Abstract:
Systems and methods for three dimensional lithography, nano-indentation, and combinations thereof are disclosed. One exemplary three dimensional lithography method, among others, includes: providing a substrate having at least one optical element, wherein the optical element is selected from a refractive element and a diffractive element; disposing a polymer layer on the substrate and the at least one optical element, wherein the polymer layer includes a polymer material selected from a positive-tone polymer material and a negative-tone polymer material; positioning a mask adjacent the polymer layer, wherein the mask does not cover at least one directly exposed portion of the polymer material directly overlaying the at least one element; and exposing the at least one directly exposed portion of the polymer material to optical energy, wherein the optical energy passes through the at least one directly exposed portion of the polymer material and interacts with the element, and the element redirects the optical energy through the polymer material forming at least one area of indirectly exposed polymer material.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to U.S. provisional application entitled, “Input/Output Leads, Lithography and Nano-Indentations” having Ser. No. 60/498,419, filed on Aug. 28, 2003, and which is entirely incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     The U.S. government may have a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of MDA972-99-1-0002 awarded by the DARPA. 
     
    
     TECHNICAL FIELD  
       [0003]     This disclosure is generally related to formation of structures in microelectronics, photonics, and MEMS, and more particularly, this disclosure is related to lithography and molding systems and methods for use in microelectronics, photonics, and MEMS applications.  
       BACKGROUND  
       [0004]     In general, lithography refers to processes for pattern transfer between various media. A lithographic coating is generally a radiation-sensitized coating suitable for receiving a projected image of the subject pattern. Once the image is projected, it is indelibly formed in the coating (e.g., polymer). However, this process can only be used to form two-dimensional structures. With the continuous integration of electronic, optoelectronic, and MEMS technology, there has become a need to form three-dimensional structures. Thus, a heretofore unaddressed need exists in the industry that addresses the aforementioned deficiencies and/or inadequacies.  
       SUMMARY  
       [0005]     Systems and methods for three dimensional lithography, nano-indentation, and combinations thereof are disclosed. One exemplary three dimensional lithography method, among others, includes: providing a substrate having at least one optical element, wherein the optical element is selected from a refractive element and a diffractive element; disposing a polymer layer on the substrate and the at least one optical element, wherein the polymer layer includes a polymer material selected from a positive-tone polymer material and a negative-tone polymer material; positioning a mask adjacent the polymer layer, wherein the mask does not cover at least one directly exposed portion of the polymer material directly overlaying the at least one element; and exposing the at least one directly exposed portion of the polymer material to optical energy, wherein the optical energy passes through the at least one directly exposed portion of the polymer material and interacts with the element, and the element redirects the optical energy through the polymer material forming at least one area of indirectly exposed polymer material.  
         [0006]     One exemplary nano-indentation method, among others, includes: providing a substrate having a polymer layer disposed on the substrate, the polymer layer includes a polymer material that is in an uncured plastic state; providing a stamp mask having a photomask and at least one nano-indentation structure for forming a physical feature on the polymer layer, wherein the photomask does not cover at least one area of the polymer material; and stamping the polymer material with the stamp mask, wherein the polymer material forms the physical feature caused by the at least one nano-indentation structure.  
         [0007]     One exemplary method of forming a structure, among others, includes: providing a substrate having at least one element and a polymer layer, the polymer layer is disposed on the substrate and the at least one element, wherein the polymer layer includes a polymer material selected from a positive-tone polymer material and a negative-tone polymer material, wherein the polymer material is in an uncured plastic state, and wherein the element is selected from a refractive element and a diffractive element; providing a stamp mask having a photomask and at least one nano-indentation structure for forming a physical feature on the polymer layer, wherein the photomask does not cover at least one directly exposed portion of the polymer material; stamping the polymer material with the stamp mask, wherein the polymer material forms the physical feature caused by the at least one nano-indentation structure; and exposing the at least one directly exposed portion of the polymer material to optical energy, wherein the optical energy passes through the at least one directly exposed portion of the polymer material and interacts with the element, and the element redirects the optical energy through the polymer material forming at least one area of indirectly exposed polymer material.  
         [0008]     Other systems, methods, features, and advantages of this disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of this disclosure, and be protected by the accompanying claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     Many aspects of this disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of this disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
         [0010]      FIG. 1  is a representative flow chart of an embodiment of a three-dimensional lithography method.  
         [0011]      FIG. 2A  is a cross-sectional view of a representative embodiment of a structure formed using the three-dimensional lithography method of  FIG. 1 , while  FIG. 2B  is another cross-sectional view of the structure of  FIG. 1  from the A-A perspective.  
