KR20200140777A - Sputtering target and manufacturing method thereof - Google Patents

Abstract

Provided is an effective method for lowering bulk resistivity (equivalent to volume resistivity) in a Ga-Sn-O-based sputtering target member containing high concentration of Ga. The sputtering target member contains Ga, Sn, and O, the remaining is composed of unavoidable impurities, the atomic ratio of Ga and Sn satisfies 0.33 <= Ga/(Ga+Sn) <= 0.75, and the ratio (I_Sn/I) of the peak area (I_Sn) of a SnO_2 phase to the total peak area (I) in the powder X-ray diffraction measurement is 0.02 or more.

Description

A sputtering target member and its manufacturing method TECHNICAL FIELD [SPUTTERING TARGET AND MANUFACTURING METHOD THEREOF}

The present invention relates to a Ga-Sn-O-based sputtering target member and a manufacturing method thereof.

Conventionally, a silicon-based material such as a polycrystalline silicon film and an amorphous silicon film has been used as a semiconductor layer used for a channel layer of a thin film transistor (TFT). However, since the silicon-based material absorbs in the visible light region, there is a problem in that the thin film transistor malfunctions due to the generation of carriers due to incident light. As a preventive measure, a light blocking layer such as metal is provided, but there is a problem that the aperture ratio decreases. In addition, in order to maintain the brightness of the screen, it is necessary to increase the brightness of the backlight, and there are disadvantages such as an increase in power consumption.

Here, in recent years, a thin film transistor using a transparent oxide semiconductor instead of a silicon-based material has been developed. A typical example is an In-Ga-Zn-O-based (IGZO) material (Patent Document 1). However, since IGZO is a multi-component system, it is difficult to optimize the properties and conditions of each raw material powder, the composition of the components, and the sintering conditions. Therefore, IGZO is considered to be a problem in that the properties of IGZO are liable to fluctuate, and nodules and abnormal discharge are caused during sputtering. In addition, since IGZO contains rare metals, it is a factor that raises the cost, and there is a fear that the supply will be short in the future.

Against this background, Ga-Sn-O-based (GTO) oxide targets with few constituent elements have been studied (Patent Documents 2 to 3).

International Publication No. 2005/088726 International Publication No. 2010/018707 Japanese Unexamined Patent Application Publication No. 2013-40394

However, in the oxide sintered body described in Patent Document 2, in addition to the gallium stannate compound phase and the tin oxide phase, in order to increase the strength of the sintered body and reduce the bulk resistance, zinc, aluminum, silicon, indium, germanium, titanium, niobium, At least one element selected from tantalum, tungsten, molybdenum, and antimony is required to be dispersed. In addition, in Patent Document 2, when only gallium oxide and tin oxide are used as raw materials, it is shown that when the gallium oxide concentration is high, the bulk resistance is increased to a degree that cannot be measured (Comparative Examples 1, 4, 6, and 7).

In addition, Patent Document 3 describes a target of an oxide sintered body for sputtering composed of gallium (Ga), tin (Sn), oxygen (O) and inevitable impurities, but the concentration of Ga ₂ O ₃ is required to be 20 mol% or less. have. In Patent Document 3, when the concentration of Ga ₂ O ₃ was set to 30 mol%, the bulk resistivity increased so as to be impossible to measure (Comparative Examples 4 and 5).

As described above, in the Ga-Sn-O-based sputtering target member containing a high concentration of Ga, a low bulk resistivity suitable for DC sputtering was not obtained. The present invention was created in view of the above circumstances, and in one embodiment, in a Ga-Sn-O-based sputtering target member containing a high concentration of Ga, it provides an effective means for lowering the bulk resistivity (same as "volume resistivity"). Make it a task.

The present inventors analyzed the crystal structure of a Ga-Sn-O-based sputtering target member containing a high concentration of Ga by powder XRD. While a large number of complex oxide phases of Ga and Sn can be seen, the amount of tin oxide phase is very small. Found something. And, based on this knowledge, as a result of repeated careful examination, if the ratio of the complex oxide phase of Ga and Sn in the Ga-Sn-O-based sputtering target member is lowered and the ratio of the tin oxide phase is increased, the volume resistivity is increased even when the total composition is the same. I found it to degrade significantly.

The present invention has been completed based on the above findings, and is illustrated as follows.

