JP4217361B2 - Magnetic disk manufacturing method and sputtering apparatus used therefor - Google Patents

Description

表１に示したように、実施例１は比較例１に比べてＩｄ／Ｉｇ及びｇピーク位置は小さな値を示した。また、密度は高い値を示した。膜の密度が高くなる理由は前述したイオンアシスト効果によるものと考えられる。この結果から高い膜質の保護膜を有する磁気ディスクであることが示された。
（耐腐食性の評価）
電源の放電パワー（放電電圧×放電電流）を調整することにより保護膜の膜厚を種々変化させて実施例１及び比較例１の磁気ディスクを作製した。このようにして得られた磁気ディスクを８０℃、８０％の恒温恒湿槽に９０時間放置した後、超純水中に浸漬させて磁性膜の材料であるＣｏ系の腐食塩が溶解された溶液を得た。この溶液を誘導結合プラズマ質量分析（ＩＣＰ−ＭＳ）法で分析することによりＣｏ溶出量を測定して耐腐食性の評価を行った。その結果を図４に示す。
【００４４】
図４から分かるように、保護膜の膜厚が薄くなるにつれ、Ｃｏ溶出量は多くなるが、実施例１の磁気ディスクは比較例１のものと比べて全体的にＣｏ溶出量が少ないことを示した。磁性膜中のＣｏは保護膜に形成された微細孔を通して溶出する。このため、実施例１は比較例１と比べて形成される微細孔の数が少なく、保護膜の密度が高いことが考えられ、耐腐食性の高い磁気ディスクであることが示された。
（欠点の評価）
電源の放電回数を種々変化させて保護膜を形成し、実施例１及び比較例１の磁気ディスクを作製した。このようにして作製された磁気ディスクの保護膜の全面を欠点検出器で測定して評価した。この欠点検出器は所定の回転数で回転している磁気ディスクに対し、レーザ光を斜め方向から入射し、異物による反射光及び散乱光の変化量をディテクターで検出するものである。その結果を図５に示す。
【００４５】
図５から分かるように、実施例１では放電回数の増加に伴う欠点数の増加はほとんど認められず、放電回数が２１０００回の場合も放電回数が１回の場合と同じく欠点数が５０個であった。これに対し、比較例１は放電回数が３０００回を越えたときから欠点数が急増することを示した。この欠点数は異常放電の際に発生するアークの回数と相関があり、アークにより欠点が発生すると考えられる。このため、実施例１は比較例１と比べてアークの発生が少ないことが考えられ、欠点のない磁気ディスクを安定して作製できることが示された。
（歩留まりの評価）
前記と同様に放電回数を種々変化させて作製された実施例１及び比較例１の磁気ディスクに対してグライド評価及びサーティファイ評価を行った。
【００４６】
グライド評価は磁気ディスクをハードディスク装置のスピンドルに装着し、ピエゾ素子付きの磁気ヘッドが磁気ディスク表面から１０ｎｍの高さで浮上するように磁気ディスクを回転させた状態で磁気ヘッドを磁気ディスク全面に対してシーク動作させることにより行う。この磁気ディスク上に突起物が存在した場合には磁気ヘッドが突起物に衝突するため、この衝撃をピエゾ素子で検知し、その出力が所定値に達した場合に異物があると判断して、異物の有無から良品又は不良品を評価する方法である。
【００４７】
サーティファイ評価はＭＲ素子付きの磁気ヘッドを使用して、前記グライド評価と同様に磁気ヘッドを磁気ディスク全面に対してシーク動作させる。このシーク動作中に磁気ディスクには所定周波数で信号が書き込まれ、この信号をＭＲ素子で再生することにより行う。この信号を再生する際、例えば磁気ディスク上に付着した異物が取れて凹部が形成されていたり等すると信号が欠如したり、低下したりする。この信号の欠如、低下等をＭＲ素子で検知し、その出力が所定値以外となる場合を欠陥と判断して、良品又は不良品を評価する方法である。
【００４８】
そして、作製した所定枚数の磁気ディスクに対する、グライド評価及びサーティファイ評価で良品とされた磁気ディスクの比率を求め、これを歩留まりとして評価を行った。その結果を図６に示す。
【００４９】
図６から分かるように、実施例１では放電回数の増減に係わらず、歩留まりは８５％前後を維持し、高歩留まりであることを示した。これに対し、比較例１は放電回数が６０００回まで歩留まりは７０％以上を維持するが、６０００回を越えたときから歩留まりが急激に低下することを示した。通常、放電回数が１回につき、磁気ディスク１枚が製造されることから、放電回数を増加しても高歩留まりを維持する実施例１は比較例１と比べて磁気ディスクの生産性を向上できることが示された。
（放電電圧の評価）
前記と同様に放電回数を変化させて実施例１及び比較例１の磁気ディスクを作製するときの電極間における放電電圧の評価を行った。その結果を図７に示す。
【００５０】
図７から分かるように、実施例１では放電回数の増加に係わらず、放電電圧は４４０〜４６０Ｖの範囲内でほぼ一定であることが示された。これに対し、比較例１では放電回数の増加に伴って、放電電圧が増加する傾向が示された。このため、実施例１は比較例１と比べて電極間における放電状態が安定していることが示された。
（膜厚の評価）
前記と同様に放電回数を変化させて実施例１及び比較例１の磁気ディスクに対して保護膜の膜厚を測定した。そして、放電回数が１回のときの膜厚を１とし、これに対する放電回数を変化させたときの膜厚の比率を求め、これを膜厚の変化率とし、その評価を行った。その結果を図８に示す。
【００５１】
図８から分かるように、実施例１では膜厚の変化率は１前後となり、放電回数の増加に係わらず、膜厚がほぼ一定であることが示された。これに対し、比較例１では膜厚の変化率が低下し、放電回数の増加に伴って、膜厚が薄くなる傾向が示された。比較例１で膜厚が薄くなる理由は、放電回数の増加によるターゲット表面におけるＣＨ膜の形成により、非エロージョン域が拡大し、ターゲットのスパッタリングされる領域（エロージョン域）が狭くなるためと考えられる。このため、実施例１は比較例１と比べて作製される磁気ディスクの品質が安定していることが示された。
