JP4851777B2 - SnO2-based sputtering target and manufacturing method thereof - Google Patents

Description

Background of the Invention

The present invention relates to a SnO ₂ -based sputtering target and a method for producing the same, and specifically, SnO ₂ -based used for forming transparent conductive films such as flat panel displays, resistive touch panels, and solar cells. The present invention relates to a sputtering target and a manufacturing method thereof.

Background Art In recent years, SnO ₂ -based transparent conductive films have been used in a wide range of applications such as flat panel displays, resistive touch panels, and solar cells. The SnO ₂ -based transparent conductive film is industrially mainly manufactured by a spray method or a CVD method. However, these methods are not suitable for making the film thickness uniform over a large area, it is difficult to control the film formation process, and furthermore, chlorine-based gas that is a contaminant during film formation can be generated. Therefore, a new production method without these drawbacks is required.

On the other hand, production of SnO ₂ -based transparent conductive films by sputtering is also attempted. However, since it is difficult to obtain a SnO ₂ -based sputtering target that can withstand use for sputtering, it has not been widely used. This is because it is difficult to produce a high-density sintered body suitable for use in sputtering because SnO ₂ is a hardly sinterable substance. Further, in order to obtain a low resistance sputtered film required as an electrode material, but with the addition of Sb ₂ O ₃ is also known SnO ₂ based sputter target having a reduced specific resistance of SnO _2, sinterability The improvement effect was small.

An SnO ₂ -based sputtering target containing Ta, Nb or the like and having a sintered density of 4.0 g · cm ³ or more is known (see, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2000-273622)). An SnO ₂ -based sputtering target containing Ta, Nb, etc. and having a specific resistance of 1 × 10 ⁷ Ω · cm or less is also known (see Patent Document 2 (Japanese Patent Laid-Open No. 2000-281431)). In the examples of these documents, the sputtering target is sintered at 1500 ° C. However, SnO ₂ -based sputtering that enables the production of sputtered films that have both low resistivity and high transmittance, which are required as transparent electrode films for plasma display panels (PDPs), which are in increasing demand in recent years. The target has not yet been reported.

JP 2000-273622 A JP 2000-281431 A

Summary of the Invention

The inventors of the present invention have SnO ₂ as a main component, Nb ₂ O ₅ and Ta ₂ O ₅ are included in a total amount of 1.15 to 10% by mass, and contain Nb ₂ O ₅ / Ta ₂ O ₅ By sintering an unsintered compact having a mass to mass ratio of 0.15 to 0.90 at 1550 to 1650 ° C., it has a high relative density, while preventing abnormal discharge and generation of particles, It was found that a high-performance SnO ₂ -based sputtering target capable of forming a sputtered film having both a low specific resistance and a high transmittance at a high film formation rate can be produced.

Therefore, the present invention can form a sputtered film having both a low specific resistance and a high transmittance at a high film formation rate while having a high relative density and preventing abnormal discharge and generation of particles. The purpose is to produce a high-performance SnO ₂ -based sputtering target.

The manufacturing method of SnO ₂ based sputtering target according to the present invention,
SnO ₂ is the main component, Nb ₂ O ₅ and Ta ₂ O ₅ are included in a total amount of 1.15 to 10% by mass, and the content mass ratio of Nb ₂ O ₅ / Ta ₂ O ₅ is 0.15 to 0.15. Prepare a green compact that is 0.90,
It is a method comprising sintering the molded body at 1550 to 1650 ° C.

The SnO ₂ -based sputtering target according to the present invention contains SnO ₂ as a main component and includes 1.15 to 10% by mass of Nb ₂ O ₅ and Ta ₂ O ₅ in a total amount, and Nb ₂ O ₅ / Ta _2. The content mass ratio of O ₅ is a SnO ₂ -based sputtering target having a content ratio of 0.15 to 0.90,
By X-ray diffraction using CuKα as the X-ray source, peaks due to Nb ₂ O ₅ at diffraction angles 2θ of 22 to 23 ° and 28 to 29 ° are not substantially observed.

