JP2012224890A - Sputtering target and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering target which is an Al-based target and is free from cracking when it is formed even if it has a high content of Cr exhibiting more excellent corrosion resistance and further which is also free from cracking during sputtering, and to provide a method for producing the sputtering target.SOLUTION: In the sputtering target, Al-enriched particles having an absolute maximum length within the range of 0.1-50 μm are dispersed in a base material having a composition containing, by atomic percentage, 5-20% of Si and 5.5-25% of Cr, with the remainder composed of Al and inevitable impurities.

Description

  The present invention relates to a sputtering target (hereinafter, referred to as “a crack for forming a reflective recording film of an optical information recording medium (hereinafter referred to as an optical disc”) for recording, reproducing, recording and reproducing, and erasing information by laser light. And the manufacturing method thereof.

  Conventionally, Au, Cu, Ag, Al, and alloys based on these have been widely used as reflective films for optical disks.

  The Al-based reflective film exhibits a sufficiently high reflectivity in a blue laser (wavelength 405 nm) used for recording / reproducing of a BD (Blu-ray disc), and is cheaper than Ag-based and Au-based materials. It is inferior in chemical stability to the reflective film. Therefore, by including Si, Cr, etc. as an alloying component of this Al-based reflective film, investigation of an Al-based reflective film that exhibits an appropriate reflectivity, excellent reproduction stability, and excellent durability is actively conducted. Has been made.

  For example, Patent Document 1 discloses, in atomic%, Si: 5 to 40 at%, Cr: 0.7 to 5 at%, Al: the remaining reflective film for an optical disk and a target for forming a reflective film for an optical disk. That is, in order to simultaneously achieve the two characteristics of an appropriate reflectivity and excellent reproduction stability of the Al alloy film, it is necessary to contain 5% or more of Si, and to change the crystal structure of the crystal grains of the reflective film (crystal grains It is disclosed that it is effective to contain a refractory metal element such as Cr in order to suppress the coarsening) and to obtain excellent durability.

JP 2010-267366 A

  Although the reflective film for optical discs disclosed in Patent Document 1 has a certain corrosion resistance, further improvement in corrosion resistance is desired as an optical disc reflective film that requires a longer life. However, if an attempt was made to produce a target having a high Cr content in order to improve the corrosion resistance, there was a problem that cracking was likely to occur during machining.

  Accordingly, an object of the present invention is to generate a crack in the Al-based target having a high Cr content that exhibits an excellent corrosion resistance function without being cracked during machining after the target is molded, and also during sputtering. It is providing the sputtering target which does not have, and its manufacturing method.

Accordingly, the present inventors have studied to obtain a target in which cracks do not occur during the preparation and sputtering of an Al-based target having a high Cr content, and have obtained the following knowledge.
(A) By subjecting a sintered body of an AlSiCr alloy having a high Cr content to a heat treatment at a predetermined temperature and time in a vacuum or in an inert gas atmosphere, no cracking occurs during machining, and A target that does not crack even during sputtering is obtained.
(B) When the cross-sectional structure was observed and analyzed with an electron microanalyzer (hereinafter referred to as EPMA), the target was Al-rich with a particle diameter (absolute maximum length) of 0.1 to 50 μm on the substrate. The structure has a structure in which various particles are dispersed.
(C) When the Al-rich particles were quantitatively analyzed at three points and the average value of the compositions was determined, they contained 97% or more of Al in atomic%.
(D) Moreover, it turned out that the area ratio which occupies for the structure | tissue of the target of Al rich particle | grains is 5 to 50%.

  Based on the above knowledge, as a result of intensive studies by the inventor, the present invention has been completed as follows.

That is, the present invention
“(1) Sputtering target whose component composition is atomic%, Si: 5 to 20%, Cr: 5.5 to 25%, the balance: Al and inevitable impurities,
A sputtering target, wherein Al-rich particles are dispersed in a composition base.
(2) The sputtering target according to (1), wherein the ratio of Al in the component composition of the Al-rich particles is atomic% and is 97% or more.
(3) The sputtering target according to (1) or (2), wherein an area ratio of the Al-rich particles in the target structure is 5 to 50%.
(4) A method for producing a sputtering target according to any one of (1) to (3),
An alloy powder preparation step of preparing an AlSiCr alloy powder having a composition comprising, in atomic%, Si: 5 to 20%, Cr: 5.5 to 25%, and the balance: Al and inevitable impurities;
A sintering step in which the alloy powder obtained in the alloy powder preparation step is sintered to form a sintered body;
A heat treatment step of performing a heat treatment of holding the sintered body obtained in the sintering step in a vacuum or in an inert gas atmosphere at 720 to 920 ° C. for 0.5 to 10 hours;
A method for producing a sputtering target, comprising: "
It is characterized by.

