Patent Application
20050263915
1. Field of the Invention
The present invention relates to an imprinting method and an imprinting apparatus, for forming a concave/convex pattern on a substrate by pressing a stamper against a resin layer formed on a surface of the substrate to thereby transfer the concave/convex pattern, and an information recording medium-manufacturing method for manufacturing an information recording medium using the concave/convex pattern formed on the substrate.
2. Description of the Related Art
Conventionally, photolithography has been known as a method of forming a fine concave/convex pattern (resist pattern) in a resist layer formed on a surface of a substrate, which is employed in processes for manufacturing semiconductor devices, information recording media, etc. The photolithography comprises irradiating the resist layer on the substrate with exposure light to form an exposure pattern in the resist layer, and then subjecting the resist layer to development treatment to thereby form a concave/convex pattern on the substrate. Further, in recent years, as a technique to meet the needs of higher-density semiconductor devices and larger-capacity information recording media, there has been developed electron beam lithography which uses an electron beam in place of light to draw a nanometer-sized pattern to thereby form a concave/convex pattern. The electron beam lithography, however, takes a long time to draw the pattern on the resist layer, which makes it difficult to execute mass production of semiconductor devices and information recording media.
As a solution to the above problem, nanoimprint lithography (imprinting method of forming a nanometer-sized concave/convex pattern: hereinafter also referred to as the “imprinting method”) is disclosed in U.S. Pat. No. 5,772,905, in which a stamper (mold) having a nanometer-sized concave/convex pattern formed thereon is pressed against a resin layer on a substrate to transfer the shapes of recesses/protrusions of the stamper to the resin layer, thereby forming the nanometer-sized concave/convex pattern on the substrate. In this imprinting method, first, the stamper is manufactured such that it has the nanometer-sized concave/convex pattern (minimum width thereof is approximately e.g. 25 nm) formed on a transferring surface thereof. More specifically, a desired pattern is drawn on a silicon substrate having a silicon oxide layer formed on a surface thereof using a electron beam lithography apparatus, and then etching treatment is performed on the substrate by a reactive ion etching apparatus to form a concave/convex pattern. The stamper is thus manufactured.
Next, for example, polymethyl methacrylate (PMMA) is spin-coated on a surface of a silicon substrate to form a resin layer having a thickness of approximately 55 nm. Then, the laminate of the substrate and the resin layer, and the stamper are both heated to a temperature (e.g. approximately 200° C.) not lower than 105° C., which is a glass transition temperature of PMMA, and then the stamper is pressed against the resin layer on the substrate at a pressure of 13.1 MPa (133.6 kgf/cm2). Subsequently, the laminate with the stamper pressed against the same is allowed to stand (cooling process) until the temperature thereof becomes room temperature, whereafter the stamper is removed from the resin layer. This transfers the concave/convex pattern of the stamper to the resin layer, whereby a nanometer-sized concave/convex pattern is formed on the substrate.
As a result of the study of the conventional imprinting method, however, the present inventors found the following problems: In the imprinting method, both of the laminate of the substrate and the resin layer, and the stamper are heated to approximately 200° C. when the stamper is pressed against the resin layer, and cooled to room temperature before the stamper is removed from the resin layer. The thermal expansion coefficient of the substrate having the resin layer formed thereon and that of the stamper are different from each other, so that there occurs a difference in the amount of shrinkage between the substrate and the stamper caused during the cooling process. Therefore, when the stamper is removed from the laminate, the resin layer (resin material) having entered concave portions of the concave/convex pattern of the stamper receives a force which causes the resin layer to move together with the stamper (force causing the resin layer to move away from the substrate), whereby the resin layer (resin material) is sometimes deformed from a state provided with desired shapes of recesses/protrusions, or has portions thereof stripped off the substrate due to the deformation. For this reason, the conventional imprinting method suffers from the problem of possibility of deformation or incompleteness of a concave/convex pattern formed on the substrate.
Further, in the conventional imprinting method, the stamper is removed from the resin layer after subjecting both the laminate of the substrate and the resin layer, and the stamper to the cooling process. In this case, if the laminate and the stamper are rapidly cooled, there is a fear that the substrate is damaged (cracked) due to the rapid decrease in temperature. Therefore, it is required to take much time to cool the laminate and the stamper once heated to approximately 200° C. to ordinary temperature. For this reason, the conventional imprinting method suffers from the problem that it takes a relatively long time to form the concave/convex pattern.
The present invention has been made in view of the above problems, and a main object thereof is to provide an imprinting method, an imprinting apparatus, and an information recording medium-manufacturing method, which are capable of forming a concave/convex pattern in a short time period without causing deformation or incompleteness of the concave/convex pattern.