[One]

It contains Ga, Sn and O, and the remainder is composed of inevitable impurities, the atomic ratio of Ga and Sn satisfies 0.33≤Ga/(Ga+Sn)≤0.75, and the total peak area (I) in powder X-ray diffraction measurement A sputtering target member having a ratio (I _Sn /I) of the peak area (I _Sn ) on SnO ₂ to that of 0.02 or more.

[2]

The sputtering target member according to [1], wherein the ratio (I _Sn /I) of the peak area (I _Sn ) of the SnO ₂ phase to the total peak area (I) in the powder X-ray diffraction measurement is 0.1 or more.

[3]

The sputtering target member described in [1] or [2] in which the ratio (I _GaSn /I) of the peak area (I _GaSn ) on the Ga ₄ SnO ₈ phase to the total peak area (I) in powder X-ray diffraction measurement is 0.3 or less .

[4]

The sputtering target member according to [3], _wherein the ratio (I _GaSn /I) of the peak area (I _GaSn ) of the Ga ₄ SnO ₈ phase to the total peak area (I) in the powder X-ray diffraction measurement is 0.25 or less.

[5]

The sputtering target member according to any one of [1] to [4], having a volume resistivity of 50,000 Ω·cm or less.

[6]

The sputtering target member according to any one of [1] to [5] having a relative density of 94% or more.

[7]

By the step of, Ga ₂ O ₃ powder and the SnO ₂ powder so that the Ga ₂ O ₃ powder in the mixed powder, the molar concentration of less than 60mol% 20mol% or more mixing and grinding the mixed powder prepared, and 1,

Step 2 of sintering the mixed powder in an oxygen-containing atmosphere at a heating temperature of 1500°C or higher for 10 hours or more to obtain a sintered body containing a Ga-Sn-O composite oxide phase; and

Step 3 of decomposing the Ga-Sn-O composite oxide phase by annealing the sintered body at a heating temperature of 1000° C. to 1400° C. for 10 hours or more in a nitrogen-containing atmosphere and generating a SnO ₂ phase,

The method for producing a sputtering target member according to any one of [1] to [6], including.

[8]

The method for manufacturing a sputtering target member according to [7] in which Steps 2 and 3 are successively performed by lowering from the heating temperature in Step 2 to the heating temperature in Step 3.

[9]

Step 3 is a method for producing a sputtering target member according to [7] or [8], which is annealed at a heating temperature of 1200°C to 1400°C.

[10]

A film forming method comprising sputtering the sputtering target member according to any one of [1] to [6].

According to an embodiment of the present invention, despite a high gallium concentration, a Ga-Sn-O-based sputtering target member having a low volume resistivity can be obtained. Further, according to one embodiment of the present invention, it is possible to provide a Ga-Sn-O-based sputtering target having a high gallium concentration suitable for DC sputtering.

(1. Composition)

The sputtering target member according to the present invention, in one embodiment, contains Ga, Sn and O, and the remainder is constituted by inevitable impurities. Inevitable impurities are usually present in raw materials in metal products or inevitably mixed in the manufacturing process, and are inherently unnecessary, but are allowed impurities because they are in trace amounts and do not affect the properties of the metal products. The total amount of inevitable impurities in the sputtering target member according to the present invention is generally 5000 mass ppm or less, typically 3000 mass ppm or less, and more typically 2000 mass ppm or less.

The sputtering target member according to the present invention satisfies the atomic ratio of Ga and Sn satisfies 0.33≦Ga/(Ga+Sn)≦0.75 in one embodiment. 0.33≦Ga/(Ga+Sn) is because the object of the present invention is to provide a Ga-Sn-O based sputtering target member containing a high concentration of Ga in one embodiment. It is also possible to set it as 0.4≦Ga/(Ga+Sn), and it is also possible to set it as 0.5≦Ga/(Ga+Sn). In addition, the reason why Ga/(Ga+Sn)≦0.75 is set is the reason that it is easy to obtain a sputtering target with a low volume resistivity. From the viewpoint of lowering the volume resistivity, preferably Ga/(Ga+Sn)≦0.7, and more preferably Ga/(Ga+Sn)≦0.5.

