STAMPER, IMPRINTING METHOD, AND METHOD OF MANUFACTURING AN INFORMATION RECORDING MEDIUM
A stamper has stamper-side concave/convex patterns formed thereupon and is capable of manufacturing an information recording medium on which data track patterns and servo patterns are formed by concave/convex patterns. A plurality of types of convex parts with different heights from a reference plane, which is set between a front surface and a rear surface of the stamper, to protruding ends of the convex parts are formed in the stamper-side concave/convex patterns. Second convex parts, at least one part of which has the height that is higher than the height of a highest first convex part out of the convex parts formed in regions corresponding to the data track patterns, are formed in regions corresponding to the servo patterns.
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1. Field of the Invention
The present invention relates to a stamper used when manufacturing an information recording medium, an imprinting method that presses a stamper into a resin layer formed on a surface of a substrate to transfer a concave/convex form of the stamper, and a method of manufacturing an information recording medium using a concave/convex pattern transferred to a resin layer.
2. Description of the Related Art
Optical lithography is conventionally known as a method of forming a fine concave/convex pattern (a resist pattern) in a resist layer (a resin layer) formed on a surface of a substrate during a process that manufactures an information recording medium or the like. When optical lithography is carried out, a resist layer formed on a subs-rate is irradiated with light to form an exposure pattern and then the resist layer is developed to form a concave/convex pattern on the substrate. In recent years, electron-beam lithography that draws a pattern of nanometer size using an electron beam instead of light to form a concave/convex pattern has been developed as a technique for forming an even finer pattern. However, electron-beam lithography has a problem in that a long time is required to draw a pattern on the resist layer, making such technique unsuited to mass production.
As a method of solving this problem, U.S. Pat. No. 5,772,905 discloses a nano-imprint lithography method (i.e., an imprinting method that forms a concave/convex pattern of nanometer size: hereinafter simply “imprinting method”) that forms a concave/convex pattern of nanometer size on a substrate by pressing a stamper on which a concave/convex pattern of nanometer size has been formed onto a resin layer on the substrate to transfer the concave/convex form of the stamper to the resin layer. With this imprinting method, first as shown in FIG. 1A of U.S. Pat. No. 5,772,905, a stamper (“mold”) 10z (hereinafter component elements disclosed in the specification of the U.S. Pat. No. 5,772,905 are indicated by reference numerals appended with “z”) that has a concave/convex pattern of nanometer size (as one example, with a minimum width of around 25 nm) formed in a transfer surface thereof is manufactured. More specifically, an electron beam lithography apparatus is used to draw a desired pattern on a resin layer formed so as to cover a thin film (“molding layer”) 14z made of silicon oxide or the like that has been formed on the surface of a silicon substrate 12z, and then the thin film 14z is etched by a reactive ion etching apparatus with the resin layer as a mask to form a concave/convex pattern with a plurality of convex parts (features) 16z within the thickness of the thin film 14z. By doing so, the stamper 10z is manufactured.
Next, as one example, polymethyl methacrylate (PMMA) is spin coated on the surface of a silicon substrate 18z to form a resin layer (a “thin film layer”) 20z with a thickness of around 55 nm. Next, after heating both the stamper 10z and a multilayer structure composed of the substrate 18z and the resin layer 20z to around 200° C., as shown in FIG. 1B of the U.S. Pat. No. 5,772,905, the convex parts 16z of the stamper 10z are pressed into the resin layer 20z on the substrate 18z with a pressure of 13.1 MPa (133.6 kgf/cm2). After this, the multilayer structure is left to cool to room temperature in a state where the stamper 10z is still pressed in (i.e., a cooling process is carried out), and then the stamper 10z is separated from the resin layer 20z. By doing so, as shown in FIG. 1C of the U.S. Pat. No. 5,772,905, the convex parts 16z of the concave/convex pattern of the stamper 10z are transferred to the resin layer 20z to form a plurality of concave parts (“regions”) 24z, thereby forming a concave/convex pattern of nanometer size (in the resin layer 20z) on the substrate 18z.
