JP2022063461A - GaN-containing sputtering target material - Google Patents

Abstract

To provide a GaN-containing sputtering target material capable of depositing stably a GaN-containing film having a uniform composition.SOLUTION: In a GaN-containing sputtering target material containing Ga, one or two or more kinds of additional elements selected from Al, Zn, Cu, Sc, and N, the content of Ga is in the range of 10 mass% or more and 75 mass% or less, the total content of one or two or more kinds of additional elements selected from Al, Zn, Cu, and Sc is in the range of 10 mass% or more and 88 mass% or less, and a GaN phase exists. Preferably the density ratio is 70% or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a GaN-containing sputtering target material used when forming a GaN-containing film.

Nitride semiconductors such as GaN and AlN are used, for example, in electronic devices using piezoelectricity, optical devices using a wide bandgap, and the like, as shown in Patent Document 1. Further, as shown in Patent Document 2, it is excellent in light emission characteristics and fluorescence characteristics, and is used in short wavelength semiconductor lasers, light emitting diodes, optical displays and the like.
Furthermore, nitride semiconductors such as GaN and AlN are used as piezoelectric films in BAW filters (bulk acoustic wave filters), which are indispensable in the millimeter wave band of 5G (5th generation mobile communication system), which has been under development in recent years. Expected to be used.

Here, as a method for forming a thin film of a nitride semiconductor such as GaN or AlN described above, for example, as shown in Patent Documents 1 and 2, a sputtering method using a sputtering target is used.
In Patent Document 1, a thin film of a nitride semiconductor such as GaN or AlN is formed by performing reactive sputtering using a metal sputtering target.
In Patent Document 2, a GaN thin film is formed using a sputtering target made of a white GaN sintered body with reduced impurities.

Japanese Unexamined Patent Publication No. 2004-346335 Japanese Unexamined Patent Publication No. 2012-219348

By the way, as shown in Patent Document 1, when reactive sputtering is performed using a metal sputtering target, there is a possibility that the nitrogen content in the formed nitride film may vary. Therefore, the film characteristics may become unstable.
Further, in Patent Document 2, as described above, a sputtering target made of a GaN sintered body is used. Here, when GaN is sintered under high temperature conditions of 1000 ° C. or higher, GaN may be decomposed to generate metal Ga, and this metal Ga may be melted out. On the other hand, when the sintering temperature is set to a low temperature condition in order to suppress the leaching of Ga, the sintering does not proceed sufficiently and the density of the GaN sintered body becomes low. When sputtering is performed using a sputtering target made of a GaN sintered body having a low density, an abnormal discharge may occur and stable film formation may not be possible.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a GaN-containing sputtering target material capable of stably forming a GaN-containing film having a uniform composition.

In order to solve the above problems, the GaN-containing sputtering target material of the present invention contains Ga, one or more additive elements selected from Al, Zn, Cu and Sc, and N, and is composed of Ga. The content is within the range of 10 mass% or more and 75 mass% or less, and the total content of one or more additive elements selected from Al, Zn, Cu, Sc is within the range of 10 mass% or more and 88 mass% or less. , GaN phase is present.

According to the GaN-containing sputtering target material having the above configuration, the Ga content is within the range of 10 mass% or more and 75 mass% or less, and since the GaN phase is present, a GaN-containing film having a uniform composition is sputtered. Can be filmed.
The Ga content is within the range of 10 mass% or more and 75 mass% or less, and the total content of one or more additive elements selected from Al, Zn, Cu, Sc is within the range of 10 mass% or more and 88 mass% or less. Therefore, the sinterability is improved by the additive element, and the density can be sufficiently improved even when sintered under low temperature conditions. Therefore, it is possible to suppress the occurrence of abnormal discharge during sputtering and stably form a GaN-containing film.

Here, in the GaN-containing sputtering target material of the present invention, the density ratio is preferably 70% or more.
In this case, since the density ratio is 70% or more, it is possible to further suppress the occurrence of abnormal discharge during sputtering, and it is possible to form a GaN-containing film more stably.

