JP5567042B2 - Copper sputtering target material for TFT - Google Patents

Description

The present invention relates to a copper sputtering target material for TFT. In particular, the present invention relates to a copper sputtering target material for the TFT can be reduced tensile stress in the copper film to be deposited.

  Conventionally, a sputtering method using a sputtering target made of a predetermined material has been used to form a metal thin film such as a wiring in an electronic device including a liquid crystal panel. As a conventional sputtering target, in a sputtering target made of a metal or alloy having a face-centered cubic structure, the plane orientation ratio calculated from ((111) plane + (200) plane) / (220) plane is 2.20. The above sputtering target is known (for example, refer patent document 1).

  The sputtering target described in Patent Document 1 can improve the sputtering rate by preferentially orienting the (111) plane and the (200) plane on the sputtering surface to increase the density of atoms on the sputtering surface.

JP 2000-239835 A

  However, the sputtering target according to Patent Document 1 cannot reduce the tensile residual stress of the material film deposited in the vacuum chamber or the like of the sputtering apparatus, and increases the thickness of the material film deposited in the vacuum chamber. It may peel off and become a generation source of particles. Moreover, to reduce the tensile stress of the material film, it is effective to reduce the pressure in the vacuum chamber or change the gas type introduced into the vacuum chamber, but the pressure in the vacuum chamber and the gas type introduced into the vacuum chamber are effective. Therefore, it is difficult to change the pressure in the vacuum chamber and the gas type introduced into the vacuum chamber for the purpose of reducing the residual stress.

Therefore, an object of the present invention is to provide copper for TFT capable of reducing the tensile residual stress in the formed copper film without changing the film formation conditions (pressure during film formation, gas type used for film formation, etc.). It is to provide a sputtering target material .

(1) The present invention is a copper sputtering target material for TFT made of a copper material in order to achieve the above object, and the copper material has one crystal orientation plane and another crystal orientation plane, with oxygen-free copper or Ranaru sputter surface consisting of inevitable impurities and one crystal orientation plane is (111) plane, other crystal orientation planes, the (200) plane and the (220) plane And the (111) plane, the occupying ratio of the (111) plane to the sum of the (111) plane, the (200) plane, the (220) plane, and the (311) plane is 15% or more. (However, 25% or more is excluded) A copper sputtering target material for TFT is provided.
(2) Further, the copper sputtering target for TFT may be a flat plate type.
(3) Further, the oxygen-free copper or copper alloy may have an oxygen content of 5 ppm or less .

According to the copper sputtering target material for TFT of the present invention, the tensile residual stress in the formed copper film can be obtained without changing the film formation conditions (pressure during film formation, gas type used for film formation, etc.). The copper sputtering target material which can reduce is able to be provided.

[Embodiment]
(Configuration of copper sputtering target)
FIG. 1 shows an example of a partial perspective view of a copper sputtering target according to an embodiment of the present invention.

  The copper sputtering target 1 according to the present embodiment is made of a predetermined copper material whose crystal structure is a face-centered cubic lattice, and a sputter surface 12 from which sputtered copper particles are ejected by irradiation with a predetermined accelerated inert gas ion. The copper sputtering target material 10 which has this, and the backing plate 14 to which the copper sputtering target material 10 (copper sputtering target material for TFT) was fixed. The copper sputtering target material 10 according to the present embodiment has a predetermined thickness and is formed in a substantially rectangular shape when viewed from above. In the modification of the present embodiment, the copper sputtering target material 10 and the backing plate 14 can be formed in a substantially circular shape.

  The copper sputtering target material 10 which concerns on this Embodiment is comprised from the copper material which consists of copper (Cu) which has a purity of 99.99% or more, and an unavoidable impurity, or a copper material which consists of oxygen-free copper, or a copper alloy. It is formed from a copper material. For example, CuNi can be used as the copper alloy. In addition, a copper alloy can also be formed including metal elements, such as Al and Ag, for example. Furthermore, the copper sputtering target material 10 according to the present embodiment is formed with an oxygen content of 5 ppm or less.