  Here, in the present invention, the composition of the target contains Si: 5 to 20%, Cr: 5.5 to 25%, and the remainder: Al and inevitable impurities are limited because Si is less than 5%. This is not preferable because the accuracy of the recording signal (reproduced signal) decreases (that is, the jitter value increases) and stable reproduction cannot be performed. On the other hand, if the Si content exceeds 20%, the amount of absorption of the Al alloy film constituting the reflective film increases, and the reflectance is relatively lowered, which is not preferable. Therefore, from the viewpoint of the balance between the reflectance and the jitter value, the Si content is determined to be 5 to 20%. On the other hand, Cr is a component necessary for imparting further corrosion resistance to the reflective film. However, if the content is less than 5.5%, sufficient corrosion resistance cannot be provided, and the content is 25. If it exceeds 50%, the reproduction stability is inferior when used as an optical disk reflective film. Therefore, the Cr content is set to 5.5 to 25%.

  Furthermore, in the present invention, Al-rich means that the content of Al is higher than that of the substrate. For example, particles containing 97% or more of Al correspond to Al-rich particles.

  If the area ratio of the Al-rich particles is less than 5%, the effect of the Al-rich particles is not sufficiently exerted, so that cracking of the target cannot be prevented. Since the film composition is shifted to the Al-rich side, the quality of the formed film, particularly moisture resistance, is lowered, which is not preferable. Therefore, the area ratio of Al-rich particles is determined to be 5 to 50%, more preferably 15% to 45%.

  In addition, since the target of the present invention has a structure having a structure in which Al-rich particles are dispersed in the base of the target, it has an effect of preventing cracks during machining after sputtering of the target and cracks during sputtering, If the particle diameter of the Al-rich particles is less than 0.1 μm, the effect of the Al-rich particles cannot be sufficiently exerted. On the other hand, if the particle diameter exceeds 50 μm, abnormal discharge tends to occur during sputtering, which is not preferable. Therefore, the particle diameter of the Al-rich particles is set to 0.1 to 50 μm, more preferably 0.5 to 35 μm. In the present invention, the particle diameter is defined by the maximum value of the distance between any two points on the particle outline, that is, the absolute maximum length.

  Even if the temperature at which the sintered body is heat-treated in a vacuum is lower than 720 ° C. or higher than 920 ° C., a structure in which Al-rich particles are precipitated cannot be obtained. 760-880 degreeC. Further, even if the heat treatment holding time is shorter than 0.5 hours or longer than 10 hours, a structure in which Al-rich particles are deposited cannot be obtained, so 0.5 to 10 hours, more preferably 1 to 7 hours. did.

  The sputtering target of the present invention contains, in atomic%, Si: 5 to 20%, Cr: 5.5 to 25%, and Al-rich particles are dispersed in a base material having a composition comprising the balance: Al and inevitable impurities. Therefore, in order to relieve the stress generated in the target during sintering and sputtering, cracks do not occur during sintering and sputtering even when the Cr content is high.

  In addition to the above-described structure, the sputter target of the present invention has the effect of preventing the above-described target cracking because the area ratio of Al-rich particles in the target structure is 5 to 50%. It is done.

  Furthermore, according to the method for producing a sputter target of the present invention, an alloy powder production process for producing an AlSiCr alloy powder, and a sintering process for sintering the alloy powder obtained in the alloy powder production process to obtain a sintered body And a sintered body obtained in the sintering step is subjected to a heat treatment step of holding at 720 to 920 ° C. for 0.5 to 10 hours in a vacuum, so that Al-rich particles can be uniformly formed. Since it can be dispersed and precipitated, the above-mentioned target can be produced with good reproducibility.

The mapping image obtained by EPMA surface analysis of this invention target 1. FIG.

