JP2017154273A - Method for manufacturing mold by electroforming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a product containing a fine structure such as photonic crystal.SOLUTION: There is provided a method which includes: manufacturing a first resin mold (master) formed by transferring a fine structure by an imprint method using a UV curable resin from a first mold containing a fine structure (step 3); and manufacturing a metal mold (stamper) from the master by electroforming (step 10), where the step 10 includes: forming a conductive film on the surface of the master (step 12); electroforming the surface of the master using a conductive film (step 13); and surface-treating the surface of the master with radical water before the step 12 (step 11).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method comprising producing a mold by electroforming.

  Patent Document 1 discloses a periodic structure including two systems (structures) having different refractive indexes, the interface between the two systems (structures) satisfies the Bragg scattering condition, and a photonic band gap. There is disclosed a semiconductor light emitting device having a photonic crystal periodic structure with a light extraction layer.

  Patent Document 2 describes providing a wavelength conversion element having high light extraction efficiency or wavelength conversion efficiency in a wide wavelength band and a light emitting device using the same. The wavelength conversion element disclosed in this document includes a phosphor layer having a plurality of phosphor particles excited by light from a light source, a matrix disposed between the plurality of phosphor particles, and a phosphor layer. A columnar structure in which at least two types of columnar bodies that are in contact with each other and have at least one of height and thickness are periodically arranged, and at least two types of columnar bodies are periodically The arranged columnar structure is a photonic crystal.

  Patent Document 3 describes providing a solar cell that increases the light absorption rate at a long wavelength and suppresses the thickness. The solar cell of this document includes a photoelectric conversion layer in which a plurality of concave portions are regularly formed on a light incident side surface, and a first transparent conductive film in which a plurality of convex portions are formed by filling at least the concave portions. A photonic crystal is formed by providing a periodicity to the difference in refractive index between the two.

  In Patent Document 4, a master for forming a stamper having a primary unevenness and a hierarchical structure surface having a fine secondary unevenness on the convex surface of the primary unevenness is produced by a photolithography method, and an electroforming method using the master Thus, it is described that a stamper having a primary unevenness and a hierarchical structure surface having fine secondary unevenness on the concave bottom surface of the primary unevenness as a shaping surface is obtained.

International Publication WO2013 / 008556 Japanese Patent Laying-Open No. 2015-8278 JP 2015-28959 A Japanese Patent Laying-Open No. 2015-80931

  A photonic crystal (photonic crystal) is a nano-sized structure whose structure such as unevenness or refractive index changes periodically, and is often used for semiconductors such as semiconductor light emitting elements and solar cells, and optical elements. There is a need for a method for efficiently and accurately producing nano-sized structures such as photonic crystals or sub-micron sized structures.

  As an imprint mold (mother) having a fine structure, one that is directly processed into quartz or silicon by an electron beam drawing apparatus is usually used. The mother uses an expensive device and processes it for a long time, so the cost is very high, and a mass production method that easily causes clogging after several hundred imprints is not economical. As a method for producing a micron-sized structure, a method for producing a stamper by electroforming is known, but a method for producing a submicron or nano-sized microstructure in combination with imprinting has not been established.

One aspect of the present invention is a method comprising the following steps.
1. Producing a first resin mold having a fine structure transferred from the first mold including the fine structure by an imprint method using a UV curable resin.
2. A mold including a fine structure is manufactured by electroforming from the first resin mold.
Manufacturing this mold includes the following steps.
A conductive film is formed on the surface of the first resin mold by a dry method or a wet method.
-Electroforming plating using a conductive film.
Before the conductive film is formed, the surface of the first resin mold is surface-treated with radical water that is water containing hydroxyl radicals. The surface treatment may include immersing the first resin mold in radical water.

  In order to ensure the adhesion of the plastic plating, a treatment for removing the oxide film and providing wettability is provided as a pretreatment. Conventionally, chromic acid treatment has been performed, but no effect has been observed for UV curable resins. In the plasma treatment or the UV treatment, the surface of the UV curable resin is too rough, and the shape of the microstructure that is a transfer target changes. On the other hand, the inventors of the present application have a close contact suitable for producing a die by electroforming with little influence on the fine structure by treating with radical water, which is water containing hydroxyl radicals. It was found that sex can be obtained.