  The sputtering surface 12 of the copper sputtering target material 10 is formed having a plurality of crystal orientation surfaces. That is, the sputter surface 12 is formed of a copper material having at least one crystal orientation plane and another crystal orientation plane. Here, one crystal orientation plane has a characteristic that the energy of sputtered particles ejected by irradiation with a predetermined accelerated inert gas ion is larger than the energy of sputtered particles ejected from another crystal orientation plane. That is, the sputtered particles ejected from one crystal orientation plane have the maximum energy among the sputtered particles including the sputtered particles ejected from the other crystal orientation plane. Furthermore, the sputter surface 12 is formed such that the occupation ratio of one crystal orientation plane with respect to the sum of one crystal orientation plane and another crystal orientation plane has a predetermined occupation ratio.

  Specifically, the sputter surface 12 has a (111) plane as one crystal orientation plane, a (200) plane, a (220) plane, and a (311) plane as other crystal orientation planes. And the ratio which the (111) plane occupies when the total of the crystal orientation planes of the (111) plane, (200) plane, (220) plane and (311) plane of the sputter surface 12 is defined as 100% That is, the copper sputtering target material 10 is formed with the sputtering surface 12 having an occupation ratio of the (111) plane of 15% or more, preferably 20% or more, more preferably 25% or more.

  Here, the occupation ratio of the (111) plane can be calculated from the relative intensity ratio of the diffraction peaks of each crystal orientation measured by X-ray diffraction, using the following equation (“Expression 1”). Since the relative intensity ratio obtained by X-ray diffraction varies depending on the diffraction surface, the correct occupation ratio can be obtained by using the value corrected by dividing the measured value by the standard data of ICDD (International Center for Diffraction Date). Can be sought.

In the above “Equation 1”, K _{s (111)} is the occupation ratio (%) of the test material, that is, the (111) plane of the copper sputtering target material 10, and I _{s (111)} , I _{s ( 200)} , I _{s (220)} , and I _{s (311)} are the relative intensity ratios of the X-ray diffraction peaks in the respective crystal orientations of the test sample, and I _{d (111)} , I _{d (200)} , I _{d (220)} and I _{d (311)} are the relative intensity ratios of the X-ray diffraction peaks in each crystal orientation of the standard data.

  The higher the energy of the sputtered particles ejected from the sputtering target material by sputtering, the denser the film generated by the sputtered particles, and the internal stress of the generated film changes from tensile stress to compressive stress. As a result of experiments, the present inventor has obtained knowledge that the energy of sputtered particles ejected from the (111) plane is the highest in the case of copper.

  Therefore, the occupation ratio of the (111) plane to the (111) plane, (200) plane, (220) plane, and (311) plane of the sputter plane 12 is increased, and sputtered particles having high energy are sputtered. It was speculated that the tensile stress of the produced copper film (TFT copper film) can be reduced by increasing the thickness. Therefore, when the occupation ratio of the (111) plane that can reduce the tensile stress was examined, if the occupation ratio of the (111) plane is 15% or more, preferably 25% or more, the internal stress of the copper film to be formed is reduced. The knowledge that an effect is acquired was acquired. As a result, as described above, the copper sputtering target material 10 is formed with the sputtering surface 12 in which the occupation ratio of the (111) surface is 15% or more. Further, for the purpose of further reducing the internal stress of the copper film to be formed, the copper sputtering target material 10 can be formed having the sputter surface 12 of 25% or more.

(Sputtering method)
FIG. 2 shows an outline of a sputtering apparatus to which the sputtering method according to the embodiment of the present invention is applied.

  The sputtering apparatus 2 is provided at a predetermined position in the vacuum chamber 26, the vacuum chamber 26, a holding unit 28 a that holds the object 6 on which the copper film 5 as a metal film is to be formed, A holding unit 28b that holds the copper sputtering target 1, a gas introduction system 22 that introduces argon gas (Ar gas) as an inert gas, and an exhaust system that exhausts the gas in the vacuum chamber 26. 24 and a power source (not shown) for applying a predetermined voltage between the copper sputtering target 1 and the object 6.

  The object 6 is, for example, a glass substrate on which a thin film transistor (TFT) used for driving a pixel of a liquid crystal panel is formed. By the sputtering method according to the present embodiment, a thin film copper wire can be formed as three kinds of thin film metal wires of a TFT gate line, a source line, and a drain line. In addition, by forming a thin film metal wire from copper, the electrical resistance of a thin film metal wire can be reduced compared with the thin film metal wire formed from aluminum, for example.

