Abstract:
The present invention is directed to a method for modulating shapes of a substrate, having first and second opposed surfaces. This is achieved by creating a pressure differential between differing regions of the first opposed surface to attenuate structural distortions in the second opposed surface that results from external forces bearing on the substrate.

Description:
[0001]    The field of invention relates generally to imprint lithography. More particularly, the present invention is directed to reducing pattern distortions during imprint lithography processes.  
           [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 had a sizeable impact is in the processing of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, 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 shown in U.S. Pat. No. 6,334,960 to Willson et al. Willson et al. disclose a method of forming a relief image in a structure. The method includes providing a substrate having a transfer layer. The transfer layer is covered with a polymerizable fluid composition. A mold makes mechanical contact with the polymerizable fluid. The mold includes a relief structure, and the polymerizable fluid composition fills the relief structure. The polymerizable fluid composition is then subjected to conditions to solidify and polymerize the same, forming a solidified polymeric material on the transfer layer that contains a relief structure complimentary to that of the mold. The mold is then separated from the solid polymeric material such that a replica of the relief structure in the mold is formed in the solidified polymeric material. The transfer layer and the solidified polymeric material are subjected to an environment to selectively etch the transfer layer relative to the solidified polymeric material such that a relief image is formed in the transfer layer. The time required and the minimum feature dimension provided by this technique is dependent upon, inter alia, the composition of the polymerizable material.  
           [0004]    U.S. Pat. No. 5,772,905 to Chou discloses a lithographic method and apparatus for creating ultra-fine (sub-36 nm) patterns in a thin film coated on a substrate in which a mold having at least one protruding feature is pressed into a thin film carried on a substrate. The protruding feature in the mold creates a recess of the thin film. The mold is removed from the film. The thin film then is processed such that the thin film in the recess is removed exposing the underlying substrate. Thus, patterns in the mold are replaced in the thin film, completing the lithography. The patterns in the thin film will be, in subsequent processes, reproduced in the substrate or in another material which is added onto the substrate.  
           [0005]    Yet another imprint lithography technique is disclosed by Chou et al. in  Ultrafast and Direct Imprint of Nanostructures in Silicon , Nature, Col. 417, pp. 835-837, June 2002, which is referred to as a laser assisted direct imprinting (LADI) process. In this process a region of a substrate is made flowable, e.g., liquefied, by heating the region with the laser. After the region has reached a desired viscosity, a mold, having a pattern thereon, is placed in contact with the region. The flowable region conforms to the profile of the pattern and is then cooled, solidifying the pattern into the substrate. An important consideration when forming patterns in this manner is to maintain control of the mold. In this fashion, distortions in the pattern resulting from, inter alia, undesired movement of the mold may be avoided.  
           [0006]    It is desired, therefore, to provide improved techniques for shaping and holding the mold so as to accurately dispose a pattern upon a wafer.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention is directed to a method for modulating shapes of a substrate, having first and second opposed surfaces, by creating a pressure differential between differing regions of the first opposed surface to attenuate structural distortions in the second opposed surface. To that end, a chuck body is provided that has first and second opposed sides, with an edge surface extending therebetween. The first side includes first and second spaced-apart recesses, defining first and second spaced-apart support regions. The substrate rests against the first and second support regions, covering the first and second recesses. The first recess and the portion of the substrate in superimposition therewith define a first chamber. The second recess and the portion of the substrate in superimposition therewith define a second chamber. A first pressure level is established within the first chamber, and a second pressure level is established in the second chamber. For example, the first chamber may be evacuated to hold the substrate against the chuck body so that separation of the substrate from the chuck body under force of gravity is prevented. The second chamber is pressurized to reduce distortions in a portion of the second side in superimposition therewith. In this manner, hydrostatic pressurization is employed to hold the substrate against the chuck and to compensate for external forces applied to the substrate so as to prevent structural distortions in the substrate. These and other embodiments of the present invention are discussed more fully below. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a perspective view of a lithographic system in accordance with the present invention;  
