Patent Application
20060258163
The present invention relates to a mold for nano-imprint wherein a fine structure is formed on a transferred substrate, which is made of resin, using a mold for forming nano meter level fine convexo-concaves, and to methods of fabricating the same, nano-imprinting equipment, and methods of nano-imprinting.
Recently, miniaturization and more integration of semiconductor integrated circuits have been progressing, and as a pattern transfer technique for realizing the fine process, higher precision of the photolithography equipment has been progressing. However, the processing method thereof has come near the wavelength of light sources in the light exposure, and the lithography technique has come near the limitations. Therefore, in order to advance the miniaturization and higher precision further, the electron beam lithography equipment, which is a type of charged particle beam equipment, is beginning to be employed instead of the lithography technique.
For the pattern formation using an electron beam, a method of drawing mask patterns, unlike a batch exposure method in the pattern formation using a light source, such as an i-line and an excimer laser, is adopted. Therefore, as the more patterns are drawn, the more exposure (drawing) time is taken, and that the pattern formation takes more time is a drawback. For this reason, as the degree of integration increases exponentially to 256 mega, 1 giga, 4 giga, and so on, the pattern formation time also will become longer exponentially accordingly, and a significant decrease of the throughput is a concern. Then, for the purpose of improvement in the speed of electron beam exposure equipment, the development of the batch pattern irradiation method, in which various shapes of masks are combined and an electron beam is irradiated to them altogether, thereby forming a complex shape of electron beams, has been progressing. As a result, while the miniaturization of patterns has been progressing, there is still a drawback in the increased cost of equipment because the size of the electron beam lithography equipment has to be increased, and a mechanism to control the mask position more accurately is needed, or the like.
On the other hand, a technique for forming fine patterns at low cost is disclosed in the following Patent Documents 1 and 2, non-Patent Document 1, or the like. In these techniques, a predetermined pattern is transferred by stamping a mold having the same pattern of convexo-concaves as the pattern, which is desired to be formed on a substrate, into a resist film layer formed in a transferred substrate face. According to the nano-imprint technique described in Patent Document 2 and non-Patent Document 1, in particular, a fine structure of 25 nm or less can be formed by transfer using a silicon wafer as the mold.
(Patent document 1) U.S. Pat. No. 5,259,926
(Patent document 2) U.S. Pat. No. 5,772,905
(Patent document 3) JP-A-2003-157520
(Non-Patent document 3) S. Y. Chou et al., Appl. Phys. Lett., vol. 67, p. 3114 (1995)
However, when the present inventors investigated the above imprint techniques, which are assumed to be able to form fine patterns, it is found that in the case where Ni is used as the mold, there are problems in releasing the mold from a transferred object after the transfer, as follows. Namely, it was revealed that because the shape to transfer is extremely fine convexo-concave, unless a strong mechanical work is applied to the substrate and the mold (i.e. the transcripts) in the case where the transfer pattern is formed across a wide area, the both can not be separated to each other, and also a phenomenon that the residue of the resin remains on the mold side is observed.
In the above Patent Document 3, a technique is disclosed wherein a buffer layer, such as a polymer sheet and a rubber sheet made of a material softer than the mold and the press face, is provided in between the mold and the pressure face thereby to eliminate the waviness or the like of the substrate and providing a uniform pressure, and thus the mold-release characteristic is improved. However, when the present inventors conducted an experiment of transfer by using, as the buffer material, a material softer than the mold and the pressure face, even if the above material is resiliently deformed to fill the gap in between the mold and the pressure face during the pressuring, repulsion from the buffer material becomes consequently large in the portion with a narrow gap as compared with the portions with a wide gap, As a result, it was revealed that in-plane pressure irregularity was not eliminated and the mold-release characteristics was not improved, either.
In view of the above technical problems, it is an object of the present invention to enable the mold to be reused multiple times by mold-releasing a Ni metal and a transferred substrate without releasing them by means of a mechanical work, in the nano-imprint method, which is a pattern transfer technique of forming a structure with fine convexo-concave shapes.
