WO2004006019A1 - A method and a stamp for transferring a pattern to a substrate - Google Patents

A method and a stamp for transferring a pattern to a substrate

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Publication number
WO2004006019A1
WO2004006019A1 PCT/SE2003/001164 SE0301164W WO2004006019A1 WO 2004006019 A1 WO2004006019 A1 WO 2004006019A1 SE 0301164 W SE0301164 W SE 0301164W WO 2004006019 A1 WO2004006019 A1 WO 2004006019A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
stamp
material
substrate
layer
film
Prior art date
Application number
PCT/SE2003/001164
Other languages
French (fr)
Inventor
Lennart Olsson
Original Assignee
Obducat Ab
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

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/003Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor characterised by the choice of material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/02Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
    • B29C43/021Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles characterised by the shape of the surface
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29DPRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D17/00Producing carriers of records containing fine grooves or impressions, e.g. disc records for needle playback, cylinder records; Producing record discs from master stencils
    • B29D17/005Producing optically read record carriers, e.g. optical discs
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B82NANOTECHNOLOGY
    • B82YSPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording 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
    • G11B7/24Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/26Apparatus or processes specially adapted for the manufacture of record carriers
    • G11B7/263Preparing and using a stamper, e.g. pressing or injection molding substrates
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/02Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
    • B29C43/021Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles characterised by the shape of the surface
    • B29C2043/023Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles characterised by the shape of the surface having a plurality of grooves
    • B29C2043/025Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles characterised by the shape of the surface having a plurality of grooves forming a microstructure, i.e. fine patterning
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/0002Lithographic processes using patterning methods other than those involving the exposure to radiation, e.g. by stamping
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03FPHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/0017Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor for the production of embossing, cutting or similar devices; for the production of casting means

Abstract

A method of transferring a pattern (10) from a stamp (4) to a substrate (1), which is provided with a moldable film (2), comprises using a stamp (4) having a similar coefficicient of thermal expansion as the substrate (1), heating the stamp (4) and the substrate (1) to a temperature at which the moldable film (2) becomes soft before pressing the stamp (4) against the moldable film (2), cooling the stamp (4) and the substrate (1) to a temperature at which the moldable film (2) becomes hard, and removing the stamp (4) from the substrate (1). A stamp (4) is provided for transferring a pattern (10) provided on the stamp (4) to a substrate (1), which is provided with a moldable film (2), by pressing the stamp (4) against the moldable film (2), by pressing the stamp (4) against the moldable film (2). The stamp (4) has a similar coefficicient of thermal expansion as the substrate (1).

Description

A METHOD AND A STAMP FOR TRANSFERRING A PATTERN TO A

SUBSTRATE

Technical Field of the Invention

The present invention relates to a method of transferring a pattern from a stamp to a substrate, which is provided with a moldable film, said method comprising pressing the stamp against the moldable film.

The present invention further relates to a stamp for transferring a pattern provided on the stamp to a substrate, which is provided with a moldable film, by pressing the stamp against the moldable film.

Background art

In connection with manufacturing of small structures, such as semiconductors, e.g. integrated circuits or memory media (CD, CD-ROM, DVD, hard disks etc.), imprint lithography may sometimes be used, particularly nanoimprint lithography, which is described in more detail in e.g. WO01/42858 and O01/69317, which are hereby incorporated by reference. Imprint lithography essentially comprises transferring a relief pattern from a stamp onto a substrate. The substrate is normally provided with a moldable film. The substrate often consists of a metal- or silicon based material which is provided with e.g. a polymer film.

During the imprint process, the stamp is pressed against the substrate at a pressure which is high enough to cause the pattern on the stamp to form an imprint in the moldable film. Subsequently, the substrate may be subjected to exposure to e.g. radiation (such as UV-radiation) or etching, whereby parts of the pattern in the moldable film are wholly or partially removed or hardened. This imprint process may be preceded by or followed by application of further layers of moldable film, further imprint steps or any treatment by means of other known semiconductor manufacturing techniques.

