TWI535876B - Silver alloy sputtering target for forming conductive film, and method for manufacturing the same - Google Patents

Description

Silver alloy sputtering target for forming conductive film and manufacturing method thereof

The present invention relates to a silver alloy sputtering target for forming a conductive film such as a reflective electrode of an organic electroluminescence (EL) element or a wiring film of a touch panel, and a method for producing the same.

The present invention claims priority based on Japanese Patent Application No. 2012-005053, filed on Jan.

In the organic EL device, a voltage is applied between the anode and the cathode formed on both sides of the organic EL light-emitting layer, and the organic EL film is injected into the positive hole by the anode, and electrons are injected from the cathode. Then, when the positive hole of the organic EL luminescent layer is combined with electrons, it emits light. The organic EL element is a light-emitting element using this light-emitting principle, and has recently attracted attention as a display device. The driving method of the organic EL element includes a passive array method and an active array method. In the active array mode, switching can be performed at high speed by providing one or more thin film transistors in one pixel. Therefore, the active matrix method is advantageous for high contrast and high definition, and is a driving method that can exhibit the characteristics of the organic EL element.

Further, the light extraction method includes a bottom emission method in which light is taken out from the transparent substrate side, and a top emission method in which light is taken out on the side opposite to the substrate, and a top emission method having a high aperture ratio is advantageous for high luminance.

The reflective electrode film of the top emission structure is to be efficiently reflected The light emitted from the organic EL layer is preferably high in reflectance and high in corrosion resistance. Further, it is preferable to use a low resistance as the electrode. As such a material, a silver alloy and an aluminum alloy are known, and in order to obtain a higher-luminance organic EL element, since the visible light reflectance is high, the silver alloy is excellent. Here, when a reflective electrode film is formed on an organic EL element, a silver alloy target is used by a sputtering method (Patent Document 1).

However, with the increase in the size of the glass substrate during the production of the organic EL element, a large-sized target has been used for the silver alloy target used for forming the reflective electrode film. Here, when sputtering is performed on a large target with high power, a phenomenon called "splash" occurs due to abnormal discharge of the target. When this occurs, the molten fine particles adhere to the substrate, causing a short circuit between the wiring or the electrodes. Therefore, there is a problem that the productivity of the organic EL element is lowered. Since the reflective electrode layer of the top emission type organic EL element is to be the lower layer of the organic light-emitting layer, higher flatness is required, and it is necessary to further suppress splash.

In order to solve such a problem, the patent document 2 and the patent document 3 propose a silver alloy target for forming a reflective electrode film of an organic EL element capable of suppressing splash even if a large amount of power is applied to the target. And its manufacturing method.

According to the silver alloy target for forming a reflective electrode film described in Patent Document 2 and Patent Document 3, it is possible to suppress splash even if large electric power is input. However, in a large silver alloy target, the number of arc discharges increases with the consumption of the target, and the splash caused by the arc discharge tends to increase. Therefore, further improvement is required. good.

In addition to the reflective electrode film for an organic EL device, a silver alloy film is also used for the conductive film such as the pull-out wiring of the touch panel. As such a wiring film, for example, when pure silver is used, short-circuit failure is likely to occur due to migration. So review the adoption of silver alloy membranes.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] International Publication No. 2002/077317

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2011-100719

[Patent Document 3] Japanese Laid-Open Patent Publication No. 2011-162876

The present invention has been made in view of such circumstances, and an object of the invention is to provide a silver alloy sputtering target for forming a conductive film which can further suppress arc discharge and splash, and a method for producing the same.

According to the results of intensive studies by the inventors of the present invention, it has been found that in order to suppress the increase in the number of arc discharges accompanying the consumption of the silver alloy target containing tin, the crystal grains are further refined to an average particle diameter of less than 120 μm. The degree is 20% or less of the average particle diameter, which is effective.

According to the related knowledge, the first aspect of the silver alloy sputtering target for forming a conductive film of the present invention is: having 0.1 to 1.5% by mass of tin, and remaining The component is composed of silver and an unavoidable impurity. The average particle diameter of the crystal grains of the alloy is 30 μm or more and less than 120 μm, and the dispersion of the particle diameter of the crystal grains is 20% or less of the average particle diameter.

Tin is solid-solubilized in silver to suppress the growth of crystal grains of the target, and is effective for refining crystal grains. Tin improves the hardness of the target, so warpage during machining is suppressed. Tin improves the corrosion resistance and heat resistance of the film formed by sputtering. When the tin content is less than 0.1% by mass, the above effect cannot be obtained. When the tin content exceeds 1.5% by mass, the reflectance or electrical resistance of the film is lowered.

