JP5793069B2 - Manufacturing method of copper target material for sputtering - Google Patents

Description

  The present invention relates to a sputtering copper target material formed from oxygen-free copper having a purity of 3N or higher and a method for producing a sputtering copper target material.

  Aluminum (Al) alloys formed by sputtering have been mainly used for electrode wiring such as thin film transistors (TFTs) used in liquid crystal display devices such as display panels. In recent years, as the resolution of liquid crystal display devices has increased, the TFT electrode wiring has been required to be miniaturized, and copper (Cu) having a resistivity (electric resistivity) lower than that of aluminum has been studied as an electrode wiring material. Yes. In connection with this, research of the copper target material for sputtering used for copper film-forming is also performed actively.

  For example, in Patent Documents 1 and 2, the crystal structure such as the grain size of the sputtering copper target material is improved in order to suppress the formation of protrusions called nodules formed on the surface of the target material by sputtering for a long time. Yes. According to these Patent Documents 1 and 2, the formation of nodules is suppressed by adjusting the crystal grain size of the target material, and the nodules are destroyed by abnormal discharge (arc) generated in the nodule portion, resulting in cluster-like particles. Can be suppressed. Therefore, adhesion of particles to the sputtering film can be suppressed and the product yield can be improved. Currently, countermeasures are often taken for arcs and particles from the aspect of the sputtering apparatus.

  On the other hand, improvement of the crystal structure of the copper target material for sputtering is performed for the purpose of improving the deposition rate of the sputtering film, reducing the tensile residual stress, and the like, as described in Patent Document 3, for example. According to Patent Document 3, by increasing the orientation ratio of the (111) plane of the surface of the copper target material for sputtering to 15% or more, the film formation rate is improved, and the tensile residual stress of the sputtering film is reduced. Can do.

  However, when the orientation ratio of the (111) plane on the surface of the sputtering copper target material is increased, the crystal grain size in the sputtering copper target material becomes coarse, and a dense sputtering film cannot be obtained or the film thickness is uniform. There is concern that the sex will deteriorate. In Patent Document 3, no consideration is given to the crystal grain size of the sputtering copper target material. For example, in Patent Document 4, the crystal grain size is prevented from becoming coarse while keeping the orientation ratio of the (111) plane high. Therefore, a very small amount of silver (Ag) that does not affect the resistivity of copper is added.

Japanese Patent Laid-Open No. 11-158614 JP 2002-129313 A JP 2010-013678 A JP 2011-127160 A

By the way, in order to further increase the frame speed and the screen size of the liquid crystal display device, it is desired to further reduce the resistance of electrode wiring using a pure copper sputtering film. However, a sputtered film made of pure copper can be used on a glass substrate or amorphous silicon (α-Si
) When formed on a film, a film containing a refractory metal such as titanium (Ti) or molybdenum (Mo) may be used as a base film. In this case, the resistivity of the sputtering film is formed on a glass substrate or the like. It is likely to be much higher than if it was done.

  Under such more severe conditions, it is necessary to avoid mixing Ag or the like, which can be a factor to increase the resistivity of the sputtering film, into the target material even if a trace amount is added as in Patent Document 4 described above. . On the other hand, the deposition rate must be maintained at a high speed because of the demand for shortening the tact time for forming the electrode wiring.

  In Patent Documents 3 and 4, the effect on the resistivity of the sputtering film formed on a film of Ti or the like is not particularly mentioned, and the influence on the crystal grain size is clearly described in Patent Document 3. Not. As described above, there is still room for study on a preferable crystal structure of the copper target material for sputtering and a method for obtaining the crystal structure.

  An object of the present invention is to provide a sputtering copper target material and a sputtering copper target material capable of forming a sputtering film made of pure copper having a low resistance on a film containing a refractory metal while obtaining a high film formation rate. It is to provide a manufacturing method.

  According to the first aspect of the present invention, it is formed from oxygen-free copper having a purity of 3N or higher, the orientation ratio of the (111) plane on the sputtering surface is 13% to 30%, and the (200) surface on the sputtering surface. A sputtering copper target material having an orientation ratio of 10% to 50% and an average crystal grain size of 0.1 mm to 0.2 mm is provided. However, the orientation ratios of the (111) plane and the (200) plane are the crystals obtained by X-ray diffraction for the (111) plane, the (200) plane, the (220) plane, and the (311) plane. This is the ratio when the total value of the values obtained by dividing the measured intensity of the peak of the plane by the relative intensity of the peak of the crystal plane corresponding to each crystal plane described in JCPDS is 100%.

  According to the second aspect of the present invention, the (111) plane orientation ratio in the sputtering surface is 20% or more, and the (200) plane orientation ratio in the sputtering surface is 30% or more. The copper target material for sputtering as described in 1 is provided.

