Patent Application
20110226625
1. Field of the Invention
The present invention relates to a method of manufacturing a master mold having thereon an uneven pattern or a reverse uneven pattern corresponding to a predetermined magnetic pattern or an uneven pattern. The invention also relates to a method of manufacturing a mold structure used for pattern transfer.
2. Description of the Related Art
Technologies for efficiently transferring two-dimensional and three-dimensional patterns to transfer receiving media (also called as “slave media”), such as a magnetic transfer to a transfer receiving medium performed in the manufacture of magnetic recording media using a magnetic transfer master disk having thereon a fine magnetic pattern, a nano-imprinting on a transfer receiving medium performed in the manufacture of discrete track media (DTM), bit patterned media (BPM), and the like using a nanoimprint mold having thereon a fine uneven pattern, and the like, have been developed as described, for example, in U.S. Patent Application Publication No. 20010028964 and U.S. Pat. No. 7,850,441. Such technologies allow the magnetic pattern or uneven pattern to be transferred to a transfer receiving medium at a time by pressing a pattern transfer mold structure (the magnetic transfer master disk or nanoimprint mold) onto a transfer receiving medium, whereby fine patterns or fine uneven patterns in the range of nanometers may be formed easily with low costs.
The mold structure needs to have a high uniformity in convex portions of the uneven pattern (high flatness in the upper surface of each convex portion and high uniformity in the height of each convex portion) due to its characteristics. For example, if a magnetic transfer master disk has a low uniformity in convex portions, some of the convex portions are not appropriately brought into contact with a transfer receiving medium when the mold is pressed onto the transfer receiving medium, thereby causing a problem that the magnetic pattern is not transferred correctly. In the mean time, if, for example, a nanoimprint mold has a low uniformity in convex portions, pressing of the mold onto a transfer receiving medium will result in non-uniform thickness of residual layers (resist films not being completely impressed out and remaining after the imprinting) formed at the bottoms of concave portions of the resist layer of the transfer receiving medium. In this case, the residual layers are typically removed through dry etching by setting the etching device such that a thickest film is removed. Here, a portion of the foundation layer with a thin residual layer may be etched or the size (e.g., line width of a line and space pattern) of the resist pattern with a thin residual layer becomes smaller that the size of the resist pattern with a thick residual layer, thereby causing a problem of a varied pattern size.
In the mean time, such mold structure is worn out through repeated use, so that it is normally replicated by electroforming using an original mold (master mold) having an uneven pattern reverse to the uneven pattern of the mold structure in consideration of the manufacturing efficiency, durability, and cost. In such a case, in order to improve the uniformity of convex portions of the mold structure, it is necessary to improve the uniformity of concave portions of the uneven pattern of the master mold (high flatness in the bottom surface of each concave portion and high uniformity in the depth of each concave portion).
As for a specific method of achieving this improvement, Japanese Patent No. 4189600 teaches a method of manufacturing a master mold through a reactive ion etching process in which an original plate constituted by a processing target layer (e.g., SiO2) and a foundation layer (e.g., Si) is used and the foundation layer is caused to act as an etch stop layer by increasing the etching selectivity of the processing target layer, thereby aligning the depth of each concave portion at the interface between the processing target layer and the foundation layer.
The method described in Japanese Patent No. 4189600 is a useful method of manufacturing conventional media, but the method may cause a problem that it is difficult to maintain a high uniformity in concave portions of a master mold in the recent manufacture of media which requires transfer technology for transferring a fine pattern in the range of several tens of nanometers. In particular, this tendency becomes significant for a pattern having coarse and fine portions, that is, a pattern in which uneven patterns that include a concave portion having a relatively wide space (wide concave portion) and a concave portion having a relatively narrow space (narrow concave portion) are arranged complicatedly, such as a servo pattern of a magnetic recording medium. More specifically, although in the method described in Japanese Patent No. 4189600, the foundation layer is caused to function as an etch stop layer, the etching can not be stopped completely at the surface of the foundation layer and the layer is etched by several nanometers. This may cause a problem for an uneven pattern that includes a wide concave portion and a narrow concave portion that the bottom of the wide concave portion is etched in an upward convex shape (convex shape) and the narrow concave portion is etched deeper than the wide concave portion.
