JP3567157B2 - Magnetic recording medium, method of manufacturing the same, and magnetic storage device - Google Patents

Description

【００１６】
第１下地膜用の合金としては、Ｍｏ、Ｔｉ、Ｚｒ、Ａｌの群から選ばれた少なくとも１種の元素とＣｒを含有する合金が基板と膜の密着性の点から好適である。さらに第１下地膜用の合金としては、Ｃｒ、Ｓｉ、Ｖ、Ｔａ、Ｔｉ、Ｚｒ、Ａｌ、Ｗの群から選ばれた少なくとも１種の元素とＣｏを含有する合金とすると、この合金が非晶質又は微結晶になりやすく組織が緻密になるため、ガラス基板を用いた場合にはガラスから膜中に侵入してくるアルカリ元素等不純物の拡散バリアになるため有効である。ここで、非晶質とはＸ線回折による明瞭なピークが観察されないこと、または、電子線回折による明瞭な回折スポット、回折リングが観察されず、ハロー状の回折リングが観察されることをいう。また、微結晶とは、結晶粒径が磁性層の結晶粒径より小さく、好ましくは平均粒径が８ｎｍ以下の結晶粒から成ることをいう。また、上記第１下地膜用の合金の中で酸化物生成標準自由エネルギーΔＧ°が最も低い元素の含有率は、それが上記成長核の数量に関係するため、５ａｔ％から５０ａｔ％の間程度が第２下地膜の結晶粒微細化に効果があるので好ましく、５ａｔ％から３０ａｔ％の間程度がより好ましい。
【００１７】
また、第１下地膜と基板の間には、第３下地膜を配置してよい。例えば、基板をガラス基板とするとき、従来例に示した種々の金属膜、合金膜、酸化物膜等を第３下地膜として用いることができる。
【００１８】
第２下地膜としては、Ｃｏ合金磁性膜との結晶格子整合性の高いＣｒ合金等のｂｃｃ構造を有するものが好ましい。例えば、Ｃｒ、Ｃｒ合金、すなわち、ＣｒＴｉ、ＣｒＶ、ＣｒＭｏ等を用いることができる。
【００１９】
第１下地膜の厚さは２０ｎｍから５０ｎｍの範囲であることが好ましく、第１下地膜の厚さは１０ｎｍから５０ｎｍの範囲であることが好ましい。
【００２０】
また、磁性膜は、磁気異方性が面内を向いている磁性膜であることが好ましい。このような磁性膜として、例えば、Ｃｏ−Ｃｒ−Ｐｔ、Ｃｏ−Ｃｒ−Ｐｔ−Ｔａ、Ｃｏ−Ｃｒ−Ｐｔ−Ｔｉ、Ｃｏ−Ｃｒ−Ｔａ、Ｃｏ−Ｎｉ−Ｃｒ等のＣｏを主成分とする合金を用いることができるが、高い保磁力を得るためには、Ｐｔを含むＣｏ合金を用いることが好ましい。さらに、磁性膜を非磁性中間層を介した複数の層で構成することもできる。
【００２１】
磁性膜の磁気特性としては、膜面内に磁界を印加して測定した保磁力を１．８キロエルステッド以上とし、膜面内に磁界を印加して測定した残留磁束密度Ｂｒと膜厚ｔの積Ｂｒ・ｔを２０ガウス・ミクロン以上、１４０ガウス・ミクロン以下とすると、１平方インチ当たり１ギガビット以上の記録密度領域において、良好な記録再生特性が得られるので好ましい。保磁力が１．８キロエルステッド未満であると、高記録密度（２００ｋＦＣＩ以上）での出力が小さくなり好ましくない。ここでＦＣＩ（ｆｌｕｘ ｒｅｖｅｒｓａｌ ｐｅｒ ｉｎｃｈ）は記録密度の単位である。また、Ｂｒ・ｔが１４０ガウス・ミクロンより大きくなると高記録密度での再生出力が低下し、２０ガウス・ミクロン未満であると、低記録密度での再生出力が小さくなり好ましくない。
なお、磁性膜を非磁性中間層を介した複数の層で構成するとき、上記Ｂｒ・ｔの計算における磁性膜の膜厚ｔは各磁性層の厚さの合計を表すものとする。
【００２２】
【発明の実施の形態】
図２は、磁気記録媒体を作製するための枚葉成膜型のスパッタリング装置の一例の模式的説明図である。実際のスパッタリング装置は、中央にメインチャンバ２９があり、その周囲に仕込み室２１、第１下地膜形成室２２、加熱室２３、酸化室２４、第２下地膜形成室２５、磁性膜形成室２６、保護膜形成室２７ａ、２７ｂ、２７ｃ、２７ｄ、取り出し室２８が円形に並んでいる。基板をある室で処理した後に次ぎの室に送る操作は、各室で同時に行う。つまりこのスパッタリング装置で複数枚同時に処理することができ、基板を各室に次々に順に送ればよい。保護膜形成室２７ａ、２７ｂ、２７ｃ、２７ｄが４室あるのは、保護膜形成は低速度で行うのが好ましいので、１つの室で所望の厚さの４分の１ずつ形成するためである。
【００２３】
このスパッタリング装置により、強化ガラスの基板２０をまず仕込み室２１に入れて真空とし、メインチャンバ２９を経て次々に各室に移動させて次のように処理する。第１下地膜として６０ａｔ％Ｃｏ−３０ａｔ％Ｃｒ−１０ａｔ％Ｚｒ合金を室温で形成し、２７０℃に加熱した後、酸化室２４でアルゴンと酸素の混合ガスの雰囲気に曝す。このとき、この混合ガスの混合比及びこの混合ガスの雰囲気に曝す時間を種々変化させる。第２下地膜として７５ａｔ％Ｃｒ−１５ａｔ％Ｔｉ合金を、磁性膜として７５ａｔ％Ｃｏ−１９ａｔ％Ｃｒ−６ａｔ％Ｐｔ合金をそれぞれ順に積層した。この間２７０℃又はそれより多少低い温度に保たれている。さらに、保護膜としてカーボンを厚さ１０ｎｍ〜３０ｎｍ形成する。
【００２４】
上述の混合ガスの混合比及び混合ガスの雰囲気に曝す時間を変えた結果、媒体ノイズと線形的な相関を示す活性化体積ｖと磁気モーメントＩｓｂの積（ｖ・Ｉｓｂ）は、この雰囲気の酸素分圧ＰＯ_２とそれに曝す時間ｔの積（ＰＯ_２・ｔ）に対し、図３に示すように、極小値をとることが分かった。ここで、ｖ・Ｉｓｂについては、ジャーナル オブ マグネティズム アンド マグネティック マテリアルズ、第１４５巻（１９９５年）、第２５５頁〜第２６０頁（Ｊ．Ｍａｇｎ．Ｍａｇｎ．Ｍａｔｅｒ．，ｖｏｌ．１４５，ｐｐ．２５５〜２６０（１９９５））に説明されている。ｖ・Ｉｓｂは磁化反転の最小単位に対応した量であり、このｖ・Ｉｓｂが小さいほど媒体ノイズが小さいことを示す。このｖ・Ｉｓｂは物理的量なので媒体ノイズを記録再生条件によらず客観的に比較できる。上記ｖ・Ｉｓｂが最小になるＰＯ_２・ｔは第１下地膜又は第２下地膜の合金組成やその組成比により変わるが、種々の実験によれば、ＰＯ_２・ｔは１×１０^−６（Ｔｏｒｒ・秒）以上、１×１０^−２（Ｔｏｒｒ・秒）以下で媒体ノイズを下げる効果があった。特に第１下地膜にＣｏが含まれている場合にはＰＯ_２・ｔが１×１０^−６（Ｔｏｒｒ・秒）以上、１×１０^−３（Ｔｏｒｒ・秒）以下で効果があった。
【００２５】
なお、磁気記録媒体は保護膜上に、さらに吸着性のパーフルオロアルキルポリエーテル等の潤滑膜を厚さ１ｎｍ〜１０ｎｍ設けることにより信頼性が高く、高密度記録が可能な磁気記録媒体となる。
また、上記加熱は、第１下地膜形成前に行っても同様の効果がある。或いは、酸化までを室温で行い、２７０℃に加熱してから第２下地膜を形成してもよい。この加熱は下地膜の結晶性を向上させ、磁性膜を高保磁力化したり、低ノイズ化させるための一般的な方法で、通常は２００℃〜３００℃程度に加熱している。
【００２６】
保護層として水素を添加したカーボン膜や、炭化シリコン又は炭化タングステン等の化合物から成る膜や、これらの化合物とカーボンの混合膜を用いると耐摺動性、耐食性を向上出来るので好ましい。また、これらの保護層を形成した後、微細マスク等を用いてプラズマエッチングすることで表面に微細な凹凸を形成したり、化合物、混合物のターゲットを用いて保護層表面に異相突起を生じせしめたり、或いは熱処理によって表面に凹凸を形成すと、ヘッドと媒体との接触面積を低減でき、ＣＳＳ動作時にヘッドが媒体表面に粘着する問題が回避されるので好ましい。
【００２７】
また、基板として、Ｎｉ−ＰをメッキしたＡｌ合金基板を用いた場合にも、ガラス基板を用いた場合と同様、磁性層の結晶粒が微細になるという効果が確認された。
さらにまた、基板としてＡｌ合金基板を用いた場合、上述のようにＮｉ−Ｐ等の第３下地膜を基板と第１下地膜の間に設けることが好ましい。基板としてガラス基板を用いた場合、通常用いられていえる種々の金属膜、合金膜、酸化物膜を基板と第１下地膜の間に設けることが好ましい。
【００２８】
図６は、本発明の一実施例の磁気ディスク装置の平面模式図及びそのＡＡ’線断面模式図である。磁気記録媒体６４を記録方向に駆動する駆動部６５と、磁気記録媒体６４の各面に対応して設けられ、記録部と再生部からなる磁気ヘッド６１と、磁気ヘッド６１を所望の位置に位置決めする磁気ヘッド駆動部６２と、磁気ヘッドへの信号入力と磁気ヘッドからの出力信号再生を行うための記録再生信号処理系６３とからなる。磁気ヘッドの再生部を磁気抵抗効果型磁気ヘッドで構成することにより、高記録密度における十分な信号強度を得ることができ、１平方インチ当たり１ギガビット以上の記録密度を持った信頼性の高い磁気ディスク装置を実現することができる。
