JP2010017865A - Method for manufacturing mold for nanoimprinting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a mold for nanoimprinting with which a high-quality mold can be obtained by forming a current seed layer without using a sputtering method for a resist pattern. <P>SOLUTION: The method includes the process (1) for preparing a substrate 10 having a conductive surface, the process (2) for forming a resist layer 20 having an uneven pattern on the substrate having the conductive surface to have the conductive pattern exposed from the recesses of the pattern of the resist layer, the process (3) for carrying out electroforming on the conductive surface exposed from the recesses of the pattern of the resist layer to form an electroformed film 40 thicker than the resist layer, and the process (4) for removing the substrate having the conductive surface and the resist layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a nanoimprint mold.

  Lines / dots for recording data having a pattern definition (line / dot repetition interval) of about 400 nm to 700 nm are formed on the surface of an optical disk such as a CD and a DVD. These optical disks are manufactured using an injection compression molding method of polycarbonate. That is, a resin is injected into a mold (also called a mold or a stamper) having an uneven pattern corresponding to data, and the pattern is transferred to the resin by compression molding. FIG. 1 shows an outline of an example of a method for manufacturing an optical disc stamper. A resist is applied to the polished and washed glass master, and pattern cutting (exposure) and development are performed to form an uneven pattern. Next, an electrode film to be a current seed layer is attached by a method such as sputtering or electroless plating. Then, a mold (stamper) is obtained by depositing nickel by electroforming and finally peeling off the glass master and the resist. The peeled glass master can be recycled after resist stripping and reused as a glass master.

  The nickel electroforming method is known to be an excellent method for accurately replicating a microstructure. An optical disc stamper has an imprint durability of several hundred thousand times, but in order to improve the production efficiency of media, the stamper is usually duplicated. That is, the convex stamper (Father stamper) obtained by the above-described method is reused as an electroforming master to obtain a concave stamper (Mother stamper). Furthermore, a Mother stamper is used as an electroforming master to obtain a convex stamper for mass production that is actually used for production of media. When 10 copies are made in each of the stage of obtaining the Mother stamper from the Father stamper and the stage of obtaining the convex stamper for quantity from the Mother stamper, 1000 convex stampers for mass production are obtained from one Father stamper. Can do.

  A mold used for nanoimprinting can also be basically manufactured by the same method as that used for manufacturing an optical disc, but various conditions such as imprinting material and pattern definition are different. In particular, in order to produce a mold for transferring a fine structure having a pattern definition of several tens of nanometers, a lithography apparatus having high drawing performance such as a stepper or an electron beam drawing apparatus is used on a silicon substrate. It is necessary to form a resist pattern. In order to perform electroforming using this resist pattern, it is necessary to form a current seed layer on the resist pattern.

  However, when the pattern definition is 100 nm or less, the coverage (particularly the uniformity of the film thickness) of the current seed layer formed on the concavo-convex pattern by sputtering decreases. That is, the film thickness of the obtained current seed layer differs at the top, side wall, and bottom of the resist pattern (the substrate exposed portion of the pattern recess, ie, the trench). In particular, in the upper part of the resist pattern, the formation of the current seed layer preferentially progresses, and there arises a problem that the trench opening (the gap between the adjacent resist pattern convex portions) is narrowed. As an example of the cross-sectional shape of the film on the concavo-convex pattern when a conventional sputtering method is used, the shape of titanium nitride formed on a semiconductor substrate is described (see Patent Document 1). That is, in the sputtering method, the semiconductor substrate and the target are disposed to face each other in a high vacuum chamber. When an inert gas such as argon is introduced into the chamber and a voltage is applied between the semiconductor substrate and the target, glow discharge is generated and the argon gas is ionized. The argon ions collide with the surface of the target and eject titanium from the target. The ejected titanium obtains sufficient energy by argon ions and flies toward the semiconductor substrate. Here, all the titanium that is ejected does not fly uniformly in a direction perpendicular to the semiconductor substrate, but has a certain degree of random orientation. For this reason, as shown in FIG. 2, when a concave portion that is a hole or a trench (trench) and a convex portion that is a ridge are formed on a substrate 210 using a resist layer 220, titanium is formed at the bottom of the hole or trench. Is difficult to deposit, and a titanium deposition film 230 having a shape having an overhang on the top of the ridge of the resist layer 220 is obtained. Thus, the conventional method has a problem in that a sputtered film cannot be formed at the bottom of the hole or trench with good coverage.