In one embodiment of the sputtering target member according to the present invention, Ga and Sn may exist in the form of an oxide. Examples of oxides include gallium oxide (Ga ₂ O ₃ ), tin oxide (SnO ₂ ), and complex oxides of Ga and Sn (eg, Ga ₄ SnO ₈ , Ga ₄ Sn ₅ O ₁₆ and Ga ₃ Sn ₄ O ₁₂ ). .

(2. XRD measurement)

In order to effectively lower the volume resistivity of the sputtering target member, the ratio (I _Sn /I) of the peak area (I _Sn ) of the SnO ₂ phase to the total peak area (I) in the powder X-ray diffraction measurement is preferably 0.02 or more, It is more preferably 0.05 or more, even more preferably 0.10 or more, still more preferably 0.15 or more, and even more preferably 0.20 or more. The upper limit of I _Sn /I is not particularly set, but is generally 0.40 or less, and typically 0.30 or less.

In order to effectively lower the volume resistivity of the sputtering target member, it is preferable that the ratio (I _GaSn /I) of the peak area (I _GaSn ) of the Ga ₄ SnO ₈ phase to the total peak area (I) in the powder X-ray diffraction measurement is 0.30 or less. And, it is more preferable that it is 0.25 or less, and it is still more preferable that it is 0.20 or less. The lower limit of I _GaSn /I is not particularly set, but is generally 0.05 or more, and typically 0.10 or more.

XRD measurement is carried out in the following order. The sputtering target member to be measured is pulverized to form a powder, and the powder under the sieve separated by sieving with a sieve having a sieve size of 100 µm is pulverized to obtain a measurement sample, and tube voltage: 40 kV using powder X-ray diffraction method, An X-ray diffraction chart in which the horizontal axis is 2θ and the vertical axis is X-ray intensity (cps) is obtained under the conditions of tube current: 30 mA, scan rate: 5°/min, and step: 0.02°. Then, the obtained X-ray diffraction chart is subjected to data processing of Kα2 removal and background removal according to the Sonneveld-Visser method.

And according to the following criteria, I _sn , I _GaSn and I are obtained, and I _Sn /I and I _GaSn /I are calculated.

The peak area (I _sn ) of SnO ₂ represents the sum of the peak areas in the respective ranges of 2θ = 26.2° to 26.9°, 33.5° to 44.2°, and 51.4° to 52.0°.

The peak area (I _GaSn ) of Ga ₄ SnO ₈ represents the sum of the peak areas in the respective ranges of 2θ=14.2° to 14.8°, 25.1° to 25.8°, 34.5° to 35.0°, and 52.9° to 53.5°.

The total peak area (I) represents the sum of the peak areas in the range of 2θ = 10° to 60°.

Each peak area is the maximum peak intensity (I _max ) of each peak in the above angular range (the height from the point where cps after background removal is 0 to the maximum peak intensity (unit: cps)), and the half-value width (Wh) ( It is calculated by multiplying the peak width (unit: 2θ) at the position where the intensity becomes I _max /2.

(3. Volume resistivity)

The sputtering target member according to the present invention has a volume resistivity of 50,000 Ω·cm or less in one embodiment. Low resistance of the sputtering target member can contribute to the stability of sputtering. The volume resistivity is preferably 25,000 Ω·cm or less, more preferably 15,000 Ω·cm or less, and may be, for example, 5,000 to 50,000 Ω·cm.

The volume resistivity is an average value obtained by measuring the volume resistivity of five arbitrary points of the sputtering target member to be measured using the direct current 4-probe method so as not to deviate from the measurement location.

(4. Relative density)

The relative density of the sputtering target member is preferably high in terms of affecting the volume resistivity. From the viewpoint of suppressing the occurrence of cracks and cracks in the sputtering target member, it is preferable that the relative density of the sputtering target member is high. The sputtering target member according to the present invention has a relative density of 94% or more in one embodiment. The relative density is preferably 95% or more, more preferably 98% or more, and may be, for example, 94 to 98%.

