KR20020079404A - Ito sputtering target - Google Patents

Abstract

PURPOSE: 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. CONSTITUTION: 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

ITO sputtering target {ITO sputtering target}

The present invention relates to an ITO sputtering target used in the manufacture of a transparent conductive thin film.

The manufacturing method of the indium tin oxide (ITO) thin film which is a transparent conductive film can be roughly divided into chemical film-forming methods, such as the spray pyrolysis method and CVD method, and physical film-forming methods, such as an electron beam vapor deposition method and sputtering method. Among them, the sputtering method using an ITO target has been used in various fields because it is easy to make a large area, there is little change over time of the resistance value and transmittance of the film obtained, and the control of the film forming conditions is easy.

In particular, the DC magnetron sputtering method in which a magnet is placed behind a sputtering target and a magnetic field is formed on the target surface to converge the plasma has a high film forming speed, and is widely employed as a mass production device. have.

Such ITO thin films are characterized by high electrical conductivity and high transmittance, and are particularly easy to perform fine processing, and are expanded to a wide range of fields such as display electrodes for flat panel displays, window materials for solar cells, and antistatic films. It is being used. In particular, in the field of flat panel displays, including liquid crystal display devices, in recent years, enlargement and high definition have been progressed, and the demand for low particle size for the ITO thin film as the display electrode is increasing.

Examples of the generation of particles include those caused by the nodule formed in the erosion portion and those caused by the yellow powder deposited on the non-erozone portion of the target.

A nodule is black deposit which generate | occur | produces on a target surface with the increase of accumulated sputtering time, when the ITP target is sputtered continuously in the mixed gas atmosphere of argon gas and oxygen gas. It is known that this black deposit, which is considered to be a lower oxide of indium, is likely to be a cause of abnormal discharge during sputtering, and these are themselves a cause of generation of particles. .

On the other hand, the yellow powder deposited on the non-erozone portion of the target surface increases in the amount of deposition as the sputtering time increases, and when it reaches a certain thickness, it is separated from the target surface, floats in vacuum, and adheres to the substrate surface. Done. This yellow powder is changed in direction by collision with gas particles (argon, oxygen, etc.) in the vacuum chamber before the target material discharged from the erozone portion reaches the opposing substrate, and thus the non-target surface is released. It is thought to be deposited in the erotic zone. When such a yellow powder adheres to a substrate, display quality, such as a liquid crystal display device, is reduced, it becomes a cause of a defect, and the production rate of a product is badly reduced.

As a means for reducing the particles caused by the nodule, for example, Japanese Patent Application Laid-Open No. 05-148635 obtains a target density and bulk resistivity within a certain range and at the same time the surface roughness Ra of the sputtered surface. It has been reported how to make 0.5 μm or less. However, this method had an effect of reducing particles due to nodules, but had no effect on reducing particles due to yellow powder.

On the other hand, as a means of reducing the particle | grains which originate in yellow powder, the method of raising the adhesion strength of a yellow powder by making a target surface rough, for example as Unexamined-Japanese-Patent No. 60-193364 is reported. However, in such a case, even if there was an effect of reducing particles due to yellow powder, there was no effect on particles due to nodule.

For this reason, the development of a new ITO target is required to simultaneously reduce particles caused by both the nodule and the yellow powder.

The problem of the present invention is that the amount of generation of particles due to yellow powder deposited on non-erozone parts and particles due to nodules generated in the erozone part increases as the accumulated use time of the ITO target increases. An object of the present invention is to provide an ITO sputtering target that can be reduced.

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

It is a figure which shows an example of the cross-sectional shape of the ITO sputtering target of this invention.

It is a figure which shows an example of the cross-sectional shape of the ITO sputtering target of this invention.

It is a figure which shows an example of the cross-sectional shape of the ITO sputtering target of this invention.

It is a figure which shows an example of the cross-sectional shape of the ITO sputtering target of this invention.

MEANS TO SOLVE THE PROBLEM The present inventors make the surface roughness of a non-erozone part rough with respect to a parallel plate-shaped target based on the said well-known technique, reduces the surface roughness of an erozone part, An experiment was conducted to investigate adhesion. However, it was not possible to reduce the amount of nodule generation with good reproducibility and to increase the adhesion of the yellow powder.

This cause is as showing in the following reasons. 1) It is difficult to specify the erozone region of the target surface. 2) Even in a cathode of the same design, the erosion part is slightly different due to the slight difference in the magnetic force of the magnet located below it. 3) If an area having a rough surface roughness is formed even at a small width in the erozone portion, most of the nodules are generated in this portion, so even in a target of the same size, the area is designed for each cathode and the surface roughness is controlled. Since it is necessary to do so, it cannot be a technique that can be used industrially.

