JP4000813B2 - Sputtering target - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ITO sputtering target used in the production of a transparent conductive thin film, and more particularly to a single wafer sputtering target in which a plurality of target members are joined on a single backing plate.
[0002]
[Prior art]
ITO (Indium Tin Oxide) thin film has characteristics such as high conductivity and high transmittance, and can be easily finely processed. Therefore, display electrodes for flat panel displays such as liquid crystal displays (LCDs) and PDPs (Plasma Displays) It is used for. The manufacturing method of the ITO thin film can be roughly divided into chemical film forming methods such as spray pyrolysis and CVD, and physical film forming methods such as electron beam evaporation and sputtering. In particular, sputtering using an ITO target is easy to increase in area, has little change over time in the resistance value and transmittance of the resulting film, and can easily control film forming conditions, so that many production lines can be used. It is adopted in.
[0003]
The ITO thin film manufacturing apparatus is roughly classified into two types: a single wafer type (stationary facing type) and an inline type (substrate passing type). Of these, the single-wafer type apparatus is in the limelight because it generates less foreign matter (particles).
[0004]
With the recent increase in size of flat panel displays, the size of glass substrates used for panel manufacture has also increased. For this reason, the size of the target used in manufacturing the thin film is increasing in accordance with the substrate size. In the target for the stationary facing sputtering apparatus, it is necessary to make the target size one size larger than the substrate size. Therefore, each side of the target size exceeds 800 mm.
[0005]
When producing such a large ITO target, the production equipment required for molding and sintering is larger than conventional products, so new capital investment is required and the moldability of the powder increases with the increase in size. Deterioration deteriorates the yield, and as a result, the manufacturing cost and productivity of the target deteriorate. For this reason, in the long target, a multi-division target in which a plurality of target members are joined on a backing plate is used.
[0006]
The bonding step for bonding the ITO sintered body to the backing plate is performed by heating the sintered body and the backing plate to the melting point or higher of the solder material, bonding using the solder material, and then cooling. During this cooling process, there was a problem that warpage and cracking occurred due to the difference in thermal expansion coefficient between the sintered body and the backing plate.
[0007]
Further, there has been a problem that cracks are generated due to warpage generated when the evacuation is performed after the completed target is attached to the sputtering apparatus and thermal stress generated during sputtering. If the target is cracked, it cannot be used for sputtering, which causes an important problem such as causing the production line to stop.
[0008]
Such a cracking problem of the target has become prominent as the target size increases. In order to solve these target cracking problems, a proposal has been made to define the grinding direction of the target surface and to reduce the surface roughness after grinding to 5 μm or less (Japanese Patent Laid-Open No. 2001-26863). This proposal is effective for a long-type in-line sputtering apparatus in which the warping direction of the target is one direction. However, a single-wafer sputtering apparatus with a target shape close to a square is not very effective because the difference between the major axis and minor axis is small and warpage occurs in either direction. For this reason, it has been desired to develop a crack prevention measure that is effective even for a target for a large single-wafer sputtering apparatus.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to attach a single-wafer ITO sputtering target whose minor axis is 0.7 to 1.0 times the major axis to the apparatus, and generate a target when evacuating and / or performing sputtering. It is in providing the ITO sputtering target which can suppress the crack of this effectively.
[0010]
[Means for Solving the Problems]
The present inventors have studied to prevent target cracking in a single-wafer ITO sputtering target having a minor axis 0.7 to 1.0 times the major axis. As a result, it was found that (1) the strength of the ITO sintered body was increased and (2) the target structure capable of absorbing the stress applied to the target was able to suppress the occurrence of cracks in the above problems. Specifically, by using a sintered body having a Vickers hardness, a three-point bending strength within a predetermined range, and by setting the thickness of the solder layer joining the sintered body and the backing plate to an appropriate thickness. The present invention has been completed by finding that the above problems can be solved.
