CN110741106A

CN110741106A - Oxide sintered body and sputtering target

Info

Publication number: CN110741106A
Application number: CN201880038930.2A
Authority: CN
Inventors: 松元谦士; 井上雅树; 中村信一郎; 矢野智泰
Original assignee: MITSUI METAL MINING CO Ltd
Current assignee: MITSUI METAL MINING CO Ltd
Priority date: 2017-08-08
Filing date: 2018-07-02
Publication date: 2020-01-31
Also published as: TWI778100B; JPWO2019031105A1; WO2019031105A1; KR20200008583A; TW201910539A; JP7086080B2; KR102375637B1

Abstract

The invention provides kinds of oxide sintered bodies, wherein the constituent elements are In, Sn, Ti and O, the content ratio of In is In₂O₃88.0 to 98.2% by mass in terms of Sn content₂1.0 to 8.0% by mass in terms of TiIn the content ratio of TiO₂Converted to 0.8 to 4.0 mass%. The oxide sintered body of the present invention can provide a sputtering target capable of forming a thin film in which a transparent conductive film having high transparency and a transparent conductive film having low resistance can be obtained without performing a high-temperature heat treatment.

Description

Oxide sintered body and sputtering target

Technical Field

The present invention relates to an oxide sintered body and a sputtering target, and more particularly, to a sputtering target capable of obtaining a thin film having high transmittance in the visible light region and low specific resistance, and an oxide sintered body capable of producing such a target.

Background

In accordance with the development of display devices mainly using liquid crystals, demands for transparent conductive films have been increasing, high transparency has been demanded for transparent conductive films, and further, low resistance has been demanded in steps, an ITO film has been widely used as a transparent conductive film in in view of the demands for high transparency and low resistance, and as a method for forming an ITO transparent conductive film, a method for forming an ITO sputtering target by sputtering has been generally used in in view of the ease of handling.

In particular, recently, with the colorization of liquid crystals, the miniaturization of elements, and the adoption of an active matrix system, there is a demand for a high-performance transparent conductive film of ITO having higher transparency and lower resistance.

Patent document 1 describes a high-transmittance, low-resistance transparent conductive film containing 1 to 20 wt% of tin oxide and 0.05 to 5 wt% of titanium oxide, and a sputtering target, and describes that the high transmittance and the low resistance of the transparent conductive film can be achieved by performing a heat treatment at 300 ℃.

Patent document 2 describes methods for manufacturing a transparent conductive film, in which a sputtering target made of an oxide such as indium oxide, tin oxide, or titanium is sputtered, and the obtained indium tin oxide thin film is crystallized by a heat treatment, and in this method, an amorphous indium tin oxide thin film obtained by sputtering is crystallized by a heat treatment at 200 ℃.

However, the method requiring heat treatment at a high temperature of 200 ℃ or higher cannot be applied to the case of forming a transparent conductive film on a resin film that deforms at 200 ℃ or higher.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 4-277408

Patent document 2: japanese patent No. 5726752

Disclosure of Invention

Problems to be solved by the invention

The present invention aims to provide a sputtering target capable of forming a thin film that can provide a transparent conductive film having high transparency and low resistance without performing a high-temperature heat treatment.

Means for solving the problems

The oxide sintered body of the present invention contains In, Sn, Ti and O as constituent elements, and the content ratio of In is In₂O₃88.0 to 98.2% by mass in terms of Sn content₂Converted to 1.0 to 8.0 mass%, and the content of Ti is calculated as TiO₂Converted to 0.8 to 4.0 mass%.

The specific resistance of the oxide sintered body is preferably 5.0X 10^-4Omega cm or less, and the relative density is preferably 95% or more.

The sputtering target of the present invention is formed of the above oxide sintered body.

The sputtering target of the present invention is obtained by bonding the sputtering target material and a base material.

In the transparent conductive film of the present invention, the In content ratio is In₂O₃88.0 to 98.2% by mass in terms of Sn content₂Converted to 1.0 to 8.0 mass%, and the content of Ti is calculated as TiO₂Converted to 0.8 to 4.0 mass%.

The method for producing a transparent conductive film of the present invention comprises subjecting a thin film formed by sputtering the sputtering target to a heat treatment at 110 to 145 ℃.

