Abstract:
The present invention is directed to a body having a first area and a second area separated by a recess. The recess is dimensioned to reduce, if not prevent, a liquid moving along a surface of the body from traveling between the first and second areas. One or more alignment marks may be positioned within one of the first and second areas. In this manner, the recess functions as a moat by reducing, if not preventing, a quantity of the liquid from being in superimposition with the alignment marks.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The field of invention relates generally to imprint lithography. More particularly, the present invention is directed to producing templates having a moat system surrounding alignment marks.  
         [0002]     Micro-fabrication involves the fabrication of very small structures, e.g., having features on the order of micro-meters or smaller. One area in which micro-fabrication has 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, micro-fabrication becomes increasingly important. Micro-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension of the structures formed. Other areas of development in which micro-fabrication has been employed include biotechnology, optical technology, mechanical systems and the like.  
         [0003]     An exemplary micro-fabrication technique is commonly referred to as imprint lithography and is described in detail in numerous publications, such as U.S. published patent applications 2004/0065976, entitled METHOD AND A MOLD TO ARRANGE FEATURES ON A SUBSTRATE TO REPLICATE FEATURES HAVING MINIMAL DIMENSIONAL VARIABILITY; 2004/0065252, entitled METHOD OF FORMING A LAYER ON A SUBSTRATE TO FACILITATE FABRICATION OF METROLOGY STANDARDS; 2004/0046271, entitled METHOD AND A MOLD TO ARRANGE FEATURES ON A SUBSTRATE TO REPLICATE FEATURES HAVING MINIMAL DIMENSIONAL 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 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 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.  
         [0004]     One manner in which to locate the polymerizable liquid between the template and the substrate is by depositing a plurality of droplets of the liquid on the substrate. Thereafter, the polymerizable liquid is concurrently contacted by both the template and the substrate to spread the polymerizable liquid over the surface of the substrate. It is desirable to properly align the template with the substrate so that the proper orientation between the substrate and template may be obtained. To that end, both the template and substrate include alignment marks.  
         [0005]     Thus, a need exists to provide alignment techniques for use in imprint lithographic processes.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention is directed to a body having a first area and a second area separated by a recess. The recess is dimensioned to reduce, if not prevent, a liquid moving along a surface of the body from traveling between the first and second areas. One or more alignment marks may be positioned within one of the first and second areas. In this manner, the recess functions as a moat by reducing, if not preventing, a quantity of the liquid from being in superimposition with the alignment marks. These and other embodiments are discussed more fully below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a perspective view of a lithographic system in accordance with the present invention;  
         [0008]      FIG. 2  is a simplified plan view of the lithographic system showing a mold included on a template shown in  FIG. 1 ;  
         [0009]      FIG. 3  is a simplified elevation view of a mold spaced-apart from the imprinting layer, shown in  FIG. 2 , after patterning of the imprinting layer;  
         [0010]      FIG. 4  is a simplified elevation view of an additional imprinting layer positioned atop of the substrate after etching of a pattern into the substrate that corresponds to the pattern in the first imprinting layer, shown in  FIG. 3 ;  
         [0011]      FIG. 5  is a plan view of an imaging system employed to sense alignment marks included on the template of  FIG. 1 ;  
         [0012]      FIG. 6  is a plan view of exemplary alignment marks utilized in the present invention;  
         [0013]      FIG. 7  is a bottom-up view of the template shown in  FIG. 1 , in accordance with a first embodiment of the present invention;  
         [0014]      FIG. 8  is a cross-sectional view of the template shown in  FIG. 7  taken along lines  8 - 8 ;  
         [0015]      FIG. 9  is a bottom-up view of the template shown in  FIG. 7 , in accordance with a second embodiment of the present invention;  
