JP2006097126A - Sputtering target, method for producing the same, and optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering target suitable for arbitrarily forming a compositionally and structurally stable film, to provide a method for producing the same, and to provide a high-density optical recording medium using the sputtering target. <P>SOLUTION: There is provided: (1) the sputtering target containing at least one element selected from among BiFeO<SB>3</SB>, Bi<SB>25</SB>FeO<SB>40</SB>, and Bi<SB>36</SB>Fe<SB>2</SB>O<SB>57</SB>as the main component, (2) a sputtering target as described in (1), wherein the atomic ratio of Bi to Fe satisfies the requirements: Bi/Fe≥0.8, (3) the method for producing the above sputtering targets comprising firing Bi<SB>2</SB>O<SB>3</SB>and Fe<SB>2</SB>O<SB>3</SB>powders, and (4) the optical recording medium having a BiFeO film prepared by using the above sputtering target. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sputtering target used for forming an oxide layer which is a constituent layer of an optical recording medium, and a method for manufacturing the sputtering target. The present invention also relates to an optical recording medium manufactured using the sputtering target, and more particularly to a write-once optical recording medium capable of high-density recording even in a blue laser wavelength region.

In order to provide a write-once optical recording medium capable of recording / reproducing at a blue laser wavelength or less, development of a blue laser capable of ultra-high-density recording is progressing rapidly, and development of a write-once optical recording medium corresponding to it. Has been done.
In the prior application (Japanese Patent Application No. 2003-110867), the present applicant has disclosed that a write-once optical recording medium using a film containing Bi, Fe, and oxygen exhibits excellent characteristics. Also disclosed is the use of sputtering as a method of forming this layer.
Sputtering has been widely known as one of thin film vapor forming methods and has been used for industrial thin film production. In the sputtering method, a target material having the same component as that of the target film is prepared. Usually, argon gas ions generated by glow discharge are collided with the target material to strike out the constituent atoms of the target material, and the substrate. Film formation is performed by depositing atoms on the top. Since oxides generally have a high melting point, methods such as vapor deposition are not preferred, and high-frequency sputtering that applies a high frequency is often used.

Sputtering has many achievements in the manufacturing process and is advantageous in terms of throughput. However, when a film made of a mixed material of two or more elements is formed, the composition of the target and the composition of the film are often not the same, and thus the target composition needs to be examined. In addition, since the structure and properties of the film are often different depending on the form of the compound constituting the target, this point needs to be studied.
As a known technique, for example, Patent Document 1 discloses a Bi-based oxide target as a sputtering target for forming a dielectric film. However, this document does not describe a target containing Fe. If the types of constituent elements are different, the composition of the target and the composition of the target compound and the structure of the film and the relationship of the composition are also different, so it is necessary to change the target configuration, and the knowledge disclosed in this document is useful for reference of the present invention. Don't be.
Patent Document 2 describes a target for manufacturing a thin film of Bi ₃ Fe ₅ O ₁₂ . However, this document is for manufacturing a so-called garnet-structured thin film having a large magneto-optic effect, and the ratio of Bi to Fe is from 3: 5 to 3.5: 4.5. Is different.

Japanese Patent Laid-Open No. 11-92922 Japanese Patent Publication No. 2-42899

  In order to realize a write-once optical recording medium capable of high-density recording, a film containing Bi, Fe, and oxygen and having a stable composition and structure is required. For this purpose, an appropriate sputtering target is required. . However, since the form, structure, impurities, etc. of the compound constituting the target affect the composition and crystallinity of the film to be formed, it is necessary to make the compound constituting the target suitable for the characteristics of the required film. There is. Accordingly, it is an object of the present invention to provide a sputtering target suitable for arbitrarily forming a film having a stable composition and structure, a method for producing the sputtering target, and a high-density optical recording medium using the sputtering target. To do.