【００５２】
なお、前記各実施形態は、次のように変更して具体化することも可能である。
・ スパッタリング装置の装置本体１１内に電極１３を１つのみ配設し、ＡＣ電源により電極１３にそれぞれ正又は負の電圧を印加して所定周波数でカソード又はアノードに変化させるとともに、装置本体１１のチャンバー壁及びシールド板をアノード又はカソードとして機能させることにより、基板１５の片面にのみ保護膜を成膜してもよい。このように構成した場合にも、極薄膜で耐久性及び耐腐食性に優れた保護膜を容易に製造することができ、製造する際の歩留まりを向上させることができる。
【００５３】
・ 各実施形態の基板１５は装置本体１１内の両電極１３間に固定されることに限定されず、両電極１３の間の中央に配設された状態で、その長手方向へ移動するように構成してもよい。このように構成すれば、装置本体１１内に連続して基板１５を投入することができる。
【００５４】
・ 図９に示すように、二組の対電極を並列に配設し、各対電極の電極１３は互いに同じ極性となるように反転させるとともに、一平面内に並列する一対の電極１３は互いに異なる極性となるように反転させるように構成してもよい。そして、基板１５を電極１３の並ぶ方向と平行に延びる方向に移動させながら、基板１５のいずれか一方の面側の電極１３のみに電圧を印加することによって、基板１５の片面だけに保護膜を形成してもよい。あるいは、全ての電極１３に電圧を印加して、基板１５の両面に保護膜を形成してもよい。このように構成した場合には所望に応じて基板１５の片面及び両面に保護膜を容易に形成することができる。
【００５５】
・ 印加する電圧の波形は正弦波、方形パルス波、極性の非対称なパルス波のいずれであってもよい。このように電圧の波形を変化させても電極１３の極性を反転させることができる。
【００５６】
さらに、本実施形態より把握できる技術的思想について以下に記載する。
・ 前記電極に電圧を印加する電源として出力周波数を調整可能な交流電源を使用し、電極の極性を所定周波数で反転させることを特徴とする請求項１から請求項４のいずれかに記載の磁気ディスクの製造方法。
【００５７】
このように構成した場合、電極の極性を所定の周波数で容易に反転させることができる。
・ 前記電極に電圧を印加する電源として直流電源を使用するとともに、この直流電源と電極の間には直流電源からの出力極性を所定間隔おきに変化させる極性変換器を接続し、電極の極性を所定周波数で反転させることを特徴とする請求項１から請求項４のいずれかに記載の磁気ディスクの製造方法。
【００５８】
このように構成した場合、電極の極性を所定の周波数で容易に反転させることができる。
【００５９】
【発明の効果】
以上詳述したように、この発明によれば、次のような効果を奏する。
請求項１に記載の発明の磁気ディスクの製造方法によれば、極薄膜で耐久性及び耐腐食性に優れた非導電性膜を容易に製造することができ、製造する際の歩留まりを向上させることができる。また、電極間における放電を安定して行うことができる。
【００６０】
請求項２に記載の発明の磁気ディスクの製造方法によれば、請求項１に記載の発明の効果に加えて、極薄膜で耐久性及び耐腐食性に優れた非導電性膜を基板の両面及び片面に容易に製造することができる。
【００６１】
請求項３に記載の発明の磁気ディスクの製造方法によれば、請求項２に記載の発明の効果に加えて、表面に微細孔等といった欠陥が少ない緻密な非導電性膜を基板の両面に成膜することができ、膜質の改善を容易かつ低コストで行うことができる。
【００６２】
請求項４に記載の発明の磁気ディスクの製造方法によれば、請求項２に記載の発明の効果に加えて、表面に微細孔等といった欠陥が少ない緻密な非導電性膜を基板の両面に同時に成膜することができ、また膜質の改善を図ることができる。
【００６４】
請求項５に記載の発明の磁気ディスクの製造方法によれば、請求項１から請求項４のいずれかに記載の発明の効果を奏する。
請求項６に記載の発明のスパッタリング装置によれば、製造する際の歩留まりを向上させつつ、極薄膜で耐久性及び耐腐食性に優れた非導電性膜を有する磁気ディスクを容易に製造することができる。また、電極間における放電を安定して行うことができる。
【図面の簡単な説明】
【図１】 スパッタリング装置を示す概念図。
【図２】 Ｉｄ／Ｉｇとメタンガス濃度との関係を示すグラフ。
【図３】 ｇピーク位置とメタンガス濃度との関係を示すグラフ。
【図４】 Ｃｏ溶出量と保護膜の膜厚との関係を示すグラフ。
【図５】 保護膜の欠点数と電極間の放電回数との関係を示すグラフ。
【図６】 歩留まりと電極間の放電回数との関係を示すグラフ。
【図７】 電極間の放電電圧と電極間の放電回数との関係を示すグラフ。
【図８】 膜厚の変化率と電極間の放電回数との関係を示すグラフ。
【図９】 別形態のスパッタリング装置を示す概念図。
【符号の説明】
１３…電極、１５…基板。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a magnetic disk in which a non-conductive film is formed on the surface of a magnetic disk substrate in a magnetic disk used for an information recording apparatus, particularly a magnetic recording medium such as a hard disk.