【００２９】
また、本発明の磁気記録媒体を磁気ディスク装置で用いる場合、磁気抵抗効果型磁気ヘッドの磁気抵抗センサ部を挟む２枚のシールド層の間隔（シールド間隔）は０．３５μｍ以下が好ましい。これは、シールド間隔が０．３５μｍ以上になると分解能が低下し、信号の位相ジッターが大きくなってしまうためである。
【００３０】
さらに、磁気抵抗効果型磁気ヘッドを、互いの磁化方向が外部磁界によって相対的に変化することによって大きな抵抗変化を生じる複数の導電性磁性層と、その導電性磁性層の間に配置された導電性非磁性層を含む磁気抵抗センサによって構成し、巨大磁気抵抗効果、或いはスピン・バルブ効果を利用したものとすることにより、信号強度をさらに高めることができ、１平方インチ当たり２ギガビット以上の記録密度を持った信頼性の高い磁気記憶装置の実現が可能となる。
【００３１】
＜実施例１＞
図４は、本実施例の磁気記録媒体の模式的に示した断面斜視図である。基板４０には２．５インチ型の化学強化されたソーダライムガラスを使用した。その上に厚さ２５ｎｍの６０ａｔ％Ｃｏ−３０ａｔ％Ｃｒ−１０ａｔ％Ｚｒ合金からなる第１下地膜４１、４１’を、厚さ２０ｎｍの８５ａｔ％Ｃｒ−１５ａｔ％Ｔｉ合金からなる第２下地膜４２、４２’を、厚さ２０ｎｍの７５ａｔ％Ｃｏ−１９ａｔ％Ｃｒ−６ａｔ％Ｐｔ合金磁性膜４３、４３’を、さらに厚さ１０ｎｍのカーボン保護膜４４、４４’を形成した。膜形成装置として、インテバック（Ｉｎｔｅｖａｃ）社製の枚葉式スパッタリング装置ｍｄｐ２５０Ａを用い、タクト１０秒で成膜した。タクトとは上記スパッタリング装置で基板が前の室からある室に送られてきた直後から、その室で処理を行い次ぎの室に送られるまでの時間を意味する。このスパッタリング装置のチャンバ構成は図２に示した通りである。各膜の形成時のアルゴン（Ａｒ）ガス圧はすべて６ｍＴｏｒｒとした。成膜中のメインチャンバ２９の酸素分圧は約１×１０^−８（Ｔｏｒｒ）である。
【００３２】
第１下地膜は基板を加熱しない状態で第１下地膜形成室２２で形成し、加熱室２３でランプヒーターにより２７０℃まで加熱し、その後酸化室２４で９９％Ａｒ−１％Ｏ_２混合ガスの圧力５ｍＴｏｒｒ（ガス流量１０ｓｃｃｍ）の雰囲気に３秒間曝し、その後その上に上記各膜を第２下地膜形成室２５、磁性膜形成室２６、保護膜形成室２７ａ、２７ｂ、２７ｃ、２７ｄで順に形成した。このときの前記ＰＯ_２・ｔは５ｍＴｏｒｒ×０．０１×３秒＝１．５×１０^−４（Ｔｏｒｒ・秒）に相当する。カーボン保護膜まで形成した後、パーフルオロアルキルポリエーテル系の材料をフルオロカーボン材料で希釈したものを潤滑膜４５、４５’として塗布した。
【００３３】
＜比較例１＞
上記実施例１で、酸化室２４で上記混合ガスを導入しない以外は上記と同一条件で作製した磁気記録媒体を比較例１とした。
【００３４】
本実施例１の磁気記録媒体の保磁力は２１７０エルステッドで比較例１の磁気記録媒体よりも約３００エルステッド程度高く、残留磁束密度Ｂｒと磁性膜厚ｔの積Ｂｒ・ｔは８９ガウス・ミクロンであった。実施例１の磁気記録媒体ではｖ・Ｉｓｂは１．０５×１０^−１５（ｅｍｕ）と比較例１の磁気記録媒体の２．２４×１０^−１５（ｅｍｕ）に対し４７％に減少したため、媒体ノイズもこれに対応し約半分に低減できた。再生出力は評価した記録密度領域では実施例１、比較例１ともに同程度であり、媒体のＳ／Ｎは媒体ノイズの低減分を向上できた。
【００３５】
実際に磁気ディスク装置に組み込んで、線記録密度１６１ｋＢＰＩ（ｂｉｔ ｐｅｒ ｉｎｃｈ）、トラック密度９．３ｋＴＰＩ（ｔｒａｃｋ ｐｅｒ ｉｎｃｈ）の条件で磁気抵抗効果型磁気ヘッドにより記録再生特性を評価したところ、実施例１の磁気記録媒体は比較例のそれに対し、Ｓ／Ｎが１．８倍高く、面記録密度１平方インチ当たり１．６ギガビットの装置仕様を充分満たした。一方、比較例１の媒体ではＳ／Ｎが不足し、装置仕様を満足できなかった。
【００３６】
本実施例１と同一条件で、第１下地膜Ｃｏ−Ｃｒ−Ｚｒ合金をガラス基板上に厚さ２５ｎｍ形成し酸化室での処理まで行ったものを、ＴＥＭ（透過電子顕微鏡）を用いてＣｏ−Ｃｒ−Ｚｒ合金膜の構造を調べたところ、ＴＥＭ像には、第１下地膜表面の局所的な酸化に対応する微細なクラスタを反映した濃淡が観察された。このクラスタは径が数ｎｍで、数ｎｍピッチにおよそ均一に形成されている。このＴＥＭ像の模式図を図１に示す。
【００３７】
また、本実施例１の磁気記録媒体及び比較例１の磁気記録媒体のＸ線回折の測定を行った結果、図５に示す回折パターンが得られた。上記第１下地層のＣｏ−Ｃｒ−Ｚｒ合金のみの単層膜を上記同一成膜条件で上記ガラス基板上に５０ｎｍ形成し、Ｘ線回折の測定を行ったところ、明瞭な回折ピークはみられなかった。比較例１の磁気記録媒体の回折パターンでは第２下地膜の体心立方構造（ｂｃｃ構造）のＣｒＴｉ（１１０）ピークは磁性膜からの六方最密構造（ｈｃｐ構造）のＣｏＣｒＰｔ（００．２）ピークと重なるため、この両者の識別も不可能である。しかし、いずれにしても第２下地膜は実施例１の磁気記録媒体のように強く（１００）配向しておらず、配向が異なる複数の結晶粒の混合相となっている。このため、磁性膜中のＣｏ−Ｃｒ−Ｐｔ合金結晶も様々な結晶配向をとっており、Ｃｏ−Ｃｒ−Ｐｔ磁性膜からは複数の回折ピークがみられる。
【００３８】
一方、実施例１の磁気記録媒体は上記のように第１下地膜のＣｏ−Ｃｒ−Ｚｒ合金単層膜では回折ピークを示さないため、図中の回折ピークは、第２下地膜からのｂｃｃ構造のＣｒＴｉ（２００）ピークと、Ｃｏ−Ｃｒ−Ｐｔ磁性膜からのｈｃｐ構造のＣｏＣｒＰｔ（１１．０）ピークである。このことから、非晶質構造のＣｏ−Ｃｒ−Ｚｒ合金層上に形成された第２下地膜のＣｒ−Ｔｉ合金は（１００）配向をとり、その上のＣｏ−Ｃｒ−Ｐｔ磁性膜はエピタキシャル成長により（１１．０）配向をとっていることが分かる。このため、Ｃｏ−Ｃｒ−Ｐｔ合金の磁化容易軸であるｃ軸の面内方向の成分が大きくなり、良好な磁気特性が得られる。
【００３９】
さらに、磁性膜のＴＥＭ観察を行ったところ、本実施例１のＣｏ−Ｃｒ−Ｐｔ合金の平均結晶粒経は１０．８ｎｍであり、比較例１のそれの１６．２ｎｍに比べて微細化されていた。また、前記単層のＣｏ−Ｃｒ−Ｚｒ合金単層膜の磁化測定を行ったところ、明瞭なヒステリシス曲線が得られなかったため、この合金膜は非磁性であると考えられる。
【００４０】
＜実施例２＞
上記実施例１と同様の膜構成で磁気記録媒体を作製した。基板には２．５インチ型の化学強化されたアルミノシリケートガラスを使用した。その上に厚さ４０ｎｍの６２ａｔ％Ｃｏ−３０ａｔ％Ｃｒ−８ａｔ％Ｔａ合金からなる第１下地膜を、厚さ２５ｎｍの８０ａｔ％Ｃｒ−２０ａｔ％Ｔｉ合金からなる第２下地膜を、厚さ２３ｎｍの７２ａｔ％Ｃｏ−１８ａｔ％Ｃｒ−２ａｔ％Ｔａ−８ａｔ％Ｐｔ合金磁性膜を、さらに厚さ１０ｎｍのカーボン保護膜を形成した。膜形成装置として実施例１と同じ枚葉式スパッタ装置を用い、タクト９秒で成膜した。各膜の形成時のアルゴン（Ａｒ）ガス圧はすべて６ｍＴｏｒｒとした。成膜中のメインチャンバの酸素分圧は約５×１０^−９（Ｔｏｒｒ）である。
【００４１】
第１下地膜は基板を加熱しない状態で第１下地膜成膜室で形成し、加熱室でランプヒーターにより２５０℃まで加熱し、その後酸化室で９８ｍｏｌ％Ａｒ−２ｍｏｌ％Ｏ_２混合ガスを用いガス圧力４ｍＴｏｒｒ（ガス流量８ｓｃｃｍ）の雰囲気に３秒間曝し、その上に各膜を形成した。これは上記ＰＯ_２・ｔで４ｍＴｏｒｒ×０．０２×３秒＝２．４×１０^−４（Ｔｏｒｒ・秒）に相当する。上記カーボン保護膜まで形成した後、実施例１と同様の潤滑膜を塗布した。
【００４２】
＜比較例２＞
上記実施例２で、酸化室で上記混合ガスを導入しない以外は上記と同一条件で作製した磁気記録媒体を比較例２とした。
【００４３】
本実施例２の磁気記録媒体の保磁力は２６４０エルステッドで比較例２の磁気記録媒体よりも約２００エルステッド程度高く、残留磁束密度と磁性膜厚の積Ｂｒ・ｔは８５ガウス・ミクロンであった。実施例２の磁気記録媒体ではｖ・Ｉｓｂは０．９８×１０^−１５（ｅｍｕ）と比較例２のそれの１．８１×１０^−１５（ｅｍｕ）に対し５４％に減少したため、媒体ノイズもこれに対応し約半分に低減できた。再生出力は評価した記録密度領域では実施例２、比較例２ともに同程度であり、磁気記録媒体のＳ／Ｎは媒体ノイズの低減分を向上できた。磁気ディスク装置に組み込んで、線記録密度２１０ｋＢＰＩ、トラック密度９．６ｋＴＰＩの条件で磁気抵抗効果型磁気ヘッドにより記録再生特性を評価したところ、実施例２の磁気記録媒体は比較例２のそれに比べＳ／Ｎが１．３倍高く、面記録密度１平方インチ当たり２．０ギガビットの装置仕様を充分満たした。一方、比較例２の磁気記録媒体ではＳ／Ｎが不足し、装置仕様を満足できなかった。
