Abstract:
A transfer mold, which has superior durability and high aspect ratio, for production of a component by electroplating and a component produced thereby are provided. A method therefor includes the steps of forming a resist pattern having a shape of a component with a desired aspect ratio on a metal substrate, a sidewall of the resist pattern forming a desired angle, creating a transfer mold by filing up the resist pattern having the shape of the component by electroplating to a predetermined thickness and providing a master mold by separating the transfer mold from the metal substrate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the National Stage of International Application No. PCT/JP2011/006355 having International filing date 15 Nov. 2011, which designated the United States of America, and which International Application was published under PCT Article 21 (s) as WO Publication 2013/072953 A1 the disclosures of which are incorporated herein by reference in their entireties. 
       BACKGROUND 
       [0002]    The presently disclosed embodiment relates to a transfer mold manufacturing method, a transfer mold manufactured thereby, and a component produced by the transfer mold. More specifically, the presently disclosed embodiment relates to a method for manufacturing a transfer mold for production of a component by electroplating, a transfer mold manufactured thereby, and a component produced thereby, wherein the transfer mold has superior durability and high aspect ratio. 
         [0003]    Electroplating allows formation of a thick film conductor with less restriction in terms of dimension. It is therefore widely used in production of display components such as a dial and hands of a watch, machine components such as a small gear, a spring, a pipe and a diaphragm (pressure sensor) and electronic components such as a wiring of a semiconductor device and a coil. 
         [0004]    Japanese Patent Application Laid-Open No. 2004-1535 discloses manufacturing a cavity insert by: first creating a machined master mold on which a fine pattern has been formed in advance; subsequently creating a transfer master mold by hot press from the machined master mold; and then creating the cavity insert by electroplating from the transfer master mold. 
         [0005]    Japanese Patent Application Laid-Open No. 2004-257861 discloses manufacturing a watch dial by the steps of: forming a mask pattern having openings on a surface of a silicon wafer; performing an anisotropic etching; forming a common electrode film; forming an electroplated film which grows on the common electrode film; etching the silicon wafer; and forming a resin watch dial having protruding portions by using the electroplated film as a transfer mask. 
         [0006]      FIGS. 6   a  and  6   b  show structural drawings of a component formed by using a conventional transfer mold. In  FIG. 6   a , for the purpose of forming a component  95 , a photoresist  30  is patterned on a metal substrate  90  to a shape of the component by partially removing the same. The metal substrate  90 , on which the resist pattern has thus been formed, is used as a transfer mold for electroplating (hereinafter referred to as “EP”) a predetermined metal (Ag, Cu, Ni, etc.) to form the component  95 . 
         [0007]    In  FIG. 6   b , the component  95  molded by EP is transferred onto an adhesive bond  85  and then adhered to a component substrate  97 . In this manner, the component having a given shape depending on its intended use is produced by EP and transferred onto the component substrate  97  for use. 
         [0008]    Here, for ease of release and transfer of the component  95 , the angles β formed at sidewalls of the photoresist  30  are each set to be a blunt angle of less than 45°. In the meantime, when providing an electronic component such as a wiring, a coil, etc. on a semiconductor substrate, there is a demand for such an aspect ratio that a line thickness is greater than the line width so that electric resistance is reduced. The thickness which the photoresist  30  is generally required to have is approximately 10 μm. 
         [0009]    The component  95  is formed by EP in such a manner that it fills up along the sidewalls of the photoresist  30  having the thickness of approximately 10 μm. As such, in a case where a wiring pattern, a conductive coil or the like is formed as a long component, it contacts the sidewalls in large area, resulting in increased release resistance in the release and transfer of the component. That is, when using a transfer mold made with patterned photoresist, the transfer of the component onto the component substrate  97  requires an application of a release force that is comparable to the increased release resistance. This causes the edge of the pattern of the photoresist  30 , which is appressed to the metal substrate  90 , to be easily stripped. In fact, the resist is stripped after a few times of use, and as a result, a problem arises that the transfer mold can then no longer be in use. 
