JP3596543B2 - Stamper, method of manufacturing the same, optical disk and blanks - Google Patents

Description

【００４１】
（但し、ρは比重、Ｃは比熱、ｋは熱伝導率を示し、それぞれｐは溶融樹脂、ｍはダイレクトスタンパーを表す。また、Ｔｐｏは溶融樹脂の温度、Ｔｍｏはダイレクトスタンパーの初期温度である。）
成形条件によっても異なるが、従来のニッケルダイレクトスタンパーを用いた場合のＤＶＤ−ＲＯＭディスクの一例では、スタンパーが取り付けられる成形機の金型の温度は１００℃で、溶融樹脂の温度は３６０℃に設定されている。溶融樹脂がスタンパー表面に接触した時の溶融樹脂の界面の温度Ｔは、ニッケルの熱伝導率が樹脂に比べ遥かに大きいため、ほとんどスタンパーの初期温度を維持し、１１０℃以下になる。そのため、溶融樹脂はスタンパー表面に接触した瞬間から冷却固化し始める。
【００４２】
本実施例のように、有機ポリマーからなる架橋性物質とフォトレジストがニッケルのダイレクトスタンパーの表面を形成しているものでは、溶融樹脂の界面の温度は上記の場合より上昇する。架橋性物質及びフォトレジストとダイレクトスタンパー表面の材料の比重、比熱および熱伝導率に差がない場合、上記の温度設定では溶融樹脂の界面の温度Ｔは約２３０℃になる。本実施例では、架橋性物質の下にヒートシンクとしてのニッケルがあるので、温度は２３０℃以下に下がると思われる。しかし、いずれにしても、本実施例でのダイレクトスタンパーは、前述したように、第２の架橋性物質の突起部は架橋により耐熱温度が２５０℃以上になっているので成形時の熱で劣化することがない。
【００４３】
（実施の形態２）
実施の形態２は、図１（Ｉ）に示す、架橋性物質１２の層とフォトレジストの突起１８の架橋を更に促進する方法（第２の架橋反応）の部分以外は、実施の形態１と同様である。この方法は、図１（Ｈ）に示す現像後の架橋性物質１２とフォトレジストの突起１８に、紫外線照射と、ベーキング処理を施すことにより、架橋性物質１２とフォトレジストの突起１８に第２の架橋反応を促進する。本件で言う紫外線は遠紫外線を含んだものである。
【００４４】
ここでフォトレジストが、化学増幅型レジストの場合は、紫外線照射後にベーキングすることにより第２の架橋反応が促進される。
【００４５】
また、フォトレジストが、化学増幅型以外のノボラック系樹脂の場合は、ベーキングによりレジスト中の水分を無くした状態で遠紫外線を照射すると第２の架橋反応が効果的に進行する。
【００４６】
本発明の実施の形態２では、フォトレジストに化学増幅型を用い、現像後の基盤に波長が２５４ｎｍの遠紫外線を照射し、その後、１５０〜２５０℃の間で１０〜２０分の間ベーキング処理を行なった。
【００４７】
この場合も実施の形態１と同様に、架橋性物質とフォトレジストの突起部の相互の架橋及び夫々の架橋が進行し、基盤全体の耐熱温度は２５０℃以上であった。この場合もレジスト突起１８は第２の架橋で少しシュリンクする。しかし、更に２５０〜３００℃の高温に曝しても更なる形状変化は確認されなかった。
【００４８】
（実施の形態３）
実施の形態３は、架橋性物質にフォトレジストと同じ物質を用いる以外は、実施の形態１と同様である。架橋性物質にフォトレジストと同じ材料を用いると、両者間の架橋がより起こりやすくなり、両者間の接着強度がさらに増加する。また、熱膨張係数も同じであるので、成形時に熱変化を繰り返し受けても境界面でせん断歪が発生せず、熱変化による耐性がより強くなる。本実施例では、どちらもノボラック型のフェノール樹脂をベースにしたポリマーを用いた。
【００４９】
（実施の形態４）
実施の形態４は、架橋性物質に光反射防止膜機能をもつ材料を用いる以外は、実施の形態１と同様である。図２は架橋性物質に光反射防止膜機能をもつ材料を用いた時の露光の状態を説明する概念図である。
【００５０】
図２において、基盤１１とフォトレジスト１３の間の架橋性物質２１は反射防止の機能を有する膜である。基盤１は、ニッケルなどの高反射率の材料であるので、実施の形態１におけるレーザ記録の際、反射光は定在波を生じる。レーザ波長をλ、架橋性物質２１およびフォトレジスト１３の屈折率と膜厚をそれぞれｎｃ，ｄｃおよびｎｒ，ｄｒとし、その関係を数２の式で示す。
【００５１】
【数２】

【００５２】
この数２の式が成り立つの時、レーザの定在波の節がフォトレジスト１３の中に存在することになる。その場合、現像後のフォトレジスト１３の突起の形状は節の影響を受けていびつな形状になる。
【００５３】
この様な場合、架橋性物質２１に光反射防止膜の特性を持つものを用いれば、露光時の、基盤１１表面で反射するレーザの強い反射光を減じるので、フォトレジスト膜中に定在波の発生を無くすことができ、突起の歪みを無くすことができる。従って、現像後に顕在化するフォトレジスト突起の形状が定在波の節に影響されず、レーザのガウシャン型プロフィールとレジスト感度によって決まる形状を持ち、良質な突起形状を形成することができる。ここでは架橋性物質として有機ポリマー系の光反射防止膜を用いた。
【００５４】
（実施の形態５）
実施の形態５は、架橋性物質と接触する基盤表面が凹凸形状である以外は、実施の形態１と同様である。図３は基盤表面が凹凸形状であるスタンパーの断面を示す概念図である。図３において基盤３１の表面は微細な凹凸を有している。そのため架橋性物質層１２と基盤３１の接触面積が増え、両者の接着強度を増すことができる。従って、成形時の熱サイクルに対して基盤３１と架橋性物質１２の熱膨張係数の違いによって生じるせん断歪みに耐えることができる。
【００５５】
基盤３１の表面に微細な凹凸を与える方法としては、基盤３１を不活性ガスのプラズマ
中に曝し、不活性ガスのイオン照射により微細な凹凸を与える方法や、或いは化学処理により基盤３１の表面に微細な凹凸を形成する方法などがある。凹凸の大きさの一例としては０．１以上１０ｎｍ以下である。
【００５６】
（実施の形態６）
図４は上記の工法で作られたダイレクトスタンパーからディスクを作る工程を模式的に示す図である。図４（Ａ）はディスクの樹脂注入を示す図である。図４（Ａ）において、ダイレクトスタンパー４１は、上記実施例の工法で作られた、図１（Ｊ）、または図３に示すダイレクトスタンパーである。スタンパー４１は成形機の固定金型４２に取付けられている。４３は移動金型で樹脂４４が型の中に注入されてから金型４２の方に加圧される。
【００５７】
図４（Ｂ）はダイレクトスタンパーからディスクの剥離工程を示す図である。図４（Ｂ）において、ディスクの加圧成形後、移動金型４３が開き、ダイレクトスタンパー４１の突起４６がピット（窪み）４７として転写されてディスク状に成形されたレプリカディスク４５がダイレクトスタンパー４１から剥離される。
【００５８】