SUMMARY OF THE INVENTIONBy investigating the conventional imprinting method described above, the present inventors found the following problems. That is, with this imprinting method, as shown in FIGS. 1A and 1B of the U.S. Pat. No. 5,772,905, a stamper 10z formed so that the heights from the bottom surfaces of the concave parts in the concave/convex pattern to the protruding ends of the convex parts 16z are uniform across the entire stamper (that is, a stamper formed so that the protruding ends of the respective convex parts 16z lie on substantially the same plane) is pressed into the resin layer 20z to form the concave/convex pattern on the substrate 18z. Various types of convex parts 16z with different lengths along a direction that corresponds to a circumferential direction (i.e., the direction of rotation) of the information recording medium (hereinafter simply “lengths in the circumferential direction”) and/or different lengths along a direction corresponding to a radial direction of the information recording medium (hereinafter simply “lengths in the radial direction”) are formed on the stamper 10z in accordance with the form of the data track patterns and the servo patterns to be formed. However, with the conventional imprinting method, since the concave/convex pattern is pressed onto the resin layer 20z with a substantially uniform pressing force across the entire stamper 10z, parts where convex parts 16z that are long in the radial direction and comparatively long in the circumferential direction, for example, have been formed are difficult to press sufficiently deeply into the resin layer 20z.
More specifically, as shown in
On the other hand, as shown in
Convex parts 16z for forming burst patterns, where individual burst regions are composed of convex parts, out of the servo patterns on the information recording medium (i.e., convex parts 16z for forming the concave parts between the individual burst regions in the burst patterns) are set so that the lengths thereof in the circumferential direction between the concave parts corresponding to the individual burst regions become gradually longer from the inner periphery to the outer periphery. Similarly, convex parts 16z for forming burst patterns, where individual burst regions are composed of concave parts, out of the servo patterns on the information recording medium (i.e., convex parts 16z for forming the individual burst regions in the burst patterns) are set so that the lengths of the convex parts 16z in the outer periphery in the circumferential direction become longer than those of the convex parts 16z in the inner periphery. Accordingly, in servo pattern forming regions in which convex parts 16z that are comparatively long in the circumferential direction are formed (in this example, the cuter peripheries of the burst pattern forming regions), it is difficult for the PMMA to move smoothly into the concave parts in the periphery of the convex parts 16z when the convex parts 16z are pressed in, making it difficult to press the convex parts 16z sufficiently deeply into the resin layer 20z. As a result, in the outer peripheries of regions where servo patterns (i.e., burst patterns) are to be formed, it is difficult to make the thickness of the residue between the protruding ends of the convex parts 16z and the substrate 18z sufficiently thin. In addition, since the surface area of the convex parts 16z for forming burst patterns where the individual burst regions are composed of convex parts is large relative to the concave parts in the burst pattern forming regions, there is the risk of difficulty in pressing the convex parts 16z sufficiently deeply into the resin layer even in the inner peripheries where the lengths of the convex parts 16z in the circumferential direction are comparatively short.
When manufacturing an information recording medium using the concave/convex pattern formed on the substrate 18z, it is necessary to remove the residue from the substrate 18z at the bottoms of the concave parts 24z of the concave/convex pattern by carrying out an etching process or the like. Accordingly, when the concave/convex pattern has been formed on the substrate 18z by the conventional imprinting method, there is the problem that a long time is required to remove the residue with the thickness T12 at positions (e.g., the outer peripheries of the regions for forming the preamble patterns and the like) where the convex parts 16z with long lengths L12 in the circumferential direction, for example, have been pressed in. Also, as described earlier, the thickness T11 of the residue at positions (i.e., the data track pattern forming regions) where convex parts 16z with short lengths L11 in the radial direction, for example, are pressed in is sufficiently thinner than the thickness T12. Accordingly, if the etching process is carried out for sufficient time to reliably remove the residue with the thickness T12, the removal of the residue with the thickness T11 will be completed before the removal of the residue with the thickness T12 is completed. As a result, at positions (i.e., the concave parts 24z with the length L11 in the radial direction) where the residue with the thickness T11 has been removed, the etching will continue until the removal of the residue with the thickness T12 is completed, so that the inner side walls of the concave parts 24z are eroded, resulting in the length in the radial direction of the concave parts 24z (this length is hereinafter referred to as the “opening length”) becoming wider. This means that with the conventional imprinting method, there is another problem in that when a concave/convex pattern is formed on the substrate 18z, it is difficult to form the lengths (i.e., opening length) of the concave parts 24z after the residue is removed (i.e., after the etching process) with the desired widths.
The present invention was conceived in view of the problems described above and it is a principal object of the present invention to provide a stamper, an imprinting method, and a method of manufacturing an information recording medium that can precisely form concave/convex patterns including concave parts with desired opening lengths.