Effects of the invention

The oxide sintered body of the present invention can provide a sputtering target capable of forming a thin film in which a transparent conductive film having high transparency and a transparent conductive film having low resistance can be obtained without performing a high-temperature heat treatment.

Drawings

FIG. 1 is a graph showing the light transmittance in the wavelength range of 300nm to 800nm of the thin film obtained by sputtering in example 15 and the transparent conductive film obtained by heat-treating the thin film at 125 ℃.

Fig. 2 is a graph showing the light transmittance in the wavelength range of 300nm to 800nm of the transparent conductive film obtained by heat-treating the thin film obtained by sputtering at 125 ℃ in example 15 and comparative examples 1 and 3.

Detailed Description

In the oxide sintered body, the In content ratio is In₂O₃In terms of SnO, the content of Sn is 88.0 to 98.2 mass%, preferably 90.0 to 97.0 mass%, more preferably 91.5 to 96.0 mass%, and further preferably 93.0 to 95.5 mass% in ₂In terms of TiO, the content of Ti is 1.0 to 8.0 mass%, preferably 2.0 to 7.0 mass%, more preferably 2.7 to 6.0 mass%, and further preferably 3.0 to 5.0 mass% in ₂0.8 to 4.0% by mass, preferably 1.0 to 3.0% by mass, more preferably 1.3 to 2.5% by mass, and further preferably 1.5 to 2.0% by mass in terms of , it goes without saying that inevitable impurities derived from raw materials and the like may be contained in the oxide sintered body of the present invention, and that inevitable impurities may be contained in the oxide sintered body of the present inventionExamples of the impurities to be avoided include Fe, Cr, Ni, Si, W, Zr and the like, and the contents thereof are usually 100ppm or less.

In the present invention, the constituent elements mean constituent elements other than inevitable impurities in the oxide sintered body or the transparent conductive film, and the content ratio of each constituent element means a content ratio of each constituent element in the entire oxide sintered body or the transparent conductive film.

The specific resistance of the oxide sintered body is preferably 5.0X 10^-4Not more than Ω cm, more preferably 4.8X 10^-4Omega cm or less, and preferably 4.5X 10 in the further steps^-4Omega cm or less. This enables sputtering using an inexpensive DC power supply, and can improve the film formation rate and suppress the occurrence of abnormal discharge.

The relative density of the oxide sintered body is preferably 95% or more, more preferably 98% or more, and further preferably 99% or more in the step, and when the relative density is 95% or more, effective sputtering without generation of nodules or breakdown can be achieved, the upper limit of the relative density is not particularly limited, and may exceed 100%.

The oxide sintered body can be produced by the following method, for example.

First, raw material powders are mixed. The raw material powder is usually In₂O₃Powder, SnO₂Powder and TiO₂And (3) powder. In₂O₃Powder, SnO₂Powder and TiO₂The powders are mixed so that the contents of In, Sn, and Ti In the obtained sintered body fall within the above ranges. In the mixed powder obtained by mixing the raw material powders₂O₃Powder, SnO₂Powder and TiO₂The content ratio of the powder to In the oxide sintered body₂O₃Converted In content ratio, SnO₂Converted Sn content ratio, and TiO₂The converted Ti content ratios were respectively.

Since the respective raw material powders are generally aggregated, they are preferably pulverized and mixed in advance, or they are pulverized while being mixed with at .

The method of pulverizing or mixing the raw material powder is not particularly limited, and for example, the raw material powder may be put in a bowl and pulverized or mixed by a ball mill.

The obtained mixed powder may be directly molded to prepare a compact and then sintered, but a binder may be added to the mixed powder and molded to prepare a compact as needed. As the binder, a binder used in obtaining a molded body by a known powder metallurgy method, for example, polyvinyl alcohol, an acrylic emulsion binder, or the like can be used. Alternatively, a dispersion medium may be added to the mixed powder to prepare a slurry, the slurry may be spray-dried to prepare particles, and the particles may be molded.

The molding method may be a method conventionally used in powder metallurgy, for example, cold pressing or CIP (cold isostatic pressing).

Alternatively, a green compact may be produced by temporarily subjecting the mixed powder to green compaction, and then subjecting the pulverized powder obtained by pulverizing the green compact to main compaction.

The molded body may be produced by a wet molding method such as a slip casting method.

