JP7008237B2 - Sputtering target and manufacturing method of sputtering target - Google Patents

Description

The present invention relates to a sputtering target used for forming a nitrogen-containing chromium film and a method for producing the sputtering target.

The above-mentioned nitrogen-containing chromium film is, for example, a photomask or the like used when forming a circuit pattern of a semiconductor integrated circuit as shown in Patent Document 1, or a pressure sensor, an acceleration sensor or the like as shown in Patent Document 2, for example. It is used as a thin film for strain gauges.
As a method for forming such a nitrogen-containing chromium film, as shown in Patent Documents 1 and 2, a sputtering method using a sputtering target has been proposed.

Here, in paragraph No. 0006 of Patent Document 1, as a conventional technique, a sputtering target made of a sintered body obtained by mixing and sintering metallic chromium powder and chromium nitride powder, and firing obtained by sintering only chromium nitride powder. A sputtering target consisting of a body is disclosed. In a sputtering target made of a sintered body obtained by mixing and sintering metallic chromium powder and chromium nitride powder, there is a problem that the dispersion of the chromium nitride powder becomes non-uniform and the distribution of nitrogen does not become uniform. I have pointed out. In addition, it is pointed out that in a sputtering target made of a sintered body obtained by sintering only chromium nitride powder, there is a problem that processing defects occur frequently and the manufacturing yield is lowered.
Then, Patent Document 1 proposes a sputtering target made of a sintered body obtained by forming a chromium nitride powder obtained by nitriding the surface of the metal chromium powder and sintering the same.

Japanese Unexamined Patent Publication No. 08-003737 Japanese Unexamined Patent Publication No. 07-306002

By the way, in the sputtering target proposed in Patent Document 1, since the chromium nitride powder obtained by sintering the surface of the metal chromium powder is sintered, the structure is such that the metal chromium phase is dispersed in the chromium nitride phase. ing. Here, in the above-mentioned chromium nitride powder, since the surface is made of chromium nitride, the sinterability tends to be insufficient, and when a sputtered film is formed for a long time, particles are generated, an abnormal discharge is generated, and the film is stable. There was a risk that the film could not be formed.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to suppress the occurrence of abnormal discharge even when a sputtered film is formed for a long time, and it is possible to form a stable film. It is an object of the present invention to provide a sputtering target capable of forming a nitrogen-containing chromium film having a uniform nitrogen concentration with little variation in nitrogen, and a method for manufacturing the sputtering target.

In order to solve the above problems, the sputtering target of the present invention is a sputtering target having a metal chromium phase and a chromium nitride phase, and the chromium nitride phase is dispersed in the parent phase of the metal chromium phase. At the same time, it is characterized by the presence of a chromium oxide phase .

According to the sputtering target of the present invention, since the chromium nitride phase is dispersed in the parent phase of the metal chromium phase, the metal chromium phases form a network and are reliably sintered. It will be. Therefore, even when the sputter film formation is performed for a long time, the occurrence of abnormal discharge can be suppressed, and the sputter film formation can be stably performed.

The method for manufacturing a sputtering target of the present invention is a method for manufacturing a sputtering target for manufacturing the above-mentioned sputtering target, which is a sintered raw material obtained by mixing chromium nitride powder, metallic chromium powder, and chromium oxide powder to obtain a sintered raw material powder. It has a powder forming step and a sintering step of heating while pressurizing the sintered raw material powder to obtain a sintered body. In the sintered raw material powder forming step, the average particle size of the chromium nitride powder is _DN . The ratio _DN / _DM to the average particle size _DM of the metal chromium powder is less than 1, and the ratio V _N / V of the volume _VN of the chromium _nitride powder to the volume VM of the metal chromium powder. It is characterized in that _M is less than 3.

