JP2004146015A

JP2004146015A - Magnetic recording medium and method for manufacturing the same

Info

Publication number: JP2004146015A
Application number: JP2002312028A
Authority: JP
Inventors: Yoshinori Honda; 本田　好範; Kiwamu Tanahashi; 棚橋　究; Yuzuru Hosoe; 細江　譲; Yotsuo Yahisa; 屋久　四男; Hiroyuki Kataoka; 片岡　宏之
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2002-10-28
Filing date: 2002-10-28
Publication date: 2004-05-20
Anticipated expiration: 2022-10-28
Also published as: JP4072417B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a vertical recording medium having excellent surface characteristics equal to or better than those of an intra-plane magnetic recording medium by preventing surface roughness from increasing in performing deposition of the magnetic recording medium of a vertical system by magnetron sputtering. <P>SOLUTION: The vertical magnetic recording medium is deposited with a soft magnetic layer 5 constituting the vertical magnetic recording medium at a film thickness of the soft magnetic layer 5 within a range from 50 to 500 nm by dividing a nonmagnetic substrate under temperature conditions from 20 to 200°C. The surface roughness of the medium can be reduced and a surfacing yield of ≥95% can be assured. In addition, a deposition tact can be made shorter without lowering a deposition rate and therefore the assurance of a great deal of productivity is made possible. Particularly the means is most effective for deposition of thick films like the soft magnetic layers of the vertical media. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は金属のスパッタリングにおけるスパッタリング方法に関する平坦化方法であり、特に磁気記録媒体の製造における下地層、軟磁性層などのメタル膜の成膜に有効である。
【０００２】
【従来の技術】