The reason why the average particle diameter is 30 μm or more and less than 120 μm is as follows. An average particle diameter of less than 30 μm does not actually cause an increase in manufacturing cost. In addition, when the average particle diameter is 120 μm or more, the tendency of abnormal discharge increases with the consumption of the target during sputtering.

When the dispersion of the average particle diameter exceeds 20%, the target is consumed during sputtering, and the tendency of abnormal discharge increases.

The second aspect of the silver alloy sputtering target for forming a conductive film of the present invention is that 0.1 to 1.5% by mass of tin is contained, and one or both of yttrium and gallium are contained in a total amount of 0.1 to 2.5 mass%, and the residual portion is silver. Further, the component composition of the unavoidable impurities is such that the average particle diameter of the crystal grains of the alloy is 30 μm or more and less than 120 μm, and the dispersion of the particle diameter of the crystal grains is 20% or less of the average particle diameter.

Niobium and gallium are solid-solubilized in silver and have an effect of inhibiting the growth of crystal grains. Niobium and gallium further improve the corrosion resistance and heat resistance of the film formed by sputtering. In particular, gallium improves the salt resistance of the film.锑 and gallium content When the amount is less than 0.1% by mass, the aforementioned effects cannot be obtained. When the total content of bismuth and gallium exceeds 2.5 mass%, not only the reflectance or electric resistance of the film is lowered, but also the thermal interstitial pressure tends to be broken.

The first aspect of the method for producing a silver alloy sputtering target for forming a conductive film of the present invention is: melting by a composition having a composition containing 0.1 to 1.5% by mass of tin, a residual portion being silver, and unavoidable impurities. Casting ingots, sequentially applying a hot pressing step, a cooling step, and a mechanical processing step to produce a silver alloy sputtering target for forming a conductive film; in the hot pressing step, the rolling reduction rate per pass is 20 to 50 %, the deformation speed is 3~15/sec, and the temperature after passing the temperature is 400~650°C, and the final retouching is performed by one or more rounds; in the above cooling step, the cooling speed is 200~1000 °C/min. cool down.

The second aspect of the method for producing a silver alloy sputtering target for forming a conductive film according to the present invention is characterized in that: 0.1 to 2.5 mass of one or both of germanium and gallium is contained by 0.1 to 1.5 mass% of tin. a molten casting ingot having a percentage consisting of silver and an unavoidable impurity, and sequentially applying a hot rolling step, a cooling step, and a mechanical processing step to produce a silver alloy sputtering target for forming a conductive film; In the heat-intercalation step, the reduction ratio is 20 to 50% per one pass, the deformation speed is 3 to 15/sec, and the temperature after passing through the temperature is 400 to 650 ° C, and the final retouching heat is passed for one or more rounds. Calendering; in the aforementioned cooling step, rapid cooling at a cooling rate of 200 to 1000 ° C / min.

The reason why the reduction ratio of one pass of the final retouching heat is 20 to 50% is as follows. The reduction ratio is less than 20%, and the crystal grain becomes finer. insufficient. To obtain a reduction ratio of more than 50%, it is not practical that the load load of the calender becomes too large.

The reason why the deformation speed is 3 to 15/sec is as follows. When the deformation speed is less than 3/sec, the grain size of the crystal grains becomes insufficient, and fine particles and coarse particles tend to be mixed. A deformation speed exceeding 15/sec makes it too impractical for the load of the calender to become too large.

When the temperature after passing one round is less than 400 ° C, the dynamics are insufficient in crystal growth, and the tendency of the dispersion of crystal grains to increase becomes remarkable. When the temperature after one round of each pass exceeds 650 ° C, the crystal grain growth progresses and the average crystal grain size becomes 150 μm or more.

Then, by rapidly cooling the mixture between the heat and suppressing the growth of the crystal grains, a target of fine crystal grains can be obtained. When the cooling rate is less than 200 ° C / min, the effect of suppressing the growth of crystal grains is very poor. Even if the cooling rate exceeds 1000 ° C / min, it does not contribute to further miniaturization.

According to the aspect of the present invention, it is possible to obtain a target which can further suppress arc discharge and splash even if a large amount of electric power is applied during sputtering, and by sputtering the target, high reflectance and excellent durability can be obtained. Conductive film.

