JP4918737B2 - Oxide sintered body and sputtering target - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oxide sintered body and a sputtering target used in the production of a transparent conductive thin film.
[0002]
[Prior art]
ITO (Indium Tin Oxide) thin film has characteristics such as high conductivity and high transmittance, and can be finely processed. Therefore, flat panel display display electrodes, film resistance touch panels, solar cell window materials, antistatic films, It is used in a wide range of fields such as anti-electromagnetic wave films, anti-fogging films, and sensors.
[0003]
Methods for producing such an ITO thin film can be roughly divided into chemical film formation methods such as spray pyrolysis and CVD, and physical film formation methods such as electron beam evaporation and sputtering. In particular, the sputtering method using an ITO target is easy to increase in area, has little change over time in the resistance value and transmittance of the obtained film, and can easily control the film formation conditions in various fields. in use.
[0004]
In recent years, attempts have been made to add a third element for the purpose of imparting a new function to the ITO thin film. For example, a method of adding Ta or Hf for the purpose of reducing the resistivity of a thin film, a method of adding Ce for the purpose of reducing the amount of nodule generation, a method of adding C, F, B or the like for the purpose of improving etching characteristics, A method of adding Al and / or Si for the purpose of increasing the resistivity of the thin film can be exemplified.
[0005]
For the purpose of improving the sintering density, for example, US Pat. No. 5,433,901 and the like have 0.05 to 0 as a sintering aid with at least one selected from aluminum oxide, magnesium oxide, yttrium oxide and silicon oxide. A method of adding 25% by weight is disclosed.
[0006]
[Problems to be solved by the invention]
The present inventors paid attention to a method of adding magnesium as the third element for the purpose of improving the durability (moisture resistance and high temperature resistance) of the ITO thin film. This magnesium-containing ITO film has the characteristics that the film surface is flat and the etching characteristics are improved, and the resistivity of the thin film is slightly higher than that of ITO. have.
[0007]
A sputtering target for obtaining such a thin film composed of In, Sn, Mg, and O has been manufactured by mixing, molding, and firing indium oxide powder, tin oxide powder, and magnesium oxide powder. However, when sputtering is performed using the target manufactured by such a method, arcing frequently occurs during sputtering. If arcing occurs during sputtering, particles adhere to the substrate and reduce the yield in the film forming process, which is an important problem to be solved.
[0008]
The subject of this invention is providing the sputtering target which consists of In, Sn, Mg, and O which is hard to generate | occur | produce arcing during sputtering.
[0009]
[Means for Solving the Problems]
In order to solve the above problem, the present inventors have examined the relationship between the structure of a sintered body made of In, Sn, Mg, and O and the occurrence frequency of arcing. It was found that there is a correlation between composition ratio and arcing frequency. As a result of further experiments based on this knowledge, the sintered body was composed of 10 to 20 atomic% tin, 0.5 atomic% or less magnesium, the remainder consisting of indium and oxygen, and tin. It is composed only of particles of 5 atomic% or less, magnesium of 0.8 to 1.5 atomic%, and the balance of indium and oxygen, and does not have other particles such as particles containing 2 atomic% or more of magnesium. It has been found that the above problems can be solved by using an oxide sintered body, and the present invention has been completed.
[0010]
That is, the present invention is substantially composed of indium, tin, magnesium and oxygen, and the structure of the sintered body is composed of 10 to 20 atomic% of tin, 0.5 atomic% or less of magnesium, and the balance is composed of indium and oxygen. Oxide sintered body characterized in that it is composed only of particles and particles of tin of 5 atomic% or less, magnesium of 0.8 to 1.5 atomic%, and the balance of indium and oxygen, or
A sintered body substantially composed of indium, tin, magnesium, and oxygen, and the structure of the sintered body is particles composed of tin, magnesium, indium, and oxygen, and the particles exceed 1.5 atomic%. The present invention relates to an oxide sintered body characterized by the absence of magnesium-containing particles, and a sputtering target comprising these sintered bodies.
[0011]
Hereinafter, the present invention will be described in detail.
