KR101621671B1 - SPUTTERING TARGET FOR FORMING Cu ALLOY THIN FILM, AND METHOD FOR MANUFACTURING SAME - Google Patents

Abstract

The present invention is a sputtering target used for forming a Cu-Mn alloy thin film which is useful as an electrode film for a display device such as a liquid crystal display or the like. In sputtering, highly cohered cluster particles are reduced and particles and splash A sputtering target for forming a Cu alloy thin film, and a manufacturing method thereof. A sputtering target for Cu alloy thin film formation according to the present invention is a Cu alloy sputtering target containing at least Mn and having a Mn content of 2 atomic% or more and 20 atomic% or less. The Vickers hardness of a t / 2 section in the thickness direction of the sputtering target Is controlled to be 50 HV or more and 100 HV or less.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a sputtering target for forming a Cu alloy thin film,

The present invention relates to a sputtering target for forming a Cu alloy thin film and a manufacturing method thereof. More particularly, the present invention relates to a sputtering target for forming a Cu alloy thin film, which can be reduced during sputtering, and which is capable of reducing abnormally coarse cluster particles called particles or splashes, and a method for producing the same. The Cu alloy sputtering target of the present invention can be used as a thin film for an electrode of a thin film transistor (TFT) used for a display device such as a liquid crystal display or an organic EL display or an electronic device such as a touch sensor, a thin film for a reflection electrode, A thin film, and the like; and a thin film such as a reflective film or a semi-transparent film used for an optical recording medium such as a CD, a DVD, an HD-DVD, or a BD.

The Cu thin film has a low electric resistance and is comparatively easy to be processed compared to Al. For example, the Cu thin film can be used as a thin film for a scan electrode or a signal electrode of a display device such as a liquid crystal display, It is used for electric connection wiring thin film of device. However, pure Cu has poor adhesion to substrates such as glass. In addition, pure Cu tends to be oxidized, so that the surface tends to discolor, and diffusion coefficient in the semiconductor is large. Therefore, in order to solve the problems of the pure Cu, various Cu alloy thin films including suitable selective elements according to the use have been proposed.

For example, Patent Document 1 discloses a Cu alloy for electrode wiring of a liquid crystal display device capable of forming an oxide coating layer capable of suppressing the progress of oxidation of Cu on a Cu surface in an oxidizing atmosphere containing oxygen, ≪ RTI ID = 0.0 > Cu < / RTI > In particular, Mn discloses that an oxide is more easily formed than Cu and an oxide which is difficult to pass oxygen is formed even though the melting point is higher than Cu.

Patent Document 2 discloses a technique for preventing or suppressing sulfuration of a Cu recording layer due to diffusion of S from a protective layer in an optical disk using a protective layer containing ZnS in particular, Metal elements such as Mn and Zn are described as elements capable of obtaining a medium.

Japanese Patent Application No. 4065959 Japanese Patent Application No. 4603044

Generally, the Cu thin film is formed by a sputtering method using a sputtering target. The sputtering method is a method in which an inert gas such as argon is first introduced into a vacuum container under a low gas pressure and a high voltage is applied between the substrate and a sputtering target containing the same material as the thin film material to generate a plasma discharge. Thereafter, a gas ionized by the plasma discharge (here argon) is accelerated and collided with the sputtering target to strike the constituent atoms of the sputtering target by inelastic collision, and the constituent elements are deposited and deposited on the substrate to form a thin film . In addition to the above-mentioned sputtering method, a vacuum deposition method can be mainly used for forming the metal thin film, but the sputtering method has an advantage that a thin film having the same composition as the sputtering target can be formed continuously. In particular, when the metal thin film to be formed is an alloy material, the sputtering method can forcibly solidify an alloy element such as a rare earth element that is not dissolved in Cu in the thin film. In addition, the sputtering method is an industrially superior film forming method, such as the ability to form a continuous stable film on a large area substrate.

