KR102268160B1 - Sputtering target for transparent conductive film - Google Patents

Abstract

In the present invention, the constituent elements are In, Sn, Si and O, or In, Si and O, the content of In is 70.0% by mass or more and less than 85.0% by mass in terms of _{In 2} O _{3 , and the content of Sn is SnO It} is 0 mass % or more and 10.0 mass % or less in _{conversion of 2} , the content rate of Si is larger than 15.0 mass % in conversion of SiO2, and it is a sputtering target for transparent conductive films which consists of an oxide sintered body which is 20.0 mass % or less, X-ray diffraction of the said sputtering target A sputtering target for a transparent conductive film in which all Si appears as a peak of an indium silicate compound having a tortweitite structure in the measurement. The sputtering target for conductive film formation of this invention has a low specific resistance, can perform DC sputtering, and there is little generation|occurrence|production of a nodule and an arcing. Moreover, the transparent conductive film which has a high film|membrane resistivity and high etching processability can be formed by sputtering.

Description

Sputtering target for transparent conductive film

The present invention relates to a sputtering target for a transparent conductive film, and more particularly, to a sputtering target for a transparent conductive film capable of DC sputtering and capable of forming a transparent conductive film having high etching workability.

A high resistance and high transmittance are calculated|required by the transparent conductive film used for an in-cell type capacitive touch panel in order to block|prevent the interference of the display operation|movement by low frequency noise. This is because, when the conductive film has a low resistance, a high-frequency signal used for touch sensing is blocked.

This conductive film is normally formed by sputtering a sputtering target.

Although ITO is mainly used as a high transmittance|permeability material, since ITO has low resistance, it cannot be used for the electroconductive film of an in-cell type capacitive touch panel.

As a technique for obtaining a high-resistance material, there is a technique for adding an insulating oxide to ITO. However, when an insulating oxide is added to ITO, there exists a fault that etching processability becomes low, In the use etc. which etch with respect to an electrically conductive film, use becomes difficult.

For example, in Patent Document 1, the main ingredient of ITO, and containing silicon of 7.2 to 11.2 at.%, Is disclosed in the specific resistance of 10 ⁰ to 10 ³ Ω㎝ the transparent conductive film. ^{Patent Document 2 discloses a transparent conductive film having a resistivity of 0.8 to 10 × 10 -3} Ωcm obtained by sputtering a sputtering target for a transparent conductive film made of indium oxide, tin oxide, and silicon oxide. However, the etching processability of any conductive film is low.

In addition, although many high-resistance films have been reported, the resistance of the target used for film formation of the film also increases. If the resistance of the target is high, sputtering cannot be performed with a DC power supply, and a high resistance film must be produced with an RF power supply, resulting in poor productivity.

Japanese Patent No. 5855948 Publication Japanese Patent No. 4424889

An object of the present invention is to provide a sputtering target that can perform DC sputtering and can form a transparent conductive film with little nodule or arcing, high specific resistance, and high etching workability.

In the sputtering target for a transparent conductive film of the present invention, constituent elements are In, Sn, Si and O, or In, Si and O, and the content of In is 70.0% by mass or more and less than 85.0% by mass in terms of _{In 2} O _{3 ,} The content rate of Sn is 0 mass % or more and 10.0 mass % or less in terms of _{SnO 2 The content rate of Si is larger than 15.0 mass % in conversion of SiO 2 In the} sputtering target for transparent conductive films which consists of an oxide sintered body which is 20.0 mass % or less,

In the X-ray diffraction measurement of the sputtering target, all Si appears as a peak of an indium silicate compound having a tortweitite-type structure.

It is preferable that the said sputtering target for transparent conductive films has a specific resistance of 2x10 ^{2 Ωcm or less.}

It is preferable that the said sputtering target for transparent conductive films has a relative density of 98.0 % or more.

In the transparent conductive film of the present invention, the constituent elements are In, Sn, Si and O, or In, Si and O, the content of In is 73.0 mass% or more and 87.0 mass% or less in terms of _{In 2} O _{3 , and the content of Sn} and the ratio is more than 0 mass% to 9.0 mass% in terms of SnO _2, and the content of Si more than 13.0% by mass in terms of SiO ₂ 18.0% by mass or less.

