JP2013057112A - Cylindrical sputtering target material, and wiring board and thin film transistor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equalize the speed of sputtering a cylindrical sputtering target material from an outer peripheral surface from an inner peripheral surface thereof.SOLUTION: The cylindrical sputtering target material 20 has a cylindrical shape, and is formed from oxygen-free copper having a purity of 3N level or higher. The hardness of the target material gradually increases from the outer peripheral surface 21 to the inner peripheral surface 22, and the orientation rate of a (111) surface gradually increases from the outer peripheral surface 21 to the inner peripheral surface 22.

Description

  The present invention relates to a cylindrical sputtering target material having a cylindrical shape, a wiring substrate having a sputtering film formed using the cylindrical sputtering target material, and a thin film transistor.

  2. Description of the Related Art In recent years, thinning of thin film transistor (TFT) array wiring has been required for high definition liquid crystal display devices such as large display panels. As such a wiring material, copper (Cu) having a low electrical resistivity is becoming the mainstream instead of conventionally employed aluminum (Al).

  The fine copper wiring on the thin film transistor substrate is formed by sputtering, for example. At that time, in a widely used disk-shaped or square-plate-type planar sputtering target material, erosion locally progresses, so that the utilization factor of the target material is very low, about 30% to 40%. is there.

  Therefore, recently, a cylindrical sputtering target material that performs sputtering while rotating the target material has been used. Thereby, since erosion progresses on the entire surface of the target material, the utilization factor of the target material is 60% or more, which is a value that is significantly higher than that of the planar type.

  As a method for producing a cylindrical sputtering target material, for example, a method of forming a molybdenum (Mo) alloy material into a cylindrical shape by spinning (see, for example, Patent Document 1), or a cylindrical ceramic firing on the outer peripheral surface of a cylindrical base material. A method (for example, refer to Patent Document 2) for joining a target material composed of a bonded body has been proposed.

JP 2007-302981 A JP 2008-184627 A

  For example, a cylindrical sputtering target material using copper can be manufactured at a lower cost by using a tube drawing process or the like instead of the method of Patent Document 1 or Patent Document 2 having a high production cost.

  However, when a cylindrical sputtering target material is manufactured by pipe drawing, the hardness gradually increases from the outer peripheral surface side to the inner peripheral surface side, and the sputter speed on the inner peripheral surface side is slower than the outer peripheral surface side. There is a problem of becoming.

  An object of the present invention is to provide a cylindrical sputtering target material capable of uniforming the sputtering rate from the outer peripheral surface side to the inner peripheral surface side, a wiring substrate using the same, and a thin film transistor.

According to the first aspect of the present invention, a cylindrical sputtering target material formed of oxygen-free copper having a purity of 3N or more and having a cylindrical shape, the hardness gradually increases from the outer peripheral surface side toward the inner peripheral surface side. There is provided a cylindrical sputtering target material that increases and gradually increases the orientation ratio of the (111) plane from the outer peripheral surface side toward the inner peripheral surface side.

  According to the second aspect of the present invention, even if the thickness of the cylindrical sputtering target material is gradually reduced by using the cylindrical sputtering target material, the outer peripheral surface side is set so that the sputtering speed of the cylindrical sputtering target material is constant. The decrease in the sputtering rate of the cylindrical sputtering target material due to the gradual increase in hardness from the outer peripheral surface side toward the inner peripheral surface side, and the orientation of the (111) plane from the outer peripheral surface side toward the inner peripheral surface side A cylindrical sputtering target material according to the first aspect is provided, which is configured to cancel out an increase in the sputtering rate of the cylindrical sputtering target material due to a gradual increase in rate.

  According to the third aspect of the present invention, the hardness is Vickers hardness, the Vickers hardness on the outer peripheral surface side is 75 HV or higher and 80 HV or lower, and the Vickers hardness on the inner peripheral surface side is 95 HV or higher. A cylindrical sputtering target material according to the first or second aspect of 100 HV is provided.

  According to the fourth aspect of the present invention, the orientation ratio of the (111) plane on the outer peripheral surface side is 10% or more and 15% or less, and the orientation ratio of the (111) plane on the inner peripheral surface side is 20%. The cylindrical sputtering target material in any one of the 1st-3rd aspect which is% -25% is provided. However, the orientation ratio of the (111) plane is the sum of values obtained by dividing the measured intensity of each peak by X-ray diffraction by the standard intensity of the peak of the crystal plane corresponding to each peak described in JCPDS card number 40836. Is a value obtained from an equation using the value obtained by dividing the measured intensity of the (111) plane peak by X-ray diffraction by the standard intensity of the (111) plane peak described in JCPDS card number 40836 as a numerator. .

  According to the 5th aspect of this invention, the cylindrical sputtering target material in any one of the 1st-4th aspect which has a crystal grain diameter in the range of 50 micrometers or more and 100 micrometers or less is provided.