【００４４】
＜実施例３＞
上記実施例１と同様の膜構成で磁気記録媒体を作製した。基板には２．５インチ型の化学強化されたアルミノシリケートガラスを使用した。その上に厚さ３０ｎｍの８５ａｔ％Ｃｒ−１５ａｔ％Ｚｒ合金からなる第１下地膜を、厚さ２５ｎｍの８０ａｔ％Ｃｒ−１５ａｔ％Ｔｉ−５ａｔ％Ｂ合金からなる第２下地膜を、厚さ２２ｎｍの７２ａｔ％Ｃｏ−１９ａｔ％Ｃｒ−１ａｔ％Ｔｉ−８ａｔ％Ｐｔ合金磁性膜を、さらに厚さ１０ｎｍのカーボン保護膜を形成した。膜形成装置として実施例１と同じ枚葉式スパッタ装置を用い、タクト８秒で成膜した。各膜の形成時のアルゴン（Ａｒ）ガス圧はすべて５ｍＴｏｒｒとした。成膜中のメインチャンバの酸素分圧は約３×１０^−９（Ｔｏｒｒ）である。
【００４５】
第１下地膜は基板を特に加熱しないで第１下地膜成膜室で形成し、加熱室でランプヒーターにより２４０℃まで加熱し、その後酸化室で７９ｍｏｌ％Ａｒ−２１ｍｏｌ％Ｏ_２混合ガスを用いガス圧力３ｍＴｏｒｒ（ガス流量６ｓｃｃｍ）の雰囲気に２秒間曝し、その上の各膜を形成した。これは上記ＰＯ_２・ｔで３ｍＴｏｒｒ×０．２１×２秒＝１．３×１０^−４（Ｔｏｒｒ・秒）に相当する。上記カーボン保護膜まで形成した後、実施例１と同様の潤滑膜を塗布した。
【００４６】
＜比較例３＞
上記実施例３で、酸化室で上記混合ガスを導入しない以外は上記と同一条件で作製した磁気記録媒体を比較例３とした。
【００４７】
本実施例３の磁気記録媒体の保磁力は２６８０エルステッドで比較例３の磁気記録媒体よりも約２００エルステッド程度高く、残留磁束密度と磁性膜厚の積Ｂｒ・ｔは６９ガウス・ミクロンであった。実施例３の磁気記録媒体ではｖ・Ｉｓｂは０．８９×１０^−１５（ｅｍｕ）と比較例３のそれの１．４４×１０^−１５（ｅｍｕ）に対し６０％に減少したため、媒体ノイズもこれに対応し約４０％低減できた。再生出力は評価した記録密度領域では実施例３、比較例３ともに同程度であり、磁気記録媒体のＳ／Ｎは媒体ノイズの低減分を向上できた。磁気ディスク装置に組み込んで、線記録密度２２５ｋＢＰＩ、トラック密度９．８ｋＴＰＩの条件で磁気抵抗効果型磁気ヘッドにより記録再生特性を評価したところ、実施例３の磁気記録媒体は比較例３のそれに比べＳ／Ｎが１．４倍高く、面記録密度１平方インチ当たり２．２ギガビットの装置仕様を充分満たした。一方、比較例３の媒体ではＳ／Ｎが不足し、装置仕様を満足できなかった。
【００４８】
＜実施例４＞
実施例１と同様の膜構成で磁気記録媒体を作製した。外径９５ｍｍ、内径２５ｍｍ、厚さ０．８ｍｍの９６ｗｔ％Ａｌ−４ｗｔ％Ｍｇの基板の両面に８８ｗｔ％Ｎｉ−１２ｗｔ％Ｐからなるメッキ層を厚さが１３μｍとなるよう形成した。この基板の表面をラッピングマシンを用いて表面中心線平均粗さＲａが２ｎｍとなるまで平滑に研磨し、洗浄、さらに乾燥した。その後、テープポリッシングマシン（例えば、特開昭６２−２６２２２７号公報に記載）を用い、砥粒の存在下で研磨テープをコンタクトロールを通して、基板を回転させながらディスク面の両側に押しつけることにより、基板表面に略円周方向のテクスチャを形成した。さらに、基板に付着した研磨剤等の汚れを洗浄、除去して乾燥した。
【００４９】
このように処理した基板の上に、厚さ２０ｎｍの６０ａｔ％Ｃｏ−３０ａｔ％Ｃｒ−１０ａｔ％Ｔａ合金からなる第１下地膜を、厚さ２０ｎｍの８５ａｔ％Ｃｒ−２０ａｔ％Ｔｉ合金からなる第２下地膜を、厚さ２０ｎｍの７２ａｔ％Ｃｏ−２０ａｔ％Ｃｒ−８ａｔ％Ｐｔ合金磁性膜を、さらに厚さ１０ｎｍのカーボン保護膜を形成した。実施例１で用いた膜形成装置によりタクト９秒で成膜した。各膜の形成時のアルゴン（Ａｒ）ガス圧はすべて５ｍＴｏｒｒとした。成膜中のメインチャンバの酸素分圧は約１×１０^−９（Ｔｏｒｒ）であった。
【００５０】
第１下地膜は基板を加熱しない状態で第１下地膜形成室で形成し、加熱室でランプヒーターにより２７０℃まで加熱し、その後酸化室で９８％Ａｒ−２％Ｏ_２混合ガスの圧力４ｍＴｏｒｒ（ガス流量８ｓｃｃｍ）の雰囲気に３秒間曝し、その上の各膜を形成した。これは上記ＰＯ_２・ｔで４ｍＴｏｒｒ×０．０２×３秒＝２．４×１０^−４乗（Ｔｏｒｒ・秒）に相当する。上記カーボン保護膜まで形成した後、パーフルオロアルキルポリエーテル系の材料をフルオロカーボン材料で希釈したものを潤滑膜として塗布した。
【００５１】
また、本発明の実施例に用いた膜形成装置に比べ、到達真空度が悪く酸素分圧が大きい膜形成装置、あるいは複数の基板に同時に膜形成できる装置のように第１下地膜形成後から第２下地膜を形成するまでの時間が長い膜形成装置では、上記実施例のように酸化室を特に設けなくても、上記の酸化による微細な成長核が形成でき、上記実施例と同様の効果が得られる。
【００５２】
＜実施例５＞
実施例１と同様の膜構成で磁気記録媒体を作製した。基板には２．５インチ型の化学強化されたアルミノシリケートガラスを使用した。その上に、厚さ２５ｎｍの６０ａｔ％Ｃｏ−３０ａｔ％Ｃｒ−１０ａｔ％Ｚｒ合金からなる第１下地膜を、厚さ２０ｎｍの８５ａｔ％Ｃｒ−１５ａｔ％Ｔｉ合金からなる第２下地膜を、厚さ２０ｎｍの７５ａｔ％Ｃｏ−１９ａｔ％Ｃｒ−６ａｔ％Ｐｔ合金磁性膜を、さらに厚さ１０ｎｍのカーボン保護膜を形成した。膜形成装置として、パレットに保持した複数枚の基板に同時に各膜形成を行う装置を用い、タクト６０秒で成膜した。各膜の形成時のアルゴン（Ａｒ）ガス圧はすべて６ｍＴｏｒｒとした。成膜中の各成膜室の酸素分圧は約１×１０^−８（Ｔｏｒｒ）であった。
【００５３】
第１下地膜は基板を加熱しない状態で形成し、次に加熱室でランプヒーターにより２７０℃まで加熱し、その後、その上の各膜を形成した。これは上記ＰＯ_２・ｔで約２×１０^−６（Ｔｏｒｒ・秒）に相当する。上記カーボン保護膜まで形成した後、パーフルオロアルキルポリエーテル系の材料をフルオロカーボン材料で希釈したものを潤滑膜として塗布した。
【００５４】
以上の実施例及び比較例について、それぞれの上記評価結果をまとめて表２に示す。
【００５５】
【表２】

【００５６】
本発明の非晶質、またはそれに近い微結晶構造のＣｏ合金を用いた第１下地膜であるＣｏ合金膜上に上記の酸化雰囲気に曝した後、第２下地膜なしに直接、磁性膜を形成した場合、磁性膜は強い（００．１）配向を示した。これは磁性層のＣｏ合金結晶のｃ軸が膜面に対して垂直方向を向いた配向であり、面内磁気記録媒体としては使用できないが、膜面に対し磁化を垂直方向に記録する垂直磁気記録媒体に適している。
【００５７】
【発明の効果】
本発明の磁気記録媒体は、媒体ノイズの低減、保磁力増大等の効果があった。本発明の磁気記録媒体の製造方法によれば、上記のような磁気記録媒体を容易に製造することができる。また、本発明の磁気記録媒体を用いた磁気記憶装置は、高い記録密度を有する。
【図面の簡単な説明】
【図１】本発明の磁気記録媒体の第１下地膜上に形成されたクラスタのＴＥＭ写真の模式図。
【図２】本発明の磁気記録媒体の膜形成装置の一例を示す模式図。
【図３】本発明の磁気記録媒体の多層下地膜形成時の条件に対する活性化堆積と磁気モーメントの積の関係図。
【図４】本発明の磁気記録媒体の模式的断面斜視図。
【図５】本発明の磁気記録媒体の一実施例及び比較例の磁気記録媒体のＸ線回折パターン図。
【図６】本発明の磁気記憶装置の一実施例の平面模式図及び断面模式図。
【符号の説明】
２０…基板、２１…仕込み室、２２…第１下地膜形成室、２３…加熱室、２４…酸化室、２５…第２下地膜形成室、２６…磁性膜形成室、２７ａ、２７ｂ、２７ｃ、２７ｄ…保護膜形成室、２８…取り出し室、２９…メインチャンバ、４０…基板、４１、４１’…第１下地膜、４２、４２’…第２下地膜、４３、４３’…磁性膜、４４、４４’…保護膜、４５、４５’…潤滑膜、６１…磁気ヘッド、６２…磁気ヘッド駆動部、６３…記録再生信号処理系、６４…磁気記録媒体、６５…駆動部。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic storage device used for an auxiliary storage device of a computer, a magnetic recording medium used for the magnetic storage device, and a method of manufacturing the same.