Hereinafter, a silver alloy sputtering target for forming a conductive film of the present embodiment will be described. Embodiments of the method of manufacturing the same. Further, "%" means % by mass unless otherwise specified.

The target surface of the target (the surface on the sputtering side of the target) has an area of 0.25 m ² or more. In the case of a rectangular target, at least one side is 500 mm or more, and the upper limit of the length is preferably 3000 mm from the viewpoint of the operation of the target. On the other hand, the upper limit of the width is preferably 1700 mm from the viewpoint of the upper limit of the size of the calender which can be generally used in the calendering step. Further, from the viewpoint of the frequency of exchange of the target, the thickness of the target is preferably 6 mm or more, and from the viewpoint of discharge stability of magnetron sputtering, it is preferably 25 mm or less.

The silver alloy sputtering target for forming a conductive film of the first embodiment is composed of a silver alloy having a composition of 0.1 to 1.5% by mass of tin and a residual portion of silver and unavoidable impurities. The average grain size of the crystal grains of the alloy is 30 μm or more and less than 120 μm, and the dispersion of the particle diameter of the crystal grains is 20% or less of the average particle diameter.

Silver has an effect of increasing the reflectance and reducing the electric resistance of the reflective electrode film of the organic EL element formed by sputtering or the wiring film of the touch panel.

Tin improves the hardness of the target, so warpage during machining is suppressed. In particular, warpage at the time of machining of a large target having an area of 0.25 m ² or more on the target surface can be suppressed. Further, tin has an effect of improving the corrosion resistance and heat resistance of the reflective electrode film of the organic EL element formed by sputtering. This effect is caused by the following effects. Tin makes the crystal grains in the film finer while making the surface roughness of the film small. Further, the tin solid is dissolved in silver to increase the strength of the crystal grains, and to suppress the coarsening of the crystal grains due to heat. Therefore, tin has an effect of suppressing an increase in the surface roughness of the film or a corrosion of the film to cause a decrease in reflectance. That is, the conductive electrode is used to form a reflective electrode film or a wiring film formed by sputtering a target with a silver alloy sputtering target, thereby improving the corrosion resistance and heat resistance of the film. Therefore, the silver alloy sputtering target for forming a conductive film contributes to the improvement of the luminance of the organic EL element or the improvement of the reliability of wiring such as a touch panel.

The reason why the tin content is limited to the above range is as follows. When the tin content is less than 0.1% by mass, the effect of adding tin as described above cannot be obtained. When the tin content exceeds 1.5% by mass, the electrical resistance of the film may increase, or the reflectance or corrosion resistance of the film formed by sputtering may be lowered. So not good. That is, the composition of the film depends on the target composition, so the tin content contained in the silver alloy sputtering target is set to 0.1 to 1.5% by mass. The tin content is preferably 0.2 to 1.0% by mass.

The silver alloy sputtering target for forming a conductive film according to the second embodiment has a tin-containing content of 0.1 to 1.5% by mass, and further contains 0.1 to 2.5 mass% of one or both of yttrium and gallium, and the residual portion is silver and is not It is composed of a silver alloy composed of components of impurities that are avoided. The average grain size of the crystal grains of the alloy is 30 μm or more and less than 120 μm, and the dispersion of the particle diameter of the crystal grains is 20% or less of the average particle diameter.

In the second embodiment, bismuth and gallium are solid-solubilized in silver and have an effect of suppressing the growth of crystal grains. The corrosion resistance and heat resistance of the film formed by sputtering are further improved. In particular, gallium improves the salt resistance of the film. When a film formed by sputtering is used for a pull-out wiring film of a touch panel, since the touch panel is operated by finger contact, it is necessary to have a pair of wiring films. The tolerance of the salt component contained in the sweat of the human body. By adding gallium, a film excellent in salt resistance can be formed.

When the total content of these bismuth and gallium is less than 0.1% by mass, the above effects cannot be obtained. When the total content of bismuth and gallium exceeds 2.5 mass%, not only the reflectance or electric resistance of the film is lowered, but also the thermal interstitial pressure tends to be broken.