The obtained compact may be degreased by a method conventionally used in powder metallurgy, if necessary. The density of the molded article is usually 50 to 75%.

Next, the obtained compact is fired to produce an oxide sintered body. The sintering furnace used for sintering is not particularly limited as long as the cooling rate can be controlled during cooling, and may be one that is generally used in powder metallurgy. As the firing atmosphere, an oxygen atmosphere is suitable.

The temperature rise rate is usually 100 to 500 ℃/h from the viewpoint of densification and prevention of cracking. The firing temperature is 1300-1600 ℃, preferably 1400-1600 ℃. When the firing temperature is within the above range, an oxide sintered body having a high density can be obtained. The holding time at the firing temperature is usually 3 to 30 hours, preferably 5 to 20 hours. When the holding time is within the above range, an oxide sintered body having a high density can be easily obtained.

The cooling rate is usually 300 ℃/hr or less, preferably 50 ℃/hr or less.

The sputtering target of the present invention is formed of the above oxide sintered body. Specifically, the oxide sintered body is cut into a desired shape as needed, and subjected to a process such as grinding, thereby obtaining a sputtering target.

The composition, specific resistance, relative density and other physical properties of the sputtering target are the same as those of the oxide sintered body.

By bonding the sputtering target material to the base material, a sputtering target can be obtained. The substrate is typically Cu, Al, Ti or stainless steel. As the bonding material, a bonding material used for bonding a conventional ITO target, for example, In metal can be used. The bonding method is also the same as the conventional method for bonding an ITO target.

By sputtering the sputtering target, a thin film can be formed. The sputtering can be performed under the conditions in sputtering using a general ITO sputtering target.

The film obtained in this manner is generally amorphous. By subjecting the thin film to heat treatment, so-called annealing, crystallization can be achieved, and a transparent conductive film having high light transmittance and low specific resistance can be obtained. The light transmittance can be significantly improved particularly in the short wavelength range, for example, in the wavelength range of 300 to 380 nm.

The temperature required for this heat treatment is 110 to 145 ℃, preferably 115 to 140 ℃, and further preferably 120 to 135 ℃ in steps, as described above, a temperature of 200 ℃ or higher is required for the heat treatment for increasing the transmittance and decreasing the resistance of the ITO thin film, which has been known in the prior art, and on the other hand, a low temperature of 110 to 145 ℃ is preferable for the heat treatment for increasing the transmittance and decreasing the resistance of the thin film obtained by sputtering the sputtering target of the present invention, and therefore, when the sputtering target of the present invention is used, even in the case of producing a transparent conductive film on a resin film or the like which causes deformation or the like at 200 ℃ or higher, it is possible to produce a transparent conductive filmWhen the transparent conductive film is heat-treated at a temperature exceeding 145 ℃ to produce a transparent conductive film having high light transmittance and low resistance without causing deformation of the film or the like, does not achieve sufficient high transmittance and low resistance, and is contrary to the conventional ITO film (In)₂O₃：SnO₂When the ratio is 90: 10 (mass ratio)) is not preferable because it tends to have a lower transmittance and a higher specific resistance.

The time required for the heat treatment is usually 0.1 to 2 hours, preferably 0.5 to 1 hour. The above heat treatment may be performed in the atmosphere.

By subjecting the thin film obtained by sputtering the sputtering target of the present invention to the above-described heat treatment, the light transmittance and the specific resistance can be improved.

Particularly, with respect to the light transmittance, by performing the heat treatment at the above temperature, it is possible to obtain an ITO thin film (In) having a wavelength region of visible light (for example, 380 to 750nm), particularly a short wavelength region (for example, 300 to 380nm), which is more excellent than that of a conventionally known ITO thin film₂O₃：SnO₂When the ratio is 90: 10 (mass ratio)).

The transparent conductive film obtained In this way has In, Sn, Ti and O as constituent elements, for example, In₂O₃In terms of SnO, the content of Sn is 88.0 to 98.2 mass%, preferably 90.0 to 97.0 mass%, more preferably 91.5 to 96.0 mass%, and further is preferably 93.0 to 95.5 mass%, and the content of Sn is SnO₂In terms of TiO, the content of Ti is 1.0 to 8.0 mass%, preferably 2.0 to 7.0 mass%, more preferably 2.7 to 6.0 mass%, and further is preferably 3.0 to 5.0 mass%, and the content of Ti is TiO₂The transparent conductive film has a high light transmittance and a low resistance as described above, and the transparent conductive film is preferably 0.8 to 4.0% by mass, more preferably 1.0 to 3.0% by mass, even more preferably 1.3 to 2.5% by mass, and further preferably 1.5 to 2.0% by mass in terms of .