図４（Ｃ）は完成したレプリカディスクの断面を示す模式図である。図４（Ｃ）において、詳細は省くがレプリカディスク４５に記録膜またはアルミなどの反射膜４８がスパッタリング法で付けられる。
【００５９】
ＣＤディスクはレプリカディスクの厚みが１．２ｍｍで、上記反射膜に保護膜をつけて完成する。ＤＶＤディスクのレプリカディスクは厚みが０．６ｍｍで、反射膜４８が付けられたレプリカディスクに信号の記録されていないダミーディスク４９が接着層５０を介して貼り合されて完成する。このタイプのディスクは、ＤＶＤ５と呼ばれる。ＤＶＤディスクはこの他にダミーディスクではなく両面に信号が記録されたものや、２層ディスクの信号を片面から読み出すタイプのディスクもある。
【００６０】
上記のようなディスクの成形工程では、高温の樹脂４４が型内に注入されてスタンパー４１の温度が上昇し、圧縮成形後、レプリカディスク４５がスタンパーから剥離された後、スタンパー４１の表面温度は室温の雰囲気に曝される。
【００６１】
図５で示した従来のスタンパーは、この温度サイクルによって、金属の基盤と架橋性物質であるフォトレジストの突起の膨張収縮差によってせん断応力が境界部に作用し、遂にはフォトレジスト突起の欠落を起こしていた。このフォトレジスト突起の欠落は約５０００〜１００００ショットの成形回数を超えると顕著になり、ＰＩエラーは規格の２８０以上になっていた。
【００６２】
本実施例のダイレクトスタンパーでは、フォトレジストの突起が直接基盤に固定されているのではなく、基盤に設けられた架橋性物質の上に一体に近い構造で固定されている。すなわち、架橋性物質層はアンカーコートの役割を演じる。そのため、成形時の突起の欠落が大幅に減少し、実験では１０万ショット以上の成形においてもフォトレジスト突起の欠陥は発見されず、ＰＩエラーの増加も確認されなかった。また、架橋性物質層の剥離もなかった。ＤＶＤの信号再生特性で最も重要な項目は、ジッターであるが、本発明によるダイレクトスタンパーによるＤＶＤディスクのジッターは規格の８％以下に対して、６％台前半を達成した。また、その値は１０万ショット前後でも不変であった。従来のダイレクトスタンパーでは１万枚が限度なため、１枚のスタンパーで多くのディスクを成形できなかったが、本発明のダイレクトスタンパーでは、１０万枚以上のディスクを一度に生産することが可能であり、品質が一定で、ディスク１枚当たりの製造コストを低く抑えられる。
【００６３】
【発明の効果】
本発明によるスタンパーは、ディスクの信号を表すフォトレジストの層に形成された突起が、架橋性物質の層の上に形成され、互いに架橋しあって結合しているので、成形時の熱サイクルや応力に対して剥がれにくい。また、架橋性物質の層が有機系ポリマーの場合、フォトレジストの熱膨張係数と非常に近い値であり、成形時の熱サイクルによる膨張、収縮によって生じるせん断歪が小さい。従って、成形時にフォトレジストの層に形成された突起が剥がれにくい。
【００６４】
従って、本発明によるスタンパーは、従来の基盤に直接レジスト突起を形成するスタンパーに比べ、ディスク成形のショット数が大幅に向上する。これにより同一スタンパーで１０万枚以上の成形が可能であり、品質、性能が一定のディスクを安価に生産することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態１〜３のダイレクトスタンパーの製造方法を示す図
【図２】本発明の実施の形態４の光反射防止膜機能有する架橋性物質の露光の状態を示す図
【図３】本発明の実施の形態５の基盤表面が凹凸形状であるスタンパーの断面を示す概念図
【図４】本発明の実施の形態６のダイレクトスタンパーからディスクを作る工程の模式図
【図５】従来のダイレクトスタンパーの製造方法を示す図
【符号の説明】
１１ 基盤
１２ 架橋性物質
１３ 第２の架橋物質であるフォトレジスト
１４ レーザビーム
１８ 突起（突起状の第２の架橋物質）
２１ 光反射防止の機能を有する架橋性物質
３１ 表面に凹凸を有する基盤[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is used for forming an optical disc and an optical disc.RusuTamper, manufacturing method thereof, and optical diskAnd blanksIt is about.
[0002]
[Prior art]
Conventionally, a stamper for manufacturing an optical disk has been manufactured in a process called mastering. This method uses a technique generally called photolithography, and starts by forming a pattern of unevenness of a photoresist corresponding to a signal on a glass disk. The positive photoresist layer on the glass disk is spirally exposed to a laser beam whose intensity has been modulated according to the signal to be recorded, and developed to form pits (pits) in the resist in a track shape. is there. Thereafter, a conductive film is formed on the surface, and a thick nickel film is formed thereon by electroforming. The thick film is about 0.3 mm, and it is peeled off from the original glass disk to form a stamper. Projections (bumps) on which the pits of the photoresist are transferred are spirally formed on the nickel disk. By subjecting this to injection molding, an optical disk having a pit row containing information can be obtained.
[0003]
The process of making this stamper involves more than 10 steps and is time consuming and costly to manufacture. In addition, since there are many processes, there are many defects due to dust and human error, and the yield has been reduced.