  According to the 6th aspect of this invention, the cylindrical sputtering target material in any one of the 1st-5th aspect formed by giving a pipe expansion drawing process and heat processing to an extrusion element pipe is provided.

  According to a seventh aspect of the present invention, there is provided a substrate and a wiring structure formed on the substrate, and at least a part of the wiring structure is a cylindrical sputtering target material according to the first aspect. There is provided a wiring board made of a sputtering film formed by using the material.

  According to an eighth aspect of the present invention, there is provided a substrate, and a wiring structure formed on the substrate and including a source electrode and a drain electrode, wherein at least a part of the wiring structure is the first aspect. The thin film transistor which consists of a sputtering film | membrane formed using the cylindrical sputtering target material as described in 1 is provided.

  According to the present invention, it is possible to make the sputtering rate uniform from the outer peripheral surface side to the inner peripheral surface side of the cylindrical sputtering target material.

It is a figure which shows the cylindrical sputtering target material which concerns on one Embodiment of this invention, Comprising: (a) is a perspective view of a cylindrical sputtering target material, (b) is a cross-sectional view of a cylindrical sputtering target material. . It is sectional drawing which shows the mode of the pipe expansion drawing process which manufactures the cylindrical sputtering target material which concerns on one Embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing which shows the mode of sputtering using the cylindrical sputtering target material which concerns on one Embodiment of this invention, (a) is a perspective view of the sputtering device with which the cylindrical sputtering target material was mounted | worn, (B) is a cross-sectional view of a cylindrical sputtering target material. It is a schematic sectional drawing of the thin-film transistor which concerns on one Embodiment of this invention. It is sectional drawing which shows the measurement position of the evaluation sample of the cylindrical sputtering target material which concerns on Examples 1-5 of this invention, and Comparative Examples 1-4.

  As described above, for example, in a cylindrical sputtering target material manufactured by tube drawing, the inner peripheral surface side is harder than the outer peripheral surface side, and thereby the inner peripheral surface side sputtering rate is slower than the outer peripheral surface side. There is a problem of becoming.

  In order to solve the above problems, the present inventors have come up with the idea that the (111) plane, which is the close-packed plane of copper (Cu), has a crystal orientation in which copper atoms are likely to jump out by sputtering. . That is, an attempt was made to distribute the orientation ratio of the (111) plane with a substantially constant increase amount from the outer peripheral surface side to the inner peripheral surface side of the cylindrical sputtering target material. As a result, it has been found that the sputtering rate is comparable between the inner peripheral surface side having a high (111) plane orientation ratio and high hardness and the outer peripheral surface side having a low (111) plane orientation ratio and low hardness.

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

<One Embodiment of the Present Invention>
(1) Cylindrical Sputtering Target Material A cylindrical sputtering target material according to an embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a view showing a cylindrical sputtering target material 20 according to the present embodiment, where (a) is a perspective view of the cylindrical sputtering target material 20, and (b) is a crossing of the cylindrical sputtering target material 20. FIG.

  As shown in FIG. 1, the cylindrical sputtering target material 20 is a metal sputtering target material having a cylindrical shape with both ends open. As an example, the cylindrical sputtering target material 20 has an outer diameter of 100 mm to 200 mm, a wall thickness of 5 mm to 40 mm, and a length in the major axis direction of 200 mm to 5000 mm. The metal constituting the cylindrical sputtering target material 20 is oxygen-free copper (OFC) having a purity of 3N (99.9%) or higher.

  Moreover, the cylindrical sputtering target material 20 has a configuration in which the hardness gradually increases from the outer peripheral surface 21 side toward the inner peripheral surface 22 side. Expressing this in terms of Vickers hardness, the outer peripheral surface 21 side is, for example, 75 HV or more and 80 HV or less, and the inner peripheral surface 22 side is, for example, 95 HV or more and 100 HV or less. The Vickers hardness is a value defined by a ratio between a load of an indenter when a square pyramid diamond indenter having a facing angle of about 136 ° is pushed into a sample surface and a surface area of a depression formed on the sample surface.

  Here, “the hardness gradually increases from the outer peripheral surface 21 side toward the inner peripheral surface 22 side” means that the hardness is distributed in a constant increase amount from the outer peripheral surface 21 side toward the inner peripheral surface 22 side. In addition to this, it includes cases where the amount of increase is not constant, but increases almost uniformly, or where it generally increases moderately.

The cylindrical sputtering target material 20 is configured such that the orientation rate of the (111) plane gradually increases from the outer peripheral surface 21 side toward the inner peripheral surface 22 side. The orientation ratio of the (111) plane is, for example, 10% or more and 15% or less on the outer peripheral surface 21 side, and is, for example, 20% or more and 25% or less on the inner peripheral surface 22 side. The orientation ratio of the (111) plane is a value obtained from the measured intensity ratio of each peak indicating various crystal planes obtained by X-ray diffraction. The measured intensity of each peak is used after being corrected with the standard intensity of the peak of the crystal plane corresponding to each peak, for example. For the standard intensity, for example, a value described in JCPDS card number 40836 is used.