         [0012]      FIGS. 3A through 3E  are a sequence of cross-sectional views illustrating the formation of the structure shown in  FIGS. 2A and 2B .  
         [0013]      FIGS. 4A through 4D  are a sequence of cross-sectional views illustrating the formation of the structure shown in  FIGS. 2A and 2B .  
         [0014]      FIG. 5  illustrates a cross-sectional view of a representative tunneled structure using a tunnel system formed by the three-dimensional lithography method of  FIG. 1 .  
         [0015]      FIG. 6  illustrates a cross-sectional view of a representative structure having slanted walls formed using the three-dimensional lithography method of  FIG. 1 .  
         [0016]      FIGS. 7A through 7E  are a sequence of cross-sectional views illustrating the formation of the sloped wall structure shown in  FIG. 6 .  
         [0017]      FIG. 8  illustrates a cross-sectional view of a structure having an “L”-shaped polymer pillar formed using the three-dimensional lithography method of  FIG. 1 .  
         [0018]      FIGS. 9A through 9F  are a sequence of cross-sectional views illustrating the formation of the structure shown in  FIG. 8 .  
         [0019]      FIGS. 10A and 10B  are cross-sectional views illustrating a system using a pair of “L”-shaped polymer pillars.  
         [0020]      FIG. 11  illustrates a cross-sectional view of a “W”-tunnel system having a “W”-cross-section formed using the three-dimensional lithography method of  FIG. 1 .  
         [0021]      FIGS. 12A through 12E  are cross-sectional views of a representative sequence to form the “W”-tunnel system shown in  FIG. 11 .  
         [0022]      FIG. 13  illustrates a cross-sectional view of “W”-shaped structure formed using the three-dimensional lithography method of  FIG. 1 .  
         [0023]      FIGS. 14A through 14E  are a sequence of cross-sectional views illustrating the formation of the “W”-shaped structure shown in  FIG. 13 .  
         [0024]      FIG. 15  is a flowchart depicting functionality of an embodiment of a method using nono-indentation to form physical features in a polymer material.  
         [0025]      FIG. 16  illustrates six polymer structures formed using the nano-indentation method of  FIG. 15 .  
         [0026]      FIGS. 17A through 17E  are a sequence of cross-sectional views illustrating the formation of the six polymer structures shown in  FIG. 16  using the nano-indentation methods of  FIG. 15 .  
         [0027]      FIGS. 18A through 18F  are cross-sectional views of various embodiments of nano-indentation physical features that can be formed using the nano-indentation methods of  FIG. 15 .  
         [0028]      FIG. 19  is a cross-sectional view of a structure formed using a combination of the three-dimensional lithography and nano-indentation methods of  FIG. 15 .  
         [0029]      FIGS. 20A through 20D  are a sequence of cross-sectional views illustrating the formation of the structure shown in  FIG. 19 . 
     
    
     DETAILED DESCRIPTION  
       [0030]     Systems and methods for three-dimensional lithography, nano-indentation, and combinations thereof, are described herein. In general, three-dimensional lithography and nano-indentation systems and methods can be used to form structures that are difficult, if not impossible, to form using other techniques. In general, three-dimensional lithography uses optical elements (e.g., mirrors and grating couplers) that are buried within a polymer layer to redirect optical energy to otherwise unexposed regions of the polymer layer to yield three-dimensional structures. In this regard, three-dimensional lithography can be used to form slanted vias, slanted walls, tunnel systems, air-cladding for optical waveguides, non-planar strucutures, RF channels, and combinations thereof. These structures can find application in electrical, optical, and MEMS technologies, for example.  
         [0031]     Nano-indentation is a simple and low cost method of transferring a pattern from a mask to a polymer film. In general, a mask is used to plastically deform a polymer. The mask is brought into contact with the polymer prior to curing and at temperatures below the glass transition temperature of the polymer. The mask includes physical features that are imparted onto the polymer. In this regard, nano-indentation can be used to form physical features in a polymer layer such as, but not limited to, structures having curves, structures having slanted walls, small structures, and combinations thereof.  
         [0032]     Combining three-dimensional lithography with nano-indentation provides methods of forming structures and devices that are otherwise difficult to fabricate. For example, three-dimensional lithography can be used to form smooth sidewalls, which can be used in optical waveguides. Adding the ability to plastically deform part of the waveguide using nano-indentation to fabricate surface-normal diffractive grating couplers provides a simple fabrication of otherwise difficult to form structures.  