However, the inventors of the present invention conducted a detailed inspection on the shape and surface roughness of the target, using a method that can be used industrially, to reduce the amount of nodule generation with good reproducibility and to increase the adhesion of the yellow powder. A thorough examination was conducted.

As a result, the thickness of the non-erozone portion is made thinner than the thickness of the aerozone portion to protrude the aerozone portion, and at the same time, the ITO having a shape in which the plane including the aerozone portion and the plane containing the non-erozone portion are connected by an obtuse inclined surface. In the sputtering target, the surface roughness Ra of the protruding aerozone portion is 0.1 μm or less, and the surface roughness Ra of the slope connecting the non-erozone portion and the aerozone portion and the non-erozone portion is 1.0 μm or more. By doing so, it was found that the particles caused by the nodule and the yellow powder can be reduced, thereby completing the present invention.

That is, in the present invention, in the ITO sputtering target using a sintered body made of indium, tin, and oxygen, the thickness of the non-erozone portion is made thinner than the thickness of the erozone portion to protrude the erozone portion, The plane including the plane and the plane containing the non-erozone portion is formed into an oblique angled slope, the surface roughness (Ra) of the protruding aerozone portion is 0.1μm or less, the non-erozone portion and the erozone portion and the non-ero The surface roughness Ra of the slope which connected the zone part is 1.0 micrometer or more, It is related with the ITO sputtering target characterized by the above-mentioned.

Hereinafter, the present invention will be described in detail.

Although the ITO sintered compact used for this invention is not specifically limited, For example, it can manufacture by the following method.

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

In addition, it is preferable that tin oxide content in a mixed powder or ITO powder shall be 2-25 weight% (oxide conversion) in which a specific resistance falls when a thin film is manufactured by sputtering method.

When indium oxide powder and tin oxide powder are used as the raw material powder, the powder is mixed first. Mixing of the powder may be performed 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 an injection method to produce an ITO molded body. In the case of producing a molded article by press molding, after filling the mixed powder into a mold having a predetermined size, the molded article is pressed by pressing at a pressure of 100-500 kg / cm ² using a press machine. At this time, if necessary, a binder such as PVA may be added.

On the other hand, in the case of producing a molded article by injection method, the raw material powder is mixed with water, a binder, and a dispersant to make a slurry, and thus the slurry having a viscosity of 50-5000 cP (centifaz) is absorbed in a desired shape. It is injected into a porous molding mold having a molded article.

The cross-sectional shape when the external appearance of the target of this invention is cut | disconnected perpendicularly with respect to the target shown in FIG. 1 and its external appearance in the plane containing A-A is shown in FIG. As the cross-sectional shape of the target of the present invention, the present invention is also effective as an annular target in which the sintered body in the center is removed, as shown in Fig. 2. Or it is effective with respect to both the thing which the sintered compact bonded to one backing plate is comprised as one sheet, and the multidivided target which bonded several sintered compacts to one backing plate.

When the injection method is used as the molding method, the molded body can be produced in a desired shape, and it is preferable because no subsequent processing step is required.

After that, the molded article thus obtained is subjected to a cold isostatic press (CIP) if necessary. At this time, the CIP pressure is preferably 1 ton / cm ² or more, preferably 2 to 5 ton / cm ² , in order to obtain a sufficient consolidation effect.

When shaping | molding is performed by the press method, it processes to a desired shape here. Although it is also possible to process after sintering, since the hardness of a molded object is much lower than that of a sintered compact, and can be processed easily, it is preferable to process at this stage, but there is no difference even if it is performed after sintering.

When the molding is carried out by the injection method, drying and debinding treatment are performed for about 5-20 hours at a temperature of 300 to 500 ° C. in order to remove moisture and organic substances such as binder remaining in the molded body after CIP. It is desirable to. Moreover, even when shaping | molding is performed by the press method, when using a binder at the time of shaping | molding, it is preferable to perform the binder removal process of the same form.

Next, the molded product thus obtained is fired. Although there is no limitation in raising temperature, it is preferable to set it as 10-400 degreeC / hour from a viewpoint of shortening a sintering time and preventing a crack.

Sintering temperature is 1450 degreeC or more and less than 1650 degreeC, Preferably you may be 1500-1600 degreeC. By doing this, it is possible to obtain a high density sintered compact.

Also in the sintering time, in order to obtain sufficient density synergistic effect, it is preferable to set it as 5 hours or more, Preferably it is 5-30 hours.