  According to the third aspect of the present invention, the cold rolling is manufactured through a casting process, a hot rolling process, and a cold rolling process, and the degree of work is more than 5% and less than 30% in the cold rolling process. The copper target material for sputtering as described in the 1st or 2nd aspect which was given is provided.

  According to the fourth aspect of the present invention, the first to third aspects used for forming a sputtering film made of pure copper having a resistivity of less than 2.0 μΩcm immediately after film formation on a film containing a refractory metal. A sputtering copper target material according to any one of the above is provided.

  According to the fifth aspect of the present invention, a casting step of casting oxygen-free copper having a purity of 3N or more to form a copper ingot, a hot rolling step of hot rolling the copper ingot to obtain a copper plate, A cold rolling step in which the hot-rolled copper plate is cold-rolled to make it thinner, and in the cold rolling step, the copper plate has a workability of more than 5% and less than 30%. A method of manufacturing a copper target material for sputtering for reducing the thickness is provided.

  According to the present invention, a high deposition rate can be obtained, and a sputtering film made of pure copper having low resistance can be formed on a film containing a refractory metal.

It is a longitudinal cross-sectional view of the sputtering device with which the copper target material for sputtering which concerns on one Embodiment of this invention was mounted | worn. It is a graph which shows the orientation rate of each crystal plane of the copper target material for sputtering which concerns on Example 11 and Comparative Example 11 of this invention. It is a figure explaining the evaluation sample formed by dividing the pure copper sputtering film into a plurality of sections in a lattice shape using the sputtering copper target material according to Example 11 and Comparative Example 11 of the present invention. It is a top view of the evaluation sample which concerns on Example 21g-26g of invention, and Comparative Examples 21g-26g, (a2) is AA sectional drawing of (a1), (b1) is Example 21t of this invention It is a top view of the evaluation sample which concerns on 26t and Comparative Examples 21t-26t, (b2) is AA sectional drawing of (b1). It is the figure which displayed the film thickness of the pure copper sputtering film | membrane in each division divided into the grid | lattice form of the evaluation sample which concerns on Example 21g and Comparative Example 21g of this invention, Comprising: (a) concerns on Example 21g of this invention. It is a schematic diagram which shows an evaluation sample, (b) is a schematic diagram which shows the evaluation sample which concerns on the comparative example 21g. It is a graph which shows the dependence with respect to the heat processing temperature of the resistivity of the pure copper sputtering film | membrane of the evaluation sample which concerns on Example 21t and Comparative Example 21t of this invention. It is a graph which shows the dependence with respect to the heat processing temperature of the resistivity of the pure copper sputtering film | membrane of the evaluation sample which concerns on Examples 21t-26t of this invention, and Comparative Examples 21t-26t.

  As described above, the resistivity of the formed pure copper sputtering film may differ depending on the base. For example, on a glass substrate, a pure copper sputtering film of about 1.7 μΩcm can be easily obtained immediately after film formation. On the other hand, when a pure copper sputtering film is formed on a film containing a refractory metal such as titanium (Ti), the resistivity increases.

  Therefore, in order to obtain a pure copper sputtering film having good crystallinity, the present inventors make sputtering particles of high kinetic energy reach a predetermined film as a base and move (migration) on the film. Therefore, it was considered necessary to arrange the sputtered particles at appropriate crystal lattice positions.

  On the other hand, when ions collide with the surface of the target material during sputtering, atoms that are more likely to be released due to ion collision with the same energy, that is, the higher the film formation rate, the higher the kinetic energy sputtering particles are released. It is thought that.

  Based on the above considerations, the present inventors have attempted to optimize the crystal structure and the like of the sputtering copper target material so as to obtain a high deposition rate. As a result of intensive studies, it has been found that the film deposition rate tends to increase as the surface of the sputtering copper target material is oriented in the (111) plane or the (200) plane.

  Subsequently, the present inventors have also intensively studied a method for producing a sputtering copper target material in which many (111) and (200) planes are oriented. In order, in the manufacturing method that goes through the casting process, the hot rolling process, the cold rolling process, and the heat treatment process, the (220) plane is oriented in the cold rolling process, and the (111) plane is oriented in the subsequent heat treatment process. Then, it was found that the (111) plane that was oriented only at 10% or less was obtained with a high orientation rate by adjusting the temperature in the hot rolling process and the degree of work in the cold rolling process.

  The present invention is based on the above findings found by the inventors.

<One Embodiment of the Present Invention>
(1) Sputtering Copper Target Material Hereinafter, a sputtering copper (Cu) target material 10 (see FIG. 1 described later) according to an embodiment of the present invention will be described. The sputtering copper target material 10 is formed in a rectangular flat plate shape having a predetermined thickness, width, and length, for example, and is pure copper used as an electrode wiring such as a thin film transistor (TFT) used in a liquid crystal display device or the like. It is configured to be used for forming a sputtering film.

