Abstract:
The present invention is directed towards a template, transmissive to energy having a predetermined wavelength, having first and second opposed sides and features a coating disposed thereon to limit the volume of the template through which the energy may propagate. In a first embodiment, the template includes, inter alia, a mold, having a plurality of protrusions and recessions, positioned on a first region of the first side; and a coating positioned upon a second region of the first side, with the coating having properties to block the energy from propagating between the first and second opposed sides.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The field of the invention relates generally to micro-fabrication techniques. More particularly, the present invention is directed to a template suitable for use in imprint lithography.  
         [0002]     The prior art is replete with examples of micro-fabrication techniques. One particularly well known micro-fabrication technique is imprint lithography. Imprint lithography is described in detail in numerous publications, such as United States published patent application 2004/0065976 filed as U.S. patent application Ser. No. 10/264,960, entitled “Method and a Mold to Arrange Features on a Substrate to Replicate Features having Minimal Dimensional Variability”; United States published patent application 2004/0065252 filed as U.S. patent application Ser. No. 10/264,926, entitled “Method of Forming a Layer on a Substrate to Facilitate Fabrication of Metrology Standards”; and United States published patent application 2004/0046271 filed as U.S. patent application Ser. No. 10/235,314, entitled “Method and a Mold to Arrange Features on a Substrate to Replicate Features having Minimal Dimensions Variability”; all of which are assigned to the assignee of the present invention. The fundamental imprint lithography technique as shown in each of the aforementioned published patent applications includes formation of a relief pattern in a polymerizable layer and transferring a pattern corresponding to the relief pattern into an underlying substrate. To that end, a template, having a mold, is employed. The mold is spaced-apart from, and in superimposition with, the substrate with a formable liquid present therebetween. The liquid is patterned and solidified to form a solidified layer that has a pattern recorded therein that is conforming to a shape of the mold. The substrate and the solidified layer may then be subjected to processes to transfer, into the substrate, a relief image that corresponds to the pattern in the solidified layer.  
         [0003]     One manner in which to locate the polymerizable liquid between the template and the substrate is by depositing the liquid on the substrate as one or more droplets, referred to as a drop dispense technique. Thereafter, the polymerizable liquid is concurrently contacted by both the template and the substrate to spread the polymerizable liquid therebetween. Actinic energy is impinged upon the polymerizable liquid to form the solidified layer. It is desirable to expose only a portion of the liquid to the actinic energy to form the solidified layer to minimize undesirable patterning of the polymerizable liquid.  
         [0004]     Thus, there is a need to provide a template to control exposure of the polymerizable liquid to the actinic energy during imprint lithographic processes.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention is directed towards a template, transmissive to energy having a predetermined wavelength, having first and second opposed sides and features a coating disposed thereon to limit the volume of the template through which the energy may propagate. In a first embodiment, the template includes, inter alia, a mold, having a plurality of protrusions and recessions, positioned on a first region of the first side; and a coating positioned upon a second region of the first side, with the coating having properties to block the energy from propagating between the first and second opposed sides. These and other embodiments of the present invention are discussed more fully below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a cross-sectional view of a template, disposed opposite to a substrate, with patterned imprinting material disposed therebetween, in accordance with the prior art;  
         [0007]      FIG. 2  is a cross-sectional view of the patterned imprinting layer shown in  FIG. 1 , having a conformal layer disposed thereon in accordance with the prior art;  
         [0008]      FIG. 3  is a simplified top down view of the conformal layer shown in  FIG. 2 , in accordance with the prior art;  
         [0009]      FIG. 4  is a cross-sectional view of a template, in accordance with the present invention;  
         [0010]      FIG. 5  is a detailed view of the template shown in  FIG. 4 , having a coating positioned thereon;  