       SUMMARY 
       [0010]    The presently disclosed embodiment has been made in order to solve the above problem, and its purpose is to provide a transfer mold having superior durability and high aspect ratio for production of a component by EP as well as to provide a component produced by the transfer mold. It is to be noted that there are four types of transfer molds which are: a master mold, a mother mold, a son mold, and a transfer mold. The master mold is a mold which serves as a prototype for component production. Usually, it is not directly used for component production. The mother mold is a mold which is created by using the master mold so as to have an inverse contour of the master mold. The mother mold as well is not directly used for the component production. The son mold is a mold which is created by using the mother mold so as to have an inverse contour of the mother mold. Therefore, the son mold has a shape that is identical with the master mold. The transfer mold is generally formed by subjecting the son mold to an insulation layer formation process, a releasing layer formation process, etc. The component production is then carried out with use of this transfer mold, and when it is worn off, a new transfer mold is created again from the master mold by way of the mother mold and the son mold. 
         [0011]    A transfer mold manufacturing method of the presently disclosed embodiment includes steps of: forming a resist pattern having a shape of a component with a desired aspect ratio on a metal substrate, a sidewall of the resist pattern on a metal substrate side forming a desired angle α (α&lt;90°); filling up the resist pattern having the shape of the component by electroplating to a predetermined thickness and then separating a mold thus formed from the metal substrate leaving the metal substrate and the resist pattern. 
         [0012]    A transfer mold manufacturing method of the presently disclosed embodiment includes steps of: forming a resist pattern having a shape of a component with a desired aspect ratio on a metal substrate, a sidewall of the resist pattern on a metal substrate side forming a desired angle α (α&lt;90°); filling up the resist pattern having the shape of the component by electroplating to a predetermined thickness and then providing a master mold by separating a mold thus formed from the metal substrate leaving the metal substrate and the resist pattern; creating a son mold by transferring by way of the master mold and a mother mold; and providing a transfer mold by performing, on the son mold, a releasing layer formation process for facilitating a release of the component to be formed by electroplating and an insulation layer formation process for forming an insulation layer in that portion which is other than a portion in which the component is to be formed. 
         [0013]    The transfer mold manufacturing method of the presently disclosed embodiment includes a step of forming a roughening layer on a surface of the metal substrate as a first step. 
         [0014]    A transfer mold manufacturing method of the presently disclosed embodiment includes steps of: forming a resist pattern having a shape of a component with a desired aspect ratio on a metal substrate side, a sidewall of the resist pattern on a metal substrate side forming an angle of approximately 90°; filling up the resist pattern having the shape of the component by electroplating to a predetermined thickness and then separating a mold thus formed from the metal substrate leaving the metal substrate and the resist pattern; removing a photoresist partially to leave a resist pattern layer in that portion of the separated mold which is other than a portion corresponding to the component to be transferred; and treating the sidewall of the shape of the component with beam irradiation using the resist pattern layer as a protective layer, the beam irradiation being modulated such that the angle at the sidewall is tailored to form approximately 90° or a desired angle α (α&lt; 90°).    
         [0015]    A transfer mold manufacturing method of the invention of the instant application includes steps of: forming a resist pattern having a shape of a component with a desired aspect ratio on a metal substrate, a sidewall of the resist pattern on a metal substrate side forming an angle of approximately 90°; filling up the resist pattern having the shape of the component by electroplating to a predetermined thickness and then separating a mold thus formed from the metal substrate leaving the metal substrate and the resist pattern; removing a photoresist partially to leave a resist pattern layer in that portion on the separated mold which is other than a portion corresponding to the component to be transferred; providing a master mold by treating the sidewall of the shape of the component with beam irradiation using the resist pattern layer as a protective layer, the beam irradiation being modulated such that the angle at the sidewall is tailored to form approximately 90° or a desired angle α (α&lt;90°); creating a son mold by transferring by way of the master mold and a mother mold; and providing a transfer mold by performing, on the son mold, a releasing layer formation process for facilitating a release of the component to be formed by electroplating and an insulation layer formation process for forming an insulation layer in that portion which is other than a portion in which the component is to be formed. 