The above problems are solved by the following inventions 1) to 9) (hereinafter referred to as the present inventions 1 to 9).
1) A sputtering target comprising at least one of BiFeO ₃ , Bi ₂₅ FeO ₄₀ , and Bi ₃₆ Fe ₂ O ₅₇ as a main component.
2) The sputtering target according to 1), comprising Bi, Fe and oxygen.
3) The sputtering target according to 1) or 2), which contains Bi ₂ O ₃ and / or Fe ₂ O ₃ .
4) The sputtering target according to any one of 1) to 3), which does not contain Bi ₂ Fe ₄ O ₉ .
5) The sputtering target according to any one of 1) to 4), wherein the contents of Co, Ca, and Cr are below a detection limit by ICP analysis (high frequency inductively coupled plasma emission spectroscopy).
6) The sputtering target according to any one of 1) to 5), wherein a packing density is 65 to 96%.
7) The sputtering target according to any one of 1) to 6), wherein an atomic ratio of Bi and Fe satisfies a condition of Bi / Fe ≧ 0.8.
8) The method for producing a sputtering target according to any one of 1) to 7), wherein a powder of Bi ₂ O ₃ and Fe ₂ O ₃ is fired.
9) An optical recording medium comprising a BiFeO film formed using the sputtering target according to any one of 1) to 7).

Hereinafter, the present invention will be described in detail.
The present invention 1 relates to a sputtering target containing at least one of BiFeO ₃ , Bi ₂₅ FeO _40, and Bi ₃₆ Fe ₂ O ₅₇ as a main component. As described above, an optical recording medium using a film containing Bi, Fe, and oxygen exhibits excellent recording characteristics. As a sputtering target for magneto-optical recording having a garnet structure, those containing Bi, Fe, and oxygen have existed conventionally. However, in view of the composition for forming a garnet structure, these are mainly the above-mentioned compounds in the present invention. It is not an ingredient. Further, since a garnet structure cannot be formed with only three elements of Bi, Fe, and oxygen, a target having this composition has never been used. Furthermore, the present invention is not a magneto-optical recording medium, but an optical recording medium that does not use magnetism (particularly a write-once type optical recording medium capable of high-density recording), which mainly contains Bi, Fe, and oxygen (hereinafter referred to as BiFeO film). It is related with the sputtering target used for formation.
The present invention 2 relates to a sputtering target composed of three elements of Bi, Fe, and oxygen. In this case, an impurity element other than the three elements may be included in a trace amount, but it is not preferable to include a trace element that impairs the characteristics of the film.

The sputtering target of the present invention is prepared by mixing and firing raw material oxide powders. It is possible to fire from Bi oxide powder and Fe oxide powder. It is also possible to prepare a powder of a compound mainly containing three elements of Bi, Fe, and oxygen and to fire the powder to make a target. As the baking method, a pressure heating baking method such as a hot press method or an HIP method can be used. Regarding the firing temperature, it is preferable that the temperature is high in order to improve the target strength. However, in the case of a compound composed of three elements of Bi, Fe, and oxygen, phase separation, melting, etc. occur at about 800 ° C. or more, and it is uniform. It becomes difficult to fire the target. Therefore, it is necessary to control the firing temperature so as not to exceed about 750 ° C.
In particular, an optical recording medium using a BiFeO film formed using a target containing at least one of BiFeO ₃ , Bi ₂₅ FeO ₄₀ , and Bi ₃₆ Fe ₂ O ₅₇ as a main component as a recording layer exhibits good characteristics. . The presence of BiFeO ₃ , Bi ₂₅ FeO ₄₀ , and Bi ₃₆ Fe ₂ O ₅₇ can be confirmed by X-ray diffraction. Cu is used as the radiation source, and the angle of 2θ is measured from 5 to 60 degrees. Here, the main component means that the content (% by weight) is the highest. Usually, as a result of X-ray diffraction, the material that forms the largest peak may be regarded as the main component, but the content ratio may not match the magnitude of the peak. In addition, when two or more of BiFeO ₃ , Bi ₂₅ FeO ₄₀ , Bi ₃₆ Fe ₂ O ₅₇ are contained as the main component, the content of these two or more is the same and more than other components It is.