  Pure copper constituting the copper target material 10 for sputtering is, for example, oxygen-free copper (OFC) having a purity of 3N (99.9%) or higher.

  Moreover, the orientation rate of the (111) plane in the surface of the copper target material 10 for sputtering, that is, the sputtering surface is, for example, 13% or more and 30% or less, more preferably 20% or more, and the orientation rate of the (200) plane is For example, it is 10% or more and 50% or less, more preferably 30% or more. The orientation ratios of the (111) plane and the (200) plane are values obtained from the measured intensity ratios with the respective peaks showing various crystal planes obtained by X-ray diffraction. The measured intensity of each peak is used, for example, corrected with the relative intensity of the peak of the crystal plane corresponding to each peak. For example, a value described in JCPDS (Joint Committee for Powder Diffraction Standards) is used as the relative intensity.

  Specifically, as represented by the following formulas (1) and (2), the orientation ratios of the (111) plane and the (200) plane are (111) plane, (200) plane, (220) plane, And, for the (311) plane, the total value of the values obtained by dividing the measured intensity of the peak of each crystal plane obtained by X-ray diffraction by the relative intensity of the peak of the crystal plane corresponding to each of the crystal planes described in JCPDS, respectively. The ratio is 100%.

  Moreover, the average crystal grain diameter of the copper target material 10 for sputtering is 0.1 mm or more and 0.2 mm or less, for example. The average crystal grain size is a value obtained by the “comparison method” of the “stretched copper product crystal grain size test method” defined in JIS H0501.

As described above, by using the copper target material 10 for sputtering whose (111) plane orientation ratio is, for example, 13% to 30% and (200) plane orientation ratio is, for example, 10% to 50%, High kinetic energy copper sputtered particles are easily released. Therefore, a high film formation speed can be obtained, and on the film containing a refractory metal such as Ti and molybdenum (Mo), for example, by migration of the sputtered particles on the reached film and arrangement at an appropriate crystal lattice position. However, it is possible to form a pure copper sputtering film having a resistivity of less than 2.0 μΩcm immediately after the film formation.

  Further, as described above, by using the sputtering copper target material 10 having an average crystal grain size of, for example, 0.1 mm or more and 0.2 mm or less, a dense pure copper sputtering film having a good film thickness uniformity can be obtained. Can be formed.

(2) Manufacturing method of copper target material for sputtering Next, the manufacturing method of the copper target material 10 for sputtering which concerns on one Embodiment of this invention is demonstrated. In the present embodiment, in order to correspond to a recent liquid crystal display device such as a large display panel, for example, a 10 m generation substrate size of about 3 m square, the casting process, the hot rolling process, and the cold rolling process are mainly performed in this order. The manufacturing method to perform is employ | adopted.

  First, in a casting process, oxygen-free copper having a purity of 3N (99.9%) or more is cast to form a rectangular copper ingot having a predetermined thickness and a predetermined width. Next, in the hot rolling process, the copper ingot heated at a temperature of 650 ° C. or higher and 900 ° C. or lower is subjected to rolling (hot rolling) to remove the surface oxide layer (black skin). A copper plate having a predetermined thickness is peeled off.

Subsequently, in the cold rolling process, the copper plate is cold-rolled at room temperature to make it thinner, and the outer shape of the copper plate is adjusted. At this time, the copper plate is thinned so that the processing degree of the copper plate is more than 5% and less than 30%, more preferably 10% or less. Further, in the cold rolling process, the cold rolling may be performed by one process, or the process may be performed in a plurality of times. The degree of processing is defined by the following formula (3).
Degree of processing (%) = ((plate thickness before processing−plate thickness after processing) / plate thickness before processing) × 100 (3)

  Next, the bending of the copper plate is corrected with a straightening machine, cut with a mill, etc., and cut into a predetermined length to obtain a copper target material 10 for sputtering having a predetermined thickness and a predetermined width. As described above, the copper target material 10 for sputtering is manufactured.

  As described above, in the present embodiment, the hot rolling process is performed at 650 ° C. or more and 900 ° C. or less. By setting the temperature to a high temperature of 650 ° C. or higher, a crystal structure with a high orientation ratio of the (111) plane can be obtained, and a predetermined amount of the (200) plane also appears. In addition, by controlling the temperature to 900 ° C. or lower, it is possible to control the oxidation of the copper ingot or improve the workability at the time of manufacture.

