TWI412619B - A Bi-Ge-O sintered body sputtering target, a method for manufacturing the same, and an optical recording medium - Google Patents

Abstract

Provided are: a sintered target comprising bismuth (Bi), germanium (Ge), and oxygen (O); a manufacturing method therefor; and an optical recording medium. Said Bi-Ge-O sintered sputtering target is characterized in that the relationship between the number of bismuth atoms and the number of germanium atoms satisfies the relation 0.57 < (Bi/(Bi+Ge)) 12GeO20, Bi4Ge3O12, and GeO2. The provided target does not crack upon sputtering, generates few particulates, allows fabrication of stably high-quality thin films, and makes it possible to obtain an optical recording medium with no errors in recorded bits.

Description

Bi-Ge-O sintered body sputtering target, manufacturing method thereof and optical recording medium

The present invention relates to a Bi-Ge-O sintered body sputtering target, a method for producing the same, and an optical recording medium, and particularly relates to a crack that does not occur at the time of sputtering, and the generation of particles is small. A Bi-Ge-O sintered sputtering target which can stably produce a high-quality film and obtain an optical recording medium which does not cause recording bit error, a method for producing the target, and an optical recording medium.

The WORM (Write Once Read Many) optical recording medium is an optical recording medium capable of high-density recording even in laser light of a blue wavelength region (350 to 500 nm), particularly having high recording sensitivity and having multiple layers. An optical recording medium of the recording layer.

In order to meet the demand for higher density, the optical disc is being made denser by multi-layering. The development of an optical recording medium for high-density recording is also being carried out in a disc using a blue LD.

In order to realize a recordable optical recording medium capable of high-density multilayer recording, a material having a stable composition and structure is not necessary, and a film having excellent light transmission characteristics is also required, and such a material is mostly an oxide, and generally has a high melting point. Sputtering is often used as a film forming method.

Therefore, there is a need for a sputtering target suitable for obtaining such a film. However, since the form, structure, and the like of the compound constituting the target also affect the sputtering characteristics, it is possible to stably perform good sputtering when the compound constituting the target is made to be suitable for the characteristics of the desired film. Plating problem.

When a film for an optical recording medium is formed on a substrate by a sputtering method, the occurrence of particles may increase due to the target material, and the quality may be degraded. Especially in high recording density media, recording bit errors caused by particles or the like are a serious problem. Therefore, the cause becomes a defective product, and the problem of a decrease in yield occurs.

Previously, the proposed optical recording medium was proposed with a variety of materials. For example, Patent Document 1 discloses an optical recording medium in which at least a recording layer is formed on a substrate, and main components of constituent elements of the recording layer are Bi and O (oxygen), contain B, and contain Ge and Li selected from the group consisting of Ge and Li. At least one element X of Sn, Cu, Fe, Pd, Zn, Mg, Nd, Mn, Ni.

Further, Patent Document 2 describes a write-once optical recording medium characterized in that the recording layer contains Bi and M (M is Mg, Al, Cr, Mn, Co, Fe, Cu, Zn, Li, Si, Ge, And at least one of Zr, Ti, Hf, Sn, Mo, V, Nb, Y, and Ta) and oxygen, and the recording mark portion on which the information is recorded includes crystals of the elements contained in the recording layer and/or the elements Crystallization of oxides.

Further, Patent Document 3 to Patent Document 8 have also been proposed. Among these, a combination of an optical recording medium composed of bismuth (Bi), germanium (Ge), and oxygen (O) is also considered, and it is also described that the optical recording is formed by sputtering of a sintered target. media. However, the Bi-Ge-O sintered body sputtering target has a problem that the thermal shock is weak, and cracks and cracks are often generated when sputtering is performed at high power, thereby causing generation of particles and impairing the recording film. Quality.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2008-210492

