Moat system for an imprint lithography template

The present invention is directed to a body having a first area and a second area separated by a recess. The recess is dimensioned to reduce, if not prevent, a liquid moving along a surface of the body from traveling between the first and second areas. One or more alignment marks may be positioned within one of the first and second areas. In this manner, the recess functions as a moat by reducing, if not preventing, a quantity of the liquid from being in superimposition with the alignment marks.

BACKGROUND OF THE INVENTION

The field of invention relates generally to imprint lithography. More particularly, the present invention is directed to producing templates having a moat system surrounding alignment marks.

Micro-fabrication involves the fabrication of very small structures, e.g., having features on the order of micro-meters or smaller. One area in which micro-fabrication has a sizable impact is in the processing of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, micro-fabrication becomes increasingly important. Micro-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension of the structures formed. Other areas of development in which micro-fabrication has been employed include biotechnology, optical technology, mechanical systems and the like.

An exemplary micro-fabrication technique is commonly referred to as imprint lithography and is described in detail in numerous publications, such as U.S. published patent applications 2004/0065976, entitled METHOD AND A MOLD TO ARRANGE FEATURES ON A SUBSTRATE TO REPLICATE FEATURES HAVING MINIMAL DIMENSIONAL VARIABILITY; 2004/0065252, entitled METHOD OF FORMING A LAYER ON A SUBSTRATE TO FACILITATE FABRICATION OF METEOROLOGY STANDARDS; 2004/0046271, entitled METHOD AND A MOLD TO ARRANGE FEATURES ON A SUBSTRATE TO REPLICATE FEATURES HAVING MINIMAL DIMENSIONAL VARIABILITY, all of which are assigned to the assignee of the present invention. The fundamental imprint lithography technique as shown in each of the aforementioned published patent applications includes formation of a relief pattern in a polymerizable layer and transferring a pattern corresponding to the relief pattern into an underlying substrate. 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 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.

One manner in which to locate the polymerizable liquid between the template and the substrate is by depositing a plurality of droplets of the liquid on the substrate. Thereafter, the polymerizable liquid is concurrently contacted by both the template and the substrate to spread the polymerizable liquid over the surface of the substrate. It is desirable to properly align the template with the substrate so that the proper orientation between the substrate and template may be obtained. To that end, both the template and substrate include alignment marks.

Thus, a need exists to provide alignment techniques for use in imprint lithographic processes.

SUMMARY OF THE INVENTION

The present invention is directed to a body having a first area and a second area separated by a recess. The recess is dimensioned to reduce, if not prevent, a liquid moving along a surface of the body from traveling between the first and second areas. One or more alignment marks may be positioned within one of the first and second areas. In this manner, the recess functions as a moat by reducing, if not preventing, a quantity of the liquid from being in superimposition with the alignment marks. These and other embodiments are discussed more fully below.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1depicts a lithographic system10in accordance with one embodiment of the present invention that includes a pair of spaced-apart bridge supports12having a bridge14and a stage support16extending therebetween. Bridge14and stage support16are spaced-apart. Coupled to bridge14is an imprint head18, which extends from bridge14toward stage support16and provides movement along the Z-axis. Disposed upon stage support16to face imprint head18is a motion stage20. Motion stage20is configured to move with respect to stage support16along X- and Y-axes. It should be understood that imprint head18may provide movement along the X- and Y-axes, as well as the Z-axis, and motion stage20may provide movement in the Z-axis, as well as the X- and Y-axes. An exemplary motion stage device is disclosed in U.S. patent application Ser. No. 10/194,414, filed Jul. 11, 2002, entitled “Step and Repeat Imprint Lithography Systems,” assigned to the assignee of the present invention, and which is incorporated by reference herein in its entirety. A radiation source22is coupled to lithographic system10to impinge actinic radiation upon motion stage20. As shown, radiation source22is coupled to bridge14and includes a power generator23connected to radiation source22. Operation of lithographic system10is typically controlled by a processor25that is in data communication therewith. An exemplary lithographic system is available under the trade name IMPRIO 100™ from Molecular Imprints, Inc. having a place of business at 1807-C Braker Lane, Suite 100, Austin, Tex. 78758. The system description for the IMPRIO 100™ is available at www.molecularimprints.com and is incorporated herein by reference.