The sputtering method is performed as follows. First, the copper sputtering target 1 and the object 6 are set in the vacuum chamber 26. Then, the inside of the vacuum chamber 26 is set to a predetermined pressure, and Ar gas as an inert gas is introduced from the gas introduction system 22 into the vacuum chamber 26. Next, a predetermined voltage is applied to the Ar gas introduced into the vacuum chamber 26 to turn the introduced Ar gas into plasma, thereby generating Ar ⁺ ions 3 as inert gas ions. Then, Ar ⁺ ions 3 are accelerated by an electric field and irradiated to the copper sputtering target material 10. As a result, the copper constituting the copper sputtering target material 10 is sputtered out as the sputtered particles 4.

  The sputtered particles 4 ejected from the copper sputtering target material 10 are deposited on the object 6, and a copper film 5 is formed on the object 6. In addition, a part of the sputtered particles 4 ejected from the copper sputtering target material 10 (for example, about half of the sputtered particles 4 ejected from the sputter surface 12) is deposited other than the object 6 such as the chamber inner wall 26a. As a result, an adhesion film is formed.

(Effect of embodiment)
In the copper sputtering target material 10 according to the present embodiment, the sum of the crystal orientation planes of the (111) plane, (200) plane, (220) plane, and (311) plane of the sputter plane 12 is 100%. Since it is formed with the sputtered surface 12 having a ratio of the (111) plane as defined, that is, the proportion of the (111) plane is 15% or more, preferably 25% or more, it is ejected from the sputtered surface 12. The energy of the sputtered particles 4 is so high that the internal stress of the formed copper film 5 becomes more dominant in compressive stress. Therefore, the tensile residual stress of the formed sputtered film can be reduced by using the copper sputtering target material 10 according to the present embodiment for sputtering.

  Further, by using the copper sputtering target material 10 according to the present embodiment, the tensile residual stress of the adhesion film adhering to the inside of the vacuum chamber 26 of the sputtering apparatus 2, that is, the chamber inner wall 26a, etc. is also reduced. The peeling of the adhesion film that occurs when the thickness of the film increases can be suppressed. As a result, the tensile residual stress of the deposited film can be reduced without changing the process pressure and process gas conditions during sputtering, and particles generated during sputtering can be reduced. Yield and productivity can be greatly improved.

In addition, since the copper sputtering target material 10 according to the embodiment of the present invention is formed with an oxygen content of 5 ppm or less, for example, it contains hydrogen gas as a reducing atmosphere gas in the TFT wiring manufacturing process of the liquid crystal panel. Even when the process gas is used, blow holes generated in the copper film due to the reaction of hydrogen gas in the process gas with oxygen in the copper film to generate H ₂ O can be suppressed.

Example 1
(Manufacture of the copper sputtering target material 10 which concerns on Example 1)
First, oxygen-free copper as a raw material having a purity of 99.99% and an oxygen content of 2 ppm was produced by a continuous casting method. The oxygen-free copper produced by the continuous casting method was in the form of an ingot having a thickness of 200 mm and a width of 500 mm. Next, in a predetermined atmosphere, the ingot was heated to 800 ° C. and hot-rolled to a predetermined thickness of 50 mm or less.

  Subsequently, the material obtained by hot rolling was repeatedly subjected to cold working and heat treatment a predetermined number of times to produce a material having a thickness of 18 mm. Here, by adjusting the cold work degree in the cold work to a predetermined cold work degree, and adjusting the heat treatment temperature in the heat treatment to the predetermined heat treatment temperature, the copper of the rolled surface calculated by “Equation 1” is adjusted. The occupation ratio of the (111) plane of the crystal was set to 15% or more.

  Next, the copper sputtering target material 10 according to Example 1 having a thickness of 16 mm was manufactured by cutting and removing both surfaces of the material having an (111) plane occupation ratio of 15% or more by machining. When this copper sputtering target material 10 was analyzed with an X-ray diffractometer, the occupation ratio of the (111) plane was 25.7%. In Example 1, 99.99% oxygen-free copper was used, but if the occupation ratio of the (111) plane is 15% or more, a sputtering target can be manufactured from a copper alloy.

