US20050189676A1 - Full-wafer or large area imprinting with multiple separated sub-fields for high throughput lithography - Google Patents

Abstract

The present invention is directed to a method of forming a layer on a substrate comprising forming a plurality of flowable regions on the substrate and contacting the flowable regions with a plurality of molds disposed on a template. Thereafter, the plurality of flowable regions is solidified. In a further embodiment, the method further includes spreading each of the plurality of flowable regions to an area.

Description

BACKGROUND OF THE INVENTION
• The field of invention relates generally to imprint lithography. More particularly, the present invention is directed to a method of depositing and patterning materials on a substrate during imprint lithography processes.
• 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 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, 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 includes forming a relief image in a structure by depositing a polymerizable fluid composition onto a transfer layer. The transfer layer may be a sacrificial layer providing a mask for patterning the substrate or the substrate itself. A mold makes mechanical contact with the polymerizable fluid. The mold includes a relief structure, and the polymerizable fluid composition fills the relief structure. The polymerizable fluid composition is then subjected to conditions to solidify and to polymerize the same, forming a solidified polymeric material on a transfer layer that contains a relief structure complimentary to that of the mold. The mold is then separated from the solid polymeric material such that a replica of the relief structure in the mold is formed in the solidified polymeric material. The solidified polymeric material is subjected to an environment to selectively etch the transfer layer relative to the solidified polymeric material such that a relief image is formed in the transfer layer. With this process, patterns with features on the scale of a few nanometers may be formed. As a result, substrates may demonstrate extreme topologies when compared to the dimensions of features formed thereon, wherein such extreme topologies may potentially prevent accurate reproduction of the pattern in the solidified polymeric layer.
• In order to maximize the throughput and to minimize the cost of micro-fabrication, an increase in the size of the wafer being subjected to patterning is desired. However, increasing the wafer size not only exacerbates the non-planarity of the substrate being patterned, but also increases the filling time needed to dispense the polymerizable fluid composition upon the substrate, both of which are undesirable.
• It is desired, therefore, to provide an improved method of dispensing and patterning a material upon a full-wafer or large area wafer.
SUMMARY OF THE INVENTION
• The present invention is directed to a method of forming a layer on a substrate comprising forming a plurality of flowable regions on the substrate and contacting the flowable regions with a plurality of molds disposed on a template. Thereafter, the plurality of flowable regions is solidified. In a further embodiment, the method further includes spreading each of the plurality of flowable regions to an area. These and other embodiments are discussed below.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of a lithographic system in accordance with the present invention;
• FIG. 2 is a simplified elevation view of a lithographic system shown inFIG. 1;
• FIG. 3 is a simplified representation of material from which an imprinting layer shown inFIG. 2 is comprised before being polymerized and cross-linked;
• FIG. 4 is a simplified representation of cross-linked polymer material into which the material shown inFIG. 3 is transformed after being subjected to radiation;
• FIG. 5 is a simplified elevation cross-sectional view of a mold spaced-apart from the imprinting layer, shown inFIG. 1, after patterning of the imprinting layer;
• FIG. 6 is a simplified elevational view of the template, shown inFIGS. 1 and 2, in accordance with the present invention;
• FIG. 7 is a simplified elevational view of a dispensing system, shown inFIG. 1, in accordance with the present invention;
• FIG. 8 is a detailed view demonstrating the non-planarity of the substrate in accordance with the prior art;
• FIGS. 9A-9B are simplified plan views of a template employed to pattern the substrate, shown in Fig.5, in accordance with the present invention;
• FIG. 10 is a simplified plan view showing the template, shown inFIG. 9A, in contact with the imprinting material disposed on the substrate, shown inFIG. 8;
• FIG. 11 is simplified plan view showing the various patterns that may be included with the template, shown inFIGS. 2 and 9A, in accordance with the present invention; and
• FIG. 12 is a simplified plan view showing the template coupled to a device to apply pressure to one side of the template in accordance with an alternate embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