Patent Document 2: Japanese Laid-Open Patent Publication No. 2006-116948

Patent Document 3: Japanese Patent Laid-Open Publication No. 2003-48375

Patent Document 4: Japanese Laid-Open Patent Publication No. 2005-161831

Patent Document 5: Japanese Laid-Open Patent Publication No. 2005-108396

Patent Document 6: Japanese Laid-Open Patent Publication No. 2007-169779

Patent Document 7: Japanese Laid-Open Patent Publication No. 2008-273167

Patent Document 8: Japanese Patent No. 4271063

An object of the present invention is to provide a Bi-Ge-O sintered body sputtering target, a method for producing the same, and an optical recording medium, and more particularly to provide a crack that does not cause a target during sputtering, and which generates less particles. A Bi-Ge-O sintered sputtering target which can stably produce a high-quality thin film and which can produce an optical recording medium in which recording bit errors are not generated, a method for producing the target, and an optical recording medium can be obtained.

In order to solve the problem, the present inventors have conducted intensive studies and obtained the following knowledge: a Bi-Ge-O sintered body having an appropriate composition can be selected to control the crystal phase, and the thermal shock of the target can be suppressed to prevent the crack of the target. It can effectively suppress the generation of particles during sputtering.

Based on this knowledge, the present invention provides:

1) A Bi-Ge-O based sintered body sputtering target comprising bismuth (Bi), germanium (Ge), and oxygen (O), characterized in that the atomic ratio of Bi to Ge is 0.57 < (Bi) /(Bi+Ge))<0.92, containing three phases of Bi ₁₂ GeO ₂₀ , Bi ₄ Ge ₃ O ₁₂ , and GeO ₂ as a crystal phase;

2) The sintered body sputtering target according to the above 1), wherein, when a thermal shock of heating at 200 ° C for 30 minutes is applied to the target, the average bending strength reduction rate before and after the thermal shock is 50% or less;

3) An optical recording medium formed by sputtering using the target of the above 1) or 2).

Also, the present invention provides:

4) A Bi-GeO based sintered body sputtering target manufacturing method of plating, comprising: a GeO ₂ powder _{0.03 ~ 89mol%, Bi 12 GeO} 20 11 ~ 99.97mol% powder as a starting material containing Bi and Ge After mixing the raw materials so that the atomic ratio is 0.57 < (Bi / (Bi + Ge)) < 0.92, the raw materials are hot-pressed at 600 to 840 ° C and a pressure of 150 to 400 kg / cm ² to prepare Bi _{12 .} a sintered body of a crystal phase of three phases of GeO ₂₀ , Bi ₄ Ge ₃ O ₁₂ and GeO ₂ ;

(5) The method for producing a Bi-Ge-O sintered body sputtering target according to the above 4), wherein the FeO ₂ powder is mixed with 14.3 mol% and the Bi ₂ O ₃ powder is 85.7 mol%, and then a solid phase reaction is carried out to prepare Bi _{12 .} GeO ₂₀ powder;

(6) The method for producing a Bi-Ge-O sintered body sputtering target according to the above 4) or 5), wherein the sintering raw material powder having a cerium oxide having an average crystal grain size of 10 to 50 μm is sintered.

The Bi-Ge-O sintered body sputtering target of the present invention has an excellent effect of not causing cracks in the target during sputtering, and there is little generation of particles, and a high-quality film can be stably produced, and it is not obtained. An optical recording medium that records bit error is generated.

The Bi-Ge-O sintered body sputtering target of the present invention is composed of bismuth (Bi), germanium (Ge), and oxygen (O), and is characterized in that the atomic ratio of Bi to Ge is 0.57 < (Bi/( Bi+Ge))<0.92, containing three phases of Bi ₁₂ GeO ₂₀ , Bi ₄ Ge ₃ O ₁₂ and GeO ₂ as a crystal phase. The recording film having such a composition is a preferable composition capable of achieving high-density recording by multilayering, and it is possible to stably perform good sputtering film formation.