A stamper according to the present invention has stamper-side concave/convex patterns formed thereupon and is capable of manufacturing an information recording medium on which data track patterns and servo patterns are formed by concave/convex patterns, wherein a plurality of types of convex parts with different heights from a reference plane, which is set between a front surface and a rear surface of the stamper, to protruding ends of the convex parts are formed in the stamper-side concave/convex patterns, and second convex parts, at least one part of which has the height that is higher than the height of a highest first convex part out of the convex parts formed in regions corresponding to the data track patterns, are formed in regions corresponding to the servo patterns. Note that the expression “the front surface of the stamper” in this specification refers to “bottom surfaces of concave parts in the stamper-side concave/convex patterns”, that is, the “formation surface of the stamper-side concave/convex patterns”. Here, when the bottom surfaces of the concave parts in the stamper-side concave/convex patterns do not lie on the same plane, a bottom surface of any of the concave parts (as one example, a bottom surface that is closest to the rear surface of the stamper out of the bottom surfaces of the concave parts) is set as the “front surface of the stamper” for the present invention. In addition, the expression “between the front surface and the rear surface” for the present invention includes both the “front surface of the stamper” and the “rear surface of the stamper”. The expression “reference plane” in this specification refers to a freely chosen plane set between the front surface and the rear surface of the stamper.
According to the stamper according to the present invention and an imprinting method described later that uses such stamper, the stamper-side concave/convex patterns are constructed so that second convex parts, at least one part of which has the height that is higher than the height of a highest first convex part out of the convex parts formed in regions corresponding to the data track patterns, are formed in regions corresponding to the servo patterns. By doing so, when the entire region (i.e., the data track pattern forming regions and the servo pattern forming regions) of the stamper is pressed into the resin layer with a uniform pressing force during imprinting, it is possible to press the convex parts in the servo pattern forming regions, which include a large number of convex parts that are difficult to press into the resin layer, sufficiently deeply into the resin layer. Accordingly, the convex parts in the data track pattern forming regions and the convex parts in the servo pattern forming regions can be pressed into the resin layer to a similar extent and sufficiently deeply, thereby making it possible to make the thickness of the residue on the substrate uniform across the entire substrate. Accordingly, since it is possible to make the time required to remove the residue substantially equal across the entire substrate, it is possible to avoid a situation where the concave parts in the concave/convex pattern transferred to the resin layer in the regions corresponding to the data track pattern regions are formed with unintentionally wide openings due to the side wall surfaces of the concave parts being eroded. By doing so, it is possible to precisely form concave/convex patterns including concave parts with the desired opening widths across the entire data track pattern forming regions and the entire servo pattern forming regions. By manufacturing an information recording medium using the concave/convex patterns that have been formed with high precision, it is possible to manufacture an information recording medium that is not susceptible to recording/reproducing errors.
On a stamper according to the present invention, in the stamper-side concave/convex patterns, third convex parts that are continuously formed along a direction corresponding to a radial direction of the information recording medium may be formed as the second convex parts, and the third convex parts may be formed so that the height thereof is higher than the height of the first convex part at positions where the length of the third convex parts in a direction corresponding to a circumferential direction of the information recording medium is longer than the length of the first convex part in the direction corresponding to the radial direction. Note that the expression “the length (of the convex parts) in the direction corresponding to the circumferential direction” in this specification refers to “the distance in the circumferential direction between opposite side wall surfaces of one convex part”. Also, the expression “the length (of the convex parts) in the direction corresponding to the radial direction” in this specification refers to “the distance in the radial direction between opposite side wall surfaces of one convex part”.
According to the stamper according to the present invention and an imprinting method described later that uses such stamper, by forming the third convex parts so that the height thereof is higher than the height of the first convex part at positions where the length of the third convex parts in a direction corresponding to a circumferential direction of the information recording medium is longer than the length of the first convex part the direction corresponding to the radial direction, it becomes possible to press the third convex parts, such as the convex parts for forming the preamble patterns and the convex parts for forming the sector address patterns whose lengths in the circumferential direction in the outer peripheries thereof are longer than the length in the radial direction of the first convex part for forming the data track patterns, into the resin layer to a similar extent to the first convex part for forming the data track patterns and sufficiently deeply into the resin layer. This means that the thickness of the residue in the regions corresponding to the data track pattern regions (i.e., in the data track pattern forming regions) and the thickness of the residue in the regions corresponding to the servo pattern regions (i.e., in the servo pattern forming regions) can be made substantially uniform.