The transparent conductive film, and the film resistivity is preferably not less than 1.0 × 10 ⁰ Ω㎝, and it is preferable that the etching rate is greater than 11.0Å / sec.

The manufacturing method of the transparent conductive film of this invention forms a film by sputtering the said sputtering target for transparent conductive films.

In the method for producing the transparent conductive film, the transparent conductive film has the specific resistance is preferably not less than 1.0 × 10 ⁰ Ω㎝, and it is preferred that the transparent conductive film The etching rate is larger than 11.0Å / sec.

The sputtering target for conductive film formation of this invention has a low specific resistance, can perform DC sputtering, and there is little generation|occurrence|production of a nodule and an arcing. Moreover, the transparent conductive film which has a high film|membrane resistivity and high etching processability can be formed by sputtering. The manufacturing method of the transparent conductive film of this invention can manufacture the transparent conductive film which has high specific resistance and high etching processability.

1 is an X-ray diffraction pattern of a sputtering target obtained in Example 3. FIG.

In the sputtering target for a transparent conductive film of the present invention, constituent elements are In, Sn, Si and O, or In, Si and O, and the content of In is 70.0% by mass or more and less than 85.0% by mass in terms of _{In 2} O _{3 ,} and when the content of Sn of more than 10.0% by mass more than 0% by mass in terms of SnO _2, the content of Si is greater than 15.0% by mass in terms of SiO _2, composed of 20.0 mass% or less, the oxide-sintered body. It goes without saying that a target made of an oxide sintered body such as the sputtering target for a transparent conductive film of the present invention may contain unavoidable impurities derived from raw materials, etc., and the sputtering target for a transparent conductive film of the present invention may also contain unavoidable impurities. Content of the unavoidable impurity in the sputtering target for transparent conductive films of this invention is 100 ppm or less normally.

In addition, in this invention, a structural element means the structural element except the unavoidable impurity in a sputtering target or a transparent conductive film, and the content rate of each structural element occupies in the sputtering target or the transparent conductive film as a whole. content ratio.

Compared with a normal ITO sputtering target, the sputtering target for transparent conductive films of this invention does not contain Sn, or the content rate of Sn is low, It is characterized by containing Si of comparatively high concentration.

The constituent elements of the oxide sintered body are In, Sn, Si and O, or In, Si and O. In the above oxide sintered body, the content of the In is In ₂ O more than 70.0% by mass to ₃ in terms of less than 85.0% by weight, preferably from 73.0 mass% to 84.0% by mass or less, and more preferably at least 76.0% by weight less than 84.0% by weight and the content of Sn _{is 0 mass % or more and 10.0 mass % or less in terms of SnO 2} , preferably 0 mass % or more and 7.0 mass % or less, more preferably 0 mass % or more and 5.0 mass % or less, and the content of Si is large, and 20.0% by mass, preferably not less than 16.0 mass% and 20.0 mass%, more preferably at least 16.0 mass% and 19.0 mass% or less than 15.0% by mass in terms of SiO _2. In addition, the composition of the said sputtering target for transparent conductive films is the same as that of the said oxide sintered compact.

Since the sputtering target for transparent conductive films which consists of an oxide sintered compact which has the said composition has low specific resistance, it is possible to perform DC sputtering. The specific resistance of the sputtering target for a transparent conductive film ^{is preferably 2.0×10 2} Ωcm or less, more preferably 1.5×10 ² Ωcm or less, and ^{still more preferably 1.0×10 2} Ωcm or less. Usually, DC sputtering can be performed if the specific resistance of a target is 10 ² ohm-cm band or less.

The sputtering target for transparent conductive films which consists of an oxide sintered compact which has the said composition can form the transparent conductive film with high film|membrane resistivity by sputtering. For this reason, when the transparent conductive film obtained from the said sputtering target for transparent conductive films is used for an in-cell type capacitive touch panel, the obstruction of the display operation|movement by low frequency noise can be prevented. Using the transparent conductive film as the sputtering target, 1.0 × 10 ⁰ Ω㎝ can be obtained a transparent conductive film having the above film resistivity. The transparent conductive film has the specific resistance is preferably 1.1 × 10 ⁰ Ω㎝, more preferably at least 1.2 × 10 ⁰ Ω㎝. Although the upper limit of the film specific resistance of the said transparent conductive film is not specifically defined, Usually, it is 5.0x10 ⁵ ohm-cm.

