WO2003073421A1 - Gravure de disque optique - Google Patents

Gravure de disque optique Download PDF

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Publication number
WO2003073421A1
WO2003073421A1 PCT/GB2003/000694 GB0300694W WO03073421A1 WO 2003073421 A1 WO2003073421 A1 WO 2003073421A1 GB 0300694 W GB0300694 W GB 0300694W WO 03073421 A1 WO03073421 A1 WO 03073421A1
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WO
WIPO (PCT)
Prior art keywords
substrate
photoresist
photosensitive material
pits
carried out
Prior art date
Application number
PCT/GB2003/000694
Other languages
English (en)
Inventor
Pascal Andre
Richard Anthony Lione
Original Assignee
Plasmon Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Plasmon Limited filed Critical Plasmon Limited
Priority to AU2003205894A priority Critical patent/AU2003205894A1/en
Publication of WO2003073421A1 publication Critical patent/WO2003073421A1/fr

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/26—Apparatus or processes specially adapted for the manufacture of record carriers
    • G11B7/261—Preparing a master, e.g. exposing photoresist, electroforming

Definitions

  • the present invention relates to low cost manufacturing of optical masters and more particularly to a mastering technique for optical discs which are of high density and/or meet requirements for differential depth of pits and/or grooves with flat bottoms.
  • This information can be recorded on to each individual disc after manufacture, but the operation is lengthy and requires much specialised equipment.
  • Replication from stampers which have the information already encoded during the mastering process avoids the cost and time of formatting the finished DVD-R medium.
  • the pre-recorded information in the form of pits in the embossed zone must be > ⁇ /8 deeper than the recording grooves (EP-A-0 67716) for the pre-recorded information to be readable.
  • pits and/or grooves are formed by exposing photosensitive material (positive photoresist material) provided on a glass substrate to a laser beam and grooves are developed in the photoresist by washing out the exposed and solubilised portion of the photoresist.
  • photosensitive material positive photoresist material
  • grooves are developed in the photoresist by washing out the exposed and solubilised portion of the photoresist.
  • the required flat bottom for the pits or grooves is achieved by developing the channels until their bottoms touch the substrate glass; this means that the depth of the channels which have a flat bottom is determined by the thickness of the photoresist.
  • This technique leads to a trapezoidal shape, wider at the top of the resist and relatively narrow at the resist/glass interface at which etching of the pits and/or grooves is to take place.
  • the kinetics of the development of a pattern created by the Airy light spot determines that when the pattern in the photoresist does not touch the glass, the bottoms of the channels are no longer flat, but triangular with a small angle.
  • the channels, at this stage, are commonly referred to as "hinge models".
  • the signal from such a pattern is distorted and difficult to read.
  • the deepest pattern may have a flat bottom, but the others are of triangular shape and further etching to the substrate surface is a problem.
  • 0418897 A2 which describes a method for forming micro pits smaller than the spot diameter determined by the optical system.
  • This method uses the photoresist material as a mask for etching pits in the glass substrate.
  • An advantage of this method lies in the pit width control which is achievable with it.
  • this method requires at least two layers of photoresist material to be provided on the glass substrate and, in particular, it leads only to pits of uniform depth, determined by the depth of laser insensitive layer which is etched below the photo mask.
  • Electron beam mastering is another known technique for manufacturing high density format discs with very small features. This technique requires expensive and specialised equipment. Nevertheless, the manufacture of differential depth pits and/or grooves is unlikely to be attained because the eventual depth of readable data will again be determined alone by the electron beam resist thickness.
  • the method is to lead to patterns having pits and/or grooves of a plurality of different depths, with all of the pits and/or grooves having the preferred shape with flat bottom needed for a good signal.
  • the method is to provide very good control of feature size and to be suitable for mastering with very small features.
  • a method of manufacturing a master for use in the production of optical discs which comprises the steps of:
  • steps e) and f) if photosensitive material remains on the substrate, repeating steps e) and f) one or more times until a required groove and/or pit pattern exists in the substrate.
  • the method of this invention is particularly suited to the production of multiple depth features for independent optimisation of the recordable and ROM regions of an optical medium. Moreover, the method of the invention is particularly well suited to the production of high density optical disc masters having small features ( ⁇ 50nm) and fine track pitch. Thus, the method of the present invention can be carried out to achieve flat bottom patterns at different depths and/or pits of narrow width and steep wall angle as will be described hereinafter.