The present invention 3 further relates to a sputtering target containing Bi ₂ O ₃ and / or Fe ₂ O ₃ . An optical recording medium using a BiFeO film formed by using these targets as a recording layer exhibits good characteristics. The presence of Bi ₂ O ₃ and / or Fe ₂ O ₃ can be confirmed by X-ray diffraction. Cu is used as the radiation source, and the angle of 2θ is measured from 5 to 60 degrees.
The present invention 4 further relates to a sputtering target that does not contain Bi ₂ Fe ₄ O ₉ . As the Bi content increases, the Bi ₂ Fe ₄ O ₉ content tends to decrease. The presence or absence of Bi ₂ Fe ₄ O ₉ is confirmed by an X-ray diffraction method. Cu is used as the radiation source, and the angle of 2θ is measured from 5 to 60 degrees. An optical recording medium using as a recording layer a BiFeO film formed using a target in which the presence of Bi ₂ Fe ₄ O ₉ is confirmed by X-ray diffraction method has insufficient recording characteristics and is suitable for high-density recording. I found that there was nothing.

The present invention 5 further relates to a sputtering target in which the contents of Co, Ca, and Cr are below the detection limit. In the case where a target including impurities is used, an impurity element is also included in the formed film. In optical recording, irradiation light is absorbed by a recording layer to raise the temperature of the recording layer and cause a physical or chemical change to perform recording. A physical or chemical change refers to a change such as crystallization, but if the film used for the recording layer contains impurities, it is not preferable because the crystallization temperature changes or the crystal size during crystallization changes. .
For the detection of impurities, quantitative analysis of the composition by ICP analysis (high frequency inductively coupled plasma emission spectroscopy) is used. Although this analysis method is suitable for trace elemental analysis, it is preferable that this analysis method still be below the detection limit.

The present invention 6 further relates to a sputtering target having a packing density of 65 to 96%. When the packing density of the target is increased, the strength of the target is increased, and since the element density is high, the film forming time tends to be shortened, but the difference between the composition of the target and the film tends to be large. In many cases, it is possible to make the composition of the target and the film closer by lowering the density of the target. However, lowering the density not only slows the film forming speed but also makes the target itself brittle and breaks during film formation. Many problems occur. Here, the packing density is a value obtained by calculating the weight when the target volume is 100% occupied by the target substance and comparing it with the weight of the actually produced target.
Table 1 shows the packing density of the target when a Bi ₁₀ Fe ₅ Ox target having a diameter of 76.2 mm and a thickness of 4 mm is used for film formation, the state of the target during film formation or after film formation, or film formation The recording characteristics of the finished media are shown. If the packing density is 50% or less, the target cannot be molded even if it is fired, and the target is not formed. At 61%, molding was possible, but because it was brittle, it was easily damaged by an applied power of 100 W. At 98%, the density was too high and hard, so it was easily damaged. On the other hand, 65 to 96% could be molded without any problem and the recording characteristics were good. Even when 61% and 98% were formed under the condition that the film was not damaged during the film formation, the recording characteristics were good. As can be seen from the above results, a packing density of 65 to 96% is a preferred range.

The present invention 7 further relates to a sputtering target in which the atomic ratio of Bi and Fe satisfies the condition of Bi / Fe ≧ 0.8. An optical recording medium having a BiFeO film formed using this target exhibits excellent characteristics and is particularly suitable for high-density recording. Assuming that Bi ₂₅ FeO ₄₀ is included as a main component, the upper limit of Bi / Fe is theoretically about 25, but is actually about 15.
The present invention 8 relates to a method for producing a BiFeO target of the present invention 1-7 by calcining a powder of _Bi 2 _{O 3} and _Fe 2 _{O 3.} Bi ₂ O ₃ exists as an ordinary Bi oxide, and Fe ₂ O ₃ exists as an ordinary Fe oxide. These powders are pulverized dry or wet and classified into powders having a uniform particle size. Next, the mixture is mixed and heated and pressed to adjust the shape, followed by firing. Firing is maintained at 750 ° C. in the air. It is also possible to improve the strength of the target by repeating the process of once pulverizing the product once fired and performing heat and pressure molding. A sputtering target is obtained by bonding the target thus fired to a backing plate made of oxygen-free copper by metal bonding or resin bonding.