  In order to solve this problem, a method is described in which a collimator in which a large number of through holes are formed is disposed between a substrate and a target to improve the coverage (see Patent Document 1). However, in this method, the target metal adheres to the collimator, and the attached metal falls as dust on the substrate, and only the sputtered metal that is perpendicularly incident on the substrate. Since it is involved in the film formation, there arises a problem that the film formation speed is reduced to about 1/5 compared with the case where the sputtering method without using a collimator is applied. In addition, a method has been proposed in which thermionic electrons collide with a titanium target to generate titanium ions, and an electric field gradient acts on the titanium ions to control the flight direction, thereby improving coverage (patent). Reference 1).

  In addition, as a stamper manufacturing method that does not use a sputtered film, a resist pattern is formed on the surface of the nickel plate, electroforming is performed using the nickel plate exposed at the bottom of the resist pattern as a current seed layer, the resist pattern is removed, and the stamper is removed. An obtaining method has been proposed (see Patent Document 2). In this method, the height of the pattern convex portion of the stamper is controlled by the electroforming time. Therefore, there is a problem that the height of the pattern convex portion cannot be precisely controlled as compared with the method of defining the height of the pattern convex portion by the resist thickness. Further, the growth surface of the electroformed film is generally satin-like and has a large surface roughness. The stamper obtained by the method of Patent Document 2 is not suitable as a nanoimprint mold that requires a small surface roughness because the growth surface of the electroformed film serves as a pressing surface.

JP-A-8-186108 JP 2001-33634 A

  An example of a method for manufacturing a mold for nanoimprinting using a current seed layer formed by a conventional sputtering method is shown in FIG. First, as shown in FIG. 3A, a resist layer 320 is applied on the substrate 310, and then the resist layer 320 is patterned to form ridges (projections) and trenches (recesses) as shown in FIG. ) Get the pattern. Next, a current seed layer 330 is deposited on the resist layer 320 by sputtering. At this time, the deposition of the current seed layer 330 proceeds preferentially on the top of the ridge of the resist layer 320, and the current seed layer 330 having an overhang shape is obtained.

  Next, when this laminate is immersed in an electroforming solution and a current is applied to the current seed layer 330, an electroformed film 340 is deposited on the entire surface of the current seed layer 330 as shown in FIG. Is started. The deposition of the electroformed film 340 proceeds isotropically. When the electroforming is further continued, the electroformed film 340 is joined above the hole or trench due to the overhang shape of the current seed layer 330, and the gap 350 is left inside the trench as shown in FIG. . Finally, the substrate 310 and the resist layer 320 are peeled off, and the mold 300 including the current seed layer 330 and the electroformed film 340 is obtained.

  However, the resulting mold 300 has low mechanical strength due to the voids 350 remaining on the protrusions. Further, the remaining gap 350 may cause a defect such as deformation of the mold 300 and a pattern defect.

  Accordingly, an object of the present invention is to provide a method for manufacturing a mold for nanoimprinting, in which a current seed layer is formed without using a sputtering method on a resist pattern, thereby obtaining a high-quality mold.

  The method for producing a mold for nanoimprinting of the present invention includes: (1) a step of preparing a substrate having a conductive surface; (2) forming a resist layer having a concavo-convex pattern on the substrate having a conductive surface; A step of exposing the conductive surface in the concave portion of the pattern; and (3) electroforming the conductive surface exposed in the concave portion of the pattern of the resist layer to have a thickness larger than the thickness of the resist layer. A step of forming a cast film; and (4) a step of removing the substrate having a conductive surface and the resist layer. Here, the substrate having a conductive surface may be a metal substrate or a laminate in which a current seed layer is formed on an insulating or semiconductor support. The current seed layer can be formed using gold, platinum, titanium, or aluminum, and preferably has a thickness of 10 nm to 100 nm. Further, the resist pattern recesses are: (a) trenches having a line width of 10 to 100 nm and arranged at intervals of 10 to 100 nm; (b) rectangular bottoms having a side of 10 to 200 nm or diameters of 10 to 200 nm. A hole having a circular bottom surface and arranged at intervals of 10 to 200 nm; or (c) a combination thereof. Here, it is desirable that the trenches and holes are arranged concentrically or spirally. Furthermore, the step (2) may include a step of applying a resist layer on the conductive surface and a step of patterning the resist layer by an electron beam drawing method.