Further, in the GaN-containing sputtering target material of the present invention, it is preferable that the additive elements are present in an island shape around the GaN phase.
In this case, the metal phase of the additive element having excellent sinterability is arranged in an island shape around the GaN phase having poor sinterability, and the density can be improved.

According to the present invention, it is possible to provide a GaN-containing sputtering target material capable of stably forming a GaN-containing film having a uniform composition.

This is an example of a microstructure photograph of the GaN-containing sputtering target material of the present embodiment. It is a flow diagram which shows the manufacturing method of the GaN-containing sputtering target material which is this embodiment.

Hereinafter, the GaN-containing sputtering target material according to the embodiment of the present invention will be described.

The GaN-containing sputtering target material of the present embodiment is used, for example, when forming a GaN-containing film that can be used as a piezoelectric film in a BAW filter that is indispensable in the millimeter wave band of 5G (5th generation mobile communication system). It is used for.

The GaN-containing sputtering target material of the present embodiment is said to contain Ga, one or more kinds of additive elements selected from Al, Zn, Cu, and Sc, and N, and has a GaN phase. Have.

In the GaN-containing sputtering target material of the present embodiment, one or more additive elements selected from Al, Zn, Cu, and Sc have a Ga content in the range of 10 mass% or more and 75 mass% or less. The total content is within the range of 10 mass% or more and 88 mass% or less. Further, the content of N (nitrogen) is preferably in the range of 2 mass% or more and 15 mass% or less. The N (nitrogen) content is more preferably in the range of 2 mass% or more and 13 mass% or less.

Further, in the GaN-containing sputtering target material of the present embodiment, the density ratio is preferably 70% or more.

Here, the GaN-containing sputtering target material of the present embodiment is composed of a sintered body of GaN powder and additive element powder. Therefore, in the GaN-containing sputtering target material of the present embodiment, as shown in FIG. 1, the structure is such that the metal phase of the additive element (Al in FIG. 1) exists around the GaN phase. That is, in the GaN-containing sputtering target material of the present embodiment, the density is improved by arranging the metal phase of the additive element having excellent sinterability in an island shape around the GaN powder having poor sinterability. There is.

Hereinafter, the reason why the composition and the density ratio of the GaN-containing sputtering target material of the present embodiment are defined as described above will be described.

(Ga)
Ga exists as GaN, and it is possible to secure piezoelectric characteristics such as the piezoelectric constant of the formed GaN-containing film.
Here, when the Ga content is less than 10 mass%, the GaN phase is not sufficiently present, and the characteristics of the formed GaN-containing film may deteriorate. On the other hand, if the Ga content exceeds 75 mass%, the amount of added elements may not be secured and the density may not be improved.
Therefore, in the present embodiment, the Ga content is set within the range of 10 mass% or more and 75 mass% or less.
In order to further secure the characteristics of the formed GaN-containing film, the lower limit of the Ga content is preferably 12.5 mass% or more, and more preferably 15 mass or more. On the other hand, in order to further improve the density, the upper limit of the Ga content is preferably 65 mass% or less, and more preferably 60 mass or less.

(Additional element)
One or more kinds of additive elements selected from Al, Zn, Cu, and Sc are more excellent in sinterability than GaN. Further, since the nitrides of these additive elements are relatively excellent in piezoelectric characteristics, the piezoelectric characteristics can be ensured even when they are present as nitrides in the formed GaN-containing film.
Here, when the total content of the above-mentioned additive elements is less than 10 mass%, the sinterability may not be improved and the density may not be sufficiently improved. On the other hand, when the total content of the above-mentioned additive elements exceeds 88 mass%, the GaN phase cannot be sufficiently secured, and the characteristics of the formed GaN-containing film may deteriorate.
Therefore, in the present embodiment, the total content of the above-mentioned additive elements is set within the range of 10 mass% or more and 88 mass% or less.
In order to further improve the density, the lower limit of the total content of the above-mentioned added elements is preferably 20 mass% or more, and more preferably 30 mass or more. On the other hand, in order to further secure the characteristics of the formed GaN-containing film, the upper limit of the total content of the above-mentioned additive elements is preferably 85 mass% or less, and more preferably 80 mass or less.

