Abstract:
The present application describes a template with feature profiles that have multiple sidewall angles. The multiple sidewall angles facilitate control over critical dimensions and reduce issues related to template release.

Description:
CROSS RELATION TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/107,360 filed Oct. 22, 2008, which is hereby incorporated by reference herein. 
     
    
     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 Application Publication No. 2004/0065976, U.S. Patent Application Publication No. 2004/0065252, and U.S. Pat. No. 6,936,194, all of which are hereby incorporated by reference herein. 
         [0004]    An imprint lithography technique disclosed in each of the aforementioned U.S. patent application publications and patent includes formation of a relief pattern in a formable (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 the formable liquid applied between the template and the substrate. 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 
         [0005]    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. 
           [0006]      FIG. 1  illustrates a simplified side view of a lithographic system in accordance with embodiments of the present invention. 
           [0007]      FIG. 2  illustrates a simplified side view of the substrate shown in  FIG. 1  having a patterned layer positioned thereon. 
           [0008]      FIGS. 3A-F  illustrate a simplified view of a process flow for fabricating a template in accordance with embodiments of the present invention. 
           [0009]      FIG. 4  illustrates a flowchart for fabricating a template. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Referring to  FIG. 1 , illustrated therein is a lithographic system  10  used to form a relief pattern on substrate  12 . Substrate  12  may be coupled to 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 herein. 
         [0011]    Substrate  12  and substrate chuck  14  may be further supported by stage  16 . Stage  16  may provide motion along the x-, y-, and z-axes. Stage  16 , substrate  12 , and substrate chuck  14  may also be positioned on a base (not shown). 
         [0012]    Spaced-apart from substrate  12  is a template  18 . Template  18  generally includes a mesa  20  extending therefrom 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 . 
         [0013]    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 . 
         [0014]    System  10  may further comprise a fluid dispense system  32 . Fluid dispense system  32  may be used to deposit 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  20  and substrate  12  depending on design considerations. Polymerizable material  34  may comprise a monomer mixture as described in U.S. Pat. No. 7,157,036 and U.S. Patent Application Publication No. 2005/0187339, all of which are hereby incorporated by reference herein. 
         [0015]    Referring to  FIGS. 1 and 2 , system  10  may further comprise an energy source  38  coupled to direct energy  40  along 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 memory  56 . 
         [0016]    Either imprint head  30 , stage  16 , or both vary a distance between mold  20  and substrate  12  to define a desired volume therebetween 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  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 a thickness t 1  and residual layer  48  having a thickness t 2 . 
         [0017]    The above-described system and process may be further implemented in imprint lithography processes and systems referred to in U.S. Pat. No. 6,932,934, U.S. Patent Application Publication No. 2004/0124566, U.S. Patent Application Publication No. 2004/0188381, and U.S. Patent Application Publication No. 2004/0211754, each of which is hereby incorporated by reference herein. 
         [0018]    During nano-imprint processing, physical separation of template  18  from patterned layer  46  may sometimes result in cohesive failure of patterned layer  46 , particularly when the aspect ratio of the features (protrusions  50  and recessions  52 ) of patterned layer  46  is high (i.e., greater than 2:1). The cohesive failure can be observed at the base of the resist feature (e.g., protrusion  50  and recessions  52 ), where the feature (e.g., protrusion  50  and recession  52 ) attaches to residual layer  48 . 
         [0019]    More specifically, upon separation of template  18  from patterned layer  46 , forces such as adhesive forces may be present between template  18  and patterned layer  46 , and more specifically, between mold  20  and protrusions  50  and recessions  52 . The adhesive forces therebetween may be of such a magnitude that upon separation of template  18  and patterned layer  46 , the features (protrusions  50  and recession  52 ), of patterned layer  46  may be compromised, distorted, or damaged. To that end, it may be desired to reduce, if not prevent, any undesirable alterations to the features of patterned layer  46  upon separation of template  18  from patterned layer  46 . 
         [0020]      FIGS. 3A-F  illustrate an embodiment of the present application, which produces a template with a feature profile that has a shallower sidewall angle at the base of the resist feature (protrusions  50  and recession  52 ) where cohesive failure is likely to occur, while maintaining a more vertical sidewall near the middle to top part of the resist feature where pattern transfer is typically defined. 