Generally, a powder of bismuth trioxide (Bi ₂ O ₃ ) and cerium oxide (GeO ₂ ) is used as a starting material to sinter the starting material, and when the composition target is produced, Bi ₁₂ GeO ₂₀ and Bi _{4 are formed.} The two phases of Ge ₃ O ₁₂ coexist.

However, since the difference in thermal expansion coefficient between Bi ₁₂ GeO ₂₀ and Bi ₄ Ge ₃ O ₁₂ is large, there is a problem that cracks occur when the thermal shock is extremely weak and the film is formed by sputtering under high power.

Accordingly, in the present invention, the thermal expansion coefficient of Bi ₁₂ GeO ₂₀ takes a value of between ₁₂ Bi ₄ Ge ₃ O of GeO ₂ as an intermediate phase, and a sintered body tissue of 3 phases coexist, whereby The GeO ₂ phase becomes a buffer phase and the thermal shock resistance is greatly improved. Further, the thermal expansion coefficient of Bi ₁₂ GeO ₂₀ is 1.39 × 10 ^-5 , and the thermal expansion coefficient of Bi ₄ Ge ₃ O ₁₂ is 6.00 × 10 ^-6 . On the other hand, GeO _{2 has} a thermal expansion coefficient of 7.59 × 10 ^-6 , which is a phase having a thermal expansion coefficient between the first two, and thus can be used as an effective buffer phase.

As a result, the following advantages can be obtained: the thermal shock resistance of the target is improved, whereby the film can be formed at a high power, and the production efficiency can be improved.

Further, it is possible to obtain an effect that the generation of particles due to cracks or cracks is remarkably reduced, a stable high-quality film can be produced, and light which can produce a recording density without causing recording bit errors and achieving high recording density can be obtained. Record media.

It is also effective to prevent the generation of particles at the time of sputtering by setting the average crystal grain size of the target to 100 μm or less.

Further, in the case where the Bi-Ge-O based sintered body sputtering target of the present invention is subjected to a thermal shock of heating at 200 ° C for 30 minutes, the average bending strength reduction rate before and after the thermal shock is 50% or less.

In the case of a target in which two phases of Bi ₁₂ GeO ₂₀ and Bi ₄ Ge ₃ O ₁₂ of the prior art are present, the average bending strength reduction rate before and after the thermal shock exceeds 80%, which is a significant improvement effect. Thereby, the crack of the target caused by the thermal shock is suppressed, and the characteristics of the target can be directly evaluated.

Further, the ratio of the three phases of the target Bi ₁₂ GeO ₂₀ , Bi ₄ Ge ₃ O ₁₂ and GeO ₂ can be arbitrarily adjusted within the range of the production conditions of the present invention. This ratio also depends on the degree of thermal shock of the target during sputtering, that is, the film forming speed (production speed) or the structure of the sputtering apparatus, and is an index for mitigating thermal shock.

The optical recording medium formed by sputtering using the above target is a stable high-quality film, and an optical recording medium which does not cause recording bit errors can be obtained.

When a Bi-Ge-O sintered body sputtering target is produced, a powder of antimony trioxide and cerium oxide is used as a starting material, and the atomic ratio of Bi to Ge is 0.57<(Bi/(Bi+Ge)). These materials were mixed in a manner of <0.92. Then, the mixed powder was hot-pressed at 600 to 840 ° C under a pressing pressure of 150 to 400 kg/cm ² . Thereby, a sintered body containing a crystal phase of three phases of Bi ₁₂ GeO ₂₀ , Bi ₄ Ge ₃ O ₁₂ and GeO ₂ can be produced.

The sintering conditions are preferred conditions for obtaining a target of uniform composition. Although the target can be produced under the sintering conditions deviating from the above range, the reproducibility of the target quality is poor, and therefore it is preferably within the above range. Further, the ratio of the atomic ratio of Bi to Ge in the raw material phase, that is, 0.57 < (Bi / (Bi + Ge)) < 0.92, is directly reflected in the target, and the target of the composition ratio can be obtained.