(Density ratio)
In the GaN-containing sputtering target material of the present embodiment, when the density ratio is 70% or more, there are few pores, and it is possible to sufficiently suppress the occurrence of abnormal discharge during sputtering film formation.
Therefore, in the GaN-containing sputtering target material of the present embodiment, the density ratio is preferably 70% or more.
In order to further suppress the occurrence of abnormal discharge during sputter film formation, the density ratio is more preferably 80% or more, further preferably 90% 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.

Next, an example of the method for manufacturing the GaN-containing sputtering target material according to the present embodiment will be described with reference to the flow chart of FIG.

(Sintered raw material powder forming step S01)
First, a GaN powder and one or more kinds of additive element powders selected from Al, Zn, Cu, and Sc are prepared. As the additive element powder, not only the element powder but also an alloy powder such as AlZn or an alloy powder with Ga such as AlGa may be used.
The average particle size of the GaN powder is preferably in the range of 1 μm or more and 50 μm or less. The average particle size of the added element powder is preferably in the range of 1 μm or more and 100 μm or less.
Then, the above-mentioned GaN powder and the additive element powder are weighed in a predetermined ratio and mixed using a mixing device such as a ball mill to obtain a sintered raw material powder.

(Sintering step S02)
The above-mentioned sintered raw material powder is filled in a molding die, pressed and heated to be sintered, and a sintered body is obtained. In this embodiment, using a carbon molding die, sintering is performed by a hot press device.
The sintering temperature at this time shall be within the range of 400 ° C. or higher and 900 ° C. or lower, the holding time at the sintering temperature shall be within the range of 60 minutes or more and 300 minutes or lower, and the pressurizing pressure shall be within the range of 15 MPa or higher and 50 MPa or lower. Is preferable. The atmosphere is preferably a vacuum atmosphere (10 Pa or less).
A sufficient density can be obtained by setting the sintering temperature to 400 ° C. or higher. On the other hand, by setting the sintering temperature to 900 ° C. or lower, it is possible to suppress the leaching of Ga caused by the decomposition of GaN.

(Machining process S03)
Next, the obtained sintered body is machined. In this embodiment, it is processed into a tile shape by lathe processing.
As a result, the GaN-containing sputtering target material of the present embodiment is manufactured.

In the GaN-containing sputtering target material of the present embodiment having the above configuration, the Ga content is within the range of 10 mass% or more and 75 mass% or less, and the GaN phase is sufficiently present. By sputtering, a GaN-containing film having a uniform composition can be formed.

The Ga content is within the range of 10 mass% or more and 75 mass% or less, and the total content of one or more additive elements selected from Al, Zn, Cu, Sc is within the range of 10 mass% or more and 88 mass% or less. Therefore, the sinterability is improved by the additive element, and the density can be sufficiently improved even when sintered under low temperature conditions. Therefore, it is possible to suppress the occurrence of abnormal discharge during sputtering and stably form a GaN-containing film.

When the density ratio of the GaN-containing sputtering target material of the present embodiment is 70% or more, the occurrence of abnormal discharge during sputtering can be further suppressed, and a GaN-containing film can be formed more stably. Is possible.
Further, in the GaN-containing sputtering target material of the present embodiment, when the metal phase of the additive element (Al in FIG. 1) is present in an island shape around the GaN phase, the density ratio can be further improved. It will be 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.
For example, in the present embodiment, the tile-shaped GaN-containing sputtering target material has been described, but the present invention is not limited to this, and GaN-containing sputtering target materials having other shapes may be used.
Further, the GaN-containing sputtering target material in the present embodiment contains Ga and one or more kinds of additive elements selected from Al, Zn, Cu, Sc, and the balance is N and unavoidable impurities, and forms a GaN phase. It is preferably composed of a GaN-containing sputtering target material.

