JP4123944B2

JP4123944B2 - Vertical double-layer patterned medium and manufacturing method thereof

Info

Publication number: JP4123944B2
Application number: JP2003012602A
Authority: JP
Inventors: 俊司竹野入; 泰志酒井
Original assignee: Fuji Electric Device Technology Co Ltd
Current assignee: Fuji Electric Co Ltd
Priority date: 2003-01-21
Filing date: 2003-01-21
Publication date: 2008-07-23
Anticipated expiration: 2023-01-21
Also published as: JP2004227639A

Description

【０００１】
【発明の属する技術分野】
本発明は各種磁気記録装置に搭載される垂直二層パターンド媒体およびその製造方法に関する。
【０００２】
【従来の技術】
磁気記録の高密度化を実現する技術として、従来の長手磁気記録方式に代えて、垂直磁気記録方式が注目されつつある。垂直磁気記録媒体は主に、硬質磁性材料の磁気記録層と、磁気記録層の表面を保護する保護膜、そしてこの記録層への記録に用いられる磁気ヘッドが発生する磁束を集中させる役割を担う軟磁性材料の裏打ち層から構成される。
【０００３】
垂直磁気記録媒体における軟磁性裏打ち層は磁気ヘッドの一部とも言われており、記録に際しては、磁気ヘッドが発生する磁束が広がらないようにして引き込み、更にその磁束を磁気ヘッドにリターンさせる役割を持つ。そのため、記録磁界を確保しかつ急峻な磁化遷移を得るためには裏打ち層の果たす役割が重要となる。従来、この軟磁性裏打ち層の作製には、スパッタリング法が用いられてきた。それは、スパッタリング法を用いることで高い飽和磁化を有する複雑な組成の軟磁性材料でも容易に薄膜が得られるからである。
【０００４】
しかし、現状では軟磁性裏打ち層の膜厚は少なくとも２００ｎｍ程度必要であると言われており、スパッタリング法で作製した場合には成膜に時間がかかり、またコストも高くなることから、低コストでかつ高い飽和磁化を持つ複雑な組成の軟磁性材料でも成膜可能なプロセスが求められていた。
【０００５】
一方、垂直磁気記録媒体よりも更に高密度化を担う技術としてパターンド媒体がある。これは、磁気記録層に規則的な微細なパターンを施すもので、磁気的に分離されたｂｉｔを規則的に配置することで、超高密度記録を達成しようという試みである。
【０００６】
図１に典型的なパターンド媒体の作製方法を示す。以下、図１に従い説明する。まず、（ａ）非磁性基体１０上に磁気記録層２０を成膜する。次に（ｂ）レジスト３０を塗布し、（ｃ）電子線リソグラフィによりパターンを描画する。引き続いて（ｄ）マスク膜４０を成膜するが、この膜４０は後で行うＲＩＥ（Reactive Ion Etching）によりエッチングされない材質を選ぶ。次に（ｅ）レジスト３０を取り除き、（ｆ）磁気記録層２０のマスクされていない部分をＲＩＥにより取り除く。最後に、（ｇ）マスク膜４０を取り除くと、非磁性基体１０上にパターニングされた磁気記録層２０が残る。
【０００７】
このようなパターンド媒体の技術は超高密度記録が狙えるばかりでなく、サーボ信号の埋め込みにも応用できる。
【０００８】
【特許文献１】
特開２０００−２１６２９号公報
【０００９】
【特許文献２】
特開２００１−１１００５０号公報
【００１０】
【特許文献３】
特開２００１−１７６０４９号公報
【００１１】
【発明が解決しようとする課題】
パターンド媒体の技術を垂直磁気記録媒体に適用することにより、超高密度記録が可能になると考えられるが、実用化を考えた場合、一見してわかるように、上記のような半導体的プロセスは生産性が低く、高コストに繋がる。そのため、コストをできるだけ低く抑えることができる簡易なプロセスが望まれていた。
【００１２】
また、軟磁性裏打ち層に関しては、予めパターニングされた基板、あるいは細孔を持つ基板に軟磁性裏打ち層を成膜すると、軟磁性裏打ち層もパターンあるいは細孔により磁気的に分断されることになる。これにより、磁束のリターンパスを充分に確保できなくなるばかりでなく、磁壁がパターンあるいは細孔内でしか動けなくなるため軟磁気特性が劣化し、これらが原因で磁気ヘッドの記録能力が低下する。実際、垂直二層パターンド媒体については報告されておらず、軟磁性裏打ち層を設けない単層媒体を用いて基礎的な検討がなされているというのが現状である。
【００１３】
本発明の目的は、垂直磁気記録媒体に規則的で微細なパターンを形成して成る垂直二層パターンド媒体において、簡易かつ低コストで、記録特性を低下させることなく軟磁性裏打ち層を付与することが可能な製造方法を提供することにより、低コスト化および高スループット化に加えて記録媒体の記録分解能の向上、高記録密度化といった記録媒体性能の向上を実現することである。
【００１４】
【課題を解決するための手段】