[0004]
In recent years, attempts have been made to manufacture a stamper with fewer steps without requiring such many steps. In Japanese Patent Publication No. 2765421, a crosslinkable inorganic or crosslinkable organic layer is provided on a substrate, and a laser beam whose intensity is modulated by a recording signal is irradiated and developed to form a projection corresponding to a signal pattern on the substrate. There is shown a method in which the substrate is directly used as a stamper after the projections are provided and the projections are strengthened by heating. A conventional example will be described with reference to FIG. In FIG. 5A, a nickel substrate 1 and a crosslinkable inorganic or organic layer 2 are shown. FIG. 5B shows that the laser beam 3 modulated by the signal is focused by the recording lens 4 to expose the crosslinkable substance 2. FIG. 5C shows a state where an exposed portion as a latent image of laser exposure is locally heated and cross-linked to form a mark 5. When this is developed, the unexposed portion dissolves and only the exposed portion remains as 6. These crosslinkable substances 2 act as a so-called negative resist. FIG. 5D shows the substrate in that state. When this is subjected to a hard baking treatment at a high temperature of 300 ° C., the cross-linking is promoted and the mark 6 becomes strong. The substrate made in this way is used as it is as a stamper. Therefore, this stamper is called a direct stamper.
[0005]
Japanese Patent Application Laid-Open No. 7-326077 discloses a method in which protrusions of a photoresist (crosslinkable substance) are formed on a substrate, crosslinking is promoted by heating at a high temperature, and the resultant is directly used as a direct stamper. This patent differs from the method of Japanese Patent Publication No. 2765421 in that a photoresist is selectively exposed to generate an acid. Thereafter, by heating the whole, the acid becomes a catalyst to cause crosslinking only in the exposed portion. Next, when the whole is exposed, an acid is generated in the previously unexposed area, and since it is not cross-linked, it is dissolved in a developing solution, and the first exposed area remains as a projection.
[0006]
[Patent Document 1]
Patent Publication No. 2765421
[Patent Document 2]
JP-A-7-326077
[0007]
[Problems to be solved by the invention]
However, all of the conventional direct stampers are formed by directly forming projections of an organic or inorganic photoresist (crosslinkable substance) on a nickel substrate. For this reason, the hardness of the photoresist is increased by the high-temperature baking, but the adhesive force between the photoresist and the metal is not originally strong. In the case of a DVD, the width of the projection of the photoresist is 0.3 μm and the length is the shortest, which is 0.4 μm, and the bonding area is very small.
