JPH10306367A - ZnO-Ga2O3-based sintered body for sputtering target and method for producing the same - Google Patents

Abstract

(57) Abstract: abnormal discharge does not generate, stable, good ZnO-Ga ₂ O ₃ based film ₂ O ₃ based sintered sputtering target for ZnO-Ga that can be deposited characteristics Provided is a method for manufacturing a compact and a sintered body including a large-sized product at a low manufacturing cost and at a low cost. SOLUTION: The sintered body of the present invention comprises (1) TiO ₂ , G
including eO ₂ , Al ₂ O ₃ , MgO, In ₂ O ₃ and SnO ₂ ,
(2) The main constituent phases of the structure are Ti, Ge, Al, Mg,
(3) a sintered density of 5.
2g / cm ³ or more, (4) Volume resistivity is 2 × 10 ^-2 Ω ·
cm or less, (5) the average crystal grain size is 2 to 10 μm, and (6) the maximum pore diameter is 2 μm or less. Further, the method of the present invention for producing the above sintered body includes the steps of (1) TiO ₂ , GeO ₂ ,
A powder made of Al ₂ O ₃ , MgO, In ₂ O ₃ or SnO ₂ and a powder made of Ga ₂ O ₃ are added to ZnO powder and mixed (the above powders have an average particle size of 1 μm or less). ,
(2) Molding of the mixed powder is performed in a cold state, and (3) sintering of the molded body is performed at 1300 to 1550 ° C. at normal pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a sputtering target for ZnO-Ga ₂ O ₃ sintered body and a manufacturing method used in forming the transparent conductive film by sputtering.

[0002]

2. Description of the Related Art A transparent conductive film used as an electrode material of a liquid crystal display or a solar cell has a low specific resistance. Therefore, an In ₂ O ₃ —SnO ₂ (hereinafter referred to as ITO) film or a ZnO—Al ₂ film is used. O ₃ -based (hereinafter referred to as AZO) films are increasingly used. These transparent conductive films are formed on a heated substrate by a sputtering method using a sputtering target as a raw material. The formed film can have a specific resistance of 2 × 10 ⁻⁴ Ω · cm or less.

[0003] However, due to the recent tendency to reduce the cost of liquid crystal displays and solar cells, ITO has a problem in terms of cost because In ₂ O _{3 as} a main component is expensive. AZO has no problem in terms of cost because the raw material powder is inexpensive, but has a problem in productivity because the range of optimal film forming conditions for obtaining a low-resistance film is narrow.

In place of the above-mentioned ITO film and AZO film, a ZnO—Ga ₂ O ₃ (hereinafter referred to as “GZO”) film having low resistance and high durability without problem in cost and productivity, and hence a GZO film is formed. GZO sputtering targets used for this purpose are attracting attention. In particular, the conductivity of the GZO film is such that ZnO as a main component is excessive in metal (ZnO).
O is a state where O is removed from O) type oxide, that is, Z
It is known that nO is caused by oxygen deficiency.

Japanese Patent Application Laid-Open No. Hei 6-25838 discloses that at the X-ray diffraction peak, (00)
2) GZO firing in which the ratio of the integrated intensity of the peak (high angle side) of the plane to the peak (low angle side) of the (002) plane of the ZnO phase in which Ga is not dissolved is 0.2 or more. Consolidation is disclosed. Then, as a method of manufacturing this GZO sintered body, a mixed powder of ZnO powder and Ga ₂ O ₃ powder is formed by using a rubber press method, and the formed body is formed into 1400 to 155.
A method of sintering at 0 ° C. is disclosed.

[0006]

However, Japanese Patent Laid-Open No. 6-2 / 1994
When a film is formed using a GZO sintered body disclosed in Japanese Patent No. 5838 as a target, the plasma discharge state becomes unstable due to the occurrence of abnormal discharge, and stable film formation is not performed. Therefore, there is a problem that the film characteristics are deteriorated.

By the way, at present, a film is formed on a large area with a large screen such as a display, so that a demand for a large-sized sintered body is becoming very strong.