(Example 2)
In the same manner as in Example 1, a copper sputtering target material 10 according to Example 2 was manufactured. When the copper sputtering target material according to Example 2 was analyzed using an X-ray diffractometer, the occupation ratio of the (111) plane was 15%.

(Example 3)
In the same manner as in Example 1, a copper sputtering target material 10 according to Example 3 was produced. When the copper sputtering target material according to Example 3 was analyzed using an X-ray diffractometer, the occupation ratio of the (111) plane was 20%.

(Comparative example)
As a comparative example, three patterns of copper sputtering target materials having a (111) plane occupation ratio of 15% or less were manufactured by adjusting the cold working degree and the heat treatment temperature. When the copper sputtering target material which concerns on a comparative example was measured with the X-ray-diffraction apparatus, the occupation ratio of the (111) plane of the copper sputtering target which concerns on a comparative example is 14.6% (comparative example 1), 7.6% ( Comparative Example 2) and 4.6% (Comparative Example 3). Further, a copper sputtering target was manufactured in the same process as in the example of the present invention except that an ingot having an oxygen content of 10 ppm was used as a raw material (Comparative Example 4).

(Evaluation of copper sputtering target material)
(Evaluation method 1: measurement of residual stress)
The residual stress in the copper foil film formed by sputtering using the copper sputtering target material according to each of Examples 1 and 2 and Comparative Examples 1 to 4 was measured. Specifically, first, for evaluation, a disk having a thickness of 5 mm and an outer shape of φ100 mm was cut out from each of the copper sputtering target materials according to Examples 1 and 2 and Comparative Examples 1 to 4. Next, the disc cut out in the batch type RF power source sputtering apparatus was set as a copper sputtering target, and a non-alkali glass substrate having a 50 mm square and a thickness of 0.7 mm was set as the object 6.

  Then, using each of the disks cut out from the copper sputtering targets according to Examples 1 and 2 and Comparative Examples 1 to 4, a 500 nm copper film was formed on a non-alkali glass substrate under conditions of a predetermined pressure in a predetermined atmosphere. Each film was formed below. Subsequently, the residual stress of each formed copper film was measured by using the parallel tilt method using an X-ray diffractometer.

(Evaluation method 2: Investigation of peelability)
The anti-peeling property of the copper film deposited in the vacuum chamber of the sputtering apparatus was evaluated. Specifically, first, for evaluation, a disk having a thickness of 5 mm and an outer shape of φ100 mm was cut out from each of the copper sputtering target materials according to Examples 1 and 2 and Comparative Examples 1 to 4. Next, a copper film having a thickness of 0.1 mm was formed on a 50 mm square, SUS304 substrate having a thickness of 1 mm using a batch type RF power source sputtering apparatus in the same manner as the evaluation method 1 described above. The presence or absence of peeling of the copper film was investigated.

(Evaluation method 3: Evaluation of the influence of oxygen in the copper film)
The influence of oxygen in the copper film formed by sputtering was evaluated. Specifically, first, for evaluation, a disk having a thickness of 5 mm and an outer shape of φ100 mm was cut out from each of the copper sputtering target materials according to Examples 1 and 2 and Comparative Examples 1 to 4. Next, in the same manner as in the evaluation method 1, a 500 nm thick copper film is formed on a 50 mm square, non-alkali glass substrate having a thickness of 0.7 mm using a batch type RF power source sputtering apparatus. Filmed. Next, the copper film was heated at 300 ° C. for 30 minutes in an H ₂ atmosphere, and then cooled to room temperature. Subsequently, the presence or absence of blowholes was examined by observing the obtained copper film with a scanning electron microscope.

  Table 1 summarizes the results of Evaluation Methods 1 to 3.

Referring to the column of Evaluation Method 1 in Table 1, it is shown that the copper film formed from the copper sputtering target material according to Examples 1 and 2 of the present invention has a tensile residual stress of 120 N / mm ² or less. The copper film formed from the copper sputtering target material according to Example 1 was shown to have the lowest tensile residual stress. Further, as can be seen by referring to the column of Evaluation Method 2 in Table 1, the copper film formed from the copper sputtering target material according to Examples 1 and 2 did not peel off from the SUS304 substrate. Furthermore, as can be seen by referring to the column of Evaluation Method 3 in Table 1, no blowholes were present in the copper film.