When manufacturing a Bi-GeO based sintered compact sputtering target, a sintering bismuth trioxide and germanium oxide raw material powder is suitably used GeO _{2 0.03 ~ 89mol%, Bi 12 GeO} 20 powder 11 ~ 99.97mol%. It is also an important condition for efficiently obtaining a sintered body containing a crystal phase of three phases of Bi ₁₂ GaO ₂₀ , Bi ₄ Ge ₃ O ₁₂ and GeO ₂ .

Further, it is preferred to use a cerium oxide (GeO ₂ ) powder having an average crystal grain size of 10 to 50 μm for sintering. The reason is that when the lower limit value is not reached, aggregation of the powder tends to occur, and it is difficult to obtain a uniform sintered body. Moreover, when it exceeds the above-mentioned upper limit, coarse particles are generated in the sintered target, and it is easy to segregate, so it is preferable to be in the above range. This range is a better powder condition, but powders outside this range can also be used by adjusting the sintering conditions.

The Bi ₁₂ GeO ₂₀ powder can be prepared by previously mixing a GeO ₂ powder of 14.3 mol% and a Bi ₂ O ₃ powder of 85.7 mol%, followed by pulverization. The particle diameter of the Bi ₁₂ GeO ₂₀ powder is not particularly limited, and is not less than 100 μm. The reason for this is that under the sintering conditions of the present invention, there is no agglomeration such as GeO ₂ .

Example

Hereinafter, description will be given based on examples and comparative examples. Furthermore, this embodiment is only an example and is not limited by this example. That is, the present invention is limited only by the scope of the patent application, and includes various modifications other than the embodiments included in the invention.

(Example 1)

A powder of 3N (99.9%) of antimony trioxide and cerium oxide was used as a starting material, and GeO ₂ powder having an average particle diameter of ₁₂ μm and Bi ₁₂ GeO ₂₀ powder having an average particle diameter of 20 μm were prepared in advance, respectively. When the atomic ratio of Bi to Ge is 0.67, the GeO ₂ powder is 83.3 mol%, and the Bi ₁₂ GeO ₂₀ powder is 16.7 mol%, and then mixed, and the mixed powder is filled in a carbon mold at a temperature of 700 ° C. The hot pressing was carried out under the conditions of a pressure of 250 kg/cm ² .

Further, in the present embodiment, GeO ₂ powder and Bi ₁₂ GeO ₂₀ powder are added in such a manner as to achieve the above molar ratio, and the combined ratios of the additions are 50.0 mol% with GeO _{2 and} 50.0 mol of Bi ₂ O _{3 .} % consistent blending is adjusted in a manner similar to that.

The sintered body after hot pressing is finished to form a target. The relative density of the target was 102% (7.44 g/cm ³ at 100% density).

The X-ray diffraction measurement of the sintered body confirmed the three-phase structure of Bi ₁₂ GeO ₂₀ , Bi ₄ Ge ₃ O ₁₂ , and GeO ₂ . The results are shown in Table 1.

Next, a thermal shock of heating at 200 ° C for 30 minutes was applied to the target. Then, the bending test of JIS Standard 1601 was carried out (measured from 5 points at any position in the target, and a test piece having a width of 4 ± 0.1 mm, a height of 3 ± 0.1 mm, and a length of 40 to 50 mm was selected, and 5 points were determined. The average value of the measurement results was measured, and the average bending strength ratio (the rate of decrease in strength) before and after the thermal shock was measured. A slight deviation occurred due to the difference in the measurement site, but either of them was less than 50%, and the rate of decrease in strength was low.

Next, using this target, sputtering was performed at a power of 2 kW. As a result, cracks or cracks did not occur in the target, and the generation of particles was remarkably smaller than in the comparative examples described below.

