JP6198177B2 - Ag alloy sputtering target - Google Patents

Description

  The present invention relates to an Ag alloy sputtering target for forming a conductive film such as a reflective electrode film of an organic EL element or a wiring film of a touch panel, and particularly relates to a large Ag alloy sputtering target having a large area sputtering surface. .

  The organic EL element applies a voltage between the anode and the cathode formed on both sides of the organic EL light emitting layer, injects holes from the anode and electrons from the cathode into the organic EL film, and generates holes in the organic EL light emitting layer. It is a light-emitting element that uses the principle of light emission when electrons and electrons are combined, and has recently attracted much attention as a display device. There are a passive matrix system and an active matrix system for driving organic EL elements. This active matrix method can be switched at high speed by providing one or more thin film transistors per pixel, which is advantageous for high contrast ratio and high definition, and can drive the characteristics of organic EL elements. It is. There are two types of light extraction methods: a bottom emission method that extracts light from the transparent substrate side, and a top emission method that extracts light from the opposite side of the substrate. A top emission method with a high aperture ratio increases the brightness. It is advantageous.

  The reflective electrode film in this top emission structure desirably has high reflectivity and high corrosion resistance in order to efficiently reflect light emitted from the organic EL layer. It is also desirable that the electrode has a low resistance. As such a material, an Ag alloy and an Al alloy are known. However, in order to obtain an organic EL element with higher luminance, the Ag alloy is excellent because of high visible light reflectance. Here, for the formation of the reflective electrode film on the organic EL element, a sputtering method is employed, and an Ag alloy sputtering target is used (for example, see Patent Document 1).

  By the way, Ag is a metal having high conductivity and reflectivity. In recent years, Ag has been used as a reflective electrode film of an organic EL panel taking advantage of these characteristics. A pure Ag film has high conductivity and reflectivity, but lacks corrosion resistance (particularly, sulfidation resistance) and thermal stability. Therefore, it is necessary to improve these characteristics in order to apply to the above applications. For this reason, an alloy in which In is added to Ag and a sputtering target thereof have been proposed (see, for example, Patent Documents 2 and 3).

  On the other hand, with the enlargement of the glass substrate at the time of manufacturing the organic EL element, a large Ag alloy sputtering target used for forming the reflective electrode film has come to be used. Here, in order to improve productivity, if high power is applied to a large sputtering target and sputtering is performed, abnormal discharge occurs, and a phenomenon called “splash” occurs, and molten fine particles adhere to the substrate. . As a result, there is a problem in that the fine particles cause a short circuit between wirings and electrodes and reduce the yield of the organic EL element. Since the reflective electrode layer of the top emission type organic EL element serves as a base layer of the organic light emitting layer, higher flatness is required, and splash must be further suppressed.

  In order to solve such a problem, in the Ag alloy sputtering targets of Patent Documents 2 and 3, the average grain size of the alloy crystal grains is set to 150 to 400 μm, and the variation in grain size of the crystal grains is determined by the average grain size. As a result, the splash is suppressed even when a large amount of power is supplied to the sputtering target accompanying the increase in the size of the sputtering target.

International Publication No. 2002/077317 JP 2011-100719 A JP 2011-162876 A

  In the sputtering film formation using the Ag alloy sputtering target disclosed in Patent Documents 2 and 3, the reflective electrode film can be formed while suppressing splash even when a large electric power is applied. The large Ag alloy sputtering target used here is manufactured as follows.

  First, Ag is melted in a high vacuum or an inert gas atmosphere, and a predetermined content of In is added to the resulting molten metal, and then melted in a vacuum or an inert gas atmosphere to form an Ag-In alloy. A melt cast ingot is produced. Next, in order to set the average grain size of the Ag—In alloy crystal grains to a predetermined value, the melt-cast ingot is hot forged. In hot forging, upsetting forging with a forging molding ratio of 1 / 1.2-1 / 2 is repeated while turning the forging direction by 90 degrees. The forged ingot is cold-rolled by a plurality of passes until a desired thickness is obtained to obtain a plate material. And the large-sized Ag-In alloy sputtering target is manufactured by machining, such as a milling process and electrical discharge machining, to the desired dimension, after the heat-treated board | plate material.