The detailed mechanism of the occurrence of this problem is unclear, but this may be due to formation of “micro trench” in which bottom portions abutting to side walls are etched deeper than the other portion when reactive ion etching is performed. That is, it is believed that, for a wide concave portion, micro trenches are formed in bottom portions abutting to side walls and the bottom is shaped in a convex shape and, for a narrow concave portion, micro trenches are merged and the depth becomes deeper as a consequence. Further, where reactive ion etching is performed on a nonconductor, such as SiO2, micro trenches are formed more significantly due to charging.
The present invention has been developed in view of the circumstances described above, and it is an object of the present invention to provide, in master mold manufacturing using a reactive ion etching process, a master mold manufacturing method capable of manufacturing a master mold having a high uniformity in concave portions of an uneven pattern that includes a wide concave portion and a narrow concave portion.
It is a further object of the present invention to provide, in mold structure manufacturing through replication by electroforming with the master mold manufactured by the master mold manufacturing method described above as the original master, a mold structure manufacturing method capable of manufacturing a mold structure having a high uniformity in convex portions of an uneven pattern that includes a wide concave portion and a narrow concave portion.
In order to solve the problem described above, a master mold manufacturing method of the present invention is a method using an original plate which includes a processing target layer and a foundation layer in which a coating layer having an opening pattern constituted by a plurality of openings is formed on the processing target layer and an etching step is performed with a reactive ion etching process using the coating layer as a mask to manufacture a master mold having thereon an uneven pattern corresponding to the opening pattern, wherein:
the opening pattern includes a wide opening having a wide width and a narrow opening having a width narrower than the width of the wide opening; and
the etching step includes:
The term “processing target layer” as used herein refers to a primary etching target layer when forming the uneven pattern of the master mold. Here, the term “primary etching target layer” as used herein refers to that the layer is etched such that concave portions of the uneven pattern has a depth roughly corresponding to the layer thickness of the layer.
The term “foundation layer” as used herein refers to a layer having a composition different from that of the processing target layer and used as an etch stop layer in the main etching step.
The term “an uneven pattern corresponding to the opening pattern” as used herein refers to an uneven pattern in which a portion of the processing target layer not covered by the coating layer is etched and formed into a concave.
The term “wide opening” as used herein refers to an opening having a relative wide width (space width contacting the processing target layer) and the term “narrow opening” as used herein refers to an opening having a width narrower than that of the wide opening.
The term “wide concave portion” as used herein refers to an area etched according to a wide opening and the term “narrow concave portion” as used herein refers to an area etched according to a narrow opening.
The term “wide bottom surface” as used herein refers to the bottom surface of a wide concave portion and the term “narrow bottom surface” as used herein refers to the bottom surface of a narrow concave portion.
The term “shaped in an upward convex” as used herein with respect to a wide bottom surface refers to that a bottom portion other than the portions abutting to side walls have a raised shape due to that the portions abutting to side walls are etched further than the other portion, that is, refers to the state in which fine trenches are formed at the portions abutting to side walls.
The term “depth” of a wide concave portion as used herein refers to an average distance from the surface of the processing target layer with respect to a wide concave portion opposite the foundation layer to a central portion of the wide bottom surface, and the term “depth” of a narrow concave portion as used herein refers to an average distance from the surface of the processing target layer with respect to a narrow concave portion opposite the foundation layer to a central portion of the narrow bottom surface.
The term “flat” as used herein with respect to a wide bottom surface refers to that difference in depth between a portion of the bottom surface abutting to a side wall (deepest portion) and a central portion of the bottom surface (shallowest portion) is small.
The term “the depth of the wide concave portion corresponds to the depth of the narrow concave portion” as used herein refers to that the difference in depth between these concave portions is small.
In the master mold manufacturing method of the present invention, it is preferable that the etching gas further includes a second gas having a greater capability to etch the foundation layer than the capability of the first gas and producing no deposit.
Further, it is preferable that the extra etching step is performed under a pressure of 1 to 12 Pa.
Still further, it is preferable that the extra etching step is performed using a diluent gas, as well as the etching gas, with an antenna power of 20 to 200 W.
Preferably, the reactive ion etching process is an etching process which uses an inductively coupled plasma generation method, a capacitively coupled plasma generation method, or an electron cyclotron resonance plasma generation method, and is capable of independently controlling the bias power and the antenna power.
