Microstructure array, mold for forming a microstructure array, and method of fabricating the same

Abstract

A method for fabricating a microstructure array, such as a microlens array, and a mold for forming the microlens array, includes the steps of forming an array of microstructures with a curved profile in a discrete form on a substrate, and uniformly forming a continuous layer on the substrate and the discrete microstructures. Optically-unusable regions between the discrete microstructures, such as microlenses, can be readily reduced or eliminated by forming the continuous layer until flat portions between the microstructures disappear.

What is claimed is:  
     
         1 . A fabrication method of a microstructure array, said method comprising the steps of: 
 (a) forming an array of microstructures with a curved profile in a discrete form on a substrate; and    (b) forming a continuous layer on the substrate and the discrete microstructures.    
     
     
         2 . The fabrication method of  claim 1 , wherein the continuous layer has an approximately uniform thickness.  
     
     
         3 . The fabrication method of  claim 1 , wherein the continuous layer is formed of one of an inorganic material and an organic material.  
     
     
         4 . The fabrication method of  claim 1 , wherein said step (b) includes a step of forming the continuous layer by one of electroplating, electroless plating, and electrodeposition.  
     
     
         5 . The fabrication method of  claim 1 , wherein said step (b) includes a step of forming the continuous layer by chemical vapor deposition (CVD).  
     
     
         6 . The fabrication method of  claim 1 , wherein said step (b) includes a step of forming the continuous layer by vacuum evaporation.  
     
     
         7 . The fabrication method of  claim 1 , wherein said step (a) forms flat portions between the discrete microstructures, and wherein in said step (b) the continuous layer is formed until the flat portions between the microstructures disappear.  
     
     
         8 . The fabrication method of  claim 1 , wherein each of the microstructures with the curved profile is formed such that an angle of contact between the one of the microstructures and the substrate reaches no less than 90 degrees.  
     
     
         9 . The fabrication method of  claim 1 , wherein each of the microstructures with the curved profile has one of a spherical shape and a cylindrical shape.  
     
     
         10 . The fabrication method of  claim 1 , wherein conditions of d/2≦l+h, h≦t, and r=l+t≧d/2 are satisfied where l is the radius of each of the microstructures with the curved profile, θ is the angle of contact between the substrate and the each of the microstructures with the curved profile, h, which is −l cos θ, is the height between the substrate and the center of the each of the microstructures with the curved profile, t is the thickness of the continuous layer, and d is the pitch of the array of the microstructures with the curved profile.  
     
     
         11 . The fabrication method of  claim 1 , wherein the microstructures with the curved profile have a common shape.  
     
     
         12 . The fabrication method of  claim 1 , wherein the microstructures with the curved profile have plural shapes.  
     
     
         13 . The fabrication method of  claim 1 , wherein the microstructures with the curved profile are regularly arranged.  
     
     
         14 . The fabrication method of  claim 1 , wherein each of the microstructures with the curved profile is formed of a resin.  
     
     
         15 . The fabrication method of  claim 1 , wherein each of the microstructures with the curved profile is formed of a metal-plated layer.  
     
     
         16 . The fabrication method of  claim 1 , wherein said step (a) includes a step of forming a plurality of thermoplastic layers in a pattern on the substrate, and a step of thermally processing the plurality of thermoplastic layers to form the array of microstructures with the curved profile.  
     
     
         17 . The fabrication method of  claim 16 , wherein each of the plurality of thermoplastic layers formed before the thermal processing step have one of a cylindrical shape and a polygonal shape.  
     
     
         18 . The fabrication method of  claim 16 , wherein each of the plurality of thermoplastic layers formed before the thermal processing step have a stripe shape.  
     
     
         19 . The fabrication method of  claim 16 , wherein the plurality of thermoplastic layers formed before the thermal processing step have a common shape.  
     
     
         20 . The fabrication method of  claim 16 , wherein the plurality of thermoplastic layers formed before the thermal processing step have plural shapes.  
     
     
         21 . The fabrication method of  claim 16 , wherein the plurality of thermoplastic layers are regularly arranged.  
     
     
         22 . The fabrication method of  claim 16 , wherein each of the plurality of thermoplastic layers is a resin layer.  
     
     
         23 . The fabrication method of  claim 16 , wherein each of the plurality of thermoplastic layers is a metal-plated layer.  
     
     
         24 . The fabrication method of  claim 1 , further comprising a step (c) of processing a surface of the substrate to become a water-repellant surface.  
     
     
         25 . The fabrication method of  claim 1 , wherein in said step (a) at least a structure for an alignment marker is also formed in an area outside an area of the array of microstructures.  
     
     
         26 . The fabrication method of  claim 1 , wherein the microstructure array is a mold for a microstructure array.  
     
     
         27 . The fabrication method of  claim 26 , wherein the mold for a microstructure array is a mold for a microlens array.  
     
     
         28 . The fabrication method of  claim 1 , wherein the substrate, the microstructures with the curved profile, and the continuous layer are all formed of transparent material.  
     
     
         29 . The fabrication method of  claim 28 , wherein the microstructure array is a microlens array.  
     