[0002]
[Prior art]
Conventionally, a magnetic disk used for the magnetic recording medium as described above has a plurality of films such as a base film sequentially formed on the surface of a substrate for the magnetic disk, and then a magnetic film is formed on the surface. It is made by. When information is written or read by a magnetic head that moves while floating on the magnetic disk with respect to this magnetic film, foreign matter may enter between the magnetic head and the magnetic film and damage the magnetic film. . In addition, since the magnetic film is made of metal, it may be corroded by oxidation or the like depending on the use environment. Further, the movement of the magnetic head becomes unstable due to the frictional force generated between the magnetic head and the magnetic film, and the magnetic head may collide with the surface of the magnetic film. In order to prevent such damage and oxidation of the magnetic film, a protective film as a non-conductive film having wear resistance, impact resistance and corrosion resistance is formed on the surface thereof. This protective film is formed to be a very thin film by a sputtering method using a sputtering apparatus in order to shorten the distance between the magnetic film and the magnetic head and improve the recording density of the magnetic disk.
[0003]
The sputtering apparatus includes a pair of electrodes arranged opposite to each other in the apparatus main body and a chamber wall disposed so as to surround the electrodes, and a substrate on which a magnetic film is formed is supported between the electrodes. . Then, when a process gas such as argon gas is introduced into the sealed apparatus body and a negative voltage is applied to both electrodes using a direct current (DC) power source, glow discharge is generated with both electrodes serving as cathodes and the chamber wall serving as an anode. Is generated, and the process gas is turned into plasma between both electrodes. At this time, positive ions in the plasma collide with the target attached to the electrode surface, the target surface is sputtered, and the sputtered target component adheres to and deposits on the magnetic film surface to form a protective film. The
[0004]
[Problems to be solved by the invention]
However, according to the sputtering method, the target component may adhere to not only the surface of the magnetic film but also the target surface and the chamber wall surface to form a film. When the DC power source is used in this state, if the film formed on the surface of the target and the chamber wall is non-conductive, the film is charged with a negative charge or a positive charge, and an arc is eventually generated. Due to the generation of this arc, the generation of plasma between the two electrodes becomes unstable, and a part of the target melts due to the thermal collision caused by arcing and adheres to the substrate as a droplet. The non-conductive film deposited in the non-erosion region of the metal adheres to the substrate due to thermal shock at the time of dielectric breakdown due to arc.
[0005]
If an ultra-thin protective film is formed under these circumstances, the yield when manufacturing a magnetic disk is reduced due to foreign matter adhering to the protective film, and at the same time, the target component is uniformly deposited on the surface of the magnetic film. The hardness of the protective film is reduced and wear resistance is reduced, and the film density is insufficient and micropores are formed on the surface of the protective film, resulting in reduced corrosion resistance. There was a problem of deterioration. In addition to the sputtering method, there is a method of forming a protective film by a chemical vapor deposition (CVD) method. In the case of an insulating substrate, the CVD method must provide a conductive film on the surface of the substrate. There are problems that the manufacturing time becomes long and it is difficult to reduce the manufacturing cost.
[0006]
The present invention has been made paying attention to the problems existing in the prior art as described above. The object is to manufacture a magnetic disk capable of easily producing a non-conductive film having excellent durability and corrosion resistance with an ultra-thin film, and to improve the yield in production, and to it. It is to provide a sputtering apparatus to be used.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, the invention of the magnetic disk manufacturing method according to claim 1 is characterized in that, after forming at least a magnetic film on the surface of the substrate, sputtering is performed on the magnetic film using a sputtering apparatus. A method of manufacturing a magnetic disk for forming a conductive film, which is a protective film as a non-conductive film using a sputtering apparatus provided with an electrode to which a target is attached and whose polarity is reversed so that the polarity is reversed FormIn addition, the polarity of the electrode is inverted at a frequency of 1 to 100 kHz.It is characterized by this.
[0008]
According to a second aspect of the present invention, there is provided a magnetic disk manufacturing method according to the first aspect, wherein at least one pair of counter electrodes each including a pair of electrodes facing each other is disposed in the sputtering apparatus. A substrate is disposed between the electrodes, and the non-conductive film is formed by changing the polarity of the pair of electrodes constituting the counter electrode so as to be reversed.
[0009]
According to a third aspect of the present invention, there is provided a magnetic disk manufacturing method according to the second aspect, wherein if one of the counter electrodes is an anode, the other electrode is a cathode, and if one electrode is a cathode, Both electrodes are changed so as to have different polarities so that the other electrode becomes an anode.
[0010]
According to a fourth aspect of the present invention, there is provided a magnetic disk manufacturing method according to the second aspect, wherein if one of the counter electrodes is an anode, the other electrode is an anode, and if one electrode is a cathode, The two electrodes are changed so as to have the same polarity so that the other electrode also becomes a cathode.
[0012]
  Claim5The invention of the magnetic disk manufacturing method according to claim 1 to claim 1.4In any one of the inventions, the protective film is any one of a carbon film, a hydrocarbon film, a silicic acid film, and a silicon carbide film.
  Claim6According to the invention of the sputtering apparatus, a protective film as a non-conductive film of a magnetic disk having at least a magnetic film on the surface of the substrate and a non-conductive film formed on the magnetic film is formed by sputtering. A sputtering apparatus for carrying out a process comprising an electrode that is attached so that the polarity is reversed while the target is attachedThe polarity of this electrode is configured to reverse at a frequency of 1 to 100 kHz.It is characterized by that.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
The first embodiment of the present invention will be described in detail below.
[0014]
A magnetic disk is manufactured from a disk-shaped substrate, a seed layer, an underlayer and a magnetic film formed in order from the surface of the substrate, and a protective film as a non-conductive film formed on the surface of the magnetic film. ing. Furthermore, a lubricating layer made of a perfluoropolyether-based lubricant may be formed on the surface of the protective film.