As a result, the embodiment of the present invention is a good target having excellent effects of not causing cracks, improving production efficiency, and stably producing a high-quality film, and obtaining an optical record which does not cause recording bit error. media.

(Example 2)

A powder of 3N (99.9%) of antimony trioxide and cerium oxide was used as a starting material, and GeO ₂ powder having an average particle diameter of ₁₂ μm and Bi ₁₂ GeO ₂₀ powder having an average particle diameter of 20 μm were prepared in advance, respectively. When the ratio of the atomic ratio of Bi to Ge is 0.80, the content of GeO ₂ powder is 66.7 mol%, and the powder of Bi ₁₂ GeO _{20 is} 33.3 mol%, and then mixed, and the mixed powder is filled in a carbon mold at a temperature of 700 ° C. The hot pressing was carried out under the conditions of a pressure of 250 kg/cm ² .

Further, in the present embodiment, GeO ₂ powder and Bi ₁₂ GeO ₂₀ powder are added in such a manner as to achieve the above molar ratio, and the combined ratios of the additions are 33.3 mol% with GeO _{2 and} 66.7 mol of Bi ₂ O ₃ . % consistent blending is adjusted in a manner similar to that.

The sintered body after hot pressing is finished to form a target. The relative density of the target was 95.9% (7.58 g/cm ³ at 100% density).

The X-ray diffraction measurement of the sintered body confirmed the three-phase structure of Bi ₁₂ GeO ₂₀ , Bi ₄ Ge ₃ O ₁₂ , and GeO ₂ . The results are shown in Table 1.

Next, a thermal shock of heating at 200 ° C for 30 minutes was applied to the target. Then, a bending test of JIS Standard 1601 was carried out, and the average bending strength ratio (rate of reduction of strength) before and after the thermal shock was measured. A slight deviation occurred due to the difference in the measurement site, but either of them was less than 50%, and the rate of decrease in strength was low.

Next, using this target, sputtering was performed at a power of 2 kW. As a result, the target does not generate cracks or cracks, and the generation of particles is small.

As a result, the embodiment of the present invention is a good target having excellent effects of not causing cracks, improving production efficiency, and stably producing a high-quality film, and obtaining an optical record which does not cause recording bit error. media.

(Comparative Example 1)

A powder of 3N (99.9%) of antimony trioxide and cerium oxide was used as a starting material, and 50.0 mol of GeO ₂ powder having an average particle diameter of 5 μm was blended so that the atomic ratio of Bi to Ge was 0.67. After the mixture and the Bi ₂ O ₃ powder having an average particle diameter of 20 μm, 50.0 mol%, the mixture was mixed, and the mixed powder was filled in a carbon mold, and hot pressed at a temperature of 730 ° C and a pressure of 250 kg/cm ² .

The sintered body after hot pressing is finished to form a target. The relative density of the target was 103% (7.44 g/cm ³ at 100% density).

The X-ray diffraction measurement of the sintered body confirmed that the crystal phase of the target was a two-phase structure of Bi ₁₂ GeO ₂₀ and Bi ₄ Ge ₃ O ₁₂ .

Next, a thermal shock of heating at 200 ° C for 30 minutes was applied to the target. Then, the average bending strength test of JIS1601 was carried out. Similarly, the measurement results of the average bending strength ratio (the rate of decrease in strength) before and after the thermal shock are shown in Table 1.

As a result, the average bending strength reduction rate was 82%. Using this target, sputtering was performed at a power of 2 kW. As a result, cracks are generated in the target during sputtering. Moreover, the generation of particles was significantly increased as compared with the examples. The cause is considered to be a crack in the target in the sputtering.