     
         30 . A microstructure array comprising: 
 an array of microstructures with a curved profile formed in a discrete form on a substrate; and    a continuous layer formed on the substrate and the discrete microstructures.    
     
     
         31 . The microstructure array of  claim 30 , wherein the continuous layer has an approximately uniform thickness.  
     
     
         32 . The microstructure array of  claim 30 , wherein the continuous layer is formed of one of an inorganic material and an organic material.  
     
     
         33 . The microstructure array of  claim 30 , wherein before the continuous layer is formed flat portions exist between the microstructures, and wherein the continuous layer is formed until the flat portions between the microstructures disappear.  
     
     
         34 . The microstructure array of  claim 30 , wherein each of the microstructures with the curved profile is formed such that an angle of contact between the one of the microstructures and the substrate reaches no less than 90 degrees.  
     
     
         35 . The microstructure array of  claim 30 , wherein each of the microstructures with the curved profile has one of a spherical shape and a cylindrical shape.  
     
     
         36 . The microstructure array of  claim 30 , wherein conditions of d/2≦l+h, h≦t, and r=l+t≧d/2 are satisfied where l is the radius of each of the microstructures with the curved profile, θ is the angle of contact between the substrate and the each of the microstructures with the curved profile, h, which is −l cos θ, is the height between the substrate and the center of the each of the microstructures with the curved profile, t is a thickness of the continuous layer, and d is the pitch of the array of the microstructures with the curved profile.  
     
     
         37 . The microstructure array of  claim 30 , wherein the array of microstructures with the curved profile is formed by forming a plurality of thermoplastic layers in a pattern on the substrate, and thermally processing the plurality of thermoplastic layers.  
     
     
         38 . The microstructure array of  claim 30 , wherein the microstructures with the curved profile have a common shape.  
     
     
         39 . The microstructure array of  claim 30 , wherein the microstructures with the curved profile have plural shapes.  
     
     
         40 . The microstructure array of  claim 30 , wherein the microstructures with the curved profile are regularly arranged.  
     
     
         41 . The microstructure array of  claim 30 , wherein each of the microstructures with the curved profile is formed of a resin.  
     
     
         42 . The microstructure array of  claim 30 , wherein each of the microstructures with the curved profile is formed of a metal-plated layer.  
     
     
         43 . The microstructure array of  claim 30 , wherein a surface of the substrate is processed to become a water-repellant surface.  
     
     
         44 . The microstructure array of  claim 30 , further comprising a structure for an alignment marker formed in an area outside an area of the array of the microstructures.  
     
     
         45 . The microstructure array of  claim 30 , wherein the microstructure array is a mold for a microstructure array.  
     
     
         46 . The microstructure array of  claim 45 , wherein the mold for a microstructure array is a mold for a microlens array.  
     
     
         47 . The microstructure array of  claim 30 , wherein the substrate, the microstructures with the curved profile, and the continuous layer are all formed of transparent material.  
     
     
         48 . The microstructure array of  claim 47 , wherein the microstructure array is a microlens array.  
     
     
         49 . A method of fabricating a microstructure array comprising the steps of: 
 (a) a plurality of thermoplastic microstructures at common intervals on a wafer;    (b) causing the plurality of thermoplastic microstructures to undergo reflow to form a plurality of spherical thermoplastic microstructures separated by flat portions; and    (c) isotropically forming a continuous layer on the spherical thermoplastic microstructures until the flat portions disappear.    
     
     
         50 . A method according to  claim 49 , further comprising the step of surface processing the wafer to form a water-repellant surface before step (a), wherein step (b) is performed by baking the wafer, and wherein step (c) is performed by forming catalyst cores on the substrate and spherical thermoplastic microstructures and performing electroless plating on the spherical thermoplastic microstructures and the substrate.  
     
     
         51 . A method according to claim  50 , further comprising the step of fabricating a mold by coating the plated layer with a remover agent to form a remover layer, performing electroplating to form an electroplated layer on the plated layer, and separating the electroplated layer by removing the remover layer to produce a mold.  
     
     
         52 . A method according to claim  51 , further comprising the step of fabricating a microlens array by laying down an radiation hardening resin over the mold, placing a glass substrate of a support on the radiation hardening resin layer, exposing the radiation hardening resin layer to radiation through the glass substrate, and separating the glass substrate with the radiation hardening resin layer from the mold.  
     
     
         53 . A method according to  claim 49 , further comprising the step of forming a pattern for an alignment marker outside of a region of the plurality of thermoplastic microstructures, wherein step (b) is performed by baking the wafer, and wherein step (c) is performed by continuously layering an electrode layer, and performing electroplating using the electrode layer as a cathode to form an electroplated layer on the electrode layer until the flat portions between the spherical thermoplastic microstructures disappear.  
     
     
         54 . A method according to  claim 49 , further comprising the steps of: 
 forming a plurality of structures for an alignment marker outside of a region of the plurality of thermoplastic microstructures; and    surface processing the wafer to form a water-repellant surface before step (a),    wherein step (b) is performed by baking the wafer, and    wherein step (c) is performed by forming catalyst cores on the substrate and the spherical thermoplastic microstructures and performing electroless plating on the spherical thermoplastic microstructures and the substrate.