JPH08144052A - Ito sputtering target - Google Patents

Abstract

PURPOSE: To prevent the occurrence of defects due to abnormal electric dis charge caused by the occurrence of a nodule on the surface of a target by arranging plural small-sized targets, packing metal indium into the gaps and using the resultant large-sized target for forming an ITO film. CONSTITUTION: Plural small-sized ITO sintered targets 3 finished to <=0.8μm average surface roughness Ra and <=7μm max. surface roughness Rmax by polishing are arranged and fixed on the surface of a large-sized backing plate 1 made of oxygen-free copper while leaving gaps 4 of 0.2-0.8mm width and high purity metal indium of >=99.9% purity is packed into the gaps 4 to obtain the objective target used at the time of forming an ITO film as a transparent electrically conductive film by sputtering on the surface of a large-sized substrate. When this target is used, a nodular deposit does not deposit on the surface of the target at the time of sputtering, abnormal electric discharge is not caused and the lowering of the formation yield of ITO films is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ITO sputtering target used when producing a transparent conductive film by sputtering.

[0002]

2. Description of the Related Art ITO (Indium Tin Oxid)
e) Thin films have the characteristics of high conductivity and high transmittance, and because they can be easily microfabricated, they are used in a wide range of fields such as display electrodes for flat panel displays, window materials for solar cells, and antistatic films. Is used. In particular, in the field of flat panel displays including liquid crystal display devices, the size and definition have been increasing in recent years, and the demand for the ITO thin film as the display electrode is also rapidly increasing. The manufacturing method of such an ITO thin film includes a spray pyrolysis method, a chemical film forming method such as a CVD method and an electron beam evaporation method,
It can be roughly classified into a physical film forming method such as a sputtering method. Among them, the sputtering method is used in various fields because it is a film forming method that can easily increase the area of the film and obtain a high-performance film.

When an ITO thin film is manufactured by the sputtering method, the sputtering target is an alloy target made of metal indium and metal tin (hereinafter referred to as IT).
A target is abbreviated) or a composite oxide target composed of indium oxide and tin oxide (hereinafter abbreviated as ITO target) is used. Among them, the method using the ITO target is less likely to change the resistance and transmittance of the film obtained with time than the method using the IT target, and the film forming conditions can be easily controlled. It is the mainstream.

With the recent increase in the size of flat panel displays, the size of glass substrates used for panel manufacturing has also increased. Therefore, the size of the ITO target used during the production of the transparent conductive film is increasing in accordance with the size of the substrate. In particular, in the case of an ITO target for a stationary facing sputtering apparatus, which has been in the limelight since the generation of foreign matters (particles) is small in recent years, it is necessary to make the target size one size larger than the substrate size. It is getting stronger.

The ITO target is generally formed by a pressing method or a slip casting method of a mixed powder of indium oxide powder and tin oxide powder or an ITO powder in which tin oxide is dissolved in a predetermined amount in indium oxide by a pressing method or a slip casting method. It is produced by sintering in a medium or an oxygen atmosphere. However, when manufacturing a large ITO target, the production equipment required for molding and sintering is larger than the conventional one, so new equipment investment is required, and the powder formability deteriorates as the size increases. Therefore, the yield is extremely reduced, and as a result, the manufacturing cost and productivity of the target are deteriorated.

Therefore, the large-sized ITO currently manufactured
The target is a relatively small I on the backing plate.
It is composed of a multi-divided target in which a plurality of TO target members are joined by solder. Generally, in such a multi-divided target, a clearance of about 0.2 to 1.0 mm is provided between two adjacent target members. This is provided to prevent the target members from colliding with each other and being damaged due to thermal contraction of the solder layer that is heated and melted at the time of joining the targets and then cooled to room temperature.

[0007]

When sputtering is continuously performed using an ITO target, black deposits called nodules are deposited on the target surface as the integrated sputtering time increases. It is known that this black deposit, which is considered to be a lower oxide of indium, is likely to cause abnormal discharge during sputtering, and that it itself is a source of generation of foreign particles (particles) on the thin film surface. As a result, when sputtering is continuously performed, foreign matter defects gradually occur in the formed thin film, which causes a reduction in manufacturing yield of flat panel displays such as liquid crystal display devices. In particular, in recent years, in the field of flat panel displays, high definition has been advanced, and such a foreign matter defect in the thin film causes a malfunction of the element, which is an important issue to be solved.

As a method for reducing the nodules generated on such an ITO target, a method of densifying an ITO sintered body is known, and recently, a density of 6.8 g / cm ³ or more as a sputtering target is known. The ITO sintered body is used.

