Abstract:
Non-uniformity may be minimized by reducing or eliminating non-uniform evaporation of a viscous liquid disposed on the surface of a substrate. At least one gas source component and one vacuum component may provide a mass flow rate of gas across the surface of the substrate to reduce or eliminate non-uniform evaporation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority to, and the benefit of, U.S. Provisional Application No. 61/106,676 filed Oct. 20, 2008, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND INFORMATION 
       [0002]    Nano-fabrication includes the fabrication of very small structures that have features on the order of 100 nanometers or smaller. One application in which nano-fabrication has had a sizeable impact is in the processing of integrated circuits. The semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, therefore nano-fabrication becomes increasingly important. Nano-fabrication provides greater process control while allowing continued reduction of the minimum feature dimensions of the structures formed. Other areas of development in which nano-fabrication has been employed include biotechnology, optical technology, mechanical systems, and the like. 
         [0003]    An exemplary nano-fabrication technique in use today is commonly referred to as imprint lithography. Exemplary imprint lithography processes are described in detail in numerous publications, such as U.S. Patent Publication No. 2004/0065976, U.S. Patent Publication No. 2004/0065252, and U.S. Pat. No. 6,936,194, all of which are hereby incorporated by reference. 
         [0004]    An imprint lithography technique disclosed in each of the aforementioned U.S. patent publications and patent includes formation of a relief pattern in a polymerizable layer and transferring a pattern corresponding to the relief pattern into an underlying substrate. The substrate may be coupled to a motion stage to obtain a desired positioning to facilitate the patterning process. The patterning process uses a template spaced-apart from the substrate and a formable liquid applied between the template and the substrate. The region between the template and substrate is subjected to an inert gas flow to remove non-gas flow molecules prior to bringing the template in contact with the formable liquid. The inert gas flow may include carbon dioxide, nitrogen, hydrogen, helium, Freon, neon, or argon gases. A non-symmetrical flow of inert gas or a non-symmetrical pressure gradient across the substrate results in non-uniform evaporation of the formable liquid, which may result in a non-uniform imprint residual thickness layer. Accordingly, additional formable liquid is selectively added to the substrate to account for the non-uniform evaporation of the formable liquid. 
         [0005]    The formable liquid is solidified to form a rigid layer that has a pattern conforming to a shape of the surface of the template that contacts the formable liquid. After solidification, the template is separated from the rigid layer such that the template and the substrate are spaced-apart. The substrate and the solidified layer are then subjected to additional processes to transfer a relief image into the substrate that corresponds to the pattern in the solidified layer. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0006]    So that the present invention may be understood in more detail, a description of embodiments of the invention is provided with reference to the embodiments illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the invention, and are therefore not to be considered limiting of the scope. 
           [0007]      FIG. 1  illustrates a simplified side view of an embodiment of a lithographic system in accordance with the present invention. 
           [0008]      FIG. 2  illustrates a simplified side view of the substrate shown in  FIG. 1  having a patterned layer positioned thereon. 
           [0009]      FIG. 3  illustrates a template chuck with gas and vacuum nozzles positioned all around. 
           [0010]      FIG. 4  illustrates an exemplary template chuck in accordance with an embodiment of the present invention for a smaller sized template. 
           [0011]      FIG. 5  illustrates an exemplary template chuck in accordance with an embodiment of the present invention for a larger sized template. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIG. 1 , illustrated therein is a lithographic system  10  used to form a relief pattern on a substrate  12 . Substrate  12  may be coupled to a substrate chuck  14 . As illustrated, substrate chuck  14  is a vacuum chuck. Substrate chuck  14 , however, may be any chuck including, but not limited to, vacuum, pin-type, groove-type, electromagnetic, and/or the like. Exemplary chucks are described in U.S. Pat. No. 6,873,087, which is hereby incorporated by reference. 
         [0013]    Substrate  12  and substrate chuck  14  may be further supported by stage  16 . Stage  16  may provide motion about the x-, y-, and z-axes. Stage  16 , substrate  12 , and substrate chuck  14  may also be positioned on a base (not shown). 