In the embodiment of the above composition, the average particle diameter of the silver alloy crystal grains in the silver alloy sputtering target is 30 μm or more and less than 120 μm. Regarding the average particle diameter of the silver alloy crystal grains, an average particle diameter of less than 30 μm is not practical and causes an increase in manufacturing cost. Further, it is difficult to produce uniform crystal grains, and the dispersion of the particle diameter becomes large. Therefore, in the sputtering of large electric power, abnormal discharge is likely to occur, and splash occurs. On the other hand, when the average particle diameter is 120 μm or more, the target material is consumed by sputtering, and the crystal orientation of each crystal grain is different to cause a difference in sputtering rate, and the unevenness of the sputtering surface is increased. Therefore, in the sputtering of large electric power, abnormal discharge is likely to occur, and splashing is likely to occur.

Here, the average particle diameter of the silver alloy crystal grains was measured as described below.

A square sample having a side of about 10 mm was taken from the 16 points in the sputtering surface of the target. Specifically, the target is divided into 16 positions of 4 in the vertical direction and 4 in the horizontal direction, and is taken from the central portion of each part. Further, in the present embodiment, a sputtering target of 500 × 500 (mm) or more, that is, a large target having an area of 0.25 m ² or more on the target surface is used, and therefore, it is generally used from a large target. A rectangular target is used to take the sample. However, in the present invention, of course, the suppression of the occurrence of the splash of the circular target can also be exerted. In this case, according to the sample taking method of the large rectangular target, 16 places are equally divided in the sputtering surface of the target. .

Next, the side of the sputtering surface of each test piece was ground. At this time, it was ground with water-resistant paper of #180 to #4000, and then polished by abrasive grains of 3 μm to 1 μm.

Further, it is etched to the extent that the grain boundary can be seen by an optical microscope. Here, the etching liquid was immersed at room temperature for 1 to 2 seconds using a mixed solution of hydrogen peroxide and ammonia water to reveal grain boundaries. Next, for each sample, a photograph having a magnification of 60 times or 120 times in an optical microscope was used. The magnification of the photo is easy to calculate the magnification of the number of crystal grains.

In each of the photographs, the line of 60 mm was formed into a well pattern (such as symbol #), and four lines were drawn vertically and horizontally at intervals of 20 mm, and the number of crystal grains cut by the respective straight lines was calculated. Further, the crystal grains at the end of the line segment were calculated in 0.5. The average slice length L (μm) was determined by L = 60000 / (M.N) (where M is the actual magnification and N is the average of the number of crystal grains cut).

Next, the average particle diameter d (μm) of the sample was calculated from d=(3/2)‧L from the obtained average slice length L (μm).

Thus, the average value of the average particle diameters of the samples sampled at 16 points was taken as the average particle diameter of the target silver alloy crystal grains.

When the dispersion of the particle diameter of the silver alloy crystal grains is 20% or less of the average particle diameter of the silver alloy crystal grains, the splash at the time of sputtering can be more reliably suppressed. Here, the dispersion of the particle size is calculated by the following method Out. The absolute value of the deviation from the average value of the average particle diameter among the 16 average particle diameters determined at 16 (|[(average particle diameter at one place)] - (average value of average particle diameter at 16 places) )]|) Become the biggest. Next, using this specific average particle diameter (specific average particle diameter), the dispersion degree of the particle diameter was calculated by the following formula.

[(Specific average particle diameter) - (average value of average particle diameter at 16 places)]|/(average value of average particle diameter at 16 places) × 100 (%)

Next, a method of producing a silver alloy sputtering target for forming a conductive film of the present embodiment will be described.

In the method for producing a silver alloy sputtering target for forming a conductive film according to the first embodiment, tin having a purity of 99.99% by mass or more and a purity of 99.9% by mass or more are used as a raw material.

First, silver is melted in a high vacuum or an inert gas atmosphere, and a specific amount of tin is added to the obtained melt. Thereafter, it is melted in a vacuum or an inert gas atmosphere to prepare a molten cast ingot containing a silver alloy composed of 0.1 to 1.5% by mass of tin and a residual portion of silver and unavoidable impurities.

Here, the melting of silver and the addition of tin are preferably carried out in the following manner. The atmosphere was once vacuumed, and then replaced with argon gas, and silver was melted in this atmosphere. Next, tin is added to the silver melt in an argon atmosphere after the silver is melted. Thereby, the composition ratio of silver and tin is stabilized.

In the method for producing a silver alloy sputtering target for forming a conductive film according to the second embodiment, tin, germanium or gallium having a purity of 99.99% by mass or more and a purity of 0.99% by mass or more is used as a raw material. For silver melt soup, add 0.1 to 1.5 mass percent of tin, and add one or both of gallium and gallium to 0.1 ~3.0 mass%. In this case, silver is also melted in a high vacuum or an inert gas atmosphere, and a specific content of tin, antimony or gallium is added to the obtained melt, followed by melting in a vacuum or an inert gas atmosphere.