In connection with imprint lithography, it may be desirable to heat the moldable film in order to make it softer and thus to facilitate the transfer of the pattern. A common procedure is to heat the substrate with the moldable film to a temperature above the temperature at which the moldable film becomes soft. The stamp is heated to substantially the same temperature and is then brought in contact with the moldable film to achieve the imprint. The stamp and the substrate are then both cooled to a temperature at which the moldable film becomes hard. The stamp is then removed from the substrate, the moldable film being provided with a pattern.

However the above described method does not always provide an accurate transfer of the pattern on the stamp.

In some cases the very small structures in the moldable film are destroyed when the stamp is removed.

Summary of the Invention It is an object of the present invention to provide a method of transferring a pattern from a stamp to a substrate which method overcomes or decreases the disadvantages of the prior art methods.

This object is achieved with a method of transferring a pattern from a stamp to a substrate, which is provided with a moldable film, said method comprising pressing the stamp against the moldable film, said method being characterized by: using a stamp having a similar coefficient of thermal expansion as the substrate, heating the stamp and the substrate to a temperature at which the moldable film becomes soft before pressing the stamp against the moldable film, cooling the stamp and the substrate to a temperature at which the moldable film becomes hard, and removing the stamp from the substrate.

The above method has proven to be very efficient in providing accurate patterns in the moldable film. Since the substrate and the stamp have similar coefficients of thermal expansion they will be contracted at the same rate during the cooling phase. Thus the pattern on the stamp and the pattern formed on the moldable film will so to say follow each other during the cooling phase. When the stamp is removed from the substrate there will be no forces acting to destroy the pattern on the moldable film.

Preferably the base material of the stamp is the same as the base material of the substrate. Using the same material is a simple way of providing the same coefficient of thermal expansion in the stamp and in the substrate.

According to a preferred embodiment a layer of a material suitable for imprinting is provided on the surface of the base material of the stamp. The base material of the stamp, which material should be chosen such that the coefficient of thermal expansion becomes similar to that of the substrate, may not always be well suited for imprinting. The base material may, as an example, not be hard enough or have the desired surface release properties to avoid adhesion of the stamp to the moldable film. By providing a thin layer of another material on the base material the imprinting surface of the stamp could be given the desired properties, the stamp still having the coefficient of thermal expansion of the base material. A further object of the invention is to provide a stamp for transferring a pattern to a substrate, said stamp overcoming or decreasing the disadvantages of the prior art stamps. This object is achieved with a stamp for transferring a pattern provided on the stamp to a substrate, which is provided with a moldable film, by pressing the stamp against the moldable film, the stamp being characterized in that the stamp has a similar coefficient of thermal expansion as the substrate.

Since the stamp has a similar coefficient of thermal expansion as the substrate the stamp and the substrate will have the same expansion and contraction characteristics during heating and cooling respectively. Thus the stamp with its pattern pressed into the moldable film will contract in the same way as the substrate during the simultaneous cooling of the stamp and the substrate. The pattern in the moldable film will thus not be affected by any lateral movement of the stamp in relation to the substrate during cooling.

According to a preferred embodiment the stamp comprises one solid base material having a similar coefficient of thermal expansion as the substrate. With a stamp formed from one material only the stamp will exhibit the coefficient of thermal expansion of that material. It will thus be easy to predict the contraction during cooling.

According to another embodiment of the invention the stamp comprises a base material having a similar coefficient of thermal expansion as the substrate, the pattern of the stamp being formed on a layer of a material suitable for imprinting. In some cases the base material is not suitable for forming a relief pattern therein. In such a case a thin layer of a material suitable for imprinting is provided on the base material. The pattern is then formed in the thin layer. The contraction characteristics of the stamp will still be decided by the base material, which is chosen so as to have a similar coefficient of thermal expansion as the substrate. Preferably the thickness of said layer is 50 nm to 50 μm, preferably 50-1000 nm. Such a thickness has proven to be a suitable thickness for forming a pattern in the layer. The thickness is however still so small in relation to the base material that the coefficient of thermal expansion will be decided by the base material and not by the material in said layer. According to still another preferred embodiment the pattern is formed on the base material, and being provided with a layer of a material suitable for imprinting. This embodiment is particularly advantageous when the base material is suitable for forming a pattern on the surface thereof but is not suitable for being the actual imprinting surface. Thus a layer is provided on the patterned surface of the base material. The layer is such that is has properties, e.g. with respect to wear and release, suitable for contacting the moldable film. Preferably the thickness of said layer is 2 nm to 50 μm, preferably 2-200 nm. Such a thickness is large enough to provide a suitable and mechanically stable layer on the patterned base material. The thickness should be not be larger since the pattern of the stamp may be affected in an unwanted way. Another reason is that a thick layer having a coefficient of thermal expansion different from that of the base material may give rise to thermal stresses or even cracks in the boundary layer between the base material and the layer of material suitable for imprinting.

