JP2008156694A - Sputtering target material and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a sputtering target with a large size at low cost, and to uniformly perform sputtering. <P>SOLUTION: A billet with a crystal grain size of ≤10 mm composed of whole face equiaxed crystals is melted using a high purity aluminum material with a purity of ≥99.999% by mass ratio, and the billet is subjected to extrusion working, so as to obtain a sputtering target material with a crystal grain size of ≤100 μm. In the extrusion working, desirably, extrusion temperature is controlled to ≤300°C and extrusion ratio is controlled to ≥10. Further, the production of a large-sized high purity aluminum sputtering target material used for an LCD for a liquid crystal television is facilitated, unevenness upon sputtering is eliminated, and a satisfactory metal thin film or the like can be deposited by sputtering. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sputtering target material used for wiring formation of a liquid crystal television panel and a manufacturing method thereof.

2. Description of the Related Art A liquid crystal display (hereinafter referred to as LCD) used for a television or the like is generally one in which a thin film transistor (hereinafter referred to as TFT) is used as a switching element for writing video data. This TFT has a structure in which electrodes and wirings made of a metal thin film are formed on a semiconductor thin film disposed on an insulating substrate such as glass. These electrodes and wirings are formed with a pattern by lithography after forming a uniform thin film by sputtering.
Various metals have been used as materials for the metal thin film, but high-purity aluminum is used for high-definition LCDs. The sputtering target material used when producing this high-purity aluminum thin film by sputtering is aluminum of 99.999% purity or more, and has a fine grain structure of 100 μm or less in order to improve the sputtering uniformity. It is required to be.

Several methods have been proposed as a method for producing the high purity aluminum sputtering target material.
As one of the methods (Patent Document 1), a method of processing a material at an extremely low temperature (−50 ° C. or lower) has been proposed. However, it is industrially difficult to apply this method to a target material having a large size (for example, a length of 2 m or more) used for a liquid crystal television or the like.
For this reason, in general, when producing a target material of a large size as for a liquid crystal television, a slab is cast by a DC casting method, then a thick plate is produced by hot rolling, and used as a target material. Disconnected.
JP 2005-509741 A

  However, in the conventional method of manufacturing by DC casting, hot rolling, and cutting, the high-purity aluminum material is soft, so that the cutting operation is not easy, and as a result, there is a problem that the cutting cost increases. Further, the hot rolling method has a problem that the crystal grain size becomes large and it is difficult to obtain a target material having fine crystal grains.

As a method of solving the above problems, the present inventors considered using an extrusion method. If the extrusion method is used, an extruded material having an arbitrary width can be produced, so that there is no need to cut in the longitudinal direction, and there is an advantage that the labor of cutting is greatly reduced.
By the way, normally, a billet produced by a DC casting method is used for extrusion, but in the case of high-purity aluminum, the billet structure becomes a columnar crystal having a large size, and the size is several centimeters at the outer periphery of the billet. When extrusion is performed using a billet having such columnar crystals, the original crystal orientation of the billet is affected, and the extruded material has a streak pattern due to the anisotropy of the crystal orientation in the extrusion direction, which is the target. It has been found that when used as a material, it causes non-uniformity during sputtering.

  The present invention has been made against the background of the above circumstances, and it is easy to produce a sputtering material having a large size, and further provides a sputtering target material capable of uniform sputtering in sputtering and a method for producing the same. Objective.

  That is, the sputtering target material of the present invention is made of pure aluminum having a purity of 99.999% or more by mass ratio, the crystal grain size is 100 μm or less, and the crystal orientation is the same crystal orientation or the same as the sputtering surface of the target material. The crystal grains having an orientation within ± 25 ° with respect to the orientation are not continuously arranged in a range of 1 mm in width and 5 mm or more in length.

  Moreover, among the manufacturing methods of the sputtering target material of the present invention, the first invention uses a high-purity aluminum material having a purity of 99.999% or more by mass ratio, and has a crystal grain size of 10 mm or less and is entirely equiaxed. A sputtering target material having a crystal grain size of 100 μm or less is obtained by melting a billet and performing extrusion using the billet.