[0011]
That is, the present invention is a multi-division target in which a plurality of sintered bodies substantially made of indium, tin, and oxygen are joined on a single backing plate, and the minor axis of the target is 0.7 to 1 having a major axis. In a single-wafer sputtering target of 0.0 times, the sintered body has a Vickers hardness of 700 to 800, and a load is applied in parallel with the grinding direction of the grinding applied to the surface to be the sputtered surface of the sintered body. The present invention relates to a sputtering target characterized in that the measured three-point bending strength is 200 MPa or more and 250 MPa or less, and the thickness of the solder layer that joins the sintered body and the backing plate is 0.5 mm or more and 1 mm or less.
[0012]
In addition, the grinding direction of the grinding process is a moving direction of the blade edge at the time of grinding, specifically, for example, a direction of a streak-like grinding mark formed on the surface of the sintered body. In the measurement of the three-point bending strength, the measurement is performed by applying a load in parallel with the grinding direction by adding the power point of the three-point bending test in parallel with the grinding direction. It means that the straight line connecting the force points is parallel to the grinding direction.
[0013]
A single-wafer target as the object of the present invention is generally rectangular or rectangular. The shape conforming to the rectangle includes a case where each corner of the rectangle is subjected to R processing. As such a single-wafer type target size, 810 mm × 910 mm can be exemplified, and for example, as shown in FIG. 1, 270 mm × 455 mm sintered bodies are divided into three rows in two rows. ing.
[0014]
Hereinafter, the present invention will be described in detail.
[0015]
Although the ITO sintered compact used for this invention and its manufacturing method are not specifically limited, For example, it can manufacture with the following methods.
[0016]
First, an ITO molded body is manufactured by adding a binder or the like to a mixed powder of indium oxide powder and tin oxide powder and molding the mixture by a molding method such as a press method or a casting method. As the molding method, either a pressing method or a casting method can be used, but a casting method that easily obtains a dense molded body is preferable. At this time, if the average particle size of the powder used is large, densification of the sintered body may not proceed. Therefore, the average particle size of the powder used is desirably 1.5 μm or less, and more preferably 0.8. 1 to 1.5 μm. The tin oxide content in the mixed powder is desirably 5 to 15% by weight at which the specific resistance decreases when a thin film is produced by the sputtering method.
[0017]
Next, consolidation processing such as CIP is performed on the obtained molded body as necessary. Here CIP pressure is sufficient for obtaining a consolidation effect 2 ton / cm ² or more, it is desirable that preferably is 2~3ton / cm ^2. Here, when the first molding is performed by a casting method, a binder removal treatment may be performed for the purpose of removing moisture remaining in the molded body after CIP and organic substances such as a binder. Even when the first molding is performed by the press method, it is desirable to perform the same debinding process when a binder is used during molding.
[0018]
The molded body thus obtained is put into a sintering furnace and sintered. Any method can be used as the sintering method, but in the air, it is desirable to sinter in the air in consideration of the cost of production facilities. The sintering conditions can be selected as appropriate, but in order to obtain a dense sintered body and to suppress evaporation of tin oxide, the sintering temperature is preferably 1450 to 1650 ° C. The atmosphere is a pure oxygen gas atmosphere in the sintering furnace from the time when the temperature rises to 800 ° C. to the end of the holding time at the sintering temperature, and oxygen when oxygen is further introduced. It is preferable that the ratio of the flow rate (L / min) and the charged weight of the compact (kg) (charged weight / oxygen flow rate) is 1.0 or less because the target becomes denser. The sintering time is preferably 5 hours or more, preferably 5 to 30 hours in order to obtain a sufficient hardness increasing effect. By doing so, a dense ITO sintered body can be obtained. The Vickers hardness of the ITO sintered body thus obtained is 700 or more and 800 or less.
[0019]
Next, the obtained ITO sintered body is processed into a predetermined shape to produce individual target members constituting a multi-segment ITO target. The size and shape of each member are not particularly limited.