  On the other hand, the copper film formed from the copper sputtering target material according to Comparative Examples 1 to 3 has a large tensile residual stress and is shown in the column of Evaluation Method 2 as can be seen by referring to the column of Evaluation Method 1 in Table 1. Thus, peeling of the copper film from the SUS304 substrate was also observed. Moreover, the copper film formed from the copper sputtering target material according to Comparative Example 4 has a low tensile residual stress as can be seen by referring to the column of Evaluation Method 1, and from the SUS304 substrate as can be seen from the column of Evaluation Method 2. No peeling of the copper film was observed. However, as can be seen by referring to the column of Evaluation Method 3, it was observed that blowholes were generated due to the high oxygen content.

  As described above, the (111) plane occupying ratio is 15% or more, preferably 25% or more, and the oxygen sputtering content is 5 ppm or less, and the film is formed by sputtering by using the copper sputtering target material as the copper sputtering target. It has been shown that the tensile residual stress in the copper film can be reduced.

  While the embodiments and examples of the present invention have been described above, the embodiments and examples described above do not limit the invention according to the claims. It should be noted that not all combinations of features described in the embodiments and examples are necessarily essential to the means for solving the problems of the invention.

Hereinafter, the claims at the beginning of the application of the parent application (Japanese Patent Application No. 2008-172718) will be appended.
(Claim 1)
Having one crystal orientation plane and another crystal orientation plane, comprising a sputtering surface made of a copper material,
The one crystal orientation plane emits sputtered particles having energy larger than the energy of sputtered particles ejected from the other crystal orientation plane by irradiation with a predetermined inert gas ion accelerated,
The copper sputtering target material whose occupation ratio of the said one crystal orientation surface with respect to the sum total of said one crystal orientation surface and said other crystal orientation surface is 15% or more.
(Claim 2)
The one crystal orientation plane is a (111) plane,
The copper sputtering target material according to claim 1, wherein the other crystal orientation plane includes a (200) plane, a (220) plane, and a (311) plane.
(Claim 3)
The copper sputtering target material according to claim 1 or 2, wherein the occupation ratio is 25% or more.
(Claim 4)
4. The copper sputtering target material according to claim 1, wherein the copper material is oxygen-free copper made of copper and unavoidable impurities, or a copper alloy. 5.
(Claim 5)
The copper sputtering target material according to claim 4, wherein the oxygen-free copper or the copper alloy has an oxygen content of 5 ppm or less.
(Claim 6)
The sputtering method which forms a copper film in a target object using the copper sputtering target material of any one of Claim 1 to 5.

It is a partial perspective view of the copper sputtering target which concerns on embodiment. 1 is a schematic diagram of a sputtering apparatus to which a sputtering method according to an embodiment is applied.

DESCRIPTION OF SYMBOLS 1 Copper sputtering target 2 Sputtering device 3 Ar ⁺ ion 4 Sputtered particle 5 Copper film 6 Object 10 Copper sputtering target material 12 Sputtering surface 14 Backing plate 22 Gas introduction system 24 Exhaust system 26 Vacuum chamber 26a Chamber inner wall 28a, 28b Holding part

Claims (3)

A copper sputtering target material for TFT made of copper material,
The copper material has one crystal orientation plane and another crystal orientation plane, and includes a sputter surface made of oxygen-free copper made of copper and inevitable impurities, and
The one crystal orientation plane is a (111) plane, and the other crystal orientation plane includes a (200) plane, a (220) plane, and a (311) plane, and the (111) plane The occupation ratio of the (111) plane with respect to the sum of the (200) plane, the (220) plane, and the (311) plane is 15% or more (however, 25% or more is excluded) TFT Copper sputtering target material.   The copper sputtering target material for TFT according to claim 1, wherein the copper sputtering target material for TFT is a flat plate type.   The copper sputtering target material for TFT according to claim 1, wherein the oxygen-free copper has an oxygen content of 5 ppm or less.

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