The present invention relates to an imprinting apparatus that transfers a recess/protrusion pattern formed in a mold to a transfer layer.
Lithography techniques generally used as techniques for pattern formation include photolithography and direct electron beam drawing. The direct electron beam drawing, for example, for manufacturing of a variety of products in small quantities. However, these lithographic techniques have various problems respectively. In the optical lithography, the pattern formation of 100 nm or less is difficult because there is a limit of the resolution due to the light wavelength. In the direct electron beam drawing, the throughput per unit time is low, and the method is not suitable for mass production. In order to overcome such limits to pattern fineness and processing capacity of the lithography techniques, which constitute a core technology of fine-structure device manufacturing technologies, considerable research on lithography employing novel methods is underway. Especially, research on nanoimprinting lithography as a technology enabling fabrication of nanometer-order design rules and being suitable for mass production is attracting attention. In this technology, a mold having a nanometer-scale concavity and convexity pattern is pressed onto a transfer layer on a substrate, and the fine concavity and convexity pattern of the mold is transferred to the transfer layer, to obtain a substrate on which is formed a fine recess/protrusion pattern.
In the usual imprinting process, the recess/protrusion pattern formed surface of a mold is pressed onto a transfer layer made of thermoplastic resin softened by heat treatment by a pressing pressure supplied from a pressure-applying piston, and keeping the pressure applied, the transfer substrate and the mold are cooled to harden the transfer layer. Then, the mold is separated from the transfer substrate, but the transfer layer and the mold are firmly stuck together and hence cannot be easily separated from each other. Accordingly, in order to make the mold easy to separate from the transfer substrate, fluorine coating or the like is performed on the recess/protrusion pattern formed surface of the mold in advance, but separating of the mold from the transfer substrate still requires a large force. Accordingly, in many imprinting apparatuses, with the mold being attached to the pressure-applying piston, the mold is separated from the transfer substrate by using a force in a separating direction generated by the pressure-applying piston.
Generally, in the imprinting process, it is necessary to align the mold and the transfer substrate in relative positions. In particular, in cases of forming fine pattern features of the order of a nanometer by imprinting, which are necessary in production processes for magnetic record media, semiconductor devices, and so on, highly accurate alignment is needed. However, the pressure-applying piston usually does not comprise a mechanism to perform alignment, and with the mold attached to the pressure-applying piston, means for alignment is limited. Further, when the pressure-applying piston goes up and down, wobbling occurs, and hence it is difficult to achieve highly accurate alignment between the mold and the transfer substrate.
In order to align the mold and the transfer substrate in relative positions with high accuracy, the mold and the pressure-applying piston need to be provided as separate units as in apparatuses described in the above references 1 and 2. However, in this case, a mechanism to separate the mold from the transfer substrate with use of compressed air, pushing-up pins, or the like is needed, thus making the apparatus complex in configuration. Further, with the separating mechanism that uses compressed air, pushing-up pins, or the like, it is difficult to obtain an enough separating force against the sticking force between the mold and the transfer substrate, and thus the separation may not be achieved. That is, with the conventional imprinting apparatuses, it is difficult to achieve both highly accurate alignment in relative positions between the mold and the transfer substrate and reliable separation between the mold and the transfer substrate.
The present invention was made in view of the above facts, and an object thereof is to provide an imprinting apparatus which enables highly accurate alignment between the mold and the transfer substrate and can reliably separate the mold from the transfer substrate.
An imprinting apparatus according to the present invention is an imprinting apparatus which includes a mold having a recess/protrusion pattern formed on a surface thereof and a pressure-applying piston that makes the mold and a transfer substrate having a transfer layer thereon come into close contact and that applies pressure to transfer shapes of the recess/protrusion pattern to the transfer layer. The imprinting apparatus comprises a mold holding unit having a mold holding surface to hold the mold; a substrate holding unit having a substrate holding surface opposed to the mold holding surface to hold the transfer substrate; and a support unit supporting the mold holding unit and the substrate holding unit in such a way as to be able to get closer to and farther from each other. The pressure-applying piston is movable along a direction intersecting with the mold holding surface and the substrate holding surface and has a pressure-applying surface that can come into contact with one of the mold holding unit and the substrate holding unit when applying pressure, and an engaging unit that can engage with one of the mold holding unit and the substrate holding unit when moving back.