Examples

The following shows the measurement methods used in the following examples and comparative examples.

1. Relative density of oxide sintered body

Of sintered oxide bodiesThe relative density was determined based on the archimedes method. Specifically, the mass in air of the oxide sintered body divided by the volume (mass in water of the oxide sintered body/specific gravity of water at the measurement temperature) will be relative to the theoretical density ρ (g/cm) based on the following formula (X)³) The value of (a) is set as a relative density (unit: %).

[ mathematical formula 1]

ρ＝(C1/100)/ρ1-(C2/100)/ρ2+…+(Ci/100)/ρi)^-1(x)

(in the formula, C1 to Ci each represent the content (mass%) of a constituent material of the oxide sintered body, and ρ 1 to ρ i each represent the density (g/cm) of a constituent material corresponding to C1 to Ci³)。)

In the following examples and comparative examples, the material (raw material) used for producing the oxide sintered body was In₂O₃、SnO₂、TiO₂So by for example mixing

C1: in used In oxide sintered body₂O₃Mass% of the raw materials

ρ1：In₂O₃Density of (7.18 g/cm)³)

C2: SnO used in oxide sintered body₂Mass% of the raw materials

ρ2：SnO₂Density of (6.95 g/cm)³)

C3: TiO used in oxide sintered body₂Mass% of the raw materials

ρ3：TiO₂Density of (4.26 g/cm)³)

The theoretical density ρ can be calculated by applying the formula (X).

2. Specific resistance of oxide sintered body

The specific resistance of the oxide sintered body was measured in AUTO RANGE mode by contacting the surface of the processed sintered body with a probe using Loresta (registered trademark) HP MCP-T410 (TYPE ESP with a four-probe in series) manufactured by mitsubishi chemical corporation. The measurement site was set to 5 points in total near the center and 4 corners of the oxide sintered body, and the average value of the measurement values was set to the bulk resistance value of the sintered body.

3. Light transmittance of film

The light transmittance of the film was measured using an ultraviolet-visible near infrared spectrophotometer UH4150 manufactured by Hitachi High-Tech Science Corporation. The measurement conditions were set to scan speed: 600nm/min, wavelength region: 200-2600 nm. First, the base glass substrate on which no film was formed was fixed to the apparatus, a base line was measured, and then the transmittance of each film formation sample was measured.

4. Specific resistance of transparent conductive film

The film specific resistance of the transparent conductive film was measured using a four-probe measuring instrument K-705RS manufactured by Kyowa Kagaku K.K.K..

[ examples and comparative examples ]

(production of oxide sintered body)

In is mixed with₂O₃Powder, SnO₂Powder and TiO₂The powders were mixed at the ratios shown in table 1 using a ball mill to prepare mixed powders.

In the mixed powder, 6 mass% of polyvinyl alcohol diluted to 4 mass% was added to the mixed powder, and the polyvinyl alcohol and the powder were mixed well using a mortar, and sieved through a 5.5-mesh sieve. The obtained powder was mixed at a ratio of 200kg/cm²The resulting green compact was pulverized in a mortar. The resulting pulverized powder was filled into a die for pressing at a pressing pressure of 1t/cm²The molding was carried out for 60 seconds to obtain a molded article.

The obtained molded body was placed in a sintering furnace, oxygen was made to flow at 10L/min in the furnace, the firing atmosphere was set to be an oxygen flowing atmosphere, the temperature rise rate was set to 350 ℃/h, the sintering temperature was set to 1550 ℃, and the holding time at the sintering temperature was set to 9h, and sintering was performed.

Then, the resultant was cooled at a cooling rate of 100 ℃ per hour to obtain an oxide sintered body.

The obtained oxide sintered body was cut to obtain a sputtering target having a surface roughness Ra of 1.0 μm, a width of 210mm, a length of 710mm, and a thickness of 6 mm. A #170 grinding wheel was used for the cutting process.