         [0011]      FIG. 6  is a cross-sectional view of the coating shown in  FIG. 4 , in accordance with an alternate embodiment;  
         [0012]      FIG. 7  is a perspective view of the template shown in  FIG. 4 , in accordance with the present invention;  
         [0013]      FIG. 8  is a perspective view of the template shown in  FIG. 4 , in accordance with a first alternate embodiment of the present invention;  
         [0014]      FIG. 9  is a cross-sectional view of the template shown in  FIG. 8  taken along lines  9 - 9 ;  
         [0015]      FIG. 10  is a perspective view of the template shown in  FIG. 4 , in accordance with a second alternate embodiment of the present invention;  
         [0016]      FIG. 11  is a cross-sectional view of the template shown in  FIG. 4 , in accordance with a third alternate embodiment of the present invention;  
         [0017]      FIGS. 12-13  show a first method of forming the coating upon the template;  
         [0018]      FIGS. 14-16  show a second method of forming the coating upon the template;  
         [0019]      FIGS. 17-18  show a third method of forming the coating upon the template; and  
         [0020]      FIG. 19  shows a fourth method of forming the coating upon the template. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     Referring to  FIG. 1 , a template  10  is shown in contact with imprinting material  12  being disposed between a mold  14  and a substrate  16  in furtherance of patterning imprinting material  12 . To that end, mold  14  is spaced-apart from substrate  16  with imprinting material  12  substantially filling a volumetric gap defined between mold  14  and a region  18  of substrate  16  in superimposition therewith. Thereafter, imprinting material  12  is solidified by exposing the same to an actinic component. In this manner, the shape of a surface  20  of mold  14 , facing imprinting material  12 , is recorded therein by formation of solidified imprinting layer  22 , shown in  FIG. 2 .  
         [0022]     Referring to  FIGS. 1 and 2 , surface  20  of mold  14  is patterned by inclusion of a plurality of protrusions  24  and recessions  26 . The apex portion of each of protrusions  24  lies in a common plane, P. It should be understood, however, that surface  20  may be substantially smooth, without protrusions  24  and recessions  26 , if not planar.  
         [0023]     The actinic component employed to solidify imprinting material  12  may be any known, depending upon the composition of imprinting material  12 . Exemplary compositions for imprinting material  12  are disclosed in U.S. patent application Ser. No. 10/789,319, filed Feb. 27, 2004, entitled “Composition for an Etching Mask Comprising a Silicon-Containing Material,” which is incorporated by reference herein in it&#39;s entirety. Furthermore, imprinting material  12  may comprises an ultraviolet curable hybrid sol-gel such as Ormoclad® available from Microresist Technology GmbH located in Berlin, Germany. As a result, the actinic component employed is typically energy comprising ultraviolet wavelengths, and template  10  and mold  14  are fabricated from a material that is substantially transparent to the actinic component, e.g., fused silica, quartz, and the like. However, other actinic components may be employed, e.g., thermal, electromagnetic, visible light, infrared, and the like.  
         [0024]     Imprinting material  12  may be deposited upon either substrate  16  and/or template  10  employing virtually any known technique, dependent upon the composition employed. Such deposition techniques include but are not limited to, chemical vapor deposition (CVD), physical vapor deposition (PVD), spin-coating, and drop dispense techniques. After formation of solidified imprinting layer  22 , mold  14  is separated therefrom, and solidified imprinting layer  22  remains on substrate  16 . Solidified imprinting layer  22  includes residual regions  28  having a thickness t 1  and projections  30  having a thickness t 2 , with t 2  being greater than t 1 . Control of the dimensions of features recorded in solidified imprinting layer  22  is dependent, inter alia, upon the volume of imprinting material  12  in superimposition with region  18 .  
         [0025]     One attempt to confine imprinting material  12  to the volumetric gap includes forming mold  14  on template  10  as a mesa. To that end, mold  14  extends from a recessed surface  21  of template  10  and terminates in plane P. Sidewall  23  functions to assist confining imprinting material  12  within the volumetric gap due to the lack of capillary attraction between imprinting material  12  and mold  14  outside the volumetric gap. Specifically, sidewall  23  is provided with sufficient length to reduce the probability that capillary attraction between recessed surface  21  and imprinting material  12  occurs.  
