JP5778636B2 - Sputtering copper target material and method for producing sputtering copper target material - 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 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 (arcing) that occurs in the nodule portion, resulting in cluster-like foreign matter (particles). ) Can be suppressed. Therefore, adhesion of particles to the sputtering film can be suppressed and the product yield can be improved.

Japanese Patent Laid-Open No. 11-158614 JP 2002-129313 A

  As described above, suppression of arcing during sputtering for forming electrode wiring has been focused as a priority issue, and many studies have been made so far. At present, however, arcing and the particles generated thereby can be considerably improved from the aspect of the sputtering apparatus. Therefore, as a next problem, 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 in the electrode wiring using the pure copper sputtering film.

  However, the resistivity of the sputtering film formed thereon may increase depending on the base material. For example, when a sputtering film using pure copper is formed on a glass substrate or an amorphous silicon (α-Si) film, a film containing a refractory metal such as titanium (Ti) or molybdenum (Mo) is used as the base film. There is. In this case, the resistivity of the sputtering film may be higher than when formed directly on a glass substrate or the like.

  The objective of this invention is providing the manufacturing method of the copper target material for sputtering which can form the low resistance sputtering film which consists of pure copper on the film | membrane containing a refractory metal, and the sputtering copper target material.

According to a first aspect of the invention,
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 15% or more and 30% or less,
A sputtering copper target material having an average crystal grain size of 0.07 mm to 0.20 mm is provided.
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 crystal plane described in JCPDS This is the ratio when the total value of the values divided by the relative intensities of the peak of the crystal plane to be taken is 100%.

According to a second aspect of the invention,
When the sputtering conditions were 12.7 W / cm ² in the input power density under an Ar atmosphere of 0.5 Pa,
The copper target material for sputtering according to the first aspect, in which the sputtering rate is 3 g / h or more and 5 g / h or less is provided.

According to a third aspect of the invention,
The orientation ratio of the (111) plane in the sputtering surface is 17% or more,
The copper target material for sputtering as described in the 1st or 2nd aspect whose said average crystal grain diameter is 0.10 mm or more is provided.

According to a fourth aspect of the invention,
The copper target material for sputtering according to any one of the first to third aspects, in which the average crystal grain size is 0.15 mm or less is provided.

According to a fifth aspect of the present invention,
Manufactured through casting process and hot rolling process,
In the hot rolling process,
The copper ingot heated to 800 ° C. or more and 900 ° C. or less has a thickness reduction rate of 85% or more and 95% or less, and the temperature at the end of rolling of the copper plate formed by rolling the copper ingot is 600 ° C. or more and 700 ° C. The copper target material for sputtering according to any one of the first to fourth aspects subjected to hot rolling so as to be the following is provided.

According to a sixth aspect of the present invention,
The copper target material for sputtering according to any one of the first to fifth embodiments 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. Provided.

According to a seventh aspect of the present invention,
A casting process in which oxygen-free copper having a purity of 3N or more is cast into a copper ingot;
The copper ingot is hot-rolled into a copper plate by hot rolling, and is manufactured by performing,
In the hot rolling process,
The copper ingot heated to 800 ° C. or more and 900 ° C. or less is hot-rolled so that the thickness reduction rate is 85% or more and 95% or less, and the temperature of the copper plate at the end of rolling is 600 ° C. or more and 700 ° C. or less. A sputtered copper target material is provided.

According to an eighth aspect of the present invention,
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,
In the hot rolling process,
The copper ingot heated to 800 ° C. or more and 900 ° C. or less is hot-rolled so that the thickness reduction rate is 85% or more and 95% or less, and the temperature of the copper plate at the end of rolling is 600 ° C. or more and 700 ° C. or less. A method for producing a copper target material for sputtering is provided.

  According to the present invention, a low-resistance sputtering film made of pure copper 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 the schematic of the detection apparatus system used for the measurement of the arcing of the copper target material for sputtering which concerns on Examples 11-19 and Comparative Examples 11-16 of this invention. It is a graph which shows the orientation rate of each crystal plane of the copper target material for sputtering which concerns on Example 11,16,17 of this invention, and Comparative Examples 11,15,16. 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 copper target material for sputtering according to Examples 11 to 19 and Comparative Examples 11 to 16 of the present invention. a1) is a plan view of an evaluation sample according to Examples 21g to 29g and Comparative Examples 21g to 26g of the present invention, (a2) is a cross-sectional view taken along line AA of (a1), and (b1) is a diagram of the present invention. It is a top view of the evaluation sample which concerns on Examples 21t-29t and Comparative Examples 21t-26t, (b2) is AA sectional drawing of (b1). 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, 26t, 27t of this invention, and Comparative example 21t, 25t, 26t. 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-29t and Comparative Examples 21t-26t of this invention.

