JP2004270021A - Method for manufacturing micrometallic structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing micrometallic structures which simplifies inter-process treatment by forming a uniform conductive layer film by electroless plating on the surface of a PMMA matrix. <P>SOLUTION: The method for manufacturing the micrometallic structures which forms the conductive layer film on the surface of the PMMA matrix 3 formed with X-ray patterns includes an etching process of roughening the surface of the PMMA matrix 3 by a high chromium acid bath, a sensitizing process, an activating process and an electroless plating process for forming the conductive layer film. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a fine metal structure. More specifically, the present invention relates to a method for manufacturing a fine metal structure in which electroforming is performed on a resin matrix on which a pattern is formed.
[0002]
[Prior art]
X-ray lithography using synchrotron radiation is an exposure technique capable of transferring a very small fine pattern on an X-ray mask onto a resist with high accuracy by using a short wavelength of X-rays. As a process for manufacturing a fine metal structure such as a mold for manufacturing a micro component such as a three-dimensional micromachine having a high aspect ratio using X-ray lithography, there is a LIGA (Lithogr Galvanoformung Abformung: German) process.
[0003]
This LIGA process is a processing method combining X-ray lithography, electroforming and molding. X-rays from an SR (synchrotron radiation) optical device are exposed on a thin-film substrate made of a material that easily transmits X-rays through an X-ray mask in which an absorber pattern that does not easily transmit X-rays is formed. By developing, a pattern is formed on a resist layer made of polymethyl methacrylate (hereinafter, referred to as PMMA) on a resist substrate for X-ray exposure, thereby forming a PMMA matrix. After a conductive layer film is formed on the surface of the PMMA matrix, electroforming is performed using the conductive layer film as an electrode to form a metal layer having an inverted pattern, thereby obtaining a fine metal structure. Further, a fine resin part can be obtained by molding using this metal layer as a mold (for example, see Patent Document 1).
[0004]
Further, by moving the X-ray mask, the energy distribution of the X-rays is continuously changed, and the resist layer is formed by using a moving mask method capable of processing a depth corresponding to the depth of the energy distribution of the X-rays. In some cases, a pattern is formed to form a PMMA matrix (for example, see Patent Document 2).
[0005]
Meanwhile, conventionally, the conductive film on the surface of the PMMA matrix has been formed by vapor deposition in which a metal or a metal compound is heated in a vacuum to evaporate, and the vapor is applied to the surface of the PMMA matrix for plating.
[0006]
[Patent Document 1]
JP 2001-146017 A (page 1-11, FIG. 1 to FIG. 10)
[Patent Document 2]
JP-A-2000-35500 (pages 1-9, FIGS. 2, 5-8)
[0007]
[Problems to be solved by the invention]
However, when the aspect ratio, which is the ratio of the height and width of the pattern formed on the resist layer, is high, there is a problem that the conductive layer film on the surface of the PMMA matrix is not formed uniformly by vapor deposition.
[0008]
In addition, the post-exposure process includes a developing process, which is a wet process using a liquid, a vapor deposition process, which is a dry process without using a liquid, and an electroforming process, which is a wet process. Therefore, a drying process is required, and handling of the process between the processes is complicated.
[0009]
Also, if a conductive layer film can be formed on the surface of the PMMA matrix by electroless plating, which is a wet process, the wet process can be continued and the handling of the inter-process can be simplified. Since the Pd catalyst serving as a catalyst nucleus has few irregularities and easily separates from the surface of the PMMA matrix, it has been difficult to form a conductive layer film by electroless plating.
[0010]
The present invention has been made in view of the circumstances and problems described above, and provides a method capable of forming a uniform conductive layer film on the surface of a PMMA matrix by electroless plating, thereby simplifying inter-process processing. It is another object of the present invention to provide a method for producing a large amount of fine metal structures at low cost.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a method for manufacturing a fine metal structure according to claim 1 comprises forming a conductive layer film on a surface of a resin matrix on which a pattern is formed, and electroforming the conductive layer film as an electrode. In the method for producing a fine metal structure, the etching step of roughening the surface of the resin matrix, the sensorizing step of adsorbing metal ions on the surface of the resin matrix, and the reducing action of the metal ions An activating step of forming a metal catalyst on the surface of the resin matrix, and an electroless plating step of forming the conductive layer film by forming a plating film using the metal catalyst as a nucleus. And
[0012]
A method of manufacturing a fine metal structure according to a second aspect is characterized in that in the etching step of the fine metal structure according to the first aspect, the surface of the resin matrix is roughened by a high chromic acid bath. .