         [0021]    Referring to  FIG. 3A , a multi-layered structure  80  is shown. Multi-layered structure  80  may be employed to form template  18 , which is described below. Multi-layered structure  80  comprises a body  60 , a hardmask layer  62 , and a patterned layer  64 , with hardmask layer  62  being positioned between body  60  and patterned layer  64 . In an embodiment, body  60  may be formed from fused silica. In an embodiment, hardmask layer  62  may be formed from a metal such as chromium and further sputtered-coated on body  60  to a thickness of 5-15 nanometers. In an embodiment, patterned layer  64  may comprise a plurality of protrusions  72  and recessions  74  defining a pattern  75 , with recessions  74  exposing portions  76  of hardmask layer  62 . Further recessions  74  may have a first width w 1  associated therewith. In an embodiment, patterned layer  64  may be a position-tone electron beam resist, such as ZEP520A available from Nippon Zeon Corporation. 
         [0022]    In an example, electron beam lithography may be employed to form pattern  75  in patterned layer  64 . Thus, areas that are imaged by the electron beam (recessions  74 ) may be soluble in a developer solution. Such solutions may comprise, but is not limited to, amyl acetate and xylenes. 
         [0023]    Referring to  FIG. 3B , multi-layered structure  80  may be subjected to an etching process to transfer the features thereof into hardmask layer  62 , defining multi-layered structure  180 . More specifically, pattern  75  of patterned layer  64  may be transferred into hardmask layer  62 , and thus segments of exposed portions  76  of hardmask layer  62 , shown in  FIG. 3   a , may be removed, defining a pattern  175  within hardmask layer  62 , with recessions  74  exposing portions  81  of body  60 . Segments of exposed portion  76  of hardmask layer  62  may be removed such that recessions  74  may have a second width w 2  at an interface  77  of hardmask layer  62  and patterned layer  64  and a third width w 3  at an interface  79  of hardmask layer  62  and body  60 , with the hardmask layer  62  varying in width therebetween. In an implementation, the varying of the width of hardmask layer  62  is substantially linear; however in a further implementation, the varying of the width of hardmask layer  62  may substantially not be linear. The second width w 2  may be substantially the same as the first width w 1 , and the third width w 3  may be less than the first width w 1  or the second width w 2 . To that end, the etching process may be a chlorine/oxygen reactive ion etch (RIE) including both single step and multi-step processes. 
         [0024]    Referring to  FIG. 3C , multi-layered structure  180 , shown in  FIG. 3B , may be subjected to an etching process to transfer the features thereof into body  60 , defining multi-layered structure  280 . More specifically, pattern  175  of hardmask layer may be transferred into body  60 , and thus segments of exposed portions  81  of body  60 , shown in  FIG. 3B , may be removed, defining a pattern  275  within body  60 . Segments of exposed portions  81  may be removed such that recessions  74  have a fourth width w 4  with respect to body  60 . The fourth width w 4  may be substantially the same as the third width w 3 . Further, segments of exposed portions  81  may be removed such that body  60  has a first height h 1  in superimposition with recessions  74  and a second height h 2  in superimposition with protrusions  72 . To that end, the etching process may be a dry etching process comprising a fluorine-based etch using Freon-23 (trifluoromethane, CHF 3 ) or sulfur hexafluoride (SF 6 ) combined with an inert diluent, such as argon or nitrogen. 
         [0025]    Referring to  FIG. 3D , patterned layer  64  may be removed, defining multi-layered structure  380 . The patterned layer  64 , shown in  FIG. 3C , may be removed employing a low power oxygen-rich RIE. 
         [0026]    Referring to  FIG. 3E , multi-layered structure  380  may be subjected to a further etching process to further define features in body  60 , defining multi-layered structure  480 . More specifically, protrusions  72  are subjected to an etching process such that recessions  74  in superimposition with a first section  83  of body  60  have the fourth width w 4  and recessions  74  at interface  79  of hardmask layer  62  and body  60  having a fifth width w 5 , with recessions  74  in superimposition with a second section  84  of body  60  having a varying width between the fourth width w 4  and the fifth width w 5 . In an implementation, the varying of the width of second section  84  is substantially linear; however, in a further embodiment, the varying of the width of second section  84  is not substantially linear. Moreover, segments of exposed portions  81  of body  60  in superimposition with recessions  74  may be further removed such that body  60  has a third height h 3  in superimposition with recessions  74 . This is analogous to deepening recessions  74 . 