         [0026]     Occasionally during the imprinting process, imprinting material  12  may extrude beyond the volumetric gap so as to lie outside of region  18 . This may be due to, inter alia, fluid pressure generated in imprinting material  12  while being compressed between substrate  16  and mold  14 . Further, the fluid pressure may cause a sufficient quantity of imprinting material  12  to extrude beyond the volumetric gap so that capillary attraction between this material and recessed surface  21  occurs. As a result, formed, proximate to the periphery of region  18 , are extrusions  32 . Extrusions  32  have a thickness t 3  that may be several orders of magnitude larger than thicknesses t 1  and t 2 , depending upon the spacing between recessed surface  21  and substrate  16 . For example, thickness t 3  may be 2 μm-15 μm. The presence of extrusions  32  may be problematic. For example, imprinting material  12  contained in extrusions  32  may not completely cure when exposed to the actinic component. This may result in imprinting material  12  accumulating at a periphery  36  of mold  14 . Additionally, upon separation of mold  14  from solidified imprinting layer  22 , imprinting material  12  in extrusions  32  may spread over the remaining portions of substrate  16  lying outside of the volumetric gap. Additionally, extrusions  32  may become cured, which can result in same remaining on substrate  16  as part of solidified imprinting layer  22 . Any of the aforementioned effects of extrusions  32  can generate unwanted artifacts during subsequent imprinting processes.  
         [0027]     Referring to  FIGS. 2 and 3 , were extrusions  32  partially cured, for example, control of the thickness of subsequently disposed layers becomes problematic. This is shown by formation of multi-layered structure  38  resulting from the deposition of a conformal layer  40  upon solidified imprinting layer  22 . In the present example, conformal layer  40  is formed employing spin-on techniques as discussed in U.S. patent application Ser. No. 10/789,319, filed on Feb. 27, 2004 entitled “Composition for an Etching Mask Comprising a Silicon-Containing Material.” The presence of extrusions  32 , however, reduces the planarity of the surface  42  ordinarily expected from spin-on deposition of conformal layer  40 . The presence of extrusions  32  results in the formation of deleterious artifacts, such as thickness variations, in conformal layer  40 . These deleterious artifacts are present as protrusions in surface  42  and are generally referred to as comets  44 . Comets  44  are, typically, undesirable artifacts, because the same produce peaks  46  and troughs  48  in surface  42 . As a result, surface  42  is provided with a roughness that hinders patterning very small features. Similar roughness problems in subsequently formed surfaces arise in the presence of artifacts generated by extrusions  32 .  
         [0028]     To avoid the deleterious artifacts, the present invention reduces, if not prevents, actinic radiation from impinging upon extrusions  32 . As mentioned above, extrusions  32  may become cured when exposed to actinic radiation, and therefore, cause generation of unwanted artifacts during subsequent imprinting processes. To that end, a coating  54 , shown in  FIG. 4 , may be selectively positioned upon template  10  such that only desired portions of imprinting material  12  are exposed to actinic radiation while excluding other portions of imprinting material  12  from exposure to actinic radiation. Coating  54 , shown in  FIG. 4 , minimizes, if not prevents, actinic radiation from impinging upon portions of imprinting material  12  in superimposition with coating  54 , and more specifically, extrusions  32 , by reflecting and/or absorbing the actinic radiation impinged thereupon, and thus, the aforementioned imprinting material  12 , or extrusions  32 , will not become cured, which is desired. As a result, the imprinting material  12  contained within extrusions  32  may thus evaporate and substantially be removed from being disposed upon substrate  16 . The evaporation of imprinting material  12  of extrusions  32  may depend on, inter alia, the volatility of imprinting material  12 .  
