JP2015059268A - Plate-shaped sputtering target, and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plate-shaped sputtering target made of a ceramic less likely to generate abnormal discharge, and having high productivity, and to provide a production method thereof.SOLUTION: A plate-shaped sputtering target is formed by bonding rear faces 3 of at least two plate-shaped sintered bodies 1 made of a ceramic and a backing plate 4 with a soldering material 6 for the rear face. In the sputtering target, the end faces 2 of the sintered bodies are bonded with a soldering material 5 for the end face having a higher melting point than the soldering material for the rear face, and the interval of a division part is below 0.1 mm, and the arithmetic average roughness of each end face 2 of bonding parts of the plate-shaped sintered bodies 1 is 1 μm or less, and the maximum height is 10 μm or lower.

Description

  The present invention relates to a flat plate sputtering target made of ceramics.

  The sputtering target made of ceramics is difficult to produce a large sintered body because of its low strength compared to a metal target. When producing a large target, a plurality of ceramic sintered bodies ( Hereinafter, a method of manufacturing a single large target by bonding a sintered body) to a metal backing plate is common.

  In a sputtering target in which such a plurality of sintered bodies are bonded to a backing tube, an interval of about 0.2 to 0.8 mm is usually provided between adjacent sintered bodies. This is because the surface of the sintered body is heated and expanded during sputtering, so that adjacent sintered bodies do not collide with each other to cause cracks or chips. This part having a certain interval is called a divided part.

  However, the stepped shape of the divided portion induces abnormal discharge during sputtering and easily generates particles. Therefore, film defects such as pinholes are generated in the manufactured film, causing a decrease in yield. Therefore, it has been strongly desired to develop a sputtering target in which the divided portion does not affect the film.

  Further, in Patent Document 1, a ceramic material having the same composition as the sintered body is interposed between a plurality of sintered bodies as a target with a small amount of impurities from the divided portion, and the ceramic material is sintered. Shows a method of joining sintered bodies. However, in this method, the sintered body once fired at 1000 ° C. or more must be heat-treated again at 1000 ° C. or more after interposing ceramics in the divided portion, which has a drawback that the process is complicated and the cost is increased. .

  Patent Document 2 discloses a method in which an alloy having a higher melting point than the bonding material of the sintered body and the backing plate is present in the divided portion as a method in which abnormal discharge is unlikely to occur in the vicinity of the divided portion. However, since the sintered body is repeatedly heated and cooled during sputtering, the interval between the divided portions also repeatedly increases and decreases. If the alloy is simply filled in the divided portions, the sintered body and the alloy are used after a long period of use. A gap was generated between them, causing abnormal discharge.

JP 59-20470 A JP 2000-144400 A

  An object of the present invention is to provide a flat plate sputtering target made of ceramics and a method of manufacturing the same, which is less likely to cause abnormal discharge from a divided portion and has high productivity.

  In order to solve the above-mentioned problems, the present inventors have conducted a detailed analysis of a ceramic flat plate sputtering target, and have considered the causes of cracks in the sintered body, abnormal discharge, and film composition changes. As a result, as shown in FIG. 1, by joining the end face 2 of the adjacent flat plate-type sintered body 1 with the end face solder material 5, even in the flat plate target used at high power, It was found that no cracking occurred. In addition, when the distance between the end faces 2 after joining with the end face solder material 5 (hereinafter sometimes referred to as the interval between the divided portions) becomes less than 0.1 mm, the occurrence of abnormal discharge rapidly decreases, and sputtering causes It was found that the composition change of the produced film was small. Further, the end face solder material 5 is made of a material having a higher melting point than that of the back surface solder material 6 used for joining the back surface 3 of the flat plate sintered body and the backing tube 4, thereby making the flat plate sputtering made of ceramics extremely simple. The present inventors have found that a target can be manufactured and have completed the present invention.