[0015]
The substrate is made of an inorganic material such as soda lime glass, aluminosilicate glass, borosilicate glass, and other non-magnetic materials such as crystallized glass other than glass, ceramics, metal such as aluminum, or ferri It is preferable to use a material having magnetism and ferromagnetism. The substrate material having ferrimagnetism and ferromagnetism is based on the inorganic material and organic material such as synthetic resin as a base material, and the base material is a strong metal such as a single metal such as iron, cobalt, nickel, and alloys thereof. It can be obtained by dispersing a magnetic material, such as a ferrimagnetic material such as ferrite. Among these materials, glass is preferable as a substrate for a magnetic disk because it is more rigid than aluminum and does not cause deformation of the substrate due to impact.
[0016]
The seed layer, the underlayer and the magnetic film are made of metal as a material and are formed by sputtering or chemical vapor deposition (CVD). Specifically, the seed layer is nickel (Ni) -aluminum (Al) layer, the underlayer is chromium (Cr) -molybdenum (Mo) layer, and the magnetic film is cobalt (Co) -platinum (Pt). Examples thereof include a chromium (Cr) -tantalum (Ta) film.
[0017]
The protective film is formed on the surface of the magnetic film by a sputtering method using a sputtering apparatus described later. The material of the protective film is preferably a material having high durability so that it can withstand the impact force when the magnetic head is landed. In addition, in order to prevent the magnetic film formed of metal from being oxidized, those having high corrosion resistance are preferable. Protective films that satisfy these conditions include carbon (C) films, hydrocarbon (CH) films, and silicic acid (SiO₂) Film, silicon carbide (SiC) film, and the like. In this embodiment, a hydrocarbon film is used as the protective film.
[0018]
Next, a sputtering apparatus for forming the protective film will be described.
As shown in FIG. 1, an apparatus main body 11 constituting a sputtering apparatus is formed in a square box shape, and a space inside the apparatus main body 11 is a film forming chamber 12. In the center of the film forming chamber 12, a pair of electrodes 13 are arranged facing each other with a predetermined distance therebetween, and these electrodes 13 constitute a counter electrode. A chamber wall and a shield plate (not shown) are disposed in the film forming chamber 12 so as to surround the pair of electrodes 13. A carbon target 14 serving as a material for the protective film is attached to the inner surface of each electrode 13. At the center of both targets 14, a substrate 15 having a magnetic film formed on its surface is supported so that the surface of the magnetic film, that is, the surface on which the protective film is formed faces the target 14.
[0019]
A plurality of gas introduction pipes 16 are connected to the apparatus main body. The film formation chamber 12 is sealed with the substrate 15 accommodated in the apparatus main body 11, and a process gas is introduced into the film formation chamber 12 from the gas introduction pipe 16. This process gas includes argon (Ar) gas, Ar and methane (CH_FourGas), Ar and hydrogen (H₂) And the like. A flow rate regulator (not shown) is connected to the gas introduction pipe 16 to adjust the supply amount of the process gas, the mixture concentration, and the like. In addition, a vacuum exhaust pump (not shown) is connected to the apparatus main body 11, and the inside of the film forming chamber 12 is decompressed by exhausting process gas, air, and the like from the sealed film forming chamber 12.
[0020]
A power source 17 disposed outside the apparatus main body 11 is connected to both electrodes 13. The power source 17 is an alternating current (AC) power source whose output frequency is adjustable. By applying a positive or negative voltage to each electrode using this AC power source, if one electrode 13 is an anode (anode), the other electrode 13 is a cathode (cathode), and if one electrode 13 is a cathode, Both electrodes 13 are changed so as to have different polarities at a predetermined frequency so that the other electrode 13 becomes an anode, and are polarized. A glow discharge occurs between the electrodes 13 to which a voltage is applied, and the process gas is turned into plasma by the glow discharge. Although a direct current (DC) power supply can be used as the power supply, in this case, a polarity converter that converts a voltage output from the DC power supply into a positive voltage or a negative voltage at a predetermined interval is connected and output. It is necessary to change the polarity.
[0021]
The polarity of the electrode 13 is preferably reversed at a frequency of 1 to 100 kHz. When the polarity of the electrode 13 is reversed at a frequency lower than 1 kHz, the effect of removing the positive charge accumulated on the non-conductive film deposited on the non-sputtered region (non-erosion region) on the surface of the target 14 is weakened, and the arc Is likely to occur and the glow discharge becomes unstable. Further, when the reversal is performed at a frequency higher than 100 kHz, the drive of the power source 17 becomes unstable, and the generation of glow discharge between the electrodes 13 becomes unstable.
[0022]
Next, a method for forming a protective film using a sputtering apparatus will be described.
As shown in FIG. 1, the substrate 15 has a seed layer, an underlayer, and a magnetic film formed in order from the surface side of the substrate 15 on the surface by CVD or sputtering. Are arranged so as to be located in the center between the electrodes 13. Subsequently, Ar gas, CH in the film forming chamber 12_FourGas, H₂While introducing the gas, the process gas, air, and the like are exhausted by a vacuum exhaust pump to reduce the pressure in the film forming chamber 12. Then, when a positive or negative voltage is alternately applied to each electrode 13 by an AC power source, both electrodes 13 are alternately changed to a cathode and an anode at a predetermined frequency, and a glow discharge is generated between both electrodes 13 before long. Ar gas in the film forming chamber 12 is in a plasma state.
[0023]
In this state, at the moment when one of the electrodes 13 becomes the cathode, argon ions (Ar⁺) Moves toward the cathode side. Ar⁺The ions collide with the surface of the target 14 during the movement, and the target 14 is sputtered to repel carbon (C) atoms as the target component. The repelled C atoms are CH in the process gas._FourInducer or H₂By reacting with this, it becomes a hydrocarbon which is a non-conductive substance, and this hydrocarbon adheres to the surface of the magnetic film and is deposited, whereby a protective film is formed on the surface of the substrate 15 on the cathode side.