  Specifically, as shown in the following formula (1), values obtained by dividing the measured intensity of each peak by X-ray diffraction by the standard intensity of the peak of the crystal plane corresponding to each peak described in JCPDS card number 40836, respectively. Is a value obtained from an equation using the value obtained by dividing the measured intensity of the (111) plane peak by X-ray diffraction by the standard intensity of the (111) plane peak described in JCPDS card number 40836 as the numerator. Is the orientation rate of the (111) plane.

  Here, the orientation rate of the (111) plane gradually increases from the outer peripheral surface 21 side toward the inner peripheral surface 22 side. The orientation rate of the (111) plane increases from the outer peripheral surface 21 side toward the inner peripheral surface 22 side. In addition to the case where is distributed at a constant increase amount, the case where the increase amount is not constant but increases almost uniformly, or the case where the increase amount increases roughly slowly.

  The cylindrical sputtering target material 20 is configured such that the crystal grain size from the outer peripheral surface 21 side to the inner peripheral surface 22 side is, for example, in the range of 100 μm or less, more preferably 50 μm or more and 100 μm or less. In addition, the said crystal grain diameter is a value calculated | required by the "comparison method" of the "stretched copper product crystal grain size test method" prescribed | regulated to JISH0501.

  The cylindrical sputtering target material 20 configured in this way is desirably manufactured by, for example, pipe expansion drawing as described above, in order to reduce production costs. However, in the pipe expansion drawing process, the hardness gradually increases from the outer peripheral surface 21 side toward the inner peripheral surface 22 side. When the hardness is increased, a collision cascade caused by collision of ions with copper atoms during sputtering, that is, a collision chain of copper atoms is less likely to occur. That is, on the inner peripheral surface 22 side with increased hardness, the movement of copper atoms repelled by ions is hindered by defects such as crystal grain boundaries and dislocations, and the copper atoms are less likely to gather together and hinder collision chains. End up.

  Thereby, in the conventional cylindrical sputtering target material, the subject that the sputtering rate of the inner peripheral surface side became slow compared with the outer peripheral surface side had arisen. Here, the sputtering rate refers to the amount of atoms released from the target material per unit time by ion sputtering or the like. As will be described later, the emission amount of atoms per unit time, that is, the sputtering rate can be represented by the film thickness of a sputtering film formed per unit time, for example.

Therefore, in this embodiment, the orientation rate of the (111) plane of the cylindrical sputtering target material 20 is changed as described above. The (111) plane is a close-packed plane of copper and has a crystal orientation in which copper atoms are likely to jump out of the cylindrical sputtering target material 20 due to ion collision during sputtering. Therefore, on the inner peripheral surface 22 side having higher hardness than the outer peripheral surface 21 side (11
1) By increasing the orientation ratio of the plane, the decrease in the sputtering rate due to the inhibition of the copper atom collision chain can be offset by the increase in the sputtering rate due to the increase in the amount of copper atoms jumping to the outside. That is, the difference in sputtering speed from the outer peripheral surface 21 to the inner peripheral surface 22 can be reduced. Alternatively, a substantially constant sputtering rate can be obtained from the outer peripheral surface 21 to the inner peripheral surface 22, for example, by completely canceling the difference in the sputtering rate.

  In the present embodiment, as described above, the crystal grain size of the cylindrical sputtering target material 20 is set within a predetermined range so that the crystal grains do not become coarse. Experience has shown that when the crystal grain size exceeds 100 μm, abnormal discharge is likely to occur during sputtering. In this embodiment, since the crystal grain size is 50 μm or more and 100 μm or less, abnormal discharge can be suppressed.

(2) Manufacturing method of cylindrical sputtering target material Next, the manufacturing method of the cylindrical sputtering target material 20 which concerns on one Embodiment of this invention is demonstrated using FIG. FIG. 2 is a cross-sectional view showing a state of the tube expansion drawing process for manufacturing the cylindrical sputtering target material 20 according to the present embodiment.

  The cylindrical sputtering target material 20 can be produced from, for example, a copper extruded element tube 9 shown in FIG. The extrusion tube 9 is obtained, for example, by casting a billet (not shown) made of oxygen-free copper having a purity of 3N or higher and molding the billet by a hot extrusion method. At this time, for example, the extruded raw tube 9 is formed into a cylindrical shape having an outer diameter of 140 mm to 160 mm and a thickness of 25 mm to 35 mm.

