Abstract:
Methods for creating nano-shaped patterns are described. This approach may be used to directly pattern substrates and/or create imprint lithography molds that may be subsequently used to directly replicate nano-shaped patterns into other substrates in a high throughput process.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit under 35 U.S.C. §119(e)(1) of U.S. Provisional Patent Application Ser. No. 61/114,239 filed Nov. 13, 2008, which is hereby incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    Nano-fabrication involves the fabrication of very small structures, e.g., having features on the order of 100 nanometers or smaller. One area in which nano-fabrication has had a sizeable impact is in the processing of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, nano-fabrication becomes increasingly important. Nano-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension of the structures formed. Other areas of development in which nano-fabrication has been employed include biotechnology, optical technology, energy systems and the like. 
         [0003]    An exemplary nano-fabrication technique is referred to as imprint lithography. Exemplary imprint lithography processes are described in detail in numerous publications, such as United States patent application publication 2004/0065976, United States patent application publication 2004/0065252, and U.S. Pat. No. 6,936,194, all of which are assigned to an assignee of the present invention. 
         [0004]    An imprint lithography technique disclosed in each of the aforementioned United States patent application publications and United States patent includes formation of a relief pattern in a formable liquid (polymerizable layer) and transferring a pattern corresponding to the relief pattern into an underlying substrate. The substrate may be positioned upon a motion stage to obtain a desired position to facilitate patterning thereof. To that end, a template is employed spaced-apart from the substrate with a formable liquid present between the template and the substrate. The liquid is solidified to form a solidified layer that has a pattern recorded therein that is conforming to a shape of the surface of the template in contact with the liquid. The template is then separated from the solidified layer such that the template and the substrate are spaced-apart. The substrate and the solidified layer are then subjected to processes to transfer, into the substrate, a relief image that corresponds to the pattern in the solidified layer. 
         [0005]    Many nano-patterning applications take advantage of the size and uniform shape of nano-scale features to achieve a desired result. Many processes employed to make nano-patterns use a “growth” process to grow a particular type and size of nano-patterns. Unfortunately, these types of processes may be slow and prone to producing nano-patterns whose size and shape may be insufficiently controlled to produce desired performance cost effectively. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  illustrates a system suitable to form a relief pattern on a substrate according to embodiments herein. 
           [0007]      FIGS. 2A-2C  illustrate cross-section views showing material layers after processing according to embodiments herein. 
           [0008]      FIGS. 3A-3C  illustrate cross-section views showing material layers after further processing according to embodiments herein. 
           [0009]      FIG. 4A  illustrates a cross-section view showing trenches etched into the substrate according to embodiments herein. 
           [0010]      FIG. 4B  illustrates a top view of the trenches of  FIG. 4A . 
           [0011]      FIG. 5A  illustrates a top view of an exemplary patterned surface having nano-structures formed by etching trenches formed by a first pattern and a second pattern. 
           [0012]      FIG. 5B  illustrates a top view of another exemplary patterned surface having nano-structures formed by etching trenches formed by a first pattern and additional overlaying patterns. 
           [0013]      FIG. 6  illustrates a flow diagram of an exemplary for forming nanostructures according to embodiments herein. 
           [0014]      FIG. 7A  illustrates a simplified cross-sectional view of a nano-pattern mold positioned above a substrate. 
           [0015]      FIG. 7B  illustrates a top down magnified view of a recession of the nano-pattern mold in  FIG. 7A . 
           [0016]      FIG. 8  illustrates a simplified cross-sectional view of a nano-pattern mold positioned above a substrate at a first height. 
           [0017]      FIG. 9  illustrates a simplified cross-sectional view of a nano-pattern mold positioned above a substrate at a second height. 
           [0018]      FIG. 10  illustrates a simplified perspective view of a nano-pattern structure formed on a substrate. 
           [0019]      FIG. 11A  illustrates a top down view of an exemplary rectangular column formed by using a first pattern and an overlaying pattern. 
           [0020]      FIG. 11B  illustrates a top down view of an exemplary hexagonal column formed by using a first pattern and overlaying patterns. 