To attain the above object, in a first aspect of the present invention, there is provided an imprinting method comprising a stamper-pressing step of pressing a stamper against a resin layer formed by applying a resin material to a surface of a substrate, in a state of the resin layer being heated to a predetermined temperature, and a stamper-removing step of removing the stamper from the resin layer while maintaining either of the state of the resin layer being heated and a state of the temperature of the heated resin layer being held, wherein the stamper-pressing step and the stamper-removing step are performed in the mentioned order, whereby shapes of recesses/protrusions of the stamper are transferred to the resin layer to form a concave/convex pattern on the substrate. It should be noted that in the present invention, the term “state of the temperature of the heated resin layer being held” is intended to mean “state where heat treatment on the resin layer is terminated”, more specifically, “state where the resin layer is allowed to stand within a thermally insulated space, such as a temperature controlled bath (state where rapid decrease in temperature is prevented)”.
To attain the above object, in a second aspect of the present invention, there is provided an imprinting apparatus including heating section for heating a resin layer formed by applying a resin material to a surface of a substrate, a moving mechanism for pressing a stamper against the resin layer and removing the pressed stamper from the resin layer, and a control section for controlling the heating section and the moving mechanism, the imprinting apparatus being configured to be capable of transferring shapes of recesses/protrusions of the stamper to the resin layer to form a concave/convex pattern on the substrate, wherein the control section causes the heating section to heat the resin layer to a predetermined temperature, and the moving mechanism to press the stamper against the resin layer, and thereafter causes the moving mechanism to remove the stamper from the resin layer while maintaining either of the state of the resin layer being heated and a state of the temperature of the heated resin layer being held.
According to these imprinting method and imprinting apparatus, in the stamper-removing step, the stamper is removed from the resin layer while maintaining either of the state of the resin layer being heated and the state of the temperature of the heated resin layer being held, thereby preventing both the substrate and the stamper from undergoing almost any change in their temperatures during a time period from a time point when the stamper is pressed against the resin layer to a time point when the stamper is removed from the resin layer, so that it is possible to form a concave/convex pattern without causing thermal expansion or thermal shrinkage in the substrate and the stamper. Further, since there is no need to allow the substrate and the stamper to stand until the temperatures thereof become ordinary temperature, that is, since the cooling process can be dispensed with, it is possible to produce a large number of intermediates for manufacturing information recording media, for example, which have the concave/convex pattern formed on a substrate thereof, in a short time.
To attain the above object, in a third aspect of the present invention, there is provided an imprinting method comprising a stamper-pressing step of pressing a stamper against a resin layer formed by applying a resin material to a surface of a substrate, in a state of the resin layer being heated to a predetermined temperature, and a stamper-removing step of terminating heating of the resin layer and removing the stamper from the resin layer in a state of the temperature of the resin layer being substantially the same as the predetermined temperature, wherein the stamper-pressing step and the stamper-removing step are performed in the mentioned order, whereby shapes of recesses/protrusions of the stamper are transferred to the resin layer to form a concave/convex pattern on the substrate. It should be noted that in the present invention, the term “state of the temperature of the resin layer being substantially the same as the predetermined temperature” is intended to mean “state of the resin layer before the temperature thereof becomes not less than 10° C. lower than a temperature (predetermined temperature) at which the stamper-pressing step is performed”.
To attain the above object, in a fourth aspect of the present invention, there is provided an imprinting apparatus including heating section for heating a resin layer formed by applying a resin material to a surface of a substrate, a moving mechanism for pressing a stamper against the resin layer and removing the pressed stamper from the resin layer, and a control section for controlling the heating section and the moving mechanism, the imprinting apparatus being configured to be capable of transferring shapes of recesses/protrusions of the stamper to the resin layer to form a concave/convex pattern on the substrate, wherein the control section causes the heating section to heat the resin layer to a predetermined temperature, and the moving mechanism to press the stamper against the resin layer, and thereafter causes the heating section to terminate heating of the resin layer, and the moving mechanism to remove the stamper from the resin layer in a state of the temperature of the resin layer being substantially the same as the predetermined temperature.
According to these imprinting method and imprinting apparatus, in the stamper-removing step, the stamper is removed from the resin layer in the state in which the temperature of the resin layer is substantially the same as the temperature (predetermined temperature) at which the stamper-pressing step is performed. This makes it possible to sufficiently reduce changes in the temperatures of both of the substrate and the stamper, occurring during the time period from the time point when the stamper is pressed against the resin layer to the time point when the stamper is removed from the resin layer. Therefore, it is possible to sufficiently reduce the difference in the amount of shrinkage between the substrate and the stamper, so that it is possible to form a concave/convex pattern without any deformation or incompleteness, or with very little deformation or very few defective portions.