  In the present embodiment, the cold rolling process is performed so that the degree of processing of the copper plate is more than 5% and less than 30%, more preferably 10% or less. In the cold rolling process, a part of the (200) plane oriented in the hot rolling process is oriented in the (220) plane. Therefore, by setting the degree of work in the cold rolling step to a predetermined value or less, the orientation rate of the (111) plane is maintained at a high level of, for example, 13% to 30%, and the orientation rate of the (200) plane is set to 10 % Or more, more preferably 30% or more. Further, the refinement of the crystal grain size is promoted by the cold rolling process. Therefore, by setting the degree of processing to, for example, more than 5%, a relatively fine crystal grain size is obtained, and the average crystal grain size in the sputtering copper target material 10 is, for example, 0.1 mm to 0.2 mm. Can do.

  Initially, the present inventors obtained knowledge that the (220) plane oriented in the cold rolling process is then oriented to the (111) plane by recrystallization in a heat treatment process at a relatively low temperature of about 400 ° C. It was. From this, the present inventors will keep the degree of work in the cold rolling process at about 30% to 50% of the conventional one, and obtain a crystal structure with a high orientation ratio of the (111) plane by various combinations with the heat treatment process. I tried. However, the degree of work in the cold rolling process can be increased only to about 50% from the viewpoint of workability, and the orientation ratio of the obtained (111) plane was 10% or less.

  In the present embodiment, based on the knowledge obtained by further efforts of the present inventors, a crystal structure having a high orientation ratio of the (111) plane is obtained in a hot rolling process at a high temperature. Since the degree of processing is suppressed to, for example, less than 30%, the sputtering copper target material 10 having a high orientation ratio of the (111) plane and the (200) plane is obtained.

(3) Film Forming Method Using Sputtering Copper Target Material Next, a method for forming a pure copper sputtering film by sputtering using the sputtering copper target material 10 according to an embodiment of the present invention will be described with reference to FIG. It explains using.

  FIG. 1 is a longitudinal sectional view of a sputtering apparatus 20 equipped with a sputtering copper target material 10 according to an embodiment of the present invention. The sputtering apparatus 20 is configured as a DC sputtering apparatus using, for example, direct current (DC) discharge. Note that the sputtering apparatus 20 shown in FIG. 1 is merely an example, and the sputtering copper target material 10 can be mounted and used in various types of sputtering apparatuses.

  As shown in FIG. 1, the sputtering apparatus 20 includes a vacuum chamber 21. A substrate holding part 22s is provided in the upper part of the vacuum chamber 21, and the substrate S to be deposited is held with the surface to be deposited facing downward. The substrate S is, for example, a glass substrate on which a film containing a refractory metal such as Ti or Mo to be a film formation surface is formed in advance.

  A target holding portion 22t is provided at the bottom of the vacuum chamber 21, and for example, the sputtering copper target material 10 is held with the sputtering surface facing upward so as to face the deposition surface of the substrate S. Note that a plurality of substrates S may be held in the sputtering apparatus 20 and these substrates S may be collectively processed or continuously processed.

  A gas supply pipe 23f is connected to one wall surface of the vacuum chamber 21, and a gas exhaust pipe 23v is connected to the other wall surface facing the gas supply pipe 23f. A gas supply system (not shown) for supplying an inert gas such as argon (Ar) gas into the vacuum chamber 21 is connected to the gas supply pipe 23f. A gas exhaust system (not shown) for exhausting the atmosphere in the vacuum chamber 21 of Ar gas or the like is connected to the gas exhaust pipe 23v.

  When film formation on the substrate S is performed by the sputtering apparatus 20, Ar gas or the like is supplied into the vacuum chamber 21, and a negative high voltage is applied to the sputtering copper target material 10 and a positive high voltage is applied to the substrate S. Thus, DC discharge power is supplied to the vacuum chamber 21.

Thereby, plasma is mainly generated between the sputtering copper target material 10 and the substrate S, and positive argon (Ar ⁺ ) ions G collide with the sputtering surface of the sputtering copper target material 10. Due to the collision of Ar ⁺ ions G, copper sputtering particles P knocked out of the sputtering copper target material 10 are deposited on the film formation surface of the substrate S, and a sputtering film made of pure copper is deposited on the substrate S. M is formed.

  As described above, when a conventional sputtering copper target material is used and pure copper or the like is sputtered onto a film such as Ti, for example, a sputtering film having a high resistivity may be obtained. Such a phenomenon is thought to be because the sputtering film formed on a film of Ti or the like has a poor crystallinity, for example, the film contains many voids or is a crystal having an irregular atomic arrangement. It is done.

Therefore, as the present inventors have considered, if the sputtered copper particles that have reached the film of Ti or the like can be moved (migrated) on the deposited film and placed at an appropriate crystal lattice position as much as possible. It is considered that a low resistivity pure copper sputtering film having good crystallinity can be formed. This migration becomes easier as the kinetic energy of the sputtered particles is higher.