  By adopting the above configuration, the electroformed film grows unidirectionally upward from the conductive surface at the pattern bottom of the resist layer, so that a nanoimprint mold having no voids inside can be obtained. . The obtained mold has sufficient mechanical strength, and does not have defects such as mold deformation and pattern defect, and has high quality. Moreover, since the height of the convex part of the mold obtained is defined by the thickness of the resist layer, it can be controlled with high accuracy. Since the upper surface of the convex part of the mold to be obtained is a surface that has been in contact with the conductive surface, the surface roughness can be reduced. Also from this point, the mold obtained by the method of the present invention is suitable for nanoimprinting.

  FIG. 4 shows an outline of the method for producing the nanoimprint mold of the present invention. First, a substrate 10 having a conductive surface is prepared. The substrate 10 having a conductive surface in the present invention may be a metal substrate (not shown), or a laminate in which a current seed layer 30 is formed on an insulating or semiconductive support 11. Also good.

  When a metal substrate is used as the substrate 10 having a conductive surface, the metal substrate can be manufactured using gold, platinum, titanium, or aluminum. As the insulating or semiconductive support 11, a glass support, a silicon support, a carbon support, or the like can be used. The material of the current seed layer 30 includes a metal such as gold, silver, platinum, titanium, and aluminum. The current seed layer 30 can be formed by depositing these metals on the insulating or semiconductive support 11 using a method such as vapor deposition, sputtering, or electrolytic plating. When a stacked body in which the current seed layer 30 is formed on the insulating or semiconductor support 11 is used, the current seed layer 30 supplies the current from the power supply means attached to the periphery of the substrate 10 over the entire surface of the substrate 10. It is desirable to have a film thickness that can be supplied. From this viewpoint, the current seed layer 30 desirably has a thickness of 10 nm to 100 nm. If necessary, the surface roughness of the conductive surface (the surface of the current seed layer 30 in FIG. 4) of the substrate 10 may be reduced by using a method such as polishing. Reducing the surface roughness of the conductive surface is effective in reducing the surface roughness of the upper surface of the convex portion of the mold 100 finally obtained.

  Next, the surface of the current seed layer 30 is oxidized to form an oxide film having a thickness of 5 nm or less, preferably 1 to 3 nm. When the current seed layer 30 is formed using an inert metal such as gold, silver, and platinum, the oxide film having the above-described thickness is formed on the current seed layer. The oxide film or oxide film having such a thickness does not interfere with the electroforming process, and it can be said that the surface of the current seed layer 30 is still conductive for the purpose of the present invention. These oxide films or oxide films facilitate separation of the current seed layer 30 and the electroformed film 40.

  Next, a resist layer 20 having a concavo-convex pattern is formed on the substrate 10 having a conductive surface, and the conductive surface is exposed in the resist pattern recesses. In this step, for example, as shown in FIG. 4B, the resist layer 20 is formed over the entire conductive surface of the substrate 10 (which is the current seed layer 30 in the example of FIG. 4), and then the step shown in FIG. The patterning of the resist layer 20 can be performed as shown in FIG.

  The formation of the resist layer 20 over the entire surface of the conductive surface can be performed using a coating method known in the art such as a spin coating method, a roll coating method, a dip coating method, or a knife coating method. The resist layer 20 desirably has a thickness of 100 nm or less, preferably 10 to 60 nm. As the material of the resist layer 20, any commercially available material can be used on condition that it is compatible with radiation (electron beam, vacuum ultraviolet ray, deep ultraviolet ray, ultraviolet ray, etc.) used in the subsequent patterning process. The material of the resist layer 20 may be a so-called negative material in which a portion exposed to radiation is cured, or may be a so-called positive material in which a portion exposed to radiation is solubilized.

