Abstract:
An imprint lithography system operable for imprinting a pattern into a material deposited between an imprint mold and a substrate, the system including, inter alia, a first set of imaging units positioned at a first angle relative to normal of the substrate; and a second set of imaging units positioned at a second angle relative to normal of the substrate, wherein the first and second angles are not equal to each other.

Description:
This application is a continuation of U.S. Ser. No. 11/694,644, filed on Mar. 30, 2007, now abandoned, which claims priority to U.S. Provisional Application No. 60/788,809, filed on Apr. 3, 2006, and U.S. Provisional Application No. 60/788,810 filed on Apr. 3, 2006, all of which are hereby incorporated by reference herein. This application is also a continuation-in-part of U.S. Ser. No. 11/000,321, filed on Nov. 30, 2004 now U.S. Pat. No. 7,630,067, which is a division of U.S. Ser. No. 11/000,331, filed Nov. 30, 2003 now U.S. Pat. No. 7,292,326, both of which are hereby incorporated by reference herein. 
    
    
     BACKGROUND INFORMATION 
     Nano-fabrication involves the fabrication of very small structures, e.g., having features on the order of nanometers or smaller. One area in which nano-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, nano-fabrication becomes increasingly important. Nano-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension 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 is commonly referred to as imprint lithography. Exemplary imprint lithography processes are described in detail in numerous publications, such as U.S. patent application Ser. No. 10/264,960, U.S. patent application Ser. No. 10/264,926, and U.S. Pat. No. 6,936,194; all of which are assigned to the assignee of the present invention and all of which are incorporated by reference herein. 
     An imprint lithography technique disclosed in each of the aforementioned U.S. Patent Applications and U.S. Patent includes formation of a relief pattern in a polymerizable layer and transferring a pattern corresponding to the relief pattern into an underlying substrate. The substrate may be positioned upon a motion stage to obtain a desired position to facilitate patterning thereof. To that end, a template is employed spaced-apart from the substrate with a formable liquid present between the template and the substrate. The liquid is solidified to form a solidified layer that has a pattern recorded therein that is conforming to a shape of the surface of the template in contact with the liquid. The template is then separated from the solidified layer such that the template and the substrate are spaced-apart. The substrate and the solidified layer are then subjected to processes to transfer, into the substrate, a relief image that corresponds to the pattern in the solidified layer. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a simplified side view of a lithographic system having a template spaced-apart from a substrate; 
         FIG. 2  illustrates an inclined microscope unit having x-y and focusing motions; 
         FIG. 3  illustrates microscopes with different inclined angles depending on the 1 st  order reflecting angle of the imaging grating; 
         FIG. 4  illustrates microscope configurations using beam re-directing optics such as prism and mirror; 
         FIG. 5  illustrates an exemplary 8-channel imaging system with four sets of the microscopes shown in  FIG. 3 ; 
         FIG. 6  illustrates a 16-channel imaging system using a beam splitter and two sets of the systems shown in  FIG. 5 ; 
         FIG. 7  illustrates relocated imaging channels corresponding to a change of imprinting field size for a case of partial field imprinting (left lower is being imprinted) where microscopes  1  through  6  are relocated; 
         FIG. 8A  illustrates a top view of a more detailed depiction of system  500 ; 
         FIG. 8B  illustrates a side view showing more detail of system  500 ; 
         FIG. 9  illustrates a more detailed depiction of system  600 ; and 
         FIG. 10  illustrates a side view of system  500 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a system  8  to form a relief pattern on a substrate  12  includes a stage  10  upon which substrate  12  is supported and a template  14 , having a patterning surface  18  thereon. In a further embodiment, substrate  12  may be coupled to a substrate chuck (not shown), the substrate chuck (not shown) being any chuck including, but not limited to, vacuum and electromagnetic. 
     Template  14  and/or mold  16  may be formed from such materials including but not limited to, fused-silica, quartz, silicon, organic polymers, siloxane polymers, borosilicate glass, fluorocarbon polymers, metal, and hardened sapphire. As shown, patterning surface  18  comprises features defined by a plurality of spaced-apart recesses  17  and protrusions  19 . However, in a further embodiment, patterning surface  18  may be substantially smooth and/or planar. Patterning surface  18  may define an original pattern that forms the basis of a pattern to be formed on substrate  12 . 
     Template  14  may be coupled to an imprint head  20  to facilitate movement of template  14 , and therefore, mold  16 . In a further embodiment, template  14  may be coupled to a template chuck (not shown), the template chuck (not shown) being any chuck including, but not limited to, vacuum and electromagnetic. A fluid dispense system  22  is coupled to be selectively placed in fluid communication with substrate  12  so as to deposit polymeric material  24  thereon. It should be understood that polymeric material  24  may be deposited using any known technique, e.g., drop dispense, spin-coating, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), and the like. 
     A source  26  of energy  28  is coupled to direct energy  28  along a path  30 . Imprint head  20  and stage  10  are configured to arrange mold  16  and substrate  12 , respectively, to be in superimposition and disposed in path  30 . Either imprint head  20 , stage  10 , or both vary a distance between mold  16  and substrate  12  to define a desired volume therebetween that is filled by polymeric material  24 . 