• FIG. 1 depicts alithographic system10 in accordance with one embodiment of the present invention that includes a pair of spaced-apart bridge supports12 having abridge14 and astage support16 extending therebetween.Bridge14 andstage support16 are spaced-apart. Coupled tobridge14 is animprint head18, which extends frombridge14 towardstage support16 and provides movement along the Z-axis. Disposed uponstage support16 to faceimprint head18 is amotion stage20.Motion stage20 is configured to move with respect tostage support16 along X- and Y-axes. It should be understood thatimprint head18 may provide movement along the X- and Y-axes, as well as the Z-axis, andmotion stage20 may 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. Aradiation source22 is coupled tolithographic system10 to impinge actinic radiation uponmotion stage20. As shown,radiation source22 is coupled tobridge14 and includes apower generator23 connected toradiation source22. Operation oflithographic system10 is typically controlled by aprocessor25 that is in data communication therewith. Anexemplary system10 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 toimprint head18, via a chuck27, is atemplate26 having amold28 thereon. An exemplary chuck is disclosed in U.S. patent application Ser. No. 10/293,224, filed Nov. 13, 2003, entitled “A Chucking System for Modulating Shapes of Substrates,” which is assigned to the assignee of the present invention and is incorporated by reference in its entirety herein.Mold28 includes a plurality of features defined by a plurality of spaced-apart recessions28aand protrusions28b. The plurality of features defines an original pattern that forms the basis of a pattern to be transferred into asubstrate30 positioned onmotion stage20. To that end,imprint head18 and/ormotion stage20 may vary a distance “d” betweenmold28 andsubstrate30. In this manner, the features onmold28 may be imprinted into a flowable region ofsubstrate30, discussed more fully below.Radiation source22 is located so thatmold28 is positioned betweenradiation source22 andsubstrate30. As a result,mold28 is fabricated from a material that allows it to be substantially transparent to the radiation produced byradiation source22.
• Referring to bothFIGS. 2 and 3, a flowable region, such as animprinting layer34, is disposed on a portion of asurface32 that presents a substantially planar profile. In the present embodiment, a flowable region consists ofimprinting layer34 being deposited as a plurality of spaced-apartdiscrete droplets36 of amaterial36aonsubstrate30, discussed more fully below. An exemplary system for depositingdroplets36 is shown as a dispensingsystem70, inFIG. 1, and is discussed more fully below with reference toFIG. 7.
• Referring again toFIGS. 2 and 3,imprinting layer34 is formed frommaterial36athat may be selectively polymerized and cross-linked to record the original pattern therein, defining a recorded pattern. An exemplary composition formaterial36ais 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.Material36ais shown inFIG. 4 as being cross-linked atpoints36b, forming across-linked polymer material36c.
• Referring toFIGS. 2, 3 and5, the pattern recorded inimprinting layer34 is produced, in part, by mechanical contact withmold28. To that end, distance “d” is reduced to allowimprinting droplets36 to come into mechanical contact withmold28, spreadingdroplets36 so as to form imprintinglayer34 with a contiguous formation ofmaterial36aoversurface32. In one embodiment, distance “d” is reduced to allow sub-portions34aofimprinting layer34 to ingress into and to fillrecessions28a.
• To facilitate filling ofrecessions28a,material36ais provided with the requisite properties to completely fillrecessions28a, while coveringsurface32 with a contiguous formation ofmaterial36a. In the present embodiment, sub-portions34bofimprinting layer34 in 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. Typically, t₁is selected so as to be no greater than twice the width u of sub-portions34a, i.e., t₁≦2 u, shown more clearly inFIG. 5.
• Referring toFIGS. 2, 3 and4, after a desired distance “d” has been reached,radiation source22 produces actinic radiation that polymerizes andcross-links material36a, formingcross-linked polymer material36c. As a result, the composition ofimprinting layer34 transforms frommaterial36atocross-linked polymer material36c, which is a solid. Specifically,cross-linked polymer material36cis solidified to form solidifiedimprinting layer134 with a side having a shape that conforms to a shape of asurface28cofmold28, shown more clearly inFIG. 5. After formation of solidifiedimprinting layer134, distance “d” is increased so thatmold28 and solidifiedimprinting layer134 are spaced-apart.
• Referring toFIG. 5, additional processing may be employed to complete the patterning ofsubstrate30. For example,substrate30 andimprinting layer34 may be etched to transfer the pattern ofimprinting layer34 intosubstrate30. To facilitate etching, the material from whichimprinting layer34 is formed may be varied to define a relative etch rate with respect tosubstrate30, as desired. The relative etch rate ofimprinting layer34 tosubstrate30 may be in a range of about 1.5:1 to about 100:1.
