JP6957815B2 - Oxide sputtering target - Google Patents

Description

The present invention relates to an oxide sputtering target used for forming an oxide film containing Si, Zr, and at least one of Nb and Ti as metal elements.

Generally, in a recording medium such as an optical disk, a low refractive index film and a high refractive index film are used for optical design.
Optical design is to optimize the reflection, absorption, and transmission of the laser emitted to the optical disc for recording and reproducing information by adjusting the refractive index and film thickness of each layer constituting the optical disc. Thereby, for example, the reproduction signal quality can be optimized, and in the case of a multi-layer disc having a plurality of recording layers, the balance of the signal strength from each layer can be optimized.

Here, as the high refractive index film, for example, as shown in Patent Documents 1-4, an oxide film having various metal elements has been proposed.
For example, Patent Documents 1 and 2 propose an oxide sintered body sputtering target for forming a high-flexibility film made of _{titanium oxide (TiO X).} In addition, in these Patent Documents 1 and 2, an oxide film in which an oxide of a metal selected from chromium, cerium, zirconium, yttrium, niobium, tantalum, silicon, and aluminum is added to titanium oxide is also proposed. ..

Further, in Patent Document 3, as a high refractive index film (refractive index n> 1.9), TiO ₂ (n = 2.4), CeO (n = 2.3), ZrO ₂ (n = 2.2). ), Nb ₂ O ₅ (n = 2.1), Ta ₂ O ₅ (n = 2.1), WO ₃ (n = 2.0).
Further, Patent Document 4 proposes a sputtering target for forming a thin film for forming an oxide film containing titanium oxide and niobium oxide.

Japanese Unexamined Patent Publication No. 07-233469 Japanese Unexamined Patent Publication No. 2004-002202 Japanese Unexamined Patent Publication No. 2000-160331 Japanese Unexamined Patent Publication No. 2006-0456666

By the way, when an oxide film is formed by using a sputtering target made of a metal oxide, it is necessary to use an RF (radio frequency) sputtering method because the oxide film generally has low conductivity. In the RF (radio frequency) sputtering method, it is possible to form a film even with an insulator, but compared to the DC (direct current) sputtering method, the equipment is expensive, the film forming speed is slow, and the productivity is low. There was a problem such as doing.

Further, in the above-mentioned oxide film, it is necessary to ensure the smoothness of the oxide film in order to suppress diffused reflection of light and stabilize the optical characteristics. Here, as described in Patent Documents 1-4, in an oxide film containing titanium oxide as a main component, when used under high temperature conditions, the film crystallizes and the oxide film becomes smooth. There was a problem that the sex was reduced.

The present invention has been made in view of the above-mentioned circumstances, has a sufficiently low specific resistance value, enables stable DC sputtering, is amorphous even when heat is applied, and smoothes the film surface. It is an object of the present invention to provide an oxide sputtering target capable of forming an oxide film capable of maintaining properties.

In order to solve the above problems, the oxide sputtering target of the present invention comprises an oxide of a metal element of Si, Zr, and at least one of Nb and Ti, and all atoms of Si, Nb, Ti and Zr. When the atomic number ratio of Si to the number is a, the atomic number ratio of Nb is b, the atomic number ratio of Ti is c, and the atomic number ratio of Zr is d.
Equation (1): f (1) = (b / 2) / (1-b / 2) + c / (1-b / 2) ≧ 0.35
Equation (2): 0.3 ≧ f (2) = a / (1-b / 2) ≧ 0.1
Equation (3): f (3) = d / (1-b / 2) ≧ 0.1
It is characterized in that it satisfies the above-mentioned equations (1), (2) and (3) and has a specific resistance value of 0.1 Ω · cm or less.

According to the oxide sputtering target of the present invention, Si, Zr, and at least one of Nb and Ti are contained as metal elements, and the number of atoms of Si with respect to the total number of atoms of Si, Nb, Ti and Zr. When the ratio is a, the atomic number ratio of Nb is b, the atomic number ratio of Ti is c, and the atomic number ratio of Zr is d, the above equation (1) is satisfied. The specific resistance value becomes low, and stable film formation becomes possible by DC sputtering.
Further, since the above-mentioned equation (2) is satisfied, it is possible to form an oxide film having a high refractive index.
Further, since the above equations (2) and (3) are satisfied, an amorphous film is formed without crystallization even when heat is applied, and the smoothness of the film surface can be maintained.

Further, since the specific resistance value is 0.1 Ω · cm or less, the oxide film can be stably formed by the DC sputtering method.

According to the present invention, the specific resistance value is sufficiently low, stable DC sputtering is possible, and an oxide film that is amorphous and can maintain the smoothness of the film surface can be formed even when heat is applied. Oxide sputtering target can be provided.

It is a flow chart which shows an example of the manufacturing method of the oxide sputtering target which is an embodiment of this invention. It is a figure which shows the XRD result of the oxide film after the heat treatment of Example 1 of this invention in an Example. It is a figure which shows the XRD result of the oxide film after the heat treatment of the comparative example 7 in an Example.

The oxide sputtering target according to the embodiment of the present invention will be described below with reference to the attached drawings.
The oxide sputtering target of the present embodiment is for forming an oxide film having a high refractive index used for, for example, an optical disk. In the present embodiment, an oxide film having a refractive index of 2.1 or more is formed.

The oxide sputtering target of the present embodiment is composed of an oxide containing Si, Zr, and at least one of Nb and Ti as metal elements, and is composed of an oxide of Si with respect to the total number of atoms of Si, Nb, Ti and Zr. When the atomic number ratio is a, the atomic number ratio of Nb is b, the atomic number ratio of Ti is c, and the atomic number ratio of Zr is d, the following equations (1), (2), and (3) are shown below. The composition satisfies the formula.

Equation (1): f (1) = (b / 2) / (1-b / 2) + c / (1-b / 2) ≧ 0.35
Equation (2): 0.3 ≧ f (2) = a / (1-b / 2) ≧ 0.1
Equation (3): f (3) = d / (1-b / 2) ≧ 0.1
Since the atomic number ratio of Si to the total atomic number of Si, Nb, Ti and Zr is a, the atomic number ratio of Nb is b, the atomic number ratio of Ti is c, and the atomic number ratio of Zr is d. It becomes a + b + c + d = 1.

Further, in the oxide sputtering target of the present embodiment, the specific resistance value thereof is 0.1 Ω · cm or less.

Hereinafter, the reason why the content ratio of the metal component element of the oxide sputtering target of the present embodiment and the specific resistance value are defined as described above will be described.

<About equation (1)>
Oxides mainly composed of Nb and Ti (for example, Nb ₂ O ₅ , TiO ₂ ) should be in a state slightly reduced from the stoichiometric ratio (for example, Nb ₂ O _4.8, etc., TiO _1.8, etc.). Therefore, it becomes conductive and the specific resistance value of the oxide sputtering target becomes low.
Here, when f (1) = (b / 2) / (1-b / 2) + c / (1-b / 2) is smaller than 0.35, the contents of Nb and Ti are small and the conductivity is low. It becomes insufficient, the specific resistance value of the oxide sputtering target becomes high, and there is a possibility that stable film formation cannot be performed by DC sputtering.
From the above, in this embodiment,
Equation (1): f (1) = (b / 2) / (1-b / 2) + c / (1-b / 2) ≧ 0.35
Is to be satisfied.
In order to further improve the conductivity, it is preferable that f (1) = (b / 2) / (1-b / 2) + c / (1-b / 2) is 0.40 or more. It is more preferably 0.50 or more.

<About equation (2)>
The formed oxide film becomes an amorphous film by containing Si, and it becomes difficult to crystallize even when heat is applied. On the other hand, as the Si content increases, the refractive index of the formed oxide film tends to decrease.
Here, when f (2) = a / (1-b / 2) is smaller than 0.1, the Si content decreases, and the oxide film tends to become crystalline when heat is applied, and the film tends to become crystalline. The smoothness of the surface may decrease. On the other hand, when f (2) = a / (1-b / 2) is larger than 0.3, the Si content increases, and the refractive index of the formed oxide film may be 2.1 or more. It may not be possible.
From the above, in this embodiment,
Equation (2): 0.3 ≧ f (2) = a / (1-b / 2) ≧ 0.1
Is to be satisfied.
In order to further suppress the crystallization of the oxide film when heat is applied, it is preferable that f (2) = a / (1-b / 2) is 0.12 or more, and 0.15. The above is more preferable. On the other hand, in order to further increase the refractive index of the formed oxide film, f (2) = a / (1-b / 2) is preferably 0.25 or less, and 0.20 or less. Is even more preferable.

