Imprint lithography method

A template is treated to provide a surfactant rich region and a surfactant depleted region. A contact angle at the surfactant rich region may be greater than, less than, or substantially similar to a contact angle of the surfactant depleted region.

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 herein.

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 (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 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 herein.

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).

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 herein. Further, chuck28may be coupled to imprint head30such that chuck28and/or imprint head30may be configured to facilitate movement of template18.

System10may further comprise 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, both of which are hereby incorporated by reference herein.

Referring toFIGS. 1 and 2, system10may further comprise energy source38coupled to direct energy40along path42. Imprint head30and stage16may be configured to position template18and substrate12in superimposition with path42. System10may be regulated by 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 a shape of surface44of substrate12and patterning surface22, defining patterned layer46on substrate12. Patterned layer46may comprise a residual layer48and a plurality of features shown as protrusions50and recessions52, with protrusions50having a thickness t1and residual layer having a thickness t2.

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 herein.

In another embodiment, the above-mentioned system and process may be employed using techniques including, but not limited to, photolithography (e.g., various wavelengths including G line, I line, 248 nm, 193 nm, 157 nm and 13.2-13.4 nm), contact lithography, e-beam lithography, x-ray lithography, ion-beam lithography, atomic lithography, and the like.

Currently, within the art, treatment of template18with surfactant molecules is provided as a diluted spray-on surfactant/solvent solution. In using the diluted spray-on surfactant/solvent solution, it is generally difficult to obtain precise distribution of the surfactant molecules on the templates.

FIGS. 3A-3Cillustrate simplified side views of an exemplary embodiment for providing precise distribution of a surfactant on template18to provide two regions: a surfactant rich region SRR and a surfactant depleted region SDR. Generally, treatment of template18, by contacting template18with surfactant (e.g., surfactant liquid60) deposited on substrate12, may provide control over distribution of surfactant liquid60to provide surfactant rich region SRR and surfactant depleted region SDR. Control of the distribution may further allow for control over the magnitude of the contact angle θSRRwithin the surfactant rich region SRR and the magnitude of the contact angle θSDRwithin the surfactant depleted region SDR. As such, the contact angle θSRRwithin the surfactant rich region SRR and the contact angle θSDRwithin the surfactant depleted region SDR may target different applications providing for θSRR>θSDR; θSRR<θSDR; and/or θSRR≈θSRR≈θSDR. Additionally, by varying the composition of surfactant liquid60, contact angles θSRRand/or θSDRmay be controlled to target different applications providing for θSRR>θSDR; θSRR<θSDR; and/or θSRR≈θSDR.

To provide surfactant liquid60to template18, imprint fluid58may be deposited on substrate12. Imprint fluid58may include, but is not limited to, polymerizable material34and surfactant liquid60. Polymerizable material34may be formed from several different families of bulk materials. For example, polymerizable material34may be fabricated from bulk materials including, but not limited to, vinyl ethers, methacrylates, epoxies, thiol-enes and acrylates, and/or the like. Bulk materials are described in further detail in U.S. Pat. No. 7,307,118, which is hereby incorporated by reference herein.

Once imprint fluid58is deposited on substrate12, generally the surfactant liquid60may migrate to the gas/liquid interface. As such, by positioning template18in contact with imprint fluid58as shown inFIG. 3B, at least a portion of surface62of template18may be treated with surfactant liquid60.

Generally, after treatment with surfactant liquid60, surface62of template18may be defined by the surfactant rich region SRR and/or the surfactant depleted region SDR as illustrated inFIG. 3C. The surfactant rich region SRR may include a layer of surfactant liquid60having a thickness t3. For example, the layer of surfactant liquid60may have a thickness t3of approximately 0.2 to 5 nm. The surfactant depleted region SDR may include a layer of surfactant liquid60having a thickness t4. Generally, the thickness t4of the surfactant depleted region SDR may be substantially reduced as compared to the thickness t3of the surfactant rich region SRR. For example, the thickness t4of the surfactant depleted region may be zero or near zero.

Distribution of surfactant liquid60on template18may provide the contact angle θSRRat the surfactant rich region SRR and the contact angle θSDRat the surfactant depleted region SDR to be θSRR>θSDR; θSRR<θSDR; and/or θSRR≈θSDR. Generally, the contact angle θSRRat the surfactant rich region SRR and the contact angle θSDRat the surfactant depleted region SDR may be less than approximately 55°.