         [0016]    The method of the presently disclosed embodiment includes a step of forming a roughening layer on a surface of the metal substrate as a first step. 
         [0017]    A transfer mold of the presently disclosed embodiment is manufactured by the above-described method and has a cross-sectional surface with a desired aspect ratio, a sidewall of the cross-sectional surface forming an angle between 45° and 88°. 
         [0018]    A transfer mold of the presently disclosed embodiment is provided by subjecting the son mold created by using the above-described master mold to only an insulation layer formation process or to the insulation layer formation process and a releasing layer formation process. 
         [0019]    A component produced by electroplating in the presently disclosed embodiment is molded by the electroplating using the above-described transfer mold and transferred. 
         [0020]    The presently disclosed embodiment makes it possible to provide a component having superior durability and high aspect ratio formed by EP in manufacturing display components, machine components and electronic components by EP. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIGS. 1   a - 1   e  are process drawings showing the steps for manufacturing a master mold by electroplating according to the presently disclosed embodiment. 
           [0022]      FIGS. 2   a - 2   d  are process drawings showing the steps for manufacturing a master mold by beam treatment according to the presently disclosed embodiment. 
           [0023]      FIGS. 3   a - 3   c  are process drawings showing the steps for manufacturing a son mold according to the presently disclosed embodiment. 
           [0024]      FIGS. 4   a - 4   f  are process drawings showing the steps for manufacturing a transfer mold according to the presently disclosed embodiment. 
           [0025]      FIGS. 5   a - 5   c  are process drawings showing the steps for manufacturing a component according to the presently disclosed embodiment. 
           [0026]      FIGS. 6   a  and  6   b  are structural drawings showing a component formed by using a conventional transfer mold. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    A first aspect of the presently disclosed embodiment is described with reference to the drawings.  FIGS. 1   a - 1   e  are process drawings showing the steps for manufacturing a master mold by electroplating according to the presently disclosed embodiment. In  FIG. 1   a,  a top surface of a metal substrate  10  is provided with a roughening layer  15  for roughening a contact surface of a master mold to be formed by EP. The roughening layer  15  may be formed by roughening the surface of the metal substrate  10  directly by hydrochloric acid treatment or the like. Alternatively, a stripe-like photo resist pattern layer, a lattice-like photo resist pattern layer or the like, which is suitable for roughening, may be formed as the roughening layer  15  by partially removing the photoresist. In a case where an insulation layer and others are formed on a son mold  60  described later with reference to  FIGS. 3   a - 3   c , the roughening layer  15  may be omitted as long as there is no problem of adhesion strength therebetween. 
         [0028]    In  FIG. 1   b , a photoresist  30  for forming a pattern of a shape of a component to be produced is applied onto the roughening layer  15  on the metal substrate  10  to a predetermined thickness. This is for the purpose of obtaining a component having such a shape that has a desired aspect ratio and desired angles α at sidewalls thereof. For example, in a case where a wiring of a semiconductor electronic component or a coil with a line width of 5 μm is to be produced, the photoresist  30  is applied to a thickness of 10 μm so that the electronic component or the coil has the thickness of 10 μm. The photoresist  30  is then subjected to an exposure effected from the direction of the arrows with an intervening photomask  40  having a pattern of a desired component.  FIG. 1   c  shows the pattern of the component formed by subjecting the resist pattern to the exposure as shown in  FIG. 1   b  and a development. The angles α formed at the respective sidewalls of the resist pattern of the component can optionally be determined depending on the material and film thickness of the applied photoresist  30  as well as the exposure condition to the irradiation performed with the intervening photomask  40  as shown in  FIG. 1   b.  Where laser light is used, a 3D lens may be employed to vary the irradiation intensity on the both sidewalls of the resist pattern. The irradiation intensity on the both sidewalls may also be varied by means of a gray mask. 