According to a first aspect of the invention, there is provided a mold for nano-imprint, having a Ni-containing oxide film with a thickness of 1 to 3 nm on an imprint side surface of a mold, at least the imprint side surface of the mold being formed from Ni or Ni alloy.
Moreover, according to a second aspect of the invention, there is provided a method of fabricating a mold for nano-imprint, comprising the steps of: acid-treating a nano-imprint side surface having a surface formed from Ni or Ni alloy to form a Ni-containing oxide film with a thickness of 1 to 3 nm.
Moreover, according to a third aspect of the invention, there is provided an imprint equipment, comprising:
means for supporting a resin film in which nano meter level convexo-concaves are to be formed;
a mold for nano-imprint having a nano-imprint face; and
a stage which supports the mold for nano-imprint as to face to the resin film surface,
wherein at least the nano-imprint face of the mold for nano-imprint is formed from Ni or Ni alloy, and the nano-imprint face has a Ni-containing oxide film with a thickness of 1 to 3 nm and a water repellent resin film covering the surface thereof.
Moreover, according to a fourth aspect of the invention, there is provided a nano-imprint method, comprising the steps of:
bringing an imprint face of a mold made of Ni or Ni alloy, the mold having a Ni-containing oxide film with a thickness of 1 to 3 nm and a water-repellent resin film covering the surface thereof, in contact with an organic resin film face, in which nano meter level convexo-concaves are to be formed;
controlling a softening and hardening of the organic resin film with heat, light, and/or a carbon dioxide gas; and
transferring the convexo-concaves of the mold for nano-imprint onto the organic resin film face.
According to the invention, excellent nano-imprinting can be carried out without increasing the release force between the mold and the resin film, which is the transferred material, during nano-imprinting. Moreover, because the nano-imprint face is difficult to subject to damages, a long-life mold for nano-imprint is obtained.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.
The present inventors believed that because in case of a Ni mold among metal molds, a Ni-oxide film is present in the surface of the mold, and a release agent tends not to be formed in layers in the mold face due to the crystal properties of the oxide, inconvenience will arise in the mold release after the transfer. Moreover, the present inventors believed the adhesive properties of the release agent are improved by adjusting the thickness of the oxide film, which led us to the present invention.
That is, the present invention is an invention of a mold for nano-imprint made of Ni or Ni alloy. The present invention is applied to a mold wherein the mold and a transferred substrate are pressurized uniformly when transferring fine convexo-concaves of the surface of the mold, the mold having the fine convexo-concaves formed in the surface thereof, onto the surface of the transferred substrate by pressure using a pressure device. The above mold has a Ni-containing oxide film on the imprint side face, and by controlling the thickness thereof within a certain range, the release of the mold (in which a resin film as the release material is formed in the imprint face thereof) from the transferred resin film during nano-imprinting can be carried out with a small force. Accordingly, there are also few damages to the mold, the mold will be long-lived, and moreover, the transcripts have few distortions and positional deviations, thus obtaining highly precise nano-imprint. Moreover, because the release force is very small, means for releasing the mold from the transferred resin film may be omitted.
According to the present invention, in the method of transferring a fine pattern, in which method a mold, in which fine convexo-concaves are formed, is stamped to a transferred substrate with the use of the pressure device thereby to transfer the fine convexo-concave pattern in the surface of the mold onto the transferred substrate, the mold, in which the fine convexo-concaves are formed, of the pressure device is formed from a Ni-containing oxide film and a release agent. The invention relates to the method of transferring a fine pattern, in which method pressurizing is carried out using the mold in which the thickness of this oxide film is controlled.
Hereinafter, more specific embodiments of the invention will be exemplified. The contact angle of the surface of a Ni-containing oxide film against water is preferably 100 degrees or more. It is preferable that a resin film for mold release be prepared on the surface of the Ni-containing oxide film. Although the thickness of the resin film as the release material is optional, it is desirably 200 nm or less. The lower limit of the thickness may be a thickness at a level of protecting the nano-imprint face from influences of the open air and at a level of not being worn out by the pressure during nano-imprinting. For example, it just needs to be 2 nm or more. It is preferable that the contact angle between the resin film and water be 100 degrees or more.