         [0033]      FIG. 1  is a flowchart depicting functionality of an embodiment of a three-dimensional lithographic method  10  of using a three-dimensional lithography system. As shown in  FIG. 1 , the method may be construed as beginning at block  12 , where a substrate having one or more optical elements disposed thereon is provided. The types of optical elements can include, but are not limited to, refractive elements, diffractive elements, and combinations thereof. The optical elements can be constructed to redirect optical energy (e.g. light) at one or more angles between about 0 and 90°. The refractive elements can include, but are not limited to, mirrors. The diffractive elements can include, but are not limited to, volume grating couplers and surface relief grating couplers. The optical elements can be disposed on the substrate using techniques such as, but not limited to, wet etching, dry etching, chemical vapor deposition, spinning and methods of metal deposition such as sputtering and evaporation.  
         [0034]     The substrate can include, but is not limited to, a printed wiring board, a printed wiring/waveguide board, and ceramic and non-organic substrates and modules. The substrate can include additional components such as, but not limited to, die pads, leads, input/output components, waveguides, planar waveguides, polymer waveguides, optical waveguides having coupling elements such as diffractive grating couplers or mirrors disposed adjacent or within the optical waveguide, photodectors, and optical sources such as VCSELS and LEDs.  
         [0035]     In block  14 , a polymer layer of polymer material is disposed on the substrate and the one or more optical elements. The polymer material can include, but is not limited to, photodefinable polymers, photosensitive thermally decomposable polymers, and combinations thereof. The photodefinable polymers and photosensitive thermally decomposable polymers can be either positive-tone polymer materials or negative-tone polymer materials. More specifically, the polymer material can include compounds such as, but not limited to, polyimides, polynorbornenes, polycarbonates, polyethers, polyesters, functionalized compounds of each, and combinations thereof. In addition, the polymer materials can include negative tone photoinitiators (e.g., photosensitive free radical generators) and positive tone photoinitiators (e.g., photoacid generators). The polymer layer can be between about 1 and 500 micrometers in thickness. The polymer layer can be formed on the substrate and optical elements using techniques such as, but not limited to, lamination, spin coating, extrusions, roller coating, and maniscus coating.  
         [0036]     In block  16 , a mask is brought into contact with the polymer layer. The mask can be designed to cover (e.g., inhibit exposure to optical energy) portions of the polymer material that are not directly above one or more of the optical elements. In addition, the mask can be designed to expose one or more portions not directly above the optical elements depending, in part, upon any other structures to be formed. The mask can be a hard mask or a soft mask.  
         [0037]     In block  18 , the polymer material not covered by the mask is exposed to optical energy. The optical energy passes through the polymer material and interacts with one or more of the optical elements. The optical element redirects the optical energy through the polymer material. In general, the optical energy is redirected at an angle from the optical element. The angle at which the optical energy is redirected through the polymer material depends, at least in part, on the type and/or construction of the optical element. The number, the type, and position of the optical elements can be used to redirect optical energy to ultimately form various polymer structures, polymer shapes, conduits, and/or tunnel systems. For example, the redirected optical energy can be used to form polymer structures and polymer structures having one or more slanted walls with various types of slopes.  
         [0038]     Now having described systems and methods in general,  FIGS. 2A and 2B ,  3 A through  3 E,  4 A through  4 D,  5 ,  6 ,  7 A through  7 E,  8 ,  9 A through  9 F,  10 A and  10 B,  11 ,  12 A through  12 E,  13 , and  14 A through  14 E and the accompanying text, describe some embodiments of methods and systems of this disclosure. While embodiments of this disclosure are described in connection with the above noted figures and accompanying text, there is no intent to limit embodiments of this disclosure to these descriptions. On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of embodiments of the present invention.  
         [0039]     In general,  FIGS. 2A and 2B ,  3 A through  3 E,  4 A through  4 D,  5 ,  6 ,  7 A through  7 E,  8 ,  9 A through  9 F,  10 A and  10 B,  11 ,  12 A through  12 E,  13 , and  14 A through  14 E, illustrate various types of structures, shapes, and tunnel systems that can be formed using the three-dimensional lithography methods of  FIG. 1  and provided herein, while also illustrating uses of some of these structures.  
         [0040]      FIG. 2A  is a cross-sectional view of a representative embodiment of a structure  20  having a tunnel system  22  formed therein using the three-dimensional lithography method described herein, while  FIG. 2B  is a cross-sectional view of the structure  20  in  FIG. 2A  through the A-A cross-section. The structure  20  includes, but is not limited to, a substrate  24 , a polymer layer  36 , two optical elements  26 , and a tunnel system  22 . The substrate  24 , the polymer layer  36 , and the two optical elements  26  are similar to the substrate, the polymer layer, and the optical elements described above in reference to  FIG. 1 . The tunnel system  22  can be used as a conduit for fluids, optical energy, and microwave signals when tunnel system  22  is metallically coated, for example. In addition, the tunnel system  22  can provide compliancy to structures (e.g., a lead) disposed above the tunnel on the polymer layer  36 . The tunnel system  22  can be from about 5 to 300 micrometers in height, about 1 to 1000 micrometers in width, and 1 to 1000 micrometers in length.  