         [0029]     Furthermore, in subsequent steps employed in semiconductor processing, imprinting material  12  contained within extrusions  32  may be exposed to a developer chemistry, wherein the developer chemistry may remove any excess imprinting material  12  in extrusions  32  that remains disposed upon substrate  16  after the aforementioned evaporation.  
         [0030]     Furthermore, coating  54 , shown in  FIG. 4 , has properties associated therewith such that the same may sustain exposure to cleaning chemistries employed in semiconductor processing steps to remove contamination from template  10  without the necessity for reapplication of the same after exposure to the aforementioned cleaning chemistries, described further below. As a result, the efficiency of the manufacturing process employed to pattern imprinting material  12  is increased as reapplication of coating  54 , shown in  FIG. 4 , is not necessitated.  
         [0031]     Coating  54  may be positioned upon template  10  in a plurality of locations. In a first embodiment, coating  54  may be positioned upon recessed surface  21  and sidewall  23  of template  10 , as shown in  FIGS. 4 and 7 . However, coating  54  may be positioned upon a backside  100  of template  10 , as shown in  FIGS. 8 and 9 , described further below.  
         [0032]     Referring to  FIGS. 4 and 5 , in a first embodiment, coating  54  comprises a multilayer film stack  55 . Multilayer film stack  55  comprises alternating layers of at least two differing materials each having an index of refraction associated therewith. The index of refraction of each of the differing materials may be substantially different, however, in a further embodiment, the indices of refraction of each of the differing materials may be substantially the same.  
         [0033]     Multilayer film stack  55  may be tuned to reflect and/or absorb desired wavelengths of the actinic radiation. The wavelengths of the actinic radiation reflected and/or absorbed by multilayer film stack  55  is dependent upon, inter alia, the number of layers comprising multilayer film stack  55 , the thickness of each of the layers comprising multilayer film stack  55 , and the indices of refraction associated with each layer comprising multilayer film stack  55 . To that end, the above-mentioned properties of multilayer film stack  55  may be selected such that the same may be employed to reflect and/or absorb ultraviolet (UV) and visible light. In a first example, multilayer film stack  55  comprises alternating layers of a metal oxide and silicon dioxide (SiO 2 ), with outer layer  60  comprising silicon dioxide (SiO 2 ). The metal oxide may be selected from a group including, but is not limited to, tantalum oxide (Ta 2 O 5 ), titanium oxide (TiO 2 ), and other similar metal oxides. In a further example, multilayer film stack  55  comprises alternating layers of a metal oxide, with outer layer  60  comprising a metal oxide. The metal oxide may be selected from a group including, but is not limited to, Tantala (Ta 2 O 5 ), Zirconia (ZrO 2 ), and other similar metal oxides. Outer layer  60  is employed to provide multilayer film stack  55  with a chemical resistance to cleaning chemistries employed in subsequent semiconductor processing steps to remove contamination from template  10 . Outer layer  60  provides multilayer film stack  55  with chemical resistance to substantially all cleaning chemistries employed in semiconductor processing excepting cleaning chemistries that are alkaline or contain hydrofluoric acid (HF). Furthermore, comprising outer layer  60  in multilayer film stack  55  minimizes surface energy variations that may occur between surface  20  and recessed surface  21  and sidewalls  23 . Outer layer  60  may have a thickness of approximately 20 nm.  
         [0034]     Referring to  FIGS. 4 and 6 , in a further embodiment, multilayer film stack  55  may comprise two layers, a first layer  70  and outer layer  60 . First layer  70  may be positioned between template  10  and outer layer  60 . First layer  70  may comprise a metal having a thickness ‘z 1 ’ associated therewith. The magnitude of thickness ‘z 1 ’ is established such that multilayer film stack  55  substantially reflects and/or absorbs the actinic radiation impinged thereupon, with such radiation including ultraviolet (UV) and visible light. First layer  70  may comprise a metal selected from a group including, but is not limited to, aluminum (Al), silver (Ag), and gold (Au). Thickness ‘z 1 ’ may lie in a range of approximately 250 nm to 1 μm, however, the thickness ‘z 1 ’ may be dependent upon, inter alia, the type of metal comprising first layer  70 . In a first example, employing aluminum (Al) as first layer  70 , thickness ‘z 1 ’ may have a magnitude of approximately 600 nm.  