[0013]
According to a third aspect of the present invention, in the method for manufacturing a fine metal structure according to the first or second aspect, the pattern is formed by exposure to synchrotron radiation, and the resin matrix is formed. It is characterized by being composed of polymethyl methacrylate.
[0014]
According to a fourth aspect of the present invention, in the method of manufacturing a fine metal structure according to any one of the first to third aspects, the pattern is formed by a moving mask method.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIG. The method for manufacturing a fine metal structure according to the embodiment of the present invention includes a step of irradiating radiation light via an X-ray mask 2 for pattern formation and developing and forming a polymethyl methacrylate (hereinafter referred to as PMMA) matrix 3. In this method, a conductive layer film is formed on a surface by electroless plating, and a metal layer 4 is formed by electroforming to produce a fine metal structure 5.
[0016]
First, as shown in FIG. 1A, the PMMA substrate 1 is formed of a resist layer made of PMMA and having a thickness of several tens to several hundreds of μm. The thickness of the PMMA substrate 1 is appropriately determined according to the size of the fine metal structure 5 to be manufactured. The PMMA substrate 1 may have a configuration in which a resist layer made of PMMA having a thickness of several tens to several hundreds of μm is provided on a metal substrate layer made of Ni having a thickness of several hundred μm by coating. The metal substrate layer may be made of a Ni alloy such as NiW or NiFe or a metal plating layer other than the Ni alloy in addition to Ni. Further, as the metal substrate layer, a metal film formed on a silicon substrate by sputtering can be used.
[0017]
An X-ray mask 2, which is a mask for X-ray lithography, is arranged in parallel above a PMMA substrate 1 at a predetermined interval. This X-ray mask 2 has an X-ray non-transmissive material, such as tungsten or gold, having a thickness of several μm, which is an X-ray absorbing material, on an X-ray transmission film 2a which is a support film having a thickness of several μm made of silicon nitride or the like. A predetermined pattern, for example, a fine linear pattern is formed by the film 2b.
[0018]
Thereafter, X-rays are exposed on the PMMA substrate 1 through an X-ray mask 2 from an SR (synchrotron radiation) light device (not shown). By using an SR optical device, high-energy X-rays can be easily generated, and lithography with high accuracy can be performed. When exposed and developed, the exposed portion of the PMMA substrate 1 is removed as shown in FIG. 1B, and a pattern of PMMA corresponding to the pattern of the X-ray non-transmissive film 2b of the X-ray mask 2 is formed. The depth of a groove or the like, which is a portion removed by exposure, is adjusted by an exposure time, a development time, or the like. Thus, a PMMA matrix 3 having a PMMA pattern is formed.
[0019]
In the case of normal X-ray exposure, a pattern having a vertical inclination cannot be formed on the PMMA substrate 1 due to the straightness of X-rays. However, the X-ray energy distribution is continuously changed by relatively moving the X-ray mask 2 in a direction parallel to the surface of the PMMA substrate 1, and processing at a depth corresponding to the depth of the X-ray energy distribution is performed. By forming a pattern using a movable mask method that can be performed, a PMMA matrix 3 having a pattern inclined in the vertical direction can be obtained (see Patent Document 2 for details).
[0020]
Subsequently, a step of forming a conductive layer film made of an electroless plating film on the surface of the patterned PMMA matrix 3 will be described. This step includes the steps of degreasing, etching (pickling), neutralization, sensorizing (sensitizing), activating (activating), and electroless plating. It should be noted that there is a washing step such as water washing between each step.
[0021]
First, the degreasing step is a step of cleaning oily dirt on the surface of the body of the PMMA matrix 3. It is carried out by a known method, but an ethanol solution of about 50% by weight is suitably used.
[0022]
Next, the etching step is a step of roughening the base surface of the PMMA matrix 3 in order to favorably adsorb metal ions in the sensorizing process. Before performing the electroless plating process, it is necessary to provide a catalyst nucleus to the unevenness on the surface of the substrate in order to form a plating film on the surface to be plated. However, the base surface of PMMA is stable with few irregularities, and even if a catalyst nucleus such as a Pd catalyst adheres, it is easily detached from the base surface, so that it is difficult to perform electroless plating. For this reason, it is necessary to roughen and roughen the surface of the PMMA matrix 3 so that the Pd catalyst does not easily desorb from the surface of the PMMA matrix 3. In order to roughen the stable surface of the PMMA matrix 3, a high chromic acid bath having a high etching ability is used. For example, as a high chromic acid bath, it is immersed in a solution composed of 300 g / L of chromic anhydride and 450 g / L of sulfuric acid at 60 ° C. for 10 minutes.