         [0016]      FIG. 10  is a bottom-up view of the template shown in  FIG. 7 , in accordance with a second embodiment of the present invention;  
         [0017]      FIG. 11  is a bottom-up view of the template shown in  FIG. 7 , in accordance with a third embodiment of the present invention; and  
         [0018]      FIG. 12  is a plan view of a template having alignment marks and a moat system disposed along an edge of the template in accordance with a fourth embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]      FIG. 1  depicts a lithographic system  10  in accordance with one embodiment of the present invention that includes a pair of spaced-apart bridge supports  12  having a bridge  14  and a stage support  16  extending therebetween. Bridge  14  and stage support  16  are spaced-apart. Coupled to bridge  14  is an imprint head  18 , which extends from bridge  14  toward stage support  16  and provides movement along the Z-axis. Disposed upon stage support  16  to face imprint head  18  is a motion stage  20 . Motion stage  20  is configured to move with respect to stage support  16  along X- and Y-axes. It should be understood that imprint head  18  may provide movement along the X- and Y-axes, as well as the Z-axis, and motion stage  20  may provide movement in the Z-axis, as well as the X- and Y-axes. An exemplary motion stage device is disclosed in U.S. patent application Ser. No. 10/194,414, filed Jul. 11, 2002, entitled “Step and Repeat Imprint Lithography Systems,” assigned to the assignee of the present invention, and which is incorporated by reference herein in its entirety. A radiation source  22  is coupled to lithographic system  10  to impinge actinic radiation upon motion stage  20 . As shown, radiation source  22  is coupled to bridge  14  and includes a power generator  23  connected to radiation source  22 . Operation of lithographic system  10  is typically controlled by a processor  25  that is in data communication therewith. An exemplary lithographic system is available under the trade name IMPRIO 100™ from Molecular Imprints, Inc. having a place of business at 1807-C Braker Lane, Suite 100, Austin, Tex. 78758. The system description for the IMPRIO 100™ is available at www.molecularimprints.com and is incorporated herein by reference.  
         [0020]     Referring to both  FIGS. 1 and 2 , connected to imprint head  18  is a template  26  having a mold  28  thereon. Mold  28  includes a plurality of features defined by a plurality of spaced-apart recessions  28   a  and protrusions  28   b . The plurality of features defines an original pattern that is to be transferred into a substrate  30  positioned on motion stage  20 . To that end, imprint head  18  and/or motion stage  20  may vary a distance “d” between mold  28  and substrate  30 . In this manner, the features on mold  28  may be imprinted into a flowable region of substrate  30 , discussed more fully below. Radiation source  22  is located so that mold  28  is positioned between radiation source  22  and substrate  30 . As a result, mold  28  is fabricated from a material that allows it to be substantially transparent to the radiation produced by radiation source  22 .  
         [0021]     Referring to  FIG. 2 , a flowable region, such as an imprinting layer  34 , is disposed on a portion of a surface  32  that presents a substantially planar profile. A flowable region may be formed using any known technique, such as a hot embossing process disclosed in U.S. Pat. No. 5,772,905, which is incorporated by reference in its entirety herein, or a laser assisted direct imprinting (LADI) process of the type described by Chou et al. in  Ultrafast and Direct Imprint of Nanostructures in Silicon, Nature , Col. 417, pp. 835-837, June 2002. In the present embodiment, however, a flowable region consists of imprinting layer  34  being deposited as a plurality of spaced-apart discrete droplets  36  of a material on substrate  30 , discussed more fully below. An exemplary system for depositing droplets  36  is disclosed in U.S. patent application Ser. No. 10/191,749, filed Jul. 9, 2002, entitled SYSTEM AND METHOD FOR DISPENSING LIQUIDS, and which is assigned to the assignee of the present invention, and which is incorporated by reference in its entirety herein. Imprinting layer  34  is formed from the material that may be polymerized and cross-linked to record the original pattern therein, defining a recorded pattern. An exemplary composition for the material is disclosed in U.S. patent application Ser. No. 10/463,396, filed Jun. 16, 2003 and entitled METHOD TO REDUCE ADHESION BETWEEN A CONFORMABLE REGION AND A PATTERN OF A MOLD, which is incorporated by reference in its entirety herein.  