[0002]
[Prior art]
With the progress of the information society, the amount of information that is handled on a daily basis is steadily increasing. Along with this, there has been a strong demand for magnetic storage devices to have high recording density and large storage capacity. Conventional magnetic heads use an electromagnetic induction type magnetic head that utilizes a voltage change accompanying a temporal change in magnetic flux. This performs both recording and reproduction with one head. On the other hand, in recent years, a composite head using a magnetoresistive head, which has a high sensitivity as a reproducing head, separately from a recording head and a reproducing head, has been rapidly adopted. The magnetoresistive head utilizes the fact that the electric resistance of the head element changes with the change of the magnetic flux leakage from the magnetic recording medium. Further, the development of a more sensitive head utilizing an extremely large magnetoresistance change (giant magnetoresistance effect or spin valve effect) generated in a magnetic layer of a type in which a plurality of magnetic layers are stacked via a nonmagnetic layer is also progressing. is there. This utilizes the fact that the relative directions of the magnetizations of the plurality of magnetic layers via the non-magnetic layer change due to the leakage magnetic field from the medium, thereby changing the electrical resistance.
[0003]
At present, in magnetic recording media put into practical use, alloys containing Co as a main component, such as Co-Cr-Pt, Co-Cr-Ta, and Co-Ni-Cr, are used as magnetic films. Since these Co alloys have a hexagonal structure (hcp structure) having an easy axis of magnetization in the c-axis direction, the c-axis of this Co alloy is used as an in-plane magnetic recording medium for recording by reversing the magnetization in the magnetic film plane. Is desirably a crystal orientation that takes an in-plane direction, that is, a (11.0) orientation. However, since this (11.0) orientation is unstable, such an orientation generally does not occur even if a Co alloy is formed directly on a substrate.
[0004]
Therefore, by utilizing the fact that the Cr (100) plane having a body-centered cubic structure (bcc structure) has good consistency with the Co (11.0) plane, a (100) oriented Cr underlayer is first formed on the substrate. A method is employed in which a Co alloy magnetic film is epitaxially grown thereon so that the Co alloy magnetic film has a (11.0) orientation in which the c-axis is in the in-plane direction. In order to further improve the crystal lattice matching at the interface between the Co alloy magnetic film and the Cr underlayer, a method of adding a second element to Cr to increase the lattice spacing of the Cr underlayer has been used. Thereby, the Co (11.0) orientation is further increased, and the coercive force can be increased. As such an example, there is an example of adding V, Ti, and the like.
[0005]
In addition, as an element necessary for high recording density, low noise can be cited as well as high coercive force of the magnetic recording medium. The magnetoresistive head as described above has a very high reproduction sensitivity and is suitable for high-density recording. However, the sensitivity to noise as well as the reproduction signal from the magnetic recording medium is also increased. For this reason, magnetic recording media are required to have lower noise than ever. In order to reduce the medium noise, it is known that it is effective to make the crystal grains in the magnetic film fine and to make the crystal grain size uniform.