[0024]
When the protective film is formed, hydrocarbons adhere to the non-erosion region of the target 14, and a hydrocarbon film is also formed in the non-erosion region. This film has Ar on its surface.⁺Ions are accumulated and charged to a positive charge, and when the amount of charge exceeds a predetermined amount, the dielectric breakdown region is reached, and the positive charge on the surface of the film and the negative charge on the surface of the target 14 pass through the inside of the film. Try to generate an arc. Here, the dielectric breakdown region is defined by the coulomb amount of charge accumulated on the surface of the insulating film and the thickness of the insulating film because the strength of the dielectric breakdown is defined by kV / mm. . In addition to this, depending on the amount of positive charge and the thickness of the film, that is, the distance between the positive charge and the negative charge, the positive charge on the surface of the film and the negative charge on the surface of the target 14 are passed through the inside of the film. Without trying to generate an arc. However, at the moment when the electrode 13 that was the cathode becomes the anode, electrons in the plasma are attracted to the anode and accumulated Ar.⁺The ions on the surface of the film in the non-erosion region are removed by static elimination.⁺Ion accumulation is suppressed.
[0025]
Then, the protective films are formed on both surfaces of the substrate 15 by reversing the polarity of the electrodes 13 so that the polarities are alternately inverted at a predetermined frequency. The formed protective film is a dense film with few defects such as fine holes on the surface.
[0026]
Here, the reason why the protective film becomes a dense film with few defects will be described. In general, when a substrate is placed in a floating state in the center of a pair of opposing cathodes, a sputtered target component adheres to the substrate surface, and at the same time, electrons are accumulated and charged with a negative charge, thereby generating a self-bias. . Since this self-bias is negative, Ar in the plasma⁺Ions are attracted and collide with the substrate surface. This Ar⁺Since the collision of ions with the substrate surface occurs simultaneously with the deposition of the sputtered target component, the migration of the target component occurs on the substrate surface due to the energy at the time of the collision. By this migration, the target components are rearranged so as to fill in the defective portions. This phenomenon is called an ion assist effect, and a film formed by the ion assist effect is a dense film with few defects.
[0027]
When positive and negative voltages are alternately applied to both opposing electrodes 13 as in the present invention to form an anode and a cathode, electrons and Ar are collected between both electrodes 13 and the probability of collision increases. . Then, Ar in the plasma⁺As the density of ions and electrons increases, the self-bias potential generated on the surface of the substrate 15 increases, and Ar present in the vicinity of the substrate 15⁺The number of ions also increases. For this reason, when the electrodes 13 are alternately used as the anode and the cathode, it is considered that the above-described ion assist effect is greatly extracted.
[0028]
In addition, when the frequency for reversing the polarity is increased, electrons move between both electrodes 13 following the frequency, whereas Ar has a larger mass than the electrons.⁺Ions cannot move between the electrodes 13 following the frequency. Adjust the frequency based on this idea, Ar⁺If the amount of ion movement is controlled, Ar⁺It is possible to increase the collision probability between the ions and the surface of the substrate 15 and to further increase the ion assist effect. However, Ar against the substrate 15⁺Since the protective film formed on the surface of the substrate 15 may be sputtered when the ion collision energy is too large, fine adjustment of the frequency is required.
[0029]
The effects exhibited by the first embodiment will be described below.
-By reversing the polarity of the pair of electrodes 13 arranged opposite to each other in the apparatus main body 11 of the sputtering apparatus, abnormal discharge can be reduced and the quality of the protective film can be improved. In addition, a high-quality protective film having excellent corrosion resistance can be easily manufactured, and the yield in manufacturing can be improved.
[0030]
By inverting both electrodes alternately so as to have different polarities, even if the material of the substrate 15 is a non-conductive material such as glass, ions are generated by the self-bias generated on the surface of the substrate 15 by the plasma. The assist effect can be brought out effectively. Therefore, a dense protective film with few defects such as micropores can be formed on the surface, and the film quality can be improved easily and at low cost.
[0031]
-Since the frequency for reversing the polarity of the electrode 13 is set within the range of 1 to 100 kHz, the discharge between the electrodes 13 can be performed stably.
(Second Embodiment)
The second embodiment of the present invention will be described in detail below. Note that the second embodiment will be described with a focus on differences from the first embodiment.
[0032]
In the sputtering apparatus of the second embodiment, if one electrode 13 of the pair of electrodes 13 is an anode, the other electrode 13 is also an anode, and if one electrode 13 is a cathode, the other electrode 13 is also a cathode. Both electrodes 13 are configured to change to the same polarity at a predetermined frequency.
[0033]
In the sputtering apparatus according to the second embodiment, when a positive or negative voltage is simultaneously applied to the pair of electrodes 13 by an AC power source, both electrodes 13 are simultaneously changed to a cathode or an anode at a predetermined frequency. Glow discharge occurs in the meantime, and the Ar gas in the film forming chamber 12 becomes a plasma state.
[0034]
The moment when both electrodes 13 become cathodes in this state, Ar⁺Ions move toward both cathodes, the target is sputtered, and protective films are simultaneously formed on both surfaces of the substrate 15. Ar accumulated in the non-erosion film on the surface of the target 14⁺Ions are neutralized at the moment when both electrodes 13 become anodes.
[0035]
When both electrodes 13 are changed so as to have the same polarity, the chamber wall and the shield plate of the apparatus body 11 function as an anode at the moment when both electrodes 13 become cathodes. At this time, electrons in the plasma are accumulated on the chamber wall and the shield plate. The electrons accumulated in the chamber wall and the shield plate optimize the frequency at which the polarities of both electrodes 13 are reversed, and Ar⁺Adjusting the amount of ion movement to the chamber wall and shield plate Ar⁺Static electricity is removed by moving ions.
