JP2002302762A - Ito sputtering target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ITO(indium-tin-oxide) target which reduces the amount of particles caused by nodules generated on an erosion part in accordance with the increase of the cumulative use time of the target and the amount of particles caused by yellow powders deposited on a nonerosion part. SOLUTION: In the ITO sputtering target substantially consisting of indium, tin and oxygen, the non erosion part is made thinner than the erosion part to project the erosion part. Further, a shape obtained by connecting the plane including the erosion part and the plane including the nonerosion part by an obtuse-angled slant is formed. The surface roughness (Ra) of the erosion part is controlled to <=0.1 μm, and the Ra of the nonerosion part and slant part obtained by connecting the erosion part and the nonerosion part is controlled to >=1.0 μm.

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 thin film.

[0002]

2. Description of the Related Art ITO (Indium) is a transparent conductive film.
The manufacturing method of a Tin Oxide 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 evaporation method and a sputtering method. In particular, the sputtering method using an ITO target is easy to increase the area, has little change over time in the resistance value and transmittance of the obtained film, and is easy to control the film forming conditions. It is used.

In particular, the DC magnetron sputtering method in which a magnet is arranged behind a sputtering target and a magnetic field is present on the surface of the target to converge plasma is characterized by a high film-forming speed, and is used in a mass production apparatus. Many are adopted.

[0004] Such an ITO thin film has features such as high conductivity and high transmittance, and can be easily subjected to fine processing, so that it can be used for display electrodes for flat panel displays, window materials for solar cells, antistatic films, and the like. Is used in a wide range of fields. In particular, in the field of flat panel displays such as liquid crystal display devices, in recent years, the size and definition have been advanced, and there has been an increasing demand for reducing the particle size of the ITO thin film, which is the display electrode.

[0005] Particles are generated due to nodules formed in the erosion portion and yellow powder deposited on the non-erosion portion of the target.

[0006] Nodules are black deposits generated on the surface of an ITO target as the cumulative sputtering time increases when the ITO target is continuously sputtered in a mixed gas atmosphere of argon gas and oxygen gas. This black deposit, which is considered to be a lower oxide of indium, precipitates on the erosion part of the target and is likely to cause abnormal discharge during sputtering, and itself may be a source of foreign matter (particles). It has been known.

On the other hand, the amount of the yellow powder deposited on the non-erosion portion of the target surface increases as the sputtering time increases, and when it reaches a certain thickness or more, the yellow powder peels off from the target surface and floats in a vacuum. It will adhere to the substrate surface. The yellow powder changes its direction by colliding with gas particles (argon, oxygen, etc.) in the vacuum chamber before the target material beaten out from the erosion portion reaches the opposing substrate, thereby changing the target surface non-uniformity. It is believed that it accumulates on the erosion. When this yellow powder adheres to the substrate, it lowers the display quality of a liquid crystal display device or the like, causes defects, and significantly lowers the production yield of products.

As means for reducing particles due to nodules, for example, Japanese Patent Application Laid-Open No. 05-148635 discloses that the density and bulk resistivity of a target are kept within certain ranges, and the surface roughness (R
It has been reported that a) is reduced to 0.5 μm or less. However, these methods had an effect of reducing particles caused by nodules, but had no effect on particle reduction caused by yellow powder.

On the other hand, as means for reducing particles caused by yellow powder, for example, Japanese Utility Model Application Laid-Open No. 60-19336
As disclosed in Japanese Patent Application Laid-Open No. 4 (1999) -1999, a method of increasing the adhesion strength of a yellow powder by roughening the target surface has been reported. However, in this case, although there was an effect of reducing particles due to yellow powder, particles due to nodules were
There was no effect.

[0010] For these reasons, there has been a demand for the development of a new ITO target capable of simultaneously reducing particles originating from both nodules and yellow powder.

[0011]

The problem to be solved by the present invention is that the IT
To provide an ITO sputtering target capable of reducing the amount of particles caused by nodules generated in the erosion part and the particles caused by yellow powder deposited in the non-erosion part due to an increase in the cumulative use time of the O target. is there.