• Referring toFIGS. 3 and 6, typicallytemplate26 includes a plurality of molds, shown as40,42,44, and46, each of which may include a common pattern or differing patterns. Further,molds40,42,46, and48 may be arranged ontemplate26 as a matrix. Although four molds are shown, any number may be present. Each ofmolds40,42,44, and46 may be described asmold28 with respective lithographic processes that apply to mold28 apply with equal measure to each ofmolds40,42,44, and46. Each ofmolds40,42,44, and46 are separated from anadjacent mold40,42,44, and46 by a recess. As shown, arecess50 is defined betweenmolds40 and42, arecess52 is defined betweenmolds42 and46, and arecess54 is defined betweenmolds46 and48. The height, h₁, h₂, and h₃, of eachrecess50,52, and54, respectively, are substantially greater than the depth ofrecession28a, shown inFIG. 2. As a result, upon application of the appropriate forces betweentemplate26 andmaterial36a,material36ain superimposition with each ofmolds40,42,44, and46 will not extrude from a region ofsubstrate30 coextensive withmolds40,42,44, and46. It is believed that this is due in part to capillary attraction betweenmolds40,42,44, and46 andmaterial36ain superimposition therewith. This allows spreading ofmaterial36ato cover an area ofsubstrate30 that has a desired shape as defined by the shape ofmolds40,42,44, and46. For example, the area ofsubstrate30 over whichmaterial36amay be spread may have any geometric shape known, e.g., circular, polygonal, and the like.
• Referring toFIGS. 6 and 7, taking advantage of these properties, imprintinglayer34 may be formed onsubstrate30 as a plurality of spaced-apart layer segments, shown as60,62,64, and66. To that end, dispensingsystem70 may include a plurality ofjet nozzles72, each of which is in fluid communication with one or more of a plurality ofmaterial reservoirs74. The number ofjet nozzles72 may be equal to an integer multiple of the number of molds present ontemplate26.Material reservoirs74 contain material to be deposited onsubstrate30, such asmaterial36a, shown inFIG. 3, or some other material.
• Referring toFIGS. 1 and 7, an exemplary system implemented asfluid dispensing system70 is described by Steinerta et al. in “An Improved 24 Channel Picoliter Dispenser Based on Direct Liquid Displacement,” published at The 12th International Conference on Solid State Sensors, Actuators and Microsystems, Boston, Jun. 8-12, 2003. Specifically, by providingmaterial reservoirs74 withmaterial36a, shown inFIG. 3, a plurality of flowable regions may be formed onsubstrate30 concurrently. As shown, the first flowable region includes droplets80; a second flowable region includes droplets82; a third flowable region includesdroplets84; and a fourth flowable region includesdroplets86.Droplets80,82,84, and86 may be dispensed uponsubstrate30 in identical patterns.
• Upon dispensingdroplets80,82,84, and86 uponsubstrate30,droplets80,82,84, and86 may be patterned according tomolds40,42,44, and46. Specifically droplets80 may be patterned bymold40 forminglayer segment60; droplets82 may be patterned bymold42 forminglayer segment62;droplets84 may be patterned bymold44 forminglayer segment64; anddroplets86 may be patterned bymold46 forminglayer segment66.
• As a result of forming the plurality of flowable regions onsubstrate30 concurrently, any evaporative effects ofmaterial36a, shown inFIG. 3, will be substantially identical withindroplets80,82,84 and86. This facilitates control of the thickness of solidified imprinting layer so that all thicknesses t₁are substantially uniform and all thicknesses t₂are substantially uniform. As a result, the dimensions of the features transferred intosubstrate30 may be precisely controlled. This minimizes undesirable etch rate differentials over the area of solidified imprinting layer. Additionally the time required to form a patterned layer is reduced, because the time in whichmultiple droplets80,82,84, and86 are dispensed and fill the features ofmold28, e.g., the fill time, is equivalent to the time required to dispense a single droplet. The fill time is on the order of seconds.
• As mentioned above, each ofmolds40,42,44, and46 makes mechanical contact withdroplets80,82,84, and86, respectively. However, the area ofsubstrate30 that is covered withdroplets80,82,84, and86 may comprise an extreme topology when compared to the dimensions of features formed thereon. An example of such an extreme topology is depicted inFIG. 8, whereinsubstrate30 appears to present a non-planar surface90. This has been traditionally found in substrates formed from gallium arsenide (GAs) or indium phosphide (InP). However, as the feature dimensions decrease, substrates that have historically been considered planar may present a non-planar surface to features formed thereon. For example,substrate30 is shown with variations in surface height.