The sputtering target for transparent conductive films which consists of an oxide sintered compact which has the said composition can form a transparent conductive film with high etching processability by sputtering. High etching processability can be evaluated as having a fast etching rate. The transparent conductive film obtained from the sputtering target for the transparent conductive film has an etching rate of preferably greater than 11.0 Å/sec, more preferably 11.3 Å/sec or more, still more preferably 15.0 Å/sec or more, and still more preferably 20.0 Å/sec or more. desirable. The etching rate of the transparent conductive film was etched by immersing a part of the transparent conductive film in a transparent conductive film etchant (ITO-07N manufactured by Kanto Chemical Co., Ltd.) heated to 40° C. for 6 minutes, and the etching was performed with the etched location. It can be calculated from the film thickness difference (step difference) and the etching time of the location where it is not.

The film specific resistance of the transparent conductive film obtained by sputtering the sputtering target for transparent conductive films which consists of an oxide sintered compact containing In, Sn, and Si becomes high, so that there is much Sn and Si content of this target. However, the etching processability of a transparent conductive film does not become high when there is much Sn content. Therefore, the transparent conductive film in order to obtain a sufficient etching workability, it is necessary that the Sn content of the target less than 0 mass% to 10.0 mass% in terms of SnO _2. Case where the Sn content of the target less than 0 mass% to 10.0 mass% in terms of SnO _2, the resistivity of the film is lowered, in order to obtain a high film resistivity, it is necessary to so increasing the Si content. Therefore, Si content is required to be more than 15.0% by mass in terms of SiO _2. On the other hand, in order to obtain a high film resistivity, Si content is 20.0% by mass as SiO ₂ in terms of sufficient and does not need as many as more than that. I.e., is greater than the transparent conductive film as the sputtering target of the invention is SnO ₂ in terms of 0 mass% to 10.0 mass% or less of Sn content and SiO ₂ in terms of 15.0% by weight, by combining the Si content is not more than 20.0% by mass, for performing DC sputtering It became possible, and the combination made it possible to make both the high film specific resistance of the transparent conductive film formed into a film, and high etching workability into a film.

The relative density of the sputtering target for a transparent conductive film becomes like this. Preferably it is 98.0 % or more, More preferably, it is 98.5 % or more, More preferably, it is 99.0 % or more. When the relative density is 98.0% or more, efficient sputtering with little occurrence of nodules or arcing is possible. The upper limit of the relative density is not particularly limited, and may exceed 100%. The said relative density is a numerical value measured based on the Archimedes method.

As for the said sputtering target for transparent conductive films, it is preferable that all Si appears as a peak of the indium silicate compound which has a tortvite type structure in X-ray-diffraction measurement. That is, the target contains an indium silicate compound having a tortweite-type structure, and when the target is subjected to X-ray diffraction measurement, all Si appears as a peak of an indium silicate compound having a tortweite-type structure. , preferably not appearing as peaks of Si compounds other than the indium silicate compound having a tortweitite structure. Sat carte is indium silicate compound having a bi-tight structure, for example, a compound represented by In ₂ Si ₂ O _7. Sat carte is Si compound other than the silicate compound having an indium-by-tight structure, for example, may be mentioned SiO _2. When the said sputtering target for transparent conductive films satisfy|fills this condition, since there will be no segregation of a partial insulator, generation|occurrence|production of an arcing or a nodule will decrease.

_{Moreover, the In 2} O ₃ phase, In ₄ Sn ₃ O ₁₂ phase, etc. are contained in the said sputtering target for transparent conductive films other than the indium silicate compound phase which has a tortvite-type structure, for example.

The said sputtering target for transparent conductive films can be manufactured by the method shown below, for example.

First, the raw material powder is mixed. Raw material powder, typically a powder, In ₂ O _3, SnO ₂ powder and SiO ₂ powder. In ₂ O ₃ powder, SnO ₂ powder and SiO ₂ powder is mixed into such a content of In, Sn and Si, respectively, the range of the obtained sintered body. _{In addition, the content ratio of In 2} O ₃ powder, SnO ₂ powder, and SiO ₂ powder in the mixed powder obtained by mixing the raw material powder is the In content ratio in terms of In ₂ O ₃ in the oxide sintered body _{, SnO 2} conversion it has been confirmed that each match the Sn content ratio and the Si content ratio in terms of SiO _2.