           [0021]      FIGS. 12A-12C  illustrate a top down view of an exemplary first pattern, an exemplary second pattern, and an exemplary patterned surface formed by the first pattern and the second pattern. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Referring to  FIG. 1 , a system  10  to form a relief pattern on a substrate  12  is shown. Substrate  12  may be coupled to a substrate chuck  14 . As shown substrate chuck  14  is a vacuum chuck, however, substrate chuck  14  may be any chuck including, but not limited to, vacuum, pin-type, groove-type, or electromagnetic, as described in U.S. Pat. No. 6,873,087 entitled “High-Precision Orientation Alignment and Gap Control Stages for Imprint Lithography Processes,” which is incorporated herein by reference. Substrate  12  and substrate chuck  14  may be supported upon a stage  16 . Further, stage  16 , substrate  12 , and substrate chuck  14  may be positioned on a base (not shown). Stage  16  may provide motion along the x, y, and z axes. 
         [0023]    Spaced-apart from substrate  12  is a master patterning device  17 . Master patterning device  17  comprises a template  28  having a mesa  20  extending therefrom towards substrate  12  with a patterning surface  22  thereon. Further, mesa  20  may be referred to as a mold  20 . Mesa  20  may also be referred to as a nano-imprint mold  20 . In a further embodiment, template  28  may be substantially absent of mold  20 . In still a further embodiment, mold  20  may be integrally formed with template  28 . Template  28  and/or mold  20  may be formed from such materials including, but not limited to, fused-silica, quartz, silicon, organic polymers, siloxane polymers, borosilicate glass, fluorocarbon polymers, metal, and hardened sapphire. As shown, patterning surface  22  comprises features defined by a plurality of spaced-apart recesses  24  and protrusions  26 . However, in a further embodiment, patterning surface  22  may be substantially smooth and/or planar. Patterning surface  22  may define an original pattern that forms the basis of a pattern to be formed on substrate  12 . Master patterning device  17  may be formed employing electron beam (e-beam) lithography. 
         [0024]    Master patterning device  17  may be coupled to a chuck  28 , chuck  28  being any chuck including, but not limited to, vacuum, pin-type, groove-type, or electromagnetic, as described in U.S. Pat. No. 6,873,087 entitled “High-Precision Orientation Alignment and Gap Control Stages for Imprint Lithography Processes.” Further, chuck  28  may be coupled to an imprint head  30  to facilitate movement of master patterning device  17 . 
         [0025]    System  10  further comprises a fluid dispense system  32 . Fluid dispense system  32  may be in fluid communication with substrate  12  so as to deposit polymerizable material  34  thereon. System  10  may comprise any number of fluid dispensers, and fluid dispense system  32  may comprise a plurality of dispensing units therein. Polymerizable material  34  may be positioned upon substrate  12  using any known technique, e.g., drop dispense, spin-coating, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), thin film deposition, thick film deposition, and the like. Typically, polymerizable material  34  is disposed upon substrate  12  before the desired volume is defined between mold  20  and substrate  12 . However, polymerizable material  34  may fill the volume after the desired volume has been obtained. 
         [0026]    Polymerizable material  34  may comprise a solvent based monomer or a spin-on material. Further, polymerizable material  34  may comprise a monomer mixture as described in U.S. Pat. No. 7,157,036 entitled “Method to Reduce Adhesion Between a Conformable Region and a Pattern of a Mold” and United States patent application publication 2005/0187339 entitled “Materials for Imprint Lithography,” both of which are incorporated herein by reference. 
         [0027]    System  10  further comprises a source  38  of energy  40  coupled to direct energy  40  along a path  42 . Imprint head  30  and stage  16  are configured to arrange master patterning device  17  and substrate  12 , respectively, to be in superimposition and disposed in path  42 . System  10  may be regulated by a processor  54  that is in data communication with stage  16 , imprint head  30 , fluid dispense system  32 , and source  38 , operating on a computer readable program stored in memory  56 . 
         [0028]    The above-mentioned system and process may be further employed in imprint lithography processes and systems referred to in U.S. Pat. No. 6,932,934, U.S. Pat. No. 7,077,992, U.S. Pat. No. 6,900,881, United States patent application publication 2004/0124566, United States patent application publication 2004/0188381, and United States patent application publication 2004/0211754, all of which are incorporated by reference herein. In a further embodiment, the above-mentioned relief pattern may be created by any known technique, e.g., photolithography (various wavelengths including G line, I line, 248 nm, 193 nm, 157 nm, and 13.2-13.4 nm), contact lithography, e-beam lithography, x-ray lithography, ion-beam lithography and atomic beam lithography. For example, the above-mentioned relief pattern may be created using techniques described in U.S. Pat. No. 5,772,905, which is hereby incorporated by reference. 
