JP2008010114A - Patterned magnetic recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a patterned medium which has a satisfactory embedded shape and low surface roughness Ra and wherein irregularity of a magnetic body is embedded in a non-magnetic embedding layer in which production of process dust can be suppressed during film-deposition. <P>SOLUTION: The patterned magnetic recording medium has a substrate, a ferromagnetic recording layer formed on the substrate and formed in projecting patterns and the non-magnetic embedding layer embedded in recessed parts between the projecting patterns of the ferromagnetic recording layer and composed of an SiOC film containing Si, O and C and having ≤0.05at% C content. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a patterned magnetic recording medium and a manufacturing method thereof.

  Research is progressing to increase the recording capacity of HDDs (hard disk drives) by improving the surface recording density of magnetic recording media. As a result, each recording bit size on the magnetic recording medium has become extremely fine, about several tens of nm. In order to obtain a reproduction output from such a fine recording bit, it is necessary to ensure as much saturation magnetization and film thickness as possible for each bit. However, the amount of magnetization per bit decreases with the miniaturization of recording bits. As the amount of magnetization per bit decreases, there is a problem that magnetization reversal due to “thermal fluctuation” easily occurs, and magnetization information is lost. That is, the magnetic anisotropy energy required to keep the magnetization direction of the magnetic particles in one direction is about the same as the thermal fluctuation energy at room temperature, and the magnetization fluctuates with time, which causes the recorded information to disappear. . In general, the smaller the value of Ku · V / kT (where Ku is the anisotropy constant, V is the minimum magnetization unit volume, k is the Boltzmann constant, and T is the absolute temperature), the greater the influence of this thermal fluctuation. From experience, it is said that when Ku · V / kT is less than 100, magnetization reversal due to “thermal fluctuation” occurs.

  As a medium for solving the problem of magnetization reversal due to thermal fluctuation, a magnetic recording medium called a “patterned medium” has attracted attention (see, for example, Patent Document 1). In general, a patterned medium is a magnetic recording medium in which a plurality of magnetic material regions each serving as a recording bit unit are independently formed in a nonmagnetic material layer. However, a magnetically continuous magnetic thin film has a size of a recording magnetic domain. It can also be said to be a divided medium. Since the patterned medium is obtained by dividing the magnetic thin film into the size of the recording magnetic domain, the minimum magnetization unit volume V can be increased, and the problem of thermal fluctuation can be avoided.

  On the other hand, in the recent improvement in the track density of HDDs, the problem of interference with adjacent tracks has become apparent. In particular, reduction of writing blur due to the magnetic head fringe effect is an important technical issue. For example, a discrete track type patterned magnetic recording medium (DTR medium) that physically separates recording tracks described in Patent Document 2 can reduce a side erase phenomenon during recording, a side read phenomenon during reproduction, and the like. Therefore, the density in the cross track direction can be increased, and a high-density magnetic recording medium can be provided. The DTR medium is a form of patterned medium.

  In order to process a perpendicular magnetic recording film (current thickness: 20 nm) into a patterned medium, it is necessary to form a concavo-convex pattern by etching the recording film to a depth of 20 nm. However, if the current floating recording / reproducing head is used for reading / writing with respect to this patterned medium, the flying height of the recording / reproducing head is about 10 nm, so there is a possibility that the recording / reproducing head and the patterned medium come into contact with each other. is there. Therefore, in order to read / write data from / to a patterned medium with the current floating recording / reproducing head, it is necessary to bury the irregularities of the magnetic layer and flatten the surface of the medium.

As a method for flattening the medium by embedding the irregularities of the magnetic layer of the magnetic recording medium, there is a method of embedding a nonmagnetic film, for example, a SiO ₂ film, using a bias sputtering method as described in Patent Document 3. Can be mentioned. Although this method is expected to produce a patterned medium with good flatness, there is a problem that a large amount of process dust is generated. Generation of process dust is an unavoidable problem as long as a bias sputtering method (a method of forming a film by an RF sputtering method while applying a substrate bias) is used.

  Therefore, a patterned medium is manufactured by using a DC sputtering method without a substrate bias and forming a film using C (carbon) as an embedding agent. Although this method hardly generates process dust, there is a problem that the embedding shape of unevenness is not so good.

As a compromise, there is a method in which an RF sputtering method is used without applying a substrate bias and a film is formed by using SiO ₂ as an embedding agent. In this case, although the local unevenness embedding shape is good, in addition to the generation of process dust, stress is applied to the deposited SiO ₂ and film peeling occurs. Further, there is a problem that the SiO ₂ film forming rate is slow. In general, it is necessary to embed approximately 100 nm in order to flatten the unevenness of the patterned medium. However, in the case of SiO ₂ , even if the sputtering pressure is optimized using a large target, it takes 330 seconds or more. This leads to an increase in cost when mass production is considered.

Patent Document 4 describes a phase change optical recording medium in which a SiOC film is formed as a protective layer by sputtering. The SiOC film described in Patent Document 4 is a protective layer laminated on a flat layer, and is not described as an embedding material for embedding irregularities to flatten the medium. The effects required as an embedding material for the patterned medium are that the surface roughness Ra is small, the process dust generated during film formation is small, and the embedding shape is good. These effects are described in Patent Document 4. Not.
JP 2001-17604 A Japanese Patent Laid-Open No. 7-85406 Japanese Patent No. 3686067 JP 2005-25851 A

  An object of the present invention is to provide a patterned medium in which irregularities of a magnetic layer are embedded by a nonmagnetic embedded layer having a small surface roughness Ra, little process dust generated during film formation, and a good embedded shape. is there.