An adhesion layer is preferably provided between the base material and said layer of a material suitable for imprinting. In some cases the layer of a material suitable for imprinting does not adhere very well to the base material. In such case an adhesion layer acting as a cement could be applied to the base material before applying the layer of a material suitable for imprinting. Preferably said layer of a material suitable for imprinting comprises a material chosen in the group of materials consisting of Ni, Ti, Al , Nb, Ta, Zr, Cr, Cu, Si, glass and mixtures thereof. These materials have proven to be hard and mechanically stable and thus provide suitable surfaces for imprinting. Many of them, in particular Ni , Si and Al , have also proven to be suitable for forming relief patterns in the nanometer scale.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereafter.

Brief Description of the Drawings

The invention will hereafter be described in more detail and with reference to the appended drawings. Fig 1 is a schematic section view and shows a substrate and a stamp according to a first embodiment of the invention.

Fig 2 is a schematic section view and shows the substrate and stamp of fig 1 as seen after the stamp has been pressed into a moldable film of the substrate.

Fig 3 is a schematic section view and shows the substrate of fig 1 and 2 after the stamp has been removed .

Fig 4 is a schematic section view and shows a stamp according to a second embodiment of the invention.

Fig 5 is a schematic section view and shows a stamp according to a third embodiment of the invention.

Fig 6 is schematic section view and shows a stamp according to a fourth embodiment of the invention.

Detailed description of the invention The present invention relates to nano imprinting, i.e. the forming of patterns in substrates by forcing a stamp having a pattern into contact with a substrate thereby transferring said pattern to the substrate. Examples of products that could be manufactured with the aid of the present invention include hard disks, optical disks, micromechanical devices, microfluid devices and microelectronic devices .

The term "nano-imprinting" should not be read as referring only to submicron structures, i.e. structures with a size in the range of 0,1-1000 nm. A pattern often includes both submicron structures and structures with a size of up to 100 micron, and larger. The present invention is applicable for forming of patterns comprising submicron structures and/or micron structures. The invention is particularly advantageous when forming patterns comprising submicron structures since these are relatively more sensitive to being affected.

The process of transferring a pattern on a stamp to a substrate is known from WO 01/42858 and WO 01/69317. In brief the process comprises the steps of heating a stamp having a pattern on a surface thereof and a substrate to a temperature at which a moldable film provided on the substrate becomes soft. The stamp is then pressed into the soft moldable film. In order to permanent the pattern in the moldable film it is necessary to cool the moldable film, and thus the stamp and the substrate, to a temperature at which the moldable film becomes hard. It has been found that the fidelity of the transferred pattern is improved if a stamp, which has a pattern, has a similar coefficient of thermal expansion as the substrate to which it is intended to transfer the pattern. Thus the stamp and the substrate will behave in the same way when cooled to the temperature at which the moldable film becomes hard.

The material in the substrate depends on the requirements of the final products, such as semiconductors, e.g. integrated circuits, memory media, e.g. CD, CD-ROM, DVD, hard disks etc., and masters for producing other products. Examples of substrate materials are aluminium (Al) , silicon (Si), Si/Siθ2, GaAs, InP, polymers such as polycarbonate (PC) , and nickel (Ni) .