         [0041]      FIGS. 3A through 3E  are a sequence of cross-sectional views illustrating the formation of the structure  20  shown in  FIGS. 2A and 2B .  FIG. 3A  illustrates the substrate  24  having two optical elements  26  disposed thereon.  FIG. 3B  illustrates the formation of a polymer layer  36  on the substrate  24  and the two optical elements  26 . The polymer layer  36  includes a photosensitive thermally decomposable polymer material that upon exposure to optical energy is chemically altered into a thermally degradable polymer material. The polymer layer  36  can be formed by techniques such as, but not limited to, lamination, spin coating, extrusions, roller coating, and maniscus coating.  
         [0042]      FIG. 3C  illustrates a mask  30  being brought into contact with the polymer layer  36  as well as exposure of the mask  30  and polymer layer  36  to the optical energy  32 . The optical energy  32  can include ultraviolet energy and infrared energy, which can be generated by mask aligner systems.  
         [0043]     The optical energy  32  interacts with the two optical elements  26  and the optical energy  32  is redirected. The area of the polymer material that the optical energy passes through is chemically altered to a thermally degradable polymer  34 , as shown in  FIG. 3D .  
         [0044]      FIG. 3E  illustrates the tunnel system shown  22  after the thermally degradable polymer  34  has been degraded. The thermally degradable polymer  34  can be degraded using techniques such as, but not limited to, a furnace, a hotplate, and the like.  
         [0045]      FIGS. 4A through 4D  are a sequence of cross-sectional views illustrating the formation of the structure  20  shown in  FIGS. 2A and 2B .  FIG. 4A  illustrates the substrate  24  having two optical elements  26 .  FIG. 4B  illustrates the formation of the polymer layer  36  on the substrate  24  and the two optical elements  26 . The polymer layer  36  includes a polymer material that upon exposure to optical energy is chemically degradable such as, but not limited to, a photodefinable polymer (e.g., a polymer and a photoacid generator). It should be noted that the polymer material could be a photosensitive thermally decomposable polymer if a thermal decomposition step is added to the method. The polymer layer  36  can be formed by techniques such as, but not limited to, lamination, spin coating, extrusions, roller coating, and maniscus coating. The polymer layer can be from about 5 to 500 micrometers in thickness.  
         [0046]      FIG. 4C  illustrates a mask  30  brought into contact with the polymer layer  36  as well as the exposure of the mask  30  and polymer material to optical energy  32 . The optical energy  32  can include ultraviolet energy and infrared energy, which can be generated by mask aligner systems.  
         [0047]     The optical energy  32  interacts with the two optical elements  26  and the optical energy  32  is redirected. The area of the polymer material that the optical energy  32  passes through is chemically degraded, as shown in  FIG. 4D , to form the tunnel system shown  22  in  FIGS. 2A and 2B .  
         [0048]      FIG. 5  illustrates a cross-section of a representative tunneled structure  40  using a tunnel system formed by the three-dimensional lithography method described herein. The tunneled structure  40  includes a first structure  42  and a second structure  52 . The first structure  42  includes a substrate  44 , a polymer layer  46 , and two optical elements  48 . The optical elements  48  were used to form two tunnel segments  50 A and  50 B in the polymer layer  46 .  
         [0049]     The second structure  52  includes a substrate  54 , a polymer layer  56 , two optical elements  58 , and two hollow structures  60 . The optical elements  58  were used to form the tunnel system  62 . The two hollow structures  60  are disposed above the portion of the tunnel system  62  above the two optical elements  46  and  58  on each substrate  44  and  54  of the tunneled structure  40 . Once the first structure and the second structure are aligned, the two tunnel segments  50 A and  50 B, the hollow structures  60 , and the tunnel system  62  form an interconnected tunnel system. The arrow  64  indicates, for example, how a fluid (e.g. air or liquid) can be flowed through the interconnected tunnel system in the first structure  42  and the second structure  52  to form a fluidic structure. Alternatively, the arrows  64  indicate how optical energy could be directed through the interconnected tunnel system in the first structure  42  and the second structure  52 .  