  Another object of the present invention is to form a non-magnetic buried layer having a small surface roughness Ra and a good filling shape at a high film-forming speed and generated process dust in the non-magnetic buried layer forming process. An object of the present invention is to provide a method for producing a patterned medium, which can be formed with a small amount.

  A patterned magnetic recording medium according to an aspect of the present invention is embedded in a concave portion between a substrate, a ferromagnetic recording layer having a convex pattern formed on the substrate, and a ferromagnetic recording layer having the convex pattern. And a nonmagnetic buried layer formed of a SiOC film containing Si, O, and C and having a C content of 0.05 at% or more.

A method of manufacturing a patterned magnetic recording medium according to another aspect of the present invention includes a step of forming a ferromagnetic recording layer on a substrate, and a ferromagnetic recording that forms a convex pattern by processing the ferromagnetic recording layer. A ferromagnetic layer forming the convex pattern by performing DC sputtering using a SiC target as a sputtering target and an Ar—O ₂ mixed gas having an oxygen content of 55 vol% or less as a process gas. A step of embedding a nonmagnetic buried layer formed of a SiOC film containing Si, O, and C and having a C content of 0.05 at% or more in the recesses between the recording layers. To do.

  According to the present invention, it is possible to provide a patterned medium in which irregularities of a magnetic layer are embedded by a nonmagnetic embedded layer having a small surface roughness Ra, little process dust generated during film formation, and a good embedded shape. .

  In addition, according to the present invention, in the nonmagnetic embedding process, a nonmagnetic embedding layer having a small surface roughness Ra and a good embedding shape is deposited at a high deposition rate and with a small amount of generated process dust. It is possible to provide a method for manufacturing a patterned medium.

We refer to SiC target as a sputtering target, and by performing DC sputtering _{Ar-O 2} mixed gas as a process gas, an SiOC film having the same embedded performance and SiO _2, and the deposition of SiO ₂ The present inventors have found that film formation can be performed at a higher film formation speed and with a small amount of generated process dust.

  FIG. 1 shows a schematic sectional view of an embodiment of the patterned medium of the present invention. In the patterned medium of FIG. 1, an underlayer 2 and a ferromagnetic recording layer 3 forming a convex pattern are formed on a substrate 1. A nonmagnetic embedded layer 7 is embedded in the recesses between the ferromagnetic recording layers 3 having a convex pattern, and the ferromagnetic recording layers 3 are separated from each other via the embedded layer 7. Further, in the medium of FIG. 1, a protective film 8 is formed so as to cover the ferromagnetic recording layer 3 and the nonmagnetic buried layer 7. A lubricant (not shown) is applied on the protective film 8.

  A pattern of the ferromagnetic recording layer 3 is schematically shown in FIG. FIG. 2A shows a surface pattern of a discrete track type patterned magnetic recording medium (DTR medium) in which a discrete track 11, a preamble portion 12, an address portion 13, and a servo portion 14 are formed as a pattern of a ferromagnetic recording layer. It is. A discrete bit type patterned magnetic recording medium (a narrowly defined patterned medium) in which the recording track portion is a discrete bit 15 as schematically shown in FIG.

  In the patterned medium of the present invention, the nonmagnetic embedded layer 7 embedded in the recesses between the ferromagnetic recording layers 3 having a convex pattern contains Si, O, and C, and the content of C is 0.05 at. It is characterized by being a SiOC film of% to 30 at%.

A SiOC film having a carbon content in the above-mentioned range has the same embedding performance as SiO ₂ , but has a high deposition rate because it is not necessary to use a bias RF sputtering method in which process dust is inevitably generated. Films can be formed by DC sputtering, and generation of process dust can be suppressed. The patterned medium in which the concave portions between the magnetic patterns are embedded by the above-described SiOC film has a good embedded shape, and therefore has a small surface roughness Ra, thereby realizing stable flying of the recording / reproducing head. Also, a good bit error rate (BER) value is shown due to the stable flying of the recording / reproducing head.

In addition, the patterned medium in which the recesses between the magnetic patterns are embedded by the SiOC film having the carbon content in the above-mentioned range, the oxygen in the embedded layer compared with the conventional medium embedded using SiO _2. Due to the effect of defects, oxidation of the recording layer during the formation of the buried layer is suppressed, and a better BER value is exhibited.

  On the other hand, in the patterned medium in which the concave portion between the magnetic patterns is embedded by the SiOC film having a carbon content of less than 0.05 at%, the oxygen defect rate of the SiOC film is low. There is an oxide film formed on the layer. Therefore, this medium is inferior in BER because the signal intensity is lowered due to the presence of the oxide film. In addition, the patterned medium in which the concave portions between the magnetic patterns are embedded by the SiOC film having a carbon content of greater than 30 at% has poor embedding performance, and therefore the recording / reproducing head cannot be expected to float stably.

  Hereinafter, a method for producing a patterned medium of the present invention will be described with reference to the drawings. The material of each component of the patterned medium will be described later.

First, as shown in FIG. 3A, an underlayer 2 (including a soft magnetic underlayer and an orientation control underlayer), a ferromagnetic recording layer 3 and a protective layer 4 are sequentially formed on a substrate 1. For example, on the glass substrate 1, a CoZrNb layer as a soft magnetic layer is 120 nm, Ru is 20 nm as an orientation control underlayer, and a CoCrPt—SiO ₂ layer is 20 nm as a ferromagnetic recording layer, and a protective layer is formed thereon. A C protective layer is deposited to 4 nm.