The present invention 9 relates to an optical recording medium having a BiFeO film formed using any one of the sputtering targets of the present invention 1-7. A necessary film is formed on a resin substrate such as polycarbonate to obtain an optical recording medium. A groove or pit for controlling tracking or the like may be formed on the resin substrate. A BiFeO film is formed by introducing argon gas in vacuum and applying high-frequency power. In addition, a metal film as a reflective layer or a protective layer for improving characteristics may be provided.
Although the present invention has been described mainly with respect to the optical recording medium, the application of the sputtering target of the present invention is not limited to the optical recording medium, and can be used for other applications as long as the performance of the film is suitable. For example, it can be used for forming a magnetic material thin film, forming a thin film for producing an optical control isolator, forming a thin film for an optical switch, and the like.
As a rough flow of the manufacturing process, it is possible to use processes of weighing raw materials, mixing with a dry ball mill, hot pressing, molding, and bonding. It is also possible to use procedures such as weighing, wet ball mill mixing, spray dryer, hot pressing, molding, and bonding.

  According to the present invention, it is possible to provide a sputtering target suitable for arbitrarily forming a film having a stable composition and structure, a manufacturing method thereof, and a high-density optical recording medium using the target.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited by these Examples.

Example 1
Bi ₂ O ₃ and Fe ₂ O ₃ powders are mixed so that the atomic ratio of Bi and Fe is 6: 5, and dry-mixed by a ball mill for 1 hour. This mixed powder was pressure-molded at 100 to 200 MPa and fired at 750 ° C. for 5 hours in the air to prepare a sputtering target. The size of the target was 152.4φ in diameter and 4 mm in thickness. This target was bonded to a backing plate made of oxygen-free copper by metal bonding to obtain a sputtering target 1. The packing density of this target was 75%.
The X-ray diffraction pattern of the sputtering target was measured. The measurement conditions are as shown in Table 2. The measurement results are shown in FIG.
A search was performed to identify the position of the diffraction peak obtained by this measurement, and a comparison was made with existing substances. (A) shown at the top of FIG. 1 is the diffraction pattern of the target 1, and (b) below it shows the position where the diffraction peak of BiFeO ₃ appears with known data. X-ray diffraction has a database of where diffracted glands of known substances come out and how strong they are based on data measured in the past, and the measured substances can be identified by comparing with the data. . As a result of searching by comparing the BiFeO ₃ data shown in (b) with the measured data in (a), the peak marked with a circle was the BiFeO ₃ peak. Similarly, (c) shows known data of Fe ₂ O ₃ and (d) shows known data of Bi ₂ O ₃ . Similarly, Bi ₂ O ₃ and Fe ₂ O ₃ were identified. The largest peak is that of BiFeO ₃ , and it was revealed that this compound is mainly present.
Further, ICP analysis was performed on the sputtering target. A part of the target was dissolved in diluted aqua regia as a sample and diluted with ultrapure water to obtain a measurement sample. This solution was analyzed for each element of Co, Ca, and Cr. As a result, no significant value was obtained for each element below the detection limit.