Embodiments of the present invention will be described below with reference to the drawings. The same reference numerals are used to denote substantially the same or equivalent constituents or parts throughout the figures cited below.
The mold 10 is made of, e.g., silicon, nickel (including alloy), glass, or so on and has a recess/protrusion pattern formed surface in which there is formed a fine recess/protrusion pattern to be transferred to the transfer layer 22 of the transfer substrate 20. The recess/protrusion pattern of the mold is formed by, e.g., electron beam lithography, photolithography, or the like. Further, the mold 10 has an alignment mark 10a formed near the outer edge of the recess/protrusion pattern for adjusting the position thereof relative to the transfer substrate 20. The alignment mark 10a may be in any form as long as image recognition is applicable and is formed by, e.g., grooves, lines drawn by a laser marker or the like, or so on.
A mold holding unit 40 has a flat, mold holding surface and holds the mold 10 on the mold holding surface by, e.g., vacuum sucking, electrostatic chucking, mechanical clamping, or so on. The mold holding unit 40 is supported over a transfer substrate holding unit 30 with application of a force urging upwards in the figure by support poles 60 and springs 61 provided on the support poles 60, each of the support poles 60 being connected at one end to the mold holding surface and at the other end to a base 31. The mold holding unit 40 can go up and down in directions of getting closer to and farther from the transfer substrate holding unit 30 by the springs 61 expanding and contracting.
The transfer substrate holding unit 30 is placed on the base 31 under the mold holding unit 40, has a flat, substrate holding surface opposed to the mold holding surface, and holds the transfer substrate 20 on the substrate holding surface by, e.g., vacuum sucking, electrostatic chucking, mechanical clamping, or so on. The transfer substrate holding unit 30 is constituted by a so-called XY stage and driven in directions parallel to the substrate holding surface, i.e., X-Y directions by a drive mechanism (not shown) so that the mold 10 held on the mold holding unit 40 and the transfer substrate 20 held on the transfer substrate holding unit 30 can be aligned in relative positions.
An image pickup device 70 is constituted by, e.g., a CCD camera or the like and detachably or movably provided between the mold holding unit 40 and the transfer substrate holding unit 30. The image pickup device 70 has image pickup elements on its opposite sides, that is, on the mold 10 side and the transfer substrate 20 side and captures the alignment mark 10a of the mold 10 held on the mold holding unit 40 and the outer edge of the transfer substrate 20 held on the transfer substrate holding unit 30 at the same time. The images captured by the image pickup device 70 are output to a monitor (not shown). The alignment in relative positions between the mold 10 and the transfer substrate 20 is performed with viewing the images captured by the image pickup device 70, by moving the transfer substrate holding unit 30 constituted by an XY stage in X-Y directions so that the outer edge of the transfer substrate 20 is located on a vertical line from the alignment mark 10a.
A pressure-applying piston 50 is placed away from the mold 10 and the mold holding unit 40 and linked to a piston drive mechanism 58 (see
A plurality of the arms 52, which constitute engaging units of the present invention, are provided on outer edge of the pressure-applying piston 50.
After the pressure-applying piston 50 went down and has applied a pressing pressure to the mold 10 and the transfer substrate 20, when going up, the arm 52 is driven into the holding state. Thus, the bent portion at the end of the arm 52 engages with the edge of the mold holding unit 40. That is, with the edge of the mold holding unit 40 being embraced by the bent portion at the end of the arm 52, the mold holding unit 40 is lifted up in the direction of the pressure-applying piston 50 going up. By this means, a strong force is exerted on the interface between the mold 10 and the transfer substrate 20 in the separating direction, thus achieving separation.
The imprinting apparatus according to the present invention comprises a heating mechanism 23 (see
The block diagram of
Next, an imprinting method using the above-described imprinting apparatus will be described with reference to a process chart shown in
The mold 10 having a desired recess/protrusion pattern formed therein is prepared, and surface treatment with a fluorine coating agent or the like is performed on the recess/protrusion pattern formed surface of the mold 10 to prevent resin or the like used for the transfer layer from sticking and to improve separability. Then, the mold 10 is attached on the mold holding surface of the mold holding unit 40 by vacuum sucking, electrostatic chucking, mechanical clamping, or so on.