  As shown in FIG. 3B, an imprint resist layer 5 is formed on the protective layer 4 by spin coating. As the imprint resist, for example, a general novolak photoresist or spin-on-glass (SOG) can be used.

  As shown in FIG. 3C, the pattern is transferred by pressing a stamper 6 onto the imprint resist layer 5 (imprint method). The stamper 6 has a concavo-convex pattern corresponding to each pattern of a track portion, a preamble portion, an address portion, and a burst portion to be transferred. By applying a fluorine-based release agent on the surface of the stamper in advance, the stamper 6 and the imprint resist layer 5 can be peeled off favorably.

  Here, pattern transfer by the imprint method will be described. Imprinting is performed using a die set. On the lower plate of the die set, the stamper 6, the substrate 1, and the buffer layer are laminated in this order, and the upper plate of the die set is installed on the die set so as to be sandwiched between the lower plate of the die set. At this time, the unevenness of the stamper 6 and the imprint resist layer 5 formed on the substrate 1 are laminated to face each other. The pressing is performed, for example, at 2000 bar for 60 seconds. 60 seconds is the movement time of the resist.

  By removing the stamper 6 after the imprint process, as shown in FIG. 3D, the substrate 1 having the imprint resist layer 5 to which the concavo-convex pattern has been transferred is obtained.

As shown in FIG. 3E, reactive ion etching (RIE) is performed to remove the resist residue remaining in the pattern recesses transferred to the imprint resist layer 5. The gas used for RIE is appropriately selected according to the material of the imprint resist layer 5. When SOG is used as the imprint resist, a fluorine-based gas such as CF ₄ or SF ₆ is preferable. However, since it may react with water in the atmosphere to generate acids such as HF and H ₂ SO ₄ , Need to do. When a novolak photoresist is used as the imprint resist, RIE using oxygen gas is suitable. The plasma source is preferably an inductively coupled plasma (ICP) capable of generating a high-density plasma at a low pressure, but an electron cyclotron resonance (ECR) plasma or a general parallel plate RIE apparatus is used. You can also

As shown in FIG. 3F, magnetic material processing is performed using the imprint resist layer 5 from which the residue has been removed as an etching mask. Etching using Ar ion beam (Ar ion milling) is suitable for magnetic processing, but RIE using Cl gas or a mixed gas of CO and NH ₃ may also be used. In the case of RIE using a mixed gas of CO and NH ₃ , a hard mask such as Ti, Ta, or W must be used as an etching mask. When these magnetic bodies RIE are used, the magnetic body unevenness is not tapered. When performing magnetic processing by Ar ion milling that can etch any material, for example, etching is performed by changing the acceleration voltage 400V and the ion incident angle from 30 ° to 70 °. Milling using an ECR ion gun can be processed with a taper on the magnetic material unevenness by etching with a stationary facing type (ion incident angle of 90 °). As a result, an uneven pattern of the ferromagnetic recording layer 3 is formed.

  As shown in FIG. 3G, the imprint resist layer 5 remaining on the convex portions of the ferromagnetic recording layer 3 is removed. For removing the resist, a method similar to that for removing the resist residue can be used.

  As shown in FIG. 3H, in order to realize stable flying of the recording / reproducing head, the uneven pattern of the ferromagnetic recording layer 3 is embedded by the nonmagnetic embedded layer 7.

In the method of the present invention, in the nonmagnetic embedding step, the SiOC buried layer 7 is formed by performing DC sputtering using an SiC target as a sputtering target and an Ar—O ₂ mixed gas as a process gas. It is characterized by.

  In the method of the present invention, Ar gas containing 5 vol% to 55 vol% oxygen is used as the process gas. If the oxygen content is less than 5 vol%, SiC cannot be converted to SiOC sufficiently, and good embedding performance cannot be obtained. On the other hand, if the oxygen content exceeds 55 vol%, excess oxygen when SiC is converted to SiOC oxidizes the recording layer and an oxide film is formed on the medium surface. As a result, the BER of the patterned medium after completion is deteriorated.

In order to flatten the unevenness of the patterned medium, it is necessary to form a nonmagnetic buried layer of about 100 nm. Conventional film formation of SiO ₂ by RF bias sputtering has a low film formation speed, and it takes much time to form the film, leading to an increase in cost. However, since the present invention uses DC sputtering with a high film formation rate, the cost can be reduced as compared with conventional SiO ₂ film formation. Further, since the buried layer can be formed by DC sputtering, process dust can be suppressed.

By forming a SiOC film containing Si, O, and C as a nonmagnetic buried layer according to the present invention, the same surface flatness as when SiO ₂ is formed can be obtained. Oxidation of is suppressed.

  As shown in FIG. 3I, etch back is performed until the ferromagnetic recording layer 3 is exposed. In the etch back process, it is preferable to use Ar ion milling. Since the silicon-based buried layer is used in the method of the present invention, RIE using a fluorine-based gas can also be performed. Etching using ECR may also be used.

As shown in FIG. 3J, the C protective layer 4 is formed. The C protective layer 4 is preferably formed by a CVD method in order to improve the coverage to the unevenness, but may be a sputtering method or a vacuum evaporation method. When the C protective layer 4 is formed by the CVD method, a DLC film containing a large amount of sp ³ bonded carbon is formed. If the film thickness is 2 nm or less, the coverage is poor, and if it is 10 nm or more, the magnetic spacing between the recording / reproducing head and the medium increases and the SNR decreases, which is not preferable. A lubricant (not shown) is applied on the protective layer 3.

(Example)
Hereinafter, embodiments of the present invention will be described in detail.