上記の目的を達成し、低コストかつ高性能の軟磁性裏打ち層を製造する方法として、本発明者らは検討を繰り返し、以下に示す方法を用いることで、軟磁性裏打ち層を有するパターンド媒体を容易に得られることを見出した。なお、本明細書において「超微粒子」とは、径がおよそ１〜１００ｎｍの粒子をいうものと定義する。
【００１６】
すなわち、
（１）媒体基板上にポリマー中に軟磁性微粒子を分散させたスラリをコーティングする。
（２）加熱下で、凹凸を形成したスタンパを押し付けて軟磁性裏打ち層にパターンを転写する。
（３）凹凸上に磁気記録層を成膜する。
（４）研磨により凸上に形成された磁気記録層を除去する。
という工程を実施してパターンド媒体を製造するというものである。
【００１７】
本発明に係る製造方法を用いることで、高い軟磁気特性を有する軟磁性裏打ち層を持つパターンド媒体が作製可能なばかりでなく、パターン形成と軟磁性裏打ち層の成膜を同時に行えることから、製造工程を簡略化でき製品のコストダウンを実現できる。
【００１８】
【発明の実施の形態】
以下、垂直磁気記録媒体に関する本発明の好ましい形態について説明する。垂直磁気記録媒体は、非磁性基体１と、非磁性基体１の上に順次設けられる軟磁性２、下地層３、中間層４、磁気記録層５、保護膜６、および液体潤滑材層７を有する。非磁性基体１としては表面が平滑である様々な基体であってよく、例えば、磁気記録媒体用に用いられる、ＮｉＰメッキを施したＡｌ合金や強化ガラス、結晶化ガラス等を用いることができる。
【００１９】
軟磁性裏打ち層２としては、ポリマー中に超微粒子を分散させた様々な材料を用いることができる。ポリマーとしては、ポリカーボネート（ＰＣ），ポリメタクリル酸メチル（ＰＭＭＡ），あるいはポリエステル系、ポリオレフィン系材料等の樹脂を用いることができる。ポリマー中に分散させる軟磁性材料としては、パーメンジュール（ＦｅＣｏＶ），パーマロイ（ＮｉＦｅ），ＦｅＮｉ，ＣｏＦｅＮｉ等を用いることができる。軟磁性材料の粒径は、ポリマー中に均一に分散し、かつ得られた膜の表面粗さが記録媒体に要求される平坦度を満足する必要があることから、１００ｎｍ以下であることが好ましい。
【００２０】
下地層３には、磁気記録層５を適切に配向させることが可能な材料が選ばれ、例えば軟磁性を有するパーマロイ系材料である、ＮｉＦｅＡｌ，ＮｉＦｅＳｉ，ＮｉＦｅＮｂ，ＮｉＦｅＭｏ，ＮｉＦｅＣｒなどを用いることができる。
【００２１】
中間層４には、非磁性で磁気記録層５を適切に配向させることが可能な材料が選ばれ、例えばＴｉ，Ｒｕ，Ｐｔ，Ｐｄ，ＣｏＣｒなどを用いることができる。また、Ｔｉ，Ｐｔ，Ｐｄのように下地層が無くても適切な配向をする中間層を用いる場合、下地層３を形成してもしなくても良い。
【００２２】
磁気記録層５は少なくともＣｏとＣｒを含む合金の強磁性材料が好適に用いられ、その六方細密充填構造のｃ軸が膜面に垂直方向に配向していることが垂直磁気記録媒体として用いるために必要である。磁気記録層５としては、ＣｏＣｒＰｔ，ＣｏＣｒＴａ，ＣｏＣｒＰｔＢ等の合金材料や、ＣｏＰｔ−ＳｉＯ_２，ＣｏＣｒＰｔＯ，ＣｏＣｒＰｔ−ＳｉＯ_２，ＣｏＣｒＰｔ−Ａｌ_２Ｏ_３，ＣｏＰｔ−Ｃｒ_２Ｏ_３などのグラニュラー材料が挙げられるが、これらに限定されるものではない。
【００２３】
保護膜６は、例えばカーボンを主体とする薄膜が用いられる。その他、磁気記録媒体の保護膜として一般的に用いられる様々な薄膜材料を使用しても良い。
【００２４】
液体潤滑材層７は、例えばパーフルオロポリエーテル系の潤滑剤を用いることができる。その他、磁気記録媒体の液体潤滑材層材料として一般的に用いられる様々な潤滑材料を使用しても良い。
【００２５】
非磁性基体１の上に積層される各層は２〜７、磁気記録媒体の分野で通常用いられる様々な成膜技術によって形成することが可能である。軟磁性裏打ち層２、液体潤滑材層７を除く各層の形成には、例えばＤＣマグネトロンスパッタリング法、ＲＦマグネトロンスパッタリング法、真空蒸着法を用いることが出来る。また、軟磁性裏打ち層２、液体潤滑材層７の形成には、例えばディップ法、スピンコート法を用いることができる。しかし、これらに限定されるものではない。
【００２６】
次に、パターンド媒体に関する本発明の好ましい形態について説明する。図３に本発明に係る垂直磁気二層パターンド媒体の断面模式図を示す。図２と図３を比較しながら本発明に係る垂直二層パターンド媒体について説明する。
【００２７】
図３に示すように、本発明に係る垂直二層パターンド媒体では、非磁性基体１上にパターニングされた軟磁性裏打ち層２が形成され、そのパターンの凹の部分に下地層３、中間層４、磁気記録層５が順次積層される。引き続いて順次積層される保護膜６、液体潤滑材層７については、一般的な垂直記録媒体と全く同様である。
【００２８】
このように、本発明に係る垂直二層パターンド媒体では、パターニングされた軟磁性裏打ち層２が存在し、その凹の部分に中間層４、下地層３および磁気記録層５が存在することを特徴とする。非磁性基体１、軟磁性裏打ち層２、下地層３、中間層４、磁気記録層５、保護膜６、液体潤滑材層７の材料や形成方法に関しては、前述の垂直磁気記録媒体と全く同様である。
【００２９】
【実施例】
以下に本発明の垂直磁気記録媒体について、参考例としての実施例１及び実施例２を含む実施例により詳細に説明するが、本発明はそれらに限定されるものではなく、本発明の要旨を逸脱しない範囲において種々変更可能であることは言うまでもない。