         [0009]    [0009]FIG. 2 is a simplified elevation view of a lithographic system shown in FIG. 1;  
         [0010]    [0010]FIG. 3 is a simplified representation of material from which an imprinting layer, shown in FIG. 2, is comprised before being polymerized and cross-linked;  
         [0011]    [0011]FIG. 4 is a simplified representation of cross-linked polymer material into which the material shown in FIG. 3 is transformed after being subjected to radiation;  
         [0012]    [0012]FIG. 5 is a simplified elevation view of a mold spaced-apart from the imprinting layer, shown in FIG. 1, after patterning of the imprinting layer;  
         [0013]    [0013]FIG. 6 is a simplified elevation view of an additional imprinting layer positioned atop of the substrate shown in FIG. 5, after the pattern in the first imprinting layer is transferred therein;  
         [0014]    [0014]FIG. 7 is a detailed perspective view of a print head shown in FIG. 1;  
         [0015]    [0015]FIG. 8 is a cross-sectional view of a chucking system in accordance with the present invention;  
         [0016]    [0016]FIG. 9 is an exploded view of an imprint head shown in FIG. 7;  
         [0017]    [0017]FIG. 10 is a bottom-up plan view of a chuck body shown in FIG. 8;  
         [0018]    [0018]FIG. 11 is a top down view of a wafer, shown in FIGS. 2, 5 and  6  upon which imprinting layers are disposed;  
         [0019]    [0019]FIG. 12 is a detailed view of FIG. 11 showing the position of the mold in one of the imprint regions;  
         [0020]    [0020]FIG. 13 is a bottom-up plan view of the chuck body shown in FIG. 8 in accordance with an alternate embodiment; and  
         [0021]    [0021]FIG. 14 is a cross-sectional view of a chuck body shown in FIG. 8 in accordance with a second alternate embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    [0022]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 . 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. A radiation source  22  is coupled to 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 .  
         [0023]    Referring to both FIGS. 1 and 2, connected to imprint head  18  is a substrate  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 , having a step height, h, on the order of nanometers, e.g., 100 nanometers. The plurality of features defines an original pattern that is to be transferred into a wafer  30  positioned on motion stage  20 . To that end, imprint head  18  is adapted to move along the Z axis and vary a distance “d” between mold  28  and wafer  30 . In this manner, the features on mold  28  may be imprinted into a flowable region of wafer  30 , discussed more fully below. Radiation source  22  is located so that mold  28  is positioned between radiation source  22  and wafer  30 . As a result, mold  28  is fabricated from material that allows it to be substantially transparent to the radiation produced by radiation source  22 .  
         [0024]    Referring to both FIGS. 2 and 3, a flowable region, such as an imprinting layer  34 , is disposed on a portion of surface  32  that presents a substantially planar profile. 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, flowable region consists of imprinting layer  34  being deposited as a plurality of spaced-apart discrete beads  36  of material  36   a  on wafer  30 , discussed more fully below. Imprinting layer  34  is formed from a material  36   a  that may be selectively polymerized and cross-linked to record the original pattern therein, defining a recorded pattern. Material  36   a  is shown in FIG. 4 as being cross-linked at points  36   b , forming cross-linked polymer material  36   c.    
         [0025]    Referring to FIGS. 2, 3 and  5 , the pattern recorded in imprinting layer  34  is produced, in part, by mechanical contact with mold  28 . To that end, imprint head  18  reduces the distance “d” to allow imprinting layer  34  to come into mechanical contact with mold  28 , spreading beads  36  so as to form imprinting layer  34  with a contiguous formation of material  36   a  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.    
         [0026]    To facilitate filling of recessions  28   a , material  36   a  is provided with the requisite properties to completely fill recessions  28   a  while covering surface  32  with a contiguous formation of material  36   a . 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. Typically, t 1  is selected so as to be no greater than twice the width u of sub-portions  34   a , i.e., t 1 ≦2u, shown more clearly in FIG. 5.  
         [0027]    Referring to FIGS. 2, 3 and  4 , after a desired distance “d” has been reached, radiation source  22  produces actinic radiation that polymerizes and cross-links material  36   a , forming cross-linked polymer material  36   c . As a result, the composition of imprinting layer  34  transforms from material  36   a  to material  36   c , which is a solid. Specifically, material  36   c  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 material  36   c , shown in FIG. 4, imprint head  18 , shown in FIG. 2, is moved to increase distance “d” so that mold  28  and imprinting layer  34  are spaced-apart.  
