Alignment for edge field nano-imprinting

Systems and methods for alignment of template and substrate at the edge of substrate are described.

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 Publication No. 2004/0065976, U.S. Patent Publication No. 2004/0065252, and U.S. Pat. No. 6,936,194, all of which are hereby incorporated by reference.

An imprint lithography technique disclosed in each of the aforementioned U.S. patent publications and patent includes formation of a relief pattern in a formable layer (polymerizable) 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 a 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.

DETAILED DESCRIPTION

Referring to the figures, and particularly toFIG. 1, illustrated therein is a lithographic system10used to form a relief pattern on substrate12. Substrate12may be coupled to substrate chuck14. As illustrated, substrate chuck14is a vacuum chuck. Substrate chuck14, however, may be any chuck including, but not limited to, vacuum, pin-type, groove-type, electrostatic, electromagnetic, and/or the like. Exemplary chucks are described in U.S. Pat. No. 6,873,087, which is hereby incorporated by reference.

Substrate12and substrate chuck14may be further supported by stage16. Stage16may provide motion along the x-, y-, and z-axes. Stage16, substrate12, and substrate chuck14may also be positioned on a base (not shown).

Spaced-apart from substrate12is a template18. Template18generally includes a mesa20extending therefrom towards substrate12, mesa20having a patterning surface22thereon. Further, mesa20may be referred to as mold20. Patterning surface22may be used to pattern a single field on template18using a step-and-repeat process as described herein. Template18and/or mold20may 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 surface22comprises features defined by a plurality of spaced-apart recesses24and/or protrusions26, though embodiments of the present invention are not limited to such configurations. Patterning surface22may define any original pattern that forms the basis of a pattern to be formed on substrate12.

Template18may be coupled to chuck28. Chuck28may be configured as, but not limited to, vacuum, pin-type, groove-type, electrostatic, 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. Further, chuck28may be coupled to imprint head30such that chuck28and/or imprint head30may be configured to facilitate movement of template18.

System10may further comprise a fluid dispense system32. Fluid dispense system32may be used to deposit polymerizable material34on substrate12. Polymerizable material34may be positioned upon substrate12using 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 material34may be disposed upon substrate12before and/or after a desired volume is defined between mold20and substrate12depending on design considerations. Polymerizable material34may comprise a monomer mixture as described in U.S. Pat. No. 7,157,036 and U.S. Patent Publication No. 2005/0187339, all of which are hereby incorporated by reference.

Referring toFIGS. 1 and 2, system10may further comprise an energy source38coupled to direct energy40along path42. Imprint head30and stage16may be configured to position template18and substrate12in superimposition with path42. System10may be regulated by a processor54in communication with stage16, imprint head30, fluid dispense system32, and/or source38, and may operate on a computer readable program stored in memory56.

Either imprint head30, stage16, or both vary a distance between mold20and substrate12to define a desired volume therebetween that is filled by polymerizable material34. For example, imprint head30may apply a force to template18such that mold20contacts polymerizable material34. After the desired volume is filled with polymerizable material34, source38produces energy40, e.g., ultraviolet radiation, causing polymerizable material34to solidify and/or cross-link conforming to shape of a surface44of substrate12and patterning surface22, defining a patterned layer46on substrate12. Patterned layer46may comprise a residual layer48and a plurality of features shown as protrusions50and recessions52, with protrusions50having thickness t1and residual layer having a thickness t2. Template18may be separated from patterned layer46may used to pattern another field in a step-and-repeat process.

The above-mentioned system and process may be further employed in imprint lithography processes and systems referred to in U.S. Pat. No. 6,932,934, U.S. Patent Publication No. 2004/0124566, U.S. Patent Publication No. 2004/0188381, and U.S. Patent Publication No. 2004/0211754, each of which is hereby incorporated by reference.

Ascertaining a desired alignment between template18and a field of substrate12may aid in the facilitation of pattern transfer between template18and substrate12. To facilitate alignment, an alignment system utilizing alignment marks on the template18and/or substrate12may be used with one alignment mark of the pair being disposed on the template18, and the remaining alignment mark being positioned on the substrate12.FIG. 3illustrates a simplified view of an alignment system60having multiple alignment measurement units62(e.g., microscopes). Examples of alignment marks and alignment systems60for use in imprint lithography processes are described in detail in U.S. Pat. Nos. 7,136,150, and 7,070,405, 6,916,584, and U.S. Patent Publication No. 2007/0231421, all of which are hereby incorporated by reference.

