TWI515315B - ITO sputtering target - Google Patents

Description

ITO sputtering target

The present invention relates to a sputtering target used in the production of a transparent conductive film by a sputtering method, and more particularly to an ITO sputtering target comprising a plurality of target materials and having a divided portion.

The ITO film for forming a transparent conductive film is widely used as a transparent electrode of a display device centered on a liquid crystal display, a touch panel, an EL display or the like. In many cases, an oxide film for forming a transparent conductive film such as ITO is formed by sputtering.

The ITO (Indium Tin Oxide) film is used for display electrodes for flat panels and the like because of its high electrical conductivity and high transmittance. In recent years, with the increase in the size of flat panel displays (FPDs), the demand for large-scale ITO targets has become stronger.

However, due to the investment in new equipment for manufacturing large ITOs or the decrease in yield due to warpage, etc., it is very difficult to enlarge the ITO target. Therefore, at present, a large-sized ITO target system uses a multi-divided target in which a plurality of small ITO members are joined together.

It is known that when a multi-split target as described above is used for long-time sputtering, black adhesion of a lower oxide called indium, which is called a nodule, is considered to be a lower oxide of indium on the surface of the target. When the substance is precipitated, it is likely to cause an abnormal discharge, and it becomes a source of the fine particles on the surface of the film.

On the other hand, in the prior art, it is described that the method of inserting indium or various alloys in the entire gap portion can suppress the occurrence of abnormal ball formation or abnormal discharge during sputtering.

For example, Patent Document 1 discloses a method of filling a gap portion with an indium-tin alloy having an atomic ratio of indium to tin of a target body. However, in this case, it is necessary to measure the atomic ratio of indium to tin of the target body, and the composition of the indium-tin alloy injected according to the result needs to be adjusted every time, so that there is a problem in productivity of the target.

Further, there is a problem in that the indium-tin alloy is injected into all of the gap portions, and the electrical properties of the film formed on the upper portion thereof are different from those of the film formed in the other portion.

Further, Patent Document 2 discloses a method of filling indium into a gap portion, and Patent Document 3 discloses a method of filling an alloy having a melting point higher than that of a bonding material.

However, in these methods, indium or the like is injected into all of the gap portions, and the electrical properties of the film formed on the upper portion thereof are different from those of the film formed in other portions.

Patent Document 4 discloses a method in which a gap portion is filled with a material having the same constituent elements as the metal oxide sintered body but having different compositions. However, when the oxygen content is small, since there is almost no difference from the usual alloy, there is a problem that the electrical properties of the film formed on the upper portion thereof are different from those of the film formed in other portions; On the other hand, when the oxygen content is large, since there is almost no difference from the characteristics of ITO, there is a problem that the low temperature cannot be melted and flows into the gap portion.

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

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

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

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

An object of the present invention is to provide a sputtering target capable of suppressing generation of a ball or abnormal discharge and obtaining characteristics of a film formed on a substrate facing a gap portion even when continuous sputtering is performed on the divided ITO target. An ITO sputtering target of a film which has no difference from the characteristics of other portions of the film, that is, a film having uniformity of film properties, particularly a sputtering target for FPD.

In order to solve the above problems, the inventors of the present invention have conducted intensive studies to obtain an ITO sputtering target from a plurality of divided targets, and design the edge portions of the plurality of divided targets to thereby form a divided target. By providing a large-sized target, it is possible to provide a sputtering target capable of reducing defects caused by the generation of fine particles at the edge portions of the respective divided targets, in particular, a sputtering target for FPD.

Based on such insights, the present invention,

1) An ITO sputtering target is provided which is formed by arranging a plurality of ITO divided targets on a backing plate and joining the substrate, and has only a side of a gap side between the aligned ITO divided targets. A coating layer selected from the group consisting of indium, indium alloys, or tin alloys.

2) The present invention provides the ITO sputtering target according to the above 1), wherein the indium alloy or the tin alloy is selected from the group consisting of In-Sn, In-Bi, In-Bi-Sn, In-Ga, In-Ga- Any one of Sn, In-Ga-Bi, Sn-Ga, Sn-Bi, and Sn-Ga-Bi.