[0008]
This direct stamper is attached to a mold of a molding machine, and forms a cavity with a mirror mold. A high-temperature resin is injected therein at a high pressure. At that time, the high-pressure resin causes the photoresist protrusion to peel off.
[0009]
Generally, the temperature of the mold is set at about 100 ° C., but the injected resin is a high temperature of about 300 ° C. or more. The thermal expansion and shrinkage in which the temperature of the direct stamper surface rises due to the injection of the resin and returns to the original temperature when the molded disk (optical disk) is removed is repeated. There is a large difference in the coefficient of thermal expansion between a metal such as nickel and the photoresist, and the stress due to the difference in thermal expansion repeatedly acts on the photoresist projections, and eventually peels off the substrate.
[0010]
When a disk such as a DVD (optical disk) is formed by a conventional direct stamper, a reproduction signal error of the DVD due to lack of a photoresist protrusion reaches an allowable limit value in about 5,000 to 10,000 shots. In DVD, an error due to a defect is called a PI error, and is determined to be 280 or less in 8 ECC blocks before error correction. Therefore, in the molding of a disc such as a DVD (optical disc) using a conventional direct stamper, it was not possible to mold about 5,000 to 10,000 shots or more.
[0011]
[Means for Solving the Problems]
To solve the above problems,Of the present inventionFirstThe manufacturing method of the stamperOn the foundationForming a layer of a crosslinkable substance on theLayer ofAfter the first cross-linking reaction, the cross-linkable substanceLayer ofForming a layer of photoresist on top of the photoresist,Layer ofExposure and development of the laser beam modulated by the signal to be recorded inAfter going, beforeCrosslinkable substance and said photoresistUpdate each layerIs subjected to a second cross-linking reaction to obtain the cross-linkable substanceLayer ofAnd the photoresistAnd layersIt is characterized by a bridge connection.
[0012]
Also,A second method for manufacturing a stamper according to the present invention includes:Crosslinkable materialOn the quality layerPhotoresistLayers are shapedLaser beam modulated by the signal to be recorded by rotating the formed baseThe desiredExpose the photoresist layer by focusing on spots,thisA latent image is spirally recorded on the photoresist layer, and thereafter, the photoresist layer is formed.ToDeveloping the photoresist layer, removing the portions other than the exposed portions, and removing the photoresist.Layer ofProtrusionThe shapeTo makeIt is characterized by.
[0013]
Also,In the first and second stamper manufacturing methods of the present invention,The photoresist is preferably a negative resist.
[0014]
Preferably, the material of the base is nickel.
[0015]
Further, it is preferable that the surface of the substrate in contact with the crosslinkable substance is subjected to an unevenness treatment of 1 nm or more and 10 nm or less.
[0016]
Next, the present inventionBuRanks isOn the foundationCrosslinkable substance layerWherein the layer of the crosslinkable substance is a layer in which the surface is incompletely crosslinked and further comprises a layer of the crosslinkable substance.uponToIt is characterized in that a photoresist layer is provided.
[0017]
Preferably, the photoresist is a negative resist.
[0018]
Preferably, the material of the base is nickel.
[0019]
In addition, it is preferable that the surface of the substrate in contact with the crosslinkable substance be subjected to an unevenness treatment of 1 nm or more and 10 nm or less.
[0020]
Next, the present inventionNoThe tamper isOn the foundationA layer of a crosslinkable substance is formed on the crosslinkable substance.Layer ofFirst crosslinking reactionAfter making the surface of the layer of the crosslinkable substance into an incomplete crosslinked state by applyingCrosslinkable substanceLayer ofA layer of photoresist on top of said photoresistLayer ofExposure and development of the laser beam modulated by the signal to be recorded inTo form protrusions in the photoresist layer.And then the crosslinkable substanceLayersThe photoresistLayer ofFurther, a second crosslinking reaction is performed, and the crosslinking substanceLayer ofAnd the photoresistLayers completelyCross-linkingOctopusAnd features.
[0021]
At this time, the laser beam modulated by the signal to be recordedThe desiredFocus on spotsTeExposing the photoresist layer,thisA latent image is recorded spirally on the photoresist layer, and then the photoresist layer is recorded.ToAnd then developing the photoresist layer to remove portions other than the exposed portions.so, The photoresistProtrusions are formed on the layer ofIt is suitable.
[0022]
Also, the second crosslinking reactionIsCrosslinkable substanceLayer ofWhenPhotoresist layerExposure to plasmaReaction, The crosslinkable substanceLayer ofWhenProtrusions formedThe Photo RegisAndCross-linking reaction takes place between the cross-linkable substancesLayer ofAnd the photoresistIn each of the layersPreferably, the crosslinking reaction is accelerated.
[0023]
Further, the second crosslinking reaction is a crosslinking substance.Layer ofWhenIn the photoresist layer where protrusions are formedUV irradiation and bakingProcessingBy the ultraviolet irradiation and the baking treatment, the crosslinkable substanceLayer ofWhenProtrusions formedThe photoresistLayer ofCross-linking reaction is carried out betweenLayer ofAnd the photoresistLayer ofIt is preferable that each of them promotes a crosslinking reaction.