         [0022]     Referring to  FIGS. 2 and 3 , the pattern recorded in imprinting layer  34  is produced, in part, by mechanical contact with mold  28 . To that end, distance “d” is reduced to allow imprinting droplets  36  to come into mechanical contact with mold  28 , spreading droplets  36  so as to form imprinting layer  34  with a contiguous formation of the material over surface  32 . In one embodiment, distance “d” is reduced to allow sub-portions  34   a  of imprinting layer  34  to ingress into and fill recessions  28   a.    
         [0023]     To facilitate filling of recessions  28   a , the material is provided with the requisite properties to completely fill recessions  28   a , while covering surface  32  with a contiguous formation of the material. In the present embodiment, sub-portions  34   b  of imprinting layer  34  in superimposition with protrusions  28   b  remain after the desired, usually minimum, distance “d”, has been reached, leaving sub-portions  34   a  with a thickness “t 1 ,” and sub-portions  34   b  with a thickness “t 2 .” Thicknesses “t 1 ,” and “t 2 ” may be any thickness desired, dependent upon the application.  
         [0024]     Referring again to  FIG. 2 , after a desired distance “d” has been reached, radiation source  22  produces actinic radiation that polymerizes and cross-links the material, forming a cross-linked polymer material. As a result, the composition of imprinting layer  34  transforms from the material to the cross-linked polymer material, which is a solid. Specifically, the cross-linked polymer material is solidified to provide side  34   c  of imprinting layer  34  with a shape conforming to a shape of a surface  28   c  of mold  28 , shown more clearly in  FIG. 5 . After imprinting layer  34  is transformed to consist of the cross-linked polymer material, the distance “d” is increased so that mold  28  and imprinting layer  34  are spaced-apart.  
         [0025]     Referring to  FIG. 3 , additional processing may be employed to complete the patterning of substrate  30 . For example, substrate  30  and imprinting layer  34  may be etched to transfer the pattern of imprinting layer  34  into substrate  30 , providing a patterned surface  32   a , shown in  FIG. 6 . To facilitate etching, the material from which imprinting layer  34  is formed from may be varied to define a relative etch rate with respect to substrate  30 , as desired. The relative etch rate of imprinting layer  34  to substrate  30  may be in a range of about 1.5:1 to about 100:1.  
         [0026]     Alternatively, or in addition to, imprinting layer  34  may be provided with an etch differential with respect to photo-resist material (not shown) selectively disposed thereon. The photo-resist material (not shown) may be provided to further pattern imprinting layer  34 , using known techniques. Any etch process may be employed, dependent upon the etch rate desired and the underlying constituents that form substrate  30  and imprinting layer  34 . Exemplary etch processes may include plasma etching, reactive ion etching, chemical wet etching and the like. The sub portions  34   b  are typically referred to as the residual layer.  
         [0027]     Additionally, it has been found beneficial to deposit a primer layer (not shown) when forming imprinting layer  34  upon substrate  32  which may or may not include any previously disposed patterned/unpatterned layer present on substrate  32 . The primer layer (not shown) may function, inter alia, to provide a standard interface with imprinting layer  34 , thereby reducing the need to customize each process to the material upon which imprinting layer  34  is to be deposited. In addition, the primer layer (not shown) may be formed from an organic material with the same etch characteristics as imprinting layer  34 . The primer layer is fabricated in such a manner so as to possess a continuous, smooth, if not planar, relatively defect-free surface that may exhibit excellent adhesion to imprinting layer  34 . The magnitude of a thickness of the primer layer (not shown) should be such that the same is able comprise the above-mentioned characteristics, but also allow the same to be substantially transparent such that underlying alignment marks, described further below, may be detected by have an optical sensor, mentioned further below. An exemplary material from which to form the primer layer (not shown) is available from Brewer Science, Inc. of Rolla Missouri under the trade name DUV30J-6. The primer layer (not shown) may be deposited using any know technique, include spin-on deposition and drop-dispense deposition.  