  The invention of the sputtering target material manufacturing method of the second invention is characterized in that, in the sputtering target material manufacturing method of the first invention, in the extrusion process, the extrusion temperature is 300 ° C. or less and the extrusion ratio is 10 or more. .

That is, the sputtering target material of the present invention has high purity and fine crystal grains, and is uniform with little crystal orientation anisotropy. Sputtering is performed.
For the above-described action, the material needs to have an aluminum purity of 99.999% or more. If the purity is less than this, sputtering tends to be non-uniform.
The crystal grain size of the target material needs to be substantially 100 μm or less. When the substantial particle diameter exceeds 100 μm, sputtering becomes non-uniform.
Furthermore, in that no streak pattern is generated by processing, the crystal orientation is 1 mm wide with respect to the sputter surface of the target material, the crystal grain having the same crystal orientation or an orientation within ± 25 ° relative to the orientation, It must be uniform with little anisotropy by not being continuously arranged in a range of 5 mm or more in length.

  Moreover, according to the manufacturing method of the sputtering target material of the present invention, a rough shape product of the target material can be obtained by performing extrusion using a billet of the entire equiaxed crystal with a crystal grain size of 10 mm or less, Cutting in the longitudinal direction and the width direction accompanied by work difficulties such as a rolled material becomes almost unnecessary. In addition, the obtained extrudate can have a crystal grain size as fine as substantially 100 μm or less, and since the crystal orientation anisotropy is small and uniform, A target material with almost no pattern can be obtained. As a result, a sputtering target material that can perform sputtering uniformly is obtained.

  The streak pattern due to the anisotropy of the crystal orientation after extrusion is affected by the structure of the billet that is the material before extrusion, and the large size columnar crystal that is the normal structure of high-purity aluminum material has a streak pattern during extrusion. Occurs. Further, even if the size of the equiaxed crystal structure is large, the structure of the extruded material is affected. If the size exceeds 10 mm, a streak pattern that can be discriminated with the naked eye is generated. For these reasons, the billet structure is an equiaxed crystal of 10 mm or less.

  For billets with a crystal grain size of 10 mm or less and full-surface equiaxed crystals, add a finer that gives vibration during casting, does not affect the sputtering performance, and adds methods such as forging to the billet. Can be obtained. The whole surface equiaxed crystal means that most of the crystals are composed of equiaxed crystals, and the equiaxed crystals account for 70% or more by the volume ratio. In the present invention, the method for producing a billet having a crystal grain size of 10 mm or less and an equiaxed crystal on the entire surface is not limited to the above method.

In the extrusion process using the billet, a rough target material close to the sputtering target shape can be obtained. In the extrusion process, it is desirable that the extrusion temperature is 300 ° C. or less and the extrusion ratio is 10 or less.
The lower the extrusion temperature, the finer the crystal grain size, and the higher the temperature, the more the crystal grains grow. And when extrusion temperature exceeds 300 degreeC, a crystal grain diameter will become large rapidly. Accordingly, the extrusion temperature (billet temperature) is 300 ° C. or less.
On the other hand, if the extrusion ratio is too small, it is greatly affected by the billet structure and causes streaks. Moreover, unless sufficient processing is applied, the crystal grains cannot be made fine. If the extrusion ratio is less than 10, a streak pattern is likely to appear, and a fine crystal grain size cannot be obtained. Therefore, the extrusion ratio is preferably 10 or more.

  That is, according to the sputtering target material of the present invention, the purity is made of pure aluminum having a mass ratio of 99.999% or more, the crystal grain size is 100 μm or less, and the crystal orientation is the same crystal with respect to the sputtering surface of the target material. Since crystal grains having an orientation or an orientation within ± 25 ° with respect to the orientation are not continuously arranged in a range of width 1 mm and length 5 mm or more, non-uniformity in sputtering is eliminated, and a good metal thin film is obtained by sputtering. Etc. can be formed.