         [0035]     Referring to  FIG. 7 , in a further embodiment, coating  54  may comprise a single layer having a thickness ‘z 2 ’ associated therewith. The magnitude of thickness ‘z 2 ’ is established such that coating  54  substantially reflects and/or absorbs the actinic radiation impinged thereupon. In a first example, coating  54  may comprise an inert metal selected from a group including, but is not limited to, niobium (Nb) and tantalum (Ta). To that end, employment of an inert metal to comprise coating  54  abrogates the necessity of an additional layer to protect the same from exposure to cleaning chemistries employed in subsequent semiconductor processing steps to remove contamination from template  10 . Coating  54  may be chemically resistant to such cleaning chemistries comprising a mixture of hydrogen peroxide (H 2 O 2 ) and sulfuric acid (H 2 SO 4 ). In a second example, coating  54  may comprise a metal selected from a group including, but is not limited to, aluminum (Al), silver (Ag), and gold (Au). As a result of coating  54  comprising a metal, coating  54  may be chemically resistant to such cleaning chemistries as oxygen plasma and other solvent cleaning chemistries. Thickness ‘z 2 ’ may lie in a range of approximately 250 nm to 1 μm, however, the thickness ‘z 2 ’ may be dependent upon, inter alia, the type of metal comprising coating  54 . In a first example, employing aluminum (Al) as coating  54 , thickness ‘z 2 ’ may have a magnitude of approximately 600 nm.  
         [0036]     Referring to  FIGS. 8 and 9 , as mentioned above, coating  54  may be positioned upon template  10  in a plurality of positions. To that end, in a second embodiment, coating  54  may be positioned upon backside  100  of template  10 . More specifically, coating  54  may be positioned upon portions of backside  100  in superimposition with recessed area  21  and sidewalls  23 , forming a window  102  in superimposition with surface  20  of mold  14 . In a further embodiment, a silicon dioxide (SiO 2 ) layer  95  may be deposited upon backside  100  of template  10 , as shown in  FIG. 10 .  
         [0037]     Referring to  FIG. 11 , in a further embodiment, coating  54  may be positioned upon backside  100  and recessed surface  21  and sidewall  23  concurrently. More specifically, coating  54  may be positioned upon recessed surface  21  and sidewall  23 , shown as coating  54   a , and portions of backside  100  in superimposition with recessed area  21  and sidewalls  23 , shown as coating  54   b . Each of coatings  54   a  and  54   b  may comprise differing embodiments of the above-mentioned embodiments for coating  54 ; however, each of coatings  54   a  and  54   b  may comprise the same embodiments of the above-mentioned embodiments.  
         [0038]     Referring to  FIGS. 1 and 9 , in a further embodiment, the pattern formed in imprinting material  12  may be dependent upon, inter alia, the positioning of coating  54  upon template  10 . More specifically, coating  54  may be selectively positioned upon backside  100  of template  10  such that window  102  facilitates transmission of the actinic radiation to a portion of the imprinting material in superimposition with a desired portion of mold  14 . As a result, only the aforementioned portion of imprinting material  12  may have recorded therein a shape of surface  20  of mold  14 . The desired portion of mold  14  may be less than an entirety of mold  14 .  
         [0039]     Coating  54  may be deposited upon template  10  in a plurality of methods, described generally below, wherein Deposition Sciences, Inc. of Santa Rosa, Calif. may provide such coatings in this fashion. Templates employed may be available from Dupont Photomasks, Inc. of Round Rock, Tex., Dai Nippon Printing Co. of Tokyo, Japan, and Photronics, Inc. of Brookfield, Conn.  