In the present invention, "relative density" is expressed as relative density = (measured density/theoretical density) x 100 (%). The theoretical density is a value of the density calculated from the theoretical density of oxides of elements other than oxygen in each constituent element of the sintered body. In the case of the Ga-Sn-O target of the present invention, gallium oxide (Ga ₂ O ₃ ) and tin oxide (SnO ₂ ) as respective constituent elements gallium, tin, and oxygen, excluding oxygen, and tin oxides, are used in the calculation of theoretical density. Use. Here, the elemental analysis value (at% or mass%) of gallium and tin in the sintered body is converted into a mass ratio of gallium oxide (Ga ₂ O ₃ ) and tin oxide (SnO ₂ ). For example, as a result of conversion, in the case of a GTO target with 25% by mass of gallium oxide and 75% by mass of tin oxide, the theoretical density is (density of Ga ₂ O ₃ (g/cm ³ ) × 25 + density of SnO ₂ (g /cm ³ ) × 75) / 100 (g / cm ³ ) is calculated. Theoretical density of the Ga ₂ O ₃ are theoretical density of 6.44g / cm ^3, SnO ₂ is calculated as 6.95g / cm ^3. On the other hand, the measured density is a value obtained by dividing the weight by volume. In the case of a sintered body, the volume is calculated by the Archimedes method.

(5. Manufacturing method)

Hereinafter, a preferred method of manufacturing the sputtering target member according to the present invention will be exemplarily described. As raw material powders, gallium oxide (Ga ₂ O ₃ ) powder and tin oxide (SnO ₂ ) powder are prepared. In order to avoid adverse effects on electrical properties due to impurities, it is preferable to use a raw material powder having a purity of 3N (99.9 mass%) or higher, and more preferably a raw material powder having a purity of 4N (99.99 mass%) or higher.

Then, Ga ₂ O ₃ powder and SnO ₂ powder are mixed and pulverized at a predetermined molar ratio to prepare a mixed powder. Ga ₂ O ₃ powder and SnO ₂ powder are mixed so that the atomic ratio of Ga and Sn in the mixed powder satisfies the above-described 0.33≦Ga/(Ga+Sn)≦0.75. Specifically, it is preferable that the Ga ₂ O ₃ powder in the mixed powder is 20 mol% or more. From the viewpoint of providing a high concentration of the Ga-Sn-O based sputtering target member containing Ga, can be mixed powder Ga ₂ O ₃ powder in more than 30mol%, and a Ga ₂ O ₃ powder in the mixed powder 40mol% It is also possible to do the above. In addition, from the viewpoint of lowering the volume resistivity of the resulting sputtering target, the Ga ₂ O ₃ powder in the mixed powder may be 60 mol% or less, and the Ga ₂ O ₃ powder in the mixed powder may be 55 mol% or less.

If mixing and pulverization are insufficient, each component is segregated in the prepared sputtering target member, resulting in a high resistivity region and a low resistivity region, and abnormalities such as arcs due to charging in the high resistivity region during sputter formation. Since it causes discharge, it is desirable to sufficiently mix and crush. As a preferable mixing and pulverizing method, for example, a method of adding raw material powder to water to disperse it to form a slurry, and pulverizing this slurry using a wet medium stirring mill (bead mill, etc.) is exemplified.

It is preferable to dry the slurry after pulverization. Although drying is not limited, for example, it can be carried out under conditions of 100 to 150°C x 5 to 48 hours with a hot air dryer. After drying, it is desirable to separate the coarse particles by separating them with a sieve. It is preferable to use a sieve having a sieve size of 500 μm or less, and more preferably a sieve having a sieve size of 250 μm or less. Here, the sieve size is measured according to JIS Z8801-1:2006.

The mixed powder obtained by mixing and grinding preferably has a median diameter of 5 µm or less, more preferably 3 µm or less, and even more preferably 1 µm or less.

The median diameter of the mixed powder is the median diameter (D50) according to the volume standard when the cumulative distribution of particle sizes is measured using a laser diffraction scattering particle size measuring device after ultrasonic dispersion for 1 minute using ethanol as a dispersion medium.

Then, a molded article is produced by filling and pressing the mixed powder in a mold having a desired shape. The surface pressure at the time of pressing can be, for example, 400 to 1000 kgf·cm ² .

* Then, the molded body is sintered for 10 hours or more at a heating temperature of 1500° C. or higher in an oxygen-containing atmosphere to obtain a sintered body containing a Ga-Sn-O composite oxide phase. Heating in an oxygen-containing atmosphere is because the density of the sintered body is improved by suppressing evaporation of SnO ₂ . Examples of the oxygen-containing atmosphere include an oxygen atmosphere and an air atmosphere. The reason why the heating temperature in the sintering step is 1500°C or higher is because the reaction rate of sintering is sufficiently fast. The heating temperature in the sintering step is preferably 1550°C or higher, and more preferably 1600°C or higher. The reason why the heating time at the heating temperature of 1500° C. or higher is 10 hours or more is because sintering is sufficiently advanced. The heating time is preferably 15 hours or more, more preferably 20 hours or more.