Further, the composition of surfactant liquid60may provide for different contact angles; surfactant liquid60may be selected to provide an approximate contact angle θSRRat the surfactant rich regions SRR and an approximate contact angle θSDRat the surfactant depleted regions SDR. As such, selection of surfactant liquid60may provide θSRR>θSDR, θSRR<θSDR, and/or θSRR≈θSDR, depending on the design considerations of an application.

Exemplary commercially available surfactant components include, but are not limited to, ZONYL® FSO, ZONYL® FSO-100, ZONYL® FSN-100, and ZONYL® FS-300, manufactured by E.I. du Pont de Nemours and Company having an office located in Wilmington, Del.; FC-4432, FC-4430, and FC-430, manufactured by 3M having an office located in Maplewood, Minn.; MASURF® FS425, MASURF® FS1700, MASURF® FS2000, MASURF® FS1239, manufactured by Mason Chemical Company having an office located in Arlington Heights, Ill.; Lodyne S-107B, Lodyne S-220N, manufactured by Ciba-Geigy Corporation having an office located in Basel, Switzerland; Unidyne NS1602, Unidyne NS1603, Unidyne NS1606a, manufactured by Daikin having an office located in Kita-ku, Osaka, Japan; MegaFace R-08 manufactured by Dainippon Ink & Chemical having an office located in Nihonbaski, Chuo, Japan.

Selection of surfactant (e.g., surfactant liquid60) may be provided through contact angle analysis. Contact angle analysis may include simulated testing of the contact angles on simulated surfactant rich regions SRRSIMand/or simulated surfactant depleted regions SDRSIM.

Referring toFIGS. 4A-4C, contact angle analysis on simulated surfactant rich regions SRRSIMmay be provided by contact angle measurement by goniometer70on testing substrate72. Testing substrate72may be formed of material that is substantially similar to template18. For example, testing substrate72may be formed of fused silica. Additionally, testing substrate72may be sized such that it is substantially similar to template18and/or sized to accommodate at least one simulated surfactant rich region SRRSIM.

Testing substrate72may be cleaned, baked dry, and stored in a nitrogen box. As illustrated inFIG. 4A, testing substrate72may be rinsed with a surfactant solution to provide film74having a thickness t5. The surfactant solution may be a diluted surfactant solution. For example, the surfactant solution may be a solution formed of a percentage of weight of surfactant molecules in Isopropyl Alcohol (IPA). Surfactant molecules within the surfactant solution may be similar to surfactant molecules within surfactant liquid60. Film74of the surfactant solution on testing substrate72may be dried, and/or a substantial portion of film74may evaporate, reducing thickness t5as illustrated inFIG. 4B. For example, after evaporation, thickness t5may be substantially zero as IPA within the surfactant solution may be substantially evaporated.

Referring toFIG. 4C, drops of imprint fluid58may be deposited on testing substrate72to form the simulated surfactant rich region SRRSIM. Each drop of imprint fluid58may have a volume VD. For example, the volume VDof each drop may be approximately 5 μL. The volume VDmay include polymerizable material34and surfactant liquid60. Surfactant liquid60may be comprised of similar surfactant molecules as compared to surfactant solution74. Alternatively, surfactant liquid60may be comprised of different surfactant molecules as compared to surfactant solution74.

The contact angle of imprint fluid58on testing substrate72may be measured at multiple locations on testing substrate72. For example, the contact angle of imprint fluid58may be measured at several locations (e.g., seven locations) using goniometer70. The contact angles at multiple locations may be averaged to provide the magnitude of the contact angle θR-SIMon the simulated surfactant rich regions SRRSIM.

Referring toFIGS. 5A-5C, contact angle analysis on simulated surfactant depleted regions SDRSIMmay be provided contact angle measurements of goniometer70on testing substrate72a. Testing substrate72amay be formed of material that is substantially similar to template18and/or material that is substantially similar to testing substrate72. For example, testing substrate72amay be formed of fused silica. Additionally, testing substrate72amay be sized such that it is substantially similar to template18and/or sized to accommodate at least one simulated surfactant depleted region SDRSIM.