  • Steps (e) and (f) can, in one embodiment, be carried out in stages to achieve different depths of groove and/or pit.
  • a 100 to 500 ran, preferably about 130 nm, thick photoresist will normally be employed. This is in contrast to the 40 to 250 nm thickness photoresists normally employed when using wet development to produce single depth grooves and/or pits, resist thicknesses normally being at the lower end of the this range.
  • the etching of the photoresist when having 40 nm thickness will lead only to about 30° inclined walls.
  • high density ( ⁇ 150 nm half width) , low track pitch ( ⁇ 0.32 nm) and steeper wall angles (>45°) are achievable because of the greater thickness used.
  • photoresists having a thickness of about 400 to 1000 nm, typically about 500 nm, may be used to obtain wall angles of more than 60°, preferably about 80°, as a result of which pits as fine as 50 nm or less may be attained.
  • quartz substrates While it is preferred to use quartz substrates because these are very flat and offer a very smooth surface, alternatively, one can use glass plates, ceramic plates, silicon wafers, metal plates, for example nickel plates, or metal sputtered plates, the plasma etching techniques used being appropriate to the substrates being used, these plates being initially coated with photoresist, baked and then cut in a laser beam recorder and developed.
  • etching of the plates may take place in a plasma chamber by Reactive Ion Etching (RIE) .
  • RIE Reactive Ion Etching
  • Etching of the quartz may take place at RF power of 150W, pressure of 50 mtorr, using CHF 3 and SF 6 gases for the etching.
  • the etching times employed at particular locations determine the depths obtained.
  • wet etching is to be contemplated. This process may be used particularly to prepare shallow features with low noise and relatively steep wall angle such as cannot be achieved by classical mastering.
  • wet etching a photoresist of specific thickness is developed in conventional manner and optionally is postbaked to further smooth its surfaces.
  • the substrate with developed photoresist is subjected to etching of the substrate by soaking with HF/NH 4 F.
  • the etching is isotropic, i.e. etching in depth and width directions take place at the same rate. Shallow, wide depressions with a wall angle determined from the photoresist thickness are created in the glass. Removal of photoresist by etching in oxygen or other resist stripping method completes the process.
  • the finished glass can be used in subsequent processing to prepare Father stampers with shallow and wide features or to prepare Mother stampers with narrow features with a steep wall angle.
  • Archive mothers are masters produced by etching pits and/or grooves in a substrate.
  • the etched masters can be subjected to metalizing electrodeposition steps in conventional manner.
  • the method of the invention also enables archive fathers to be produced if photosensitive material is to be retained on a substrate on which a pattern of grooves and/or pits has been formed.
  • Figure la to Figure le illustrate steps in the production of pits and/or grooves of different depth
  • Figures 2a to Figure 2c illustrate steps in the production of a master having pits of narrow width
  • Figures 2A to 2C illustrate comparable steps in the production of a master, but using a photoresist of reduced thickness.
  • Figure 3a to Figure 3c show steps in the production of a master having narrow pits in a particularly high density
  • Figure 3A shows the result of high density pit production when using a photoresist of much reduced thickness typical of classical techniques.
  • Figure 4 is a schematic representation of development of exposed photoresist to different depths when pit in groove end groove formation only are required;
  • Figures 5a to 5e illustrate steps in the production of a master having pits in grooves, i.e. different flat bottom depths
  • Figures 6a to 6d illustrate steps in the production of a master having protruding narrow features with steep angle walls
  • Figures 7a to 7c illustrate steps in the production of a master having very shallow features with relatively steep angle walls, using wet etching.
  • a 150mm x 3mm quartz substrate 1 was coated with a 130 nm thick positive photoresist (Shipley 1805) and baked in accordance with conventional practice.
  • the photoresist was cut with (exposed to) a laser beam recorder under two conditions and developed in a conventional manner for 20 sees, to achieve partial removal of developed photoresist to a depth of 90 nm where grooves are to be produced and 130 nm depth removal at locations where pits are to be formed (Fig. la) .
  • Full depth channels A of trapezoidal form and partial depth channels B of triangular form were produced in this way.
  • Etching of the quartz plate at the 130 nm depth development locations was now carried out by placing the quartz plate in a plasma chamber and etching the quartz plate by reactive sputtering in a reactive gas mixture of CHF 3 and SF 5 gases using RF power of 150 watts and 50 mtorr pressure. An etching rate of 30 nm/min was obtained. After etching for 200 seconds, etching in the quartz to a depth of 100 nm had taken place (Fig. lb) . The photoresist was then etched with oxygen for 60 seconds, during which time a layer of photoresist 40nm in depth was removed and the triangular channels had been taken to the substrate surface and had assumed a wide trapezoidal form (Fig. lc) .