In the above case, in the stamper-pressing step, the resin layer can be heated by setting the predetermined temperature to a temperature not lower than the glass transition temperature of the resin material. This makes it possible to easily push convex portions of the concave/convex pattern of the stamper into the resin layer. As a result, it is possible to accurately and easily transfer the concave/convex pattern of the stamper to the resin layer on the substrate to form a concave/convex pattern thereon.
To attain the above object, in a fifth aspect of the present invention, there is provided a method of manufacturing an information recording medium using the concave/convex pattern formed on the substrate by the aforementioned imprinting method.
According to this information recording medium-manufacturing method, an information recording medium is manufactured using the concave/convex pattern formed on the substrate by the imprinting method described above. Therefore, the concave/convex pattern does not suffer from deformation or incompleteness, so that it is possible to manufacture an information recording medium which is free from a recording error or a reproduction error which can be caused by the deformation or incompleteness of the pattern.
It should be noted that the present disclosure relates to the subject matter included in Japanese Patent Application No. 2004-156981 filed May 27, 2004, and it is apparent that all the disclosures therein are incorporated herein by reference.
These and other objects and features of the present invention will be explained in more detail below with reference to the attached drawings, wherein:
Hereafter, an imprinting method, a method of manufacturing an information recording medium, and an imprinting apparatus, according to a preferred embodiment of the present invention, will be described with reference to the accompanying drawings.
First, a description will be given of the arrangement of the imprinting apparatus 1 according to the present invention.
The imprinting apparatus 1 shown in
As shown in
On the other hand, as shown in
Referring to
Next, a process for forming the concave/convex pattern on the intermediate 10 by the imprinting method according to the present invention will be described with reference to drawings.
First, the stamper 20 is fabricated. More specifically, as shown in
Then, as shown in
Next, the intermediate 10 and the stamper 20 are set in the pressing machine 2. More specifically, as shown in
Subsequently, the control section 3 causes the vertical movement mechanism 5 to lower the hot plate 4b toward the hot plate 4a, whereby as shown in
Then, as shown in
Next, a process for manufacturing the information recording medium 40 according to the information recording medium-manufacturing method of the present invention will be described with reference to drawings.
First, the resin material (residue) remaining on a bottom surface of each concave portion of the concave/convex pattern 34 on the resin layer 14 is removed by an oxygen plasma treatment. Then, etching treatment using a gas for metal etching is performed using (the convex portions of) the concave/convex pattern 34 as a mask. At this time, as shown in
Next, surface-finishing treatment is executed. In the surface-finishing treatment, first, the grooves (not shown) are filled with e.g. silicon dioxide and then the surfaces of the discrete tracks and the silicon dioxide are flattened by a CMP (chemical mechanical polishing) device. Then, a protective film is formed on the flattened surfaces e.g. by DLC (Diamond Like Carbon), and finally lubricant is applied to the protective film. Thus, the information recording medium 40 is completed. Since the information recording medium 40 is manufactured using the concave/convex pattern 34 free from deformation and incompleteness, so that the concave/convex pattern 36 (data-recording tracks, servo patterns, and the like) formed by using the concave/convex pattern 34 (concave/convex pattern 35) are also free from deformation and incompleteness. This makes it possible to prevent occurrence of a recording error or a reproduction error.
In contrast, instead of executing the imprinting method, if both of the intermediate 10 and the stamper 20 are cooled to approximately 60° C. before the stamper 20 is removed from the intermediate 10, and then the stamper 20 is removed from the resin layer 14, there occurs deformation in the concave/convex pattern 34 on the magnetic layer 12, and incompleteness of the pattern (peeling of portions of the resin layer 14 from the magnetic layer 12) at largely deformed portions of the concave/convex pattern 34. More specifically, the thermal expansion coefficient of the stamper 20 is higher than that of the disk-shaped substrate 11, so that when both of the intermediate 10 and the stamper 20 are cooled before the stamper 20 is removed from the intermediate 10, the stamper 20 is more largely shrunk than the resin layer 14. Therefore, the concave/convex pattern 34 on the magnetic layer 12 is sometimes deformed such that it is displaced toward the center of the disk-shaped substrate 11. For this reason, when the information recording medium 40 is manufactured using the concave/convex pattern 34 formed by removing the stamper 20 after cooling the intermediate 10 and the stamper 20, the concave/convex pattern 36 as well suffers from deformation or incompleteness, so that it becomes difficult to prevent occurrence of a recording error or a reproduction error.