[0012]

Means for Solving the Problems The present inventors have made the surface roughness of the non-erosion part and the surface roughness of the erosion part lower for a parallel plate-shaped target based on the above-mentioned known technique, An experiment was conducted to examine the occurrence of nodules and the adhesion of the yellow powder. But,
It was not possible to reduce the amount of nodules generated with good reproducibility and increase the adhesion of the yellow powder.

The reason is as follows. It is difficult to identify the erosion area on the target surface.
The erosion portion is slightly different due to a slight difference in magnetic force of a magnet placed thereunder. If a region with a small surface width is formed in the erosion portion with a rough surface, many nodules are generated in the portion. Therefore, even for targets of the same size, it is necessary to design the regions separately for each cathode and control the surface roughness, and this is not a very industrially usable technique.

Therefore, the present inventors have conducted various studies on the shape and surface roughness of the target, and by using a method that can be industrially produced, can reduce the amount of nodules generated with good reproducibility and increase the adhesion of the yellow powder. We studied diligently on how to make it work.

As a result, the thickness of the non-erosion portion is made smaller than the thickness of the erosion portion so that the erosion portion protrudes, and the plane including the erosion section and the plane including the non-erosion section are connected by an obtuse slope. In an ITO sputtering target having an irregular shape, the surface roughness (Ra) of the protruded erosion portion is set to 0.1 μm or less, and the surface roughness (R) of a non-erosion portion and a slope connecting the erosion portion and the non-erosion portion is reduced.
By setting a) to be 1.0 μm or more, it has been found that particles due to nodules and yellow powder can be reduced, and the present invention has been completed.

That is, according to the present invention, in an ITO sputtering target using a sintered body substantially consisting of indium, tin and oxygen, the thickness of a non-erosion portion is made smaller than the thickness of an erosion portion to protrude the erosion portion. A flat surface including the erosion portion and a flat surface including the non-erosion portion are connected by an obtuse slope, and the surface roughness (Ra) of the protruded erosion portion is 0.1 μm or less, and the non-erosion portion is formed. And a surface roughness (Ra) of a slope connecting the erosion portion and the non-erosion portion is 1.0 μm or more.
It relates to a TO sputtering target.

Hereinafter, the present invention will be described in detail.

The ITO sintered body used in the present invention is not particularly limited, but can be produced, for example, by the following method.

As the raw material powder, a mixed powder of an indium oxide powder and a tin oxide powder or an ITO powder obtained by a coprecipitation method or the like can be used. If the average particle diameter of the powder used is large, the density after sintering may not be sufficiently increased. Therefore, in order to obtain a sintered body having a higher sintered density, the average particle diameter of the powder used is 1. 5 μm or less, more preferably 0.1 to 1.5 μm
It is.

The tin oxide content in the mixed powder or the ITO powder is 5 to 25% by weight (in terms of oxide) at which the specific resistance decreases when a thin film is produced by a sputtering method.
It is desirable that

When indium oxide powder and tin oxide powder are used as the raw material powder, the powders are mixed first. The powder may be mixed by wet or dry mixing using, for example, a ball mill.

The powder thus obtained is molded by a molding method such as a press method or a casting method to produce an ITO molded body. In the case of manufacturing a molded body by press molding, after filling the mixed powder into a mold having a predetermined size, the molded body is pressed by a press at a pressure of 100 to 500 kg / cm ² . At this time, a binder such as PVA may be added as needed.

On the other hand, in the case of producing a molded body by the casting method, the raw material powder is mixed with water, a binder and a dispersant to form a slurry, and the thus obtained 50 to 500
A slurry having a viscosity of 0 centipoise is poured into a water-absorbing porous mold having a desired shape to produce a molded article.