• The variations in surface height ofsubstrate30 frustrates the patterning ofdroplets80,82,84, and86 because of the resulting differences in distances betweensurface regions92 and94 as measured from abackside96 ofsubstrate30, as h₁and h₂, respectively. The height differential, Δh, betweenregions92 and94 is defined as follows:
  Δh=|h₁−h₂|  (1)
  Height differential, Δh, may be problematic during the imprinting process and/or one or more post imprinting process, e.g., etching.
• Referring toFIGS. 8 and 9A, to overcome the problems resulting from height differential, Δh,template26 may be made to conform to non-planar surface90 for patterning liquids, such asmaterial36a, shown inFIG. 3, disposed onsubstrate30. Specifically,template26 includes abody100 having opposedfirst surface102 andsecond surface104.First surface102 includes a plurality of recessedregions106 withmolds40,42,44, and46 being disposed between adjacent recessedregions106. Specifically, recessedregions106 defineflexure regions108 about which each ofmolds40,42,44, and46 may move independent of one another. As shown,molds40,42,44, and46 are areas ofsecond surface104 positioned betweenadjacent flexure regions108.
• Referring toFIG. 9B, in a further embodiment,body100 comprises athird surface105.Third surface105 includes a plurality of recessedregions107, wherein recessedregions107 defineflexure regions109 and may be described analogously to recessedregions106, shown inFIG. 9A.
• Referring to bothFIGS. 3 and 10, during imprinting ofmaterial36a,template26compresses material36abetweensecond surface104 and non-planar surface90 formingimprinting layer34, and more specifically mold40compresses material36aforminglayer segment60 ofimprinting layer34;mold42compresses material36aforminglayer segment62 ofimprinting layer34;mold44compresses material36aforminglayer segment64 ofimprinting layer34; andmold46compresses material36aforminglayer segment66 ofimprinting layer34. Recessedregions106 allow flexing ofbody100 about the plurality offlexure regions108. In this manner,template26 conforms to the profile of non-planar surface90 defined, in part, by the height differential Δh.Material36amay be disposed on non-planar surface90 and solidified, as described above with respect toFIGS. 1-5. As mentioned above,molds40,42,44, and46 may comprise any type of pattern, such as uniform periodic features having common shapes, as well as features having differing shapes. Exemplary patterns include a series of linear grooves/projections110, a series of L-Shaped grooves/projections112, a series of intersecting grooves/projections defining amatrix114, a series of arcuate grooves/projections116, andpillars118 that have any cross-sectional shape desired, e.g., circular, polygonal, etc., shown inFIG. 11.
• Referring toFIG. 12, to facilitate conformingtemplate26 to a surface, a fluid source, such as apump120, may be placed in fluid communication withfirst surface102 to vary a pressure present. To that end, afluid chamber122 includes aninlet124 and athroughway126.Template26 is mounted inthroughway126 to substantially restrict fluid flow there through. As aresult template26 andsides128,130, and132 define avolume136.Sides128,130, and132 may be more rigid thantemplate26. In this fashion,template26 may be more sensitive to variations in pressure changes occurring involume136 thansides128,130, and132. As a result, pump120 may pressurize or evacuatevolume136 as desired to vary a shape oftemplate26 to facilitate conformation oftemplate26 with a surface adjacent tosecond side104.
• Referring toFIGS. 1, 3 and6, the characteristics ofmaterial36aare important to efficientlypattern substrate30 in light of the unique deposition process employed. As mentioned above,material36ais deposited onsubstrate30 as a plurality of discrete and spaced-apartdroplets36. The combined volume ofdroplets36 is such that the material36ais distributed appropriately over an area ofsurface32 whereimprinting layer34 is to be formed. As a result,imprinting layer34 is spread and patterned concurrently with the pattern being subsequently set by exposure to radiation, such as electromagnetic activation radiation. As a result of the deposition process, it is desired thatmaterial36ahave certain characteristics to facilitate rapid and even spreading ofmaterial36aindroplets36 oversurface32 so that the all thicknesses t₁are substantially uniform and all thickness t₂are substantially uniform. Exemplary materials are disclosed in U.S. patent application Ser. No. 10/463,396, filed Jun. 17, 2003, entitled “Method to Reduce Adhesion between a Conformable Region and a Pattern of a Mold,” and which is incorporated by reference herein in its entirety.
• The embodiments of the present invention described above are exemplary. For example, anomalies in processing regions other than film thickness may be determined. For example, distortions in the pattern may formed in imprinting layer may be sensed and the cause of the same determined employing the present invention. As a result, 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.