As described above, according to the imprinting method implemented by the imprinting apparatus 1, during the stamper-removing step, the stamper 20 is removed from the resin layer 14 while maintaining the state of the resin layer 14 being heated, whereby there hardly occurs any change in the temperatures of the intermediate 10 and the stamper 20 during a time period from a time point when the stamper 20 is pressed against the resin layer 14 to a time point when the stamper 20 is removed from the resin layer 14. This makes it possible to form the concave/convex pattern without causing any thermal expansion or thermal shrinkage in either of the intermediate 10 and the stamper 20. Further, since there is no need to allowing the intermediate 10 and the stamper 20 to stand until the temperatures thereof become ordinary temperature, that is, the cooling process can be dispensed with, it is possible to produce a large number of intermediates 10 having the concave/convex pattern 34 formed on the magnetic layer 12 thereof in a short time.
Further, according to the imprinting method implemented by the imprinting apparatus 1, during the stamper-pressing step, the resin layer 14 is heated to a temperature (170° C. in the above example) not lower than the glass transition temperature of a resin material (approximately 70° C. in the above example, which is the glass transition temperature of the novolak resin used for forming the resin layer 14), whereby the convex portions of the concave/convex pattern 33 of the stamper 20 can be easily pushed into the resin layer 14. This makes it possible to accurately and easily transfer the concave/convex pattern 33 of the stamper 20 onto the resin layer 14 on the magnetic layer 12 to form the concave/convex pattern 34.
Furthermore, the information recording medium 40 is manufactured using the concave/convex pattern 34 formed on a substrate (laminate of the disk-shaped substrate 11 and the magnetic layer 12, in the above example) by the above-described imprinting method, so that the concave/convex pattern 36 is free from deformation and incompleteness. This makes it possible to manufacture the information recording medium 40 which is free from occurrence of a recording error or a reproduction error which can be caused by the deformation or incompleteness of the pattern.
It should be noted that the present invention is not limited to the above-described construction and method. For example, although in the imprinting apparatus 1, the heat treatment on both of the intermediate 10 and the stamper 20 is continuously executed during a time period from a time point before the start of the stamper-pressing step in which the stamper 20 is pressed against the intermediate 10 until a time point of completion of the stamper-removing step in which the stamper 20 is removed from the intermediate 10, this is not limitative, but it is also possible, for example, to terminate the heat treatment on both of the intermediate 10 and the stamper 20 after the stamper 20 is pressed against the intermediate 10 to a certain sufficiently degree, and then employ a step in which the stamper 20 is removed before the temperatures of the intermediate 10 and the stamper 20 are largely lowered (in a state where the temperatures of the intermediate 10 and the stamper 20 are substantially the same as a temperature thereof at which the stamper-pressing step is performed: e.g. before the temperatures of the intermediate 10 and the stamper 20 become not less than 10° C. lower than the temperature thereof at which the stamper-pressing step is performed).
Although in the above case, by starting the stamper-removing step as early as possible after termination of the heat treatment, the removal of the stamper 20 can be completed before the temperatures of the intermediate 10 and the stamper 20 are largely lowered, it is preferable to maintain the temperatures of the intermediate 10 and the stamper 20 such that the temperatures are not rapidly lowered during the stamper-pressing step and the stamper-removing step. In doing this, it is more preferable to maintain the temperatures of the intermediate 10 and the stamper 20 such that the temperatures do not become lower than the glass transition temperature of the resin material forming the resin layer 14. This makes it possible to sufficiently reduce the difference in the amount of shrinkage between the intermediate 10 (the disk-shaped substrate 11) and the stamper 20 caused before completion of removal of the stamper, compared with the conventional imprinting method in which the stamper is removed after the laminate and the stamper are cooled to a temperature much lower than the glass transition temperature of the resin material. As a result, similarly to the formation of the concave/convex pattern 34 by the imprinting apparatus 1, it is possible to form a concave/convex pattern which is free from deformation or incompleteness, or with very little deformation and very few defective portions.
Further, the heating section for heating the intermediate 10 and the stamper 20 is not limited to the hot plates 4 of the imprinting apparatus 1, but it is possible to employ various types of heating devices, such as heating devices that electrically or electromagnetically heat the intermediate 10 and the stamper 20, and heating devices that heat the intermediate 10 and the stamper 20 using a heat wave. Furthermore, although in the above imprinting apparatus 1, the concave/convex pattern 34 is formed on one surface of the disk-shaped substrate 11 by pressing a single stamper 20 against the intermediate 10 having the resin layer 14 formed on the one surface of the disk-shaped substrate 11 thereof, this is not limitative, but it is also possible to form concave/convex patterns on both the front and reverse surfaces of the substrate of the intermediate by pressing two stampers against the intermediate having resin layers formed on the opposite surfaces of the substrate thereof in a manner sandwiching the same. Additionally, the use of the concave/convex pattern formed by the imprinting method according to the present invention is not limited to manufacturing of discrete track-type information recording media, but the concave/convex pattern can be employed for manufacturing patterned media including patterns other than the track-shaped patterns, and devices (e.g. electronic component parts) other than the information recording media.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-156981 | May 2004 | JP | national |