[0024]
Finally, the optical disc of the present inventionManufactured by any of the above stampersIt is characterized by the following.
[0025]
Thereby, the binding between the projecting photoresist and the crosslinkable substance can be strengthened. Therefore, when molding an optical disc such as a DVD (optical disc) using a direct stamper having a protruding photoresist, a DVD reproduction signal error due to a lack of the protruding photoresist of the direct stamper can reduce a DVD reproduction error of 10,000 shots or more. Even molding can be prevented.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 4 show an embodiment of the present invention.
[0027]
(Embodiment 1)
FIG. 1 shows an embodiment of a method for manufacturing a direct stamper according to the present invention.
[0028]
FIG. 1A is a diagram showing a state after a crosslinkable substance 12 is applied to the front surface of a base 11 such as nickel by a spin coating method. The crosslinkable substance 12 is, for example, an inorganic material such as an organic polymer or silicon oxide. In this embodiment, the crosslinkable substance 12 is an organic polymer. In this embodiment, the base 11 is made of nickel. However, other than metal such as nickel alloy, silicon, aluminum, and copper, glass and ceramic may be used.
[0029]
First, the crosslinkable substance 12 is crosslinked. When the crosslinkable substance 12 is a chemically amplified resist, the baking treatment shown in FIG. 1B is performed as a pre-bake for the purpose of evaporating the solvent of the crosslinkable substance 12 after the application of the crosslinkable substance 12. It is performed at a relatively low temperature of from 90 to 90 ° C. Subsequently, as shown in FIG. 1C, the entire substrate 11 is irradiated with ultraviolet rays to crosslink the polymer chains of the crosslinkable substance 12 through the baking treatment shown in FIG. 1D. The ultraviolet light in this case isFar ultraviolet raysIs included. The ultraviolet ray used was a low-pressure mercury lamp having a wavelength of 254 nm. It is necessary to select an optimal wavelength for the ultraviolet ray depending on the crosslinkable substance to be used. In the case of a phenolic resin, ultraviolet light having a wavelength of about 300 nm is effective for crosslinking. FIG. 1 (D) shows what is called post-exposure baking in baking after exposure. At this time, the acid generated by the exposure acts as a catalyst to cause a first crosslinking reaction in the crosslinking substance 12.
[0030]
In addition, some materials of the crosslinkable substance 12 are crosslinked by heat. In this case, the ultraviolet irradiation step of FIG. 1C and the post-exposure baking step of FIG. 1D are omitted, and the first crosslinking reaction of the crosslinkable substance 12 is performed only by the baking treatment of FIG. Wake up.
[0031]
In any case, the first cross-linking reaction of the cross-linkable substance 12 at this stage does not completely cross-link but makes a semi-cross-linked state. To the extent, in the next step of FIG. 1E, a photoresist 13 is applied on the crosslinkable substance 12 by the same spin coating method, and the crosslinkable substance 12 is substantially added to the solvent of the photoresist 13. So that it does not melt. As a specific determination method, a cross-linkable substance is immersed in a photoresist solvent for one minute, pulled up, and then the film thickness is measured. The film thickness is determined from the film thickness before and after immersion in the solvent. When the value is 5 nm or less, a certain degree of crosslinked state is obtained. That is, the crosslinking is performed to such an extent that the crosslinking substance 12 is not substantially affected by the solvent of the photoresist 13.
Generally, an organic polymer becomes insoluble in a solvent when a few percent of crosslinking proceeds.
[0032]
FIG. 1E shows a state in which a photoresist 13 is formed on the crosslinkable substance 12. This photoresist 13 uses a negative resist. However, even when the photoresist 13 is a positive type resist, it may be used as a negative type as a result by a method known as a so-called image reversal method. Regardless of the type of the photoresist 13, the crosslinkable substance 12 is in a crosslinked state by a few percent, so that it is not affected by the solvent of the photoresist 13. The negative resist used in this embodiment is based on a novolak type phenol resin.
[0033]
Next, the photoresist layer 13 is exposed to a laser beam 14 modulated by a signal to be recorded as shown in FIG. The device used here is called a laser beam recorder. In the figure, a laser beam 14 after being modulated with a signal to be recorded, a recording lens 15 for narrowing the laser beam 14 to a fine spot of about 0.3 μm, and Only the rotation driving member 17 for rotating the blanks (composed of 11, 12, 13) around the rotation axis 16 is shown. Since the recording lens 15 moves in the radial direction of the rotating blank, a latent image is spirally recorded on the photoresist 13 layer.
[0034]
FIG. 1G is a diagram showing a baking process after exposure. The acid generated in the exposed portions of the photoresist 13 by the exposure serves as a catalyst, and a crosslinking reaction occurs in the exposed portions of the photoresist 13 by this baking treatment. Such a reaction occurs in a type of resist generally called a chemically amplified resist. Although the resist of this example was a chemically amplified resist,NoFor photoresists, post-exposure baking is not necessary.