Detailed description of the invention

Manufacturing method of SnO ₂ -based sputtering target In the method of the present invention, first, SnO ₂ is the main component, Nb ₂ O ₅ and Ta ₂ O ₅ are included in a total amount of 1.15 to 10% by mass, and Nb ₂ An unsintered molded body having an O ₅ / Ta ₂ O ₅ content mass ratio of 0.15 to 0.90 is prepared. When the total amount of Nb ₂ O ₅ and Ta ₂ O ₅ is 1.15 to 10% by mass, it is possible to prevent an increase in film resistivity due to an increase in Ta and Nb that cannot be dissolved while improving the sintered density. It becomes easy to realize a low film specific resistance. The total amount of preferably _Nb 2 _{O 5} and _Ta 2 _{O 5} is from 1.15 to 8 wt%, more preferably from 3.5 to 6 wt%, more preferably from 4 to 6 wt%. Further, by setting the content mass ratio of Nb ₂ O ₅ / Ta ₂ O ₅ to 0.15 to 0.90, the amount of Nb ₂ O ₅ that contributes to high density by liquid phase sintering is ensured and sintered. It is possible to prevent an increase in the specific resistance of the sputtered film while preventing a decrease in the consolidation density. The content mass ratio of preferably _{Nb 2 O 5 / Ta 2 O} 5 is 0.15 to 0.60, more preferably 0.17 to 0.33, more preferably 0.20 to 0.33 It is.

In the present invention, the unsintered molded body may be formed by any method as long as the raw material powder containing the above composition is molded. For example, SnO ₂ powder, Nb ₂ O ₅ powder, Ta _The raw material powder can be prepared by mixing ₂ O ₅ powder at a blending ratio that satisfies the above composition, and the raw material powder can be formed.

  According to a preferred embodiment of the present invention, it is preferable that the green compact formed from the raw material powder is easily given a predetermined shape by adding a binder to the raw material powder. Such a binder is not limited as long as it is a known binder that disappears or scatters by heating, and an aqueous polyvinyl alcohol solution or the like can be used. Therefore, in this embodiment, it is preferable that the green compact is dried and then heated (degreasing) so that the binder is scattered or disappears prior to sintering. Although the method of drying and heating is not limited, it is preferable to first dry at 50 to 130 ° C. for 5 to 30 hours, and then degrease by heating at 500 to 800 ° C. for 6 to 24 hours.

According to a preferred embodiment of the present invention, the green compact further contains Fe ₂ O ₃ , NiO ₂ , CoO, In ₂ O ₃ , or a mixture thereof to further improve the sintered density. Can do. When adding these metal oxides, the total addition amount is preferably 100 to 7000 ppm, more preferably 350 to 7000 ppm, and still more preferably 700 to 7000 ppm.

According to another preferred embodiment of the present invention, the green compact further contains Al ₂ O ₃ , SiO ₂ , Y ₂ O ₃ , or a mixture thereof to further reduce the specific resistance of the sputtering target. can do. When adding these metal oxides, it is preferable that the total amount of these metal oxides, Nb ₂ O ₅ , and Ta ₂ O ₅ be 20 mass% or less.

According to still another preferred embodiment of the present invention, the green compact is further improved in the sintered density by Ga ₂ O ₃ , Bi ₂ O ₃ , Mn ₂ O ₃ , Fe ₂ O ₃ , NiO. , CoO, or a mixture thereof. When adding these metal oxides, it is preferable that the total amount of these metal oxides, Nb ₂ O ₅ , and Ta ₂ O ₅ be 20 mass% or less.

Next, in the method of the present invention, the green compact prepared as described above is sintered at 1550 to 1650 ° C. By performing the sintering within this temperature range, the liquid phase sintering can proceed sufficiently to increase the sintering density, and the transmittance at the time of the specific resistance value can be increased in the sputtered film. Furthermore, it is possible to prevent the SnO ₂ from melting and to easily produce a sintered body having a desired shape. The preferred sintering temperature is 1550-1600 ° C. Within this temperature range, the temperature difference inside the sintered body can be reduced, so that the warping of the sintered body can be effectively prevented and the productivity can be further improved.

  According to a preferred embodiment of the present invention, the sintering is preferably performed for 2 to 20 hours, more preferably 3 to 12 hours, and further preferably 4 to 8 hours. Within this range, it is possible to sufficiently sinter while suppressing power consumption and ensuring high productivity.

  According to a preferred embodiment of the present invention, the sintering is preferably performed in an oxygen-containing atmosphere in order to ensure a high sintering density, for example, in an oxygen-pressurized atmosphere, an oxygen atmosphere, or an air atmosphere. Can be done.

