Patent Publication Number: US-2010112220-A1

Title: Dispense system set-up and characterization

Description:
CROSS RELATION 
     This application claims priority to U.S. Provisional Patent U.S. Provisional Patent Application No. 61/110,630 filed Nov. 3, 2008; U.S. Provisional Patent Application No. 61/111,109 filed Nov. 4, 2008; and U.S. Provisional Patent No. 61/144,016 filed Jan. 12, 2009; all of which are hereby incorporated by reference herein. 
    
    
     BACKGROUND INFORMATION 
     Nano-fabrication includes the fabrication of very small structures that have features on the order of 100 nanometers or smaller. One application in which nano-fabrication has had a sizeable impact is in the processing of integrated circuits. The semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, therefore nano-fabrication becomes increasingly important. Nano-fabrication provides greater process control while allowing continued reduction of the minimum feature dimensions of the structures formed. Other areas of development in which nano-fabrication has been employed include biotechnology, optical technology, mechanical systems, and the like. 
     An exemplary nano-fabrication technique in use today is commonly referred to as imprint lithography. Exemplary imprint lithography processes are described in detail in numerous publications, such as U.S. Patent Application Publication No. 2004/0065976, U.S. Patent Application Publication No. 2004/0065252, and U.S. Pat. No. 6,936,194, all of which are hereby incorporated by reference herein. 
     An imprint lithography technique disclosed in each of the aforementioned U.S. patent application publications and patent includes formation of a relief pattern in a formable (polymerizable) layer and transferring a pattern corresponding to the relief pattern into an underlying substrate. The substrate may be coupled to a motion stage to obtain a desired positioning to facilitate the patterning process. The patterning process uses a template spaced apart from the substrate and the formable liquid applied between the template and the substrate. The formable liquid is solidified to form a rigid layer that has a pattern conforming to a shape of the surface of the template that contacts the formable liquid. After solidification, the template is separated from the rigid layer such that the template and the substrate are spaced apart. The substrate and the solidified layer are then subjected to additional processes to transfer a relief image into the substrate that corresponds to the pattern in the solidified layer. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       So that the present invention may be understood in more detail, a description of embodiments of the invention is provided with reference to the embodiments illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the invention, and are therefore not to be considered limiting of the scope. 
         FIG. 1  illustrates a simplified side view of a lithographic system. 
         FIG. 2  illustrates a simplified side view of the substrate shown in  FIG. 1  having a patterned layer positioned thereon. 
         FIG. 3  illustrates a simplified side view of a fluid dispensing system. 
         FIG. 4  illustrates a simplified side view of a defect analysis tool. 
         FIG. 5  illustrates a perspective view of a dispense fixture. 
         FIG. 6  illustrates a method for setting-up and characterizing lithographic systems. 
         FIG. 7  illustrates another method for characterizing lithographic systems. 
         FIG. 8  illustrates a drop pattern for characterizing the orientation of dispense heads. 
         FIG. 9  illustrates a 3-drop saw tooth pattern. 
         FIGS. 10A ,  10 B, and  10 C illustrate a drop pattern for characterizing rotational (theta) orientation of dispense heads as shown without ( FIG. 10A ) and with ( FIG. 10B ) dispense head theta. 
         FIGS. 11A and 11B  illustrate a drop pattern for characterizing reverse pass offset affects of dispense head as shown without ( FIG. 11A ) and with ( FIG. 11B ) reverse pass offset affects. 
         FIG. 12  illustrates a drop pattern to characterize lithographic systems with two dispense heads using two passes. 
         FIG. 13  illustrates a drop pattern to characterize lithographic systems with two dispense heads using four passes. 
         FIG. 14  illustrates a flow chart of a method for positioning dispense heads adjacent to substrates. 
         FIG. 15  illustrates a plan view of a substrate having a drop pattern dispensed thereon. 
         FIG. 16  illustrates a drop pattern selected to characterize lithographic systems. 
         FIG. 17  illustrates an image of drops on a substrate. 
         FIG. 18  illustrates a plot diagram of dispense locations captured in the scan shown in  FIG. 17 . 
         FIGS. 19A and 19B  illustrate a drop pattern and a plot diagram of dispense locations being registered. 
         FIG. 20  illustrates a portion of a plot diagram of extra, missing, and mis-located drops. 
         FIG. 21  illustrates a plot diagram of missing drops and extra drops. 
         FIG. 22  illustrates a plot diagram of drop placement errors. 
         FIG. 23  illustrates a flow chart of a method for correcting imprint defects within drop patterns. 
         FIG. 24  illustrates a flow chart of a method for establishing lithographic system performance specifications. 
         FIG. 25  illustrates a flow chart of a method for evaluating the quality of lithographic systems. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , illustrated therein is a lithographic system  10  used to form a relief pattern on substrate  12 . Substrate  12  may be coupled to substrate chuck  14 . As illustrated, substrate chuck  14  is a vacuum chuck. Substrate chuck  14 , however, may be any chuck including, but not limited to, vacuum, pin-type, groove-type, electromagnetic, and/or the like. Exemplary chucks are described in U.S. Pat. No. 6,873,087, which is hereby incorporated by reference herein. 
     Substrate  12  and substrate chuck  14  may be further supported by stage  16 . Stage  16  may provide motion along the x-, y-, and z-axes. Stage  16 , substrate  12 , and substrate chuck  14  may also be positioned on a base (not shown). 
     Spaced-apart from substrate  12  is a template  18 . Template  18  generally includes a mesa  20  extending therefrom towards substrate  12 , mesa  20  having a patterning surface  22  thereon. Further, mesa  20  may be referred to as mold  20 . Template  18  and/or mold  20  may be formed from such materials including, but not limited to, fused-silica, quartz, silicon, organic polymers, siloxane polymers, borosilicate glass, fluorocarbon polymers, metal, hardened sapphire, and/or the like. As illustrated, patterning surface  22  comprises features defined by a plurality of spaced-apart recesses  24  and/or protrusions  26 , though embodiments of the present invention are not limited to such configurations. Patterning surface  22  may define any original pattern that forms the basis of a pattern to be formed on substrate  12 . 
     Template  18  may be coupled to chuck  28 . Chuck  28  may be configured as, but not limited to, vacuum, pin-type, groove-type, electromagnetic, and/or other similar chuck types. Exemplary chucks are further described in U.S. Pat. No. 6,873,087, which is hereby incorporated by reference herein. Further, chuck  28  may be coupled to imprint head  30  such that chuck  28  and/or imprint head  30  may be configured to facilitate movement of template  18 . 
     System  10  may further comprise a fluid dispense system  32 . Fluid dispense system  32  may be used to deposit polymerizable material  34  on substrate  12 . Polymerizable material  34  may be positioned upon substrate  12  using techniques such as drop dispense, spin-coating, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), thin film deposition, thick film deposition, and/or the like. Polymerizable material  34  may be disposed upon substrate  12  before and/or after a desired volume is defined between mold  20  and substrate  12  depending on design considerations. Polymerizable material  34  may comprise a monomer mixture as described in U.S. Pat. No. 7,157,036 and U.S. Patent Application Publication No. 2005/0187339, all of which are hereby incorporated by reference herein. 
     Referring to  FIGS. 1 and 2 , system  10  may further comprise an energy source  38  coupled to direct energy  40  along path  42 . Imprint head  30  and stage  16  may be configured to position template  18  and substrate  12  in superimposition with path  42 . System  10  may be regulated by a processor  54  in communication with stage  16 , imprint head  30 , fluid dispense system  32 , and/or source  38 , and may operate on a computer readable program stored in memory  56 . 
     Either imprint head  30 , stage  16 , or both vary a distance between mold  20  and substrate  12  to define a desired volume therebetween that is filled by polymerizable material  34 . For example, imprint head  30  may apply a force to template  18  such that mold  20  contacts polymerizable material  34 . After the desired volume is filled with polymerizable material  34 , source  38  produces energy  40 , e.g., broadband ultraviolet radiation, causing polymerizable material  34  to solidify and/or cross-link conforming to shape of a surface  44  of substrate  12  and patterning surface  22 , defining a patterned layer  46  on substrate  12 . Patterned layer  46  may comprise a residual layer  48  and a plurality of features shown as protrusions  50  and recessions  52 , with protrusions  50  having a thickness t 1  and residual layer  48  having a thickness t 2 . 
     The above-described system and process may be further implemented in imprint lithography processes and systems referred to in U.S. Pat. No. 6,932,934, U.S. Patent Application Publication No. 2004/0124566, U.S. Patent Application Publication No. 2004/0188381, and U.S. Patent Application Publication No. 2004/0211754, each of which is hereby incorporated by reference herein. 