Preferably, the reactive ion etching process is an etching process which uses the inductively coupled plasma generation method;
the processing target layer consists primarily of SiO2 and the foundation layer consists primarily of Si; and
The term “primarily consisting of” SiO2 or Si as used herein refers to that the content of SiO2 or Si in each layer is 90% by mass or more.
Further, it is preferable that the extra etching step is performed under a flow ratio of 3:1 to 8:1 between the first gas and the second gas, a flow ratio of 1:5 to 1:15 between the etching gas and the diluent gas, a pressure of 4 to 8 Pa, and an antenna power of 30 to 100 W.
Preferably, the first gas is at least one type of gas selected from the group consisting of CF4, CH2F2, CH3F, C4F8, C4F6, and C5F8, and the second gas is SF6.
Preferably, the first gas is CH3F, the second gas is SF6, and the diluent gas is Ar.
A mold structure manufacturing method of the present invention is a method, including the steps of:
forming, through electroforming of a metal material, a metal substrate made of the metal material on the uneven pattern of a master mold manufactured by the master mold manufacturing method described above; and
detaching the metal substrate from the master mold to obtain a mold structure, which is the metal substrate, having an uneven pattern reverse to the uneven pattern of the master mold.
In the method of manufacturing a master mold having thereon an uneven pattern corresponding to an opening pattern of coating layer by performing an etching step with a reactive ion etching process, the master mold manufacturing method of the present invention includes two separate etching steps, a main etching step and an extra etching step, and, in particular, etching is performed in the extra etching step using an etching gas that includes a first gas capable of etching the foundation layer and producing a deposit with a bias power of not greater than 15 W. For an original plate in which a wide bottom surface is shaped in an upward convex and a narrow concave portion is etched deeper than a wide concave portion by the main etching step, this allows the wide bottom surface to be flattened out, and the depth of the wide concave portion and the depth of the narrow concave portion to be equalized. This advantageous effect is obtained by employing an etching gas which includes a first gas capable of etching the foundation layer and producing a deposit to make use of the phenomenon that the deposit is more likely to be accumulated at a bottom portion abutting to a side wall, thereby causing a wide bottom portion other than a wide bottom portions abutting to side walls to be etched more than the wide bottom portions abutting to side walls and limiting the bias power to 15 W or less to cause RIE (reactive ion etching) lag (a phenomenon in which a wider concave portion is etched deeper). As a result, in the master mold manufacturing using a reactive ion etching process, a master mold having high uniformity in concave portions of an uneven pattern that includes a wide concave portion and a narrow concave portion may be manufactured.
The mold structure manufacturing method of the present invention includes the steps of forming, through electroforming of a metal material, a metal substrate made of the metal material on the uneven pattern of a master mold manufactured by the master mold manufacturing method described above, and detaching the metal substrate from the master mold to obtain a mold structure, which is the metal substrate, having an uneven pattern reverse to the uneven pattern of the master mold. Since the master mold manufactured by the master mold manufacturing method described above has high uniformity in concave portions of the uneven pattern, a mold structure having high uniformity in convex portions of an uneven pattern may be manufactured in mold structure manufacturing in which a mold structure is replicated through electroforming using the master mold as the original master.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the invention is not limited to these embodiments. Note that each component in the drawings is not necessarily drawn to scale in order to facilitate visual recognition.
[Master Mold Manufacturing Method]
As illustrated in
The method of manufacturing master mold 10 includes four steps, a step of forming coating layer 4 having an opening pattern, a main etching step, an extra etching step, and a step of removing coating layer 4, each of which will now be described in detail.