Atmosphere at the time of sintering is 1.0 or less in ratio of oxygen amount (L / min) and injection amount of a molded object (kg) when oxygen is introduced in a furnace at the time of sintering at 1.0 or less Shall be. By doing in this way, a high density sintered compact is easy to be obtained.

The higher the sintered density is, the better the nodule reduction effect is, so 99.0% or more is preferable. More preferably, it is 99.5% or more, Especially preferably, it is 99.7% or more.

Further, the relative density is (D) according to the present invention, represents a relative value of the theoretical density (d), which is available from In ₂ O ₃ and commercial average (相加平均) the true density of the SnO ₂ (眞密度). Theoretical density (d), which can be obtained from the average of the averages, refers to the true density of In ₂ O ₃ and SnO ₂ when the mixed amount (g) of In ₂ O ₃ and SnO ₂ powder is a and b in the sintered body composition, respectively. Using 7.18, 6.95 (g / cm ³ ),

It can obtain | require by d = (a + b) / ((a / 7.18) + (b / 6.95)). Therefore, if the measured density of a sintered compact is d1, the relative density D (%) can be calculated | required by Formula: D = (d1 / d) * 100.

Next, a blasting process is performed with respect to the sputtering surface (with an aerozone part and a non-erozone part) of an ITO sintered compact. As a specific method, it is performed by making a blast material collide with a to-be-processed surface at high speed, for example, by spraying gas, such as air containing a blast material, or liquid, such as water, to a to-be-processed surface.

Alumina, glass, zirconia, SiC, etc. can be used for a blast material (powder used for a blasting process), but the spherical zirconia powder which formed each particle | grain of zirconia spherically is made into the blasted target surface ( The surface to be treated) is particularly preferable because it is not contaminated.

As the shape of the blasting material, acicular, granular, spherical and the like can be used, and the particle diameter thereof is preferably 10-500 µm, particularly preferably 10-200 µm.

The pressure (blast pressure) applied to a fluid such as air used as a medium to impinge the blast material onto the target surface is preferably about 1-10 kg / cm ² , particularly preferably 2-7 kg / cm ² , , 3-5 kg / cm ² is more preferred. If this pressure is high, the collision with the target surface will become strong, and it will not only cause a crack, but also a large capacity compressor will be needed and cost will become high.

As for the distance of the nozzle which blows out a blast material, and a target surface, about 50-300 mm is preferable. When the distance is close, the effective area to which a blasting process is performed becomes small and it is inefficient.

Although the blast processing time of a target surface changes also with a blast pressure, a kind of blast material, etc., it is preferable to process at 0.05-1.0 second / cm <^2> . By doing in this way, Ra of the whole sputtering surface of an ITO sintered compact becomes 1.0 micrometer or more, and Ry becomes 8.0 micrometers or more.

Next, the protruding aerozone portion is processed using a planar grinding machine or the like to reduce the surface roughness. First, the first grinding is performed using the # 120 grindstone (grindstone), and then the second grinding is performed using the # 400 grindstone, and then polished using the # 800 grindstone. By doing in this way, it is possible to make Ra of the protruding erozone part into 0.1 micrometer or less. Although the effect of this invention is fully acquired even if it does in this way, it is further more preferable to make Ry into 1.0 micrometer or less by processing using the grindstone having a small number of times, or processing using the slurry made from alumina.

The target shape is a shape in which the erosion portion is protruded, so that the generation of nodules is suppressed and the adhesion of the yellow powder is enhanced, i.e., due to the nodules and the yellow powder, without being influenced by the misalignment of the magnet arrangement and the strength. It is possible to industrially produce an ITO target capable of suppressing substrate adhesion of all of the resulting particles.

In addition, the definition and the measuring method of Ra and Ry in this invention are based on what was described in JIS B0601-1994.

The ITO sintered body thus obtained can be bonded to a backing plate made of oxygen-free copper or the like using indium inversion or the like and easily targeted.

In the case of sputtering, as a sputtering gas, oxygen gas or the like is added to an inert gas such as argon or the like if necessary, and is usually performed while suppressing these gas pressures at 2-10 mTorr. As a power application method for sputtering, DC, RF, or a combination thereof can be used.

In addition, the sputtering target by this invention is effective also in the target which added the 3rd element in order to have additional function to ITO. As the third element, for example, Mg, Al, Si, Ti, Zn, Ga, Ge, Y, Zr, Nb, Hf, Ta and the like can be exemplified. The amount of such elements added is not particularly limited, but in order not to lower the excellent electro-optical properties of ITO, (totalization of oxides of the third element) / (totalization of oxides of the third element) / 100 is more than 0%. It is preferable to set it as 20% or less (weight ratio).