Then, the transfer substrate 20 is prepared. As the transfer substrate 20, there is used the thing obtained by coating thermoplastic resin such as acryl or polycarbonate over a flat substrate 21 constituted by, e.g., a silicon substrate, a glass substrate, an aluminum substrate, or the like by a spin coating method, a dispensing method, or the like to form the transfer layer 22. After the transfer layer 22 is formed on the substrate 21, the transfer substrate 20 is attached on the substrate holding surface of the transfer substrate holding unit 30 by vacuum sucking, electrostatic chucking, mechanical clamping, or so on (
Then, the alignment in relative positions between the mold 10 and the transfer substrate 20 is performed. In the present embodiment, the alignment is performed in the following procedure using the alignment mark 10a formed on the mold 10. First, the image pickup device 70 is placed between the mold holding unit 40 and the transfer substrate holding unit 30, and images of the alignment mark 10a are captured by the image pickup element provided on the mold 10 side, and at the same time, images of the outer edge and its neighborhood of the transfer substrate 20 are captured by the image pickup element provided on the transfer substrate 20 side. Then, with monitoring the images captured by the image pickup device 70, the transfer substrate holding unit 30 is moved in X-Y directions so that the outer edge of the transfer substrate 20 is located on a vertical line from the alignment mark 10a. Thereby, the alignment in relative positions between the mold 10 and the transfer substrate 20 is finished (
Next, the mold 10 and the transfer substrate 20 are heated to the softening temperature of the transfer layer 22 or higher by the heating mechanism 23. The softening temperature of the transfer layer 22 is at the transition temperature (Tg) in the case where the transfer layer 22 is made of polymer material. In contrast, in the case where the transfer layer 22 is made of crystalline polymer material, the layer may not soften even when the temperature exceeds Tg and may soften at close to the melting temperature. Further, a heat distortion temperature (Td) that is defined as the temperature at which material having a certain load imposed thereon becomes deformed by a certain amount is also referred to as the softening temperature.
When the transfer layer 22 has soften, the piston drive mechanism 58 is driven to lower the pressure-applying piston 50 linked thereto so as to cause the bottom surface, i.e., the pressure-applying surface of the pressure-applying piston 50 to come into contact with the top of the mold holding unit 40. At this time, the arms 52 are driven to be in the open state so as not to interfere with the mold holding unit 40 (
When the pressure-applying piston 50 further goes down, the mold holding unit 40 together with the pressure-applying piston goes down, so that the recess/protrusion pattern formed surface of the mold 10 and the transfer layer 22 of the transfer substrate 20 come into close contact. With the mold 10 and the transfer substrate 20 being in close contact, the pressure-applying piston 50 keeps applying the pressing pressure until a predetermined time has passed. Since the transfer layer 22 has been softened by heating, the transfer layer 22 is deformed along the fine shapes of the recess/protrusion pattern of the mold 10. Because the mold 10 itself is also heated to the softening temperature of the transfer layer 22, the softening of the transfer layer 22 is promoted. The pressure to press the mold 10 onto the transfer layer 22 and its duration are set as needed according to the shapes of the recess/protrusion pattern of the mold 10, the material of the transfer layer 22, and the like (
Then, the mold 10 and the transfer substrate 20 are cooled by the cooling mechanism 24 to harden the transfer layer 22. Note that the cooling of the mold 10 and the transfer substrate 20 is not limited to forced cooling by the cooling mechanism 24 but may be performed by natural heat radiation or lowering stepwise the heating temperature of the heating mechanism 23.
Next, the mold 10 is separated from the transfer substrate 20. At this time, first, the arms 52 connected to the pressure-applying piston 50 are driven to be in the holding state (
By undergoing the above steps, the fine recess/protrusion pattern of the mold 10 is transferred to the transfer layer 22 on the transfer substrate 20.