<Step of Forming Coating Layer Having Opening Pattern>
A of
There is not any specific restriction on the material of processing target layer 3, and an appropriate material is selected according to etching conditions of etching steps (main etching step and extra etching step). Here, a material is selected such that the etching selectivity of processing target layer 2 to coating layer 2 becomes not less than 2, preferably not less than 3, and more preferably not less than 5 (indicating that processing target layer 3 is likely to be etched more than coating layer 2). Generally, the selectivity ratio of not less than 2 may ensure a desired etching depth in processing target layer 3 taking into account the layer thickness of coating layer 4. The selectivity ratio can not be determined merely by the type of the material used and it also depends largely on etching conditions. As such, it is preferable to select a material that does not demand a difficult etching condition. In view of ease of film forming and processing, a Si oxide (SiO2) or a Si nitride (SiN4) is preferably used as the material of processing target layer 3. The thickness of processing target layer 3 serves as a rough guide of the depth of a concave portion of an uneven pattern of master mold 10 to be manufactured and, therefore, the thickness is selected appropriately according to a desired depth of the concave portion, which may be, for example, 20 to 150 nm. There is not any specific restriction on the film forming method of processing target layer 3, and sputtering, deposition, ion plating, ALD (atomic layer deposition), CVD (chemical vapor deposition), and the like may be used. Processing target layer 3 may also be formed by oxidizing or nitriding the surface of a material substrate to be formed into foundation layer 2.
There is not any specific restriction on the material of foundation layer 2. But, it is preferable that the material is selected such that the etching selectivity of foundation layer 2 to processing target layer 3 becomes ⅕, more preferably 1/10 in the main etching step while it becomes not less than 5, more preferably not less than 10 in the extra etching step. Selection of the material in the manner as described above may prevent the space of a concave portion from being broadened in the extra etching step. In view of the cost and ease of processing, Si is preferably used as the material of foundation layer 2.
In view of the circumstances with respect to processing target layer 3 and foundation layer 2, a Si wafer with a thermal oxide film is preferably used as original plate 1 which is the base material of master mold 10.
There is not any specific restriction on the material and film forming method of coating layer 4. For example, it may be formed by spin coating an electron beam resist or the like.
B of
In the main etch step, coating layer 4, in which an opening pattern having a wide opening A1 and a narrow opening A2 is formed, is used as a mask and etching is performed on processing target layer 3 from the surface thereof through openings of the opening pattern by a reactive ion etching process with foundation layer as an etch stop layer. Preferably, an amount of over etching is roughly 10% of the depth of a concave portion (either a wide concave portion or a narrow concave portion and, for example, a wide concave portion is used herein).
Preferably, the reactive ion etching (RIE) is an etching process having high perpendicular anisotropy (ion movement tends to occur in the depth direction of a concave portion) in order to prevent undercut (side etching), and an inductively coupled plasma (ICP)-RIE, a capacitively coupled plasma (CCP)-RIE, or an electron cyclotron resonance (ECR)-RIE is particularly preferable. Further, it is preferable, in the present invention, that the bias power (power for forming a bias between the plasma and lower electrode) is controlled independent of the antenna power (power for forming plasma) in order to facilitate control thereof.
The etching condition is set such that etching selectivity of foundation layer 2 to processing target layer 3 becomes ⅕, preferably 1/10 in order to cause foundation layer 2 to act as an etch stop layer as described above. For example, when the major component of processing target layer 3 is SiO2 and the major component of foundation layer 2 is Si, etching is performed by the ICP-RIE using CHF3 and CF4 as the etching gas under the pressure of 0.4 to 10.0 Pa with an antenna power of 50 to 500 W, a bias power of 10 to 150 W, and a lower electrode temperature of 60° C.
As coating layer 4 having an opening pattern that includes a wide opening A1 and a narrow opening A2 is used as a mask in the main etching step, a wide concave portion R1 and a narrow concave portion R2 corresponding to these openings are formed in original plate 1. At that time, as shown in C of
As a method for preventing the formation of a micro trench T, it is conceivable, for example, to increase the pressure. This is because a high pressure may reduce the ion perpendicular anisotropy and actively cause ion scattering on a side wall, thereby preventing increase in ion flux incident only on a portion of a bottom surface abutting to the side wall. In this case, however, another problem of increase in edge roughness of the electron beam resist or non-progress of etching any further (self etch-stop) may possibly occur.
In the mean time, it seems theoretically possible to solve the aforementioned problem by performing etching under a condition in which the etching selectivity of the processing target layer is further increased such that the foundation layer is not almost etched. Unfortunately, however, such condition has not been found so far in forming a fine uneven pattern, and the etching selectivity is up to about 10. Further, even if the selectivity ration were further increased, another problem of self etch-stop may possibly occur and, therefore, it is difficult to essentially solve the problem of improving the uniformity of concave portions by increasing the etching selectivity.