An object of the present invention is to provide a GZ for a sputtering target which can stably form a GZO film having excellent characteristics without occurrence of abnormal discharge in view of the above-mentioned situation.
An object of the present invention is to provide an O-sintered body and a method for manufacturing the GZO-sintered body including a large-sized one at a low manufacturing cost.

To solve the above problems, the present inventors have conducted intensive studies. As a result, the GZO sintered body disclosed in Japanese Patent Application Laid-Open No. 6-25838 has a low sintered density and a volume resistivity of 5%. It was found that the resistance was as high as 10 ⁻² Ω · cm or more.

The present inventors have further analyzed the GZO sintered body and arrived at the present invention.

[0011]

The GZO sintered body for a sputtering target of the present invention comprises (1) titanium oxide,
It contains at least one selected from the group consisting of germanium oxide, aluminum oxide, magnesium oxide, indium oxide and tin oxide in an amount of 1 to 5% by weight, and (2) the main constituent phases of the structure are Ga, Ti, Ge, and Al. , A ZnO phase in which at least one selected from the group consisting of Mg, In and Sn is dissolved, (3) a sintered density of 5.2 g / cm ³ or more;
(4) The volume resistivity is 2 × 10 ⁻² Ω · cm or less, (5) the average crystal grain size is 2 to 10 μm, and (6) the maximum pore size is 2
μm or less.

Further, the method for producing a GZO sintered body for a sputtering target according to the present invention is a method of adding gallium oxide powder to zinc oxide powder and mixing the resulting mixture, molding the mixed powder, and sintering the molded product under normal pressure. In (1) the average particle size is 1 μm
m and at least one selected from the group consisting of titanium oxide, germanium oxide, aluminum oxide, magnesium oxide, indium oxide and tin oxide using the gallium oxide powder having an average particle diameter of 1 μm or less. Seed, powder having an average particle size of 1 μm or less is further added, and the mixing is performed. (2) The molding is performed cold,
(3) The sintering is performed at a sintering temperature of 1300 to 1550 ° C.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The GZO sintered body for a sputtering target of the present invention comprises (1) at least one selected from the group consisting of titanium oxide, germanium oxide, aluminum oxide, magnesium oxide, indium oxide and tin oxide. (2) Ga, Ti, G
e, at least one member selected from the group consisting of Al, Mg, In and Sn is preferably a solid solution of 2% by weight or more.
The nO phase is the main constituent phase of the tissue. Other constituent phases include a ZnO phase in which at least one of the above is not dissolved, and ZnG
This is an intermediate compound phase represented by a ₂ O ₄ (spinel phase).
And (3) a sintered density of 5.2 g / cm ³ or more,
Satisfies (4) volume resistivity of 2 × 10 ⁻² Ω · cm or less, (5) average crystal grain size of 2 to 10 μm, and (6) maximum pore size of 2 μm or less. Even if any of the above six items is not satisfied, abnormal discharge cannot be sufficiently suppressed.

Among the above six items, the addition of components other than gallium oxide, the average crystal grain size, and the maximum pore size will be further described.

(1) Addition of components other than gallium oxide By adding at least one kind selected from the group consisting of titanium oxide, germanium oxide, aluminum oxide, magnesium oxide, indium oxide and tin oxide,
The evaporation of ZnO during sintering is suppressed and the sintering behavior of the ZnO powder is improved, that is, a reaction product with ZnO is formed before the evaporation of ZnO is activated. Therefore, the sintered density is 5.2 g / cm ³ or more and the maximum pore diameter is 2 μm.
m or less can be manufactured.

Further, gallium oxide and the above-mentioned components added in addition to gallium oxide form a solid solution in ZnO,
O oxygen deficiency increases. Therefore, 2 × 10 ^-2 Ω · cm
The following low volume resistivity is obtained.

(2) Average grain size If the grain size is large, the transverse rupture strength of the sintered body is low. Therefore, if a sharp power is applied during film formation, cracks may occur or crystal grains may fall off. Then, local abnormal discharge frequently occurs. Therefore, in the GZO sintered body of the present invention, the average crystal grain size is set to 2 to 10 μm.