However, in the sputtering method, abnormal coarsely clustered particles called particles and splashes are generated at the time of sputtering and are sometimes introduced into the thin film. When the coarsely clustered particles are introduced into the thin film, protrusions remain on the surface of the thin film, which may cause electrical shorts or cause problems in forming wiring patterns, resulting in pattern anomalies resulting in occurrence of electrical disconnection It causes harm. The causes of such abnormal cluster particles are various. As for the material, it is considered that there are many cases in which the structure and the grain irregularity of the sputtering target, the shape of the sputtering target, foreign matter incorporation into the sputtering target, and the segregation of the alloying element in the sputtering target occur.

Although the Cu alloy thin films described in Patent Documents 1 and 2 described above are formed by the sputtering method, there is no mention at all of the problems in sputtering described above. Further, in the embodiment of Patent Document 2, the Cu alloy thin film is not formed by using the sputtering target, and the protective film of ZnS is covered only with the Cu-Mn ingot produced in a pseudo manner. Therefore, the above-mentioned problem in using the sputtering target is not fully grasped.

Among the various alloying elements described in the above patent documents, Mn is preferentially reacted with oxygen to suppress oxidation of Cu or prevent or suppress sulfuration of the Cu recording layer due to diffusion of S from the ZnS-containing protective layer, useful. As a result, the Cu-Mn alloy containing Mn is expected to be used as a thin film forming material such as an electrode thin film of a display device or the like. However, since Mn tends to be concentrated on the surface, Mn-containing Cu-Mn alloy sputtering target tends to be segregated during sputtering, and abnormal discharge such as splashing may occur more remarkably.

The present invention has been made in view of the above circumstances. The object of the present invention is to provide a sputtering target used for forming a Cu-Mn alloy thin film which is useful as an electrode film for a display device such as a liquid crystal display or the like. In sputtering, highly clustered cluster particles are reduced and particles and splash A sputtering target for forming a Cu alloy thin film, and a manufacturing method thereof.

A sputtering target for forming a Cu alloy thin film of the present invention capable of solving the above problems is a Cu alloy sputtering target containing at least Mn and having a Mn content of 2 atomic% or more and 20 atomic% or less. / 2 cross-section has a Vickers hardness of 50 HV or more and 100 HV or less.

In a preferred embodiment of the present invention, the sputtering target has a Mn content of 2 atomic% or more and 10 atomic% or less.

In a preferred embodiment of the present invention, the Vickers hardness of the t / 2 cross section in the thickness direction of the sputtering target is 60 HV or more and 90 HV or less.

A method for producing a sputtering target for forming a Cu alloy thin film according to the present invention, which has solved the above problems, is characterized in that the Cu alloy satisfying the above composition is subjected to annealing after hot rolling at a total rolling reduction of 50% And is carried out at a temperature of 450 DEG C or more and 600 DEG C or less for 2 hours or more.

In a preferred embodiment of the present invention, the total rolling reduction during hot rolling is 50% or more and 75% or less.

In a preferred embodiment of the present invention, the annealing temperature after the hot rolling is 450 DEG C or more and 550 DEG C or less.

In a preferred embodiment of the present invention, the annealing time after the hot rolling is not less than 2 hours and not more than 5 hours.

The use of the Cu-Mn alloy sputtering target of the present invention reduces the abnormal discharge such as particles and splash generated at the time of sputtering. Therefore, it is possible to form the film by the sputtering method stably for a long time from the beginning of sputtering to the life end, .

Further, according to the present invention, a Cu-Mn alloy thin film having less variation in composition, film thickness, electric resistance, and in-plane uniformity within a substrate surface (in the same plane) is obtained for a large-area substrate. As a result, the yield of the final product such as a display device including the Cu-Mn thin film is remarkably improved.

1 is a graph showing the results of an EPMA test of a Cu-Mn alloy sputtering target No. 16 in Table 1 in Example 1. Fig.