     Fluid dispense system  32  may be used to deposit polymerizable material  34  on substrate  12 .  FIG. 3  illustrates a fluid dispense system  32  comprising a dispense head  60  and a dispense system  62  for depositing polymerizable material  34  on substrate  12 . Dispense head  60  may comprise micro-solenoid valves or piezo-actuated dispensers. Piezo-actuated dispensers are commercially available from MicroFab Technologies, Inc., Plano, Tex. 
     Generally, polymerizable material  34  propagating through dispense head  60  egresses from at least one nozzle  64  of dispense system  62 . It should be noted that a single nozzle  64  or multiple nozzles  64  may be used depending on design considerations. 
     As illustrated in  FIG. 3 , fluid dispense system  32  may optionally be connected to a vision system  70 . Vision system  70  may comprise a microscope  72  (e.g. optical microscope) to provide images  74  of polymerizable material  34  placement on substrate  12 . Microscope  72  may be regulated by processor  54 , and further may operate on a computer readable program stored in memory  56 . Images  74  may be provided at periodic intervals during the imprinting process. 
     Generally, the as-dispensed drops  66  may be analyzed using defect analysis tools known within the industry and other tools. Exemplary defect analysis tools are further described in U.S. Pat. No. 7,019,835, U.S. Pat. No. 6,871,558, U.S. Pat. No. 7,060,402, and U.S. Patent Publication No. 20070246850, all of which are hereby incorporated by reference herein.  FIG. 4  illustrates an exemplary defect analysis tool  82  having one or more energy sources  84  (e.g., light sources) providing energy  86  (e.g., light) focused to impinge on one or more regions of the substrate  12 . Energy  86  may be reflected and/or deflected to a sensor  88  (for instance, an optical sensor) to provide for capturing images of the substrate  12 . For example, the reflected energy  86  may contain information regarding characteristics such as the film thickness (when a patterned layer is being imaged), the size of the drops (when a drop pattern is being imaged), the location of the drops  66 , the size of the drops  66 , the shape of the drops  66 , and/or the like. The information detected by the sensor  88  may be transmitted to the processor  54 . The processor  54  may quantize the received information received from the sensor  88  to information contained in memory  56  (e.g., look-up table) regarding the desired pattern. 
     Referring to  FIG. 5 , illustrated therein is a perspective view of a dispense fixture  80 . The dispense fixture  80  holds a plurality of dispense heads  60  each including a plurality of nozzles  64  disposed across the operative surface of the dispense head  60 . In some embodiments, the nozzles  64  are disposed in staggered, offset groups of three. These nozzle groupings facilitate dispensing fluid from the individual nozzles  64  by allowing a first subgroup of nozzles  64  to dispense fluid at a first time and a second subgroup, differing from the first subgroup, of nozzles  64  to dispense fluid at a second time. In an embodiment, one nozzle  64  of the group dispenses fluid at one time and the other nozzles  64  of the group dispenses fluid at other times. In some embodiments, the timing is such that no two adjacent nozzles  64  dispense fluid at the same time. Thus, timing between nozzles  64  can be a consideration in the dispensing of fluid from the overall dispense head  60  of some embodiments. 
     While  FIG. 5  illustrates that the dispense fixture  80  includes 3 dispense heads  60 , dispense fixtures  80  having fewer or more dispense heads  60  are within the scope of the disclosure. The dispense heads  60  can be from the same, or different manufacturers and/or have the same or different model numbers. However, it is often the case that each dispense head  60  in the dispense fixture  80  is from one manufacturer and of one model number. However, each dispense head  60  typically has associated therewith a serial number which (in conjunction with the manufacturer and model number or standing alone) uniquely identifies the particular dispense head  60 . In some embodiments, the serial number and other identifying information can be labeled on the particular dispense heads  60 , can be stored in a memory device in the dispense heads  60 , or a combination thereof. 
     Furthermore, each of the dispense heads  60  is positioned in the dispense fixture  80  in a fixed relationship to the dispense fixture  80  and to the other dispense heads  60 . Thus, by controlling the dispense heads  60  in the dispense fixture  80  in certain manners, the processor  54  can cause the dispense heads  60  to operate as a single unit in dispensing fluid. Indeed, the processor  54  of many embodiments controls the nozzles  64  of the various dispense heads  60  to dispense a pattern of drops  66 . 
       FIG. 5  also illustrates a substrate  12  (which can be a wafer) in relationship to the dispense fixture  80 . Thus, the distance d s  between the nozzles  64  and the substrate  12  is illustrated by  FIG. 5 . In addition, any given dispense head  60  has a center (or other reference point) which defines its location in the dispense fixture  80 . The substrate  12  also has a center (or other reference point) which defines its location. Since the lithographic system  10  often holds the dispense fixture  80  and substrate  12  in fixed relationship to one another, the centers of the dispense heads  60  and the substrate  12  can be expressed in terms of the same coordinate system by points such as (P head0 , P head1 ) and (P disk0 , P disk1 ) where the illustrative substrate  12  is a disk. Thus an offset or a distance d=SQRT(ΔX 2 +ΔY 2 ) can exist between the center of any particular dispense head  60  and a particular substrate  12  where ΔX is the x component of offset and ΔY is the y component. Due to manufacturing tolerances, variations in how the various dispense heads  60  mount to the dispense fixture  80 , etc., these distances ΔX and ΔY can vary between substrates  12 , dispense heads  60 , dispense fixtures  80 , and/or from time-to-time (for instance, after a particular dispense head  60  is removed and re-installed in the dispense fixture  80 ). As a result of the variations in the distances ΔX and ΔY, the performance of the lithographic system  10  (see  FIG. 1 ) can vary between the dispensing of one set of drops  66  and the dispensing of another set of drops  66 . 
     Typically, the substrate  12  is a wafer or disc of some material such as silicon or silicon oxide. These discs often have an inner annular region  71  and an outer annular region  73 . The chuck  14  can hold the substrate  12  by way of the inner and/or the outer annular regions  71  and  73 . As mentioned, in some cases, the substrate  12  may be a silicon wafer with a flattened side (created during its formation) which can be used as a key to aid in positioning and locating the wafer on the chuck  14 . 
     Other sources of variation in the performance of the overall lithographic system  10  arise from a variety of sources. For instance, the performance of the nozzles  64 , dispense heads  60 , processor  54  (and associated circuitry and software), and fluid components in the lithographic system  10  can vary. Moreover, environmental and other conditions can cause variations in the performance of the lithographic system  10 . Thus ambient pressures, temperatures, humidity, etc. and pressures, temperatures, fluids, pressurizing agents, etc. in communication with the nozzles  64  can also cause performance variations of the lithographic system  10 . While the users of the lithographic system  10  typically control some or all of the foregoing variables (among many others) it may be desirable to characterize the performance of the lithographic system  10  to account for these sources of performance variations. Moreover, the characterization of the lithographic system  10  can occur during or after its set up, during its operation, etc. 
     Embodiments disclosed herein provide methods and systems for characterizing lithographic systems. Some of the provided methods include associating a selected pattern (with a selected orientation) of drops with a particular dispense head. In the current embodiment, the selected pattern is selected to characterize the particular dispense head. Each nozzle of that dispense head is controllable to dispense a drop (which has a selected location and size). These methods also include attempting to dispense the selected pattern by controlling the nozzles to dispense a first pattern of drops wherein this first as-dispensed pattern has a first as-dispensed orientation and each as-dispensed drop has a first as-dispensed location and size. Moreover, the methods also include (relative to the selected pattern) characterizing the first as-dispensed pattern. Furthermore, the methods include associating the characterization of the first as-dispensed pattern with the particular dispense head. 
     As desired, the methods can include a number of other operations such as:
         determining the first as-dispensed orientation of the first as dispensed drop pattern relative to the substrate,   determining whether each nozzle dispensed a drop according to how it was controlled during the dispensing of the first as-dispensed pattern,   determining the sizes of the as-dispensed drops,   determining whether any of the as-dispensed locations are farther from the corresponding selected locations by more than a corresponding threshold distance,   determining whether any of the as-dispensed locations (which are farther from the corresponding selected locations by more than the corresponding threshold distances) indicate timing issues between any two or more of the nozzles,   determining whether any two as-dispensed locations indicate the presence of a reverse pass offset greater than a corresponding threshold offset,   determining a position of the particular dispense head relative to a substrate on which the first as-dispensed pattern was dispensed, and/or   determining whether a position of the particular dispense head is farther from a selected position associated with the selected pattern by more than a threshold distance.       