<Knowledge obtained by the present inventors>
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. This is presumably because the crystallinity of the pure copper sputtering film formed on the refractory metal film is inferior.

  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 serving as a base and migrate on the film (migration) I guessed that I should do it. This is because the sputtering particles can be arranged at appropriate crystal lattice positions.

  On the other hand, when ions collide with the surface of the target material during sputtering, atoms are more likely to be released in response to ion collisions of the same energy, that is, the higher the sputtering rate, the higher the sputtered particles immediately after being emitted. It is thought to have kinetic energy.

Based on the above considerations, the present inventors have attempted to optimize the crystal structure of the sputtering copper target material so that a high sputtering rate can be obtained. As a result of diligent research, the sputtering rate tends to increase as the surface of the sputtering copper target material is oriented to the (111) plane or the (200) plane, and as the crystal grain size in the target material is coarser. It turns out that it is obtained.

  Subsequently, the present inventors conducted extensive research on a method for producing a sputtering copper target material in which many (111) and (200) planes are oriented and the crystal grain size becomes coarse. According to the conventional manufacturing method, the casting process, the hot rolling process, the cold rolling process, and the heat treatment process are performed. In such a manufacturing method using the conventional technique, the method of orienting the (220) plane in the cold rolling step and orienting the (111) plane in the subsequent heat treatment step causes sufficient crystal grain coarsening. There wasn't. On the other hand, by adjusting the temperature and thickness reduction rate (working degree) in the hot rolling process, the (111) plane and the (200) plane have a high orientation ratio without going through the cold rolling process or heat treatment process. It was found that a crystal structure with a coarse grain size was obtained.

  The present invention is based on such knowledge 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 into a rectangular flat plate type (planar type) having a predetermined thickness, width and length, for example, and is an electrode such as a thin film transistor (TFT) used for a liquid crystal display device, for example. It is configured to be used for forming a pure copper sputtering film to be a wiring.

  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.

  The orientation ratio of the rolled surface (rolled surface) of the sputtering copper target material 10, that is, the (111) plane in the sputtering surface is, for example, 13% or more and 30% or less, more preferably 17% or more. The orientation ratio of the (200) plane is, for example, 15% or more and 30% or less. 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 (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 crystal plane described in JCPDS, respectively. The ratio is 100%.

  Moreover, the average crystal grain diameter of the copper target material 10 for sputtering is 0.07 mm or more and 0.20 mm or less, for example, More preferably, it is 0.10 mm or more. Further, the upper limit value may be 0.15 mm or less for the reason described later. 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, the orientation ratio of the (111) plane is, for example, 13% or more and 30% or less, the orientation ratio of the (200) plane is, for example, 15% or more and 30% or less, and the average crystal grain size is, for example, 0. By using the sputtering copper target material 10 having a thickness of 0.07 mm or more and 0.20 mm or less, copper sputtering particles having high kinetic energy are easily released. Therefore, a high sputtering rate can be obtained. The sputtering rate is preferably 3 g / h or more and 5 g / h or less when the input power density is 12.7 W / cm ² in an Ar atmosphere of 0.5 Pa, for example. As described above, by setting the (111) plane orientation ratio to 17% or more and the average crystal grain size to 0.10 mm or more, the sputtering rate can be more reliably kept within such a range. .

  The (111) plane and the (200) plane are crystal planes with a high atom packing density. Therefore, it is considered that atoms are easily knocked out by collision of ions in the discharge plasma, that is, they are easily sputtered and a high sputtering rate can be obtained. The crystal grain boundary is a defect portion in the crystal structure and absorbs collision energy when ions collide. Like the copper target material 10 for sputtering, since the crystal grain boundary is smaller as the crystal grain is coarser, it is considered that the absorption of collision energy is suppressed and the loss of energy consumed for sputtering is reduced. Therefore, a high sputtering rate can be obtained also by setting the coarse particle diameter.

  As a result, sputtered particles with high kinetic energy are released, and migration on the reached film and placement at appropriate crystal lattice positions occur. Therefore, even on a film containing a refractory metal such as Ti or molybdenum (Mo), a pure copper sputtering film having a resistivity of less than 2.0 μΩcm immediately after the film formation 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 this embodiment, the manufacturing method which mainly performs a casting process and a hot rolling process in this order is taken.