     Referring to  FIG. 1  typically, polymeric material  24  is disposed upon substrate  12  before the desired volume is defined between mold  16  and substrate  12 . However, polymeric material  24  may fill the volume after the desired volume has been obtained. After the desired volume is filled with polymeric material  24 , source  26  produces energy  28 , e.g., broadband energy that causes polymeric material  24  to solidify and/or cross-link conforming to the shape of a surface  25  of substrate  12  and patterning surface  18 , defining a patterned layer  50  on substrate  12 . 
     The broadband energy may comprise an actinic component including, but not limited to, ultraviolet wavelengths, thermal energy, electromagnetic energy, visible light and the like. The actinic component employed is known to one skilled in the art and typically depends on the material from which imprinting layer  12  is formed. Control of this process is regulated by a processor  32  that is in data communication with stage  10 , imprint head  20 , fluid dispense system  22 , source  26 , operating on a computer readable program stored in memory  34 . 
     Embodiments of the present invention are an enhancement of a previously disclosed system referred to as the iMAT system, described in U.S. Pat. No. 7,292,326 which is assigned to the assignee of the present invention and is incorporated by reference herein. The embodiments have the following advantages: 
     1. More microscopes (i.e., &gt;6) and hence more data points are measured; and 
     2. Fully automated for all absolute positioning. (A unique feedback scheme is also explained for field size reconfiguration.) 
       FIG. 2  illustrates an inclined microscope unit  200  that can capture the alignment mark images without blocking the UV beam path. This imaging unit  200  is attached on an absolute positioning X-Y stage  201  and it has a focusing automation. Such an absolute X-Y positioning is necessary to relocate each microscope  200  according to the field size or the location of the alignment marks. On practical embodiment is to use a set of small motion range linear sliders that are coupled with actuators and LVDTs (Linear Variable Differential Transformers). Other proposed feedback devices are potentiometers and laser distance measuring sensors, etc. 
     Precise imprinting requires alignment systems that align the imprint mold in precise alignment with the substrate (wafer) and portions thereof. Multiple imaging systems are utilized to align with marks on the substrate. 
     When it is necessary to fit multiple microscope units so that multiple alignment marks can be imaged, mechanical interference must be handled carefully. As presented in U.S. Pat. No. 7,292,326, alignment measurement systems in this invention do not use a large NA (Numerical Aperture) microscope. However, the relative small field sizes where multiple alignment marks are positioned make the microscope configuration task very difficult even with low NA (&lt;0.1) microscopes. If the imprint field size is 26 mm by 33 mm, it may be necessary to position two imaging units next to each other where their beam paths are spaced by less than 26 mm. Further, if the two alignment marks are closer to each other, the space between their corresponding imaging units needs to be smaller too. In order to overcome the limited space problems, alternative microscope configurations are herein disclosed. 
       FIG. 3  illustrates two microscope units  200  with different inclined angles (8 degrees and 16 degrees). By altering the inclined angles, it is possible to bring their focusing points much closer as compared to the case of the same inclined angle configuration. Inclined angles are mainly governed by the grating pitch. As shown, microscope  200  at the 8 degree pitch aligns to alignment mark  302  on substrate  301 , while microscope  200  at the 16 degree pitch aligns to alignment mark  303 . 
     Referring to  FIGS. 4A and 4B , there are illustrated two alternative microscope configurations utilizing microscope  200  with either beam offset optics (prism)  401  or mirrors  402 . Prism  401  can either off-set or bend the beam path from microscope  200  so that two focusing points can be positioned closely. Mirrors  402  may be used also to bend the beam path. Further, microscope angles may be altered as illustrated. 
       FIG. 5  illustrates a top view of an 8-channel alignment system  500 . Each microscope can be relocated along its measuring side of the field. The system comprises four sets of the image capturing units  310 ,  312  positioned around the imprint field  301 . Since more microscopes can be used, more alignment targets can be captured. 
       FIG. 10  illustrates a more detailed side view of system  500 .  FIG. 8A  illustrates a more detailed top view of system  500  as it may be used in the iMAT system.  FIG. 8B  illustrates a side view of system  500  shown in  FIG. 8A . 
     When a multiple channel imaging unit is assembled on the tool, it may be necessary to calibrate their final position. Typical accuracy of such calibration is in the range of 50 microns or less. Therefore, the accuracy in the fabrication or assembly itself would not be sufficient. This problem can be solved by using a reference template/wafer that contains grating based marks so that imaging system can read during the initial tool set up. 
     Referring to  FIG. 6 , when more than 8 channels are required, it is possible to use a beam splitter  601  and two 8-channel units  500  to compose a 16-channel unit  600 .  FIG. 9  illustrates a more detailed depiction of system  600  as it may be used in an iMAT system. 
     As already presented in U.S. Pat. No. 7,292,326, similar inclined imaging systems may be used for whole substrate imprinting processes, where the imaging unit does not block the curing UV beams. By combining both low resolution marks and high resolution moiré marks on the substrate and template, a modified microscope system may be used to capture the alignment target for whole substrate imprinting processes. Typically, low resolution alignment can provide micron-level accuracy. Such a micro level accuracy may be used also to define a “region of interest (ROI)” for the moiré pattern processing. For the systems presented herein, it may be necessary to make both the low resolution marks and moiré grating with identical pitch. 
     The embodiments of the present invention described above are exemplary. Many changes and modifications may be made to the disclosure recited above, while remaining within the scope of the invention. Therefore, the scope of the invention should not be limited by the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalent.