JP2022028300A - Sputtering target - Google Patents

Abstract

To provide a sputtering target that can stably deposit an oxide film containing Al and Si.SOLUTION: A sputtering target has a structure having an Si content of 70 mass% or more and 99 mass% or less and an Al content of 0.5 mass% or more and 16 mass% or less with the balance being O and unavoidable impurities, in which the Al is included in the form of oxides, and an aluminum oxide phase is dispersed in the base phase of the metal Si phase, and the average particle size of the aluminum oxide phase is set to 20 μm or less.SELECTED DRAWING: None

Description

The present invention relates to a sputtering target used when forming an oxide film containing Al and Si.

The oxide film containing Al and Si is used, for example, as an optical functional film for adjusting the refractive index and a transparent water vapor barrier film.
Here, the above-mentioned oxide film containing Al and Si is formed by a sputtering method using a sputtering target. For example, Patent Document 1 proposes a sputtering target containing Si and Al elements or Si—Al alloys and a metal oxide.

Special Table 2016-599246 Gazette

By the way, when a sputtering target made of a Si—Al alloy is used when forming an oxide film containing Al and Si, a metallic Al phase is present on the sputtered surface of the sputtering target. Here, since the metallic Al phase has a higher sputtering rate than the metallic Si phase, Al is preferentially consumed during sputtering, and as the sputtering progresses, unevenness is generated on the sputtering surface of the sputtering target. For this reason, charge concentration occurs during sputtering, abnormal discharge is likely to occur, and there is a risk that stable film formation cannot be performed.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sputtering target capable of stably forming an oxide film containing Al and Si.

In order to solve the above problems, the sputtering target of the present invention has a Si content in the range of 70 mass% or more and 99 mass% or less, an Al content in the range of 0.5 mass% or more and 16 mass% or less, and the balance is O. Al exists as an oxide and has a structure in which the aluminum oxide phase is dispersed in the matrix phase of the metallic Si phase, and the average particle size of the aluminum oxide phase is 20 μm or less. It is characterized by being.

According to the sputtering target having this configuration, since the Al content is 0.5 mass% or more, it is possible to form an oxide film having a high refractive index. Further, since the Al content is 16 mass% or less, it is possible to suppress the occurrence of abnormal discharge due to aluminum oxide during sputtering.
Since Al exists as an oxide, Al is not preferentially consumed during sputtering, and even if sputtering progresses, unevenness is unlikely to occur on the sputtered surface of the sputtering target, and the occurrence of abnormal discharge is suppressed. can.
Further, since the average particle size of the aluminum oxide phase is 20 μm or less, it is possible to suppress the occurrence of abnormal discharge caused by the aluminum oxide phase.
From the above, in the sputtering target of the present invention, an oxide film containing Al and Si can be stably sputtered and formed.

Here, in the sputtering target of the present invention, it is preferable that the maximum particle size of the aluminum oxide phase is 60 μm or less.
In this case, it is possible to further suppress the occurrence of abnormal discharge due to the aluminum oxide phase.

Further, in the sputtering target of the present invention, the density ratio is preferably 95% or more.
In this case, since the density ratio is 95% or more, it is possible to suppress the generation of particles during sputtering film formation, and it is possible to perform sputtering film formation more stably.

Further, in the sputtering target of the present invention, it is preferable that the specific resistance is 1.0 Ω · cm or less.
In this case, since the specific resistance is sufficiently low and the conductivity is ensured, it becomes possible to form a sputtered film more stably.

According to the present invention, it is possible to provide a sputtering target capable of stably forming an oxide film containing Al and Si.

It is a figure which shows the XRD analysis result of the sputtering target which concerns on one Embodiment of this invention. It is a microstructure photograph of a sputtering target which concerns on one Embodiment of this invention. It is an element mapping diagram of the sputtering target which concerns on one Embodiment of this invention. It is a flow figure which shows the manufacturing method of the sputtering target which concerns on one Embodiment of this invention.

Hereinafter, the sputtering target according to the embodiment of the present invention will be described with reference to the attached drawings.

The sputtering target according to the present embodiment is used when forming an optical functional film for adjusting the refractive index or an oxide film containing Al and Si used as a transparent water vapor barrier film.