[0012]
As the raw material powder, indium oxide, tin oxide, magnesium oxide, magnesium hydroxide, or the like can be used. Use of magnesium hydroxide is preferable because the rate of occurrence of cracks in the molded product is reduced from the molding to the firing step. Hereinafter, although the case where magnesium hydroxide is used is described, it is needless to say that the same result can be obtained even when magnesium oxide is used.
[0013]
Each powder to be used is preferably a powder having a maximum secondary particle size of 1 μm or less and an average particle size of 0.4 μm or less. The average particle size in the present invention means the particle size of the powder corresponding to 50% of the volume-based cumulative distribution of particle size. This makes it easier to obtain a high-density sintered body.
[0014]
Next, although these powders are mixed, in order to obtain the oxide sintered body of the present invention, it is preferable to perform this mixing process in two stages. Specifically, first, a predetermined amount of indium oxide powder, tin oxide powder, and magnesium hydroxide powder are weighed and mixed using, for example, a shaker mixer or the like without using a medium such as a ball. In this mixing, it is important to increase the mixing degree of the powder and loosen the tertiary particles formed by aggregation of the secondary particles. Here, when a medium such as a nylon ball is used and mixed using, for example, a ball mill, the powder is not sufficiently loosened, and the powder is compacted in an insufficiently mixed state, which is not preferable.
[0015]
The mixing time in this step is preferably 10 minutes or more, and although there is no particular upper limit, it is sufficient to carry out for 1 hour.
[0016]
Subsequently, the powder mixed in this way is put into a pot of a ball mill together with a medium such as a nylon ball to perform second mixing and compaction of the powder. The mixing time in this step is preferably 10 to 30 hours. Since the compacted powder obtained in this way may be aggregated into coarse particles, the obtained mixed powder is passed through a sieve having an opening of about 300 μm to remove coarse particles that do not pass through the sieve. To do.
[0017]
The amount of tin oxide mixed is preferably 1.9 to 14% in terms of an atomic ratio of Sn / (Sn + In). More preferably, it is 4 to 11%. This is because, when a thin film is produced using the target of the present invention, the resistivity of the film is the lowest.
[0018]
The mixing amount of the magnesium hydroxide powder is preferably 0.1 to 20% in terms of the atomic ratio of Mg / (In + Sn + Mg). More preferably, it is 0.1-10%, More preferably, it is 0.5-5%. If the amount of magnesium hydroxide powder added is less than the above range, the etching characteristics and durability may be inferior, and if it exceeds the above range, the resistivity may be too high.
[0019]
Next, the obtained mixed powder is molded by a molding method such as a press method or a casting method to produce a molded body. In the case of producing a molded body by press molding, the mixed powder is filled in a mold having a predetermined size and then pressed at a pressure of 100 to 500 kg / cm ² using a press machine to obtain a molded body. At this time, a binder such as PVA may be added as necessary.
[0020]
On the other hand, in the case of producing a molded body by a casting method, the raw material powder is mixed with water, a binder and a dispersing agent to form a slurry, and the slurry having a viscosity of 50 to 5000 centipoise thus obtained is formed into a desired water-absorbing property. A molded body is prepared by pouring into a porous mold.
[0021]
The molded body thus obtained is treated by cold isostatic pressing (CIP) as necessary. At this time, since the pressure of the CIP to obtain a sufficient compaction effect 1 ton / cm ² or more, it is desirable that preferably is 2~5ton / cm ^2.
[0022]
When molding is performed by a casting method, a drying process and a debinding process are performed at a temperature of 300 to 500 ° C. for about 5 to 20 hours in order to remove moisture and organic substances such as a binder remaining in the molded body after CIP. It is preferable to apply. Even when the molding is performed by a press method, it is preferable to perform the same debinding process when a binder is used during molding.
[0023]
Next, the molded body thus obtained is fired. The temperature raising rate is not particularly limited, but is preferably 10 to 400 ° C./hour from the viewpoint of shortening the sintering time and preventing cracking.
[0024]
The sintering temperature is preferably 1450 ° C. to less than 1650 ° C., and preferably 1500 to 1600 ° C. in order to obtain a higher density sintered body.