従来より磁気記録媒体の成膜方法として良く用いられているスパッタリング法には、磁場を用いたマグネトロンスパッタリングがある。この方法において成膜した場合、ＲＦスパッタリングなどに比べ成膜速度が数倍以上速い特徴がある。特に金属の薄膜を得るには有効な手段として用いられている。また、比較的厚い軟磁性層の成膜においては、結晶構造の乱れなどによって表面性が悪化するため、表面粗さを低減する方法として特許文献１に記載されているよう軟磁性層を薄い層に分割し、且つ軟磁性層とは組成の異なる組成を持つ非磁性の分離層を間に挟むことにより、結晶構造の乱れを防止し、結晶の微細化と結晶面の配向を制御することで軟磁性層表面の表面性の向上（表面粗さの低減）が出来るとしている。この方法によれば磁気記録媒体の表面粗さ：Ｒａが５ｎｍ以下、好ましくは４．５ｎｍ以下で成膜技術、材料で制約を受けるが、Ｒａ０．７ｎｍから０．８ｎｍ程度が最も表面性の良い磁気記録媒体の表面粗さＲａであるとしている。また、特許文献１の実施例では５００ｎｍの成膜を分割＋分離層で行なった例の比較として連続成膜５００ｎｍで比較されている。これらの結果から分割することが表面粗さを低減する方法ではなく分離層を入れることが同時に表面粗さを低減する結果となっており、膜厚は最大透磁率と膜厚の積で決定される。結果として、表面粗さは連続成膜でＲａ６．７ｎｍに対して特許文献１に記載の分割成膜でＲａ４．２ｎｍである。この結果から分割成膜を行なってもそれほど大きな改善は出来ない事、また、現在の磁気記録媒体の表面粗さは磁気ヘッドの浮上量が７ｎｍ未満である事を前提とした場合、Ｒａを０．６ｎｍ程度とする必要がある事から、従来方法と比較してもその優位性が見出せないと考えられる。
【０００３】
従って、従来例で述べているような原因だけでは説明できず、更なる改善が必要と判断した。
【特許文献１】特開２００１−２５０２２３号公報
【発明が解決しようとする課題】
従来のマグネトロンスパッタリングに於いてはその特徴である成膜速度が速い事から膜厚を厚く成膜するには有効な手段として用いられてきた。しかし、我々はこのマグネトロンスパッタリングにおいて垂直方式の磁気記録媒体厚付け成膜を行った際、磁気記録媒体としてはあってはならない表面粗さが増大することを問題視し、これを大幅に低減する事で従来の面内記録媒体と同等若しくはそれ以上に優れた表面性を持つ垂直記録媒体を製造する事を目的とする。
【０００４】
【課題を解決するための手段】
つまり、成膜速度を早く、且つ膜厚を厚くするほど成膜後の膜表面の表面粗さは粗くなり、特に磁気記録媒体における高密度化に必須である磁気ヘッドの低浮上化の妨げになる事は明白である。この原因としては成膜速度が速い事による急激な結晶成長、マグネトロンを使用するためプラズマ密度が高いことによるターゲット表面及び基板表面の温度上昇、特に金属膜の場合、厚付けするほどエピタキシャル成長を増長するため結晶粒の増大につながる事、これらの要因から成膜中に基板表面、膜表面温度が上がり、結晶成長を促す為、膜の表面粗さが増大すると考えられる。また、金属膜の中でもアモルファスにおいても結晶成長に限らず表面が荒れてくる、これはひとえに、膜厚が厚くなることにより、単純に基板表面の粗さを受け継ぐ物であり、たとえ、アモルファスといえども、異常成長は必ず生じ、きっかけとなるのは基板表面の微笑突起であり、成膜時の基板表面温度の上昇に他ならない事を示していると考え成膜時の温度上昇を押さえる事で膜表面の粗さを押さえる事が望ましいと考えた。
【０００５】
本発明では上述の問題点を解決するため基板温度、膜表面温度を上げずに厚付けする方法として一つの層を１回のスパッタで行うのではなく、分割して数回に分ける事で成膜速度を落とさず、上げたままでも、一回の成膜時の温度上昇を押さえる事で膜の表面粗さを低減する事が可能であると考えた。
【０００６】
【発明の実施の形態】
本発明の実施にあたって使用した成膜装置の外観略図を図１に示した。装置の構成及び工程の流れとしては図７に示す。
【０００７】
まず、成膜装置は洗浄された基板の投入を行なうロードロック室とそれに連なる各プロセスチャンバーがシード層、下地層、反強磁性層、軟磁性層の成膜順にそれぞれ並び、特に軟磁性層のチャンバーは膜厚が５０〜５００ｎｍと厚いため最高で１０回に分けて成膜出来るよう１０チャンバーとなっている。次に磁性膜用の下地膜を成膜するため基板加熱室があり、続いて磁性膜の成膜室に続く。その後、軟磁性膜の特にＮｉＦｅ等の場合には磁区固定が必要なため磁区固定用磁石の設置された処理室があり、最後に保護膜のＤＬＣ成膜を行うためのチャンバーで成膜が完了し、アンロードロックから基板が排出される。以上が流れと構成である。
【０００８】
尚、評価としては成膜後の表面粗さをＡＦＭを用いて測定し、その膜の表面粗さとして、Ｒａ：中心線平均粗さ、Ｒｐ：最大高さで比較した。測定に使用したＡＦＭはＤＩ３０００型ナノスコープ３（デジタルインスツルメンツ社製）である。Ｒａ，Ｒｐの定義は本装置の取扱説明書に記載されている通りである。
【０００９】