         [0028]    Referring to FIG. 5, additional processing may be employed to complete the patterning of wafer  30 . For example, wafer  30  and imprinting layer  34  may be etched to transfer the pattern of imprinting layer  34  into wafer  30 , providing a patterned surface  32   a , shown in FIG. 6. To facilitate etching, the material from which imprinting layer  34  is formed may be varied to define a relative etch rate with respect to wafer  30 , as desired. The relative etch rate of imprinting layer  34  to wafer  30  may be in a range of about 1.5:1 to about 100:1. 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 wafer  30  and imprinting layer  34 . Exemplary etch processes may include plasma etching, reactive ion etching, chemical wet etching and the like.  
         [0029]    Referring to both FIGS. 1 and 2, an exemplary radiation source  22  may produce ultraviolet radiation. Other radiation sources may be employed, such as thermal, electromagnetic and the like. The selection of radiation employed to initiate the polymerization of the material in imprinting layer  34  is known to one skilled in the art and typically depends on the specific application which is desired. Furthermore, the plurality of features on mold  28  are shown as recessions  28   a  extending along a direction parallel to protrusions  28   b  that provide a cross-section of mold  28  with a shape of a battlement. However, recessions  28   a  and protrusions  28   b  may correspond to virtually any feature required to create an integrated circuit and may be as small as a few tenths of nanometers.  
         [0030]    It may be desired to manufacture components of system  10  from materials that are thermally stable, e.g., have a thermal expansion coefficient of less than about 10 ppm/degree centigrade at about room temperature (e.g. 25 degrees Centigrade). In some embodiments, the material of construction may have a thermal expansion coefficient of less than about 10 ppm/degree Centigrade, or less than 1 ppm/degree Centigrade. To that end, bridge supports  12 , bridge  14 , and/or stage support  16  may be fabricated from one or more of the following materials: silicon carbide, iron alloys available under the trade name INVAR®, or name SUPER INVAR™, ceramics, including but not limited to ZERODUR® ceramic. Additionally table  24  may be constructed to isolate the remaining components of system  10  from vibrations in the surrounding environment. An exemplary table  24  is available from Newport Corporation of Irvine, Calif.  
         [0031]    Referring to FIGS. 7 and 8, substrate  26 , upon which mold  28  is present, is coupled to imprint head housing  18   a  via a chucking system  40  that includes chuck body  42 . Specifically, substrate  26  includes opposed surfaces  26   a  and  26   b  a periphery surface  26   c  extending therebetween. Surface  26   b  faces chuck system  40 , and mold  28  extends from surface  26   a . To ensure that fluid from beads  36 , shown in FIG. 2, do not spread beyond the area of mold  28 , surface  28   c , shown in FIG. 8, of mold  28  is spaced-apart from surface  26   a  of substrate  26  a distance on the order of micron, e.g., 15 microns. A calibration system  18   b  is coupled to imprint head housing  18   a , and chuck body  42  couples substrate  26  to calibration system  18   b  vis-a-vis a flexure system  18   c . Calibration system  18   b  facilitates proper orientation alignment between substrate  26  and wafer  30 , shown in FIG. 2, thereby achieving a substantially uniform gap distance, “d”, therebetween.  
         [0032]    Referring to both FIGS. 7 and 9, calibration system  18   b  includes a plurality of actuators  19   a ,  19   b  and  19   c  and a base plate  19   d . Specifically, actuators  19   a ,  19   b  and  19   c  are connected between housing  18   a  and base plate  19   d . Flexure system  18   c  includes flexure springs  21   a  and flexure ring  21   b . Flexure ring  21   b  is coupled between base plate  19   d  and flexure springs  21   a . Motion of actuators  19   a ,  19   b  and  19   c  orientates flexure ring  21   b  that may allow for a coarse calibration of flexure springs  21   a  and, therefore, chuck body  42  and substrate  26 . Actuators  19   a ,  19   b  and  19   c  also facilitate translation of flexure ring  21   b  to the Z-axis. Flexure springs  21   a  include a plurality of linear springs that facilitate gimbal-like motion in the X-Y plane so that proper orientation alignment may be achieved between wafer  30  and substrate  26 , shown in FIG. 2.  