(3) Maximum pore diameter If the maximum pore diameter in the GZO sintered body is large, crystal grains fall off. Then, local abnormal discharge frequently occurs. Therefore, in the GZO sintered body of the present invention, the maximum pore diameter is 2 μm.
Do the following.

GZ for sputtering target of the present invention
The method for manufacturing an O-sintered body is a method for manufacturing a GZO-sintered body that satisfies the above six items. This manufacturing method will be described below.

(1) Raw Material Powder The raw material powder includes zinc oxide powder having an average particle diameter of 1 μm or less, gallium oxide powder having an average particle diameter of 1 μm or less, titanium oxide, germanium oxide, aluminum oxide, magnesium oxide, indium oxide and The powder is at least one selected from the group consisting of tin oxide and has an average particle size of 1 μm or less. When zinc oxide powder having an average particle size of more than 1 μm, gallium oxide powder having an average particle size of more than 1 μm, or at least one of the powders having an average particle size of more than 1 μm is used, the sintered density is 5.2 g / cm ^3. As described above, the maximum pore size is 2 μm or less, and the average crystal grain size is 2 to 10 μm.
It is difficult to manufacture a GZO sintered body satisfying the following conditions. When the at least one kind of powder is two or more kinds of powders, it is preferable that each of the two or more kinds of powders has an average particle diameter of 1 μm or less.

(2) Mixing Mixing zinc oxide powder, gallium oxide powder, and at least one powder selected from the group consisting of titanium oxide, germanium oxide, aluminum oxide, magnesium oxide, indium oxide and tin oxide. The ratio is preferably (87-97) :( 2-8) :( 1-5) by weight.
As mixed.

When mixed at the above preferable mixing ratio, the sintering behavior of ZnO powder is improved and Ga
In addition, the solid solution in ZnO with the above-mentioned components added in addition to Ga effectively progresses, and 2 to 8% by weight of these components can be dissolved. Therefore, the sintered density is 5.2 g / c.
It becomes easier to obtain a sintered body satisfying m ³ or more, maximum pore diameter of 2 μm or less, and volume resistivity of 2 × 10 ⁻² Ω · cm or less. At the same time, the durability of the film to be formed can be improved. The above-mentioned film having a solid solution amount of less than 2% by weight and having insufficient durability is liable to be deteriorated by a high-temperature treatment applied during the production of a liquid crystal display. On the other hand, the solid solution amount is 8
Weight percent is sufficient.

The mixing can be performed by a ball mill, a vibration mill or the like, either in a wet manner or in a dry manner. Among the mixing methods, a wet ball mill mixing method is most preferable for obtaining uniform fine crystal grains and fine holes (thus having a small maximum diameter). The mixing time in the wet ball mill mixing method is 12
~ 78 hours are preferred. If the mixing time is less than 12 hours, it is difficult to obtain uniform and fine crystal grains and fine pores. On the other hand, if mixing is performed for more than 78 hours, it is difficult to obtain a further mixing effect, and conversely, impurities are likely to be mixed.

When a granulated product is formed in the forming in the subsequent step, a binder is added and mixed together. Examples of the binder used include polyvinyl alcohol and vinyl acetate.

(3) Forming The mixture is dried and granulated as required, and then cooled using a cold forming machine such as a cold press or a cold isostatic press.
This is performed by applying a pressure of at least ton / cm ² . When hot forming is performed using a hot press or the like, manufacturing costs are increased and a large-sized sintered body is difficult to manufacture.

(4) Sintering The sintering is normal pressure sintering. The reason why the pressure sintering also serving as the forming is not performed is for the same reason as not performing the hot forming described above.

The sintering is performed at a sintering temperature of 1300 to 1550 ° C, preferably 1400 to 1500 ° C. If the sintering temperature is lower than 1300 ° C., it is difficult to obtain a sintered body satisfying a sintering density of 5.2 g / cm ³ or more and a maximum pore diameter of 2 μm or less. On the other hand, when the temperature exceeds 1550 ° C., the crystal grain growth of the sintered body becomes remarkable, and the pores become coarse and, consequently, the maximum pore diameter increases, so that the maximum pore diameter is 2 μm or less, and the average crystal grain size is Satisfies 2 to 10 μm. Since sintering is performed at a sintering temperature of 1300 to 1550 ° C., Ga and the above-mentioned component added in addition to Ga are dissolved in ZnO to increase oxygen deficiency of ZnO, and 2 × 10 ⁻² Ω · cm or less.