         [0014]    Spaced-apart from substrate  12  is a template  18 . Template  18  generally includes a mesa  20  extending there from towards substrate  12 , mesa  20  having a patterning surface  22  thereon. Further, mesa  20  may be referred to as mold  20 . Template  18  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, hardened sapphire, and/or the like. As illustrated, patterning surface  22  comprises features defined by a plurality of spaced-apart recesses  24  and/or protrusions  26 , though embodiments of the present invention are not limited to such configurations. Patterning surface  22  may define any original pattern that forms the basis of a pattern to be formed on substrate  12 . 
         [0015]    Template  18  may be coupled to chuck  28 . Chuck  28  may be configured as, but not limited to, vacuum, pin-type, groove-type, electromagnetic, and/or other similar chuck types. Exemplary chucks are further described in U.S. Pat. No. 6,873,087, which is hereby incorporated by reference herein. Further, chuck  28  may be coupled to imprint head  30  such that chuck  28  and/or imprint head  30  may be configured to facilitate movement of template  18 . 
         [0016]    System  10  may further comprise a fluid dispense system  32 . Fluid dispense system  32  may be used to deposit a polymerizable material  34  on substrate  12 . Polymerizable material  34  may be positioned upon substrate  12  using techniques such as drop dispense, spin-coating, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), thin film deposition, thick film deposition, and/or the like. Polymerizable material  34  may be disposed upon substrate  12  before and/or after a desired volume is defined between mold  22  and substrate  12  depending on design considerations. Polymerizable material  34  may comprise a monomer as described in U.S. Pat. No. 7,157,036 and U.S. Patent Publication No. 2005/0187339, all of which are hereby incorporated by reference. An exemplary composition, as incorporated by reference herein from U.S. Pat. Pub. 2005/0187339, has a viscosity associated therewith and further including a surfactant, a polymerizable component, and an initiator responsive to a stimuli to vary said viscosity in response thereto, with said composition, in a liquid state, having said viscosity being lower than 100 centipoises, a vapor pressure of less than 20 Torr, and in a solid cured state, a tensile modulus of greater than 100 MPa, a break stress of greater than 3 MPa, and an elongation at break of greater than 2%. 
         [0017]    Referring to  FIGS. 1 and 2 , system  10  may further comprise an energy source  38  coupled to direct an energy  40  along a path  42 . Imprint head  30  and stage  16  may be configured to position template  18  and substrate  12  in superimposition with path  42 . System  10  may be regulated by a processor  54  in communication with stage  16 , imprint head  30 , fluid dispense system  32 , and/or source  38 , and may operate on a computer-readable program stored in a memory  56 . 
         [0018]    Either imprint head  30 , stage  16 , or both vary a distance between mold  20  and substrate  12  to define a desired volume there between that is filled by polymerizable material  34 . For example, imprint head  30  may apply a force to template  18  such that mold  20  contacts polymerizable material  34 . After the desired volume is filled with polymerizable material  34 , source  38  produces energy  40 , e.g., broadband ultraviolet radiation, causing polymerizable material  34  to solidify and/or cross-link conforming to shape of a surface  44  of substrate  12  and patterning surface  22 , defining a patterned layer  46 , as shown in  FIG. 2 , on substrate  12 . Patterned layer  46  may comprise a residual layer  48  and a plurality of features shown as protrusions  50  and recessions  52 , with protrusions  50  having thickness t 1  and residual layer  48  having a thickness t 2 . 
         [0019]    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. Patent Publication No. 2004/0124566, U.S. Patent Publication No. 2004/0188381, and U.S. Patent Publication No. 2004/0211754, each of which is hereby incorporated by reference herein. 
         [0020]    Referring to  FIG. 3 , a gas and vacuum system  300  may also be implemented to provide one or more sources of inert gases, such as carbon dioxide, nitrogen, hydrogen, helium, Freon, neon, argon, and/or the like, and/or one or more sources of a vacuum, which may be applied during various stages of the aforementioned processes. One example of application of inert gases is further described in U.S. Pat. No. 7,090,716, which is hereby incorporated by reference herein in its entirety. 