  However, in the above-described manufacturing method, the plate material for manufacturing the sputtering target is manufactured from an Ag-In alloy melt-cast ingot through hot forging and cold rolling processes. In the process, voids are generated. In addition, a small amount of oxygen (O) is originally present in the Ag raw material for producing the Ag—In alloy sputtering target, and further, oxygen may be taken in during the casting process. Some of these oxygens are present in solid solution in the ingot. These solute oxygens tend to be fixed at void crushing parts such as voids.

Then, oxygen in the void or solid solution oxygen in the ingot changes In to In oxide, resulting in segregation of a high resistance material around the void. This void itself is crushed in the cold rolling process to form a void crushing portion, and the inclusion of the high resistance substance remains even after the sputtering target is manufactured. There is a problem that the inclusion of the high resistance substance causes a splash phenomenon during sputtering film formation.
Because of this problem, it cannot be said that the production yield of organic EL elements is sufficiently increased, and further improvement is required.
The void crushing portion described above includes a case where the void is completely crushed and closed, and a case where the void is crushed and deformed even if the void is not completely closed.

  An object of the present invention is to provide a large Ag-In alloy sputtering target that can reduce generation of a void crushing portion included in the target as much as possible and further suppress the occurrence of splash during sputtering. .

  As described above, if one large Ag-In alloy sputtering target is to be produced from one melt-cast ingot, the generation of fine voids is unavoidable in the process of forming the cast ingot. In the Ag—In alloy sputtering target, a void crushing portion in which the void is crushed is included. Therefore, in order to further suppress the generation of splash during sputtering, it is found that the amount of oxygen present in the casting ingot should be reduced as much as possible to reduce the generation of voids and suppress the generation of void collapsed portions. was gotten.

Therefore, the present invention has been obtained from the above findings, and the following configuration has been adopted in order to solve the above problems.
(1) The Ag alloy sputtering target of the present invention contains In: 0.1 to 1.5 mass%, the balance is made of Ag and inevitable impurities, and the oxygen concentration is 50 mass ppm or less as the inevitable impurities. It is an Ag alloy sputtering target having an area ratio of a void crushing portion measured by an ultrasonic flaw detector over the entire thickness direction of the target, being 1 × 10 ⁻⁴ or less with respect to the area of the sputtering surface. Features.
(2) The Ag alloy sputtering target of (1) further contains 0.02 to 2.0% by mass of one or more of Sb, Mg, Pd, Cu, and Sn.
(3) The area of the sputtering surface of the Ag alloy plate material in the Ag alloy sputtering target according to (1) or (2) is 0.25 m ² or more.

  As described above, the composition of the Ag alloy sheet according to the Ag alloy sputtering target of the present invention contains In: 0.1 to 1.5% by mass, and the balance is made of Ag and inevitable impurities, or One or more of Sb, Mg, Pd, Cu, and Sn are contained in an amount of 0.02 to 2.0 mass%. In is easy to form an oxide film on the surface of the sputtered film, and this has the effect of improving the sulfidation resistance. However, at 0.1 or less, the sulfidation resistance is not improved, and at 1.5 or more, Since the reflectance of the formed film is lowered, the In content is preferably 0.1 to 1.5% by mass. Furthermore, by adding 0.02 to 2.0% by mass of one or more of Sb, Mg, Pd, Cu and Sn to the Ag—In alloy, the heat resistance of the formed Ag alloy thin film, Moisture resistance and corrosion resistance (sulfuration resistance, salt water resistance) are further improved, and Ag alloy thin film changes during processing after film formation (heat treatment, chemical etching, etc.) and after shipping as a product ( It is possible to further suppress deterioration of characteristics due to heat aggregation and corrosion. If these contents are less than 0.02% by mass, the above-mentioned characteristics cannot be obtained. On the other hand, if the content exceeds 2.0% by mass, the electrical properties of the formed Ag alloy thin film Resistance becomes too high or reflectivity decreases. In addition, the Ag alloy plate material according to the Ag alloy sputtering target of the present invention has an oxygen concentration of 50 ppm by mass or less, but if the oxygen concentration exceeds 50 ppm by mass, the oxidation of In formed around the void crushing part. Since the number of particles increases, it causes abnormal discharge and splash during sputtering.