[0020]
Next, surface grinding is performed to adjust the thickness of each member. The surface grinding is performed so that the grinding direction of each divided member surface is within ± 10 degrees from the longer side or the shorter side of the multi-division target assembled as a target. Preferably, it is within ± 5 degrees, particularly preferably within ± 1 degree. Here, the grinding direction refers to the direction of the grinding trace, although a streak-like grinding trace is formed on the surface of the sintered body by the surface grinding machine. By doing so, the strength against cracking is improved. Further, the surface roughness Ra of the sputtering surface is adjusted to 0.1 μm or less. When the surface of the sintered body is subjected to surface grinding, the three-point bending strength of the sintered body depends on the surface roughness after grinding. By setting the surface roughness Ra after processing of a sintered body having a Vickers hardness of 700 or more to 0.1 μm or less, the three-point bending strength measured by applying a load parallel to the grinding direction is set to 200 MPa or more and 250 MPa or less. It becomes possible.
[0021]
The obtained plurality of target members are arranged at predetermined positions on a backing plate made of one piece of oxygen-free copper and joined together using indium solder or the like. At this time, the thickness of the solder layer is adjusted to 0.5 mm or more and 1.0 mm or less. When the thickness of the solder layer is 0.5 mm or more, the stress applied to the target can be absorbed by the solder layer, and the occurrence rate of cracks is reduced. However, exceeding 1.0 mm is not preferable because the thickness of the entire target becomes too thick. As a method for controlling the thickness of the solder layer to 0.5 mm to 1.0 mm, for example, a method of inserting inclusions having a thickness of 0.5 mm to 1.0 mm in the solder layer can be mentioned.
[0022]
A single-wafer sputtering target having a minor axis of 0.7 to 1.0 times the major axis produced in this manner is a target generated during vacuum exhaustion and / or sputtering after being attached to a vacuum apparatus. Can be effectively suppressed.
[0023]
The definition and measurement method of Vickers hardness in the present invention is JIS-R1610-1991, the definition and measurement method of three-point bending strength is JIS-R1601-1991, and the definition and measurement method of surface roughness is JIS B0601. -As described in 1994.
[0024]
【Example】
Examples of the present invention will be described below, but the present invention is not limited thereto. In the examples and comparative examples, the Vickers hardness and the three-point bending strength were measured by cutting out a test piece from a molded body that was made slightly larger in advance.
[0025]
Example 1
90 parts by weight of indium oxide powder having an average particle diameter of 1.3 μm and 10 parts by weight of tin oxide powder having an average particle diameter of 0.7 μm are mixed with a dispersant, a binder and ion-exchanged water in a pot containing a nylon ball containing an iron core for 5 hours. To prepare a slurry. After sufficiently defoaming the obtained slurry, pressure casting using a resin mold was performed to obtain a molded body. This compact was subjected to densification treatment with CIP at a pressure of 3 ton / cm ² . Next, this compact was placed in a pure oxygen atmosphere sintering furnace and sintered under the following conditions.
(Sintering conditions)
Firing temperature: 1500 ° C., heating rate: 30 ° C./Hr, sintering time: 15 hours, atmosphere: pure oxygen gas from 800 ° C. during heating to 400 ° C. during cooling (feed weight / oxygen flow rate) The Vickers hardness of the sintered body obtained by introduction at 0.8 was measured to be 720. The obtained sintered body was processed into a 455 mm × 270 mm rectangular shape as shown in FIG. 1 to prepare each target member. At this time, grinding was performed on the sputtering surface of each sintered body using a # 800 grindstone in the direction indicated by a double-headed arrow at the lower end of FIG. It was 0.07 micrometer when surface roughness Ra of the obtained sintered compact was measured. At this time, the three-point bending strength measured by applying a load parallel to the grinding direction was 210 MPa.
[0026]
Each target member and backing plate thus obtained were heated to 160 ° C., and then indium solder was applied to each joint surface. At this time, a nickel wire having a diameter of 0.5 mm was placed on the backing plate, and the sintered body and the backing plate were joined so as to sandwich the wire, thereby adjusting the thickness of the solder layer to 0.5 mm. In this manner, six sintered bodies were sequentially arranged at predetermined positions as shown in FIG. 1 on the backing plate, and then cooled to room temperature to obtain a target.