  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, a hot rolling process is performed as a high temperature processing process. That is, for example, a copper ingot heated at a temperature of 800 ° C. or higher and 900 ° C. or lower is rolled into a copper plate (hot rolling). In the hot rolling process, the hot rolling may be performed in one process, or the process may be performed in a plurality of times. At this time, the temperature of the copper plate after passing the final pass, that is, at the end of rolling is set to be 600 ° C. or higher and 700 ° C. or lower. Also, at the end of rolling, the thickness reduction rate is 85% or more and 95
% So that it is below%. The thickness reduction rate (working degree) is defined by the following equation (3).
Thickness reduction rate (%) = ((plate thickness before processing−plate thickness after processing) / plate thickness before processing) × 100 (3)

  The surface oxide layer (black skin) of the hot-rolled copper plate is removed (peeled) to a predetermined thickness.

  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 this embodiment, the hot rolling process is performed at 800 ° C. or more and 900 ° C. or less, and the thickness reduction rate is 85% or more and 95% or less. By such a rolling process, the (220) plane can be oriented. Further, the heating temperature in the hot rolling process is set to a high temperature of 800 ° C. or higher, and the temperature of the copper plate at the end of rolling is kept within the above-described predetermined value, whereby a crystal structure with a high orientation rate of the (111) plane is obtained. Along with the recrystallization, a predetermined amount of (200) plane also appears. Further, the grain growth is promoted, and the crystal grains can be coarsened. In order to coarsen the crystal grains, it is also effective to keep the thickness reduction rate low. Moreover, the oxidation of a copper ingot can be controlled by making heating temperature 900 degrees C or less, and the workability | operativity at the time of manufacture can be ensured.

  Initially, the present inventors have adopted a manufacturing method that has undergone a casting process, a hot rolling process, a cold rolling process, and a heat treatment process as usual. And then, by recrystallization in a heat treatment process at a relatively low temperature of about 400 ° C., it was found that the (220) plane oriented in the cold rolling process decreased and oriented to the (111) plane. Further, the higher the thickness reduction rate in the cold rolling process, the finer the crystal grains, although the orientation rate of the (111) plane increases. From this, the present inventors tried various combinations of the cold rolling process and the heat treatment process to obtain a crystal structure having a high (111) plane orientation ratio and coarse crystal grains. However, in the heat treatment process, although the orientation to the (111) plane was observed, only a crystal grain size up to about 0.10 mm was obtained. Grain growth was attempted at a high temperature of about 500 ° C. to 700 ° C. in the heat treatment process, but no coarsening of 0.10 mm or more occurred even by such a technique.

  The driving force for recrystallization is mainly caused by strain applied in the cold rolling process. This strain accumulates mainly at grain boundaries. In the heat treatment step, recrystallization proceeds with a grain boundary having accumulated strain as a starting point (nucleus). When the thickness reduction rate in the cold rolling process is increased so as to obtain a large number of (111) planes, a large number of nuclei serving as starting points for recrystallization are generated, and the grain size after recrystallization becomes fine. In addition, grain growth in the heat treatment process also occurs using this strain as a driving force. Once the strain is released by the heat treatment, no further grain growth occurs. Also from this, it is considered that the particle size of about 0.10 mm is the limit in the method by adjusting the cold rolling process and the heat treatment process as described above.

  In this embodiment, by rolling the copper ingot heated at a high temperature in a hot rolling process at a predetermined thickness reduction rate based on the knowledge obtained by further efforts by the present inventors ( 220) The plane was oriented. On the other hand, since the predetermined heat remains even after the hot rolling process ends, recrystallization and grain growth of the (111) plane are promoted, and the orientation ratio of the (111) plane and the (200) plane is high, A copper target material 10 for sputtering having a coarse particle diameter 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.

  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 having a cooling mechanism such as water cooling (not shown) is provided at the bottom in the vacuum chamber 21, and a backing plate (not shown) to which, for example, a sputtering copper target material 10 is bonded is held. Thus, the Cu—Mn alloy sputtering target material 10 is held with the sputtering surface facing upward so as to face the film formation 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, the sputtering copper target material 10 is grounded (grounded), and a positive high voltage is applied to the substrate S. DC discharge power (DC power) is applied to the vacuum chamber 21 so that is applied.

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.

  During this time, the sputtering copper target material 10 is cooled by water cooling or the like via the backing plate, and an unnecessary temperature rise can be suppressed.

  Thus, the sputtering film M made of pure copper is formed on the substrate S.

  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.

Sputtering is a phenomenon in which Ar ⁺ ions and the like in the discharge plasma collide with the surface of the target material, and bonds between atoms constituting the target material are broken and atoms are released. 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. In other words, it is considered that the higher the erosion rate of the sputtering copper target material, the higher the kinetic energy sputtering particles are released.