(Example 1)
In this example, a patterned medium was manufactured according to the method shown in FIG.

First, a 120 nm CoZrNb layer as a soft magnetic layer, a 20 nm Ru layer as an orientation control underlayer, a 20 nm CoCrPt—SiO ₂ layer as a ferromagnetic recording layer, and a 4 nm carbon as a protective layer were sequentially formed on a glass substrate. .

  Thereafter, SOG as an imprint resist layer was applied on the protective film to a thickness of 100 nm by spin coating. Next, the imprint stamper on which the concavo-convex pattern corresponding to the pattern shown in FIG. 2A was formed was pressed onto the SOG layer to perform imprinting, and the concavo-convex pattern was transferred to the SOG layer.

After the pattern transfer, RIE was performed in the ICP etching apparatus to remove the imprint residue in the recessed portion of the transferred uneven pattern. The RIE was performed for 30 seconds under the following conditions: process gas; CF ₄ , chamber pressure; 2 mTorr, Coil RF; 100 W, Platen RF;

  After removing the resist residue, the imprint resist was used as an etching mask, and the ferromagnetic recording layer was processed by ion milling. Ion milling was performed in the etching apparatus for 3 minutes under the following conditions: process gas; Ar, plasma source; ECR ion gun, microwave power; 800 W, acceleration voltage: 500 V. After etching by ion milling, the protective layer and the ferromagnetic recording layer were completely removed in the concave portion, and a concave / convex pattern having a height difference of 24 nm from the upper surface of the convex portion to the upper surface of the concave portion was formed.

After processing the magnetic material, SOG remaining on the ferromagnetic recording layer having a convex pattern was removed by RIE. RIE was performed for 1 minute under the following conditions: process gas; CF ₄ , chamber pressure; 2 mTorr, Coil RF; 100 W, Platen RF;

After removing the resist, in the sputtering apparatus, the concave portion of the pattern of the magnetic layer was embedded with a nonmagnetic layer for the purpose of stable flying of the recording / reproducing head. Film formation was performed for 140 seconds under the following conditions, and a nonmagnetic buried layer was formed to a thickness of 100 nm: film formation method; DC sputtering method, sputtering target; SiC target, process gas; Ar—O ₂ mixed gas (flow rate: Ar; 80 sccm) , O ₂ ; 20 sccm (oxygen content: 20 vol%)).

  With the nonmagnetic buried layer formed, the composition of the nonmagnetic buried layer was analyzed by SIMS (secondary ion mass spectrometry). The composition obtained by the analysis was Si; 42.0 at%, O; 57.5 at%, C; 0.5 at%. Hereinafter, the nonmagnetic buried layer obtained by this method is referred to as a SiOC film.

  Next, the nonmagnetic buried layer was etched back. Etchback was performed by ion milling using an ECR ion gun for about 5 minutes under the following conditions: process gas; Ar, microwave power; 800 W, acceleration voltage; The end point of etch back was detected when Co on the surface of the magnetic layer was detected using a quadrupole mass spectrometer (Q-mass).

  After the etch back, a patterned medium of this example was obtained by forming a DLC protective layer on the surface by CVD (chemical vapor deposition) and applying a lubricant thereon.

When AE (Acoustic emission) measurement was performed on the completed medium using a glide head, no AE signal was observed. When the medium was installed in the drive and the BER (bit error rate) was measured, a good value of 1.0 × 10 ⁻⁶ was obtained.

(Comparative Example 1)
In the nonmagnetic embedding step, a patterned medium was produced by the same method as in Example 1 except that a nonmagnetic embedding layer was formed under the following conditions: film forming method; bias sputtering method, sputtering target; SiO ₂ target, process Gas: Pure Ar gas.

In this example, it took 500 seconds to form the SiO ₂ buried layer with a thickness of 100 nm.

  When the AE measurement was performed on the completed medium using a glide head, a spike-like AE signal presumably due to dust was observed. Since an AE signal was observed, drive evaluation was impossible and BER evaluation was not performed.

(Comparative Example 2)
In the nonmagnetic embedding step, a patterned medium was produced by the same method as in Example 1 except that a nonmagnetic embedding layer was formed under the following conditions: film forming method; DC sputtering, sputtering target; C, process gas; Ar gas.

When AE measurement was performed on the completed medium using a glide head, no AE signal was observed. When the medium was installed in the drive and the BER (bit error rate) was measured, a value of 3.0 × 10 ⁻⁶ was obtained.

When the results of Example 1 and Comparative Example 1 are compared, a buried layer is formed at a deposition rate approximately 3.6 times higher than that of SiO ₂ bias sputtering by producing a patterned medium using the method of the present invention. It can be seen that a film can be formed. Further, the patterned medium subjected to embedding with SiO ₂ in Comparative Example 1 (conventional example) has an AE signal due to dust, but the patterned medium of Example 1 is subjected to the formation of the nonmagnetic buried layer. Since process dust can be suppressed by using DC sputtering, the surface property is good and no AE signal is observed.

  When the result of Example 1 is compared with the result of Comparative Example 2, it can be seen that the BER of Comparative Example 2 is three times the BER of Example 1 and the BER is deteriorated. The reason for this is that the medium of Comparative Example 2 is embedded using C, so that the embedded shape is poor, and the flying of the recording / reproducing head is thereby unstable. In contrast, the patterned medium of Example 1 shows a good BER value, which indicates that the flying shape of the recording / reproducing head is stable because the embedding shape is good and the surface roughness Ra is small.

(Example 2)
A patterned medium was produced in the same manner as in Example 1 except that in the nonmagnetic embedding step, a sputtering target with various carbon contents was used.