Subsequently, as shown in FIG. 2, for example, a rod 15 r provided with an end portion of a tube expansion plug 15 p having a tapered cylindrical shape is inserted into the tube of the extruded element tube 9. Next, with the tube expansion plug 15p fixed, the outer diameter is expanded at a tube expansion rate of 5% or more and 15% or less, for example, by pulling out the extruded element tube 9 from the small diameter side to the large diameter side of the tube expansion plug 15p. The expanded tube 10 is obtained. The tube expansion ratio R (%) is expressed by the following equation (2), where D1 (mm) is the outer diameter of the extruded element tube 9 before tube expansion, and D2 (mm) is the outer diameter of the tube 10 after tube drawing. ,
R = ((D2-D1) / D1) × 100 (2)
Is a value obtained by

  Next, heat treatment was applied to the expanded tube 10 after the tube expansion drawing process, for example, at a temperature of 450 ° C. or more and 600 ° C. or less until the whole became a substantially uniform temperature, and subjected to processing strain or the like by the tube expansion drawing process. Recrystallization of the structure of the expanded tube 10 is attempted. Therefore, if the size of the expanded tube 10 is increased, the heat treatment time required for recrystallization becomes longer. Thereafter, the expanded tube 10 is cut out to a predetermined length, and the outer peripheral surface 11 and the inner peripheral surface 12 are subjected to machining such as mirror polishing.

  Thus, the cylindrical sputtering target material 20 is manufactured.

  As described above, in the expanded tube 10 after the expanded tube drawing process, the hardness on the inner peripheral surface 12 side is higher than that on the outer peripheral surface 11 side. This is because, on the inner peripheral surface 12 side, in addition to the tensile stress in the axial direction and the compressive stress in the radial direction, shear stress acts due to friction generated between the tube expansion plug 15p and the inner peripheral surface 12 of the extruded element tube 9. .

  On the other hand, if the tube expansion ratio is increased, it becomes easier to control the structure such as the orientation ratio of the (111) plane and the crystal grain size in the tube expansion 10, and the orientation ratio and crystal grain size of the predetermined (111) plane Is easy to obtain.

Therefore, in this embodiment, the tube expansion rate is set to, for example, 5% or more, and the controllability of the orientation rate of the (111) plane and the crystal grain size is improved. Thereby, the orientation ratio and crystal grain size of a predetermined (111) plane can be obtained. Further, as described above, the tube expansion rate is set to, for example, 15% or less, and the occurrence of cracks due to excessive tube expansion of the tube expansion 10 is suppressed. Such tube expansion cracks are particularly likely to occur on the inner peripheral surface 12 and cause leakage of cooling water or the like supplied into the cylinder of the cylindrical sputtering target material 20 during sputtering, or abnormal discharge during sputtering. .

  Further, in the above heat treatment that promotes recrystallization of the expanded tube 10, sufficient recrystallization does not occur if the temperature of the heat treatment is too low, and coarsening of the crystal grains proceeds if the temperature is too high. In the present embodiment, since the temperature of the heat treatment is set to 450 ° C. or higher, for example, recrystallization can be promoted sufficiently. Moreover, since the temperature is set to 600 ° C. or less, for example, excessive coarsening of crystal grains can be suppressed. Thereby, the crystal grain size can be kept within a predetermined range.

  As described above, in the present embodiment, it is possible to manufacture a high-quality and inexpensive cylindrical sputtering target material 20 that suppresses the difference in sputtering speed while applying pipe expansion drawing processing with low production cost.

(3) Film Forming Method Using Cylindrical Sputtering Target Material Next, a method for forming a sputtering film by sputtering using the cylindrical sputtering target material 20 according to an embodiment of the present invention will be described with reference to FIG. I will explain.

  FIG. 3 is a schematic explanatory view showing a state of sputtering using the cylindrical sputtering target material 20 according to the present embodiment. FIG. 3A is a perspective view of the sputtering apparatus 25 on which the cylindrical sputtering target material 20 is mounted. FIG. 3B is a cross-sectional view of the cylindrical sputtering target material 20. Note that the sputtering apparatus 25 shown in FIG. 3 is merely an example, and the cylindrical sputtering target material 20 can be used by being mounted on various types of sputtering apparatuses.

  As shown in FIG. 3, the sputtering is performed in an atmosphere of an inert gas such as argon (Ar) gas in the sputtering apparatus 25. In the vicinity of the bottom of the sputtering apparatus 25, the substrate S to be deposited is disposed with the surface on which the deposition is performed as the top surface. Note that a plurality of substrates S may be arranged in the sputtering apparatus 25, and these substrates S may be processed collectively or continuously.

  Above the substrate S, the cylindrical sputtering target material 20 is disposed such that its long axis is parallel to the upper surface of the substrate S. That is, the outer peripheral surface 21 facing downward of the cylindrical sputtering target material 20 is disposed so as to face the upper surface of the substrate S. The cylindrical sputtering target material 20 is rotatably supported around its central axis by a rotation mechanism (not shown).