[0036]
Therefore, according to the sputtering apparatus of the second embodiment, the protective film can be simultaneously formed on both surfaces of the substrate 15.
[0037]
【Example】
Hereinafter, the first embodiment will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited to those Examples.
Example 1
A Ni—Al seed layer, a Cr—Mo underlayer, and a Co—Pt—Cr—Ta magnetic film were sequentially formed on the surface of the aluminosilicate glass substrate by sputtering. Next, Ar and CH are formed on the surface of the magnetic film._FourA protective film was formed by sputtering under a mixed gas atmosphere. An AC power source was used as a power source for the sputtering apparatus, and the polarity of both electrodes was reversed at a frequency of 40 kHz. This was used as the sample of Example 1.
(Comparative Example 1)
A Ni—Al seed layer, a Cr—Mo underlayer, and a Co—Pt—Cr—Ta magnetic layer were sequentially formed on the surface of the aluminosilicate glass substrate by sputtering. Next, Ar and CH are formed on the surface of the magnetic film._FourA protective film was formed by sputtering under a mixed gas atmosphere. A DC power source was used as the power source of the sputtering apparatus. This was used as a sample of Comparative Example 1.
(Evaluation of film quality)
Ar and CH_FourCH in mixed gas_FourMagnetic disks of Example 1 and Comparative Example 1 were manufactured with various gas concentrations. By measuring Raman scattering light with a Raman spectrophotometer on the protective film of the magnetic disk thus obtained, the Id / Ig and g peak positions, which are the ratio of sp2 bonds to sp3 bonds in the film, are obtained. Asked. The result is shown. Based on this result, the optimum conditions for producing the protective film were determined.
[0038]
Here, Id / Ig and g peak positions will be described. When the hydrocarbon film is measured with a Raman spectrophotometer, 1350 cm^-1D peak with a peak in the vicinity (disorder band) and 1570 cm^-1Two peaks, a g peak with a peak in the vicinity, appear. The heights of the d and g peaks from the baseline are called Id and Ig, respectively. From the paper which the present inventors referred to when evaluating the film quality from the Id / Ig and g peak positions, the CH where the Id / Ig and g peak positions show the minimum values._FourProducing a protective film with a gas concentration is considered to have the highest film hardness and improved wear resistance {J. Vac. Sci. Tech. A16 (5), 1988, p2941, IEEE TRANS. ON MAG. , Vol. 33, no. 5, 1997, p3148, IEEE TRANS. ON MAG. , Vol. 33, no. 5, 1997, p3109, IEICE Technical Report MR92-68, CPM92-145 (1992-12)}.
[0039]
According to these papers, the d peak shows the vibration of the bond near the carbon at the end of the graphite crystallite, that is, the peak due to the sp3 bond. The shift of this d peak toward the low wavenumber side indicates the asymmetry of the bond and 4 It means that the coordination bond increases, and it is said that it is differentiated into a crystalline phase and an amorphous phase. The g peak shows in-plane vibration of graphite, that is, a peak due to sp2 bonds, and shifting this g peak to the low wavenumber side means that the symmetry of the bond angle is reduced. Is said to become amorphous-like.
[0040]
It is said that the decrease in the value of Id / Ig is related to an increase in sp3 binding in the film and a decrease in the size or number of sp2 crystallites. A hydrocarbon film has a structure in which a plurality of microcrystals composed of sp2 bonds are connected by sp3 bonds. When a hydrogen component is added to this, the sp3 bond part grows, and a molecular group (cluster) composed of sp2 bonds. The separation of each other proceeds, and excess hydrogen in the membrane is -CH₂-It is believed that polymerization is promoted by increasing the bonds.
[0041]
This result shows that the smaller the g peak position is, the smaller the Id / Ig is, the smaller the sp2 cluster size and the smaller the sp2 crystallite size or number, so that more small clusters are bonded together, which is desirable for improving the film quality. It suggests. For this reason, the inventors of the present invention have a CH value where the Id / Ig and g peak positions are minimum values._FourThe gas flow rate was optimized for the production of the protective film.
[0042]
As can be seen from FIGS. 2 and 3, Example 1 shows the CH in the mixed gas._FourThe gas concentration was 2%, and the Id / Ig and g peak positions showed minimum values. In contrast, Comparative Example 1 is CH_FourWhen the gas concentration was 4% and Id / Ig was 3.3%, the g peak position showed the minimum value. The Id / Ig, g peak position and film density (g / cm in Example 1 and Comparative Example 1 under the optimum conditions thus determined.^Three) And are summarized in Table 1. Note that the thickness of the formed protective film was 5 nm.
[0043]
[Table 1]

As shown in Table 1, Example 1 showed smaller values of Id / Ig and g peak positions than Comparative Example 1. Moreover, the density showed a high value. The reason why the density of the film is increased is considered to be due to the ion assist effect described above. From this result, it was shown that the magnetic disk had a high quality protective film.
(Evaluation of corrosion resistance)
The magnetic disks of Example 1 and Comparative Example 1 were manufactured by changing the thickness of the protective film by adjusting the discharge power (discharge voltage × discharge current) of the power source. The magnetic disk thus obtained was left in a constant temperature and humidity chamber at 80 ° C. and 80% for 90 hours, and then immersed in ultrapure water to dissolve the Co-based corrosion salt as the material of the magnetic film. A solution was obtained. The solution was analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to measure the amount of Co elution and evaluate the corrosion resistance. The result is shown in FIG.
[0044]
As can be seen from FIG. 4, the Co elution amount increases as the thickness of the protective film decreases, but the magnetic disk of Example 1 has a smaller Co elution amount as a whole than that of Comparative Example 1. Indicated. Co in the magnetic film is eluted through the micropores formed in the protective film. For this reason, Example 1 has a smaller number of micropores formed than Comparative Example 1, and the density of the protective film is considered to be high, indicating that the magnetic disk has high corrosion resistance.