  Next, the resist layer 20 is patterned. From the viewpoint of pattern definition, this step is desirably performed using, for example, an electron beam drawing method. In the electron beam drawing method, the resist layer 20 is exposed in a pattern to an electron beam, and the exposed portion is cured or solubilized. Thereafter, the resist layer 20 is immersed in a developing solution to remove uncured portions or solubilized portions, thereby forming a plurality of concave portions. Further, the hardened part and the non-solubilized part become convex parts and constitute a ridge. The developer can be appropriately selected according to the material of the resist layer 20 used. In the present invention, the conductive surface of the substrate 10 (the surface of the current seed layer 30 in the example of FIG. 4) needs to be exposed at the bottom surface of the recess.

  In the present invention, the recess of the resist layer 20 may be either a hole or a trench, or a combination thereof. When forming a hole in the resist layer 20, it is desirable that the hole has a rectangular bottom with a side of 10 nm to 200 nm or a circular bottom with a diameter of 10 nm to 200 nm. In addition, the interval between two adjacent holes is preferably 10 nm to 200 nm. Moreover, when forming a trench (namely, groove | channel) in the resist layer 20, it is desirable for a trench to have a line width of 10-100 nm. Moreover, it is desirable that the interval between two adjacent trenches be 10 nm to 100 nm. The holes or trenches are desirably arranged concentrically or spirally on the substrate 10. The “concentric arrangement of holes” in the present invention means that a plurality of concentric circles are formed when the center lines of the holes are connected. In addition, the “hole spiral arrangement” in the present invention means drawing a spiral whose radial position changes at an equal pitch each time it rotates, when the center lines of the holes are connected. Further, even when the concave portion is formed by combining holes and trenches, it is desirable to arrange the holes and trenches in a concentric or spiral pattern. The “concentric arrangement as a whole hole and trench” in the present invention means that a plurality of concentric circles are formed when the center lines of the hole and trench are connected. Further, in the present invention, “spiral arrangement as the whole hole and trench” means that a spiral whose radial position changes at an equal pitch every rotation is made when the center lines of the hole and the trench are connected. To do.

  On the other hand, the height of the ridge of the resist layer 20 in the present invention is determined by the film thickness of the resist layer 20. The height of the ridge corresponds to the height of the unevenness of the mold finally obtained, and is desirably 100 nm or less, preferably 10 to 60 nm.

  Next, the obtained laminate is immersed in an electroforming solution, and electroforming is performed on the conductive surface exposed in the recesses of the resist layer 20 to form the electroformed film 40. The electroformed film 40 can be formed using Ni, Cu, Au, Ni—P alloy, Ni—Co alloy, Ni—Fe alloy, or the like. In particular, it is preferable to form an electroformed film using Ni. As the electroforming liquid, a solution having an arbitrary composition known in the art can be used. For example, when the electroformed film 40 made of Ni is formed, a solution containing nickel sulfate, nickel chloride, boric acid as a main component, a solution containing nickel sulfamate and boric acid as main components, or nickel chloride as a main component. The solution can be used as an electroforming liquid. Further, the conductive surface (current seed layer 30 in the case of FIG. 4) is used as a cathode, and is supplied with current from, for example, power supply means (not shown) attached to the peripheral portion of the substrate 10. The anode at the time of electroforming may be formed using the same metal (Ni or the like) as the material of the electroformed film 40 and used as a supply source of the material of the electroformed film 40. Alternatively, an anode made of an insoluble metal may be used. In this case, the metal salt used as the material of the electroformed film 40 may be supplemented in the electroforming liquid as necessary.