Consequently, the present invention includes a step of further performing etching (extra etching) on original plate 1 in which a wide bottom surface B1 of a wide concave portion R1 is shaped in a convex shape and a narrow concave portion R2 is etched deeper than the wide concave portion R1 such that the wide bottom surface B1 is flatten out and a depth D1 of the wide concave portion R1 corresponds to a depth D2 of the narrow concave portion R2. That is, the present invention has changed the conventional concept of how to stop etching at the surface of foundation layer 2 acting as an etch stop layer and includes a step of further etching foundation layer 2 (bottom surface of concave portion) to reshape concave portions of original plate 1 shown in C of
The term “flat” as used herein with respect to a wide bottom surface refers to that the difference in depth between a portion of the bottom surface abutting to a side wall (deepest portion) and a central portion of the bottom surface (shallowest portion) is small. Here, the difference in depth with respect to a wide concave portion is obtained by extracting, for example, 5 wide concave portions as samples, calculating the depths of the bottom surface portion abutting to a side wall and the central bottom surface portion of each extracted wide concave portion through shape measurement by an atomic force microscope (AFM) to obtain a difference between the depths, and averaging the differences. A specific value of the difference in depth with respect to a wide concave portion depends on a precision required of a master mold to be manufactured, but a difference in depth of 0.2 nm or less may sometimes be required in the manufacture of media, such as DTM, BPM, and the like, which requires pattern transfer technology for transferring a fine pattern in the range of several tens of nanometers.
The term “depth” of a wide concave portion as used herein refers to an average distance from the surface of the processing target layer opposite the foundation layer to the central portion of the wide bottom surface, and the term “depth” of a narrow concave portion as used herein refers to an average distance from the surface of the processing target layer opposite the foundation layer to the central portion of the narrow concave portion. Further, the term “the depth of a wide concave portion corresponds to the depth of a narrow concave portion” as used herein refers to that the difference in depth between these concave portions is small. Here, the depths of the wide concave portion and narrow concave portion are obtained through shape measurement by the AFM. A specific value of the difference in depth between these concave portions depends on a precision required of a master mold to be manufactured, but a difference in depth of 0.3 nm or less may sometimes be required in the manufacture of media, such as DTM, BPM, and the like, which requires pattern transfer technology for transferring a fine pattern in the range of several tens of nanometers.
The present inventor has taken the note that at least the following two functions are necessary in the extra etching step in order to realize etching conditions (type of etching gas and flow rate, use or non-use of diluent gas and pressure during etching, antenna power, bias power, lower electrode temperature, and the like) in which the wide bottom surface B1 is flattened and the depth D1 of a wide concave portion R1 corresponds to the depth D2 of a narrow concave portion R2.
(Function 1): A portion of wide bottom surface B1 other than portions abutting to side walls is etched more than the portions abutting to side wails.
(Function 2): A wide concave portion R1 is etched more than a narrow concave portion R2.
As a result of deep consideration of the two required functions described above, the present invention performs extra etching using a first gas, as the etching gas, capable of etching foundation layer 2 and producing a deposit in order to obtain the aforementioned function 1. This makes use of the fact that the deposit produced during etching is more likely to be accumulated at a bottom portion abutting to a side wall, whereby function 1 may be obtained. The reason why the deposit is more likely to be deposited at a bottom portion abutting to a side wall may be presumed that the equilibrium vapor pressure is low at the bottom portion abutting to a side wall in comparison with the other bottom portion and when focusing on a certain product and/or a bi-product produced during etching, there are more solid surfaces on which these product and bi-product are attached adjacent to the bottom portion abutting to a side wall.
In order to obtain function 2 described above, the present invention performs the extra etching with a bias power of 15 W or less. In comparison with a several hundreds of watts used as the bias power in General RIE, the bias power of the present invention is set to a low value. The low bias power reduces the ion perpendicular anisotropy and ions become less likely to go into a narrow concave portion R2 (geometrical shadowing effects) and inhibits etching by the ion assisted reaction, thereby causing a RIE lag and providing function 2. The bias power is preferable to be not greater than 10 W, and particularly preferable to be 0 W in order to minimize the ion perpendicular anisotropy and to promote RIE lag.