However, in the large-sized multi-divided target as described above, even if the sintering density of each target member is increased, a clearance exists in the divided portion between the target members unlike the integrated type target. However, there is a problem that abnormal discharge is likely to occur in the vicinity of the divided portion, a large amount of nodules are generated as a result, and a sufficient particle reduction effect cannot be obtained even by using a stationary facing sputtering apparatus with few particles.

As a method of reducing the abnormal discharge in the vicinity of the divided portion, the indium and tin atoms in the target body are provided in the clearance between the target members of the multi-divided ITO target having the interval of 0.3 to 2 mm. A method of injecting an indium-tin alloy having the same ratio has been proposed (JP-A-1-230768). In this method, since the indium-tin alloy is injected into the clearance, there is no step on the target surface, and as a result, the occurrence of abnormal discharge is suppressed and the transmittance and resistance of the ITO thin film produced are also affected. It is shown not to give.

However, in order to inject the indium-tin alloy having the atomic ratio of indium and tin of the target body into the clearance between the target members by the above method,
Measure the atomic ratio of indium and tin in the target body,
Based on the result, it is necessary to adjust the composition of the indium-tin alloy to be injected each time, so there is a difficulty in improving the productivity of the target. Furthermore, the amount of tin contained in the ITO target needs to be adjusted within the range of 3 to 20 wt% according to the application, so an indium-tin alloy corresponding to each tin atomic amount must be prepared and the target preparation There is a problem that the process becomes complicated.

An object of the present invention is to deposit nodules on the surface of a target, which causes defects in the film even when a large multi-split ITO target is used in the sputtering of an ITO thin film used for a transparent electrode of a flat panel display. The object is to provide an ITO sputtering target that does not easily occur.

[0013]

The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, in a multi-divided target having a clearance in a divided portion between target members, metallic indium is provided in the clearance portion. The present invention has been completed by finding that the filling can easily reduce the amount of nodule generated in the vicinity of the divided portion regardless of the amount of tin atoms in the target body.

That is, according to the present invention, a multi-divided I formed by bonding a plurality of ITO target members on a backing plate.
A multi-split ITO sputtering target in which a clearance between target members is filled with indium metal in a TO sputtering target.

The present invention will be described in detail below.

A multi-divided IT in which metallic indium is filled in a clearance of a divided portion between target members according to the present invention.
The O sputtering target can be manufactured by the following method.

First, a binder or the like is added to a raw material powder having an amount of tin atoms in the range of 3 to 20 wt%, which is produced by using a mixed powder of indium oxide powder and tin oxide powder or ITO powder, and then pressing or casting. An ITO molded body is formed by molding by a molding method such as an embedding method, and if necessary, a compaction treatment such as CIP and a binder removal treatment are performed. Next, this compact is subjected to atmospheric pressure sintering or pressure sintering in an atmosphere containing oxygen gas such as an atmosphere of pure oxygen or an inert gas atmosphere to obtain an ITO sintered body.

Next, the finished ITO sintered body is mechanically ground into individual target members constituting a multi-divided ITO target. At this time, it is desirable that the grinding process be a wet process. When grinding is performed by dry processing, processing scratches may occur on the surface of the sintered body during processing, which may increase the amount of nodules generated during sputtering using this. Of the end faces of each target member to be processed, the angle with the upper surface of the surface adjacent to the other target member may be a right angle as shown in FIG. 1 (a), and FIG. 90 ° or more (90 ° +
Although it may be processed in a state where an angle of (θa °) is added, 90
In the case of processing at an angle of 90 ° or more, when these target members are joined, the angle of the end face of another adjacent target member is set to the opposite angle (90 ° -θa) as shown in FIG. It is preferable to process so as to have a temperature of (°) so that the bonding state becomes close to each other.

Further, it is desirable to chamfer the corners of each side constituting the sputtering surface of each target member. Specifically, round the corners of each side to 3 mm or less,
Alternatively, thread chamfering to 3 mm or less. As a result, it is possible to prevent damage to the end portion of the target member that occurs during the bonding work.

Of the surfaces of the respective target members, the surface which constitutes the sputtering surface after joining is subjected to ordinary grinding and then further polished as necessary to obtain a surface roughness Ra of the sputtering surface. More preferably, it is 0.8 μm or less and Rmax is 7 μm or less. By performing such a surface treatment, nodules generated on the sputtering surface can be effectively suppressed.

It is desirable that the processed target member is degreased and washed with alcohol or the like, further washed with pure water, and then dried.