  As shown in FIG. 3B, a cylindrical magnet 23 is inserted into the cylinder of the cylindrical sputtering target material 20 so as to be in contact with the inner peripheral surface 22. Inside the cylindrical magnet 23 is a flow path 24 through which a coolant such as cooling water, an organic solvent, or dry air flows. By supplying the coolant into the flow path 24, the temperature rise of the cylindrical sputtering target material 20 can be suppressed during sputtering.

In this state, as shown in FIG. 3A, while the cylindrical sputtering target material 20 is rotated in the circumferential direction, a negative high voltage is applied to the cylindrical sputtering target material 20 and a positive high voltage is applied to the substrate S. Discharge power is applied so that it is applied. As a result, plasma discharge occurs mainly between the cylindrical sputtering target material 20 and the substrate S, and argon (Ar ⁺ ) that has become positive ions becomes the outer peripheral surface 21 of the cylindrical sputtering target material 20, particularly the substrate S. Collides with the opposite lower surface. The magnet 23 inserted into the cylindrical sputtering target material 20 attracts argon ions and further accelerates the collision of argon ions.

  Due to the collision of the argon ions, the copper atoms constituting the cylindrical sputtering target material 20 are ejected from a predetermined position, jumped out of the cylindrical sputtering target material 20 (sputtered), and a part thereof to the upper surface of the substrate S. Adhere to. By continuing the sputtering for a predetermined time, copper is deposited on the upper surface of the substrate S at a predetermined sputtering rate.

  At this time, as shown in FIG. 3A, the substrate S is moved in the horizontal direction at a predetermined speed and passed through a position immediately below the cylindrical sputtering target material 20 on which copper is more easily deposited. A copper film having a thickness is formed on the upper surface of the substrate S. By making the moving speed of the substrate S constant or variously changed, it is possible to form a sputtering film such as a copper film having a uniform film thickness or a copper film having a predetermined film thickness distribution.

  On the other hand, as described above, the cylindrical sputtering target material 20 is sputtered substantially uniformly from the outer peripheral surface 21 side to the inner peripheral surface 22 side while rotating in the circumferential direction, and the erosion of the surface proceeds. Go. At this time, as described above, the hardness of the cylindrical sputtering target material 20 increases as the erosion progresses toward the inner peripheral surface 22 side, that is, as the thickness of the cylindrical sputtering target material 20 gradually decreases as a result of use. Thus, the collision chain of copper atoms is hindered. On the other hand, the orientation ratio of the (111) plane is also increased and the amount of jumping out of copper atoms is increased. Thereby, both effects are offset, and the difference in the sputtering rate from the outer peripheral surface 21 to the inner peripheral surface 22 is reduced, or a substantially constant sputtering rate can be obtained.

  At this time, as the erosion progresses, the surface area of the cylindrical sputtering target material 20 decreases. However, it is hardly necessary to consider the influence on the sputtering rate. The plasma discharge is generated in a very narrow region near the surface of the cylindrical sputtering target material 20 facing the substrate S. Even if the entire surface area of the cylindrical sputtering target material 20 is slightly reduced by erosion, the surface area exposed to the plasma discharge hardly varies. Since copper atoms are mainly emitted only from a narrow region exposed to this plasma discharge, the influence of the erosion on the sputtering rate is insignificant.

  For this reason, in order to keep the sputtering rate substantially constant, as described above, mainly considering only the amount of increase in the hardness of the cylindrical sputtering target material 20, the amount of increase in the orientation ratio of the (111) plane is set. Just decide.

  Even when the original size of the cylindrical sputtering target material 20 varies in size, it is considered that the sputtering rate is hardly affected as described above. Therefore, as described above, for example, in the cylindrical sputtering target material 20 having an outer diameter of 100 mm to 200 mm, a wall thickness of 5 mm to 40 mm, and a length in the major axis direction of 200 mm to 5000 mm, a substantially constant sputtering rate is obtained. can get.

  As described above, in the cylindrical sputtering target material 20, the difference in the sputtering rate from the new state to the end of the life is reduced, and it is possible to obtain the sputtering characteristics with little change with time. Therefore, the film thickness of the sputtering film becomes substantially constant over a certain sputtering time, and it is possible to form a sputtering film with little characteristic difference between the individual substrates S.

Further, since the difference in sputtering rate is reduced in the entire cylindrical sputtering target material 20, it is possible to increase the utilization rate by delaying the replacement time of the target material. In addition, the processing time for the individual substrates S can be made substantially constant, and the throughput of the sputtering apparatus 25 can be improved. Therefore, it is possible to reduce the cost of the production process.

  The substrate S on which the sputtering film is formed as described above is used as various wiring substrates after the wiring structure is formed by patterning the sputtering film in a desired wiring pattern, for example.