         [0029]    Nano-structures with varying geometric cross-sections may be fabricated using techniques described herein. Generally, this process may include two phases. In Phase 1, a combination of multiple lithographic steps may be used to create an imprint template with shaped cross-sections (referred to here as nano-shaped templates). The multiple lithographic steps may use one or more kinds of lithography processes such as electron beam, imprint lithography or photolithography. In Phase 2, the nano-shaped template may be used in conjunction with an imprint lithography process to obtain a high-speed approach for replicating the nano-shapes. 
       Phase 1: Formation of Nano-Shaped Template 
       [0030]    Generally, Phase 1 may comprise multiple process steps. For simplification in description, the formation of the nano-shaped template is described herein using imprint lithography. However, it should be noted that the patterning steps may use photolithography, electron beam lithography, and the like. 
         [0031]    Generally, a thin layer of first material (e.g., non-wet strippable material), including polymers, dielectrics, metals, etc., may be deposited on a desired substrate made of a nano structure material. A layer of second resist (e.g., wet strippable material) may be deposited over the first material. The second resist may be selectively wet-stripped with the first material substantially remaining intact. A formable imprint lithography material may be deposited over the second resist material and the lithography material may be imprinted to form a relief pattern. The mold used to create the relief pattern using imprinting may be comprised of simple geometries formable from an e-beam process (e.g., lines, dots, holes, and the like). An optional adhesion material may be deposited between the second resist material and the third formable material to facilitate adhesion of the formable material to the underlying substrate. Adhesive layer may be formed of adhesion materials as further described in U.S. Publication No. 2007/0212494, which is hereby incorporated by reference. The relief pattern in the formable layer may be optionally etched to produce raised patterns of formable material, wherein the raised patterns have a smaller size as compared to the size prior to the etch. 
         [0032]    An overcoat material may be deposited over the etched formable layer. Overcoat material may be blanket etched to expose a top surface of the thin raised lines. The exposed formable material may be etched to form trenches extending down to the non wet strippable first resist material. Non-wet strippable resist may be dry etched stopping when the substrate is reached. The formable layer material and the wet strippable material may be stripped leaving the non-wet strippable material with trenches extending down to the substrate. The substrate may be etched down to a desired depth if a pattern in the surface is final. Finally, the imprint mold may be modified in form and/or orientation and the process is repeated from step  2  if the pattern in the surface is not final. 
         [0033]      FIGS. 2A-4B  illustrate an exemplary formation of a nano-shaped template having nano-patterned structures.  FIG. 2A  illustrates a cross-section view of a substrate  201  with resist layer  202  (e.g., a non-wet strippable) and resist layer  203  (e.g., a wet strippable) disposed over layer  202 . A formable material  204  may be deposited over the two resist layers and imprinted to form exemplary features (e.g., lines)  205  with spaces  208 , that may be of equal dimensions using system and methods described in relation to  FIG. 1 . 
         [0034]      FIG. 2B  illustrates a cross-section view of the multiplayer structure of  FIG. 2A  after the formable material  204  has been etched thereby thinning features  205  to form features that have a high aspect ratio of height to width. Substrate  201 , resist layer  202  and resist layer  203  are also visible in this view. 
         [0035]      FIG. 2C  illustrates a cross-section view of the multi-layer structure of  FIG. 2B  after an overcoat layer  206  has been applied over the surface to a height above the features  205 . This overcoat layer may be a silicon-containing polymer similar to the disclosure in the U.S. Pat. No. 7,186,656, which is hereby incorporated by reference. Substrate  201 , resist layer  202 , and resist layer  203  are again visible in this view. 
         [0036]      FIG. 3A  illustrates a cross-section view of the structure of  FIG. 2C  after overcoat layer  206  has been planarized to expose the tops of the features  205  above surface  207 . Substrate  201 , resist layer  202 , resist layer  203 , and overcoat layer  206  are visible in this view. 