Referring to bothFIGS. 1 and 2, connected to imprint head18is a template26having a mold28thereon. Mold28includes a plurality of features defined by a plurality of spaced-apart recessions28aand protrusions28b. The plurality of features defines an original pattern that is to be transferred into a substrate30positioned on motion stage20. To that end, imprint head18and/or motion stage20may vary a distance “d” between mold28and substrate30. In this manner, the features on mold28may be imprinted into a flowable region of substrate30, discussed more fully below. Radiation source22is located so that mold28is positioned between radiation source22and substrate30. As a result, mold28is fabricated from a material that allows it to be substantially transparent to the radiation produced by radiation source22.

Referring toFIG. 2, a flowable region, such as an imprinting layer34, is disposed on a portion of a surface32that presents a substantially planar profile. A flowable region may be formed using any known technique, such as a hot embossing process disclosed in U.S. Pat. No. 5,772,905, which is incorporated by reference in its entirety herein, or a laser assisted direct imprinting (LADI) process of the type described by Chou et al. inUltrafast and Direct Imprint of Nanostructures in Silicon, Nature, Col. 417, pp. 835-837, June 2002. In the present embodiment, however, a flowable region consists of imprinting layer34being deposited as a plurality of spaced-apart discrete droplets36of a material on substrate30, discussed more fully below. An exemplary system for depositing droplets36is disclosed in U.S. patent application Ser. No. 10/191,749, filed Jul. 9, 2002, entitled SYSTEM AND METHOD FOR DISPENSING LIQUIDS, and which is assigned to the assignee of the present invention, and which is incorporated by reference in its entirety herein. Imprinting layer34is formed from the material that may be polymerized and cross-linked to record the original pattern therein, defining a recorded pattern. An exemplary composition for the material is disclosed in U.S. patent application Ser. No. 10/463,396, filed Jun. 16, 2003 and entitled METHOD TO REDUCE ADHESION BETWEEN A CONFORMABLE REGION AND A PATTERN OF A MOLD, which is incorporated by reference in its entirety herein.

Referring toFIGS. 2 and 3, the pattern recorded in imprinting layer34is produced, in part, by mechanical contact with mold28. To that end, distance “d” is reduced to allow imprinting droplets36to come into mechanical contact with mold28, spreading droplets36so as to form imprinting layer34with a contiguous formation of the material over surface32. In one embodiment, distance “d” is reduced to allow sub-portions34aof imprinting layer34to ingress into and fill recessions28a.

To facilitate filling of recessions28a, the material is provided with the requisite properties to completely fill recessions28a, while covering surface32with a contiguous formation of the material. In the present embodiment, sub-portions34bof imprinting layer34in superimposition with protrusions28bremain after the desired, usually minimum, distance “d”, has been reached, leaving sub-portions34awith a thickness “t1,” and sub-portions34bwith a thickness “t2.” Thicknesses “t1,” and “t2” may be any thickness desired, dependent upon the application.

Referring again toFIG. 2, after a desired distance “d” has been reached, radiation source22produces actinic radiation that polymerizes and cross-links the material, forming a cross-linked polymer material. As a result, the composition of imprinting layer34transforms from the material to the cross-linked polymer material, which is a solid. Specifically, the cross-linked polymer material is solidified to provide side34cof imprinting layer34with a shape conforming to a shape of a surface28cof mold28, shown more clearly inFIG. 5. After imprinting layer34is transformed to consist of the cross-linked polymer material, the distance “d” is increased so that mold28and imprinting layer34are spaced-apart.

Referring toFIG. 3, additional processing may be employed to complete the patterning of substrate30. For example, substrate30and imprinting layer34may be etched to transfer the pattern of imprinting layer34into substrate30, providing a patterned surface32a, shown inFIG. 6. To facilitate etching, the material from which imprinting layer34is formed from may be varied to define a relative etch rate with respect to substrate30, as desired. The relative etch rate of imprinting layer34to substrate30may be in a range of about 1.5:1 to about 100:1.