The present inventors have found that even when a Cu-Mn alloy containing at least Mn is processed into a sputtering target such as a sheet and formed on a large-area substrate, the uniformity in the surface such as composition and film thickness is excellent, Mn alloy sputtering target that can form a Cu-Mn alloy thin film for a long time without occurrence of the above-described problems. As a result, (A) the Vickers hardness of the t / 2 end face (t is the thickness of the sputtering target) in the thickness direction of the sputtering target (the direction perpendicular to the rolling direction) is controlled within a predetermined range to achieve the desired purpose (B) Such a Cu-Mn alloy sputtering target can be produced by a melt-casting method using a Cu-Mn alloy, and in particular, the total rolling reduction during hot rolling and the annealing condition after hot rolling The present inventors have completed the present invention.

That is, the sputtering target for Cu alloy thin film formation of the present invention is a Cu alloy sputtering target containing at least Mn and having a Mn content of 2 atomic% or more and 20 atomic% or less, and the sputtering target having a t / 2 cross section And the Vickers hardness is 50 HV or more and 100 HV or less.

First, the composition of the Cu alloy will be described. Hereinafter, a Cu alloy containing Mn may be described as a Cu-Mn alloy.

The Cu-Mn alloy contains at least Mn and contains Mn in a range of 2 at% to 20 at%. Mn is an element that is dissolved in the Cu metal but not in the Cu oxide film. As described in the above-mentioned Patent Documents 1 and 2, Mn is preferentially reacted with oxygen more preferentially than Cu to form an oxide film that suppresses the oxidation of Cu, or diffuses S from the ZnS-containing protective layer It is very useful as an element capable of preventing or suppressing sulfuration of the Cu recording layer. When the Cu alloy containing Mn is oxidized by heat treatment or the like in the film forming process by the sputtering method, it is considered that Mn is diffused and concentrated to the grain boundary or interface, and the adhesion with the transparent substrate is improved by the thickened layer.

In order to effectively exhibit the effect of Mn, the Mn content in the Cu alloy is 2 atomic% or more. , Preferably not less than 4 atomic%, and more preferably not less than 8 atomic%. However, when the upper limit of the Mn content exceeds 20 atomic%, there is a problem such as brittleness, so the upper limit is set to 20 atomic% or less. Preferably not more than 15 atomic%, more preferably not more than 10 atomic%.

The Cu alloy may contain at least Mn in the above range, and the remaining portion is Cu and inevitable impurities.

The Cu alloy may further contain the following elements for the purpose of imparting other characteristics or the like.

For example, at least one element selected from the group consisting of Ag, Au, C, W, Ca, Mg, Ni, Al, Sn and B may be added in an amount of 0.2 to 10 atomic%. As a result, the adhesion with the substrate is improved. These elements may be added alone, or two or more of them may be used in combination. The above content is the sole amount when the above element is contained singly, and the total amount when two or more kinds are included.

Similarly, Zn may be added in the range of 0.2 to 10 atomic%. As a result, the adhesion with the substrate is improved.

The Cu alloy sputtering target of the present invention has the above-described composition and has the greatest feature that the Vickers hardness at the t / 2 cross section in the thickness direction of the sputtering target is 50 HV or more and 100 HV or less. The use of the Cu alloy sputtering target having the Vickers hardness properly controlled in this way reduces the occurrence of splash during sputtering film formation. When a Cu-Mn alloy sputtering target including at least Mn in the range of 2 to 20 atomic% is used as in the present invention, even when the hardness of the sputtering target is excessively high, splashing It has become clear that it is likely to occur. The preferable Vickers hardness is 50 HV or more and 100 HV or less, more preferably 60 HV or more and 90 HV or less.

Here, the t / 2 cross section in the thickness direction of the sputtering target is a surface parallel to the rolling direction among the cross sections perpendicular to the rolled surface, and the thickness t of the sputtering target is t (thickness) x 1/2 Quot; means a section in the range.