FIG. 1 shows the appearance of the target of the present invention, and FIG. 2 shows a cross-sectional shape of this target taken along a plane including AA and perpendicular to the illustrated target. The cross-sectional shape of the target of the present invention is shown in FIG.
The present invention is also effective for an annular target from which the central sintered body is removed as shown in FIGS. Further, the present invention is effective for both a single sintered body to be bonded to one backing plate and a multi-divided target in which a plurality of sintered bodies are bonded to one backing plate. .

It is preferable to use a casting method as a molding method since a molded article can be formed into a desired shape and a later processing step is not required.

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

When the molding is performed by the press method, it is processed into a desired shape here. Although it is possible to work after sintering, the hardness of the molded body is much lower than that of the sintered body and it can be easily worked. Therefore, it is preferable to work at this stage. Absent.

When molding is performed by the casting method, CI
In order to remove water and organic substances such as a binder remaining in the molded body after P, a temperature of 300 to 500 ° C. and a temperature of 5 to 2 are removed.
It is preferable to perform a drying treatment and a binder removal treatment for about 0 hours. Even when molding is performed by a press method, when a binder is used at the time of molding, it is preferable to perform the same binder removal treatment.

Next, the thus obtained molded body is fired. The rate of temperature rise is not particularly limited, but from the viewpoint of shortening the sintering time and preventing cracking, it is 10 to 400 ° C. /
Preferably, it is time.

The sintering temperature is 1450 ° C. or more and less than 1650 ° C., preferably 1500 to 1600 ° C. By doing so, a high-density sintered body can be obtained.

It is desirable that the sintering time is 5 hours or more, preferably 5 to 30 hours, in order to obtain a sufficient density increasing effect.

The atmosphere during sintering is an oxygen gas flow, and the oxygen flow rate (L / min) when introducing oxygen into the furnace during sintering.
And the ratio of the charged amount (kg) of the compact (charged weight / oxygen flow rate)
Is set to 1.0 or less. This makes it easier to obtain a high-density sintered body.

The higher the sintering density, the more nodule reduction effect can be obtained. It is more preferably at least 99.5%, particularly preferably at least 99.7%.

The relative density (D) referred to in the present invention is:
The relative values to the theoretical density (d) obtained from the arithmetic mean of the true densities of In ₂ O ₃ and SnO ₂ are shown. The theoretical density determined from the arithmetic mean (d), in the sintered body composition, when In ₂ O ₃ and mixtures of SnO ₂ powder (g) respectively were a, and b, In ₂ O ₃ and SnO ₂ Using the true densities of 7.18 and 6.95 (g / cm ³ ), d
= (A + b) / ((a / 7.18) + (b / 6.9)
5)). Then, assuming that the measured density of the sintered body is d1, the relative density D (%) is represented by the formula: D = (d1
/ D) × 100.

Next, blasting is performed on the sputtering surface (both erosion and non-erosion) of the ITO sintered body. As a specific method, for example, the method is performed by injecting a gas such as air containing blast material or a liquid such as water onto the surface to be processed, thereby causing the blast material to collide with the surface to be processed at high speed.

Alumina, glass, zirconia, SiC or the like can be used as the blast material (powder used for the blast treatment). Spherical zirconia powder in which individual particles of zirconia are formed into a spherical shape is used for the blasting target surface. It is particularly preferable that the (processed surface) is less likely to be contaminated.

The shape of the blast material can be needle-like, granular, spherical or the like, and the particle size is preferably from 10 to 500 μm, particularly preferably from 10 to 200 μm.

The pressure applied to the fluid such as air using a blast material as a medium in order to bombard the target surface (blasting pressure) is preferably about 1 to 10 kg / cm ^2, in particular 2~7kg / cm ² preferably , And 3 to
5 kg / cm ² is preferred. If the pressure is too high, the impact on the target surface will be strong, causing not only cracks but also a large-capacity compressor, which may increase the cost.

The distance between the nozzle for jetting the blast material and the target surface is preferably about 50 to 300 mm. If this distance is too short, the effective area to be subjected to the blasting process becomes small, which is not efficient. On the other hand, if the distance is too large, the pressure becomes insufficient and the blasting process takes a long time.

