WO2016013514A1 - Cu-ga alloy cylindrical sputtering target and cu-ga alloy cylindrical ingot - Google Patents

Abstract

A Cu-Ga alloy cylindrical sputtering target that forms a cylindrical shape extending along an axial line (O), wherein: the Cu-Ga alloy cylindrical sputtering target includes Ga in a range of 18 - 35 atomic percent with the remainder being Cu and inevitable impurities; the difference in measured values for Ga concentration on the same circumference in a cross-section orthogonal to the axial line (O) is within 1.0 atomic percent; and the average value for Ga concentration in the cross-section is calculated, and the difference in the average value for Ga concentration calculated in each of a plurality of cross-sections on the axial line is within a range of 1.5 atomic percent.

Description

Cu-Ga alloy cylindrical sputtering target and Cu-Ga alloy cylindrical ingot

Cu-Ga alloy cylindrical sputtering target used for forming a Cu-Ga alloy thin film by sputtering, and a Cu-Ga alloy cylindrical ingot used as a material for the Cu-Ga alloy cylindrical sputtering target It is.
This application claims priority based on Japanese Patent Application No. 2014-151128 for which it applied to Japan on July 24, 2014, and uses the content here.

Conventionally, CIGS solar cells including a light absorption layer made of a Cu—In—Ga—Se quaternary alloy thin film have been widely provided as thin film solar cells made of a compound semiconductor.
Here, as a method of forming a light absorption layer made of a Cu—In—Ga—Se quaternary alloy thin film, a method of forming a film by vapor deposition is known. Although the solar cell provided with the light absorption layer formed by the vapor deposition method has an advantage that the energy exchange efficiency is high, there is a problem that the film formation rate is low and the production efficiency is low.

Therefore, as a method of forming a light absorption layer made of a Cu—In—Ga—Se quaternary alloy thin film, a laminated film of an In film and a Cu—Ga film is formed, and this laminated film is heat-treated in an Se atmosphere. Thus, a method for selenizing the above-described laminated film is provided. Here, when forming the In film and the Cu—Ga film, a sputtering method using an In sputtering target and a Cu—Ga alloy sputtering target is applied.

As a Cu—Ga alloy sputtering target, for example, Patent Documents 1-3 propose a flat plate sputtering target manufactured by a melting method and a cylindrical sputtering target. In Patent Documents 2 and 3, a cylindrical ingot that is a material of a cylindrical sputtering target is manufactured by a continuous casting method.
Here, since the outer surface of the cylindrical sputtering target is a sputtering surface and sputtering is performed while rotating the target, it is suitable for continuous film formation as compared with the case of using a flat plate sputtering target. And it has the advantage that it is excellent in the use efficiency of a sputtering target.

Japanese Unexamined Patent Publication No. 2012-144787 (A) International Publication No. 2013/031381 Pamphlet (A) Japanese Unexamined Patent Publication No. 2013-076129 (A)

By the way, when a Cu—Ga alloy ingot that is a material for a Cu—Ga alloy sputtering target is manufactured by a continuous casting method, the heat transfer coefficient between the ingot and the mold is locally determined by casting and casting during casting. May change, and segregation of Ga concentration may occur. In particular, the concentration segregation described above becomes significant in a Cu—Ga alloy having a high Ga concentration. For this reason, in the Cu—Ga alloy sputtering target obtained in Patent Documents 2 and 3, Ga concentration segregation has not been sufficiently eliminated. Further, since Cu—Ga alloy is a brittle material, it is difficult to eliminate Ga concentration segregation by hot working after casting, and it is important to eliminate Ga concentration segregation in the ingot. Got.

Here, in the Cu—Ga alloy, an intermetallic compound phase such as a ζ phase and a γ phase is generated according to the Ga content. For this reason, when Ga concentration segregation occurs in the Cu—Ga alloy sputtering target as described above, the ratio of intermetallic compound phases such as ζ phase and γ phase may locally change on the sputtering surface. It was. When a film is formed using such a Cu—Ga alloy sputtering target, the film thickness and composition of the formed thin film vary, and there is a risk that performance as a solar cell cannot be secured.

The present invention has been made in view of the above-described circumstances, and is a Cu-Ga alloy cylindrical sputtering target capable of stably forming a thin film having a small Ga concentration segregation and a uniform film thickness and composition, and An object of the present invention is to provide a Cu—Ga alloy cylindrical ingot that is a material of the Cu—Ga alloy cylindrical sputtering target.