(Comparative Example 2)

A powder of 3N (99.9%) of antimony trioxide and cerium oxide was used as a starting material, and GeO ₂ powder having an average particle diameter of 5 μm and Bi ₁₂ GeO ₂₀ powder having an average particle diameter of 20 μm were prepared in advance, respectively. When the ratio of the atomic ratio of Bi to Ge is 0.67, the GeO ₂ powder is 83.3 mol%, and the Bi ₁₂ GeO ₂₀ powder is 16.7 mol%, and then mixed, and the mixed powder is filled in a carbon mold at a temperature of 700 ° C. The hot pressing was carried out under the conditions of a pressure of 250 kg/cm ² .

Further, in the present embodiment, GeO ₂ powder and Bi ₁₂ GeO ₂₀ powder are added in such a manner as to achieve the above molar ratio, and the combined ratios of the additions are 50.0 mol% with GeO _{2 and} 50.0 mol of Bi ₂ O _{3 .} % consistent blending is adjusted in a manner similar to that.

The sintered body after hot pressing is finished to form a target. The relative density of the target was 103% (7.58 g/cm ³ at 100% density).

The X-ray diffraction measurement of the sintered body confirmed the total amount of GeO reaction, and was a two-phase structure of Bi ₁₂ GeO ₂₀ and Bi ₄ Ge ₃ O ₁₂ .

Next, a thermal shock of heating at 200 ° C for 30 minutes was applied to the target. Then, the average bending strength test of JIS1601 was carried out. Similarly, the measurement results of the average bending strength ratio (the rate of decrease in strength) before and after the thermal shock are shown in Table 1.

As a result, the rate of decrease in the average bending strength was 80%. Using this target, sputtering was performed at a power of 2 kW. As a result, cracks are generated in the target during sputtering. Moreover, the generation of particles was significantly increased as compared with the examples. The cause is considered to be a crack in the target in the sputtering.

Industrial availability

According to the Bi-Ge-O sintered body sputtering target of the present invention and the method for producing the target, there is an excellent effect that cracks of the target are not generated during sputtering, and generation of particles is small, and high quality can be stably produced. The film is obtained, and an optical recording medium that does not cause a recording bit error is obtained. It is possible to provide a target which is capable of improving the production efficiency of film formation of an optical recording medium and is suitable for manufacturing an optical recording medium.

Claims (6)

A Bi-Ge-O sintered body sputtering target consisting of bismuth (Bi), germanium (Ge), and oxygen (O), characterized in that the atomic ratio of Bi to Ge is 0.57<(Bi/(Bi) +Ge)) < 0.92, containing three phases of Bi ₁₂ GeO ₂₀ , Bi ₄ Ge ₃ O ₁₂ and GeO ₂ as a crystal phase. The sintered body sputtering target according to claim 1, wherein when the target is subjected to a thermal shock of heating at 200 ° C for 30 minutes, the average bending strength reduction rate before and after the thermal shock is 50% or less. An optical recording medium formed by sputtering using a target of claim 1 or 2. Bi-GeO one kind of sintered body sputtering target manufacturing method of plating, comprising: a GeO ₂ powder _{0.03 ~ 89mol%, Bi 12 GeO} 20 11 ~ 99.97mol% powder as a starting material, the atoms of Bi and Ge After mixing the raw materials in such a manner that the number ratio is 0.57 < (Bi / (Bi + Ge)) < 0.92, the raw material is hot-pressed at 600 to 840 ° C and a pressure of 150 to 400 kg / cm ² to prepare Bi ₁₂ GeO _{20 .} A sintered body of a crystal phase of three phases of Bi ₄ Ge ₃ O ₁₂ and GeO ₂ . A method for producing a Bi-Ge-O sintered body sputtering target according to the fourth aspect of the invention, wherein the GeO ₂ powder is 14.3 mol% and the Bi ₂ O ₃ powder is 85.7 mol%, and then a solid phase reaction is performed. Bi ₁₂ GeO ₂₀ powder. The method for producing a Bi-Ge-O sintered body sputtering target according to the fourth or fifth aspect of the invention, wherein the sintered raw material powder having a mean crystal grain size of 10 to 50 μm is sintered.