         [0040]     Referring to  FIGS. 12 and 13 , in a first example, coating  54  may be applied to template  10  prior to formation of mold  14  on template  10 . To that end, as shown in  FIG. 12 , a chrome layer  90  and a photoresist layer  92  may be formed on a portion  91  of template  10 , with portion  91  comprising protrusions  24  and recessions  26 . Template  10  may be exposed to a buffered oxide etch (BOE) to form mold  14  thereon, with mold  14  being in superimposition with portion  91 . Coating  54  may be subsequently applied to template  10 , forming multilayered structure  94 , shown in  FIG. 13 .  
         [0041]     Referring to  FIGS. 4 and 13 , to remove chrome layer  90 , photoresist layer  92 , and a portion of coating  54  in superimposition with mold  14 , template  10  may be exposed to a chrome etching chemistry. As a result, coating  54  may be selectively positioned upon recessed surface  21  and sidewall  23  of template  10 , shown in  FIG. 4 , which is desired. The chrome etching chemistry may comprise perchloric acid (HClO 4 ) and ceric ammonium nitrate (NH 4 ) 2 Ce (NO 3 ) 6 .  
         [0042]     Referring to  FIGS. 4 and 14 , in a second example, coating  54  may be applied to template  10  subsequent to formation of mold  14  on template  10 . To that end, as shown in  FIG. 14 , a photoresist layer  96  may be formed on template  10 . Portions of photoresist layer  96  in superimposition with recessed surface  21  and sidewall  23  may be removed, as shown in  FIG. 15 .  
         [0043]     Referring to  FIG. 16 , after removing the aforementioned portions of photoresist layer  96 , coating  54  may be applied to template  10 . Photoresist layer  96  and portions of coating  54  in superimposition with mold  14  may be removed by exposing template  10  to acetone (C 3 H 6 O). As a result, coating  54  may be selectively positioned upon recessed surface  21  and sidewall  23  of template  10 , as shown in  FIG. 4 , which is desired.  
         [0044]     Referring to  FIGS. 17 and 18 , in a first example to form coating  54  upon backside  100  of template  10 , a photoresist layer  120  may be formed on a portion  121  of template  10 , with portion  121  being in superimposition with surface  20  of mold  14 . Coating  54  may be applied to template  10 , forming multilayered structure  122 , as shown in  FIG. 18 . Photoresist layer  120  and portions of coating  54  in superimposition with portion  121  may be removed such that coating  54  may be selectively positioned upon portions of backside  100  in superimposition with recessed surface  21  and sidewall  23 , as shown in  FIGS. 8 and 9 . To remove the aforementioned portions of coating  54 , the same may be subjected to a buffered oxide etch (BOE) solution containing hydrofluoric acid (HF) or a fluorine containing dry etch such as trifluoromethane (CHF 3 ) or sulfur fluoride (SF 6 ) reactive ion etch (RIE). To remove photoresist layer  120 , coating  54  may be removed in a manner such that portions of photoresist layer  120  may be exposed, with such portions being subjected to acetone (C 3 H 6 O) to remove photoresist layer  120 . In a second example to expose a portion of photoresist layer  120  such that the same may be subjected to acetone (C 3 H 6 O), coating  54  may be directionally deposited upon template  10 .  
         [0045]     Referring to  FIG. 19 , in a second example to form coating  54  upon backside  100  of template  10 , coating  54  may be deposited on substantially the entire backside  100 . Coating  54  may then be masked to define an area in superimposition with recessed  21  and sidewall  23 , as shown in  FIGS. 8 and 9 , with the aforementioned area of coating  54  being subjected to an etching chemistry to remove the same. To remove the aforementioned portions, coating  54  may be subjected to a buffered oxide etch (BOE) solution containing hydrofluoric acid (HF) or a fluorine containing dry etch such as trifluoromethane (CHF 3 ) or sulfur fluoride (SF 6 ) reactive ion etch (RIE).  
         [0046]     The 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 the appended claims along with their full scope of equivalents.