In addition, the above melting. The casting is preferably carried out in an atmosphere of vacuum or inert gas replacement, and a melting furnace may be used in the atmosphere. When a melting furnace is used in the atmosphere, an inert gas may be blown to the surface of the molten stone, or a carbon-based solid sealing material such as charcoal may be used to cover the molten surface while being dissolved. Casting. Thereby, the content of oxygen or non-metallic impurities in the ingot can be reduced.

In the melting furnace, it is preferable to use an induction heating furnace for the purpose of homogenizing the components.

Further, although it is preferable to cast a rectangular parallelepiped ingots in an angular shape, it is also possible to process a cylindrical ingot cast in a circular mold to obtain an ingot having a substantially rectangular parallelepiped shape.

The obtained rectangular parallelepiped is heated and calendered to a specific thickness, followed by rapid cooling.

In this case, the condition of the final retouching of the heat between the final stages of the inter-heat rolling is important, and by appropriately setting this final refining heat rolling, a silver alloy sheet having fine and uniform crystal grains can be produced.

Specifically, in the final finishing heat rolling, the rolling reduction rate per pass is 20 to 50%, the deformation speed is 3 to 15/sec, and the temperature after passing is 400 to 650 °C. This final finish is calendered for more than one round. The total rolling ratio of the entire inter-heat rolling is, for example, 70% or more.

Here, the so-called final retouching heat is for the rolled sheet. A calendering procedure that has a strong influence on the crystal grain size, including the final calendering procedure, and, if necessary, may be the third step from the final calendering procedure. After the final rolling, in order to adjust the thickness of the sheet, a rolling reduction of 7% or less may be applied in the rolling temperature range.

Further, the deformation speed ε (sec ^-1 ) is expressed by the following equation.

In the former formula, H ₀ : plate thickness (mm) on the entry side of the calender roll, n: calender roll rotation speed (rpm), R: calender roll radius (mm), r: reduction ratio (%), and r '=r/100.

By making the reduction rate per pass of 20 to 50% and the deformation speed of 3 to 15/sec, it is possible to carry out strong processing at a relatively low temperature by a large amount of energy. Thereby, the mixing of coarse crystal grains is prevented, and fine and uniform crystal grains are generated in the whole by dynamic recrystallization. When the reduction ratio per one pass is less than 20%, the refinement of crystal grains becomes insufficient. To obtain a reduction ratio of more than 50%, it is not practical that the load load of the calender becomes too large. Further, when the deformation speed is less than 3/sec, the grain size of the crystal grains becomes insufficient, and fine particles and coarse particles tend to be mixed. To obtain a deformation speed of more than 15/sec, it is not practical to make the load of the calender too large.

The rolling temperature after each round is calendered at a low temperature of 400 to 650 ° C. Thereby, coarsening of crystal grains can be suppressed. Calendering temperature less than 400 At °C, the dynamics of the crystal grains become insufficient, and the tendency of the dispersion of crystal grains to increase becomes remarkable. When the rolling temperature exceeds 650 ° C, the growth of crystal grains proceeds, and the average crystal grain size exceeds 120 μm.

This final final retouching heat cycle is performed by one round (趟), and multiple rounds (趟) can be performed as necessary.

The better condition for finishing the hot rolling is that the rolling reduction rate is 25~50% for each pass, the deformation speed is 5~15/sec, and the rolling temperature after one round is 500~600°C. It is preferable to carry out calender calendering for 3 or more rounds.

Further, the rolling start temperature may not be 400 to 650 ° C, and the rolling start temperature and each wheel schedule may be set so that the temperature at the end of each round of the final finishing heat rolling in the final stage is 400 to 650 ° C.

Next, after such hot-rolling processing, the temperature is rapidly cooled at a cooling rate of 200 to 1000 ° C/min from a temperature of 400 to 650 ° C, for example, to a temperature of 200 ° C or lower. By this rapid cooling, the growth of crystal grains is suppressed, and a rolled sheet of fine crystal grains can be obtained. When the cooling rate is less than 200 ° C / min, the effect of suppressing the growth of crystal grains is very poor. Even if the cooling rate exceeds 1000 ° C / min, it does not contribute to further miniaturization. As a method of quenching, it is possible to carry out watering for about 1 minute.