[0035]
FIG. 1H is a view showing a state in which the portions other than the cross-linked portions of the photoresist 13 are melted and flown in the subsequent development processing. In this embodiment, the developing process is performed by applying an alkali developing solution. As a result, exposed portions of the photoresist remain as protrusions 18. In this state, the protrusions 18 of the photoresist and the crosslinkable substance layer 12 are not yet firmly bonded.
[0036]
FIG. 1 (I) is a step of further promoting the crosslinking of the photoresist of the protrusions 18 with the layer of the crosslinking substance 12. As described above, in the step of FIG. 1H, the cross-linking reaction of the layer of the cross-linkable substance 12 is not completely completed. Further, only a part of the crosslinking of the projections 18 of the photoresist exposed by the recording laser has progressed. In the step of FIG. 1 (I), the cross-linking of the two is further advanced as a second cross-linking reaction, whereby the polymer of the protrusions 18 of the photoresist and the polymer of the cross-linkable substance 12 are cross-linked to each other. Strengthen the bond. In addition, the crosslinkable substance 12 itself and the protrusions 18 of the photoresist are crosslinked to be strengthened, giving strength to withstand heat and stress during molding.
[0037]
One specific method for accelerating the crosslinking reaction (second crosslinking reaction) is to expose the entire substrate after development to plasma. As the plasma in this method, plasma using fluorine gas was used, and the entire substrate after development was exposed to the plasma, so that the effect was high. When a cross-linkable substance (photoresist) is exposed to the plasma, the projections of the photoresist are shaved and changed in shape by ions and radicals in the plasma. Therefore, the plasma exposure time is set to about several seconds. The cross-linkable substance and the protrusions of the photoresist that have been subjected to the plasma treatment for several seconds are hardened to the inside, and the hardness rate of the cross-linkable substance after the plasma treatment with the fluorine gas is 180 times greater than that after the oxygen ashing. Hardened near. The resist protrusion 18 slightly shrinks due to the second bridge. However, the heat-resistant temperature increased, and the shape of the projection 18 did not change even when heated to 250 to 300 ° C.
[0038]
FIG. 1 (J) shows that after the second crosslinking, the protrusions 18 of the photoresist and the layer of the crosslinking substance 12 are crosslinked.
It is a figure which shows that it has become the structure 19 integrated by coupling. The base 11 on which the integrated structure 19 is formed on the front surface is processed into an inner and outer diameter so as to fit a mold of a molding machine, and the back surface is cut as required, whereby a direct stamper is completed. Note that these processes may be performed before the crosslinkable substance is applied to the base, that is, before FIG. 1A.
[0039]
Here, assuming that the temperature at the interface between the direct stamper and the molten resin injected into the surface thereof is T, T is obtained by the following equation (1).
[0040]
(Equation 1)

[0041]
(Where ρ is specific gravity, C is specific heat, k is thermal conductivity, p is molten resin, m is direct stamper, respectively, Tpo is the temperature of the molten resin, and Tmo is the initial temperature of the direct stamper. .)
Although it depends on the molding conditions, in the case of a conventional DVD-ROM disc using a nickel direct stamper, the temperature of the mold of the molding machine to which the stamper is attached is set to 100 ° C., and the temperature of the molten resin is set to 360 ° C. Have been. When the molten resin comes into contact with the surface of the stamper, the temperature T at the interface of the molten resin is almost equal to the initial temperature of the stamper and becomes 110 ° C. or less because the thermal conductivity of nickel is much higher than that of the resin. Therefore, the molten resin starts to cool and solidify from the moment it contacts the stamper surface.
[0042]
In the case where the cross-linkable substance made of an organic polymer and the photoresist form the surface of the direct stamper made of nickel as in this embodiment, the temperature of the interface of the molten resin is higher than in the above case. When there is no difference in specific gravity, specific heat and thermal conductivity between the crosslinkable substance and the material of the photoresist and the surface of the direct stamper, the temperature T at the interface of the molten resin is about 230 ° C. at the above temperature setting. In this embodiment, since the heat sink has nickel under the crosslinkable substance, the temperature is expected to drop to 230 ° C. or less. However, in any case, the direct stamper according to the present embodiment is deteriorated by heat during molding because the heat-resistant temperature of the protrusion of the second crosslinkable substance is 250 ° C. or higher due to crosslinking as described above. I can't.
[0043]
(Embodiment 2)
The second embodiment is different from the first embodiment except for the method (second cross-linking reaction) shown in FIG. The same is true. In this method, the cross-linkable substance 12 and the projections 18 of the photoresist are subjected to ultraviolet irradiation and baking treatment to the cross-linkable substance 12 and the projections 18 of the photoresist shown in FIG. Accelerates the crosslinking reaction of UV light in this caseFar ultraviolet raysIs included.
[0044]
Here, when the photoresist is a chemically amplified resist, baking after irradiation with ultraviolet rays promotes the second crosslinking reaction.
[0045]
When the photoresist is a novolac resin other than the chemically amplified type, irradiation with far ultraviolet rays in a state where the moisture in the resist has been eliminated by baking effectively promotes the second crosslinking reaction.