この装置を用いて、本発明の目的である表面粗さの低減検討をまずは単層膜で進めた。最初に確認のために軟磁性膜の膜厚に対して表面粗さがどのように変化するかをＮｉＦｅ、ＣｏＴａＺｒそれぞれの単層膜について５０ｎｍ〜５００ｎｍまで膜厚を変化させて１回の成膜でサンプリングし、測定を行なった。その結果が図２である。これより、ＮｉＦｅのような結晶性の膜でも、ＣｏＴａＺｒのようなアモルファスな膜においても膜厚が厚いほど表面粗さは増大する事が判った。従って、結晶性の乱れのみで表面粗さが増大するのではない事が判る。
【００１０】
また、本発明のポイントとなる温度の影響について同様に成膜を行なった。その結果が図３である。因みにこの時の膜厚は５００ｎｍ一定で成膜時の圧力は１Ｐａとした。これから判るように連続成膜を行なったＮｉＦｅ，ＣｏＴａＺｒ共に基板温度の高いほうが急激に表面粗さが大きくなり、分割成膜（ここでは５分割）した場合にも温度の高いほうがやはり粗さは大きくなる傾向にある。つまり、基板温度が低く分割成膜することで一度の成膜での温度上昇を押さえる事で表面粗さは十分に低減できるとともに、高温、連続成膜においても従来例にようなＲａ５ｎｍの大きさの表面粗さは生じない。本実施の形態では、分割成膜する場合の基板温度を２０℃〜２００℃の範囲としており、この範囲においては、媒体表面の保護膜の表面粗さＲａを０．６ｎｍ以下に低減することができる。このとき、軟磁性膜がＣｏＴａＺｒの場合には、表面粗さＲａを０．３ｎｍ以下に低減することができる。また更に、分割成膜する場合の基板温度を２０℃〜１００℃とした場合には、表面粗さＲａを０．５ｎｍ以下に低減することができ、磁気ヘッドの浮上量が７ｎｍ以下である場合でも、安定したヘッド走行制御が可能な磁気記録媒体を提供できる。
【００１１】
次に成膜時のＡｒ圧力の依存性を確認した。その結果が図４である。この時の材料はＮｉＦｅで、膜厚は５００ｎｍ一定とし基板温度は常温とした。この結果から成膜時の圧力は低いほうが表面粗さＲａ，Ｒｐ共に低減できる事が判る。更に同様に分割回数を変化させ成膜を行なった。その結果が図５である。この時の成膜圧力は１Ｐａで膜厚は５００ｎｍとし、基板温度は常温とした。分割回数は１〜２０回で行なった。図５より分割回数が３回以上では急激に表面粗さが低減され１０回以上ではほぼ一定となり変化しない事が判る。
【００１２】
以上の本発明の検討結果から、従来例のような分離層を挟んだ複雑な構造を取ること無く表面粗さを低減する方法により、軟磁性膜が１層で、膜厚が厚くとも従来例に比べ、一桁以上表面性の良い磁気記録媒体が供給できる。また、成膜装置によって基板温度の上昇による、表面粗さの発生状況は異なるが一般的にターゲットと基板との距離（以下Ｔ／Ｓ距離）が遠いほど、投入パワーが小さいほど（成膜速度が小さいほど）、成膜時の圧力が低いほど表面粗さは小さくなる傾向を示す。従って、より効果的に表面粗さを低減するにはこれらのファクターを適正化することが必要となる
次に垂直媒体の層構成として以下に示す内容で総合成膜を行い、軟磁性層の膜厚のみを変化させてサンプリングした。サンプリングに当たっては、まず、基板としてＨＯＹＡ社製ガラス基板：ＯＤ：φ６５ｍｍ×ＩＤ：φ２０ｍｍ×０．６３５ｍｍｔ、Ｒａ：０．３１２ｎｍ、Ｒｐ：３．３２１ｎｍをアルカリ、超音波純水洗浄を行い、ＩＰＡ（イソプロピルアルコール）蒸気洗浄乾燥を施した後、シード層としてＣｏＣｒＺｒ：３０ｎｍ、下地層としてＣｏＣｒ：５ｎｍ、反強磁性層としてＭｎＰｔ：３０ｎｍ、軟磁性層としてＮｉＦｅを：５０から５００ｎｍ成膜を行ない、その後、下地層と磁性層をそれぞれＣｏＣｒ：７ｎｍ、ＣｏＣｔＰｔＢ：１５ｎｍ成膜した。保護膜としてはＤＬＣ（ダイヤモンドライクカーボン膜）をＲＦ−ＣＶＤで５ｎｍ成膜した。本実施例に於いては軟磁性層以外は成膜時の圧力を９．３Ｅ−１Ｐａ一定とし、軟磁性層は０．６Ｐａ一定で行なった。また、軟磁性層の分割数は１〜１０とした。
【００１３】
この結果が図８である。この検討結果より、垂直媒体の全構成が入っていても軟磁性膜の膜厚及び分割数は表面粗さに影響しており、分割数が多いほど、膜厚が薄いほど表面粗さＲａは小さくなる事が判る。以上の結果から磁気ディスクとしての浮上性を確保するための表面粗さとして磁気ヘッドの浮上量を６ｎｍ以下を想定すると表面粗さＲａは大凡０．８ｎｍ以下が望ましい。この為には成膜膜厚が２００ｎｍ以下の場合には分割数を３以上１０までで、２００ｎｍを超す場合には５以上１０までが望ましい。更に生産性を考慮すると分割数は多いほどターゲット一枚当たりの成膜膜厚の低減が可能となるため、分割数を５以上１０までにするのが最良である。