Further, the present invention provides the ITO sputtering target according to the above 1) or 2), wherein the gap between the ITO divided targets is 0.2 to 0.8 mm.

The ITO sputtering target according to any one of the above 1), wherein the thickness of the coating layer is 0.04 to 0.35 mm, and the thickness of the coating layer is subtracted from the size of the gap. The size of the gap is 0.1 to 0.72 mm. The above-described adjusted sputtering target of the present invention can provide the characteristics of the film formed on the substrate facing the gap portion even when the continuous sputtering of the divided ITO target is performed, and the generation of the ball or the abnormal discharge can be suppressed. An ITO sputtering target of a film which has no difference in characteristics from other portions, that is, a film having high uniformity of film characteristics, particularly a sputtering target for FPD, and has an ability to improve film formation and improve product quality. advantage.

The ITO sputtering target of the present invention is an ITO sputtering target formed by arranging a plurality of ITO divided targets on a substrate and bonded to the substrate, and is selected only from the side of the gap side between the aligned ITO segmentation targets. A coating layer of one of indium, indium alloy or tin alloy is used as a basis.

That is, the plurality of ITO split targets arranged on the bottom plate are not closely adhered to each side surface but have a fixed interval (gap). Figure 2 shows a conceptual diagram thereof. On the other hand, Fig. 1 is a cross-sectional view showing a representative ITO sputtering target of the present invention.

Each member of the divided ITO target can be produced by the method described below. First, indium oxide powder and tin oxide powder were weighed so that the tin oxide became 10 wt%.

The tin oxide concentration of the usual ITO is 10 wt%, but the concentration of the tin oxide may be in the range of 3 to 40 wt% within a range in which the properties of the transparent conductor are allowed.

Then, the raw material powder to be weighed is mixed and pulverized by a wet medium agitating mill or the like, and granulation for improving fluidity is performed. However, in order to increase the strength of the molded body, PVA may be added to the slurry at the time of granulation. Equivalent bonding agent.

Next, after press forming, atmospheric pressure sintering is performed in an oxygen atmosphere or an atmospheric environment to obtain an ITO sintered body.

The obtained ITO sintered body was machined to divide each member of the ITO target. At this time, it is preferable to perform chamfering processing on the diagonal to perform processing for reducing surface roughness. The number of divided ITO targets can be determined, for example, according to the size of a large ITO target in order to be suitable for FPD.

Such an ITO target is generally rectangular in plan view, so that a plurality of rectangular divided ITO targets can be arranged in accordance with this. However, the divided ITO target is not limited to a rectangular shape, and may of course be formed into other shapes such as a square, a triangle, a sector, or a suitable combination of the shapes. The present invention encompasses such situations.

On the side surface of each member of the ITO target produced as described above, indium or an indium alloy or the like is coated on the side surface to form a coating layer of the above substance. The method for forming the coating layer is not particularly limited, and may be formed, for example, by using a solder composed of indium or an indium alloy bonded to the bottom plate described below. For other methods, a thermal spray method, a plating method, or the like can be used. Further, it is also possible to reduce the side surface by electrolysis only to form an In-based metal.

After the formation of the coating layer, a solder composed of indium or an indium alloy is used for the substrate made of copper or a copper alloy or the like, and bonding is performed as shown in FIG. 1 described above.

When the indium or the like is adhered to the side surface, if the indium or the like is not adhered, abnormal discharge such as the end portion of the gap between the members of the divided target of the ITO target is likely to occur, and conversely, When indium or the like is entirely embedded in the gap as in the conventional example, the electrical properties of the film formed on the upper portion of the portion are different from those of the film formed in the other portion.

It is necessary to adjust the gap (interval) between the members of the divided target of the ITO target, and the gap is set to 0.2 to 0.8 mm. The gap between the ITO split targets at this time forms a gap before the coating layer. A coating layer selected from the group consisting of indium, indium alloy, or tin alloy is formed only on the side of the gap side of the ITO split target. Thereafter, they are arranged on the bottom plate and joined to the bottom plate.