         [0021]    System  300 , or any portion thereof, may be under control of algorithms in programs stored in memory  56  and run in processor  54 .  FIG. 3  illustrates a plan view of chuck  28  and template  18  showing a positioning of one or more nozzles  301 ,  302  around a periphery of the chuck  28 . For example, gas nozzles  301  and vacuum nozzle  302  may be coupled to system  300  shown in  FIG. 1 .  FIG. 1  only shows a pair of nozzles  301 ,  302  for the sake of simplicity of illustration and should not be considered limiting as multiple pairs of nozzles  301 ,  302  and/or singular nozzles  301  or  302  may be used. Further, other means for transporting a gas and/or vacuum to the imprinting area in system  10  may be used to achieve a similar transportation function. 
         [0022]    Nozzles  301 ,  302  may be positioned on one, two, three, or all four sides of the chuck  28  (or any number of sides of chuck  28 , should its shape have other than four sides). Although  FIG. 3  illustrates nozzles  301 ,  302  on four sides, nozzles may be limited to less than four sides or greater than four sides. For example, nozzles  301 ,  302  may be disposed radially around periphery of substrate  12  or template  18  having square, rectangular, triangular or any fanciful shape, and as such, may result in less than or greater than four sides. In one embodiment, nozzles  301  may be positioned as opposing pairs. For example, a first nozzle  301  may be positioned on side  504  with an opposing second nozzle  301  positioned on side  502  directly opposite first nozzle  301 . First nozzle  301  and second nozzle  301  may be positioned perpendicular to side  504  and  502  of template  18  respectively. Alternatively, first nozzle  301  and second nozzle  301  may be positioned at an angle to side  504  and  502  of template  18  respectively. 
         [0023]    Voids in the patterned layer  46  that are filled with inert gas molecules may disappear with a higher rate due to the higher rate of diffusion and/or dissolution of inert gases into the monomer  34 . As such, an inert gas environment may be created between the template  18  and the substrate  12 . For example, nozzles  301 ,  302  located near three sides (e.g., sides  501 ,  502 , and  503 ) of the template  18  may be adjusted to provide inert gas subsequent to dispensing of monomer  34  on substrate  12  in relation to  FIGS. 1 and 2 . For example, nozzles  301 ,  302  located near sides  501 ,  502 , and/or  503  may be adjusted to provide inert gas substantially simultaneously after the monomer  34  is dispensed onto the substrate  12 . Alternatively, nozzles  301 ,  302  located near sides  501 ,  502 , and/or  503  may be adjusted to provide inert gas at consecutive times after the monomer  34  is dispensed onto the substrate  12 . 
         [0024]    Imprint head  30  may remain at a distance from substrate  12  to provide a dwell time in which inert gas may fill volume between template  18  and substrate  12 . Imprint head  30  may then be positioned toward substrate  12  such that distance between template  18  and substrate  12  is reduced. Template  18  may be placed in contact with monomer  34  facilitating spread of monomer between template  18  and substrate  12 . Nozzles  301 ,  302  may be adjusted to discontinue inert gas flow subsequent to spreading of monomer  34  between template  18  and substrate  12 . 
         [0025]    As can be noted, imprint throughput (how quickly the imprint process can be completed so that a next substrate  12  can be processed) may be affected by, inter alfa, inert gas dwell time. For example, the longer the dwell time the fewer amount of substrates  12  may be processed per unit of time. Additionally, inert gas molecules may escape from side  504  of template  18 . During the flow of inert gas, a portion of the monomer  34  dispensed on the substrate  12  in proximity to the fourth side  504  may evaporate, or may evaporate at a higher rate than monomer  34  dispensed in proximity to the first through third sides  501 - 503 . The higher rate of monomer  34  evaporation loss on the fourth side  504  may likely impact the resultant uniformity of the imprint residual layer thickness (RLT). 
         [0026]    Referring again to  FIGS. 1 and 3 , embodiments of the present invention may establish an inert gas environment that eliminates or minimizes dwell time. In one embodiment, system  300  may adjust flow of inert gas from nozzles  301  (e.g., simultaneously) located on the sides (e.g., four sides) of template  18  and template chuck  38  after monomer  34  is dispensed on the substrate  12 . For example, flow of inert gas for each nozzle may be between approximately 5 slm and 20 slm. In another example, the inert gas flow may be configured to instantaneously achieve a threshold concentration of inert gas in a region above the substrate  12  (e.g., the threshold concentration in the region above the substrate  12  may be greater than or equal to approximately 90%). 