【００１４】
以上の検討結果を纏めると軟磁性膜の成膜に際しては基板温度上昇を防止し、媒体表面の表面粗さを０．８ｎｍ以下に低減する為に基板温度は１００℃以下、成膜時圧力はスパッタ電極の能力によるが極力低く（本検討では０．７Ｐａ以下）、分割回数は総じて３〜１０にする事が、より、磁気ヘッドの浮上性を確保し信頼性の高い磁気ディスクを得る事になる。
【００１５】
次に図８で行なったと同じ方法でサンプリングを行い、浮上性の評価を行なった。その時の軟磁性膜の諸条件と表面粗さ、ピークカウント（２ｎｍでスライスした場合の突起の数）、及び磁気ヘッド浮上性の歩留りを評価した。浮上性は磁気ヘッドの浮上量を５ｎｍとし、メディアの全面（Ｒ１５−３１の両面）を評価し、磁気ヘッドと円板面の突起とが接触した時の信号をピエゾ素子を搭載した磁気ヘッドにて評価した。この浮上性の目安としては５個以下とした。
【００１６】
評価結果及び諸条件を表１に示す。
【００１７】
【表１】

【００１８】
この結果からやはり、上述の検討結果と同様の傾向で軟磁性膜の成膜時の圧力は低く、分割数は多いほうが浮上性は良好であり、比較例のように単に表面粗さがＲａ０．８ｎｍを達成していたとしてもピークカウント数、表面粗さＲｐが大きくなる物は浮上歩留りが落ちている事が明白である。
【００１９】
これらから、分割して成膜した本発明の媒体においては、いずれもＲａ：０．３３ｎｍ以下、Ｒｐ：３．５ｎｍ以下でほぼ基板の表面粗さと同等であり、１回で成膜した比較例１、２、３に於いてはいずれも明らかに粗いことが判る。従って、本発明で成膜した媒体は分割成膜することで極低浮上に耐えうる表面粗さを保持しうることが判った。更にＡＦＭの結果からＰｅａｋＣｏｕｎｔ数を解析した結果、本実施の形態では数個レベルに対して比較例では１００個以上と多い事が判る。これを反映して磁気ヘッド浮上量：５ｎｍでは本発明品の歩留りが９５％以上であるのに対し比較例では数十％とほとんどが極低浮上に対応できないことが明確である。
【００２０】
更に、本発明では軟磁性層としてＣｏＴａＺｒのアモルファス膜を同様に成膜したが同様の効果を得ることが出来ることを確認できた。また、磁性層としてＣｏ／Ｐｄの積層膜（超格子膜）：４０ｂｉ−Ｌａｙｅｒを用いた場合においてもこの効果は得られることを確認している。
【００２１】
従って、本発明の効果は層構成、材料の違いに依らず、実施例のみに限定される物ではない。
図６に本発明の実施例で行なった垂直媒体の層構成の一例を示した。下から順に１−ガラス基板，２−シード層，３−下地層１，４−反強磁性層，５−軟磁性層，６−下地層、７−磁性層，８−保護膜層の構成になっており，図２−Ｂでは磁性層が９−超格子磁性層からなる場合である。
【００２２】
【発明の効果】
以上の本発明の方法によれば媒体の表面粗さを低減でき浮上歩留りを９５％以上確保でき、且つ、成膜タクトが成膜速度を落とさずに短く出来ることから大幅な生産性の確保が可能となる。特に垂直媒体における軟磁性層のような厚い膜の成膜に対しては最も有効な手段である。
【図面の簡単な説明】
【図１】本実施例で使用した成膜装置概略図
【図２】表面粗さの膜厚依存性
【図３】表面粗さの基板温度依存性
【図４】表面粗さの成膜時圧力依存性
【図５】表面粗さの分割数依存性
【図６】本発明の垂直媒体の層構成例
【図７】本発明の実施例での磁気ディスク製造フローチャート
【図８】本発明の実施例での軟磁性膜成膜条件と表面粗さの評価結果
【符号の説明】
１−ガラス基板，２−シード層，３−下地層１，４−反強磁性層，５−軟磁性層、５ａ〜５ｅ−軟磁性層５の分割成膜状態を示す。６−下地層，７−磁性層，８−保護膜層、９−超格子磁性層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a flattening method relating to a sputtering method in metal sputtering, and is particularly effective for forming a metal film such as an underlayer and a soft magnetic layer in the manufacture of a magnetic recording medium.