         [0050]      FIG. 6  is a cross-sectional view of a structure  70  having a slanted wall structure  72  formed using the three-dimensional lithography method described herein. The structure  70  includes a substrate  74 , two optical elements  76 , a polymer layer  84 , and a slanted wall structure  72 . The substrate  74 , two optical elements  76 , and the polymer layer  84  are similar to the substrate, two optical elements, and the polymer layer (polymer material) described above in reference to  FIG. 1 . The slanted wall structure  72  is formed of the same polymer material as the polymer layer  84 . The slanted walls of the slanted wall structure  72  have slopes determined, at least in part, by the type and construction (e.g., angle of reflection) of optical elements  76  disposed on the substrate  74 . For example, changing the angle of reflection of the optical element  76  could alter the slope of the walls. The structure  70  can be from about 5 to 500 micrometers in height, about 1 to 1000 micrometers in width, and about 1 to 1000 micrometers in length.  
         [0051]      FIGS. 7A through 7E  are a sequence of cross-sectional views illustrating the formation of the sloped wall structure  72  shown in  FIG. 6 .  FIG. 7A  illustrates the substrate  74  having two optical elements  76 .  FIG. 7B  illustrates the formation of the polymer layer  78  on the substrate  74  and the two optical elements  76 . The polymer layer  78  includes a polymer material that upon exposure to optical energy is chemically degradable such as, but not limited to, a photodefinable polymer. It should be noted that the polymer material could be a photosensitive thermally decomposable polymer if a thermal decomposition step is added to the method. The polymer layer  78  can be formed by techniques such as, but not limited to, lamination, spin coating, extrusions, roller coating, and maniscus coating.  
         [0052]      FIG. 7C  illustrates a mask  80  brought into contact with the polymer layer  78  and the exposure of the mask  80  and polymer material to optical energy  82 . The optical energy  82  can include ultraviolet energy and infrared energy and can be generated by mask aligner systems.  
         [0053]     The optical energy  82  interacts with the two optical elements  76  and the optical energy  82  is redirected. The area of the polymer material that the optical energy  82  passes through is chemically degraded to form an air-region  86 , as shown in  FIG. 7D . The mask  80  is removed to reveal the slanted wall structure  72  shown in  FIG. 6 .  
         [0054]      FIG. 8  illustrates a cross-section of a structure  90  having an “L”-shaped polymer pillar  92  disposed thereon. The structure  90  includes a substrate  94 , an optical element  96 , and the “L”-shaped polymer pillar  92 . The substrate  94 , the optical element  96 , and the polymer material that the “L”-shaped polymer pillar  92  is made of are similar to the substrate, the optical elements, and the polymer material described in reference to  FIG. 1 .  
         [0055]     The “L”-shaped polymer pillar  92  includes a vertical pillar  92   a  having an upper horizontal portion  92   b  extending from the top portion of the vertical pillar  92   a . The vertical pillar  92   a  and the upper horizontal portion  92   b  are formed using a mask, the optical element, and optical energy. The optical energy is redirected by the optical element to form the upper horizontal portion  92   b , as discussed in additional detail in reference to  FIGS. 9A through 9F .  
         [0056]     The “L”-shaped polymer pillar  92  can be from about 10 to 300 micrometers in height, about 2 to 500 micrometers in width, and about 2 to 500 micrometers in length. The upper horizontal portion  92   b  can be from about 5 to 50 micrometers in length and 2 to 500 micrometers in width.  
         [0057]      FIGS. 9A through 9F  are a sequence of cross-sectional views illustrating the formation of the structure  90  shown in  FIG. 8 .  FIG. 9A  illustrates the substrate  94  having one optical element  96 .  FIG. 9B  illustrates the formation of a polymer layer  98  on the substrate  94  and the optical element  96 . The polymer layer  98  includes a polymer material that upon exposure to optical energy is chemically altered into a thermally degradable polymer material. It should be noted that the polymer material could be a photosensitive thermally decomposable polymer if a thermal decomposition step is added to the method. The polymer layer  98  can be formed by techniques such as, but not limited to, lamination, spin coating, extrusions, roller coating, and maniscus coating.  
         [0058]      FIG. 9C  illustrates a mask  100  brought into contact with the polymer layer  98 .  FIG. 9D  illustrates the exposure of the mask  100  and polymer material to optical energy  102 . The optical energy  102  can include ultraviolet energy and infrared energy and can be generated by mask aligner systems  
         [0059]     The mask  100  is positioned on the polymer layer  98  so that only a portion of the optical element  96  is directly above the open portion of the mask  100 . Thus, when the optical energy  102  passes through the open portion of the mask  100 , the optical energy  102  interacts with the exposed portion of optical element  96 . The optical energy  102  is redirected at an angle that overlaps with a portion of the vertical polymer material already exposed to the optical energy  102  and also an area that corresponds to where the upper horizontal portion  92   b  is to be formed. In other words, the combination of exposed areas of the polymer material form an “L”-shape. The exposed “L”-shaped area of the polymer material is chemically altered (e.g., crosslinked) to a thermally stable polymer relative to the unexposed polymer material, as shown in  FIG. 9E .  