     Moreover, the methods can include dispensing a second pattern of drops; characterizing a particular fluid dispensing system (of which the particular dispense head is a portion); and associating the characterization of the particular fluid dispensing system with the particular fluid dispensing system and the particular dispense head. 
     In the alternative, or in addition, the methods can include adjusting the particular dispense head; dispensing a second pattern of drops with the as-adjusted dispense head; characterizing the second as-dispensed pattern; and associating the characterization of the second as-dispensed pattern with the particular dispense head. 
     The methods can also include developing a plot diagram of a pattern of drops based on a performance specification; dispensing a second pattern of drops on a particular substrate; evaluating the second as-dispensed pattern (relative to the plot diagram); and associating, with the particular dispense head, the evaluation of the second as-dispensed pattern. Moreover, the plot diagram can be used to evaluate the particular dispense head as used with the particular substrate. The evaluation of the second as-dispensed pattern can include correlating the as-dispensed drops with the plot diagram after the second as-dispensed pattern is solidified. In the alternative, or in addition, the performance specification can include a parameter related to the thickness of a residual layer. Thus, the evaluation of the as-dispensed pattern can include correlating the second as-dispensed drop size of at least one drop with that thickness. Furthermore, the substrate can be a wafer on which the second as-dispensed pattern is used to form an imprinted layer. 
     Another embodiment provides a system for characterizing lithographic systems. The system includes a vision system (for characterizing drop patterns dispensed by the lithographic systems), a processor, and a memory in communication with each other. The memory stores processor executable instructions which when executed by the processor cause the processor to perform one or more of the foregoing methods for characterizing lithographic systems using the vision system, the processor, and the memory. Optionally, the dispense heads can be a portion of a nano-lithography system or any other type of fluid dispensing system. For instance, the fluid dispensing system could be used with logical, pharmaceutical, semi-conductor, etc. types of fluids. The system can include, if desired, a graphic user interface for displaying data and/or information related to the characterization of the image of the first as-dispensed pattern. 
     Referring now to  FIG. 6 , illustrated therein is a method for characterizing a lithographic system  10 . The illustrative method  100  includes certain operations  102 ,  104 ,  106 ,  108 , and  110  such as operation  102  in which the lithographic system  10  is set up. The set-up of the lithographic system  10  includes fixedly mounting one or more dispensing heads  60  to the dispense fixture  80  (thereby placing the nozzles  64  in fluid communication with the fluid in the fluid dispense system  32 ), selecting and placing the substrate  12  in the chuck  14 , selecting a fluid to be dispensed, filling the lithographic system  10  with that fluid, and setting pressures, temperatures, etc. in the fluid dispense system  32 , etc. See operation  102 . Moreover, identifying data regarding the dispense heads  60  (and other aspects of the lithographic system  10 , fluid dispense system  32 , and substrate  12 ) can be recorded. See operation  104 . 
     The initial characterization of the lithographic system  10  includes some or all of the operations illustrated by, and disclosed, with reference to  FIGS. 7-15  (although other operations could be included). See operation  106 . While, operation  106  is referred to as an initial characterization of the lithographic system  10 , it is understood that operation  106  can occur when desired by the user and is not constrained to be performed only once. Actions such as those discussed with reference to operations  102 ,  104 , and  106  can occur during the initial set up of the lithographic system  10 ; when the lithographic system  10  is moved or otherwise modified; when the lithographic system is in an operational environment; etc. 
     Nonetheless, at some time, a user may desire to place the lithographic system  10  in operation as indicated by operation  108 . Thus, the lithographic system  10  might be modified in one or more manners to prepare it for operations such as dispensing fluid(s) on various substrates  12 . Since performance variations might affect the imprints produced with the lithographic system  10 , some lithographic system  10  characterizations can be performed on an ongoing or as-desired basis. See operation  110 . For instance, the characterizations of the lithographic system  10  illustrated by operation  110  could occur periodically during production. 
     With reference again to  FIG. 6 , operation  112  illustrates that the various portions of method  100  can repeat as desired. For instance, when the user modifies the lithographic system  10  or its use, the method  100  can repeat from operation  102 . In other circumstances (for instance, the lithographic system  10  remains in production for some selected number of dispense cycles, some selected time period, etc.) method  100  can repeat from operation  106 . Otherwise, the method  100  can end as indicated at operation  112 . 
     With reference now to  FIGS. 7-15 , methods of initially characterizing the lithographic system  10  are disclosed (see operation  104 ). With reference to  FIGS. 15-25 , methods of characterizing the lithographic system  10  on an as-desired basis are also disclosed herein (see operation  108 ). 
       FIG. 7  illustrates a flow chart of a method  200  for characterizing the lithographic system  10  and, more particularly, the fluid dispense system  32 . Since the operation of the fluid dispense system  32  can influence the lithographic imprints formed by the lithographic system  10 , it may be desirable to gather data regarding the operation of the fluid dispense system  32  and to make adjusts to its operation based on the gathered data Generally, characterization of the fluid dispense system  32  includes software, mechanical, and other adjustments for registering nozzles  64 , dispense systems  62 , and/or dispense heads  60  to generate a coherent drop pattern using the dispense heads  60 . The results obtained (and data pertaining to those results and the performance of the fluid dispense system  32 ) can be recorded for subsequent use. For instance, once one or more dispense heads  60  are characterized, the characterization data can be used to select dispense heads  60  for various applications, to adjust the operation of the lithographic system  10 , and for other purposes. 