[0002]
[Prior art]
Conventionally, magnetron sputtering using a magnetic field is a sputtering method often used as a film forming method for a magnetic recording medium. When a film is formed by this method, there is a feature that the film forming speed is several times or more higher than that of RF sputtering or the like. Particularly, it is used as an effective means for obtaining a metal thin film. Further, in forming a relatively thick soft magnetic layer, the surface property is deteriorated due to disorder of the crystal structure or the like. Therefore, as described in Patent Document 1, a thin soft magnetic layer is used as a method for reducing the surface roughness. By interposing a non-magnetic separation layer having a composition different from that of the soft magnetic layer between the soft magnetic layers, disorder of the crystal structure can be prevented, and crystal refinement and control of crystal plane orientation can be achieved. It is stated that the surface property of the soft magnetic layer surface can be improved (surface roughness can be reduced). According to this method, the surface roughness of the magnetic recording medium: Ra is 5 nm or less, preferably 4.5 nm or less, and the film forming technique and materials are restricted, but Ra of about 0.7 nm to 0.8 nm has the best surface properties. It is assumed that the magnetic recording medium has a surface roughness Ra. Further, in the example of Patent Document 1, a continuous film formation of 500 nm is compared as an example in which a film formation of 500 nm is performed by a division + separation layer. From these results, splitting is not a method of reducing surface roughness, but the result of inserting a separation layer and simultaneously reducing surface roughness, and the film thickness is determined by the product of the maximum magnetic permeability and the film thickness. You. As a result, the surface roughness is Ra of 6.7 nm in the continuous film formation, but is Ra of 4.2 nm in the divisional film formation described in Patent Document 1. From these results, it can be seen that even if the divided film formation is performed, not so much improvement can be achieved, and the surface roughness of the current magnetic recording medium is set to Ra = 0 if the flying height of the magnetic head is less than 7 nm. Since it is necessary to be about 0.6 nm, it is considered that superiority cannot be found even in comparison with the conventional method.
[0003]
Therefore, it cannot be explained only by the causes described in the conventional example, and it is determined that further improvement is necessary.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-250223 [Problems to be Solved by the Invention]
Conventional magnetron sputtering has been used as an effective means for forming a thick film because of its characteristic high film forming speed. However, when we performed perpendicular magnetic recording medium thick film deposition in this magnetron sputtering, we saw the problem that surface roughness, which should not be a magnetic recording medium, would increase, and significantly reduced this. Accordingly, it is an object of the present invention to manufacture a perpendicular recording medium having a surface property equal to or better than that of a conventional in-plane recording medium.
[0004]
[Means for Solving the Problems]
In other words, the higher the film forming speed and the thicker the film thickness, the rougher the surface roughness of the film surface after film formation, and particularly, the lower the flying height of the magnetic head which is indispensable for high density in a magnetic recording medium. It is obvious. This can be caused by rapid crystal growth due to the high deposition rate, temperature rise on the target surface and substrate surface due to the high plasma density due to the use of the magnetron, and particularly in the case of metal films, the epitaxial growth increases as the thickness increases. For these reasons, it is considered that the crystal surface is increased due to the increase in the crystal grain, and the temperature of the substrate surface and the film surface is increased during the film formation to promote crystal growth. In addition, even in the case of amorphous metal films, the surface is roughened, not limited to crystal growth. This is simply a matter of inheriting the roughness of the substrate surface by increasing the film thickness. However, abnormal growth always occurs, and the trigger is a smile protrusion on the substrate surface, which is considered to be nothing but an increase in the substrate surface temperature during film formation, and by suppressing the temperature increase during film formation It was considered desirable to suppress the roughness of the film surface.
[0005]
In the present invention, in order to solve the above-mentioned problems, as a method of thickening the substrate without raising the substrate temperature and the film surface temperature, one layer is not divided by one sputtering but divided into several layers. It was considered that the surface roughness of the film could be reduced by suppressing the temperature rise during one film formation even if the film speed was increased without being decreased.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic view of the appearance of a film forming apparatus used in carrying out the present invention. FIG. 7 shows the configuration of the apparatus and the process flow.