As described above, sputtering is a phenomenon in which Ar ⁺ ions or the like in the discharge plasma collide with the surface of the target material, and bonds between atoms constituting the target material are broken to release atoms. Therefore, it is considered that the kinetic energy immediately after the emission is higher for the atoms that are more likely to be released in response to ion collision with the same energy. That is, it is considered that the higher the kinetic energy sputtering particles are released, the higher the erosion rate (erosion) rate of the sputtering copper target material or the deposition rate of the sputtering film.

  In the present embodiment, a high erosion rate and a film formation rate were obtained by the inventors' diligent research, and a copper target material for sputtering 10 having a high orientation ratio on the (111) plane in which atoms were likely to be released. It is said. Similarly, the orientation rate of the (200) plane where the next highest deposition rate was obtained after the (111) plane is also increased. As a result, while obtaining a high deposition rate, the sputtering particles P with high kinetic energy are released and deposited on the film, causing the placement on the appropriate crystal lattice position by migration on the film, and good crystallinity. A pure copper sputtering film M having a low resistivity can be obtained.

  In this embodiment, since the average crystal grain size in the sputtering copper target material 10 is kept relatively small, for example, 0.1 mm or more and 0.2 mm or less, the sputtering film M can be a dense film. Moreover, the uniformity of the film thickness can be kept good. Furthermore, abnormal discharge (arc) or the like during sputtering hardly occurs, and particles on the sputtering apparatus 20 or on the sputtering film M can be reduced.

  Note that, as described above, at present, considerable improvements have been observed with regard to adverse effects such as arcs and particles due to measures from the device side. For example, a magnet for attracting ions is placed on the back surface of the target material, and the magnet is oscillated to constantly move the portion where erosion occurs, so that nodules are formed on the target material. Also good. In addition, if a multi-cathode type device with a rectangular target material to be used as a cathode electrode is used, a stable plasma is generated by alternating current (AC) sputtering that loads an AC power source between adjacent cathode electrodes, thereby generating an arc. It is also possible to suppress this.

  The pure copper sputtering film M formed on the substrate S as described above is subjected to, for example, a desired patterning and is used as an electrode wiring for various semiconductor elements including TFTs.

<Other Embodiments of the Present Invention>
As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, It can change variously in the range which does not deviate from the summary.

  For example, in the above-described embodiment, the sputtering copper target material 10 is a rectangular flat plate type, but the shape of the sputtering copper target material is not limited to this, and may be a disk shape or other shapes.

  Moreover, in the above-mentioned embodiment, although the hot rolling process was performed as a high-temperature processing process according to the method for manufacturing the sputtering copper target material 10, the high-temperature processing process is not limited to this, for example, at a high temperature such as a hot extrusion process. What is necessary is just the process of heating and performing plastic working.

  In the above embodiment, the sputtering copper target material 10 is used and a pure copper sputtering film is formed on a film of Ti or the like. However, a film containing a refractory metal serving as a base of the pure copper sputtering film is other than this. This film may be used. Specifically, in addition to Ti and Mo, films of tungsten (W), tantalum (Ta), cobalt (Co), nickel (Ni), etc., alloy films of these metals, or alloy films of these and other metals Etc. The base of the sputtering film may be an α-Si film or a glass substrate.

(1) Evaluation of Sputtering Copper Target Material Next, the evaluation results of the sputtering copper target material according to Examples 11 to 16 of the present invention will be described together with Comparative Examples 11 to 16.

(Manufacture of copper target material for sputtering)
First, oxygen-free copper having a purity of 3N (99.95%) was cast by the same method and procedure as in the above-described embodiment to produce a rectangular copper ingot having a thickness of 150 mm and a width of 300 mm.

  Next, a copper target material for sputtering according to Example 11 was manufactured from this copper ingot. That is, the copper ingot was heated in a heating furnace maintained at 800 ° C. in an Ar gas atmosphere for 2 hours, taken out from the heating furnace, and immediately subjected to a hot rolling process to obtain a copper plate having a thickness of 30 mm. After removing the surface oxide layer of the copper plate, in the cold rolling process, the copper plate was thinned to a thickness of 28 mm by one treatment (working degree: about 7%). Thereafter, cutting was performed with a milling cutter until the thickness became 20 mm, whereby a sputtering copper target material according to Example 11 was obtained.

  Further, in the same manner and procedure as in Example 11, the temperature of the hot rolling process and the degree of work in the cold rolling process are variously changed within the range of the above-described predetermined values, and Examples 12 to 16 are obtained. The copper target material for sputtering was manufactured together.

