JP2003064471A - ITO target and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide an ITO that generates a small amount of nodules and can stably form a film until its life end even when the thickness of a sintered body used as a target is thicker than before. Provide a sputtering target. A sputtering target having a sintered body substantially consisting of indium, tin and oxygen, in which the number of agglomerated particles of tin oxide having a diameter of 10 μm or more is one or less per 0.27 mm ² .

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 for producing a transparent conductive film, and more particularly to an ITO sputtering target free from nodules.

[0002]

2. Description of the Related Art ITO (Indium Tin Oxi)
de) The thin film is characterized by high conductivity and high transmittance,
Further, since fine processing can be easily performed, it is used in a wide range of fields such as display electrodes for flat panel displays, window materials for solar cells, and antistatic films. 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 can be roughly classified into a chemical film forming method such as a spray pyrolysis method and a CVD method and a physical film forming method such as an electron beam vapor deposition method and 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 and can obtain a high-performance film.

When an ITO thin film is manufactured by a sputtering method, the sputtering target used is an alloy target made of metal indium and metal tin (hereinafter abbreviated as IT target) or a composite oxide target made of indium oxide and tin oxide (hereinafter IT).
O target) is used. Of these, IT
Compared with the method using the IT target, the method using the O target has less change in the resistance value and transmittance of the obtained film over time, and the film forming conditions can be easily controlled. Has become.

When an ITO target is continuously sputtered in a mixed gas atmosphere of argon gas and oxygen gas, black deposits called nodules are deposited on the target surface as the integrated sputtering time increases. This black deposit, which is considered to be a low-grade oxide of indium, precipitates around the erosion part of the target, which easily causes abnormal discharge during sputtering, and is itself a source of foreign particles (particles). Is known to be.

As a result, when sputtering is continuously performed, foreign matter defects 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 foreign matter defects in the thin film cause malfunction of the device, which is an important issue to be solved.

In the conventional production of an ITO thin film, in order to prevent the occurrence of such a defect in the thin film, measures such as periodically removing the nodules on the target surface have been taken. However, since such a target cleaning operation causes a significant decrease in productivity, it has been strongly desired to develop an ITO target in which nodule is unlikely to occur.

A method for reducing nodules generated in such an ITO target has been reported so far.

For example, it has been reported that nodules can be reduced by carrying out sintering in a pressurized oxygen atmosphere of 1 atm or more to obtain a high density sintered body (Japanese Patent Publication No.
30905 publication). However, in order to perform the sintering in a pressurized state as described above, it is necessary to install the entire sintering furnace in a pressure vessel, which makes the manufacturing equipment expensive and large-scaled, and it is difficult to increase the size of the manufacturing equipment. There was a problem that I said.

Therefore, a method for improving the density of the sintered body has been devised without requiring large-scale equipment. JP-A-9
In the invention described in Japanese Patent No. 25567, the density of the sintered body is improved and the nodules are reduced by defining the particle size distribution of the raw material tin oxide powder or indium oxide powder.

Further, there is an invention that the nodule can be reduced not only by reducing the density but also by reducing the surface roughness (Ra) and the maximum height (Rmax) of the sputtering surface of the sintered body (Japanese Patent Laid-Open No. 08- Furthermore, it is disclosed that nodule can be reduced by using an indium-tin alloy as a solder material used when joining the ITO sintered body and the backing plate (JP-A-2000-345325). ).

As a result of these wonderful inventions, at present, a sintering density of 99% or more has been achieved in a large-scale production line, and Ra and Rmax have been lowered, and the bonding material has been changed. Almost no nodules are generated, and it has become possible to use the target surface without cleaning it from the initial use to the target life end.

At present, the ITO targets generally used in the production line are roughly classified into a target for a single-wafer type device and a target for an in-line type device, and the thickness thereof is 8 mm for the single-wafer type device and for the in-line device. 8 mm (hereinafter referred to as 5/8 mm) is predominant in the thin portion of 5 mm and the thick portion of 5 mm.

However, recently, in order to reduce the cost for manufacturing a liquid crystal panel, the thickness of the ITO sintered body to be bonded onto the target is increased and the replacement cycle of the target is lengthened. The movement to increase the occupancy rate is increasing. For example, from 8 mm to 10 mm in the single-wafer type, (5/8
The thickness increase from (mm) to (8/10 mm) can be illustrated.