More specifically, the Vickers hardness of the sputtering target is calculated as follows. First, the sputtering target is cut so that the end face (measurement face) is exposed. At this time, the cut pieces are taken from three places (in the rolling direction, the front end portion, the center portion, and the rear end portion). Then, in order to smooth the measurement surface, polishing is carried out by polishing with an emery paper or diamond paste or the like. Thereafter, electrolytic etching was performed with Barker's solution [HBF ₄ (tetrafluoroboric acid) and water in an aqueous solution at a ratio of 1:30 by volume ratio] to measure the hardness at the center of the thickness of the measurement surface, The measurement is carried out using a Vickers hardness tester (AVK-G2, manufactured by Akashi Kasei Co., Ltd.). The average value of the hardness of the three cut pieces measured is taken as Vickers hardness.

In the present invention, in measuring the Vickers hardness of the sputtering target, the measurement target of the t / 2 cross section in the thickness direction is that uniformity of the structure is taken into consideration.

In the present invention, the reason why the occurrence of splash or the like can be reduced by appropriately controlling the Vickers hardness of the Cu-Mn alloy sputtering target is unclear in detail, but is estimated as follows. In order to stabilize discharge by reducing occurrence of splashing and the like, it is effective to raise the annealing temperature and the like to recrystallize. However, if the Vickers hardness becomes too high, the structure (crystal grain or the like) becomes uneven and the discharge is not stable. On the other hand, if the Vickers hardness is too low, it is presumed that the precipitation of Mn proceeds and becomes segregated, so that the discharge may become uneven.

The Cu alloy sputtering target of the present invention has been described above.

Next, a method of manufacturing the Cu alloy sputtering target will be described.

In the present invention, the Cu alloy sputtering target is manufactured by employing a melt casting method for the purpose of reducing the manufacturing cost, the manufacturing process, and the yield. The melt casting method is a method for producing an ingot from a molten Cu alloy, and is generally used for manufacturing a sputtering target.

According to the melt casting method, the sputtering target is usually produced by melt casting, (hot forging if necessary), hot rolling, and annealing (if necessary, cold rolling to annealing). In the present invention, since the Cu-Mn alloy sputtering target in which the Vickers hardness is appropriately controlled is manufactured, it is possible to appropriately control the hot rolling condition (in particular, the total rolling reduction during hot rolling) and the annealing conditions (annealing temperature, It is important.

Hereinafter, the production method of the present invention will be described in detail for each step.

(Melt casting)

The melt-casting process is not particularly limited, and a process commonly used for producing a sputtering target can be suitably employed so that a Cu-Mn alloy ingot having a desired composition can be obtained. Examples of the casting method include DC (semi-continuous) casting, continuous casting of thin plate (twin roll type, belt caster type, propeller type, block caster type and the like) and the like.

(Hot forging as required)

After the ingot of the Cu-Mn alloy ingot is subjected to hot rolling as described above (details will be described later), hot forging may be carried out to align the shape if necessary. The hot forging in this case also serves as a crack treatment. In order to control the Vickers hardness, it is preferable to control the hot forging temperature to about 800 to 900 DEG C and the heating time for hot forging to about 3 to 18 hours.

(Hot rolling)

The above hot forging is carried out as required, followed by hot rolling. For Vickers hardness control, the total rolling reduction during hot rolling is controlled to 50% or more. It is preferably at least 55%. From the viewpoint of Vickers hardness control, the higher the total reduction ratio is, the better, but if it is too high, there is a problem such as cracking, and therefore, the upper limit is preferably 75% or less. More preferably, it is 70% or less.

In the present invention, the total rolling reduction during hot rolling may be controlled within the above range. For example, the maximum reduction ratio per pass is not particularly limited, but is preferably about 5 to 10%.

In the present invention, the hot rolling starting temperature and the hot rolling finishing temperature are not particularly limited. However, in consideration of the controllability of Vickers hardness, it is preferable to control the hot rolling start temperature to about 600 to 800 DEG C and the hot rolling end temperature to about 400 to 500 DEG C.

(Annealing)

After hot rolling as described above, annealing is performed. For the Vickers hardness control, it is necessary to anneal for 2 hours or more at a temperature range of 450 to 600 캜.