  The carbon content of the sputtering target was changed by changing the target to be used to a SiC target, a Si-SiC composite target, or a SiC-C composite target.

  As in Example 1, the composition of the nonmagnetic buried layer was analyzed by SIMS in a state where the nonmagnetic buried layer was formed. From the analysis results, it was found that the carbon content of the nonmagnetic buried layer can be changed by changing the carbon content of the sputtering target.

  Next, in order to investigate the dependency of the recording layer oxidation prevention on the carbon content of the nonmagnetic buried layer, the composition analysis in the depth direction was performed on the fabricated patterned medium by Auger electron spectroscopy (AES). The film thickness of the oxide film was measured from the analysis result. FIG. 4 is a plot of the oxide film thickness versus the carbon content of the nonmagnetic buried layer. As apparent from FIG. 4, no oxide film was detected in the medium having a carbon content of the nonmagnetic buried layer of 0.05 at% or more.

(Example 3)
In the non-magnetic embedding step, a patterned medium is produced by the same method as in Example 1 except that the process gas is Ar—O ₂ mixed gas with flow rates of Ar; 180 sccm, O ₂ ; 20 sccm (oxygen content: 10 vol%). did.

  As in Example 1, the composition of the nonmagnetic buried layer was analyzed by SIMS with the nonmagnetic buried layer formed, and as a result, the nonmagnetic buried layer of this example was Si; 42.52 at%, O; 57 It was found to be a SiOC film having a composition of .4 at%, C; 0.08 at%.

When AE measurement was performed using a grind head after completion of the medium, no AE signal was detected. As a result of measuring the BER by incorporating the medium into the drive, a good value of 1.0 × 10 ⁻⁶ was obtained.

(Comparative Example 3)
In the non-magnetic embedding step, the patterned medium was prepared in the same manner as in Example 1 except that the process gas was an Ar—O ₂ mixed gas having a flow rate of Ar: 20 sccm and O ₂ : 80 sccm (oxygen content 80 vol%). Produced.

  As in Example 1, as a result of analyzing the composition of the nonmagnetic buried layer by SIMS in the state where the nonmagnetic buried layer was formed, the nonmagnetic buried layer was found to have Si: 34.98 at%, O: 65.0 at%, C: It was found to be a SiOC film having a composition of 0.02 at%.

When AE measurement was performed using a grind head after completion of the medium, no AE signal was detected. As a result of measuring the BER by incorporating the medium into the drive, a value of 1.0 × 10 ⁻⁵ was obtained. The reason for the poor BER is considered to be that the oxygen defect effect of the nonmagnetic buried layer is not sufficiently exhibited, the recording layer is oxidized during the nonmagnetic filling step, and the signal intensity is lowered.

  From the results of Example 2, it can be seen that if the carbon content of the SiOC film which is a nonmagnetic buried layer is 0.05 at% or more, the recording layer has no oxide film due to the oxygen defect effect of the buried layer. . Furthermore, from the results of Example 1 and Example 3, if the recording medium has a carbon content of the SiOC film of 0.05 at% or more, the recording layer does not have an oxide film and exhibits a good BER value. I understood.

  On the other hand, according to the result of Comparative Example 3, the patterned medium having a carbon content of less than 0.05 at% in the nonmagnetic buried layer does not sufficiently exhibit the oxygen defect effect of the nonmagnetic buried layer, so that an oxide film is formed on the recording layer. As a result, it was found that good BER cannot be obtained.

Example 4
A patterned medium was produced in the same manner as in Example 1 except that the oxygen content of the Ar—O ₂ mixed process gas used was variously changed in the nonmagnetic embedding step.

In this example, the oxygen content of the Ar—O ₂ mixed process gas was changed by fixing the flow rate of O ₂ to 20 sccm and changing the flow rate of Ar.

  In order to investigate the relationship between the oxygen content of the process gas used in the nonmagnetic embedding process and the formation of the oxide film of the recording layer, each of the manufactured components was obtained using the result of composition analysis in the depth direction by AES as in Example 2. The oxide film thickness of the recording layer of the medium was examined. FIG. 5 is a diagram in which the oxide film thickness is plotted against the oxygen content of the process gas.

  As is apparent from FIG. 5, when the oxygen content of the process gas is 50 vol% or less, the oxide film thickness is zero, and the recording layer was not oxidized during the nonmagnetic embedding process. When the oxygen content is 55 vol%, the oxide film thickness is 1 nm or less. However, considering that the natural oxide film is about 1 nm, there is no problem in the process.

On the other hand, it has been found that when the oxygen content exceeds 55 vol%, excess oxygen in converting SiC to SiO ₂ oxidizes the recording layer.

(Example 5)
In the non-magnetic embedding step, a patterned medium is produced in the same manner as in Example 1 except that the process gas is Ar—O ₂ mixed gas having flow rates of Ar; 20 sccm, O ₂ ; 20 sccm (oxygen content 50 vol%). did.

  As in Example 1, as a result of analyzing the composition of the nonmagnetic buried layer by SIMS in the state where the nonmagnetic buried layer was formed, the nonmagnetic buried layer was found to have Si: 42.2 at%, O: 56.1 at%, C: It was found to be a SiOC film having a composition of 1.7 at%.

  After completion of the medium, it was examined whether or not an oxide film was present in the recording layer using the composition analysis result in the depth direction by AES as in Example 2. From the recording layer of the medium produced in this example, An oxide film was not observed.

After completion of the medium, AE measurement was performed using a grindhead, and no AE signal was detected. As a result of measuring the BER by incorporating the medium into the drive, a good value of 1.0 × 10 ⁻⁶ was obtained.