         [0033]    Referring to FIGS. 8 and 10 chuck body  42  is adapted to retain substrate  26  upon which mold  28  is attached employing vacuum techniques. To that end, chuck body  42  includes first  46  and second  48  opposed sides. A side, or edge, surface  50  extends between first side  46  and second side  48 . First side  46  includes a first recess  52  and a second recess  54 , spaced-apart from first recess  52 , defining first  58  and second  60  spaced-apart support regions. First support region  58  cinctures second support region  60  and the first  52  and second  54  recesses. Second support region  60  cinctures second recess  54 . A portion  62  of chuck body  42  in superimposition with second recess  54  is transparent to radiation having a predetermined wavelength, such as the wavelength of the actinic radiation mentioned above. To that end, portion  62  is made from a thin layer of transparent material, such as glass. However, the material from which portion  62  is made may depend upon the wavelength of radiation produced by radiation source  22 , shown in FIG. 2. Portion  62  extends from second side  48  and terminates proximate to second recess  54  and should define an area at least as large as an area of mold  28  so that mold  28  is in superimposition therewith. Formed in chuck body  42  are one or more throughways, shown as  64  and  66 . One of the throughways, such as throughway  64  places first recess  52  in fluid communication with side surface  50 . The remaining throughway, such as throughway  66 , places second recess  54  in fluid communication with side surface  50 .  
         [0034]    It should be understood that throughway  64  may extend between second side  48  and first recess  52 , as well. Similarly, throughway  66  may extend between second side  48  and second recess  54 . What is desired is that throughways  64  and  66  facilitate placing recesses  52  and  54 , respectively, in fluid communication with a pressure control system, such a pump system  70 .  
         [0035]    Pump system  70  may include one or more pumps to control the pressure proximate to recesses  52  and  54 , independently of one another. Specifically, when mounted to chuck body  42 , substrate  26  rests against first  58  and second  60  support regions, covering first  52  and second  54  recesses. First recess  52  and a portion  44   a  of substrate  26  in superimposition therewith define a first chamber  52   a . Second recess  54  and a portion  44   b  of substrate  26  in superimposition therewith define a second chamber  54   a . Pump system  70  operates to control a pressure in first  52   a  and second  54   a  chambers.  
         [0036]    For example, the pressure may be established in first chamber  52   a  to maintain the position of substrate  26  with chuck body  42  and reduce, if not avoid, separation of substrate  26  from chuck body  42  under force of gravity, g. The pressure in second chamber  54   a  may differ from the pressure in first chamber  52   a  to reduce, inter alia, out of surface distortions in the pattern, defined by the features on mold  28 , which occur during imprinting. Out of surface distortions may occur, for example, from an upward force R against mold  28  that occurs as a result of imprinting layer  34 , shown in FIG. 2, contacting mold  28 . By modulating a shape of substrate  26 , shown in FIG. 8, out of surface distortions in the pattern may be attenuated, if not avoided. For example, pump system  70  may apply a positive pressure in chamber  54   a  to compensate for force R. This produces a pressure differential between differing regions of side  46  so that bowing of substrate  26  and, therefore, mold  28  under force R is controlled or attenuated to provide substrate  26  and, therefore mold  28 , with a desired predetermined shape. Exemplary shapes that substrate  26  and mold  28  may take includes ellipsoidal, arcuate, planar, parabolic, saddle-shape and the like.  
         [0037]    Referring to FIGS. 2 and 8, imprint head  18  may include a pressure sensor  18   d  to detect a magnitude of force R to which mold  28  is subjected during an imprinting process. Information is produced by sensor that is transmitted to a processor  71  in data communication therewith. In response to the information obtained from sensor  18   d , processor  71  may control pump system  70  to establish the pressure within chambers  52   a  and  54   a  to compensate for force R so that substrate  26  and, therefore mold  28 , have a desired predetermined shape.  