On the stamper according to the present invention, in the stamper-side concave/convex patterns, parts corresponding to individual burst regions in burst patterns out of the servo patterns may be composed of concave parts and fourth convex parts may be formed around the concave parts as the second convex parts, and the fourth convex parts may be formed so that the height thereof is higher than the height of the first convex part in at least one part of each of the fourth convex parts. Note that the expression “individual burst regions” in this specification refers to a plurality of convex parts or a plurality of concave parts that are substantially parallelogram-shaped or substantially oval (which includes circular forms) and are disposed in the circumferential direction of the information recording medium.
According to the stamper according to the present invention and an imprinting method described later that uses such stamper, by forming the fourth convex parts so that the height thereof is higher than the height of the first convex part in at least one part of each of the fourth convex parts, it is possible to press the outer peripheries of the fourth convex parts for forming the burst patterns that are difficult to press into the resin layer during the imprinting process into the resin layer to a similar extent as the first convex part for forming the data track patterns and sufficiently deeply into the resin layer. This means that the thickness of the residue in the regions corresponding to the data track pattern regions (i.e., in the data track pattern forming regions) and the thickness of the residue in the regions corresponding to the burst pattern regions (i.e., in the burst pattern forming regions) can be made substantially uniform.
On the stamper according to the present invention,
the fourth convex parts may be formed so that the height thereof is higher than the height of the first convex part across the entire forth concave parts.
According to the stamper according to the present invention and an imprinting method described later that uses such stamper, by forming the fourth convex parts so that the height thereof is higher than the height of the first convex part across the entire forth concave parts, the fourth convex parts for forming the burst patterns that are difficult to press into the resin layer due to their surface area being large relative to the concave parts can be pressed into the resin layer sufficiently deeply across the entire range from the inner periphery to the outer periphery.
An imprinting method according to the present invention carries out a stamper pressing process, which presses the stamper-side concave/convex patterns of any of the stampers described above onto a resin layer formed by applying a resin material onto a surface of a substrate, and a stamper separating process, which separates the stamper from the resin layer, in the mentioned order to transfer a concave/convex form of the stamper-side concave/convex patterns to the resin layer.
A method of manufacturing an information recording medium according to the present invention uses a concave/convex pattern transferred to the resin layer by the imprinting method described above.
According to the method of manufacturing an information recording medium according to the present invention, by manufacturing the information recording medium using the concave/convex pattern transferred to the resin layer by the imprinting method described above, it is possible to manufacture an information recording medium where servo signals can be reliably obtained and a magnetic head can be properly kept on a desired data recording track so that data can be properly recorded on the data recording tracks and data can be properly read from the data recording tracks.
It should be noted that the disclosure of the present invention relates to a content of Japanese Patent Application 2005-329601 that was filed on 15 Nov. 2005 and the entire content of which is herein incorporated by reference.
BRIEF DESCRIPTION OF THE DRAWINGSThese and other objects and features of the present invention will be explained in more detail below with reference to the attached drawings, wherein:
Preferred embodiments of a stamper, an imprinting method, and a method of manufacturing an information recording medium according to the present invention will now be described with reference to the attached drawings.
First, the construction of an imprinting apparatus 100 for manufacturing an information recording medium using the stamper according to the present invention will be described with reference to the drawings.
The imprinting apparatus 100 shown in
Also, as shown in
On the other hand, as shown in
More specifically, as shown in
Here, the convex parts 35a formed in the data track pattern forming regions Ats and the convex parts 35a formed in the servo pattern forming regions Ass have lengths (hereinafter, “lengths in the radial direction”) in a direction corresponding to the radial direction of the information recording medium 1 (hereinafter, a direction for the stamper 20 that corresponds to the radial direction of the information recording medium 1 is also referred to as the “radial direction”) and lengths (hereinafter, “lengths in the circumferential direction”) in a direction corresponding to the circumferential direction (i.e., direction of rotations of the information recording medium 1 (hereinafter, a direction for the stamper 20 that corresponds to the circumferential direction of the information recording medium 1 is also referred to as the “circumferential direction”) set in accordance with the forms of the data track patterns and servo patterns of the information recording medium 1. More specifically, as shown in
Also, as shown in
In addition, the convex parts 35a (not shown) formed in a sector address pattern forming region of each servo pattern forming region Ass are convex parts for forming the concave parts 5b used as sector address patterns of the information recording medium 1, and in the same way as the convex parts 35a2 for forming the concave parts 5b used as the preamble patterns described earlier, are continuously formed along the direction corresponding to the radial direction of the information recording medium 1 as belt-like shapes elongated in the radial direction. Accordingly, in the following description, the convex parts 35a for forming the sector address patterns are assigned the same reference numerals as the convex parts 35a2 for forming the preamble patterns. The convex parts 35a2 are another example of “third convex parts” for the present invention (one type of “second convex parts” for the present invention) and the lengths thereof in the radial direction are set corresponding to the length from the inner periphery Ai to the outer periphery Ao of the information recording medium 1. The convex parts 35a2 for forming the sector address patterns have lengths thereof in the circumferential direction (the length L2 shown in
As shown in
Also, as shown in
More specifically, as shown in
Also, the convex parts 35a3 for forming the burst patterns whose length L3 in the circumferential direction between two adjacent concave parts 35b3 (the concave parts 35b that correspond to the individual burst regions) is 56 nm in the inner periphery and 147 nm in the outer periphery are formed so that the height from the reference plane X and the protruding end of the convex part 35a3 between two concave parts 35b3 (that is, the height H3 shown in
On the other hand, as shown in
Next, the method of manufacturing the stamper 20 will be described with reference to the drawings.