上記光記録媒体に対し、パルステック工業（株）製の光ディスク評価装置ＤＤＵ−１０００（波長：４０５ｎｍ、ＮＡ：０．６５）を用いて、以下の条件で二値記録を行った。
＜記録条件＞
・変調方式 ：８−１６変調
・記録線密度 ： １Ｔ＝０．０９１７（μｍ）
最短マーク長３Ｔ＝０．２７５（μｍ）
・記録線速度 ： ６．０（ｍ／ｓ）
・波形等化 ： ノーマルイコライザ
その結果、図２に示すように、記録パワーが６．１ｍＷで１０．２％という良好なジッタ値が得られ、良好な記録特性を実現することができた。 Example 2
An optical recording medium was prepared using the sputtering target prepared in Example 1.
On a polycarbonate substrate having a guide groove (groove depth 50 nm, track pitch 0.44 μm), a BiFeO thin film having a film thickness of 15 nm is provided by sputtering, and a dye represented by the following [Chemical Formula 1] by spin coating. An organic material thin film (average film thickness of about 30 nm) is provided, an Ag reflective layer having a film thickness of 150 nm is formed thereon by sputtering, and a film thickness of about 5 μm made of an ultraviolet curable resin is further formed thereon by spin coating. A write-once type optical recording medium was obtained by providing a protective layer. The dye of [Chemical Formula 1] is a material used for conventional DVD-R and DVD + R, and is a material that hardly absorbs in the blue laser region.

Binary recording was performed on the above optical recording medium under the following conditions using an optical disc evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
<Recording conditions>
Modulation method: 8-16 modulation Recording linear density: 1T = 0.0917 (μm)
Shortest mark length 3T = 0.275 (μm)
・ Recording linear velocity: 6.0 (m / s)
Waveform equalization: Normal equalizer As a result, as shown in FIG. 2, a good jitter value of 10.2% was obtained at a recording power of 6.1 mW, and good recording characteristics could be realized.

Example 3
A sputtering target 2 was obtained in the same manner as in Example 1 except that powders of Bi ₂ O ₃ and Fe ₂ O ₃ were mixed so that the atomic ratio of Bi and Fe was 35: 5. The packing density of this target was 67%.
The X-ray diffraction pattern of the sputtering target was measured. The measurement conditions are as shown in Table 2. The measurement results are shown in FIG.
A search was performed to identify the position of the diffraction peak obtained by this measurement, and a comparison was made with existing substances. It can be said that the peak of the pattern measured as shown in FIG. 3 is only the peak corresponding to Bi ₂₅ FeO ₄₀ . Therefore, naturally, the largest peak is the peak of Bi ₂₅ FeO ₄₀ , and it was revealed that this compound is mainly present.

Example 4
An optical recording medium was prepared using the sputtering target prepared in Example 3.
On a polycarbonate substrate having a guide groove (groove depth 50 nm, track pitch 0.44 μm), a ZnS—SiO ₂ thin film having a thickness of 50 nm and a BiFeO thin film having a thickness of 15 nm are sequentially laminated by sputtering, and spins are formed thereon. An organic material thin film (average film thickness of about 30 nm) composed of the dye represented by the above [Chemical Formula 1] is provided by a coating method, an Ag reflection layer having a thickness of 150 nm is provided thereon by a sputtering method, and spin coating is further provided thereon. A write-once optical recording medium was obtained by providing a protective layer made of an ultraviolet curable resin and having a thickness of about 5 μm. The dye of [Chemical Formula 1] is a material used for conventional DVD-R and DVD + R, and is a material that hardly absorbs in the blue laser region.
Binary recording was performed on the above optical recording medium under the following conditions using an optical disc evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
<Recording conditions>
Modulation method: 8-16 modulation Recording linear density: 1T = 0.0917 (μm)
Shortest mark length 3T = 0.275 (μm)
・ Recording linear velocity: 6.0 (m / s)
Waveform equalization: normal equalizer As a result, as shown in FIG. 4, a good jitter value of 8.6% was obtained at a recording power of 7.0 mW, and good recording characteristics could be realized.
In addition, even when the recording power exceeds the optimum recording power, the reproduction signal level (RF Level) of the recording mark portion does not change greatly, and a write-once type optical recording medium having a high modulation degree and a wide recording power margin is realized. We were able to.