         [0038]    The pressure in chambers  52   a  and  54   a  may be established based upon a priori knowledge of force R from previous imprinting processes that was detected by pressure sensor  18   d . As a result, the pressure in chambers  52   a  and  54   a  may be established either before or after contact is made between mold  28  and imprinting layer  34  in order to ensure that substrate  26  and, therefore, mold  28 , has a desired predetermined shape. In some instances it may be desirable to pressurize chamber  54   a  on-the-fly, or dynamically, during imprinting process. For example, it may be advantageous to establish the pressure in chamber  54   a  to properly shape substrate  26 , as desired, after mold  28  contacts imprinting layer  34 . The positive pressure established in chamber  54   a  to obtain a desired predetermined shape of substrate  26  and, therefore, mold  28 , may be greater than the vacuum pressure established in chamber  52   a . This would cause substrate  26  to decouple from chuck body  42 .  
         [0039]    To maintain the relative position between chuck body  42  and substrate  26  during imprinting, the pressure in chamber  54   a  may be established dynamically after mold  28  contacts imprinting layer  34 . In this manner, both force R and the vacuum pressure in chamber  52   a  ensures that the relative position between chuck body  42  and substrate  26  is maintained in the face of a positive pressure in chamber  54   a . After mold  28  imprints the pattern in imprinting layer  34 , pressure in chamber  54   a  may be adjusted to establish a vacuum therein. In this manner, all chambers  52   a  and  54   a  have a vacuum to facilitate separation of mold  28  from imprinting layer  34 , while maintaining the relative position between chuck body  42  and substrate  26 .  
         [0040]    Coupled to substrate  26  is a means to compress the same in X and Y directions, with the understanding that the Y-direction is into the plane of FIG. 8. In the present example the means to compress includes a fluid-tight bladder system surrounding periphery surface  26   c  having one or more bladders, two of which are shown as  72   a  and  72   b  that extend along the Y axis, with the understanding that bladders extending along the X axis of periphery surface  26   c  are not shown for the sake of clarity, but are included in the present embodiment. Other devices capable of compressing substrate  26  may be employed in addition to, or in lieu of, bladder system, such as a vice or piezoelectric actuators that function as a vice. Bladders  72   a  and  72   b  are in fluid communication with pump system  70  to control the fluid pressure in bladders  72   a  and  72   b . In this manner, bladders  72   a  and  72   b  may be used to apply forces to substrate  26  to vary the dimensions of the same and reduce in-surface distortions in the pattern recorded into imprinting layer  34 , shown in FIG. 2.  
         [0041]    In-surface distortions in the pattern recorded into imprinting layer  34  may arise from, inter alia, dimensional variations of imprinting layer  34  and wafer  30 . These dimensional variations, which may be due in part to thermal fluctuations, as well as, inaccuracies in previous processing steps that produce what is commonly referred to as magnification/run-out errors. The magnification/run-out errors occur when a region of wafer  30  in which the original pattern is to be recorded exceeds the area of the original pattern. Additionally, magnification/run-out errors may occur when the region of wafer  30 , in which the original pattern is to be recorded, has an area smaller than the original pattern. The deleterious effects of magnification/run-out errors are exacerbated when forming multiple layers of imprinted patterns, shown as imprinting layer  124  in superimposition with patterned surface  32   a , shown in FIG. 6. Proper alignment between two superimposed patterns is difficult in the face of magnification/run-out errors in both single-step full wafer imprinting and step-and-repeat imprinting processes.  
         [0042]    Referring to FIGS. 11 and 12, a step-and-repeat process includes defining a plurality of regions, shown as, a- 1 , on wafer  30  in which the original pattern on mold  28  will be recorded. The original pattern on mold  28  may be coextensive with the entire surface of mold  28 , or simply located to a sub-portion thereof, but it should be understood that substrate  26  has an area that is greater than each of regions a- 1 . Proper execution of a step-and-repeat process may include proper alignment of mold  28  with each of regions a- 1 . To that end, mold  28  includes alignment marks  114   a , shown as a “+” sign. One or more of regions a- 1  include fiducial marks  110   a . By ensuring that alignment marks  114   a  are properly aligned with fiducial marks  110   a , proper alignment of mold  28  with one of regions a- 1  in superimposition therewith is ensured. To that end, machine vision devices (not shown) may be employed to sense the relative alignment between alignment marks  114   a  and fiducial marks  110   a . In the present example, proper alignment is indicated upon alignment marks  114   a  being in superimposition with fiducial marks  110   a . With the introduction of magnification/run-out errors, proper alignment becomes very difficult.  