     Thus, with continuing reference to  FIG. 7  and in operation  202 , one or more dispense heads  60  may be installed in the dispense fixture  80  of the fluid dispense system  32 . More particularly, the dispense heads  60  can be installed in the dispense fixture  80  and fixedly aligned with one another therein. In operation  204 , initial software inputs related to the dispense heads  60  may be entered and adjusted with processor  54 . In operation  206 , the serial numbers of the dispense heads  60  may be identified and provided to processor  54 . Identifying the print heads  60  with their serial numbers, manufacturers, model numbers and other identifying information allows data gathered during the characterization of the fluid dispense system  32  to be associated with the dispense heads  60  installed therein. 
     In operation  208 , the distance d s  between the substrate  12  and the nozzles  64  may be evaluated and adjusted to provide the drops  66  to be dispensed on the substrate  12  without smearing or spraying of the drops  66  caused by the nozzles  64  being respectively either too close or too far from the substrate  12 . In operation  210 , the voltage V applied to the actuator(s) of the dispense head(s)  60  may be evaluated and adjusted to attain the desired drop sizes. In operation  212 , the nozzles  64  of the dispense heads  60  may be evaluated for non-functioning and functioning nozzles  64  by determining whether any drops  66  in an as-dispensed drop pattern are missing, duplicated, etc. as compared to a drop pattern selected to verify and/or characterize the operations of the nozzles  64 . In operation  214 , a drop pattern  300  (shown in  FIG. 8 ) may be dispensed by nozzles  64  to characterize and/or adjust the overall orientation of the drop pattern. See operation  214 . 
     Furthermore, in operation  216 , a drop pattern  302  (shown in  FIG. 9 ) may be dispensed to characterize and/or adjust the nozzle firing order. In operation  218 , another drop pattern  304  (shown in  FIG. 10 ) may be dispensed by the dispense heads  60  to characterize and/or adjust for any theta motion and/or misalignment of the dispense heads  60 . In operation  220 , yet another drop pattern  306  (shown in  FIG. 11 ) may be dispensed to characterize and adjust for reverse pass offset affects that might be detectable in the drop pattern  306 . In operation  222 , and if multiple dispense heads  60  are installed in the fluid dispense system  32 , dispense systems  62  (including circuitry associated with delivering a voltage to each of the nozzles  64  in a particular dispense head  60 ) for each dispense head  60  may be adjusted to fire the nozzles  64  in a pre-determined order based on the location of the nozzles  64  and the affects that the firing order might have on yet to be dispensed patterns. 
     In operation  224 , the positions of the dispense heads  60  in the dispense fixture  80  may be adjusted based on the as-dispensed patterns due to possible mis-alignments associated with the dispense heads within the dispense fixture  80 . In operation  226 , another drop pattern  308  (shown in  FIG. 12 ) may be dispensed with two (or more) of the dispense heads  60  installed in the fluid dispense fixture  80  and with two or more passes of the dispense fixture  80  over (or along) the substrate  12  to characterize the dispense heads  60  as they are installed (and aligned) in the dispense fixture  80 . In operation  228 , another drop pattern  312  (shown in  FIG. 13 ) may be dispensed using these two dispense heads  60  and using four or more passes to further characterize the as-installed, as-aligned dispense heads  60 . While the two pass characterization of operation  226  can reveal some misalignment of the heads  60  between the passes, the four pass characterization of operation  226  is more likely to reveal such pass-to-pass misalignments since the third and fourth pass provide additional opportunities for any misalignment present to evidence itself. This result is so because as the mechanism which drives the stage  16  switches print directions, backlash and other sources of reverse pass offset might accumulate between passes. 
     In some embodiments, some of the foregoing operations may be omitted or repeated without departing from the scope of the disclosure. Other modifications to method  200  may also be made without departing from the scope of the disclosure. For instance, many of the foregoing operations can be accomplished using one common as-dispensed pattern of drops  66  to characterize many aspects of the lithographic system  10 . More information regarding certain of the foregoing operations are disclosed in further detail herein. 
     Installation of Dispense Head 
     For instance and with reference again to operation  202  of method  200  (see  FIG. 7 ), at some time, the fluid dispense system  32  may be set up. Part of the set up can include selecting and installing one or more dispense heads  60  in the dispense fixture  80 . The selection of the dispense heads  60  often depends upon the application to which they will be applied. The selected dispense heads  60  may have stitched nozzles  64 , interleaved nozzles  64 , or other nozzle patterns depending on design, production, and other considerations on which the selection of the dispense heads  60  might bear. Regardless of the type of dispense head(s) selected, the fluid dispense system  32  can be characterized with the selected dispense heads  60  installed in the dispense fixture  80 . 
     Fluid Dispense System Set-Up 
     Since each type of dispense head  60  may differ in some aspects, the user may input (into the processor  54 ) parameters regarding pertinent system settings for the installed dispense heads  60 . See operation  204  of method  200 . For instance, the gray level volume, the maximum gray level, the gray-scale remap, the nozzle  64  spacing, the number of nozzles  64 , the gap between the nozzles  64 , the spacing between the dispense heads  60 , encoder parameters, stage orientation parameters, nominal dispense head locations, and/or the like may be input into the processor  54 . 
     For example, an encoder used for a particular type of dispense head  60  may have a 0.5 μm frequency after passing through an encoder splitter. The associated equation for print frequency is: 
     