Comparative Example 1
A sputtering target 3 was obtained in the same manner as in Example 1 except that powders of Bi ₂ O ₃ and Fe ₂ O ₃ were mixed so that the atomic ratio of Bi and Fe was 1: 5. The packing density of this target was 67%.
The X-ray diffraction pattern of the sputtering target was measured. The measurement conditions are as shown in Table 2. The measurement results are shown in FIG.
A search was performed to identify the position of the diffraction peak obtained by this measurement, and a comparison was made with existing substances. As a result, peaks corresponding to Bi ₂ Fe ₄ O ₉ , Bi ₂ O ₃ and Fe ₂ O ₃ were present, but none of the other peaks were applicable. The largest peak is that of Bi ₂ Fe ₄ O ₉ , and it was revealed that this compound is mainly present.

Comparative Example 2
An optical recording medium was prepared using the sputtering target prepared in Comparative Example 1.
On a polycarbonate substrate having a guide groove (groove depth 50 nm, track pitch 0.44 μm), a ZnS-SiO ₂ thin film having a thickness of 50 nm and a BiFeO thin film having a thickness of 10 nm are sequentially laminated by sputtering, and spins are formed thereon. An organic material thin film (average film thickness of about 30 nm) made of a dye represented by the following [Chemical Formula 1] is provided by a coating method, an Ag reflective layer having a thickness of 150 nm is provided thereon by a sputtering method, and spin coating is further provided thereon. A write-once optical recording medium was obtained by providing a protective layer made of an ultraviolet curable resin and having a thickness of about 5 μm. The dye of [Chemical Formula 1] is a material used for conventional DVD-R and DVD + R, and is a material that hardly absorbs in the blue laser region.
Binary recording was performed on the above optical recording medium under the following conditions using an optical disc evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
<Recording conditions>
Modulation method: 8-16 modulation Recording linear density: 1T = 0.0917 (μm)
Shortest mark length 3T = 0.275 (μm)
・ Recording linear velocity: 6.0 (m / s)
-Waveform equalization: Normal equalizer As a result, good jitter could not be obtained such that the recording power was 8.1 mW and the jitter value was 22.6%.
Furthermore, when the thickness of the BiFeO film was changed to 15 nm and 20 nm, the jitter became worse and measurement was impossible.

Example 5
A sputtering target 4 was obtained in the same manner as in Example 1 except that Bi ₂ O ₃ and Fe ₂ O ₃ powder were mixed so that the atomic ratio of Bi and Fe was 4: 5. The packing density of this target was 77%.
The X-ray diffraction pattern of the sputtering target was measured. The measurement conditions are as shown in Table 2. The measurement results are shown in FIG.
The diffraction pattern obtained by this measurement is shown in (a). A search was performed to identify the substance, and the peak positions of the existing substance (b) BiFeO ₃ and (c) Bi ₂ Fe ₄ O ₉ were compared. As a result, it was found that there were only peaks corresponding to BiFeO ₃ and Bi ₂ Fe ₄ O ₉ . The largest peak is that of BiFeO ₃ , and it was revealed that this compound is mainly present.

Example 6
An optical recording medium was prepared using the sputtering target prepared in Example 5.
On a polycarbonate substrate having a guide groove (groove depth 50 nm, track pitch 0.44 μm), a ZnS-SiO ₂ thin film having a thickness of 50 nm and a BiFeO thin film having a thickness of 10 nm are sequentially laminated by sputtering, and spins are formed thereon. An organic material thin film (average film thickness of about 30 nm) composed of the dye represented by the above [Chemical Formula 1] is provided by a coating method, an Ag reflection layer having a thickness of 150 nm is provided thereon by a sputtering method, and spin coating is further provided thereon. A write-once optical recording medium was obtained by providing a protective layer made of an ultraviolet curable resin and having a thickness of about 5 μm. The dye of [Chemical Formula 1] is a material used for conventional DVD-R and DVD + R, and is a material that hardly absorbs in the blue laser region.
An optical disk evaluation apparatus DDU-10 manufactured by Pulstec Industrial Co., Ltd. is used for the optical recording medium.
Binary recording was performed using 00 (wavelength: 405 nm, NA: 0.65) under the following conditions. The shortest mark length was set to 0.205 (μm) to check whether high density recording was possible.
<Recording conditions>
Modulation method: 1-7 modulation Recording linear density: Shortest mark length 2T = 0.205 (μm)
・ Recording linear velocity: 6.0 (m / s)
-Waveform equalization: Normal equalizer The result is shown in FIG.