Next, on the bonding surface of each target member obtained by performing the above-mentioned processing and cleaning and the bonding surface of the backing plate made of oxygen-free copper etc. which has been subjected to the same cleaning treatment, metal indium solder or the like is applied. Apply bonding material. I
Since solder does not directly adhere to the TO sintered body, a thin film layer of copper, nickel or the like having excellent wettability with solder is formed on the joint surface of each target member in advance by a sputtering method, a plating method or the like. Apply the solder by heating the sintered body above the melting point of the solder used, or by using ultrasonic waves.
Solder is directly applied to the joint surface of the TO sintered body. On the other hand, when a material having poor wettability with solder is used as the material of the backing plate, the solder can be applied by performing the same process. Before applying the solder, it is preferable to apply a masking process to unnecessary portions of the solder using polyamide tape or the like, if necessary, in order to prevent the portions other than the bonding surface from being contaminated with the solder.

Next, the target member thus treated and the backing plate are joined. At the time of joining, the backing plate coated with solder is heated above the melting point of the solder used to melt the solder layer on the surface, then each target member is placed in a predetermined place and joined, and then at room temperature. Cool it all down. At this time, between each target member,
A clearance of 0.2 to 0.8 mm is provided to prevent damage to the target member due to thermal contraction during cooling of the solder layer. At this time, if the clearance is set to be smaller than 0.2 mm, it is not preferable because adjacent target members may collide and be damaged due to thermal contraction during cooling of the solder layer. On the other hand, when the clearance after cooling the solder layer exceeds 0.8 mm, the ITO formed on the substrate facing the divided portion at the time of film formation due to the influence of metallic indium fused to this portion by the method described later. The variation of the resistance value of the thin film is larger than that of its surroundings, and a uniform thin film is not formed, which is not preferable.

FIG. 2 shows the state of the divided parts of the target when the joining of the target members is completed. In the figure, 1 is a backing plate, 2 is a solder layer, 3 is a target member, and 4 is a clearance portion.

Next, the clearance portion of the divided portion is filled with indium metal, and as the indium metal used here, a powder having a purity of 99.9% or more or a metal plate corresponding to the size of the clearance portion is used.

The metal indium powder or the metal plate inserted in the clearance portion of the divided portion of the target member is heated to a temperature (150 to 160 ° C.) higher than the melting point of indium to be melted, so that the clearance portion is densely filled. However, at this time, using a polyamide tape or the like to prevent the melt of the indium melted from flowing out to the target outer peripheral portion other than the filling portion, the outer peripheral portion of the target member is previously sealed and melted. It is desirable to do. The heating and melting of the metal can be performed by, for example, bringing an ultrasonic soldering iron or the like into contact with the portion filled with the metal. It is more preferable to melt the metal under reduced pressure because bubbles can be prevented from remaining in the clearance portion.

In this way, the clearance portion of the divided portion of the target member can be densely filled with metallic indium. However, if the clearance portion is not sufficiently filled with metallic indium by one filling operation, it is re-filled again. It is preferable to add the same filling operation as described above and repeat this operation until no step is formed in the clearance portion.

The state of the divided portion of the target when the filling is completed is shown in FIG. In the figure, 5 indicates a portion filled with metallic indium. After the metal is filled, this target is washed again with alcohol and pure water and dried to obtain an ITO target.

Although the present invention is one in which a plurality of target members are joined together, the shape of each target member is appropriately determined according to the final target shape, and the joint portions have the above-mentioned clearance. It can be obtained by arranging them and filling their clearances with the metal used in the present invention by the method described above.

[0030]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1 Indium oxide powder and tin oxide powder were mixed in a weight ratio of 9: 1, and a mixed powder was put in a pressing die and 300 Kg /
The molded body obtained by pressurizing at a pressure of cm ² was CIP treatment at a pressure of 3 ton / cm ² to prepare an ITO molded body. In this way, two molded bodies were obtained. The densities of the obtained molded articles after the CIP treatment were all 3.9 g / cm ³ . Next this IT
The O compact was subjected to atmospheric pressure sintering in an oxygen atmosphere at 1500 ° C. for 5 hours to obtain an ITO sintered body having a size of 130 mm × 90 mm and a thickness of 5.5 mm. The density of each of the obtained sintered bodies was 6.8 g / cm ³ . Each of these sintered bodies was mechanically ground by wet processing to be processed into 127 mm × 89 mm × 5 mm sintered bodies. The end faces of each target member were all processed at right angles. At the same time, the angle of each side that constitutes the sputtering surface of each sintered body is R
= 0.5 mm. After that, the sputtering surface of each sintered body was sequentially wet-polished under the following conditions using # 320, # 500, and # 800 polishing paper.