The sintering is preferably carried out while introducing oxygen into the atmosphere at a rate of 2 to 20 l / min per 0.1 m ^{3 of the} internal volume of the sintering furnace so that the atmosphere contains a certain amount or more of oxygen. (hereinafter, oxygen in the sintering, and the non-oxidizing gas in the later-described reduction, the introduction amount per inner volume 0.1 m ³ reactor, in unit notation l / min / m ^3). The oxygen is introduced to suppress the evaporation of ZnO and further promote the densification of the sintered body. When the amount of oxygen introduced is less than 2 liters / minute / m ³ , the above effect is weakened. on the other hand,
If it exceeds 20 l / min / m ³ , the uniformity of the temperature in the sintering furnace tends to be disturbed.

When the temperature is raised to the sintering temperature, 1000
The temperature range of 1 to 1300 ° C is preferably set to a heating rate of 1 to 10 ° C / min, and more preferably 3 to 5 ° C / min. If the rate of temperature rise is lower than 1 ° C./min, the crystal grain growth of the sintered body becomes remarkable, and the pores become coarse and the maximum pore diameter increases. On the other hand, if it is faster than 10 ° C./min,
The uniformity of the temperature in the sintering furnace is reduced, and the amount of expansion and contraction in the sintered body varies, so that the sintered body is easily broken. The reason why the heating rate is defined in the temperature range of 1000 to 1300 ° C. is that sintering of the GZO sintered body is most active in this temperature range.

The holding time at the sintering temperature is preferably 3 to 15 hours. When the holding time is less than 3 hours, the sintered density is 5.2 g / cm ³ or more, and the maximum pore size is 2
It is difficult to obtain a sintered body satisfying μm or less. On the other hand, when the time exceeds 15 hours, the crystal grain growth of the sintered body becomes remarkable,
This results in coarsening of the pores and consequently an increase in the maximum pore diameter.

(5) Reduction In order to promote oxygen deficiency of ZnO and further reduce the volume resistivity, it is preferable to reduce the sintered body after sintering.

The reduction may be performed, for example, at normal pressure while introducing a non-oxidizing gas such as nitrogen, argon, carbon dioxide, helium or the like, or preferably in a vacuum atmosphere of 2 Pa or less.
It can be carried out by a method of heating at 000 to 1300 ° C., but since the production cost can be further reduced, the method of carrying out the above-mentioned normal pressure is advantageous. Next, an example of the method performed at normal pressure will be described.

After sintering, the temperature is decreased from the sintering temperature to a reduction temperature of 1100 to 1400 ° C. at a rate of 1 to 10 ° C./min (sintering is performed while introducing oxygen, and the sintering is performed). If a sintering furnace was carried out perform the reduction after was the temperature is lowered to stop the introduction of oxygen), 3 a reductive temperature while introducing non-oxidizing gas at a rate between 2 and 20 liters / min / m ³ Hold for 10 hours.

When the reduction temperature is lower than 1100 ° C., the above-mentioned reduction action by the non-oxidizing gas is weakened. On the other hand, when the temperature exceeds 1400 ° C., the evaporation of ZnO is activated and the composition is easily shifted, and the life of the furnace material and the heater is shortened and the productivity is easily deteriorated. If the cooling rate is lower than 1 ° C./min, the crystal growth of the sintered body becomes remarkable. On the other hand, if it is faster than 10 ° C./min,
The uniformity of the temperature inside the reduction furnace is reduced, and the amount of expansion and contraction in the sintered body varies, so that the sintered body is easily broken. If the amount of the non-oxidizing gas introduced is less than 2 liters / minute / m ³ , the above effect is weakened. On the other hand, if it exceeds 20 l / min / m ³ ,
The uniformity of the temperature inside the reduction furnace is easily disturbed. If the holding time is less than 3 hours, it is difficult to further reduce the volume resistivity. On the other hand, when the time exceeds 10 hours, the crystal grain growth of the sintered body becomes remarkable, the pores become coarse, and the maximum pore diameter increases.