As demonstrated in the later examples, when the annealing temperature is less than 450 DEG C, desired Vickers hardness can not be obtained even if the annealing time is controlled to be 2 hours or more. On the other hand, if the annealing temperature exceeds 600 ° C, there is a problem such as grain boundary coarsening. The preferred annealing temperature is 550 DEG C or less.

Similarly, if the annealing time is less than 2 hours, desired Vickers hardness can not be obtained. For Vickers hardness control, when annealing is performed in the above annealing temperature range, it is preferable that the annealing time is long. However, if the annealing time is excessively long, there is a problem such as crystal grain coarsening and the like, preferably 5 hours or less. A more preferable annealing time is 4 hours or less.

(Cold rolling to annealing, if necessary)

The Vickers hardness of the Cu-Mn alloy sputtering target can be controlled to a predetermined range by the above-described method. After that, cold rolling to annealing (annealing for second rolling and deformation correction) may be further performed. For the Vickers hardness control, the cold rolling condition is not particularly limited, but it is preferable to control the annealing conditions. For example, it is recommended to control the annealing temperature to approximately 150 to 250 DEG C and the annealing time to approximately 1 to 5 hours. The cold rolling ratio at the time of cold rolling may be in the usual range (for example, 20 to 40%).

Thereafter, when machining is performed in a predetermined shape, a sputtering target is obtained. The obtained sputtering target may be bonded to a desired backing plate as required.

This application claims the benefit of priority based on Japanese Patent Application No. 2012-173279 filed on August 3, 2012. The entire contents of the specification of Japanese Patent Application No. 2012-173279 filed on August 3, 2012 are hereby incorporated by reference herein.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples, but it should be understood that the present invention is not limited to the following Examples, and the present invention can be carried out in addition to the above- All of which are included in the technical scope of the present invention.

(Example 1)

First, a Cu-Mn alloy ingot (thickness: 100 mm) containing various amounts of Mn shown in Table 1 was rolled by the DC casting method.

Specifically, Cu of 4N purity and electrolytic Mn of 3N purity were dissolved at 1250 deg. C, held at 1200 deg. C for 10 minutes and then cooled to room temperature at an average cooling rate of 8 to 10 deg. C / To form a supersaturated solid solution (ingot).

The ingots were annealed under the conditions shown in Table 1 after hot forging → hot rolling (hot rolling finish temperature: 600 ° C) to form a thin plate having a thickness of 20 mm under the conditions shown in Table 1. In the present embodiment, subsequent cold rolling and annealing are not performed. Although the total rolling reduction ratio (total reduction ratio) of hot rolling is 50% and the annealing time is 2 hours in the present embodiment, if the total rolling reduction ratio is 50% to 75% and the annealing time is 2 hours to 5 hours, Is obtained.

Next, machining (round blanking and lathe machining) was performed to produce a disc-shaped Cu-Mn alloy sputtering target (size: 101.6 mm in diameter x 5.0 mm in thickness).

The Vickers hardness (average value at three measurement points) of the t / 2 cross section in the thickness direction of each sputtering target thus produced was measured by the above-mentioned method. In the column of Vickers hardness in Table 1, in addition to the average value, the measurement values of each of the three points are described in the columns (1), (2), and (3).

Next, each of the above-mentioned sputtering targets was processed into a shape of 4 inches 占 5 mmt, and the presence or absence of splash occurring when sputtering was performed under the following conditions was observed.

First, DC magnetron sputtering was performed on a Si wafer substrate (size: 101.6 mm in diameter × 0.50 mm in thickness) using a magnetron sputtering apparatus of "Sputtering System HSR-542S" manufactured by Shimadzu Corporation. The sputtering conditions are as follows.