The sputtering target of the present embodiment has a composition in which the Si content is in the range of 70 mass% or more and 99 mass% or less, the Al content is in the range of 0.5 mass% or more and 16 mass% or less, and the balance is O and unavoidable impurities. It is said that.
Al exists as an oxide, and as shown in FIG. 2, it has a structure in which granular aluminum oxide phase 12 is dispersed in the matrix phase of the metal Si phase 11.
The average particle size of the aluminum oxide phase 12 is 20 μm or less.

Here, in the sputtering target of the present embodiment, as shown in FIG. 1, as a result of XRD analysis, a peak of metallic Si and a peak of aluminum oxide (Al ₂ O ₃ ) are present, and the metallic Al is present. , The peak of Si—Al alloy has not been confirmed. That is, in the sputtering target of the present embodiment, Al exists as an oxide and does not exist as a metallic Al or a Si—Al alloy. Further, in the sputtering target of the present embodiment, Si exists as a metal and does not exist as a Si—Al alloy or an oxide.

Further, in the sputtering target of the present embodiment, as shown in FIGS. 2 and 3, as a result of microstructure observation and EPMA analysis, granular aluminum oxide phase 12 is dispersed in an island shape in the matrix phase of the metal Si phase 11. It is confirmed that the organization has been established.
The element distribution image by EPMA is originally a color image, but in the photograph of FIG. 3, it is converted into a black-and-white image and shown. Therefore, in the photograph, the whiter the element, the higher the concentration of the element. ing. Specifically, in the distribution image relating to Al, the Al element is distributed in white and granular form, in the distribution image relating to Si, the Si element is present as a whole except for the portion where the Al element is present, and in the distribution image relating to O, the Si element is present as a whole. It is observed that the O element is present in the portion where the Al element is present.

Here, in the sputtering target of the present embodiment, the maximum particle size of the aluminum oxide phase 12 is preferably 60 μm or less.
Further, in the sputtering target of the present embodiment, the density ratio is preferably 95% or more, and more preferably 98% or more.
Further, in the sputtering target of the present embodiment, it is preferable that the specific resistance is 1.0 Ω · cm or less.

Hereinafter, in the sputtering target of the present embodiment, the reason why the composition, the structure, the average particle size of the aluminum oxide phase 12, the maximum particle size of the aluminum oxide phase 12, the density ratio, and the specific resistance are defined as described above will be described. do.

(composition)
In the sputtering target of the present embodiment, an oxide film containing Al and Si is formed, and as described above, the composition contains Si, Al, and oxygen (O).
Here, if the Al content is less than 0.5 mass%, the refractive index of the formed oxide film containing Al and Si may be lowered. On the other hand, if the Al content exceeds 16 mass%, abnormal discharge may occur during sputtering.
Therefore, in the present embodiment, the Al content is set within the range of 0.5 mass% or more and 16 mass% or less.
In order to further increase the refractive index of the formed oxide film containing Al and Si, the lower limit of the Al content is preferably 2 mass% or more, and more preferably 3 mass% or more. On the other hand, in order to further suppress the occurrence of abnormal discharge during sputtering, the upper limit of the Al content is preferably 10 mass% or less, and more preferably 5 mass% or less.

In the sputtering target of the present embodiment, Al exists as an oxide, and as shown in FIGS. 2 and 3, the structure is such that granular aluminum oxide phase 12 is dispersed in the matrix phase of the metal Si phase 11. There is.
Here, since Al exists as an oxide and does not exist as a metal Al, a solid solution, or a Si—Al alloy, preferential consumption of Al during sputtering is suppressed, and the sputtering proceeds. However, unevenness is less likely to occur on the spattered surface, and it is possible to suppress the occurrence of abnormal discharge.
Further, by forming the structure in which the granular aluminum oxide phase 12 is dispersed in the matrix phase of the metal Si phase 11, the specific resistance can be suppressed low, and the occurrence of abnormal discharge during sputtering can be suppressed. Become.

(Average particle size of aluminum oxide phase)
In the sputtering target of the present embodiment, when the average particle size of the aluminum oxide phase 12 exceeds 20 μm, abnormal discharge may easily occur due to the aluminum oxide phase 12 during sputtering.
Therefore, in the present embodiment, the average particle size of the aluminum oxide phase 12 is set to 20 μm or less.
In order to further suppress the occurrence of abnormal discharge, the upper limit of the average particle size of the aluminum oxide phase 12 is preferably 18 μm or less, and more preferably 15 μm or less.
The smaller the average particle size, the better, and the lower limit is not limited, but for example, it may be 0.001 μm or more, 0.01 μm or more, or 0.1 μm or more. good.