The blasting time of the target surface depends on the blast pressure, the type of the blasting material, and the like.
Preferably, the treatment is performed at about 1.0 second / cm ² . By doing so, Ra on the entire sputtering surface of the ITO sintered body becomes 1.0 μm or more, and Ry becomes 8.0 μm or more.

Next, the protruding erosion portion is processed using a surface grinder or the like to reduce the surface roughness. First, after primary grinding using a grindstone of about # 120,
Secondary grinding is performed using a grinding wheel of about 00, and then # 80
Polish with a grindstone of about 0. By doing this,
Ra of the protruding erosion portion can be set to 0.1 μm or less. Although the effect of the present invention can be sufficiently obtained as it is, it is more preferable that Ry is set to 1.0 μm or less by processing using a finer grindstone or processing using an alumina slurry. .

By forming the target shape such that the erosion portion is protruded, the generation of nodules is suppressed and the adhesion of the yellow powder is strengthened without being affected by the small displacement and strength of the magnet. It is possible to industrially manufacture an ITO target, that is, an ITO target that can suppress the adhesion of both the nodule-based particles and the yellow powder-based particles to the substrate.

The definition and measuring method of Ra and Ry according to the present invention are in accordance with JIS B0601-1994.
The O-sintered body can be easily bonded to a backing plate made of oxygen-free copper or the like by using indium solder or the like.

At the time of sputtering, an oxygen gas or the like is added as necessary to an inert gas such as argon as a sputtering gas, and usually 2 to 10 mTorr.
This is performed while controlling these gas pressures to r. As a power application method for sputtering, DC, RF, or a combination thereof can be used.

The sputtering target according to the present invention is also effective for a target to which a third element is added for the purpose of imparting an additional function to ITO. As the third element, for example, Mg, Al, Si, T
i, Zn, Ga, Ge, Y, Zr, Nb, Hf, Ta and the like can be exemplified. The addition amount of these elements is not particularly limited. However, in order not to deteriorate the excellent electro-optical characteristics of ITO, (the total amount of oxides of the third element)
0% at // (ITO + sum of oxides of third elements) / 100
Over 20% (weight ratio).

[0046]

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

Example 1 900 g of indium oxide powder having an average particle diameter of 1.3 μm and 100 g of tin oxide powder having an average particle diameter of 0.7 μm were put in a polyethylene pot and mixed for 72 hours by a dry ball mill. Manufactured.
When the tap density of the mixed powder was measured, it was 2.0 g /
cm ³ .

Next, a dispersant, a binder, and ion-exchanged water were added to the mixed powder and mixed by a ball mill to prepare a casting slurry. Subsequently, an antifoaming agent was added to the slurry, and a degassing treatment was performed in a vacuum.

This was poured into a mold capable of forming the shape shown in FIG. 4 and cast-molded to obtain an ITO molded body. After drying, the compact was subjected to a CIP treatment at a pressure of 3 ton / cm ² . Thereafter, in order to remove the dispersant and the binder present in the molded body, the molded body was placed in an air firing furnace, and dewaxing was performed under the following conditions. (Dewaxing conditions) Dewaxing temperature: 450 ° C, heating rate: 5 ° C / Hr, holding time: none Next, the compact after dewaxing was placed in a pure oxygen atmosphere sintering furnace, and the following conditions were applied. Sintered. (Sintering conditions) Sintering temperature: 1500 ° C, heating rate: 25 ° C
/ Hr, sintering time: 10 hours, atmosphere: 800 ° C. at elevated temperature
To a temperature of 400 ° C. when the temperature was lowered, and pure oxygen gas was introduced into the furnace at (charge weight / oxygen flow rate) = 0.8. The size of the obtained sintered body was 101.6 × 177.8 mm.
The thickness of the erosion portion was 8 mm, and the thickness of the non-erosion portion was 6 mm. The density of this sintered body is determined according to JISR163
It was measured by the Archimedes method based on 4-1998.
Table 1 shows the results.