Alignment system60may be used for a field-by-field alignment process. As illustrated inFIGS. 1,3, and4, during imprinting, stage16may be moved such that template18is oriented over the desired field70of the substrate12based on coordinates stored in memory54. Each field70of the substrate12may include two or more alignment marks72corresponding to alignment marks on the template18. The alignment marks on the template18may then be aligned with alignment marks72at a specific field70being imprinted on the substrate12. Once the field70is imprinted, stage16may be moved to orient template18over another field70of the substrate12. As such, alignment may be conducted within individual fields70of the substrate12. On the edge74of substrate12, however, portions76of fields70may be outside of the area of substrate12leading to alignment error on edge74of substrate12and, as such, a decrease in die yield.

Reconfigurable Alignment System

FIGS. 5A and 5Billustrate an exemplary reconfigurable alignment system90. Generally, in system90, alignment marks72amay be present, not only at the corners of field70a, but also may be present within each sub-field92of field70a.

Field70amay be divided according to the number of sub-fields92within field70a. For example, inFIG. 5A, field70aincludes eight possible sub-fields92; however, any number of sub-fields92may be within field70adepending on design considerations. Each sub-field92may include one or more potentially yielding dies.

Further, each sub-field92may contain multiple alignment marks72a. Placement of alignment marks72awithin field70aand/or sub-field92may be designed to limit the surface area allocated to alignment marks72aon substrate12. In one example, alignment marks72amay be within each corner of the sub-field92. In another example, alignment marks72amay be placed in a gap between sub-fields92. In another example, alignment marks72amay be placed in a gap between potentially yielding dies.

At the edge of substrate12, not all sub-fields92provide yielding dies as described above. As illustrated inFIG. 5A, potentially yielding sub-fields92are marked with hatched box. In this example, row R1provides for no potentially yielding sub-fields92. In the magnification of field70aon the edge74a, only four of the eight sub-fields92may be considered potentially yielding sub-fields.

In one example, alignment measurement system90may be reconfigured to detect alignment marks72ain potentially yielding sub-fields92in addition to or in lieu of alignment marks72of field70. Generally, alignment measurement system90is configured to not only detect alignment marks72within one or more corners of field90, but also is configured to detect alignment marks72awithin sub-fields92. As illustrated inFIG. 5B, alignment measurement units62within region94may be re-configured to detect alignment marks72awithin the potentially yielding sub-field92in addition to or in lieu of alignment marks70of field90. For example, alignment measurement units62may be moveably positioned (e.g., movement in x, y or z direction to physically relocate to be in optical communication with at least one alignment mark72asuitable for detection) and/or reconfigured (e.g., configured with additional hardware to provide optical communication with at least one alignment mark72asuitable for detection).

In another example, as illustrated inFIGS. 5B-5D, re-configuration of the alignment measurement system90may be in a pattern208that provides for detection of one or more sub-fields92. For example, inFIG. 5C, field70amay be divided into four quadrants, Q1, Q2, Q3, and Q4. Each quadrant Q may be formed of at least two sub-fields92. The alignment measurement system90may be re-configured to a pattern208that provides for detection of a quadrant Q. The alignment measurement system90may then be moved to each quadrant Q1-4to detect alignment marks within each sub-field92.

To facilitate movement without increasing particle generation and/or to increase throughput, alignment measurement system90may driven by a scanning stage200as illustrated inFIG. 5D. Alignment measurement system90or portions of alignment measurement system90may be fixably connected to scanning stage200.

Scanning stage200may comprise a first direction stage202(e.g., X stage) adjacent to a second direction stage204(e.g., Y stage). X stage202may include a plurality of sides206. Sides206may be positioned about an open area208. Sides206may form any shape formation including, but limited to, square, rectangle, hexagonal, circular, and/or any fanciful shape. Y stage204may includes a plurality of side210. Sides210may be positioned about open area208. Sides210may form any shape formation including, but limited to, square, rectangle, hexagonal, circular, and/or any fanciful shape. Shape formation of sides210may be similar to shape of sides206or different from shape of sides206.