         [0060]      FIG. 9F  illustrates the “L”-shaped structure  92  after the polymer layer has been degraded. The polymer layer  98  can be degraded using thermal energy, ultraviolet energy, infrared energy, and the like.  
         [0061]      FIGS. 10A and 10B  are cross-sectional views of a system  110  using a pair of “L”-shaped polymer pillars. The system  110  includes a first structure  112  and a second structure  122 . The first structure  122  includes a substrate  114 , a vertical waveguide pillar  118  having a metal layer  120  surrounding the vertical waveguide pillar  118 , and an optical source  116 . The second structure  122  includes a substrate  124 , two optical elements  126 , two “L”-shaped polymer pillars  130 , and an optical detector  128 . The two “L”-shaped polymer pillars  130  have a metal layer  132  surrounding the “L”-shaped polymer pillars  130 . The metal layer  120  of the vertical waveguide pillar  118  and the metal layer  132  of the two “L”-shaped polymer pillars  130  can be used to communicate electrical energy. The optical source  116  and the vertical waveguide pillar  118  can be used to guide optical energy  134  from the first structure  112  to the optical detector  128  of the second structure  122 . The “L”-shaped polymer pillars  130  can be used to align the vertical waveguide pillar  118  to communicate optical energy  134  from the first substrate  112  to the second substrate  122 .  
         [0062]      FIGS. 11 and 13  are cross-sections of two structures  140  and  152  that can be fabricated using the three-dimensional lithography methods disclosed herein.  FIG. 11  illustrates a “W”-tunnel system  142  having a “W”-cross section, while  FIG. 13  illustrates a “W”-shaped structure  152 . As discussed in reference to  FIGS. 12A through 12E  and  14 A through  14 E, the “W”-tunnel system  142  and the “W”-shaped structure  152  are formed using the same type of optical element  146 . However, the polymer material used to form the “W”-tunnel system  142  is a photosensitive positive tone polymer material, while the polymer material used to form the “W”-shaped structure  152  is a photosensitive negative tone polymer material.  
         [0063]     The “W”-tunnel system  142  can be about 2 to 1000 micrometers in length, about 2 to 1000 micrometers in width, and about 5 to 300 micrometers in height. The “W”-shaped structure can be about 2 to 1000 micrometers in width, and about 5 to 300 micrometers in height.  
         [0064]      FIGS. 12A through 12E  are cross-sections of a representative sequence to form the “W”-tunnel system  142  shown in  FIG. 11 .  FIG. 12A  illustrates a substrate  144  having one optical element  146 .  FIG. 12B  illustrates the formation of a polymer layer  148  on the substrate  144  and the optical element  146 . The polymer layer  148  includes a photosensitive positive-tone polymer material that upon exposure to optical energy is chemically degradable. The polymer layer  148  can be formed by techniques such as, but not limited to, lamination, spin coating, extrusions, roller coating, and maniscus coating.  
         [0065]      FIG. 12C  illustrates a mask  150  brought into contact with the polymer layer  148  and the exposure of the mask  150  and polymer material to optical energy  152 . The optical energy  152  can include ultraviolet energy and infrared energy and can be generated by mask aligner systems.  
         [0066]     The optical energy  152  interacts with the optical element  146  and the optical energy  152  is redirected in two directions. The “W”-shaped area of the polymer material that the optical energy  152  passes through is chemically degraded, as shown in  FIG. 12D .  FIG. 12E  illustrates the removal of the mask  152  to reveal the “W”-tunnel system  142  shown in  FIG. 11 .  
         [0067]      FIGS. 14A through 14E  are a sequence of cross-sectional views illustrating the formation of the “W”-shaped structure  152  shown in  FIG. 13 .  FIG. 14A  illustrates a substrate  154  having one optical element  156 .  FIG. 14B  illustrates the formation of a polymer layer  158  on the substrate  154  and the optical element  156 . The polymer layer  158  includes a photosensitive negative-tone polymer material that upon exposure to optical energy is chemically altered into a non-degradable polymer material. Subsequent developing removes the unexposed polymer regions. The material can also be a thermally decomposable material that is also photosensitive. The polymer layer  158  can be formed by techniques such as, but not limited to, lamination, spin coating, extrusions, roller coating, and maniscus coating.  