  The erosion rate of the sputtering copper target material 10, that is, the amount per unit time of the sputtered particles P emitted from the sputtering copper target material 10 is the sputtering rate (g / h) according to this embodiment. is there. Further, the deposition rate of the released sputtered particles P on the substrate S, that is, the deposition rate (nm / min) of the sputtering film M has a relationship corresponding to the sputtering rate (g / h), and is in principle. Should correlate with this.

  As a result of intensive research by the present inventors, in this embodiment, there was a tendency for atoms to be easily released, and the (111) plane orientation ratio obtained at a high sputtering rate, followed by a high sputtering rate. The copper target material 10 for sputtering having a high (200) plane orientation ratio is used. Similarly, it has a crystal structure including a large number of coarse crystal grains with a high sputtering rate. As a result, sputtered particles P with high kinetic energy are released and deposited on the film, and migration to an appropriate crystal lattice position is caused on the film to provide pure copper with good crystallinity and low resistivity. The sputtering film M can be obtained.

At this time, the sputtering rate of the sputtering copper target material 10 is preferably 3 g / h or more when the input power density is 12.7 W / cm ² in an Ar atmosphere of 0.5 Pa, for example. As described above, the sputtering film M having excellent crystallinity and low resistivity can be obtained by increasing the sputtering rate. Further, since there is a demand for shortening the tact time for forming electrode wiring such as TFT, it is preferable that the sputtering rate can be increased and the deposition rate of the sputtering film M can be maintained at a high speed.

  On the other hand, the following two states exceeding 5 g / h were verified, and it was found that the sputtering rate was preferably 5 g / h or less.

  The state in which the sputtering rate exceeds 5 g / h can be obtained experimentally, for example, by increasing the DC discharge power (input power density). Under such conditions, abnormal discharge (arcing) during sputtering is likely to occur. It is considered that the arcing frequency increased because the emission density of the sputtered particles increased.

  A state in which the sputtering rate exceeds 5 g / h can also be obtained by making the crystal grains in the target material coarser. In order to increase the size of the crystal grains, for example, the hot rolling process is performed at a higher temperature and a higher thickness reduction rate. For example, under conditions where the temperature is 900 ° C. and the thickness reduction rate exceeds 100%, a target material that is coarser and has a higher (111) plane or (200) plane orientation ratio can be obtained. The sputtering rate also exceeded 5 g / h, and as a result, arcing during sputtering was observed.

  From the above, by setting the sputtering rate to 5 g / h or less, arcing or the like during sputtering hardly occurs, and foreign matter (particles) on the sputtering apparatus 20 or the sputtering film M can be reduced.

Moreover, it is also the same viewpoint that the upper limit as mentioned above was provided to the average crystal grain size of the crystal grains in the copper target material for sputtering. That is, as described above, the sputtering rate can be increased as the average crystal grain size is larger, but arcing is likely to occur. Further, for example, in a crystal structure having an average crystal grain size of more than 0.20 mm, recrystallization of a fine (111) plane occurs, and a mixed grain state is likely to occur. For this reason, sputtering speed becomes non-uniform | heterogenous and the target material surface erosion tends to become non-uniform | heterogenous. It is considered that arcing due to excessive increase in the average crystal grain size is caused by such a cause. Therefore, as described above, the occurrence of arcing can be suppressed by setting the average crystal grain size to 0.20 mm or less, or 0.15 mm or less.

  As described above, at present, a considerable improvement has been observed with respect to harmful effects such as arcing and particles by 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 equipped with a rectangular target material serving as a cathode electrode is used, a stable plasma is generated by alternating current (AC) sputtering in which an alternating current power source is loaded between adjacent cathode electrodes, and arcing, etc. It is also possible to suppress the occurrence.

  In the sputtering apparatus 20 described above, measures against particles are also taken by arranging the sputtering copper target material 10 below the apparatus and the substrate S with the film-forming surface facing down. With such an arrangement, it is possible to reduce the influence of particles generated from arcing or an apparatus. However, the sputtering copper target material 10 is used by being mounted on various types of sputtering devices such as a device in which the vertical position of the target material and the substrate is reversed, or a device in which the target material and the substrate are vertically opposed to each other. be able to.

  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. According to the present invention, an effect of further reducing the resistivity can be obtained not only on a film containing a refractory metal but also on a sputtering film formed on, for example, a glass substrate. For example, in a TFT, an electrode wiring including a gate electrode is formed on a glass substrate. The present invention can also be applied to such a case.