         [0037]      FIG. 3B  illustrates a cross-section view of the structure of  FIG. 3A  after the formable material  204  has been etched through to resist layer  203 . Further, non-wet etching (e.g., with O 2 ) removes resist layer  202  in the trenches stopping at substrate  201 . Substrate  201 , resist layer  202 , resist layer  203 , formable layer  204 , and overcoat layer  206  are visible in this view. Channel  301  may be formed when features  205  are etched. Further, removal of the layers  202 - 204  in channel  301  may extend channel depth  302  to a surface of substrate  201 . 
         [0038]      FIG. 3C  illustrates a cross-section view of the structure in  FIG. 3B  after overcoat layer  206 , formable material  204 , and resist layer  203  have been stripped leaving only the resist layer  202  with grooves  304  to the substrate  201 . Forming nano-patterns or surface features of a particular shape may be provided by repeating the process steps of  FIG. 2A-FIG .  3 C until a desired surface pattern corresponding to the desired nanostructure(s) has been achieved. 
         [0039]      FIG. 4A  illustrates a cross-section view of the exemplary pattern of  FIG. 3C  etched to a particular depth forming grooves  401 . Substrate  201  and resist layer  202  are visible in this view.  FIG. 4B  illustrates a top view of grooves  401  in substrate  201 . 
         [0040]      FIG. 5A  illustrates a top view of the substrate  201  after processing with a first pattern  501  using process steps of  FIGS. 2A-4B . A rhombus shaped surface pattern  502  may thereby be formed using this process sequence. The trenches and surface pattern  502  may be used to increase the surface area of structure  500 . 
         [0041]      FIG. 5B  illustrates a top view of the substrate  201  after processing with an additional overlayed pattern  503  using process steps of  FIGS. 2A-4B . A triangular shaped surface pattern  504  may thereby be formed using this process sequence. The trenches and the surface pattern  504  may be used to increase the surface area of structure  510 . In another embodiment, the trenches are etched through thereby producing uniform nano-shaped patterns that have the triangular cross-section and a length corresponding to the substrate thickness. 
         [0042]      FIG. 6  is a flow diagram of process steps for formation of an exemplary nano-shaped template having nano-shaped structures. In step  601 , a thin layer of first resist may be deposited on a substrate. In step  602 , an overlay of second resist may be deposited. For example, second resist may include a wet strippable material, a soluble material, such as PMGI (Polymethylglutarimide), and/or the like. PMGI may be wet-stripped by tetramethylammonium hydroxide (TMAH) that may be obtained under the trade name CD260 from Shipley Company, L.L.C. (now Rohm Haas). Alternatively, the second resist may be any negative photoresist, for example poly hydroxyl styrene. Each resist layer may include an intermediate layer for adhesion purposes such as the material disclosed in U.S. Publication No. 2007/0212494. In step  603 , a layer of formable material may be deposited and imprinted with an imprint mold to form a third resist layer that has relief patterns of raised patterns separated by depressions as spaces. In one embodiment, the width of the raised patterns and spaces are equal. In step  604 , the relief pattern may be etched forming smaller raised patterns with a large height to width ratio. In step  605 , an overcoat of silicon-containing organic material may be applied to cover the raised lines. In one embodiment, overcoat layer may be a silicon-containing polymer similar to the disclosure in the U.S. Pat. No. 7,186,656. In step  606 , a blanket etch may expose the top surface of the raised lines. In step  607 , the formable material may be etched to form trenches down to the first resist material, which responds to a different etch chemistry. In step  608 , the first resist material may be dry etched (e.g., with oxygen) stopping at the substrate. In step  609 , the formable material and the second resist may be stripped leaving trenches through the first resist down to the substrate. In step  610 , a decision may be made if the pattern formed in the surface of the substrate is the final pattern. If the decision is NO, then in step  611 , the imprint mold may be modified either by an overlaying pattern, alterations to the current pattern, and/or rotation of an existing pattern. For example, a branch may be taken back to step  602  wherein some of the process steps may be repeated forming a second pattern overlaying the first pattern in the substrate. If the decision in step  610  is YES, then in step  612 , the substrate may be etched through the patterned first resist layer to a desired depth thereby forming a shaped nano-structure on the substrate. In step  613 , the first resist material may be stripped away. 