  Furthermore, as the example which the present inventors examined initially, as an example which tries the increase in the orientation rate of a (111) plane by adjusting a cold rolling process and a heat treatment process, it changes from said copper ingot to the comparative example 11. A copper target material for sputtering was produced. That is, a copper plate having a thickness of 60 mm was manufactured by a hot rolling process in which the temperature was set to 800 ° C. by substantially the same method and procedure as in Example 11 above. In the cold rolling process, the copper plate was thinned to a thickness of 30 mm (working degree: 50%), and the temperature in the heat treatment process was set to 400 ° C. Through the subsequent steps, a copper target material for sputtering according to Comparative Example 11 having a final thickness of 20 mm was obtained.

  Further, in the same method and procedure as in Comparative Example 11 above, the temperature of the hot rolling process and the degree of work in the cold rolling process were variously changed to include values outside the above predetermined value range, and Comparative Example The copper target material for sputtering which concerns on 12-16 was manufactured together.

(Measurement of sputtering copper target material)
Subsequently, with respect to the crystal structure obtained by cutting the block material from the sputtering copper target material before machining and polishing the rolled surface corresponding to the sputtering surface, measurement of the orientation rate and average crystal grain size of each crystal surface Went.

  First, X-ray diffraction measurement was performed on the copper target materials for sputtering according to Examples 11 to 16 and Comparative Examples 11 to 16, and the orientation ratio of each crystal plane on the sputtering surface was examined. That is, the peak intensity of the (111) plane, (200) plane, (220) plane, and (311) plane is measured by X-ray diffraction, and the relative peak of the crystal plane corresponding to each of the crystal planes described in JCPDS is measured. Using the strength, the orientation ratios of the (111) plane and the (200) plane were determined from the above formulas (1) and (2).

  Moreover, about the copper target material for sputtering which concerns on Examples 11-16 and Comparative Examples 11-16, the average crystal grain diameter was measured based on the "comparison method" of the "stretched copper product crystal grain size test method" prescribed | regulated to JISH0501. . That is, the average grain size was identified by comparing a standard photograph published in JIS H0501 with a photograph of the crystal structure of each sputtering copper target material.

  In FIG. 2, the measurement result of Example 11 and Comparative Example 11 is shown. The horizontal axis of the graph of FIG. 2 is the crystal planes of the (111) plane, the (200) plane, the (220) plane, and the (311) plane, and the vertical axis is the orientation ratio (%) of the crystal plane in the sputtering plane. It is. In the graph, the data of Example 11 is indicated by ♦ and a solid line, and the data of Comparative Example 11 is indicated by ■ and a broken line. In the table above the graph, the Vickers hardness Hv is shown as a reference value together with the average crystal grain size (mm) and the orientation ratio (%) of each crystal plane.

  As shown in FIG. 2, in Example 11 in which the degree of work in the cold rolling process was about 7%, compared to Comparative Example 11 in which the degree of work in the cold rolling process was 50%, the (111) plane and A copper target material for sputtering having a high (200) plane orientation ratio was obtained. Further, the average crystal grain size of Example 11 was somewhat coarser than that of Comparative Example 11, but a relatively fine crystal structure was obtained.

  Table 1 below shows all data of Examples 11 to 16 and Comparative Examples 11 to 16. In the table, values outside the predetermined value are shown in parentheses.

  As shown in Table 1, in Examples 11 to 16 in which the degree of work in the cold rolling process is within a predetermined value, the orientation ratio of the (111) plane and the (200) plane and the average crystal grain size are both predetermined. A numerical value within the range was obtained. In Examples 11 and 14 to 16, in which the temperature in the hot rolling process is particularly high, the orientation ratio of the (111) plane is 20% or more, and the orientation ratio of the (200) plane is 30% or more. It is a desirable value.

  On the other hand, in Comparative Examples 11 to 16, the degree of work in the cold rolling process was 30% to 50% as in the conventional case, and the orientation ratio of the (111) plane was 10% or less.

  From the above results, the temperature of the hot rolling process is set to 650 ° C. or more, and the degree of work in the cold rolling process is more than 5% and less than 30%, more preferably 10% or less, so that the average of the copper target material for sputtering is While maintaining the crystal grain size at 0.1 mm or more and 0.2 mm or less, the orientation ratio of the (111) plane on the sputtering surface is 13% or more and 30% or less, more preferably 20% or more, and the orientation ratio of the (200) plane is It has been found that it can be made 10% to 50%, more preferably 30% or more.

(2) Evaluation of Pure Copper Sputtering Film Next, evaluation results of the pure copper sputtering film according to Examples 21 to 26 of the present invention will be described together with Comparative Examples 21 to 26.

(Production of evaluation samples)
Using the sputtering copper target materials according to Examples 11 to 16 and Comparative Examples 11 to 16 described above, pure copper sputtering films 53g and 53t are latticed on the glass substrate 51 or the Ti film 52, respectively, as shown in FIG. An evaluation sample formed into a plurality of sections was manufactured.