After the sintering process, when a predetermined annealing process is performed, the Ga-Sn-O composite oxide phase is decomposed to form a SnO ₂ phase. Accordingly, the ratio of the SnO ₂ phase increases, and the volume resistivity decreases significantly. The annealing is preferably carried out for 10 hours or more at a heating temperature of 1000°C to 1400°C in a nitrogen-containing atmosphere. Heating in a nitrogen-containing atmosphere is due to the purpose of reducing the bulk resistivity of the sintered body by reduction of SnO ₂ . Examples of the nitrogen containing atmosphere include a nitrogen atmosphere and an air atmosphere. The heating temperature in the annealing process is preferably 1000°C or higher, more preferably 1100°C or higher, and still more preferably 1200°C or higher, where the reaction rate of decomposition is sufficiently fast. In addition, the heating temperature in the annealing step is preferably 1400°C or less at which no Ga-Sn-O composite oxide is generated, and more preferably 1300°C or less. The reason why the annealing is performed for 10 hours or more at a heating temperature of 1000°C to 1400°C is because the decomposition reaction proceeds sufficiently. The heating time is preferably 15 hours or more, more preferably 20 hours or more.

As the heating temperature in the sintering step is lowered to the heating temperature in the annealing step, it is preferable in terms of production efficiency to continuously perform the sintering step and the annealing step. However, after the sintering step, after cooling to room temperature, the sintered body may be heated again to the annealing temperature.

The oxide sintered body obtained by the above process can be finished into a sputtering target member by processing it into a desired shape with a processing machine such as a plane grinding machine, a cylindrical grinding machine, or a machining machine, if necessary. The sputtering target member may be used alone, or may be suitably bonded to the backing plate and used. As a bonding method with the backing plate, a method of bonding an indium alloy or the like to a copper backing plate as a bonding metal is exemplified.

(6. Tabernacle Method)

According to one embodiment of the present invention, a film forming method including sputtering a sputtering target member is provided. The sputtering method is not limited, but an RF magnetron sputtering method, a DC magnetron sputtering method, an AC magnetron sputtering method, a pulse DC magnetron sputtering method, and the like can be preferably used. In one embodiment of the sputtering target member according to the present invention, since the volume resistivity is low, it is particularly preferable for the DC magnetron sputtering method and the pulsed DC magnetron sputtering method.

[Example]

Hereinafter, examples for easily understanding the present invention and its advantages are shown, but the present invention is not limited to the examples.

Various measurements and evaluations are required in Examples and Comparative Examples shown below, but the conditions are shown below.

(Medium diameter)

The median diameter of various powders is the median by volume standard when the cumulative distribution of particle sizes is measured using a laser diffraction scattering particle size measuring device (Made by Nikkiso Corporation, Microtrac MT3000) after ultrasonic dispersion for 1 minute using ethanol as a dispersion medium. It shows the diameter (D50).

(Volume resistivity)

Using a resistivity measuring device (manufactured by NPS Corporation, type FELL-TC-100-SB-Σ5+, measuring jig RG-5) using a direct current 4-probe method, the volume resistivity of the sputtering target member is measured by the method described above.

(Relative density)

The measured density of the sputtering target member to be measured is determined by the Archimedes method, and the relative density is determined by relative density = measured density/theoretical density.

(XRD measurement)

XRD measurement is carried out in accordance with the measurement conditions described above using a fully automatic multipurpose X-ray diffraction apparatus manufactured by Rigaku Corporation (form: Ultima), and I _sn /I and I _GaSn /I are calculated from the obtained XRD chart.