【００３０】
［実施例１］
非磁性基体として表面が平滑な化学強化ガラス基板（例えばＨＯＹＡ社製Ｎ−１０ガラス基板）を用い、その上にスピンコートによりパーメンジュール（Ｆｅ４９Ｃｏ２Ｖ）軟磁性裏打ち層を形成した。スピンコートには、クロロホルム中にＰＭＭＡを０．３ｗｔ％溶解し、そこに平均粒径３０ｎｍのＦｅ４９Ｃｏ２Ｖ超微粒子を１０ｖｏｌ％分散させた溶液を用いた。
【００３１】
次に、表面粗さが０．２ｎｍであるＭｏスタンパを用い、スタンパおよび上記基板を１９０℃に加熱した後、１３ＭＰａで基板をプレスし、軟磁性裏打ち層を有する垂直磁気記録媒体用基板とした。なお、プレス後の軟磁性裏打ち層の膜厚を測定したところ約２００ｎｍであった。
【００３２】
［比較例１］
非磁性基体として表面が平滑な化学強化ガラス基板（例えばＨＯＹＡ社製Ｎ−１０ガラス基板）を用い、これを洗浄後スパッタ装置内に導入し、Ｆｅ４９Ｃｏ２Ｖターゲットを用いてＦｅＣｏＶ軟磁性裏打ち層を２００ｎｍの膜厚に成膜した。
【００３３】
実施例１および比較例１のサンプルの飽和磁化（Ｂｓ）および保磁力（Ｈｃ）を振動試料磁力計（ＶＳＭ）で、表面粗さを原子間力顕微鏡（ＡＦＭ）で測定した。測定結果を表１に示す。表からわかるように、Ｂｓは実施例１の方が若干劣るものの、保磁力Ｈｃは実施例１の方が小さくなっており、スパッタリング法で作製した軟磁性裏打ち層と比較しても遜色の無いものができた。また、Ｒａは実施例１の方が小さくなっており、本発明による方法により、記録媒体に要求される平坦な表面が得られることが明らかとなった。
【００３４】
【表１】

【００３５】
［実施例２］
非磁性基体として表面が平滑な化学強化ガラス基板（例えばＨＯＹＡ社製Ｎ−１０ガラス基板）を用い、その上にスピンコートによりパーマロイ（Ｎｉ２２Ｆｅ）軟磁性裏打ち層を形成した。スピンコートには、クロロホルム中にＰＭＭＡを０．３ｗｔ％溶解し、そこに平均粒径２０ｎｍのＮｉ２２Ｆｅ超微粒子を１０ｖｏｌ％分散させた溶液を用いた。
【００３６】
次に、表面粗さが０．２ｎｍであるＭｏスタンパを用い、スタンパおよび上記基板を１９０℃に加熱した後、１３ＭＰａで基板をプレスし、軟磁性裏打ち層を有する垂直磁気記録媒体用基板とした。
【００３７】
これを洗浄後スパッタ装置内に導入し、次にパーマロイ系合金であるＮｉ１２Ｆｅ９Ｎｂターゲットを用いてＮｉＦｅＮｂ下地層を２０ｎｍの膜厚に成膜した。引き続いて、Ｒｕターゲットを用いて、Ａｒガス圧４．０Ｐａ下でＲｕ中間層を５ｎｍの膜厚に成膜した。引き続いてＣｏ７Ｃｒ１４Ｐｔ−１０ＳｉＯ_２ターゲットを用いてＣｏＣｒＰｔ−ＳｉＯ_２磁気記録層を１５ｎｍの膜厚に成膜した。
【００３８】
最後に、カーボンターゲットを用いてカーボンからなる保護膜を１０ｎｍの膜厚に成膜後、真空装置から取り出した。Ｒｕ中間層の成膜を除くこれらの成膜はすべてＡｒガス圧０．６７Ｐａ下でＤＣマグネトロンスパッタリング法により行なった。その後、パーフルオロポリエーテルからなる液体潤滑材層を２ｎｍの膜厚にディップ法により形成し、垂直磁気記録媒体とした。
【００３９】
［比較例２］
非磁性基体として表面が平滑な化学強化ガラス基板（例えばＨＯＹＡ社製Ｎ−１０ガラス基板）を用い、これを洗浄後スパッタ装置内に導入し、Ｎｉ２２Ｆｅターゲットを用いてＮｉＦｅ軟磁性裏打ち層を２００ｎｍの膜厚に成膜した。以下、実施例１と全く同様にして、下地層、中間層、磁気記録層、保護膜、液体潤滑材層を形成し、垂直磁気記録媒体とした。
【００４０】
ソニーテクトロニクス社製のリード・ライトテスタを用いて、実施例２および比較例２の記録媒体の電磁変換特性を測定した。図４に規格化ノイズの線記録密度依存性を、図５にＳＮＲ（信号対ノイズ比）の線記録密度依存性を示す。実施例２および比較例２の記録媒体では、出力特性はほぼ同等であったが、図４に示すように実施例２に係る記録媒体の方が低ノイズであった。そのため、図５に示すように、実施例２に係る記録媒体の方がＳＮＲで約３ｄＢ高くなった。
【００４１】
ノイズの原因を調べたところ、実施例２と比較例２の差は軟磁性起因のノイズの差であり、本発明による軟磁性裏打ち層が、スパッタリング法により作製した軟磁性裏打ち層よりも低ノイズであることが分かった。
【００４２】
このように、本発明による軟磁性裏打ち層は、真空チャンバ等を必要とせず従来に比べて低コストで簡易な方法で作製できるだけではなく、軟磁性層起因のノイズを低減して記録媒体の特性を向上させることが可能であることが明らかとなった。
【００４３】
［実施例３］
図６に本実施例に係る垂直二層パターンド媒体の製造工程の断面模式図を示す。以下、図６に従い本実施例に係る垂直二層パターンド媒体の製造方法について説明する。
【００４４】
（ａ）非磁性基体として表面が平滑な化学強化ガラス基板（例えばＨＯＹＡ社製Ｎ−１０ガラス基板）を用い、その上にスピンコートによりパーマロイ（Ｎｉ２２Ｆｅ）軟磁性裏打ち層を形成した。スピンコートには、ジクロロメタン中にポリカーボネートを０．２５ｗｔ％溶解し、そこに平均粒径２０ｎｍのＮｉ２２Ｆｅ超微粒子を１０ｖｏｌ％分散させた溶液を用いた。
【００４５】