It is preferable that the nano-imprint side surface of the mold be terminated with oxygen and a hydroxyl group. Although when Ni is oxidized in the atmosphere, NiO is usually formed, Ni (OH)2 may be formed through a reaction with water (water vapor) in the atmosphere, thereby becoming the top surface. Moreover, it is preferable that the mold surface be covered with a resin film after being terminated with oxygen and a hydroxyl group. The contact angle between the resin film and water is preferably 100 degrees or more.
Here, it is preferable that Ni, Ni alloy, or Ni plating be used as the metal mold. Namely, this is because in atmospheric environment it is difficult to maintain a fine pattern shape with metal of which surface shape changes by corrosive action. Moreover, while the oxide film becomes a NiO crystal as a natural oxide film, it may become in an amorphous state where the crystal form is generally obscure, or otherwise may become a compound of which top surface layer is replaced by a hydroxyl group. Moreover, it is preferable that the release agent formed in the surface be a fluorine compound or a heat-resistant resin made of a fluorine mixture. In particular, an organic resin known as the water repellent material with the contact angle against water of 100 degrees or more is preferable.
It is preferable that metal used for the mold of the invention have a high thermal conductivity in order to transfer energy from the heating element to the mold and the transferred substrate efficiently. Moreover, it is preferable that the thermal deformation amount of the mold of the invention be small at temperatures below the glass-transition temperature of the transferred substrate. With the use of such a metal, almost no oxidization effect due to corrosion is observed at room temperature, the storage and handling become easy, and highly precise transfer can be secured taking advantage of the thermal conductivity during the heat transfer.
Here, the method of molding a transferred substrate to be used in the invention is preferably selected from (1) A method of heating a resin substrate or a resin film on a substrate thereby to deform, or (2) A method of photo-curing after pressure-forming a resin substrate or a resin film on a substrate.
A pressure device to be used in the invention comprises a press stage and a press head having two press faces at upper and lower portions for pressuring the mold and the transferred substrate altogether, and a pressure thrust generation mechanism to apply pressure to them. Here, it is preferable that the press head and the press stage include an induction coil for inductive heating the mold, and a cooling mechanism for cooling the mold and the transferred substrate. Moreover, the pressure thrust generation mechanism generates a thrust using an oil pressure force, an air pressure force, an electric force by a torque motor, or the like. Furthermore, a vacuum chamber may be included that enables the transfer under vacuum conditions by decompressing the whole of the press stage and press head, as required.
A mold for nano-imprint of the invention and a method of nano-imprinting will be described with reference to
In
The nano-imprint method will be described with reference to
Next, the mold and the resin are cooled and cured (
The nano-imprint method has features such as (1) An extremely fine integrated pattern can be transferred efficiently, (2) Equipment cost is low, and (3) Complex shapes can be accommodated and pillar formation or the like are also possible.
The application field of the nano-imprint method of the invention, taking advantage of these features, extensively includes (1) Various biotechnology devices, such as a DNA chip and an immunity analysis chip, especially a disposable DNA chip, or the like, (2) Semiconductor multilayer interconnection, (3) Printed circuit boards and RF MEMS, (4) Optical or magnetic storage, (5) Optical devices, such as a waveguide, a diffraction grating, a micro lens, and a polarization element, and a photonic crystal, (6) Sheets, (7) LCD display, (8) FED display, or the like. The present invention is preferably applied to these fields.
In the invention, the nano-imprint refers to transfer in the range from approximately several hundreds μm to several nm. In the invention, the mold for nano-imprint refers to the one having a fine pattern to be transferred, and the method of forming this pattern onto the mold for nano-imprint is not limited in particular. For example, a photolithography, an electron beam lithography method, or the like are selected according to the desired processing accuracy.
In the invention, although the material to be a substrate is not limited in particular, it may be the one having a predetermined strength. Specifically, silicon, various metal materials, glass, ceramics, plastics, or the like are preferably exemplified.