[0027]
The two targets thus obtained were each placed in a vacuum apparatus, evacuated, and then sputtered under the introduction of argon gas and oxygen gas. When either of the two targets was used, no target cracking was observed.
[0028]
Example 2
An ITO sintered body was produced under the same conditions as in Example 1 except that the firing temperature was 1600 ° C. It was 760 when the Vickers hardness of the obtained sintered compact was measured. The obtained sintered body was processed in the same manner as in Example 1. Ra was 0.06 μm, and the three-point bending strength measured in the same manner was 230 MPa.
[0029]
Next, an ITO target having a solder layer thickness of 0.5 mm was produced in the same manner as in Example 1. The two obtained targets were each sputtered by the same method as in Example 1, but no cracks occurred in the targets.
[0030]
Example 3
An ITO target was produced in the same manner as in Example 2 except that the solder layer thickness was 0.8 mm. The two obtained targets were each sputtered by the same method as in Example 1, but no cracks occurred in the targets.
[0031]
Comparative Example 1
An ITO sintered body was produced under the same conditions as in Example 1. It was 760 when the Vickers hardness of the obtained sintered compact was measured. After processing the obtained sintered body into a desired shape, grinding was performed in the same manner as in Example 1 except that a # 400 grindstone was used. The obtained sintered body had an Ra of 0.6 μm, and a three-point bending strength measured by applying a load parallel to the grinding direction was 190 MPa.
[0032]
Next, an ITO target having a solder layer thickness of 0.5 mm was produced in the same manner as in Example 1. When the obtained two targets were sputtered by the same method as in Example 1, both of them were broken in one hour from the start of sputtering.
[0033]
Comparative Example 2
An ITO sintered body was produced under the same conditions as in Example 1 except that the amount of oxygen introduced into the furnace during firing was (charged weight / oxygen flow rate) = 1.2. It was 690 when the Vickers hardness of the obtained sintered compact was measured. The obtained sintered body was processed in the same manner as in Example 1. Ra was 0.09 μm, and the three-point bending strength measured in the same manner was 190 MPa.
[0034]
Next, an ITO target having a solder layer thickness of 0.5 mm was produced in the same manner as in Example 1. When the obtained two targets were sequentially sputtered by the same method as in Example 1, both of them were broken in one hour from the start of sputtering.
[0035]
Comparative Example 3
An ITO sintered body was produced under the same conditions as in Example 1. It was 760 when the Vickers hardness of the obtained sintered compact was measured. The obtained sintered body was processed in the same manner as in Example 1. Ra was 0.07 μm, and the three-point bending strength measured in the same manner was 210 MPa.
[0036]
Next, an ITO target was produced in the same manner as in Example 1 except that the thickness of the solder layer was 0.3 mm. When the obtained two targets were sequentially sputtered by the same method as in Example 1, both of them were broken in one hour from the start of sputtering.
[0037]
【The invention's effect】
In a single wafer sputtering target in which the short axis of the target is 0.7 to 1.0 times the long axis, the sintered body of the present invention has a Vickers hardness of 700 to 800 and a load is applied parallel to the grinding direction. By using an ITO sputtering target having a measured three-point bending strength of 200 MPa to 250 MPa and a solder layer thickness of 0.5 mm to 1 mm for joining the sintered body and the backing plate, Cracks that occur during sputtering can be effectively suppressed.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a form of a single-wafer multi-division target.

Claims (1)

A multi-piece target in which a plurality of sintered bodies made of indium , tin, and oxygen are joined on a single backing plate, and the short axis of the target is 0.7 to 1.0 times the long axis. In the sputtering target, the target has a rectangular shape with a major axis length of 800 mm or more or a shape corresponding to a rectangle, and the sintered body has a Vickers hardness of 700 to 800 and is applied to a surface to be a sputtering surface of the sintered body. The three-point bending strength measured by applying a load in parallel to the grinding direction of the grinding process is 200 MPa to 250 MPa, and the thickness of the solder layer that joins the sintered body and the backing plate is 0.5 mm to 1 mm. A sputtering target characterized by:

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