<About equation (3)>
The formed oxide film becomes an amorphous film by containing Zr, and it becomes difficult to crystallize even when heat is applied.
Here, when f (3) = d / (1-b / 2) is smaller than 0.1, the content of Zr decreases, and the oxide film tends to become crystalline when heat is applied, and the film tends to become crystalline. The smoothness of the surface may decrease. From the above, in this embodiment,
Equation (3): f (3) = d / (1-b / 2) ≧ 0.1
Is to be satisfied.
In order to further suppress the crystallization of the oxide film when heat is applied, it is preferable that f (3) = d / (1-b / 2) is 0.15 or more, and 0.20. The above is more preferable.
Further, if f (3) = d / (1-b / 2) becomes too large, the Zr content becomes too large, the specific resistance of the target increases, and an abnormal discharge may easily occur. From the above, f (3) = d / (1-b / 2) is preferably smaller than 0.5, and more preferably 0.4 or less.

(Specific resistance value: 0.1Ω ・ cm or less)
If the specific resistance value of the oxide sputtering target exceeds 0.1 Ω · cm, there is a risk that DC sputtering cannot be performed stably. In addition, abnormal discharge is likely to occur, which may cause particles to be generated.
From the above, in the oxide sputtering target of the present embodiment, the specific resistance value is preferably 0.1 Ω · cm or less, and more preferably 0.05 Ω · cm or less.

Next, the method for manufacturing the oxide sputtering target according to the present embodiment will be described with reference to the flow chart shown in FIG.

First, silicon oxide powder, titanium oxide powder, niobium oxide powder, and zirconium oxide powder are prepared. These oxide powders preferably have a purity of 99.9% by mass or more.
Then, these oxide powders are mixed using a ball mill or the like so as to have a composition ratio satisfying the above-mentioned equations (1), (2) and (3) to prepare a mixed raw material powder. (Mixed raw material powder preparation step S01).

Next, the obtained mixed raw material powder is filled in a mold and heated while pressurizing to be sintered to obtain a sintered body (sintering step S02). In the present embodiment, the raw material powder is filled in the graphite mold and vacuum hot pressed to obtain a sintered body.
In this sintering step S02, a part of the niobium oxide powder and the titanium oxide powder is reduced, and the conductivity of the sintered body is ensured.

The sintering temperature in the sintering step S02 is in the range of 1100 ° C. or higher and 1300 ° C. or lower, the holding time at the sintering temperature is in the range of 120 min or higher and 300 min or lower, and the pressurizing pressure is 14.7 MPa or higher and 34.3 MPa or lower. It is preferably within the range. The atmosphere is preferably a vacuum atmosphere (0.5 Pa or less).

Next, the obtained sintered body is machined (machining step S03). As a result, the oxide sputtering target of the present embodiment is manufactured.

The oxide sputtering target of the present embodiment having the above configuration contains Si, Zr, and at least one of Nb and Ti as metal elements, and Si, Nb, Ti, and Zr. When the atomic number ratio of Si to the total atomic number of is a, the atomic number ratio of Nb is b, the atomic number ratio of Ti is c, and the atomic number ratio of Zr is d.
Equation (1): f (1) = (b / 2) / (1-b / 2) + c / (1-b / 2) ≧ 0.35
Therefore, the contents of niobium oxide and titanium oxide are secured, and a part of niobium oxide and titanium oxide is reduced in the sintering step S02, so that the conductivity of the sintered body is improved. Therefore, the specific resistance value of the oxide sputtering target becomes low, and stable film formation can be performed by DC sputtering.