Since each raw material powder is normally agglomerated by particle|grains, it is preferable to grind|pulverize and mix beforehand, or to grind|pulverize while mixing.

There is no restriction|limiting in particular in the grinding|pulverization method or mixing method of raw material powder, For example, raw material powder can be put into a pot, and grinding|pulverization or mixing can be performed with a ball mill.

The obtained mixed powder may be molded as it is to obtain a molded body, and this may be sintered. However, if necessary, a binder may be added to the mixed powder and molded to form a molded body. As this binder, the binder used when obtaining a molded object in a well-known powder metallurgy method, for example, polyvinyl alcohol, an acrylic emulsion binder, etc. can be used. Moreover, a dispersion medium may be added to mixed powder to prepare a slurry, this slurry may be spray-dried to produce granules, and this granule may be shape|molded.

As the forming method, a method conventionally employed in powder metallurgy, for example, cold press, CIP (cold isostatic pressure forming), or the like can be used.

Moreover, you may produce a molded object by temporarily pressing the mixed powder temporarily to produce a provisional compact, and grinding|pulverizing this and the pulverized powder obtained by bone-pressing.

Moreover, you may produce a molded object using wet molding methods, such as a slip casting method.

The relative density of the molded article is usually 50 to 75%.

A sintered compact can be obtained by baking the obtained molded object. The kiln used for sintering is not particularly limited as long as the cooling rate can be controlled at the time of cooling, and a kiln generally used in powder metallurgy may be used. As the firing atmosphere, an oxygen-containing atmosphere is suitable.

The temperature increase rate is usually 100 to 500°C/h from the viewpoint of densification and crack prevention. The firing temperature is 1300 to 1600°C, preferably 1400 to 1600°C. If the firing temperature is within the above range, a high-density sintered body can be obtained. The holding time at the above firing temperature is usually 3 to 30 h, preferably 5 to 20 h. When holding time is in the said range, it will be easy to obtain a high-density sintered compact.

After the maintenance at the above temperature is completed, the temperature in the kiln is generally lowered to 300°C/hr or less, preferably 100°C/hr or less to perform cooling.

The sputtering target for transparent conductive films can be obtained by cutting and grinding the sintered compact obtained in this way into a desired shape as needed.

The shape of the sputtering target for a transparent conductive film is not particularly limited, such as a flat plate shape and a cylindrical shape.

The said sputtering target for transparent conductive films is used by bonding to a base material normally. The substrate is usually made of Cu, Al, Ti or stainless steel. As a bonding material, the bonding material used for the bonding of the conventional ITO target material, for example, In metal can be used. The bonding method is also the same as the bonding method of the conventional ITO target material.

A transparent conductive film can be formed into a film by sputtering the said sputtering target for transparent conductive films. As mentioned above, since the said sputtering target for transparent conductive films has a low specific resistance, it is also possible to perform DC sputtering as well as RF sputtering.

By sputtering the said sputtering target for transparent conductive films, the transparent conductive film which has In, Sn, Si and O, or In, Si, and O as a structural element can be obtained. The content rate of Sn and the content rate of Si of the transparent conductive film obtained tend to become lower than the content rate of Sn and the content rate of Si of the said sputtering target for transparent conductive films. Therefore, in the said transparent conductive film, the content rate of In _{is 73.0 mass % or more and 87.0 mass % or less in conversion of In 2} O ₃ , Preferably they are 74.0 mass % or more and 87.0 mass % or less, and the content rate of Sn is 0 in conversion of _{SnO 2} mass% to 9.0 mass%, preferably more than 0 mass% to 8.0 mass%, the content of Si more than 13.0% by mass as SiO ₂ in terms of 18.0% by mass or less, preferably at least 13.0 mass% to 16.0 mass% to be. As mentioned above, the obtained transparent conductive film has high film|membrane resistivity and etching processability. Moreover, like the case of the said sputtering target for transparent conductive films, an unavoidable impurity may be contained also in the said transparent conductive film. Content of the unavoidable impurity in the said transparent conductive film is 100 ppm or less normally.