In the invention, although the resin film to which a fine structure is transferred is not limited in particular, it is selected according to the desired processing accuracy. Specifically, there are listed thermoplastic resins, such as polyethylene, polypropylene, polyvinyl alcohol, polyvinylidene chloride, polyethylene terephthalate, polyvinyl chloride, polystyrene, ABS resin, AS resin, acrylic resin, polyamide, polyacetal, poly butylene terephthalate, glass reinforced polyethylene terephthalate, polycarbonate, modified polyphenylene ether, polyphenylene sulfide, polyether ether ketone, mesomorphism polymer, fluororesin, poly allate, poly sulfone, polyether sulfone, polyamide imide, polyether imide, and thermoplastic polyimide. Moreover, there are also listed thermosetting resins, such as phenol resin, melamine resin, urea resin, epoxy resin, unsaturated polyester resin, alkyd resin, silicone resin, diallyl phthalate resin, polyamide bismaleimide, and polybisamide triazole. Furthermore, materials made by blending two or more kinds of these may be used.
Hereinafter, the examples of the invention will be described.
The characteristic of the surface oxide-film of a Ni mold, which is one of the embodiments of the invention, will be described using
It was found that as the Ni surface oxide film to serve as the substrate becomes thinner, the contact angle becomes larger, and that in the Ni surface treated with the release agent, the mold-release characteristic improves remarkably if the Ni-oxide film is 5 nm thick or less. Because the contact angle is 100 degrees or more, it is an excellent release agent.
Next, the transfer experiment using the mold of the invention was carried. Hereinafter, a method of fabricating a mold, in which fine convexo-concaves are formed, to be used in this transfer will be described using
Next, the mold of the invention is stacked, by means of the pressure device, onto the stage, and the transferred substrate, in which a polystyrene thin film with a thickness of 0.5 μm is formed on a silicon wafer of 6 inch Φ, thereby conducting the transfer experiment. The transfer conditions were at the transfer temperature of 200° C., under the pressure of 10 kgf/cm2, and for the holding-time of 3 minutes. During the transfer, the measurements of heat-up time from 60° C. to 200° C., and of cool down time from 200° C. to 60° C., and also the in-plane pattern formation were evaluated. As a result, the heat-up time and the cool down time were one minute or less. Moreover, the in-plane variation of the transfer pattern was not observed, and transfer irregularities did not occur across the 6 inch Φ, and an excellent transfer pattern was obtained. On the background that the uniform transfer was achieved, there is a fact that the whole transfer substrate could be released from the mold without receiving external force actions thanks to the invention. The principle of this is considered to be based on a fact that the adhesive strength (the physical force (van der Waals force) and the chemical force (ionic bonding force) between the resin and the mold) produced between the substrate and the mold is reduced by using the oxide-film layer and the release agent layer of the invention. As a result, the mold release was uniformly realized across the whole surface.
The force required for the release between the mold and the transferred substrate, which is one of the embodiments of the invention, will be described using
Hereinafter, several fields, to which the nano-imprint using the mold with the release mechanism of the invention is preferably applied, will be described.
The invention is applied to a mold used for biochip preparation.
Because the incident light onto a light sensitive detector 907 decreases by approximately 4% when the DNA passes therethrough, the DNA chain length in the sample can be analyzed by the output signal from the light sensitive detector 907. The signal detected at the light sensitive detector 907 is inputted to a signal processing chip 909 via a signal wiring 908. Signal wiring 910 is coupled with the signal-processing chip 909, and the signal wiring 910 is coupled with an output pad 911 and connected to a terminal from the outside. In addition, the electric power was supplied to each part from a power supply pad 912 installed in the surface of the substrate 901.
A sectional view of the molecule filter 905 is shown in
Accordingly, it is possible to closely contact the upper substrate 1001 to the protrusion assembly 100. With such a configuration, the sample will not leak out of the gap between the protrusions and the upper substrate 1001, allowing a highly sensitivity analysis to be made. As a result of the actual analysis on the DNA chain length, it was found that while the resolution of a base pair was 10 base pairs in full-width at half maximum in the protrusion assembly 100 made of glass, the resolution of the base pair can be improved to 3 base pairs in full-width at half maximum in the protrusion assembly 100 made of an organic substance. In the molecule filter of this embodiment, a structure is formed in which the protrusion comes in directly contact with the upper substrate, however, for example, if a structure is formed in which a film made of the same material as the protrusion is formed in the upper substrate, and the protrusion comes in contact with this film, then the adhesion can be improved.