In this way, the plate thickness of the target becomes thicker,
When ITO is continuously formed for a longer time than before, there arises a problem that the number of nodules reduced by the conventional technique increases again. When a large amount of nodules are generated, the yield at the time of film formation is reduced as described above, and continuous film formation cannot be performed. Then, the meaning of increasing the plate thickness of the sintered body becomes meaningless, so nodules are less likely to occur even when using such a thick sintered body.
Development of an O sintered body was desired.

[0015]

SUMMARY OF THE INVENTION The object of the present invention is to produce a stable amount of nodules even when the thickness of the sintered body used as the target is thicker than before, and to stably form a film until the life end. The present invention is to provide an ITO sputtering target that can be used.

[0016]

DISCLOSURE OF THE INVENTION The inventors of the present invention have studied in detail the cause of the occurrence of a large amount of nodules in the sintered body having a thickness of 10 mm and the occurrence of abnormal discharge.
By increasing the thickness of the target, the density of the target decreased, and the decrease in the density caused an increase in nodules and abnormal discharge. 2) Aggregation of tin oxide of 10 μm or more present in the ITO sintered body It was found that the presence of the part increases nodules and abnormal discharge.

Therefore, the inventors of the present invention investigated a method for producing an ITO sintered body which can simultaneously achieve high density of a sintered body having a large plate thickness and reduction of tin oxide agglomerated particles of 10 μm or more. By applying ultrasonic waves to a slurry containing tin oxide and then molding and firing, it is possible to stably densify the ITO sintered body and make it 10 μm.
The inventors have found that the aggregated particles of tin oxide can be reduced, and have completed the present invention.

That is, the present invention relates to an acid having a diameter of 10 μm or more.
The number of agglomerated particles of tin oxide is 0.27 mm ²Less than 1 per
A firing consisting essentially of indium, tin and oxygen
Sputtering target having oxide and oxide oxide
It is obtained by slurrying a raw material containing indium and tin oxide.
After applying ultrasonic waves to the slurry, molding and firing
ITO sputtering target characterized by
Manufacturing method.

The present invention will be described in detail below.

The sintered body according to the present invention and the sputtering target made of this sintered body are manufactured by the following method.

First, indium oxide powder and tin oxide powder are put in a pot for a ball mill at a desired ratio and mixed by dry or wet to prepare a mixed powder. The average particle size of the powder used is preferably 1.5 μm or less, more preferably 0.1 to 1.5 μm. By using such powder, an effect of increasing the density of the sintered body can be obtained. In the present invention, the content of tin oxide in the mixed powder is preferably SnO ₂ / (In ₂ O ₃ + SnO ₂ ) of 5 to 15% by weight. By doing so, the resistivity of the thin film obtained when the film is formed by the sputtering method decreases.

Water and a dispersant are added to the powder thus obtained.
An organic material such as a binder is added to prepare a slurry. The viscosity of the slurry is preferably 200 to 4000 cp, more preferably 500 to 2000 cp.

Next, a frequency of 1 was applied to the obtained slurry.
An ultrasonic wave of k to 1000 kHz is applied. By doing so, the aggregated particles of tin oxide are crushed to reduce the number of aggregated particles of tin oxide when a sintered body is obtained. Preferably 10
k to 100 kHz.

The ultrasonic wave applying device is not particularly limited, and an ultrasonic bath, a homogenizer or the like can be used, but a homogenizer is preferable in terms of grinding efficiency.

By carrying out such a treatment, the agglomerated particles of tin oxide are efficiently crushed, and a sintered body having a plate thickness of 99% or more is obtained by molding and firing using the slurry. It is possible to reduce the number of tin oxide agglomerated particles having a size of 10 μm or more while achieving high density.

Next, molding is performed using the slurry thus treated. As a molding method, either a cast molding method or a press molding method can be adopted.

When casting is performed, the obtained slurry is filled in a casting mold to produce a molded body. The time from ultrasonic treatment to casting is preferably within 10 hours. This is because a phenomenon (thixotropic property) that the slurry viscosity increases with the passage of time occurs.