         [0028]     Referring to  FIGS. 3 and 4 , to form an additional imprinting layer, such as a layer  31  atop of surface  32   a , or a primer layer (not shown) correct placement of mold  28  with respect to substrate  30  is important. To that end, overlay alignment schemes may include alignment error measurement and/or alignment error compensation and/or placement error measurement and correction. Placement error, as used herein, generally refers to X-Y positioning errors between a template and a substrate (that is, translation along the X- and/or Y-axis). Placement errors, in one embodiment, are determined and corrected for by using an optical imaging system  40 , shown in  FIG. 5 , to sense alignment marks discussed below with respect to  FIG. 6 .  
         [0029]     Referring to  FIG. 5 , optical imaging system  40  includes a light source  42  and an optical train  44  to focus light upon substrate  30 . Optical imaging system  40  is configured to focus alignment marks lying in differing focal planes onto a single focal plane, P, wherein an optical sensor  46  may be positioned. As a result, optical train  44  is configured to provide wavelength-dependent focal lengths. Differing wavelengths of light may be produced in any manner known in the art. For example, light source  42  may comprise a single broadband source of light that may produce wavelengths, shown as light  48 , which impinges impinge upon optical train  44 . Optical band-pass filters (not shown) may be disposed between the broadband source and the alignment marks (not shown). Alternatively, a plurality of sources of light (not shown) may be employed, each one of which produces distinct wavelengths of light. Light  48  is focused by optical train  44  to impinge upon alignment marks (not shown) at one or more regions, shown as region R 1  and region R 2 . Light reflects from regions R 1  and R 2 , shown as a reflected light  50 , and is collected by a collector lens  52 . Collector lens  52  focuses all wavelengths of reflected light  50  onto plane P so that optical sensor  46  detects reflected light  50 .  
         [0030]     Referring to  FIGS. 1 and 6 , alignment marks may be of many configurations and are arranged in pairs with one of the alignment marks of the pair being disposed on template  26 . The remaining alignment mark being positioned on substrate  30 , e.g., in a previously deposited imprinting layer or etched into substrate  30  or a previously deposited layer disposed thereon. For example, alignment marks may include first and second polygonal marks  54  and  56 , depicted as squares, but may be any polygonal shape desired. Another configuration for alignment marks are shown as crosses, shown as  58  and  60 . Also additional alignment marks may be employed, such as vernier marks  62  and  64 , as well as Moiré gratings, shown as  66  and  68 .  
         [0031]     Referring to  FIGS. 2, 7 , and  8 , wavelengths are selected to obtain a desired focal length, depending upon the gap between mold  28  and substrate  30  or an imprinting layer disposed on substrate  30 . Under each wavelength of light used, each alignment mark may produce two images on the imaging plane. First polygonal alignment mark  54 , using a specific wavelength of light, presents as a focused image on sensor  46 . Second polygonal alignment mark  56 , using the same wavelength of light, presents as an out-of-focus image on sensor  46 . In order to eliminate each out-of-focus image, several methods may be used.  
         [0032]     Another concern with overlay alignment for imprint lithography processes that employ UV curable liquid materials may be the visibility of the alignment marks. For the overlay placement error measurement, two overlay marks, such as the marks discussed above with respect to  FIG. 8 , are employed, referred to collectively as alignment marks  84 . However, since it is desirable for template  26  to be transparent to a curing agent, the template overlay marks, in some embodiments, are not opaque lines. Rather, the template overlay marks are topographical features of the template surface. In some embodiments, the overlay marks are made of the same material as the template. In addition, UV curable liquids may have a refractive index that is similar to the refractive index of the template materials, e.g., quartz or fused silica. Therefore, when the UV curable liquid fills the gap between template  26  and substrate  30 , template overlay marks may become very difficult to recognize. If the template overlay marks are made with an opaque material, e.g., chromium or nickel, the UV curable liquid below the overlay marks may not be properly exposed to the UV light, e.g., having wavelengths in a range of 310 to 365 nm. This frustrates patterning an underlying surface to include alignment mark for subsequent processing, were it desired to form alignment marks in substrate  30  by imprinting the pattern corresponding to the alignment marks into imprinting layer  34  with mold  28  and subsequently etching the alignment marks into substrate. Therefore, several reasons exist to prevent imprinting material from being in superimposition with alignment marks.  