         [0043]    However, in accordance with one embodiment of the present invention, magnification/run-out errors are reduced, if not avoided, by creating relative dimensional variations between mold  28  and wafer  30 . Specifically, the temperature of wafer  30  is varied so that one of regions a- 1  defines an area that is slightly less than an area of the original pattern on mold  28 . Thereafter, the final compensation for magnification/run-out errors is achieved by subjecting substrate  26 , shown in FIG. 8, to mechanical compression forces using bladder  72   a  or  72   b , which are in turn transferred to mold  28  shown by arrows F 1  and F 2 , orientated transversely to one another, shown in FIG. 12. In this manner, the area of the original pattern is made coextensive with the area of the region a- 1  in superimposition therewith.  
         [0044]    Referring to both FIGS. 5 and 8, subjecting substrate  26  to compressive forces, however, modulates the shape of the same through bending action. Bending of substrate  26  may also introduce distortions in the pattern imprinted into imprinting layer  34 . The pattern distortions attributable to bending of substrate  26  may be reduced, if not prevented, by positioning bladders  72   a  or  72   b  so that the bending of substrate  26  is controlled to occur in a desired predetermined direction. In the present example, bladders  72   a  or  72   b  are positioned to compress substrate  26  so as to bow in a direction parallel to, and opposite of, force R. By controlling the bending of substrate  26  in this manner, chucking system  40  may be employed to counter the bending force, B, so as to ensure that mold  28  remains substantially planar. Pump system  70  may be employed to pressurize chamber  54   a  appropriately to that end. For example, assuming bending force, B, is greater than force R, pump system  70  would be employed to evacuate chamber  54   a  with sufficient vacuum to compensate for bending force B. Were bending force B weaker than force, R, pump system  70  would be employed to pressurize chamber  54   a  appropriately to obtain a desired predetermined shape of substrate  26  and, therefore, mold  28 . The exact pressure levels may be determined with a priori knowledge of the forces R and B which then may be analyzed by processor  71  that may be included in pump system  70  to pressurize chambers  52   a  and  54   a  to the appropriate levels. Also, the forces R and B may be sensed dynamically using known techniques, such as pressure sensor  18   d  and processor  71  discussed above, so that the pressure within chambers  52   a  and  54   a  may be established dynamically during operation to maintain substrate  26  with a desired shape. The magnitude of the bending for is dependent upon many factors, such as the shape of periphery surface  26   c , e.g., whether periphery surface  26   c  extends orthogonally to first and second surface  26   a  and  26   b  or forms an oblique angle with respect thereto, as well as the location on periphery surface  26   c  that bladders  72   a  and  72   b  apply a force, as well as the pattern of beads  36  on surface  32 , shown in FIG. 2. Means for applying a single compressive force is shown on opposing regions of periphery surface, such as bladders  72   a  and  72   b . It should be understood that multiple compressive forces can be applied to opposing regions of periphery surface  26   c , shown as forces F 3 , F 4 , F 5  and F 6 . Forces F 3 , F 4 , F 5  and F 6  may have identical or differing magnitudes as required to provide substrate  26  with a desired predetermined shape.  
         [0045]    Referring again to FIG. 8, when compressing substrate  26  with bladders  72   a  or  72   b , relative movement between substrate  26  and support regions  58  and  60  occurs along the X and Y axes. As a result, it is desired that support regions  58  and  60  have surface regions  58   a  and  60   a , respectively, formed thereon from a material adapted to conform to a profile of said substrate  26  and resistant to deformation along the X and Y axes. In this manner, surface regions  58   a  and  60   a  resist relative movement of substrate  26  with respect to chuck body  42  in the X and Y directions.  