  In addition, when one or more elements of Sb, Mg, Pd, Cu, and Sn are added to the Ag—In alloy, when these elements are more oxidizable than In, the elements are added to In. Instead, it reacts with the oxygen in the void or the solid solution oxygen in the ingot to act as an element oxide. Here, when one or more elements of Sb, Mg, Pd, Cu, and Sn are added to the Ag-In alloy, the heat resistance, moisture resistance, and corrosion resistance (sulfuration resistance, saltwater resistance) of the film are improved. In order to further suppress the deterioration of the characteristics due to the further improvement and the deterioration (aggregation and corrosion due to heat) of the Ag alloy film after being shipped, the added Sb, Mg, Pd, Cu and Sn are added. It is more preferable to limit the composition range for each element. Sb: 0.1-2 mass%, Mg: 0.02-0.5 mass%, Pd: 0.1-2.0 mass%, Cu: 0.2-1.5 mass%, Sn: 0.0. 1 to 2.0% by mass. When the lower limit of each range is not satisfied, the above effect cannot be obtained. On the other hand, when the upper limit of each range is exceeded, the electrical resistance of the formed Ag alloy film becomes too high, or the The reflectivity may decrease.

  As described above, the addition of one or more elements of Sb, Mg, Pd, Cu, and Sn to the Ag—In alloy is performed by sputtering using an Ag—In alloy sputtering target to which these elements are added. In the formed Ag alloy thin film, for example, heat resistance and moisture resistance can be improved by adding Sb, heat resistance and salt water resistance can be improved by adding Mg, and moisture resistance and sulfide resistance can be improved by adding Pd. It has been found that the salt water resistance can be improved by adding Cu to improve heat resistance and sulfidation resistance, and the addition of Sn can improve heat resistance, moisture resistance and sulfidation resistance.

Thus, since In oxide is formed around the void crushing portion, in the present invention, the area ratio of the void crushing portion is set to 1 × 10 ⁻⁴ or less. When the area ratio exceeds 1 × 10 ⁻⁴ , the occurrence of abnormal discharge and splash cannot be suppressed.
Moreover, normally, when the sputtering target is enlarged, problems such as abnormal discharge are likely to occur. However, according to the Ag alloy sputtering target of the present invention, even when the surface area is 0.25 m ² or more, while suppressing the splash, It is possible to form a sputtering film with a large power input, and to form a reflective electrode film.

  According to the present invention, an Ag—In alloy sputtering target capable of further suppressing abnormal discharge and splash even when a large electric power is applied during sputtering is obtained. This Ag—In alloy sputtering target, or Sb By sputtering using an Ag-In alloy sputtering target containing one or more of Mg, Pd, Cu, and Sn, the reflectivity is high, and excellent heat resistance, moisture resistance, and corrosion resistance (sulfur resistance) , A conductive film having salt water resistance) can be obtained.

The image of the ultrasonic flaw inspection which concerns on the target raw material after cold rolling and machining is shown. It is an element distribution image of each element which carried out EPMA measurement about the defect part cross section in one specific example of an Ag-In alloy sputtering target.

  Hereinafter, embodiments of the Ag—In alloy sputtering target of the present invention will be described with reference to examples.

〔Example〕
The manufacturing procedure of the Ag—In alloy sputtering target of the present invention is as follows.
First, as a raw material for producing the Ag—In alloy sputtering target of the present invention, purity: 99.99 mass% or more of Ag, purity: 99.9 mass% or more of In, and purity of 99.9 mass% of Sb, Mg, Pd, Cu and Sn were prepared.
A high-frequency vacuum melting furnace was charged with Ag, In, and one or more selected from Sb, Mg, Pd, Cu, and Sn as raw materials at the mass ratio shown in Table 1. The total mass when dissolved was about 300 kg. After evacuating the inside of the vacuum chamber, replacing Ar gas, melting Ag, adding In, and then adding any of Sb, Mg, Pd, Cu and Sn in the Ar atmosphere, Was cast into a graphite mold. Casting after melting was performed by unidirectional solidification. This unidirectional solidification is carried out by preheating the side with resistance heating while casting the bottom of the mold with water, casting molten metal into the mold, and then gradually lowering the set temperature of the resistance heating section at the bottom of the mold. did. After casting, an ingot upper portion of the ingot containing foreign matter such as an oxide film floating on the surface of the molten metal is cut and removed, and an Ag-In alloy ingot (φ290 × 370 mm) used for the next process of about 260 kg as a healthy portion; did. In the present embodiment, the melting was performed in an inert gas atmosphere, but the same effect can be obtained by melting in a vacuum atmosphere.
In the present embodiment, casting is performed by unidirectional solidification, but the same effect can be obtained by using a complete continuous casting method or a semi-continuous casting method.