Regarding each of the ITO split targets bonded to the substrate, a gap to be fixed as described above is required because if the gap is less than 0.2 mm, it is difficult to prevent the bonding of the members of the multi-divided ITO target to the substrate after the bonding. The layer (using a solder joint layer) is damaged by a collision between adjacent target members caused by heat shrinkage upon cooling.

Further, the reason is that, if it is wider than 0.8 mm, indium or the like is formed on the side surface of each target member, since the electrical properties of the film formed on the side surface are slightly different from those of the target member, the gap (interval) is formed. The opening is too large to deteriorate the in-plane uniformity of the film during sputtering.

In addition, during the sputtering and cooling of the ITO target, slight thermal expansion and contraction occur repeatedly, but since the gap between the divided targets has a function of appropriately adjusting this, there is also an effect of preventing cracking or cracking of the target. .

The thickness of the coating layer formed on the side surface of each ITO split target is set to 0.04 to 0.35 mm. The thickness of the coating layer refers to the thickness of one side facing the gap. The purpose of the coating layer is to suppress the occurrence of ball formation or abnormal discharge, and the characteristics of the film formed on the substrate facing the gap portion are not different from those of the other portions.

If the thickness of the coating layer is less than 0.04 mm, this effect is not obtained. If it exceeds 0.35 mm, it is necessary to increase the gap of the divided target itself, which causes a problem in the uniformity of the film. Therefore, it is preferable to coat the thickness of the layer. Set to 0.04 to 0.35 mm. Of course, the thickness of the coating layer is adjusted in the above range according to the gap of the divided target. As a result of the above, it is preferable to set the size (size) of the gap obtained by subtracting the thickness of the coating layer from the size of the gap to 0.1 to 0.72 mm.

The material attached to the side surface of the split target is preferably indium, an indium alloy, or a tin alloy. This is because the metal or alloy has a relatively low melting point and is likely to adhere to the side surface. Further, examples of the indium alloy and the tin alloy include In-Sn, In-Bi, In-Bi-Sn, In-Ga, In-Ga-Sn, In-Ga-Bi, Sn-Ga, and Sn. -Bi, Sn-Ga-Bi. These alloys, especially in the case of alloys with indium, have a lower melting point and are a better material.

Example

Hereinafter, description will be made based on examples and comparative examples. Furthermore, the present embodiment is merely an example, and the present invention is not limited by this example. That is, the present invention is limited only by the scope of the patent application, and includes various modifications other than the embodiments included in the invention.

(Example 1)

As a raw material, a mixed powder obtained by mixing an indium oxide powder having a specific surface area of 5 m ² /g and a tin oxide powder in a weight ratio of 9:1 is mixed and pulverized by a wet medium agitating mill using a bead mill. The mixture was placed in a die for a press and molded at a pressure of 700 Kg/cm ^{2 to} prepare an ITO formed body.

Next, the ITO formed body was heated from room temperature to 1500 ° C at a temperature increase rate of 5 ° C/min in an oxygen atmosphere, and then kept at 1500 ° C for 20 hours, and then cooled in a furnace to complete the sintering.

The surface of the sintered body obtained as described above was ground to a thickness of 6.5 mm using a No. 400 diamond grindstone in a surface grinder, and the side was cut into a size of 127 mm × 508 mm with a diamond cutter to prepare an ITO target member. Two pieces of such processed bodies were produced.

These sintered bodies were placed on a hot plate set to a temperature of 200 ° C and heated, and only 0.05 mm thick indium was adhered to the side surface.

Next, a substrate made of oxygen-free copper was placed on a hot plate set at a temperature of 200 ° C, and indium was used as a solder so as to have a thickness of about 0.2 mm. On the substrate, two ITO sintered bodies having indium adhered to the side surface as described above were placed so as to face each other with a gap of 0.4 mm, and left to cool to room temperature. According to the above, the distance (interval) between the coating layers of the adjacent divided targets is 0.3 mm.