         [0068]      FIG. 14C  illustrates the formation of a mask  160  on the polymer layer  158 . In addition,  FIG. 14D  illustrates the exposure of the mask  160  and polymer material  158  to optical energy  162 . The optical energy  162  can include ultraviolet energy and infrared energy, which can be generated by mask aligner systems  
         [0069]     The optical energy  162  interacts with the optical element  156  and the optical energy  162  is redirected in two directions. The “W”-shaped area of the polymer material that the optical energy  162  passes through is chemically altered to a non-degradable stable polymer material, as shown in  FIG. 14D .  
         [0070]     The areas not exposed to optical energy  162  are exposed to thermal energy and are degraded as shown in  FIG. 14E . The removal of the mask to reveal the “W”-shaped structure shown  152  in  FIG. 13 . The polymer material can be degraded using thermal energy, ultraviolet energy, infrared energy, and the like.  
         [0071]      FIG. 15  is a flowchart depicting functionality of an embodiment of a method of using nono-indentation  170  to form physical features in a polymer material. As shown in  FIG. 15 , the method may be construed as beginning at block  172 , where a substrate having a polymer layer disposed thereon. The polymer layer includes a polymer material in an uncured or plastic state such as those described above. The substrate is similar to the substrate discussed in reference to  FIG. 1 .  
         [0072]     In block  174 , a stamp mask is provided. The stamp mask includes a photomask and one or more nano-indentation structures for forming a physical feature in the polymer material. The photomask is designed to cover portions of the polymer material and prevent those portions from being exposed to optical energy. The photomask can be made of materials such as, but not limited to, glass, quartz, and the like. The stamp mask can be made of materials such as, but not limited to, glass, quartz, silicon, metals, and other hard materials.  
         [0073]     The nano-indentation structures (e.g., molds) are used to stamp physical features into the polymer material disposed on the substrate. The physical features can include, but are not limited to, triangular features, rectangular features, spherical features, elliptical features, and combinations thereof. The physical features can range in size from about 0.01 to 20 micrometers in height, from about 0.01 to 1000 micrometers in width, and from about 0.01 to 1000 micrometers in length.  
         [0074]     In block  176 , the polymer material is stamped by the stamp mask. The polymer material forms (e.g. molded) into the shape of the physical feature when the stamp mask is stamped into the polymer material. The polymer material molds into the shape of the physical features because the polymer material is in an uncured or plastic state. Subsequently, the molded polymer material can be cured so that the physical features are made permanent.  
         [0075]     Alternatively, prior to curing the polymer material, the polymer material can be exposed to optical energy. The optical energy passes through the uncovered areas of the photomask and impinges upon the polymer material thereunder. The polymer material exposed to the optical energy is chemically altered into an unstable polymer material. Subsequently, the molded polymer material can be cured so that the physical features are made permanent and the unstable polymer material is decomposed and removed in one or more steps. Thus, the photomask can be designed to form polymer structures in areas corresponding to the position of the physical features.  
         [0076]     For example,  FIGS. 16 and 17 A through  17 E illustrate six polymer structures  184 ,  186 ,  188 ,  190 ,  192 , and  194  and the method of forming the polymer structures, that can be formed using nano-indentation in conjunction with exposure to optical energy.  FIG. 16  illustrates a structure  180  that includes six exemplary structures  184 ,  186 ,  188 ,  190 ,  192 , and  194  disposed on a substrate  182  that can be formed using nano-indentation methods described herein. The six structures include a multi-tooth polymer pillar  184 , a “seat” shaped polymer pillar  186 , a single point (triangle tip) polymer pillar  188 , a double point (inverted triangle tip) polymer pillar  190 , a crescent shaped polymer pillar  192 , and a half-circle polymer pillar  194 . It should be noted that these are only representative structures that can be formed using nano-indentation methods described herein. The structures can be used as optical devices (e.g., grating couplers, mirrors, and lenses) and RF components (filters and electrical devices).  
         [0077]      FIG. 17A  illustrates a stamping structure  202  and a stamped structure  210 . The stamping structure  202  includes a stamp mask  206  disposed onto a structure  204 . The stamped structure  210  includes a polymer layer  214  disposed on a substrate  212 . The polymer layer  214  includes a polymer material in an uncured or plastic state. The polymer layer  214  can be formed by techniques such as, but not limited to, lamination, spin coating, extrusions, roller coating, and maniscus coating.  
         [0078]     The stamp mask  206  includes six sets of nano-indentation structures  206   a  . . .  206   f  and a photomask  208 . The nano-indentation structures  206   a  . . .  206   f  are molds designed to form the multi-tooth physical feature  206   a , the “seat” shaped physical feature  206   b , the single point (triangle tip) physical feature  206   c , the double point (inverted triangle tip) physical feature  206   d , the crescent shaped physical feature  206   e , and the half-circle physical feature  206   f.    