(Evaluation of defects)
A protective film was formed by changing the number of discharges of the power supply variously, and magnetic disks of Example 1 and Comparative Example 1 were produced. The entire surface of the protective film of the magnetic disk thus produced was measured with a defect detector and evaluated. In this defect detector, laser light is incident on a magnetic disk rotating at a predetermined rotational speed from an oblique direction, and the amount of change in reflected light and scattered light due to a foreign object is detected by a detector. The result is shown in FIG.
[0045]
As can be seen from FIG. 5, in Example 1, the increase in the number of defects with the increase in the number of discharges was hardly observed, and the number of defects was 50, as in the case of one discharge. there were. On the other hand, Comparative Example 1 showed that the number of defects suddenly increased when the number of discharges exceeded 3000. The number of defects is correlated with the number of arcs generated during abnormal discharge, and it is considered that defects occur due to arcs. For this reason, it is considered that the arc generation in Example 1 is less than that in Comparative Example 1, and it was shown that a magnetic disk free from defects can be manufactured stably.
(Evaluation of yield)
Glide evaluation and certification evaluation were performed on the magnetic disks of Example 1 and Comparative Example 1 manufactured by changing the number of discharges in the same manner as described above.
[0046]
For glide evaluation, the magnetic disk is mounted on the spindle of the hard disk device, and the magnetic head is rotated with respect to the entire surface of the magnetic disk while the magnetic disk is rotated so that the magnetic head with the piezoelectric element floats at a height of 10 nm from the surface of the magnetic disk By performing a seek operation. If there are protrusions on this magnetic disk, the magnetic head will collide with the protrusions, so this impact is detected by a piezo element, and when the output reaches a predetermined value, it is determined that there is a foreign object, This is a method for evaluating a non-defective product or a defective product based on the presence or absence of foreign matter.
[0047]
In the certification evaluation, a magnetic head with an MR element is used, and the magnetic head is subjected to a seek operation over the entire surface of the magnetic disk in the same manner as the glide evaluation. During this seek operation, a signal is written on the magnetic disk at a predetermined frequency, and this signal is reproduced by an MR element. When this signal is reproduced, for example, if the foreign matter attached to the magnetic disk is removed and a recess is formed, the signal is missing or lowered. This is a method in which the absence or decrease of this signal is detected by an MR element, and when the output is other than a predetermined value, it is judged as a defect and a non-defective product or a defective product is evaluated.
[0048]
Then, the ratio of magnetic disks determined to be non-defective by glide evaluation and certification evaluation with respect to a predetermined number of magnetic disks manufactured was obtained, and evaluation was performed using this as a yield. The result is shown in FIG.
[0049]
As can be seen from FIG. 6, in Example 1, the yield was maintained at around 85% regardless of the increase or decrease in the number of discharges, indicating that the yield was high. On the other hand, in Comparative Example 1, the yield was maintained at 70% or more until the number of discharges was 6000, but the yield decreased rapidly after exceeding 6000. Normally, one magnetic disk is manufactured per discharge, so that the first embodiment that maintains a high yield even if the number of discharges is increased can improve the productivity of the magnetic disk as compared with the first comparative example. It has been shown.
(Evaluation of discharge voltage)
In the same manner as described above, the discharge voltage between the electrodes when the magnetic disks of Example 1 and Comparative Example 1 were produced by changing the number of discharges was evaluated. The result is shown in FIG.
[0050]
As can be seen from FIG. 7, in Example 1, the discharge voltage was shown to be substantially constant within the range of 440 to 460 V regardless of the increase in the number of discharges. On the other hand, in Comparative Example 1, there was a tendency that the discharge voltage increased as the number of discharges increased. For this reason, it was shown that the discharge state between the electrodes of Example 1 was more stable than that of Comparative Example 1.
(Evaluation of film thickness)
In the same manner as described above, the thickness of the protective film was measured for the magnetic disks of Example 1 and Comparative Example 1 by changing the number of discharges. Then, the film thickness when the number of discharges was 1 was set to 1, and the ratio of the film thickness when the number of discharges was changed was obtained, and this was set as the rate of change of the film thickness. The result is shown in FIG.
[0051]
As can be seen from FIG. 8, in Example 1, the change rate of the film thickness was around 1, indicating that the film thickness was almost constant regardless of the increase in the number of discharges. On the other hand, in Comparative Example 1, the rate of change in film thickness decreased, and the tendency for the film thickness to decrease with increasing number of discharges was shown. The reason why the film thickness is reduced in Comparative Example 1 is considered to be because the non-erosion region is expanded and the target sputtering region (erosion region) is narrowed by the formation of the CH film on the target surface due to the increase in the number of discharges. . For this reason, it was shown that the quality of the magnetic disk produced in Example 1 is more stable than that in Comparative Example 1.
[0052]
In addition, each said embodiment can also be changed and actualized as follows.
Only one electrode 13 is provided in the apparatus main body 11 of the sputtering apparatus, and a positive or negative voltage is applied to the electrode 13 by an AC power source to change the cathode or anode at a predetermined frequency. A protective film may be formed only on one surface of the substrate 15 by causing the chamber wall and the shield plate to function as an anode or a cathode. Even in such a configuration, it is possible to easily manufacture a protective film that is an extremely thin film and has excellent durability and corrosion resistance, and it is possible to improve the yield in manufacturing.
[0053]
The substrate 15 of each embodiment is not limited to being fixed between both electrodes 13 in the apparatus main body 11, and is moved in the longitudinal direction in a state of being disposed in the center between both electrodes 13. It may be configured. If comprised in this way, the board | substrate 15 can be thrown in in the apparatus main body 11 continuously.