In order to solve the above-described problems, a Cu—Ga alloy cylindrical sputtering target according to the present invention is a cylindrical Cu—Ga alloy cylindrical sputtering target extending along an axis, and includes 18 atoms of Ga. % Within a range of 35% or more and 35% or less, the balance being made of Cu and inevitable impurities, and the difference in measured values of Ga concentration on the same circumference of the cross section orthogonal to the axis is within 1.0 atomic% In addition, the average value of the Ga concentration in the cross section is calculated, and the difference in the average value of the Ga concentration calculated in each of the plurality of cross sections in the axial direction is within a range of 1.5 atomic% or less. It is characterized by that.

According to the Cu—Ga alloy cylindrical sputtering target of the present invention having such a configuration, the difference in measured values of Ga concentration on the same circumference of the cross section perpendicular to the axis is within 1.0 atomic%. Therefore, variation in Ga concentration on the circumference is sufficiently suppressed, and even when Ga is relatively contained in the range of 18 atomic% to 35 atomic%, the ζ phase, γ The ratio of the intermetallic compound phase such as the phase is stabilized.
And since the difference of the average value of the Ga concentration calculated in each of the plurality of cross sections in the axial direction is within the range of 1.5 atomic% or less, the variation in the Ga concentration in the axial direction is sufficiently suppressed. As a result, the sputtering rate becomes stable, and a thin film having a uniform film thickness and composition can be stably formed. Moreover, it is more preferable that the difference between the average values of Ga concentrations calculated for each of the plurality of cross sections in the axial direction is 1.0 atomic% or less.

A Cu—Ga alloy cylindrical ingot according to the present invention has a cylindrical shape extending along an axis, and is a Cu—Ga alloy cylindrical ingot used as a Cu—Ga alloy cylindrical sputtering target. In the range of 18 atomic% or more and 35 atomic% or less, with the balance being Cu and inevitable impurities, the difference in the measured Ga concentration on the same circumference of the cross section orthogonal to the axis is 1.0 atom And the average value of Ga concentration in the cross section is calculated, and the difference in the average value of Ga concentration calculated in each of the plurality of cross sections in the axial direction is within a range of 1.5 atomic% or less. It is characterized by being.

According to the Cu—Ga alloy cylindrical ingot of the present invention having such a configuration, the difference in measured values of Ga concentration on the same circumference of the cross section perpendicular to the axis is 1 at the ingot stage. Since the difference in the average value of the Ga concentration calculated within a plurality of the cross sections in the axial direction is within the range of 1.5 atomic% or less, and Ga concentration segregation is suppressed. Thus, it is possible to reliably manufacture the Cu—Ga alloy cylindrical sputtering target.

According to the present invention, a Cu—Ga alloy cylindrical sputtering target capable of stably forming a thin film having a small Ga concentration segregation and a uniform film thickness and composition, and this Cu—Ga alloy cylindrical sputtering target A Cu—Ga alloy cylindrical ingot as a raw material can be provided.

It is a schematic explanatory drawing of the Cu-Ga alloy cylindrical sputtering target concerning one embodiment of the present invention, and is a sectional view orthogonal to an axial direction. It is a schematic explanatory drawing of the Cu-Ga alloy cylindrical sputtering target which concerns on one Embodiment of this invention, and is a side view orthogonal to an axial direction. It is a flowchart which shows an example of the manufacturing method of the Cu-Ga alloy cylindrical sputtering target which concerns on one Embodiment of this invention. It is explanatory drawing which shows an example of the continuous casting apparatus used when manufacturing the Cu-Ga alloy cylindrical ingot which is one Embodiment of this invention. In an Example, it is explanatory drawing which shows the method of measuring the film thickness of the formed Cu-Ga alloy film.

Hereinafter, a Cu—Ga alloy cylindrical sputtering target 10 according to an embodiment of the present invention and a Cu—Ga alloy cylindrical ingot 20 as a material of the Cu—Ga alloy cylindrical sputtering target 10 will be described with reference to the accompanying drawings. Will be described with reference to FIG.
The Cu—Ga alloy cylindrical sputtering target 10 according to the present embodiment sputters a Cu—Ga alloy thin film to form a light absorption layer made of a Cu—In—Ga—Se quaternary alloy thin film, for example, in a solar cell. Is used when forming a film.

As shown in FIGS. 1A and 1B, the Cu—Ga alloy cylindrical sputtering target 10 has a cylindrical shape extending along the axis O. For example, the outer diameter D is within a range of 100 mm ≦ D ≦ 200 mm. The inner diameter d is in the range of 50 mm ≦ d ≦ 150 mm, and the length L in the axis O direction is in the range of 100 mm ≦ L ≦ 3000 mm.
Here, the outer peripheral surface of the Cu—Ga alloy cylindrical sputtering target 10 is a sputtering surface.