(1) Evaluation of Sputtering Copper Target Material Next, the evaluation results of the sputtering copper target material according to Examples 11 to 19 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, from this copper ingot, by adjusting the temperature and thickness reduction rate in the hot rolling process, the copper target material for sputtering according to Example 11 was prepared without performing the cold rolling process or the heat treatment process. Produced. That is, the copper ingot was heated in a heating furnace maintained at 850 ° 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 22 mm. The temperature of the copper plate at the end of rolling was 670 ° C., and the thickness reduction rate was 85.3%. The copper oxide material for sputtering according to Example 11 was obtained by removing the surface oxide layer of the copper plate to a thickness of 20 mm.

  Moreover, the copper target material for sputtering according to Examples 12 to 19 was changed by variously changing the temperature and thickness reduction rate of the hot rolling step within the above-described predetermined values in the same manner and procedure as in Example 11. Was also produced.

  In addition, as initially studied by the inventors, as an example of adjusting the cold rolling step and the heat treatment step to try to increase the orientation ratio of the (111) plane and increase the crystal grain size, the above copper A sputtering copper target material according to Comparative Example 11 was produced from the ingot. 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 described above. After removing the surface oxide layer, in the cold rolling process, the copper plate was thinned to a thickness of 30 mm (thickness reduction rate: 50%) and recrystallized at a temperature of 400 ° C. or less in the heat treatment process. Then, the bending of the copper plate was corrected with a straightening machine, and cutting was performed by milling to obtain a copper target material for sputtering according to Comparative Example 11 having a final thickness of 20 mm.

  Moreover, the copper target material for sputtering which concerns on the comparative examples 15 and 16 is variously changed by the method and procedure similar to the above-mentioned comparative example 11, changing the temperature of a hot rolling process, and the thickness reduction rate of a cold rolling process. Produced together. In addition, using a technique that does not perform the cold rolling process and the heat treatment process as in the above-described embodiment, the temperature and thickness reduction rate of the hot rolling process are variously changed to include values outside the above-described predetermined value range. And the copper target material for sputtering which concerns on other comparative examples 12-14 was manufactured.

  In Table 1 below, conditions at the time of manufacturing the copper target material for sputtering according to Examples 11 to 19 are shown together with Comparative Examples 11 to 16. In the table, values that deviate from the predetermined value are shown in bold underlined. In Comparative Examples 11, 15, and 16, since the target material was manufactured by a completely different method from that of the Example, the description of the conditions in the hot rolling process was omitted.

(Evaluation of crystal structure)
Each block material was cut out from the sputtering copper target material before machining, and the orientation ratio and average crystal grain size of each crystal plane were measured for the crystal structure of the rolled surface corresponding to the sputtering surface.

  First, X-ray diffraction measurement was performed on each of the above-described block materials, and the orientation rate of each crystal plane on the sputtering surface was examined. That is, the peak intensities of the (111) plane, (200) plane, (220) plane, and (311) plane were measured by X-ray diffraction, and the relative peak peaks of the crystal planes corresponding to these crystal planes described in JCPDS Using the strength, the orientation ratios of the (111) plane and the (200) plane were determined from the above formulas (1) and (2).

  Similarly, for each block material, the average crystal grain size was measured based on the “comparison method” of the “copper grain size test method” defined in JIS H0501. That is, the average crystal grain size was identified by comparing a standard photograph published in JIS H0501 with a photograph of the crystal structure of each block material.

(Sputtering evaluation)
Next, the sputtering rate and the number of arcing of the sputtering copper target materials according to Examples 11 to 19 and Comparative Examples 11 to 16 were measured by the following methods.

  That is, in order to adapt to the sputtering experimental machine 120 shown in FIG. 2, first, the copper target material for sputtering according to the above-described Examples 11 to 19 and Comparative Examples 11 to 16 is machined to have a thickness of 5 mm and a diameter of 5 mm. Cut into a 100 mm circle. Next, each of the circular copper target materials for sputtering was mounted on a DC discharge type sputtering experimental machine 120 having substantially the same function as the sputtering apparatus 20 according to the above-described embodiment. As shown in FIG. 2, an arcing detection device system 30 is connected to the sputtering experimental machine 120. Subsequently, sputtering was performed on each sputtering copper target material under the conditions shown in Table 2 below.

As shown in Table 2, the inside of the vacuum chamber was set to an Ar atmosphere of 0.5 Pa, and 1 kW of DC discharge power was applied to a target material having a diameter of 100 mm. That is, the input power density is 12.7 W / cm ² . When the total sputtering time was 2 hours, the amount of decrease in the mass of each sputtering copper target material was measured, and the sputtering rate (g / h) was calculated.

  Moreover, the number of times of arcing was measured by the above-described detection apparatus system 30 during the above-described sputtering.