  Next, in order to make the average particle diameter of the Ag—In alloy crystal grains a predetermined value, the melt cast ingot was hot forged. In hot forging, after heating at 800 ° C. for 2 hours, the forging direction is repeatedly rotated 90 degrees at a time, and the casting direction: z, z, and any direction of 90 degrees: x, z direction, and x Forging in all directions of 90 degrees direction: y. More specifically, an ingot cast into a columnar shape was first forged into a square shape. Thereafter, the square ingot was rotated 90 degrees with the previous forging direction, and forging was repeated. At this time, the rectangular ingot was rotated so as to perform forging in all the vertical, horizontal, and height directions. The forging molding ratio per one time was 1 / 1.2-1 / 2, and the upsetting forging was repeated 15 times while changing the direction. The film was expanded by the 16th forging and formed into a size of approximately 600 × 910 × 45 (mm). By repeating the forging in this way, the average particle diameter of the Ag—In alloy crystal grains of the Ag—In sputtering target was set to a desired value, and the variation in the grain diameter of the Ag—In alloy crystal grains was controlled.

  Next, the ingot after forging was cold-rolled to a desired thickness to obtain a plate material of approximately 1200 × 1300 × 16 (mm). The rolling reduction per pass in this cold rolling was 5 to 10%, and a total of 10 passes were performed. Total rolling reduction: {(thickness of ingot before cold rolling) − (thickness of ingot after cold rolling)} / (thickness of ingot before cold rolling) was 64%. After rolling, the plate material was heated and held at 600 ° C. for 2 hours, and recrystallized.

  Next, the obtained plate material was machined to a size of 1100 × 1200 × 12 (mm) to produce a large Ag—In alloy sputtering target of Examples 1 to 21.

[Comparative Example]
For comparison with the present invention, Ag-In alloy sputtering targets of Comparative Examples 1 to 6 were produced according to the same production procedure as the Ag-In alloy sputtering target of Examples 1 to 21. However, casting after melting was not performed by unidirectional solidification but by casting into a normal graphite mold. In Comparative Example 1, the amount of In added was the same as in Example 2, but the oxygen concentration in the target healthy part where no void crushing part was present was set to 80 mass ppm. In Comparative Example 2, the amounts of In and Sb added were the same as in Example 5, but the oxygen concentration in the target healthy part was set to 75 mass ppm. In Comparative Example 3, the amounts of In and Mg added were the same as in Example 8, but the oxygen concentration in the target healthy part was set to 85 mass ppm. In Comparative Example 4, the amounts of In and Pd added were the same as in Example 11, but the oxygen concentration in the target healthy part was set to 90 mass ppm. In Comparative Example 5, the amounts of In and Cu added were the same as in Example 14, but the oxygen concentration in the target healthy part was set to 70 mass ppm. Furthermore, in Comparative Example 6, the addition amounts of In and Sn were the same as in Example 17, but the oxygen concentration in the target healthy part was set to 80 mass ppm.

<Observation of void crushing part in target>
The void crushing portion remaining inside the target with an Ag-In alloy was observed using an ultrasonic flaw detector (PDS-3400, manufactured by Kraut Kramer Co., Ltd.). When the presence of void crushing in the case of casting by unidirectional solidification and in the case of normal casting was observed, the reflection that can be seen as a void crushing part in both cases of unidirectional solidification casting and normal casting Was confirmed.

<Measurement of oxygen concentration in target>
It measured about the oxygen concentration in the target in the Examples 1-21 produced as mentioned above and the Ag-In alloy sputtering target of Comparative Examples 1-6. The results are shown in Table 1.
In measuring the oxygen concentration, chips are collected from the ingot manufactured by casting as described above by machining, and the chips are analyzed by an oxygen gas analyzer (EMGA-550, manufactured by Horiba, Ltd.). The oxygen concentration was determined.