The relative density and specific resistance of the oxide sintered body were measured by the methods described above. The results are shown in table 1.

In each of examples and comparative examples, it was confirmed that the content of each element measured when each raw material powder was prepared was equal to the content of each element in the obtained oxide sintered body. The content of each element in the oxide sintered body can be measured by, for example, ICP-AES (Inductively Coupled Plasma Atomic emission Spectroscopy).

(production of sputtering target)

The sputtering target was produced by bonding the sputtering target material to a copper backing plate with In solder.

(production of transparent conductive film)

The sputtering was carried out under the following conditions using the above sputtering target, and a thin film having a thickness of 100nm was formed on the glass substrate.

The device comprises the following steps: vacuum machine Industrial Co., Ltd EX-3013M

(DC magnetron sputtering device)

Ultimate vacuum degree: less than 1.0X 10^-4Pa

Sputtering gas: Ar/O₂Mixed gas

Sputtering gas pressure: 0.4Pa

Oxygen flow rate: 0 to 2.0sccm

Substrate: glass substrate (EAGLE XG (registered trademark) manufactured by Corning corporation)

Substrate temperature: at room temperature

Sputtering power: 3W/cm²

In each of the examples and comparative examples, it was confirmed that the content of each element in the oxide sintered body used for the sputtering target was equal to the content of each element in the transparent conductive film to be formed. The content of each element in the transparent conductive film can be measured by, for example, ICP-AES (Inductively Coupled Plasma Atomic emission spectroscopy).

The obtained film was heat-treated at 125 ℃ for 1 hour in the air to produce a transparent conductive film.

The light transmittance at wavelengths of 350nm and 550nm and the specific resistance of the transparent conductive film were measured by the above methods. The results of light transmittance and specific resistance are shown in table 1.

The specific resistance was compared with that of the transparent conductive film (In) obtained In comparative example 1 which is a conventional ITO thin film₂O₃：SnO₂When the ratio is 90: 10 (mass ratio)) specific resistance of 4.8 × 10^-4Ω cm (hereinafter referred to as reference specific resistance) was compared and evaluated, and a transparent conductive film having a specific resistance of less than 1.0 times the reference specific resistance was evaluated as "a", a transparent conductive film having a specific resistance of 1.0 times or more and less than 1.1 times the reference specific resistance was evaluated as "B", a transparent conductive film having a specific resistance of 1.1 times or more and less than 1.2 times the reference specific resistance was evaluated as "C", and a transparent conductive film having a specific resistance of 1.2 times or more the reference specific resistance was evaluated as "D".

Further, the transmittance of the thin film obtained by sputtering in example 15 and the transparent conductive film obtained by heat-treating the thin film at 125 ℃ in the wavelength range of 300nm to 800nm is shown in fig. 1, and the transmittance of the transparent conductive film obtained by heat-treating the thin film obtained by sputtering at 125 ℃ in example 15 and comparative examples 1 and 3 in the wavelength range of 300nm to 800nm is shown in fig. 2. In FIG. 1, "as-depo" means that heat treatment is not performed.

TABLE 1

Claims

1, kinds of oxide sintered bodies, wherein the constituent elements are In, Sn, Ti and O, the content ratio of In is In₂O₃88.0 to 98.2% by mass in terms of Sn content₂Converted to 1.0 to 8.0 mass%, and the content of Ti is calculated as TiO₂Converted to 0.8 to 4.0 mass%.

2. According to claimThe oxide sintered body of 1, wherein the specific resistance is 5.0X 10^-4Omega cm or less.

3. The oxide sintered body according to claim 1 or 2, wherein the relative density is 95% or more.

4, kinds of sputtering targets, which are formed of the oxide sintered body according to of any one of claims 1 to 3.

5, kinds of sputtering targets, which is formed by bonding the sputtering target material according to claim 4 and a base material.

6, kinds of transparent conductive film, which has In, Sn, Ti and O as constituent elements, the In content ratio being In₂O₃88.0 to 98.2% by mass in terms of Sn content₂Converted to 1.0 to 8.0 mass%, and the content of Ti is calculated as TiO₂Converted to 0.8 to 4.0 mass%.

7, A method for producing a transparent conductive film, wherein a thin film formed by sputtering the sputtering target according to claim 5 is subjected to a heat treatment at 110 to 145 ℃.