According to the method for producing a sputtering target of the present invention, in the sintering raw material powder forming step, the ratio _DN / _DM of the average particle size _DN of the chromium nitride powder to the average particle size _DN of the metal chromium powder is determined. Since it is less than 1 and the ratio _VN / _VM of the volume _VN of the chromium nitride powder to the volume _VM of the metal chromium powder is less than 3, the metal chromium powder is deformed and covers the chromium nitride powder. , The metal chrome powders are sintered together, and a sintered body having a structure in which the chrome nitride phase is dispersed in the matrix phase of the metal chrome phase can be obtained. Therefore, the metal chromium phases can form a network and can be reliably sintered. As a result, it is possible to manufacture a sputtering target capable of stably performing sputter film formation by suppressing the occurrence of abnormal discharge even when sputter film formation is performed for a long time.

According to the present invention, it is possible to suppress the occurrence of abnormal discharge and stably form a film even when sputtered film is formed for a long time, and nitrogen having a uniform nitrogen concentration with little variation in nitrogen is possible. It is possible to provide a sputtering target capable of forming a film containing a chromium film and a method for manufacturing the sputtering target.

It is explanatory drawing which shows the measurement position of the nitrogen concentration on the sputter surface of a sputtering target which has a flat target shape and a circular sputter surface. It is explanatory drawing which shows the measurement position of the nitrogen concentration on the sputter surface of a sputtering target which has a flat plate shape of a target shape, and a rectangular sputter surface. It is explanatory drawing which shows the measurement position of the nitrogen concentration on the sputter surface of a sputtering target which the target shape is a cylinder, and the sputter surface is the outer peripheral surface of a cylinder. It is a flow figure which shows the manufacturing method of the sputtering target which concerns on one Embodiment of this invention.

Hereinafter, a sputtering target according to an embodiment of the present invention and a method for manufacturing the sputtering target will be described. The sputtering target of the present embodiment is used when forming a nitrogen-containing chromium film.

The sputtering target of the present embodiment is composed of a sintered body of metallic chromium powder and chromium nitride powder, has a metallic chromium phase and a chromium nitride phase, and the chromium nitride phase is contained in the parent phase of the metallic chromium phase. It is said to be a decentralized organization.

In the sputtering target of the present embodiment, the variation in the nitrogen content on the sputtering surface is 25% or less.
The variation in nitrogen content on the sputtered surface is calculated by the following formula.
(Variation)% = standard deviation / mean value x 100

Here, in the present embodiment, when the shape of the sputtering target is a flat plate and the sputtering surface is circular, as shown in FIG. 1, it passes through the center of the circle (1) and the center of the circle. The nitrogen content is measured at five points on the outer peripheral portions (2), (3), (4), and (5) on two straight lines orthogonal to each other, and the variation in the nitrogen content on the sputtered surface is determined.

When the shape of the sputtering target is a flat plate and the sputtering surface is rectangular, as shown in FIG. 2, the intersections (1) where the diagonal lines intersect and the corner portions (2) and (3) on the diagonal lines are formed. , (4), and (5), the nitrogen content is measured at five points, and the variation in the nitrogen content on the sputtered surface is determined.

Further, when the shape of the sputtering target is a cylinder and the sputtering surface is a cylindrical outer peripheral surface, as shown in FIG. 3, 90 ° intervals from a half point in the axis O direction to the outer peripheral direction (1) and (2). , (3), (4), and the nitrogen content is measured at a total of 8 points (5), (6), (7), (8) at 90 ° intervals in the outer peripheral direction at the end in the O direction of the axis. Then, the variation in the nitrogen content on the sputtered surface is obtained.

Here, the chromium nitride phase is mainly CrN or _Cr2N . The chromium oxide phase may be present together with the chromium nitride phase in the sputtering target.
Further, in the sputtering target of the present embodiment, the nitrogen content is within the range of 1 mass% or more and 15 mass% or less.
Further, in the sputtering target of the present embodiment, the relative density is set to 98% or more.