First, as shown in
Next, by carrying out reactive ion etching using a mixture of CF4 and O2, for example, with the nickel layer 26 (a mask pattern 33) en the disk-shaped base plate 25 as a mask, the disk-shaped base plate 25 is etched as shown in
Next, the disk-shaped base plate 25 in this state is soaked in potassium permanganate solution, for example, to oxidize the surface of the concave/convex pattern 34 (the surface of the nickel layer 26 on the disk-shaped base plate 25). By doing so, a master matrix (not shown) is completed. Next, as shown in
Next, a process that forms a concave/convex pattern on the preform 10 using the stamper 20 described above in accordance with the imprinting method according to the present invention will be described with reference to the drawings.
First, the preform 10 and the stamper 20 are set in the press 110. More specifically, the preform 10 is attached to the hot plate 111 with the formation surface of the resin layer 14 facing upward and the stamper 20 is attached to the hot plate 112 with the formation surface of the concave/convex patterns 35 facing downward. After this, the control unit 120 controls the hot plates 111, 112 so that both the preform 10 and the stamper 20 are heated. At this time, the hot plates 111, 112 heat both the preform 10 and the stamper 20 to around 170° C., which is around 100° C. higher than the glass transition point (in this example, around −70° C.) of the novolac resin forming the resin layer 14. By doing so, the resin layer 14 softens and becomes easy to mold. Here, heating to a temperature in a range of 70° C. to 120° C., inclusive higher than the glass transition point of the resin material is preferable, with heating to at least 100° C. higher than the glass transition point being more preferable. By doing so, as described later, it becomes easy to press the stamper 20 onto the resin layer 14.
Next, the control unit 120 controls the raising/lowering mechanism 113 to lower the hot plate 112 toward the hot plate 111 to press, as shown in
Here, as described earlier, on the stamper 20 used by the imprinting apparatus 100, the concave/convex patterns 35 are formed so that out of the convex parts 35a that are formed in the servo pattern forming regions Ass, the convex parts 35a2 whose lengths in the circumferential direction are longer than the length in the radial direction of the convex parts 35a1 in the data track pattern forming regions Ats (i.e., out of the convex parts 35a2, convex parts 35a2 whose length in the circumferential direction is longer than the length in the radial direction of the convex parts 35a1) have higher heights from the reference plane X to the protruding ends of the convex parts. Accordingly, when the stamper 20 is pressed onto the resin layer 14 with uniform pressing force being applied across the entire stamper 20, the convex parts 35a with the longer lengths in the circumferential direction (in this example, the convex parts 35a2) are pressed deeply into the resin layer 14 in the same way as the convex parts 35a1 and the like. Also, as described earlier, the convex parts 35a3 for forming the burst patterns are formed so that the height from the reference plane X to the protruding ends of the convex parts between two adjacent concave parts 35b3 in the circumferential direction gradually increases from the inner periphery to the outer periphery and is higher than the height H1 of the convex parts 35a1 across the entire range from the inner periphery to the outer periphery. Accordingly, when the stamper 20 is pressed onto the resin layer 14 with uniform pressing force being applied across the entire stamper 20, the convex parts 35a3 that are difficult to press into the resin layer 14 due to their large surface area relative to the concave parts 35b3 are also deeply pressed into the resin layer 14 in the same way as the convex parts 35a1, 35a2, and the like described above. As a result, the convex parts 35a with different lengths in the radial direction and different lengths in the circumferential direction are pressed into the resin layer 14 substantially uniformly.