The target was mounted on a magnetron sputtering device (BSC-7011) manufactured by SHINCRON, and the input power was DC power, 2.3 W/cm ² , gas pressure was 0.6 Pa, and sputtering gas was argon (Ar). The gas flow rate was 300 Sccm, and the integral power consumption was 120 WHr/cm ² .

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

After the sputtering integrated power consumption amount reached 160 WHr/cm ² , CORNING #1737 was set as the substrate, and the film thickness was set to 200 nm, and the substrate surface facing the gap portion and the distance from the opposite direction were 2 cm and A sheet resistance of 5 points in total of 4 cm from each other, and the deviation between the average value and the sheet resistance (=100×2 (maximum sheet resistance value-maximum sheet resistance value)/(maximum sheet resistance value+maximum sheet resistance) was determined. Value) %), thereby evaluating the film resistance uniformity (R1).

Table 1 shows the results of R1 (sheet resistance, average value, and sheet resistance deviation of 5 points) of the first embodiment.

Further, Table 1 also shows the results of the adhesion state of the gap, the indium adhered to the gap, the cumulative number of micro-arc generations integrated to 120 WHr/cm ² , and the film characteristics.

As shown in the above Table 1 and FIG. 1, the following results were obtained: the material coated on the side surface of the split target of Example 1 was indium (In), the thickness of the coating layer was 0.05 mm, the gap was 0.4 mm, and the number of times of micro-arc generation was obtained. For 260 times, the average value of the sheet resistance was 10.3 Ω/□, the sheet resistance deviation was 7.3%, the average value of the sheet resistance was a moderate value, the sheet resistance was less varied, and the number of generations of the micro-arc was also small.

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

(Example 2)

The same conditions as in Example 1 were carried out except that the thickness of the coating layer was changed to 0.1 mm. The results are also shown in Table 1 and Figure 1. The distance (interval) between the coating layers of the adjacent divided targets was 0.2 mm.

The following results were obtained: the number of generations of the micro-arc was 232 times, the average value of the sheet resistance was 10.2 Ω/□, the sheet resistance was 7.0%, the sheet resistance was a moderate value, the sheet resistance was less biased, and the micro-arc was generated. The number of times is also small.

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

(Example 3)

The same conditions as in Example 1 were carried out except that the gap was changed to 0.2 mm. The distance (interval) between the coating layers of the adjacent divided targets was 0.1 mm. The results are also shown in Table 1 and Figure 1.

The following results were obtained: the number of generations of the micro-arc was 210, the average value of the sheet resistance was 10.3 Ω/□, the sheet resistance deviation was 4.9%, the sheet resistance was a moderate value, the sheet resistance was less biased, and the micro-arc was generated. The number of times is also small.

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

(Example 4)

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

The following results were obtained: the number of generations of the micro-arc was 212, the average value of the sheet resistance was 10.4 Ω/□, the sheet resistance deviation was 5.8%, the sheet resistance was a moderate value, the sheet resistance was less biased, and the micro-arc was generated. The number of times is also small.

In the case of ITO, the sheet resistance can be used to evaluate the characteristics of the film on the substrate, and the variation in the sheet resistance means that the film is uniformly formed on the substrate.

(Comparative Example 1)

The same conditions as in Example 1 were carried out except that the gap between the divided targets was set to 0.4 mm without adhering any substance to the side surface of the ITO split target. The results are also shown in Table 1. Further, since the coating layer was not formed on the side surface of the ITO segmentation target, the structure was as shown in FIG.

The following results were obtained: the number of times of generation of the micro-arc was 750, the average value of the sheet resistance was 10.2 Ω/□, the deviation of the sheet resistance was 3.9%, the average value of the sheet resistance was a moderate value, and the variation of the sheet resistance was small, but The number of times the micro-arc is generated becomes extremely large.

(Comparative Example 2)

The same conditions as in Example 1 were carried out except that 0.02 mm of indium (In) was adhered to the side surface of the ITO split target. The results are also shown in Table 1 and Figure 1. The distance (interval) between the coating layers of the adjacent divided targets was 0.3 mm.