The substrate is provided with a moldable film. The thickness of the moldable film is typically 50-400 nm. The film comprises a suitable thermoplastic which becomes soft at an elevated temperature. An example of a thermoplastic is 950K PMMA. This thermoplastic may be applied to a substrate as a liquid film and then be baked at 180°C during 24 hours. During the imprint the film is heated to about 170°C. The stamp is pressed into the film which is then cooled to about 80 °C before the stamp is removed .

It is, however, also possible to use a substrate which has a surface that in itself is softened by the heating. In such a case it is the surface of the substrate itself that acts as a moldable film. One example of this is CD and DVD's where an imprint is made by injection moulding a disk in a mold having a relief patterned stamp as one of the walls in the mold. The material in the substrate is often given by the product to be produced. Thus the coefficient of thermal expansion of the substrate is usually fixed. According to the present invention the material of the stamp is chosen such that it provides a similar coefficient of thermal expansion. A common measure of the thermal expansion properties of a material provided in data tables is the coefficient of linear heat expansion, usually with the unit 1/K. Tables of coefficients of linear heat expansion are thus useful for providing information of materials suitable for making a stamp for imprinting a certain substrate .

Preferably the difference between the stamp and the substrate in coefficient of linear heat expansion is less than +/- 3*10"6/K. For a substrate of aluminium having a coefficient of linear heat expansion of 24*10"e/K the stamp would preferably have a coefficient of linear heat expansion in the range of 21-27*10"6/K. It should be noted that the coefficient of linear heat expansion is temperature dependent . Thus the stamp and substrate should have similar coefficients of linear heat expansion in the temperature range at which the cooling step is performed.

For practical reasons it is often preferable to provide a stamp having the same base material as the substrate. In the present description "base material" refers to that material of the stamp or the substrate that mainly decides the coefficient of linear heat expansion of the stamp or the substrate respectively. Usually the base material of the stamp is the material that forms the major part of the stamp. In the case with an aluminium substrate the base material of the stamp is preferably also made of aluminium thus ensuring that the coefficient of linear heat expansion will be the same for the substrate and the stamp regardless of the temperature .

The stamp should be able to transfer the pattern provided on its surface to many substrates. Thus the stamp, and in particular the patterned surface, must be hard, have good mechanical strength, resist wear and have good release properties. The release properties are decided by the surface characteristics. In some cases an antisticking mono molecular layer is applied to the patterned surface. WO 01/53889 describes a fluoroalkyl compound having a mercapto group which reacts with a nickel surface of a stamp to form a monomolecular antisticking layer on the patterned surface of the stamp. Thus a layer of nickel is in some cases preferably provided on the base material of the stamp since an antisticking layer may be attached to the nickel layer.

In some cases the base material of the stamp is not suitable for forming a pattern. In such cases the base material is preferably provided with a thin layer of a material suitable for forming patterns. The layer should be so thin that the coefficient of linear heat expansion of the stamp is decided by the base material . On the other hand the thickness of the layer must be sufficient for forming the pattern and for obtaining a good mechanical stability. Thus the thickness of the layer is preferably 50 nm to 50 μm, still more preferred 50-1000 nm. Preferably the layer is suitable also for contacting the moldable film and thus suitable for the actual imprinting process. Examples of materials suitable for forming a pattern and for the imprinting process are Ni, Ti, Al (preferably after oxidising the surface to harden it), and Si. In some cases a second layer may be applied on the first layer. The second layer could be a material that is suitable as a surface layer, but in some cases not suitable for the forming of patterns. Examples of such surface materials suitable for the imprinting process include Nb, Ti, Ta, Zr, Al . The second layer could be applied on the layer with the pattern with the help of known methods such as magnetron sputtering and deposition of a metal vapour. Examples of methods could be found in "Handbook of deposition technologies for films and coatings: Science, technology and applications", edited by Rointan F. Bunshah, second ed. , Noyes Publications, Westwood, NJ, USA 1994, ISBN 0-8155- 1337-2. The preferable methods are deposition of metal vapour in vacuum, described in section 4 of the above mentioned Handbook, and sputtering, which is described in section 5. The thickness of such a surface layer is preferably 2-200 nm.