       
         
           
             
               
                 
                   I 
                   p 
                 
                 ⋆ 
                 
                   E 
                   d 
                 
               
               
                 E 
                 m 
               
             
             = 
             
               O 
               p 
             
           
         
       
     
     wherein I p  is the input pitch of the encoder (e.g., 0.5 μm), E d  is the encoder divide, E m  is the encoder multiply, and O p  is the output pitch. E d  and E m  are typically integers. The input pitch I p  may be fixed based on the system stage encoder, and the encoder multiply E m  and encoder divide E d  may be adjusted to provide the output pitch O p  equal to the nozzle  64  stagger for the dispense system  62  of the dispense head  60  under consideration. For example, dispense head  60  may include a nozzle stagger of 28.16667. Providing an encoder divide E d  of 169 and encoder multiply E m  of 3 at an input pitch I p  of 0.5 μm may produce an output pitch O p  of 28.16667. In another example, providing an encoder divide E d  of 56 and encoder multiply E m  of 1 at an input pitch I p  of approximately 0.5 μm, however, may produce an output pitch O p  of 28 μm resulting in pattern shrinkage of 0.16667 every 28.16667 μm or approximately 0.6%. Thus, these parameters as well as others may be input into the processor  54  for some or all of the dispense head  60  installed in the dispense fixture  80  thereby enabling the fluid dispense system  32  to accurately dispense desired drop patterns. 
     Identification of Serial Number 
     With continuing reference to  FIG. 7 , and operation  206 , the dispense heads  60  may be uniquely identified. More particularly, the serial number (and manufacturer and model number) of each dispense head  60  may be input into the processor  54  to enable the processor  54  to associate data regarding the characterization of the fluid dispense system  32  with the dispense heads  60  installed therein during that characterization. The serial number may also provide a unique label for the individual dispense heads  60  when multiple dispense heads  60  are installed in the fluid dispense system  32 . 
     Characterizing and Adjusting the Nozzle-to-Substrate Distance d s    
     With reference now to operation  208 , since the distance d s  (see  FIG. 3 ) between the substrate  12  and the nozzles  64  can affect the quality of the drops dispensed onto the substrate  12 , the distance d s  may be characterized and adjusted. The adjustment may be a mechanical adjustment to the position of the stage  16 , the chuck  14 , the dispense head(s)  60 , the dispense fixture  80 , etc. In some embodiments, the distance d s  between the substrate  12  and the nozzles  64  may be less than approximately 700 microns although other distances are within the scope of the disclosure. 
     Characterizing and Adjusting Control Voltage 
     Moreover, since the voltage V applied to the dispense heads  60  can affect the size of the dispensed drops  66 , that voltage V may be adjusted (see operation  210  of  FIG. 7 ). For example, dispense head  60  may be provided an initial voltage V of 17.0 volts. Using the initial voltage, the dispense heads  60  may dispense a pre-determined number of drops  66  so that the resulting drop sizes and/or drop placement fidelity may be determined. For instance, the drop sizes may be determined using the defect analysis tool  82 . These as-dispensed drop sizes may be adjusted by increasing or decreasing initial voltage V. Moreover, this process may be repeated until the as-dispensed drop sizes and/or drop  66  placement fidelity is determined to be acceptable to the user. 
     Moreover, as the drops  66  dispensed by the various nozzles  64  are evaluated for size, it will likely be apparent whether any particular nozzle  64  fails to dispense a drop. Thus, in operation  212  of method  200 , the nozzles  64  can be evaluated to determine whether they are functioning. 
     Characterizing and Adjusting Dispense Head Orientation 
     As illustrated in  FIG. 8 , in operation  214 , the drop pattern  300  may be dispensed from the dispense heads  60  to characterize the overall orientation of the various dispense heads  60 . Should the as-dispensed orientation of the drop pattern  300  reveal that a dispense head  60  is incorrectly installed (for example, the lines of the drop pattern  300  run in the y direction instead of the x direction as is illustrated), the dispense head  60  can be re-installed or otherwise adjusted to obtain the desired orientation. If desired, the drop pattern  300  can be dispensed again to verify the as-dispensed orientation at operation  214 . 
     Characterizing and Adjusting Dispense Head Firing Order 
     Additionally, the same drop pattern  300  may be used or a separate drop pattern may be dispensed to characterize the firing order of the nozzles  64 . In some embodiments, the fluid dispense system  32  uses 3-cycle, shared wall, dispense heads  60 . Generally, these types of dispense heads  60  have three “cycles” of nozzles  64  in a given row. Nozzles  64  in the A cycle may be aligned along the dispense head  60  in the print head at one location while nozzles  64  in the B cycle may be shifted back ⅓ of the pitch in the print direction from that location. Nozzles  64  in the C cycle may be further shifted back from the location of the A cycle nozzles  64  another ⅓ of the pitch from nozzles  64  in the B cycle. Thus, it may be desirable to have a short delay in time between the firing of the nozzles  64  in the A and B cycles, and another delay in time between the firing of the nozzles  64  in the B and C cycles. Generally, the nozzles  64  of the current embodiment are strictly ABC alternating although other arrangements are within the scope of the disclosure. As such, in the current embodiment, no two adjacent nozzles  64  fire simultaneously. Accordingly, depending on the print direction, it may be desirable to fire the nozzles  64  in the order ABC, to fire the nozzles  64  in the order CBA, or in some other order. 
     The drop pattern  300  may be analyzed to verify that the nozzle firing order is adequate by (for instance) determining whether the as-dispensed drop pattern has a straight edge pattern along an edge running in the y direction (typically desired and indicative of correct firing order) or a 3-drop saw tooth pattern (typically not desired and indicative of a less than optimal firing order). A straight edge drop pattern  300  (along the edges running in the y direction) is illustrated in  FIG. 8  and a 3-drop saw tooth pattern  302  is illustrated in  FIG. 9 . If the dispense system  62  dispenses a 3-drop saw tooth pattern  302 , the firing of the nozzles  64  may be adjusted so as to provide the straight edge drop pattern  300  or any other desired drop pattern. 
     Characterizing and Adjusting Theta Offset and/or Motion 
     Since, in some lithographic systems  10 , relative rotational motion between the substrate  12  and the dispense fixture  80  (see  FIG. 5 ) is possible, it may be desirable to characterize the degree of radial offset between the substrate  12  and the dispense heads  60  in the dispensing fixture. For example, as illustrated in  FIG. 10A , dispense system  62  may dispense a drop pattern  304 A that can include a drop from every nozzle  64  in a particular row of nozzles  64  in a dispense head  60 . That drop pattern  304 A may be dispensed as another drop pattern  304 B offset by some distance (for instance, 50 mm off) in one direction (for instance, the y-direction) while using the same location in an orthogonal or other direction (for instance the x-direction). 
     Generally, this may produce a region  305  of overlap between the one as-dispensed pattern  304 B and the other as-dispensed pattern  304 B. This region  305  may be on the order of a few mms although other degrees of overlap might exist. In the alternative, or in addition, to a lateral offset, a theta offset might evidence itself as a difference in orientation of the two as-dispensed patterns  304 A and  304 B.  FIG. 10A  illustrates a situation in which the two as-dispensed drop patterns  304 A and  304 B align with each other meaning that little or no offset exists.  FIG. 10B , though, illustrates a situation in which the two as-dispensed drop patterns  304 A and  304 B exhibit some degree of misalignment as indicated at θ in  FIG. 100  (which may be a few degrees). 
     The dispense system  62  may then be adjusted until the offset in the selected direction (for instance, the x-direction, y-direction, or the radial offset θ) between the first drop pattern  304 A and the second drop pattern  304 B is acceptable to the user. The theta offset and/or motion may be adjusted using a picomotor connected to dispense head  60 , manually, or otherwise. Additionally, if there is pairing in a direction other than the print direction (for instance the y-direction) wherein two adjacent drops are closer together than expected and that pair is followed by a large gap in that same direction before the next drop  66 , the motion of the dispense head  60  may be adjusted to eliminate a potential offset that might be affecting the dispense heads  60 . See for instance, operation  218  of method  200 . Thus, operation  218  illustrates that the theta offset can be characterized, eliminated, and/or minimized. 