Next, the surface of the sintered body to be the sputter surface was blasted. Blast pressure is 4kg / c
m ² , the distance between the nozzle and the target surface is 150 mm, and the blast material has a particle size in the range of 25 to 106 μm (average particle size 5
3 μm) spherical zirconia beads were used, and the blasting time was 80 seconds. After the blast treatment, Ra and Ry of the sputtering surface (blast treatment surface) of the target were measured. Table 1 shows the results.

Next, the surface of the protruding portion was processed using a surface grinder. First use # 120 whetstone, # 4
00, # 800 and the number of whetstones were sequentially increased. Ra and Ry of the protrusion after grinding were measured. Table 1 shows the results.

Next, this sintered body was joined on a backing plate made of oxygen-free copper using indium solder, and
An O target was obtained.

This target was sputtered under the following sputtering conditions for 60 hours near the target life end. (Sputtering conditions) DC power: 300 W, sputtering gas: Ar + O ₂ , gas pressure: 5 mTorr, O ₂ / Ar:
0.1% Thereafter, a Si wafer is put into the apparatus, an ITO film of 150 nm is formed on the wafer again under the above conditions, and the number of particles of 1 μm or more adhered on the wafer is measured using a laser particle counter. did. Table 1 shows the results. Only a few particles adhered.

Observation of the target surface after use revealed that the amount of nodules generated was small and the yellow powder was firmly adhered to the target surface.

(Embodiment 2) In the same manner as in Embodiment 1, the IT
An O-sinter was obtained. Table 1 shows the result of measuring the density of the obtained sintered body. A blast treatment was performed on this sintered body in the same manner as in Example 1. Table 1 shows Ra and Ry of the treated surface. Next, the protruding erosion portion was subjected to surface grinding in the same manner as in Example 1, and then # 120
Grinding was performed using a whetstone of 0. Ra and R after grinding
Table 1 shows y.

Next, after the target was formed in the same manner as in Example 1, the same sputtering as in Example 1 was performed. Table 1 shows the results. Only a few particles adhered.

Observation of the target surface after use revealed that the amount of nodules generated was small and the yellow powder was firmly adhered to the target surface.

(Comparative Example 1) A casting slurry was prepared in the same manner as in Example 1, and poured into a mold capable of forming a parallel plate-shaped molded body, and subjected to cast molding to obtain an ITO molded body. Thereafter, drying was performed in the same manner as in Example 1, and CI
P, dewaxing and sintering, 101.6 × 177.8
A sintered body having a thickness of 8 mm and a thickness of 8 mm was obtained. Table 1 shows the measurement results of the density of the obtained sintered body.

The sintered body was subjected to blasting of the sputtering surface in the same manner as in Example 1. R of processing surface
Table 1 shows a and Ry.

Next, after the target was formed in the same manner as in Example 1, the same sputtering as in Example 1 was performed. Table 1 shows the results. Many particles adhered to the substrate.

Observation of the target surface after use showed that a large amount of nodules was generated although the yellow powder was firmly attached to the target surface.

(Comparative Example 2) A casting slurry was prepared in the same manner as in Example 1, and poured into a mold capable of forming a parallel plate type molded body, and subjected to cast molding to obtain an ITO molded body. Thereafter, drying was performed in the same manner as in Example 1, and CI
P, dewaxing and sintering, 101.6 × 177.8
To obtain a sintered body having a thickness of 8 mm. Table 1 shows the measurement results of the density of the obtained sintered body.

The sintered body was subjected to surface processing on a sputtering surface using a surface grinder. First, using # 120 whetstone, the number of whetstones was sequentially increased to # 400, # 800. Table 1 shows the measurement results of Ra and Ry of the protrusion after grinding.

Next, after the target was formed in the same manner as in Example 1, the same sputtering as in Example 1 was performed. Table 1 shows the results. Many particles adhered to the substrate.