  Specifically, as shown in FIG. 2, a substrate holding unit is provided by a detector 31 provided between a substrate holding unit 122 s serving as a substrate electrode and an output side of a DC power supply 124 connected to the substrate holding unit 122 s. A current and a voltage applied between 122 s and a target holding portion 122 t that is opposed to the substrate holding portion 122 s and serves as a cathode electrode were detected. The detected current and voltage were monitored by an arc monitor 32 controlled by a control unit 33 comprising a computer or the like to determine whether or not arcing occurred and the number of arcing occurrences was measured.

(Measurement result of copper target material for sputtering)
FIG. 3 shows a part of the measurement results of Examples 11, 16, and 17 and Comparative Examples 11, 15, and 16 manufactured by the prior art among the Examples and Comparative Examples. The horizontal axis of the graph of FIG. 3 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 solid line, the data of Example 16 is indicated by □ and solid line, and the data of Example 17 is indicated by Δ mark and solid line. Further, the data of Comparative Example 11 is indicated by x and broken lines, the data of Comparative Example 15 is indicated by * and broken lines, and the data of Comparative Example 16 is indicated by ◯ and broken lines. In the table above the graph, numerical values of average crystal grain size (mm), orientation ratio (%) of each crystal plane, and sputtering rate (g / h) are shown. In the table of FIG. 3, values that deviate from the predetermined value are shown in bold underlined.

  As shown in FIG. 3, the average crystal grain sizes of Examples 11, 16, and 17 are within the above-described predetermined values, and are coarser than the average crystal grain sizes of Comparative Examples 11, 15, and 16. . In addition, the orientation ratio of the (111) plane is high. For this reason, all of Examples 11, 16, and 17 are easier to be sputtered than Comparative Examples 11, 15, and 16, and the sputtering rate is higher. Therefore, it is expected that the kinetic energy of the sputtered particles is also high.

  In Example 16 and Comparative Example 15 having the same particle diameter, the orientation rate of the (111) plane is higher in Example 16, and this sufficiently exhibits the effect of increasing the sputtering rate. In the present embodiment, since a process at a higher temperature than in the prior art is performed, a high (111) plane orientation ratio is easily obtained even with the same particle size.

  Table 3 below shows all data of Examples 11 to 19 and Comparative Examples 11 to 16. In the table, values that deviate from the predetermined value are shown in bold underlined.

(2) Evaluation of Pure Copper Sputtering Film Next, evaluation results of the pure copper sputtering film according to Examples 21 to 29 of the present invention will be described together with Comparative Examples 21 to 26.

(Production of evaluation samples)
Evaluation samples according to Examples 21 to 29 and Comparative Examples 21 to 26 were manufactured using the copper target materials for sputtering according to the above Examples 11 to 19 and Comparative Examples 11 to 16, respectively. In each evaluation sample, as shown in FIG. 4, pure copper sputtering films 53 g and 53 t are formed on a glass substrate 51 or a Ti film 52 so as to be divided into a plurality of sections in a lattice shape.

  That is, each sputtering copper target material cut out in a circular shape was mounted on a sputtering experimental machine 120 similar to the above-described example. Subsequently, film formation by sputtering was performed on the glass substrate 51 or the Ti film 52, respectively.

  The evaluation samples according to Examples 21g to 29g and Comparative Examples 21g to 26g shown in FIGS. 4A1 and 4A2 are for sputtering according to Examples 11 to 19 and Comparative Examples 11 to 16, respectively, on a glass substrate 51. It has a pure copper sputtering film 53g formed using a copper target material. 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 4 below shows film forming conditions by sputtering.

  The evaluation samples according to Examples 21t to 29t and Comparative Examples 21t to 26t shown in FIGS. 4B1 and 4B2 are the Examples 11 to 19 and Comparative Example, respectively, on the Ti film 52 formed on the glass substrate 51. The pure copper sputtering film | membrane 53t formed into a film using the copper target material for sputtering which concerns on 11-16 is provided. 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 lattice. 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 5 below shows film forming conditions by sputtering.

(Measurement of deposition rate of evaluation sample)
Using each of the above evaluation samples, the deposition rates of the pure copper sputtering films 53g and 53t on the glass substrate 51 and the Ti film 52 were measured.

  First, using the evaluation samples according to Examples 21g to 29g and Comparative Examples 21g to 26g, the film thickness of the pure copper sputtering film 53g was measured. The film thickness was measured by measuring the level difference between each section of the pure copper sputtering film 53g divided into a lattice and the glass substrate 51 using a Keyence Color 3D laser microscope VK-8700. Further, from the measured film thickness, the deposition rate of the pure copper sputtering film 53g on the glass substrate 51 was 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.