  • a second reactive sputtering was carried out to achieve etching at both A and B operating locations. Again, use was made of CHF 3 and SF 6 gases and the aforementioned etching conditions, etching being carried out for 320 seconds during which etching of quartz by an additional 160 nm took place (Fig. Id) .
  • a layer of positive photoresist material (Shipley 1805) having a thickness of 500 nm was applied to a quartz substrate and baked in accordance with conventional practice.
  • the photoresist P was cut in a laser beam recorder (krypton at 413 nm) and developed in conventional manner down to a depth reaching the substrate S (Fig. 2a). This measure avoids the lifting off of the resist.
  • an angle of about 80° was achieved in the resist, with a small bottom width to the grooves GP being achieved at the same time.
  • the exposed substrate S was then etched in a reactive mixture of CHF 3 and SF 6 gases (Figure 2b) to the required depth, retaining the narrow widths and steep wall angle of the grooves GP of the resist P in the grooves GS in the substrate S.
  • Figures 2A to 2C illustrate the progress of a comparable etching technique carried out with a like photomask on a much thinner layer of photoresist (20- 80nm) .
  • the photoresist thickness reducing step of Fig. 2b could be omitted, but wide channels were formed in the photoresist with the shallower angle leading to large pit size.
  • greater thickness of photoresist enables small features to be produced with ready control of fineness during the course of manufacture.
  • Fig. 3a depicts the result achieved when starting with 500 nm thick photoresist. This was followed by a precleaning step in which oxygen etching was carried out for 60 seconds to reduce photoresist thickness to 43 nm. The surface of the photoresist is, in this case, as shown in Figure 3c.
  • a 130 nm thick positive photoresist (Shipley 1805) layer was coated on a substrate in the same manner as in Example 1 before being cut with (exposed to) a single laser beam, which was modulated in such a way as to achieve exposure down to a level -of 90 nm from the ground intensity of the beam for groove formation and exposure down to a level of 130 nm at peak intensity of the beam for pit formation.
  • the respective extents of exposure are shown schematically in Figure 4 of the accompanying drawings, with the dark areas representing completely unexposed photoresist.
  • Figure 5 shows in section the substrate with photoresist thereon
  • Figure 5a represents the condition of the coated developed photoresist/substrate at the stage thus reached with zone B indicating progress of groove production and zone A indicating progress of pit in groove production with 40 nm pits having been created at the bottom of 90 nm deep grooves as a result of the developing.
  • the substrate with the thus partially developed photoresist was then etched to create a 70-80 nm pit in substrate (Fig. 5b zone A) . Resist was then etched to achieve the correct groove profile (Fig. 5c) . Subsequent etching of the substrate analogous to that used in Example 1 to achieve the result of Fig. Id (Fig. 5d) and cleaning of photoresist analogous to that used to achieve the result of Figure le ( Figure 5e) complete the process, in which pits in groove are produced.
  • masters which feature narrow width and steep wall angle substrate material in an inverse pattern in the substrate, i.e. "bumps" instead of "pits".
  • Such masters can also be produced by the method of invention .
  • a standard thickness 130 nm deep photoresist was applied to a substrate and was exposed and fully developed in 20 seconds to obtain trapezoidal pits with flat bottoms (Fig 6).
  • the photoresist was dry developed further by etching with oxygen to a required new width, while retaining the wall angle (Fig. 6) in such a way as to satisfy the preliminary requirements of narrow features.
  • Example 2 Following the procedure in Example 2, the substrate was then etched with CHF 3 -SF 6 mixed gas to the required depth, retaining the narrow width and wall angle feature in the form or a protrusion.
  • Fig 6c In a final step the remaining photoresist was removed as in Example 1, to produce a pattern of narrow features with steep angle was subjected by metallisation and electronic processes to yield a mother which could be used as a master.
  • a standard thickness 130nm deep photoresist was applied to a glass substrate and fully developed in 20 seconds to obtain trapezoidal pits with flat bottoms as in
  • Example 1 (see Figure 7a) .
  • the developed photoresist was then postbaked to further smooth- the photoresist.
  • the substrate with the developed photoresist thereon was etched with HF/NH 4 F. During this step, the substrate was etched at the same rate with respect to depth and width, to create shallow and wide features in the glass. After 20 seconds, this isotropic etching was stopped by rinsing with water. Features with 43nm depth and 40° wall angle were created in the glass, (Fig. 6b) .
  • the substrate thus furnished with protruding narrow features with steep angles was subjected to metallisation and galvanic processes to yield the required master.