As a specific example, as shown in
Also, on the stamper 20, in the servo pattern forming regions Ass in which the convex parts 35a2 for forming the (eight bits long) sector address patterns with a length in the circumferential direction of 226 nm in the inner periphery and of 587 nm in the outer periphery are formed (in this example, sector address pattern forming regions in which the eight-bit long sector address patterns are formed), the convex parts are formed so that the height thereof from the reference plane X so the protruding ends of the convex parts gradually increases from the inner periphery to the outer periphery from 90 nm to 98 nm, meaning that the convex parts 35a2 protrude further out than the convex parts 35a1. This means that the convex parts 35a2 can be pressed sufficiently deeply and to a similar extent as the convex parts 35a1 into the resin layer 14. In addition, in the servo pattern forming regions Ass (the burst pattern forming region Abs) where the length in the circumferential direction of the convex parts 35a3 for forming burst patterns between two adjacent concave parts 35b in the circumferential direction is 56 nm in the inner periphery and is 147 nm in the outer periphery, the convex parts are formed so that the height from the reference plane X to the protruding ends of the convex parts gradually increases from the inner periphery to the outer periphery from 92 nm to 101 nm, meaning that the protruding ends of the convex parts 35a3 protrude further out than the convex parts 35a1. This means that the convex parts 35a3 can be pressed sufficiently deeply and to a similar extent as the convex parts 35a1 into the resin layer 14. Accordingly, the thickness of the residue at positions where the various types of convex parts 35a with different lengths in the circumferential direction and the radial direction are pressed in is substantially equal across the entire range of the data track pattern forming regions Ats and the servo pattern forming regions Ass. Next, while controlling the hot plates 111, 112 to have the heating process continued (to keep the temperature in a range of 170° C.±1° C.), as shown in
Next, the process for manufacturing the information recording medium 1 according to the method of manufacturing an information recording medium according to the present invention will be described with reference to the drawings.
First, the resin material (residue) remaining on the bottom surfaces of the concave parts in the concave/convex pattern 36 in the resin layer 14 is removed by an oxygen plasma process. When doing so, since the thickness of the residue on the metal layer 13 is substantially even in a range of 25 nm to 32 nm, inclusive, across the entire preform 10, it is possible to avoid a situation where the openings of the concave parts change to unintentionally wide openings (that is, where the side wall surfaces of the concave parts are badly eroded) when the residue is removed. Next, an etching process that uses a metal-etching gas is carried out with the concave/convex pattern 36 (i.e., the convex parts) as a mask. When doing so, as shown in
Next, the metal layer 13 remaining on the magnetic layer 12 is removed by carrying out an etching process using a metal-etching gas. By doing so, as shown in
In this way, according to the stamper 20 and the imprinting method that uses the stamper 20, the concave/convex patterns 35 are constructed so that in at least part of the servo pattern forming regions Ass, convex parts 35a (in this example, the convex parts 35a2, 35a3, and the like) are formed with higher heights than the highest convex parts 35a (in this example, the convex parts 35a1) out of the convex parts 35a formed in the data track pattern forming regions Ats. By doing so, when the stamper 20 is pressed into the resin layer 14 with a uniform pressing force across the entire stamper 20 (the data track pattern forming regions Ats and the servo pattern forming regions Ass) during imprinting, the convex parts 35a in the servo pattern forming regions Ass, which includes a large number of convex parts 35a that are difficult to press into the resin layer 14, can be pressed sufficiently deeply into the resin layer 14. Since the convex parts 35a in the data track pattern forming regions Ats and the convex parts 35a in the servo pattern forming regions Ass can be pressed in to a similar extent and sufficiently deeply into the resin layer 14, the thickness T of the residue on the metal layer 13 can be made uniform across the entire preform 10. Accordingly, since the time required to remove the residue can be made substantially equal across the entire preform 10, it is possible to avoid a situation where the concave parts 36b in the concave/convex pattern 36 transferred to the resin layer 14 in the regions corresponding to the data track pattern regions are formed with unintentionally wide openings due to the side wall surfaces of the concave parts 36b being eroded. By doing so, it is possible to form the concave/convex pattern 36 including concave parts with the desired opening widths across the entire range of both the data track pattern regions and the servo pattern regions. In addition, by manufacturing the information recording medium 1 using the concave/convex pattern 36 that has been formed with high precision, it is possible to manufacture an information recording medium that is not susceptible to recording/reproducing errors.