Aspects of the present invention are as follows.
(1) In the flat-plate-type sputtering target formed by joining the back surface of the flat plate-shaped sintered body and the backing plate with the back-surface solder material, the end surfaces of at least two flat-plate-shaped sintered bodies are more than the back-surface solder material. A ceramic flat plate sputtering target, which is joined with a solder for an end face having a high melting point, and the interval between the divided portions is less than 0.1 mm.
(2) The arithmetic mean roughness (Ra) of each end face of the joint portion of the flat plate-shaped sintered body is 1 μm or less, and the maximum height (Ry) is 10 μm or less. Sputtering target.
(3) The sputtering target according to (1) or (2), wherein each end face of the joined portion of the flat plate-like sintered body has a mirror finish.
(4) The sputtering target according to any one of (1) to (3), wherein the bonding strength between the sintered bodies bonded at the end faces is 1 MPa or more.
(5) At least two or more flat plate-shaped sintered bodies are bonded and solidified with an end face solder material, and then the sintered body and a backing plate are joined using a back surface solder material. (4) The manufacturing method of the sputtering target in any one of.

  Hereinafter, the present invention will be described in detail.

  In the present invention, the end faces of at least two or more flat plate-shaped sintered bodies are joined with an end face solder material having a melting point higher than that of the solder material, and the interval between the divided portions is less than 0.1 mm. The present invention relates to a ceramic flat plate sputtering target.

The flat sintered body used in the present invention is not particularly limited as long as it is a ceramic, but for example, as a transparent conductive film material, ITO (indium, tin oxide), AZO (aluminum, zinc oxide), IZO (indium, zinc oxide) Material). In addition, a semiconductor material such as IGZO (indium, gallium, zinc oxide) has a great influence on the film quality due to abnormal discharge at the divided portion, and the present invention is particularly effective. Furthermore, it is also suitable for optical materials such as TiO ₂ (titanium oxide), Nb ₂ O ₅ (niobium oxide), and SiO ₂ (silicon oxide).

  The density of the sintered body is not particularly limited, but when the density is low, chipping and cracking are likely to occur due to the processing of the end face of the flat plate-like sintered body, and the split portion of the end face solder material in the present invention Sealing tends to be insufficient. Further, if the density is low, the flatness of the end face of the sintered body is deteriorated, so that sealing is still insufficient. Therefore, the density is preferably 90% or more, and more preferably 95% or more.

  The thickness of the flat sintered body used in the present invention is not particularly limited, but is preferably 3 mm or more and 15 mm or less. If it is thinner than 3 mm, the target utilization rate is low and not economical. Further, the area of the end face of the sintered body is small, and sealing at the end face tends to be insufficient. If the thickness is greater than 15 mm, uneven density of the sintered body is likely to occur, and it is difficult to obtain a target having uniform quality up to the central portion.

  As for the end face of the flat sintered body used in the present invention, the smaller the arithmetic average roughness (Ra) and the maximum height (Ry), the stronger the bonding strength with the end face solder material, which is preferable. Ra is preferably 1 μm or less, and more preferably 0.5 μm or less. Further, it is desirable to have a mirror finish. Ry is preferably 10 μm or less, more preferably 5 μm or less, and particularly preferably 0.5 μm or less.

  The surface roughness of the inner and outer surfaces of the sintered body is not particularly limited, but it is not economical to reduce the surface roughness because it takes a long time to grind, and there is no problem even if Ra is 1 μm or more.

  The length of the sintered body is not particularly limited as long as it can be handled, but it is preferably as long as possible to reduce the number of divided parts, and the length of the long side of the sintered body is preferably 100 mm or more, 200 mm The above is more preferable.

  In the present invention, the interval between the divided portions is less than 0.1 mm. More preferably, it is less than 0.01 mm. The space | interval of a division part refers to the distance of the end surfaces of the flat plate-shaped sintered compact after joining with the solder material for end surfaces.

  Next, the manufacturing method of the sputtering target of this invention is demonstrated for every process.