Alternatively, or in addition to, imprinting layer34may be provided with an etch differential with respect to photo-resist material (not shown) selectively disposed thereon. The photo-resist material (not shown) may be provided to further pattern imprinting layer34, using known techniques. Any etch process may be employed, dependent upon the etch rate desired and the underlying constituents that form substrate30and imprinting layer34. Exemplary etch processes may include plasma etching, reactive ion etching, chemical wet etching and the like. The sub portions34bare typically referred to as the residual layer.

Additionally, it has been found beneficial to deposit a primer layer (not shown) when forming imprinting layer34upon substrate32which may or may not include any previously disposed patterned/unpatterned layer present on substrate32. The primer layer (not shown) may function, inter alia, to provide a standard interface with imprinting layer34, thereby reducing the need to customize each process to the material upon which imprinting layer34is to be deposited. In addition, the primer layer (not shown) may be formed from an organic material with the same etch characteristics as imprinting layer34. The primer layer is fabricated in such a manner so as to possess a continuous, smooth, if not planar, relatively defect-free surface that may exhibit excellent adhesion to imprinting layer34. The magnitude of a thickness of the primer layer (not shown) should be such that the same is able comprise the above-mentioned characteristics, but also allow the same to be substantially transparent such that underlying alignment marks, described further below, may be detected by have an optical sensor, mentioned further below. An exemplary material from which to form the primer layer (not shown) is available from Brewer Science, Inc. of Rolla Missouri under the trade name DUV30J-6. The primer layer (not shown) may be deposited using any know technique, include spin-on deposition and drop-dispense deposition.

Referring toFIGS. 3 and 4, to form an additional imprinting layer, such as a layer31atop of surface32a, or a primer layer (not shown) correct placement of mold28with respect to substrate30is important. To that end, overlay alignment schemes may include alignment error measurement and/or alignment error compensation and/or placement error measurement and correction. Placement error, as used herein, generally refers to X-Y positioning errors between a template and a substrate (that is, translation along the X- and/or Y-axis). Placement errors, in one embodiment, are determined and corrected for by using an optical imaging system40, shown inFIG. 5, to sense alignment marks discussed below with respect toFIG. 6.

Referring toFIG. 5, optical imaging system40includes a light source42and an optical train44to focus light upon substrate30. Optical imaging system40is configured to focus alignment marks lying in differing focal planes onto a single focal plane, P, wherein an optical sensor46may be positioned. As a result, optical train44is configured to provide wavelength-dependent focal lengths. Differing wavelengths of light may be produced in any manner known in the art. For example, light source42may comprise a single broadband source of light that may produce wavelengths, shown as light48, which impinges impinge upon optical train44. Optical band-pass filters (not shown) may be disposed between the broadband source and the alignment marks (not shown). Alternatively, a plurality of sources of light (not shown) may be employed, each one of which produces distinct wavelengths of light. Light48is focused by optical train44to impinge upon alignment marks (not shown) at one or more regions, shown as region R1and region R2. Light reflects from regions R1and R2, shown as a reflected light50, and is collected by a collector lens52. Collector lens52focuses all wavelengths of reflected light50onto plane P so that optical sensor46detects reflected light50.

Referring toFIGS. 1 and 6, alignment marks may be of many configurations and are arranged in pairs with one of the alignment marks of the pair being disposed on template26. The remaining alignment mark being positioned on substrate30, e.g., in a previously deposited imprinting layer or etched into substrate30or a previously deposited layer disposed thereon. For example, alignment marks may include first and second polygonal marks54and56, depicted as squares, but may be any polygonal shape desired. Another configuration for alignment marks are shown as crosses, shown as58and60. Also additional alignment marks may be employed, such as vernier marks62and64, as well as Moiré gratings, shown as66and68.