This Cu—Ga alloy cylindrical sputtering target 10 has a composition corresponding to the thin film to be formed, specifically, the Ga content is in the range of 18 atomic% to 35 atomic%, The balance is made of a Cu—Ga alloy made of Cu and inevitable impurities.
In the present embodiment, as described above, since the Ga content is relatively high as 18 atomic% or more and 35 atomic% or less, Ga concentration segregation occurs, and intermetallic compounds such as ζ phase and γ phase occur. Phase ratio may vary.

Here, in the Cu—Ga alloy cylindrical sputtering target 10 according to the present embodiment, the difference in the measured value of the Ga concentration on the same circumference of the cross section perpendicular to the axis O is within 1.0 atomic%. ing.
In this embodiment, as shown in FIG. 1A, the measured values of Ga concentration at the measurement point 1, the measurement point 2, the measurement point 3, and the measurement point 4 located on the same circumference R of the cross section orthogonal to the axis O. This difference is within 1.0 atomic%. In this embodiment, the measurement point 1, the measurement point 2, the measurement point 3, and the measurement point 4 are set at 90 ° intervals. The circumference R is the circumference on the cross section of the Cu—Ga alloy cylindrical sputtering target 10 orthogonal to the axis O, and the center point is the point where the axis O intersects.

Further, in the Cu—Ga alloy cylindrical sputtering target 10 according to the present embodiment, when the average value of the Ga concentration in the cross section orthogonal to the axis O is calculated, each of the cross sections in the direction of the axis O is calculated. The difference in the average value of the Ga concentration is within the range of 1.5 atomic% or less.
In the present embodiment, as shown in FIGS. 1A and 1B, the average value of the Ga concentration at the measurement points 1, 2, 3, and 4 located on the same circumference R of the cross section A orthogonal to the axis O, the axis On the same circumference R of the cross section C perpendicular to the axis O and the average value of the Ga concentration of the measurement points 1, 2, 3, 4 positioned on the same circumference R of the cross section B perpendicular to O The difference in the average value of the Ga concentration at the measurement points 1, 2, 3, and 4 is set to be in the range of 1.5 atomic% or less. In the present embodiment, the cross section A, the cross section B, and the cross section C are set at intervals of 300 mm in the axis O direction.

Next, an embodiment of a method for manufacturing the Cu—Ga alloy cylindrical sputtering target 10 having the above-described configuration will be described with reference to the flowchart of FIG.
A casting step S01 for casting the Cu—Ga alloy cylindrical ingot 20 according to the present embodiment, a heat treatment step S02 for performing a heat treatment on the Cu—Ga alloy cylindrical ingot 20, and a heat treatment step S02 were performed. Machining step S03 for machining the Cu—Ga alloy cylindrical ingot 20.

In the casting step S01, the Cu—Ga alloy cylindrical ingot 20 is continuously produced and cut into a predetermined length using various continuous casting apparatuses such as a vertical continuous casting apparatus and a horizontal continuous casting apparatus.
Here, the continuous casting apparatus 30 used in casting process S01 is demonstrated with reference to FIG.
The continuous casting apparatus 30 includes a casting furnace 31, a continuous casting mold 40 connected to the casting furnace 31, and a pinch roll 38 that pulls out the Cu—Ga alloy cylindrical ingot 20 produced from the continuous casting mold 40. And.

The casting furnace 31 heats and melts the melting raw material to produce and hold a molten copper having a predetermined composition, a crucible 32 that holds the melting raw material and the molten copper, and heating means for heating the crucible 32 ( (Not shown).
The pinch roll 38 sandwiches the Cu—Ga alloy cylindrical ingot 20 produced from the continuous casting mold 40 and pulls it in the pulling direction F. In the present embodiment, the Cu—Ga alloy cylindrical ingot 20 is intermittently pulled out.

The continuous casting mold 40 includes a cylindrical mold 41 into which the supplied molten copper is poured, a mandrel 45 inserted into the mold 41, and a cooling unit 48 that cools the mold 41. Here, in this embodiment, as shown in FIG. 3, the casting furnace 31 is arranged on one side (left side in FIG. 3) of the continuous casting mold 40.
As shown in FIG. 3, the cooling unit 48 is a water cooling jacket disposed on the outer peripheral side of the mold 41, and is configured to cool the mold 41 by circulating cooling water.