（ｂ）基板およびスタンパを２００℃まで加熱し、スタンパを１５ＭＰａの圧力で基板上に押し付け、１００℃まで冷却した後、離型した。なお、スタンパには電子ビームリソグラフィを用いてφ１００ｎｍのパターンが形成されている。ここで、軟磁性裏打ち層にパターンを形成する時の凹部の深さが、「下地層３＋中間層４の合計膜厚（第1の合計厚み）」よりも深く、「下地層３＋中間層４＋磁気記録層５の合計膜厚（第２の合計厚み）」以下となるように、軟磁性裏打ち層２の膜厚、加熱温度、成形圧力を調整した。
【００４６】
（ｃ）次に基板を再びスパッタ装置内に導入し、Ｎｉ１５Ｆｅ２５Ｃｒターゲットを用いてＮｉＦｅＣｒ下地層を１０ｎｍの膜厚に、Ｒｕターゲットを用いて、Ａｒガス圧４．０Ｐａ下でＲｕ中間層を１０ｎｍの膜厚に、Ｃｏ２０Ｃｒ１０Ｐｔターゲットを用いてＣｏＣｒＰｔ磁気記録層を３５ｎｍの膜厚に、順次成膜した。
【００４７】
（ｄ）その後、再び真空装置から取り出し、ダイヤモンドスラリを用いてパターンの凸上に成膜された磁気記録層を除去した。研磨量はレーザー変位計によりモニターし、変位量の変化が急激に低下したところを終点とした。
【００４８】
（ｅ）引き続いてこれを洗浄して、スパッタ装置内に導入し、カーボンターゲットを用いてカーボンからなる保護膜を１０ｎｍの膜厚に成膜後、真空装置から取り出した。その後、パーフルオロポリエーテルからなる液体潤滑材層を２ｎｍの膜厚にディップ法により形成し、垂直二層パターンド媒体とした。
【００４９】
なお、ＮｉＦｅＣｒ下地層、ＣｏＣｒＰｔ磁気記録層およびＣ保護膜の成膜はすべてＡｒガス圧０．６７Ｐａ下で行い、真空装置内における全ての成膜はＤＣマグネトロンスパッタリング法により行なった。
【００５０】
完成した垂直二層パターンド媒体の表面が記録媒体として適切かどうかを判断するため、ＡＦＭを用いて表面粗さを測定した。その結果、表面のＲａは０．８２［ｎｍ］であり、記録媒体の表面としては十分に平滑であることがわかった。
【００５１】
次いで、完成した垂直パターンド媒体の磁気特性をＫｅｒｒ効果（外部磁界を印加しながら、反射光の偏光面の回転角を測定）を用いて評価した。その結果、３２３０［Ｏｅ］の保磁力Ｈｃが得られた。本法では加熱成膜を行わないと保磁力Ｈｃが１０００［Ｏｅ］以下になる組成の磁気記録層材料を用いているにもかかわらず、比較的高い保磁力Ｈｃが得られたことから、パターニングによる磁気記録層のｂｉｔの磁気的な分離が良好になされていることが分かった。
【００５２】
以上のように、本発明による垂直二層パターンド媒体では、記録媒体に必要な表面を得ることが可能であり、またそれぞれのｂｉｔが分離していて、パターニングが有効に機能していることが分かった。
【００５４】
【発明の効果】
以上述べたように本発明によれば、半導体的な手法と比較して低コストかつ高スループットで垂直二層パターンド媒体を製造することが可能になる。また、軟磁性裏打ち層の特性を損ねることなく垂直二層パターンド媒体が作製できることから、ヘッドの記録分解能を低下させることなくパターンド媒体が実現され、記録媒体の高記録密度化が可能になる。
【図面の簡単な説明】
【図１】典型的なパターンド媒体の製造工程を示す断面模式図である。
【図２】垂直磁気記録媒体の断面模式図である。
【図３】本発明に係る垂直二層パターンド媒体の断面模式図である。
【図４】実施例２および比較例２に係る媒体の規格化ノイズの線記録密度依存性を示す特性図である。
【図５】実施例２および比較例２に係る媒体のＳＮＲの線記録密度依存性を示す特性図である。
【図６】実施例３に係る垂直二層パターンド媒体の製造工程を示す断面模式図である。
【符号の説明】
１非磁性基体
２軟磁性裏打ち層
３下地層
４中間層
５磁気記録層
６保護膜
７液体潤滑材層
１０非磁性基体
２０磁気記録層
３０レジスト
４０マスク膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to onboard Ru vertical two-layer patterned medium and a manufacturing method thereof to various magnetic recording apparatus.
[0002]
[Prior art]
As a technique for realizing a high density magnetic recording, a perpendicular magnetic recording system is drawing attention in place of the conventional longitudinal magnetic recording system. Perpendicular magnetic recording media mainly play a role in concentrating magnetic flux generated by a magnetic recording layer of hard magnetic material, a protective film for protecting the surface of the magnetic recording layer, and a magnetic head used for recording on the recording layer. Consists of a backing layer of soft magnetic material.