[0046]
In the second embodiment of the present invention, a chemically amplified photoresist is used, and the substrate after development is irradiated with far ultraviolet rays having a wavelength of 254 nm, and then baked at 150 to 250 ° C. for 10 to 20 minutes. Was performed.
[0047]
In this case, as in the first embodiment, the cross-linking of the cross-linkable substance and the protrusions of the photoresist and the respective cross-links proceeded, and the heat resistance temperature of the entire substrate was 250 ° C. or higher. Also in this case, the resist protrusion 18 slightly shrinks at the second bridge. However, no further change in shape was observed even when further exposed to a high temperature of 250 to 300 ° C.
[0048]
(Embodiment 3)
The third embodiment is the same as the first embodiment except that the same substance as the photoresist is used as the crosslinkable substance. When the same material as the photoresist is used as the crosslinkable substance, crosslinking between the two becomes easier to occur, and the adhesive strength between the two further increases. Further, since the thermal expansion coefficient is the same, no shear strain is generated at the boundary surface even when repeatedly subjected to a thermal change during molding, and the resistance due to the thermal change is further enhanced. In this example, a polymer based on a novolak type phenol resin was used in both cases.
[0049]
(Embodiment 4)
The fourth embodiment is the same as the first embodiment, except that a material having a light reflection preventing film function is used for the crosslinkable substance. FIG. 2 is a conceptual diagram illustrating an exposure state when a material having a light reflection preventing film function is used as a crosslinkable substance.
[0050]
In FIG. 2, the crosslinkable substance 21 between the substrate 11 and the photoresist 13 is a film having an antireflection function. Since the substrate 1 is made of a material having a high reflectivity such as nickel, the reflected light generates a standing wave during laser recording in the first embodiment. The laser wavelength is λ, the refractive index and the film thickness of the crosslinkable substance 21 and the photoresist 13 are nc, dc and nr, dr, respectively.
[0051]
(Equation 2)

[0052]
When the equation 2 is satisfied, a node of the laser standing wave exists in the photoresist 13. In this case, the shape of the protrusions of the photoresist 13 after development becomes an irregular shape due to the influence of the nodes.
[0053]
In such a case, if the cross-linkable substance 21 having a property of an anti-reflection film is used, the strong reflected light of the laser reflected on the surface of the substrate 11 at the time of exposure is reduced. Can be eliminated, and distortion of the projection can be eliminated. Accordingly, the shape of the photoresist protrusion that becomes apparent after development is not affected by the nodes of the standing wave, and has a shape determined by the Gaussian profile of the laser and the resist sensitivity, so that a good-quality protrusion shape can be formed. Here, an organic polymer-based antireflection film was used as the crosslinkable substance.
[0054]
(Embodiment 5)
The fifth embodiment is the same as the first embodiment, except that the surface of the base in contact with the crosslinkable substance has an uneven shape. FIG. 3 is a conceptual diagram showing a cross section of a stamper in which the substrate surface has an uneven shape. In FIG. 3, the surface of the substrate 31 has fine irregularities. Therefore, the contact area between the crosslinkable substance layer 12 and the base 31 increases, and the adhesive strength between them can be increased. Therefore, it is possible to withstand the shear strain caused by the difference in the coefficient of thermal expansion between the substrate 31 and the crosslinkable substance 12 with respect to the thermal cycle during molding.
[0055]
As a method for providing fine irregularities on the surface of the substrate 31, a method using an inert gas plasma
There is a method in which fine irregularities are given by irradiating the inside of the substrate 31 with ions of an inert gas, or a method in which fine irregularities are formed on the surface of the substrate 31 by a chemical treatment. An example of the size of the unevenness is 0.1 to 10 nm.
[0056]
(Embodiment 6)
FIG. 4 is a diagram schematically showing a process of making a disc from the direct stamper made by the above-described method. FIG. 4A is a diagram showing resin injection of a disk. In FIG. 4A, a direct stamper 41 is the direct stamper shown in FIG. 1J or FIG. 3 manufactured by the method of the above embodiment. The stamper 41 is attached to a fixed mold 42 of the molding machine. Reference numeral 43 denotes a moving mold, which is pressed toward the mold 42 after the resin 44 is injected into the mold.
[0057]
FIG. 4B is a diagram showing a step of separating the disk from the direct stamper. In FIG. 4B, after pressing the disk, the movable die 43 is opened, and the protrusion 46 of the direct stamper 41 is transferred as a pit (recess) 47, and the replica disk 45 formed into a disk is transferred to the direct stamper 41. Peeled off from
[0058]
FIG. 4C is a schematic view showing a cross section of the completed replica disk. In FIG. 4C, a recording film or a reflective film 48 of aluminum or the like is applied to the replica disk 45 by a sputtering method, although details are omitted.