Example 7
An optical recording medium produced in the same manner as in Example 6 was evaluated under the same conditions using a sputtering target produced in the same manner as in Example 5 except that the atomic ratio of Bi and Fe was changed. The results are shown in FIG. As can be seen from the figure, when Bi / Fe ≧ 0.8 [that is, Bi / (Bi + Fe) ≧ 4/9 in the figure], the jitter is around 14%, which is good even in high-density recording. It was confirmed that a good jitter was obtained. Further, it can be seen that even when Bi / Fe ≧ 0.6 [that is, Bi / (Bi + Fe) ≧ 3/8 in the figure], the jitter is considerably improved and effective.

Example 8
A sputtering target 5 was obtained in the same manner as in Example 1 except that powders of Bi ₂ O ₃ and Fe ₂ O ₃ were mixed so that the atomic ratio of Bi and Fe was 10: 5. The packing density of this target was 85%.
The X-ray diffraction pattern of the sputtering target was measured. The measurement conditions are as shown in Table 2. The measurement results are shown in FIG.
A search was performed to identify the position of the diffraction peak of the diffraction pattern (a) obtained by this measurement, and the peak positions (b) to (e) of the existing substances were compared. As a result, peaks corresponding to Bi ₂₅ FeO ₄₀ , BiFeO ₃ , Bi ₂ O ₃ , and Fe ₂ O ₃ existed, but none of the other peaks corresponded. The largest peak was that of Bi ₂₅ FeO ₄₀ , and it was revealed that this compound was mainly present.
Further, ICP analysis was performed on the sputtering target. A part of the target was dissolved in diluted aqua regia as a sample and diluted with ultrapure water to obtain a measurement sample. This solution was analyzed for each element of Co, Ca, and Cr. As a result, no significant value was obtained for each element below the detection limit.
Further, in the same manner as described above, a sputtering target 6 was produced in which 0.003% by weight of Al and 0.001% by weight of Co were detected as impurities.

Example 9
An optical recording medium was produced using the sputtering targets 5 and 6 produced in Example 8, respectively.
On a polycarbonate substrate having a guide groove (groove depth 50 nm, track pitch 0.44 μm), a ZnS—SiO ₂ thin film having a thickness of 50 nm and a BiFeO thin film having a thickness of 15 nm are sequentially laminated by sputtering, and spins are formed thereon. An organic material thin film (average film thickness of about 30 nm) composed of the dye represented by the above [Chemical Formula 1] is provided by a coating method, an Ag reflection layer having a thickness of 150 nm is provided thereon by a sputtering method, and spin coating is further provided thereon. A write-once optical recording medium was obtained by providing a protective layer made of an ultraviolet curable resin and having a thickness of about 5 μm. The dye of [Chemical Formula 1] is a material used for conventional DVD-R and DVD + R, and is a material that hardly absorbs in the blue laser region.
Binary recording was performed on the above optical recording medium under the following conditions using an optical disc evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
<Recording conditions>
Modulation method: 8-16 modulation Recording linear density: 1T = 0.0917 (μm)
Shortest mark length 3T = 0.275 (μm)
・ Recording linear velocity: 6.0 (m / s)
・ Waveform equalization: Normal equalizer As a result, the recording power using the target 5 is 8.4% at 5.0 mW, and the recording power using the target 6 is 8.2% at 5.0 mW. Good jitter values were obtained and good recording characteristics could be realized.
In addition, even when the recording power exceeds the optimum recording power, the reproduction signal level (RF Level) of the recording mark portion does not change greatly, and a write-once type optical recording medium having a high modulation degree and a wide recording power margin is realized. We were able to.