The results of the evaluation test for evaluating the action and effect of the present invention will be described below.

As raw material powders, a GaN powder having an average particle size of 5 μm and a purity of 99.99 mass% or more and an additive element powder having an average particle size of 50 μm and a purity of 99.9 mass% or more were prepared.
These raw material powders were weighed so as to have the preparation composition shown in Table 1, charged into a pot together with zirconia balls, the inside of the pot was made into an Ar gas atmosphere, and mixed at a rotation speed of 85 rpm for 6 hours using a ball mill device. This was sieved with a 1 mm sieve to obtain a sintered raw material powder.

The obtained sintered raw material powder was filled in a carbon mold, and hot-pressed under the conditions of the sintering temperature shown in Table 1 for 2 hours and a pressure of 350 kgf / cm ² (34.3 MPa).
By lathe processing the obtained sintered body, a tile-shaped GaN-containing sputtering target material was produced.

The following items were evaluated for the obtained GaN-containing sputtering target materials of the present invention example and the comparative example.

(Composition of GaN-containing sputtering target material)
An observation sample was collected from the center of the obtained GaN-containing sputtering target material (φ125 mm × 5 mm thickness), and the composition was analyzed by an ICP-OES apparatus. For the amount of N, a gas analyzer was used. The evaluation results are shown in Table 1.

(Density ratio of GaN-containing sputtering target material)
The volume was calculated from the obtained GaN-containing sputtering target material, and the dimensional density of the GaN-containing sputtering target material 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 1.
Calculated density (g / cm ³ ) = 100 / {GaN charge amount (mass%) / GaN density (g / cm ³ ) + additive element charge amount (mass%) / additive element density (g / cm ³ )}

(Abnormal discharge)
The above-mentioned GaN-containing sputtering target material was bonded to a backing plate made of Cu using In solder to obtain a sputtering target. Then, a GaN-containing film was sputter-deposited under the following conditions.
Target size: φ125mm x 5mm thickness Pressure: 5mTorr
Gas type: Ar + N ₂
Gas flow rate: 25 sccm (Ar: 13 sccm, N ₂ : 12 sccm)
Power supply: Pulse DC
Power: 615W

Sputter film formation was carried out for 30 minutes under the above conditions, and the number of abnormal discharge occurrences was counted. The case where the number of abnormal discharges was less than 10 was evaluated as "⊚", the case where the number of abnormal discharges was 10 or more and less than 50 was evaluated as "◯", and the case where the number of abnormal discharges was 50 or more was evaluated as "x". The evaluation results are shown in Table 1.

In Comparative Example 1, no additive element was contained and the sintering temperature was set to 640 ° C., so that sintering was insufficient. Therefore, it was not possible to obtain a sintered body.
In Comparative Example 2, no additive element was contained, the sintering temperature was set to 1000 ° C., and Ga was leached out during sintering. Therefore, it was not possible to obtain a sintered body.
In Comparative Examples 3 to 7, the content of the additive element was less than 10 mass%, and the density ratio was not sufficiently improved. Therefore, the evaluation of abnormal discharge was "x".

On the other hand, in Examples 1 to 12 of the present invention, the additive element was contained, the density ratio was sufficiently improved, and the evaluation of the abnormal discharge was “◯” or “⊚”.

From the above, it was confirmed that according to the example of the present invention, it is possible to provide a GaN-containing sputtering target material capable of stably forming a GaN-containing film having a uniform composition.

Claims (3)

Contains Ga, one or more additive elements selected from Al, Zn, Cu, Sc, and N.
The Ga content is within the range of 10 mass% or more and 75 mass% or less, and the total content of one or more additive elements selected from Al, Zn, Cu, Sc is within the range of 10 mass% or more and 88 mass% or less. And
A GaN-containing sputtering target material characterized by the presence of a GaN phase. The GaN-containing sputtering target material according to claim 1, wherein the density ratio is 70% or more. The GaN-containing sputtering target material according to claim 1 or 2, wherein the additive element is present in an island shape around the GaN phase.

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