[0059]
The CD disk has a replica disk thickness of 1.2 mm and is completed by providing a protective film on the reflective film. The replica disk of the DVD disk has a thickness of 0.6 mm and is completed by bonding a dummy disk 49 on which no signal is recorded via an adhesive layer 50 to the replica disk provided with the reflective film 48. This type of disc is called DVD5. In addition to DVD discs, there are DVD discs in which signals are recorded on both sides instead of dummy discs and discs of a type in which signals of a double-layer disc are read from one side.
[0060]
In the above-described disk molding process, the high-temperature resin 44 is injected into the mold, and the temperature of the stamper 41 rises. After the compression molding, the replica disk 45 is peeled off from the stamper. Exposure to room temperature atmosphere.
[0061]
In the conventional stamper shown in FIG. 5, due to this temperature cycle, the shear stress acts on the boundary due to the difference in expansion and contraction of the protrusions of the metal substrate and the photoresist, which is a crosslinkable substance, and eventually the lack of the photoresist protrusions occurs. Was awake. The lack of the photoresist protrusion became remarkable when the number of moldings exceeded about 5,000 to 10,000 shots, and the PI error was 280 or more of the standard.
[0062]
In the direct stamper of this embodiment, the protrusions of the photoresist are not directly fixed to the base but are fixed on a cross-linkable substance provided on the base in a structure almost integral with the base. That is, the crosslinkable material layer plays the role of an anchor coat. For this reason, the lack of protrusions during molding was significantly reduced, and no defects in the photoresist protrusions were found even in molding of 100,000 shots or more, and no increase in PI error was confirmed in experiments. In addition, there was no peeling of the crosslinkable substance layer. The most important item in the DVD signal reproduction characteristics is the jitter. The jitter of the DVD disk by the direct stamper according to the present invention has achieved the lower 6% level compared with 8% or less of the standard. The value was not changed even after about 100,000 shots. Since the conventional direct stamper has a limit of 10,000, it was not possible to mold many discs with one stamper. However, the direct stamper of the present invention can produce 100,000 or more discs at a time. Yes, the quality is constant, and the manufacturing cost per disc can be kept low.
[0063]
【The invention's effect】
According to the inventionRusuTamper is a photoresist that represents the signal on the discFormed in the layer ofThe protrusion is a cross-linkable substanceLayer ofAre formed on top of each other and are cross-linked to each other, so that they are not easily peeled off due to a thermal cycle or stress during molding. Also, a crosslinkable substanceLayer ofIs an organic polymer, the value is very close to the thermal expansion coefficient of the photoresist, and the shear strain caused by expansion and contraction due to the thermal cycle during molding is small. Therefore, during moldingFormed in a layer of photoresistThe protrusions are difficult to peel off.
[0064]
Therefore, according to the present invention,RusuThe tamper greatly increases the number of shots for disk forming as compared to a conventional stamper in which resist projections are formed directly on a substrate. As a result, 100,000 or more sheets can be molded with the same stamper, and disks with constant quality and performance can be produced at low cost.
[Brief description of the drawings]
FIG. 1 is a diagram showing a method for manufacturing a direct stamper according to first to third embodiments of the present invention.
FIG. 2 is a diagram showing an exposure state of a crosslinkable substance having a light reflection preventing film function according to a fourth embodiment of the present invention.
FIG. 3 is a conceptual diagram showing a cross section of a stamper according to a fifth embodiment of the present invention in which the base surface has an uneven shape.
FIG. 4 is a schematic view of a process of making a disc from a direct stamper according to a sixth embodiment of the present invention.
FIG. 5 is a diagram showing a conventional direct stamper manufacturing method.
[Explanation of symbols]
11 Base
12 Crosslinkable substances
13. Photoresist as the second cross-linking substance
14 Laser beam
18. Projection (projection-like second cross-linking substance)
21 Crosslinkable substance having antireflection function
31 Substrate with uneven surface

Claims (5)

After forming a negative type photoresist layer on a substrate, performing a baking process on the photoresist layer, and then irradiating ultraviolet rays to make the surface incompletely crosslinked, the photoresist layer A photoresist layer of the same material as that of the photoresist is further formed on the photoresist layer, and thereafter, exposure and development of a laser beam modulated by a signal to be recorded on the photoresist layer are performed. A method of manufacturing a stamper , wherein each of the photoresist layers is further baked to completely cross-link the two photoresist layers . The substrate on which the two negative photoresist layers are formed is rotated, and a laser beam modulated by a signal to be recorded is focused on a desired spot, and the outermost photoresist layer among the photoresist layers is formed. Is exposed, a latent image is spirally recorded on the photoresist layer, and thereafter, the baking treatment is performed on the photoresist layer, and then the photoresist layer is developed. 2. The method according to claim 1, wherein a protrusion is formed on the photoresist layer. The method for manufacturing a stamper according to claim 1, wherein a material of the base is nickel. Having a negative photoresist layer on the substrate, performing a baking treatment on the negative photoresist layer, and then irradiating ultraviolet light to make the surface incompletely crosslinked, further comprising the photoresist A blanks manufacturing method, comprising: providing a photoresist layer of the same substance as described above . The method according to claim 4, wherein the material of the base is nickel.

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