The surface treatment may include immersing in a radical water having a hydroxyl radical concentration Cr and a temperature Tr for a time Hr. However, the unit of concentration is μmol / liter, the unit of temperature is ° C., and the unit of time is minutes.
9 ≦ Cr ≦ 21 (1)
15 ≦ Tr ≦ 25 (2)
10 ≦ Hr ≦ 40 (3)

  Below this range, the adhesion between the first resin mold and the mold in the electroforming plating process is insufficient, and the coating may be broken in the electroforming plating process, so that the plating solution may penetrate. If this range is exceeded, the adhesiveness is too strong, and when the mold (electroformed mold) is peeled from the first resin mold, there is a possibility that a part of the resin mold adheres to the mold side. .

  The fine structure includes an uneven structure of 1 nm to 10 μm. The size of the fine structure is desirably 10 nm or more, and more preferably 50 nm or more. The size of the fine structure is more preferably 1 μm or less. A typical fine structure is a photonic crystal structure.

  In forming the conductive film, it is desirable to form the conductive film on the surface of the resin mold by a wet method. Low cost and difficult to affect the microstructure.

  An example of the mold is a stamper for generating a second resin mold that transfers the fine structure to the resist to be etched, and an example of the first resin mold is a master for the stamper.

This method may be a method of forming a fine structure on the substrate. That is, the method may include the following steps.
-Producing a second resin mold having a fine structure transferred from the mold by imprinting.
Transfer the fine structure from the second resin mold to the resist provided on the substrate that is the object to be etched by the imprint method.
-Microstructure is formed on the substrate by etching.

This method may be a method of manufacturing a semiconductor light emitting device. That is, the method may include the following steps.
A semiconductor light emitting device is manufactured by stacking a semiconductor layer on a substrate.

The flowchart explaining the process regarding manufacture of LED including the process of creating a stamper using electroforming. The figure which shows a mode that a stamper is created from a master. The figure which shows the structure of the system which performs surface treatment with radical water. The table | surface which shows the method of surface modification. The table | surface which shows the electrically conductive film formation method. A table showing some experimental examples.

  FIG. 1 is a flowchart showing a process for manufacturing a semiconductor light emitting device (LED) including a substrate (sapphire substrate) onto which a photonic crystal (photonic crystal) is transferred.

  In step 1, the shape of the microstructure is designed. The microstructure in this example is a photonic crystal. Photonic crystals are nanostructures whose refractive index changes periodically. The way in which light (electromagnetic wave having a wavelength of several hundred to several thousand nm) is transmitted can be controlled by the nanostructure. That is, the microstructure of this example includes a concavo-convex structure of 1 μm or less, and may include a concavo-convex structure of submicron, for example, 10 μm or less. Nickel electroforming, which becomes a stamper in the following processes, can generally reproduce a surface having a surface roughness of about 0.050 μm (50 nm) with high accuracy. Therefore, it is suitable that the fine structure has a concavo-convex structure of 50 nm or more.

  Specifically, the fine structure in this example is a pillar structure (cylindrical structure) having a diameter of about 260 nm, a pitch of 460 nm, and a height of 200 nm. When the inventors evaluated the transmittance in the visible light region of a semiconductor light emitting device (LED) in which a semiconductor layer, for example, gallium nitride (GaN), is stacked on a sapphire substrate having this structure, a sample without a fine structure As a result, the transmittance was improved.

  In Step 2, a mother mold (mother) including a fine structure is manufactured. The mother is manufactured by processing a fine structure on a quartz or silicon substrate with an electronic drawing apparatus. The mother is manufactured by processing for a long time using an expensive apparatus. For this reason, the completed mother mold (mother) becomes very expensive. For this reason, if it is used for mass production in which imprints are repeated hundreds of times or more, clogging is likely to occur, and it is not practical to use the mother as it is.

  Therefore, in this example, as a substitute for an expensive mother, a master was prepared by transferring the microstructure by imprinting the mother (Step 3), and the microstructure was transferred again from the master by nickel electroforming. A stamper is created (step 10).

  As shown in FIG. 2, the master 20 is obtained by transferring a fine structure (photonic crystal) 100 onto a PET film 21 using a UV curable resin 22. The stamper 30 is a mold (nickel mold) in which the microstructure 100 is transferred again by nickel electroforming. Imprint (imprint method, UV imprint) is a technology that reverses the structure using a UV curable resin from a mold having a fine structure, and is a technology that transfers micro-sized and nano-sized structures. .

  The VU curable resin is a resin that is cured by irradiating with ultraviolet light, has no electrical conductivity, and forms an insulating master 20. For this reason, the step 10 of producing (manufacturing) the stamper (mold) 30 by electroforming is a step of forming a conductive film on the surface of the insulator master (first resin mold) 20 by a dry method or a wet method. 12 and a step 13 of electroforming plating using a conductive film. Furthermore, before the step 12 of forming the conductive film, a step 11 of surface-treating the surface of the master (first resin mold) 20 with radical water which is water containing hydroxyl radicals (hydroradicals) is included.