[0025]
The sintering time is preferably 5 hours or more, preferably 5 to 30 hours in order to obtain a sufficient density increasing effect.
[0026]
The atmosphere during sintering is in an oxygen stream, and the ratio of the oxygen flow rate (L / min) and the charged amount of the compact (kg) when introducing oxygen into the furnace during sintering (charge weight / oxygen flow rate), 1.0 or less. By doing so, it becomes easy to obtain a high-density sintered body.
[0027]
The higher the sintered density (relative density), the better, preferably 95.0% or more. More preferably, it is 98.0% or more, and particularly preferably 99.0% or more.
[0028]
Note that the relative density in the present invention (D) shows the relative value with respect to In ₂ O _3, SnO ₂ and the theoretical density determined from the true density of the arithmetic mean of MgO (d). The theoretical density determined from the arithmetic mean (d), in the sintered body composition, In ₂ O _3, SnO ₂ and mixtures of MgO powder (g), respectively a, b, when the c, In ₂ O ₃ , using SnO ₂ and MgO true densities of 7.18, 6.95, 3.58 (g / cm ³ ),
d = (a + b + c) / ((a / 7.18) + (b / 6.95) + (c / 3.58)). When the measured density of the sintered body is d1, the relative density D (%) is obtained by the formula: D = (d1 / d) × 100.
[0029]
When magnesium hydroxide is used as the raw material powder, the magnesium hydroxide contained in the added magnesium hydroxide is all converted to magnesium oxide, and calculated by converting the added weight of magnesium hydroxide into the added weight of magnesium oxide. do it.
[0030]
The oxide sintered body thus obtained was composed of particles containing 10 to 20 atomic percent of tin, 0.5 atomic percent or less of magnesium, 15 to 25 atomic percent of indium, and the balance of oxygen and 5 percent of tin. It is composed only of particles of atomic% or less, magnesium of 0.8 to 1.5 atomic%, indium of 35 to 40 atomic%, and the balance of oxygen. Further, the particles constituting this sintered body are characterized in that there are no particles containing magnesium exceeding 1.5 atomic%.
[0031]
The composition of each particle can be measured using, for example, EPMA (Electron Probe Micro Analysis). In the present invention, MgO, Sn, and InAs were used as standard samples, and measurements were performed under conditions of an acceleration voltage of 15 kV and an irradiation current of 0.02 μA.
[0032]
The sintered body obtained in this manner can be processed and polished as necessary, and then joined with an indium solder or the like on a backing plate made of oxygen-free copper or the like for easy targeting.
[0033]
In sputtering, oxygen gas or the like is added as necessary to an inert gas such as argon as the sputtering gas, and is usually performed while controlling the gas pressure to 2 to 10 mTorr. As a power application method for sputtering, DC, RF, or a combination thereof can be used.
[0034]
In addition, the sputtering target according to the present invention is also effective in a target to which a fourth element is added for the purpose of providing an additional function. Examples of the fourth element include Al, Si, Ti, Zn, Ga, Ge, Y, Zr, Nb, Hf, and Ta. The addition amount of these elements is not particularly limited, but it does not deteriorate the excellent electro-optical characteristics of ITO. Therefore, (total of oxides of fourth element) / (total of oxides of ITO + fourth element) ) / 100, preferably exceeding 0% and not more than 20% (weight ratio).
[0035]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.
[0036]
Example 1
Shaker mixer with 450 parts by weight of indium oxide powder (average particle size 0.4 μm), 50 parts by weight of tin oxide powder (average particle size 0.3 μm) and 0.25 parts by weight of magnesium hydroxide powder (average particle size 0.4 μm) For 20 minutes. The Sn amount (Sn / (Sn + In)) in the mixed powder was 9.3% by atomic ratio, and the Mg amount (Mg / (In + Sn + Mg)) was 0.12% by atomic ratio.
[0037]
Next, the obtained mixed powder is put into a polyethylene pot together with nylon balls, mixed and compacted by a dry ball mill for 72 hours to prepare a mixed powder, and then the obtained powder is passed through a sieve having an opening of 300 μm to obtain coarse particles. Was removed.
[0038]
The mixed powder thus obtained was put into a mold and pressed at a pressure of 300 kg / cm ² to obtain a molded body. These molded bodies were subjected to CIP treatment at a pressure of 3 ton / cm ² .
[0039]
Next, the obtained molded body was placed in a pure oxygen atmosphere sintering furnace and fired under the following conditions.
(Sintering conditions)
Temperature increase rate: 50 ° C./hour, sintering temperature: 1600 ° C., sintering time: 5 hours, atmosphere: pure oxygen gas in the furnace from 800 ° C. during temperature increase to 400 ° C. during temperature decrease (feed weight / oxygen flow rate) ) = 0.8,
When the density of the obtained sintered body was measured by the Archimedes method, it was 99.2%.
[0040]
From this sintered body, a target sintered body having a thickness of 5 × 7 inches and a thickness of 6 mm and a sample for analysis were cut out by wet processing. The composition ratio of each particle was measured using EPMA. Particles composed of 13 to 17 atomic% tin, 0 to 0.3 atomic% magnesium, 25 atomic% indium, and the balance oxygen, tin 2-3 atomic%, magnesium 0.9-1. Particles composed of 3 atomic%, indium from 36 to 39 atomic%, and the balance consisting of oxygen were observed.
[0041]
On the other hand, the target sintered body was bonded to an oxygen-free copper backing plate using indium solder to obtain a target. This target was continuously discharged under the following sputtering conditions to examine the amount of arcing.
(Sputtering conditions)
DC power: 300 W, gas pressure: 5.0 mTorr, sputtering gas: Ar + oxygen, oxygen gas concentration in sputtering gas (O ₂ / Ar): 0.05%, discharge time: 66 hours (remaining target 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 most reduced.
[0042]
The cumulative number of arcing occurrences during 66 hours of continuous discharge was as low as 140 times.
[0043]
Comparative Example 450 parts by weight of indium oxide powder (average particle size 0.4 μm), 50 parts by weight of tin oxide powder (average particle size 0.3 μm) and 0.25 parts by weight of magnesium hydroxide powder (average particle size 0.4 μm) The mixture was put in a polyethylene pot together with nylon balls and mixed and compacted for 72 hours by a dry ball mill to prepare a mixed powder. The obtained mixed powder was put into a mold and pressed at a pressure of 300 kg / cm ² to obtain a molded body. These molded bodies were subjected to CIP treatment at a pressure of 3 ton / cm ² .
[0044]
Next, the obtained molded body was fired under the same conditions as in the examples.
[0045]
It was 98.9% when the density of the obtained sintered compact was measured by the Archimedes method.
[0046]
From this sintered body, a target sintered body having a thickness of 5 × 7 inches and a thickness of 6 mm and a sample for analysis were cut out by wet processing. The composition ratio of each particle was measured using EPMA. Particles composed of 13 to 17 atomic% tin, 0 to 0.3 atomic% magnesium, 25 atomic% indium, and the balance oxygen, tin 2-3 atomic%, magnesium 0.9-1. In addition to particles composed of 3 atomic%, indium 36-39 atomic% and the balance consisting of oxygen, particles containing 2 atomic% magnesium in one particle were observed.
[0047]
On the other hand, the target sintered body was bonded to an oxygen-free copper backing plate using indium solder to obtain a target. This target was discharged under the same conditions as in Example 1 to examine the amount of arcing. The cumulative number of arcing occurrences after the end of the discharge was very high at 445 times.
[0048]
【Effect of the invention】
As described above, according to the present invention, it is possible to provide a sputtering target that is substantially made of indium, tin, magnesium, and oxygen with low occurrence of arcing during sputtering.

Claims (3)

Lee indium, tin, a sintered body made of magnesium and oxygen, 10-20 atomic% tissue tin of the sintered body, magnesium 0.5 atomic% or less, the crystal grains and the balance of indium and oxygen And an oxide sintered body comprising only 5 atomic% or less of tin, 0.8 to 1.5 atomic% of magnesium, and the remainder being crystal grains made of indium and oxygen. 2. The sintered body according to claim 1, wherein the relative density of the sintered body is 95% or more. A sputtering target made of a sintered body according to claim 1 or 2.