Next, a method for manufacturing a sputtering target according to the present embodiment will be described.
First, chromium nitride powder and metallic chromium powder are mixed to obtain a sintered raw material powder (sintered raw material powder forming step S01).
Here, as the metallic chromium powder, it is preferable to use one having a purity of 99.99% or more (4N) or more in terms of mass ratio.
Further, as the chromium nitride powder, CrN powder, _Cr2N powder, and a mixed powder thereof can be used. It is preferable to use CrN powder and _Cr2N powder having a mass ratio of Cr of 99% or more (2N) or more in the metal component.
In addition to the metallic chromium powder and the chromium nitride powder, chromium oxide powder may be added. As the chromium oxide powder, for example _, Cr _2O3 powder having a mass ratio of Cr of 99% or more (2N) or more in the metal component can be used.

In this sintered raw material powder forming step _S01 , the ratio _DN / _DM of the average particle size _DN of the chromium nitride powder to the average particle size DM of the metallic chromium powder is set to less than 1.
Further, in the sintering raw material powder forming step _S01 , the ratio _VN / _VM of the volume _VN of the chromium nitride powder to the volume VM of the metal chromium powder is set to less than 3.
Here, the nitrogen content in the sputtering target is adjusted by adjusting the nitrogen content in the sintered raw material powder and the above _- mentioned volume ratio _VN / VM.

The weighed chromium nitride powder and metal chromium powder are mixed by a mixing device such as a ball mill, a Henschel mixer, or a blender to obtain a raw material powder. At this time, in order to prevent the oxidation of the metallic chromium powder, it is preferable that the atmosphere in the mixing device is an inert gas atmosphere such as Ar.
In the sintered raw material powder forming step S01, the nitrogen content in the sintered body can be made uniform by sufficiently mixing the chromium nitride powder and the metallic chromium powder.

Next, the above-mentioned sintered raw material powder is sintered by heating under pressure to obtain a sintered body (sintering step S02).
In this sintering step S02, sintering may be performed using a hot press device. In this case, it is preferable to carry out the sintering temperature under the conditions of 1100 ° C. or higher and 1400 ° C. or lower, the holding time of 2 hours or more and 5 hours or less, and the pressure of 20 MPa or more and 40 MPa or less. The sintering temperature is preferably in the range of 1250 ° C. or higher and 1350 ° C. or lower.
Further, in the sintering step S02, sintering may be performed using a HIP apparatus. In this case, after filling the sintering raw material powder, degassing treatment is performed under the conditions of a vacuum degree of 1.5 Pa or less, a holding temperature of 500 ° C. or higher and 600 ° C. or lower, and a holding time of 5 hours or longer, and then sintering with a HIP device. It is preferable to carry out under the conditions that the temperature is in the range of 1100 ° C. or higher and 1400 ° C. or lower, the holding time is 1 hour or more and 3 hours or less, and the pressure is 90 MPa or more and 110 MPa or less. The sintering temperature is preferably in the range of 1200 ° C. or higher and 1300 ° C. or lower.

Then, the sintered body obtained in the sintering step S02 is machined so as to have a predetermined size (machining step S03).
As described above, the sputtering target according to the present embodiment is manufactured.

In the sputtering target of the present embodiment having the above configuration, the structure is such that the chromium nitride phase is dispersed in the parent phase of the metal chromium phase, and the metal chromium phases form a network with each other. , Metallic chromium is sufficiently bonded by sintering, and even when sputtered film formation is performed for a long time, the occurrence of abnormal discharge can be suppressed, and sputtered film formation can be stably performed. ..

Further, in the sputtering target of the present embodiment, since the variation of the nitrogen content on the sputtering surface is 25% or less, it is possible to form a nitrogen-containing chromium film having a uniform nitrogen concentration.

Further, in the sputtering target of the present embodiment, the nitrogen content is in the range of 1 mass% or more and 15 mass% or less, so that the nitrogen-containing chromium film can be reliably formed.
Further, in the sputtering target of the present embodiment, since the relative density is 98% or more, it is possible to further suppress the occurrence of abnormal discharge during sputtering film formation, and it is possible to stably perform sputtering film formation.