<Measurement of area ratio of void crushing part>
It measured about the area ratio of the void crushing part in Examples 1-21 produced as mentioned above and the Ag-In alloy sputtering target of Comparative Examples 1-6. The results are shown in Table 1.
In the measurement of the area ratio, flaw detection was performed over the entire surface of the sputtering target made of the Ag—In alloy using the ultrasonic flaw detection apparatus. The ultrasonic frequency at this time was 10 MHz, and the gain was 40 dB. An image having the flaw detection result shown in FIG. 1 was obtained.
In the actual image obtained by the flaw detection, the color display is performed, and the portion where the reflection of the ultrasonic wave can be detected (excluding the surface reflection and the bottom reflection) is displayed in red. In the image shown in FIG. 1, since this color image is displayed in black and white, this detected portion appears as white spots. This white spot portion was determined as a void crushing portion.
The obtained image of the flaw detection result was binarized, and the area ratio with respect to the entire void crushing portion was measured by commercially available image processing software for PC.

<Measurement of abnormal discharge times>
When sputtering film formation was performed using the Ag-In alloy sputtering targets of Examples 1 to 21 and Comparative Examples 1 to 6, the number of abnormal discharges was measured.
From the portion of the target plate material of Examples 1 to 3 and Comparative Example in which a reflection that is seen as a void crushing portion was detected, a disk having a diameter of 152.4 mm was cut out to a thickness of 6 mm by machining, and this was oxygen-free. Each of the sputtering targets for evaluation was manufactured by bonding to a copper backing plate using In solder.

  The sputtering target for evaluation was mounted on a sputtering apparatus, and sputtering discharge was performed for 1 hour under the conditions of 1000 W DC power and Ar gas pressure of 0.5 Pa. The number of abnormal discharges generated during this discharge was measured by DC. Measurement was performed using the abnormal discharge detection function installed in the power supply. The results are shown in Table 1.

<Observation of void collapsed part>
After the test, the sputtering target for evaluation was peeled off from the backing plate, cut, cut out from the portion considered to have a casting defect from the result of ultrasonic flaw detection, filled with resin, polished, and then EPMA. Cross section observation and elemental analysis (surface analysis) were performed.

  FIG. 2 shows an element distribution image of each element obtained by EPMA measurement on a defect section in a specific example of the Ag—In alloy sputtering target. According to this element distribution image, it is observed that the voids that were originally present are crushed by cold rolling or the like and become streaks as void collapsed portions. It is observed that In is segregated in the form of streaks in the defect portion, and the concentration of oxygen (O) is also high along the In streaks. From these facts, it can be seen that in the void crushing portion, segregated In is oxidized by oxygen (O) in the void and exists in a streak form as In oxide.

According to this result, in the Ag-In alloy sputtering targets of Examples 1 to 21 in which the oxygen concentration in the target is low, the area ratio of the void crushing portion is small, and the number of abnormal discharges during sputtering does not hinder DC sputtering. It was confirmed to be low.
On the other hand, in the Ag-In alloy sputtering targets of Comparative Examples 1 to 6 in which the oxygen concentration in the target is high, it is confirmed that the area ratio of the void crushing portion is large and the number of abnormal discharges during sputtering is large. There was an obstacle to sputtering.

As described above, according to the present invention, it is possible to obtain a large Ag-In alloy sputtering target in which splash can be suppressed and a reflective electrode film can be formed even when a large amount of power is applied in sputtering film formation. It was confirmed.

Claims (3)

In: an Ag alloy sputtering target containing 0.1 to 1.5% by mass, the balance being made of Ag and inevitable impurities, and having an oxygen concentration of 50 ppm by mass or less as the inevitable impurities,
An Ag alloy sputtering target, wherein the area ratio of the void crushing portion measured by an ultrasonic flaw detector is 1 × 10 ⁻⁴ or less with respect to the area of the sputtering surface in the entire thickness direction of the target.   Furthermore, 0.02-2.0 mass% of 1 or more types in Sb, Mg, Pd, Cu, and Sn is contained, The Ag alloy sputtering target of Claim 1 characterized by the above-mentioned. The Ag alloy sputtering target according to claim 1, wherein an area of the sputtering surface is 0.25 m ² or more.