(4) Structure of Thin Film Transistor As described above, the sputtering film formed using the cylindrical sputtering target material 20 is used for wiring materials in various wiring boards including thin film transistors used in liquid crystal display devices and the like.

  Here, an example of a wiring substrate that includes a substrate and a wiring structure formed on the substrate, and at least a part of the wiring structure is formed of a sputtering film formed using the cylindrical sputtering target material 20 described above. The structure of the thin film transistor 40 shown in FIG. 4 will be described. FIG. 4 is a schematic cross-sectional view of the thin film transistor 40 according to this embodiment.

  As shown in FIG. 4, the thin film transistor 40 includes, for example, a glass substrate 48, a gate electrode 47 formed on the glass substrate 48, a source electrode 41s and a drain electrode 41d formed on the gate electrode 47 (hereinafter referred to as source − Drain electrodes 41s and 41d). These electrodes 47, 41s, 41d are formed on the glass substrate 48 for each thin film transistor 40 by patterning using, for example, wet etching or dry etching, and are covered with a protective film 49 made of, for example, silicon nitride (SiN). . Alternatively, the glass substrate 48 may be formed with a plurality of thin film transistors 40 arranged in an array.

  The gate electrode 47 formed on the glass substrate 48 is made of, for example, copper (Cu). The gate electrode 47 is connected to a gate bus line (not shown) made of, for example, copper.

On the gate electrode 47, for example, a predetermined pattern including the source-drain electrodes 41 s and 41 d is formed through a gate insulating film 46 made of silicon nitride and a semiconductor film 44 made of amorphous silicon (α-Si). A laminated structure is formed. That is, on the semiconductor film 44, for example, contact films 43s and 43d made of amorphous silicon (n ⁺ -α-Si) doped with phosphorus (P) or the like, and molybdenum (Mo), titanium (Ti), or the like. Each of the barrier films 42s and 42d and the source-drain electrodes 41s and 41d made of pure copper (Cu) or the like are stacked in this order. The channel length between the source-drain electrodes 41s and 41d is, for example, about 10 μm.

  A source bus line (not shown) mainly made of pure copper, for example, is connected to the source electrode 41s. A transparent electrode 45 for driving a liquid crystal display device or the like is connected to the drain electrode 41d.

  The wiring structure according to this embodiment is mainly composed of the source-drain electrodes 41s and 41d, the source bus line, the transparent electrode 45, the gate electrode 47, the gate bus line, and the like. At least a part of the wiring structure, for example, a source bus line and a gate bus line made of pure copper (Cu) are made of a sputtering film formed by using the cylindrical sputtering target material 20.

As described above, the sputtering film constituting at least a part of the wiring structure is formed by using the cylindrical sputtering target material 20 in which the difference in the sputtering rate is reduced, so that the substantially homogeneous sputtering films are individually provided. Thus, it is possible to obtain the thin film transistor 40 with little difference in characteristics between elements.

  Further, since there is little change in sputtering characteristics over time, the utilization rate of the target material can be increased, the cost of the production process can be reduced, and a cheaper thin film transistor 40 can be obtained.

  In addition, the structure of the thin film transistor which can introduce | transduce the sputtering film | membrane using the cylindrical sputtering target material 20 is not restricted to the above-mentioned thing. For example, the source-drain electrode may have a laminated structure made of not only pure copper but also a copper alloy or the like. Also, the gate electrode may be made of, for example, not only copper but also a copper alloy. In such a configuration, a copper alloy such as copper-manganese (Cu-Mn) may be used as the barrier film.

  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.

  Next, Examples 1 to 5 according to the present invention will be described together with Comparative Examples 1 to 4 with reference to Table 1 below.

(1) Production of evaluation sample First, a billet made of oxygen-free copper having a purity of 4N (99.99%) was cast, and the outer diameter was 150 mm and the wall thickness was 30 mm by hot extrusion as in the above-described embodiment. An extruded tube was formed. Next, in the same manner as in the above-described embodiment, pipe expansion was performed to form a pipe expansion. At this time, Table 1
As shown in FIG. 1, the pipe expansion rates were different in Examples 1 to 5 and Comparative Examples 1 to 4, respectively. For example, in Example 1, a tube expansion rate was 10%, an outer diameter was 165 mm, and a wall thickness was 25 mm.

  Subsequently, as in the above-described embodiment, each pipe expansion was subjected to heat treatment. At this time, as shown in Table 1, in Examples 1 to 5 and Comparative Examples 1 to 4, different temperatures were used, and the heat treatment time was 180 minutes. Four predetermined points were cut out in the major axis direction from each of the expanded tubes thus manufactured, and four sets of evaluation samples were manufactured for all of Examples 1 to 5 and Comparative Examples 1 to 4. Each evaluation sample was cut out from the approximate center in the long axis direction excluding both ends.