Referring toFIGS. 2,7, and8, wavelengths are selected to obtain a desired focal length, depending upon the gap between mold28and substrate30or an imprinting layer disposed on substrate30. Under each wavelength of light used, each alignment mark may produce two images on the imaging plane. First polygonal alignment mark54, using a specific wavelength of light, presents as a focused image on sensor46. Second polygonal alignment mark56, using the same wavelength of light, presents as an out-of-focus image on sensor46. In order to eliminate each out-of-focus image, several methods may be used.

Another concern with overlay alignment for imprint lithography processes that employ UV curable liquid materials may be the visibility of the alignment marks. For the overlay placement error measurement, two overlay marks, such as the marks discussed above with respect toFIG. 8, are employed, referred to collectively as alignment marks84. However, since it is desirable for template26to be transparent to a curing agent, the template overlay marks, in some embodiments, are not opaque lines. Rather, the template overlay marks are topographical features of the template surface. In some embodiments, the overlay marks are made of the same material as the template. In addition, UV curable liquids may have a refractive index that is similar to the refractive index of the template materials, e.g., quartz or fused silica. Therefore, when the UV curable liquid fills the gap between template26and substrate30, template overlay marks may become very difficult to recognize. If the template overlay marks are made with an opaque material, e.g., chromium or nickel, the UV curable liquid below the overlay marks may not be properly exposed to the UV light, e.g., having wavelengths in a range of 310 to 365 nm. This frustrates patterning an underlying surface to include alignment mark for subsequent processing, were it desired to form alignment marks in substrate30by imprinting the pattern corresponding to the alignment marks into imprinting layer34with mold28and subsequently etching the alignment marks into substrate. Therefore, several reasons exist to prevent imprinting material from being in superimposition with alignment marks.

Referring toFIG. 7, the present invention reduces, if not prevents, material in imprinting layer34from entering a region of substrate30in superimposition with alignment marks84. To that end, alignment marks84are surrounded by a moat system100. Segments102,104,106, and108of moat system100separate molds92,94,96, and98. Specifically, segments102,104,106, and108have a depth associated therewith, e.g., 30 microns, to minimize the egression of the material in imprinting layer34therein from adjacent active molds92,94,96, and98due to capillary forces. Additionally, moat system100may include a segment109that surrounds molds92,94,96, and98. As mentioned previously, when the desired gap defined between molds92,94,96and98and substrate30, or a layer previously deposited on substrate30occurs, the material in imprinting layer34forms a contiguous region of material therebetween. As a result of capillary attraction of the material of imprinting layer34to both mold28and substrate30, the material of imprinting layer34does not typically extend to regions of substrate30in superimposition with moat system100. Rather, the material of imprinting layer typically remains confined within a region of substrate30that is in superimposition with one of the molds92,94,96and98.

Referring toFIG. 8, the material of imprinting layer34forms a meniscus105at the periphery of mold94due to the surface tension of the material in imprinting layer34and the same is substantially absent from segment104. The surface tension associated with the material in meniscus105substantially reduces the probability that the material extends through into segment104. It was determined, however, that the probability that the material of imprinting layer34ingressing into moat system100, such as segment104would be substantially minimized by minimizing surface discontinuities in the surfaces defining moat system100. Specifically, it was determined that surface discontinuities, such as sharp edges, right angles and the like, might cause the material of imprinting layer34to ingress into moat system100and be located in regions of substrate30in superimposition with alignment marks84, shown inFIG. 7, which is undesirable.

Referring toFIGS. 7,8and9, therefore, to minimize, if not prevent, material of the imprinting layer34from being disposed upon a region of substrate30in superimposition with alignment marks84, moat system100abrogates most, if not all sharp corners by including portions110,112,114, and116defined by arcuate boundaries. Portions110,112,114, and116surround alignment marks84. Specifically, portion110is disposed between segments104and106; portion112is disposed between segments106and108; portion114is disposed between segments102and108; and portion116is disposed between segments102and104.