         [0033]     Referring to  FIG. 7 , the present invention reduces, if not prevents, material in imprinting layer  34  from entering a region of substrate  30  in superimposition with alignment marks  84 . To that end, alignment marks  84  are surrounded by a moat system  100 . Segments  102 ,  104 ,  106 , and  108  of moat system  100  separate molds  92 ,  94 ,  96 , and  98 . Specifically, segments  102 ,  104 ,  106 , and  108  have a depth associated therewith, e.g., 30 microns, to minimize the egression of the material in imprinting layer  34  therein from adjacent active molds  92 ,  94 ,  96 , and  98  due to capillary forces. Additionally, moat system  100  may include a segment  109  that surrounds molds  92 ,  94 ,  96 , and  98 . As mentioned previously, when the desired gap defined between molds  92 ,  94 ,  96  and  98  and substrate  30 , or a layer previously deposited on substrate  30  occurs, the material in imprinting layer  34  forms a contiguous region of material therebetween. As a result of capillary attraction of the material of imprinting layer  34  to both mold  28  and substrate  30 , the material of imprinting layer  34  does not typically extend to regions of substrate  30  in superimposition with moat system  100 . Rather, the material of imprinting layer typically remains confined within a region of substrate  30  that is in superimposition with one of the molds  92 ,  94 ,  96  and  98 .  
         [0034]     Referring to  FIG. 8 , the material of imprinting layer  34  forms a meniscus  105  at the periphery of mold  94  due to the surface tension of the material in imprinting layer  34  and the same is substantially absent from segment  104 . The surface tension associated with the material in meniscus  105  substantially reduces the probability that the material extends through into segment  104 . It was determined, however, that the probability that the material of imprinting layer  34  ingressing into moat system  100 , such as segment  104  would be substantially minimized by minimizing surface discontinuities in the surfaces defining moat system  100 . Specifically, it was determined that surface discontinuities, such as sharp edges, right angles and the like, might cause the material of imprinting layer  34  to ingress into moat system  100  and be located in regions of substrate  30  in superimposition with alignment marks  84 , shown in  FIG. 7 , which is undesirable.  
         [0035]     Referring to  FIGS. 7, 8  and  9 , therefore, to minimize, if not prevent, material of the imprinting layer  34  from being disposed upon a region of substrate  30  in superimposition with alignment marks  84 , moat system  100  abrogates most, if not all sharp corners by including portions  110 ,  112 ,  114 , and  116  defined by arcuate boundaries. Portions  110 ,  112 ,  114 , and  116  surround alignment marks  84 . Specifically, portion  110  is disposed between segments  104  and  106 ; portion  112  is disposed between segments  106  and  108 ; portion  114  is disposed between segments  102  and  108 ; and portion  116  is disposed between segments  102  and  104 .  
         [0036]     The arcuate junctions/boundaries of portions  110 ,  112 ,  114 , and  116  minimize surface discontinuities in the surfaces the define moat system  100 , thereby minimizing imprinting material, such as imprinting material in meniscus  105 , from crossing moat system  100  when meniscus coming into contact therewith. This, it is believed, reduces the probability of, if not prevent, the material in imprinting layer  34  from becoming disposed upon a region of substrate  30  in superimposition with alignment marks  84 .  