The rolled sheet thus obtained is corrected by a corrective extrusion, a roll leveler, and the like, and then subjected to machining such as milling processing and electric discharge machining, and finally finished to a desired size. The sputter surface of the finally obtained sputtering target preferably has an arithmetic mean surface roughness (Ra) of 0.2 to 2 μm.

In the silver alloy sputtering target for forming a conductive film of the present embodiment, the abnormal discharge can be suppressed and the occurrence of splash can be suppressed even if large electric power is applied during sputtering. By sputtering this target, a conductive film having high reflectance and excellent durability can be obtained. Further, by using the silver alloy sputtering target for forming a conductive film to perform sputtering, a conductive film having good corrosion resistance and heat resistance and further low resistance can be obtained. The special target size is effective for a large target of 500 mm wide, 500 mm long, and 6 mm thick or more.

[Examples] (Example 1)

Silver having a purity of 99.99% by mass or more is prepared, and tin having a purity of 99.9 mass% or more as an additive material is loaded into a high frequency induction melting furnace composed of graphite crucible. The total mass at the time of melting is about 1100 kg.

At the time of melting, silver was first melted, and silver was melted and dropped, and then the raw material was added so as to have a target composition shown in Table 1. The alloy melt was sufficiently stirred by the stirring effect by induction heating, followed by casting in a cast iron mold.

The shrinkage portion of the ingot obtained by the casting was cut out, and the surface of the mold was removed, and a rectangular parallelepiped shape having a rough size of 640 × 640 × 180 (mm) was obtained as a whole.

The ingot was heated to 780 ° C and repeatedly rolled in one direction from 640 mm to 1700 mm. This was rotated by 90 degrees, and then the rolling of the other side in the direction of 640 mm was repeated, and it was roughly 1700 × 2200 × 19 (mm) size plate.

This heat is rolled, and all of them are repeated for 12 rounds (趟). Among them, the final round counts the conditions of the first three rounds (趟) (deformation speed per one round, reduction rate, sheet temperature after each round) as shown in Table 1. The total rolling ratio of the inter-heat rolling is 90%.

After the hot rolling was completed, the rolled sheet was cooled under the conditions shown in Table 3.

After cooling, the sheet was passed through a roller leveller to correct deformation due to rapid cooling, and machined to a size of 1600 x 2000 x 15 (mm) to become a target.

(Examples 2 to 10, Comparative Examples 1 to 10)

In the same manner as in the first embodiment, the heating temperature of the ingot before the hot rolling was 510 to 880 ° C, the thickness after the final rolling was 9.5 to 25.6 mm, and the total number of times of the overturn was 11 to 14 (趟), and the total rolling ratio was Changed in the range of 86~95%. Next, the target composition shown in Table 3, the final wheel shown in Tables 1 and 2, the conditions of the respective wheels up to the first three rounds, and the conditions of the cooling rate after the heat-to-heat rolling shown in Table 3 were produced. The target. In Table 3, the person who describes the cooling rate is cooled by water spray, and "cooled without water" is placed only for cooling. Among them, the thickness of the machined target is in the range of 6 to 21 mm.

(Examples 11 to 13 and Comparative Example 11)

Melting and casting were carried out in the same manner as in the first embodiment, and an ingot having a rough size of 640 × 640 × 60 (mm) was produced. Heat the ingot at 680 ° C, then heat The calendering was carried out into a sheet having a rough size of 1200 × 1300 × 15 (mm).

This heat is rolled, and all of them are repeated for 6 rounds. Among them, the final round counts the conditions of the first three rounds (趟) (deformation speed per one round, reduction rate, sheet temperature after each round) as shown in Table 2. The total rolling ratio of the inter-heat rolling is 75%.

After the hot rolling was completed, the rolled sheet was cooled under the conditions shown in Table 3.

After cooling, the sheet was passed through a roller leveller to correct deformation due to rapid cooling, and machined to a size of 1000 × 1200 × 12 (mm) to become a target.

(Examples 14 to 21, Comparative Examples 12 to 14)

Silver having a purity of 99.99% by mass or more and tin, antimony or gallium having a purity of 99.9 mass% or more as an additive raw material are prepared. In a high-frequency induction melting furnace composed of graphite crucible, silver is first melted, silver is melted and dropped, and then a raw material is added so as to have a target composition shown in Table 3. The alloy melt was sufficiently stirred by the stirring effect by induction heating, followed by casting in a cast iron mold.