(Maximum particle size of aluminum oxide phase)
In the sputtering target of the present embodiment, when the maximum particle size of the aluminum oxide phase 12 is 60 μm or less, it is possible to further suppress the generation of abnormal discharge due to the aluminum oxide phase 12 during sputtering. ..
Therefore, in the present embodiment, the maximum particle size of the aluminum oxide phase 12 is preferably 60 μm or less.
In order to further suppress the occurrence of abnormal discharge, the upper limit of the maximum particle size of the aluminum oxide phase 12 is more preferably 50 μm or less, and further preferably 40 μm or less.
The maximum particle size is preferably as small as possible, and the lower limit is not limited, but for example, it may be 0.001 μm or more, 0.01 μm or more, or 0.1 μm or more. good.

(Density ratio)
In the sputtering target of the present embodiment, when the density ratio is 95% or more, there are few pores, and it is possible to suppress the generation of particles during sputtering film formation.
Therefore, in this embodiment, the density ratio is preferably 95% or more.
In order to further suppress the generation of particles during sputter film formation, the density ratio is more preferably 96% or more, further preferably 97% or more. The upper limit of the density ratio is not particularly limited, but is, for example, 100% as the upper limit that can be manufactured by a normal manufacturing method.

(Specific resistance)
In the sputtering target of the present embodiment, when the specific resistance is 1.0 Ω · cm or less, the conductivity is ensured and the sputtering film can be stably formed.
Therefore, in this embodiment, it is preferable that the specific resistance is 1.0 Ω · cm or less.
In order to form a more stable sputtering film formation, the upper limit of the specific resistance is more preferably 0.8 Ω · cm or less, and further preferably 0.5 Ω · cm or less.
The lower the specific resistance, the better, and the lower limit is not limited, but it may be, for example, 0.001 Ω · cm.

Next, a method for manufacturing a sputtering target according to the present embodiment will be described with reference to FIG.

(Powder mixing step S01)
In the present embodiment, first, as shown in FIG. 4, the metallic Si powder and the aluminum oxide powder are weighed and mixed so as to have a predetermined composition ratio to obtain a sintered raw material powder.
Here, the mixing method is not particularly limited, but in the present embodiment, a ball mill device is used.
Further, it is preferable that the purity of the metallic Si powder is 99.9 mass% or more and the average particle size is in the range of 0.1 μm or more and 20 μm or less. The purity of the aluminum oxide powder is preferably 99.9 mass% or more, and the average particle size is preferably in the range of 0.1 μm or more and 1.0 μm or less.

(Sintering step S02)
Next, the above-mentioned sintered raw material powder is sintered by heating while pressurizing to obtain a sintered body. In this embodiment, sintering was carried out in vacuum using a hot press device.
The sintering temperature in the sintering step S02 is in the range of 1100 ° C. or higher and 1500 ° C. or lower, the holding time at the sintering temperature is in the range of 4 hours or more and 10 hours or less, and the pressurizing pressure is in the range of 20 MPa or more and 50 MPa or less. It was inside.

(Machining process S03)
Next, the obtained sintered body is machined to have a predetermined size. As a result, the sputtering target according to the present embodiment is manufactured.

According to the sputtering target of the present embodiment having the above configuration, the Si content is within the range of 70 mass% or more and 99 mass% or less, and the Al content is 0.5 mass% or more and 16 mass% or less. Since it is within the range and the balance is O and unavoidable impurities, it is possible to form an oxide film with a high refractive index and suppress the occurrence of abnormal discharge due to aluminum oxide during sputtering. be able to.

Further, as shown in FIG. 1, since Al exists as an oxide and does not exist as a metallic Al or a Si—Al alloy, Al is not preferentially consumed during sputtering, and sputtering occurs. Even if it progresses, unevenness is less likely to occur on the sputtered surface of the sputtering target, and the occurrence of abnormal discharge can be suppressed.
Further, since the average particle size of the aluminum oxide phase 12 is 20 μm or less, it is possible to suppress the occurrence of abnormal discharge caused by the aluminum oxide phase 12.

In the sputtering target of the present embodiment, when the maximum particle size of the aluminum oxide phase 12 is 60 μm or less, it is possible to further suppress the generation of abnormal discharge caused by the aluminum oxide phase 12.

Further, in the sputtering target of the present embodiment, when the density ratio is 95% or more, the generation of particles during the sputtering film formation is suppressed, and the sputtering film formation can be performed more stably.