[0007]
First, in the film forming apparatus, the load lock chamber for loading the cleaned substrate and the process chambers connected to the load lock chamber are arranged in the order of forming the seed layer, the underlayer, the antiferromagnetic layer, and the soft magnetic layer. The chamber has a large thickness of 50 to 500 nm, and has 10 chambers so that the film can be divided into 10 times at the maximum. Next, there is a substrate heating chamber for depositing a base film for a magnetic film, and then to a chamber for depositing a magnetic film. Thereafter, in the case of a soft magnetic film, particularly in the case of NiFe or the like, it is necessary to fix a magnetic domain. Therefore, there is a processing chamber in which a magnet for fixing a magnetic domain is provided. Then, the substrate is discharged from the unload lock. The above is the flow and configuration.
[0008]
In addition, as an evaluation, the surface roughness after film formation was measured using AFM, and the surface roughness of the film was compared by Ra: center line average roughness, and Rp: maximum height. The AFM used for the measurement is DI3000 Nanoscope 3 (manufactured by Digital Instruments). The definitions of Ra and Rp are as described in the operation manual of this apparatus.
[0009]
Using this apparatus, the study on the reduction of surface roughness, which is the object of the present invention, was first carried out with a single-layer film. First, to confirm how the surface roughness changes with respect to the film thickness of the soft magnetic film, a single film formation is performed by changing the film thickness from 50 nm to 500 nm for each of the single-layer films of NiFe and CoTaZr. And sampled. FIG. 2 shows the result. From this, it was found that the surface roughness increases as the film thickness increases, even in a crystalline film such as NiFe or an amorphous film such as CoTaZr. Therefore, it is understood that the surface roughness is not increased only by the disorder of the crystallinity.
[0010]
In addition, film formation was performed in the same manner with respect to the influence of temperature, which is a point of the present invention. FIG. 3 shows the result. Incidentally, the film thickness at this time was constant at 500 nm, and the pressure at the time of film formation was 1 Pa. As can be seen from the figure, the surface roughness of NiFe and CoTaZr formed by continuous film formation increases sharply when the substrate temperature is high, and the roughness also increases when the temperature is high even when divided film formation (here, five divisions) is performed. Tend to be. In other words, the substrate temperature is low and the surface roughness can be sufficiently reduced by suppressing the temperature rise in a single film formation by forming the film separately, and the Ra5 nm size as in the conventional example can be obtained even at a high temperature and a continuous film formation. No surface roughness occurs. In this embodiment, the substrate temperature in the case of divided film formation is in the range of 20 ° C. to 200 ° C. In this range, it is possible to reduce the surface roughness Ra of the protective film on the medium surface to 0.6 nm or less. it can. At this time, when the soft magnetic film is CoTaZr, the surface roughness Ra can be reduced to 0.3 nm or less. Further, when the substrate temperature in the case of the divided film formation is set to 20 ° C. to 100 ° C., the surface roughness Ra can be reduced to 0.5 nm or less, and the flying height of the magnetic head is 7 nm or less. However, it is possible to provide a magnetic recording medium capable of performing stable head traveling control.
[0011]
Next, the dependency of Ar pressure upon film formation was confirmed. FIG. 4 shows the result. At this time, the material was NiFe, the film thickness was constant at 500 nm, and the substrate temperature was room temperature. From this result, it is understood that the lower the pressure during film formation, the lower both the surface roughness Ra and Rp. Further, the film formation was performed by changing the number of divisions in the same manner. FIG. 5 shows the result. At this time, the film forming pressure was 1 Pa, the film thickness was 500 nm, and the substrate temperature was normal temperature. The number of divisions was 1 to 20 times. It can be seen from FIG. 5 that when the number of divisions is three or more, the surface roughness is sharply reduced, and when the number of divisions is ten or more, the surface roughness is substantially constant and does not change.