Example

The measuring method used in the following Example and a comparative example is shown below.

1. Relative Density of Target

The relative density of the sputtering target for transparent conductive films was measured based on the Archimedes method. Specifically, the air mass of the target material is divided by the volume (mass in water of the target material / specific gravity of water at the measured temperature), and the value of the percentage with respect to the theoretical density ρ (g/cm 3 ) based on the following formula (X) is relative It was referred to as the density (unit: %).

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

(In the formula, C1 to Ci respectively represent the content (mass %) of the constituent substances of the target material, and ρ1 to pi represent the density (g/cm 3 ) of each constituent material corresponding to C1 to Ci.)

Substance (a raw material) used for producing the target material in the following examples and comparative _{examples, In 2 O 3, SnO 2} , since the SiO _2, e.g.

C1: Mass % _{of the In 2} O ₃ raw material used for the target

ρ1: _{Density of In 2} O ₃ (7.18 g/cm 3 )

C2: Mass % of _{SnO 2} raw material used for target

ρ2: _{Density of SnO 2} (6.95 g/cm 3 )

C3:% by mass of the SiO ₂ raw material used for the target

ρ3: _{density of SiO 2} (2.20 g/cm 3 )

By applying to formula (X), the theoretical density ρ can be calculated.

2. Target's resistivity

The specific resistance of the sputtering target was measured in AUTO RANGE mode by placing the probe on the surface of the sintered body after processing using Loresta (registered trademark) HP MCP-T410 (series 4 probe probe TYPE ESP) manufactured by Mitsubishi Chemical.

3. Presence state of Si in the sputtering target

The presence state of Si in the sputtering target was measured under the following conditions using Rigaku's X-ray diffraction apparatus SmartLab (registered trademark).

· Source: CuKα radiation

· Tube voltage: 40kV

· Tube current: 30mA

· Scan speed: 5deg/min

· Step: 0.02deg

· Scan range: 2θ = 20 degrees to 80 degrees

4. Film resistivity of transparent conductive film

The film resistivity of the transparent conductive film was measured using Kyowariken Co., Ltd. 4-probe measuring instrument K-705RS.

5. Etching rate of transparent conductive film

The etching rate of the transparent conductive film is etched by immersing a part of the transparent conductive film in a transparent conductive film etching solution (ITO-07N manufactured by Kanto Chemical Co., Ltd.) heated to 40° C. for 6 minutes, KLA-Tencor Corporation, stylus type surface shape Using the measuring instrument P-15, the level difference between the location which performed etching and the location which did not implement was measured, and it computed by dividing the level difference by the etching time.

6. Content ratio of In, Sn and Si of the transparent conductive film

The transparent conductive film formed into a film on copper foil was used for the measurement. The content of In and Sn was measured by the acid decomposition ICP-OES method using an ICP emission spectrometer 720 ICP-OES manufactured by Agilent Technologies, and the content of Si was measured using a spectrophotometer U-2900 manufactured by Hitachi Seisakusho. , was measured by molybdenum blue absorptiometry.

[Examples and Comparative Examples]

(Manufacture of sputtering target)

In ₂ O ₃ powder, SnO ₂ powder, and SiO ₂ powder were mixed in the ratio shown in Table 1 using a ball mill, and mixed powder was prepared.

6 mass % of polyvinyl alcohol diluted to 4 mass % was added to the said mixed powder with respect to the mixed powder, polyvinyl alcohol was mixed well with the powder using a mortar, and it was made to pass through a 5.5 mesh sieve. The obtained powder was temporarily pressed under the condition of 200 kg/cm 2 , and the obtained provisional molded product was pulverized in a mortar. The obtained pulverized powder was filled in a mold for press, and molded at a press pressure of 1 t/cm 2 for 60 seconds to obtain a molded product.

Put the obtained molded body in a kiln, flow oxygen at 1 L/h in the furnace, make the sintering atmosphere an oxygen flow atmosphere, set the temperature increase rate to 350 ° C./h, sintering temperature to 1550 ° C., and set the holding time at the sintering temperature to 9 h and fired Then, it cooled at the temperature-fall rate of 100 degreeC/h. In Comparative Example 7, the firing temperature was set to 1250°C.

As described above, an oxide sintered body was obtained.