     Characterizing and Adjusting for Reverse Pass Offset 
     As illustrated in  FIG. 11A  (and at operation  226  of  FIG. 7 ), another drop pattern  306  may be dispensed to determine reverse pass offset affects and to enable their elimination (or minimization) as may be desired. Reverse offset pass typically causes a stagger S between drops  66 A of a drop pattern  306  dispensed using passes in one print direction  307 A and drops  66 B of that drop pattern  306  deposited after the print direction  307 B has been reversed. The resulting as-dispensed drop pattern  306  exhibits that stagger S in the print direction (often designated as the x-direction). Thus, the drop pattern used in characterizing the reverse pass offset affect(s) can include single rows of drops  66 , each row dispensed one at a time with print directions  307  being reversed between these rows. 
     More particularly, the edge (running in the y direction) of the drop pattern  306 A of  FIG. 11A  illustrates a drop pattern without such stagger wherein all drops  66  along the edge are aligned. In contrast, drop pattern  306 B illustrates the stagger S between alternating drops  66  along the edge of the drop pattern  306 B. More specifically,  FIG. 11B  illustrates a 2-drop repeating stagger S 2  in which alternating rows of drops  66  show the stagger S 2  between themselves. With reference again to  FIG. 9 , a 3-drop repeating stagger S 3  exhibits itself along the edge (running in the y direction) of the drop pattern  302 . The 3-drop repeating stagger S 3  includes offsets between the two successive pairs of drops  66  in any three rows in the drop pattern  302 . 
     Regardless of the type of stagger S exhibited, the stagger S can be compensated for since the space between the drops  66  within the drop pattern  306 B (or  302 ) may be used to estimate the extent or scale of the stagger. Typically, each row of drops  66  may be evaluated separately and the average offset determined. Moreover, stagger S may exist in any direction in the drop pattern  306 B. For instance, reverse pass offset affects may cause the drops along the edges of the drop pattern  306 B to exhibit a stagger S between adjacent rows of drops. Stagger might therefore occur in either the x direction of the y direction. Regardless of the direction in which the stagger S exhibits itself, the mechanism which drives the stage  16  may be adjusted to eliminate or minimize the stagger S as may be desired. 
     Characterizing and Adjusting Dispense Head Position 
     In some situations, it might be the case that one or more print heads  60  are installed with an offset between their desired position in the dispense fixture  80  and their actual position in the dispense fixture  80 . Hence, in such situations, a corresponding offset will likely exist between the actual position of the dispense head  60  and the position of the substrate  12 . Accordingly, it may be desirable to characterize the actual position of the dispense heads  60  relative to the substrate  12 . Corresponding position adjustments may be performed on dispense head  60  to eliminate or minimize such offsets. 
     More particularly, if some number of rows (either in the x direction or the y direction) of drops  66  in a drop pattern fail to appear on the substrate  12  (or target area thereof), one or more dispense heads  60  may be offset from its desired position in the dispense fixture  80 . While drop rows can be used to measure the offsets, other measures (for instance, the positions of various features which appear or fail to appear in a target area) can be used without departing from the scope of the disclosure. Operation  226  of  FIG. 7  illustrates that the positions of various dispense heads  60  can be characterized and corresponding position adjustments to the dispense head  60  can be made. 
     More particularly,  FIGS. 12 and 13  illustrate a situation in which a selected drop pattern  308  includes a two row border  310  of drops  66  around its circumference. In contrast, the as-dispensed drop pattern  312  illustrates that the border  310  exists along only three sides of the as-dispensed drop pattern  312 . Along the fourth side, a portion  314  of the border  310  failed to dispense (or was dispensed outside of the target area of the substrate  12 ). Accordingly, the corresponding dispense head  60  is likely to have been installed with an offset corresponding in magnitude to the missing portion  314  of the as-dispensed drop pattern  312 . The affected dispense head  60  may be re-positioned to eliminate or minimize such an offset. 
     Two Dispense Heads, Two Pass Characterization and Adjustment 
     As discussed herein, drop patterns such as drop pattern  308  may be dispensed using multiple dispense heads  60 . These multiple dispense heads  60  may make two or more passes over the substrate  12  to dispense drop pattern  308 . Drop pattern  308  may be analyzed to determine if affects related to reverse pass offset, dispense head  60  placement, and/or the like might exist in the drop pattern  308 . For example, if two drops in drop pattern  308  are close together in the x-direction followed by a large gap before the next drop  66  in the x-direction, then the stage  16  may be adjusted to eliminate or minimize reverse pass offset affects. 
     Two Dispense Heads, Four Pass Characterization and Adjustment 
     As illustrated in  FIG. 13 , another drop pattern  312  may be dispensed using multiple dispense heads  60 . Dispense heads  60  may make four or more passes to provide more sensitivity to the affects of reverse pass offset by allowing more print direction reversals during which the affects of reverse pass offset might accumulate. Drop pattern  312  may be analyzed to determine if the affects of reverse pass offset, dispense head  60  placement, and/or the like exist in the drop pattern  312 . As illustrated, drop pattern  312  exhibits more reverse pass offset affects than the drop pattern  308  as shown by the increased number of gaps  313  in the four-pass drop pattern  312  as compared to the two-pass drop pattern  308 . 
     Dispense Head Location Characterization 
       FIGS. 5 ,  14 , and  15  illustrate a method  400  for locating a dispense head(s)  60  relative to a substrate  12 . More particularly, the center of the dispense head  60  and the center of the substrate  12  may be registered with each other so that drop patterns can be accurately and precisely dispensed onto the substrate  12  by the dispense head  60 . In some situations, it might be desirable to center the dispense head  60  over or adjacent to the substrate  12 . In the alternative, or in addition, it might be desirable to characterize any offset between the centers of the substrate  12  and the dispense head  60 . Moreover, in some situations, it might be desirable to eliminate or minimize the offset. 
     To characterize the offset between the substrate  12  and the dispense head  60 , method  400  can be used. In method  400  the offset can be determined using the geometry of the inner annular region  71  and/or the outer annular region  73  (see  FIG. 15 ) or other points on the substrate  12  with known locations or locations which can be determined. Generally, two or more drops  66  are dispensed onto the substrate  12  and their locations are mathematically compared to two or more points or other known positions on the substrate  12 . 
     Thus, in method  400  at operation  402 , the dispense head  60  is placed over the substrate  12  at a distance d s  deemed satisfactory for dispensing drops  66  onto the substrate  12 . In operation  404 , the dispense head  60  dispenses a drop pattern  500  on the substrate  12 . This drop pattern  500  can include at least two, and in some embodiments, three drops  66  dispensed to be equidistant from the center of the drop pattern  500  of which they are a portion. In some embodiments the drops  66  of drop pattern  500  lay at known distances from some reference point associated with the drop pattern. The coordinates (a 0 , a 1 ), (b 0 , b 1 ), and (c 0 , c 1 ) of these drops  66  may be determined. For instance, the coordinates of these drops may be obtained by moving the stage  16  to center each drop  66  in the image  74  (see  FIG. 3 ) from the microscope  72  and obtaining the stage location or the absolute stage location from instrumentation on the stage  16  (see  FIG. 1 ) or associated therewith. In some embodiments, other methods can be used to determine the drop coordinates. 
     In operation  406 , the center at the coordinates (Phead 0 , Phead 1 ) of the dispense head  60  relative to the substrate  12  is determined from the coordinates of the drops  66  as obtained in operation  404 . For instance, the center of the dispense head  60  may be determined by the coordinates of drops (a 0 , a 1 ), (b 0 , b 1 ), and (d 0 , d 1 ) using the following equations: 
     