The mold 41 has a substantially cylindrical shape. In this embodiment, as shown in FIG. 3, one side (left side in FIG. 3) has a large diameter portion 42 and the other side (right side in FIG. 3) has a small diameter. It has a two-stage cylindrical shape as a portion 43. In addition, the small diameter part 43 is made into the taper shape so that a diameter may become small gradually as it goes to the other side. In the present embodiment, as shown in FIG. 3, the above-described cooling part 48 is disposed on the outer peripheral side of the small diameter part 43 of the mold 41.

The mold 41 is provided with a through hole penetrating from one side to the other side, and a mandrel 45 is inserted from one side of the through hole. Then, the mandrel 45 is disposed at a distance from the inner wall of the through hole of the mold 41, and a cavity having an annular cross section is defined in the mold 41.

Here, in this embodiment, the Cu—Ga alloy cylindrical ingot 20 is intermittently drawn by the pinch roll 38, and the intermittent drawing conditions are set as follows.
When the instantaneous moving speed V1 (mm / sec) with respect to the mold 41, the moving distance M (mm) per cycle with respect to the mold 41, and the stop time T1 (sec), X = (V1 × M) / T1 is 0. .Ltoreq.X.ltoreq.250.

In the Cu—Ga alloy cylindrical ingot 20 according to the present embodiment manufactured as described above, the same cross-section orthogonal to the axis O is the same as the Cu—Ga alloy cylindrical sputtering target 10 described above. The difference between the measured values of the Ga concentration on the circumference is within 1.0 atomic%, and the difference between the average values of the Ga concentrations calculated for each of the plurality of cross sections in the direction of the axis O is 1.5 atomic% or less. It is within the range. That is, Ga concentration segregation is suppressed at the time of the Cu—Ga alloy cylindrical ingot 20.

According to the Cu—Ga alloy cylindrical sputtering target 10 of the present embodiment configured as described above, the difference in measured values of Ga concentration on the same circumference of the cross section orthogonal to the axis O is 1. Specifically, as shown in FIG. 1A, measurement points 1, 2, which are located at 90 ° intervals on the same circumference R of the cross section perpendicular to the axis O, Since the difference between the measured values of Ga concentration at measurement point 3 and measurement point 4 is within 1.0 atomic%, variation in Ga concentration on the circumference is sufficiently suppressed, and Ga is 18 atomic% or more. Even when it is contained within the range of 35 atomic% or less, the proportion of intermetallic compound phases such as ζ phase and γ phase is stabilized.

In addition, the difference between the average values of Ga concentrations calculated in a plurality of cross sections in the axis O direction is within a range of 1.5 atomic% or less, and specifically, they are located at intervals of 300 mm in the axis O direction. In a plurality of cross sections A, B, and C, the difference in the average value of the Ga concentration calculated from the Ga concentration measured at the measurement point 1, the measurement point 2, the measurement point 3, and the measurement point 4 is 1.5 atomic% or less. Therefore, the variation in Ga concentration in the axis O direction is sufficiently suppressed, and the ratio of intermetallic compound phases such as ζ phase and γ phase does not change locally, and the sputtering rate is stabilized. Thus, a thin film having a uniform film thickness and composition can be stably formed.

Furthermore, according to the Cu—Ga alloy cylindrical ingot 20 of the present embodiment, the difference in the measured value of the Ga concentration on the same circumference of the cross section perpendicular to the axis is within 1.0 atomic%. In addition, the difference in the average value of the Ga concentration calculated in each of the plurality of cross sections in the axial direction is within a range of 1.5 atomic% or less, and at the time of the Cu—Ga alloy cylindrical ingot 20, Therefore, the Cu—Ga alloy cylindrical sputtering target 10 according to this embodiment can be reliably manufactured.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, in this embodiment, the solar cell is used when forming a Cu—Ga alloy thin film by sputtering in order to form a light absorption layer made of a Cu—In—Ga—Se quaternary alloy thin film. Although described, the present invention is not limited to this, and a Cu—Ga alloy cylindrical sputtering target used for other applications may be used.

Further, in the present embodiment, as shown in FIG. 3, it has been described that a Cu—Ga alloy cylindrical ingot is manufactured by a continuous casting apparatus that draws the ingot horizontally, but the present invention is not limited thereto. Alternatively, the Cu—Ga alloy cylindrical ingot may be manufactured using a continuous casting apparatus that pulls the ingot downward or a continuous casting apparatus that pulls the ingot upward.