Preferably, the amount of etching in the extra etching step, as a guide, is such that a wide bottom surface B1 is etched about 2 nm under etching conditions in which the etching selectivity of foundation layer 2 to processing target layer 3 becomes not less than 5, and preferably not less than 10 as described above. If the amount of etching in the extra etching step exceeds 10% of a depth D1 of a wide concave portion R1, a central portion of the wide bottom surface B1 is likely to be etched too much. Since a desired depth of concave portions has already been ensured by the main etching, it is preferable that the amount of etching in the extra etching step is set to a value only necessary for fine adjustment in depth between a wide concave portion R1 and a narrow concave portion R2.
As for the material of the first gas, fluorocarbon gases which are more likely to produce a deposit can be used, and CF4, CH2F2, CH3F, C4F8, C4F6, and C5F8 are preferably used, among of which CH3F which produces an appropriate amount of deposit is particularly preferable from the viewpoint of controllability of etching conditions. Use of a gas that produces an excessive amount of deposit may lead to degraded etching controllability.
While foundation layer 2 may be etched only with the first gas, it is preferable that the function of producing a deposit and the function of etching foundation layer 2 are assumed by different gases from the viewpoint of controllability of etching conditions. Accordingly, it is preferable, in the present invention, that a second gas having a greater capability of etching foundation layer 2 than that of the first gas and producing no deposit is mixed and used as the etching gas other than the first gas. As for the material of the second gas, sulfur fluoride gases may be used and SF6 is preferably used.
It is further preferable to use a diluent gas (inert gas) with the etching gas. Use of the diluent gas will lead to improved controllability of etching conditions.
It is preferable that the pressure is set to a higher value than a pressure (less than 1 Pa) in general etching conditions. A high pressure may reduce the ion perpendicular anisotropy and cause a more amount of RIE lag.
As for the antenna power, it is preferable to use a low power in order to control the etching rate and improve controllability.
Specific values of etching conditions, including the flow rates of etching gas (first gas and second gas) and diluent gas, pressure, antenna power, and lower electrode temperature, can be set appropriately according to the etching target of original plate 1. For example, if the major component of processing target layer 3 is SiO2 and the major component of foundation layer 2 is Si, preferable etching conditions for carrying out the extra etching of the present invention include a flow ratio of 1:1 to 15:1 between the first and second gases, a flow ratio of 1:1 to 1:20 between the etching and diluent gases, a pressure of 1 to 12 Pa, an antenna power of 20 to 200 W, and a bias power of 0 to 15 W. In this case, further preferable etching conditions include a flow ratio of 3:1 to 8:1 between the first and second gases, a flow ratio of 1:5 to 1:15 between the etching and diluent gases, a pressure of 4 to 8 Pa, an antenna power of 30 to 100 W, a bias power of 0 to 15 W, and a lower electrode temperature of 10 to 60° C.
There may be a concern that a side wall of a concave portion (processing target layer 3) is etched unnecessarily by the extra etching, and the width of the concave portion, side wall angle, and the like may possibly be changed. But, in the present invention, the bias power is set to low to reduce the kinetic energy given to ions, whereby etching of a side wall of a concave portion is prevented and virtually no variations in the width of a concave portion and side wall angle are observed. More specifically, when the extra etching is performed such that a wide bottom surface B1 is etched by 2 nm under etching conditions in which the etching selectivity of foundation layer 2 to processing target layer 3 becomes 10 or more, the etched amount of a side wall is about 0.2 nm.
A desired master mold 10 improved in the uniformity of concave portions as shown in E of
As described above, in the method of manufacturing master mold 10 having thereon an uneven pattern corresponding to an opening pattern of coating layer 4 by performing etching step with a reactive ion etching process, the method of manufacturing master mold 10 according to the present embodiment includes two separate etching steps, a main etching step and an extra etching step, and, in particular, etching is performed in the extra etching step using an etching gas that includes a first gas capable of etching foundation layer 2 and producing a deposit with a bias power of not greater than 15 W. For negative 1 in which a wide bottom surface B1 is shaped in an upward convex and a narrow concave portion R2 is etched deeper than a wide concave portion R1 by the main etching, this allows the wide bottom surface B1 to be flattened out and the depth D1 of the wide concave portion R1 and the depth D2 of the narrow concave portion R2 to be equalized. As the result, in the method of manufacturing master mold 10 using a reactive ion etching process, master mold 10 having an uneven pattern constituted by a wide concave portion R1 and a narrow concave portion and improved in the uniformity of concave portions of the pattern may be manufactured.
