium, etc. to the voids, the cumulative number of micro-arc discharge occurrences up to a cumulative 120 WHr/cm ² , and film properties are also shown in Table 1.

Table 1

As shown in the above Table 1 and Figure 1, the material covered on the side surface of the divided target in Example 1 is indium (In), the thickness of the covering layer is 0.05 mm, the gap is 0.4 mm, and the number of micro-arcs is 260 times. The average value of the sheet resistance was 10.3Ω/□, and the variation of the sheet resistance was 7.3%. The average value of the sheet resistance was a moderate value, the variation of the sheet resistance was small, and the number of occurrences of micro-arcs was small.

In the case of ITO, the properties of the film on the substrate can be evaluated by the sheet resistance, and the small variation in the sheet resistance means that the film is formed uniformly on the substrate.

(Example 2)

It carried out under the same conditions as Example 1 except having changed the thickness of a cover layer into 0.1 mm. The results are similarly shown in Table 1 and FIG. 1 . The distance (interval) between the covering layers of adjacent divided targets was 0.2 mm.

The number of occurrences of micro-arcs was 232 times, the average value of the square resistance was 10.2Ω/□, and the deviation of the square resistance was 7.0%. The result was that the square resistance was a moderate value, the deviation of the square resistance was small, and the number of occurrences of micro-arcs was small. .

In the case of ITO, the properties of the film on the substrate can be evaluated by the sheet resistance, and the small variation in the sheet resistance means that the film is formed uniformly on the substrate.

(Example 3)

It carried out under the same conditions as Example 1 except having changed the gap into 0.2 mm. The distance (interval) between the covering layers of adjacent divided targets was 0.1 mm. The results are also shown in Table 1 and FIG. 1 .

The number of occurrences of micro-arcs was 210 times, the average value of sheet resistance was 10.3Ω/□, and the variation of sheet resistance was 4.9%. The result was that the sheet resistance was moderate, the variation of sheet resistance was small, and the number of occurrences of micro-arcs was small. .

In the case of ITO, the properties of the film on the substrate can be evaluated by the sheet resistance, and the small variation in the sheet resistance means that the film is formed uniformly on the substrate.

(Example 4)

It carried out under the same conditions as Example 1 except having changed the indium attached to the side surface of the ITO split target into the In-Sn alloy whose tin concentration was 10 at%. The results are also shown in Table 1 and FIG. 1 . The distance (interval) between the covering layers of adjacent divided targets was 0.3 mm.

The number of occurrences of micro-arcs was 212 times, the average value of the square resistance was 10.4Ω/□, and the deviation of the square resistance was 5.8%. The result was that the square resistance was a moderate value, the deviation of the square resistance was small, and the number of occurrences of micro-arcs was small. .

In the case of ITO, the properties of the film on the substrate can be evaluated by the sheet resistance, and the small variation in the sheet resistance means that the film is formed uniformly on the substrate.

(comparative example 1)

It carried out under the same conditions as Example 1 except not adding anything to the side surface of an ITO split target, but having set the space|gap of a split target to 0.4 mm. The results are also shown in Table 1. In addition, since no cover layer is formed on the side surface of the ITO split target, the structure is as shown in FIG. 2 .

The number of occurrences of micro-arc is 750 times, the average value of square resistance is 10.2Ω/□, and the deviation of square resistance is 3.9%. Too many results.

(comparative example 2)

It carried out under the same conditions as Example 1 except having added 0.02 mm of In to the side surface of the ITO split target. The results are also shown in Table 1 and FIG. 1 . In addition, the distance (interval) between the covering layers of adjacent divided targets was 0.3 mm.

The number of occurrences of micro-arc was 736 times, the average value of the square resistance was 10.2Ω/□, and the deviation of the square resistance was 3.9%. Too many results.

(comparative example 3)

It carried out under the same conditions as Example 1 except not adding anything to the side surface of the ITO split target, and setting the gap of the split target at 0.2 mm. The results are also shown in Table 1. In addition, since no cover layer is formed on the side surface of the ITO split target, the structure is as shown in FIG. 2 .