[0035]

【Example】

Example 1 ZnO having an average particle diameter of 1 μm or less
Powder, Ga ₂ O ₃ powder and TiO ₂ powder were used as raw material powders. The mixture ratio of the ZnO powder, the Ga ₂ O ₃ powder, and the TiO ₂ powder was 94: 5: 1 by weight, and the mixture was wet-mixed. For the wet mixing, a wet ball mill mixing method is used. The balls are hard ZrO ₂ balls, and the binder is polyvinyl alcohol (1% by weight based on the total raw material powder amount).
Addition) and the mixing time was 18 hours. The slurry after mixing was taken out, dried and granulated. The granulated raw material powder was molded by applying a pressure of 3 ton / cm ² with a cold isostatic press to obtain a disk-shaped molded body having a diameter of 100 mm and a thickness of 8 mm.

Next, the compact was sintered. Sintering is performed in an air atmosphere at a temperature of 1000 ° C. up to 1000 ° C./min.
The temperature was raised from 400 ° C. at 3 ° C./min to a sintering temperature of 1400
C. was maintained for 5 hours.

With respect to the obtained sintered body, the sintered density, the average crystal grain size, the maximum pore size and the volume resistivity were measured. Here, the average crystal grain size and the maximum pore size are determined by cutting the sintered body in the depth direction, mirror-polishing the cut surface, thermally eroding the cut surface to precipitate crystal grain boundaries, and then performing SEM observation. Was measured. The volume resistivity was measured using a four-probe method at a position 2 mm from the skin surface on the mirror-polished cut surface.

Further, the obtained sintered body was 75 m in diameter.
m, and processed into a disk shape with a thickness of 6 mm to produce a sputtering target. Thereafter, a film was formed by DC magnetron sputtering using this sputtering target. Sputtering conditions at this time were an input power of 200 W and an Ar gas pressure of 0.7 Pa. Then, the number of abnormal discharges occurring per 10 minutes after the elapse of 10 hours from the start of film formation, and the specific resistance of the film at this time were measured.

The results obtained above are shown in Table 1 (the same applies to Examples 2 to 8 and Comparative Examples 1 to 3 described later).

[Examples 2 to 6] Instead of TiO ₂ powder, GeO ₂ powder (Example 2), Al ₂ O ₃ powder (Example 3), MgO powder (Example 4), In ₂ O ₃ powder A test was performed in the same manner as in Example 1 except that (Example 5) and SnO ₂ powder (Example 6) (both having an average particle diameter of 1 μm or less) were used.

Example 7 A test was performed in the same manner as in Example 3 except that the mixing ratio of ZnO powder, Ga ₂ O ₃ powder, and Al ₂ O ₃ powder was changed to 92: 5: 3 by weight.

Example 8 A test was performed in the same manner as in Example 5, except that the mixing ratio of ZnO powder, Ga ₂ O ₃ powder, and In ₂ O ₃ powder was 90: 5: 5 by weight.

Comparative Example 1 (1) TiO ₂ powder was not used, and the average particle size was 1 μm
m and ZnO powder and Ga ₂ O ₃ powder as raw material powders, (2) the mixing ratio of ZnO powder and Ga ₂ O ₃ powder is 95: 5 by weight, and (3) 1000-1400 ° C. is 0%. The test was performed in the same manner as in Example 1 except that the temperature was raised at 0.5 ° C./min.

[Comparative Example 2] In sintering, 1000 to 1
The temperature was raised from 500 ° C. at 0.5 ° C./min to a sintering temperature of 15 ° C.
The test was performed in the same manner as in Comparative Example 1 except that the temperature was kept at 00 ° C. for 15 hours.

Comparative Example 3 (1) Al ₂ O ₃ powder having an average particle size of 2 μm was used.
In sintering, a test was performed in the same manner as in Example 3 except that the temperature was raised from 1000 to 1500 ° C. at 0.5 ° C./min and the sintering temperature of 1500 ° C. was maintained for 5 hours.

[0046]

[Table 1]

[0047]

The G for the sputtering target of the present invention
According to the ZO sintered body, a GZO film having excellent characteristics can be stably formed without occurrence of abnormal discharge.