Similar to testing substrate72inFIG. 4, testing substrate72ainFIG. 5Amay be cleaned, baked dry, and stored in a nitrogen box. Testing substrate72amay then be rinsed with a solvent (e.g., IPA) to provide film78having a thickness t6. Film78of solvent on testing substrate72amay be dried and/or at least a portion of film78of solvent may evaporate reducing thickness t6as illustrated inFIG. 5B. For example, thickness t6may be substantially zero after evaporation of a substantial portion of IPA.

Referring toFIG. 5C, drops of imprint fluid58may be deposited on testing substrate72ato form the simulated surfactant depleted region SDRSIM. Each drop of imprint fluid58may have a volume VD2. For example, the volume VD2of each drop may be approximately 5 μL. The volume VD2may be substantially similar to the volume VDof drops on testing substrate72inFIG. 4. The volume VD2of drops on testing substrate72ainFIG. 5Cmay include polymerizable material34and surfactant liquid60.

The contact angle of imprint fluid58on testing substrate72amay be measured at multiple locations on testing substrate72a. For example, the contact angle of imprint fluid58may be measured at several locations (e.g., seven locations) by goniometer70. The contact angles at multiple locations may be averaged to provide the magnitude of the contact angle θD-SIMon the simulated surfactant depleted regions SDRSIM.

Variations of surfactant liquid60within imprint fluid58deposited on testing substrate72amay provide control over the contact angles within the simulated surfactant rich regions SRRSIMand/or the simulated surfactant depleted regions SDRSIMleading to control over the surfactant rich regions SRR and the surfactant depleted regions SDR during imprinting. For example, imprint fluid58formed of surfactant liquid60having approximately 0.17% FC4432 and 0.33% FC4430 and polymerizable material34may provide for θR-SIMof approximately 20° and θD-SIMof approximately 22° such that θR-SIM≈θD-SIM. In another example, imprint fluid58formed of surfactant liquid60having approximately 0.5% R-08 and polymerizable material34may provide for θR-SIMof approximately 15° and θD-SIMof approximately 22° such that θR-SIM<θD-SIM. In another example, imprint fluid58formed of surfactant liquid60having approximately 0.5% FS2000 and polymerizable material34may provide for θR-SIMof approximately 18° and θD-SIMof approximately 10° such that θR-SIM>θD-SIM.

Controlling Contact Angle to Provide Suitable Wetting Characteristics

FIG. 6illustrates a flow chart of exemplary method300for providing suitable wetting characteristics between template18and polymerizable material34. Suitable wetting characteristics may be created by controlling the contact angles θSRRand θSDR. For example, by using results obtained from the contact angle analysis of the simulated surfactant rich region SRRSIMand the simulated surfactant depleted region SDRSIM, surfactant liquid60providing approximate the contact angles θR-SIMand θD-SIMmay be selected such that θSRR>θSDR. Application of surfactant liquid60on template18may then be controlled to provide the surfactant rich region SRR and the surfactant depleted region SDR on template18. The reduced contact angle θSDRin the surfactant depleted region SDR on template18, as compared to the contact angle θSRRin the surfactant rich region SRR, may provide polymerizable material34an additional driving force to wet the surfactant depleted region SDR. As such, voids formed within patterned layer46(shown inFIG. 2) may be significantly reduced during imprinting.

In a step302, multiple surfactant solutions74and/or multiple surfactant liquids60may be provided. In a step304, the contact angle θR-SIMin the simulated surfactant rich regions SRRSIMon testing substrate72rinsed with surfactant solution74may be determined for each surfactant liquid60. Alternatively, the contact angle θR-SIM may be determined by a reference document (e.g., a database) from prior testing using surfactant liquid60and surfactant solution74. In a step306, the contact angle θD-SIMin the simulated surfactant depleted region SDRSIMon testing substrate72arinsed in solvent78may be determined for each surfactant liquid60. Alternatively, the contact angle θD-SIMmay be determined by a reference document (e.g., database) from prior testing using surfactant liquid60and solvent78. In a step308, surfactant liquid60suitable for imprinting may be determined. For example, surfactant liquid60that provides θSRR>θSDRmay be selected. In a step310, imprint material58formed of polymerizable material34and surfactant liquid60may be deposited on substrate12. It should be noted that surfactant liquid60may be applied directly to template18and need not be directly added to polymerizable material34prior to contact of template18with polymerizable material34. Generally, surfactant liquid60in imprint fluid58may migrate towards the gas/liquid interface. In a step312, template18may contact imprint fluid58providing at least a portion of surfactant liquid60on surface62of template18to form at least one surfactant rich region SRR and at least one surfactant depleted region SDR. The approximate contact angle θSRRprovided within at least one surfactant rich region SRR during imprinting may be less than, greater than, or substantially similar to the approximate contact angle θSDRwithin at least one surfactant depleted region SDR during imprinting. In a step314, polymerizable material34may be solidified to provide patterned layer46.