Further, the outer diameter, the inner diameter, and the length L in the direction of the axis O of the Cu—Ga alloy cylindrical sputtering target are not limited to those defined in the present embodiment, and may be any size according to the sputtering apparatus and the like. be able to.
Further, the measurement position and the number of measurements of Ga concentration are not limited to the present embodiment, and are preferably set according to required characteristics.

Below, the result of the confirmation experiment performed in order to confirm the effectiveness of this invention is demonstrated.
A continuous casting apparatus shown in FIG. 3 continuously casts a Cu—Ga alloy cylindrical ingot to obtain a Cu—Ga alloy cylindrical sputtering target having an outer diameter D of 170 mm, an inner diameter d of 120 mm, and an axial length L of 600 mm. Manufactured. The Ga concentration segregation was varied by changing the conditions for intermittent drawing in the continuous casting apparatus.

<Ga concentration measurement>
In the above-described Cu—Ga alloy cylindrical sputtering target, the Ga concentration was measured at the positions shown in FIGS. 1A and 1B, and the average value of the Ga concentration in each cross section was calculated. The Ga concentration was measured by the following procedure. In FIG. 1A, a range of φ15 from four points of 1 (0 °), 2 (90 °), 3 (180 °), and 4 (270 °) on the same circumference as φ ((D + d) / 2) A boring sample was collected and the Ga concentration was measured with an ICP mass spectrometer, and the same measurement was performed at three locations A (0 mm), B (300 mm), and C (600 mm) in FIG. 1B. The measurement results are shown in Table 1.

<Thickness variation>
A Cu—Ga alloy film was formed using the above-described Cu—Ga alloy cylindrical sputtering target. A mask of 500 mm × 500 mm 1.1 mm thick (substrate) is masked as shown in FIG. 4, and a Cu—Ga alloy with a target film thickness of 500 nm is formed by direct current sputtering with an input power of 5 kW / m using a magnetron sputtering apparatus. A film was formed. The Ar pressure during sputtering was 0.5 Pa, the distance between the target and the substrate was 60 mm, and the substrate was not heated during film formation.
The film is peeled off after film formation, and the film thickness of the formed Cu-Ga alloy film is measured by reading the step between the part where the film is attached and the part where the film is not attached with a step gauge DEKTAK-XT did. The measurement was performed at nine points (1) to (9) in FIG. 4, and the difference between the maximum value and the minimum value of the film thickness with respect to the target film thickness (500 nm) was evaluated. The evaluation results are shown in Table 1.

As shown in Table 1, in Comparative Example 1-3 in which the concentration segregation of Ga is large, the difference between the maximum value and the minimum value of the film thickness is large with respect to the target film thickness, and variations in film thickness were observed. It is presumed that due to the segregation of Ga concentration, the ratio of intermetallic compound phases such as ζ phase and γ phase fluctuated in the sputtering surface, and the sputtering rate was partially different.
On the other hand, in Example 1-3 of the present invention in which the concentration segregation of Ga was suppressed, the variation in film thickness was sufficiently suppressed, and the Cu—Ga alloy film could be formed stably. confirmed.

The film formation efficiency of the Cu—In—Ga—Se quaternary alloy thin film can be further increased, and as a result, the CIGS solar cell can be manufactured with higher efficiency.

10 Cu—Ga alloy cylindrical sputtering target 20 Cu—Ga alloy cylindrical ingot

Claims (2)

A Cu-Ga alloy cylindrical sputtering target having a cylindrical shape extending along an axis,
Ga is contained in the range of 18 atomic% or more and 35 atomic% or less, and the balance consists of Cu and inevitable impurities,
While the difference in the measured value of Ga concentration on the same circumference of the cross section perpendicular to the axis is within 1.0 atomic%,
An average value of Ga concentration in the cross section is calculated, and a difference between the average values of Ga concentration calculated in each of the plurality of cross sections in the axial direction is within a range of 1.5 atomic% or less. Cu-Ga alloy cylindrical sputtering target. A Cu-Ga alloy cylindrical ingot used as a Cu-Ga alloy cylindrical sputtering target having a cylindrical shape extending along an axis,
Ga is contained in the range of 18 atomic% or more and 35 atomic% or less, and the balance consists of Cu and inevitable impurities,
While the difference in the measured value of Ga concentration on the same circumference of the cross section perpendicular to the axis is within 1.0 atomic%,
An average value of Ga concentration in the cross section is calculated, and a difference between the average values of Ga concentration calculated in each of the plurality of cross sections in the axial direction is within a range of 1.5 atomic% or less. Cu-Ga alloy cylindrical ingot.

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