  FIG. 4D shows the shape of the electroformed film 40 in the initial stage of this process. Unlike the case where the electroformed film 340 grows in all directions from the entire surface of the current seed layer 330 having a concavo-convex pattern as shown in FIG. 3D, in the method of the present invention, a plurality of electroformed films are formed. 40 grows unidirectionally upward from the conductive surface (current seed layer 30 in FIG. 4) exposed at the bottom of the hole or trench of resist layer 20. Therefore, no void is generated inside the electroformed film 40 inside the hole or trench.

  In the present invention, as shown in FIG. 4E, a plurality of electroformed films 40 in the holes or trenches are integrated beyond the ridge of the resist layer 20, and the integrated electroformed film grows to a sufficient thickness. Until this is done, electroforming continues further. Depending on the desired application, it is preferable that the electroformed film 40 has a maximum film thickness of 50 to 300 μm (portion in contact with the current seed layer 30 in FIG. 4E) from the viewpoint of mechanical strength and the like. .

  Finally, the substrate 10 having the conductive surface (the insulating or semiconductive support 11 and the current seed layer 30 in FIG. 4) and the resist layer 20 are removed, and the mold 100 made of the electroformed film 40 is obtained. Separation of the electroformed film 40 and the substrate 10 having a conductive surface can be performed with the aid of an oxide film or an oxide film formed on the surface of the current seed layer 30. Furthermore, the resist layer 20 can be removed from the electroformed film 40 by performing oxygen plasma treatment or immersion in an alkaline solution after the separation.

  The obtained mold 100 has sufficient mechanical strength because there are no voids therein, and has no defects such as deformation of the mold 100 and pattern defects, and has high quality. Moreover, since the height of the convex part of the mold 100 to be obtained is defined by the thickness of the resist layer 20, it can be controlled with high accuracy. Furthermore, since the upper surface of the convex part of the mold 100 to be obtained is a surface that has been in contact with the conductive surface (the current seed layer 30 in FIG. 4), the surface roughness can be reduced. Also from this point, the mold 100 obtained by the method of the present invention is suitable for nanoimprinting.

It is a figure which shows the outline of an example of the manufacturing method of the stamper for optical discs. It is the schematic which shows the coverage of the titanium deposit film produced by the conventional sputtering method. It is a figure which shows the manufacturing method of the mold for nanoimprint which forms a current seed layer using the conventional sputtering method, (a)-(f) is a figure which shows each process. It is a figure which shows the manufacturing method of the mold for nanoimprint of this invention, (a)-(f) is a figure which shows each process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate with conductive surface 11 Insulating or semi-conductive support 210, 310 Substrate 20, 220, 320 Resist layer 30, 330 Current seed layer 230 Titanium deposited film 40, 340 Electroformed film 100, 300 Mold

Claims (6)

(1) preparing a substrate having a conductive surface;
(2) forming a resist layer having a concavo-convex pattern on a substrate having a conductive surface, and exposing the conductive surface in a concave portion of the pattern of the resist layer;
(3) performing electroforming on the conductive surface exposed in the recesses of the resist layer pattern to form an electroformed film having a film thickness larger than the film thickness of the resist layer;
(4) A method for producing a mold for nanoimprint, comprising a step of removing a substrate having a conductive surface and a resist layer.   The method for producing a mold for nanoimprinting according to claim 1, wherein the substrate having a conductive surface is a metal substrate or a laminate in which a current seed layer is formed on an insulating or semiconductive support.   The method according to claim 2, wherein the current seed layer is made of gold, platinum, titanium, or aluminum.   The method of manufacturing a nanoimprint mold according to claim 3, wherein the current seed layer has a thickness of 10 nm to 100 nm. The recess of the resist pattern
(A) trenches having a line width of 10 to 100 nm and arranged at intervals of 10 to 100 nm;
(B) a hole having a rectangular bottom surface with a side of 10 to 200 nm or a circular bottom surface with a diameter of 10 to 200 nm and arranged at an interval of 10 to 200 nm; and (c) a combination thereof, and the trench The method for producing a mold for nanoimprinting according to claim 1, wherein the holes and the holes are arranged concentrically or spirally.   2. The method for producing a nanoimprint mold according to claim 1, wherein the step (2) includes a step of applying a resist layer on the conductive surface and a step of patterning the resist layer by an electron beam drawing method. .

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