         [0043]    In another embodiment,  FIG. 6  may involve using a metal film (such as chromium). For example, the metal film may be included in Step  601 . Step  602  may be eliminated. Steps  604 - 608  may be as is in  FIG. 6 . However, step  609  may be replaced by a halogen and O 2  plasma ashing processes to remove all the organic materials leaving behind the etched pattern in the metal film. This process may be repeated as many times as needed to create nano-shapes. Additionally, an optional adhesion layer (described earlier) may be used just prior to the imprinting step in Step  603 . 
         [0044]    In another embodiment of the process of  FIG. 6 , Steps  604 - 606  may be eliminated and the formable imprinted material of Step  603  may be directly etched into materials put down in earlier steps (whether it is a wet strippable second material and a non-wet strippable first material or a metal film such as chromium used without the wet strippable material). This embodiment leads to patterns that have the opposite tone of the patterns obtained in the process steps  603 - 606  in  FIG. 6 . 
         [0045]    In another embodiment of the process of  FIG. 6 , Steps  601  and  602  may be eliminated and a metal film (e.g., chromium) may be deposited on the substrate. Formable material of Step  603  may be imprinted and etched, however, the pattern may be etched directly into the substrate. Steps  605 - 608  may be eliminated and formable material stripped leaving trenches in the metal film and the substrate. The process may then be repeated as many times as needed to create nano-shapes. 
         [0046]    The  FIGS. 2-5  illustrate process steps that result in a substrate with shaped nano-structures which are valuable in many applications. Nano-structures other than those shown may be produced by the method described herein and are considered within the scope of the present invention. Additionally, elements of process systems and methods disclosed in U.S. Pat. No. 7,186,656, U.S. Pat. No. 7,252,777, and U.S. Pat. No. 7,261,831, may be used to aid in formation of nano-structures, all of which are hereby incorporated by reference in their entirety. 
         [0047]    Exemplary nano-structures are illustrated in  FIGS. 11-12 . For example,  FIGS. 11A and 11B  illustrate shapes such as rectangles, squares, and hexagons that may be created. It should be noted that other shape may be formed including, but not limited to triangles, and any other fanciful shape. In  FIG. 11A , a first pattern  1100  may be overlayed by a second pattern  1102  providing a surface pattern  1104  having a plurality of nanoshapes  1106  having at least one sharp edge  1108 . In  FIG. 11B , first pattern  1100   a  may be overlayed by second pattern  1102  and additional pattern  1102   a.    
         [0048]    In some embodiments, the second pattern  1102  and/or additional patterns may be substantially similar to first pattern  1100 , for example, a rotation of the pattern. Alternatively, the second pattern  1102  and/or additional patterns may be substantial different than first pattern  1100 . For example,  FIG. 12A  illustrates first pattern  1100  and  FIG. 12B  illustrates second pattern  1102 . As shown in  FIG. 12C , overlay of first pattern  110  and second pattern  1102  may provide surface pattern  1104  having a plurality of nanoshapes  1106  having at least one sharp edge  1108 . 
         [0049]    The above detailed description describes a process where nano-patterns for a final product or for fabricating an imprint mold may be realized. For certain nano-patterns, it may not be practical to directly create a mold using a typical e-beam process. In this case, the disclosed process may be used to create a first imprint mold that has desired nano-patterns with desired sharp corners or edges. This first imprint mold may then be used to repeatedly pattern a new substrate to create more complex nano-patterns, again with the desired sharp corners or edges. Once the desired complex nano-patterns are achieved on the new substrate, it in turn may be used in a step and repeat process to fabricate a large area imprint mold that now is able to produce the complex nano-pattern for production that is both fast and cost effective. 
       Phase 2: Nano-Pattern Structure Replication 
       [0050]      FIGS. 7-10  illustrate side views of exemplary formation of nano-pattern structures  702 . Generally, polymerizable material  34  may be deposited on the surface  706  of a substrate  708  and contacted by a nano-pattern mold  700  to form the nano-pattern structures  702  using the imprint lithography process described herein in relation to  FIG. 1 . The nano-pattern structures  702  may include a residual layer  712  and features (e.g. protrusions  720  and/or recessions  722 ) having at least one sharp edge. Residual layer  712  may have a thickness t R . A thin residual layer  712  may reduce the occurrence of rounded features (e.g. protrusions  720 ) during subsequent processing of nano-pattern structures  702 . For example, residual layer  712  may have a thickness t R  of 1-25 nm to reduce the occurrence of rounded features. 