(Comparative Example 4)
In the non-magnetic embedding step, a patterned medium is produced by the same method as in Example 1 except that the process gas is Ar—O ₂ mixed gas with flow rates of Ar; ₂ sccm, O ₂ ; 20 sccm (oxygen content 90 vol%). did.

  After completion of the medium, it was examined whether or not an oxide film was present in the recording layer by using the composition analysis result in the depth direction by AES in the same manner as in Example 2. As a result, an oxide film of 6.5 nm was observed.

After completion of the medium, AE measurement was performed using a grindhead, and no AE signal was detected. As a result of measuring the BER by incorporating the medium into the drive, a value of 1.0 × 10 ⁻⁴ was obtained. The reason why the BER deteriorated is considered to be that the signal intensity was reduced to 1/3 or less because the film thickness of the magnetic material was 20 nm while the oxide film occupied about 1/3.

From the results of Example 4, it can be seen that the oxidation of the recording layer can be suppressed by using SiC as a sputtering target and using an Ar—O ₂ mixed gas having an oxygen content of 55 vol% or less as a process gas in the embedding process. . Further, from the results of Example 5, by using an Ar—O ₂ mixed gas having an oxygen content in the above range as a process gas, it is possible to suppress the oxidation of the recording layer and to produce a patterned medium showing a good BER value. I understood. On the other hand, from the result of Comparative Example 4, when an Ar—O ₂ mixed gas having an oxygen content exceeding 55 vol% is used as a process gas, the recording layer is oxidized in the embedding process, the signal intensity is lowered, and the result is completed. It has been found that the BER value of the obtained medium is deteriorated.

(Example 6)
A SiOC film having a thickness of 100 nm was formed on a 3-inch Si substrate under the following conditions: film formation method; DC sputtering method, sputtering target; SiC target, process gas; Ar—O ₂ mixed gas (Ar; 80 sccm, O ₂ ; 20 sccm (oxygen content: 20 vol%)). FIG. 6A shows a particle map of the SiOC film formed in Example 6.

  When the number of particles of process dust on the formed SiOC film was counted with a particle counter (TeraStar manufactured by KLA-Tencor), it was 200.

(Comparative Example 5)
A SiO ₂ film having a thickness of 100 nm was formed on a 3-inch Si substrate by bias sputtering under the following conditions: film formation method; bias sputtering method, sputtering target; SiO ₂ target, process gas; pure Ar gas. FIG. 6B shows a particle map of the SiO ₂ film formed in Example 6.

When the number of process dust particles on the deposited SiO ₂ film was counted in the same manner as in Example 6, it was 2150.

Comparing the results of Example 6 and Comparative Example 5, in the method of the present invention, the nonmagnetic embedding layer is formed by DC sputtering, and compared with the conventional nonmagnetic uneven embedding method by bias sputtering of SiO _2. It can be seen that the process dust is 10 times less. Therefore, by using the method of the present invention, it is possible to form a non-magnetic buried layer with reduced process dust and a small surface roughness Ra, whereby no AE signal is observed and stable head flying can be achieved. It can be seen that a patterned medium exhibiting BER can be produced.

(Example 7)
In the imprint process, pattern printing is performed in the same manner as in Example 1, except that the imprint stamper on which the uneven pattern corresponding to the pattern as shown in FIG. A medium was made.

  The completed medium was a discrete bit patterned medium having rectangular recording bits with a cross track direction of 120 nm and a down track direction of 25 nm and a recording density equivalent to 130 Gbpsi.

  After completion of the medium, AE measurement was performed using a grindhead, and no AE signal was detected. Further, when a composition analysis in the depth direction by AES was performed on the recording layer in the same manner as in Example 2, it was found that there was no oxide film in the recording layer.

  From the result of Example 7, even if it is a discrete bit patterned medium like Example 7, by using this invention, the same effect as the discrete track type patterned magnetic recording media of Examples 1 to 6 can be obtained. You can see what you can expect.

  Hereinafter, the material used for each layer of the patterned medium according to the embodiment of the present invention and the laminated structure of each layer will be described.

<Board>
As the substrate, for example, a glass substrate, an Al-based alloy substrate, ceramic, carbon, a Si single crystal substrate having an oxidized surface, and those obtained by plating such a substrate with NiP or the like can be used. As the glass substrate, there are amorphous glass and crystallized glass, and general-purpose soda lime glass and aluminosilicate glass can be used as the amorphous glass. Further, as the crystallized glass, lithium-based crystallized glass can be used. As the ceramic substrate, a sintered body mainly composed of general-purpose aluminum oxide, aluminum nitride, silicon nitride, or the like, or a fiber reinforced material thereof can be used. As the substrate, a substrate in which a NiP layer is formed on the surface of the metal substrate or the nonmetal substrate by using a plating method or a sputtering method can also be used. Further, only the sputtering method has been described below as a method for forming a thin film on the substrate, but the same effect can be obtained by a vacuum deposition method or an electrolytic plating method.

<Soft magnetic underlayer>
The soft magnetic underlayer (SUL) is one of the functions of a magnetic head that circulates a recording magnetic field from a magnetic head for magnetizing a perpendicular magnetic recording layer, for example, a single magnetic pole head, to the magnetic head side in the horizontal direction. It can play the role of applying a steep and sufficient perpendicular magnetic field to the recording layer of the magnetic field to improve the recording / reproducing efficiency.