(Polishing conditions) Abrasive materials: # 320, # 500, # 800 / SiC water resistant abrasive paper, abrasive material rotation speed: 300 rpm, sintered body rotation speed:
150 rpm, weight: 66 g / cm ² , polishing time: 5 minutes / 1 step, polishing sequence: # 320 → # 500 → # 800 The surface roughness of the sputtering surface after polishing was measured according to Japanese Industrial Standards (JIS B0601). After doing R
a = 0.5 μm and R max = 5.1 μm. After polishing, these sintered bodies were ultrasonically cleaned in ethanol for 10 minutes, further ultrasonically cleaned in pure water for 10 minutes, and then naturally dried. After the completion of drying, these sintered bodies were put in a sputtering apparatus, and a copper thin film was laminated on the bonding surface of each sintered body by about 200 nm by DC sputtering. After that, the side surfaces around the joint surface of these sintered bodies are masked with polyamide tape, and then the bonding surface (127 mm
X 89 mm) facing upwards and placed on a hot plate set at 200 ° C, indium solder is applied to the entire bonding surface where copper thin films are laminated so that the thickness is about 0.2 mm, and then removed from the hot plate. And cooled to room temperature.

Next, ultrasonic cleaning with ethanol and pure water and backing plate made of oxygen-free copper that has been naturally dried (joint area: 127 mm x 178.5 mm) are similarly masked on the areas where soldering is unnecessary. After that, the joint surface was placed upward on a hot plate set at 200 ° C., and indium solder was applied to the entire joint surface so that the thickness was about 0.2 mm. Then, two ITO sintered bodies were placed on the backing plate with a gap (clearance) of 0.5 mm so that the joint surfaces were opposed to each other and allowed to cool to room temperature. After cooling, the clearance between the two sintered bodies was 0.4 mm.

Next, the side surface of this target was divided into parts using a polyamide tape, and then a thin plate of indium metal (purity: 99.99%) (127 mm × 5.1 mm × 0.
4 mm) was inserted, an ultrasonic soldering iron was applied to the thin plate to melt the thin plate, and the clearance portion was filled with indium metal. The joint target cooled after filling was washed again with alcohol and pure water and dried.

This target was attached to a sputtering device and sputtering was carried out under the following conditions.

(Sputtering conditions) DC power: 600 W (2.7 W / cm ² ), gas pressure: 5 m To
rr, Ar gas flow rate: 50 SCCM, Oxygen gas flow rate: 1 SCCM Due to the sputtering, nodules were slightly generated at the end of the target life, but the generation conditions were uniform over the entire target surface, and nodules were generated at the divided parts. There was no tendency to concentrate.

Example 2 A two-divided ITO target was prepared in the same manner as in Example 1 except that indium powder was used as the metallic indium to be inserted in the clearance. When the obtained target was sputtered under the same conditions as in Example 1, nodules were still generated at the end of the target life, but no nodules tended to be concentrated in the divided parts.

Comparative Example Two-divided IT in which the clearance is not filled with metal
An O target was produced in the same manner as in Example 1. When the obtained target was sputtered under the same conditions as in Example 1, nodules gradually started to be generated in the divided portions from the beginning of target use, and nodules were clearly concentrated in the divided portions at the end of target use. Was confirmed.

[0039]

INDUSTRIAL APPLICABILITY The ITO sputtering target having the split portion of the present invention is easy to manufacture, and nodules are concentrated near the split portion of the target during sputtering using the ITO sputtering target, as compared with the conventional split target. Can be effectively suppressed with good reproducibility. As a result, the sputtering surface cleaning process for removing the nodules is unnecessary or can be drastically reduced in number. Therefore, defects in the thin film due to the nodules can be stably and effectively prevented, and thus the production of displays such as LCDs can be performed. It is possible to dramatically improve the sex.

[Brief description of drawings]

FIG. 1 is a view showing an end face shape of a target member.

FIG. 2 is a view showing a joining state in a divided portion of a target and a backing plate.

FIG. 3 is a view showing a bonding state when a metal is filled in a divided portion of a target and a backing plate.

[Explanation of symbols]

 1: Backing plate 2: Solder layer 3: Target member 4: Clearance part between target members 5: Clearance part filled with metallic indium

Claims (2)

[Claims] 1. A multi-divided ITO sputtering target composed of a plurality of ITO target members bonded on a backing plate, wherein the clearance between the target members is filled with indium metal. . 2. The target according to claim 1, wherein the surface roughness Ra of the surface constituting the sputtering surface is 0.8 μm or less and Rmax is 7 μm or less.