         [0029]    In  FIG. 1   d,  a desired metal, e.g., Ni, is electroplated to a predetermined thickness so as to cover the resist pattern  30  shown in  FIG. 1   c,  thereby creating a master mold  20 . In  FIG. 1   e , the master mold  20  created by EP in  FIG. 1   d  is separated from the metal substrate  10 . Here, the rough surface profile of the roughening layer  15  has been transferred to a roughened surface layer  17  of the master mold. The angles α at the both sidewalls remain to be the angles α in  FIG. 1   d.    
         [0030]    It is intended that the roughened surface layer  17  of the master mold is transferred to the son mold  60 , which is eventually used as the transfer mold and illustrated in  FIG. 3 , for the sake of increased adhesion strength to an insulation layer to be formed thereon. As such, it is not necessarily required. In addition, making the angles α as acute as 45° to 88° allows the pattern density of an intended device to be improved. The 10 μm thickness of the photoresist  30  in  FIG. 1   c  is maintained in the inverted master mold  20  by being transferred. 
         [0031]      FIGS. 2   a - 2   d  are process drawings showing the steps for manufacturing a master mold by beam treatment according to the presently disclosed embodiment. This is a second aspect of the presently disclosed embodiment.  FIG. 2   a  shows the master mold  20  created by the method illustrated in  FIGS. 1   a - 1   e . Here, the angles α are each approximately 90°. In  FIG. 2   b , the photoresist  30  for forming a reverse pattern of the shape of the component is applied to a predetermined thickness. The photoresist  30  is then subjected to an exposure effected from the direction of the arrows with an intervening photomask  40  having the reverse pattern of the component. As a result, that portion of the resist which corresponds to the component is developed and removed, thereby leaving the photoresist  30  only on the flat roughened surface layer  17  of the master mold. 
         [0032]    In  FIG. 2   c , the resist pattern formed in  FIG. 2   b  is used as a protective film in treating the sidewalls of the pattern of the component with beam irradiation. Here, the irradiation beam is modulated in such a manner that the angles α are tailored to form predetermined degrees. The arrows show the direction of the beam. The treated master mold  20  shown in  FIG. 2   d  has not only the same shape but also the same function and characteristics as the master mold  20  shown in  FIG. 1   d.  The irradiation beam may be an electron beam, an ion beam, or a FIB (Focused Ion Beam) whose irradiation strength is variable by focusing the beam with a lens. 
         [0033]      FIGS. 3   a - 3   c  are process drawings showing the steps for manufacturing a son mold according to the presently disclosed embodiment. In  FIG. 3   a , a desired metal, e.g., Ni, is electroplated to a predetermined thickness on that surface of the master mold  20  manufactured in  FIGS. 1   a - 1   e  or  2   a - 2   d  on which the pattern of the component has been formed. A mother mold  50  created thereby is then separated. In  FIG. 3   b , a desired metal, e.g., Ni, is electroplated to a predetermined thickness on that surface of the mother mold  50  on which the pattern of the component has been formed, so that a son mold  60  is created in the same manner. In  FIG. 3   c , the son mold  60  thus created by EP is separated from the mother mold  50 . 
         [0034]    In this way, the son mold  60  is created by transferring the mother mold  50  created by transferring the master mold  20 . As such, it takes over the same function and characteristics as those of the master mold  20 . Furthermore, the son mold  60  is integrally formed of one metal material. This, with the releasing layer formation process and the insulation layer formation process performed on a roughened surface layer  19  of the son mold as will be explained next, makes it possible to obtain a transfer mold which has a desired aspect ratio and angles α, does not break even after repetitive use, and is highly suitable for quantity production. 
         [0035]      FIGS. 4   a - 4   f  are process drawings showing the steps for manufacturing a transfer mold according to the presently disclosed embodiment.  FIG. 4   a  shows the son mold  60  created in  FIG. 3   c . In  FIG. 4   b , the son mold  60  is subjected to heat treatment under prescribed conditions for ease of release and transfer of the component to be produced. This is followed by the releasing layer formation process for forming a NiOx film  70  having a predetermined thickness on the surface of the son mold  60 . Since the NiOx film  70  is conductive, it does not hinder EP. Moreover, the low adhesive property thereof to the electroplated component allows an easy release. 