Further, according to the method for manufacturing a sputtering target according to the present embodiment, in the sintering raw material powder forming step _S01 , the ratio DN of the average particle size DN of the chromium nitride powder to the average particle size _DN of the metal chromium powder is _DN . Since / _DM is less than 1, and the ratio _VN / _VM of the volume _VN of the chromium nitride powder to the volume _VM of the metal chromium powder is less than 3, the metal chromium powder is deformed and the chromium nitride powder is deformed. The metal chrome powders are sintered together, and a sintered body having a structure in which the chromium nitride phase is dispersed in the matrix phase of the metal chromium phase can be obtained. Therefore, even when a sputtering film is formed for a long time, it is possible to suppress the occurrence of abnormal discharge and manufacture a sputtering target capable of stably performing a sputtering film formation.
Further, the chromium nitride powder is uniformly dispersed, and the variation in the nitrogen content on the sputtered surface can be 25% or less.

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.
In the present embodiment, it has been described that sintering is performed using a hot press device or a HIP device, but the present invention is not limited to this, and other sintering devices may be used.

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

As raw material powder, metallic chromium powder (purity: 99.9 mass% or more), CrN powder (purity of Cr in metal component: 99 mass% or _more ), Cr 2N powder (purity of Cr in metal component: 99 mass% or more) , Cr ₂ O ₃ powder (purity of Cr in metal component: 99 mass% or more, average particle size 3 μm) was prepared.
Then, the metal chromium powder, CrN powder, and _Cr2N powder having the average particle diameter shown in Table 1 were mixed at the volume ratio shown in Table 1. In Examples 11 and 12 of the present invention, the amount of _Cr2O3 powder shown in Table ₁ was added.
Further, in the conventional example, the metal chromium powder was subjected to a nitriding treatment to prepare a metal chromium powder having a chromium nitride layer formed on the surface. In the nitriding treatment, the temperature was raised to 900 ° C. after vacuum argon substitution in a rotary kiln furnace, and then a mixed gas of argon gas and nitrogen gas was flowed so as to have the nitrogen concentration of the conventional example, and the mixture was heated for 30 minutes.

These raw material powders are put into a polyethylene container (10 L) of a dry ball mill device having an Ar gas atmosphere. At this time, 5 kg of zirconia balls having a diameter of 5 mm and 5 kg of zirconia balls having a diameter of 10 mm were put into a polyethylene container. Then, the mixture was mixed at a rotation speed of 73 rpm for 18 hours. As a result, a sintered raw material powder was obtained.

Then, as shown in Table 2, the obtained sintered body is sintered by the HIP method or the hot press (HP) method, and the obtained sintered body is machined to obtain a disk shape (diameter 6 inches, thickness 6 mm). Alternatively, a cylindrically shaped sputtering target (outer diameter 160 mm, inner diameter 135 mm, length 600 mm) was obtained.

In the HIP method, the sintering conditions were a holding temperature of 1300 ° C., a pressure of 98 MPa, and a holding time of 2 hours.
In the hot press (HP) method, the sintering conditions were a holding temperature of 1350 ° C., a pressure of 35 MPa, and a holding time of 3 hours.

The sputtering targets obtained as described above were evaluated for the following items.

(Composition of sputtering target)
The nitrogen content in the sputtering target was measured by the Inert gas melting-thermal conductivity detection method, and the balance was defined as Cr. The oxygen content was also measured by the Inert Gas Melting-Heat Conduction Detection Method. The evaluation results are shown in Table 2.

(Relative density of sputtering target)
The density was calculated from the weight and dimensions. Then, the theoretical density was calculated with Cr: 7.19 g / cm ³ , Cr ₂ N: 6.51 g / cm ³ , Cr N: 5.90 g / cm ³ , and Cr ₂ O ₃ : 5.21 g / cm ³ . The relative density was calculated.
As a result of the measurement, the relative density of all the prepared sputtering targets was 95% or more.

(Relative density of sputtering target)
The structure of the sputtering target was observed. Elemental mapping was performed at an acceleration voltage of 15 kV using EPMA (Electron Probe Microanalyzer) JXA9500F, and the structure was observed.
Here, the metal chromium phase is used as a matrix phase, the chromium nitride phase is dispersed in the metal chromium phase as “A”, the chromium nitride phase is used as the matrix phase, and the metal chromium phase is dispersed in the chromium nitride phase. The above is shown in Table 2 as "B", and the one of the chromium nitride phase alone is shown as "C".