Abstract

L'invention concerne un disque maître utilisé dans la production de disques optiques adoptant un format parmi une grande variété de formats lorsque l'épaisseur de la photorésine appliquée à une photorésine est adaptée aux étapes de traitement ultérieures mises en oeuvre une ou plusieurs fois dans un ordre spécifique afin d'obtenir des rainures et/ou des dépressions régulières du type désiré et/ou au profil combiné désiré.
PCT/GB2003/000694 2002-02-26 2003-02-17 Gravure de disque optique WO2003073421A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003205894A AU2003205894A1 (en) 2002-02-26 2003-02-17 Optical disc mastering

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0204496A GB0204496D0 (en) 2002-02-26 2002-02-26 Optical disc mastering
GB0204496.4 2002-02-26

Publications (1)

Publication Number Publication Date
WO2003073421A1 true WO2003073421A1 (fr) 2003-09-04

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AU (1) AU2003205894A1 (fr)
GB (1) GB0204496D0 (fr)
WO (1) WO2003073421A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110140303A1 (en) * 2009-12-11 2011-06-16 Doo Hee Jang Methods of fabricating imprint mold and of forming pattern using the imprint mold
CN102243437A (zh) * 2011-06-14 2011-11-16 扬中市华瑞通讯仪器有限公司 光纤阵列组件凹槽基板的制造方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0168763A2 (fr) * 1984-07-14 1986-01-22 Victor Company Of Japan, Limited Méthode de fabrication d'une matrice pour disque d'enregistrement
EP0418897A2 (fr) * 1989-09-20 1991-03-27 Sony Corporation Méthode de fabrication d'un milieu d'enregistrement optique de haute densité
EP0449462A2 (fr) * 1990-03-15 1991-10-02 Canon Kabushiki Kaisha Rouleau de gaufrage pour former la couche porteuse pour milieux d'enregistrement d'information, procédé pour la preparation du même et procédé pour la production des couche porteuse pour milieux d'enregistrement d'information
EP0503961A2 (fr) * 1991-03-15 1992-09-16 Sharp Kabushiki Kaisha Méthode pour la fabrication d'un substrat en verre pour disque
JPH05251399A (ja) * 1992-03-06 1993-09-28 Nec Corp 枚葉式エッチャーによるシリコン窒化膜のエッチング方法
EP1160775A2 (fr) * 2000-06-01 2001-12-05 Samsung Electronics Co., Ltd. Disque ayant des creux et des sillons de profondeurs différentes, et procédé de fabrication de ce disque

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0168763A2 (fr) * 1984-07-14 1986-01-22 Victor Company Of Japan, Limited Méthode de fabrication d'une matrice pour disque d'enregistrement
EP0418897A2 (fr) * 1989-09-20 1991-03-27 Sony Corporation Méthode de fabrication d'un milieu d'enregistrement optique de haute densité
EP0449462A2 (fr) * 1990-03-15 1991-10-02 Canon Kabushiki Kaisha Rouleau de gaufrage pour former la couche porteuse pour milieux d'enregistrement d'information, procédé pour la preparation du même et procédé pour la production des couche porteuse pour milieux d'enregistrement d'information
EP0503961A2 (fr) * 1991-03-15 1992-09-16 Sharp Kabushiki Kaisha Méthode pour la fabrication d'un substrat en verre pour disque
JPH05251399A (ja) * 1992-03-06 1993-09-28 Nec Corp 枚葉式エッチャーによるシリコン窒化膜のエッチング方法
EP1160775A2 (fr) * 2000-06-01 2001-12-05 Samsung Electronics Co., Ltd. Disque ayant des creux et des sillons de profondeurs différentes, et procédé de fabrication de ce disque

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 018, no. 008 (E - 1486) 7 January 1994 (1994-01-07) *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110140303A1 (en) * 2009-12-11 2011-06-16 Doo Hee Jang Methods of fabricating imprint mold and of forming pattern using the imprint mold
US8728331B2 (en) * 2009-12-11 2014-05-20 Lg Display Co., Ltd. Methods of fabricating imprint mold and of forming pattern using the imprint mold
CN102243437A (zh) * 2011-06-14 2011-11-16 扬中市华瑞通讯仪器有限公司 光纤阵列组件凹槽基板的制造方法

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GB0204496D0 (en) 2002-04-10
AU2003205894A1 (en) 2003-09-09

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