When press molding is performed, a binder or the like is added to the obtained slurry, the water content is adjusted if necessary, and the powder is dried with a spray dryer or the like to obtain a powder. After filling the obtained powder into a mold of a predetermined size,
Using a pressing machine, pressing is performed at a pressure of 100 to 300 kg / cm ² to obtain a molded body. The thickness of the molded body at this time is set to a thickness at which a sintered body having a thickness of 10 mm or more can be obtained in consideration of shrinkage due to the subsequent CIP step and firing step.

Next, the molded body thus obtained is subjected to a cold isostatic pressing (CIP) treatment, if necessary.
At this time, the pressure of CIP is 1 t in order to obtain a sufficient consolidation effect.
On / cm ² or more, preferably ² to 5 ton / cm ² .

300 to 600 ° C. with respect to the obtained molded body
After the binder removal treatment is performed at the temperature of 1, the firing is performed.
The heating rate is not particularly limited, but it is preferably 2 to 100 ° C./hour from the viewpoint of preventing cracking. The sintering temperature is 1550 ° C. or higher and lower than 1650 ° C., preferably 1580 ° C. or higher and lower than 1620 ° C. By doing so, a high-density sintered body can be obtained more reliably. The thus obtained sintered body has a plate thickness of 10 mm or more and a density of 99.0% or more.

The sintered density (D) in the present invention means
The relative value to the theoretical density (d) obtained from the arithmetic mean of the true densities of In ₂ O ₃ and SnO ₂ is shown. The theoretical density (d) obtained from the arithmetic mean is the true density of each of the target compositions when the mixing amounts of In ₂ O ₃ and SnO ₂ powder are a (g) and b (g), respectively. Using 7.18 (g / cm ³ ) and 6.95 (g / cm ³ ), d = (a + b) / ((a / 7.18) + (b / 6.9)
5)). When the measured density of the sintered body obtained by the Archimedes method is d1, the sintered density is obtained by D = d1 / d × 100 (%).

The number of tin oxide agglomerated particles in the sintered body can be measured as follows. First, a small piece for analysis is cut out from the obtained sintered body, and the observation surface of this small piece is polished. This polished surface is treated with EPMA (Electron P
The presence of agglomerated particles of tin oxide is investigated using Rove Micro Analysis). In the present invention, EPMA (JCMA-733) manufactured by JEOL Ltd. is used, and an acceleration voltage of 1
Surface analysis of the characteristic X image of tin was performed under the conditions of 5 kV, sample current 0.05 to 0.3 μA, and magnification of 200 times, and the obtained results were output to an image of 125 mm × 90 mm, and then aggregated tin particles of 10 μm or more were collected. I counted. The above work was repeated 10 times for one sintered body, and the average was 0.27.
The average number of aggregated particles per mm ² was calculated.

A target can be obtained by bonding the obtained sintered body to a backing plate made of oxygen-free copper or the like using indium solder or the like.

[0034]

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 90 parts by weight of indium oxide powder having an average particle size of 0.5 μm and 10 parts by weight of tin oxide powder having an average particle size of 0.5 μm were placed in a polyethylene pot, and 72 parts were formed by a dry ball mill.
The mixture was mixed for a time to prepare a mixed powder. In the obtained powder,
Water, a dispersant and a binder were added to make a slurry.
The viscosity of the obtained slurry was 1000 cp. Then, using a homogenizer for the obtained slurry, 20
Ultrasonic waves of kHz 600 W were applied. Ten minutes after the slurry was prepared, this slurry was cast into a casting mold to prepare a molded body having a thickness of 14 mm. This molded body is 3t
The treatment with CIP was performed at a pressure of on / cm ² . Next, this molded body was placed in a pure oxygen atmosphere sintering furnace and sintered under the following conditions.

(Sintering conditions) Temperature rising rate: 100 ° C./hour, Sintering temperature: 1600 ° C., Sintering time: 6 hours, Atmosphere during sintering: Pure oxygen from 800 ° C. to 400 ° C. Gas was charged into the furnace, (charged weight (kg) / oxygen flow rate (L / min)) = 0.
Introduced in 8 and cooling rate: 1600 ° C to 1200 ° C, 100 ° C / hour, thereafter 50 ° C / hour, the obtained sintered body has a plate thickness of 10.4 mm, and the density measured by the Archimedes method is shown in Table 1. It was shown to.