(2) Measurement of evaluation sample Next, using each evaluation sample of Examples 1 to 5 and Comparative Examples 1 to 4 one by one, tube cracking investigation and crystal grain size evaluation shown below, Vickers hardness test and Crystal orientation measurement and sputtering rate measurement were performed. At this time, as shown in FIG. 5, the region from the outer peripheral surface 31 to the inner peripheral surface 32 of each evaluation sample 30 is divided into five regions from e to a in the radial direction, and each measurement is performed in each region. went. That is, in the case of Example 1 having a wall thickness of 25 mm, each measurement value was obtained in the areas ea divided by 5 mm in the radial direction.

(Investigation of expansion crack and evaluation of crystal grain size)
Hereinafter, the results of the pipe expansion crack investigation and the crystal grain size evaluation will be described. First, it mirror-polished and etched with respect to 1 set of evaluation samples of Examples 1-5 and Comparative Examples 1-4. Next, each of the regions ea was observed with an optical microscope, and the presence / absence of tube expansion cracks and the measurement result of the crystal grain size were obtained. As for the pipe expansion crack, it was judged as “present” if there was even one crack within the range of 20 mm width in the circumferential direction, and only “no” was judged as having no crack. The crystal grain size (μm) was measured based on the “comparative method” of the “stretched copper crystal grain size test method” defined in JIS H0501.

  As shown in Table 1, in Examples 1 to 5, no pipe expansion crack occurred. On the other hand, in Comparative Examples 1 to 4, pipe expansion cracks occurred in Comparative Example 1 and Comparative Example 4 having a large pipe expansion rate. Therefore, Comparative Example 1 and Comparative Example 4 do not satisfy the quality as a cylindrical sputtering target material.

  Moreover, as shown in Table 1, in Examples 1-5, all the crystal grain sizes were 100 micrometers or less. Therefore, in Examples 1-5, it is expected that the frequency of occurrence of abnormal discharge during sputtering is low. On the other hand, the crystal grain size measured for Comparative Examples 2 and 3 where there was no pipe cracking exceeded 100 μm in Comparative Example 2 where the heat treatment temperature was particularly high.

(Vickers hardness test)
Below, the result of a Vickers hardness test is demonstrated. Vickers hardness test for one set of evaluation samples of Examples 1 to 5 and Comparative Examples 1 to 4, more specifically, a micro Vickers hardness capable of measuring a fine crystal by reducing a load applied by an indenter. The test was conducted. At this time, measurement was performed five times in each region ea of each evaluation sample, and the average value was defined as the Vickers hardness (HV) in that region.

  As shown in Table 1, in any of the evaluation samples of Examples 1 to 5, the Vickers hardness gradually increased from the outer peripheral surface side toward the inner peripheral surface side. In particular, in Examples 1 to 3, the value was within the range defined above, that is, the outer peripheral surface side was 75 HV to 80 HV, and the inner peripheral surface side was 95 HV to 100 HV. Moreover, although the comparative example 2 and the comparative example 3 also deviated from the specified value, the tendency of increasing hardness from the outer peripheral surface side toward the inner peripheral surface side was the same.

(Crystal orientation measurement)
Hereinafter, the results of the crystal orientation measurement will be described. About 1 set of evaluation samples of Examples 1-5 and Comparative Examples 1-4, the peak intensity which shows a various crystal plane was measured using the X-ray-diffraction apparatus. Subsequently, the measured intensity of each peak and the standard intensity of each peak described in JCPDS card number 40836 were applied to the above formula (1), and the orientation ratio (%) of the (111) plane was obtained.

  As shown in Table 1, in Examples 1 to 5, the orientation ratio of the (111) plane gradually increased from the outer peripheral surface side toward the inner peripheral surface side. More specifically, in any of the evaluation samples of Examples 1 to 5, the outer peripheral surface side is within a range of 10% to 15%, and the inner peripheral surface side is within a range of 20% to 25%. I was able to. On the other hand, in Comparative Example 2, the orientation rate of the (111) plane is substantially constant from the outer peripheral surface side to the inner peripheral surface side, and in Comparative Example 3 with a small tube expansion rate, the outer peripheral surface. On the side, the orientation ratio of the (111) plane has become very small.

(Sputtering speed measurement)
Hereinafter, the results of the sputtering rate measurement will be described. Each set of evaluation samples of Examples 1 to 5 and Comparative Examples 1 to 4 was mounted on the same sputtering apparatus as in the above-described embodiment, and the sputtering rate of each evaluation sample was measured. Specifically, sputtering was performed for 3 minutes using argon gas with a discharge power of 33 kW, and a sputtering film was formed on a glass substrate. Thereafter, the film thickness of the sputtering film was measured with a laser microscope, converted into a film thickness formed per minute, and this was used as the sputtering rate (nm / min).