Next, the control of the operation of the imprinting apparatus by the main control unit 500 in the above series of imprinting process steps will be described with reference to the flow chart of
When an instruction to start the imprinting apparatus is input from the operation input unit 90 (step S1), the main control unit 500 supplies a drive signal to the electromagnetic valve 56 to drive the electromagnetic valve 56 to be open. By this means, the electromagnetic valve 56 gets in an open valve state to cause pressure inside the cylinder 54b of the arm drive mechanism 54 to be at the atmospheric pressure, driving the arms 52 to be in the open state (step S2). Subsequently, the mold 10 is attached on the mold holding unit 40, and the transfer substrate 20 is attached on the transfer substrate holding unit 30. After the alignment between the two is finished, when the heating temperature of the mold 10 and the transfer substrate 20 is input from the operation input unit 90, the main control unit 500 receives an instruction to set the temperature from the operation input unit 90 and supplies the heating mechanism 23 with a control signal according to the specified temperature. In the heating mechanism 23, the temperature controller (not shown) controls the heat generation of the heating elements (not shown) based on this control signal so that the mold 10 and the transfer substrate 20 are at the specified temperature (step S3). Subsequently, the main control unit 500 determines whether the temperature of the transfer substrate 20 has reached the specified temperature based on the temperature detected signal supplied from the temperature sensor 25 (step S4). When the temperature of the transfer substrate 20 has reached the specified temperature, the main control unit 500 supplies a drive signal to the piston drive mechanism 58 to lower the pressure-applying piston 50 (step S5). By this means, the pressure-applying piston 50 comes into contact at the bottom surface with the top of the mold holding unit 40 and lowers the mold holding unit 40. Then, the pressure-applying piston 50 makes the mold 10 and the transfer substrate 20 come into close contact and presses the mold 10 onto the transfer substrate 20 by a predetermined pressing pressure. After a predetermined time has passed from the time when the pressure-applying piston 50 started applying pressure (step S6), the main control unit 500 supplies the cooling mechanism 24 with a control signal to start cooling (step S7). The cooling mechanism 24 cools the mold 10 and the transfer substrate 20 according to this control signal to harden the transfer layer 22 formed on the transfer substrate 20. Then, after supplying the electromagnetic valve 56 with a drive signal to drive the electromagnetic valve 56 to be closed, the main control unit 500 supplies the pressure-applying pump 57 with a control signal to start supplying compressed air. By this means, compressed air is fed into the cylinder 54b of the arm drive mechanism 54, driving the arms 52 to be in the holding state (step S8). Subsequently, the main control unit 500 supplies a drive signal to the piston drive mechanism 58 to raise the pressure-applying piston 50 (step S9). The arms 52 are driven in the holding state, and the pressure-applying piston 50 goes up. Thereby the mold holding unit 40 is embraced by the arms 52 and the separation between the mold 10 and the transfer substrate 20 is performed. When the mold 10 has been separated from the transfer substrate 20 and the pressure-applying piston 50 has gone up to an initial position, the main control unit 500 supplies a drive signal to drive the electromagnetic valve 56 to be in the open valve state after stopping the driving of the pressure-applying piston 50 and the pressure-applying pump 57. By this means, the arms 52 are driven to be in the open state, thus releasing the transfer substrate holding unit 30.
The imprinting method according to the present invention can be applied to production processes of magnetic record media such as patterned media. Discrete track media, that are a type of patterned media, are record media configured to have grooves formed between data tracks made of magnetic material, where by filling these grooves with nonmagnetic material, the data tracks are separated physically and magnetically. Discrete track media are attracting attention as a breakthrough technology for achieving further higher record densities of magnetic record media because a harmful effect such as side write or crosstalk due to the record density becoming higher can be reduced. A production process of a discrete track media including the above imprinting process will be described with reference to a production process chart shown in
First, a mold 300 having a desired recess/protrusion pattern on a surface of a base material made of silicon, glass, or the like is produced. The recess/protrusion pattern is formed on the surface of the mold 300 by using electron beam lithography or another method to form a resist pattern, and then using the resist pattern as a mask to perform dry etching or similar. The completed mold 300 is surface-treated with a silane coupling agent or similar to improve separation properties. Note that a duplicate of nickel (including alloy) or the like produced by a method such as electroforming with the mold 300 as a master may be used as a mold for pattern transferring.