This oxide sintered compact was cut and the sputtering target was manufactured. The relative density of this sputtering target, the specific resistance, and the presence state of Si in the sputtering target were measured by the above method. A result is shown in Table 1.

In the "state of presence of Si" in Table 1, _{the notation "In 2} Si ₂ O ₇ " indicates that all Si in the sputtering target appears as a peak of _{In 2} Si ₂ O _{7 in X-ray diffraction measurement,} notation of "SiO ₂ + in ₂ Si ₂ O _7" indicates that the sputtering target in the Si, that appears as the peak of SiO ₂ and a peak of in ₂ Si ₂ O _7.

Moreover, the X-ray-diffraction pattern of the sputtering target obtained in Example 3 is shown in FIG. In FIG. 1 , a black circle _{indicates a peak of In 2} O ₃ , and a black triangle indicates a peak of In ₂ Si ₂ O ₇ . Also, the embodiment 3 Si in the sputtering target obtained in both, soil carte was confirmed that Si exists as silicate indium compound In ₂ Si ₂ O ₇ with a by-tight in the structure from the first.

(Manufacture of transparent conductive film)

The sputtering target is bonded to a copper backing plate with In solder, and sputtering is performed under the following conditions to form a transparent conductive film with a thickness of 1000 Å on a glass substrate for measuring specific resistance and etching rate, and further, Sn of the transparent conductive film A transparent conductive film having a thickness of 15000 angstroms was formed on a copper foil with a thickness of 1.1 mm for measurement of the content rate and the Si content rate. Moreover, in the comparative example 6, since the specific resistance of a target was high and discharge did not generate|occur|produce, DC sputtering could not be performed. In addition, in the target of Comparative Example 7, arcing and nodules occurred frequently, and film formation could not be performed stably. Therefore, the film formation evaluation could not be performed either.

Device: DC magnetron sputter device, exhaust system cryopump, rotary pump

Reached vacuum: 1×10 ^-4 Pa

Sputter pressure: 0.4Pa

Oxygen flow rate: 0 to 3.0 sccm

The film specific resistance, etching rate, In content rate, Sn content rate, and Si content rate of the obtained transparent conductive film were measured by the said method. The conditions of the oxygen flow rate were suitably adjusted to the conditions under which an amorphous transparent conductive film was obtained, and also the specific resistance of a film|membrane becomes the lowest. A result is shown in Table 1.

Claims (9)

The constituent elements are In, Sn, Si and O, or In, Si and O, the content rate of In is 70.0 mass % or more and less than 85.0 mass % in conversion of _{In 2} O ₃ , and the content rate of Sn is 0 in conversion of _{SnO 2} and the mass% or more than 10.0% by mass, the transparent conductive film made of a large, the content of Si, 20.0% by weight or less than 15.0% by mass of the oxide-sintered body as a sputtering target in terms of SiO _2,
In X-ray diffraction measurement of the said sputtering target, Si appears as a peak of the indium silicate compound which has a tortweite-type structure in all, sputtering target for transparent conductive films. The sputtering target for transparent conductive films of Claim 1 ^{whose specific resistance is 2.0x10 2 ohm-cm or less.} The sputtering target for transparent conductive films of Claim 1 or 2 whose relative density is 98.0 % or more. The constituent elements are In, Sn, Si and O, or In, Si and O, the content of In is 73.0 mass% or more and 87.0 mass% or less in terms of _{In 2} O ₃ , and the content rate of Sn is 0 in terms of _{SnO 2} the mass% or more and less than 9.0% by mass, the content of Si more than 13.0% by mass in terms of SiO ₂ 18.0% by mass or less, a transparent conductive film. The transparent conductive film according to claim 4, wherein the film specific resistance is 1.0×10 ⁰ Ωcm or more. The transparent conductive film according to claim 4 or 5, wherein the etching rate is greater than 11.0 Å/sec. The manufacturing method of the transparent conductive film which forms into a film by sputtering the sputtering target for transparent conductive films in any one of Claims 1-2. The method of claim 7 wherein at least the transparent conductive film has resistivity 1.0 × 10 ⁰ Ω㎝, method of producing the transparent conductive film. The method for producing a transparent conductive film according to claim 7, wherein the etching rate of the transparent conductive film is greater than 11.0 Å/sec.

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