       
         
           
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     In operation  408 , the coordinates of two or more locations on the inner annular region  71  of substrate  12  may be obtained. For instance, in  FIG. 15 , the points having the coordinates (a′ 0 , a′ 1 ), (b′ 0 , b′ 1 ), and (c′ 0 , c′ 1 ) may be selected for use in locating the dispense head  60  relative to the substrate  12 . The coordinates of these points may be obtained by centering these points in the image  74  by using the stage  16  and the position instrumentation associated therewith or by other methods. 
     In operation  410 , the coordinates (Pdisk 0 , Pdisk 1 ) of the center of the substrate  12  may be determined from the points selected on the inner annular region  71  (or other points) of substrate  12 . For instance, the center (Pdisk 0 , Pdisk 1 ) of the substrate  12  may be determined from the coordinates (a′ 0 , a′ 1 ), (b′ 0 , b′ 1 ), and (c′ 0 , c′ 1 ) of the points on the inner annulus region  71  using the following equations: 
     
       
         
           
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     With continuing reference to  FIGS. 5 ,  14 , and  15  and in operation  412 , the x-positional difference LX between the center (at coordinates Phead 0 , Phead 1 ) of the dispense head  60  and the center (at coordinates Pdisk 0 , Pdisk 1 ) of the substrate  12  may be determined by subtracting the x-components of the respective locations. In operation  414 , the y-positional difference ΔY between the center (Phead 0 , Phead 1 ) of the dispense head  60  and the center (Pdisk 0 , Pdisk 1 ) of the substrate  12  may be determined by subtracting the y-components of the respective locations. 
     In operation  416 , the location of the dispense head  60  may be adjusted or modified by the x-positional difference LX and/or the y-positional difference LW to eliminate or minimize the offset. For example, the location of the dispense head  60  may be modified such that the center of the dispense head  60  lies at the point (Phead 0 ±ΔX, Phead 1 ±ΔY). 
     In operation  418 , the dispense head  60  may re-dispense another version of the drop pattern  500  on the substrate  12 . For example, the dispense head  60  placed at location (Phead 0 ±ΔX, Phead 1 ±ΔY) may re-deposit the drop pattern  500  on the substrate  12 . In the alternative, or in addition, the dispense head  60  can be placed elsewhere with the processor  54  adjusting which nozzles  64  it fires to dispense the drop pattern  500  despite the off-center placement of the dispense head  60 . 
     In operation  420 , the results of the re-positioning of the dispense head  60  may be evaluated using the vision system  70  (see  FIG. 4 ). Further, drops  66  may again be dispensed using the methods described herein to obtain the dispense head  60  center, the substrate  12  center, the x-positional difference ΔX, and the y-positional difference ΔY. If the location of the as-deposited drop pattern  500  relative to the substrate  12  is acceptable to the user (i.e., within a threshold distance from a targeted area), method  400  can end if desired. If, however, the as-deposited drop pattern  500  is determined to be in a location not desired by the user, method  400  may be repeated until the dispense head  60  position is acceptable to the user. 
     In some embodiments the coordinates (Pdisk 0 , Pdisk 1 ) of the center (or other reference point) of the substrate  12  may be determined using three points on the outer annular region  73  of substrate  12 . In the alternative, or in addition, a reference point associated with the dispense head  60  other than its center may be used to characterize the location of the dispense head  60  relative to the substrate  12 . 
     Thus, various portions of methods  200  and  400  allow the fluid dispense system  32  to be set up and characterized. For instance,  FIGS. 16-25  illustrate the characterization of other aspects of the lithographic system  10 . 
     Characterization and Adjustment of Other Aspects of the Fluid Dispensing System 
     Other aspects of lithographic systems  10  (which might influence the quality of imprints produced thereby during production) can be characterized and adjusted. For instance, with reference now to  FIGS. 1 ,  16 , and  17 , the fluid dispense system  32  may be used to deposit drops  66  on the substrate  12  in a pre-determined drop pattern  500  having one or more drop locations to create a plot diagram for use in these characterizations. The drop pattern  600  illustrated by  FIG. 16  is but one of numerous drop patterns and represents a drop pattern selected to characterize aspects of the lithographic system  10  and, more particularly, the fluid dispense system  32 . As such, as-dispensed drops  66  that are extra or missing, and/or drops  66  having a volume, diameter, size, location, and/or the like, different than that of the selected drop pattern  600  are sometimes not desired by some users. For instance, an as-dispensed volume other than the selected volume for one or more drops  66  may result in extrusions, void defects, non-uniform thickness t 2  (see  FIG. 2 ) of residual layer  48 , and/or the like. 
     To characterize aspects of the fluid dispense system  32  which might be related to such situations, the drops  66  dispensed while attempting to create the selected drop pattern  600  may be analyzed to quantify the placement and size of the as-dispensed drops  66 . The resulting quantitative data may be used to alter subsequent drop patterns dispensed on the substrate  12  to reduce the number and size of extrusions and void defects in the resulting patterned layer  46 . In addition, or in the alternative, the data may be used to provide a uniform thickness t 2  of the residual layer  48  depending on user desires, considerations for objects produced by the lithographic system  10 , etc. Further, the data may be used in preventative maintenance schemes to maintain yields for production of patterned layers  46  (in manufacturing environments) and/or for other purposes. 
     Referring now to  17 , the defect analysis tool  68  (see  FIG. 4 ) may provide an image  604  on a graphical user interface  605  of the drops  66  on the substrate  12 . Moreover, the drops  66  may be dispensed on the substrate  12  and solidified prior to obtaining the image  604 . Thus, the image  604  may provide information regarding the as-dispensed location of the drops  66 , the as-dispensed size of the drops  66 , and/or the like. The memory  56  may store threshold values for one or more parameters for comparison to the information regarding the as-dispensed drops  66 . For example, the memory  56  may store thresholds for contrast values, size values, shape values, aspect ratio values, drop perimeter lengths, drop circularity, and/or the like. The information obtained by the sensor  88  can provide as-dispensed locations (for instance, x-y coordinates) for each drop  66 . Using the information in the image  604 , a plot diagram  606  of the as-dispensed locations of each drop  66  may be developed and/or compiled and stored in memory  56  as a data file (for instance, as a text file, a comma delimited file, etc.). 
     Registration of As-Dispensed and Selected Drop Patterns 
     Referring now to  FIG. 19 , the plot diagram  606  of the as-dispensed drops  66  may be aligned to, or registered with, the selected drop pattern  600  to characterize aspects of the fluid dispense system  32 . More specifically, the plot diagram  606  may be X, Y and θ registered with the selected drop pattern  600 . For instance, two specific drop locations  610   a  and  610   b  in the plot diagram  606  may be aligned with the locations of two corresponding as-dispensed drops  602   a  and  602   b  in the selected drop pattern  600  to bring the plot diagram  606  into registration with the selected drop pattern  600 . 
     The plot diagram  606  (or an image thereof) may be manually (or mathematically) rotated and shifted to register the locations of the as dispensed drops  66  with the desired locations of the corresponding drops  602   a  and  602   b .  FIGS. 19A and 19B  illustrated these locations being registered with one another wherein the plot diagram  606  is rotated through an angle f to register with the selected drop pattern  600 . Moreover, the plot diagram  606  might also be translated through some displacement (in the x and/or y-directions) to register the plot diagram  606  with the selected drop pattern  600  although (for the sake of clarity) such translations are not illustrated. Furthermore, although  FIGS. 19A and 19B  illustrate the as-dispensed drop locations  610   a  and  610   b  and the locations of the drops  602   a  and  602   b  near certain edges of the plot diagram  606  and the selected drop pattern  600 , other locations can be used to register the plot diagram  606  with the desired drop pattern  600 . In embodiments where an image of the plot diagram  606  is registered with the selected drop pattern  600 , a least-squares analysis or other mathematical algorithm can be used to perform the registration. 
     Characterizing and Adjusting for Missing, Extra, and Mis-Located Drops 
     Referring to  FIGS. 16 ,  18 , and  20 , the selected locations of the drops in the selected drop pattern  600  may be compared to the locations of the as-dispensed drops  66  of the plot diagram  606  to characterize the as-dispensed drops  66 . The resulting characterization of the as-dispensed drop pattern can be used to adjust the performance of the fluid dispense system  32  (i.e., the lithographic system  10 ) and improve the consistency between the selected and as-dispensed drop locations thereby improving the imprints produced by the lithographic system  10 . 