Further, according to the production method of the present invention, the above-mentioned GZO sintered body for a sputtering target of the present invention can be produced at a low production cost and including a large-sized one.

Claims (12)

[Claims] (1) At least one selected from the group consisting of titanium oxide, germanium oxide, aluminum oxide, magnesium oxide, indium oxide, and tin oxide.
1 to 5% by weight of the seed, and (2) the main constituent phase of the structure is G
a, a ZnO phase in which at least one selected from the group consisting of Ti, Ge, Al, Mg, In and Sn is dissolved;
(3) a sintered density of 5.2 g / cm ³ or more, (4) a volume resistivity of 2 × 10 ⁻² Ω · cm or less, (5) an average crystal grain size of 2 to 10 μm, and (6) a maximum empty space pore size is 2μm or less sputtering target for ZnO-Ga ₂ O ₃ oxide sintered. 2. The ZnO phase in which at least one selected from the group consisting of Ga, Ti, Ge, Al, Mg, In and Sn is dissolved in at least one of the ZnO phases in an amount of 2% by weight.
Or a sputtering target for ZnO-Ga ₂ O ₃ system sintered body according to claim 1. 3. A method of adding and mixing gallium oxide powder to zinc oxide powder, forming a mixed powder, and sintering the molded product under normal pressure, wherein (1) the zinc oxide having an average particle size of 1 μm or less. Powder and the gallium oxide powder having an average particle diameter of 1 μm or less, and at least one selected from the group consisting of titanium oxide, germanium oxide, aluminum oxide, magnesium oxide, indium oxide and tin oxide, The powder is further mixed by adding 1 μm or less, (2) the compaction is performed cold, and (3) the sintering temperature is 1
Method for producing a sputtering target for ZnO-Ga ₂ O ₃ sintered body and performing a sintered as 300 to 1,550 ° C.. 4. A zinc oxide powder, a gallium oxide powder,
The mixing ratio with at least one kind of powder to be added other than the gallium oxide powder is (87 to 97) by weight: (2 to
8) :( 1-5) a method for producing a sputtering target for ZnO-Ga ₂ O ₃ sintered body according to claim 3. 5. The ZnO— for a sputtering target according to claim 3, wherein the mixing is performed by a wet ball mill mixing method using a binder and a mixing time of 12 to 78 hours.
A method for producing a Ga ₂ O ₃ based sintered body. 6. The ZnO— for a sputtering target according to claim 3, wherein the sintering is performed while introducing oxygen at a rate of 2 to 20 liters / minute per 0.1 m ^{3 of the} inner volume of the sintering furnace.
A method for producing a Ga ₂ O ₃ based sintered body. 7. When the temperature is increased to 1000 to sintering temperature,
The Zn for a sputtering target according to claim 3, wherein the temperature rising rate in a temperature range of 1300 ° C is 1 to 10 ° C / min.
Method for producing O-Ga ₂ O ₃ sintered body. 8. The holding time at the sintering temperature is 3 to 15
Method for producing a sputtering target for ZnO-Ga ₂ O ₃ sintered body of claim 3 is the time. 9. The method for producing a ZnO—Ga ₂ O ₃ sintered body for a sputtering target according to claim 3, wherein reduction is performed after sintering. 10. A reduction, after cooling at a cooling rate of 1 to 10 ° C. / min from the sintering temperature to 1100 to 1400 ° C. is a reducing temperature, reduction furnace volume 0.1 m ³ per 2-20 l / min method for producing a sputtering target for ZnO-Ga ₂ O ₃ sintered body of claim 9, the said reduction temperature while introducing non-oxidizing gas at a rate of performing by holding 3-10 hours. 11. The method for producing a ZnO—Ga ₂ O ₃ based sintered body for a sputtering target according to claim 10, wherein the non-oxidizing gas is nitrogen, argon, carbon dioxide or helium. 12. The reduction is performed in a vacuum atmosphere of 2 Pa or less.
Method for producing a sputtering target for ZnO-Ga ₂ O ₃ sintered body according to claim 9 carried out at 000 to 1,300 ° C..