  Subsequently, using the evaluation samples according to Examples 21t to 29t and Comparative Examples 21t to 26t, the step between the pure copper sputtering film 53t and the Ti film 52 was measured as in the case of the glass substrate 51 described above. Thereby, the film thickness obtained was divided by the film formation time of 3 minutes, and the film formation speed of the pure copper sputtering film 53t on the Ti film 52 was determined.

(Resistivity measurement of evaluation sample)
Next, the resistivity of the pure copper sputtering films 53g and 53t on the glass substrate 51 and the Ti film 52 was measured using each evaluation sample described above.

  That is, using the evaluation samples according to Examples 21g to 29g and Comparative Examples 21g to 26g, the sheet resistance of the pure copper sputtering film was measured to determine the resistivity of the pure copper sputtering film 53g on the glass substrate 51.

  As a method for measuring the sheet resistance, a van der Pauw method in which electrode needles are applied 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 53g, was used. The resistivity was obtained by multiplying the sheet resistance by the film thickness of the pure copper sputtering film 53g measured by the same method as described above.

  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 as described above by the film thickness measured with the laser microscope described above, and was used as the resistivity of the pure copper sputtering film 53 g on the glass substrate 51.

  Subsequently, using the evaluation samples according to Examples 21t to 29t and Comparative Examples 21t to 26t, the sheet resistance of the pure copper / Ti laminated film (film thickness is 300 nm / 50 nm) is measured as in the case of the glass substrate 51 described above. The resistivity of the pure copper sputtering film 53t on the Ti film 52 was obtained. According to such a measuring method, the conduction to the underlying Ti film 52 is also taken into account, but the resistivity of Ti is one digit or more higher than that of pure copper. The Ti film 52 is thinner than the pure copper sputtering film 53t. For this reason, it is considered that the influence on the resistivity of the Ti film 52 is small. In addition, by comparing the values of the respective examples and comparative examples relative to each other, it is possible to determine superiority or inferiority among the values of the pure copper sputtering film 53t on the Ti film 52.

  For the pure copper sputtering film 53t on the Ti film 52, the resistivity before and after the heat treatment was obtained. About heat processing, it performed at several temperature in the range of 200 to 300 degreeC which a pure copper sputtering film | membrane can receive in the manufacture process of TFT with respect to the evaluation sample which concerns on Examples 21t-29t and Comparative Examples 21t-26t.

(Measurement result of evaluation sample)
As described above, the resistivity is one of the physical property values of the pure copper sputtering films 53g and 53t, and a low value is exhibited when the pure copper sputtering films 53g and 53t have few defects such as voids and good crystallinity. In addition, the minimum resistivity as a bulk material of pure copper is 1.67 μΩcm. Based on this, the measurement results of Examples 21t, 26t, and 27t and Comparative Examples 21t, 25t, and 26t shown in FIG. 5 will be described below.

  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, data of Example 21t is indicated by ◇ and solid line, data of Example 26 is indicated by □ and solid line, and data of Example 27 is indicated by Δ mark and solid line. Further, the data of Comparative Example 21t is indicated by x and broken lines, the data of Comparative Example 25 is indicated by * and broken lines, and the data of Comparative Example 26 is indicated by o and broken lines.

As shown in FIG. 5, even in the state without heat treatment immediately after film formation (As depo.), Example 21t showed a lower resistivity than Comparative Example 21t. In Example 21t, it can be seen that even on the Ti film 52, a purely crystalline pure copper sputtering film 53t is obtained. In both cases, the resistivity decreased after the heat treatment at 200 ° C. to 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. Similar results were obtained for other Examples 26 and 27 and Comparative Examples 25 and 26.

  FIG. 6 shows all data of Examples 21t to 29t 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 6 below shows all data of Examples 21 to 29 and Comparative Examples 21 to 26.

  As described above, the sputtering copper target material according to Example 11 was manufactured under the conditions within the predetermined value range. Moreover, the copper target material for sputtering which concerns on Examples 12-19 was manufactured on the conditions within the above-mentioned predetermined value about the temperature and thickness reduction rate in a hot rolling process on the basis of the manufacturing conditions of Example 11. (See Table 1). Therefore, in the evaluation samples according to Examples 21 to 29 manufactured using Examples 11 to 19, respectively, good results were obtained in any measurement as shown in Table 6.

  According to this result, not only the pure copper sputtering film 53t having a low resistivity was obtained on the Ti film 52, but also the effect of reducing the resistivity of the pure copper sputtering film 53g on the glass substrate 51 was recognized. Such an effect is that the resistivities of Examples 21 to 29 are lower than the resistivities of the pure copper sputtering film 53g on the glass substrate 51 in Comparative Examples 21 to 26 to be described later, excluding the Comparative Example 24. It is clear from that.