         [0027]    Referring to  FIG. 3F , hardmask layer  62 , shown in  FIG. 3E , may be removed, defining multi-layered structure  580 . The hardmask layer  62 , shown in  FIG. 3E , may be removed employing a chromium wet etch, such as a ceric ammonium nitrate solution. 
         [0028]    To that end, multi-layered structure  580  is shown having protrusions  72  having a sidewall  89 , with sidewall  89  having a varied width associated therewith. More specifically, a first segment  91  of protrusions  72  has a sixth width w 6  associated therewith. Sixth width w 6  is substantially constant throughout first segment  91  of protrusions  72 . Further, protrusions  72  have a seventh width w 7  at a surface  95  thereof, with a second segment  93  of protrusions  72  having a varying width between the sixth width w 6  and the seventh width w 7 . Second segment  93  is positioned between first segment  91  and surface  95 . In an implementation, the varying of the width of second segment  93  of protrusions  72  is substantially linear; however, in a further embodiment, the varying of the width of second segment  93  of protrusions  72  is not substantially linear. The seventh width w 7  may be less than the sixth width w 6 . 
         [0029]    Further, an angle φ 1  of portion  96  of sidewall  89  with respect to the horizontal may be approximately 45°; and in a further embodiment, may be within a range of approximately 45°-80°; and in still a further embodiment, may be within a range of approximately 60°-70°. Moreover, the angle φ 1  of portion  96  of sidewall  89  is chosen to facilitate a low release force with respect to patterned layer  46 . Further, an angle φ 2  of portion  97  of sidewall  89  with respect to the horizontal may be approximately 90°; however in a further embodiment, may be within a range of approximately 80°-90°; and in still a further embodiment, may be within a range of approximately 85°-89°. 
         [0030]    To that end, multi-layered structure  580  corresponds to template  18  shown in  FIG. 1 . Template  18  corresponds to body  60 ; mesa/mold  20  corresponds to mesa/mold  99 ; recess  24  corresponds to recess  74 ; and protrusion  26  corresponds to protrusion  72 . As a result of multi-layered structure  580  (template  18 ) having protrusions  72  with a varying width of a second segment  93 , separation of multi-layered structure  580  with patterned layer  46 , shown in  FIG. 2 , is facilitated. Effectively, the aspect ratio of a feature, such as the recess and the protrusion, at the place where it is attached to residual layer  48  is lower. Features of higher aspect ratio (thinner critical dimension) have a higher probability of experiencing adhesive/cohesive failure upon separation. 
         [0031]    Referring to  FIG. 4 , a process  400  of creating template  18  is shown. The process  400  is illustrated as a collection of referenced acts arranged in a logical flow graph. The order in which the acts are described is not intended to be construed as a limitation, and any number of the described acts can be combined in other orders and/or in parallel to implement the process. 
         [0032]    At step  402 , a multi-layered structure is created by positioning a hard mask layer and patterned layer on a body, the hardmask layer being positioned between the body and the patterned layer. Further, the multi-layered structure comprising a plurality of protrusions and recessions, the recession exposing portions of the hardmask layer. 
         [0033]    At step  404 , segments of the portions of the hardmask layer are removed to define a first width at a first interface of the hardmask layer and the patterned layer and a second width at a second interface of the hardmask layer and the body. 
         [0034]    At step  406 , a pattern of the hardmask layer is transferred into the body, with the recession in superimposition with the body having the second width. 
         [0035]    At step  408 , the patterned layer is removed. 
         [0036]    At step  410 , portions of the body are removed such that the recessions have the second width at a first section of the body; a third width at the second interface; and a varying width at a second section of the body between the first section and the second interface. 
         [0037]    At step  412 , the hardmask layer may be removed. 
       CONCLUSION 
       [0038]    Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter 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 claims.