Further, in the oxide sputtering target of the present embodiment,
Equation (2): 0.3 ≧ f (2) = a / (1-b / 2) ≧ 0.1
Therefore, the Si content can be suppressed to a low level, and an oxide film having a high refractive index can be formed. Further, by containing Si in a certain amount or more, the oxide film is less likely to crystallize even when heat is applied, and the smoothness of the film surface can be improved.

Further, in the oxide sputtering target of the present embodiment,
Equation (3): f (3) = d / (1-b / 2) ≧ 0.1
By containing Zr in a certain amount or more, the oxide film is less likely to crystallize even when heat is applied, and the smoothness of the film surface can be improved.

Further, in the oxide sputtering target of the present embodiment, the specific resistance value is 0.1 Ω · cm or less, so that the resistance is sufficiently low and an oxide film is stably formed by DC sputtering. It becomes possible.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and can be appropriately changed without departing from the technical idea of the invention.

The results of the confirmation experiment conducted to confirm the effectiveness of the present invention will be described below.

As raw material powders, silicon oxide powder (SiO ₂ powder: purity 99.9 mass% or more, average particle size 1.4 μm) and niobium oxide powder (Nb ₂ O ₅ powder: purity 99.9 mass% or more, average particle size 6. 4 μm), titanium oxide powder (TiO ₂ powder: purity 99.8 mass% or more, average particle size 2.7 μm) and zirconium oxide powder (ZrO ₂ powder: purity 99.9 mass% or more, average particle size 10.9 μm) And prepared.
These oxide powders were weighed so as to have a predetermined composition ratio.

Weighed silicon oxide powder, niobium oxide powder, titanium oxide powder and zirconia oxide powder were put into a ball mill device together with zirconia balls having a diameter of 5 mm and a solvent (Solmix A-11 manufactured by Nippon Alcohol Sales Co., Ltd.) for 16 hours. It was crushed and mixed. After pulverization and mixing, the zirconia balls were separated and recovered to obtain a slurry containing the mixed powder and the solvent. The slurry was heated to dry and remove the solvent to give a mixed powder.

Next, the obtained mixed powder was filled in a carbon mold having a diameter of 165 mm, loaded into a vacuum hot press device, and heated to a temperature of 1200 ° C. in vacuum (0.5 Pa or less) at 350 kgf /. Sintering was performed by pressing at a pressure of cm ² (34.3 MPa) to prepare two disc-shaped sintered bodies having a diameter of 165 mm and a thickness of 8 mm.
The obtained sintered body was machined to prepare two disk-shaped oxide sputtering targets having a diameter of 152.4 mm and a thickness of 6 mm.

For the oxide sputtering target obtained as described above, the metal element was analyzed and the resistivity value was measured by the following procedure. In addition, a sputtering test was carried out using the obtained oxide sputtering target to evaluate the oxide film formed.
One of the two oxide sputtering targets produced was used for measuring the resistivity value. In addition, after measuring the resistivity value, a sample piece was taken from this oxide sputtering target and analyzed for metal elements. Furthermore, the remaining one was used for the sputtering test and the film evaluation.

(Atomic ratio of metal elements of oxide sputtering target)
A sample piece collected from the above-mentioned oxide sputtering target was analyzed by a fluorescent X-ray analyzer (XRF) to obtain atomic ratios of Si, Nb, Ti, and Zr. Further, the above-mentioned f (1), f (2), and f (3) were calculated from this analysis result. The calculation results are shown in Table 1.

(Specific resistance value of oxide sputtering target)
The resistivity value was measured by the four-probe method. The measurement was carried out at the center point of the target sputtered surface (circle). The measurement results are shown in Table 2.

(Spatter test)
The oxide sputtering target was soldered to a backing plate made of oxygen-free copper, and this was mounted on a magnetron type sputtering device, and sputtering was performed under the following conditions. The battery was continuously discharged for 60 minutes under the following conditions, and the number of abnormal discharges during that period was measured by the abnormal discharge measurement function mounted on the DC power supply. Even if an abnormal discharge was detected during this period, it was judged that DC was possible if the discharge continued. The evaluation results are shown in Table 2.
Ultimate vacuum: 5 x ^10-5 Pa or less Discharge gas flow rate: Ar = 47 sccm, O ₂ = 3 sccm
Total discharge gas pressure: 0.67Pa
Discharge power: DC1000W

(Confirmation of membrane composition)
Separately from the above, an oxide film was formed on a polycarbonate substrate having a diameter of 12 cm at a film thickness of 500 nm, and the obtained oxide film was analyzed using an inductively coupled plasma emission spectroscopy (ICP) apparatus. As a result, it was confirmed that the oxide film had almost the same composition as the oxide sputtering target.