[0006]
An important requirement for a magnetic disk medium is improvement in impact resistance. In particular, in recent years, magnetic disk drives have been mounted on portable information devices such as notebook personal computers, and from the viewpoint of improving reliability, this impact resistance improvement has become a very important issue. The impact resistance of the magnetic disk medium can be improved by using a glass substrate or a crystallized glass substrate whose surface has been strengthened instead of the conventional Al alloy substrate having Ni-P plating on the surface. . Since the glass substrate has a smoother surface than a conventional Ni-P plated Al alloy substrate, it is advantageous in reducing the floating spacing between the magnetic head and the magnetic recording medium, and is suitable for high recording density. However, when a glass substrate is used, problems such as poor adhesion to the substrate and impurity ions from the substrate or adsorbed gas on the substrate surface penetrate into the Cr alloy base film. For these, various measures have been taken, such as forming various metal films, alloy films, and oxide films between the glass substrate and the Cr alloy base film.
In addition, as techniques related to these, JP-A-62-293511, JP-A-2-29923, JP-A-5-135343, and the like can be mentioned.
[0007]
[Problems to be solved by the invention]
It is known that miniaturization and uniformization of crystal grains in a magnetic film are effective in reducing medium noise as described above. However, a trial production of a magnetic disk drive using a magnetic recording medium having a recording density of about 900 megabits per square inch and a high-sensitivity magnetoresistive head using the above-mentioned conventional technology shows that about 1 gigabit per square inch. Or, sufficient electromagnetic conversion characteristics to obtain a higher recording density could not be obtained. In particular, when a glass substrate was used as the substrate of the magnetic recording medium, a result was obtained in which the electromagnetic conversion characteristics in a high linear recording density region were poor. When the cause was investigated, the Cr alloy base film formed directly on the glass substrate or via the various metals or their alloys found in the above-mentioned known examples was formed on the Ni-P plated Al alloy substrate. Was not as strongly (100) oriented as in the case of For this reason, the crystal plane other than (11.0) of the Co alloy magnetic film grew parallel to the substrate, and the degree of in-plane orientation of the c-axis, which is the axis of easy magnetization, was small. As a result, the coercive force was reduced, and the reproduction output at a high linear recording density was reduced. Also, when a glass substrate was used, the crystal grains of the magnetic film were enlarged as compared with the case where an Al alloy substrate was used, and the particle size distribution of the crystal grains was also increased by about 20% to 30%. . For this reason, the medium noise increased and the electromagnetic conversion characteristics deteriorated. Further, even if an amorphous or microcrystalline film disclosed in JP-A-4-153910 is formed between a glass substrate and a base film, the crystal grain size of the magnetic film may be reduced to some extent, but it is not sufficient. Did not. Furthermore, there was almost no effect on the reduction of the particle size distribution, and good electromagnetic conversion characteristics could not be obtained.
[0008]
A first object of the present invention is to provide a magnetic recording medium with low noise by improving the orientation of a magnetic film, making crystal grains of the magnetic film finer and more uniform.
A second object of the present invention is to provide a method for manufacturing such a magnetic recording medium.
A third object of the present invention is to provide a magnetic storage device having a high recording density.
[0009]
[Means for Solving the Problems]
In order to achieve the first object, in the magnetic recording medium of the present invention, a first underlayer is disposed on a substrate directly or via a third underlayer, and a second underlayer is formed on the first underlayer. Are disposed directly, and a magnetic film is disposed on the second underlayer, and clusters having a large amount of oxygen are dispersed at the interface between the first underlayer and the second underlayer.
[0010]
In order to achieve the second object, a method of manufacturing a magnetic recording medium according to the present invention comprises forming a first underlayer directly or via a third underlayer on a substrate, and forming the first underlayer on the substrate. In an atmosphere having oxygen, PO ₂ · t (where PO ₂ is an oxygen partial pressure of the atmosphere and t is a time of exposure to this atmosphere) is 1 × 10 ⁻⁶ (Torr · sec) or more and 1 × 10 ⁻² (Torr · sec). (Torr.sec) or less, a second underlayer is formed directly on the first underlayer exposed to this atmosphere, and a magnetic film is formed on the second underlayer.
[0011]
In order to achieve the third object, a magnetic storage device according to the present invention includes a magnetic head, which is provided corresponding to each surface of the magnetic recording medium and includes a recording unit and a reproducing unit. A drive unit for changing a relative position between the magnetic recording medium and the magnetic head; a magnetic head drive unit for positioning the magnetic head at a desired position; a signal input to the magnetic head and an output signal from the magnetic head It is configured to include a recording / reproducing signal processing system for performing reproduction.
[0012]
The first underlayer is preferably an alloy composed of two or more elements. When an element having a different oxidizability is included in this alloy, when the first underlayer is exposed to an atmosphere of a certain oxygen partial pressure for a certain time, a uniform oxide film whose surface is continuous in the plane is formed. Instead, a region rich in the easily oxidizable element locally forms a cluster having a large amount of oxygen, and this cluster serves as a growth nucleus of the second underlayer, and the crystal grains of the second underlayer growing thereon are refined and uniform. It is presumed that the average grain size of the magnetic film can be reduced and the grain size can be made uniform.
[0013]
FIG. 1 shows a schematic diagram of a cluster formed on the surface of the first underlayer. This is done by forming a single-layer film of only a 68 at% Co-24 at% Cr-8 at% W alloy film as a first underlayer on a glass substrate, and further forming a cluster on the surface thereof by a transmission electron microscope (TEM). It is a schematic diagram of what investigated the structure using. Here, the clusters are assumed to be fine particles as shown in FIG. 1 and are uniformly dispersed at intervals of several nm. The standard free energy of oxide formation is used as an index for the degree of oxidization of the element, and the difference in the standard free energy of oxide formation ΔG ° at a temperature of 250 ° C. is 150 (kJ) in the alloy forming the first underlayer. / Mol O ₂ ) or more (however, when the oxide is an element having two or more kinds of oxides (for example, Fe is an oxide such as Fe ₂ O ₃ or Fe ₃ O ₄ )), the above ΔG ° is selected to be the lowest value. )), More preferably 180 (kJ / mol O ₂ ) or more, more preferably 200 (kJ / mol O ₂ ) or more. Most preferably, two or more elements are contained. Although there is no particular upper limit for this difference, it is up to about 1000 for a general combination of elements.
[0014]
Further, since the alloy contains an element having a standard oxide formation free energy ΔG ° of −750 (kJ / mol O ₂ ) or less, an effect can be obtained by supplying a small amount of oxygen. Here, Table 1 shows various elements, their corresponding oxides, and their standard free energy of formation ΔG ° at a temperature of 250 ° C. This ΔG ° is a value read from a graph showing the relationship between ΔG ° and temperature shown by Coughlin. This is shown on pages 291 to 292, published by the Japan Institute of Metals, non-ferrous metal refining (new metal refining edition) (1964).
[0015]
[Table 1]

[0016]
As the alloy for the first underlayer, an alloy containing at least one element selected from the group consisting of Mo, Ti, Zr, and Al and Cr is preferable from the viewpoint of the adhesion between the substrate and the film. Further, when the alloy for the first underlayer is an alloy containing at least one element selected from the group consisting of Cr, Si, V, Ta, Ti, Zr, Al, and W and Co, the alloy is non-metallic. When a glass substrate is used, it is effective because it becomes a diffusion barrier for impurities such as alkali elements penetrating into the film from the glass, because the structure is likely to become crystalline or microcrystalline and the structure becomes dense. Here, the term “amorphous” means that a clear peak due to X-ray diffraction is not observed, or a clear diffraction spot or diffraction ring due to electron beam diffraction is not observed and a halo-shaped diffraction ring is observed. . Further, the term “microcrystal” means that the crystal grain has a crystal grain size smaller than that of the magnetic layer, and preferably has an average grain size of 8 nm or less. Further, among the alloys for the first underlayer, the content of the element having the lowest oxide standard free energy ΔG ° is about 5 at% to 50 at% because it is related to the number of the growth nuclei. Is effective in reducing the crystal grain size of the second underlayer, and is preferably about 5 at% to 30 at%.
[0017]
Further, a third base film may be provided between the first base film and the substrate. For example, when the substrate is a glass substrate, various metal films, alloy films, oxide films, and the like described in the conventional example can be used as the third base film.
[0018]
As the second base film, a film having a bcc structure such as a Cr alloy having high crystal lattice matching with the Co alloy magnetic film is preferable. For example, Cr, a Cr alloy, that is, CrTi, CrV, CrMo, or the like can be used.
[0019]
The thickness of the first underlayer is preferably in the range of 20 to 50 nm, and the thickness of the first underlayer is preferably in the range of 10 to 50 nm.
[0020]
Further, the magnetic film is preferably a magnetic film whose magnetic anisotropy is in the plane. As such a magnetic film, for example, Co such as Co-Cr-Pt, Co-Cr-Pt-Ta, Co-Cr-Pt-Ti, Co-Cr-Ta, or Co-Ni-Cr is used as a main component. Although an alloy can be used, it is preferable to use a Co alloy containing Pt in order to obtain a high coercive force. Further, the magnetic film may be composed of a plurality of layers via a non-magnetic intermediate layer.