  As shown in Table 1, in Examples 1 to 5, a substantially constant sputtering rate was obtained from the outer peripheral surface to the inner peripheral surface. Although not shown in Table 1, also in Comparative Example 1 and Comparative Example 4 in which the tube expansion rate was 5% or more, a substantially constant value was obtained for the sputtering rate. In contrast, in Comparative Example 2 in which the orientation ratio of the (111) plane was substantially constant and in Comparative Example 3 in which the orientation ratio of the (111) plane was small on the outer peripheral surface side, the inner peripheral surface side was changed from the outer peripheral surface side. The sputter rate decreased with increasing heading.

  As described above, in Examples 1 to 5, good results were obtained for any of the expansion cracking, crystal grain size, and sputtering rate. At this time, when the difference in Vickers hardness between the outer peripheral surface side and the inner peripheral surface side is 75 HV or more and 80 HV or less at least on the outer peripheral surface side, and 95 HV or more and 100 HV or lower on the inner peripheral surface side, If the difference in the orientation ratio of the (111) plane from the inner peripheral surface side is at least 10% to 15% on the outer peripheral surface side and 20% to 25% on the inner peripheral surface side, It was found that a substantially constant sputtering rate was obtained from the surface to the inner peripheral surface.

  Moreover, it turned out that said Vickers hardness and the orientation rate of (111) plane are obtained by making a pipe expansion rate into 5% or more. On the other hand, when the tube expansion rate is 15% or less, tube cracking is suppressed, and when the heat treatment temperature after tube expansion drawing is 450 ° C. or more and 600 ° C. or less, the crystal grain size is less likely to cause abnormal discharge. It was found that the following can be controlled.

DESCRIPTION OF SYMBOLS 9 Extrusion pipe | tube 10 Expanded pipe 11,21,31 Outer peripheral surface 12,22,32 Inner peripheral surface 15p Expanded plug 15r Rod 20 Cylindrical sputtering target material 23 Magnet 24 Channel 25 Sputtering device 30 Evaluation sample 40 Thin film transistor 41 Source electrode 42 Drain Electrode 43 Auxiliary electrode film 44 Electrode film 45 Barrier film 46 N-type semiconductor film 47 Protective film 48 Semiconductor film 49 Gate insulating film 50 Gate electrode 51 Glass substrate S substrate

Claims (8)

A cylindrical sputtering target material formed of oxygen-free copper having a purity of 3N or more and having a cylindrical shape,
While the hardness gradually increases from the outer peripheral surface side to the inner peripheral surface side,
A cylindrical sputtering target material, wherein the orientation ratio of the (111) plane gradually increases from the outer peripheral surface side toward the inner peripheral surface side. Even if the thickness gradually decreases due to the use of the cylindrical sputtering target material, the sputtering rate of the cylindrical sputtering target material is constant.
A decrease in the sputtering rate of the cylindrical sputtering target material due to a gradual increase in hardness from the outer peripheral surface side toward the inner peripheral surface side, and from the outer peripheral surface side toward the inner peripheral surface side (111 2. The cylindrical sputtering target material according to claim 1, wherein the cylindrical sputtering target material is configured to cancel out an increase in the sputtering rate of the cylindrical sputtering target material due to a gradual increase in the orientation ratio of the surface. The hardness is Vickers hardness,
3. The cylindrical sputtering target material according to claim 1, wherein the outer peripheral surface side has a Vickers hardness of 75 HV or more and 80 HV or less, and the inner peripheral surface side has a Vickers hardness of 95 HV or more and 100 HV. The orientation ratio of the (111) plane on the outer peripheral surface side is 10% or more and 15% or less, and the orientation ratio of the (111) plane on the inner peripheral surface side is 20% or more and 25% or less. The cylindrical sputtering target material according to claim 1.
However, the orientation ratio of the (111) plane is
The sum of the values obtained by dividing the measured intensity of each peak by X-ray diffraction by the standard intensity of the peak of the crystal plane corresponding to each peak described in JCPDS card number 40836, as the denominator,
This is a value obtained from an equation in which a value obtained by dividing the measured intensity of the (111) plane peak by X-ray diffraction by the standard intensity of the (111) plane peak described in JCPDS card number 40836 is a numerator. 5. The cylindrical sputtering target material according to claim 1, wherein the crystal grain size is in a range of 50 μm to 100 μm. The cylindrical sputtering target material according to any one of claims 1 to 5, wherein the cylindrical sputtering target material is formed by subjecting an extruding element tube to pipe expansion drawing and heat treatment. A substrate,
A wiring structure formed on the substrate,
At least a part of the wiring structure is
A wiring substrate comprising a sputtering film formed using the cylindrical sputtering target material according to claim 1. A substrate,
A wiring structure formed on the substrate and including a source electrode and a drain electrode;
At least a part of the wiring structure is
A thin film transistor comprising a sputtering film formed using the cylindrical sputtering target material according to claim 1.

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