[0054]
As shown in FIG. 9, two pairs of counter electrodes are arranged in parallel, the electrodes 13 of each counter electrode are inverted so that they have the same polarity, and the pair of electrodes 13 arranged in parallel in one plane You may comprise so that it may invert so that it may become a different polarity. Then, while moving the substrate 15 in a direction extending in parallel with the direction in which the electrodes 13 are arranged, a voltage is applied only to the electrode 13 on one surface side of the substrate 15, whereby a protective film is applied only to one surface of the substrate 15. It may be formed. Alternatively, a protective film may be formed on both surfaces of the substrate 15 by applying a voltage to all the electrodes 13. When configured in this manner, a protective film can be easily formed on one side and both sides of the substrate 15 as desired.
[0055]
-The voltage waveform to be applied may be a sine wave, a square pulse wave, or an asymmetric pulse wave. Thus, even if the voltage waveform is changed, the polarity of the electrode 13 can be reversed.
[0056]
Further, technical ideas that can be grasped from this embodiment will be described below.
5. The magnetism according to claim 1, wherein an AC power source capable of adjusting an output frequency is used as a power source for applying a voltage to the electrode, and the polarity of the electrode is inverted at a predetermined frequency. Disc manufacturing method.
[0057]
When configured in this manner, the polarity of the electrode can be easily reversed at a predetermined frequency.
A DC power source is used as a power source for applying a voltage to the electrode, and a polarity converter is connected between the DC power source and the electrode to change the output polarity from the DC power source at predetermined intervals. 5. The method of manufacturing a magnetic disk according to claim 1, wherein the magnetic disk is inverted at a predetermined frequency.
[0058]
When configured in this manner, the polarity of the electrode can be easily reversed at a predetermined frequency.
[0059]
【The invention's effect】
  As described in detail above, the present invention has the following effects.
  According to the magnetic disk manufacturing method of the first aspect of the present invention, it is possible to easily manufacture a non-conductive film having excellent durability and corrosion resistance with an ultra-thin film, and to improve the yield in manufacturing. be able to.Moreover, the discharge between electrodes can be performed stably.
[0060]
According to the method for manufacturing a magnetic disk of the invention described in claim 2, in addition to the effect of the invention described in claim 1, a non-conductive film having excellent durability and corrosion resistance is formed on both surfaces of the substrate. And can be easily manufactured on one side.
[0061]
According to the method for manufacturing a magnetic disk of the invention described in claim 3, in addition to the effect of the invention described in claim 2, a dense non-conductive film having few defects such as fine holes on the surface is formed on both surfaces of the substrate. A film can be formed, and the film quality can be improved easily and at low cost.
[0062]
According to the method for manufacturing a magnetic disk of the invention described in claim 4, in addition to the effect of the invention described in claim 2, a dense non-conductive film having few defects such as micropores on the surface is formed on both surfaces of the substrate. A film can be formed at the same time, and the film quality can be improved.
[0064]
  Claim5According to the method of manufacturing a magnetic disk of the invention described in claim 1 to claim 1.4The effect of the invention described in any of the above is achieved.
  Claim6According to the sputtering apparatus of the invention described in (1), it is possible to easily manufacture a magnetic disk having a non-conductive film with excellent durability and corrosion resistance while improving the yield in manufacturing.Moreover, the discharge between electrodes can be performed stably.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a sputtering apparatus.
FIG. 2 is a graph showing the relationship between Id / Ig and methane gas concentration.
FIG. 3 is a graph showing the relationship between g peak position and methane gas concentration.
FIG. 4 is a graph showing the relationship between the amount of Co elution and the thickness of the protective film.
FIG. 5 is a graph showing the relationship between the number of defects of a protective film and the number of discharges between electrodes.
FIG. 6 is a graph showing the relationship between yield and the number of discharges between electrodes.
FIG. 7 is a graph showing the relationship between the discharge voltage between electrodes and the number of discharges between electrodes.
FIG. 8 is a graph showing the relationship between the rate of change in film thickness and the number of discharges between electrodes.
FIG. 9 is a conceptual diagram showing a sputtering apparatus according to another embodiment.
[Explanation of symbols]
13 ... Electrode, 15 ... Substrate.

Claims (6)

A method of manufacturing a magnetic disk, wherein after forming at least a magnetic film on a surface of a substrate, a non-conductive film is formed on the magnetic film by sputtering using a sputtering apparatus,
While forming a protective film as a non-conductive film using a sputtering apparatus provided with an electrode that is reversed so that the polarity is reversed while the target is attached ,
A method of manufacturing a magnetic disk, wherein the polarity of the electrode is inverted at a frequency of 1 to 100 kHz .   In the sputtering apparatus, at least one pair of counter electrodes made of a pair of electrodes facing each other is disposed, a substrate is disposed between the counter electrodes, and the polarities of the pair of electrodes constituting the counter electrode are reversed. The method of manufacturing a magnetic disk according to claim 1, wherein the non-conductive film is formed by changing to a magnetic field.   If one of the counter electrodes is an anode, the other electrode is a cathode, and if one electrode is a cathode, the other electrode is an anode. The method of manufacturing a magnetic disk according to claim 2, wherein:   If one of the counter electrodes is an anode, the other electrode is also an anode, and if one electrode is a cathode, the other electrode is also a cathode. The method of manufacturing a magnetic disk according to claim 2, wherein: 5. The magnetism according to claim 1 , wherein the protective film is any one of a carbon film, a hydrocarbon film, a silicic acid film, and a silicon carbide film. Disc manufacturing method. A sputtering apparatus for forming a protective film as a non-conductive film of a magnetic disk having at least a magnetic film on a surface of a substrate and a non-conductive film formed on the magnetic film by sputtering,
A sputtering apparatus characterized by comprising an electrode that is reversed so that the polarity is reversed while the target is attached, and the polarity of the electrode is reversed at a frequency of 1 to 100 kHz.

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