[0021]
As the magnetic characteristics of the magnetic film, the coercive force measured by applying a magnetic field to the film surface is set to 1.8 kOe or more, and the residual magnetic flux density Br and the film thickness t measured by applying the magnetic field to the film surface are measured. The product Br · t is preferably not less than 20 gauss microns and not more than 140 gauss microns, because good recording and reproduction characteristics can be obtained in a recording density region of 1 gigabit per square inch or more. If the coercive force is less than 1.8 kOe, the output at a high recording density (200 kFCI or more) becomes undesirably small. Here, FCI (flux reversal per inch) is a unit of recording density. On the other hand, when Br · t is larger than 140 Gauss / micron, the reproduction output at a high recording density is reduced, and when it is less than 20 Gauss / micron, the reproduction output at a low recording density is undesirably small.
When the magnetic film is composed of a plurality of layers via a non-magnetic intermediate layer, the thickness t of the magnetic film in the calculation of Br · t represents the total thickness of each magnetic layer.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 2 is a schematic explanatory view of an example of a single-wafer deposition type sputtering apparatus for producing a magnetic recording medium. In an actual sputtering apparatus, there is a main chamber 29 in the center, around which a charging chamber 21, a first base film forming chamber 22, a heating chamber 23, an oxidizing chamber 24, a second base film forming chamber 25, and a magnetic film forming chamber 26. , Protective film forming chambers 27a, 27b, 27c, 27d, and a take-out chamber 28 are arranged in a circle. The operation of processing a substrate in one chamber and then sending the substrate to the next chamber is performed simultaneously in each chamber. That is, a plurality of substrates can be simultaneously processed by this sputtering apparatus, and the substrates may be sequentially sent to each chamber one after another. The four protective film forming chambers 27a, 27b, 27c, and 27d are provided so that the protective film is preferably formed at a low speed, so that one chamber has a quarter of a desired thickness. .
[0023]
With this sputtering apparatus, the substrate 20 of tempered glass is first placed in the preparation chamber 21 to be evacuated, and then moved to each chamber one after another via the main chamber 29 to be processed as follows. A 60 at% Co-30 at% Cr-10 at% Zr alloy is formed at room temperature as a first underlayer, heated to 270 ° C., and then exposed to an atmosphere of a mixed gas of argon and oxygen in the oxidation chamber 24. At this time, the mixing ratio of the mixed gas and the time of exposure to the atmosphere of the mixed gas are variously changed. A 75 at% Cr-15 at% Ti alloy was sequentially laminated as a second underlayer, and a 75 at% Co-19 at% Cr-6 at% Pt alloy was sequentially laminated as a magnetic film. During this time, the temperature is maintained at 270 ° C. or slightly lower. Further, carbon is formed to a thickness of 10 nm to 30 nm as a protective film.
[0024]
As a result of changing the mixing ratio of the mixed gas and the time of exposing the mixed gas to the atmosphere, the product (v · Isb) of the activation volume v and the magnetic moment Isb that shows a linear correlation with the medium noise is represented by the oxygen of the atmosphere. It was found that the product (PO ₂ · t) of the partial pressure PO ₂ and the exposure time t takes a minimum value as shown in FIG. Here, regarding v · Isb, Journal of Magnetics and Magnetic Materials, Vol. 145 (1995), pp. 255-260 (J. Magn. Magn. Mater., Vol. 145, pp. 255) To 260 (1995)). v · Isb is an amount corresponding to the minimum unit of magnetization reversal, and a smaller v · Isb indicates that the medium noise is smaller. Since v · Isb is a physical quantity, the medium noise can be objectively compared regardless of the recording / reproducing conditions. PO ₂ · t at which v · Isb is minimized varies depending on the alloy composition of the first underlayer or the second underlayer and the composition ratio thereof. According to various experiments, PO ₂ · t is 1 × 10 ^−6. (Torr · sec) or more and 1 × 10 ⁻² (Torr · sec) or less provided an effect of reducing medium noise. Especially if it contains Co in the first base film ^{_{PO 2 · t 1 × 10 -6}} (Torr · sec) or more, was effective at less than 1 × ¹⁰ -3 (Torr · sec).
[0025]
The magnetic recording medium is a highly reliable magnetic recording medium capable of performing high-density recording by providing a lubricating film such as perfluoroalkylpolyether having a thickness of 1 nm to 10 nm on the protective film.
The same effect can be obtained even if the heating is performed before the formation of the first underlayer. Alternatively, the second base film may be formed after performing the steps up to oxidation at room temperature and heating to 270 ° C. This heating is a general method for improving the crystallinity of the underlying film, increasing the coercive force of the magnetic film, and reducing the noise, and is usually heated to about 200 ° C. to 300 ° C.
[0026]
It is preferable to use a carbon film to which hydrogen is added, a film made of a compound such as silicon carbide or tungsten carbide, or a mixed film of these compounds and carbon as the protective layer because sliding resistance and corrosion resistance can be improved. In addition, after forming these protective layers, plasma etching is performed using a fine mask or the like to form fine irregularities on the surface, or a heterogeneous projection is generated on the protective layer surface using a compound or mixture target. Alternatively, it is preferable to form irregularities on the surface by heat treatment, since the contact area between the head and the medium can be reduced, and the problem of the head sticking to the medium surface during CSS operation is preferable.
[0027]
Also, when an Al alloy substrate plated with Ni-P was used as the substrate, the effect of making the crystal grains of the magnetic layer finer was confirmed as in the case of using a glass substrate.
Furthermore, when an Al alloy substrate is used as the substrate, it is preferable to provide the third underlayer such as Ni-P between the substrate and the first underlayer as described above. In the case where a glass substrate is used as the substrate, it is preferable to provide various metal films, alloy films, and oxide films that can be generally used between the substrate and the first base film.
[0028]
FIG. 6 is a schematic plan view of a magnetic disk drive according to an embodiment of the present invention, and a schematic cross-sectional view taken along line AA 'of FIG. A driving unit 65 for driving the magnetic recording medium 64 in the recording direction, a magnetic head 61 provided corresponding to each surface of the magnetic recording medium 64 and comprising a recording unit and a reproducing unit, and positioning the magnetic head 61 at a desired position And a recording / reproducing signal processing system 63 for inputting a signal to the magnetic head and reproducing an output signal from the magnetic head. By constructing the reproducing portion of the magnetic head with a magnetoresistive effect type magnetic head, it is possible to obtain a sufficient signal intensity at a high recording density, and to obtain a highly reliable magnetic recording having a recording density of 1 gigabit per square inch or more. A disk device can be realized.
[0029]
When the magnetic recording medium of the present invention is used in a magnetic disk drive, the distance (shield distance) between two shield layers sandwiching the magnetoresistive sensor portion of the magnetoresistive head is preferably 0.35 μm or less. This is because when the shield interval is 0.35 μm or more, the resolution is reduced and the phase jitter of the signal is increased.
[0030]
Further, the magneto-resistance effect type magnetic head is composed of a plurality of conductive magnetic layers that generate a large resistance change when their magnetization directions are relatively changed by an external magnetic field, and a conductive layer disposed between the conductive magnetic layers. By using a giant magnetoresistive effect or a spin valve effect to form a magnetoresistive sensor including a conductive nonmagnetic layer, the signal strength can be further increased, and recording of 2 gigabits or more per square inch can be achieved. A highly reliable magnetic storage device having a high density can be realized.
[0031]
<Example 1>
FIG. 4 is a cross-sectional perspective view schematically illustrating the magnetic recording medium of the present embodiment. For the substrate 40, 2.5-inch chemically strengthened soda lime glass was used. A first underlayer film 41, 41 'made of a 60 at% Co-30 at% Cr-10 at% Zr alloy having a thickness of 25 nm is formed thereon, and a second underlayer film 42 made of an 85 at% Cr-15 at% Ti alloy having a thickness of 20 nm is formed. , 42 ′, 75 at% Co-19 at% Cr-6 at% Pt alloy magnetic films 43 and 43 ′ with a thickness of 20 nm, and carbon protective films 44 and 44 ′ with a thickness of 10 nm. As a film forming apparatus, a single-wafer sputtering apparatus mdp250A manufactured by Intevac was used, and a film was formed in a tact time of 10 seconds. Tact means the time from immediately after a substrate is sent from a previous chamber to a certain chamber by the above sputtering apparatus, until processing is performed in that chamber and then sent to the next chamber. The chamber configuration of this sputtering apparatus is as shown in FIG. The argon (Ar) gas pressure during the formation of each film was 6 mTorr. The oxygen partial pressure of the main chamber 29 during the film formation is about 1 × 10 ⁻⁸ (Torr).