In these Examples 14 to 21 and Comparative Examples 12 to 14, after casting, in the same manner as in the above-described Examples 11 to 13 and Comparative Example 11, the size of the ingot obtained by casting was approximately 640 × 640 × 60 ( Ingots of mm). Subsequently, the ingot was heated to 680 ° C, and then hot-rolled in the same manner as described above to obtain a sheet having a rough size of 1200 × 1300 × 15 (mm).

This heat is rolled, and all of them are repeated for 6 rounds. Among them, the most The conditions of the first three rounds (趟) of the final wheel (deformation speed, reduction ratio, and sheet temperature after each round) are shown in Table 2. The total rolling ratio of the inter-heat rolling is 75%. Next, it was cooled under the conditions shown in Table 3. Next, the sheet material was passed through a roller leveller to correct deformation due to rapid cooling, and machined to a size of 1000 × 1200 × 12 (mm) to become a target.

The warpage, the average particle diameter, and the dispersion thereof after the mechanical processing were measured for the obtained target. Further, the target was mounted on a sputtering apparatus to measure the number of abnormal discharges at the time of sputtering. Further, the surface roughness, the reflectance, the salt resistance, and the specific resistance of the conductive film obtained by sputtering were measured.

(1) Warpage after machining

The amount of warpage per one meter length was measured for the silver alloy sputtering target after machining, and the results are shown in Table 4.

(2) Average particle size, dispersion

The particle size of the silver alloy crystal grains was measured by the method described in the aspect of the invention. Specifically, samples were taken uniformly at 16 locations of the target manufactured as described above, and the average particle diameter of the appearance surface was measured from the sputtering surface of each sample. Next, the average particle diameter of the silver alloy crystal grains of the average value of the average particle diameter of each sample and the dispersion degree of the average particle diameter of the silver alloy crystal grains were calculated.

(3) Abnormal discharge times during sputtering

From any part of the target manufactured as described above, a circular plate having a diameter of 152.4 mm and a thickness of 6 mm was cut out and welded to a back plate made of copper. This welded target was used as a target for evaluation of splash at the time of sputtering, and the number of abnormal discharges during sputtering was measured.

In this case, the welded target is mounted on a conventional magnetron sputtering apparatus and exhausted to 1 × 10 ^-4 Pa. Next, sputtering was performed under the conditions of Ar gas pressure: 0.5 Pa, input power: DC 1000 W, and distance between target substrates: 60 mm. The number of abnormal discharges generated in the initial 30 minutes of use was measured. In addition, the exchange of blank sputtering and the anti-adhesion plate for 4 hours was repeated, and the target was consumed by intermittently performing sputtering for 20 hours. Thereafter, sputtering was further performed, and the number of abnormal discharges generated within 30 minutes after consumption (20 hours of sputtering) was measured. The number of these abnormal discharges was measured by the arc count function of a DC power source (model: RPDG-50A) manufactured by MKS Instruments.

(4) Evaluation of basic characteristics as a conductive film (4-1) Surface roughness of the film

Using the above-mentioned evaluation target, sputtering was performed under the same conditions as described above, and a silver alloy film having a film thickness of 100 nm was formed on a glass substrate of 20 × 20 (mm). Further, in order to evaluate heat resistance, the silver alloy film was subjected to heat treatment at 250 ° C for 10 minutes. Thereafter, the average surface roughness (Ra) of the silver alloy film was measured by an atomic force microscope.

(4-2) Reflectance

A silver alloy film was formed on the glass substrate of 30 × 30 (mm) in the same manner as described above. Next, the absolute reflectance of the silver alloy film at a wavelength of 550 nm was measured by a spectrophotometer.

Further, in order to evaluate the corrosion resistance, the silver alloy film was kept at a constant temperature and high humidity bath at a temperature of 80 ° C and a humidity of 85% for 100 hours. Thereafter, the absolute reflectance of the silver alloy film at a wavelength of 550 nm was measured by a spectrophotometer.

(4-3) Salt tolerance

In order to confirm the effect of adding gallium, a target of adding gallium (Examples 18 to 21, Comparative Examples 13 and 14) was used to form a silver alloy film in the same manner as described above. Next, a 5 wt% aqueous solution of sodium chloride was sprayed on the film surface of the silver alloy film. The spray was carried out in a direction parallel to the film surface at a height of 20 cm from the film surface and 10 cm from the substrate end, and the sodium chloride aqueous solution sprayed on the film was allowed to fall freely and adhered to the film. The spray was sprayed 5 times every 1 minute, and then rinsed 3 times with pure water. Spray dry air to blow off moisture for drying.