  For the soft magnetic underlayer, a material containing Fe, Ni, and Co can be used. Examples of such materials include FeCo alloys such as FeCo and FeCoV, FeNi alloys such as FeNi, FeNiMo, FeNiCr, and FeNiSi, FeAl alloys, FeSi alloys such as FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu, and FeAlO. Examples thereof include FeTa, FeTaC, and FeTaN, and FeZr alloys such as FeZrN. Further, a material having a fine crystal structure such as FeAlO, FeMgO, FeTaN, FeZrN or the like containing 60 at% or more of Fe or a granular structure in which fine crystal particles are dispersed in a matrix can be used.

  As another material of the soft magnetic underlayer, a Co alloy containing Co and at least one of Zr, Hf, Nb, Ta, Ti, and Y can be used. Co is preferably contained at 80 at% or more. When such Co alloy is formed by sputtering, an amorphous layer is likely to be formed, and amorphous soft magnetic materials do not have magnetocrystalline anisotropy, crystal defects, and grain boundaries, and thus have excellent soft magnetism. Show. Further, the use of this amorphous soft magnetic material can reduce the noise of the medium. Examples of suitable amorphous soft magnetic materials include CoZr, CoZrNb, and CoZrTa-based alloys.

  Under the soft magnetic underlayer, an underlayer can be further provided in order to improve the crystallinity of the soft magnetic underlayer or the adhesion to the substrate. As the underlayer material, Ti, Ta, W, Cr, Pt, alloys containing these, oxides or nitrides thereof can be used.

  An intermediate layer made of a nonmagnetic material can be provided between the soft magnetic underlayer and the recording layer. There are two roles of the intermediate layer: blocking the exchange coupling interaction between the soft magnetic underlayer and the recording layer, and controlling the crystallinity of the recording layer. As the intermediate layer material, Ru, Pt, Pd, W, Ti, Ta, Cr, Si, alloys containing these, oxides or nitrides thereof can be used.

  In order to prevent spike noise, the soft magnetic underlayer may be divided into a plurality of layers and antiferromagnetically coupled by inserting 0.5 to 1.5 nm of Ru. Alternatively, a hard magnetic film having in-plane anisotropy such as CoCrPt, SmCo, or FePt, or a pinned layer made of an antiferromagnetic material such as IrMn or PtMn and a soft magnetic layer may be exchange coupled. At that time, in order to control the exchange coupling force, a magnetic (for example, Co) or nonmagnetic film (for example, Pt) may be laminated before and after the Ru layer.

<Ferromagnetic recording layer (general structure)>
The perpendicular magnetic recording layer is preferably made of an alloy containing Co as a main component and containing Pt because high anisotropy can be achieved. The recording layer may further be made of a material containing an oxide. As this oxide, silicon oxide, titanium oxide, or an oxide of a metal constituting the magnetic recording layer is particularly suitable.

  In the perpendicular magnetic recording layer, magnetic particles (crystal grains having magnetism) are preferably dispersed in the layer. The magnetic particles preferably have a columnar structure penetrating the perpendicular magnetic recording layer vertically. By forming such a structure, the orientation and crystallinity of the magnetic particles in the perpendicular magnetic recording layer are improved, and as a result, a signal / noise ratio (S / N ratio) suitable for high-density recording can be obtained. it can. In order to obtain such a structure, the amount of oxide to be contained is important. The oxide content is preferably 3 mol% or more and 12 mol% or less with respect to the total amount of Co, Cr, and Pt. More preferably, it is 5 mol% or more and 10 mol% or less. The above range is preferable as the content of the oxide in the perpendicular magnetic recording layer because, when the layer is formed, the oxide is precipitated around the magnetic particles, so that the magnetic particles can be isolated and refined. It is. When the oxide content exceeds the above range, the oxide remains in the magnetic particles, and the orientation and crystallinity of the magnetic particles are impaired. This is not preferable because a columnar structure in which magnetic particles penetrate vertically through the perpendicular magnetic recording layer is not formed. Further, when the oxide content is less than the above range, separation and miniaturization of magnetic particles are insufficient, resulting in an increase in noise during recording and reproduction, and a signal / noise ratio (S) suitable for high-density recording. / N ratio) is not obtained. The content of Cr in the perpendicular magnetic recording layer is preferably 0 at% or more and 16 at% or less. More preferably, it is 10 at% or more and 14 at% or less. The Cr content is in the above range because the uniaxial crystal magnetic anisotropy constant Ku of the magnetic particles is not lowered too much, and high magnetization is maintained, resulting in recording / reproduction characteristics suitable for high-density recording and sufficient heat. This is because fluctuation resistance is suitable. When the Cr content exceeds the above range, the Ku of the magnetic particles becomes small, so the thermal fluctuation resistance deteriorates, and the crystallinity and orientation of the magnetic particles deteriorates, resulting in poor recording / reproducing characteristics. Therefore, it is not preferable. The Pt content in the perpendicular magnetic recording layer is preferably 10 at% or more and 25 at% or less. The Pt content is in the above range because Ku required for the perpendicular magnetic layer is obtained, and the crystallinity and orientation of the magnetic particles are good. As a result, heat fluctuation resistance suitable for high density recording, recording / reproducing characteristics This is preferable because it is obtained. When the Pt content exceeds the above range, a layer having an fcc structure is formed in the magnetic particles, and crystallinity and orientation may be impaired. Also, when the Pt content is less than the above range, it is not preferable because Ku for obtaining thermal fluctuation resistance suitable for high density recording cannot be obtained.