         [0051]    The residual layer thickness t R  may be controlled by the volume of polymerizable material  34 , surface energy, and/or the like. The description below outlines methods for controlling residual layer thickness t R  to reduce and/or eliminate occurrence of rounded features and provide sharp edges. 
       Volume Control 
       [0052]    The selection for the volume of polymerizable material  34  may be determined by three features: 1) drop volume, 2) drop spreading, and 3) template volume. 
         [0053]    Polymerizable material  34  may be a low viscosity polymerizable imprint solution having a pre-determined drop volume. Drop volume of polymerizable material  34  may be selected based on how far drops spread before contact between the nano-pattern mold  700  and substrate  708  due to high capillary forces at the perimeter of the drop. For example, polymerizable material  34  may have a drop volume of 0.5-50 cps. 
         [0054]    Drop spread is generally a function of the drop volume, volume of nano-pattern mold  700 , surface energy of nano-pattern mold  700  and/or surface energy of substrate  708 . For example, for a blank nano-pattern mold  700 , a 6 pl drop volume may provide a drop spread of approximately seven times the dispensed diameter of the drop. This drop volume may further result in the residual layer  712  having a range of between 10 and 15 nm. 
         [0055]    Generally, the residual layer may further be defined by the excess polymerizable material  34  above the volume of the nano-patterned mold  700  within the area that the drop will spread over a given time. In some cases, the volume of polymerizable material  34  per drop spread area may be significantly large compared to the volume of nano-patterned mold  700 . This may result in a thick residual layer  712 , e.g. &gt;5 nm. 
         [0056]    The surface energies enable the polymerizable material  34  to wet the nano-patterned mold  700  and surface  706  of the substrate  708  such that the polymerizable material  34  may be transported over large distances well in excess of the initial drop size, i.e. &lt;100 um diameter. Fluid movement once the nano-patterned mold  700  contacts the polymerizable material  34  may be driven by capillary action and the contact geometry between the nano-patterned mold  700  and substrate  708 . For example, drops may expand up to 6 or 7 times their drop diameter to form a uniform film. However, it is important there is not a great excess of monomer above the template volume, or the residual layer thickness will be &gt;5 nm. 
       Dummy Volume Fill Features 
       [0057]    Dummy volume fill features may be introduced in certain nano-patterned mold  700  regions to “soak” up the excess polymerizable material  34 . The need for such structures may be determined by the following equation. If the nano-patterned mold  700  feature volume is small compared to the local drop volume, dummy fill may be required for &lt;5 nm residual layer thickness t R . 
         [0058]    Definition of Variables 
         [0059]    r=the drop radius 
         [0060]    ri=as-dispensed drop radius 
         [0061]    is =drop spreading time 
         [0062]    t=time 
         [0063]    Vd=as-dispensed drop volume 
         [0064]    Vf=template feature volume 
         [0065]    df=template feature depth 
         [0066]    v=template duty cycle in the case of a grating 
         [0067]    af=area occupied by features 
         [0068]    RLT=residual layer thickness 
         [0069]    ad=drop spread area 
         [0070]    Residual layer thickness t R  over the area where a drop spreads for a grating structure is defined by: 
         [0000]        ad=[ri +( dr/dt )* ts]̂ 2 *v    
         [0000]        Vf=af*df/v  for the case of a grating structure 
         [0000]        RLT=[Vd −( af*df/v )]/{[ ri +( dr/dt )* ts]̂ 2 *v}   
         [0071]    If the residual layer thickness t R  is positive and &gt;5 nm, then dummy fill may be required such that Vf is on the order of the drop volume for a given spread area. If the residual layer thickness t R  is negative, then additional polymerizable material may be added. 
         [0072]    If the feature area is too small or etch depth too shallow for a given drop spread area, dummy fill may be required to consume the excess volume within the drop spread area. The drop spread area is a function of the feature area and depth and can limit the spread of a drop as the volume of the polymerizable material  34  is consumed. 
       Surface Energy 
       [0073]    The area over which the drop will spread may be a function of the surface energies between polymerizable material  34 , nano-patterned mold  700  and substrate  708 , the viscosity of the polymerizable material  34 , and/or capillary forces. If the capillary forces are high, spreading may occur fast and as such may require low viscosity fluids and a thin film within the drop area. 