  In FIG. 3, the outline | summary of the system which processes the surface of the master 20 with radical water is shown. The main purpose of this treatment is to take out the oxide film of the master 20 to give wettability. FIG. 4 shows the main methods of surface modification. The chromic acid treatment has no effect on the UV curable resin and has a large environmental impact. The effect of the plasma treatment is not recognized, and the surface of the UV curable resin is too rough, and the shape of the fine structure to be transferred changes. Although the UV treatment is effective as a treatment for the UV curable resin, the surface of the UV curable resin is too rough, and the shape of the fine structure to be transferred changes. Although it processed with ozone nano valve water, the result which resulted in the improvement of adhesiveness was not obtained. On the other hand, when treatment with radical water was performed, it was found that the adhesion of the electroformed mold (stamper) 30 to the master 20 can be improved under predetermined conditions.

  The surface treatment system 50 includes a radical water supply device 51. An apparatus (radical water supply apparatus) 51 for supplying water containing hydroxyl radicals (radical water) is disclosed in international publications WO2010 / 140581 and WO2015 / 125739. The radical water supply device 51 includes a mixer 55 for mixing an additive substance aqueous solution 53 and a hydrogen peroxide solution 54 with respect to ozone water 52 in which ozone is previously dissolved in pure water or tap water, and a hydroxyl radical concentration meter 56. . An example of the additive substance is hydrazine, a salt of an inorganic acid, an inorganic acid, or a water-soluble organic substance. In the radical water supply device 51, the ozone concentration of the ozone water 52, the addition amount of the additive substance aqueous solution 53, and the addition amount of the hydrogen peroxide solution 54 are determined by the ozone output, and the radical water output by the hydroxyl radical concentration meter 56. A radical concentration of 57 is measured.

  The surface treatment system 50 further includes a chiller 58 that controls the temperature of the radical water 57 and a chamber 59 in which the radical water 57 is stored, and the surface of the master 20 is treated (modified) by immersing the master 20 in the chamber 59. To do. The radical water 57 contains a hydroxy radical (.OH). This hydroxy radical introduces a hydroxyl group (—OH) into the resin surface. Since the OH group has hydrophilicity, it is considered that wettability is increased and a chemical reaction is likely to occur.

  FIG. 5 shows a process in the step of forming a conductive film on the master 20 of the insulator (step 12). Examples of the method for forming the conductive film include a dry method (dry coating) and a wet method (wet coating). Dry coating is a method of forming a conductive film on an insulator by a sputtering method or a vapor deposition method. The cost is high, the master 20 is damaged, and it is difficult to form a conductive film depending on the aspect ratio of the fine structure. There is a drawback. The wet coating is a method of forming a conductive film by electroless plating, and can form a stable conductive film at a low cost on the surface of the insulator master 20. In this example, electroless nickel phosphorus plating was adopted.

  Specifically, after treating the master 20 with radical water, alkaline degreasing with water containing potassium hydroxide and ethanol, treating with a conditioner, and then alternately dipping in an aqueous solution of tin chloride and an aqueous solution of palladium chloride, Thereafter, a conductive film was formed by electroless nickel phosphorus plating. Thereafter, nickel electroforming plating was performed using the conductive film, and a nickel electroforming mold (mold) to be the stamper 30 was created (manufactured).

  Returning to FIG. 1, an etching master (PDMS mold) is formed by room temperature imprinting using PDMS (polydimethylsiloxane) in step 4 using a stamper 30 of an electroforming mold. In step 5, the microstructure 100 is imprinted on the resist applied on the sapphire substrate using a PDMS mold. In step 6, etching is performed to produce a sapphire substrate having a photonic crystal (fine structure). In step 7, a semiconductor layer such as gallium nitride is stacked on a sapphire substrate to manufacture an LED.

  FIG. 6 shows the evaluation of adhesion when the stamper 30 is formed by electroforming plating in several cases where the conditions for surface treatment with radical water in Step 11 are changed. In the experiment, the ozone output of the radical water supply device 51 was changed to change the radical concentration (μmol / liter) in the radical water, and the temperature (° C.) of the radical water was controlled by the chiller 58. Moreover, the immersion time of the master 20 was controlled. The surface roughness of the master 20 was measured in units of 0.001 μm (nm) before and after immersion using a laser microscope (LESXTOLS 4000 manufactured by Olympus).