<Example>

Hereinafter, the present invention will be described in detail as 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 placed in a polyethylene pot and mixed for 72 hours by a dry ball mill to prepare a mixed powder. It was 2.0 g / cm <^{3> when} the tap density of the said mixed powder was measured.

Next, a dispersant, a binder, and ion-exchanged water were added to the mixed powder, followed by ball mill mixing to prepare a slurry for injection. Subsequently, an antifoaming agent was added to this slurry, and degassing treatment was performed in vacuo.

These were flowed into the mold which can form the shape shown in FIG. 4, injection molding was performed, and the ITO molded object was obtained. After drying, this molded object was subjected to CIP treatment at a pressure of 3 ton / cm ² . Subsequently, in order to remove the dispersing agent and binder which exist in a molded object, the said molded object was installed in the air baking furnace, and the dewaxing process was performed on condition of the following.

(Dewaxing condition)

Dewaxing temperature: 450 ℃, Heating rate: 5 ℃ / Hr, Holding time: None

Next, the molded body after dewaxing was installed in the pure oxygen atmosphere sintering furnace, and it sintered on condition of the following.

(Sintering condition)

Sintering temperature: 1500 ° C, Heating rate: 25 ° C / Hr, Sintering time: 10 hours, Atmosphere: Pure oxygen gas from furnace at 800 ° C to 400 ° C at high temperature, (injection weight / oxygen flow rate) = Introduced at 0.8.

The obtained sintered compact size was 101.6x177.8 mm, and the thickness of an aerozone part was 8 mm and the thickness of a non-erozone part 6 mm. The density of this sintered compact was measured by the Archimedes method based on JISR 1634-1998. The results are shown in Table 1.

Next, the surface of the surface which consists of the sputter surface of this sintered compact was blasted. The blast pressure is 4 kg / cm ² , the distance between the nozzle and the target surface is 150 mm, and the blast material uses spherical zirconia beads in the range of 25 to 106 μm (average particle size: 53 μm), and the blast treatment time is It was set as 80 second. Ra and Ry of the sputtering surface (blast processing surface) of a target after blast processing were measured. The results are shown in Table 1.

Next, the surface processing of the part which protruded was performed using the planar grinder. Initially, the # 120 grindstone was used, and the number of grindstones was sequentially increased to # 400 and # 800. Ra and Ry of the protrusion part after grinding were measured. The results are shown in Table 1.

Next, this sintered compact was bonded to a backing plate made of oxygen-free copper using indium inversion to obtain an ITO target.

This target was sputtered for 60 hours close to the target life end under the following sputtering conditions.

(Sputtering condition)

DC power: 300 W, sputter gas: Ar + O ₂ , gas pressure: 5 mTorr, O ₂ / Ar: 0.1%

Thereafter, a Si wafer was introduced into the apparatus to form an ITO film of 150 nm on the wafer once again under the above conditions, and then the number of particles of 1 μm or more deposited on the wafer was measured using a laser particle counter. The results are shown in Table 1. Very little particles are attached.

As a result of observing the target surface after use, the amount of nodule generation was reduced, and the yellow powder was firmly attached to the target surface.

(Example 2)

An ITO sintered body was obtained in the same manner as in Example 1. The result of having measured the density of the obtained sintered compact is shown in Table 1. This sintered compact was blasted in the same manner as in Example 1. Ra and Ry of the treated surface are shown in Table 1. Next, after surface-grinding was performed with respect to the protruding erozone part by the method similar to Example 1, it grind | polished further using the grindstone of # 1200. Ra and Ry after grinding are shown in Table 1.

Next, after targeting in the same manner as in Example 1, the same sputtering as in Example 1. The results are shown in Table 1. Very little particles are attached.

As a result of observing the target surface after use, the generation of nodules was less, and the yellow powder was firmly attached to the target surface.

(Comparative Example 1)

Injecting slurry was produced in the same manner as in Example 1, and poured into a mold capable of forming a parallel plate-shaped molded product, followed by injection molding to obtain an ITO molded product. After this, drying, CIP, dewaxing and sintering were carried out in the same manner as in Example 1 to obtain a 8 mm thick sintered body as 101.6 x 177.8 mm. The result of having measured the density of the obtained sintered compact is shown in Table 1.

The sintered body was blasted on the sputtering surface in the same manner as in Example 1. Ra and Ry of the treated surface are shown in Table 1.

Next, after targeting in the same manner as in Example 1, the same sputtering as in Example 1. The results are shown in Table 1. A large amount of particles were attached to the substrate.

As a result of observing the used target surface, yellow powder was firmly attached to the target surface, but a large amount of nodules occurred.