  That is, in order to adapt to the sputtering experimental machine described below, first, the copper target material for sputtering according to the above-described Examples 11 to 16 and Comparative Examples 11 to 16 is machined to have a thickness of 5 mm and a diameter of 100 mm. Cut into a circle. Next, each of the circular copper target materials for sputtering was mounted on a DC discharge type sputtering experimental machine having substantially the same function as the sputtering apparatus 20 according to the above-described embodiment. Subsequently, film formation by sputtering was performed on the glass substrate 51 or the Ti film 52 by a rotational film formation method in which the glass substrate 51 passes directly above the sputtering copper target material by rotation of the substrate holding part.

  The evaluation samples according to Examples 21g to 26g and Comparative Examples 21g to 26g shown in FIGS. 3 (a1) and (a2) use the sputtering copper target materials according to Examples 11 to 16 and Comparative Examples 11 to 16, respectively. A pure copper sputtering film 53g is formed. In such a configuration, a metal mask (not shown) having 100 squares (10 squares by 10 squares) with 3 mm square openings at 2 mm intervals is held on a 50 mm square glass substrate 51, and a pure copper sputtering film 53g is formed. It was obtained by forming 100 sections on a glass substrate 51 by dividing into a 3 mm square grid. Table 2 below shows film forming conditions by sputtering.

The evaluation samples according to Examples 21t to 26t and Comparative Examples 21t to 26t shown in FIGS. 3B1 and 3B2 use the copper target materials for sputtering according to Examples 11 to 16 and Comparative Examples 11 to 16, respectively. A pure copper sputtering film 53t is formed. In forming each evaluation sample, a Ti film 52 was previously formed on the entire surface of the glass substrate 51 using a Ti target material. A metal mask similar to that described above was held on the Ti film 52, and a pure copper sputtering film 53t was formed on the Ti film 52 by dividing it into a 3 mm square grid. The film thicknesses of the Ti film 52 and the pure copper sputtering film 53t were about 50 nm and about 300 nm, respectively. Table 3 below shows film forming conditions by sputtering.

(Measurement of film thickness of evaluation sample)
First, the film thickness of the pure copper sputtering film 53g was measured using the evaluation samples according to Examples 21g to 26g and Comparative Examples 21g to 26g. The film thickness was measured by measuring the level difference between each section of the pure copper sputtering film 53g divided into a lattice shape and the glass substrate 51 using a laser microscope. Moreover, from the measured film thickness, the average value of the film thickness, the standard deviation indicating the film thickness distribution, and the film formation speed were determined. The film formation rate (nm / min.) Is a value obtained by dividing the measured film thickness by 10 minutes of the film formation time.

  FIG. 4 shows the measurement results of Example 21g and Comparative Example 21g. Fig.4 (a) is a schematic diagram which shows the evaluation sample which concerns on Example 21g of this invention, FIG.4 (b) is a schematic diagram which shows the evaluation sample which concerns on the comparative example 21g. In the schematic diagram, the film thickness of the pure copper sputtering film 53g in each section is displayed at a position corresponding to each (10 × 10) sections of each evaluation sample. In the upper table of the figure, numerical values of the film thickness average value (nm), the standard deviation (nm), and the film formation rate (average value) (nm / min.) Of each evaluation sample are shown.

  As shown in FIG. 4, the deposition rate of the pure copper sputtering film 53g is about 10% higher in Example 21g than in Comparative Example 21g, and the sputtering copper having a high orientation ratio on the (111) plane and (200) plane. This is probably because the target material was used.

  On the other hand, the standard deviation of the film thickness was the result that Example 21g was larger. However, the average value of the film thickness is larger in Example 21g, and the ratio of the standard deviation to the average value (coefficient of variation) is 0.64% for Example 21g and 0.52% for Comparative Example 21g. It can be seen that there is no significant difference in film thickness variation. In the copper target material for sputtering according to Example 11 corresponding to Example 21g, the average crystal grain size is controlled to 0.15 mm, thereby maintaining the uniformity of the film thickness of the pure copper sputtering film 53g as described above. I was able to.

(Resistivity measurement of evaluation sample)
Next, a heat treatment step was performed on the evaluation samples according to Examples 21t to 26t and Comparative Examples 21t to 26t at a temperature of 200 ° C. to 300 ° C. that can be received by the pure copper sputtering film in the TFT manufacturing process. Then, the sheet resistance of the pure copper / Ti laminated film (film thickness: 300 nm / 50 nm) was measured before and after the heat treatment, and the resistivity of the pure copper sputtering film 53t on the Ti film 52 was obtained.

As a method for measuring the sheet resistance, van der Pauw is performed by applying electrode needles to the upper surface of each 3 mm square section, that is, near the four corners of the surface of the pure copper sputtering film 53t.
The method was used. The resistivity was obtained by multiplying this sheet resistance by the film thickness of the pure copper sputtering film 53t measured by the same method as described above.