  The perpendicular magnetic recording layer contains at least one element selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re in addition to Co, Cr, Pt, and oxide. Can do. By including the above elements, it is possible to promote miniaturization of magnetic particles or improve crystallinity and orientation, and to obtain recording / reproduction characteristics and thermal fluctuation resistance suitable for higher density recording. The total content of the above elements is preferably 8 at% or less. If it exceeds 8 at%, a phase other than the hcp phase is formed in the magnetic particles, so that the crystallinity and orientation of the magnetic particles are disturbed, resulting in recording / reproduction characteristics suitable for high-density recording and resistance to thermal fluctuations. It is not preferable because it is not possible.

  In addition to the above, the perpendicular magnetic recording layer is at least selected from the group consisting of CoPt alloys, CoCr alloys, CoPtCr alloys, CoPtO, CoPtCrO, CoPtSi, CoPtCrSi, and Pt, Pd, Rh, and Ru. A multilayer structure of an alloy mainly composed of one kind and Co, and CoCr / PtCr, CoB / PdB, CoO / RhO, and the like obtained by adding Cr, B, and O to these can be used.

  The thickness of the perpendicular magnetic recording layer is preferably 5 to 60 nm, more preferably 10 to 40 nm. Within this range, the magnetic recording / reproducing apparatus suitable for higher recording density can be operated. If the thickness of the perpendicular magnetic recording layer is less than 5 nm, the reproduction output tends to be too low and the noise component tends to be higher. If the thickness of the perpendicular magnetic recording layer exceeds 40 nm, the reproduction output is too high. There is a tendency to distort the waveform. The coercive force of the perpendicular magnetic recording layer is preferably 237000 A / m (3000 Oe) or more. When the coercive force is less than 237000 A / m (3000 Oe), the thermal fluctuation resistance tends to be inferior. The perpendicular squareness ratio of the perpendicular magnetic recording layer is preferably 0.8 or more. When the vertical squareness ratio is less than 0.8, the thermal fluctuation resistance tends to be inferior.

<Protective layer>
The protective layer is provided for the purpose of preventing corrosion of the perpendicular magnetic recording layer and preventing damage to the medium surface when the magnetic head comes into contact with the medium. Examples of the material include those containing C, SiO ₂ and ZrO ₂ . The thickness of the protective layer is preferably 1 to 10 nm. Thereby, the distance between the head and the medium can be reduced, which is suitable for high-density recording.

Carbon can be classified into sp ² bonded carbon (graphite) and sp ³ bonded carbon (diamond). Durability and corrosion resistance are superior to sp ³ -bonded carbon, but since it is crystalline, surface smoothness is inferior to graphite. Usually, the carbon film is formed by sputtering using a graphite target. In this method, amorphous carbon in which sp ² bonded carbon and sp ³ bonded carbon are mixed is formed. Those having a large proportion of sp ³ bonded carbon are called diamond-like carbon (DLC). Since it is excellent in durability and corrosion resistance and is excellent in surface smoothness due to being amorphous, it is used as a surface protective film of a magnetic recording medium. DLC film formation by the CVD (Chemical Vapor Deposition) method excites and decomposes the source gas in plasma and generates DLC by a chemical reaction. By adjusting the conditions, DLC richer in sp ³ bond carbon can be obtained. Can be formed.

<Lubrication layer>
Examples of the lubricant used in the lubricating layer include conventionally known materials such as perfluoropolyether, fluorinated alcohol, and fluorinated carboxylic acid.

Sectional drawing which shows an example of the patterned medium of this invention. The top view which shows the example of the magnetic pattern of the patterned medium of this invention. Sectional drawing which shows an example of the manufacturing method of the patterned medium of this invention. The figure which shows the relationship between C content in the SiOC embedding film of the patterned medium in the Example of this invention, and the film thickness of the oxide film in a recording layer. Shows the oxygen content of Ar-O ₂ mixed process gas used in the nonmagnetic embedding step in the embodiment of the present invention, the relationship between the thickness of the oxide film in the recording layer. ₂ is a particle map of a SiOC film formed using the method of the present invention and a SiO ₂ film formed using a conventional method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Underlayer, 3 ... Ferromagnetic recording layer, 4 ... Protective layer, 5 ... Imprint resist layer, 6 ... Imprint stamper, 7 ... SiOC embedding layer, 8 ... Protective layer.

Claims (6)

A substrate,
A ferromagnetic recording layer having a convex pattern formed on the substrate;
A nonmagnetic buried layer formed of a SiOC film containing Si, O, and C and having a C content of 0.05 at% or more, embedded in the recesses between the ferromagnetic recording layers forming the convex pattern A patterned magnetic recording medium comprising:   2. The patterned magnetic recording medium according to claim 1, wherein the ferromagnetic recording layer forming the convex pattern includes a discrete track.   2. The patterned magnetic recording medium according to claim 1, wherein the ferromagnetic recording layer forming the convex pattern includes a discrete bit. Forming a ferromagnetic recording layer on the substrate;
Processing the ferromagnetic recording layer to form a ferromagnetic recording layer having a convex pattern;
By performing DC sputtering using an SiC target as a sputtering target and an Ar—O ₂ mixed gas having an oxygen content of 55 vol% or less as a process gas, the concave portions between the ferromagnetic recording layers forming the convex pattern are formed. And a step of embedding a nonmagnetic buried layer formed of a SiOC film containing Si, O, and C and having a C content of 0.05 at% or more. Production method.   5. The method of manufacturing a patterned magnetic recording medium according to claim 4, wherein the ferromagnetic recording layer forming the convex pattern includes a discrete track.   5. The method of manufacturing a patterned magnetic recording medium according to claim 4, wherein the ferromagnetic recording layer forming the convex pattern includes a discrete bit.

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