Observation of the target surface after use revealed that although nodule generation was small, a part of the yellow powder was peeled off from the target surface.

(Comparative Example 3) A casting slurry was prepared in the same manner as in Example 1, and poured into a mold capable of forming a parallel plate-shaped molded body, and subjected to cast molding to obtain an ITO molded body. Thereafter, drying was performed in the same manner as in Example 1, and CI
P, dewaxing and sintering, 101.6 × 177.8
To obtain a sintered body having a thickness of 8 mm. Table 1 shows the measurement results of the density of the obtained sintered body.

The sintered body was subjected to surface processing on the sputtering surface using a surface grinder. First # 120
, The number of the grinding stones was sequentially increased in the order of # 400 and # 800. Table 1 shows the measurement results of Ra and Ry of the protrusion after grinding.

Next, the erosion area was determined based on the target after the sputtering used in Comparative Example 2,
The portion corresponding to the erosion region was subjected to a masking process on the sintered body being manufactured in Comparative Example 3. In the same manner as in Example 1 for the masked sintered body,
A blast treatment was performed on the sputtering surface. Table 1 shows Ra and Ry of the surface not subjected to the masking treatment.

Next, after the target was formed in the same manner as in Example 1, the same sputtering as in Example 1 was performed. Table 1 shows the results. Many particles adhered to the substrate.

Observation of the target surface after use showed that the generation of nodules was generally small, and that the yellow powder had adhered to the target surface. However, a part of the erosion area was blasted, and a large amount of nodules was generated in this area. In addition, a non-erosion region not subjected to blasting was formed, and peeling of the yellow powder was observed in this portion.

(Comparative Example 4) IT was performed in the same manner as in Example 1.
An O-sinter was obtained. Table 1 shows the measurement results of the density of the obtained sintered body. A blast treatment was performed on this sintered body in the same manner as in Example 1. Table 1 shows Ra and Ry after the treatment.

Next, after the target was formed in the same manner as in Example 1, the same sputtering as in Example 1 was performed. Table 1 shows the results. Many particles adhered to the substrate.

Observation of the target surface after use revealed that a large amount of nodules was generated although the yellow powder was firmly attached to the target surface.

[0074]

[Table 1]

According to the present invention, it is possible to industrially produce an ITO sputtering target capable of suppressing both nodule-based particles and yellow powder-based particles.

[0075]

[Brief description of the drawings]

FIG. 1 is a view showing the appearance of an ITO sputtering target of the present invention.

FIG. 2 is a diagram showing an example of a cross-sectional shape of an ITO sputtering target of the present invention.

FIG. 3 is a diagram showing an example of a cross-sectional shape of an ITO sputtering target of the present invention.

FIG. 4 is a diagram showing an example of a cross-sectional shape of an ITO sputtering target of the present invention.

FIG. 5 is a diagram showing an example of a cross-sectional shape of an ITO sputtering target of the present invention.

Claims (4)

[Claims] 1. An ITO sputtering target substantially consisting of indium, tin and oxygen, wherein a thickness of a non-erosion portion is made smaller than a thickness of an erosion portion so that the erosion portion protrudes, and a flat surface including the erosion portion is formed. The surface including the non-erosion portion is connected by an obtuse slope, the protruding erosion portion has a surface roughness (Ra) of 0.1 μm or less, the non-erosion portion and the slope connecting the erosion portion and the non-erosion portion. An ITO sputtering target, characterized by having a surface roughness (Ra) of 1.0 μm or more. 2. The ITO sputtering target according to claim 1, wherein the relative density of the ITO sintered body is 99% or more. 3. The ITO sputtering target according to claim 1, wherein a maximum height (Ry) of the protruding erosion portion is 1.0 μm or less. 4. The maximum height (Ry) of the slope connecting the non-erosion part, the erosion part and the non-erosion part is 8.
The ITO sputtering target according to claim 1, wherein the thickness is 0 μm or more.