         [0046]    Referring to FIGS. 8 and 13, in another embodiment, chuck body  142  may include one or more walls, or baffles, shown as  142   a ,  142   b ,  142   c  and  142   d  extending between first and second support regions  158  and  160 , respectively. In this fashion, walls/baffles  142   a ,  142   b ,  142   c  and  142   d  segment recess  152  into a plurality of sub-regions  152   a ,  152   b ,  152   c  and  152   d  that function as sub-chambers once substrate  26  is placed in superimposition therewith. Sub-chambers  152   a ,  152   b ,  152   c  and  152   d  may be fluid-tight which would result in each have a throughway (not shown) placing the same in fluid communication with pump system  70 . Alternatively, or in conjunction therewith, sub-chambers  152   a ,  152   b ,  152   c  and  152   d  may not form fluid-tight chambers once substrate  26  is placed in superimposition therewith. Rather walls  142   a ,  142   b ,  142   c  and  142   d  would be spaced apart from substrate  26  to function as a baffle for fluid transfer across the same. As a result, with the appropriate pressure level being provided by pump system  70  to recess  152 , a pressure differential could be provided between sub-chambers  152   a ,  152   b ,  152   c  and  152   d , as desired. In a similar fashion one or more baffles, shown as  142   e  may be positioned to extend between opposing areas of support region  160  to form sub-chambers  154   a  and  154   b , if desired.  
         [0047]    Referring to both FIGS. 2 and 13, providing walls/baffles  142   a ,  142   b ,  142   c  and  142   d  this configuration, sub-chambers  152   a ,  152   b ,  152   c  and  152   d  may be concurrently provided with differing pressure levels. As a result, the amount of force exerted on substrate  26  when being pulled-apart from imprinting layer  34  may vary across the surface of substrate  26 . This allows cantilevering, or peeling-off, of substrate  26  from imprinting layer  34  that reduces distortions or defects from being formed in imprinting layer  34  during separation of substrate  26  therefrom. For example, sub-chamber  152   b  may have a pressure established therein that is greater than the pressure associated with the remaining sub-chambers  152   a ,  152   c  and  152   d . As a result, when increasing distance “d” the pulling force of the portion of substrate  26  in superimposition with sub-chambers  152   a ,  152   c  and  152   d  is subjected to is greater than the pulling force to which the portion of substrate  26  in superimposition with sub-chamber  152   b  is subjected. Thus, the rate that “d” increases for the portion of substrate  26  in superimposition with sub-chambers  152   a ,  152   c  and  152   d  is accelerated compared to the rate at which “d” increases for the portion of substrate  26  in superimposition with sub-chamber  152   b , providing the aforementioned cantilevering effect.  
         [0048]    In yet another embodiment, shown in FIG. 14, chuck body  242  includes a plurality of pins  242   a  projecting from a nadir surface  252   a  of out recess  252 . Pins  242   a  provide mechanical support for the wafer (not shown) retained on chuck body  242  via vacuum. This enables support regions  258  and  260  to have surface regions  258   a  and  260   a , respectively, formed from material that is fully compliant with the surface (not shown) of the wafer (not shown) resting against support regions  258  and  260 . In this manner, surface regions  258   a  and  260   a  provide a fluid-tight seal with the wafer (not shown) in the presence of extreme surface variation, e.g., when particulate matter is present between the surface (not shown) of the wafer (not shown) and the surface regions  258   a  and  260   a . Mechanical support of the wafer (not shown) in the Z direction need not be provided by surface regions  258   a  and  260   a . Pins  242   a  provide this support. To that end, pins  242   a  are typically rigid posts having a circular cross-section.  
         [0049]    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. For example, by pressurizing all chambers formed by the chuck body-substrate combination with positive fluid pressure, the substrate may be quickly released from the chuck body. Further, many of the embodiments discussed above may be implemented in existing imprint lithography processes that do not employ formation of an imprinting layer by deposition of beads of polymerizable material. Exemplary processes in which differing embodiments of the present invention may be employed include a hot embossing process disclosed in U.S. Pat. No. 5,772,905, which is incorporated by reference in its entirety herein. Additionally, many of the embodiments of the present invention may be employed using 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. Therefore, the scope of the invention should be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.