Claims (20)

1. A method of forming a layer on a substrate, said method comprising:

forming a plurality of flowable regions on said substrate;

contacting said flowable regions with a plurality of molds disposed on a template; and

solidifying said plurality of flowable regions.

2. The method as recited inclaim 1, wherein forming further includes forming said plurality of flowable regions as an integer multiple of said plurality of molds.

3. The method as recited inclaim 1 further including spreading a material in said plurality of flowable regions over said substrate while confining said material associated with each of said plurality of flowable regions to an area.

4. The method as recited inclaim 1, wherein contacting further includes flexing said template to conform to a topography of said substrate.

5. The method as recited inclaim 1, wherein solidifying further includes applying electromagnetic activation energy to said plurality of flowable regions.

6. The method as recited inclaim 1, wherein contacting further includes flexing said template at a region between adjacent molds of said plurality of molds.

7. The method as recited inclaim 1, wherein forming further includes forming said plurality of flowable regions concurrently.

8. The method as recited inclaim 1, wherein forming further includes forming each of said plurality of flowable regions to be spaced-apart from adjacent flowable regions of said plurality of flowable regions.

9. A method of forming a layer on a substrate, said method comprising:

forming a plurality of flowable regions on a surface of said substrate;

providing each of said plurality of flowable regions with a surface having a desired shape; and

solidifying said plurality of flowable regions.

10. The method as recited inclaim 9, wherein providing further includes contacting said plurality of flowable regions with a plurality of molds disposed on a template.

11. The method as recited inclaim 10, wherein forming further includes forming said plurality of flowable regions as an integer multiple of said plurality of molds.

12. The method as recited inclaim 10, wherein contacting further includes flexing said template to conform to a topography of said substrate.

13. The method as recited inclaim 9, wherein solidifying further includes applying electromagnetic activation energy to said plurality of flowable regions.

14. The method as recited inclaim 10, wherein contacting further includes flexing said template at a region between adjacent molds of said plurality of molds.

15. The method as recited inclaim 9 further including spreading a material in said plurality of flowable regions over said substrate while confining said material associated with each of said plurality of flowable regions to an area.

16. A method of forming a layer on a substrate, said method comprising:

forming a plurality of flowable regions on said substrate;

spreading a material in said plurality of flowable regions over said substrate while confining said material associated with each of said plurality of flowable regions to an area;

contacting said flowable regions with a plurality of molds disposed on a template; and

solidifying said plurality of flowable regions.

17. The method as recited inclaim 16, wherein forming further includes forming said plurality of flowable regions as an integer multiple of said plurality of molds.

18. The method as recited inclaim 16, wherein contacting further includes flexing said template to conform to a topography of said substrate.

19. The method as recited inclaim 16, wherein solidifying further includes applying electromagnetic activation energy to said plurality of flowable regions.

20. The method as recited inclaim 16, wherein contacting further includes flexing said template at a region between adjacent molds of said plurality of molds.

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