(1) Flat-plate-shaped sintered body manufacturing process The flat-plate-shaped sintered body manufacturing method can be appropriately selected from a molding method and a firing method suitable for the sintering behavior of the raw material powder, and is not particularly limited. Absent. The molding method is not particularly limited, and a molding method capable of molding the raw material powder into a desired shape can be appropriately selected. Examples of the molding method include a press molding method, a casting molding method, and an injection molding method. The density of the molded body is not particularly limited, but the higher the density, the fewer the cracks of the molded body due to handling, and the higher the density of the sintered body after firing, the higher the density possible. preferable. Therefore, it is also possible to use a method such as cold isostatic pressing (CIP) molding. Examples of the firing method include an electric furnace, a gas furnace, HIP (isotropic hot press), HP (hot press), and a microwave furnace.

  The obtained sintered body is ground into a flat plate shape using a machining machine such as a surface grinder, a cylindrical grinder, a lathe, a cutting machine, or a machining center.

  Moreover, it is preferable to chamfer the outer peripheral end surface of the flat plate-shaped sintered body used in the present invention. This is because ceramics are highly brittle, so that sharp portions are easily cracked, and sharp end surfaces are likely to be cracked when the target surface is heated and expanded during sputtering. If the chamfering is large, the life of the target is reduced, so R1 or less and C1 or less are preferable. More preferably, R0.5 or less and C0.5 or less are preferable. More preferably, thread chamfering is preferable.

(2) Joining process of end face of flat plate-shaped sintered body Next, an end face solder material is applied to the end face of the flat plate-shaped sintered body. The end face solder material used here must be higher than the melting point of the back face solder material. If a solder material lower than the melting point of the back surface solder material is used, each end surface is heated to a temperature equal to or higher than the melting point of the end surface solder in the process of joining the sintered body and the backing plate using the back surface solder material. This is because the sintered body joined in step 1 is peeled off.

  Moreover, it is preferable that the solder material used for joining of a division part is a material with higher heat conductivity and electrical conductivity than a sintered compact. Because the heat and electricity generated during sputtering are conducted and joined to the adjacent sintered bodies, the sintered bodies exhibit the same characteristics as a single sintered body, so the crack prevention effect of the sintered body is enhanced. It is.

  The material of the end face solder material and the back face solder material is not particularly limited as long as the melting point satisfies the above conditions. For example, tin, tin / silver and tin / copper solders are used as the end face solder material. In addition, indium, indium-based and tin / bismuth-based solder materials can be used as the backside solder material. Further, it is desirable to select a material contained in the film for the end face solder material in order to reduce the influence of impurities on the film.

  A method of applying the end face solder material to the end face of the sintered body is not particularly limited, and for example, a soldering iron, an ultrasonic soldering iron, a plating method, a sputtering method, a vapor deposition method, or the like can be used. When the wettability between the solder material and the end face of the sintered body is poor, it is preferable to clean the end face before applying the solder material. Examples of the cleaning method include acid cleaning, alcohol cleaning, and UV cleaning. Moreover, you may form the thin base layer for wettability improvement and adhesive force improvement in a sintered compact end surface.

  The thickness of the end face solder is preferably 80 μm or less, more preferably 50 μm or less, and particularly preferably 10 μm or less. If the thickness is 80 μm or less, the solder material mixed into the film substantially decreases to a negligible level. However, if the thickness of the end face solder is smaller than twice the maximum height (Ry) of the sintered body end face, sufficient adhesive strength may not be obtained. .

  Next, as shown in FIG. 1, the plurality of sintered bodies coated with the end face solder material are placed so that the end portions are in contact with each other, and are firmly adhered to each other using a jig or the like. In this state, the solder is heated to the melting point of the solder for the end face to melt the solder at one end, and then cooled to completely bond the sintered bodies together. In the present invention, the presence of solder is not sufficient, and it is necessary to bond completely. The bonding strength is not particularly limited, but is preferably 1 MPa or more so as not to be peeled off during sputtering.

(3) Joining process of flat plate-shaped sintered body back surface Next, an assembly of sintered bodies obtained by joining the backing plate and the plurality of sintered bodies is joined by a solder material for the back surface. In the bonding method, the backing plate, the back surface solder material, and the sintered body bonded to each other end surface are heated so that the temperature is not lower than the melting point of the back surface solder material and not higher than the end surface solder material. Thereafter, a solder material for the back surface is arranged between the sintered body and the backing plate, and is cooled and solidified to join the sintered body and the backing plate.