[0012]
From the above examination results of the present invention, the method of reducing the surface roughness without taking a complicated structure sandwiching the separation layer as in the conventional example can be used. As compared with the above, a magnetic recording medium having a surface property of one digit or more can be supplied. In addition, although the state of occurrence of surface roughness due to an increase in the substrate temperature differs depending on the film forming apparatus, generally, the longer the distance between the target and the substrate (hereinafter, T / S distance) and the smaller the input power (the film forming speed). The smaller the pressure during film formation, the lower the surface roughness. Therefore, in order to reduce the surface roughness more effectively, it is necessary to optimize these factors. Next, as a layer structure of the perpendicular medium, a general film is formed by the following contents, and the film of the soft magnetic layer is formed. Sampling was performed with only the thickness changed. At the time of sampling, first, a glass substrate manufactured by HOYA: OD: φ65 mm × ID: φ20 mm × 0.635 mmt, Ra: 0.312 nm, Rp: 3.321 nm was washed with alkali and ultrasonic pure water, and IPA ( (Isopropyl alcohol) After vapor cleaning and drying, a film of CoCrZr: 30 nm as a seed layer, CoCr: 5 nm as an underlayer, MnPt: 30 nm as an antiferromagnetic layer, and NiFe: 50 to 500 nm as a soft magnetic layer are formed. An underlayer and a magnetic layer were formed with CoCr: 7 nm and CoCtPtB: 15 nm, respectively. As a protective film, DLC (diamond-like carbon film) was formed to a thickness of 5 nm by RF-CVD. In this example, the pressure during film formation was constant at 9.3E-1 Pa except for the soft magnetic layer, and the soft magnetic layer was constant at 0.6 Pa. The number of divisions of the soft magnetic layer was 1 to 10.
[0013]
FIG. 8 shows the result. From this examination result, even when the entire structure of the perpendicular medium is included, the thickness and the number of divisions of the soft magnetic film affect the surface roughness. The surface roughness Ra increases as the number of divisions increases and the film thickness decreases. You can see that it gets smaller. From the above results, assuming that the flying height of the magnetic head is 6 nm or less as the surface roughness for ensuring the flying property of the magnetic disk, the surface roughness Ra is desirably approximately 0.8 nm or less. For this purpose, when the film thickness is 200 nm or less, the number of divisions is preferably 3 or more and 10 or more, and when it exceeds 200 nm, 5 or more and 10 is desirable. In consideration of productivity, the larger the number of divisions, the more the film thickness per target can be reduced. Therefore, it is best to set the number of divisions to 5 or more and 10 or less.
[0014]
Summarizing the above study results, in forming the soft magnetic film, the substrate temperature is set to 100 ° C. or less, and the pressure during the film formation is set to prevent the substrate temperature from rising and to reduce the surface roughness of the medium surface to 0.8 nm or less. Depending on the capability of the sputter electrode, it should be as low as possible (0.7 Pa or less in this study), and the number of divisions should be 3 to 10 in general, in order to obtain a magnetic disk with higher flying height and higher reliability. Become.
[0015]
Next, sampling was performed in the same manner as in FIG. 8 to evaluate the levitation. At that time, various conditions and surface roughness of the soft magnetic film, peak count (the number of protrusions when sliced at 2 nm), and the yield of the magnetic head flying property were evaluated. The flying height of the magnetic head was set at 5 nm, the entire surface of the medium (both sides of R15-31) was evaluated, and a signal when the magnetic head and the protrusion on the disk surface came into contact was transferred to a magnetic head equipped with a piezo element. Was evaluated. The standard of the levitation was 5 or less.
[0016]
Table 1 shows the evaluation results and various conditions.
[0017]
[Table 1]

[0018]
From this result, the pressure at the time of forming the soft magnetic film is low, and the larger the number of divisions, the better the levitation, and the surface roughness is simply Ra0. Even if 8 nm is achieved, it is apparent that those having a large peak count number and surface roughness Rp have a low floating yield.
[0019]
From these results, in the medium of the present invention formed by dividing the film, Ra: 0.33 nm or less and Rp: 3.5 nm or less are almost the same as the surface roughness of the substrate. It is apparent that all of the

samples

1, 2, and 3 are coarse. Therefore, it was found that the medium formed by the present invention can maintain a surface roughness capable of withstanding extremely low levitation by forming a divided film. Further, as a result of analyzing the PeakCount number from the result of the AFM, it is found that the number of peak counts in the present embodiment is more than 100 in the comparative example compared to several levels. Reflecting this, it is clear that the yield of the product of the present invention is 95% or more when the flying height of the magnetic head is 5 nm, whereas it is tens of percent in the comparative example, and almost all cannot cope with the extremely low flying height.