In some cases the base material is suitable for forming a pattern but not for contacting a moldable film.

In such cases the pattern is provided on the base material. A layer of a material suitable for contacting the moldable film and thus for the imprinting process is then applied on the patterned base material . Examples of materials suitable for this layer include Ni, Nb, Ti, Ta, Zr, Al . The layer of a material suitable for imprinting may be applied to the base material by metal vapour deposition or sputtering as described above. The thickness of the layer applied to the patterned base material is preferably 2-200 nm.

The layer of a material suitable for imprinting must be firmly secured to the base material . The material in said layer could be nickel (Ni) having a coefficient of linear heat expansion of 13*10"6/K. If, as an example, nickel is applied as a layer of a material suitable for imprinting on a base material of aluminium there will be certain thermal stresses in the interface between nickel and aluminium during the heating and cooling of the stamp. The nickel layer must be sufficiently secured to the base material and sufficiently thin to follow the thermal movements of the aluminium base material. The base material may not be directly suitable for the deposition of a layer of a material suitable for imprinting. In such cases an adhesive layer is first applied to the base material, which may or may not comprise the pattern. The layer of a material suitable for imprinting and/or suitable for the forming of a pattern may then be applied to the adhesive layer. An example of such a material suitable as adhesive layer is copper which may act as epitaxial layer between the base material and the layer of a material suitable for imprinting.

Once a suitable stamp has been chosen the following steps are conducted. The substrate and the stamp are heated to a temperature at which the moldable film becomes soft. The heating could be done with the help of an electrical coil, a hot fluid, such as a gas, or in some other suitable way. The actual temperature depends on the actual moldable film. The pattern on the stamp is then pressed into the moldable film. The substrate and the stamp are then cooled to a temperature at which the moldable film becomes hard. The temperature to which the substrate and stamp are cooled would be typically 10- 100°C lower than the temperature at which the moldable film becomes soft. The cooling could be performed by contacting a cold fluid, such as a gas, with the flat sides of the substrate and the stamp being remote from the moldable film. Preferably the substrate and the stamp are cooled simultaneously and at the same rate such that the pattern on the moldable film is not affected by any variations in contraction between the stamp and the substrate. The stamp is then removed and the substrate having a pattern with high fidelity in the moldable film is ready for further processing such as etching, coating etc.

The hardening of the moldable film after pressing the stamp into it may, in addition to the cooling, be made with the help of UV-light. In such a case the substrate and the base material of the stamp is preferably made from a transparent material, such as polycarbonate .

Detailed Description of Preferred Embodiments of the Invention

Fig 1 shows a substrate 1. The substrate 1 is made of aluminium. The thermal expansion characteristics of the substrate 1 may be expressed in the form of the coefficient of thermal expansion or the coefficient of linear heat expansion for the material in question. The coefficient of linear heat expansion is about 24*10"6/K for aluminium at room temperature. At one surface, the lower surface as seen in fig 1, the substrate 1 is provided with a moldable film in the form of a polymer film 2. The polymer film has a softening temperature of about 350°C. The thickness TS of the substrate 1 is about 0,2 mm and the thickness TF of the moldable film 2 is about 200 nm. A stamp 4 is made of a base material 6 being aluminium. The coefficient of thermal expansion and thus the coefficient of linear heat expansion is the same for the stamp 4 as for the substrate 1. On its upper surface 8 the stamp is provided with a relief pattern 10 comprising a number of protrusions 12 formed in the base material 6 of the stamp 4. The thickness TB of the base material 6 and thus of the stamp 4 is about 0,2 mm. The protrusions 12 typically have a width of 200 nm and a height of about 150 nm.