Further, in the sputtering target of the present embodiment, when the specific resistance is 1.0 Ω · cm or less, the specific resistance is sufficiently low and the conductivity is ensured, and the sputtering film formation is more stable. Is 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 evaluation test for evaluating the action and effect of the sputtering target according to the present invention will be described below.

Metal Si powder and aluminum oxide powder (Al ₂ O ₃ powder) are weighed so as to have the target composition ratio shown in Table 1, 570 g of this is filled in a 2 L pot, 1.7 kg of a φ5 mm ball is charged, and then 1.7 kg is charged. The mixture was mixed with a ball mill device at 85 rpm for 5 hours to obtain a sintered raw material powder.
Here, a commercially available metal Si powder having a purity of 99.99 mass% and an average particle size of 3.6 μm is shown in Table 1 as an aluminum oxide powder _{( Al2O3} powder) having a commercially available purity of 99.99 mass%. The one having an average particle size was used.

The average particle size of the aluminum oxide powder (Al ₂ O ₃ powder) was measured as follows.
Prepare 100 mL of an aqueous solution having a sodium hexametaphosphate concentration of 0.2 vol%, add 10 mg of each raw material powder to this aqueous solution, and use a laser diffraction / scattering method (measuring device: Microtrac MT3000 manufactured by Nikkiso Co., Ltd.) to distribute the particle size (volume). Reference) was measured.
From the obtained particle size distribution (volume basis), the average particle size of the aluminum oxide powder (Al ₂ O ₃ powder) was determined.

Using the above-mentioned sintered raw material powder, sintering was performed by hot pressing to obtain a sintered body.
The sintered raw material powder was filled in a carbon hot press mold (φ135 mm × 210 mm) and hot pressed in vacuum at a sintering temperature of 1380 ° C. and a pressurized load of 35 MPa for 8 hours to prepare a sintered body. ..
In Comparative Example 6, melt casting was performed with the target composition shown in Table 1 to prepare an Al—Si alloy ingot.

These sintered bodies and Al—Si alloy ingots were machined to 126 mm × 178 mm × 6 mm, and then attached to a backing plate made of Cu with In solder to prepare a sputtering target.

As described above, the obtained sputtering target was evaluated for the following items.

(Composition of sputtering target)
An observation sample was collected from the surface of the sputtered surface of the obtained sputtering target, and the composition was analyzed by an ICP-OES apparatus. The evaluation results are shown in Table 1.

(Constituent phase of sputtering target)
An observation sample was taken from the obtained sputtering target, and a constituent phase analysis was performed by an XRD apparatus. As a result, in Example 1-7 of the present invention and Comparative Example 1-5, peaks of the metal Si and Al ₂ O ₃ were confirmed, and it was confirmed that Al was present as an oxide. In Comparative Example 6, peaks of metallic Si and metallic Al were confirmed.

(Sputtering target structure)
An observation sample was collected from the surface of the sputtered surface of the obtained sputtering target, embedded in an epoxy resin, polished, and then subjected to an electron probe microanalyzer (EPMA) device at a magnification of 300 times 360 μm × 270 μm. Element mapping was performed for the range of.
The obtained image was binarized by Brightness using the image processing software ImageJ. At this time, the threshold value of Brightness was set to 129.

After binarization, the area of each particle was determined for the obtained image using the Particle measurement function. The average particle area was obtained by dividing the total particle area, which is the sum of the areas of each particle, by the number of particles. The diameter of a perfect circle corresponding to the average particle area (circle equivalent diameter) was taken as the average particle diameter in the image. The diameter of a perfect circle corresponding to the area of the particle having the largest particle area was taken as the maximum particle diameter in the image. The above procedure is performed on an image of 5 fields randomly selected for each target, and the average value of the 5 average particle diameters is the average particle diameter, and the maximum value of the 5 maximum particle diameters is the maximum particle. The diameter was set. The evaluation results are shown in Table 2.