(Refractive index of film)
Under the above sputtering conditions, an oxide film having a film thickness of 30 nm was formed on the Si substrate. At this time, the distance between the substrate and the target was set to 70 mm.
The refractive index of this oxide film was measured using a spectroscopic ellipsometer at an incident angle of 75 ° and a measurement wavelength of 405 nm. The evaluation results are shown in Table 2.

(Crystallinity of membrane)
Under the above sputtering conditions, an oxide film having a film thickness of 100 nm was formed on the Si substrate. At this time, the distance between the substrate and the target was set to 70 mm.
After confirming that the oxide film before the heat treatment is amorphous by XRD (θ-2θ method), the above oxide film is heat-treated under the conditions shown below, and the oxide film after the heat treatment is XRD ( It was evaluated whether or not it was amorphous by the θ-2θ method). The evaluation results are shown in Table 2. The XRD result of Example 1 of the present invention in which the oxide film after heat treatment was amorphous is shown in FIG. 2, and the XRD result of Comparative Example 7 in which the oxide film after heat treatment was crystalline is shown in FIG. ..
Reactor used: Infrared gold image Reactor Atmosphere: Vacuum Holding temperature: 600 ° C
Holding time: 30 minutes

Equation (1): In Comparative Examples 1 to 3 that do not satisfy f (1) = (b / 2) / (1-b / 2) + c / (1-b / 2) ≥ 0.35, the number of abnormal discharges It was difficult to sustain the discharge, and it was not possible to form a film by DC sputtering. It is presumed that the content of Nb or Ti was low and the resistivity value was high. In Comparative Examples 1 to 3, since the oxide film could not be formed, the refractive index and the crystal state of the film after the heat treatment were not evaluated.

Equation (2): In Comparative Examples 4 to 6 in which the upper limit of 0.3 ≧ f (2) = a / (1-b / 2) ≧ 0.1 is exceeded, the refractive index of the formed oxide film is low. became. It is presumed that the Si content increased.

Equation (2): 0.3 ≧ f (2) = a / (1-b / 2) ≥ 0.1 below the lower limit, or Equation (3): f (3) = d / (1-b) / 2) In Comparative Examples 7 to 10 that did not satisfy ≧ 0.1, the oxide film after the heat treatment became crystalline. It is presumed that the content of Si or Zr was insufficient.

On the other hand, in Examples 1 to 6 of the present invention satisfying the equations (1), (2) and (3), the number of abnormal discharges was small and stable film formation could be achieved by DC sputtering. .. In addition, the refractive index of the formed oxide film was as high as 2.2 or more. Further, the oxide film after the heat treatment became amorphous, and the smoothness of the film surface was maintained.

From the above, according to the example of the present invention, the specific resistance value is sufficiently low, stable DC sputtering is possible, and oxidation that is amorphous and can maintain the smoothness of the film surface even when heat is applied. It was confirmed that it is possible to provide an oxide sputtering target capable of forming a film.

Claims (1)

Consists of oxides of metallic elements of Si, Zr, and at least one of Nb and Ti.
When the atomic number ratio of Si to the total atomic number of Si, Nb, Ti and Zr is a, the atomic number ratio of Nb is b, the atomic number ratio of Ti is c, and the atomic number ratio of Zr is d.
Equation (1): f (1) = (b / 2) / (1-b / 2) + c / (1-b / 2) ≧ 0.35
Equation (2): 0.3 ≧ f (2) = a / (1-b / 2) ≧ 0.1
Equation (3): f (3) = d / (1-b / 2) ≧ 0.1
Satisfying the above equations (1), (2) and (3) ,
An oxide sputtering target having a specific resistance value of 0.1 Ω · cm or less.

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