Next, a discrete track media substrate (hereinafter called a media substrate) 200 is produced. The media substrate 200 is formed by laying a recording layer 202 and a metal mask layer 203 one over the other on a substrate 201 formed of, e.g., specially treated chemically reinforced glass, a silicon wafer, an aluminum substrate, or the like. The recording layer 202 is formed by sequentially laying a soft magnetic underlying layer, an intermediate layer, and a ferromagnetic layer one over another by a sputtering method, and the metal mask layer 203 is formed of, e.g., Ta, Ti, or the like by a sputtering method (
Then, the recess/protrusion pattern of the mold 300 is transferred by the above imprinting method to a transfer layer 204 formed over the media substrate 200. That is, the transfer layer 204 of thermoplastic material is formed by spin coating or the like over the media substrate 200 prepared by the above process, and after the mold 300 is attached on the mold holding unit and the media substrate 200 is attached on the transfer substrate holding unit 30, the relative positions of the media substrate 200 and the mold 300 are adjusted (
When the alignment has finished, the media substrate 200 and the mold 300 are heated. When it has reached the softening temperature of the transfer layer 204, the mold 300 and the media substrate 200 are put in close contact, and by applying pressure, pattern transfer is performed (
Subsequently, the mold 300 and the media substrate 200 are cooled to harden the transfer layer 204. Then, the arms 52 are driven into the holding state, and the pressure-applying piston 50 is raised. The mold 300 is separated from the media substrate 200 by using the force of the pressure-applying piston 50 going up with the mold holding unit 40 being embraced by the arms 52. Through the above process, the recess/protrusion pattern of the mold 300 is transferred to the transfer layer 204 formed over the media substrate 200 (
Then, because a remaining film of the transfer layer 204 is left on parts of the substrate corresponding to the protrusions of the mold 300, the remaining film is removed by oxygen reactive ion etching (RIE) (
Then, after the remaining transfer layer 204 on the media substrate 200 is removed by wet etching or dry ashing, the metal mask layer 203 is used as a mask in dry etching to etch the recording film layer 202, to form grooves in the recording film layer 202 (
Then, a surface protective layer 206 of diamond-like carbon (DLC) excellent in lubricity and hard to wear or the like is formed by a CVD method or a sputtering method, and further a lubricant of perfluoropolyether (PFPE) diluted with a solvent, or the like is coated over by a dipping method or a spin coating method to form a lubricant layer 207 (
By undergoing the above process steps, a discrete track media to which the imprinting method according to the present invention has been applied is finished.
As apparent from the above description, with the imprinting apparatus according to the present invention, because the mold is not fixed to the pressure-applying piston, the alignment between the mold and the transfer material can be performed with high accuracy. Further, the plurality of arms to engage with the mold holding unit when the pressure-applying piston goes up are provided on the pressure-applying piston, and the mold holding unit is raised in the going-up direction of the pressure-applying piston with being embraced by the arms. Hence, the mold can be separated from the transfer substrate by using the strong force which raises the pressure-applying piston. That is, with the imprinting apparatus according to the present invention, a stronger separating force can be obtained than with the conventional apparatuses equipped with a separating mechanism that uses compressed air, pushing-up pins, or the like, and thus the separation between the mold and the transfer material can be reliably performed.
In the above embodiments, the pressure-applying piston is made to come into contact with the mold holding unit and to lower the mold holding unit, thereby performing the pattern transfer, and the arms are made to engage with the mold holding unit and then the mold holding unit is raised, thereby performing the separation. However, the pressure-applying piston may be made to come into contact with the transfer substrate and to lower the transfer substrate, thereby performing the pattern transfer, and the arms may be made to engage with the transfer substrate and then the transfer substrate may be raised, thereby performing the separation.
Further, although in the above embodiments the imprinting apparatus is configured such that when the pressure-applying piston goes down, the pressing pressure is applied and that when it goes up, the separation is performed, it may be configured such that when the pressure-applying piston goes up, the pressing pressure is applied and that when it goes down, the separation is performed.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2007/060497 | 5/23/2007 | WO | 00 | 1/6/2010 |