  Although the material of a backing plate is not specifically limited, Materials, such as titanium and SUS, are illustrated. Titanium is preferable because it has a thermal expansion coefficient close to that of a ceramic material.

  The back surface of the sintered body and the surface of the backing plate may have been subjected to pretreatment such as UV irradiation cleaning treatment or wettability improvement treatment with ultrasonic soldering iron in order to improve solder wettability. .

  In this method, the portion indicated by (7) in FIG. 1 is brought into contact with the already-solidified end face solder material and the molten back surface solder material. However, since the end face solder material is solidified, a thin oxide film is formed on the surface. Therefore, in order to prevent the end face solder material and the back surface solder material from directly contacting each other, both the solder materials are in contact with each other. Crystal formation can be prevented.

  Since the interval between the divided parts produced by the present invention is less than 0.1 mm, there is little abnormal discharge in sputtering and the amount of the end face solder material is very small, so there is almost no influence of impurities on the film.

  Further, a simple metal such as indium or tin can be used for the solder material, and it is not necessary to use a complicated alloy for adjusting the melting point. Moreover, since it is not necessary to fill the gap between the divided portions with an alloy after forming the divided portions, the operation is extremely simple, and the target can be manufactured at low cost.

  By using the ceramic flat plate sputtering target of the present invention, it is expected that abnormal discharge due to sputtering is reduced and that impurities are mixed into a film obtained by sputtering.

It is a figure which shows the cross section of the flat plate target made from ceramics.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

Example 1
A flat plate IGZO sintered body (density 97%, atomic composition ratio In: Ga: Zn = 1: 1: 1) was prepared, and two sintered bodies having a size of 64 mm × 254 mm and a thickness of 6 mm were prepared using a surface grinder. Got ready. The arithmetic average roughness (Ra) of the sintered body end face was 0.1 μm, the maximum height (Ry) was 0.7 μm, the rear face Ra was 1.6 μm, and Ry was 10.6 μm.

  Next, the sintered body was washed with pure water with an ultrasonic cleaner to remove impurities, and after drying, the end surfaces and the back surface of the sintered body were irradiated with UV to decompose and remove organic substances. A portion other than the short-side end where the sintered bodies were joined was covered with a masking tape, and a 2 μm tin film was formed on the end by sputtering. The melting point of tin is 231.9 ° C., the thermal conductivity is 66.8 W / (m · K), the electrical resistivity is 150 nΩcm, the thermal conductivity of IGZO is 4 W / (m · K), and the electrical resistivity is 0.02 Ωcm. In comparison with the above, the thermal conductivity is remarkably high and the electrical resistivity is remarkably low.

  Next, the end surfaces of the short sides of the sintered body were butted together and firmly fixed with a jig. The sintered body assembly was heated at 270 ° C. for 30 minutes, then cooled to 160 ° C., and the divided portions were firmly joined to form an assembly.

  Next, indium (melting point 157 ° C.) was placed on a backing plate made of oxygen-free copper and heated to 160 ° C. to melt indium on the backing plate. The assembly of the sintered body was placed while being slid gradually so as to have a constant indium thickness, cooled and solidified, and the sintered body and the backing plate were joined to produce a flat plate type IGZO sputtering target. Table 1 shows the result of observation of the interval between the divided portions with an optical microscope.

The target thus produced was evaluated by sputtering. The sputtering conditions are shown below. Table 1 shows the arcing numbers. From the sputtered film, no impurity components such as Sn were observed from the divided portions.
(Sputtering conditions)
Power supply: DC power supply MDX (5kW)
Magnetic field: 500G
Rotation speed: 6rpm
Pressure: 0.35 Pa
Examples 2-4
As a sintered body, an ITO sintered body (density 99%, weight composition ratio In ₂ O ₃ : SnO ₂ = 90: 10) and a flat plate AZO sintered body (density 99%, weight composition ratio ZnO: Al ₂ O ₃ = 98: 2) were used to produce flat ITO sputtering targets and flat AZO sputtering targets, respectively. Each target was produced by the same manufacturing method as in Example 1 except for the thickness of the sintered body and / or the end face solder material. Table 1 shows the interval between the divided portions and the results of sputtering evaluation observed with an optical microscope. From the sputtered film, no impurity components such as Sn were observed from the divided portions, and no cracks in the sintered body occurred.