(Variation of nitrogen content)
In the disk-shaped sputtering target, as shown in FIG. 1, the nitrogen content is measured at the five measurement points (1) to (5) in the sputtering surface by the inert gas melting-heat conductivity detection method. did.
In the cylindrical sputtering target, as shown in FIG. 3, the nitrogen content was measured at eight measurement points (1) to (8) in the sputtering surface by the inert gas melting-heat conductivity detection method. ..
Then, the variation in nitrogen content was evaluated by the following formula.
(Variation)% = standard deviation / mean value x 100

(Number of abnormal discharges)
For the obtained sputtering target, the number of abnormal discharges generated during sputtering was measured by the following procedure.
The disk-shaped sputtering target was mounted on a Cu backing plate and subjected to a film forming test under the following film forming conditions.
Ultimate vacuum: 7 × 10 ^-4 Pa
Gas flow rate: Ar 50sccm
Spatter atmosphere: 0.67Pa
Power: 500W
Total pressure: 0.4Pa

Further, the cylindrical sputtering target was mounted on a backing tube made of SUS, and a film forming test was conducted under the following film forming conditions.
Ultimate vacuum: 7 × 10 ^-4 Pa
Gas flow rate: Ar 50sccm
Spatter atmosphere: 0.67Pa
Power: 1000W

Sputtering was performed for 12 hours under the above film forming conditions, and the number of occurrences of abnormal discharge was automatically measured by an arcing counter attached to the sputtering power supply device during the subsequent 6 hours of sputtering.

In the conventional examples 1 and 2 using the metallic chromium powder obtained by subjecting the metallic chromium powder to a nitriding treatment and forming a chromium nitride layer on the surface, the metallic chromium phase has a structure in which the metallic chromium phase is dispersed. Therefore, the number of abnormal discharges became very large, and it was not possible to stably form a spatter film.

In Comparative Examples 1-5 and 7 in which the particle size ratio and the volume ratio of the metal chromium powder and the chromium nitride powder do not satisfy the range of the present invention, the structure in which the metal chromium phase is dispersed in the chromium nitride phase is provided. Therefore, the number of abnormal discharges increased, and it was not possible to stably form a spatter film.
In Comparative Example 6 in which only the chromium nitride powder was used, the number of abnormal discharges increased and stable sputtering film formation could not be performed.

On the other hand, in Examples 11 and 12 of the present invention in which the particle size ratio and the volume ratio of the metallic chromium powder and the chromium nitride powder satisfy the range of the present invention, the structure in which the chromium nitride phase is dispersed in the metallic chromium phase The number of abnormal discharges was small, and spatter film formation could be performed stably.

As described above, according to the example of the present invention, it is possible to suppress the occurrence of abnormal discharge, stably form a film even when sputtered film is formed for a long time, and the variation of nitrogen is small. It was confirmed that it is possible to provide a sputtering target capable of forming a nitrogen-containing chromium film having a uniform nitrogen concentration.

Claims (2)

A sputtering target having a metal chromium phase and a chromium nitride phase.
A sputtering target characterized in that the chromium nitride phase is dispersed in the mother phase of the metal chromium phase and the chromium oxide phase is present . A method for manufacturing a sputtering target for manufacturing the sputtering target according to claim 1.
A step of forming a sintered raw material powder by mixing a chromium nitride powder, a metallic chromium powder, and a chromium oxide powder to obtain a sintered raw material powder, and a sintering step of heating the sintered raw material powder while pressurizing to obtain a sintered body. And have
In the sintered raw material powder forming step, the ratio _DN / _DM of the average particle size _DN of the chromium nitride powder to the average particle size _DM of the metal chromium powder is set to less than 1, and the chromium nitride powder is used. A method for producing a sputtering target, wherein the ratio _VN / _VM of the volume _VN to the volume _VM of the metal chromium powder is less than 3.

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