An imprint process usually comprises the following steps. A substrate 1 is provided with a moldable film 2 made of a suitable polymer. The material of the substrate 1 and the coefficient of thermal expansion of the substrate 1 is assessed. A base material 6 having a similar coefficient of thermal expansion as the substrate 1 is chosen. A pattern 10 having protrusions 12 is provided on the base material 6 with the help of a known patterning method, such as etching, to obtain a stamp 4 having a relief pattern 10 on its surface 8. The substrate 1 and the stamp 4 are heated to a temperature being well above the temperature at which the moldable film 2 gets soft. With a moldable film having a softening temperature of 350°C the stamp 4 and the substrate 1 would both be heated to typically about 375°C. The pattern 10 of the stamp 1 is then pressed against the moldable film 2. As can be seen from fig 2 the protrusions 12 of the pattern 10 penetrate into the moldable film 2 and form a pattern in the moldable film 2. The stamp 4 and the substrate 2 are then cooled to a temperature well below the softening temperature of the moldable film 2. In the case with the moldable film 2 described above the temperature to which the stamp 4 and the substrate 1 would be cooled is about 325 °C. Since the stamp 4 and the substrate 1 have similar coefficients of thermal expansion they will have a similar contraction during the cooling. Thus a pattern formed in the moldable film 2 will not be affected by the protrusions 12 of the pattern 10 of the stamp 4 during the cooling. After cooling the pattern of the moldable film 2 has hardened and the stamp 4 is removed from the substrate 1. The substrate 1, which, as shown in fig 3, has the pattern 14 on its moldable film 2, may in subsequent process stages be etched, provided with additional layers or other moldable films for transfer of other patterns etc. or be subjected to other treatments to obtain a final product. In fig 4 a second embodiment of the invention is shown. In this case a stamp 104 comprises a base material 106. The coefficient of thermal expansion and thus the coefficient of linear heat expansion of the base material 106 is similar to that of the substrate on which the stamp 104 is intended to form a pattern. On a surface 105 of the base material 106 a layer of a material suitable for imprinting in the form of a nickel layer 107 is applied. The thickness TB of the base material 106 is about 0,2 mm and the thickness T of the nickel layer 107 is about 400 nm. On the surface 108 of the layer 107 a pattern 110 comprising protrusions 112 has been formed with the aid of a known patterning method, such as etching. Since the layer 107 is very thin in relation to the base material 106 the coefficient of thermal expansion of the stamp 104 will be determined by the base material 106 and not by the material of the layer 107. In fig 5 a third embodiment of the invention is shown. In this case a stamp 204 comprises a base material 206 of aluminium. The coefficient of thermal expansion and thus the coefficient of linear heat expansion of the base material 206 is similar to that of the aluminium substrate on which the stamp 204 is intended to form a pattern. On a surface 208 of the base material 206 a pattern 210 comprising a protrusion 212 has been formed with the aid of a known patterning method, such as etching. An adhesion layer 214 of copper has been applied to the patterned surface 208 of the base material. The copper layer, which has a thickness of about 10 nm, is provided to work as an epitaxial layer between the surface 208 of the base material 206 and a layer of a material suitable for imprinting in the form of a nickel layer 207. The thickness of the nickel layer 207 is about 20 nm. Since the nickel layer 207 and the adhesion layer 214 are very thin in relation to the base material 206, which has a thickness TB of about 0,2 mm, the coefficient of thermal expansion of the stamp 204 will be determined by the base material 206 and not by the material of the layer 207 and the adhesion layer 214.

In fig 6 a fourth embodiment of the invention is shown. In this case a stamp 304 comprises a base material 306 of polycarbonate. The coefficient of thermal expansion and thus the coefficient of linear heat expansion of the base material 306 is similar to that of a polycarbonate substrate on which the stamp 304 is intended to form a pattern. On a surface 308 of the base material 306 a nickel layer 307 being a layer of a material suitable for forming patterns has been applied. On the nickel layer 307 a pattern 310 comprising a protrusion 312 has been formed with the aid of a known patterning method, such as etching. An titanium layer 316 forming a second layer suitable for contacting the moldable film has been applied to the patterned surface 309 of the nickel layer 307. The titanium layer 316, which has a thickness of about 20 nm has excellent surface properties for the imprinting process. As an example an oxidized titanium layer has good properties for the binding of a mono olecular antisticking layer thereto. The thickness of the nickel layer 307 is about 400 nm. Since the nickel layer 307 and the titanium layer 316 are very thin in relation to the base material 306, which has a thickness TB of about 0,2 mm, the coefficient of thermal expansion of the stamp 304 will be determined by the base material 306 and not by the material of the layer 307 and the second layer 316.