  The evaluation of adhesion was performed visually, and it was determined that the case in which the stamper 30 was swollen or cracked had insufficient adhesion (evaluation was x). Further, when the stamper 30 was peeled off from the master 20, it was determined that the case in which the resin was adhered to the stamper 30 or the resin on the master 20 side was removed was too strong (evaluation) Is x). Cases in which neither phenomenon was observed were evaluated as “good” because appropriate adhesion was obtained. In addition, although the swelling is not seen visually, the case where there is no difference in the surface roughness of the master 20 before and after the immersion is evaluated as △ because the surface modification effect may not be sufficient. .

  From these evaluations, it was found that when the immersion time exceeds 40 minutes, the adhesion tends to be too strong to peel off, and when the immersion time is less than 10 minutes, the adhesion tends to be insufficient. On the other hand, if the radical concentration exceeds 21 μmol / liter, the surface of the master 20 becomes rough and the adhesiveness becomes too strong, making it difficult to control the adhesiveness. It turns out that there is a possibility of shortage. Regarding the radical water temperature, it was found that the lower the temperature, the stronger the reaction, and the higher the temperature, the longer the treatment time. For this reason, when radical water temperature exceeded 25 degreeC, processing time became long too much, and when it fell below 15 degreeC, it turned out that reaction is too strong and adjustment of processing time is difficult. For this reason, it turned out that it is desirable for the treatment of radical water to satisfy the following conditions (1) to (3). Within this range, the surface roughness is also appropriate and the fine structure can be transferred well.

9 ≦ Cr ≦ 21 (1)
15 ≦ Tr ≦ 25 (2)
10 ≦ Hr ≦ 40 (3)
However, the concentration Cr of the hydroxyl radical, the unit of concentration is μmol / liter, the temperature Tr, the unit of temperature is ° C., the radical water immersion time (treatment time) Hr, and the unit of time is minutes.

  Considering the ease of controlling adhesion, the lower limit of condition (1) is preferably 14 μmol / liter, and the upper limit is preferably 19 μmol / liter. Moreover, it is preferable that the minimum of condition (2) is 18 degreeC, and it is preferable that an upper limit is 23 degreeC, It is more preferable that it is 19-22 degreeC, It is more preferable that it is 20-21 degreeC. The lower limit of condition (3) is preferably 15 minutes, and the upper limit is preferably 30 minutes.

  In addition, with respect to the radical water supply device 51, it is more likely that the concentration of radicals is higher than the method of circulating the waste water from the chamber 59, and the adhesion of tap water is more likely to improve than distilled water. Results were obtained.

  As mentioned above, radical water treatment of a master to produce a stamper that has been transferred again by nickel electroforming from a master that has been transferred by imprinting as an alternative to expensive mothers has adequate adhesion. It was found to be effective to obtain

20 master (resin mold), 30 stamper (electroformed mold)

Claims (9)

Producing a first resin mold in which the microstructure is transferred from the first mold including the microstructure by an imprint method using a UV curable resin;
Producing a mold including the microstructure by electroforming from the first resin mold,
Manufacturing the mold includes forming a conductive film on the surface of the first resin mold by a dry method or a wet method;
Electroforming plating using the conductive film;
Before forming the conductive film, surface-treating the surface of the first resin mold with radical water which is water containing hydroxyl radicals. In claim 1,
The surface treatment includes immersing the first resin mold in the radical water. In claim 2,
The surface treatment includes immersing the radical water at a concentration Cr of the hydroxyl radicals and the radical water at a temperature Tr for a time Hr. However, the unit of concentration is μmol / liter, the unit of temperature is ° C., and the unit of time is minutes.
9 ≦ Cr ≦ 21
15 ≦ Tr ≦ 25
10 ≦ Hr ≦ 40 In any of claims 1 to 3,
The method wherein the microstructure comprises a concavo-convex structure of 1 nm to 10 μm. In any of claims 1 to 4,
The method wherein the microstructure comprises a photonic crystal structure. In any of claims 1 to 5,
Forming the conductive film includes forming a conductive film on a surface of the first resin mold by a wet method. In any of claims 1 to 5,
The mold is a stamper for generating a second resin mold for transferring the fine structure to a resist to be etched, and the first resin mold is a master for the stamper. In claim 7,
Producing the second resin mold having the microstructure transferred from the mold by an imprint method;
Transferring the fine structure from the second resin mold to the resist provided on the substrate which is the etching object by an imprint method;
Forming the microstructure on the substrate by etching. In claim 8,
A method comprising fabricating a semiconductor light emitting device by laminating a semiconductor layer on the substrate.

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