Also, according to the stamper 20, by forming the “third convex parts” for the present invention (in this example, the convex parts 35a2) in the servo pattern forming regions Ass so that the third convex parts are higher than the convex parts 35a1 at positions where the length in the circumferential direction of the convex parts 35a2 is longer than the length L1 in the radial direction of the convex parts 35a1, as examples convex parts 35a (such as the convex parts 35a2 for forming the preamble patterns and the convex parts 35a2 for forming the sector address patterns) whose lengths in the circumferential direction in the outer periphery are longer than the length L1 in the radial direction of the convex parts 35a1 for forming the data track patterns can be pressed into the resin layer 14 to a similar extent as the convex parts 35a1 for forming the data track patterns and sufficiently deeply into the resin layer 14. This means that the thickness of the residue inside the regions corresponding to the data track pattern regions (i.e., the data track pattern forming regions Ats) and the thickness of the residue inside the regions corresponding to the servo pattern regions (i.e., the servo pattern forming regions Ass) can be made substantially uniform.
In addition, according to the stamper 20, by forming the fourth convex parts (in this example, the convex parts 35a3) for the present invention in the burst pattern forming regions Abs inside the servo pattern forming regions Ass so as to be higher than the convex parts 35a1 across the entire stamper 20, it becomes possible to press the convex parts 35a3 for forming the burst pattern regions that are difficult to press into the resin layer 14 due to their large surface area compared to the concave parts 35b3 sufficiently deeply into the resin layer 14 across the entire range from the inner periphery to the outer periphery.
Also, according to the method of manufacturing
-
- the information recording medium 1 using the stamper 20, by manufacturing the information recording medium 1 using the concave/convex pattern 36 transferred to the resin layer 14 by the imprinting method described above, it is possible to manufacture an information recording medium 1 where servo signals can be reliably obtained and therefore the magnetic head can be properly kept on a desired track. As a result, data can be properly recorded on the data recording tracks and data can be properly read from the data recording tracks.
Note that the present invention is not limited to the construction and method described above. For example, although an example has been described where the convex parts 35a3 inside the burst pattern forming regions Abs are formed higher than the convex parts 35a1 inside the data track pattern forming regions Ats across the entire range from the inner periphery to the outer periphery, if the length in the circumferential direction between the adjacent concave parts 35b3 in the inner periphery (i.e., the length in the circumferential direction of the convex parts 35a3) is shorter than on the stamper 20 described above, for example, the convex parts 35a3 can be formed lower than the convex parts 35a1 in such positions. In such example, the positions (the outer peripheries of the convex parts 35a3) where the convex parts 35a3 are formed higher than the height H1 of the convex parts 35a1 correspond to the “at least one part” for the present invention. In this way, by forming the fourth convex parts for the present invention in the burst pattern forming regions Abs inside the servo pattern forming regions Ass so that the fourth convex parts (in this example, the convex parts 35a3 or the like) are higher than the convex parts 35a1 in at least one part of each of the fourth convex parts, during the imprinting process, it is possible to press the outer peripheries of the convex parts 35a3 for forming the burst patterns that are difficult to press into the resin layer 14 reliably into the resin layer 14 to a similar extent as the convex parts 35a1 for forming the data track patterns and sufficiently deeply into the resin layer 14. This means that the thickness of the residue inside regions corresponding to the data track pattern regions (i.e., inside the data track pattern forming regions Ats) and the thickness of the residue inside regions corresponding to the burst pattern regions (i.e., inside the burst pattern forming regions Abs) can be made substantially uniform.
Also, although the stamper 20 with the concave/convex patterns 35 where parts corresponding to the individual burst regions of the information recording medium 1 are constructed by the concave parts 35b3 has been described, like the stamper 20A shown in
Also, although the stampers 20, 20A with burst patterns where parallelogram-shaped individual burst regions are disposed in the circumferential direction have been described, it is possible to apply the present invention to a stamper that can form burst patterns where approximately oval or circular individual burst regions are arranged in the circumferential direction. In addition, like the stamper 20B shown in
In addition, like the stamper 20C shown in
Also, although the stamper 20 is manufactured by the method of manufacturing described above forming the electrode film 21 and the nickel layer 22 so as to cover the concave/convex pattern 34 formed by etching the disk-shaped base plate 25 using the nickel layer 26 (the mask pattern 33) as a mask, the method of manufacturing the stamper according to the present invention is not limited to this. As one example, it is also possible to manufacture the stamper 20 by forming the resist layer 27 on the disk-shaped base plate 25, forming a concave/convex pattern (not shown) by forming concave parts with different depths in the resist layer 27, and then forming the electrode film 21 and the nickel layer 22 so as to cover the concave/convex pattern. In addition, it is also possible to manufacture the stamper according to the present invention by using a stamper manufactured by transferring the concave/convex form of the stamper 20 described above to a stamper forming material as a master stamper and transferring the concave/convex form of the master stamper to another stamper forming material, or in other words, by transferring the concave/convex form of the stamper 20 described above an even number of times.
In addition, although a heating process is continuously carried out on both the preform 10 and the stamper 20 from before the start of the process that presses the stamper 20 onto the preform 10 until the process that separates the stamper 20 is completed in the imprinting method that uses the imprinting apparatus 100 described above (i.e., in the method of manufacturing the information recording medium 1), the present invention is not limited to this and it is possible to use a process that stops the heating process for the preform 10 and the stamper 20 after the stamper 20 has been sufficiently pressed onto the preform 10, and separates the stamper 20 afterward. In addition, it is possible to cool both the stamper 20 and the preform 10 to the glass transition point of the resin layer 14 or below before the stamper 20 is separated. It is also possible to use a method that forms the resin layer for the present invention using a resin material whose glass transition point is lower than room temperature (as one example, around 25° C.) and forms concave/convex patterns in the resin layer without carrying out a heating process or a cooling process from the stamper pressing process to the stamper separating process. In addition, it is possible to use a method that forms a concave/convex pattern in a resin layer by forming the resin layer using a UV-curing resin or an electron-beam curing resin as the “resin material” for the present invention, and irradiating the resin layer with UV rays or an electron beam after the stamper pressing process to harden (or semi-harden) the resin layer, and then carrying out the stamper separating process.
Concave/convex patterns formed by the imprinting method according to the present invention are not limited to being applied to manufacturing discrete track type information recording media and can be used when manufacturing a patterned medium with patterns aside from track-type patterns and/or when manufacturing various types of information recording media aside from magnetic recording media, such as optical recording media and magneto-optical recording media.
Claims
1. A stamper on which stamper-side concave/convex patterns are formed and which is capable of manufacturing an information recording medium on which data track patterns and servo patterns are formed by concave/convex patterns,
- wherein a plurality of types of convex parts with different heights from a reference plane, which is set between a front surface and a rear surface of the stamper, to protruding ends of the convex parts are formed in the stamper-side concave/convex patterns, and second convex parts, at least one part of which has the height that is higher than the height of a highest first convex part out of the convex parts formed in regions corresponding to the data track patterns, are formed in regions corresponding to the servo patterns.
2. A stamper according to claim 1, wherein in the stamper-side concave/convex patterns, third convex parts that are continuously formed along a direction corresponding to a radial direction oft the information recording medium are formed as the second convex parts, and
- the third convex parts are formed so that the height thereof is higher than the height of the first convex part at positions where the length of the third convex parts in a direction corresponding to a circumferential direction of the information recording medium is longer than the length of the first convex part in the direction corresponding to the radial direction.
3. A stamper according to claim 1, wherein in the stamper-side concave/convex patterns, parts corresponding to individual burst regions in burst patterns out of the servo patterns are composed of concave parts and fourth convex parts are formed around the concave parts as the second convex parts, and
- the fourth convex parts are formed so that the height thereof is higher than the height of the first convex part in at least one part of each of the forth convex parts.
4. A stamper according to claim 3, wherein the fourth convex parts are formed so that the height thereof is higher than the height of the first convex part across the entire stamper-side concave/convex patterns.
5. An imprinting method comprising;
- a stamper pressing process, which presses the stamper-side concave/convex patterns of a stamper according to claim 1 onto a resin layer formed by applying a resin material onto a surface of a substrate; and
- a stamper separating process, which separates the stamper from the resin layer, wherein the stamper pressing process and the stamper separating process are carried out in the mentioned order to transfer a concave/convex form of the stamper-side concave/convex patterns to the resin layer.
6. A method of manufacturing an information recording medium using a concave/convex pattern transferred to the resin layer by the imprinting method according to claim 5.
Type: Application
Filed: Sep 29, 2006
Publication Date: May 17, 2007
Applicant: TDK CORPORATION (Tokyo)
Inventors: Kazuhiro HATTORI (Tokyo), Kazuya SHIMAKAWA (Tokyo)
Application Number: 11/536,954
International Classification: C23F 1/00 (20060101);