[0037]

[Table 1] The obtained sintered body was processed by a wet processing method into a sintered body having a size of 4 × 7 inches and a thickness of 10 mm and a small piece for analysis.

After specular polishing of a small piece for analysis, EPMA was used.
Was used to analyze the aggregation state of tin. An example of the obtained results is shown in FIG. In FIG. 1, one at the tip of the arrow, 10 μm
The tin oxide agglomerates of are observed. 10 similar observations
Table 1 shows the calculation results of the average number of agglomerated tin particles per 0.27 mm ² when the measurement was performed at various locations.

Next, the sintered body processed to have a size of 4 inches × 7 inches was bonded to a backing plate made of oxygen-free copper by using indium-tin solder to obtain a target. This target was continuously discharged under the following sputtering conditions, and the generation amount of nodules and abnormal discharge was examined.

(Sputtering conditions) DC power: 300 W, gas pressure: 7.0 mTorr, sputtering gas: Ar + oxygen, oxygen gas concentration in sputtering gas (O ₂ / Ar):
0.05%, discharge time: 120 hours (target remaining thickness is about 1 mm) Here, the oxygen gas concentration was set to a value at which the resistivity of the obtained thin film was the lowest.

Table 1 shows the number of occurrences of abnormal discharge and the amount of nodules generated on the target surface. The nodule generation amount was calculated by using an image processing using a computer of an external appearance photograph of the target after the discharge. Good results have been obtained.

Example 2 An ultrasonically treated slurry was prepared in the same manner as in Example 1. Ten minutes after the slurry was prepared, this slurry was dried with a spray dryer to prepare powder for press molding.

The pressing powder thus obtained was filled in a mold and 3
It was pressed at a pressure of 00 kg / cm ² to produce a molded body. This molded body was treated 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 same conditions as in Example 1.

The plate thickness of the obtained sintered body was 10.4 mm. Table 1 shows the densities measured by the Archimedes method. Next, in the same manner as in Example 1, the presence state of agglomerated tin in the sintered body was examined and a continuous discharge test was performed.
The results are shown in Table 1. Good results have been obtained.

Comparative Example 1 An ITO sintered body was produced in the same manner as in Example 1 except that the treatment with ultrasonic waves was not carried out. The plate thickness of the obtained sintered body was 10.5 mm. Table 1 shows the densities measured by the Archimedes method.

Next, in the same manner as in Example 1, the presence state of agglomerated tin in the sintered body was examined and a continuous discharge test was carried out. The results are shown in Table 1. Many abnormal discharges and arcing occurred.

Comparative Example 2 An ITO sintered body was produced in the same manner as in Example 2 except that the treatment with ultrasonic waves was not carried out. The plate thickness of the obtained sintered body was 10.5 mm. Table 1 shows the densities measured by the Archimedes method.

Next, in the same manner as in Example 1, the presence state of agglomerated tin in the sintered body was examined and a continuous discharge test was conducted. The results are shown in Table 1. Many abnormal discharges and arcing occurred.

[0049]

EFFECTS OF THE INVENTION The present invention provides an ITO sputtering target capable of stably forming a film up to the life end of a sintered body even when an ITO sintered body having a large plate thickness is used, with a small amount of nodule generated. be able to.

[Brief description of drawings]

1 is an EPMA image of a small piece for analysis obtained in Example 1, with a magnification of 200 times (the white bar in the figure is 100 μ).
m length). White tin oxide agglomerates are recognized at the tips of the arrows (numbered 1 to 5) in FIG.

Claims (4)

[Claims] 1. A sputtering target having a sintered body consisting essentially of indium, tin and oxygen, in which the number of aggregated particles of tin oxide having a diameter of 10 μm or more is 1 or less per 0.27 mm ² . 2. The sputtering target according to claim 1, which has a sintered density of 99.0% or more. 3. A method for producing an ITO sputtering target, which comprises forming a raw material containing indium oxide and tin oxide into a slurry, applying ultrasonic waves to the obtained slurry, and then forming and firing. 4. A raw material containing indium oxide and tin oxide is slurried, ultrasonic waves are applied to the obtained slurry, and then molding and firing are performed. Manufacturing method of ITO sputtering target.