         [0074]    To enable efficient fluid spreading and feature filling, the contact angles of the polymerizable material  34  with the nano-patterned mold  708  and/or substrate  708  may be controlled. The contact angles may be managed by applying Transpin™ or ValMat™ adhesion promoters to the substrate  708 , and through the use of surfactants in the polymerizable material  34  that may coat the nano-patterned mold  700 . As such, the contact angle of the polymerizable material  34  with the nano-patterned mold  700  may be about &lt;500, while the contact angle of the polymerizable material  34  with the substrate  708  may be about &lt;150. The contact angles as a measure of surface energies may enable the features of the nano-patterned mold  700  to readily fill the nano-patterned mold  700  and the polymerizable material  34  to readily spread large distances over the substrate  708 . Long distance spreading may be controlled by surface energies, viscosity and capillary forces. The ability to control surface energies may enable the monomer to spread over large distances. 
       Formation of Nano-Shaped Structures 
       [0075]      FIGS. 7A and 7B  illustrate nano-pattern mold  700  positioned above substrate  708  having polymerizable material  34  deposited thereon. Nano-pattern mold  700  may have features (e.g., recessions  714  and/or protrusions  716 ). Recessions  714  and/or protrusions  716  may be formed having sharp edges using the process described herein. For example, nano-pattern mold  700  may be formed having recessions  714  in a triangular shape as illustrate in  FIG. 7B . Although a triangular shape is illustrated, it should be noted that any shape having sharp edges and features may be formed including, but not limited to, rectangular, hexagonal, or any other fanciful shape. 
         [0076]      FIGS. 8-9  illustrate the spread of polymerizable material  34  as nano-pattern mold  700  positioned at a height h 1  ( FIG. 8 ) moves to height h 2  ( FIG. 9 ). Nano-pattern mold  700  may have a thickness t N . For example, nano-pattern mold  700  may have a thickness of 0.5 mm-10 mm. 
         [0077]    The spreading of polymerizable material  34  during movement of the nano-pattern mold  700  from height h 1  to height h 2  is generally capillary driven with some additional applied forces. For example, an amount of force F may be provided by imprint head  38  (shown in  FIG. 1 ) on nano-pattern mold  700  to position nano-pattern mold  700  at height h above substrate  708 . The force F, however, may be minimal (e.g. 0-10 N). Additionally, chuck  28  (shown in  FIG. 1 ) may apply pressure P. Pressure P may also be just enough to provide suitable positioning of nano-pattern mold  700  without substantial bowing or other substantial deformations. For example, pressure P may be approximately 0-0.1 atm. Minimal applied forces (e.g., force F and pressure P) may reduce deformation of the residual layer  712 . Additionally, it should be noted, that chuck  14  may provide minimal force to substrate  12  to reduce deformation of residual layer  712  during formation and separation of nano-pattern structure  702 . 
         [0078]      FIG. 10  illustrates the formed nano-pattern structure  702  with residual layer  712  having thickness t R  and protrusions  720  having sharp edges. It should be noted that with such thin residual layers, and the fact that adhesion layers may be 1 nm thick, pattern transfer that begins with the substrate etch and no descum is enabled. To this end, an imprint pattern transfer manufacturing process may include: Vapor coat adhesion layer (1 nm thick), drop on demand resist dispense (dispense pattern and monomer volume is based on template volume calculation), imprint patterning (dummy fill if needed) with &lt;5 nm RLT, substrate only etch (no descum), strip and clean substrate. It should be noted that if a descum etch is needed, it may be for removing a thin residual film, and as such may not impact the shape of the shaped nano-structures substantially. This may allow for etching of the substrate while retaining the nano-shapes present in the mold. This is in contrast to conventional imprint lithography wherein the following steps are taken: Vapor coat adhesion layer (1 nm thick), spin on imprint material, imprint patterning&gt;5 nm RLT, substantial imprint resist descum (by O 2  plasma), substrate etch, strip and clean substrate. 
         [0079]    Embodiments of the present invention described above are exemplary. Many changes and modifications may be made to the disclosure recited above while remaining within the scope of the invention. Therefore, the scope of the invention should not be limited by the above description, but instead should be determined with reference to any appended claims along with their full scope of equivalents.