Drop Pattern Shifting Applications Using Contact Angle Analysis

As illustrated inFIGS. 3A-3C, distribution of surfactant on template18may provide two regions: the surfactant rich region SRR and the surfactant depleted region SDR. During this stage, the surfactant rich region SRR on template18is generally located at the point of contact between template18and imprint fluid58. During filling of the desired volume between mold20and substrate12, as illustrated inFIGS. 7A and 7B, surfactant liquid60within imprint fluid58may migrate to the gas/liquid interface as template18contacts imprint fluid58and imprint fluid58spreads on surface44of substrate12. As such, surfactant liquid60may build up in localized regions on template18forming surfactant depleted regions SDR at drop locations80and surfactant rich regions SRR between drop locations80. The surfactant rich regions SRR between drop locations80generally form interstitial areas where voids may occur.

Drop shifting may even out surfactant distribution on template18. For example,FIG. 7Billustrates surfactant depleted regions SDR and surfactant rich regions SRR after a first drop pattern imprint. In a subsequent imprint, a second drop pattern may be used that provides drop locations80at a shifted location as compared to the first drop pattern. The shifted location of drops80in the subsequent drop pattern may be positioned such that at least one of drops80of imprint fluid58contacts template18at a surfactant rich region SRR.

During imprinting of multiple substrates12, drop shift patterning may be used successively or sporadically. For example, a first drop pattern may be used to imprint followed by one or more drop shifted patterns. Alternatively, a first drop pattern may be used multiple times prior to one or more drop shifted patterns being used. In a similar fashion, a first drop pattern may be used once followed by multiple uses of one or more drop shifted patterns.

Further, by reducing the contact angle θSDRof the surfactant depleted region SDR as compared to the contact angle θSRRof the surfactant rich region SRR such that θSRR>θSDR, the lower contact angle θSDRof the surfactant depleted region SDR may provide additional driving force for polymerizable material34to wet and fill the surfactant depleted region SDR.

FIG. 8illustrates a flow chart of another exemplary method400for providing suitable wetting characteristics between a template and a polymerizable material using drop pattern shifting. In a step402, multiple surfactant solutions74and/or multiple surfactant liquids60may be provided. In a step404, the contact angle θR-SIMin the simulated surfactant rich regions SRRSIMon testing substrate72rinsed with surfactant solution74may be determined for each surfactant liquid60. In a step406, the contact angle θD-SIMin the simulated surfactant depleted region SDRSIMon testing substrate72arinsed in solvent78may be determined for each surfactant liquid60. In a step408, surfactant liquid60that provides a suitable contact angle may be selected. For example, surfactant liquid60that provides contact angles θSRR>θSDRmay be selected.

In a step410, imprint material58formed of polymerizable material34and surfactant liquid60may be dispensed on substrate12in a first pattern. Generally, surfactant liquid60in imprint fluid58may migrate towards the gas/liquid interface. In a step412, template18may contact imprint fluid58. In a step414, imprint fluid58may be solidified to provide first patterned layer46. In a step416, template18may be separated from first patterned layer46with template18having the surfactant rich regions SRR and the surfactant depleted regions SDR upon removal.

In a step418, imprint material58formed of polymerizable material34and surfactant liquid60may be dispensed in a second drop pattern on second substrate12. The second drop pattern may be substantially similar to the first drop pattern and shifted a position x and/or a position y such that at least one drop location contacts at least one surfactant depleted region SDR of template18. In a step420, template18may contact imprint fluid58. In a step422, imprint fluid58may be solidified to provide second patterned layer46. The second patterned layer46may have limited or no voids.