[0023]
The neutralization step is a step of neutralizing the PMMA matrix 3 oxidized in the etching step using an alkaline solution.
[0024]
The sensor sizing step is a step in which metal ions are adsorbed on the surface of the base material of the PMMA matrix 3 by immersion in a sensor typer (sensitizer) solution. As the sensorizer solution, any solution containing a known divalent metal ion composed of Sn, Ti, Pb, Hg, or the like may be used, but a tin (II) chloride or tin (II) sulfide solution is preferably used.
[0025]
In the activation step, the metal particles having strong catalytic activity are reduced and precipitated by immersion in the activation solution, thereby reducing the metal ions adsorbed on the substrate surface of the PMMA matrix 3 by the sensorizing process. This is a step of forming a uniform distribution on the surface of the PMMA matrix 3. The activating solution may be a known aqueous solution of a noble metal salt such as Pd, Pt, Au, or Ag, but a palladium chloride solution is preferably used.
[0026]
After the activating step, the PMMA matrix 3 is washed by running water washing, immersion washing or the like in order to remove the activating solution attached to the surface of the matrix.
[0027]
Electroless plating is widely used for plating on a non-conductive substrate. Since the metal fine particles as catalyst nuclei are adsorbed on the surface of the substrate by the activating step, the electroless plating reaction can be advanced. Nickel plating is generally used as electroless plating. In this case, a known plating bath containing a reducing agent such as a water-soluble nickel salt, an organic acid salt (a complexing agent) and a hypophosphite (such as sodium hypophosphite) is used as the plating solution. In the electroless plating step, a plating film made of nickel (not shown) is formed on the surface of the PMMA matrix 3.
[0028]
Since a plating film as a conductive layer film is formed on the base surface of the PMMA matrix 3 by electroless plating, a uniform conductive layer film can be formed even if the formed pattern has a high aspect ratio.
[0029]
Subsequently, electroplating is performed using the plating film formed on the surface of the PMMA matrix 3 as a conductive layer film, and as shown in FIG. 1C, the gap between adjacent patterns has the same thickness as the patterns. The metal pattern layer 4 made of Ni, Cr, or the like is formed. The electroforming method is a method in which a cathode electrode and an anode electrode serving as a matrix are placed in an electroplating bath filled with an electroforming bath, and a metal layer is electrodeposited on the cathode by the principle of plating to obtain a predetermined thickness. It is a way to get a duplicate version of the original. When nickel electroforming is performed using the PMMA matrix 3 as a cathode electrode, it is preferable to use a sulfamic acid bath which has a low internal stress and can be performed at high speed.
[0030]
Thereafter, when the pattern of PMMA is removed by a solvent, a fine metal structure 5 is obtained as shown in FIG. This fine metal structure 5 can be used as a mold for a fine resin molded part or the like, or as it is as a fine metal part.
[0031]
Since a conductive layer film is formed on the base surface of the PMMA matrix 3 by electroless plating, the post-exposure process is a development process, an electroless plating process, an electroforming process, and a wet process is continuous. Is simplified, and the fine metal structure 5 can be manufactured in large quantities at low cost.
[0032]
Next, a method of manufacturing the fine resin component 9 by hot embossing using the fine metal structure 5 as a mold will be described with reference to FIG. First, the resin plate 6 has a resin layer 8 formed on a metal plate 7 as shown in FIG. The resin plate 6 has a configuration in which a plate-like acrylic resin having a thickness equal to or greater than the thickness of the metal pattern layer 4 in the mold 5 is formed on a metal plate 7 made of stainless steel or the like. After the mold 5 is treated with a release agent, as shown in FIG. 2B, the mold 5 is held upside down from the state of FIG. 1D and the resin plate 6 is heated. Presses the mold 5 against the resin layer 8 on the resin plate 6 and waits until the acrylic resin of the resin layer 8 solidifies. As shown in FIG. 2C, when the mold 5 and the metal plate 7 are removed from the acrylic resin after the acrylic resin has solidified, a fine resin component 9 made of the acrylic resin is completed. The fine resin component 9 may be obtained by injection molding, reactive injection molding, or the like in addition to hot embossing. In addition to the acrylic resin, a resin such as polystyrene, epoxy resin, acrylic resin, or the like may be used.
[0033]
In addition, by forming a pattern on the PMMA substrate 1 by the moving mask method, a mold 5 which is inverted from the PMMA matrix 3 having a pattern inclined in the vertical direction is obtained. Obtainable.