The number of occurrences of micro-arc is 508 times, the square resistance is 10.2Ω/□, and the deviation of square resistance is 3.0%. The average value of square resistance obtained is a moderate value, and the deviation of square resistance is small. Slightly reduced compared to Example 1, but still extremely large results.

(comparative example 4)

The arrangement of the split targets, that is, the gap between the split targets was set to 0.4 mm, but indium (In) was embedded between the ITO split targets. There are gaps between the divided targets, but other substances are put in between, and the gaps are substantially eliminated. Except for this, it carried out under the same conditions as Example 1. The results are also shown in Table 1.

The generation number of micro-arc is 240 times, the average value of square resistance is 9.4Ω/□, the deviation of square resistance is 38.2%, the generation number of micro-arc is the same degree as embodiment, but the average value of square resistance is poor, the square resistance The deviation is huge.

In the case of ITO, the properties of the film on the substrate can be evaluated by the sheet resistance, and a large variation in the sheet resistance means that the film is not formed uniformly on the substrate.

(comparative example 5)

The arrangement of the split targets, that is, the gap between the split targets was set to 0.2 mm, but indium (In) was embedded between the ITO split targets. There are gaps between the divided targets, but other substances are put in between, and the gaps are substantially eliminated. Except for this, it carried out under the same conditions as Example 1. The results are also shown in Table 1.

The number of times of generation of micro-arc is 198 times, the average value of square resistance is 9.9Ω/□, the deviation of square resistance is 17.6%, the number of times of generation of micro-arc is about the same degree as the embodiment, but the average value of square resistance is poor, square resistance The deviation is extremely large.

In the case of ITO, the properties of the film on the substrate can be evaluated by the sheet resistance, and a large variation in the sheet resistance means that the film is not formed uniformly on the substrate.

It is clear from the above-mentioned examples and comparative examples that the ITO sputtering target formed by arranging a plurality of ITO segmented targets on a backing plate and bonding to the backing plate has a space only between the arranged ITO segmented targets. It is extremely important that the sides of the sides have a covering layer of a substance selected from indium, an indium alloy or a tin alloy.

Accordingly, nodulation and abnormal discharge can be suppressed, and a film formed on the substrate opposite to the void can have the same film properties as other parts, that is, a film with high uniformity in film properties can be obtained.

Industrial applicability

The sputtering target of the present invention has the following remarkable advantages: Even when continuous sputtering of the divided ITO target can be provided, the generation of nodules and abnormal discharge can be suppressed, and the sputtering target formed on the substrate opposite to the void portion can be obtained. The characteristics of the film are no different from those of other parts of the film, that is, the ITO sputtering target of the film with high uniformity of film characteristics, and can improve the yield of film formation, improve the quality of the product, and thus provide the ability to reduce the cost caused by segmentation. Since it is a large sputtering target with a high failure rate due to particle generation at the target portion, it is especially useful as a sputtering target for FPDs.

Claims (3)

1. An ITO sputtering target, constituted by arranging a plurality of ITO segmented targets on a backing plate and bonding to the backing plate, wherein only the side surfaces on the side of the gap between the arranged ITO segmented targets have indium , an indium alloy or a coating of a substance of a tin alloy, The thickness of the cover layer is 0.04 to 0.35 mm, and the size of the gap obtained by subtracting the thickness of the cover layer from the size of the void is 0.1 to 0.72 mm. 2. ITO sputtering target as claimed in claim 1, is characterized in that, indium alloy or tin alloy is selected from In-Sn, In-Bi, In-Bi-Sn, In-Ga, In-Ga-Sn, Any one of In-Ga-Bi, Sn-Ga, Sn-Bi and Sn-Ga-Bi. 3. The ITO sputtering target according to claim 1 or 2, wherein the gap between the divided ITO targets is 0.2-0.8 mm.