Example 10
A sputtering target 7 was obtained in the same manner as in Example 1 except that powders of Bi ₂ O ₃ and Fe ₂ O ₃ were mixed so that the atomic ratio of Bi and Fe was 10: 5. The packing density of this target was 71%.
The X-ray diffraction pattern of the sputtering target was measured. The measurement conditions are as shown in Table 2. The measurement results are shown in FIG.
A search was performed to identify the position of the diffraction peak obtained by this measurement, and a comparison was made with existing substances. (A) shown at the top of FIG. 9 is the diffraction pattern of the target 7, and (b) below it shows the position where the diffraction peak of Bi ₃₆ Fe ₂ O ₅₇ appears with known data. It is. X-ray diffraction has a database of where the diffraction lines of known substances come out and how strong they are based on the data measured in the past, and the measurement substance can be identified by comparing with the data. . (C) shows the known data of BiFeO ₃ , and (d) shows the known data of Fe ₂ O ₃ . The largest peak is that of Bi ₃₆ Fe ₂ O ₅₇ , and it was revealed that this compound is mainly present.

Example 11
An optical recording medium was produced using the sputtering target produced in Example 10.
On a polycarbonate substrate having guide grooves (groove depth 21 nm, track pitch 0.44 μm), a BiFeO thin film having a thickness of 5 nm, a ZnS—SiO ₂ film having a thickness of 14 nm, and an Ag reflecting layer having a thickness of 100 nm are sequentially formed by sputtering. A write-once optical recording medium was obtained by laminating and providing a protective layer having a thickness of about 5 μm made of an ultraviolet curable resin by spin coating.
Binary recording was performed on the above optical recording medium under the following conditions using an optical disc evaluation apparatus DDU-1000 (wavelength: 405 nm, NA: 0.65) manufactured by Pulstec Industrial Co., Ltd.
<Recording conditions>
Modulation method: 8-16 modulation Recording linear density: 1T = 0.0917 (μm)
Shortest mark length 3T = 0.275 (μm)
・ Recording linear velocity: 6.0 (m / s)
Waveform equalization: Normal equalizer As a result, a good jitter value of 6.2% was obtained at a recording power of 10.1 mW, and good recording characteristics could be realized.

The figure which shows the X-ray-diffraction pattern of the sputtering target 1. FIG. FIG. 4 is a diagram showing recording characteristics of an optical recording medium manufactured using a sputtering target 1. The figure which shows the X-ray-diffraction pattern of the sputtering target 2. FIG. FIG. 4 is a diagram showing recording characteristics of an optical recording medium manufactured using a sputtering target 2. The figure which shows the X-ray-diffraction pattern of the sputtering target 3. FIG. The figure which shows the X-ray-diffraction pattern of the sputtering target 4. FIG. The figure which shows the recording characteristic of the optical recording medium produced using the sputtering target from which Bi / Fe ratio differs. The figure which shows the X-ray-diffraction pattern of the sputtering target 5. FIG. The figure which shows the X-ray-diffraction pattern of the sputtering target 7. FIG.

Claims (9)

A sputtering target comprising at least one of BiFeO ₃ , Bi ₂₅ FeO ₄₀ , and Bi ₃₆ Fe ₂ O ₅₇ as a main component.   The sputtering target according to claim 1, comprising Bi, Fe, and oxygen. Bi ₂ O ₃ and / or Fe ₂ O ₃ are contained, The sputtering target of Claim 1 or 2 characterized by the above-mentioned. The sputtering target according to any one of claims 1 to 3, which does not contain Bi ₂ Fe ₄ O ₉ .   The sputtering target according to any one of claims 1 to 4, wherein the contents of Co, Ca and Cr are not more than a detection limit by ICP analysis (high frequency inductively coupled plasma emission spectroscopy).   The sputtering target according to any one of claims 1 to 5, wherein a packing density is 65 to 96%.   The sputtering target according to any one of claims 1 to 6, wherein the atomic ratio of Bi and Fe satisfies a condition of Bi / Fe ≧ 0.8. Bi ₂ O ₃ in the method of manufacturing the sputtering target according to any one of claims 1 to 7, characterized in that the baking powder Fe ₂ O _3. An optical recording medium comprising a BiFeO film formed using the sputtering target according to claim 1.

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