[0034]
【Example】
As a PMMA matrix 3, a 30 mm × 50 mm × 1.2 mm Nitto Resin PMMA substrate was used as a sample and etched using a high chromic acid bath and a high sulfuric acid bath based on the electroless plating conditions shown in FIG. went. As a result, when etching was performed in a high chromic acid bath, uniform plating film formation was observed, but when etching was performed in a high sulfuric acid bath, no plating film formation was observed.
[0035]
Further, using a 100 mm × 100 mm × 1.5 mm sample, the PMMA mother die 3 was electroformed to obtain a mold 5, and subsequently, the resin part 9 was molded by hot embossing using the mold 5. The pattern transferability was confirmed. The size of the electroformed area in the sample is 90 mm × 90 mm. The composition of the electroforming bath was 450 g / L for nickel sulfamate, 30 g / L for boric acid, and 10 mL / L for pitless S (R). The electroforming conditions were a temperature of 50 ° C., a pH of 4.0, and a current density of 2 A / L. a dm ^2. Incidentally, Pitless S (R) is a pit prevention agent manufactured by Nippon Chemical Industry Co., Ltd.
[0036]
As a result, the channel depth of the die 5 after electroforming was 61.6 μm, while the channel depth of the PMMA matrix 3 was 61.6 μm, and the corresponding convex portion of the resin component 9 molded by hot embossing. The height of the portion was 62.0 μm, and it was confirmed that the pattern transferability was very good. The flow path depth means the distance between the flow path bottom surface as a mold and the substrate reference plane, and the height of the corresponding convex portion of the resin component is the flow path obtained by measuring the flow path depth of the mold. Means the height from the reference plane of the projection formed by inverting the pattern.
[0037]
【The invention's effect】
As is apparent from the above description, according to the method for manufacturing a fine metal structure of the first aspect, the conductive layer film is formed on the surface of the resin matrix on which the pattern is formed by a plating film formed by electroless plating. Therefore, a uniform conductive layer film can be formed even if the pattern has a high aspect ratio. In addition, the process after exposure is a development process, an electroless plating process, and an electroforming process, and a wet process is continuous, so that handling between processes is simplified, and a large amount of fine metal components can be manufactured at low cost.
[0038]
In the method of manufacturing a fine metal structure according to claim 2, since the surface of the resin matrix is roughened by using a high chromic acid bath having a high etching ability in the etching step, the core of the plating film adhered to the surface of the resin matrix. Can be prevented from being desorbed, and a uniform conductive layer film can be formed.
[0039]
In the method for manufacturing a fine metal structure according to the third aspect, the pattern is exposed by synchrotron radiation that can easily generate high-energy X-rays, and high-precision lithography can be performed. Can be manufactured. Further, since the resin matrix is made of polymethyl methacrylate and the pattern is transferred with high precision by X-rays, a highly accurate fine metal structure can be manufactured.
[0040]
The method for manufacturing a fine metal structure according to claim 4, wherein the pattern is formed by a moving mask method, whereby the fine metal structure having a vertically inclined pattern is inverted from the resin matrix on which the vertically inclined pattern is formed. A metal structure can be obtained. Further, by using this fine metal structure as a mold, a resin molding mold having a suitable draft angle can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory cross-sectional view showing a method for manufacturing a fine metal structure according to an embodiment of the present invention along the procedure.
FIG. 2 is a cross-sectional explanatory view showing a method of manufacturing a fine resin component by using a mold as a fine metal structure according to an embodiment of the present invention along the procedure.
FIG. 3 is a table showing electroless plating processing conditions according to an example of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 PMMA substrate 2 X-ray mask 3 PMMA matrix 4 Metal pattern layer 5 Fine metal structure, mold 6 Resin plate 7 Metal plate 8 Resin layer 9 Fine resin parts

Claims (4)

Forming a conductive layer film on the surface of the resin matrix on which the pattern is formed, in the method of manufacturing a fine metal structure to perform electroforming using the conductive layer film as an electrode,
An etching step for roughening the surface of the resin matrix,
A sensor tiling step of adsorbing metal ions on the surface of the resin matrix,
An activating step of distributing and forming a metal catalyst on the surface of the resin matrix by a reducing action of the metal ions;
An electroless plating step of forming the conductive layer film by forming a plating film using the metal catalyst as a nucleus, and a method for producing a fine metal structure. 2. The method according to claim 1, wherein in the etching step, a surface of the resin matrix is roughened by a high chromic acid bath. 3. 3. The method according to claim 1, wherein the pattern is formed by exposure to synchrotron radiation, and the resin matrix is made of polymethyl methacrylate. 4. 4. The method for manufacturing a fine metal structure according to claim 1, wherein the pattern is formed by a moving mask method.

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