         [0079]      FIG. 17B  illustrates the stamping of the stamping structure  202  onto the stamped structure  210 . The polymer material conforms to the nano-indentation structures  206   a  . . .  206   f  to form the physical features described above.  
         [0080]      FIG. 17C  illustrates the exposure of the polymer material to optical energy  216 . The optical energy  216  impinges upon the polymer material that is not covered by the photomask  208  and chemically alters the polymer to a more stable polymer than the unexposed polymer. In particular, the photomask  208  was designed to expose areas of the polymer material inline with the nano-indentation structures  206   a  . . .  206   f  so that the polymer structures listed above are formed.  
         [0081]      FIG. 17D  illustrates the removal of the stamping structure  202  from the stamped structure  210 . The physical features are present on the surface of the polymer layer  214 . In addition, the areas of unstable polymer material  218  are shown.  FIG. 17E  illustrates the curing of the stable polymer material and the removal (e.g., decomposition) of the unstable polymer material. The removal of the polymer material reveals the multi-tooth polymer pillar  184 , the “seat” shaped polymer pillar  186 , the single point (triangle tip) polymer pillar  188 , the double point (inverted triangle tip) polymer pillar  190 , the crescent shaped polymer pillar  192 , and the half-circle polymer pillar  194 .  
         [0082]      FIGS. 18A through 18F  are cross-sections of various embodiments of nano-indentation physical features that can be formed using the nano-indentation methods described herein.  FIG. 18A  illustrates a right angle saw tooth nano-indentation physical feature  222 , while  FIG. 18B  illustrates a recessed right angle saw tooth nano-indentation physical feature  224 .  FIG. 18C  illustrates a square saw tooth nano-indentation physical feature  226 , while  FIG. 18D  illustrates a square recessed right angle saw tooth nano-indentation physical feature  228 .  FIG. 18E  illustrates a triangle saw tooth nano-indentation physical feature  230 , while  FIG. 18F  illustrates a triangle recessed right angle saw tooth nano-indentation physical feature  232 . In particular, the nano-indentation physical features shown in  FIGS. 18A through 18F  can be used as optical surface relief gratings for surface-normal (or off normal axis) preferential order coupling and focusing.  
         [0083]      FIG. 19  is a cross-section of a structure  240  formed using a combination of the three-dimensional lithography and nano-indentation methods described herein. The structure  240  includes a substrate  242 , a polymer layer  244 , two optical elements  246 , a tunnel system  248 , and a triangle saw tooth nano-indentations physical feature  250 . The substrate  242 , polymer layer  244 , and optical elements  246  are similar to those described in reference to  FIG. 1 .  
         [0084]      FIGS. 20A through 20D  are a sequence of cross-sectional views illustrating the formation of the structure  240  shown in  FIG. 19 .  FIG. 20A  illustrates the substrate  242  having two optical elements  246 .  FIG. 20B  illustrates the formation of a polymer layer  244  on the substrate  242  and the two optical elements  246 . The polymer layer  244  includes a polymer material that upon exposure to optical energy is chemically degradable. The polymer materials are similar to those described hereinabove. The polymer layer  244  can be formed by techniques such as, but not limited to, lamination, spin coating, extrusions, roller coating, and maniscus coating.  
         [0085]      FIG. 20C  illustrates the stamping of a stamp mask  252  onto the polymer layer  244  and the exposure of the stamp mask  252  and polymer material  244  to optical energy  256 . The stamp mask  252  includes a photomask  258  and a nano-indentation structure  260  for forming the saw tooth physical feature in the polymer material. The photomask  260  is designed to cover portions of the polymer material and prevent those portions from being exposed to optical energy  256 . The photomask  260  exposes portions of the polymer material directly above the two optical elements  246  through two openings in the photomask  260 .  
         [0086]     The optical energy  256  can include ultraviolet energy and infrared energy, which can be generated by mask aligner systems. The optical energy  256  passes through the openings of the photomask  252  and interacts with the two optical elements  246 . The optical energy  256  is redirected to form the tunnel system  248 . The area of the polymer material that the optical energy  256  passes through is chemically degraded, as shown in  FIG. 20D . In addition, the stamp mask  252  is removed to reveal the structure shown in  FIG. 19 .  
         [0087]     It should be emphasized that the above-described embodiments of this disclosure are merely possible examples of implementations, set forth for a clear understanding of the principles of this disclosure. Many variations and modifications may be made to the above-described embodiment(s) without departing substantially from the spirit and principles of this disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.