Comparative Examples 1-5
Using the same IGZO sintered body, ITO sintered body, and AZO sintered body as those in the example, a target was prepared in the same manner as in the example except for the method described in Patent Document 1 and the thickness of the end face solder material. Table 1 shows the interval between the divided portions and the results of sputtering evaluation observed with an optical microscope. From the sputtered film, some cracks were observed due to the generation of indium particles of the backside solder material component that seemed to jump out of the split part, and interference between sintered bodies due to thermal expansion during sputtering. .

Comparative Example 6
A flat plate IGZO sintered body (density 97%, atomic composition ratio In: Ga: Zn = 1: 1: 1) similar to that of Comparative Example 1 was prepared, and was 64 mm × 254 mm and 6 mm thick using a surface grinder. Two sintered bodies were prepared. The arithmetic average roughness (Ra) of the sintered body end face is 0.1 μm, the maximum height (Ry) is 0.7 μm, the rear face Ra is 1.6 μm, and Ry is 10.6 μm. Thus, a sputtering target having a spacing of 0.3 mm between the divided parts was produced.

  Next, a low-melting point alloy material to be filled in the divided portion was produced. Gallium, tin, and indium were mixed at a ratio of 62.5Ga: 21.5In: 16.0Sn (weight ratio) as a eutectic point at 120 ° C. to obtain a low-melting-point alloy that was liquid at room temperature. Next, a commercially available 20 wt. A copper-tin alloy powder containing% tin was used and further pulverized to obtain a fine powder. The average particle size of the obtained alloy powder was 30 μm. Then, 50.0 parts by weight of the obtained low melting point alloy and 44.5 parts by weight of the alloy powder were mixed at room temperature to form a paste, and filled into the divided parts of the flat plate target to prepare a flat plate type IGZO sputtering target. The paste solidified completely after 48 hours.

  Table 1 shows the distance between the divided portions observed with an optical microscope and the number of arcing by sputtering. In this comparative example, by heating the target surface during sputtering, each flat plate sintered body independently repeats severe expansion and contraction, and as a result, the sintered bodies contact each other at the clearance portion, and a large number of the vicinity of the clearance. Chipping occurred and an increase in the number of arcs was observed. In addition, cracks occurred in the target that was thought to be due to this contact. Moreover, generation | occurrence | production of the particle | grains considered to jump out of the alloy composition interposed in the division part was also confirmed.

DESCRIPTION OF SYMBOLS 1 Flat plate sintered body 2 End surface of sintered body 3 Back surface of sintered body 4 Backing plate 5 Solder material for end surface 6 Solder material for back surface 7 Contact part of solder material for end surface and solder material for back surface

Claims (5)

In the flat plate sputtering target formed by joining the back surface of the flat plate sintered body and the backing plate with the back surface solder material, the end surfaces of at least two flat plate sintered bodies have a melting point higher than that of the back surface solder material. A ceramic flat plate sputtering target characterized in that it is joined by a soldering material for an end face, and the interval between the divided portions is less than 0.1 mm. 2. The sputtering target according to claim 1, wherein the arithmetic average roughness (Ra) of each end face of the joint portion of the flat plate-shaped sintered body is 1 μm or less and the maximum height (Ry) is 10 μm or less. . 3. The sputtering target according to claim 1, wherein each end face of the joined portion of the flat plate-like sintered body has a mirror finish. The sputtering target according to any one of claims 1 to 3, wherein the bonding strength between the sintered bodies bonded at the end faces is 1 MPa or more. The sintered body and the backing plate are joined using a back surface solder material after at least two or more flat plate sintered bodies are bonded and solidified with an end surface solder material. A method for producing a sputtering target according to claim 1.

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