[0032]
The first base film is formed in the first base film formation chamber 22 without heating the substrate, heated to 270 ° C. by a lamp heater in the heating chamber 23, and then mixed with 99% Ar-1% O ₂ gas in the oxidation chamber 24. At a pressure of 5 mTorr (gas flow rate: 10 sccm) for 3 seconds, and thereafter, the above films are sequentially placed in the second base film forming chamber 25, the magnetic film forming chamber 26, and the protective film forming chambers 27a, 27b, 27c, 27d. Formed. The PO ₂ · t at this time corresponds to 5 mTorr × 0.01 × 3 seconds = 1.5 × 10 ⁻⁴ (Torr · second). After the carbon protective film was formed, a material obtained by diluting a perfluoroalkyl polyether-based material with a fluorocarbon material was applied as lubricating films 45 and 45 '.
[0033]
<Comparative Example 1>
Comparative Example 1 was a magnetic recording medium manufactured under the same conditions as in Example 1 except that the mixed gas was not introduced into the oxidation chamber 24.
[0034]
The coercive force of the magnetic recording medium of the first embodiment is 2170 Oe, which is about 300 Oe higher than that of the magnetic recording medium of the first comparative example, and the product Br · t of the residual magnetic flux density Br and the magnetic film thickness t is 89 Gauss / micron. there were. In the magnetic recording medium of Example 1, v · Isb was 1.05 × 10 ⁻¹⁵ (emu), which is 47% of 2.24 × 10 ⁻¹⁵ (emu) of the magnetic recording medium of Comparative Example 1. The noise was reduced to about half in response to this. The reproduction output was almost the same in both the example 1 and the comparative example 1 in the evaluated recording density region, and the S / N of the medium was able to improve the reduction of the medium noise.
[0035]
When the recording / reproduction characteristics were evaluated by using a magnetoresistive magnetic head under the conditions of a linear recording density of 161 kBPI (bit per inch) and a track density of 9.3 kTPI (track per inch), the recording / reproducing characteristics were evaluated. The S / N ratio of the magnetic recording medium is 1.8 times higher than that of the comparative example, and the magnetic recording medium sufficiently satisfies the device specification of 1.6 gigabits per square inch of areal recording density. On the other hand, the medium of Comparative Example 1 was insufficient in S / N and could not satisfy the device specifications.
[0036]
Under the same conditions as in Example 1, a first underlayer film of Co—Cr—Zr alloy formed on a glass substrate to a thickness of 25 nm and processed in an oxidation chamber was subjected to Co treatment using a TEM (transmission electron microscope). Examination of the structure of the -Cr-Zr alloy film revealed that the TEM image showed shading reflecting fine clusters corresponding to local oxidation of the surface of the first underlayer. These clusters have a diameter of several nm and are formed almost uniformly at a pitch of several nm. FIG. 1 shows a schematic diagram of this TEM image.
[0037]
Further, as a result of measuring the X-ray diffraction of the magnetic recording medium of Example 1 and the magnetic recording medium of Comparative Example 1, the diffraction patterns shown in FIG. 5 were obtained. When a single-layer film of only the Co—Cr—Zr alloy of the first underlayer was formed on the glass substrate under the same film formation conditions as above under a thickness of 50 nm and X-ray diffraction was measured, a clear diffraction peak was observed. Did not. In the diffraction pattern of the magnetic recording medium of Comparative Example 1, the CrTi (110) peak of the body-centered cubic structure (bcc structure) of the second underlayer was CoCrPt (00.2) of the hexagonal close-packed structure (hcp structure) from the magnetic film. Since they overlap with the peak, it is impossible to distinguish between the two. However, in any case, the second underlayer is not strongly (100) oriented as in the magnetic recording medium of Example 1, but is a mixed phase of a plurality of crystal grains having different orientations. Therefore, the Co—Cr—Pt alloy crystal in the magnetic film also has various crystal orientations, and a plurality of diffraction peaks are observed from the Co—Cr—Pt magnetic film.
[0038]
On the other hand, since the magnetic recording medium of Example 1 does not show a diffraction peak in the Co—Cr—Zr alloy single layer film of the first underlayer as described above, the diffraction peak in FIG. These are the CrTi (200) peak of the structure and the CoCrPt (11.0) peak of the hcp structure from the Co-Cr-Pt magnetic film. Therefore, the Cr—Ti alloy of the second underlayer formed on the Co—Cr—Zr alloy layer having the amorphous structure has a (100) orientation, and the Co—Cr—Pt magnetic film thereon is epitaxially grown. It can be understood from the above that the (11.0) orientation is obtained. For this reason, the component in the in-plane direction of the c-axis, which is the axis of easy magnetization of the Co—Cr—Pt alloy, increases, and good magnetic characteristics can be obtained.
[0039]
Further, TEM observation of the magnetic film revealed that the average crystal grain size of the Co—Cr—Pt alloy of Example 1 was 10.8 nm, which was smaller than that of Comparative Example 1 of 16.2 nm. I was In addition, when the magnetization of the single-layer Co—Cr—Zr alloy single-layer film was measured, no clear hysteresis curve was obtained, and this alloy film is considered to be nonmagnetic.
[0040]
<Example 2>
A magnetic recording medium was manufactured with the same film configuration as in Example 1 above. A 2.5-inch chemically strengthened aluminosilicate glass was used for the substrate. A first underlayer made of a 62 at% Co-30 at% Cr-8 at% Ta alloy having a thickness of 40 nm, a second under film made of an 80 at% Cr-20 at% Ti alloy having a thickness of 25 nm, and a thickness of 23 nm were formed thereon. Of a 72 at% Co-18 at% Cr-2 at% Ta-8 at% Pt alloy magnetic film and a carbon protective film having a thickness of 10 nm. The same single-wafer sputtering apparatus as in Example 1 was used as a film forming apparatus, and a film was formed in 9 seconds of tact. The argon (Ar) gas pressure during the formation of each film was 6 mTorr. The oxygen partial pressure of the main chamber during the film formation is about 5 × 10 ⁻⁹ (Torr).
[0041]
The first underlayer is formed in a first underlayer deposition chamber without heating the substrate, heated to 250 ° C. by a lamp heater in a heating chamber, and then using a 98 mol% Ar-2 mol% O ₂ mixed gas in an oxidation chamber. The film was exposed to an atmosphere at a gas pressure of 4 mTorr (gas flow rate: 8 sccm) for 3 seconds, and each film was formed thereon. This is equivalent to ⁴ mTorr × 0.02 × 3 seconds = 2.4 × 10 ⁻⁴ (Torr · second) in PO ₂ · t. After forming up to the carbon protective film, the same lubricating film as in Example 1 was applied.
[0042]
<Comparative Example 2>
Comparative Example 2 was a magnetic recording medium manufactured under the same conditions as in Example 2 except that the mixed gas was not introduced into the oxidation chamber.
[0043]
The coercive force of the magnetic recording medium of Example 2 was 2640 Oersted, which was about 200 Oe higher than that of Comparative Example 2, and the product Br.t of the residual magnetic flux density and the magnetic film thickness was 85 Gauss microns. . Because was reduced to 54% with respect to the v · Isb is 0.98 × ¹⁰ -15 (emu) and Comparative Example 2 that of 1.81 × ¹⁰ -15 (emu) in the magnetic recording medium of Example 2, also the medium noise Correspondingly, it was reduced to about half. In the evaluated recording density region, the reproduction output was almost the same in both Example 2 and Comparative Example 2, and the S / N of the magnetic recording medium was able to improve the reduction of the medium noise. When the recording / reproducing characteristics were evaluated using a magnetoresistive magnetic head under the conditions of a linear recording density of 210 kBPI and a track density of 9.6 kTPI, the magnetic recording medium of Example 2 was compared with that of Comparative Example 2 by S / N is 1.3 times higher, sufficiently meeting the device specification of 2.0 gigabits per square inch of areal recording density. On the other hand, the magnetic recording medium of Comparative Example 2 was insufficient in S / N, and could not satisfy the device specifications.
[0044]
<Example 3>
A magnetic recording medium was manufactured with the same film configuration as in Example 1 above. A 2.5-inch chemically strengthened aluminosilicate glass was used for the substrate. A first underlayer made of an 85 at% Cr-15 at% Zr alloy having a thickness of 30 nm, a second underlayer made of an 80 at% Cr-15 at% Ti-5 at% B alloy having a thickness of 25 nm, and a thickness of 22 nm were formed thereon. A 72 at% Co-19 at% Cr-1 at% Ti-8 at% Pt alloy magnetic film and a 10 nm thick carbon protective film were further formed. The same single-wafer sputtering apparatus as in Example 1 was used as a film forming apparatus, and a film was formed in 8 seconds of tact. The argon (Ar) gas pressure during the formation of each film was 5 mTorr. The oxygen partial pressure of the main chamber during the film formation is about 3 × 10 ⁻⁹ (Torr).