  That is, for measurement of the film thickness, a color 3D laser microscope VK-8710 manufactured by Keyence Corporation was used. For measurement of sheet resistance, a 2612A type 2ch system source meter manufactured by Keithley Instruments Inc. was used. With such a source meter, the current value was swept from -100 mA to 100 mA and the voltage was measured. Next, the sheet resistance was obtained from the measured current value and the voltage value according to the calculation formula of the van der Pauw method. At this time, the average of the resistance values at −100 mA and 100 mA was taken, and the offset was cancelled. The film resistivity (μΩcm) was obtained by multiplying the sheet resistance value obtained above by the film thickness measured with the laser microscope, and was used as the resistivity of the pure copper sputtering film 53 t on the Ti film 52.

  The resistivity is one of the physical property values of the pure copper sputtering film 53t. The pure copper sputtering film 53t shows a low value when it is a film having few defects such as voids and good crystallinity. In addition, the minimum resistivity as a bulk material of pure copper is 1.67 μΩcm.

  FIG. 5 shows the measurement results of Example 21t and Comparative Example 21t. The horizontal axis in FIG. 5 is the heat treatment temperature (° C.), and the vertical axis is the resistivity (μΩcm) of the pure copper sputtering film 53t. In the figure, the data of Example 21t is indicated by ♦ and solid lines, and the data of Comparative Example 21t is indicated by ■ and dashed lines.

  As shown in FIG. 5, even after the deposition (As depo.), Example 21t showed a lower resistivity than Comparative Example 21t, and in Example 21t, it was on the Ti film 52. It can be seen that a pure crystalline sputtering film 53t having good crystallinity is obtained. In both cases, the resistivity decreased after the heat treatment at 200 ° C. and 300 ° C., and it was found that the crystal defects were corrected by the heat treatment. However, even after the heat treatment, the comparative example 21t still has a higher resistivity than the example 21t, and it is considered that the crystal state immediately after the film formation has an influence.

  FIG. 6 shows all data of Examples 21t to 26t and Comparative Examples 21t to 26t. In Examples 21t to 26t and Comparative Examples 21t to 26t, the same tendency as described above was observed.

  Table 4 below shows all data of Examples 21 to 26 and Comparative Examples 21 to 26.

  As shown in Table 4, Examples 21 and 24-26 corresponding to Examples 11 and 14-16, in which the temperature in the hot rolling process was high and the orientation ratios of the (111) plane and (200) plane were particularly high. Is 90 nm / min. A film forming speed exceeding 1 was obtained.

  On the other hand, in Comparative Examples 21 to 26 corresponding to Comparative Examples 11 to 16 in which the orientation ratio of the (111) plane was 10% or less, both the film formation rate and the resistivity were worse than those of Examples 21 to 26, and the sputtering characteristics. Is considered inferior.

  From the above results, by controlling the orientation ratio and average grain size of the predetermined crystal plane of the copper target material for sputtering as described above, even on a film containing a refractory metal such as Ti, high film formation is possible. It was found that pure copper sputtering films 53g and 53t having good crystallinity with a resistivity of less than 2.0 μΩcm immediately after film formation can be obtained as well as speed.

DESCRIPTION OF SYMBOLS 10 Sputtering copper target material 20 Sputtering apparatus 51 Glass substrate 52 Ti film 53g, 53t Pure copper sputtering film | membrane S board | substrate

Claims (1)

Formed from oxygen-free copper of purity 3N or higher,
The orientation ratio of the (111) plane on the sputtering surface is 13% or more and 30% or less,
The orientation rate of the (200) plane in the sputtering surface is 10% or more and 50% or less,
A method for producing a sputtering target material, wherein the average crystal grain size is 0.1 mm or more and 0.2 mm or less,
The manufacturing method of the copper target material for sputtering is as follows:
A casting process in which oxygen-free copper having a purity of 3N or more is cast into a copper ingot;
A hot rolling step of hot rolling the copper ingot to form a copper plate;
A cold rolling process in which the hot-rolled copper sheet is further cold-rolled and further thinned;
Without performing heat treatment of the cold-rolled copper plate , a sputtering copper target material production step of producing a sputtering copper target material having a predetermined thickness and a predetermined width by cutting,
The hot rolling step is performed at 650 ° C. or more and 900 ° C. or less,
In the cold rolling step, the copper plate is thinned so that the degree of processing of the copper plate is more than 5% and less than 30%.
However, the orientation ratio of the (111) plane and the (200) plane is
For the (111) plane, the (200) plane, the (220) plane, and the (311) plane, the measured intensity of the peak of each crystal plane obtained by X-ray diffraction corresponds to each of the crystal planes described in JCPDS. This is the ratio when the sum of the values divided by the relative intensities of the crystal plane peaks is 100%.

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