It will be appreciated that numerous modifications of the embodiments described above are possible within the scope of the appended claims .

Claims

1. A method of transferring a pattern (10; 110; 210; 310) from a stamp (4; 104; 204; 304) to a substrate (1), which is provided with a moldable film (2) , said method comprising pressing the stamp (4; 104; 204; 304) against the moldable film (2), c h a r a c t e r i z e d by: using a stamp (4; 104; 204; 304) having a similar coefficient of thermal expansion as the substrate (1) , heating the stamp (4; 104; 204; 304) and the substrate (1) to a temperature at which the moldable film (2) becomes soft before pressing the stamp (4; 104; 204; 304) against the moldable film (2) , cooling the stamp (4; 104; 204; 304) and the substrate (1) to a temperature at which the moldable film (2) becomes hard, and removing the stamp (4; 104; 204; 304) from the substrate (1) .
2. A method according to claim 1, wherein the base material (6; 106; 206; 306) of the stamp (4; 104; 204; 304) is the same as the base material of the substrate (1) .
3. A method according to claim 2, wherein a layer (107; 207) of a material suitable for imprinting is provided on the surface (105; 208) of the base material (106; 206) of the stamp (104; 204) .
4. A stamp for transferring a pattern (10; 110; 210; 310) provided on the stamp (4; 104; 204; 304) to a substrate (1) , which is provided with a moldable film
(2), by pressing the stamp (4; 104; 204; 304) against the moldable film (2), c h a r a c t e r i z e d in that the stamp (4; 104; 204; 304) has a similar coefficient of thermal expansion as the substrate (1) .
5. A stamp according to claim 4, wherein the stamp (4) comprises one solid base material (6) having a similar coefficient of thermal expansion as the substrate (1) .
6. A stamp according to claim 4, wherein the stamp (104) comprises a base material (106) having a similar coefficient of thermal expansion as the substrate (1) , the pattern (110) of the stamp (104) being formed on a layer of a material (107) suitable for imprinting.
7. A stamp according to claim 6, wherein the thickness (TL) of said layer is 50 nm to 50 μm, preferably 50-1000 nm.
8. A stamp according to claim 4, wherein the pattern (210) is formed on the base material (206) , and being provided with a layer of a material (207) suitable for imprinting.
9. A stamp according to claim 8, wherein the thickness of said layer is 2 nm to 50 μm, preferably 2- 200 nm.
10. A stamp according to any one of claims 6-9, wherein an adhesion layer (214) is provided between the base material (106; 206) and said layer of material (107; 207) suitable for imprinting.
11. A stamp according to claim 4, wherein the stamp (304) comprises a base material (306) having a similar coefficient of thermal expansion as the substrate (1) , the pattern (310) of the stamp (304) being formed on a layer of a material (307) suitable for forming a pattern, a second layer (316) suitable for imprinting being applied to the surface (309) of said layer (307) having said pattern (310) .
12. A stamp according to any one of claims 6-11, wherein said layer of a material (107; 207; 316) suitable for imprinting comprises a material chosen in the group of materials consisting of Ni , Ti, Al , Nb, Ta, Zr, Cr, Cu, Si, glass and mixtures thereof.
PCT/SE2003/001164 2002-07-08 2003-07-04 A method and a stamp for transferring a pattern to a substrate WO2004006019A1 (en)

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EP1710624A2 (en) * 2005-04-06 2006-10-11 Hitachi, Ltd. Methods of fabricating nano-scale and micro-scale mold for nano-imprint, and mold usage on nano-imprinting equipment
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EP2172320A1 (en) * 2007-05-24 2010-04-07 Asahi Glass Company, Limited Mold, method for production of the mold, and method for production of substrate having replicated fine pattern
EP2172320A4 (en) * 2007-05-24 2011-07-06 Asahi Glass Co Ltd Mold, method for production of the mold, and method for production of substrate having replicated fine pattern
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