     For instance, a “die-to-database” comparison of the selected drop pattern  600  and the plot diagram  606  may be performed. The desired locations of the drops may be correlated to the locations of the as-dispensed drops as reflected in the plot diagram  612  of  FIG. 20 . The correlation may identify any selected drop locations which have no as-dispensed drops  66  in the corresponding locations in the plot diagram  612  (illustrated as region A of  FIG. 20 ). The correlations may also identify any as-dispensed locations in the plot diagram  612  which have no drops in the corresponding locations in the selected drop pattern  600  (illustrated as region B of  FIG. 20 ). In addition, or in the alternative, the correlation can identify as-dispensed locations reflected in the plot diagram  612  mis-located from the corresponding selected drop locations in the selected drop pattern  600  (illustrated as region C of  FIG. 20 ). 
     Furthermore,  FIG. 21  illustrates another plot diagram  614  which summarizes the foregoing results of the characterization of the foregoing aspects of fluid dispense system  32 . Thus, with information pertaining to missing, extra, and mis-located drops, the lithographic system  10  (and, more particularly, the dispense heads  60 , dispense systems  62 , and nozzles  64  and/or their manner of their use) may be adjusted to compensate for such missing, extra, or mis-located drops. 
     Characterizing and Adjusting for Placement Accuracy 
     Furthermore, for mis-located drops, the as-dispensed locations reflected in the plot diagram  614  may be further characterized to determine placement error values for the locations of each as-dispensed drop  66 . Thus, the accuracy of the drop-placements can be characterized. For example, some as-dispensed locations may be located within at least 20 μm of the corresponding as-desired locations.  FIG. 22  illustrates another plot diagram  616  which incorporates placement error classifications. Moreover, placement error classifications may be identified in intervals as illustrated in  FIG. 22 . For instance, as-dispensed locations having approximately 20 μm to 40 μm placement accuracy may be defined as one interval, dispense locations having approximately 40 μm to 500 μm placement accuracy may be defined as other intervals in 20 μm increments as illustrated by  FIG. 22 . The foregoing placement accuracy classifications are non-limiting and other increments and other classification schemes may be used without departing from the disclosure. Nonetheless, the placement accuracy characterizations may be used to adjust the lithographic system  10 . 
       FIG. 23  illustrates a method  700  for adjusting the lithographic system  10  to account for any missing, extra, or mis-located drops. In operation  702 , correlation data between the selected drop pattern  600  and the as-dispensed locations reflected in the plot diagrams  612 ,  614 , or  616  may be determined. In operation  704 , missing as-dispensed locations may be determined based on the correlation data. In operation  706 , the fluid dispense system  32  may be analyzed using the missing as-dispensed locations to determine whether the hardware in the fluid dispense system  32  (for instance, the dispense heads  60  or nozzles  64 ) can be adjusted to provide drops  66  at the missing locations. More particularly, in operation  708 , the as-dispensed drop pattern as reflected in the plot diagram  612 ,  614 , or  616  may be analyzed to determine whether additional drops  66  may be dispensed at the missing locations. The addition of drops  66  and an increased accuracy in the placement of the additional drops  66  might improve the consistency between the as-dispensed drop pattern and the selected drop pattern  600 . 
     Performance Specifications 
     As disclosed herein, the lithographic system  10  (including the fluid dispense system  32 ) may be used to create imprinted patterns upon various substrates  12 . Thus, the performance of the fluid dispense system  32  contributes to the imprinted patterns. In some embodiments, a performance specification and a corresponding drop pattern  600  are developed to direct the operation of the fluid dispense system  32  during the dispensing of drop patterns on particular substrates. Thus, the drop pattern  600  is selected to characterize the lithographic system  10  with regard to various features of lithographic imprints for which the performance specification provides the performance parameters. 
       FIG. 24  illustrates an exemplary method  800  for establishing performance specifications (including selected performance parameters and thresholds therefore) for lithographic systems  10 . In operation  802 , an initial performance specification may be determined. For instance, one parameter in the performance specification may be a pre-determined magnitude for the thickness t 2  of residual layer  48  (see  FIG. 2 ). In operation  804 , an initial drop pattern  500  may be developed with the goal of providing imprints possessing the parameters of the pre-determined performance specification (for instance, the thickness t 2 ) following the hardening of the residual layer  48 . 
     A drop pattern may be dispensed on the substrate  12  in an attempt to create the selected drop pattern  600 . As the fluid dispense system  32  dispenses the as-dispensed pattern certain drops  66  might not be dispensed, certain extra drops  66  might be dispensed, some dispensed drops  66  might be mis-located, some dispensed drops  66  might be under/over sized, etc. Thus, the as-dispensed drop pattern might correlate to the selected drop pattern  600  in some aspects and might correlate to a lesser degree in other aspects. 
     In operation  806 , the as-dispensed drop pattern can be characterized relative to the selected drop pattern  600  to obtain correlation data between the same. For instance, plot diagrams  606 ,  612 ,  614 , and  616  and the underlying data may be determined. Furthermore, the plot diagrams  606 ,  612 ,  614 , and  616  can be analyzed to determine whether the as-dispensed drop pattern meets the performance specification. 
     In addition, or in the alternative, the residual layer  48  (see  FIG. 2 ) can be created from the as-dispensed drop pattern  506  and hardened to form an imprint on the substrate  12 . In some embodiments the resulting imprint can be inspected to determine whether it meets or exceeds the performance specification and the performance parameters therein. 
     If the plot diagrams and/or the imprint meet the performance specification, as illustrated at operation  808 , the selected drop pattern  506  and the performance specification may be accepted based on the correlation data. See operation  810 . If not, operation  808  illustrates that method  800  may be repeated to iterate the selected drop pattern  600  and the performance specification as desired. 
     Method of Manufacturing an Imprint 
       FIG. 25  illustrates a method  900  for manufacturing an imprint which includes characterizing a lithographic system  10 . In operation  902 , a drop pattern  600  including placement accuracy parameters may be selected (for instance, a placement accuracy between 0 μm±40 μm may be selected). In operation  904 , the lithographic system  10  may deposit and solidify drops  66  on substrate  12 . In operation  906 , an image may be captured of the as-dispensed drop pattern and plot diagrams  606 ,  612 ,  614 , and  616  may be determined. In operation  908 , placement accuracies between the as-dispensed drops  66  and the desired drop pattern  600  may be analyzed using the plot diagrams  612 ,  614 , and  616 . In operation  910 , the lithographic system  10  may be evaluated and adjusted using the placement accuracy information and/or other information in the plot diagrams  612 ,  614 , and  616 . 
     In operation  912 , the adjusted lithographic system  10  can be used to dispense another version of the drop pattern  600 . These subsequent, as-dispensed, drop patterns can be evaluated and developed into an imprint which may also be evaluated to characterize the lithographic system  10 . See operation  912 . 
     In operation  914 , the fluid dispense system  32  may be adjusted again after use (and perhaps during production) based on the data developed during the foregoing characterization method  900 . For instance, preventative maintenance and/or replacement of components within the fluid dispense system  32  may occur to ensure or improve process yields or for other reasons. 
     Thus, systems and methods have been disclosed which correlate as-dispensed drop patterns with drop patterns selected to characterize lithographic systems and, more particularly, fluid dispensing systems thereof. More particularly, lithographic systems can be characterized by techniques and technologies disclosed herein to determine drop size, drop shape, drop placement, etc. data. As a result, the quality and quantity of imprints produced using lithographic systems characterized as disclosed herein can be increased. Furthermore, the time, resources, and manpower used to install, set-up, and maintain lithographic systems can be reduced while maintaining or improving the quality and quantity of the imprints produced thereby.