(Comparative Example 2)

An injection slurry was produced in the same manner as in Example 1, flowed into a mold capable of forming a parallel plate-shaped molded product, and an ITO molded product subjected to injection molding was obtained. After this, drying, CIP, dewaxing and sintering were carried out in the same manner as in Example 1 to obtain a 8 mm thick sintered body as 101.6 x 177.8 mm. The result of having measured the density of the obtained sintered compact is shown in Table 1.

The surface processing of the sputtering surface was performed about the sintered compact using the planar grinding mill. Initially, the grindstone of # 120 was used, and the number of grindstones was sequentially increased to # 400 and # 800. After grinding, the measurement results of Ra and Ry of the protrusions are shown in Table 1.

Next, after targeting in the same manner as in Example 1, the same sputtering as in Example 1. The results are shown in Table 1. A large amount of particles were attached to the substrate.

As a result of observing the used target surface, the amount of nodules was reduced, but part of the yellow powder was peeled off from the target surface.

(Comparative Example 3)

An injection slurry was produced in the same manner as in Example 1, flowed into a mold capable of forming a parallel plate-shaped molded product, and an ITO molded product subjected to injection molding was obtained. After this, drying, CIP, dewaxing and sintering were carried out in the same manner as in Example 1 to obtain a 8 mm thick sintered body as 101.6 x 177.8 mm. The result of having measured the density of the obtained sintered compact is shown in Table 1.

The surface processing of the sputtering surface was performed about this sintered compact using the planar grinding mill. Initially, the grindstone of # 120 was used, and the number of grindstones was sequentially increased to # 400 and # 800. After grinding, the measurement results of Ra and Ry of the protrusions are shown in Table 1.

Next, the original sputtered target used in Comparative Example 2 was discriminated from the original erosion area, and the sintered compact during fabrication in Comparative Example 3 was masked for the portion corresponding to the erosion area. About the masked sintered compact, the blasting of the sputtering surface was performed by the method similar to Example 1. Table 1 shows Ra and Ry of the unmasked surface.

Next, after targeting in the same manner as in Example 1, the same sputtering as in Example 1. The results are shown in Table 1. A large amount of particles were attached to the substrate.

As a result of observing the used target surface, the amount of nodules was generally reduced, and yellow powder was attached to the target surface. However, part of the erosion region was formed in the blast region, and a large amount of nodules occurred in this portion. In addition, a non-blasted non-erosion region was formed, and peeling of the yellow powder was observed in this portion.

(Comparative Example 4)

An ITO sintered body was obtained in the same manner as in Example 1. Table 1 shows the measurement results of the density of the obtained sintered compact. The sintered compact was blasted in the same manner as in Example 1. Ra and Ry after the treatment are shown in Table 1.

Next, after targeting in the same manner as in Example 1, the same sputtering as in Example 1. The results are shown in Table 1. A large amount of particles were attached to the substrate.

As a result of observing the used target surface, yellow powder was strongly adhered to the target surface, but a large amount of nodule was generated.

Table 1

density[%] Erojon Wealth Non-erosion part and inclination part Particle Attachment [pcs] Ra [μm] Ry [μm] Ra [μm] Ry [μm] Example 1 99.7 0.07 1.10 1.40 10.60 2 Example 2 99.7 0.06 0.64 1.35 10.45 2 Comparative Example 1 99.7 1.40 10.66 1.42 10.70 20 Comparative Example 2 99.7 0.07 1.08 0.07 1.08 26 Comparative Example 3 99.7 0.07 1.09 1.40 10.58 12 Comparative Example 4 99.7 1.41 10.77 1.41 10.76 19

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

Claims (4)

In an ITO sputtering target made substantially from indium, tin and oxygen, the non-erozone portion is made thinner than the thickness of the erozone portion to protrude the erozone portion, and at the same time, the plane including the erozone portion and the non-erozone The plane including the portion is formed in a shape connected to an obtuse slope, and the surface roughness Ra of the protruding aerozone portion is 0.1 μm or less, and the surface roughness of the slope connecting the non-erozone portion and the non-erozone portion ( Ra) is 1.0 micrometer or more, The ITO sputtering target characterized by the above-mentioned. The ITO sputtering target according to claim 1, wherein the ITO sintered body has a relative density of 99% or more. The ITO sputtering target according to claim 1 or 2, wherein the maximum height Ry of the protruding aerozone portion is 1.0 µm or more. The ITO sputtering target according to any one of claims 1 to 3, wherein a maximum height Ry of a slope connecting the non-erozone portion and the non-erozone portion and the non-erozone portion is 8.0 µm or more.