         [0027]    Imprint head  30  may be positioned toward the substrate  12  when a region above substrate  12  exceeds a threshold concentration of the inert gas. Template  18  may be positioned towards substrate  12  at a velocity between 1 mm/sec and 50 mm/sec. Monomer  34  may spread between template  18  and substrate  12 . System  300  may then reduce flow of inert gas. 
         [0028]    Polymerizable material  34  may evaporate in a substantially uniform fashion, and as such, there may be no need for compensation of thickness t 2  of residual layer  48  resulting from evaporation of monomer  34 . For example, pressure gradient of inert gas may be symmetrically distributed such that there is no significant unsymmetrical gas flow from center of template  18  towards edge of mold  20  prior to contact of template  18  to monomer  34  as described in relation to  FIGS. 1 and 2 . Symmetrical distribution of pressure or gas flow may substantially prevent non-uniform evaporation of monomer  34 . Adding monomer  34  to specific portions of substrate  12  to account for non-uniform evaporation may no longer be required. Also, evaporation may be substantially limited once template  18  is in contact with monomer  34  as template  18  and substrate  12  conform to each other in a very short time avoiding further evaporation of monomer  34 . 
         [0029]    Gas flow may be driven by a pressure gradient. For example, moving velocity of gas flow may be proportional to the pressure increase at gas nozzle  301  and/or gas nozzles  301 ,  302  distributed around template  18  as illustrated in  FIG. 3 . Using gas nozzles  301 ,  302  from sides  501 - 504  of template  18  may provide a high-pressure region within the center of the region between template  18  and substrate  12 . In one example, a pressure gradient may be symmetrically decreasing from a center of the high-pressure region towards the edge of template  18 . Reducing the gas flow velocity or minimizing the pressure gradient between template  18  and substrate  12  may reduce the evaporation rate of the liquid monomer  34 . As such, a substantially uniform residual layer  48  may be provided. 
         [0030]    In the method as described above, an inert gas was purged from three sides ( 501 - 503 ) of the template  18 . Since a substantially uniform fluid film is generally desired, the evaporated monomer  34  had to be compensated for by adding more monomer  34  in those areas based on a model of the evaporation. It should be noted that a drop pattern for deposition of monomer  34  may be simplified as compensation for evaporation of monomer  34  may be reduced by providing gas flow as described herein. For example, a substantially uniform evaporation profile may be created by using system  300  and methods to provide symmetrical pressure gradient and/or a known unsymmetrical pressure gradient. As such, additional compensation of monomer  34  due to evaporation may be minimized and/or eliminated. 
         [0031]    Referring to  FIGS. 4 and 5 , for a template  518  having an increase in area as compared to template  18  of  FIG. 1 , inert gas pressure drop (e.g., the fluid flow based on pressure differentials, such as those from areas of high pressure to areas of low pressure; the pressure drop is this pressure differential between the area of high pressure and the area of low pressure) may be increased by adding one or more vacuum nozzles  302  on the one side of template  18  to vacuum gas molecules from the opposite side. For example, nozzles  302  may operate in the range of approximately −10 kPa to −80 kPa. 
         [0032]    For example,  FIG. 4  shows gas nozzles  301  around the periphery of template chuck  28  for template  18 .  FIG. 5  shows template  518 , wherein vacuum nozzles  302  may be positioned on a single side  504  of chuck  28 . An inert gas environment may be established. For example, system  300  may be adjusted to provide a gas flow from nozzles  301  located on side  501 , side  503 , and/or bottom side  502  of template  18  (e.g., simultaneously, consecutively). System  300  may be adjusted to provide gas flow from nozzles  302  located at side  504  of template  18  and/or chuck  28 . Imprint head  30  may be positioned toward substrate  12 . For example, template  18  may be positioned toward substrate  12  at a velocity between 1 mm/sec and 50 mm/sec. System  300  may adjust nozzles  302  located at side  504  of template  18  to reduce gas flow. System  300  may adjust nozzles  301  located at side  504  of template  18 . Monomer may spread between template  18  and substrate  12 . System  300  may adjust nozzles  301  to reduce gas flow once spread of monomer  34  is complete. 
         [0033]    Although the device and method has been described in language specific to structural features and/or methodological acts, it is to be understood that the method defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the claimed system and method.