DC: 260W

Pressure: 2 mTorr

Ar gas pressure: 2.25 x ^10-3 Torr

Ar gas flow rate: 30 sccm,

Interpole distance: 51.6㎜

Substrate temperature: room temperature

Sputtering time: 81 seconds

In this embodiment, the presence or absence of splash generated at the time of discharge was evaluated by observing the surface of the thin film with an optical microscope (magnification: 1000 times). In this case, the one having a protrusion of 1 占 퐉 or larger was regarded as splashing, and the one showing splashing was observed in the above observation field, and the splashing channel was evaluated.

The test results are shown in Table 1.

From Table 1, it can be considered as follows.

First, Nos. 1 to 4 are examples in which the amount of Mn in the Cu-Mn alloy is 2 atomic%. Among them, No. 4 is an example produced by a method that meets the requirements of the present invention, and since the Vickers hardness was appropriately controlled, the occurrence of splash was not recognized. On the other hand, in Nos. 1 to 3, since the annealing temperature was low, Vickers hardness exceeded the range specified in the present invention, and splash occurred.

The same results as above were obtained for the samples No. 5 to 8 (Mn amount = 4 atomic%), No. 9 to 12 (Mn amount = 8 atomic%), No. 13 to 16 (Mn amount = 10 atomic% .

Further, according to the present invention, in order to confirm that a sputtering target without Mn segregation serving as a starting point of splashing was obtained, the sputtering target No. 16 of the above Table 1 (the present invention) , The Mn distribution was mapped using EPMA for the rolling direction and the horizontal plane (t / 2). The measurement conditions of EPMA are as follows.

Analytical Apparatus: JEOL "Electron Beam Microanalyzer JXA8900RL"

Analysis condition

Acceleration voltage: 15.0 kV

Survey current: 5.012 × 10 ^-8 A

Beam diameter: Minimum (0 탆)

Measurement time: 100.00㎳

Measurement point: 400 × 400

Measurement interval: 1 ㎛

Measuring area: 400 탆 400 탆

Measuring position: Center in the plate thickness direction

Number of measurements: 1 o'clock

The results are shown in Fig. In Fig. 1, CP means a reflected electron image. As shown in Fig. 1, it can be seen that Mn segregation is not seen, and that Mn is uniformly dispersed. That is, when there is Mn segregation, the electric field becomes locally concentrated as a protrusion due to the difference in conductivity and sputtering rate, an anomalous discharge is generated to cause splash, and particles adhere to the surface of the film. The occurrence of coarse particles can be reduced.

Claims (7)

And a Cu alloy sputtering target containing Mn and having a Mn content of 2 atomic% or more and 20 atomic% or less,
Wherein the Vickers hardness of the t / 2 section in the thickness direction of the sputtering target is 50 HV or more and 100 HV or less. The sputtering target for forming a Cu alloy thin film according to claim 1, wherein the content of Mn is 2 at% or more and 10 at% or less. The sputtering target for forming a Cu alloy thin film according to claim 1 or 2, wherein the Vickers hardness of the t / 2 cross section in the thickness direction of the sputtering target is 60 HV or more and 90 HV or less. A method of manufacturing a sputtering target for forming a Cu alloy thin film according to any one of claims 1 to 3,
A method for producing a Cu alloy which satisfies the content of Mn according to any one of claims 1 to 3, wherein the total rolling reduction during hot rolling is at least 50%, the annealing after hot rolling is performed at a temperature of not less than 450 캜 and not more than 600 캜 for not less than 2 hours Then,
Wherein the Vickers hardness of the t / 2 section in the thickness direction of the sputtering target is 50 HV or more and 100 HV or less. The manufacturing method of a sputtering target for forming a Cu alloy thin film according to claim 4, wherein the total rolling reduction during hot rolling is 50% or more and 75% or less. The method for producing a sputtering target for forming a Cu alloy thin film according to claim 4, wherein the annealing after the hot rolling is performed at a temperature of 450 캜 or more and 550 캜 or less. The method of manufacturing a sputtering target for forming a Cu alloy thin film according to claim 4, wherein the annealing after the hot rolling is performed for 2 hours to 5 hours.

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