         [0037]     In a further embodiment, moat system  100  comprises a plurality of non-linear segments surrounding molds  92 ,  94 ,  96 , and  98  to further minimize, if not prevent, the material in imprinting layer  34  becoming disposed upon a region of substrate  30 , shown in  FIG. 8 , in superimposition with alignment marks  84 . Specifically, connecting any two linear segments of moat system  100  is a non-linear segment, i.e., an arcuate segment. An example of a non-linear segment connecting two linear segments of moat system  100  is shown in  FIG. 7 . More specifically, disposed between a linear segment  120  and a linear segment  122  is a non-linear segment  124 , wherein non-linear segment  124  comprises arcuate portions  126  and  128 , i.e., portions with a smooth contour lacking corners. In another example, disposed between linear segment  120  and a linear segment  130  is a non-linear segment  132 , wherein non-linear segment  132  comprises an arcuate portion  134 , i.e. a portion with a smooth contour lacking corners. Non-linear segments  124  and  132  may be described analogously to the arcuate boundaries of portions  120 ,  112 ,  114 , and  116 , as mentioned above, and thus, non-linear segments  124  and  132  reduce the probability of, if not prevent, the material in imprinting layer  34  from becoming disposed upon a region of substrate  30  in superimposition with alignment marks  84 .  
         [0038]     Referring to  FIG. 10 , in another embodiment, an additional set of alignment marks  136  may be placed within a mold, shown as a mold  138 , of template  90 . However, the region of mold  138  in which alignment marks  136  are positioned does not include any patterned features. Alignment marks  136  are surrounded by a moat system  140  so as to prevent the material in imprinting layer  34  from coming into contact therewith for the reasons discussed above with respect to  FIGS. 7 and 8 . Moat system  140  comprises a plurality of linear segments, with two linear segments of the plurality being connected by a non-linear segment. An example of a non-linear segment connecting two linear segments of moat system  140  is shown as a linear segment  142  and a linear segment  144  having a non-linear segment  146  disposed therebetween. Non-linear segment  146  is analogous to non-linear segments  124  and  132 , mentioned above, and thus non-linear segment  146  reduces the probability, if not prevent, the imprinting material from becoming disposed upon a region of substrate  30 , shown in  FIG. 8 , in superimposition with alignment marks  136 . Alignment marks  136  may be in addition to alignment marks  84 , wherein alignment marks  84  are surrounded by moat system  100 .  
         [0039]     Alternatively, referring to  FIG. 11 , alignment marks  136  may not be surrounded by a moat system, with alignment marks  136  being disposed within mold  138 . However, alignment marks  84  may be surrounded by moat system  100 . It has been found desirable to have at least one of alignment marks  84  and  136  not surrounded by a moat system and not formed from opaque material.  
         [0040]     In a further embodiment, referring to  FIG. 12 , alignment marks  148  may be disposed along an edge  150  of template  90  located between molds  238  and  239 . A moat system  152 , analogous to moat system  100  described above, surrounds alignment marks  148  and comprises arcuate portions  154  and  156 , which are analogous to arcuate portions  110 ,  112 ,  114 , and  116 , and thus arcuate portions  154  and  156  reduce the probability of, if not prevent, the imprinting material from becoming disposed upon a region of substrate  30 , shown in  FIG. 13 , in superimposition with alignment marks  148 .  
         [0041]     Alignment marks may be located at an edge of molds  438  and  538 , shown as alignment marks  448  and  548 , respectively. A moat system  452 , analogous to moat system  100  described above, surrounds alignment mark  448  and comprises arcuate portions  454 ,  455 ,  456  and  457 , which are analogous in function to the arcuate boundaries of portions  110 ,  112 ,  114 , and  116 . Specifically, each of arcuate portions  454 ,  455 ,  456  and  457  reduce the probability of, if not prevent, the material in imprinting layer  34  from becoming disposed upon a region of substrate  30 , shown in  FIG. 13 , in superimposition with alignment marks  448 .  
         [0042]     It should be understood that it is not necessary for an arcuate segment to couple transversely extending linear segments. For example, moat system  552  includes a first linear segments  560  and a second linear segments  562  coupled together via a corner segment, which in this case is shown as a right angle  563 , but may be formed from an acute angle or an obtuse angle. It was found that the presence of corner segments positioned at the boundary of mold  538  did not greatly undermine the problem solved by the present invention, i.e., deminimus amounts of the material in imprinting layer  34  extend into moat system  552 .  
         [0043]     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.