SnO ₂ based sputtering target produced by the method of the present invention described above SnO ₂ based sputtering target, an SnO ₂ as a main component, 1.15 to 10 wt% of _Nb 2 _{O 5} and _Ta 2 _{O 5} in the total amount The content mass ratio of Nb ₂ O ₅ / Ta ₂ O ₅ is 0.15 to 0.90, and by X-ray diffraction using CuKα ray (λ = 1.54050Å) as an X-ray source, The peaks attributable to Nb ₂ O ₅ at diffraction angles 2θ of 22 to 23 ° and 28 to 29 ° can be substantially not observed, but are not necessarily limited to those manufactured by the manufacturing method of the present invention. It is not limited to this. That is, in the production method of the present invention, an unsintered molded body is sintered at 1550 to 1650 ° C., but according to the knowledge of the present inventors, a sintered body obtained at a sintering temperature within this range. In that case, by X-ray diffraction using Cu as an X-ray source, no peaks due to Nb ₂ O ₅ at diffraction angles 2θ of 22 to 23 ° and 28 to 29 ° are observed. Such a SnO ₂ -based sputtering target of the present invention has a high relative density and prevents both abnormal discharge and generation of particles while at the same time having a high film formation rate and a low specific resistance and a high transmittance. A film can be formed.

According to a preferred aspect of the present invention, the X-ray diffraction is measured using an X-ray diffractometer (MXP3, manufactured by MAC Science), tube voltage: 40 kV, tube current: 30 mA, sampling interval: 0.02 °. The scanning speed is preferably 4 ° C./min, the diverging slit: 1 °, the scattering slit: 1 °, and the light receiving slit: 0.3 mm. According to a preferred aspect of the present invention, the maximum value of the X-ray intensity (Intensity) is less than 100 at diffraction angles 2θ of 22 to 23 ° and 28 to 29 ° by X-ray diffraction under the above-mentioned preferred conditions. Is preferred. Even if a peak due to Nb ₂ O ₅ is observed by X-ray diffraction with higher sensitivity than the X-ray diffraction under the above-mentioned preferred conditions, Nb ₂ O _{5 is obtained} by X-ray diffraction under the above-mentioned preferred conditions. Unless a peak due to is substantially observed, it is included in the scope of the present invention.

According to a preferred embodiment of the present invention, the SnO ₂ -based sputtering target preferably has a relative density of 90% or more as measured by the Archimedes method, preferably 93% or more, and more preferably 96% or more. By having such a high relative density, abnormal discharge and generation of particles during sputtering can be effectively prevented. The measurement by the Archimedes method is preferably performed at room temperature.

According to a preferred aspect of the present invention, the SnO ₂ -based sputtering target is preferably used for the production of a sputtered film having a film specific resistance value of 1 × 10 ⁻² Ω · cm or less. According to the SnO ₂ -based sputtering target of the present invention, it is possible to produce a sputtered film having a high transmittance while ensuring such a low film specific resistance value.

According to a preferred embodiment of the present invention, the SnO ₂ -based sputtering target is used for manufacturing a sputtered film having a peak transmittance of light of a wavelength of 500 to 600 nm measured by an ultraviolet-visible spectrophotometer of 96% or more. It is preferable. According to the SnO ₂ -based sputtering target of the present invention, it is possible to produce a sputtered film having a low film resistance value while ensuring such a high light transmittance.

Example 1
First, the following three kinds of raw material powders were prepared.
SnO ₂ powder: purity 99.99% (4N), average particle size 0.7 to 1.1 μm, specific surface area 2.0 to 2.7 m ² / g
Ta ₂ O ₅ powder: purity 99.9% (3N), average particle size 0.6 to 0.8 μm, specific surface area 2.0 to 3.1 m ² / g
Nb ₂ O ₅ powder: purity 99.9% (3N), average particle size 0.6-1.0 μm, specific surface area 2.1-2.7 m ² / g

Next, 96.5% by mass of the SnO ₂ powder, 3% by mass of the Ta ₂ O ₅ powder, and 0.5% by mass of the Nb ₂ O ₅ powder were mixed with a ball mill for 21 hours. An aqueous polyvinyl alcohol solution was added to the mixed powder, filled in a 400 × 800 mm mold, and press molded at a pressure of 800 kg / cm ² . The molded body was dried at 80 ° C. for 12 hours and then degreased at 600 ° C. for 4 hours. This degreased body was fired at a firing temperature of 1600 ° C. for 4 hours in an air atmosphere to obtain a sintered body. At this time, the rate of temperature rise and the rate of temperature fall were both controlled to 100 ° C./hour. The obtained sintered body was processed to obtain a SnO ₂ -based sputtering target having a diameter of 6 inches (152 mm) and a thickness of 5 mm.