  Hereinafter, the sputtering target of the present invention and the method for producing the sputtering target will be specifically described with reference to examples. However, the present invention is not limited to this embodiment.

First, as a raw material, purity: 99.99% or more of Al, purity: 99.999% or more of Si, and purity: 99.99% or more of Cr were prepared.
Next, these raw materials were weighed so as to have the blending composition shown in Table 1 and charged into an alumina crucible. The alumina crucible was set in a gas atomizer and AlSiCr alloy powder was obtained by a gas atomization method using Ar gas injection. The gas atomization conditions were a melting temperature of 1200 ° C., an injection Ar gas pressure of 28 kgf / cm ² , and a crucible nozzle diameter of 1.5 mm. Thereafter, the powder was classified with a sieve having an opening of 100 μm, and the powder under the sieve was collected to obtain a raw material powder. This raw material powder was filled in a graphite mold having a diameter of 165 mm, and held for 3 hours under a vacuum hot press at a temperature of 700 ° C. and a pressure of 150 kgf / cm ² to obtain an AlSiCr alloy sintered body. This sintered body was heat-treated in a vacuum furnace under the conditions shown in Table 1 in a vacuum.

  The obtained sintered body was cut into a disk having a diameter of 152.4 mm and a thickness of 6 mm by cutting using a lathe. Although the surface of this invention target 1-9 was observed visually, all were not generating the crack.

  Then, it bonded to the backing plate made from oxygen-free copper with In solder, and it was set as this invention targets 1-9 which have the same component composition as the compounding composition of Table 1.

  Furthermore, the present invention targets 1 to 9 were mounted on a sputtering apparatus, and after discharging for 1 hour under conditions of Ar gas pressure 0.5 Pa and direct current 1000 W, the surface was visually observed, but no cracks were generated. It was.

Next, in order to observe the structure of the sintered body shown in Table 1, after burying a small piece in a resin and mirror polishing with a sample polishing apparatus, observation and analysis of the cross-sectional structure with EPMA (JEOL, JXA-8500F) Carried out. The analysis conditions for EPMA are:
Acceleration voltage: 15 kV,
Irradiation current: 5E-8A
Beam system: 1 μm
It was. The spectral crystals used for the analysis are Al: TAPH, Cr: LIF, Si: PETH.

  The cross-sectional structure of the inventive targets 1 to 9 was subjected to surface analysis at a field of magnification of 500 times to obtain an element distribution image of a field of view of 240 μm × 180 μm and analyzed. As a result, the particle size (absolute maximum length) 0.5 It was found that a ~ 35 μm Al-rich particle was dispersed. For example, FIG. 1 is a mapping image obtained by EPMA surface analysis of the target 1 of the present invention, and it can be seen that Al-rich particles of 0.5 to 35 μm are dispersed.

  A predetermined amount of these Al-rich particles was analyzed within the field of view to determine the average composition. The results are shown in Table 1. All were found to contain more than 97 atomic% Al.

Table 1 also shows the area ratio in the field of view where the peak intensity of characteristic X-rays of Al corresponding to Al-rich particles exceeds 562 in the Al composition image obtained as a result of the surface analysis of EPMA. The peak intensity is a numerical value of “LV” displayed in the mapping image obtained by the EPMA surface analysis shown in FIG. 1 as an example, and “the area ratio of the portion where the peak intensity count exceeds 562”. Indicates the total value of the values of “Area%” in the portion where the peak intensity count in FIG.
[Comparative Examples 1-4]
In the same manner as in the examples of the present invention, Al: purity of 99.99% or more, Si: purity of 99.99% or more, and Cr of purity: 99.99% or more were prepared as raw materials.
Next, these raw materials were weighed so as to have the blending composition shown in Table 1 and charged into an alumina crucible. Then, this alumina crucible was set in a gas atomizer, and AlSiCr was produced by a gas atomization method by Ar gas injection under the same conditions as in the examples. Then, the powder was classified with a sieve having an opening of 100 μm, and the powder under the sieve Was recovered and used as a raw material powder. A sintered body of an AlSiCr alloy was obtained by vacuum hot pressing of this raw material powder under the same conditions as in the example. This sintered body was heat-treated in a vacuum furnace under the conditions shown in Table 1 in a vacuum.