         [0036]    Subsequently, an insulation layer is formed in order to prevent EP in that portion of the surface which is other than the portion in which the component is to be formed. This is accomplished by the insulation layer formation process for forming a SiO 2  film  80  chemically by CVD (Chemical Vapor Deposition) or physically by sputtering on said portion of the surface. Alternatively, the SiO 2  film  80  is formed by applying polysilazane and treating it with heat. In  FIG. 4   c , in order to remove the SiO 2  film  80  formed on the pattern of the component, the photoresist  30  to be patterned to a predetermined shape is applied on the SiO 2  film  80 . After that, the photoresist is partially removed by subjecting the same to an exposure effected from the direction of the arrows with an intervening photomask  40  having the reverse pattern of the component. Then, in  FIG. 4   d , with use of the patterned photoresist  30  as a mask, the SiO 2  film  80  is removed physically by beam irradiation from the direction of the arrows or chemically by hydrofluoric acid treatment or the like. 
         [0037]    Depending on the shape of the patterned photoresist  30  and the removal conditions of the SiO 2  film  80 , the transfer mold is completed either by removing the SiO 2  film  80  only in the bottom portion so that it is left on the sidewalls as shown in  FIG. 4   e  or by removing the SiO 2  film  80  both on the sidewalls and in the bottom portion as shown in  FIG. 4   f . In a case where polysilazane is used, similar steps as in screen printing are carried out. That is, following the formation of the NiOx film in  FIG. 4   b , polysilazane is printed in that portion of the surface of the NiOx film  70  which is other than the pattern of the component for forming the component. It is then treated with heat. In this manner, the same shape as shown in  FIG. 4   f  can be obtained. 
         [0038]    The releasing layer formation process is performed by, as shown in  FIG. 4   b , depositing metal oxides (AlOx, TiOx, etc.), nitrides or organic substances (resist) on the son mold  60  to such a thickness of 1 to 1000 Å that allows the conductivity thereof to be maintained. For the insulation layer formation process, an insulator such as resist may be used instead of SiO 2 . Note that the releasing layer formation process and the insulation layer formation process may be performed in reverse order. 
         [0039]    Now, description is made for the component produced by EP with use of the transfer mold according to the presently disclosed embodiment.  FIGS. 5   a - 5   c  are process drawings showing the steps for manufacturing a component using the transfer mold according to the presently disclosed embodiment. In  FIG. 5   a , a desired metal (Ag, Cu, Ni, etc.) is electroplated on the son mold  60  to form the component  95 . In  FIG. 5   b , the component  95  molded by EP is, as in the case shown in  FIG. 6   b , transferred onto the adhesive bond  85  and then adhered to the component substrate  97 . Alternatively, the component  95  is adhered to a green sheet  98  which is then treated with heat for curing. Where the component  95  is adhered to the green sheet  98 , the use of the adhesive bond  85  is eliminated by such softness of the green sheet  98  before curing that the component  95  is buried therein. In this way, the component  95  of an optional shape having a desired aspect ratio and angles α is provided by EP. It can be repetitively molded and transferred onto the device substrate  97  or green sheet  98  for diverse intended use. 
         [0040]    As described above, the presently disclosed embodiment is able to provide a component having superior durability and high aspect ratio in production, by EP, of display components such as a dial and hands of a watch, machine components such as a small gear, a spring, a pipe and a diaphragm (pressure sensor), and electronic components such as a wiring of a semiconductor device and a coil. 
       DESCRIPTION OF REFERENCE NUMERALS 
       [0000]    
       
           10  metal substrate 
           15  master mold roughening layer 
           17  roughened surface layer of master mold 
           18  roughened surface layer of mother mold 
           19  roughened surface layer of son mold 
           20  master mold 
           30  photoresist 
           40  photomask 
           50  mother mold 
           60  son mold 
           70  NiOx 
           80  SiO 2 /polysilazane 
           85  adhesive bond 
           90  metal substrate 
           95  component 
           97  component substrate 
           98  green sheet 
         α angle at sidewall 
         β angle at sidewall