The arcuate junctions/boundaries of portions110,112,114, and116minimize surface discontinuities in the surfaces the define moat system100, thereby minimizing imprinting material, such as imprinting material in meniscus105, from crossing moat system100when meniscus coming into contact therewith. This, it is believed, reduces the probability of, if not prevent, the material in imprinting layer34from becoming disposed upon a region of substrate30in superimposition with alignment marks84.

In a further embodiment, moat system100comprises a plurality of non-linear segments surrounding molds92,94,96, and98to further minimize, if not prevent, the material in imprinting layer34becoming disposed upon a region of substrate30, shown inFIG. 8, in superimposition with alignment marks84. Specifically, connecting any two linear segments of moat system100is a non-linear segment, i.e., an arcuate segment. An example of a non-linear segment connecting two linear segments of moat system100is shown inFIG. 7. More specifically, disposed between a linear segment120and a linear segment122is a non-linear segment124, wherein non-linear segment124comprises arcuate portions126and128, i.e., portions with a smooth contour lacking corners. In another example, disposed between linear segment120and a linear segment130is a non-linear segment132, wherein non-linear segment132comprises an arcuate portion134, i.e. a portion with a smooth contour lacking corners. Non-linear segments124and132may be described analogously to the arcuate boundaries of portions120,112,114, and116, as mentioned above, and thus, non-linear segments124and132reduce the probability of, if not prevent, the material in imprinting layer34from becoming disposed upon a region of substrate30in superimposition with alignment marks84.

Referring toFIG. 10, in another embodiment, an additional set of alignment marks136may be placed within a mold, shown as a mold138, of template90. However, the region of mold138in which alignment marks136are positioned does not include any patterned features. Alignment marks136are surrounded by a moat system140so as to prevent the material in imprinting layer34from coming into contact therewith for the reasons discussed above with respect toFIGS. 7 and 8. Moat system140comprises a plurality of linear segments, with two linear segments of the plurality being connected by a non-linear segment. An example of a non-linear segment connecting two linear segments of moat system140is shown as a linear segment142and a linear segment144having a non-linear segment146disposed therebetween. Non-linear segment146is analogous to non-linear segments124and132, mentioned above, and thus non-linear segment146reduces the probability, if not prevent, the imprinting material from becoming disposed upon a region of substrate30, shown inFIG. 8, in superimposition with alignment marks136. Alignment marks136may be in addition to alignment marks84, wherein alignment marks84are surrounded by moat system100.

Alternatively, referring toFIG. 11, alignment marks136may not be surrounded by a moat system, with alignment marks136being disposed within mold138. However, alignment marks84may be surrounded by moat system100. It has been found desirable to have at least one of alignment marks84and136not surrounded by a moat system and not formed from opaque material.

In a further embodiment, referring toFIG. 12, alignment marks148may be disposed along an edge150of template90located between molds238and239. A moat system152, analogous to moat system100described above, surrounds alignment marks148and comprises arcuate portions154and156, which are analogous to arcuate portions110,112,114, and116, and thus arcuate portions154and156reduce the probability of, if not prevent, the imprinting material from becoming disposed upon a region of substrate30, shown inFIG. 13, in superimposition with alignment marks148.

Alignment marks may be located at an edge of molds438and538, shown as alignment marks448and548, respectively. A moat system452, analogous to moat system100described above, surrounds alignment mark448and comprises arcuate portions454,455,456and457, which are analogous in function to the arcuate boundaries of portions110,112,114, and116. Specifically, each of arcuate portions454,455,456and457reduce the probability of, if not prevent, the material in imprinting layer34from becoming disposed upon a region of substrate30, shown inFIG. 13, in superimposition with alignment marks448.

It should be understood that it is not necessary for an arcuate segment to couple transversely extending linear segments. For example, moat system552includes a first linear segments560and a second linear segments562coupled together via a corner segment, which in this case is shown as a right angle563, but may be formed from an acute angle or an obtuse angle. It was found that the presence of corner segments positioned at the boundary of mold538did not greatly undermine the problem solved by the present invention, i.e., deminimus amounts of the material in imprinting layer34extend into moat system552.

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 equivalents.