(Density ratio of sputtering target)
The volume of the sputtering target was calculated from the dimensions of the obtained processed sputtering target, and the dimensional density of the sputtering target was calculated by dividing the measured weight value by the volume. The ratio of dimensional density divided by calculated density is shown in the table as "Density Ratio". The calculated density was calculated according to the following formula. The evaluation results are shown in Table 2.
Calculated density (g / cm ³ ) = 100 / {Metal Si charge amount (mass%) / Metal Si density (g / cm ³ ) + Al ₂ O ₃ charge amount (mass%) / Al ₂ O ₃ density (g / cm) ³ )}

(Specific resistance of sputtering target)
The values measured by the four-probe method using a low resistivity meter (Loresta-GP) manufactured by Mitsubishi Chemical Corporation for the center of the sputtered surface of the obtained sputtering target are shown in the table. The temperature at the time of measurement was 23 ± 5 ° C., and the humidity was 50 ± 20%. An ASP probe was used as the probe at the time of measurement. The evaluation results are shown in Table 2.

(Dynamic rate)
Using an in-line sputtering device, the above-mentioned sputtering target is flowed in a sputtering chamber with Ar at 40 sccm and O ₂ at 10 sccm, and the total pressure in the chamber is 0.67 Pa, and pulse DC is used between the sputtering target and the substrate. An oxide film containing Al and Si was formed on the surface of the glass substrate at a transfer rate of 1.0 mm · sec at 2.7 W / cm ² with a distance of 60 mm, and the film thickness on the glass substrate was measured. The dynamic rate (deposition rate) was obtained by measuring with a stylus step meter and multiplying the film thickness value by the transport speed value. The evaluation results are shown in Table 3.

(Measurement of abnormal discharge frequency)
Using an in-line sputtering device, Ar is flowed in the sputtering chamber at 40 sccm and O ₂ is flown at 10 sccm, and the total pressure in the chamber is 0.67 Pa, and the pulse DC is 2.7 W / cm ² as described above. The sputtering target was discharged.
The number of abnormal discharges with a cumulative spatter time of 0 hours to 1 hour was recorded as the initial state of abnormal discharge, and the number of abnormal discharges with a cumulative spatter time of 23 hours to 24 hours was recorded as the end of abnormal discharge. As a power supply, a multifunctional DC power supply device HPK06Z-SW6 manufactured by Kyosan Electric Manufacturing Co., Ltd. was used. The evaluation results are shown in Table 3.

(Refractive index of film)
A film-forming sample was obtained by forming an oxide film containing Al and Si on the surface of the Si substrate at 50 nm under the same conditions as in the above-mentioned dynamic rate measurement.
The refractive index of this film was calculated using UVISEL-HR320 (spectral ellipsometry manufactured by HORIBA, Ltd.). The evaluation results are shown in Table 3.

In Comparative Example 1, the average particle size of the aluminum oxide phase was larger than the range of the present invention, the initial number of abnormal discharges was 239, and continuous sputter film formation could not be performed.
In Comparative Examples 2 and 3, the Al content was lower than the range of the present invention, and the refractive index of the formed oxide film containing Al and Si was low.
In Comparative Examples 4 and 5, the Al content is higher than the range of the present invention, the resistivity is high, the initial number of abnormal discharges is 367 times and 233 times, and spatter film formation can be continuously performed. could not.
In Comparative Example 6, it was composed of a Si—Al alloy, the dynamic rate was slow, and the number of abnormal discharges at the final stage was as large as 538 times. It is presumed that the metal Al was preferentially consumed during sputtering, the spattering progressed, unevenness was generated on the sputtered surface, and abnormal discharges occurred frequently.

On the other hand, in Example 1-7 of the present invention, a film having a high refractive index could be stably formed. In Example 7 of the present invention in which the maximum particle size of the aluminum oxide phase exceeds 60 μm and in Example 5-7 of the present invention in which the specific resistance exceeds 1.0 Ω · m, some abnormal discharge occurred, but it is practical. Was fine.

From the above, it was confirmed that according to the example of the present invention, it is possible to provide a sputtering target capable of stably forming an oxide film containing Al and Si.

11 Metal Si phase 12 Aluminum oxide phase

Claims (4)

The Si content is in the range of 70 mass% or more and 99 mass% or less, the Al content is in the range of 0.5 mass% or more and 16 mass% or less, and the balance is O and unavoidable impurities.
Al exists as an oxide and has a structure in which the aluminum oxide phase is dispersed in the parent phase of the metallic Si phase.
A sputtering target characterized in that the average particle size of the aluminum oxide phase is 20 μm or less. The sputtering target according to claim 1, wherein the maximum particle size of the aluminum oxide phase is 60 μm or less. The sputtering target according to claim 1 or 2, wherein the density ratio is 95% or more. The sputtering target according to any one of claims 1 to 3, wherein the specific resistance is 1.0 Ω · cm or less.

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