(Design Changes of Master Mold Manufacturing Method)
The master mold manufacturing method of the present invention has been described as a method having four steps, but the other step, such as the step of forming a magnetic layer, step of performing surface treatment, or the like, may also be included as appropriate.
[Mold Structure Manufacturing Method]
A method of manufacturing mold structure 20 of the present invention is a method of manufacturing a mold structure, through replication, by electroforming using master mold 10 manufactured by the master mold manufacturing method as the original master and according to the steps shown in
More specifically, the method includes the steps of forming conductive layer 5 along the surface of an uneven pattern of master mold 10 used as the original master (A of
The electroforming is performed by immersing master mold 10 in an electrolyte of electroforming equipment which includes the metal material described above and applying electricity between conductive layer 5, used as the cathode, and the anode. Here, it is necessary to provide optimum conditions so that metal substrate 6 (mold structure) produced has no deformation by adjusting the concentration of the material in the electrolyte, pH of the electrolyte, way of applying electric current, and the like. As for the metal material, Ni is preferably used from the viewpoint of ease of detachment and durability when formed into a mold structure.
As for the material of conductive layer 5, metals, such as Ni, may be used and a plurality of conductive layers 5 may be formed on top of each other. There is not any specific restriction on the method of forming conductive layer and sputtering, deposition, ion plating, ALD (atomic layer deposition), CVD (chemical vapor deposition), electroless plating, and the like may be used. There is not any specific restriction on the layer thickness of conductive layer 5 and it is generally a several tens of nanometers. Note that a conductive layer is not necessarily required when master mold 10 alone has sufficient conductivity for electroforming, such as the case in which master mold 10 includes a metal layer in its structure.
As described above, the method of manufacturing mold structure 20 according to the present embodiment includes the steps of forming, through electroforming of a metal material, metal substrate 6 made of the metal material on the surface of the uneven pattern of master mold 10 manufactured by the master mold manufacturing method described above and detaching metal substrate 6 from master mold 10, thereby obtaining mold structure 20, i.e., metal substrate 6, having a reverse uneven pattern to the uneven pattern of master mold 10. Master mold 10 manufactured by the master mold manufacturing method described above has a high uniformity in convex portions of the uneven pattern. Consequently, mold structure 20 having a high uniformity in convex portions of the uneven pattern may be manufactured in the manufacture of mold structure 20 through replication by electroforming using master mold 10 as the original master.
An example of the master mold manufacturing method of the present invention will now be described.
An original plate having a 60 nm SiO2 layer (processing target layer) and a 750 μm Si layer (foundation layer) were provided and an 80 nm resist layer was formed on the SiO2 layer of the original plate. An L&S type opening pattern having a wide opening with an opening width of 150 nm and a narrow opening with an opening width of 75 nm was formed in the resist by electron beam exposure of the resist with an electron beam writing apparatus and subsequent development.
Thereafter, etching was performed, as the main etching, on the original plate with an ICP-RIE system (E620, available from Panasonic Solutions Company) using the resist layer having the opening pattern formed therein as the mask under etching conditions for achieving an etching selectivity of about 10 for the SiO2 layer with respect to the Si layer in which CHF3 with a flow rate of 30 sccm and CF4 with a flow rate of 15 sccm were used as the etching gas with a pressure of 0.6 Pa, an antenna power of 190 W, a bias power of 30 W, and a lower electrode temperature of 10° C. The amount of over etching was set to 10% (6 nm) of the layer thickness of the SiO2 layer as a guide.
After the main etching, etching was performed, as the extra etching, on the original plate with the same ICP-RIE system using the resist having the opening pattern formed therein as the mask under etching conditions for achieving an etching selectivity of about 12 for the Si layer with respect to the SiO2 layer in which CHF3 with a flow rate of 10 sccm and SF6 with a flow rate of 2 sccm were used as the etching gas with a pressure of 6.0 Pa, an antenna power of 50 W, a bias power of 0 W, and a lower electrode temperature of 10° C. The amount of extra etching in the extra etching step was set such that a wide bottom surface was etched by 2 nm.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-061903 | Mar 2010 | JP | national |