[0045]
The first underlayer is formed in the first underlayer deposition chamber without particularly heating the substrate, heated to 240 ° C. by a lamp heater in a heating chamber, and then using a 79 mol% Ar-21 mol% O ₂ mixed gas in an oxidation chamber. The film was exposed to an atmosphere at a gas pressure of 3 mTorr (gas flow rate: 6 sccm) for 2 seconds to form each film thereon. This is equivalent to 3 mTorr × 0.21 × 2 seconds = 1.3 × 10 ⁻⁴ (Torr · second) in the above PO ₂ · t. After forming up to the carbon protective film, the same lubricating film as in Example 1 was applied.
[0046]
<Comparative Example 3>
Comparative Example 3 was a magnetic recording medium manufactured under the same conditions as in Example 3 except that the mixed gas was not introduced into the oxidation chamber.
[0047]
The coercive force of the magnetic recording medium of Example 3 was 2680 Oersted, which was about 200 Oersted higher than that of Comparative Example 3, and the product Br.t of the residual magnetic flux density and the magnetic film thickness was 69 Gauss microns. . In the magnetic recording medium of the third embodiment, v · Isb is 0.89 × 10 ⁻¹⁵ (emu), which is 60% of 1.44 × 10 ⁻¹⁵ (emu) of that of the third comparative example. Correspondingly, a reduction of about 40% was achieved. The reproduction output was almost the same in the evaluated recording density region in both Example 3 and Comparative Example 3, and the S / N of the magnetic recording medium was able to improve the reduction of the medium noise. The magnetic recording medium of Example 3 was compared with that of Comparative Example 3 by evaluating the recording and reproducing characteristics of the magnetic recording medium of Comparative Example 3 under the conditions of a linear recording density of 225 kBPI and a track density of 9.8 kTPI. / N is 1.4 times higher, sufficiently meeting the device specification of 2.2 gigabits per square inch of areal recording density. On the other hand, the medium of Comparative Example 3 was insufficient in S / N and could not satisfy the device specifications.
[0048]
<Example 4>
A magnetic recording medium was manufactured with the same film configuration as in Example 1. A plating layer made of 88 wt% Ni-12 wt% P was formed on both surfaces of a 96 wt% Al-4 wt% Mg substrate having an outer diameter of 95 mm, an inner diameter of 25 mm, and a thickness of 0.8 mm to a thickness of 13 μm. The surface of this substrate was polished smoothly using a lapping machine until the surface center line average roughness Ra became 2 nm, washed, and further dried. Then, using a tape polishing machine (for example, described in JP-A-62-262227), a polishing tape is passed through a contact roll in the presence of abrasive grains, and pressed against both sides of the disk surface while rotating the substrate. A substantially circumferential texture was formed on the surface. Further, dirt such as an abrasive attached to the substrate was washed, removed, and dried.
[0049]
On the substrate treated in this manner, a first underlayer made of a 60 at% Co-30 at% Cr-10 at% Ta alloy having a thickness of 20 nm was formed on a second base made of an 85 at% Cr-20 at% Ti alloy having a thickness of 20 nm. As a base film, a 72 at% Co-20 at% Cr-8 at% Pt alloy magnetic film having a thickness of 20 nm was formed, and a carbon protective film having a thickness of 10 nm was further formed. The film was formed in 9 seconds by the tact time using the film forming apparatus used in Example 1. The argon (Ar) gas pressure during the formation of each film was 5 mTorr. The oxygen partial pressure of the main chamber during the film formation was about 1 × 10 ⁻⁹ (Torr).
[0050]
The first base film is formed in a first base film forming chamber without heating the substrate, heated to 270 ° C. by a lamp heater in a heating chamber, and then, in an oxidation chamber, a pressure of 98% Ar-2% O ₂ mixed gas of 4 mTorr. (For a gas flow rate of 8 sccm) for 3 seconds to form each film thereon. This is equivalent to ⁴ mTorr × 0.02 × 3 seconds = 2.4 × 10 ⁻⁴ power (Torr · second) in PO ₂ · t. After forming the carbon protective film, a material obtained by diluting a perfluoroalkyl polyether-based material with a fluorocarbon material was applied as a lubricating film.
[0051]
Also, as compared with the film forming apparatus used in the embodiment of the present invention, the film forming apparatus has a low ultimate vacuum and a large oxygen partial pressure, or a film forming apparatus that can form a film on a plurality of substrates at the same time after the first base film is formed. In a film forming apparatus having a long time until the formation of the second base film, a fine growth nucleus can be formed by the above-described oxidation without particularly providing an oxidation chamber as in the above-described embodiment. The effect is obtained.
[0052]
<Example 5>
A magnetic recording medium was manufactured with the same film configuration as in Example 1. A 2.5-inch chemically strengthened aluminosilicate glass was used for the substrate. A first underlayer made of a 60 at% Co-30 at% Cr-10 at% Zr alloy having a thickness of 25 nm and a second under film made of an 85 at% Cr-15 at% Ti alloy having a thickness of 20 nm were further formed thereon. A 20 nm 75 at% Co-19 at% Cr-6 at% Pt alloy magnetic film was formed, and a 10 nm thick carbon protective film was further formed. As a film forming apparatus, an apparatus for simultaneously forming each film on a plurality of substrates held on a pallet was used, and the film was formed in a tact time of 60 seconds. The argon (Ar) gas pressure during the formation of each film was 6 mTorr. During the film formation, the oxygen partial pressure in each film formation chamber was about 1 × 10 ⁻⁸ (Torr).
[0053]
The first base film was formed without heating the substrate, and then heated to 270 ° C. by a lamp heater in a heating chamber, and then each film thereon was formed. This corresponds to about 2 × 10 ⁻⁶ (Torr · sec) in the above PO ₂ · t. After forming the carbon protective film, a material obtained by diluting a perfluoroalkyl polyether-based material with a fluorocarbon material was applied as a lubricating film.
[0054]
Table 2 summarizes the above evaluation results of the above Examples and Comparative Examples.
[0055]
[Table 2]

[0056]
After exposing the above-mentioned oxidizing atmosphere to a Co alloy film which is a first base film using a Co alloy of the present invention having an amorphous structure or a microcrystalline structure similar thereto, a magnetic film is directly formed without a second base film. When formed, the magnetic film showed a strong (00.1) orientation. This is an orientation in which the c-axis of the Co alloy crystal of the magnetic layer is oriented perpendicular to the film surface, and cannot be used as an in-plane magnetic recording medium, but perpendicular magnetic recording in which magnetization is perpendicular to the film surface. Suitable for recording media.
[0057]
【The invention's effect】
The magnetic recording medium of the present invention has effects such as a reduction in medium noise and an increase in coercive force. According to the method of manufacturing a magnetic recording medium of the present invention, the above-described magnetic recording medium can be easily manufactured. Further, a magnetic storage device using the magnetic recording medium of the present invention has a high recording density.
[Brief description of the drawings]
FIG. 1 is a schematic TEM photograph of a cluster formed on a first underlayer of a magnetic recording medium of the present invention.
FIG. 2 is a schematic view showing an example of a film forming apparatus for a magnetic recording medium according to the present invention.
FIG. 3 is a diagram showing the relationship between the activation deposition and the product of the magnetic moment with respect to the conditions when forming a multilayer underlayer of the magnetic recording medium of the present invention.
FIG. 4 is a schematic sectional perspective view of a magnetic recording medium of the present invention.
FIG. 5 is an X-ray diffraction pattern diagram of a magnetic recording medium according to one embodiment of the present invention and a magnetic recording medium according to a comparative example.
FIG. 6 is a schematic plan view and a schematic sectional view of an embodiment of the magnetic storage device of the present invention.
[Explanation of symbols]
Reference numeral 20: substrate, 21: preparation chamber, 22: first base film formation chamber, 23: heating chamber, 24: oxidation chamber, 25: second base film formation chamber, 26: magnetic film formation chamber, 27a, 27b, 27c, 27d: protective film forming chamber, 28: take-out chamber, 29: main chamber, 40: substrate, 41, 41 ': first base film, 42, 42': second base film, 43, 43 ': magnetic film, 44 , 44 ': protective film, 45, 45': lubricating film, 61: magnetic head, 62: magnetic head driving unit, 63: recording / reproducing signal processing system, 64: magnetic recording medium, 65: driving unit.

Claims (4)

A substrate,
A first base film made of two or more alloys formed on the substrate and having a standard oxide generation energy of 150 (kJ / mol O ₂ ) or more;
A second base film formed on the first base film;
A magnetic film formed on the second underlayer.
A magnetic recording medium, wherein clusters formed by locally oxidizing a region containing a large number of easily oxidizable elements are dispersed at an interface between the first underlayer and the second underlayer. 2. The magnetic recording medium according to claim 1, wherein the substrate is a glass substrate. 2. The magnetic recording medium according to claim 1, wherein the substrate is an aluminum alloy substrate. 4. The magnetic recording medium according to claim 1, wherein a protective film is formed on the magnetic film, and a lubricating film is applied on the protective film.

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