The silver alloy film surface was visually observed after the salt water spray described above, and the state of the surface was evaluated. As a criterion for evaluation of salinization resistance, the target could not be confirmed as turbid or speckled or only a part could be confirmed as "good". Those who are white turbid or spotted can be fully confirmed and evaluated as "bad". Thereby, the state of the surface is evaluated in two stages. For the target to which no gallium is added, no evaluation is performed, so the table is indicated by "-".

(4-4) specific resistance of the film

The specific resistance of the silver alloy film formed by the film formation was measured in the same manner as above.

The results of these evaluations are shown in Tables 4-6.

In the target material of the embodiment, the average particle diameter of the silver alloy crystal grains is in the range of 30 μm or more and less than 120 μm, and the dispersion of the particle diameter of the silver alloy crystal grains is within 20% of the average particle diameter of the silver alloy crystal grains. The warpage after machining is also small, and the number of abnormal discharges during sputtering is small at the beginning of use and after consumption. Further, the target in which yttrium and gallium are added tends to have a smaller average crystal grain size, and the number of abnormal discharges is as small as one or less. However, the target in which the amount of lanthanum and gallium added was too large (total of more than 2.5 mass%) was broken at the end of the final heat treatment, and the warpage could not be measured.

Further, the conductive film obtained by the target material of the examples was excellent in reflectance and specific resistance, and the surface roughness Ra was also 2 μm or less, which was considerably small.

Further, the conductive film obtained by adding a target of gallium is excellent in salt resistance, and it is known that it can be effectively applied to a conductive film such as a touch panel.

Further, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

[Industrial use possibility]

When the target of this embodiment is sputtered, the occurrence of arc discharge and splash is suppressed. Further, the conductive film obtained by sputtering the target of the present embodiment is excellent in reflectance and specific resistance, and has a small surface roughness. Therefore, the target of the present embodiment can be suitably applied to a target for forming a conductive film such as a reflective electrode of an organic electroluminescence (EL) element or a wiring film of a touch panel.

Claims (4)

A silver alloy sputtering target for forming a conductive film, which is characterized in that it has a composition of 0.1 to 1.5% by mass of tin containing an element dissolved in silver, a residual portion of silver and an unavoidable impurity, and crystal grains of the alloy The average particle diameter is 30 μm or more and less than 120 μm, and the dispersion of the particle diameter of the crystal grains is 20% or less of the average particle diameter. A silver alloy sputtering target for forming a conductive film, characterized in that it has 0.1 to 1.5% by mass of tin containing an element dissolved in silver, and further contains one or both of cerium and gallium which are solid-soluble in silver. 0.1 to 2.5 mass%, the residual portion is composed of silver and unavoidable impurities. The average particle diameter of the crystal grains of the alloy is 30 μm or more and less than 120 μm, and the dispersion of the particle diameter of the crystal grains is an average particle diameter. 20% or less. A method for producing a silver alloy sputtering target for forming a conductive film, characterized by: a molten casting ingot comprising a composition comprising 0.1 to 1.5 mass% of tin, a residual portion of silver, and unavoidable impurities, The hot-rolling step, the cooling step, and the mechanical processing step are applied to produce a silver alloy sputtering target for forming a conductive film. In the heat-calendering step, the rolling reduction rate per pass is 20 to 50%, and the deformation speed is It is 3 to 15/sec, and the temperature after passing through the temperature is 400 to 650 ° C, and the final finishing heat rolling is performed for one or more rounds; in the cooling step, the cooling is rapidly performed at a cooling rate of 200 to 1000 ° C / min. A method for producing a silver alloy sputtering target for forming a conductive film, characterized in that: 0.1 to 2.5 mass% of the total or both of yttrium and gallium is contained in 0.1 to 1.5 mass% of tin, and the remainder is A molten casting ingot composed of a component composed of silver and an unavoidable impurity is sequentially subjected to an inter-heat rolling step, a cooling step, and a mechanical processing step to produce a silver alloy sputtering target for forming a conductive film, and calendering between the heats In the step, the reduction ratio is 20 to 50% per one pass, the deformation speed is 3 to 15/sec, and the temperature after passing through the temperature is 400 to 650 ° C, and the final retouching is performed by one or more rounds; The cooling step is rapidly cooled at a cooling rate of 200 to 1000 ° C / min.