On the other hand, the copper target material for sputtering according to Comparative Examples 11, 15, and 16 was manufactured through all steps of a casting process, a hot rolling process, a cold rolling process, and a heat treatment process (see Table 1). In these copper target materials for sputtering, a plurality of values among the orientation ratio of the (111) plane and the (200) plane, the average crystal grain size, and the sputtering rate do not satisfy predetermined conditions (see Table 3). Therefore, in the evaluation samples according to Comparative Examples 21, 25, and 26 manufactured using Comparative Examples 11, 15, and 16, respectively, as shown in Table 6, the pure copper sputtering film 53g on the glass substrate 51 and the Ti film 52 is obtained. , 53t, the resistivity was higher than that of the above-described embodiment.

  Moreover, although the copper target material for sputtering which concerns on the comparative example 12 has the temperature of a hot rolling process higher than the above-mentioned predetermined value (refer Table 1) and a coarse crystal grain size was obtained, (111) plane or ( The orientation rate of the (200) plane was low and the sputtering rate was also low (see Table 3). Therefore, in the evaluation sample according to the comparative example 22 manufactured using the comparative example 12, as shown in Table 6, the above-described pure copper sputtering films 53g and 53t on the glass substrate 51 and the Ti film 52 have the above-described characteristics. As a result, the resistivity was higher than that of the example. From this, when the temperature in the hot rolling process is high, grain growth is likely to occur, but processing strain is difficult to enter, and recrystallization to the (111) plane or the (200) plane is unlikely to occur. Conceivable.

  Moreover, the copper target material for sputtering according to Comparative Example 13 has a temperature of the hot rolling process lower than the above-described predetermined value (see Table 1) and a high orientation ratio of the (111) plane, but the crystal grain size is fine, The sputtering rate was also low (see Table 3). Therefore, in the evaluation sample according to the comparative example 23 manufactured using the comparative example 13, as shown in Table 6, the pure copper sputtering films 53g and 53t on the glass substrate 51 and the Ti film 52 are both in the above-described manner. As a result, the resistivity was higher than that of the example.

  Moreover, while the copper target material for sputtering which concerns on the comparative example 14 had the temperature and thickness reduction rate of a hot rolling process higher than the above-mentioned predetermined value (refer Table 1), coarse crystal grain size was obtained, ( The orientation ratio of the (111) plane and the (200) plane was high (see Table 3). Therefore, in the evaluation sample according to the comparative example 24 manufactured using the comparative example 14, as shown in Table 6, the pure copper sputtering films 53g and 53t on the glass substrate 51 and the Ti film 52 are both in the above-described manner. A low resistivity comparable to the example was obtained.

  However, in the sputtering copper target material according to Comparative Example 14, the sputtering rate exceeded a predetermined value, resulting in high arcing frequency (see Table 3). Therefore, even if the obtained pure copper sputtering film 53 has a low resistance, there is a concern about particles when the film is formed. Such a copper target material for sputtering is not a preferable configuration.

  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 a sputtering film having good crystallinity with a speed 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 device 30 Arcing detection device system 51 Glass substrate 52 Ti film 53g, 53t Pure copper sputtering film

Claims (5)

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 15% or more and 30% or less,
The orientation ratio of (220) plane in the sputtering surface is 31% or more and 37% or less,
The orientation ratio of the (311) plane in the sputtering plane is 19% or more and 32% or less,
A copper target material for sputtering, wherein an average crystal grain size is 0.07 mm or more and 0.20 mm or less.
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 crystal plane described in JCPDS This is the ratio when the total value of the values divided by the relative intensities of the peak of the crystal plane to be taken is 100%. When the sputtering conditions were such that the input power density was 12.7 W / cm ² under an Ar atmosphere of 0.5 Pa,
2. The copper target material for sputtering according to claim 1, wherein the sputtering rate is 3 g / h or more and 5 g / h or less. The orientation ratio of the (111) plane in the sputtering surface is 17% or more,
The copper target material for sputtering according to claim 1 or 2, wherein the average crystal grain size is 0.10 mm or more. The said average crystal grain diameter is 0.15 mm or less, The copper target material for sputtering in any one of Claims 1-3 characterized by the above-mentioned. 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,
In the hot rolling process,
The copper ingot heated to 800 ° C. or more and 900 ° C. or less is hot-rolled so that the thickness reduction rate is 85% or more and 95% or less, and the temperature of the copper plate at the end of rolling is 600 ° C. or more and 700 ° C. or less. The manufacturing method of the copper target material for sputtering characterized by the above-mentioned.

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