The following results were obtained: the number of generations of the micro-arc was 736, the average value of the sheet resistance was 10.2 Ω/□, the deviation of the sheet resistance was 3.9%, the average value of the sheet resistance was a moderate value, and the variation of the sheet resistance was small, but The number of generations of micro-arcs becomes extremely large.

(Comparative Example 3)

The same conditions as in Example 1 were carried out except that the gap of the divided target was set to 0.2 mm without adhering any substance to the side surface of the ITO split target. The results are also shown in Table 1. Further, since the coating layer was not formed on the side surface of the ITO segmentation target, the structure was as shown in Fig. 2 .

The following results were obtained: the number of generations of the micro-arc was 508, the sheet resistance was 10.2 Ω/□, the sheet resistance deviation was 3.0%, the average sheet resistance was a moderate value, and the sheet resistance was less varied, but compared with the comparative example. 1 is slightly reduced, and the number of generations of micro-arcs becomes extremely large.

(Comparative Example 4)

The arrangement of the divided targets, that is, the gap between the divided targets was set to 0.4 mm, but indium (In) was filled between the ITO split targets. There is a gap between the split targets, but other substances are filled in between, and the gap is virtually eliminated. Other than that, the same conditions as in the first embodiment were employed. The results are also shown in Table 1.

The number of generations of the micro-arc was 240 times, the average value of the sheet resistance was 9.4 Ω/□, and the deviation of the sheet resistance was 38.2%. The number of generations of the micro-arc was the same as that of the example, but the average value of the sheet resistance was deteriorated, and the sheet was thin. The deviation of the resistance becomes extremely large.

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

(Comparative Example 5)

The arrangement of the divided targets, that is, the gap between the divided targets was set to 0.2 mm, but indium (In) was filled between the ITO split targets. There is a gap between the split targets, but other substances are filled in between, and the gap is virtually eliminated. Other than that, the same conditions as in the first embodiment were employed. The results are also shown in Table 1.

The number of generations of the micro-arc was 198, the average value of the sheet resistance was 9.9 Ω/□, and the deviation of the sheet resistance was 17.6%. The number of generations of the micro-arc was almost the same as that of the example, but the average value of the sheet resistance was deteriorated. The deviation of the sheet resistance becomes extremely large.

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

According to the above-described examples and comparative examples, it is extremely important to have a structure in which an ITO sputtering target in which a plurality of ITO divided targets are arranged on a substrate and bonded to the substrate is arranged only. The side surface on the gap side between the ITO divided targets has a coating layer selected from one of indium, an indium alloy, or a tin alloy.

Thereby, generation of a ball or abnormal discharge can be suppressed, and the characteristics of the film formed on the substrate facing the gap portion are not different from the characteristics of the film of the other portion, that is, a film having high uniformity of film characteristics can be obtained.

The sputtering target of the present invention can provide the occurrence of ball formation or abnormal discharge even when continuous sputtering is performed on the divided ITO target, and can obtain characteristics and other portions of the film formed on the substrate facing the gap portion. The ITO sputtering target of the film having no difference in the characteristics of the film, that is, the uniformity of the film characteristics, has the advantage of being able to improve the yield of the film formation and improving the quality of the product, and can provide a lowering cause. A large-sized sputtering target that is defective in the generation of fine particles in the target portion is particularly effective as a sputtering target for FPD.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional explanatory view of a representative ITO sputtering target of the present invention.

Fig. 2 is an explanatory view of a conventional type target arranged at regular intervals (gap).

Claims (3)

An ITO sputtering target is formed by arranging a plurality of ITO split targets on a bottom plate and bonding with the bottom plate: the side of the gap side between the aligned ITO split targets is selected from the group consisting of indium, indium alloy or tin. A coating layer of one of the alloys, and the thickness of the coating layer is 0.04 to 0.35 mm, and the size of the gap obtained by subtracting the thickness of the coating layer from the gap is 0.1 to 0.72 mm. The ITO sputtering target according to claim 1, wherein the indium alloy or the tin alloy is selected from the group consisting of 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. The ITO sputtering target according to claim 1 or 2, wherein the gap between the ITO divided targets is 0.2 to 0.8 mm.