In addition, although in this embodiment the count of the passage 902 was one, it is also possible to carry out different analysis simultaneously by arranging a plurality of passages 902 in which the protrusions with different sizes are installed. Moreover, although in this embodiment DNA was investigated as the sample, a specific oligosaccharide, protein, and antigen may be analyzed by modifying the surface of the protrusion assembly 100 with a molecule in advance, which reacts with oligosaccharide, protein, and antigen. In this way, by modifying the surface of the protrusions with antibody, the sensitivity of immunity analysis can be improved.
By applying the invention to biochips, it is possible to obtain an effect that the protrusions used for the analysis on an organic material with a nano scale diameter can be formed easily. Moreover, it is also possible to obtain an effect that the position, diameter, and height of the protrusions made of an organic material can be controlled by controlling the convexo-concaves in the surface of the mold and the viscosity of the thin film of organic material. Microchips used for highly sensitive analysis can be provided.
A Ni mold of the invention can be applied to nano-imprint for producing a multilayer interconnection substrate (1006).
Moreover, other steps for producing the multilayer interconnection substrate will be described. In dry etching the exposed region 703 from the state shown in
By applying the invention to multilayer interconnection substrates, it is possible to form wiring with high dimensional accuracy. According to the embodiment of the invention, in transferring a fine convexo-concave pattern onto resin on a substrate or onto resin by means of nano-imprint using a metal mold, especially a Ni mold, the mold release failure after the transfer can be eliminated by using a mold, in which the transfer surface of a Ni metal mold is composed of a thin oxide film and a release agent. Moreover, thermal conductivity to the mold surface can be improved due to an effect of thinning the thickness of the oxide film. The means for releasing may not be provided, and thus the heat conduction can be improved. Thereby, time required for the transfer can be reduced and the repetitive usage of the mold is allowed, and moreover, the durability of the mold can be improved due to the hardness given by the oxide film.
Production of a magnetic recording medium by means of nano-imprint using the Ni mold according to this embodiment is possible.
On the other hand, as the mold, a Ni mold is prepared in which a groove is formed as to be concentric with respect to a hole in the center of the magnetic recording medium. Dimensions of the groove are 88 nm wide, and 200 nm deep, and the distance between the grooves was set to 110 nm. Because the convexo-concaves of the mold are very fine, they were formed by photolithography using an electron beam. Next, as shown in
Moreover, by removing the residual film that remained in the bottom of the resin pattern with dry etching, a pattern like
In the magnetic recording medium of this embodiment, the magnetic anisotropy is secured with the fine pattern using the nano-imprint method, and a high-density record as large as 400 Gb/square inch could be realized. In addition, the pattern formation by the nano-imprint is not limited to the circumferential direction, but a non-magnetic bulkhead can be formed in the radial direction. Furthermore, the magnetic-anisotropy effect described in this embodiment is not particularly limited according to the material of the seed layer, substrate layer, magnetic layer, and protective layer.
In this embodiment, an example will be described in which an optical device, in which the traveling direction of an incident light is changed, is applied to an optical information processing equipment.
In the optical circuit 500, signal lights of ten different kinds of wavelengths can be superimposed to be outputted, and because the traveling directions of the lights can be changed, the width of the optical circuit 500 can be made very narrow to 5 mm, providing an effect of enabling the optical communication to be miniaturized. Moreover, because the protrusions 406 can be formed by pressing the mold, an effect of reducing the manufacturing cost is also obtained. Although in this embodiment the device in which the input lights are superimposed has been described, it is apparent that the optical waveguide 503 is useful for all the optical devices that control the traveling course of light.
By applying the invention to the optical waveguide, an effect that the traveling directions of light can be changed by forcing the signal light to travel through the structure, in which the protrusions made of an organic substance as the principal component are disposed periodically, is obtained. Moreover, since the protrusions can be formed by a simple manufacturing technology of pressing a mold, an effect that the optical devices can be manufactured at low cost is obtained.
It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-109943 | Apr 2005 | JP | national |