[0003]
The soft magnetic underlayer in a perpendicular magnetic recording medium is also said to be a part of the magnetic head. During recording, the magnetic head generates a magnetic flux so that the magnetic flux does not spread, and further returns the magnetic flux to the magnetic head. Have. Therefore, the role of the backing layer is important in order to secure a recording magnetic field and obtain a steep magnetization transition. Conventionally, a sputtering method has been used to produce this soft magnetic underlayer. This is because a thin film can be obtained easily even with a soft magnetic material having a complicated composition having high saturation magnetization by using a sputtering method.
[0004]
However, at present, it is said that the film thickness of the soft magnetic underlayer is required to be at least about 200 nm, and when it is produced by the sputtering method, it takes a long time to form the film and the cost becomes high. In addition, a process capable of forming a film with a soft magnetic material having a complicated composition and high saturation magnetization has been demanded.
[0005]
On the other hand, there is a patterned medium as a technique for achieving higher density than the perpendicular magnetic recording medium. This is an attempt to achieve ultra-high density recording by regularly arranging magnetically separated bits by applying a regular fine pattern to the magnetic recording layer.
[0006]
FIG. 1 shows a typical method for producing a patterned medium. Hereinafter, a description will be given with reference to FIG. First, (a) the magnetic recording layer 20 is formed on the nonmagnetic substrate 10. Next, (b) a resist 30 is applied, and (c) a pattern is drawn by electron beam lithography. Subsequently, (d) a mask film 40 is formed. A material that is not etched by RIE (Reactive Ion Etching) to be performed later is selected for the film 40. Next, (e) the resist 30 is removed, and (f) an unmasked portion of the magnetic recording layer 20 is removed by RIE. Finally, (g) when the mask film 40 is removed, the patterned magnetic recording layer 20 remains on the nonmagnetic substrate 10.
[0007]
Such a patterned medium technology can be applied not only to ultra-high density recording but also to embedding servo signals.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-21629
[Patent Document 2]
Japanese Patent Laid-Open No. 2001-110050
[Patent Document 3]
JP 2001-176049 A
[Problems to be solved by the invention]
By applying the technology of patterned media to perpendicular magnetic recording media, it is thought that ultra-high density recording will be possible, but when considering practical use, as seen at a glance, the semiconductor process as described above is Productivity is low, leading to high costs. Therefore, a simple process that can keep the cost as low as possible has been desired.
[0012]
As for the soft magnetic backing layer, if the soft magnetic backing layer is formed on a substrate patterned in advance or a substrate having pores, the soft magnetic backing layer is also magnetically separated by the pattern or pores. . As a result, not only a sufficient return path for the magnetic flux cannot be secured, but also the domain wall can move only within the pattern or the pores, so that the soft magnetic characteristics are deteriorated, which causes the recording performance of the magnetic head to be lowered. Actually, there is no report on a vertical double-layer patterned medium, and a basic study has been made using a single-layer medium without a soft magnetic backing layer.
[0013]
An object of the present invention is a double-layered perpendicular patterned medium by forming a regular and fine pattern to vertical magnetic recording medium, in easy easy, low-cost, soft magnetic backing layer without reducing the record properties By providing a manufacturing method capable of providing the recording medium, it is possible to realize an improvement in recording medium performance such as an improvement in recording resolution and an increase in recording density of the recording medium in addition to a reduction in cost and an increase in throughput.
[0014]
[Means for Solving the Problems]
As a method for producing the low-cost and high-performance soft magnetic backing layer that achieves the above object, the present inventors have repeatedly studied and by using the following method, a patterned medium having a soft magnetic backing layer is used. It was found that can be easily obtained. In this specification, “ultrafine particle” is defined as a particle having a diameter of about 1 to 100 nm.
[0016]
That is,
(1) A slurry in which soft magnetic fine particles are dispersed in a polymer is coated on a medium substrate.
(2) The pattern is transferred to the soft magnetic backing layer by pressing a stamper having irregularities under heating.
(3) A magnetic recording layer is formed on the unevenness.
(4) The magnetic recording layer formed on the protrusion by polishing is removed.
The patterned medium is manufactured by performing the process.
[0017]
By using the manufacturing method according to the present invention, not only can a patterned medium having a soft magnetic backing layer having high soft magnetic properties be produced, but also pattern formation and film formation of the soft magnetic backing layer can be performed simultaneously. The manufacturing process can be simplified and the cost of the product can be reduced.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention relating to a perpendicular magnetic recording medium will be described. The perpendicular magnetic recording medium includes a nonmagnetic substrate 1, a soft magnet 2, an underlayer 3, an intermediate layer 4, a magnetic recording layer 5, a protective film 6, and a liquid lubricant layer 7 that are sequentially provided on the nonmagnetic substrate 1. Have. The nonmagnetic substrate 1 may be various substrates having a smooth surface. For example, an Al alloy plated with NiP, tempered glass, crystallized glass or the like used for a magnetic recording medium can be used.
[0019]
As the soft magnetic backing layer 2, various materials in which ultrafine particles are dispersed in a polymer can be used. As the polymer, resins such as polycarbonate (PC), polymethyl methacrylate (PMMA), polyester-based, and polyolefin-based materials can be used. Permendur (FeCoV), permalloy (NiFe), FeNi, CoFeNi, etc. can be used as the soft magnetic material dispersed in the polymer. The particle diameter of the soft magnetic material is preferably 100 nm or less because it is necessary to uniformly disperse in the polymer and the surface roughness of the obtained film must satisfy the flatness required for the recording medium. .