Examples 2-7 and Comparative Examples 1-5 and 9
A SnO ₂ -based sputtering target was produced in the same manner as in Example 1 except that the raw material powder was mixed at the composition ratio shown in Table 1.

Example 8
A SnO ₂ -based sputtering target was produced in the same manner as in Example 1 except that the raw material powders were mixed at the composition ratio shown in Table 1 and the firing temperature was 1550 ° C.

Comparative Examples 6 and 7
A SnO ₂ -based sputtering target was produced in the same manner as in Example 1 except that the raw material powders were mixed at the composition ratio shown in Table 1 and the firing temperature was 1500 ° C.

Comparative Example 8
An attempt was made to produce a SnO ₂ -based sputtering target as a sintered body in the same manner as in Example 1 except that the raw material powder was mixed at the composition ratio shown in Table 1 and the firing temperature was 1700 ° C. . However, since SnO ₂ was melted, the shape collapsed and a desired shape could not be obtained.

Evaluations (1) to (3) were performed on the sputtering targets produced in Evaluation Examples 1 to 8 and Comparative Examples 1 to 7 and 9.
(1) Measurement of relative density The relative density of each sputtering target was measured by the Archimedes method. In this case, each raw material density of ^{_{SnO 2: 6.95g / cm 3,}} Ta 2 O 5: 8.74g / cm 3, Nb 2 O 5: Weighted average density of 4.47 g / cm ³ (theoretical density) The relative density was calculated with the weighted average density as 100%. The results were as shown in Table 1.

(2) Measurement of film formation rate Each sputtering target was metal bonded to a backing plate made of oxygen-free copper. At this time, when the center line average roughness Ra of the sputtering surface of the sputtering target was measured, it was 0.6 μm or less. Moreover, when the composition of each sputtering target was analyzed by ICP, it was the same as the composition of the mixed powder used as a raw material. And about each sputtering target which carried out metal bonding, magnetron sputtering using a DC power supply was performed on the conditions shown below, and it sputter-deposited on the alkali free glass substrate.
Ultimate pressure: 1 × 10 ⁻⁴ Pa
Substrate temperature: room temperature Argon partial pressure introduced: 0.5 Pa
Introduced oxygen flow rate (partial pressure): 0 to 3 sccm (0 to 2 × 10 ⁻² Pa)
DC applied power: 300W
Film thickness: about 140nm
Substrate: alkali-free glass

  The thickness of the formed film was measured with a stylus type surface shape measuring instrument (Dektak 6M, manufactured by ULVAC), and the obtained film thickness was divided by the film forming time, thereby calculating the film forming speed. The results of the film formation rate when the introduced oxygen flow rate was 0 sccm were as shown in Table 1.

(3) Measurement of film specific resistance After sputtering film formation, annealing was performed at 500 ° C. for 1 hour in an air atmosphere. When the minimum value of each film specific resistance was measured, the result as shown in Table 1 was obtained. The specific resistance was measured by a four-probe method using a sheet resistance measuring instrument (MCP-TP06P, manufactured by Dia Instruments Co., Ltd.). The obtained sheet resistance was measured with a stylus type surface shape measuring instrument (Dektak 6M). And the film thickness measured by ULVAC).

(4) Measurement of transmittance For Examples 2 and 4 and Comparative Examples 6 and 7, the transmittance was measured as follows. About the sample of the oxygen partial pressure conditions whose specific resistance value became the minimum after annealing, the transmittance | permeability of light with a wavelength of 300-800 nm was measured using the ultraviolet visible spectrophotometer (UV-2550, Shimadzu Corporation make). At this time, blank glass was used as a reference. For all the samples of Examples 2 and 4 and Comparative Examples 6 and 7, a transmittance peak was observed at a wavelength of 500 to 600 nm, and the transmittance peak value was as shown in Table 2.

(5) Evaluation of oxygen flow rate (partial pressure) dependency of specific resistance and transmittance peak value after annealing Annealing of the sputtered films obtained using the sputtering targets prepared in Example 2 and Comparative Example 6 The relationship between the subsequent specific resistance and transmittance peak values and the oxygen flow rate (partial pressure) was as shown in FIG. As can be seen from FIG. 1, the sputtered film obtained using the sputtering target produced in Example 2 that was fired at 1600 ° C. was produced in Comparative Example 6 that was fired at 1500 ° C. Compared with a sputtered film obtained using a sputtering target, the difference between the introduced oxygen flow rate at which a low specific resistance is obtained and the introduced oxygen flow rate at which a high transmittance is obtained is small, and the specific resistance is at or near the minimum oxygen partial pressure. It can be seen that a high transmittance can be realized at the same time. That is, by performing sputter film formation using the sputtering target of the present invention, two important performances of low specific resistance and high transmittance are achieved in a wide range of introduced oxygen flow rate, preferably 0.8 to 3.0 sccm or more, It can be seen that it can be realized simultaneously over an introduced oxygen flow rate range of 0.9 to 2.5 sccm, more preferably 1.0 to 2.0 sccm, and most preferably 1.0 to 1.5 sccm.