(Comparative Example 1)

As raw material powders, Ga ₂ O ₃ powder (median diameter 2.60 μm) and SnO ₂ powder (median diameter 1.25 μm) were prepared. Ga ₂ O _3: was slurried in the Ga ₂ O ₃ powder and the SnO ₂ powder in a molar ratio of 1 input to the water: SnO ₂ = 1. This slurry was ground and mixed using a bead mill. The slurry after pulverization and mixing was dried with a hot air dryer for 120°C for 20 hours, sieved through a sieve having a sieve size of 250 µm, separated, and the mixed powder under the sieve was recovered. The median diameter of the mixed powder was 0.84 µm. Then, 1000 g of the obtained mixed powder was filled into a ø210 mm mold and pressed with a surface pressure of 400 to 1000 kgf/cm ² to obtain a disc-shaped molded body. This molded body was heated at a temperature of 1600° C. in an oxygen atmosphere, and held for 10 hours to obtain a sintered body (sputtering target member).

(Comparative Example 2)

The molded article produced under the same conditions as in Comparative Example 1 was heated to a temperature of 1550°C in an oxygen atmosphere, and held for 10 hours to obtain a sintered body (sputtering target member).

(Comparative Example 3)

The molded article produced under the same conditions as in Comparative Example 1 was heated to a temperature of 1600° C. in an air atmosphere, and held for 10 hours to obtain a sintered body (sputtering target member).

(Example 1)

The molded article produced under the same conditions as in Comparative Example 1 was heated to a temperature of 1600° C. in an oxygen atmosphere and held for 10 hours. Thereafter, the temperature was lowered to 1000°C and held in an air atmosphere for 20 hours to obtain a sintered body (sputtering target member).

(Example 2)

The molded article produced under the same conditions as in Comparative Example 1 was heated to a temperature of 1600° C. in an oxygen atmosphere and held for 10 hours. Thereafter, the temperature was lowered to 1200°C and held in an air atmosphere for 20 hours to obtain a sintered body (sputtering target member).

(Example 3)

A mixed powder was produced under the same conditions as in Example 1, except that the Ga ₂ O ₃ powder and the SnO ₂ powder were mixed in a molar ratio of Ga ₂ O ₃ :SnO ₂ =20:80. The median diameter of the mixed powder was 0.92 µm. Then, the molded body was produced and sintered under the same heating conditions as in Example 1 to obtain a sintered body (sputtering target member).

[Table 1]

<Consideration>

In Comparative Examples 1 to 3 and Examples 1 to 2, although the raw material composition is the same, since I _Sn /I is large, it can be understood that Examples 1 to 2 significantly lowered the volume resistivity. Further, from the results of Example 3, it can be understood that the volume resistivity is further reduced by lowering the molar ratio of Ga.

Claims (8)

It contains Ga, Sn, and O, and the remainder is composed of inevitable impurities, the atomic ratio of Ga and Sn satisfies 0.4≤Ga/(Ga+Sn)≤0.75, and the total peak area (I) in powder X-ray diffraction measurement The sputtering target member whose ratio (I _Sn /I) of the peak area (I _Sn ) of the SnO ₂ phase to the SnO ₂ is 0.02 or more. It contains Ga, Sn and O, and the remainder is composed of inevitable impurities, the atomic ratio of Ga and Sn satisfies 0.33≤Ga/(Ga+Sn)≤0.75, and the total peak area (I) in powder X-ray diffraction measurement A sputtering target member having a ratio (I _Sn /I) of the peak area (I _Sn ) of the SnO ₂ phase to the SnO ₂ is 0.02 or more and a volume resistivity of 0.082 to 13.2 Ω·cm. The method according to claim 1 or 2,
A sputtering target member in which the ratio (I _Sn /I) of the peak area (I _Sn ) of the SnO ₂ phase to the total peak area (I) in the powder X-ray diffraction measurement is 0.1 or more. The method according to claim 1 or 2,
A sputtering target member in which the ratio (I _GaSn /I) of the peak area (I _GaSn ) on Ga ₄ SnO ₈ to the total peak area (I) in powder X-ray diffraction measurement is 0.3 or less. The method of claim 4,
A sputtering target member in which the ratio (I _GaSn /I) of the peak area (I _GaSn ) on the Ga ₄ SnO ₈ phase to the total peak area (I) in the powder X-ray diffraction measurement is 0.25 or less. The method of claim 1,
Sputtering target member with a volume resistivity of 50,000 Ω·cm or less. The method according to claim 1 or 2,
Sputtering target member having a relative density of 94% or more. A film forming method comprising sputtering the sputtering target member according to claim 1 or 2.