The obtained sintered body was cut using a lathe to obtain a disk having a diameter of 152.4 mm and a thickness of 6 mm. In Comparative Example 1, cracks were generated during the cutting process. In Comparative Examples 2 to 4, no crack was generated, and a disk having a predetermined size could be obtained.
Thereafter, the sintered bodies of Comparative Examples 2 to 4 were bonded to an oxygen-free copper backing plate with In solder to obtain Comparative Examples Targets 2 to 4 having the same component composition as the composition shown in Table 1.

  Further, Comparative Examples Targets 2 to 4 were mounted on a sputtering apparatus, and after discharging for 1 hour under the same conditions as in the Examples, the surface was visually observed.

Further, when surface analysis and quantitative analysis were performed on the comparative targets 1 to 4 by EPMA in the same manner as in the examples, the atomic ratio of Al, Si, and Cr was about 73: 8: 19 in the case of the comparative target 1 and Al. , Si and Cr atomic ratios of approximately 85: 1: 14 and Al, Si, Cr atomic ratios of approximately 62:19:19 were observed. The particles were found to be absent. As a result of conducting the same analysis for Comparative Examples Targets 2 to 4, it was found that there were no Al-rich particles.
[Comparative Example 5]
For comparison, in the same manner as in the example, as raw materials, Al of purity 99.99% or higher, Si of 99.99% or higher, and Cr of purity 99.99% or higher were prepared and charged into an alumina crucible. And after setting this alumina crucible in a gas atomizer and making it an AlSiCr alloy powder by a gas atomizing method by Ar gas injection, the powder is classified with a sieve having an opening of 100 μm, and the powder under the sieve is collected, did. This raw material powder was filled in a graphite mold having a diameter of 165 mm, and held for 3 hours under a vacuum hot press at a temperature of 700 ° C. and a pressure of 150 kgf / cm ² to obtain an AlSiCr alloy sintered body.

  The obtained sintered body was cut without heat treatment so as to be a disk having a diameter of 152.4 mm and a thickness of 6 mm using a lathe, but cracks were generated during the processing.

  Further, when surface analysis and quantitative analysis were performed on this comparative target 5 by EPMA in the same manner as in the example, it was found that there were no Al-rich particles.

以上の結果から分かるように、本発明ターゲットは、Ａｌの素地中にＡｌリッチの粒子を含有しているので、Ａｌの素地に生じる応力をＡｌリッチの粒子によって緩和されるので、Ｃｒの含有量が多いにもかかわらず、成形中およびスパッタ中に割れることを防止できる。

As can be seen from the above results, since the target of the present invention contains Al-rich particles in the Al substrate, the stress generated in the Al substrate is relieved by the Al-rich particles, so the content of Cr In spite of the large amount, cracking during molding and sputtering can be prevented.

  On the other hand, the comparative example target in which Al-rich particles are not dispersed in the target substrate is cracked during machining or sputtering after forming the target due to the stress caused by the high Cr content. You can see that

  The sputtering target of the present invention can form a reflective recording film having better corrosion resistance, and further, no cracking occurs during machining and sputtering after forming the target. Since it can be used suitably for formation, industrial applicability is very large.

Claims (4)

The component composition is atomic%, Si: 5 to 20%, Cr: 5.5 to 25%, the balance: a sputtering target that is Al and inevitable impurities,
A sputtering target, wherein Al-rich particles are dispersed in a composition base.   2. The sputtering target according to claim 1, wherein the proportion of Al in the component composition of the Al-rich particles is atomic% and is 97% or more.   The sputtering target according to claim 1, wherein an area ratio of the Al-rich particles in the target structure is 5 to 50%. It is a manufacturing method of the sputtering target in any one of Claims 1 thru | or 3, Comprising:
An alloy powder preparation step of preparing an AlSiCr alloy powder having a composition comprising, in atomic%, Si: 5 to 20%, Cr: 5.5 to 25%, and the balance: Al and inevitable impurities;
A sintering step in which the alloy powder obtained in the alloy powder preparation step is sintered to form a sintered body;
A heat treatment step of performing a heat treatment of holding the sintered body obtained in the sintering step in a vacuum or in an inert gas atmosphere at 720 to 920 ° C. for 0.5 to 10 hours;
A method for producing a sputtering target, comprising:

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