(6) Evaluation by X-ray diffraction method X-ray diffraction of the sputtering target having a thickness of 5 mm produced in Examples 4 and 8 and Comparative Example 7 was performed using an X-ray diffractometer (MXP3, manufactured by MAC Science). When measured under the following conditions, the results shown in FIGS. 2 to 4 were obtained.
Radiation source: CuKα ray (λ = 1.54050 mm)
Tube voltage: 40 kV
Tube current: 30 mA
Diffraction angle 2θ range: 20-40 °
Sampling interval: 0.02 °
Scanning speed: 4 ° C / min Diverging slit: 1 °
Scattering slit: 1 °
Receiving slit: 0.3mm

As shown in FIGS. 2 to 4, in the X-ray diffraction of the sputtering targets of Examples 4 and 8 that were fired at 1550 ° C. or higher, the sputtering target of Comparative Example 7 that was fired at 1500 ° C. In X-ray diffraction, no peak due to Nb ₂ O ₅ observed at diffraction angles 2θ of 22 to 23 ° and 28 to 29 ° was observed. The X-ray diffraction intensity (Intensity) in the 2θ range is as shown in Table 3. Under the above measurement conditions, if the maximum value of the X-ray diffraction intensity (Intensity) is less than 100, Nb ₂ O ₅ It can be said that the resulting peak was not substantially observed. From this, within the composition range of the present invention, when the firing is performed at a temperature exceeding 1500 ° C., for example, a temperature of 1550 ° C. or more, the X-ray diffraction peak due to Nb ₂ O ₅ disappears. Conceivable.

It is a figure which shows the relationship between the specific resistance and transmittance | permeability peak value after annealing, and oxygen flow rate (partial pressure) about the sputtered film obtained using the sputtering target produced in Example 2 and Comparative Example 6. . 6 is a diagram showing X-ray diffraction of a sputtering target produced in Example 4. FIG. 10 is a diagram showing X-ray diffraction of a sputtering target produced in Example 8. FIG. 10 is a diagram showing X-ray diffraction of a sputtering target produced in Comparative Example 7. FIG.

Claims (9)

SnO ₂ is the main component, Nb ₂ O ₅ and Ta ₂ O ₅ are included in a total amount of 1.15 to 10% by mass, and the content mass ratio of Nb ₂ O ₅ / Ta ₂ O ₅ is 0.15 to 0.15. Prepare a green compact that is 0.90,
Comprising the sintering the molded body at 1550 to 1650 ° C., the manufacturing method of SnO ₂ based sputtering target.   The method according to claim 1, wherein the sintering is performed for 2 to 20 hours.   The method according to claim 1, wherein the sintering is performed in an oxygen-containing atmosphere.   The green body further comprises a binder, and the green body is dried and then heated so that the binder scatters or disappears prior to the firing. 4. The method according to any one of 3. SnO ₂ is the main component, Nb ₂ O ₅ and Ta ₂ O ₅ are included in a total amount of 1.15 to 10% by mass, and the content mass ratio of Nb ₂ O ₅ / Ta ₂ O ₅ is 0.15 to 0.15. An SnO ₂ -based sputtering target of 0.90,
A SnO ₂ -based sputtering target in which peaks due to Nb ₂ O ₅ at diffraction angles 2θ of 22 to 23 ° and 28 to 29 ° are not substantially observed by X-ray diffraction using CuKα rays as an X-ray source. The relative density measured by the Archimedes method is 90% or more, SnO ₂ based sputtering target according to claim 5. Film resistivity values are used in the manufacture of the following sputtered film ^{1 × 10 -2 Ω · cm,} SnO 2 based sputtering target according to claim 5 or 6. SnO as described in any one of Claims 5-7 used for manufacture of the sputtered film whose peak value of the transmittance | permeability of the light of the wavelength of 500-600 nm measured with an ultraviolet visible spectrophotometer is 96% or more. ₂ system sputtering target. Claimed manufactured by the method according to any one of claims 1 to 4, SnO ₂ based sputtering target according to any one of claims 5-8.

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