  Further, according to the method for producing a sputtering target material of the present invention, a billet of equiaxed crystals with a crystal grain size of 10 mm or less is melted using a high-purity aluminum material having a purity of 99.999% or more by mass ratio. In addition, since the sputtering target material having a crystal grain size of 100 μm or less is obtained by performing extrusion using the billet, it is easy to produce a large high-purity aluminum sputtering target material used for LCDs for liquid crystal televisions, and the like. A sputtering target material capable of uniform sputtering is obtained.

Hereinafter, an embodiment of the present invention will be described.
A high-purity aluminum whose purity is adjusted to 99.999% or more is cast into an equiaxed billet. As described above, the equiaxing can employ methods such as adding a micronizing agent that gives vibration during casting, does not affect the sputtering performance, and adds processing such as forging to the billet.
This billet has a crystal grain size of 10 mm or less and an equiaxed crystal structure on the entire surface by this manufacturing method. In general DC casting, it is difficult to adopt because it has a columnar crystal structure.
This billet is extruded at an extrusion temperature of 300 ° C. or less and an extrusion ratio of 10 or more. As a result, an extruded product having a crystal grain size of 100 μm or less and having no streak pattern is obtained.
The extruded product is subjected to secondary processing such as cutting, if necessary, to be a sputtering target. The sputtering target is formed in a large size (2 m or more) and can be used for sputtering when forming electrodes and wirings on a TFT substrate of a liquid crystal display. As described above, the target material of the present invention is suitable for the production of a sputtering target having a large size. However, the size of the target material is not particularly limited as the present invention, and it is naturally applicable to a smaller size. Is possible.

In addition, the use of the sputtering target is not limited to the liquid crystal display field as described above, and can be used as a sputtering target in various applications.
Although the present invention has been described based on the above embodiment, the present invention is not limited to the description of the above embodiment, and appropriate modifications can be made without departing from the present invention. .

Examples of the present invention will be described below.
An equiaxed billet having a cross-sectional size of 330 mm diameter was produced using high-purity aluminum having a purity of 99.999%. Using this high-purity aluminum billet, an extrusion material having a cross-sectional shape of 20 mm thickness × 200 mm width was produced by changing the extrusion temperature (extrusion ratio 21.3). For comparison, a test material having an extrusion ratio of 8 was produced.

Regarding the extruded product, the crystal orientation and the crystal grain size of each crystal grain were measured using EBSP (EI Electron Back Scattered Pattern: manufactured by Tex SEM Laboratories, USA). In addition, etching was performed using aqua regia, and a streak pattern due to the arrangement of the same crystal grains was visually observed. The results are also shown in Table 1.
As is apparent from Table 1, the specimen No. obtained by extrusion using a billet that is not equiaxed. In 3, the generation of streaks was inevitable. In addition, even in the case of equiaxed crystals, the specimen No. No. 1 was extruded using a billet having a crystal grain size exceeding 10 mm. In No. 4, the crystal grain size of the extrudate became coarse. Furthermore, test material No. using billet with equiaxed crystal and appropriate grain size. Even when the extrusion temperature is high, the crystal grain size becomes coarse. In No. 6, since the extrusion ratio was small, the crystal grain size became coarse and the generation of streaks was observed.

Claims (3)

  The purity is 99.999% or more of pure aluminum by mass ratio, the crystal grain size is 100 μm or less, and the crystal orientation is within the same crystal orientation with respect to the sputtering surface of the target material or within ± 25 ° with respect to the orientation. A sputtering target material, wherein crystal grains having orientations are not continuously arranged in a range of 1 mm in width and 5 mm in length or more.   By using a high-purity aluminum material having a purity of 99.999% or more by mass ratio, a billet of equiaxed crystals with a crystal grain size of 10 mm or less is melted, and extrusion is performed using the billet. A sputtering target material having a thickness of 100 μm or less is obtained.   3. The method for producing a sputtering target material according to claim 2, wherein in the extrusion process, the extrusion temperature is 300 [deg.] C. or less and the extrusion ratio is 10 or more.