In another example, as illustrated inFIG. 5E, one or more additional alignment measurement units62xmay be added to alignment measurement system60shown inFIG. 3. Typical numbers and placement of alignment measurement units62are further described in U.S. Pat. No. 7,292,326 and U.S. Ser. No. 11/000,321, which are both hereby incorporated by reference in their entirety. Additional alignment measurement units62xmay be introduced into the systems described in these references and configured to detect alignment marks72apositioned within sub-fields92. For example, as illustrated inFIG. 5E, alignment measurement units62and62xwithin region95may be configured to detect alignment marks72ain the potentially yielding sub-field92.

FIG. 6illustrates a flow chart of an exemplary method100for aligning template18and substrate12. In a step102, a field70having multiple sub-fields92on the edge74aof substrate12may be provided. Alignment system90may be configured to be in optical communication with alignment marks72of field70. Alignment marks72may be positioned at outer boundary of field70. Each sub-field92may comprise multiple alignment marks72a. In a step104, at least one potentially yielding sub-field92may be identified. Potentially yielding sub-fields92may have one or more potentially yielding dies. In a step106, alignment measurement system90may be re-configured such that alignment measurement units62capture alignment marks72awithin potentially yielding sub-field92or a combination of one or more potentially yielding sub-fields92. For example, alignment measurement system90may be repositioned to be in optical communication with alignment marks72aof the potentially yielding sub-field92. In one embodiment, alignment measurement system90may be repositioned in optical communication with alignment marks72abut outside of a beam path from an energy source focused through template18for solidification of polymerizable material34. In a step108, potentially yielding field70amay be imprinted to provide for one or more yielding dies with suitable alignment. For example, alignment data from phase information using alignment marks72aof sub-field of substrate12and overlaying template alignment marks may be collected. Images (e.g., moiré first order microscope images) may be captured by diffracting light from one of alignment marks72aor template alignment marks. Normal distance between alignment marks72aand template alignment marks may be altered (e.g., from 100 microns to less than 10 nm). Relative spatial parameters (e.g., alignment, magnification, distortion parameters, and the like) between substrate12and template18may be determined using the images. Using the relative spatial parameters, template18may align with sub-field92of substrate12. Polymerizable material34may be deposited on area in superimposition with sub-field92of substrate. Template18may be positioned in contact with polymerizable material34and polymerizable material34may conform between template18and substrate12. Polymerizable material34may be solidified forming patterned layer46. Template18may be separated from polymerizable material34forming potentially yielding die in sub-field92.

Independent Theta Measurement

Referring toFIGS. 1,3and7, alignment between template18and substrate12on edge74of substrate12may include the use of alignment system60or90and a theta measuring unit120. Exemplary theta measuring units120may include laser interferometers, capacitance sensors, and/or any other precision sensors having a pre-determined accuracy. Generally, at least two alignment marks72and/or alignment marks72awithin each field70or sub-field92may provide X and Y values for alignment. For example, as shown in the figures, alignment marks72may provide X and Y values for field70b. Data obtained from the theta measuring unit120may be combined with the X and Y values to provide sufficient data for alignment of x, y, and theta. It should be noted that by using only x, y and theta, magnification detection may be eliminated in sub-field92alignment.

FIG. 8illustrates an exemplary method140for aligning template18and substrate12using a theta measuring unit120. In a step142, at least one field70bhaving at least two alignment marks72may be provided. In a step144, alignment system60or90may provide X and Y values using alignment marks72. In a step146, theta measuring unit120may provide the theta value. In a step148, X, Y, and theta values may be combined to provide for alignment of template18and substrate12. In a step150, substrate may be imprinted.

Neighboring Field Alignment

Referring toFIGS. 1,3and9, alignment between template18and substrate12on edge74of substrate12may include the use of alignment marks72on adjacent fields70. For example, as illustrated inFIG. 9, alignment on the edge74of substrate12may contain a field70dhaving a potentially yielding sub-field92. As the potentially yielding sub-field92may only contain one viable alignment mark72d, alignment marks72e,72f, and/or72gfrom adjacent fields70e,70f, and/or70gmay be used to facilitate alignment between template18and substrate12for imprinting potentially yielding field70d.