[0020]
For the underlayer 3, a material capable of appropriately orienting the magnetic recording layer 5 is selected. For example, NiFeAl, NiFeSi, NiFeNb, NiFeMo, NiFeCr, etc., which are permalloy materials having soft magnetism, can be used. .
[0021]
For the intermediate layer 4, a material that is nonmagnetic and capable of appropriately orienting the magnetic recording layer 5 is selected. For example, Ti, Ru, Pt, Pd, CoCr, or the like can be used. Further, when an intermediate layer having an appropriate orientation is used even if there is no underlayer such as Ti, Pt, and Pd, the underlayer 3 may or may not be formed.
[0022]
For the magnetic recording layer 5, a ferromagnetic material of an alloy containing at least Co and Cr is preferably used, and the c-axis of the hexagonal close-packed structure is oriented perpendicularly to the film surface for use as a perpendicular magnetic recording medium. Is necessary. Examples of the magnetic recording layer 5 include alloy materials such as CoCrPt, CoCrTa, and CoCrPtB, and granular materials such as CoPt—SiO ₂ , CoCrPtO, CoCrPt—SiO ₂ , CoCrPt—Al ₂ O ₃ , and CoPt—Cr ₂ O _3. However, it is not limited to these.
[0023]
For example, a thin film mainly composed of carbon is used as the protective film 6. In addition, various thin film materials generally used as a protective film of a magnetic recording medium may be used.
[0024]
For the liquid lubricant layer 7, for example, a perfluoropolyether lubricant can be used. In addition, various lubricating materials that are generally used as liquid lubricant layer materials for magnetic recording media may be used.
[0025]
Each layer laminated on the nonmagnetic substrate 1 can be formed by various film forming techniques usually used in the field of magnetic recording media. For example, a DC magnetron sputtering method, an RF magnetron sputtering method, or a vacuum deposition method can be used to form each layer except the soft magnetic backing layer 2 and the liquid lubricant layer 7. For forming the soft magnetic backing layer 2 and the liquid lubricant layer 7, for example, a dipping method or a spin coating method can be used. However, it is not limited to these.
[0026]
Next, the preferable form of this invention regarding a patterned medium is demonstrated. FIG. 3 shows a schematic sectional view of a perpendicular magnetic double-layer patterned medium according to the present invention. The vertical double-layer patterned medium according to the present invention will be described with reference to FIG. 2 and FIG.
[0027]
As shown in FIG. 3, in the vertical two-layer patterned medium according to the present invention, a patterned soft magnetic backing layer 2 is formed on a nonmagnetic substrate 1, and an underlayer 3 and an intermediate layer are formed in the concave portion of the pattern. 4 and the magnetic recording layer 5 are sequentially laminated. The protective film 6 and the liquid lubricant layer 7 that are successively laminated successively are the same as those of a general perpendicular recording medium.
[0028]
Thus, in the perpendicular double-layer patterned medium according to the present invention, the patterned soft magnetic backing layer 2 exists, and the intermediate layer 4, the underlayer 3 and the magnetic recording layer 5 exist in the concave portion. Features. The materials and forming methods of the nonmagnetic substrate 1, the soft magnetic backing layer 2, the underlayer 3, the intermediate layer 4, the magnetic recording layer 5, the protective film 6, and the liquid lubricant layer 7 are exactly the same as those of the aforementioned perpendicular magnetic recording medium. It is.
[0029]
【Example】
Hereinafter, the perpendicular magnetic recording medium of the present invention will be described in detail with reference to Examples including Example 1 and Example 2 as reference examples, but the present invention is not limited thereto, and the gist of the present invention is described below. It goes without saying that various changes can be made without departing from the scope.
[0030]
[Example 1]
A chemically strengthened glass substrate (for example, N-10 glass substrate manufactured by HOYA) having a smooth surface was used as a nonmagnetic substrate, and a permendur (Fe49Co2V) soft magnetic backing layer was formed thereon by spin coating. For spin coating, a solution prepared by dissolving 0.3 wt% of PMMA in chloroform and dispersing 10 vol% of Fe49Co2V ultrafine particles having an average particle diameter of 30 nm therein was used.
[0031]
Next, using a Mo stamper having a surface roughness of 0.2 nm, the stamper and the substrate were heated to 190 ° C., and then the substrate was pressed at 13 MPa to obtain a perpendicular magnetic recording medium substrate having a soft magnetic backing layer. . The thickness of the soft magnetic backing layer after pressing was measured and found to be about 200 nm.
[0032]
[Comparative Example 1]
A chemically tempered glass substrate (for example, N-10 glass substrate manufactured by HOYA) having a smooth surface is used as a nonmagnetic substrate, and this is introduced into a sputtering apparatus after cleaning. The film was formed to a film thickness.
[0033]
The saturation magnetization (Bs) and coercive force (Hc) of the samples of Example 1 and Comparative Example 1 were measured with a vibrating sample magnetometer (VSM), and the surface roughness was measured with an atomic force microscope (AFM). The measurement results are shown in Table 1. As can be seen from the table, Bs is slightly inferior to Example 1, but coercive force Hc is smaller in Example 1 and is comparable to a soft magnetic backing layer produced by sputtering. Things were made. In addition, Ra is smaller in Example 1, and it has been clarified that the method according to the present invention provides a flat surface required for the recording medium.
[0034]
[Table 1]

[0035]
[Example 2]
A chemically strengthened glass substrate (for example, N-10 glass substrate manufactured by HOYA) having a smooth surface was used as the nonmagnetic substrate, and a permalloy (Ni22Fe) soft magnetic backing layer was formed thereon by spin coating. For spin coating, a solution prepared by dissolving 0.3 wt% of PMMA in chloroform and dispersing 10 vol% of Ni22Fe ultrafine particles having an average particle diameter of 20 nm therein was used.
[0036]
Next, using a Mo stamper having a surface roughness of 0.2 nm, the stamper and the substrate were heated to 190 ° C., and then the substrate was pressed at 13 MPa to obtain a perpendicular magnetic recording medium substrate having a soft magnetic backing layer. .
[0037]
This was introduced into the sputtering apparatus after cleaning, and then a NiFeNb underlayer was formed to a thickness of 20 nm using a Ni12Fe9Nb target which is a permalloy alloy. Subsequently, using a Ru target, a Ru intermediate layer was formed to a thickness of 5 nm under an Ar gas pressure of 4.0 Pa. Subsequently, a CoCrPt—SiO ₂ magnetic recording layer was formed to a thickness of 15 nm using a Co7Cr14Pt-10SiO ₂ target.
[0038]
Finally, a protective film made of carbon was formed to a thickness of 10 nm using a carbon target, and then taken out from the vacuum apparatus. All of these film formations except the Ru intermediate layer film formation were performed by the DC magnetron sputtering method under an Ar gas pressure of 0.67 Pa. Thereafter, a liquid lubricant layer made of perfluoropolyether was formed to a thickness of 2 nm by a dip method to obtain a perpendicular magnetic recording medium.
[0039]
[Comparative Example 2]
A chemically strengthened glass substrate (for example, N-10 glass substrate manufactured by HOYA) having a smooth surface is used as a non-magnetic substrate, and this is introduced into a sputtering apparatus after cleaning. The film was formed to a film thickness. Thereafter, in the same manner as in Example 1, a base layer, an intermediate layer, a magnetic recording layer, a protective film, and a liquid lubricant layer were formed to obtain a perpendicular magnetic recording medium.
[0040]
The electromagnetic conversion characteristics of the recording media of Example 2 and Comparative Example 2 were measured using a Sony Tektronix read / write tester. FIG. 4 shows the dependence of normalized noise on the linear recording density, and FIG. 5 shows the dependence of SNR (signal to noise ratio) on the linear recording density. In the recording media of Example 2 and Comparative Example 2, the output characteristics were almost the same, but the recording medium according to Example 2 had lower noise as shown in FIG. Therefore, as shown in FIG. 5, the recording medium according to Example 2 has an SNR of about 3 dB higher.
[0041]
When the cause of noise was investigated, the difference between Example 2 and Comparative Example 2 was the difference in noise caused by soft magnetism, and the soft magnetic backing layer according to the present invention was lower in noise than the soft magnetic backing layer produced by the sputtering method. It turns out that.
[0042]
As described above, the soft magnetic backing layer according to the present invention can be manufactured by a simple method at a lower cost than the conventional one without the need for a vacuum chamber or the like, and the characteristics of the recording medium can be reduced by reducing noise caused by the soft magnetic layer. It has become clear that it is possible to improve.
[0043]
[Example 3]
FIG. 6 shows a schematic cross-sectional view of the manufacturing process of the vertical double-layer patterned medium according to this example. Hereinafter, a method for manufacturing a vertical double-layer patterned medium according to the present embodiment will be described with reference to FIG.
[0044]
(A) A chemically strengthened glass substrate having a smooth surface (for example, N-10 glass substrate manufactured by HOYA) was used as a nonmagnetic substrate, and a permalloy (Ni22Fe) soft magnetic backing layer was formed thereon by spin coating. For spin coating, a solution was used in which 0.25 wt% of polycarbonate was dissolved in dichloromethane and 10 vol% of Ni22Fe ultrafine particles having an average particle diameter of 20 nm were dispersed therein.
[0045]
(B) The substrate and stamper were heated to 200 ° C., the stamper was pressed onto the substrate with a pressure of 15 MPa, cooled to 100 ° C., and then released. The stamper is formed with a pattern of φ100 nm using electron beam lithography. Here, the depth of the recess when the pattern is formed on the soft magnetic underlayer is deeper than “total thickness of the underlayer 3 + intermediate layer 4 (first total thickness)”, and “undercoat layer 3 + intermediate layer 4+”. The film thickness, heating temperature, and molding pressure of the soft magnetic backing layer 2 were adjusted so that the total film thickness of the magnetic recording layer 5 (second total thickness) "or less.
[0046]
(C) Next, the substrate is again introduced into the sputtering apparatus, the NiFeCr underlayer is formed to a thickness of 10 nm using a Ni15Fe25Cr target, and the Ru intermediate layer is formed to 10 nm under an Ar gas pressure of 4.0 Pa using a Ru target. A CoCrPt magnetic recording layer was sequentially formed to a thickness of 35 nm using a Co20Cr10Pt target.
[0047]
(D) Thereafter, the magnetic recording layer formed on the convex of the pattern was removed using a diamond slurry again from the vacuum apparatus. The amount of polishing was monitored with a laser displacement meter, and the point at which the change in the amount of displacement rapidly decreased was taken as the end point.
[0048]
(E) Subsequently, this was washed and introduced into the sputtering apparatus, and a protective film made of carbon was formed to a thickness of 10 nm using a carbon target, and then taken out from the vacuum apparatus. Thereafter, a liquid lubricant layer made of perfluoropolyether was formed to a thickness of 2 nm by the dipping method to obtain a vertical two-layer patterned medium.
[0049]
The NiFeCr underlayer, the CoCrPt magnetic recording layer, and the C protective film were all formed under an Ar gas pressure of 0.67 Pa, and all film formation in the vacuum apparatus was performed by a DC magnetron sputtering method.
[0050]
In order to judge whether the surface of the completed vertical double-layer patterned medium is suitable as a recording medium, the surface roughness was measured using AFM. As a result, the surface Ra was 0.82 [nm], and it was found that the surface of the recording medium was sufficiently smooth.
[0051]
Next, the magnetic properties of the completed vertical patterned medium were evaluated using the Kerr effect (measurement of the rotation angle of the polarization plane of reflected light while applying an external magnetic field). As a result, a coercive force Hc of 3230 [Oe] was obtained. In this method, a relatively high coercive force Hc was obtained despite the use of a magnetic recording layer material having a composition in which the coercive force Hc is 1000 [Oe] or less unless heating film formation is performed. It was found that the magnetic separation of the magnetic recording layer bits was excellent.
[0052]
As described above, in the vertical double-layer patterned medium according to the present invention, it is possible to obtain the surface necessary for the recording medium, and that each bit is separated and the patterning functions effectively. I understood.
[0054]
【The invention's effect】
As described above, according to the present invention, it is possible to manufacture a vertical two-layer patterned medium at a low cost and a high throughput as compared with a semiconductor method. In addition, since a perpendicular double-layer patterned medium can be produced without impairing the characteristics of the soft magnetic underlayer, the patterned medium can be realized without reducing the recording resolution of the head, and the recording medium can have a high recording density. .
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a typical patterned medium manufacturing process.
FIG. 2 is a schematic cross-sectional view of a perpendicular magnetic recording medium.
FIG. 3 is a schematic cross-sectional view of a vertical double-layer patterned medium according to the present invention.
4 is a characteristic diagram showing the linear recording density dependence of standardized noise of media according to Example 2 and Comparative Example 2. FIG.
5 is a characteristic diagram showing the linear recording density dependence of the SNR of media according to Example 2 and Comparative Example 2. FIG.
6 is a schematic cross-sectional view showing a manufacturing process of a vertical double-layer patterned medium according to Example 3. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Nonmagnetic base | substrate 2 Soft magnetic backing layer 3 Underlayer 4 Intermediate layer 5 Magnetic recording layer 6 Protective film 7 Liquid lubricant layer 10 Nonmagnetic base 20 Magnetic recording layer 30 Resist 40 Mask film

Claims

A perpendicular two-layer patterned medium in which a soft magnetic backing layer, an underlayer, an intermediate layer, a magnetic recording layer, a protective film, and a liquid lubricating layer are laminated in order on a nonmagnetic substrate,
The soft magnetic backing layer is made of a polymer and soft magnetic ultrafine particles, and a plurality of concave portions and convex portions are alternately formed on the surface by patterning, and the underlayer, intermediate layer, and magnetic recording layer are laminated in the concave portions. Has been
The perpendicular magnetic recording layer is characterized in that the magnetic recording layer is removed on the convex portion and magnetically separated from each other in the concave portion, and an easy axis of magnetization is oriented in a direction perpendicular to the substrate surface. Patterned medium.

The vertical bilayer patterned medium of claim 1 ,
The depth dimension of the recess is larger than the total thickness of the base layer and the intermediate layer, and the surface of the magnetic recording layer formed on the intermediate layer in the recess is flat with respect to the surface of the protrusion. A vertical double-layer patterned medium characterized by the above.

A first step of forming a soft magnetic backing layer comprising a polymer and soft magnetic ultrafine particles on a non-magnetic substrate; a second step of subjecting the soft magnetic backing layer to surface treatment; an underlayer on the surface-treated soft magnetic backing layer; A third step of forming an intermediate layer, a fourth step of forming an intermediate layer on the underlayer, a fifth step of forming a magnetic recording layer on the intermediate layer, and a sixth step of forming a protective film on the magnetic recording layer. A process for producing a vertical two-layer patterned medium comprising a step, a seventh step of forming a liquid lubricant layer on the protective film,
The second step is a heat treatment step for heating the soft magnetic backing layer, and the soft magnetic layer that faces the underlayer using a stamper having a pattern in which a plurality of concave portions and convex portions are alternately formed. Patterning is performed by pressing the surface of the backing layer with the pattern to pattern the surface according to the pattern, and forming a plurality of concave portions and convex portions corresponding to the plurality of convex portions and concave portions of the stamper on the surface. Process,
Further, after the fifth step and before the sixth step, the underlayer, the intermediate layer, and the layer laminated on the convex portion of the soft magnetic backing layer by the third to fifth steps. A method for producing a perpendicular double-layer patterned medium, comprising a step of removing a magnetic recording layer.

In the manufacturing method of the perpendicular double layer patterned media according to claim 3 ,
In the removing step, the surface of the formed material on the nonmagnetic substrate at the end of the fifth step is polished, and the underlayer laminated at the end of the fifth step on the concave portion of the soft magnetic backing layer A method for producing a vertical double-layer patterned medium, wherein the surface of the intermediate layer and the magnetic recording layer is flat with respect to the surface of the convex portion of the soft magnetic underlayer.

The method for producing a vertical double-layer patterned medium according to claim 4 ,
In the concave portion of the soft magnetic backing layer, the first total thickness of the base layer and the intermediate layer is smaller than the depth dimension of the concave portion, and the base layer, the intermediate layer, and the magnetic recording layer are combined. The perpendicular double-layer patterned medium, wherein the soft magnetic underlayer, the underlayer, the intermediate layer, and the magnetic recording layer are each formed to have a predetermined thickness so that the second total thickness is increased. Manufacturing method.

In the manufacturing method of the perpendicular double layer patterned media according to claim 5 ,
By adjusting at least one of the film thickness when forming the soft magnetic backing layer, the heating temperature in the heat treatment step, and the molding pressure in the patterning step, the depth dimension and the first and second total thicknesses are adjusted. And forming the soft magnetic backing layer, the underlayer, the intermediate layer, and the magnetic recording layer so as to satisfy the above relationship.