[0020]
Furthermore, in the present invention, a CoTaZr amorphous film was similarly formed as the soft magnetic layer, but it was confirmed that the same effect can be obtained. It has also been confirmed that this effect can be obtained even when a Co / Pd laminated film (superlattice film): 40 bi-Layer is used as the magnetic layer.
[0021]
Therefore, the effects of the present invention are not limited only to the examples, regardless of the difference in the layer constitution and the material.
FIG. 6 shows an example of the layer structure of the perpendicular medium performed in the embodiment of the present invention. In order from the bottom, 1-glass substrate, 2-seed layer, 3-underlayer 1, 4-antiferromagnetic layer, 5-soft magnetic layer, 6-underlayer, 7-magnetic layer, 8-protective layer FIG. 2B shows a case where the magnetic layer is composed of a 9-superlattice magnetic layer.
[0022]
【The invention's effect】
According to the method of the present invention described above, the surface roughness of the medium can be reduced, the floating yield can be maintained at 95% or more, and the film forming tact can be shortened without reducing the film forming speed, so that a large productivity can be ensured. It becomes possible. In particular, this is the most effective means for forming a thick film such as a soft magnetic layer in a perpendicular medium.
[Brief description of the drawings]
FIG. 1 is a schematic view of a film forming apparatus used in the present embodiment. FIG. 2 is a diagram showing a dependency of a surface roughness on a film thickness. FIG. 3 is a diagram showing a dependency of a surface roughness on a substrate temperature. FIG. Pressure dependence FIG. 5 Surface roughness division number dependence FIG. 6 Example of layer structure of perpendicular medium of the present invention FIG. 7 Magnetic disk manufacturing flowchart in embodiment of the present invention FIG. Evaluation results of soft magnetic film deposition conditions and surface roughness in Examples [Description of symbols]
1 shows a divided film formation state of 1-glass substrate, 2-seed layer, 3-underlayer 1, 4-antiferromagnetic layer, 5-soft magnetic layer, 5a to 5e-soft magnetic layer 5. 6-underlayer, 7-magnetic layer, 8-protective layer, 9-superlattice magnetic layer

Claims

In a perpendicular magnetic recording medium having at least a seed layer, an underlayer, an antiferromagnetic layer, a soft magnetic layer, an underlayer, a magnetic layer, and a protective film layer on a nonmagnetic substrate, the soft magnetic layer has a thickness of 50 to 500 nm. A perpendicular magnetic recording medium, wherein the soft magnetic layer is formed by a film forming process in which the non-magnetic substrate is divided under a temperature condition of 20 ° C. to 200 ° C.

In a perpendicular magnetic recording medium having at least a seed layer, an underlayer, an antiferromagnetic layer, a soft magnetic layer, an underlayer, a magnetic layer, and a protective film layer on a nonmagnetic substrate, the soft magnetic layer has a thickness of 50 to 500 nm. The soft magnetic layer is formed by a film forming process in which the non-magnetic substrate is divided under a temperature condition of 20 ° C. to 200 ° C. to form a surface roughness Ra of the medium surface to 0.6 nm or less. A perpendicular magnetic recording medium, comprising:

3. The perpendicular magnetic recording medium according to claim 1, wherein the number of divisions when forming the soft magnetic layer is in the range of 3 to 10.

In a method for manufacturing a perpendicular magnetic recording medium having at least a seed layer, an underlayer, an antiferromagnetic layer, a soft magnetic layer, an underlayer, a magnetic layer, and a protective film layer on a nonmagnetic substrate, the film thickness may be in the range of 50 to 500 nm. A method for manufacturing a perpendicular magnetic recording medium, comprising forming a certain soft magnetic layer by dividing the nonmagnetic substrate under a temperature condition of 20 ° C to 200 ° C.

5. The method for manufacturing a perpendicular magnetic recording medium according to claim 4, wherein the number of divisions when forming the soft magnetic layer is in the range of 3 to 10.

A magnetic storage device using the perpendicular magnetic recording medium according to claim 1.